CA1199284A

CA1199284A - High temperature cyclone separator for gasification system

Info

Publication number: CA1199284A
Application number: CA000427784A
Authority: CA
Inventors: Ram G. Seth
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1982-05-12
Filing date: 1983-05-10
Publication date: 1986-01-14
Also published as: EP0094098A1; ES522283A0; IN156704B; ES8404203A1; AU1397783A; ZA833021B; KR840004873A; JPS58205555A

Abstract

ABSTRACT OF THE DISCLOSURE
This invention discloses a cyclone separator for use in a carbonaceous material gasification system. The invention comprises a cyclone separator having a porous inner shell cooled by transpiration through the inner shell. The gas moves through the porous inner shell either through pores or through holes which are fabricated in the inner shell.

Description

50, 17 HIGH TEMPERATURE: CYCLONE
SEPARATOR FOR GAS IFI C:ATION ~ Y ~

BACKGROUND OF THE INVENTION
Field o the Invention:
This inv~lltion relates to gasification of c:ar~
bonaceous materi~ls, and mora particularly to apparatus 5 for removaL of entrained particl~s from the product gas of 1uidized bed gasification reactors.
D~scription of the Prior Art:
In r~actors for the gasification of carbonacPous materials, such as coal, a conlbustible product gas is 10 produced, as well as solid waste proclucts such as a~glom-erated ash. In the Proc~ss Development Unit (PDU) fluid-ized bed gasification reac:tor bein<3 operated for l:he United States Governm~nt, particulate coal is i~jected through one of a number of concentric tubes e3ctian~i ng lS upwardly into the center of a vertical bed~containing pressure vessel. Fluidization occurs in the upper sec-tions .
In th~ Pl:3U fluidizecl bed gasificat:ion reactor, the product gas from gasi:Eied coal contairls a significant 20 amount of entraill~d particles, a lar~e percentage of which are molten at the gasifier exit temperatures o~ between ~700~F and 1900F, typically approximately 1800F. These particles, which are of varying chemical compo~ition~ will stick both to metalliG and non~metallic sur:Eaces r~gard-~
25 less of the angle of incidence of the gas flow to the

2 50, 1 72 surace, as the gas ~lows rom the gasifier exit. It has b~en demonstrated that eventually flow passages will plug almost c:losed with solidii~ied material, an~ the efficiency O:e the cyclone separator will fall correspondiIlgly.
Prese}lt information in technical papers and from experimental data obtainecl from PDtJ c~p~rations indicate that deposition of ~hese mol~en particles as th~y exit from the gasifier will not occur if either of the two following conditions are maintain~d:
lQ (a) Th-o gas temperature does not exceed. 1300F.
(b) The surîaces through which the gas passes or on whic:h it is allowed to impact are metallic and are maintained at less tharl 500F at the gas/metal interfac~.
Condition ( a~ has been achiev~d by water spray quench, buk this method i~ not energy efIicient or cer-tain operations.
Condition (b) has been achieved by water cooling OI a~ uniIlsulated metal plate, but erosiorl of the plate has been significant and the pr~ssure differential across th~3 plate necessitat~s ASME Boiler and Pressure Vessel Code Section VIII code stamping of th~ hardw~re.
It is thus desirable to provide gasifier systems with cyclone ~eparators which will not have significa~t entrained particle deposition. It is also desirable to provide gasifier systems with cyclone separators which will not require a reduction in the raw gas temperature in order to continue to operate over long periods without fre~uant repair or maintenance.
BRIEF SUMMARY OF T~E INVENTION
This inv~ntion di~clos~s a cyclone separator for us~ in a carbonaceous material gasification system. The in~ention comprises a cyclon~ separator having a porous inner shell cooled by transpiration through the inner shell. The gas moves through the porous inner shell either through pores or through holes which are f~bri~
cated in the inn~r sh~ll.

3 ~0,172 BRIEF DESCRIP~ION OF THE DRAWINGS
~ 'he advantages, nature arld additional features of -the invention will become more apparent from the o]-lowing description, ~aken in connection with the accom-panying drawing, in which:
Figure 1 is a cross sectional view of a cyclone separator in accordance with the invention.
Figure 2 is a plan view taken along the line 2-2 o~ Figure 1.
Figure 3 is a partial cross-sectional view of a wall of a cyclone separator in accordance with the invention.
Figure 4 is a partial cross-sectional view of a wall of a cyclone separator in accordance with the invention.
Figures 3 and 4 show in cross-section wall sections of the cyclone.
DESCRIPTION OE THE PREFERRED EMBODIMENTS
Referring now to Figures 1 and 2I there is shown a cyclone separator 20 in accordance with the invention.
The cyclone separator ~0 comprises an outer shell 22, a porous inner shell 24 disposed within the outer shell 22, a product gas inlet 26, tangentially disposed through the outer shell 22 and the inner shell 24, a product gas outlet 28 disposed through the outer shell 22 and the inner shell 24, a~ the top of the cyclone separator 20, a particle outlet 30 disposed through the outer shell 22 and the inner shell 24, at the bottom of the cyclone separator 20 and a cooling gas inlet 32 disposed through the outer shell 22. A cavity 3~ is formed be~ween the inner shell 24 and the outPr shell 22, and an interior plenum 36 is formed inside the inner shell 24. The porous inner shell 24 can be made of a corrosion resistant material such as Inconel or a refractory ceramic. The porous quality derives from the ability of a gas to move through the material. One embodiment may be an inherently porous material such as refractory ceramic, while another may be a metal with a plurality of holes for passage of the gas throu~h the metal.

.,.~

3~
3cl 50,172 The cyclone separator 2() operates as follows. A
gas containi.ng entrained particles, such as the product gas from a carbonaceous ma-terial gasifi2r system which contains molten and solid entrained particles, enters the interior plenum 36 tangentially through the product gas inlet 26. As the gas spins around the interior plenum 36, h`
'. ,., ~

p~

4 50,172 the entralned particles impinge against the inner shell 7.4. E~entually the entrained particles' velocity falls and the particles ~all to the bottom of the interior plenum 36, where they are di.schax~ed through the particle outlet 30.
Duxing operation, a cooliny gas, at a pressure greater (typically 1 psi t:o 15 psi greater) than the pressure of the product ga~, enters the cavity 34 through the coolin~ gas inlet 32. This gas moves through the porou~ inner shell 24 by transpiration through pore~ or a plurality Qf fabricated small holes which may be direcked generally downward to the center of the plenum 36 and distributed throughout the inner shelL 24. The tempera-ture of the cooling gas may be between 75F and 150F and ~typically approximately 100F, and this gas will cool the inner shell 24 to a temperature of about 400~F.
The product gas from which a quantity of en-trained particles has been removed exits the interior plenum 36 through the raw gas outlet 28.
Looking now to Figures 3 and 4, transpiration cooling involves the passage of a fluid coolant 40 through a material, by either th~ u~e in the porous inner shelL 24 o numerous holes 42 or o a material with numerous pores 44. The holes 42 or pores 44 provide a very high ratio of heat transfer area to coolant flow rate. SomP of the benefits resulting rom the use of transpiration cooling are that 1) entrained particle deposition on the porous inner ~hell 24 of the cyclone separator 20 is reduced, 2~
the temperature of th~ product gas is not significantly affected and 3) the thicknass of the porous inner ~hell 24 may be reduced.
~h~ use of transpiration cooli~g will allow ~ha porous i~nar shell 24 to be at or near 400F. As a result, very little depo~ition o~ paxticl~s will occur.
Because of the intimate contact o the fluid coola~t 40 wi~h the porou6 innar sh~ll 24, a small volum~
of fluid coolant 40 is required to achieve the dasired 3~

5 50, 17~
cooling e~fect. Thus th~ te!mperature o the product gas is not significantly e~fected since the addition o a large volume of coolant gas i5 not necessary.
Since the porous inner shell ~4 is continuously cooled, it i5 not subjected to extreme th~rmal stresses and can be made thirmer than withollt t:he c :701ing. This reduce the cost and complexity of fabrication, repair or replacement of the porous inner shell 24.
The speci~ics of hole size and hole surface density ~number of holes per unit surface area of the inner shell 24), or alternatively of material porosity, must be l~ased s:n the exact cooling characteristics re-quired. Ea~tors such as cyclone separator 20 height and diam ter, product gas temperature and particl loading, fluid coolant 40 t~mperature and flow ~olume will 211 efect the amount of coolirlg capacity required. ~is in turn will effect the amount of heat transfer area on whic the hole sizing and hole surface density, or material porosity is based.
In the preferred embodiment the fluid coolant 40 used will be product gas which has been processed by 5001ing and removal OI substantially all l:h~ entrained particles. The aclvantage of this method is that there is no chemical change in the product exiting the cyclone separator 20 due to the addition o~ a cooling gas o another chemical composition.

Claims

I claim:
l. A process for treating a product gas dis-charged from a carbonaceous material gasification reactor, said product gas comprising entrained molten particles, said process comprising the steps of:
a) discharging said product gas from said reactor at a temperature of between 1700° and 1900°F;
b) flowing said gas tangentially into an interior plenum of a cyclone separator, said separator comprising an outer shell, an inner shell, and a cavity therebetween, and said inner shell further defining said interior plenum within said inner shell;
c) discharging said product gas from said cyclone;
d) inletting a cooling gas into said cavity from outside said cyclone separator, said cooling gas being at a higher pressure than said product gas;
e) transpiring said cooling gas through said inner shell to said interior plenum;
f) solidifying said molten particles by contact of said molten particles with said transpired cooling gas and said inner shell;
g) discharging said solidified particles from said cyclone separator.
2. The process according to claim 1 wherein said cooling gas comprises said product gas.
3. The process according to claim 1 wherein the pressure of said cooling gas exceeds the pressure of said pro-duct gas by between 1 psi to 15 psi.
4. The process according to claim 1 wherein the temperature of said cooling gas is between 75°F and 150°F.
5. The process according to claim 4 wherein the temperature of said cooling gas is approximately 100°F.
6. A process for reducing deposition of entrained particles in a cyclone separator wherein said cyclone separator treats a product gas discharged from a carbonaceous material gasification reactor, said product gas comprising said en-trained molten particles, said process comprising the steps of:
a) discharging said product gas from said reactor at a temperature of between 1700° and l900"F, b) flowing said product gas tangentially into an interior plenum formed by a wall of said cyclone separator;
c) cooling said wall to a temperature of about 400°F by transpiring a cooling gas into said plenum through said wall, said cooling gas being at a temperature of between 75° and 150°F;
d) solidifying said molten particles by contact of said particles with said transpired cooling gas;
e) discharging said product gas from said separator;
f) discharging said particles from said separator.
7. The process according to claim 6 wherein said step b) further comprises flowing said product gas tangentially into an interior plenum formed by a porous refractory ceramic wall of said cyclone separator.