Note: Descriptions are shown in the official language in which they were submitted.
CA 0224198~ 1998-06-30
A METHOD OF COALS GASIFICATION
AND AN APPARATUS FOR CARRYING OUT THE SAME
Field of the Invention
This invention relates to power engineering, in particular, to thermal processing
of coals, and may be used in heat electric power plants for the improvement of low
grade coals and for the production of ecologically clean synthesis gas.
Description of the Prior Art
Known is the method of coals gasification - the Luhrgie process - which
comprises feeding of lump coal and a gasifying agent into the chamber of a gasifier. As
the gasifying agent used are steam or oxygen. This method is referred to autot~errn~l
(self - heating) processes of gasification since the needed energy is received as the
result of combustion of a part of the fuel. The process temperature is 900 - 1400
degrees K.; sizes of coal lumps are from 5 to 50 mm (H. Firrat "Predstavlenije
electrostantsiji kombinirovannogo tsikla na osnove gzificatsiji uglja"/"Provision of a
Combined Cycle Based on Coal Gasification for Electric Power Plants",
Metallgesellschaft, 1991~ [1].
However, the known method shows poor quality of the obtained synthesis gas
due to high CO content therein. In addition, said lump coal processing, while reducing
the reacting surface, decreases the efficiency of the process.
Known in the aTt is a gasifier for carrying out the Luhrgie process comprising avertical chamber, a charging device for feeding lump coal arranged at the top of said
chamber, as well as lances for supplying a gasifying agent which are located at the
bottom of the chamber. The synthesis gas is removed out of the chamber from the top
thereof, while the slag is discharged from the bottom of the chamber [ 1].
However, the known gasifier does not provide the production of quality synthesisgas and its efficiency is not high.
CA 0224198F7 1998-06-30
A method of coal gasification in a pulverulent stream according to the
Koppers - Tohtzeck method, comprising feeding pulverized coal with steam and
5 oxygen into the chamber of the gasifier through nozzles by blowing, is the method
most close, in the technical essence, to the proposed invention. The formed gas is
removed from the top of the gas generator, while the liquid slag is discharged from the
bottom thereof. With the steam - oxygen gasification of the pulverized fuel high level
of carbon conversion is obtained., the undesirable products of coal semicoking are
10 absent and there is a possibility to process any type of coal ("Khimicheskije veshestva
iz uglija"/"Chemical Substances Out of Coal", Edited by Yu. Falbe, Moscow,
"Khimija" Publishing House, 1980, page 615) [2].
However, subst~n~l carbon dioxide content in the obtained gas, which is
a~lo~illlately 10 %, is typical for the known process of gasification. This is due to the
15 compensation of the reaction endothermic effect by the combustion of a part of the
coal. Besides that, the known method is associated with the necessity to use a
considerable amount of oxygen what subst~nti~lly increases the cost of the obtained
synthesis gas.
The Koppers - Tohtzeck gasifier [2] is the one most close to the proposed
20 apparatus, which gasifier comprises a horizontal chamber provided with nozzles for
feeding the reagents which are arranged opposite each other at the faces thereof. The
formed gas is removed from the top of the gas generator, while the liquid slag is
discharged from the bottom thereof.
Yet, in order to keep the combustion and to increase gas caloricity, oxygen is
25 used in the known gasifier and the combustion chamber of large ~limen~ions isrequired. Besides that, it is difficult to optimize the process of combustion with oxygen
and air blowing, what results in higher carbon dioxide content and incomplete
conversion of coal.
30 Summary of the Invention
The task resolved by the proposed invention resides in the implementation of thepreliminary electrothermochemical preparation of a fuel portion so as to provide the
progress of endothermic reactions during the process of gasification and to provide
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stabilization of combustion subsequently introducing the products of combustion into
the chamber of the gasifier. The electrothermochemical plepalalion improves reactivity
of the fuel and permits to conduct the controlled process of combustion whereby to
improve the quality of the produced synthesis gas and to increase the yield thereof.
According to the invention, in order to achieve the technical result provided bythe invention, in the method of coal gasification comprising feeding of the pulverized
fuel with a gasifying agent into the reaction chamber by blowing, the
10 electrothermochemical preparation of a fuel portion is performed by passing the
air - pulverized coal ~ e through the plep~alion chambers in which a
low - temperature plasma stream is generated and adrnixed with the pulverized fuel and
the latter is heated and ignited; then the process of burning is m~int~ined in the
preheated muffle and after that the products of combustion are directed to the reaction
15 chamber to which chamber the main flow of the pulverized fuel and the gasifying agent
are t~ngenti~lly introduced, and complete fuel gasification is thus performed.
Air is used, thelewi~l, as the oxidizer and superheated steam is used as the
gasifying agent.
The all;~ ent of the technical result provided by the invention has become
20 possible due to the implementation of the apparatus for the coal gasification compri~ing
a cylindrical reaction chamber, means for feeding the re~gent~ and discharging the
reaction products which apparatus, according to the invention, is provided with at least
two preparation chambers arranged diametrically opposite each other and connected to
the lower portion of the reaction chamber located vertically; each of said plepalalion
25 chambers being made in the form of a muffle provided with a built - in plasmagenerator; said muffles being tangenti~lly connected to the reaction chamber anddirected towards each other; and said means for feeding the reagent~ being installed
diametrically opposite each other between said pl~al~lion chambers and tangentially
connected to the reaction chamber.
This combination of the design features provides, according to the method, said
preliminary electrothermochemical preparation of the fuel, its combustion in thepreheated muffle and after - burning of a fuel portion in the reaction chamber in order
to increase the reactivity of the main portion of the processed fuel.
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The electrothermochemical preparation (ETCP) of a fuel portion permits to
accelerate the progress of chemical reactions drastically due to the advantages of
plasma processes of gasification, and namely, due to the provision of a great number of
active centers (excited atoms, molecules, ions, electrons, photons). The particles of
coal in the preparation chambers, entering the zone of high temperatures, undergo the
thermal impact which pulverizes coal so that it becomes finely dispersed what
increases the reactivity of the fuel. The products of combustion from the muffle, having
10 a high temperature (1600 degrees C), are entering the reactor space, increasing the
temperature, where they react with coal carbon and, according to the Boudoir reaction,
are reduced to CO, thus, increasing caloricity of the fuel gas. High concentration of
energy in the reaction chamber allows to reduce dimensions of the gasifier.
The proposed method of coals gasification in the accoll-pallying flow, as distinct
15 from the known methods, is an intermediate one between autothçrm~l (self - heating)
and allothermal gasification processes, since, partially, heat is generated due to the
electric arc of the plasma generator intended for carrying out said ETCP, due to the
combustion of a portion of coal in the preheated muffle and due to the after - burning
in the reactor chamber.
Thus, proposed is the two - stage coal gasification in the accompanying (mixed)
flow, according to which: at the first stage the electrothermochemical preparation of a
fuel portion is performed by passing the air - pulverized coal nli~lu~e (APCM) through
the plasma stream (in the form of two flares) into the muffles preheated by plasma
generators. When a temperature sufficient for said coal gasification is reached in the
25 reactor, the superheated steam and the pulverized coal are fed into the reactor (the
second stage). At this time the complete gasification of the re~g~nt~ takes place with
the oxidizer being in short supply. High efficiency of gasification is attained due to
t~ngenti~l feeding of the APCM and the pulverized coal, as well as the ejected
superheated steam, into the cylindrical reactor, whereby the reagents are m~int~ined in
30 the reaction zone for a time sufficient for perfolming the complete gasification thereof.
Brief Description of the Drawings
The essence of the invention is further explained by the accompanying drawings,
35 wherein:
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Fig. 1 schematically illustrates the proposed apl)alalus for fuel gasification.
Fig . 2 shows the cross section along line II - II, wherein unit A is the means for
5 charging the main flow of the pulverized coal and a gasifying agent, and unit B is the
prel)al~lion chamber.
Preferable Embodiment of the Invention
The apparatus for fuel gasification comprises (Fig. 1) a vertically arranged
cylindrical reaction chamber 1, lined with a refractory material such as Carborundum
(silicon - carbide abrasive). The a~palalus is provided with at least two preparation
chambers 2 and 3 for said electrothermochemical preparation (ETCP) of the fuel
connected to the lower portion of the reaction chamber 1 and arranged diametrically
15 opposite each other. Each of said plepal~lion chambers (Fig. 2) is made in the form of
a muffle 4 provided with a built - in plasma generator 5; said muffles being t~ngçnti~lly
connected to the reaction chamber 1 and directed towards each other for creating a
twisted air - pulverized coal flow. Muffles 4 of the preparation chambers 2 and 3 are
connected to pulverized coal ducts 6 for feeding the air - pulverized coal ~ lule
20 (APCM). Feeding of air necessary for m~int~ining the combustion in the ETCP
chamber is provided by means of a blowing fan and is controlled by a gate (not shown
in the drawing). Power supply to said plasma generators 5 is provided by a DC source
from a thyristor - type converter. The main flow of the pulverized coal is t~ngto,nti~lly
supplied into the reaction chamber 1 by means of two pulverized coal feeders of the
25 star - shape type; steam - jet ejectors for supplying superheated steam being built - in at
the points of said pulverized coal feeding arranged diametrically opposite each other.
The gas formed in the process of gasification is removed from the top of the
reaction chamber 1 and is supplied into cyclone 7 while the liquid slag is directed to
slag collector 8 located at the bottom of the reaction chamber 1.
Depending on power and dimensions, the proposed apparatus for coal
gasification may have more plepalalion chambers than mentioned in the above, forexample, it may contain four or six preparation chambers, said chambers may be
staggered in tiers along the height of the reaction chamber.
The proposed method of coals gasification is carried out as follows.
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A portion of the pulverized fuel with an oxidizer, which may comprise oxygen or
air, is fed into the preparation chambers for said electrothermochemical preparation of
the fuel; a low - temperature plasma stream is pre - generated. The air - pulverized
coal mixture, after passing through the low - temperature plasma stream and the
muffles preheated by the plasma generators, is t~ngenh~lly supplied, in the form of two
flares into the space of the reaction chamber. When a temperature sufficient for coal
gasification is reached, the main flow of the pulverized coal and the gasifying agent
10 comprising the superheated steam are t~ngenh~lly supplied into the reaction chamber.
The products of combustion having a high temperature (1300 degrees K), which aresupplied from the preparation chambers into the reaction chamber, react with coal
carbon and, according to the Boudoir reaction, are reduced to CO, thus, increasing
caloricity of the fuel gas. Said tangential feeding of the products of combustion from
15 the plepalalion chambers, the pulverized coal and the ejected superheated steam into
the reaction chamber allows to m~int~in the reagents in the reaction zone for a time
sufficient for performing the complete gasification.
The gas formed in the process of gasification is supplied into cyclone where said
gas is purified from dust, and after that it may be burnt in a furnace (in a fire box) or
20 may be cooled for heating and steam formation or may be compressed and supplied to
customers through pipe lines. The liquid slag is directed to slag collector located under
the reaction chamber.
The proposed method of coals gasification is illustrated by the following example
of the actual embodiment of the invention.
The appal~lus for coals gasification comprising two chambers for the ETCP with
built - in plasma generators of 66 kW power has been used to realize said method.
Compressed air and cooling water are supplied to plasma generators 5 and the
plasma generators are started. When the preparation chambers 2 and 3 are warmed up,
the air - pulverized coal mixture is fed therein at a rate being adjusted at 130 kg of coal
30 and 400 cubic meters of air per hour. The air - pulverized coal lllixlule, after passing
through the plasma stream and the muffles 4 preheated by the plasma generators, is
tangentially supplied, in the form of two flares, into the space of the reactionchamber 1 in which the main flow of the pulverized coal at a rate of 200 kg per hour
and the superheated steam at a rate of 300 kg per hour and at the temperature of 380
35 degrees C are t~ngent~ y supplied.
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The products of combustion supplied from the preparation chambers 2 and 3 into
the reaction chamber 1 provide drastic acceleration of the chemical reactions progress,
5 thus, increasing caloricity of the fuel. The tangential feeding of the re~gent~ allows to
prolong the time of staying thereof in the reaction zone. The average mass temperature
of the process is 1300 degrees K. The gas formed as the result of gasification is
supplied into cyclone 7 while the liquid slag is directed to slag collector 8. The
composition of the produced synthesis gas (according to the results of the analysis
10 obtained using Chromatograph "AXl- 002 - l"/"AHG 002 - 1") is as follows: oxygen
content - 0 % by volume; carbon dioxide content (CO2) - 4.8 % by volume;
hydrogen content (H2) - 18.2 % by volume; carbon oxide content (CO) - 19.1 % by
volume; methane content (CH4) - 2.1 % by volume.
The use of the proposed method of coals gasification and the appa-~us for
15 carrying out the same permits to decrease considerably energy costs due to the
combustion of a portion of coal in plasma. The electrothermochemical prepalalion(ETCP) of ~e fuel improves reacting capability of the fuel and allows to carry out the
controlled combustion process. High concentration of energy in the reaction chamber
due to the electrothermochemical preparation (ETCP) allows to reduce ~limen~ions of
20 the main equipment. Besides that, the quality and the output of the produced synthesis
gas are increased.
