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EP0754091A1 - Procede a lit fluidise ameliore - Google Patents

Procede a lit fluidise ameliore

Info

Publication number
EP0754091A1
EP0754091A1 EP94923148A EP94923148A EP0754091A1 EP 0754091 A1 EP0754091 A1 EP 0754091A1 EP 94923148 A EP94923148 A EP 94923148A EP 94923148 A EP94923148 A EP 94923148A EP 0754091 A1 EP0754091 A1 EP 0754091A1
Authority
EP
European Patent Office
Prior art keywords
particulate material
bed
fluidized bed
titanium containing
gas
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.)
Ceased
Application number
EP94923148A
Other languages
German (de)
English (en)
Inventor
Ran Abed
James W. Reeves
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
EIDP Inc
Original Assignee
EI Du Pont de Nemours and Co
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by EI Du Pont de Nemours and Co filed Critical EI Du Pont de Nemours and Co
Priority claimed from PCT/US1994/003671 external-priority patent/WO1995026809A1/fr
Publication of EP0754091A1 publication Critical patent/EP0754091A1/fr
Ceased legal-status Critical Current

Links

Definitions

  • This invention relates to an improved fluidized bed process.
  • Fluidized bed processes are used commercially for the chlorination of titanium containing materials, ore roasting or refining, combustion of solid carbonaceous material such as coal, etc.
  • particulate material, air, oxygen or other oxidizing agents are fed into a reaction chamber, and suitable temperature and pressure are maintained. The flow rates are adjusted so that the particulate material becomes fluidized, i.e., it is maintained in a state of suspension and has the appearance of boiling.
  • a good example of a commercial fluidized bed process is that for chlorinating titanium containing material.
  • particulate coke, particulate titanium containing material, chlorine and optionally oxygen or air are fed into a reaction chamber, and a suitable reaction temperature, pressure and flow rates are maintained to sustain the fluidized bed.
  • Gaseous titanium tetrachloride and other metal chlorides are exhausted from the reactor chamber. The gaseous titanium tetrachloride so produced can then be separated from the other metal chlorides and used to produce titanium dioxide pigment or titanium metal.
  • a problem, however, which has not been satisfactorily solved in the foregoing fluidized bed processes is that particulate material of fine size tends to becomes entrained in the hot gases exiting the process.
  • fine particulates have a short residence time in the reaction zone of the process, and often exit the reactor in an unreacted state. While the fine particulates can be recycled to the process, they still tend to exit before reacting and therefore generally must be removed from the process. The unreacted fines therefore are a disposal problem and a waste of the fuel, metallic, or other values in the materials being processed.
  • the fine particulate material typically is present due to the attrition and degradation of particulate materials of larger particle size which are fed to the fluidized bed process.
  • U.S. Patent 2,701,179 discloses a commercial fluidized bed process for chlorinating titanium containing material wherein the particulates are fed pneumatically with chlorine into the bottom of the fluidized bed reactor.
  • Zinc Roasters by N. J. Themelis and G. M. Freeman appeared in the August 1984 issue of the Journal of Metals. It discloses the commercial fluidized bed roasting of zinc ores wherein the ore is fed to the reactor above the fluidized bed.
  • an improvement to reduce said entrainment which comprises introducing the particulate material into the process. in the substantial absence of a gas which transports the particulate material, at one or more points which are below the surface of the bed of fluidized particulate material.
  • the concept of this invention can be used in any fluidized bed process which is susceptible to entrainment of fine particulate material in the gases exiting the bed.
  • fluidized bed processes which can utilize the concept of this invention include combustion of carbonaceous material (such as coal, wood, peat, etc.), ore refining or roasting (such as chlorination of titanium containing material) , and processing of metallic ores including those containing zinc, copper or iron.
  • the particulate material should be introduced into the process, at a point below the surface of the fluidized bed, in the substantial absence of any gas which transports the particulate material.
  • gas which transports the particulate material is meant gas which has a superficial velocity greater than the terminal settling velocity of the particulate material.
  • “superficial velocity” in this context is meant the velocity of the gas in the conduit used to feed the particulate material to the process, in the absence of such material.
  • Suitable feed means for the particulate material include a screw device, a gravity fed hopper, power ram device, etc. Also, any of these feed means can be used with an "L"-shaped exit pipe or exit pipe with a bend which tends to minimize back flow of particulate material due to pressure in the reactor. While there should be a substantial absence of gas which transports the particulate material, sufficient amounts of gas such as air, nitrogen, chlorine, etc. can be injected into the particulate material being fed to the process to act as a lubricant or agent to lessen the binding of such particulate material.
  • such gas acting as a lubricant or agent to lessen the binding of the particulate material can thereby help to control the flow rate of the particulate material.
  • gas acting as a lubricant or such agent should be present in an amount of about 0.001-0.1, preferably about 0.0025-0.04, and most preferably about 0.005-0.02 part by weight of gas per part by weight of particulate material and have a superficial gas velocity of about 0.1-10, preferably about 0.5-5, and most preferably about 0.75-3 feet per second. It should be understood that the amount of such gas acting as a lubricant or such agent and its velocity will depend upon the particle size, particle density, and particle shape, and gas density.
  • Suitable amounts of such gas and its velocity can readily be determined by empirical testing with a device such as was used in the Example. If such gas acting as a lubricant or such agent is used in conjunction with an "L" valve or pipe with a bend, preferably such gas should be injected at or near the vacinity of the 90 * "L" or bend.
  • the particle size of the particulate material which is susceptible to entrainment can vary depending upon its terminal settling velocity and the superficial velocity of the gases in the fluidized bed, i.e., the velocity of the gases in the fluidized bed reactor in the absence of particulates. Generally, when the terminal settling velocity of a particle is less than that of the superficial velocity of the gases in the bed, then it usually will be entrained in the gases. For ore roasting or refining (including chlorination of titanium containing ore) , the particulate material which is entrained usually has a particle size of less than about 70 microns. For combustion of carbonaceous materials such as coal, the particulate material which becomes entrained also typically has a particle size of less than about 70 microns.
  • the source of the material which is susceptible to entrainment can be that generated by the degradation or attrition in the fluidized bed process of material having a particle size in excess of about 70 microns.
  • the material so generated will generally be entrained in the hot gases exiting the process and can be removed by a cyclone or other separator and recycled to the process.
  • the source of the material having a particle size of less than about 70 microns can be material having such particle size which is initially fed to the process.
  • Particulate limestone can also be included in the fluidized bed to control the emission of sulfur oxides and/or other pollutants.
  • the fluidized bed process for chlorinating titanium containing ore is known and is described, for example, in U.S. Patent 2,701,179 and in the article "Fluidized Bed Chlorination of Rutile", which is summarized in the Background of the Invention. Both such patent and article are hereby incorporated by reference.
  • Typical conditions for commercial fluidized beds for chlorinating titanium containing material are as follows: reaction temperature of about 900-1300'C, pressure of about 1.5-3 atmospheres, reactor size of about 6-25 feet in diameter with multiple chlorine jets in the base, reactor superficial velocity of about 0.5-1.5 feet per second, and a settled bed depth of about 6-25 feet.
  • the titanium containing material initially fed has a particle size of about 70-800 microns in diameter and the coke initially fed has a particle size of about 300-3000 microns in diameter.
  • the titanium containing material can be any suitable titanium-bearing source material such as titanium containing ores including rutile, ilmenite or anatase ore; beneficiaates thereof; titanium containing by-products or slags; and mixtures thereof.
  • the coke which is suitable for use in the fluidized bed process for chlorinating titanium containing material is any carbonaceous material which has been subjected to a coking process.
  • Preferred is coke or calcined coke which is derived from petroleum, or coal or mixtures of such cokes.
  • At least part of the coke and/or titanium containing material used in this invention should have a fine particle size, i.e. a diameter of less than about 70, more preferably, less than about 60, and most preferably less than about 50 microns.
  • the source of such fine particle coke and/or material can be that generated by the degradation or attrition in the process of titanium containing material and/or coke, having a particle size in excess of about 70 microns.
  • the fine particle coke and/or material so generated will tend to be entrained in the hot gases exiting the process, and can be removed by a cyclone or other separator and recycled to the process.
  • the source of the fine particle coke and/or material can be such fine particulate coke or material which is initially fed to the process.
  • the influence on pneumatic versus nonpnuematic feed of fine particle material in a fluidized bed simulated reactor was evaluated.
  • the simulated reactor was 3 feet in diameter by 23 feed high and had a settled bed height of 6 feet.
  • the particulate feed stream material was 97 weight percent silica sand (mean particle size of 250 microns in diameter) and 3 weight percent fluid cracking catalyst (mean particle size of 30 microns in diameter) .
  • Such particulate material was fed continuously at the rate of 500 pounds per hour through a one inch diameter nozzle located 2 feet up from the base of the simulated reactor.
  • sodium chloride tracer (having a mean particle size of 30 microns in diameter) was fed into the particulate feed stream over a 20-second period.
  • the runs made were for pneumatic and nonpneumatic feed for fluidized bed superficial velocities of 0.6, 0.75, 0.90 and 1.05 feet per second.
  • the influence of fine particulate material was determined by measuring the rate at which the sodium chloride tracer was entrained from the bed. This was done by collecting all entrained particulate material (i.e., contained in the air exiting the simulated reactor) with a high-efficiency cyclone and weighing and analyzing for the tracer over timed intervals. The results of these analyses are shown in the Table, which sets forth the entrainment times for cumulative percentages of sodium chloride for nonpneumatic feed and the pneumatic feed. The cumulative percentages were 5, 10, 15, 20 and 25 percent, measured at simulated reactor gas superficial velocities of 0.6, 0.75, 0.9 and 1.05 feet per second. The data show that the time required for sodium chloride entrainment for nonpneumatic feed was greater than that for the pneumatic feed in all cases. This means that the fine particles are retained in the fluidized bed for longer times with the nonpneumatic feed.

Landscapes

  • Devices And Processes Conducted In The Presence Of Fluids And Solid Particles (AREA)

Abstract

L'invention concerne un procédé à lit fluidisé utilisant un lit de particules fluidisées, où au moins certaines des particules sont susceptibles d'être entraînées par les gaz qui sortent du lit. Une amélioration visant à diminuer l'entraînement consiste à introduire les particules dans l'installation sensiblement en absence du gaz qui transporte les particules, en un ou en plusieurs points se trouvant en-dessous de la surface du lit fluidisé de particules.
EP94923148A 1994-04-04 1994-04-04 Procede a lit fluidise ameliore Ceased EP0754091A1 (fr)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US1994/003671 WO1995026809A1 (fr) 1992-09-30 1994-04-04 Procede a lit fluidise ameliore

Publications (1)

Publication Number Publication Date
EP0754091A1 true EP0754091A1 (fr) 1997-01-22

Family

ID=1340863

Family Applications (1)

Application Number Title Priority Date Filing Date
EP94923148A Ceased EP0754091A1 (fr) 1994-04-04 1994-04-04 Procede a lit fluidise ameliore

Country Status (1)

Country Link
EP (1) EP0754091A1 (fr)

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9526809A1 *

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Legal Events

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