Note: Descriptions are shown in the official language in which they were submitted.
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.
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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.
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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
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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.
