CA1190459A - Closed loop leaching system - Google Patents
Closed loop leaching systemInfo
- Publication number
- CA1190459A CA1190459A CA000399604A CA399604A CA1190459A CA 1190459 A CA1190459 A CA 1190459A CA 000399604 A CA000399604 A CA 000399604A CA 399604 A CA399604 A CA 399604A CA 1190459 A CA1190459 A CA 1190459A
- Authority
- CA
- Canada
- Prior art keywords
- article
- leaching solution
- reaction container
- container
- assembly
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
- C23F1/00—Etching metallic material by chemical means
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
- C23F1/00—Etching metallic material by chemical means
- C23F1/08—Apparatus, e.g. for photomechanical printing surfaces
Abstract
ABSTRACT OF THE DISCLOSURE
A closed loop assembly for dissolving a layer from an article by exposing the article to a leaching solution having a predetermined boiling temperature. The assembly includes a sealed reaction container including an inner compartment to contain the leaching solution and the article, a recirculation system connected to the reaction container for receiving boiled off leaching solution vapor and condensing the vapor and returning the vapor to the reaction container, and a heater for heating the article within the reaction container above the boiling temperature of the leaching solution.
The assembly performs a method of dissolving the layer from an article by exposing the article to the leaching solution. The steps include placing the article in the inner compartment of the sealed reaction container containing the leaching solution, heating the article to a temperature above the boiling temperature of the leaching solution to increase the corrosion rate of the outer layer of the article, conducting and condensing boiled of leaching solution vapor in the recirculation system, and selectively returning the collected leaching solution to the reaction container.
A closed loop assembly for dissolving a layer from an article by exposing the article to a leaching solution having a predetermined boiling temperature. The assembly includes a sealed reaction container including an inner compartment to contain the leaching solution and the article, a recirculation system connected to the reaction container for receiving boiled off leaching solution vapor and condensing the vapor and returning the vapor to the reaction container, and a heater for heating the article within the reaction container above the boiling temperature of the leaching solution.
The assembly performs a method of dissolving the layer from an article by exposing the article to the leaching solution. The steps include placing the article in the inner compartment of the sealed reaction container containing the leaching solution, heating the article to a temperature above the boiling temperature of the leaching solution to increase the corrosion rate of the outer layer of the article, conducting and condensing boiled of leaching solution vapor in the recirculation system, and selectively returning the collected leaching solution to the reaction container.
Description
BACKGROUND OF THE lN~iNllON
~l) FieI~ of the Invention The subject invention relates to a leaching asse~bly and method for dissolving an owter layer from an article.
~2) Des¢ription of khe Prior Art Several methods have been de~i~ed for aonsolidating powder metalO In one method, a thick-walled container o the powder metal is hot-co~solidated by the application lQ of heat and pressure, either by means of an autoclave or by a mechanical press. Subse~uent to hot consolidation it is necessary to remove the container from the consolidated powder metalO Generally, the removal of the container is accomplished by a combination of a ~-ch;ning and a leaching lS operation~
Prior art leaching operations have proceeded at a vexy slow rate. The instant invention provid2s an improved leaching apparatus and mekhod which is capable of removing the low carbon s~eel con~ainer material a~ a much faster rate than methods previously employed.
SUMMARY OF THE lNY~LION
A closed loop assembly dissolves an outex layer ~rom an article by exposing the article to a leaching solution having a predeterml~ed boiling temperatureO The assembly includes a sealed reaction container having an inner compartment adapted to contain the leaching solution and ~he article. ~ recirculation ~ystem is connec~ed to the reaction con~ainer for receiving boiled of leaching solution vapor and xeaction gaseous products and condensing ~o~
the vapor and returning the vapor -to the reaction container as secondary feature. A heater is included for heating the ar-ticle within -the reaction container above the boiling -temprature oE the leaching solution -to increase the corrosion rate oE the article The invention also includes a method o~
dissolving a layer ~rom an article by exposing the article to a leaching solution having a predetermined boiling temperature by placing the ar-ticle in an inner compartment oE a reaction container containing the leaching solution and heating the article -to a temperature above the boiling tempera-ture of the leaching solu-tion -to increase the corrosion rate o~ -the outer layer of the article.
PRIOR ART STATEMENT
The United States Patent 3,261,733 to Bellinger issued Ju:Ly 13, 1966 teaches a method oE dissolving a metal core in an etching bath wherein the metal core may be a low carbon steel and the etching bath i5 a nitric acid solution. Cooling coils are used Eor controlling frothing of a reaction mixture and scrubbers are used for cleaning the fumes generated by the reaction.
The United States Patent 2.235,658 to ~aterman issued March 18, 1941 teaches the use oE an acid solution which is reclaimed by continuously draining the acid solution and precipitate from the reatciton vessel and conducting i-t to a still appara-tus in which the agent is boiled off. The ~apor then passes through a condenser O_ ~
including a coollng coil and the condenser agent is returned -to the reac-tion vessel.
Nei-ther of the above-ci-ted paten-ts teaches a closed loop leaching system in which vapor generated by boiling the acid solution is collected, condensed, and returned -to -the reaction vessel. Addi-tionally, neither patent -teaches the method of heating a workpiece -to a temperature above the boiling temperature of the leaching solution -to increase the corrosion rate.
BRIEF DESCRIPTION OF T~IE DRAWINGS
Other advantages of the present inven-tion will be readily appreciated as the same becomes better understood by reference to the following detailed description when con-sidered in connection with the accompanying drawings wherein:
FIGURE 1 is a cross-sectional schematic elevational view oE the subjec-t apparatus;
FIGURE 2 is an enlarged fragmen-tary cross-sec-tional view of the subject reaction container; and FIGURE 3 is an enlarged fragmentary cross-sec-tional view of a second embodiment of the reaction container.
DESCRIPTION OF PREFERRED EMBODIMENT
To explain the resul-ts obtained with the instant invention, a theory involves the observation -tha-t bubbles 17 are formed about the article 11 being leached during the exothermic reaction of the corrosive acid 16 with the ar-ticle 11 within the reaction container 18, as shown in Figure 2.
The bubbles 17 are actually escaping gas surrounded by a layer o~ acid. The gas within -the bubbles 17 insula-te -the ar-ticle 11 so -that the article -temperature is increased , 1 ~ (3~
above that of the surrounding acid~ Accordingly, the bubbles 17 ~urrounding the ar~icle 11 provide an insulation about the article 11 and ~he insula~ion maintains the article 11 at a temperature signiflcantly greater than the temperature of the surrounding acid 16. By maintaining the article 11 at a temperature above the temperature of ~he surrounding acid 16, the rate o the leaching reaction is increased. More specifically, the exothermic leaching reaction creates heat which increases the temperature of the suxrounding acid and the article. For exanple, in a typi~al reac~ion, the`
acid can be made ~o boil from ~he heat initially generaked by the reaction~ The higher the ~emperature at ~he point of leaching of the corrosive layer, the greater is the leaching rate. Frequently, the outermost layer of the article 11 is leached from the articlQ bu~ material rem~
in crevices about the article 11. The generated b~bbles 17 have access to these crevices and~ thusly, as deæcribed above, promote the leachin~ reaction thereabout. ~owever, when the outermos~ corrosi~e layer has been leached away from the article and there axe no bubbles in certain area~
of the article~ the article will lose heat ~o the surrounding acid in those areas. Additionally; it is impractical to insula~e khe reaction container, hencei heat is lost from the acid. Thusly, the rate of ~he leaching reac~ion in the other areas still having the outermost layer kher~in is reduced. Accordingly, as a result of the instant inventionO
the article is heat~d above the temparature of the leachin~
solution ~o main~in andJor increase the rate of lea~h; n~
reaction with the outermost corrosive layexO Consequently, ; 4 _ ~he reaction rate is maintained and the residual material is leached from the article llo In other words, the xate of ~he reaction is dependent upon the ~urace nature oE the article and the appropriate external on~iro~mentO The instant invention provides the appropriate external environW
ment~
Prior art leaching systems have not provided an ass~mbly or method in which the temperature of the article could be raised above ~le boiling temperature of the le~ching ~olution ~o as ~o ~ignificantly increase the corrosion rate of ~he leaching xeaction. The instant in~
vention is an improvement over ~he prior art in that it does provide a closed system in which the temperature o the article can be raised above the boiling temperature of the leach.ing solution 90 as to ~igni~icantly increa~e khe corrosion rate of the leaching reaction.
A closed loop asse~bly constructed in accordance with the instant invention is generally shown at 10~ The assembly 10 is adapted ~or dissolving a low carbon ste~l container 12 from a consolidated powder metal 14 by expos~
ing the steel container 12 to a nitric acid solution 16;
the nitric acid solution having a predatermined b~ilins temperature~ ~he assembly can be used to dissolve o~her materials with various leaching solutionsO For example 9 an aluminum layer can be dissolved with sodium hydroxide solution~
Additionally, ths instant invention can be used to di~solve material inside of an article D For example~ ~he fluid die can include an inner insert disposed wi~hin the ar~icle~ The instant invention can be used to dissolve ~he insert.
~ ~(.3 The assembly 10 includes a sealed reaction con-tainer generally indicated at 18 having an inner compartment 20 adapted to contain the ni~ric acid 16. The container con~ists o a ~e~sel 22 for containing the acid 16 and a sealed lid or cover member 240 ~ recirculation means, generally indicated at 25 is connected to the reac~ion container 18 fox receiving boiled off leachiny solution vapor and gaseous reactant products, condensing ~he vapox and returning the. vapor to the reaction container 180 The recirculatlon mean~ 25 in-cludes a irst conduit member 26 having first and second end portions 38 and 30 respectively. The fixst end portion 28 is opexatively connected to the reaction container 18.
The recirculation means 25 further includes a condenser generally indicated at 32. The condenser is adapted for collecting ~he nitric acid vapor from the reaction container via the first conduit member 26~ The condenser 32 includes a cooling jacket or container 3~ and a cooling coil 36. The cooling coil 36 is operatively connected to or in ~luid communication with the second end portion 30 of the first conduit member 26~ The cooling coi~ 36 is disposed within ~he cooling jacket 34. The cooling jacket 34 is adapted to circulata eoola~t about the first cooling coil 36~ The jacket 34 includes a coolan inlet 38 and outlet ~0 adapted ~o be connPcted to a cir~
culatio~ system~ Common coolants, such as wa~erO can be used in ~his system.
The recirculation means 25 further includes a reservoir container 42 which is operatively con~ec ed to P-~30 or in fluid c~ n~cation with the irst cooling coil 36 by a conduit 44. The reservoir container 42 is adapted to store ~he nitxic acid 16 which is condensed in the condenser 32.
A second conduit member 46 is operatively con nected between the reservoir container 42 and ~he reaction container 18 to establish fluid C~mmtln; cation therebetween-The second conduit member 46 include~ control means generally indicated at 48 for selea~ively opening and closing the second condui~ 46 to control flow of the nitric acid lfi from the reservoir container 42 to ~he. reaction container 18~ In other words, the control means 48 is a valve con-trolling the flow of nitric acid 16 from ~he reservoir container 42 to the reaction container 18, thus c~mpleting the closed loop system.
Ga5 purifieation means, generally indicated at 50, are opera~ively connected to the reservoir container 42.
The yas purification means is adapted for purifying gaseous products from the l~hi ng of the outer layer 12 of the article 140 ~he ga~ purification means conqists of various containers for removing impuri~ies; catalytically converting dangerous gases to harmless ones9 and cleaning ~he gases before they escape to the atmosphere. This sy~tem may in-clude several vessels 52 containing reactant chemical liquids which neutraliz~ and catalytically ~on~ert the reaetion products to ha~mles~ one~O The ves6els can con~ain lime-like solution or neutralizing the acid gasesO Th~
vessels 52 are interconnected by an appropriate tubing S4~
Addi~ionally~ a container 56 i5 couple~ in series wi~h the ~ 7 -P-330 ~ ~ ~O'~
vessels 52 and is adapted for cont~i n; ng solid chemical reactants~ such as activated charcoal ox a device similar to an automotive cakalytical aonverter fo~ further puriying and cleanin~ the gaseous product~ beore they escape to the atmosphere.
The entire assembly 10 is subjected to corrosive fumes; hence, the interior of the ch~nbers and vessels, as well as the conduits and tubings~ must be adapted to be inert in the presence of ~he strong leaching solutions and chemical products of the leaching reaction. Generally, stainless steel or gla~ lined vessels and glass tubing are used.
A second cooling coil 58 is disposed within the inner compar~lent 20 of ~he reaction container 18~ The second cooling coil 58 includes a coolant inlet 60 and outlet 62. ~he second coolant coil 58 provides control of the frothing of the leaching solution occurring within the container 18. When excess f~othing occurs in the reaction container 18, coolant is pumped ~hrough the second cooling coil 58 to retard the fro~hing~
An electric resistance hot plate, ~enerally indicated at 64, includes a heating element 66 disposed directly adjacent to the reaction con~ainer 18 ~or heating the article 11 above the predetermined boiling point of the nitric acid 16 so as to facilitate the dissolviny of the low carbon steel container 12 from the consolid2ted p~wd~r metal 1~ The heating element 66 engages the bottom exterior surface of ~he container 1~ opposi~e to the position of ~he article 11 within ~he con~ainer. Ge~erally~ as ~he reaotlon P~330begin~, a large area o the article 11 is exposed to the acid 16. This initial external reaction can ~ometimes create suficient heat so that ~le external heat will not be re-~uixed. However, as the reaction progresses and the corrosive area of the article 11 decreases, the total heat ~enerated by ~he reaction decreases. The extexnal heat is then applied, thereby increasing the reaction rate.
Thusly, the assembly 10 provides a closed system in which the rate of the reaction between the low carbon steel layer 12 and the nitric acid 16 ls increa~ed by the raising of the temperature of ~he article above the boiling temperature of the nitric acid. ~dditionally, an environment is created in which the article is insulated to maintain the article at a temperature ~ignificantly greatar than the surrounding acid~
The instant invention provides a method of dis-solving a layer 12 from the article 11 by exposing the article 11 to the leaching ~olution 16, the leaching ~olution having a predetermined boiling temperatureO The method includes the steps of placing the article 11 in ~he inner compar~ment 20 of the sealed reactio~ container 18 which contains the leaching solution 160 In other words~ the article 11 is placed within the reaction chamber 18 ~o as ~o be immersed wi~hin ~le leaching solution 16~
The article 11 is heated to a temperature above the boiling temperature of the leaching solution 16 to increase the corrosion rate of the outer layer 12 of the article 11. If a nitxic acid~water ~olutlon is used as the leaching solution~ the ax~icle is rai~d to a temperature _ g _ r ~ ~
above 300F. This exposure of the article 11 to the extremely hiyh t~mperature increases the corrosion rake (rate of reaction between the outer layer 12 and the nitric acid 16) signiicantly in comparison to prior art methods wherein the temperature of ~he leaching solution would generally be raised fro~ 175F to 200F.
The heating element 65 of the heater is placed directly adjacent to the outer surface of tha reaction container, as shown in ~he drawingO Alternatively, an induction coil can be placed around the reaction ontainer 18 to heat the artiale 11.
Alternatively, the bottom of the reaction chamber lR may include a recess 70 filled with mercury 72. The article 11 is placed in the recess 70. The heating element 64 is placed in direct contact with the outer surface of the recess 70~ The article 11 is heated via conduction of he~t through ~he mercury 72~ The object in this system is to provide a m; n i~ area of ~he heated mercury 72 that is exposed to the acid 160 Another method of heating ~he article 11 involves disposing the article wi~hin a heating basket~ ~he basket being electrically connected to a heat ~ource.
All oux of the aforementioned means for heatl~g the arti~le provides a souxce of heat which directl~ heats the article 11 to a tempexaturP above ~he boiling ~emper-ature of the surrounding acidO O~her methods can also be employed to accomplish the same result in accordance with ~he inskant invention.
The ~oiled off leac~ing solution is conducted and condensed in the recirculation systPm 2$ and selectively returned to the reaction container 18. More specifically, the boiled off leaching solution vapor i~ circulated from the reaction container 18 into a first cooling coil 36.
~ coolant, such as water, is circulated through the cooling jacket 34 and about the ~irst cooling coil 36, thereby cone n.~;ng ~le leaching golution 16 within the coil 36. The condensed leaching ~olution is collected and ~tored in the reservoir container 424 Finally, th~ leaching ~olution 16 is selectively returned to the reaction chamber 18 to maintain a pxedetermined level o le~ch;ng solution 16 within ~he chamber 18.
The method further includes the step of controlling the temperature within ~he inner compartment 20 of the reaction con~ainer 18 into a irst cooling coil 360 A coolant, ~uch as water, is circulated through the cooling jacket 3~ and about the first cooling coil 36~ thereby condensing the leaching solution 16 within the coil 36. The condensed leaching solution is collected and ~ored in the re~ervoir container 42. Finally, the le~ch;ng ~olu~ion 16 i~ selectively xeturned to the reaction chamber 18 to maintain a pr~det~rm;nP~ level of leaching solution 16 within the ch~nber 18.
The method further include~ the step of control~
ling the temperature within ~he inner compart~ent 20 o~ ~he reaction container 18 by dispoqing a cooling coil 58 there-within having coolant pumped therethroughO In other word~, there are two temperature controlling inputs into the reac-tion chamber 18; ~he heater ~4 and ~he cooling coil ~aO
~ 11 ~
P-33~
The heater is used to raise the temperature of the article 11 within the reaction chamber 18 above the hoiling temper~
ature of the leaGhing solution 16. If the temperature within the reaction chamber 18 xises so as to cause excess frothing of the leaching solution 16, coolant is pumped through the cooling coil 58 to retard the frothing.
Since the reaction o~ ~he leaching solution 16 with the outer layer 12 of ~he article generally produces gaseous products including impurities and dangerous gases, the instant method further inaludes the step of puriying ~lese gaseous waste products from the condensed leaching solution wi~hin the recirculation system 25. A~ previously described, this step includes the passing of the gaseous waste products through a series of containers 52 for remov-ing impurities, cat~lytically aonverting dangerous gases toharmless ones~ and cleaning the gases before they esc~pe to the atmosphexP~
The invention has been described ~n an illustrative manner and it is ~o be ~nderstood that the terminology which has been used is intended to be in the nakure of words of description rather tha~ of limitation.
ObviouslyO many modifications and variations of the present invention are possible in light of the above ~eachings~ It is; therefore, to be unders~ood ~hat wi~hin the scope o the appended claims wherein refexence nurnerals are not to be in any way limiting, the invention may be practiced otherwise ~han as specifically described~
~l) FieI~ of the Invention The subject invention relates to a leaching asse~bly and method for dissolving an owter layer from an article.
~2) Des¢ription of khe Prior Art Several methods have been de~i~ed for aonsolidating powder metalO In one method, a thick-walled container o the powder metal is hot-co~solidated by the application lQ of heat and pressure, either by means of an autoclave or by a mechanical press. Subse~uent to hot consolidation it is necessary to remove the container from the consolidated powder metalO Generally, the removal of the container is accomplished by a combination of a ~-ch;ning and a leaching lS operation~
Prior art leaching operations have proceeded at a vexy slow rate. The instant invention provid2s an improved leaching apparatus and mekhod which is capable of removing the low carbon s~eel con~ainer material a~ a much faster rate than methods previously employed.
SUMMARY OF THE lNY~LION
A closed loop assembly dissolves an outex layer ~rom an article by exposing the article to a leaching solution having a predeterml~ed boiling temperatureO The assembly includes a sealed reaction container having an inner compartment adapted to contain the leaching solution and ~he article. ~ recirculation ~ystem is connec~ed to the reaction con~ainer for receiving boiled of leaching solution vapor and xeaction gaseous products and condensing ~o~
the vapor and returning the vapor -to the reaction container as secondary feature. A heater is included for heating the ar-ticle within -the reaction container above the boiling -temprature oE the leaching solution -to increase the corrosion rate oE the article The invention also includes a method o~
dissolving a layer ~rom an article by exposing the article to a leaching solution having a predetermined boiling temperature by placing the ar-ticle in an inner compartment oE a reaction container containing the leaching solution and heating the article -to a temperature above the boiling tempera-ture of the leaching solu-tion -to increase the corrosion rate o~ -the outer layer of the article.
PRIOR ART STATEMENT
The United States Patent 3,261,733 to Bellinger issued Ju:Ly 13, 1966 teaches a method oE dissolving a metal core in an etching bath wherein the metal core may be a low carbon steel and the etching bath i5 a nitric acid solution. Cooling coils are used Eor controlling frothing of a reaction mixture and scrubbers are used for cleaning the fumes generated by the reaction.
The United States Patent 2.235,658 to ~aterman issued March 18, 1941 teaches the use oE an acid solution which is reclaimed by continuously draining the acid solution and precipitate from the reatciton vessel and conducting i-t to a still appara-tus in which the agent is boiled off. The ~apor then passes through a condenser O_ ~
including a coollng coil and the condenser agent is returned -to the reac-tion vessel.
Nei-ther of the above-ci-ted paten-ts teaches a closed loop leaching system in which vapor generated by boiling the acid solution is collected, condensed, and returned -to -the reaction vessel. Addi-tionally, neither patent -teaches the method of heating a workpiece -to a temperature above the boiling temperature of the leaching solution -to increase the corrosion rate.
BRIEF DESCRIPTION OF T~IE DRAWINGS
Other advantages of the present inven-tion will be readily appreciated as the same becomes better understood by reference to the following detailed description when con-sidered in connection with the accompanying drawings wherein:
FIGURE 1 is a cross-sectional schematic elevational view oE the subjec-t apparatus;
FIGURE 2 is an enlarged fragmen-tary cross-sec-tional view of the subject reaction container; and FIGURE 3 is an enlarged fragmentary cross-sec-tional view of a second embodiment of the reaction container.
DESCRIPTION OF PREFERRED EMBODIMENT
To explain the resul-ts obtained with the instant invention, a theory involves the observation -tha-t bubbles 17 are formed about the article 11 being leached during the exothermic reaction of the corrosive acid 16 with the ar-ticle 11 within the reaction container 18, as shown in Figure 2.
The bubbles 17 are actually escaping gas surrounded by a layer o~ acid. The gas within -the bubbles 17 insula-te -the ar-ticle 11 so -that the article -temperature is increased , 1 ~ (3~
above that of the surrounding acid~ Accordingly, the bubbles 17 ~urrounding the ar~icle 11 provide an insulation about the article 11 and ~he insula~ion maintains the article 11 at a temperature signiflcantly greater than the temperature of the surrounding acid 16. By maintaining the article 11 at a temperature above the temperature of ~he surrounding acid 16, the rate o the leaching reaction is increased. More specifically, the exothermic leaching reaction creates heat which increases the temperature of the suxrounding acid and the article. For exanple, in a typi~al reac~ion, the`
acid can be made ~o boil from ~he heat initially generaked by the reaction~ The higher the ~emperature at ~he point of leaching of the corrosive layer, the greater is the leaching rate. Frequently, the outermost layer of the article 11 is leached from the articlQ bu~ material rem~
in crevices about the article 11. The generated b~bbles 17 have access to these crevices and~ thusly, as deæcribed above, promote the leachin~ reaction thereabout. ~owever, when the outermos~ corrosi~e layer has been leached away from the article and there axe no bubbles in certain area~
of the article~ the article will lose heat ~o the surrounding acid in those areas. Additionally; it is impractical to insula~e khe reaction container, hencei heat is lost from the acid. Thusly, the rate of ~he leaching reac~ion in the other areas still having the outermost layer kher~in is reduced. Accordingly, as a result of the instant inventionO
the article is heat~d above the temparature of the leachin~
solution ~o main~in andJor increase the rate of lea~h; n~
reaction with the outermost corrosive layexO Consequently, ; 4 _ ~he reaction rate is maintained and the residual material is leached from the article llo In other words, the xate of ~he reaction is dependent upon the ~urace nature oE the article and the appropriate external on~iro~mentO The instant invention provides the appropriate external environW
ment~
Prior art leaching systems have not provided an ass~mbly or method in which the temperature of the article could be raised above ~le boiling temperature of the le~ching ~olution ~o as ~o ~ignificantly increase the corrosion rate of ~he leaching xeaction. The instant in~
vention is an improvement over ~he prior art in that it does provide a closed system in which the temperature o the article can be raised above the boiling temperature of the leach.ing solution 90 as to ~igni~icantly increa~e khe corrosion rate of the leaching reaction.
A closed loop asse~bly constructed in accordance with the instant invention is generally shown at 10~ The assembly 10 is adapted ~or dissolving a low carbon ste~l container 12 from a consolidated powder metal 14 by expos~
ing the steel container 12 to a nitric acid solution 16;
the nitric acid solution having a predatermined b~ilins temperature~ ~he assembly can be used to dissolve o~her materials with various leaching solutionsO For example 9 an aluminum layer can be dissolved with sodium hydroxide solution~
Additionally, ths instant invention can be used to di~solve material inside of an article D For example~ ~he fluid die can include an inner insert disposed wi~hin the ar~icle~ The instant invention can be used to dissolve ~he insert.
~ ~(.3 The assembly 10 includes a sealed reaction con-tainer generally indicated at 18 having an inner compartment 20 adapted to contain the ni~ric acid 16. The container con~ists o a ~e~sel 22 for containing the acid 16 and a sealed lid or cover member 240 ~ recirculation means, generally indicated at 25 is connected to the reac~ion container 18 fox receiving boiled off leachiny solution vapor and gaseous reactant products, condensing ~he vapox and returning the. vapor to the reaction container 180 The recirculatlon mean~ 25 in-cludes a irst conduit member 26 having first and second end portions 38 and 30 respectively. The fixst end portion 28 is opexatively connected to the reaction container 18.
The recirculation means 25 further includes a condenser generally indicated at 32. The condenser is adapted for collecting ~he nitric acid vapor from the reaction container via the first conduit member 26~ The condenser 32 includes a cooling jacket or container 3~ and a cooling coil 36. The cooling coil 36 is operatively connected to or in ~luid communication with the second end portion 30 of the first conduit member 26~ The cooling coi~ 36 is disposed within ~he cooling jacket 34. The cooling jacket 34 is adapted to circulata eoola~t about the first cooling coil 36~ The jacket 34 includes a coolan inlet 38 and outlet ~0 adapted ~o be connPcted to a cir~
culatio~ system~ Common coolants, such as wa~erO can be used in ~his system.
The recirculation means 25 further includes a reservoir container 42 which is operatively con~ec ed to P-~30 or in fluid c~ n~cation with the irst cooling coil 36 by a conduit 44. The reservoir container 42 is adapted to store ~he nitxic acid 16 which is condensed in the condenser 32.
A second conduit member 46 is operatively con nected between the reservoir container 42 and ~he reaction container 18 to establish fluid C~mmtln; cation therebetween-The second conduit member 46 include~ control means generally indicated at 48 for selea~ively opening and closing the second condui~ 46 to control flow of the nitric acid lfi from the reservoir container 42 to ~he. reaction container 18~ In other words, the control means 48 is a valve con-trolling the flow of nitric acid 16 from ~he reservoir container 42 to the reaction container 18, thus c~mpleting the closed loop system.
Ga5 purifieation means, generally indicated at 50, are opera~ively connected to the reservoir container 42.
The yas purification means is adapted for purifying gaseous products from the l~hi ng of the outer layer 12 of the article 140 ~he ga~ purification means conqists of various containers for removing impuri~ies; catalytically converting dangerous gases to harmless ones9 and cleaning ~he gases before they escape to the atmosphere. This sy~tem may in-clude several vessels 52 containing reactant chemical liquids which neutraliz~ and catalytically ~on~ert the reaetion products to ha~mles~ one~O The ves6els can con~ain lime-like solution or neutralizing the acid gasesO Th~
vessels 52 are interconnected by an appropriate tubing S4~
Addi~ionally~ a container 56 i5 couple~ in series wi~h the ~ 7 -P-330 ~ ~ ~O'~
vessels 52 and is adapted for cont~i n; ng solid chemical reactants~ such as activated charcoal ox a device similar to an automotive cakalytical aonverter fo~ further puriying and cleanin~ the gaseous product~ beore they escape to the atmosphere.
The entire assembly 10 is subjected to corrosive fumes; hence, the interior of the ch~nbers and vessels, as well as the conduits and tubings~ must be adapted to be inert in the presence of ~he strong leaching solutions and chemical products of the leaching reaction. Generally, stainless steel or gla~ lined vessels and glass tubing are used.
A second cooling coil 58 is disposed within the inner compar~lent 20 of ~he reaction container 18~ The second cooling coil 58 includes a coolant inlet 60 and outlet 62. ~he second coolant coil 58 provides control of the frothing of the leaching solution occurring within the container 18. When excess f~othing occurs in the reaction container 18, coolant is pumped ~hrough the second cooling coil 58 to retard the fro~hing~
An electric resistance hot plate, ~enerally indicated at 64, includes a heating element 66 disposed directly adjacent to the reaction con~ainer 18 ~or heating the article 11 above the predetermined boiling point of the nitric acid 16 so as to facilitate the dissolviny of the low carbon steel container 12 from the consolid2ted p~wd~r metal 1~ The heating element 66 engages the bottom exterior surface of ~he container 1~ opposi~e to the position of ~he article 11 within ~he con~ainer. Ge~erally~ as ~he reaotlon P~330begin~, a large area o the article 11 is exposed to the acid 16. This initial external reaction can ~ometimes create suficient heat so that ~le external heat will not be re-~uixed. However, as the reaction progresses and the corrosive area of the article 11 decreases, the total heat ~enerated by ~he reaction decreases. The extexnal heat is then applied, thereby increasing the reaction rate.
Thusly, the assembly 10 provides a closed system in which the rate of the reaction between the low carbon steel layer 12 and the nitric acid 16 ls increa~ed by the raising of the temperature of ~he article above the boiling temperature of the nitric acid. ~dditionally, an environment is created in which the article is insulated to maintain the article at a temperature ~ignificantly greatar than the surrounding acid~
The instant invention provides a method of dis-solving a layer 12 from the article 11 by exposing the article 11 to the leaching ~olution 16, the leaching ~olution having a predetermined boiling temperatureO The method includes the steps of placing the article 11 in ~he inner compar~ment 20 of the sealed reactio~ container 18 which contains the leaching solution 160 In other words~ the article 11 is placed within the reaction chamber 18 ~o as ~o be immersed wi~hin ~le leaching solution 16~
The article 11 is heated to a temperature above the boiling temperature of the leaching solution 16 to increase the corrosion rate of the outer layer 12 of the article 11. If a nitxic acid~water ~olutlon is used as the leaching solution~ the ax~icle is rai~d to a temperature _ g _ r ~ ~
above 300F. This exposure of the article 11 to the extremely hiyh t~mperature increases the corrosion rake (rate of reaction between the outer layer 12 and the nitric acid 16) signiicantly in comparison to prior art methods wherein the temperature of ~he leaching solution would generally be raised fro~ 175F to 200F.
The heating element 65 of the heater is placed directly adjacent to the outer surface of tha reaction container, as shown in ~he drawingO Alternatively, an induction coil can be placed around the reaction ontainer 18 to heat the artiale 11.
Alternatively, the bottom of the reaction chamber lR may include a recess 70 filled with mercury 72. The article 11 is placed in the recess 70. The heating element 64 is placed in direct contact with the outer surface of the recess 70~ The article 11 is heated via conduction of he~t through ~he mercury 72~ The object in this system is to provide a m; n i~ area of ~he heated mercury 72 that is exposed to the acid 160 Another method of heating ~he article 11 involves disposing the article wi~hin a heating basket~ ~he basket being electrically connected to a heat ~ource.
All oux of the aforementioned means for heatl~g the arti~le provides a souxce of heat which directl~ heats the article 11 to a tempexaturP above ~he boiling ~emper-ature of the surrounding acidO O~her methods can also be employed to accomplish the same result in accordance with ~he inskant invention.
The ~oiled off leac~ing solution is conducted and condensed in the recirculation systPm 2$ and selectively returned to the reaction container 18. More specifically, the boiled off leaching solution vapor i~ circulated from the reaction container 18 into a first cooling coil 36.
~ coolant, such as water, is circulated through the cooling jacket 34 and about the ~irst cooling coil 36, thereby cone n.~;ng ~le leaching golution 16 within the coil 36. The condensed leaching ~olution is collected and ~tored in the reservoir container 424 Finally, th~ leaching ~olution 16 is selectively returned to the reaction chamber 18 to maintain a pxedetermined level o le~ch;ng solution 16 within ~he chamber 18.
The method further includes the step of controlling the temperature within ~he inner compartment 20 of the reaction con~ainer 18 into a irst cooling coil 360 A coolant, ~uch as water, is circulated through the cooling jacket 3~ and about the first cooling coil 36~ thereby condensing the leaching solution 16 within the coil 36. The condensed leaching solution is collected and ~ored in the re~ervoir container 42. Finally, the le~ch;ng ~olu~ion 16 i~ selectively xeturned to the reaction chamber 18 to maintain a pr~det~rm;nP~ level of leaching solution 16 within the ch~nber 18.
The method further include~ the step of control~
ling the temperature within ~he inner compart~ent 20 o~ ~he reaction container 18 by dispoqing a cooling coil 58 there-within having coolant pumped therethroughO In other word~, there are two temperature controlling inputs into the reac-tion chamber 18; ~he heater ~4 and ~he cooling coil ~aO
~ 11 ~
P-33~
The heater is used to raise the temperature of the article 11 within the reaction chamber 18 above the hoiling temper~
ature of the leaGhing solution 16. If the temperature within the reaction chamber 18 xises so as to cause excess frothing of the leaching solution 16, coolant is pumped through the cooling coil 58 to retard the frothing.
Since the reaction o~ ~he leaching solution 16 with the outer layer 12 of ~he article generally produces gaseous products including impurities and dangerous gases, the instant method further inaludes the step of puriying ~lese gaseous waste products from the condensed leaching solution wi~hin the recirculation system 25. A~ previously described, this step includes the passing of the gaseous waste products through a series of containers 52 for remov-ing impurities, cat~lytically aonverting dangerous gases toharmless ones~ and cleaning the gases before they esc~pe to the atmosphexP~
The invention has been described ~n an illustrative manner and it is ~o be ~nderstood that the terminology which has been used is intended to be in the nakure of words of description rather tha~ of limitation.
ObviouslyO many modifications and variations of the present invention are possible in light of the above ~eachings~ It is; therefore, to be unders~ood ~hat wi~hin the scope o the appended claims wherein refexence nurnerals are not to be in any way limiting, the invention may be practiced otherwise ~han as specifically described~
Claims (20)
1. A closed loop assembly adapted for dissolving a layer from an article by exposing the article to a leaching solution having a predetermined boiling temperature, said assembly comprising; a sealed reaction container including an inner compartment adapted to contain the leaching solution and the article, and characterized by recirculation means connected to said reaction container for receiving boiled off leaching solution vapor and reaction gaseous products and condensing the vapor and returning the condensed vapor to said reaction container, said assembly including heating means for heating the article within said reaction container above the boiling temperature of the leaching solution.
2. An assembly as set forth in claim 1 wherein said reaction container includes cooling means disposed within said inner compartment for selectively lowering the temperature therewithin.
3. An assembly as set forth in claim 2 wherein said recirculation means includes gas purification means for purifying gaseous products resulting from the leaching of the article.
4. An assembly as set forth in claim 3 wherein said heating means includes a heating element disposed adjacent the exterior of said reaction container opposite to the position of the article within said reaction container.
5. An assembly as set forth in claim 4 wherein said reaction container includes a floor having a recessed portion, said recessed portion adapted to contain mercury between the article and said recessed portion, said heating element being disposed directly adjacent the exterior of said recessed portion.
6. An assembly as set forth in claim 4 wherein said recirculation means includes a condenser adapted for capturing and condensing the leaching solution vapor from said reaction container.
7. An assembly as set forth in claim 6 wherein said condenser includes a cooling jacket and a first cooling coil, said first cooling coil being operatively connected to said reaction container and disposed within said cooling jacket whereby said cooling jacket is adapted to circulate coolant about said first cooling coil so as to facilitate the condensation of the leaching solution vapor.
8. An assembly as set forth in claim 4 wherein said recirculation means includes a reservoir container operatively connected to said condenser for storing the condensed leaching solution collected in said container.
9. An assembly as set forth in claim 8 wherein said recirculation means includes a conduit member operatively connected between said reservoir container and said reaction container and including control means for selectively opening and closing said conduit to control the flow of the leaching solution from said reservoir container to said reaction container.
10. An assembly as set forth in claim 9 wherein said cooling means includes a second cooling coil disposed within said inner compartment of said reaction container and including a coolant inlet and outlet whereby said second cooling coil is adapted for circulating coolant fluid therethrough.
11. An assembly adapted for dissolving a layer from an article by exposing the article to a leaching solution having a predetermined boiling temperature, said assembly comprising; a reaction container including an inner compartment adapted to contain the leaching solution and the article and characterized by heating means for heating the article within said reaction container above the boiling temperature of the leaching solution.
12. A closed loop assembly adapted for dissolving a low carbon steel container from a consolidated powder metal by exposing the steel container to a nitric acid solution having a predetermined boiling temperature, said assembly comprising; a sealed reaction container including an inner compartment adapted to container the nitric acid; a first conduit member having a first and second end portion, said first end portion being operatively connected to said reaction container; a condenser adapted for collecting the nitric acid vapor from said reaction container and including a cooling jacket and a cooling coil, said cooling coil being operatively connected to said second end portion of said first conduit and disposed within said cooling jacket so that said cooling jacket circulates a coolant about said first cooling coil; a reservoir container operatively connected to said first cooling coil and adapted to store the nitric acid condensed in said condenser, a second conduit member operatively connected between said reservoir container and said reaction container and including control means for selectively opening and closing said second conduit to control flow of the nitric acid from the reservoir container to said reaction container; gas purification means operatively connected to said reservoir container and adapted for purifying gaseous products resulting from the leaching of the article; a second cooling coil disposed within said inner compartment of said reaction container and including a coolant inlet and outlet so that said second cooling coil circulates a coolant fluid therethrough; and a heating element engaging the exterior of said reaction container for heating the article above the predetermined boiling point of the nitric acid so as to facilitate the dissolving of the low carbon steel container from the consolidated powder metal.
13. A method of dissolving a layer from an article by exposing the article to a leaching solution having a predetermined boiling temperature, said method comprising the steps of; placing the article in an inner compartment of a sealed reaction container which contains the leaching solution; conducting and condensing boiled off leaching solution vapor in a recirculation system and selectively returning the collected leaching solution to the reaction container, and heating the article to a temperature above the boiling temperature of the leaching solution to increase the corrosion rate of the layer of the article.
14. A method as set forth in claim 13 including the step of controlling the temperature within the inner compartment of the reaction container by disposing a second cooling coil therewithin and pumping coolant therethrough.
15. A method as set forth in claim 14 including the step of purifying the gaseous waste products from the condensed leaching solution within the recirculation system.
16. A method as set forth in claim 15 including the steps of circulating the boiled off leaching solution vapor from the reaction container into a first cooling coil of the recirculation system and circulating a coolant about the first cooling coil to condense the leaching solution therewithin.
17. A method as set forth in claim 16 including the steps of collecting and storing the condensed leaching solution in a reservoir container that is operatively connected to the cooling coil and selectively returning the leaching solution to the reaction chamber to maintain a predetermined level of the leaching solution.
18. A method as set forth in claim 17 including the step of heating the article to a temperature above 200°F.
19. A method of dissolving a layer from an article by exposing the article to a leaching solution having a predetermined boiling temperature, said method comprising the steps of; placing the article in an inner compartment of a reaction container containing the leaching solution and heating the article to a temperature above the boiling temperature of the leaching solution to increase the corrosion rate of the outer layer of the article.
20. A method as set forth in claim 19 including the step of placing the heating element of a heater adjacent to the exterior surface of the reaction container opposite to the position of the article.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US268,878 | 1981-06-01 | ||
| US06/268,878 US4383884A (en) | 1981-06-01 | 1981-06-01 | Closed loop leaching system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1190459A true CA1190459A (en) | 1985-07-16 |
Family
ID=23024897
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000399604A Expired CA1190459A (en) | 1981-06-01 | 1982-03-29 | Closed loop leaching system |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US4383884A (en) |
| EP (1) | EP0066358B1 (en) |
| JP (1) | JPS5828322B2 (en) |
| AT (1) | ATE26132T1 (en) |
| CA (1) | CA1190459A (en) |
| DE (1) | DE3275840D1 (en) |
Families Citing this family (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4740249A (en) * | 1984-05-21 | 1988-04-26 | Christopher F. McConnell | Method of treating wafers with fluid |
| US4633893A (en) * | 1984-05-21 | 1987-01-06 | Cfm Technologies Limited Partnership | Apparatus for treating semiconductor wafers |
| US4738272A (en) * | 1984-05-21 | 1988-04-19 | Mcconnell Christopher F | Vessel and system for treating wafers with fluids |
| US4856544A (en) * | 1984-05-21 | 1989-08-15 | Cfm Technologies, Inc. | Vessel and system for treating wafers with fluids |
| US4836302A (en) * | 1986-12-03 | 1989-06-06 | Heilhecker Joe K | Apparatus and method for removing and recovering oil and/or other oil-based drilling mud additives from drill cuttings |
| JP3209426B2 (en) * | 1991-10-04 | 2001-09-17 | シーエフエムティ インコーポレイテッド | Cleaning microparts with complex shapes |
| US7766329B1 (en) | 1992-10-02 | 2010-08-03 | Sierra Design Group | Wheel indicator and ticket dispenser apparatus |
| US5292127C1 (en) | 1992-10-02 | 2001-05-22 | Arcade Planet Inc | Arcade game |
| US7976022B1 (en) | 1992-10-02 | 2011-07-12 | Bally Gaming, Inc. | Video wheel indicator |
| US6136724A (en) * | 1997-02-18 | 2000-10-24 | Scp Global Technologies | Multiple stage wet processing chamber |
| US6328809B1 (en) | 1998-10-09 | 2001-12-11 | Scp Global Technologies, Inc. | Vapor drying system and method |
| US7775870B2 (en) | 2003-11-21 | 2010-08-17 | Sierra Design Group | Arcade game |
| US7823883B1 (en) | 2008-02-29 | 2010-11-02 | Bally Gaming Inc. | Wheel indicator and ticket dispenser apparatus |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2235658A (en) * | 1938-02-23 | 1941-03-18 | Aerovox Corp | Art of reclaiming reagent |
| US2516930A (en) * | 1944-04-14 | 1950-08-01 | Sperry Corp | Filament forming method |
| GB905282A (en) * | 1960-08-03 | 1962-09-05 | Kestner Evaporator And Enginee | A method of pickling metal parts in nitric acid |
| US3192084A (en) * | 1961-12-18 | 1965-06-29 | Brunswick Corp | Method of removing malleable cores from metallic tubular members |
| US3261733A (en) * | 1963-07-02 | 1966-07-19 | Conversion Chem Corp | Method of dissolving a plug from a bimetallic metal core and etching bath |
| US3443991A (en) * | 1965-12-06 | 1969-05-13 | Georges F Kremm | Process for pickling metal |
| DE1546042A1 (en) * | 1966-04-16 | 1969-12-11 | Telefunken Patent | Process for surface treatment of workpieces |
| US3737367A (en) * | 1968-11-25 | 1973-06-05 | Brunswick Corp | Passage structure |
| US4094709A (en) * | 1977-02-10 | 1978-06-13 | Kelsey-Hayes Company | Method of forming and subsequently heat treating articles of near net shaped from powder metal |
-
1981
- 1981-06-01 US US06/268,878 patent/US4383884A/en not_active Expired - Lifetime
-
1982
- 1982-03-29 CA CA000399604A patent/CA1190459A/en not_active Expired
- 1982-04-05 EP EP82301787A patent/EP0066358B1/en not_active Expired
- 1982-04-05 DE DE8282301787T patent/DE3275840D1/en not_active Expired
- 1982-04-05 AT AT82301787T patent/ATE26132T1/en not_active IP Right Cessation
- 1982-06-01 JP JP57093942A patent/JPS5828322B2/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| EP0066358B1 (en) | 1987-03-25 |
| US4383884A (en) | 1983-05-17 |
| DE3275840D1 (en) | 1987-04-30 |
| EP0066358A2 (en) | 1982-12-08 |
| JPS5816004A (en) | 1983-01-29 |
| JPS5828322B2 (en) | 1983-06-15 |
| EP0066358A3 (en) | 1983-05-04 |
| ATE26132T1 (en) | 1987-04-15 |
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| MKEX | Expiry |