CA1195363A

CA1195363A - Gas-entrained particulate

Info

Publication number: CA1195363A
Application number: CA000416259A
Authority: CA
Inventors: Kenneth D. Ives
Original assignee: USS Engineers and Consultants Inc
Current assignee: USS Engineers and Consultants Inc
Priority date: 1981-12-02
Filing date: 1982-11-24
Publication date: 1985-10-15
Also published as: DE3244108A1; GB2110652B; US4363470A; FR2517284A1; JPS58108415A; ES8401137A1; FR2517284B1; GB2110652A; ES517848A0

Abstract

ABSTRACT OF THE DISCLOSURE
Apparatus is provided for preventing pressur-ized gas in a flow control valve from affecting measure-ments of particulate feed rate, where such measurements are made using weighing devices to determine the amount of particulate in a supply container over time. The apparatus includes expansion joints and means for applying sufficient compressive prestress to spacer bars, which limit expansion of the expansion joints, to prevent extension of the spacer bars arising from flow of the pressurized gas through the valve. Movement of the container arising from such extension is prevented and particulate feed rate errors are substantially eliminated.

Description

~3~i3 GAS-ENTRAINED PARTICUL~TE
FEED SYSTEM
This invention relates to pressurized gas-entrained particulate feea systems, and particularly to systems in which feed rate is determined from measurements on a particulate supply container.
In certain steelmaking processes, ilux materials such as limestone, burned lime or fluorospar may be introduced into a steelmaking vessel by injecting them in powdered form, entrained in a pressurized refining gas.
A system for controlling injection of 1uxes to be intro-duced in this manner is shown in United States Patent 5pecification No. 4~136,857. In this system, the flux feed rate is measured by measuring the weight of a feed hopper by means of load cells mounted between the hopper and its supports~
The feed rate measurements have been subject to some degree of error, generally attributed to load cell inaccurracy, movement of a flow control valve and unknown factors. The primary cause of error was not readily 3~i~

apparent, although it was recognize~ that the degree of error varied generally in proportion to operating gas pressure~ Efforts have been made to eliminate the effect of valve movement by providing sturdier supports, but these have not been notably successful.
According to the present invention, there is provide~ an apparatus for supplying particulate material entrained in a pressurized gas to a process vessel, comprising a container for said particulate material, means for measuxing the weight of said container to determine feed rate of said material from the container, a pipe for connecting said container to the process vessel, means for supplying pressurized gas to said container and pipe, a valve having an inlet connected to the container and an outlet connected to the pipe for regulating flow of gas and particulate material, expan-sion joints connected to the valve to permit vertical movement of said valve and container with respect to said pipe and compensate for reaction forces on said valve ~Q arising from the pressurized gas, spacer bars which limit expansion of the expansion joints, and by means apply.ing compressive prestress to said spacer bars to substantially preven~ extension of the spacex bars arising from the pressuriz~d gas.

3~i;3 The invention is further described, by way of /example, with reference to the accompanying drawing which is a side elevation of a flux injection system for a steelmaking converter showing an apparatus of this invention. Referring to the drawing, a hopper 10 is provided for storage of particulate lime or other material to be supplied to a s~eelmaking vessel ~not shown). To provide a measure of the weight of the hopper 10, load cells are mounted between th hopper and its supports. Generally three spaced load cells are provided defining a plane of support, one being schematically illustrated at 11 in the drawing. A
flow regulation valve 12 is connected between the outlet 16 of the hopper 10 and pipe 14 which extends to the stePlmaking vessel. ~he valve 12 is operated by a motor dri~e 18. A system 20 of branch pipes introduces pressurized gas into the hopper 10 to as5ist in the entrainment of particulate material in the gas flowing thxough the valve 12.
In order to be weighed, the hopper 10 must be able to move in a vertical direction without restraint by the pipe 14. To accomplish this an expansion bellows 19 is conencted between flanged plates 21 and 23 of the pipeline 14 and valve 12, respectively. ~ second 5 expansion bellows 25 is provided to compensate for tj3~3 reaction forces on the valve 12 arising from the pressurized gas. This latter expansion bellows 25 is mounted between plates 27 and spacer bars, one of which is shown at 35, limit the expansion of the bellows l9 and 25 and also serve as guides for movement of the valve 12 and hopper lO with respect to the fixed pipe 14. The bars are secured to the outer p:Lates 21 and 27 but are slidably mounted in holes through the inner plates 23 and 29. Threaded sleeves 39, 41 allow adjust-ment of the lengths of the spacer bars 37. Spacer bars43 and 45 are slidably mounted in the plate 27 and secured to the plate 29 to limit expansion of the bellows 25.
Tie rods 36 apply su~ficient compressive pre-stress to the spacer bars 37 to substantially prevent ext~nsion of thei.r length when pressurized gas is flow-ing through ~he ~alve 12. Thus, movement of the valve 12 and hopper lO arising from the pressurized gas is prevented. The tie rods 36 are connected between upper and lower plates 30 and 32. The lower plate 32 is desirably fixed directly to the pipe 14 by welds as illustrated, or is mo~mted beneath an elbow 38, of the pipe 14, or if desired may be mounted independently of the pipe itself. The upper plate 30 is located above the expansion bellows 25, abutting either directly against i3~;3 plate 27 or, as shown, against a compression spring 34.
It will be apparent that variations on the embodiment disclosed will accomplish a similar result.
For example, a fluid powered cylinder or screwjack or a weight may be provided to exert downward force on the plate 27 to create the desired compressive prestress in the spacer bars 37.

Claims

The Embodiments of the Invention In Which An Exclusive Property or Privilege is Claimed Are As Follows:-

1. An apparatus for supplying particulate material entrained in a pressurized gas to a process vessel, comprising a container for said particulate material, means for measuring the weight of said con-tainer to determine feed rate of said material from the container, a pipe for connecting said container to the process vessel, means for supplying pressurized gas to said container and pipe, a valve having an inlet connected to the container and an outlet connected to the pipe for regulating flow of gas and particulate material, expansion joints connected to the valve to permit vertical movement of said valve and container with respect to said pipe and compensate for reaction forces on said valve arising from the pressurized gas, spacer bars which limit expansion of the expansion joints, and by means applying compressive prestress to said spacer bars to substantially prevent extension of the spacer bars arising from the pressurized gas.

2. An apparatus as claimed in claim 1, in which the means applying compressive prestress comprises tie rods extending from the pipe across the expansion joints.

3. An apparatus as claimed in claim 2, in which the tie rods compress the spacer bars by way of a com-pression spring.