CA2521982A1

CA2521982A1 - Apparatus and method for coal gasification

Info

Publication number: CA2521982A1
Application number: CA002521982A
Authority: CA
Inventors: Karel Vlok; Fredrico Van Zyl
Original assignee: COGAS, LLC
Current assignee: COGAS LLC
Priority date: 2004-11-17
Filing date: 2005-10-03
Publication date: 2006-05-17
Also published as: AU2005203534A1; US20060101715A1; CN1782037A; MXPA05008871A

Abstract

A process and apparatus for converting a coal into a substitute natural gas generates raw gas in a conventional coal gasification unit and passes at least a portion of the raw gas into a partial oxidation unit to convert the at least portion of the raw gas into a secondary raw synthesis gas substantially devoid of higher hydrocarbons. Optionally, the raw gas is quenched and only the resulting condensate is passed to the partial oxidation unit for conversion to the secondary raw synthesis gas.

Description

Attorney ~ket No. 2245-t~0a2 APPARATUS AND METHOD FC?R
C~~t_ GASIFIG~TIQN
BA~KGRt3Ul~ll~ OF THE INVENTION
[1~00~1The invention concerns an apparatus and process for converting coal into a substitute natural gas. More particularly, the invention concerns converting, via non-catalytic partial oxidation, liquid condensates Pram a primary gasification process into secondary synthesis gas, resulting in utilization of substantially all lay-product streams for production of additional raw gas, thereby minimizing undesirable effluent produced by the gasification process.
[Clt~l~~ Coal gasification technology is well known and has been in commercial use, for example, in South Africa for many years. The most comrnoniy employed coal gasifier is that developed by Irurgi k~vhle and I~ineraloeltechnik GmbH. The l..urgi process utilizes a fixed bed gasifier into which coal of a selected particle size is fed countercurrently to a stream of steam and oxygen.
[~~~D3~ Goal gasification processes are accompanied by the generation of by-products essentially comprised of oil, tar and phenolics. Disposition of this by-product presents significant environmental and economic problems.
[tf0~4Therefore, there is seen to be a need in the art for an apparatus and process which will utilize essentially all of the by-pr~l~t streams of a gasification process for production of further raw gas to maximize the synthesis gas produced by the gasificatit~n process.

Att~~ney Dt>cket No. 2245-t~.7~52 SUMMARY OF THEONVENTtON
[t~O] Accordingly, process for converting coal into a substitute natural gas begins by placing a charge of coat into a coal gasification unit and causing gasification of at least a portion crf the charge by exposing the charge to a gasifying agent and heat. Primary raw gas is recovered at an outlet of the coal gasification unit and at least a pardon of the primary raw gas is passed into a port-catalytic partial oxidation unit where a partial oxidation agent and the temperature is maintained to convert the at least portion of the primary raw gas Into a secondary raw synthesis gas substantially devoid of higher hydrocarbons.
~0001~] In another aspect of the invention, a process for converting coal into a substitute natural gas begins by placing a charge of coal into a coal gasification unit and causing gasification of at least a portion of the charge by exposing the charge to a gasifying agent and heat in the coal gasification unit.
Primary rave gay is ~ecavered at an outlet of the coal gasification unit and subjected to quenching to separate condensable hydrocarbon containing liquid therefrom.
The liquid is then subjected to a non-catalytic parCial oxidation in the presence of a partial oxidizing agent at a temperature sufificient to convert the liquid into a secondary raw synthesis gas substantially devoid of hydrocarbons other than carbon monoxide, carbon dioxide and methane.
[!gQ01] In still another aspect of the invention, apparatus for converting coal iryto substitute natural gas includes a plurality of coal gasiftcation units, each operable to cause c~asification of at least a portion of a charge of coal fed thereto Attorney Docket No. 2245-D~?~0~2 and to produce a primary raw gas at a gasifieatian unit output. A quenching system having an input coupled to each of the gasification unit outputs receives the primary raw gas therefrom and is operative to separate condensable hydrocarbons in liquid form from the primary rarrr gas, to deliver the liquid to a quenching system liquid output and t0 deliver cooled raw gay as the substitute natural gas to a quenching system gas output. A partial oxidation unit having an input coupled to the quenching system liquid output is operative to subject received liquid hydrocarbons t0 partial oxidation at a temperature sufficient to convert the liquid hydrocarbons into a seCOndary raw synthesis gas substantially devoid of hydrocarbons at a gas r~utput of the partial oxidation unit.
BRIEF DESCRIPTIt~I~ OF THE DRAWING
[Ot?01~~ The objects arrd features of the invention will became apparent from a reading of a detailed description, taken in conjunction with the drawing, in which:
jOQ(t] Figure 1 is a block diagram of a coal gasification system arranged in accordance with the principles of the invention;
[~01~~ Figure 2 is a block diagram showing a primary gasification unit and a partial oxidation unit coupled via an optional quenching system; and [t?01't~ Figure 3 is a block diagram c~f an exemplary gasification plant using a single partial oxidation unit with four primary coal gasification units and a mufti-stage quenching system, arranged in accordance with the principles of the invention.

Attorney Docket t~ia. X245-UC>Ut~52 DETAILED ~ESCRIPT1(~N
[00~12~ As used in this description, the term "higher hydroca~ans" refers to hydrocarbons having a composition GnH",, where n and m are integers and n is 2 or higher.
[tt'tWith refierence to I=ig. 1, a basic block diagram sl~ca~rving the optional arrangements of the invention is displayed. Primary gasifier 10~
directs raw gas at ifs output 11 ~i to either a quench and liquor separation unit 1 Q6 via path 11 UA
or via path 110B to a non-catalytic partial oxidizer unit 104. If path llt~B
is utilized, then the input to partial oxidizer 104 is basically in gaseous fiarm. If the quench and liquor separation unit 106 is used, then the input 116 to partial oxidizer unit 104 is in liquid form, being condensate generated by the cooling process taking place in unit 1 Ofi.
[Otll ~.It will be apparent to those skilled in the art, that only a portion of the raw gas 110 may be fed via optional path 1108 to the partial oxidizer unit 1 t14.
j~016] When the raw gas 110 is subjected to quenching via path 110A
prior to being fed to partial oxidizer it34, the resultant generated secondary synthesis gas at output 114 would then be routed' via path 114A back to an input ofi quenching system 1(36 for fiurther cooling. t~therwise, if quenching is not perfiormed prior to partial oxidation, the secondary raw synthesis gas at 114 may be directed to system output 11 ~ via path 114B.
[00't~6~ What differentiates the instant invention firam known gasificatian processes is the inclusion of a non-catalytic partial oxidation unit 10~..
Unit 104 A~ffJrll~~ DC~~Cet ~0. 22~~-~2 produces additic~nai raw synthesis gas from the tars and oils present in raw gas stream 110 in gaseous form or at input 116 in liquid form. Hence, aI6 by-producf streams are utilized for the production of raw gas, minimizing the effluent produced from the process.
[~0~ 7~ Partial oxidizer 1 Q4 converts higher hydrocarbons into carbon monoxide and hydrogen and some inadvertent carbon diaxide. This is accomplished at a very high temperature using direct contact with a hot flame burner in a substoichiometric oxygen atmosphere which prevents a vast majority of the generated carbon mont~xide from converting to carbon dioxide.
[0018, C~irect feed of raw gas 11fl via path llflB makes sense in those applications where methane is not desired in the final substitute natural gas end product. However, when using the quench and liquor separation system 1 f~~, only the derived liquor is passed to the partial oxidizer and not the raw gas exiting at path 11 t~. In this type of application, methane is usually a desirable component of the raw substitute gas at system output 1' 12 and will be passed directly thereto via system 1 U6 without going to partial oxidizer 104. , [t3t~19~ Wifih reference to Fig. 2, a basic arrangement of the primary gasifier, nan-catalytic partial oxidizer and an optianal quenching system 212 are depicted.
[~fl2~#~ A coal lock hopper 2~4 is a pressure vessel and allows the gasafier 2~6 to be fed in a batch operation. Coa! lock 204 has a bottom and top closure which are operated hydraulically. Goal flows through a disposal chute 2iJ2 into the coal lock 2fi34 when coal lock 244 is at atmospheric pressure (with the bottom cone Attflmey C?flcket ~Ifl. 2245-D~~052 enclosed and the tap cane open). After coal lack 204 ifull, the tap cone is closed and coal lack 2g4 is pressurized with a raw gas taken downstream of the, gas cooling unit. Final pressurizing is dare through a direct Line Pram the tap section of the gasifier 2g6 to the coal loch 204.
[pp2l~ When coal lath 2p4 is at the gasifier pressure, a bottom cone opens and coal begins flay#~in g into gesifier 20~ uia a distri~utar 208, preferably comprised of a cyclone skirt. When coal lock U4 is empty the bottom cone closes and is ready for r~cyclinc~.
[~U22] Gasifier 2018 is a double-walled pressure vessel. High pressure boiler feed water is kept i~ the jacket farmed by the double walls so as to limit jacket and gasifier wall temperatures. High pressure boiler feed water is circulated through the jacket by dawncarne~s. During operation, a considerable amount of heat is transferred from the fuel bed to the jacket. The jacket steam is added to the high pressure steam and the total steam is mixed with oxygen at a ratio of approximately U.4 pounds of steam per SGF oxygen. This gasificatian agent is routed via a rotating grate 2g9 into the gasifier fuel beck. Gansequently, grate 2t~9 is cooled by the gasification agent. Grate 2C~9 is papered by alternating current drives and serves to first, enable distribution of the gasificatian agent an the cross section of gasifier 2~8 via gasificatian agent ring slats. The distribution is completed in the ash bed.
[0~2~] Secondly, grate 2~6 carries ash towards the ash lock hopper 210, helps disintegrate ash aglamerates and grinds ash lumps to a maximum size to avail blockages of the ash lack canes. Finally, grate 209 heaps the fuel bed in oration.

AttdfrsEy C30e~et h~4. 22~~-~~U052 [U~4] Grate 2(79 is automatically speed controlled by the oxygen flow to adapt the ash turn out to the ash production. Manual corrections of the grate speed are also possible. The turn-out capacity of grate 2(79 is determined by the number of plows installed underneath the grate and the speed of the grate 209. Crate 209 runs continuously and is only stopped for chart periods when the ash lack 21 U
cycle begins.
[gt725~ The gasificatian agent, far example, a mixture of oxygen at conduit 233 and steam at conduit 23~, is passed through the following reaction zones in vessel 2g6.
~~~6~ In the ash bed 206A, the gasification agent is superheated by ash leaving combustion zone 20613 at a temperature of approximately 273t?°F. lender the assumption that a sufficient ash bed 206A is established, the ash is coated dawn to a temperature higher than that of the gasification agent while the gasification agent is heated up gentry into vessel 206.
[U627j In a combustion zone 2068, carbon and oxygen are converted to carbon dioxide and heat. The temperatures of the gaseous flaw going upwards and the ash which has a carbon content of approximately 2°la) sinking downwards, increases to nearly 27f33°1~.
[OtI~B~ The gas streaming upwards frarn the combustion zone 268 consists mainly of carbon dioxide and steam and reacts in the gasificatian zone 2060 at an average temperature of approximately 15607°F. The dominating reaction in gasification zone 2g60 is the conversion of carbon and water into carbon Attorney Docket No. 2245-OOflt152 monoxide, hydrogen and heat. A methanation reaction has a minor influence on the composition of the gas leaving gasif(cation zone 2U6C.
~g029] In a carbonization zone 2(~&D, volatiies in the coal are expelled.
The carbonization reaction is heat consuming. Consequently, the gasification raw gas streaming upwards from the asif(cation zone 2Q~~ must heat up the downflowing coai and de(iver heat for carbonization. Additionally, in carbonization zone 2ga, recycled dusty tar is cracked to oil and coke.
~00~~ Ash lock 210 is pressure vessel having hydraulically operated bottom and flop closures, Ash lock 210 serves to remove ash from gasifier 2Q6 and is operated in cycles, each having the following steps.
[gg~'1 ] The continuously running grate 209 turns the ash out of gasifier 2f~6 through hydraulically actuated top cone into ash lock 21 ~ with its bottom cone closed at gasifier pressure. As soon as ash lock 2~0 (s full, grate 209 is stopped.
After the ash lock top cone is shut and sealed, grate 2g~ is restarted.
jt~0~2] Ash lock 210 is then lowered to atmospheric pressure, the bottom cone of the ash lock 210 is Opened and ash flows out of ash lock ~1g into a sluice-way 25where it is quenched and hydraulically carried away to an ash plant.
[t1Q3a Flaw gas generated by gas(fier unit 2Uf> ex(ts at conduit 235 and is directed -to optional quenching system 2t2 whose o~rtput X37 contains liquid candensates from the quenching process. Alternatively, in a direct feed system quenching system X12 is not utilized and raw gas is fed to partial oxidizer unit 266..
[004 In the optional scrubbing/cooling apparatus 212, excess water, certain condensable hydrocarbons and a small quantity of solids are separated from Att~!rney ar.,cket Na. 2245-OtH7052 the raw gas stream in conduit 235. The liquid stream in conduit X37 serves as a feedstack to the partial oxidation unit 2~ 6.
[C11751 In the non-catalytic partial oxidation unit 216 the feedstock reacts with oxygen in the presence of steam as ~ moderator to raw synthesis gas, Hot raw gas is cooled by direct injection of water in quench pipe X18 and quench uessel 2~t~.
A separation vessel carries away slag at its output 249.
jl~Ct36~ flan-catalytic partial oxidation unit 216 partially oxidizes the heavy fractions at a temperature of approximately 25011°F. and at a pressure of about 435 psig. C7xygen at conduit 239 and steam at conduit X41 are added to the incoming feedstock in conduit 237 via a partial oxidation burner unit 214.
Burner 21 ~ ensures intensive mixing of the feed, which is necessary far a high conversion into the desired raw synthesis gas.
[4~7~ In ors injection zone of reactor ~~6, the feed is partly oxidized in the flame of burner 214. The gross reactions in unit 216 essentially convert higher hydrocarl3ons to carbon monoxide and hydrogen in two phases.
[U038~ lr~ a first heating and cracking phase, feed and oxygen leave burner 214 at respective preheating temperatures. Prior to actual combustion, the reactants are further heated by the heat reflected from the flame and glowing brickwork of vessel 216f the high hydrocarbons of the feed crack into radicals.
[Otl~9~ Next, in a reaction phase, on reaching ignition temperature, a portion of the hydrocarbons react with the oxygen in an exothermic reaction forming carbon dioxide and water. Practically, all of the oxygen available is consumed in this Attorney Doei~et No. 2245-OOOt352 phase. The non-oxidized portion of the hydrocarbons reacts with steam and the reaction products are mainly carbon monoxide and hydrogen.
[004g~ ~s mentioned previously, feedstock, oxygen and steam enter reactor 216 via burner 214, which is mounted at a top portion of reactor 216.
~umer 214 preferably has a four-nozzle design with a central dummy tube which takes up the start-up burner. At start-up, the central tube bears the ignition and start-up burner, which is equipped with a flame control sensor. For heating up reactor 216, plant air and fuel gas are fed via the start-up burner at conduit 243. At higher temperatures, when higher heating duties are required, air and fuel gas are also fed via four lances of the burner. At a reactor temperature well above the self-ignition temperature of the fuel gas, normally at about 1470°F, the start-up burner is removed and replaced by a steam-purged dummy.- wring the final heating up to approximately 2260°F, fuel gas and air are fed through the four burner nozzles.
[~~41To maximize the volumetric capacity of partial oxidation reactor 216, fine coal may optionally be added to the liquid feedstock via lance burner 2i 4.
[~t14~~ burner 21 ~4 is cooled with cooling water and by the media passing therethrough. The reactor outlet to quench pipe 218 is also cooled in order to minimize refractory wear at this point.
~~t143~ The conversion of hydrocarbons by partial oxidation occurs in refractory lined reactor 216. The refractory material is selected according to ash load and ash properties of the feed stock. The ash must melt at the reactor operating temperature to guarantee free flow of molten ash from reactor 216 to the quench vessel 226 and tc~ avoid blockage of reactor 216 and quench pipe 218.

A'~ftSrrlG'Y CJOG~G~~ CIO. ~~45~~2 [Ott~~~ Hot raw secondary synthesis gas from reactor 2U6 is routed via quench pipe 218 to quench vessel 22Q. The secondary synthesis gas is instantar~eouly cooled from about 247°F to an equilibrium temperature of approximately 4t~~F by water injection. i_iquid slag flowing with the gas solidifies into particles. The particles could be leached in either an acid or alkali medium.
Gas is separated from surplus guench water and slag particles below quench pipe 21 ~ and the quench vessel 220. Gas is withdrawn through a separate nozzle and the slag water collected is routed via level control to slag separator 222.
The slag is separated from the soot water leaving the quench vessel via conduit 25~ in a slag-like system having slag separation vessel 222. The heavy slag particles settle from the soot water in the slag separation vessel 222 and are collected in a bottom cone for discharge via conduit 243.
i0tt45~ Collected soot and ash may be mixed info a soot slurry and sent to a metal ash recovery system where the soot slurry is flashed to atmospheric pressure in a slurry tank. The slurry is filtered resulting in a filter cake and clear water usable for quenching and scrubbing operations.
[0~4~~ Fig. 3 presents a block diagram of a gasification plant using a single non~cata,lytic partial oxidation unit with four primary coal gasification units.
This type of arrangement takes advantage of the fact that only the pyroiysis products from the ra~v gas generated from the primary gasification units are being partially oxidized. Hence, one needs only the capacity of a single partial oxidation unit for several pup to five} primary fixed bed degasifier units, ~1~8i'n~~ ~G~CBt N0. '~c4~-[0Q47] As seen from Fig. 3, sources of coal to be gasified 361 a-d are respectively fed to a disposal chute 3ia0 of each of four fixed hed gasifier units 802a-302d. From input chute 350 the coal is passed into input lock hoper 352 which is coupled to the processing vessel. Near the tap at the inlet to the processing vessel a cyclone skirt 354 assists in distributing the coal charge which flaws dawnwardly through the vessel countercurrent to the flaw of the gasification agent supplied to respective inputs of vessels 3f?2a-d from oxygen source 3f?5 and steam source 3tt7. A rotating grate 356 distributes the gasificatian agent and processes ash within the system as described above with respect to Fig. 2.
~~Q~B~ Raw gas from the process is collected at outputs 303a-d which are coupled tr~gether at conduit 313 as a gaseous input to quenching system 3U6.
As mentioned above, the gasification agent is a mixture of oxygen and steam.
[0049 Quenching system 33G is comprised of a serial connection of five heat exchange units ~i~8, 31t~, 312, 314 and 316. The initial stages 308 and receive a relatively high temperature gas input and generate high pressure steam from the heat exchange process. Condensates from 308 and 31Q exit the units at liquid outputs 30ga and 309b and are comprised primarily of thicker tars and ash.
[I~il66Z Subsequent stages of the quenching system 306 result in generation of medium pressure steam and the condensation of lighter oils. As seen from Fig. 3, the gas output of each stage is connected to the gas input of a succeeding stage up until the final stage 316 whose output X11 farms the primary system output carrying cooled raw substitute natural gas.

Atfarn~y Docket No. 2245-00052 [005't] Hence, gaseous output 317 is coupled to an input of heat exchanger 31 ~ whose gaseous output 319 is in turn coupled to the input of heat exchanger 312. Gaseous output 321 of unit 312 is connected to the input of unit 313 and output 3~3 of unit 314 is coupled to an input of the final stage heat exchanger unit 1 ~.
jt?052The liquid outputs 30a-a are coupled together at one primary quenching system liquid output 3C?9.
~~t13~ (liquid hydrocarbons in conduit 309 are coupled to an input of non-catalytic partial oxidation unit 30~. Oxygen from source 365. and steam from source 307 are additionally coupled to the input of unit 3Qand the secondary raw synthesis gas comprised mostly of hydrogen and carbon monoxide exits unit 304 via conduit 315 and directed back to an input 313 of the quenching system 3f~f for further cooling.
~0~4~ Plant Output 311 therefore contains quenched raw substitute natural gas at approximately 9~°I= which is essentially free of the pyrolysi's products generated in the primary gasifiers 3f72a-d.
E?CA1VIP~E
[O~tiS~ Unreactive coal ~i.e., coal containing more than about 3t?°l~
non-combust'sble cc~ntarninants~ having ash content up to about 50 wt.l°l° is fed to a primary gasifier arranged as shown in Pigs. ~ or 3 and a primary raw gas is produced at the output of the primary gasifier having a composition by volume percent of ~8,°l° carbon dioxide, t3.65°~'°
hydrogen sulfide, 0.69°f° higher Attamey Docket ~Jo. 2245-Clf3~3CZ52 hydrocarbons, ~2.6fi°lp carbon monoxide, 38,51 °lQ hydrogen, 9.5°la methane and .39°I~ nitrogen. Raw gas as produced above is then directed to a quenching system wherein the products of pyroiysis and other figuids are condensed out of the gas stream and passed to the input of a non-catalytic partial oxidation unit running at a reaction temperature of about 2578°F. The raw gas from the gasifier is then reformed in the partial oxidation unit, crackeei and hydrolysed, and the established process in c~asificatior3 reaction conditions result in the following typical gas compCanents at the output of the partial oxidation unit expressed by volume percent:
1.9°!~ carbon dioxide, U.O~°lo hydrogen sulfide, ~% carbon monoxide, 45.1°f~
hydrogen, ~.~°~ methane and ~.~2°l~ nitrogen.
[~~56] The application has been described with respect to a specific embodiment for the sake of example only. The scope and spirit of the invention are to be determined from appropriately interpreted claims,

Claims

1. A process for converting coal into a substitute natural gas comprising:
placing a charge of coal into a coal gasification unit;
causing gasification of at least a portion of the charge by exposing the charge to a gasifying agent and heat in the coal gasification unit;
recovering primary raw gas at an outlet of the coal gasification unit;
and passing at least a portion of the primary raw gas into a non-catalytic partial oxidation unit, adding a partial oxidation agent, and maintaining a temperature effective to convert the at least a portion of the primary raw gas into a secondary raw synthesis gas substantially devoid of higher hydrocarbons.

2. The process of claim 1 further comprising adding the secondary raw synthesis gas to the primary raw gas.

3. The process of claim 1 wherein the at least a portion of the primary raw gas is subjected to quenching to separate condensable hydrocarbons therefrom for transmittal to a non-catalytic partial oxidation unit to convert the condensable hydrocarbons into a secondary raw synthesis gas substantially devoid of higher hydrocarbons.

4. The process of claim 1 wherein the partial oxidation agent comprises a mixture of oxygen-containing gas and steam.

5. The process of claim 1 wherein substantially all higher hydrocarbons present in the at least a portion of the primary raw gas are cracked and hydrolized in the non-catalytic partial oxidation unit.

6. The process of claim 3 wherein substantially all higher hydrocarbons present in the condensable liquids separated from the primary raw gas are cracked and hydrolized in the non-catalytic partial oxidation unit.

7. The process of claim 1 wherein substantially all of the primary raw gas is passed into the non-catalytic partial oxidation unit.

8. The process of claim 3 wherein substantially all of the primary raw gas is subjected to quenching prior to transmittal of separated condensable hydrocarbons to the non-catalytic partial oxidation unit.

9. A process for converting coal into a substitute natural gas comprising:
placing a charge of coal into a coal gasification unit;
causing gasification of at least a portion of the charge by exposing the charge to a gasifying agent and heat in the coal gasification unit;
recovering primary raw gas at an outlet of the coal gasification unit;

subjecting the primary raw gas to quenching to separate condensable hydrocarbon containing liquid therefrom; and subjecting the liquid to non-catalytic partial oxidation in the presence of a partial oxidizing agent at a temperature sufficient to convert the liquid into a secondary raw synthesis gas substantially devoid of hydrocarbons other than carbon monoxide, carbon dioxide and methane.

10. The process of claim 9 further comprising adding the secondary raw synthesis gas to the primary rave gas.

11. The process of claim 9 wherein the partial oxidizing agent comprises oxygen and steam.

12. The process of claim 9 wherein the temperature to which the liquid is subjected is sufficient to crack and hydrolize substantially all higher hydrocarbons present in the liquid.

13. The process of claim 12 wherein the liquid is subjected to partial oxidation at a temperature of from about 237°F to about 2782°F.

14. The process of claim 12 wherein the liquid is subjected to partial oxidation at a temperature of about 2578°F and at a pressure of about 400 psig.

15. The process of claim 9 wherein the charge is composed of coal having at least about 30% by weight non-combustible contaminants.

16. The process of claim 15 wherein the primary raw gas comprises about 28% by volume carbon dioxide less than about 1% by volume hydrocarbons, about 23% by volume carbon monoxide, about 38.5% by volume hydrogen, and about 9.5% by volume methane.

17. The process of claim 15 wherein the secondary raw synthesis gas comprises less than about 2% by volume carbon dioxide, greater than about 50%
by volume carbon monoxide and greater than about 45% by volume hydrogen.

18. The process of claim 9 wherein the charge is comprised of coal having ash and non-combustible contaminants of up to about 50% by weight.

19. The process of claim 9 wherein the charge is comprised of coal having an oxygen content of up to about 3% by weight.

20. Apparatus for converting coal into substitute natural gas comprising;
a plurality of coal gasification units, each operable to cause gasification of at least a portion of a charge of coal fed thereto and to produce a primary raw gas at a gasification unit output;

a quenching system having an input coupled to each of the gasification unit outputs for receipt of primary raw gas and operative to separate condensable hydrocarbons in liquid form from the primary raw gas, to deliver the liquid to a quenching system liquid output and to deliver cooled raw gas as the substitute natural gas to a quenching system gas output; and a partial oxidation unit having an input coupled to the quenching system liquid output and operative to subject received liquid hydrocarbons to partial oxidation and a temperature sufficient to convert the liquid hydrocarbons into a secondary raw synthesis gas substantially devoid of higher hydrocarbons at a gas output of the partial oxidation unit.

21. The apparatus of claim 20 wherein the gas output of the partial oxidation unit is coupled to the quenching system input.

22. The apparatus of claim 20 wherein each gasification unit comprises a fined bed gasifier having an input lock hopper having an input coupled for receipt of a coal charge and an output;
a pressure vessel having a coal input coupled for receipt of coal from the input lock hopper output, a coal distributing cyclone skirt in the vessel coupled to the coal input, and a rotating grate positioned in a combustion zone of the vessel for combusting a portion of the coal and distributing ash towards a solids output of the vessel, and a gasification input for receipt of a gasifying agent coupled to the rotating grate; and an ash lock hopper having an input coupled to the solids output of the vessel.

23. The apparatus of claim 20 wherein the quenching system further comprises:
a plurality of serially connected heat exchanger units, each having an input for receiving an input gas, a condensate output for presenting liquid condensed from the input gas, and a gas output presenting gas cooled by the heat exchanger unit, wherein the condensate outputs of the plurality of heat exchanger units are coupled together to form the quenching system liquid output, and the gas output of each heat exchanger unit is coupled to the input for receiving gas of a succeeding heat exchanger unit, except for the last heat exchanger unit in the serial connection, whose gas output comprises the quenching system gas output.