WO2001088258A1 - Thermal conversion of biomass to valuable fuels, chemical feedstocks and chemicals - Google Patents

Abstract

A continuous process for the conversion of biomass to form a chemical feedstock is described. The biomass and an exogenous metal oxide, preferably calcium oxide, or metal oxide precursor are continuously fed into a reaction chamber (61) that is operated at a temperature of at least 1400 °C to form reaction products including metal carbide. The metal oxide or metal oxide precursor is capable of forming a hydrolizable metal carbide. The reaction products are quenched to a temperature of 800 °C or less. The resulting metal carbide is separated from the reaction products or, alternatively, when quenched with water, hydrolyzed to provide a recoverable hydrocarbon gas feedstock.

Description

THERMAL CONVERSION OF BIOMASS TO VALUABLE FUELS, CHEMICAL FEEDSTOCKS AND CHEMICALS

The present application claims the benefit of U.S. provisional application number 60/204,800, filed on May 16, 2000, incorporated herein by reference.

FIELD OF THE INVENTION The present invention relates to plasma conversion of biomass having lignin and/ or cellulose containing materials to valuable fuels, chemical feedstocks and chemicals, particularly, to metal carbides, carbon monoxide and hydrogen while also recovering useful inorganic compounds such as sodium compounds. In particular, waste pulping liquors can be converted to valuable products with the recovery of pulping chemicals.

BACKGROUND OF THE INVENTION

In the pulp and paper industry, economic and environmental factors necessitate recycle of pulping chemicals and recovery of value from the organic residues of pulping. These residues are not traditionally useful for fiber making. Also, it would be environmentally and economically useful to convert other forms of biomass, e.g., wood, municipal and agricultural wastes, energy crops, etc., to premium products. It is useful to recover metals, metal oxides, and metal carbides from any type of biomass that contains metals or other precursors to these substances. In pulping processes, for example, it is desirable to recover from spent pulping liquors compounds that are equivalent to, or closely chemically similar to, spent or partially spent pulping chemicals.

Current technologies use thermal or biological means to convert biomass to energy, e.g., by direct burning or gasification, sometimes with further combustion of the resulting gas to generate mechanical energy or electric power. Thermal and biological means are also used to convert biomass to chemicals or chemical feedstocks. An example is gasification of biomass to form synthesis gas, i.e., mixtures of CO and H2 that, by means of catalytic processing, can be converted to a wide range of fuels and chemicals. Biomass is also being used by at least one automobile manufacturer to fabricate body parts for busses.

Plasma gasification of black liquor has been extensively studied, but lower operating temperatures were utilized and different results were obtained. Few of these technologies, other than niche markets such as energy recovery in the forest products industry have seen substantial, economically- successful commercialization .

Chemical treatment of wood and other biomass is the dominant technology now used to produce pulp, i.e. cellulose or cellulose-rich material, for subsequent conversion to paper and paper products. Chemical treatment typically involves digestion of sized pieces of wood etc. in basic (Kraft process) or acidic (sulfite process) liquors at temperatures of 120 to 180°C for times of 0.5 to 14 hours. By-products of this treatment are so-called waste liquors, which are aqueous suspensions of spent or partially-spent inorganic pulping chemicals and various organic residues that include lignin and lignin-derived compounds. To control costs and avoid environmental damage, it is essential to recycle the pulping chemicals and recover value from the organic wastes. At present, some premium substances are recovered from organic residues of pulping, but generally at modest scale. For example, the U.S. pulp and paper industry recovered about 30 million gallons per year (c. 1995) of turpentine (a volatile mixture of monoterpenes), which is distilled from various pine woods at temperatures < 132°C during heating in the pulping digester. Tall oil, a by-product of saponified fatty acids (30-60%), resin acids (40-60%, including mostly abietic and pimaric acids), and unsaponifiables (5-10%) are obtained from waste liquors produced in Kraft processing of softwoods. Organic wastes from sulfite pulping remit hexoses, which are fermented to ethanol, and lignosulfonate salts, which are used in leather tanning, ore floatation, resins, drilling mud dispersants, and manufacture of artificial vanilla. These recoveries account for relatively small fractions of the organic wastes. Thus, in 1995, the U.S. pulp and paper industry recovered about 450,000 tons/yr of tall oil. One U.S. firm alone produced about six million tons of waste lignin from pulping.

Most of the Mgnin and other organic wastes from pulping are "upgraded" by converting them to energy to raise steam for internal process applications, and in some circumstances generation of electric power for external sales. These wastes are combusted in recovery boilers or recovery furnaces, so-named because they also partially process spent pulping chemicals for eventual recycle after further, post-furnace treatment.

The pulping wastes enter the recovery furnaces as concentrated suspensions of solids in water, i.e. as "waste pulping liquors". The solids consist of organic residues from pulping and inorganic substances, primarily spent or partially spent pulping chemicals. These processes are the Kraft process, also called alkaline or sulfate pulping, and the sulfite or acid process. Waste pulping liquors from the Kraft and sulfite processes, respectively, typically may contain about 65 to 70 wt %, and 55 wt % solids in water, and are denoted "black liquors" and "brown" (or "red") liquors.

In the recovery furnaces, waste liquors and their constituents undergo various physical and chemical transformations. It is an instructive approximation to conceptualize a recovery furnace as a process vessel divided into zones dominated by (further) drying and concentration of the waste liquor, devolatilization (pyrolysis) of organics, gasification of organics-derived char and of inorganics (e.g., 2NaOH + CO2 — > Na2CO3 + H2O), chemical reduction of inorganics, and oxidation of organics-derived volatiles and of inorganics (e.g., Na2S + 2O2 — > Na2SO4 ). These phenomena collectively cause the breakdown of organics to intermediates and their subsequent combustion to produce energy, as well as the oxidation and reduction steps that regenerate pulping chemicals or their precursors. For example, in the Kraft process Na2S (an actual pulping chemical) and Na2CO3 (a precursor to NaOH another pulping agent) are bottom-tapped from the recovery furnace as a molten mixture

("smelt"). Recovery boilers are the most expensive single capital cost item in a modern Kraft mill, costing about $100 million for a 2500 to 3000 ton per day paper mill (c. 1995 dollars). Safety is an important issue in Kraft recovery boilers, with roughly 1% of these furnaces having at least one accident per year, e.g., smelt- water explosions.

Various patents describe methods for chemical recovery from waste liquors obtained in wood pulp production. U.S. 4692209 describes a process where the liquor is fed into the combustion zone (preferably 1000-1300°C) of a reactor together with a supply of external thermal energy. The vaporized reaction products pass to a cooling zone (preferably 600-900°C) and a melt or aqueous solution containing inorganic compounds, particularly NaOH, Na₂S and small amounts of Na₂CO₃ are removed via a lower outlet. An H₂ and CO gas mixture is withdrawn at an upper outlet. Temperature and 0₂ potential in the combustion zone are controlled by regulation of the energy supply and optional addition of carbonaceous material and/ or O₂ containing gas. The liquor is first subjected to low temperature pyrolysis, e.g., at 600-800°C and the Na₂CO₃ and reduced solid carbon mixture obtained is fed to the combustion zone to form small amounts of NaOH and Na₂CO₃. The mixture is scrubbed with gas from the pyrolysis to obtain an aqueous white liquor containing NaOH, NaHS and Na₂CO₃. Melt-H₂O explosions are avoided.

US 4710269 describes a method for increasing capacity and improving the chemical recovery process when using a conventional soda recovery boiler for recovering chemicals from a spent sulfate liquor. The sulfate liquor is supplied to a liquor gasifier while external energy independent of combustion is simultaneously supplied. The temperature and oxygen are controlled independently. The gas product thus obtained containing Na, CO and H₂ is introduced into a soda recovery boiler and organic constituents are withdrawn primarily as a gas.

US 5439557 describes a process for recovering energy and chemicals from a spent hquor which, after thickening to a dry content of 50-90%, is fed into a reaction chamber having a plurality of zones. The liquid phase is converted to a steam phase. Spent liquor is thermally decomposed to form gaseous organic substances and solid and/ or molten organic and inorganic substances, which are reduced and oxidized during the thermal decomposition with oxygen or oxygen containing gas being supplied to the reaction chamber in a controlled amount to maintain the reactions, which comprise combustion of organic substances, and a bed of solid and/ or molten substances is formed in a lower temperature zone in the reaction chamber. The steps are carried out during exposure to low frequency sound.

In US 4808264, a process is described for recovering chemicals and energy from cellulose waste liquors, preferably black kraft hquor. First, the concentrated black liquor is gasified in a pressurized reactor by flash pyrolysis at 700 to 1300°C (by introducing oxygen or an oxygen containing gas into the reactor), normally 800-900°C, whereby an energy rich gas is produced and wherein the inorganic chemicals of the black liquor are contained in the form of molten suspended droplets, mainly comprising sodium carbonate and sodium sulfide. Then, the gas from the gasification reactor is rapidly cooled through direct contact with water, and with green liquor, which is formed when the molten droplets and hydrogen sulfide are dissolved in the quench liquid. The cooled gas subsequently passes through a scrubber. In the lower section of the scrubber, the gas is washed with green liquor and, in the upper section of the scrubber, the gas is washed with sodium hydroxide (or carbonate) solution and water for complete removal of any remaining sulfur bearing components. Finally, the sulfur and particulate free gas is used as a fuel for generating steam or for production of electric power.

US 4917763 describes a method for recovering chemicals from spent liquors while utilizing energy liberated during the process. The spent liquors are gasified and partially disintegrated in a reactor with thermal energy independent of combustion being supplied by a plasma generator simultaneously to the reaction zone. Then, the resultant melt containing mainly sodium sulfide is separated at substantially the temperature prevailing at combustion. The gaseous product thereby obtained is quenched in a quenching and cooling zone to a temperature below 950°C. The product gas contains substantially no sulfur impurities. Alkali compounds in liquid form are also obtained from the quenching and cooling zone.

In US 4601786, a method is described for recovery of chemicals from waste liquor from wood pulp processes, primarily black liquor, while utilizing energy liberated. Controlled total vaporization of the pulp waste liquor at high temperature and low oxygen potential is achieved by external supply of energy using a plasma generator. Subsequent condensation and separation of a melt or water solution is obtained which, without causticizing, can be used for the preparation of white Hquor. Also, an energy rich gas consisting primarily of carbon monoxide and hydrogen, and mainly free of sulfur, is obtained.

US 4116759 describes a method for regenerating pulping or bleaching chemicals from spent Hquor containing salts of polybasic organic acids. The Hquor is evaporated and then burned so that organic matter will be discharged as carbon dioxide and water, and a carbonate residue is formed. Dissolving the residue in water regenerates the alkaline salts for pulping or bleaching.

In US 4738835, a method is described for recovering alkaH chemicals from a material containing dissolved inorganic compounds. The material is gasified in a reactor by an external heat source at a temperature over about 1000°C producing a gas in which the sodium is substantiaUy in a gaseous state. The gas is cooled by contact with an adequate amount of cooled recirculated soHd particles in a sublimation chamber of a circulating bed cooler to decrease the temperature of the gas rapidly below the sublimation temperature of the sodium compounds so that sodium compounds are condensed onto the soHd particles. The gas and soHd particles pass upwardly through a heat exchanger to cool the soHd particles and some of the soHd particles are removed from the gas.

JP 1006191 A describes a recovery process wherein the Hquor is fed at the top of a reaction zone while external heat energy is simultaneously fed independently of the burning. The temperature and oxygen potential in the reaction zone are independently controHed by the controUed heat energy fed and, if necessary, feeding carbon material and/ or oxygen containing gas. Thus, aU of the alkaH and sulfur are separated from the gaseous phase and combined to the fusion phase which is removed from the reactor. The organic portion of the spent Hquor is in the gaseous state.

At the 1989 International Chemical Recovery Conference, L. Stigsson, "A New Concept For Kraft Recovery," pp. 191-194, disclosed the use of plasm generators for supporting and stabilizing the gasification reactions for recovery of chemicals and energy from kraft waste Hquor s.

As reported by R. Grant, Pulp & Paper International, Vol. 36, No. 2, page 53 (3) (Feb. 1994), the trend to burning higher black Hquor soHds continues. Available processes aHow more efficient burning of black Hquor in the recovery boiler at up to 90% soHds reduction efficiency or better and sulfur dioxide emissions are significantly reduced. Gasification is seen as the key to unlocking incremental recovery capacity for mϋls where the recovery boiler is the bottleneck. Gasification turns black Hquor into two separate streams, one (from the organic components) that can be burnt in a gas turbine or elsewhere, and another (from the inorganic components) that provides the green liquor.

However, none of the reported processes use a non-combustion conversion process for obtaining higher value compounds from the organic materials in the spent pulp waste Hquors. Further, none of the processes convert other sources of biomass to higher value compounds. Thus, there stiH exists a need for a commercial process to convert biomass to higher value fuels and chemicals.

SUMMARY OF THE INVENTION The present invention provides chemical methods for converting biomass, including organic residues in waste pulping Hquors, containing materials having Hgnin and /or ceUulose, or other such organic compounds, to valuable products, i.e. metal carbides, acetylene, ethylene, or other hydrocarbons useful as fuels or chemical feedstocks, and to CO and H2. Further, when the biomass includes pulping residues, the methods of the present invention can concurrently recover inorganic pulping chemicals for reuse or recycle.

Thus, the method comprises continuously feeding into a reaction chamber at a temperature of at least 1400 °C a biomass material with a metal oxide or metal oxide precursor, wherein the metal oxide is capable of forming a hydroHzable metal carbide, to form reaction products; and quenching the reaction products to a temperature of 800 °C or less. Preferably, the resulting metal carbide is separated from the reaction products. Alternatively, when water is used for quenching, the metal carbide is hydrolyzed in the quenching step producing a hydrocarbon gas, e.g., acetylene. When the biomass is a waste pulping Hquor containing significant amounts of sodium, Na and/ or Na₂S are directly produced by preferred methods of the present invention. The methods of the present invention are of particular interest for, but by no means limited to, appHcations in the pulp and paper industry, where economic and environmental factors necessitate recycle of pulping chemicals and recovery of value from the organic residues of pulping. These residues are not traditionaUy useful for fiber making. The invention is broadly appHcable to converting aU forms of biomass, e.g., wood, municipal and agricultural wastes, energy crops, etc., to the premium products noted above. In this regard the invention also provides a means for recovering useful metals, metal oxides, and metal carbides from any type of biomass that contains metals or other precursors to these substances, for example compounds equivalent to, or closely chemicaUy similar to spent or partiaUy spent pulping chemicals.

In preferred embodiments of the present invention, the biomass is converted to metal carbides such as CaC₂ by reacting CaO (or other metal oxides) with the biomass. Preferably, a plasma generator is used to obtain the higher temperatures needed for CaC₂ formation whereas conventional plasma gasification of biomass employs lower temperatures. Thus, the present invention provides for "carbidization" of biomass including waste pulping Hquors instead of the gasification provided by conventional processes. Preferably, 10% or more by weight, more preferably 50% or more by weight, of the initial carbon in the biomass is converted to a metal carbide such as, for example, CaC₂.

In another embodiment of the invention, when the biomass is a waste pulping Hquor (or other source containing substantial sodium compounds), preferably 10% or more by weight, more preferably 50% or more by weight, of the sodium is converted to elemental Na. When the biomass contains sulfur and sodium compounds, the sodium and sulfur are converted to NaS₂ and, preferably, excess sodium is converted to elemental Na.

As used in the present appHcation, the term "biomass" refers to Hving matter formed by photosynthesis, for example plants, trees, grasses etc., as weU as useful materials and wastes derived from Hving sources including animals and humans in time scales that are smaH compared to those for the formation of fossil fuels. Examples of useful materials and wastes derived from Hving sources include municipal wastes, as weU as finished products, recycled materials, and wastes from agriculture, forestry, construction, and human and animal habitat. Thus, biomass includes any of wood, ceUulose, hemiceUulose, Hgnin, HgnoceHulosic materials, or mixtures thereof, paper, as weU as wastes and residues from forests, animals, and humans, including municipal waste, that are at least partiaHy organic in their makeup, and any plant material or residue of a plant, whether such plant or residue is living or not.

As used herein, the term "carbideable char carbon" ("CCC") or "carbideable carbon" means the amount of carbon remaining in the feed after oxygen in the feed is converted stoichiometricaHy to carbon monoxide.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates schematic diagram of a plasma reactor and associated gas and solids processing equipment including product coHection equipment used in a laboratory operation of an embodiment of the process of the present invention.

FIG. 2 is a schematic illustration of a plasma reactor useful in connection with the equipment illustrated in FIG. 1 to conduct the process of the present invention.

FIG. 3 is a schematic iHustration of the plasma reactor, cooling chamber and a coUection probe for withdrawing samples from the reactor.

FIG. 4 is a graph illustrating Arc power (O) and arc current (D) for an experiment run in accord with the present invention using lignin and calcium oxide as feed materials.

FIG. 5 is a graph iUustrating Arc power (O) and arc current (D) for another experiment run in accord with the present invention using Hgnin and calcium oxide as feed materials.

FIG. 6 is a graph iUustrating a XRD ("x-ray diffraction") spectrum providing information about the molecular identity of crystalline substances produced in accord with the invention in Example IP18.

FIG. 7 is a graph iUustrating a XPS ("x-ray photoelectron spectroscopy") spectrum identifying particular types of chemical bonds at or near the surface of soHds produced in accord with the invention in Example IP18.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a new process chemistry to convert biomass including residues of HgnoceHulosic pulping operations, i.e., waste pulping Hquors, to value-added products, i.e., acetylene, ethylene, other hydrocarbons, CO and H2. CO and H2 and acetylene are valuable as fuels and as chemical feedstocks. Ethylene can be used as a fuel although it is of far greater value as a feedstock, for example for making polyethylene polymers of various molecular weights and densities. In this invention acetylene is obtained by converting a portion of the biomass carbon to calcium carbide CaC2, or other suitable metal carbide and then producing acetylene by hydrolysis of the metal carbide. Ethylene is obtained by hydrogenation of the acetylene produced in this way. Thus in this regard what is being claimed is a method of converting biomass to ethylene via metal carbides.

Further, when the starting material contains spent or partially spent pulping chemicals, as would typicaUy be the case for residues of HgnoceUulosic pulping, this invention provides a means to convert or recycle those substances to pulping chemicals or to products that can readily be converted to pulping chemicals. Examples of pulping chemicals obtainable from the methods of this invention are: NaOH, Na2S, Mg(HSO₃)2, Ca(HSO3)2, and Na2SO3. Pulping chemical precursors obtainable from this invention are Na, Na2CU3, and Na₂O₂.

At least two major commercial benefits of this invention are (1) conversion of organic substances in pulping residues to value-added products plus recovery of pulping chemicals; and (2) conversion of biomass to high quality fuels, chemical feedstocks, and chemicals. In accord with the present invention, biomass is heated with an inorganic metal oxide such as, for example, calcium oxide, to a temperature of at least 1400 °C and more preferably to 1700 °C or higher for a time period of about 0.1 to about 100 seconds. Desired reaction products are preserved by quenching the high temperature effluent stream of the heating furnace or reaction chamber to 800 °C or lower, preferably 400 °C or lower, at a rate of cooling sufficiently high to inhibit substantial product losses. Undesired product losses can be caused by reactions of desired products with carbon monoxide or other gases present in the furnace effluent. The heating can be provided by any suitable means such as by combustion of a suitable fuel but is preferably provided by a thermal plasma. In the case of direct heat exchange, e.g., by combustion, the oxidant or the fuel can be preheated, and air can be enriched with an oxidant such as O2- However, the amount of added oxidant should be carefully determined by stoichiometry when high yields of metal carbide are desired because carbon in the feedstream can preferentiaUy form carbon monoxide under certain operating conditions, thus, lowering the yield of carbide.

When the methods of the present invention are appHed to pulping residues, the residues preferably are preconcentrated by evaporation of water prior to introduction of the residues to the high temperature heating region of the reaction chamber. Preferably, the preconcentration is carried out by evaporating water using heat recovered from the high temperature furnace. In the methods of this invention, when the reactants are heated as described, organic, inorganic, and metal-organic substances from within the biomass and/or externally added, react to produce, among other products, metals, metal carbides, metal hydroxides, metal oxides, metal peroxides, metal carbonates, metal sulfides, carbon monoxide (CO), molecular hydrogen (H2), hydrogen sulfide (H2S), and/ or sulfur dioxide (SO2). The yields and particular products wiU depend upon the elemental composition of the feed, upon whether or not exogenous metal oxide such as, e.g., CaO, MgO, and the like, is deHvered to the furnace with the biomass feedstream, and upon the manner of operation of the furnace including steps taken to preserve products, for example, the rate of quenching of effluents of the high temperature reaction, and, for example, the position of the tad of the plasma flame when one or more plasma torches are used to heat the feedstock.

Specific examples of process chemistries that can be obtained with this invention are described below. However, in general:

(1) organically-bound elemental oxygen in the biomass feed wiU be converted to CO by carbon in the biomass feed;

(2) substantial portions of the biomass feed carbon remaining after (1) can be converted to calcium carbide if stoichiometricaUy sufficient quantities of metal oxide, e.g., CaO, are fed to the furnace with the biomass; and

(3) sulfur in the feed can be converted to sodium sulfide (Na2S) if there is stoichiometricaUy sufficient sodium, i.e., in the biomass feed or added to the feed as a separate reactant. Na2S is a valuable pulping chemical. In pulping residues, the organic constituents in the feed can include lignin and Hgnin-derived compounds, whereas the inorganic constituents include spent or partiaUy spent pulping chemicals, typically consisting of salts and bases of the alkaH and alkaline earth metals. The composition of the metal-organics depends on the pulping technology and can include metaUic salts of Hgnosulfonic acids. Further information about the substances found in liquors from the chemical pulping of wood is iUustrated in Table 1.

TABLE 1. Organic And Inorganic Substances In Fresh And used Liquors From Chemical Pulping of Wood

Preferably, an exogenous metal oxide, e.g., CaO, is added to the pulping Hquor to convert organic carbon in the residues to metal carbides such as CaC2_? which can be hydroHzed to produce acetylene. To effect desired reactions in the proper sequence, the biomass and the metal oxide, preferably CaO, (and any other added substances) and their reaction products can be contacted with one or more plasma torches in stages. In one embodiment of the process, metal carbide products, which are soHds at lower temperatures, are separated from the gaseous CO and H2. Then, in one or more separate reaction vessels, the carbides are selectively reacted with water or steam to generate acetylene gas, a valuable fuel and chemical feedstock. Other valuable hydrocarbons besides, or instead of acetylene, can be generated, depending on the metal element in the carbide, e.g., methane from the hydrolyzation of beryUium carbide and methyl acetylene or propadiene from the hydrolyzation of magnesium carbide. Further, ethylene can be produced from the acetylene by further reaction with hydrogen (H2) in a separate reactor.

If substantial amounts of sodium carbide, or sodium bicarbide, or both are formed, these products can be converted to valuable pulping chemicals such as sodium sulfide and sodium sulfite, by treating these carbides with H2S or sulfurous acid, respectively. If sufficient CaO, is included with the feed the formation of substantial amounts of sodium carbide, or sodium bicarbide seems unlikely because the formation of calcium carbide is thermodynamicaUy favored.

Thus, the methods of the present invention can provide: (1) more valuable products from Hgnin and lignin derived substances and other organic residues of pulping; (2) the abiHty to upgrade organic residues and regenerate pulping chemicals in one integrated process; (3) major downsizing and possibly total elimination of the high capital cost and not totaUy accident free, waste Hquor recovery boUers currently used to burn organic residues and initiate pulping chemicals recovery; (4) the abUity to generate and recycle sodium sulfite (Na2SO3), which is now of interest for innovative chemical pulping technologies; (5) the abiHty to recycle Ca(HSO3)2, which historicaUy has been unrecoverable from sulfite pulping technologies; (6) the deodorization of mercaptans and other suHur compounds; and (7) a process for converting aU forms of biomass, including but not limited to, wood, wood wastes, energy crops, municipal soHd waste, etc. to metal carbides, acetylene, ethylene, other hydrocarbon fuels and chemical feedstocks, and H2, and CO.

IUustrative process chemistries are presented below as examples for the foUowing four exemplary cases: (1) Conversion of biomass more generaUy e.g., wood, municipal wastes, trees or parts thereof, energy crops, straw, grass, animal, agricultural, and human wastes, sewage sludge, plants Hving or dead, etc. to value-added products; (2) Conversion of waste pulping Hquors to valuable products with regeneration of pulping chemicals; (3) Production of ethylene from biomass via metal carbides; and (4) a variation on Case (2) where sodium carbides, or sodium bicarbides, or both, are formed in the process in substantial quantities. That can occur if insufficient calcium oxide (CaO) is fed to the furnace. To Ulustrate Case (4), lignin (empirical formula C5H5O2) is used to represent organic substances in, or derived from, pulping Hquors as weU as biomass more generaUy. Calcium oxide, CaO is used to Ulustrate the effects of adding a metal oxide to the residue-treatment reactor. Any of a number of other metal oxides, or mixtures of metal oxides, or precursors thereof, which react with organic components of biomass to produce metal carbides that yield valuable hydrocarbon products upon hydrolysis, can be utiHzed. Many examples of such metal carbides are presented in the book: Carbides Properties, Production, and Applications, by T. Ya. Kosolapova, translated from the Russian by N.B. Vaughan, Plenum Press, New York, (1971).

An exemplary process chemistry for the conversion of biomass to valuable fuels, chemical feedstocks, and chemicals is Ulustrated below using the empirical formulas for ceUulose and Hgnin, two of the major constituents of biomass, and calcium oxide (CaO). However, it is recognized that the processes of the present invention can apply to aU forms of biomass and, further, that a variety of metal oxides can be used to form metal carbides that, upon hydrolysis, give useful hydrocarbon fuels or feedstocks:

CaO + 3C₆H₁₀O₅ (otiose) > CaC₂ + 15H₂ + 16CO (1)

CaO + C₅H₆O₂ (Kgnin) > CaC₂ + 3H₂ + 3CO (2)

Reaction (3) Ulustrates reaction of the CaC2 with water or steam to form acetylene plus calcium hydroxide:

CaC₂ + 2H₂O > Ca(OH)₂ + C₂H₂ (3) It is recognized that other metal carbides also wiU react with water or steam to form acetylene or other hydrocarbons, plus the metal hydroxide. Such other metal carbides also are useful in the practice of the present invention.

By heating the metal hydroxide, the metal oxide can be regenerated for recycling to the high temperature furnace where it wiU react with more biomass. This is Ulustrated by regeneration of calcium oxide (Hme, or quicklime) from calcium hydroxide (slaked Hme), but it is recognized that other metal oxides can be regenerated by heating their hydroxide.

Ca(OH)₂ > CaO + H₂O (4)

An exemplary process chemistry for the conversion of waste pulping Hquors to valuable products with recovery of pulping chemicals is illustrated below. Waste pulping Hquors typically contain carbon, hydrogen, sulfur, oxygen, sodium, and traces of calcium, and are composed of organic and inorganic soHds suspended in water (see Table 7, below). Here, the process chemistry is Ulustrated for the case of reactions of dried black Hquor char (DBLC). This DBLC material is the soHd product obtained by drying black Hquor and then pyrolyzing the resulting material. The process chemistry can be represented by the foUowing sequence of steps labeUed Reactons (5) to (9):

^Na1.18^c2.81^H0.86^s0.09°1.88 PB Q ---->

1.18 Na + 0.0.43 H₂ + 0.09 S + 1.88 CO + 0.93 C_ccc (5) where the formula on the left hand side is an approximate empirical formula for a sample of DBLC obtained from a paper manufacturing company, and the symbol C_ccc refers to feedstock carbon that is not consumed in converting feedstock oxygen to CO. For the DBLC case of Reaction (5) 0.93 mole of this material, which may be caUed "carbideable char carbon" (CCC), is produced. Up to 2/3 of this CCC can be reacted with CaO to produce calcium carbide. This is Ulustrated by Reaction (6):

0.93 C_ccc + 0.31 CaO = 0.31 CaC₂ + 0.31 CO (6)

In general, the elemental sulfur and sodium products [Reaction (5)] wiU further react to form products that can be directly used as pulping chemicals, i.e, Na2S, or which can be easily converted to pulping chemicals, e.g., Na2©2 (by reaction with water to form NaOH) and Na2CO3 (by reaction with CaO to form

NaOH, using technology routinely practiced in the pulping industry, i.e., recausticizer technology). IUustrative reactions for formation of these products are:

S + 2Na > Na₂S (7)

2Na + 2CO > Na₂O₂ + 2C (7A)

2Na + 3CO > Na2CO₃ + 2C (8) Experiments have found that Na2CO3 and elemental Na, respectively accounted for 18% and 24% of the sodium in the DBLC. It is recognized that elemental Na is a facUe pulping chemical precursor because it can be readUy converted to NaOH by reacting it with water yielding H2 as a valuable co-product:

2Na + 2H₂O > 2NaOH + H₂ (9)

Reaction (9) can also occur in the main treatment furnace between sodium Hberated by the process and water derived from moisture in the pulping residues.

An exemplary process chemistry for the production of ethylene from biomass via metal carbides is Ulustrated below. In one preferred embodiment of the present invention, ethylene is produced from biomass by means of the foUowing sequence of process steps: (i) conversion of the biomass to calcium carbide (see, for example, Reactions (1), (2), (5) and (6) or other metal carbide by reacting the biomass with calcium oxide or other suitable metal oxide; (H) conversion of the calcium carbide (or other metal carbide) to acetylene by reaction of the carbide with water (see, for example, Reaction (3)); and then (Hi) production of ethylene by hydrogenation of the acetylene.

C2H2 (acetylene) ⁺ H-2 ^> O2H4 (ethylene) (9A) where the hydrogen (H2) also can be obtained by conversion of the biomass according to the methods of the present invention (see, for example, see Reactions (1), (2), (5)), or by gasification, or by other means of conversion of biomass or fossil fuels such as natural gas, or by any means convenient. Reaction (9 A) can be operated at elevated pressures (i.e., > 1 atm up to as much as 100 atm or more) of H2, C2H2, or both, and a suitable hydrogenation catalyst can be used.

An alternative exemplary process chemistry for the conversion of waste pulping Hquors to valuable products with recovery of pulping chemicals is iUustrated below. This method provides indirect production of pulping chemicals via carbide intermediates. This embodiment of the invention particularly relates to cases where sodium is present in the biomass feed and calcium oxide is not present in any substantial amounts, focusing in particular on pulping residues. The sodium is converted in the thermal treatment

(plasma) furnace primarily to sodium carbide or sodium bicarbide (or both products).

An exemplary process for providing recycle sodium hydroxide from waste pulping Hquor and, at the same time, generating high value products, i.e., molecular hydrogen, carbon monoxide, and acetylene or other hydrocarbon fuels and/ or chemical feedstocks is iUustrated below. It is Ulustrated here by a reaction with lignin in the pulping residue, but it is recognized that other organic materials in the residue or exogenously added also can be used. 6NaOH ^ waste) + 4C₅H₆O₂ > 3Na₂C₂ + 14CO + 15H₂ (10)

Na₂C₂ + 2H₂O > 2NaOH (separated from waste) + C₂H₂ (1 1)

NaOH _{(iπ was}te) + C₅H₆O₂ > NaHC₂ + 3CO + 3H₂ (12) NaHC₂ + H₂O > NaOH _(separated from waste) + C₂H₂ (13)

where Reactions (10) and (12) occur within the high temperature residue -treatment reactor, and reactions (11) and (13) are performed outside that reactor at lower temperature after separation of the Na2C2 and NaHC2 as soHds.

An exemplary process for providing recycle sodium sulfide from waste pulping Hquor and, at the same time, generating high value products, i.e., molecular hydrogen, carbon monoxide, and acetylene or other hydrocarbon fuels and/ or chemical feedstocks is iUustrated below. As above, it is Ulustrated here by a reaction with lignin in the pulping residue, but it is recognized that other organic materials in the residue or exogenously added also can be used.

3Na₂S ,in waste) + 2C₅H₅O₂ > 3Na₂C₂ + 3H₂S + 4CO + 3H₂ (14) Na2C2 + H2S > Na2S (_separated from waste) + C2H2 (15)

3Na₂S (_{m W}a_Ste) + 4C₅H₆O₂ > 6NaHC₂ + 3H₂S + 8CO + 6H₂ (16)

2NaHC₂ + H₂S > Na₂S _(separated from waste) + 2C₂H₂ ( 17) An exemplary process for providing recycle sulfites from waste pulping Hquor and, at the same time, generating high value products, i.e., molecular hydrogen, carbon monoxide, and acetylene or other hydrocarbon fuels and/or chemical feedstocks is iUustrated below. As above, it is iUustrated here by a reaction with lignin in the pulping residue, but it is recognized that other organic materials in the residue or exogenously added also can be used.

Na₂SO_{3 (in} waste) + C₅H₆O₂ > Na₂C₂ + SO₂ + 3CO + 3H₂ (18)

SO₂ + H₂O > H₂SO₃ (19) Na₂C₂ + H₂SO₃ > Na₂SO₃ (separated from waste) + C₂H₂ (20)

3Na₂SO_{3 (in} was e) + 5C5H₆O₂ > 6NaHC₂ + 3SO₂ + 13CO + 12H₂ (21)

SO₂ + H₂O > H₂SO₃ (19)

2NaHC₂ + H₂SO₃ > Na₂SO₃ (separated from waste) + 2C H₂ (22)

CaSOs (inwaste) + C5H6O2 > CaC2 + SO2 + 3CO + 3H₂ (23) SO + H₂O > H₂SO₃ (19)

CaC2 + H2SO3 > CaSO3 (separated from waste) + C2H2 (24)

An exemplary process for providing recycle bisulfites from waste pulping Hquor and, at the same time, generating high value products, i.e., molecular hydrogen, carbon monoxide, and acetylene or other hydrocarbon fuels and/ or chemical feedstocks is Ulustrated below. As above, it is iUustrated here by a reaction with lignin in the pulping residue, but it is recognized that other organic materials in the residue or exogenously added also can be used. 6NaHSO₃ (_m waste) + 4C₅H₆O₂ > 3Na₂C₂ + 6SO₂ + 14CO + 15H₂ (25)

SO₂ + H₂O > H₂SO₃ (19)

Na₂C₂ + 2H₂SO₃ > 2NaHSO_{3 {aepmtβd fro}m waste) + C₂H₂ (26)

NaHSO₃ (in waste) + C5H₆O₂ > NaHC₂ + SO₂ + 3CO + 3H₂ (27)

SO₂ + H₂O > H₂SO₃ (19)

NaHC₂ + H₂SO3 > NaHSO₃ (_Separated from waste) + C₂H₂ (28)

3Ca(HSO₃)₂ (in waste) + 4C₅H₆O₂ > 3CaC₂ + 6SO₂ + 14CO + 15H₂ (29)

SO₂ + H₂O > H SO₃ (19)

CaC₂ + 2H₂SO₃ > Ca(HSO₃)₂ (separated from waste) + C₂H₂ (30)

The process chemistry can be manipulated to favor bisulfite or sulfite production by manipulation of the molar ratio of suHurous acid to metal carbide, i.e., this ratio is adjusted to 2 to favor Reactions (26) and (30), the ratio is adjusted to 1 to favor Reactions (20), (24), and (28), and the ratio is adjusted to 0.5 to favor Reaction (22).

An exemplary process for the regenerating Na2S from makeup Na2SO4 (saltcake) with the production of acetylene by-product is Ulustrated below.

Na₂SO₄ (_added to waste) + 2C₅H₆O₂ > Na₂C₂ + H₂S + 8CO + 5H₂ (31) a2C2 + H2S > Na2S (_{separated fro}m waste) + 0^2 (15)

3Na2SO4 (added to waste) + 8C5H6O2 > 6NaHC₂ + 3H₂S + 28CO + I8H2 (32)

2NaHC₂ + H₂S > Na₂S (sep_ar_ated fr_om waste) + 2C₂H₂ (17) A process for management of organo-sulfur compounds is iUustrated below. Here, the process is iUustrated using mercaptans and CaO. However, it is recognized that analogous reactions occur with organic sulfϊdes and disulfides, and for other metal oxides.

R-CH₂-CH₂-SH > R-CH=CH₂ + H S (33)

H₂S + CaO > CaS + H₂O (34)

An exemplary process for generating sodium sulfite by recycling sodium sulfide is illustrated below.

3Na2S (_m waste) + 2C5H6O2 > 3Na2C₂ + 3H2S + 4CO + 3H (14)

2H₂S + 3O₂ > 2H₂SO₃ (35) Na₂C2 + H₂SO3 > Na₂SO_{3 (separate}d from w_aste) + C₂H₂ (20)

3Na₂S (_mwaste) + 4C₅H₆O2 > 6NaHC₂ + 3H₂S + 8CO + 6H₂ (16)

2H₂S + 3O₂ > 2H₂SO₃ (35)

2NaHC₂ + H₂SO₃ > Na₂SO₃ (separated from waste) + 2C₂H₂ (22)

By the methods of this invention, biomass in general including pulping residues is converted to valuable products, i.e., acetylene or ethylene (or other valuable hydrocarbon fuels and chemical feedstocks), CO, and H₂. Further, for the case of pulping residues, pulping chemicals are regenerated. For biomass containing inorganic matter, metals and useful metaUic salts can be generated. Commercialization of this approach can result in multiple technical, economic, and environmental benefits: (1) more valuable products from Hgnin and other organic residues of pulping; (2) abiHty to upgrade organic residues and regenerate pulping chemicals in an integrated, synergistic process; (3) major downsizing and possibly total elimination of the high capital cost, and not totaUy accident free waste Hquor recovery boUers currently used to burn organic residues and initiate pulping chemicals recovery; (4) abiHty to generate and recycle sodium sulfite (Na2 (803)2), which is now of interest for innovative chemical pulping technologies; (5) abUity to recycle Ca(HSO3)2, which historicaUy has been unrecoverable from sulfite pulping technologies; (6) deodorization of mercaptans and other sulfur compounds; (7) a process for converting aU forms of biomass, including but not limited to, wood, wood wastes, energy crops, municipal soHd waste, etc. to metal carbides, acetylene, ethylene, other hydrocarbon fuels and chemical feedstocks, and H2, and CO.

In the process of the present invention the biomass is prepared as a powder or granular material preferably having an average particle size of about 2-3 mm. or less, more preferably about 1 mm. or less. TypicaUy, less then 15 wt % of the particles are greater than about 1 cm in average size; preferably less than 5 wt % are greater than about 1 cm in average size. In some embodiments, depending upon the particular equipment used, it may be preferred to use even smaUer particle size distribution, e.g., 85 wt % or more of the particles having an average size of about 0.2 mm. or less. As used herein, the term "average size" means the particle size diameter or equivalent diameter of the; article.

Materials added to the biomass feed preferably wUl have a similar particle size. The biomass material typicaUy is mixed with a metal oxide such as CaO, MgO, or the like, entrained in a carrier gas, typicaUy argon or hydrogen, and fed into the reaction chamber. In the chamber, the mixture is rapidly heated to a temperature sufficiently high that the process chemical reactions occur, forming the metal carbide and one or more valuable gaseous co-products, such as carbon monoxide (CO) and molecular hydrogen (H₂). A temperature of at least about 1400°C is required. Reaction products are quenched and then transferred to a products separation chamber, which separates elemental soHds from the product stream.

The feed materials preferably are fed into a premixing chamber first, which can be a dense phase fluidized bed, a transfer line, an entrainment tube, or other suitable gas-soHds mixing apparatus, which are weU known to those skUled in the art. Preferably, the premixing chamber is heated, particularly when the biomass is a Hquid waste and preconcentration and/ or drying is desired. The metal oxide typicaUy is added after drying the biomass material to avoid formation of a hydroxide, which is not desirable in the feed stream. The premixer is typically operated at a temperature low enough to prevent appreciable unwanted chemical reactions of the feed materials, generaUy less than 650°C, preferably at a temperature of 250°C or less, and more preferably 125°C or less. The feed mixture then is conveyed from the premixer to a main reactor chamber. The temperature in the reaction chamber should be at least 1400°C, preferably at least 1800°C, and can be much higher (2000°C or more), particularly if certain means of feed heating, such as a thermal plasma, are employed.

The pressures in the premixer, the main reactor chamber, the effluent and transfer Hnes, and the separation chamber, are typically maintained above the prevailing atmospheric pressure to prevent leakage of atmospheric air into the process equipment. The pressures can be different in these regions and generaUy wUl be at least a few inches of water above the atmospheric pressure. For certain embodiments, the pressure can be as high as several tens of atmospheres for the most efficient operation of the equipment.

The cooling of the reaction products and unconverted feed can be accompHshed by any of a number of means weU known to those skUled in the art. Such means of cooling include, for example: (i) extraction of heat from the immediate environs of the products, i.e., by transfer of heat through the waUs of the reaction chamber 4; or (ii) introduction of appropriate "quenching agents" (to which reference may be made herein as "Q") or "quenching/ recovery agents" (to which reference may be made herein as "Q-R"), or both Q and Q-R. In the case of using quenching agents, heat is extracted from the reaction products by transfer of the heat to the quenching agent by physical means, or by virtue of a phase change or by endothermic chemical reaction involving one or more ingredients in the quenching agent, or by any combination of these means. The quenching/recovery agents also can extract heat from the reaction products by any of the means noted. However, the quenching/recovery agents also can serve to help redeploy the reaction products to a form more suited to separation, storage, or recovery, e.g., by operations carried out in a separation chamber, or to a form more suited for purification or a specific utilization.

The quenching agents or quenching/recovery agents can be introduced to the stream of reaction products at a location within the main reactor chamber, i.e., by means of an injector plenum, which is already positioned in or, as desired, which can be brought into communication with the products. The location(s) for injection of the Q or Q-R agents are selected to help achieve high levels of the desired product and, further, to avoid or reduce to acceptable levels, the generation of undesired by-products.

Examples of quenching - Q - agents suitable for the practice of the present invention include non-reactive soHd particles (e.g., refractory ceramic particles), Hquid droplets, vapors and gases, or mixtures thereof. Properties of the soHd particles that can be selected to enhance separation of the product are particle size distribution, shape (e.g., spherical or rod-like, etc.), internal surface area, total surface area, pore size distribution, surface texture, morphology, and the like, etc. Liquid droplets can also be varied in size distribution to enhance product coUection. Further, such agents can be capable of undergoing endothermic changes of state by physical or chemical means (e.g., melting, evaporating, subHming, change of crystal form, etc.) at temperatures suitable for quenching elemental sodium, calcium carbide, or other desired products of the process. When water is used as the quenching agent, the metal carbide is hydrolyzed to produce a hydrocarbon gas product.

Examples of quenching/ recovery - Q-R - agents suitable for the practice of the present invention also include solid particles, Hquid droplets, gases, vapors, and mixtures thereof, from which the desired products can be readdy separated. Q-R agents are typically selected because they exhibit one or more of the chemical or physical attributes Hsted above with respect to Q agents. However, it wUl be recognized by those skiUed in the art that specific properties can receive greater or lesser emphasis for Q-R agents than they do for Q agents. However, although Q and Q-R agents can be similar materials, Q-R agents are selected to enhance recovery and can bind or carry the desired products such that they can be readUy extracted. As such, Q-R agents can increase product recovery, product purity, etc.

Separation methodologies can include any techniques common in the separation of gases and vapors from solids, e.g., cyclones, centripeters, staged cascade i pactors, etc. However, as noted above, recovery agents can be utilized to capture and retain elemental sodium, calcium carbide, or other desired products. These agents can be gases, vapors, Hquids, or solids of particular chemical composition and, in the case of Hquids, having a selected droplet size distribution, and in the case of soHds, having a selected particle size distribution, total surface area, internal surface area, shape, pore size distribution, surface texture and morphology, as desired for particular equipment and operating conditions.

Preferably, the feed stream is rapidly heated to a desired temperature. Rapid heating of the feed stream can be accompHshed by a variety of methods weU known to those skiUed in the art. In a preferred embodiment of the invention, an electrical arc discharge is struck between a cathode (negative) and an anode (positive) to heat the feed stream to the desired reaction temperature.

Equipment for operating the process can be structured and arranged as a series of interconnected fluidized bed or entrained bed vessels that separately, or H suitable combinations, fulfiU the functions described above for the premixing chamber, the main reactor chamber, and the products separation chamber.

The process of the present invention was run on experimental apparatus substantially as Ulustrated in FIGs. 1 to 3. The experimental apparatus 50 consists of a plasma reactor 61 containing a plasma generator system, a powder feeder 52, a post reactor cooling chamber 53 for thermaUy quenching the reactor effluent, and a sample coUection system 54, 93, etc. The plasma generator system consists of an arc discharge d.c. plasma torch providing the plasma reactor, a high frequency osciUator 76 (for initiating the arc), a control console and an AIRCO d.c. power supply unit 77 rated by the manufacturer at up to 83 kUowatts ("kW") and capable of providing open circuit output voltages of 80, 160 and 320 volts ("V"). The plasma reactor 61 as originaUy constructed is Ulustrated in further detaU in FIG. 2. It was made of a 0.75 inch O.D. graphite cathode and a 1 inch I.D. graphite anode. The anode 62 was held by pipe threads in a water cooled brass anode holder 64, which is mounted on the top flange 58 of the cooling chamber 53. A cooling channel 74 is provided in the anode holder 64. The upper portion of the graphite anode was electrically insulated by a ring 63 made from boron nitride. The cathode assembly 65 included a nylon part 66 that provides a support for the water cooled copper section 67 forming the upper part of the cathode (cooling water was supplied through concentric tubes 72). The nylon part 66 also electricaUy insulated the cathode from the anode and was secured to the anode holder and to the top flange 58 of the cooling chamber 53 by three screws (one shown at 58-1). A low density alumina ring 68 was used to thermaUy insulate the nylon support 66 from the anode 62. A high density alumina tube 69 thermaUy insulated the nylon support from arc radiation. The cathode tip 70 was made of a 1.5 inch long piece of 0.75 inch graphite rod, which was drUled and tapped to be attached to the copper section of the cathode. An annular opening 71 was formed between the anode and cathode, through which gas and other feed materials were fed into the reactor.

In accord with practices weU known to those skilled in the art, a solenoid

75 was used to apply a magnetic field perpendicular to the arc current, which induces in the charged particles a velocity component perpendicular to their original direction of travel. Consequently, the path of charged particles moving in a plane perpendicular to the magnetic field wUl curve. However, the mean free path of the particles remains practically unaltered. Under these conditions, the electrical conductivity of the plasma is more anisotropic resulting in a better confined plasma.

Powder was fed with argon as the carrier gas to the reactor gas inlet 78 using a MiUer Thermal, Inc. Model 1270 mechanical wheel- type powder feeder 52. The plasma reactor was mounted on the top of a steel, post reactor cooHng chamber 53, which has a water cooled waU for cooling of the reactor effluent and rapid quenching to recover soHd and gaseous reaction products. The gaseous products were aspirated from the cooling chamber 53 with two vacuum pumps 80,81 (i) through a sintered disc 93 at the bottom of the chamber and a filter train 85 downstream of the chamber into a ventilation stack 86 and (H) through the probe 90, as described further below.

Part of the product quenching and coUection system consisted of a movable, water cooled and gas quenched coUection probe 90 that is mounted at the bottom of the cooling chamber 53. The probe was designed so that the distance of separation between the tip of the plasma "flame" and the entrance 91 to the probe can be adjusted. SoHd reaction products were coUected for further examination on a sintered stainless steel filter cup 54 located downstream of the probe. In addition, solid reaction products were coUected on the sintered disc 93 at the bottom and on the waUs of the cooling chamber 53. Gas samples were coUected in a sampling bulb 91 using a sampling pump 92. Other lines Ulustrated in FIG. 1 are the main gas line 100 to the plasma reactor, the start gas Hne 101 to the plasma reactor, the powder carrier gas lines 102, 103, the probe radial gas Hne 104, and the probe quench gas line 105. A pressure controUer is shown at 110. DUution nitrogen gas can be added at 115.

A typical operating procedure was as foUows. An argon plasma was first estabHshed to operate the plasma reactor. Feeding of the biomass and metal oxide powder was started. The powder (at the desired feed rate) was entrained H argon or other suitable carrier gas (at ambient temperature) and introduced into the plasma.

FIG. 3 Ulustrates the plasma reactor 61 on top of cooling chamber 53. CoUection probe 90 is mounted at the bottom of the cooling chamber. The distance between the tip of the plasma flame (not Ulustrated) and the probe 90 can be adjusted by locating the tip 91 of the probe at the desired position in the cooling chamber.

The invention wiU be demonstrated further by the examples that foUow. The examples are presented merely as Ulustrations and do not limit the scope of the present invention. Unless otherwise specified Hi the examples, the percents are weight percents. EXAMPLES IP- 1 - IP-5

In Examples IP-1 - IP-5, powdered Hgnin with powdered CaO were premised in a known and pre-selected molar ratio. This feed material was deHvered at a controUed mass rate from a wheel feeder to a carrier gas (typically argon) in which it becomes entrained. The resulting Hgnin/ CaO /Ar mixture was conveyed into a non transferred arc (thermal plasma flame) estabHshed between a graphite cathode and a graphite anode at approximately 1 atm total pressure (FIG. 2). Argon, plus products and unconverted reactants, if any, exit the plasma region and enter a cooHng chamber where they are coUected on filters or sampled into a movable probe for further filtering of soHds and quantification of gas flows, gas composition and products yields (FIGs. 1 and 3).

Carbides were assayed by hydrolysis of solids recovered from the reactor, using water or dUute aqueous acids as appropriate, foUowed by gas chromatographic quantitation of the evolved gases. Assuming that CaC₂ undergoes hydrolysis according to Equation (3) above, and that the only source of acetylene is CaC₂, then the acetylene yield upon water treatment of product soHds furnishes the CaC₂ yield. In some cases where acetylene was already found in the headspace of the flask containing the soHds before hydrolysis, to obtain the carbide yield, the amount of acetylene measured after hydrolysis was corrected by subtracting the amount of acetylene present before hydrolysis. Reagents

Lignin

Aldrich # 37,095-9, alkaH (Kraft)

Appearance: brown powder

50.87 %, H: 5.30 %, N: 0.07 %

Loss on ignition (750°C): 88 wt%

Moisture (105°C): 11 wt% (< 106 μ size fraction of as received material)

For aU experiments the Hgnin was dry sieved to < 106 μm using an ASTM screen (150 mesh). The coarse fraction was made up of particles with different morphologies. The major fraction of the coarse resembled the fine fraction. Some smaUer black, shiny particles and some big, char-like particles were also found in the coarse fraction. The ash from the loss on ignition determination is very different for the fines and the coarse. Although the coarse yield a black residue, the fines form an ash composed of a whitish area, clearly separated from a blue residue. The composition of this ash has not been determined. It apparently is formed by some oxides of elements commonly found in wood: Ca, K, Na, Mg, Si, P. The blue fraction resembles CuSO₄ ^• 5 H₂O, but it is unHkely that the water of crystaUization would be retained by heating to 750°C because CuSO₄ ^• 5 H₂O gives off its fifth mole of water at 250°C. Other compounds that are blue and might be formed are: Co₂(SO₄)₃ and CoCl₂.

Using the elemental analysis and moisture and ignition loss measurements, the foUowing chemical composition was derived for the Hgnin: Moisture: 11 %, ash: 12 %, organic matter: 77 % (100 %-ash-moisture) C: 50.87 %, H: 5.3 %, N: 0.07 %, O: 20.76 % (by difference based on organic matter) Empirical formulas: C₅H₆Oι.53 or C6.53Hs.10O2 or Cι₀Hι₂O₃.₀6

2. Calcium oxide (quicklime)

• Runs IP-1 to IP-3: EM Science # CX0265-3, no analysis available

• Runs IP-4 and IP-5: Aldrich # 20,815-9

• Appearance: white powder • Purity: 99.9 %

• Titration: 96.0 % (with NaOH)

• Trace analysis: Sr 230 ppm, Si 25 ppm, Mg 10 ppm, Ba 8 ppm, Al 4 ppm, Cu 3 ppm, Mn/Ni 1 ppm

• Loss on ignition (750°C): 2.5 wt% (< 106 μm size fraction prepared by dry sieving as received material)

Run conditions

C-to-Ca feed ratios were chosen assuming the foUowing stoichiometry:

CaO + C₅H₆O₂ → CaC₂ + 3 H₂ + 3 CO (36)

Lignin composition is expressed by the formula C5H6O2. A stoichiometric mixture of Hgnin and CaO would contain 1 calcium atom per 5 atoms of carbon, i.e., C:Ca = 5: 1. For the Examples IP-1 to IP-3, an excess of Hme of 10 % was calculated without accounting for moisture in the Hgnin, i.e., 1.1 calcium atoms per 5 atoms of carbon (C:Ca = 4.55: 1). The actual C-to-Ca ratio turned out to be 4.0:1 because of the high moisture content of the Hgnin.

In Examples IP-4 and IP-5, a threefold excess of lime over the carbon in the Hgnm was calculated without accounting for moisture in the Hgnin, i.e., 3 Ca per 5 C, C:Ca = 1.67:1. Due to the moisture content the true C-to-Ca ratio was 1.5: 1.

For the runs IP-1 to IP-3, the fraction that passed an ASTM 150 mesh (106 μm) screen was used. Because sieving of the Hgnm and the CaO were performed manuaUy, fractions significantly smaUer than 106 μm were very time consuming to obtain. For the runs IP-4 and IP-5, CaO from a different suppHer provided a sufficient amount of a fraction < 63 μm.

In Example IP- 1, hydrogen was used as the main gas. Excessive wear on the electrodes under the operating conditions required switching to argon as main gas for runs IP-2 to IP-5. SoHd feed rates were lowered graduaUy from run to run to respond to a soHds buUdup in the interelectrode gap.

Table 2: Run Conditions

(1) H₂ as main gas

(2) Ar as main gas

(3) Aimed at higher arc power (« 30 kW)

(4) Higher Ca-to-C ratio; lower soHds feed rate; higher gas feed rate

(5) Modified electrode configuration; attempt to dry soHds

* Premised CaO-Hgnin mixture was dried at 105°C and stored over P₂O₅. Ca(OH)₂, presumably formed from the moisture in the Hgnm and the CaO, does not react back to CaO + H₂O under these conditions . Overview

Arc power (O) and arc current (D) for run # IP-3 are Ulustrated in Fig. 4. Arc power (O) and arc current (□) for run # IP-4 are Ulustrated in Fig. 5. The continuous Hnes in the figures represent adjacent averaging of 5 data points.

Using hydrogen as the main arc gas (Run IP-1) lead to a severe degradation of the electrodes (Table 3). The weight loss on the cathode tip was 11 %, whUe the anode insert lost 14 % of its weight. Weight loss of the electrodes produces unsteady run conditions due to a change of surface area giving rise to a changing current density and flow geometry, and provides an additional source of carbon which must either be marginalized or accounted for quantitatively in order to distinguish between Hgnin and electrode contributions to carbon in the products.

With argon as main gas, wear on the electrodes was greatly reduced

(Table 3). Nevertheless the remaining weight loss of up to 0.75 g is still a significant carbon source, of the same order of magnitude as the total carbon fed as Hgnin in some runs, e.g. IP-3 and IP-4.

Table 3: Electrode weight losses (n.d. = not determined)

*Basis: corrected to 60 s run time.

**The anode insert was fused to the anode holder and could not be recovered for weighing.

The Kraft Hgnin used in the experiments (Aldrich # 37,095-9) was found to contain 11 wt% moisture. Upon mixing with the CaO some Ca(OH) may have formed. Thus the soHds feed consisted of Hgnin, CaO, and Ca(OH)2. The water bound in the calcium hydroxide is liberated at temperatures above 580°C. This water is suspected to interfere with other species formed before, in, or after the plasma zone. Table 4 Hsts the soHds feed composition based on the conversion of CaO to Ca(OH)₂ because of the reaction of the Hgnin moisture with the Hme.

Table 4: Actual feed composition and carbon-to-calcium molar ratios.

Preferably, for the apparatus used, the Hgnin should be dried to < 1 wt% moisture before mixing with the CaO to avoid forming Ca(OH)2 and thus introducing water into the arc zone.

EXAMPLES IP-6 - IP- 12 Additional experiments were run using conditions as set forth in

Examples IP-1 to IP-5, except that dry Hgnm or DBLC (i.e., "DBLP char") was used and the operating parameters were set as listed below Hi Tables 5 and 6.

Table 5: Run conditions for runs IP-6 to IP-9.

* not determined, because no caHbration of the wheel feeder with pure CaO was made.

Table 6

Operating Conditions For Plasma Furnace Reactions of Premixed DBLP Pyrolysis Char- Calcium Oxide Powders.

Example /Run No.

For most of the duration of Runs IP-1 1 and IP- 12, the arc power was < 20 kW, and there was no quaHtative or quantitative evidence of carbide formation in either experiment. In notable contrast, the arc power in Run IP10 shot up to

30 kW immediately after beginning solids feeding. Further, despite only 10 seconds of solids feeding time, product solids recovered from the bottom flange of the furnace cooHng chamber exhibited intense reactivity in open air, consistent with that seen in other experiments known to produce copious amounts of metal carbides. Interestingly, however, soHds recovered from the sampler cup in this same run showed no reactivity to water in off-Hne testing.

For the two DBLP-char runs showing no evidence of carbide formation, (IP-11, IP-12) insufficient specific enthalpy is indicated. Run IP- 10, which exhibited strong quaHtative indications of carbide formation despite its very short duration (10 sec), also was characterized by a very large upswing in arc power (up to about 30 kW) immediately after feeding the solids had begun. Thus, this run provided sufficiently high specific enthalpy to effect DBLP-char conversion to carbides.

The reason for the higher arc power in Run IP- 10 is thought to be the presence in the arc gas of light hydrocarbons and other volatiles released by pyrolysis of a small amount of unpyrolyzed Hgnin contaminant left over in the powder feeder from the eariier runs. Most of this impurity was apparently expeUed from the feeder during Run IP- 10. It is known that the use of non-inert gases as an arc gas aUows the arc to assimilate additional power.

This is because chemical bond breaking provides an additional sink for uptake of chemical enthalpy.

The absence of water reactivity in off-line experiments in soHds recovered from the sampling for Run IP- 10, despite the quaHtative indications of carbide formation from the soHds coUected on the bottom flange of the cooHng chamber, requHes explanation. Because the arc only operated for 10 s after the soHds feeding had begun, it appears that the soHds in the sampling cup primarily or exclusively represent "product" soHds sampled after the arc had shut down.

It has been proposed that the high reactivity of the flange soHds immediately after exposure to air may reflect sodium reactions with O₂ or moisture. The presence of Na can be distinguished from the Na₂C₂ and CaC₂ carbide products of interest, by controlled hydrolysis -the metal giving H as a product, both carbides giving C₂H₂. The main point is that strong reactivity was present Hi the flange soHds from Run IP- 10 which exhibited a high arc power, and strong reactivity was absent from the lower power runs IP-11 and IP- 12.

EXAMPLES IP- 13 to IP-20 A soHds feed mixture was prepared by adding some unpyrolyzed but dried Hgnin (1-10 wt%) to the existing CaO + pyrolyzed black Hquor powder mixture. The Hgnin was added to faciHtate increased arc power due to the volatUes it wUl release during heat up. The upper bound on the amount of Hgnin must be such that no plugging wUl occur. The lower bound is imposed by the desire to attain a certain arc power (i.e., 30-40 kW).

The specific objectives of these experiments were to react: 1) dried black Hquor (DBL) with CaO to produce CaC₂ and synthesis gas, and 2) dried black Hquor char (DBLC) and dried black Hquor (DBL) with CaO to produce CaC₂ and synthesis gas on a laboratory scale using a thermal plasma furnace according to the global reaction equation:

CaO + 3 C_DB , DBLC = CaC₂ + CO (37)

Preparation of reactants

Two samples were provided by a paper manufacturing company: dried black Hquor (DBL) and dried black Hquor char (DBLC). The elemental compositions of the DBL and DBLC are shown in Table 7. The DBL and DBLC were reacted with exogenous CaO Hi the laboratory scale thermal plasma reactor FIGs. 1-3.

Table 7: Elemental compositions of the DBLC and DBI

a two determinations reported The empiric formula based on the elemental analysis of the DBL is Na₀.8 C₂.8₉H₃.₂ιSo.i6θ₂.ι and for the DBLC Na₁.ι₈C₂.₈ιHo.86So.ιOι.88- However, the total carbon determined by elemental analysis in the DBL or DBLC is not avaUable for carbide formation but an appreciable amount of the carbon wUl form by-products. Based on thermodynamic considerations, it appears that the oxygen in the DBL or DBLC wUl first consume some of the carbon to form CO, which is the most thermodynamicaUy favorable species Hi the relevant temperature regime (1000-6000 °C). Furthermore, it appears that during CO formation, sodium, sulfur and hydrogen are converted to theH stable element form:

Naι.ι₈C₂.8iHo.86S₀.ιOι.88 = 1.18 Na + 0.86/2 H₂ + 0.1/8 S₈ + 1.88 CO + 0.93 C_ccc

(38) For the DBLC, this results in 0.93 mol "carbideable char carbon" (CCC). CCC is then available to react with CaO to form CaC₂:

0.93 C_ccc + 0.93/3 CaO = 0.93/3 CaC₂ + 0.93/3 CO (39)

According to the stoichiometry of the above Reactions, 1 mole of CCC wiU produce 1/3 mole of CaC₂. In these experiments, instead of using 1/3 of 1 mole of CaO per mole of CCC, a 25 % excess of CaO was used. This results in a mixture of 100 g DBLC and 21.7 g CaO. For other experiments with 50 % DBL and 50 % DBLC, a 25 % excess of CaO over that needed to convert 2/3 of the Cccc to CaC₂ again was used. Experimental conditions

The feed material was deHvered at a controUed mass rate from a wheel feeder to a carrier gas (typically argon) Hi which it becomes entrained. The suspended soHds entrained Hi argon are added to the main gas. As main gas, hydrogen instead of argon was used in order to increase the arc power, substantially. The resulting DBLC/DBL/CaO/Ar/H₂ mixture was conveyed into a non transferred arc (thermal plasma flame) estabHshed between a graphite cathode and a graphite anode at approximately 1 atm total pressure. The effluent gas exited the plasma region and entered a cooHng chamber where it was cleaned from condensed particulates by filters or sampled into a movable probe for further filtering of soHds and quantification of gas flows, gas composition and products yields.

Table 8 summarizes the experimental conditions in runs IP- 13 to IP-20. Using hydrogen as the main arc gas led to a severe degradation of the graphite electrodes, which might result in additional carbide formation. Therefore, a blank run IP 13 was conducted where CaO without any black Hquor material was introduced into the plasma and the background was measured.

In the runs IP- 14 to IP- 17 difficulties emerged in coUecting a representative sample by quenching and sampling with the probe. Therefore, only the material which was recovered from the filters downstream of the reactor was analyzed. Unfortunately, these samples were exposed to air for a few minutes causing to some extent decomposition of possible carbides. By shutting off the quench gas in run IP 18 and IP19, solids were collected by the probe in reasonable quantities for a subsequent analysis.

Table 8: Experimental conditions

^Congestion of reactor orifice by DBL. Run IP-20 aborted

Product analysis

The gaseous products and reactants were sampled during the run Hi a gas bulb and are analyzed quantitatively and identified by GC ("gas chromatograph"). The soHd products and unconverted soHd reactants were coUected Hi a filter cup via a probe. The entrance to the probe was positioned approximately 4 inches below the anode. After each run, approximately 50 mg of the soHd sample were transferred under argon atmosphere into a 50 ml flask and sealed with a septum stopper. Sequentially, 1 ml neon as internal standard and 5 ml of 2-M- HCl solution to initiate hydrolysis were injected into the flask. The head space gas above the soHds after hydrolysis was analyzed by GC. The protocol for quantification of yields of solid products was as foUows: Calcium carbide, which was expected to be the only stable carbide formed, was assayed by hydrolysis with hydrochloric acid resulting in the evolution of acetylene:

CaC₂ + 2 HCl_(aq) > CaCl_2(aq) + C₂H₂,_(g) (40)

Sodium derived from the DBLC was assumed to form metal, which undergoes hydrolysis with release of hydrogen and sodium carbonate, which evolve CO₂ Hi hydrochloric acid:

Na + HCl_(aq) NaCl_(aq) + V₂ H₂,_(g) (41)

Na₂CO₃ + 2 HCl_(aq) > 2 NaCl_(aq) + CO_2>(g) + H₂O (42)

After hydrolysis, the solution was filtered and the filtrate was analyzed by ICP ("inductively coupled plasma emission spectrum") to determine the total amounts of soluble Na and Ca. The amounts of gaseous species detected Hi the gas bulb and H the head space by GC analysis can be directly related to the yields of CaC₂, Na, and Na₂CO₃ produced Hi the plasma process.

The analytical procedure is limited H identification of aU solid product species within the complex Na-Ca-C-O-H system. Therefore, in addition, one sample showing the highest yields was analyzed by x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS). XRD gives information on the molecular identity of crystaUine substances whUe XPS can directly identify the chemical composition at or near the surface of soHds.

Results During runs IP- 13 to IP- 17, no soHds were sampled by the probe due to a relatively small amounts of particles in the gas phase as a consequence of using reduced feed rates to increase the specific enthalpy. Only by shutting down the quench gas was it possible to coUect soHds in the filter cup (e.g., IP- 18 and IP- 19). Nevertheless, soHds of Run IP-13 to IP-17, removed from filters but exposed to air for some minutes, were used to obtain quaHtative results. Based on their analysis the yields presented in Table 9 were calculated.

The blank run IP- 13, where CaO was fed to a hydrogen arc, showed no significant formation of CaC₂, although the abrasion on the graphite electrodes was quite severe. This suggests that the contribution of electrode derived carbon is negHgible Hi comparison to carbon of the DBLC.

In run IP- 14, some of the CaO was converted into calcium carbide (yield = 12 % of the CaO); the total DBLC carbon conversion to CaC₂ was 3.3 %. 30 % of the sodium of the DBLC fed emerged as Na₂CO₃; no sodium metal was detected. In run IP- 15, the gap between the electrodes clogged and no material could be coUected. After drying the CaO/DBLC sample at 105 °C in an oven overnight, no further problems with clogging appeared. One run, IP- 16, was conducted with an argon arc without H₂, but no carbides were found. In run IP-17, the findings of run IP-14 were confirmed with a CaO to CaC₂ yield of 3.4 % of the DBLC total carbon and a somewhat higher sodium carbonate yield of 41.5 % of the Na in the feed.

TABLE 9 Results For The Synthesis Of Carbide By Reaction Of DBLC And CaO In A

Thermal Plasma

CaO -Ca - converted to DBLC -C ^■ converted to DBLC/CaO -O- converted to Na2C03 -Na- converted t

Run N" H2-conc VH2.0 DBLC CaO C/Ca-ratio Power Δπ_{s βc} XcaO Yc o Yc, ^YCaC2 YcaC2 YNa2C03 Yco YcaO Yco Y|Ja2C03 Y_Na

H I%] [l/min [g/min] [g/min] [mol/mol] [kW] [kWh/kg-C] [%] [%] [%] [%] [%] [%] [%] [%] [%] [%] [%] [%]

13 78 15.0 0 4.7 0 27.3 4.3 95.7 3.5 0.8 95.7 - -

14 78 15.0 10.68 2.32 7.25 25.15 116.4 12.0 88.0 0.0 12.0 3.3 6.3 48.1 15.1 59.6 23.3 30.0 0.0

15 78 15.0 8.16 1.77 7.25 24.82 150.4 0.0 100.0 0.0 0.0 80.2 17.1 99.5 0.0 0.0

Ul -4 16 0 22.0 10.68 2.32 7.25 18.9 87.5 1.5 98.5 0.0 1.5 0.4 14.3 18.6 16.9 23.1 53.2 68.4 0.0

17 75 13.0 10.68 2.32 7.25 27.5 127.3 12.2 87.8 0.0 12.2 3.4 8.7 49.8 15.0 61.8 32.3 41.5 0.0

18 75 13.0 10.68 2.32 7.25 24.6 113.9 80.7 19.3 0.0 80.7 22.3 3.8 74.6 3.3 92.4 14.2 18.3 23.6

19 75 12.5 10.68 2.32 7.25 24.6 113.9 40.6 59.4 0.0 40.6 11.2 10.0 63.5 10.2 78.7 37.3 48.0 0.0

20 75 13.0 10.58 2.14 7.87

Run IP- 13: Control run with CaO, no DBLC

Run IP- 15: Clogging of the reactor inlet apparently from excess moisture in the soHd feed

Run IP- 16: Argon as main gas

Run IP-13 to IP-17: Sampling problems

Run IP-18, IP-19: Best runs so far

Run IP-20: 50% DBLC and 50% DBL as carbon source, run aborted because of congestion of reactor inlet, apparently from sticky products of DBL

However, in run IP- 18, by shutting down the quench gas and by coUectHig a representative sample Hi the filter cup, a yield of 80.7 % conversion of CaO to CaC₂ was obtained. By using the filter cup, the sample was maintained under an argon shield gas which guarded against exposure to ambient oxygen or moisture. This yield of 80.7 % CaO to CaC₂ implies that

100 % of the "carbideable char carbon" (i.e., CCC) or 22.3 % of the total carbon of the DBLC was converted into CaC₂ because 25 % excess of CaO was fed with respect to CCC. This yield was not reproduced H run IP- 19, but a carbide yield of 40.6 % was stUl obtained. This corresponds to conversions of about 50 % of the CCC to CaC₂. In run IP- 18, also an elemental sodium yield of 23.6 % of the sodium H the feed was found.

After hydrolysis of the soHd products with HCl, an odor of H₂S was clearly perceptible upon opening the reaction flask, suggesting that some of the DBLC sodium combined with the DBLC sulfur to product Na₂S. SoHd products from run IP- 18 were analyzed by XRD and XPS. XRD gives information on the molecular identity of crystaUine substances wtule XPS can identify particular types of chemical bonds at or near the surface of soHds. The XRD spectrum (FIG. 6) corifirmed the presence of Na₂CO₃ and of elemental Na. Further, it detected CaO and NaOH, as weU as Na₂S and Na₂O₂. The XRD spectrum was not calibrated for quantitative analyses. However, it was apparent that the

Na₂S and Na₂O₂ were present H smaU concentrations. The XRD measurements did not detect CaC₂ or Na₂C₂. This initially surprising result for CaC₂ is further discussed below. The XPS measurements (FIG. 7) detected sodium, carbon, and oxygen bonds, but not Na₂C₂ or CaC₂. Because the presence of CaC₂ has already been estabHshed by wet chemical plus GC analyses, the absence of an XRD signal for CaC₂ suggests this compound may have been present in amorphous rather than crystalline form. This would be consistent with another finding of the XRD measurements on sample IP- 18, namely that 60% of the soHds are non-crystaUH e. The absence of CaC₂ Hi XPS suggests that this compound is absent from the near surface region of the product solids.

High conversions of the carbon Hi dried black Hquor char (DBLC) to calcium carbide (CaC₂) have been demonstrated at bench scale (nominaUy 5 lb/hr soHds feeds) using a plasma furnace. These conversions represent 50 to 100% of the apparent maximum amount of DBLC carbon avaUable for carbide production. The maximum amount of carbon in DBLC carbon that can be converted to CaC₂ is H ited by the oxygen content of the DBLC, because this oxygen preferentiaUy converts DBLC carbon to CO.

Sodium Hi the DBLC produces Na₂CO₃, elemental Na, Na₂S, NaOH, and Na₂O₂. Additional chemical analyses are needed to quantify the yields of the last three compounds. However, in an experiment showing essentiaUy 100% conversion of available DBLC carbon to CaC₂, Na₂CO₃ and elemental Na respectively accounted for 18 and 24% of the DBLC sodium (Run IP- 18, Table 9). If the Na₂S quaHtatively identified by X-ray diffraction accounts for most of the DBLC sulfur, it would consume 17% of the DBLC sodium. Carbon monoxide is a major co-product of this process chemistry, accounting for most (78 to >90%) of the oxygen fed to the system as DBLC and as CaO.

A hydrogen arc is favorable versus an argon arc because it enables a higher absolute arc power, implying higher specific enthalpies, and can provide radicals for a rapid degradation of the soHd feed.

A substantial fraction (almost 1/4) of the DBLC Na is converted to elemental sodium (Run IP- 18, Table 9). This can be readUy converted to NaOH by hydrolysis, showing that this process chemistry does indeed provide for simplified recycle of pulping chemicals.

Likewise, Na₂CO₃ accounted for less than about 1/5 of the sodium in the DBLC, showing that the present process offers the possibUity of substantially reduced loads on a recausticizer (Run IP- 18, Table 9).

The foUowing table Ulustrates potential maximum CaC₂ yields obtainable from various forms of biomass, assuming they obey si Uar process chemistries to those exhibited by the present DBLC: Table 10

Theoretical

5 Maximum % Feed

Feedstock C/O Ratio C Convertible to CaC₂

Dried Black Liquor 1.38 18 0 Dried Black Liquor Char 1.49 22

Softwood Lignin 2.84 43

Hardwood Lignin 2.36 38 5

Douglas Fir 1.72 28

Douglas Fir Bark 2.04 34 0 Maple 1.62 26

CeUulose 1.20 13

Various HemiceUuloses 1.00 0 OC

Methane N.A. 67

Table 10 shows that Hgnin and Hgnm rich wastes provide appreciably0 higher CaC₂ yields than the DBLC. Note however that even for the Hmiting case of zero oxygen H the feed, Ulustrated here by methane, the maximum amount of feedstock carbon convertible to CaC₂ is 2/3, owing to the consumption of 1/3 of the feed carbon by the oxygen in the CaO. Thus, the higher the C/O ratio of the biomass or pulping waste feedstock, the greater the yields of CaC₂. 5 Similarly, Hi processing pulping wastes of especiaUy low C/O ratio (e.g., materials rich in hemiceUulosees), CaC₂ yields can be enhanced by mixing Hi other feeds of higher C/O ratio, e.g., wood wastes, bark, waste oUs, or even natural gas or petroleum substances, when such is avaUable at low cost. The invention has been described Hi detail with reference to preferred embodiments thereof. However, it wUl be appreciated that, upon consideration of the present specification and drawings, those skUled H the art may make modifications and improvements within the spirit and scope of this invention as defined by the claims.

Claims

WHAT IS CLAIMED IS:

1. A continuous process for the conversion of biomass, which contains carbon, to form a chemical feedstock, the process comprising: continuously feeding into a reaction chamber at a temperature of at least 1400 °C a biomass material and an exogenous metal oxide or metal oxide precursor, wherein the metal oxide is capable of forming a hydrolizable metal carbide, to form reaction products including said metal carbide; and quenching the reaction products to a temperature of 800 °C or less.

2. The process of claim 1, wherein the biomass contains significant amounts of sodium and wherein the reaction products further include a product selected from the group consisting of Na, NaOH, Naaθ2 and NaaS.

3. The process of claim 2, wherein at least 10% of the sodium in the biomass is recovered as elemental Na.

4. The process of claim 2, wherem the biomass contains sulfur and wherein at least 10% of the sulfur in the biomass is recovered as NaaS.

5. The process of claim 1, wherein at least 10% of the carbideable carbon in the biomass is converted to metal carbide.

6. The process of claim 1, wherein at least 50% of the carbideable carbon in the biomass is converted to metal carbide.

7. The process of claim 1, wherein the metal oxide is CaO.

8. The process of claim 1, wherein the metal oxide is MgO.

9. The process of claim 1, wherein the biomass is a material selected from the group consisting of wood; municipal waste; trees or parts thereof; forest product residues; energy crops; straw; grass; animal, agricultural and human wastes; sewage sludge; and living or dead plants.

10. The process of claim 9, wherein the metal oxide is CaO.

11. The process of claim 9, wherein the metal oxide is MgO.

12. The process of claim 1, wherein the biomass is a waste pulping liquor and wherein the reaction products further include a product selected from the group consisting of Na, NaOH, Naaθ2 and Na₂S.

13. The process of claim 12, wherein at least 10% of the sodium in the biomass is recovered as elemental Na.

14. The process of claim 12, wherein the biomass contains sulfur and wherein at least 10% of the sulfur in the biomass is recovered as Na2S.

15. The process of claim 12, wherein at least 10% of the carbideable carbon in the biomass is converted to metal carbide.

16. The process of claim 12, wherein at least 50% of the ca ;bideable carbon in the biomass is converted to metal carbide.

17. The process of claim 1, further comprising hydrolyzing the metal carbide to produce a recoverable hydrocarbon gas.

18. The process of claim 17, wherein the metal carbide is calcium carbide and the recoverable hydrocarbon gas is acetylene.

19. The process of claim 18, further comprising producing ethylene from the acetylene.

20. The process of claim 17, wherein the metal carbide is magnesium carbide and the recoverable hydrocarbon gas is methyl acetylene or propadiene.

21. The process of claim 20, further comprising producing propylene from the methyl acetylene or propadiene.

22. The process of claim 1, wherein the reaction products further comprise CO and H2.

23. The process of claim 1, wherein the temperature in the reaction chamber is provided by a plasma arc.

24. The process of claim 1, wherein the biomass material is entrained in a stream of hydrogen.

25. The process of claim 1, further comprising separating the resulting metal carbide from the reaction products.

26. The process of claim 1, wherein the quenching step utilizes water and produces a recoverable hydrocarbon gas.

27. The process of claim 26, wherein the metal carbide is calcium carbide and the recoverable hydrocarbon gas is acetylene.

28. The process of claim 27, further comprising producing ethylene from the acetylene.

29. The process of claim 26, wherein the metal carbide is magnesium carbide and the recoverable hydrocarbon gas is methyl acetylene or propadiene.

30. The process of claim 29, further comprising producing propylene from the methyl acetylene or propadiene.