CA1108857A

CA1108857A - Coal gasification system

Info

Publication number: CA1108857A
Application number: CA303,856A
Authority: CA
Inventors: Robert A. Mccallister
Original assignee: Foster Wheeler Energy Corp
Current assignee: Foster Wheeler Energy Corp
Priority date: 1977-07-11
Filing date: 1978-05-23
Publication date: 1981-09-15
Also published as: FR2397451A1; ES470592A1; JPS5417901A; GB1598178A; IT7824090A0; IT1095180B; JPS6032671B2

Abstract

COAL GASIFICATION SYSTEM
ABSTRACT
A coal gasification system is provided for produc-ing a product gas. An oxygen containing gas is preheated in a combustion chamber before introducing the oxygen contain-ing gas to the gasifier.

Description

COAL GASIFICATION SYSTEM
BACKGROUND OF THE IN~IENTION
In view of the shortages of natural gas and petroleum in recent times there has developed considerable interest in the use of coal as a source of energy. Typically coal ls burned in various devices to generate hot gases which are later used to produce electrical energy.
A specific illustration of the use of coal is use in a gas turbine. Coal is gasified with an oxygen containing gas such as air, the resultant is purlfied, and then burned to yield hot gases which power a ~as turbine. The gas turbine can be used to generate electric power, and the turbine exhaust gases can also be used to generate high pressure steam which then would be used to generate electric power.
The temperature of the OXyCJen introduced to the gasi-fier is important since higher temperatures yield a more effi-cient gasifier operation. The oxygen can be preheated by using conventional equipment to about 800F. without encounterlng any unusual material problems. However, preheating above 1000F.
would require special equipment.
The instant invention provides a system and process for preheating oxygen to temperatures above l000~F. through the use of conventional components.
SUMMARY OF THE INvENrrIoN
In accordance with an illustrative embodiment demon-strating features and advantayes of the present invention a coal gasification system is provided for producing a product gas. The system includes a coal gasifier, means for introduc-ing coal feedstock to the gasifier, means for introducing an 3Q oxygen containing gas to the gasifier, and means for pre-heating the oxygen eontaining gas before in-troducing it to the gasifier. The preheating means includes a combustion chamber ln which a portion of the oxygen combusts with a fuel thereby heating the remaining oxygen.
More partieularly, one broad aspect of the lnvention comprehends a eoal gasifieation process for manufaeturing low BTU gas which comprises the steps of passing a stream of air to a first compressor for compression therein and after the compression, passing the stream of air -to a combustion chamber. The process further includes passing a stream of fuel to the combustion ehamber and eombusting the fuel wi-th a portion of the oxygen eontained in the stream of air wi-thin the eombustion chamber, thereby raising the temperature of the remaining portion of the air, inelud:Lng the remaining porti.on of oxygen eontained in the stream of air. The remaining portion of air including the remainincJ portion of oxygen is passed at a raised temperature to a gasifier, and a eoal feedstock is introdueed to the gasifier, the eoal feedstock being reaeted with the remaining portion of oxygen at a raised temperature within the gasiEier -to produce a low BTU produet c3as.

r~7 BRIEF DESCRIPTION OF T~IE DRAWING
The above brief description, as well as further objects, features~ and advantages of the present invention will be more fully appreciated by reference to the following detailed description of a presently preferred but nonetheless illustrative embodiment in accordance with the present inven- -tion, when taken in connection with the accompanying drawing wherein the Figure is a schematic representation of a coa:L

gasification system incorporating the present inven~ion, and showing the preheating means of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The drawing shows a schematic arrancJement of a coal gasiEication system utilizing the instant invention in combina~
tion with a gas turbine. It should however be understood that the instant invention can be used in a coal gasification system in combination with various other devices which use the pro-duct gas produced by a gasification system, for example, steam generators which use the product gas as a fuel for producing heat from combustion~
~ coal gasifier 10 receives coal feeds-tock through line 12 and air through line 14. The gasifier is o~ a known design and produces a product gas known as low BTU gas. The low BTU gas contains among o-ther components nitrogen, carbon monox-ide and hydrogen.

~ r~J

Gasifier 10 product gas is passed through line 16 to heat recovery and purification station 18. At station 18 the heated product gas may be passed in heat exchange relation-ship with another fluid for recovery of heat generated during gasification. Also, the product gas is purified at 18 in order to pass on a clean product gas for use as a fuel else- ~
where.
Part of the product gas is passed through branch line 22 to compressor 24. The remainder of the product gas is passed through line 26 to gas turbine 28. Gas turbine 28 has a combustion section 30 wherein the product gas is combined with air introduced from compressor section 32 and combusted there-in. The hot combustion gas products are passed via 34 to turbine section 26. Thereafter the product gases are exhausted through line 38. It is to be understood that although not shown the exhaust gases could be used elsewhere, such as in a steam gen-erator to produce steam, and need not be exhausted to the am-bient air.
That portion of the product gas passed through line 22 is compressed in compressor 24 and then passed to combus-tion chamber 40 through line 41 as a fuel gas or partial combus-tion in chamber 40. It is to be understood that the fuel supplied to chamber 40 need not be some of the product gas pro-duced in the gasification system, but could be provided from some other source. It should also be understood that while the fuel is compressed before introduction to chamber 40 in the preferred embodiment, compression of the fuel is not always requlred. For example, fuel could be provided direct-ly from another gasifier at a high enough pressure such that compression prior to introduction to chamber 40 would not be required.

Air is also introduced to chamber 40 ! through line 42. In the preferred embodirnent, the air supplied to chamber 40 is taken from the gas turbine compressor section 32 as bleed air. It is however to be understood that air could be provided from another source. The bleed air taken from compressor section 32 is passed through line 44 to an air boost compressor 46 in order to raise the air to a high enough pressure for use in gasifier 10. Boost compressor 46, as well as ~uel compressor 24 is driven a by motor 48.
Part of the air from line 42 and all of the fuel from line 41 combust in chamber 40, thereby introducing heat to the interior of chamber 40. Some of this heat is absorbed by the remaining air in chamber ~0, thereby raising the temp-eratuxe of the remaining air. The combustion chamber 40 and downstream equipment can be lined with refractory thereby allowing for temperatures of 1400F. or more within chamber 40 and downstream equipment. The air supplied from chamber 40 to gasifier 10 can therefore be preheated to temperatures of 1400F. or higher. Temperature measuring device 50 i9 pro-vided for determining the temperature of the preheated air.
It is to be understood that while in the preferred embodiment the oxygen containing gas to be used in the gasifier is air taken from a compressor associated with a gas turbine, other oxygen containing gas streams, including pure oxygen, can also be used, as well as other sources of such an oxygen containing gas.
A latitude of modification, change, and substitution is intended in the foregoing disclosure and in some instances some features of the invention will be employed without a corresponding use of other features. Accordingly, it is appro-priate that the appended claims be construed broadly and in a manner consistent with the spirit and scope of the invention herein.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A coal gasification process for manufacturing low BTU gas comprising the steps of:
a) passing a stream of air to a first compressor for compression therein, b) after said compression, passing said stream of air to a combustion chamber, c) passing a stream of fuel to said combustion chamber, d) combusting said fuel with a portion of the oxygen contained in said stream of air within said combustion chamber, thereby raising the temperature of the remaining portion of said air, including the remaining portion of oxygen contained in said stream of air, e) passing said remaining portion of air including said remaining portion of oxygen at a raised temperature to a gasifier, f) introducing a coal feedstock to said gasifier, and g) reacting said coal feedstock with said remaining portion of oxygen at a raised temperature within said gasifier to produce a low BTU product gas.

2. The process of Claim 1, wherein said stream of fuel comprises a portion of said low BTU product gas.

3. The process of Claim 1, further comprising the step of compressing said stream of fuel before passing said stream to said combustion chamber.

4. The process of Claim 3, further comprising the step of passing said stream of compressed air from said first compressor to a second compressor for further compression therein before passing said compressed stream of air to said combustion chamber.

5. The process of Claim 4, further comprising the step of passing said low BTU product gas to a purifier for purification of said product gas after production of said low BTU product gas within said gasifier.