FR2478121A1 - PROCESS FOR INDUSTRIALLY PREPARING CLEAN FUEL GAS FROM COAL - Google Patents

Abstract

PROCESS FOR GAZEIFYING A COAL BY PYROLYSIS FOLLOWED BY THE CARBONIFICATION OF THE COKE OBTAINED USING WATER VAPOR AND A GAS CONTAINING OXYGEN. THE CHARCOAL PARTICLES CONTAINING VOLATILE COMBUSTIBLE MATERIALS ARE PYROLYZED BY CONTACT IN A NON-OXIDIZING ATMOSPHERE WITH SOLID MATERIALS SERVING THE TRANSFER OF HEAT AT A TEMPERATURE OF 370 TO 815C, THUS ELIMINATE PRACTICALLY THE VOLATIBLE VAPORISED COMBUSTIBLE MATERIALS, AND VARIOUSLY PRODUCED VESSELS, AND ALL FORMED VAPES CONDENSABLE GASES AND A COKE WHOSE VOLATILE MATERIALS HAVE BEEN PARTLY ELIMINATED, THOSE WHICH REMAIN IN COKE PARTICLES CONTAINING PRACTICALLY NO CONDENSABLE TAR, THE COKE PARTICLES WHICH HAVE BEEN ELIMINATED IN PART OF THE MATERIAL HAVE BEEN REMOVED THE SOLID MATERIALS SERVING FOR THE TRANSFER OF HEAT, VAPORS AND CONDENSABLE GASES, THE COKE PARTICLES ARE TRANSFERRED IN A CARBONATION ZONE IN WHICH THEY ARE CARBONIZED USING WATER VAPOR AND A GAS CONTAINING L ' OXYGEN AT A TEMPERATURE OF 540 AT 1370C, FORMING A CLEAN COMBUSTIBLE GAS, PRACTICALLY TAR-FREE, WITH ASH ONLY PO UR RESIDUES.

Description

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  The present invention relates to a process for gasifying coal by pyrolysis of the latter and gasification of the

  coke formed with water vapor and a gas containing oxy-

  gene. For some time, there has been interest in the use of coal in the production of combustible gases,

  which can, among other things, themselves be used for

  duction of electrical energy. One of the proposed methods for converting

  firing coal into combustible gases involves the gasification of

  good using water vapor and oxygen and the combustion of gas formed in a gas combustion turbine for the production of electrical energy. The gas produced in this type of coal gasification must be washed for removal of its impurities and the process has many disadvantages. So, for example, the

  The gas contains variable amounts of volatile combustible

  tiles (MCV) and some of these materials consist of coal tar that is sticky and difficult to handle. Tar, in combination with certain dusty materials produced during the gasification of coal, is present in

  gasification. These two materials clog and foul the Vlap-

  This makes it extremely difficult to recover heat from the gases produced from the coal. In addition, if the gasification operation is combined with cyclic energy production, the operation of the gasification apparatus and the combined cyclical power plant is

  interdependent so that the start and control of the

  integrated installation are impossible without an external fuel and auxiliary equipment which add in a proportion

considerable expense.

  Another proposed process for treating coal is described in an article entitled "Production of Low Btu Gas Involving Coal Pyrolysis and Gasification", by Wen et al., Of the Chemical Engineering Department of West Virginia University, Morgantown, West Virginia 26,506 (pages 36 to 54). In this article,

  it is proposed to pyrolyze coal in a fluidized bed at a time

  about 760 ° C. The coke formed in the pyrolysis operation

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  is separated from the effluent gases and then reacted with air and steam, thereby giving the fluidizing gases of the coal pyrolysis apparatus. However, in this article, it is emphasized that, in order to gasify coke, it is necessary to add raw coal in order to maintain the correct temperature in the gasification apparatus and if it is furthermore necessary to produce a quantity sufficient gas to fluidize the coal. Because the coal is pyrolyzed in a fluidized bed and raw coal has to be added to the pyrolysis coke, this process has most of the disadvantages

  of the prior method described above.

  Another prior process is described in U.S. Patent No. 1,758,630 in which it is proposed to pyrolyze coal in a fluidized bed so as to remove any volatile fuel matter therefrom, after which the coke obtained is charged. in contact with air and water vapor to produce a gas. This process is also inefficient in part because of the

how coke is produced.

  As far as the applicant is aware, none of the processes of the prior art have described the preparation

  coal coke from which the volatile substances have been removed.

  in part only by pyrolysis carried out in such a way that

  coke is ideally suited for gasification. Gasification

  cation of such a coke gives a gas free of tar and which is ideally suited for combustion, especially in mixture with the vapors and gases (ie after removal of the products).

  condensables) produced during the pyrolysis operation.

  The invention relates first of all to a simple process for the industrial preparation of a fuel gas from a particular type of a coal coke, the volatiles of which have been partially removed by gasification of this coke with the aid of steam.

  of water and a gas containing oxygen.

  The process according to the invention makes it possible to prepare a combustible gas which can be used in a gas combustion turbine from a coal coke which contains certain materials

  Volatile fuels, but no constituents forming tars.

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  The method according to the invention for forming a fuel gas from a coke which has been removed in part volatile matter, the gas being for use in gas combustion turbines and being essentially free of heavy coal tar and dust, so that it can not cause clogging of the heat exchange apparatus

and downstream processing.

  The method according to the invention makes it possible to prepare a fuel gas with an average calorific value from a coal coke by mixing gas obtained by pyrolysis of the coal with the gases obtained by gasification of a coke which has been partly removed.

  volatile matter, using steam and a gas containing

  oxygen, the gaseous mixture obtained being free of tar

heavy coal.

  Other features and advantages of the invention

  will be more clearly apparent from the detailed description given

  hereinafter, in which, unless otherwise specified, all the indica-

  parts and percentages are by weight, with reference to

  in the single figure of the attached drawing which shows schematically

  a complete operating cycle of the process according to the invention in

  some preferred embodiments given by way of example.

  According to the invention, the coal is pyrolyzed in a particular manner, and in such a way as to obtain a coke whose volatiles have been partially removed and which is ideally suited for gasification using steam and steam. a gas containing oxygen, this gasification giving a gas free of tar. Coke which has only partially removed the volatiles is substantially non-swelling, has a relatively high bulk density and is very reactive to gasification with water vapor. In addition to coke partially free of materials

  volatiles obtained in the pyrolysis operation, one also forms

  vapors and condensable gases. Vapors can be used for their heat capacity and condensable gases, after condensation, are valuable hydrocarbon liquids that can be used in the petroleum or petrochemical industries

  or that can be burned for their heat capacity.

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  The pyrolysis operation is carried out in a pyrolysis zone in a particularly critical manner which comprises the

  contact of the coal particles with solid trans-

  carrying the heat in a non-oxidizing atmosphere and, preferably, in the absence of other foreign gases. The solids for heat transfer come into contact with the dry carbon particles and heat them to the desired pyrolysis temperature, for example from about 370 to 815 ° C, preferably from about 425 to 650 ° C, and for example from about 425 to 540C. The coal particles are heated by the heat carrying solids for a sufficient time and at a temperature sufficient to remove substantially all the tare forming MCVs from the coal particles. Also produced in the pyrolysis zone are vapors, condensable gases (i.e., hydrocarbons which at room temperature are liquid) and coke particles from which only volatile materials, MCV remaining in the treated coke particles containing virtually no condensable tar. It has been found that these coke particles, from which only the volatiles have been removed, are remarkably suitable for steam gasification because these coke particles contain some of the CVMs and, preferably, almost all the CVMs that do not form. no tar, but do not contain

  practically more MCV forming tars. In addition, the

  parts of the volatile matter have a relatively high bulk density (eg more

  320 g and preferably more than 400 g / l), which makes them equal

  very interesting as raw materials for gasification

  cation. Moreover, the coke particles which have been eliminated in

  the volatile materials according to the invention are extremely

  reactive, that is, they require less steam

of water for their gasification.

  The combustible gas produced by gasification of

  coke particles from which the volatile

  tiles has many applications. Thus, this fuel gas obtained by gasification of coke which was eliminated in part the

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  volatiles with water vapor and air (and not pure oxygen) can be mixed with the vapors produced in the pyrolysis zone, the mixture then constituting a medium calorific gas (this is that is, a gas with a calorific value of about 7440 to 22 300 J / m3) that can be burned in existing heaters and furnaces without modifying the burners or reducing the power of the installation. It is known in the industry that it is impossible to produce a medium calorific gas by oxidation of the carbon contained in the coal by using air as an oxidizing agent to raise the temperature. But, as the vapors produced in the pyrolysis operation are not diluted by foreign gases such as nitrogen,

  the process gives a medium calorific gas under conditions of

  very simple and inexpensive.

  Apart from the use of the fuel gas obtained by gasification of the coke, the volatiles of which have been removed in part in the production of a medium calorific gas,

  This combustible gas can still be used to produce energy.

  in a combustion turbine and can be used to compress air and produce the water vapor

  gasification of coke from which the volatiles have been removed

  tiles, this without fouling downstream equipment, etc., by

  impurities such as tar, which, as mentioned before,

  complicate heat recovery from the product

  gasification. In addition, the use of the gasification product

  tion as described above removes the need for an external fuel and some ancillary equipment that would make

  relatively expensive operations and perhaps not even

tables.

  In general, it is preferable to grind the raw coal prior to pyrolysis into particles of dimensions ranging, for example, from 3 to 13 mm. After grinding, it is also preferable to remove moisture from the carbon in pre-heating and, for example, heating the carbon particles at a temperature of 93 to 315 ° C for a time sufficient to remove substantially all of the moisture . If the coal tends to take in mass, or if

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  it is a coal coming from the East of the United States of America, it is generally preferable to treat it also before, after during the drying so as to eliminate the pieces taken in mass by contact with an oxidizing gas for example containing from 1 to 20% by volume of oxygen, as described in US Pat. No. 3,184,293. In addition to the removal of caked chips,

  such an operation virtually eliminates all moisture from

  good. After the drying operation and / or this pretreatment, most coals contain from 20 to 50% by weight of MCV

and from 75 to 50% fixed carbon.

  In the pyrolysis stage according to the invention, the CVMs which contain the tar are practically eliminated and, in

  the amount of CVM contained in the coal after the

  The pyrolysis ration is from about 10 to 20% by weight, excluding moisture. The temperature and the duration

  the pyrolysis operation are not particular factors

  critically, but> in general, one can pyrolyze at a time

  any temperature between about 370 and 815 ° C, the preferred temperature range being about 425 to 650 ° C and / or, more preferably, 425 to 5400 ° C. The time required to conduct the pyrolysis operation also varies to a great extent depending on the temperature and amount of MCV contained in the raw coal. If, for example,

  it operates at a temperature of 5100C and if the coal contains about

  40 to 45% by weight of MCV, a transit time of 5 min

  to give a coke which has been partly removed from

  tiles and in which the contained MCVs practically

no tar.

  The pyrolysis operation according to the invention is also

  conducted in a non-oxidizing atmosphere and, preferably, in the absence of foreign gases, so that the vapors produced in the pyrolysis operation are not diluted; these vapors, after

  condensable gases, have a calorific value relative to

  and, for example, 29 700 J / m3 after elimination

condensable gases.

  The dried coal particles are pyrolyzed in a non-oxidizing atmosphere by contact with solids

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  to transfer the heat which must be inert with respect to the coal, with respect to the partial coke and with respect to the vapors formed during the pyrolysis operation. The particular type of these solids for heating the coal particles can vary widely and these solids can be of any desired shape. Thus, for example, it may be metal or ceramic material in the form of beads having a diameter of about 6 to 12.5 mm. In the preferred embodiment given by way of example, the solids for heat transfer are beads

  of alumina having a diameter of about 12.5 mm. In addition, to

  to make separation easier, these solids must have a dimensioti distinctly different from that of the particles of coke, of which the volatiles have been eliminated. In general, it is preferred that these solid materials for heat transfer have a diameter greater than that of the coke particles which are

  has partially eliminated volatile matter.

  To transfer the heat of the solids to the particles of coal, it is necessary that these materials and particles

  of coal come into contact. Preferably, the pyro operation

  lysis is performed in a rotary retort. The rotational speed of the retort should be sufficient to allow mixing of the heat transfer solids and the carbon particles and to achieve good heat transfer between the carbon particles and the solids. The particular rotational speed of the retort can vary within wide limits and depends on the diameter of the retort. When the pyrolysis is complete, the heat transfer solids and the partial coke particles and the vapors are separated.

  and the condensable gases produced during the pyrolysis operation.

  The coke from which the volatiles have been removed is then transferred to a gasification zone in which it is gasified with steam. The operating conditions in the gasification operation are not critical factors and, in general, these are the known conditions. The temperature in the gasification zone must be sufficient for the water vapor to react with the carbon contained in the partial coke with the formation of a combustible gas consisting mainly of carbon monoxide and hydrogen. The temperature may vary within wide limits, for example from 540 to 13700C, and is primarily a function of the presence or absence of a gasification catalyst in the zone. When a gasification catalyst is used, the temperature is between about 540 and 815 or 8700C, whereas in the absence of

  gasification (ie in a thermal reaction) the temperature

  more than 870 ° C and, for example, from 870 to 1100 ° C or even

more (for example 13700C).

  Like the gasification temperature, the pressure observed for gasification of carbon with water vapor is also not a critical factor and can vary widely from atmospheric pressure to pressure.

  140 bar gauge; in fact, there is no upper limit

theoretical pressure.

  As mentioned above, the reaction of gasification

  may be carried out with or without a catalyst; if a catalyst is used, the temperature can range from 540 to 815 or 870 ° C. Gasification catalysts are well known in the art and,

  therefore, no detailed description will be given here.

  However, it is generally used alkali metal salts, for example sodium, potassium and lithium salts among which hydroxides, carbonates, oxides, sulphates

and sulphides.

  The concentration of the catalyst in the gasification zone

  It may also vary within wide limits and generally ranges from about 1 to 50% by weight of the total solids contained in the gasification zone. The preferred concentration for the catalyst is from about 4 or 5% by weight up to or 30% by weight. The amount of water vapor used to gasify the coke from which the volatiles have been removed must be sufficient to cause substantially complete gasification of the fixed carbon contained in the coke. In general, the amount of water vapor is from about 0.1 to 1 part by weight and

  the hour per part by weight of carbon present in the gasification zone

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  the preferred amount ranging from about 0.2 to 0.6 parts

in weight.

  The desired temperature is maintained in the gasification zone by introducing a gas which contains oxygen such as air in order to oxidize a part of the carbon contained in the coke, of which the volatiles have been eliminated, this reaction of oxidation being exothermic; the amount of oxygen introduced

  must be sufficient to maintain the temperature at the desired level.

  Referring now to the single figure of the accompanying drawing which represents a preferred embodiment of the method according to the invention, the coal particles, before pyrolysis, are introduced at the top of the drying zone 10; at the foot of the same zone, a hot gas is introduced, the drying temperature

  approximation being around 1200C in zone 10. After the

  and if Wyodak coal is used, the coal contains about 7.6% ash, 43.9% volatile

48.5% carbon.

  It should be noted that, if a coal from the eastern United States of America is used, it is sometimes necessary to carry out a pre-treatment before or after drying. This pretreatment is used to demolish the coal and in general, according to a known technique, it consists in putting the coal in contact with an oxidizing gas. After the drying operation, the dry charcoal is sent to a preheating zone 12. which is brought to a temperature slightly lower than the pyrolysis temperature. In the embodiment shown in the figure of the appended drawing, the preheating temperature is about 2300C and the oxidizing gas used for preheating the coal particles is preferably a gas which contains about 10% by volume of oxygen . Coal particles leaving

  the preheating zone 12 have approximately the same composition

  dry coal particles entering this area.

  When the coal particles have reached a temperature of 30 ° C, they are sent into the retort 20 in

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  which is carried out the pyrolysis operation in the absence of oxygen and other non-foreign gases. In the retort 20, the coal particles are heated to a temperature of about 370 to 815 ° C (in the preferred embodiment at a temperature of about 425 to 540 ° C). In retort 20 solid materials are used

  heat transfer to heat the coal particles.

  These solid materials for heat transfer are preferably

  ceramic balls which are heated to an appropriate temperature in a heater 14; the ceramic balls reach a temperature of about 650 to 705 ° C depending on the

  temperature at which it is desired to conduct the pyrolysis operation.

  The relative proportions by weight of solids

  The amount of heat transfer and charcoal is about 2.8: 1.

  The solids for heat transfer and the coal particles are introduced into the retort 20 which rotates about its axis at a relatively low speed, for example at a speed of 3 rpm, thus causing the solids to mix with the solid. coal. When the pyrolysis has been pushed to the desired point, condensable vapors and gases, solids for heat transfer and coke are separated. The

  separated solids are recycled by the elevator 24 to the warming

  14, and the coke particles which have been partly

  volatile materials are sent to the gasification apparatus 30.

  The vapors and the condensable gases are transferred to the oil and gas recovery zone 22 in which the high calorific gas is separated from the volatile oils and, if it is

Desire, we eliminate sulfur.

  Table I below shows the composition of

  coke which has been partially removed from three different operations; the temperature of the retort during these operations is indicated in the top line of Table I. In Test 1 of Table I, the coal used is a Wyodak coal different from that used in Tests 2

and 3.

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  Tables II and III, respectively, are

  the composition of the oil and gases obtained in the operation

pyrolysis test 1 to 3.

  The coke particles from the retort 20 are transferred to the gasification apparatus 30. This may consist of any air-blowing apparatus, for example a fluidized bed apparatus with a driven current or

  moving bed, in each case with or without catalyst.

  The temperature at which gas is heated

  This is not a particularly critical factor.

  In the preferred embodiment, the gasification apparatus 30 is an inflation fluidized bed apparatus.

  air pressure at moderate pressure (eg pressure

  metric of 1.4 to 14 bar). Coke enters the gasification apparatus

  30 at a temperature between 450 and 480 ° C. The air and the water vapor sent to the gasification apparatus 30 are

  at a temperature of about 315 ° C and the ratio of water vapor / oxy-

  gene is about 2.6. Gasification produces a combustible gas at a temperature of about 930eC which is discharged through the top of

  the device. The ashes are evacuated at the foot of the apparatus and

  jetties. The gases leave the gasification apparatus 30 and pass into the heat exchanger 32 where steam is produced, a portion of which is used in the gasification apparatus 30. The fuel gas is then passed to the apparatus recovering the accompanying products 34 in which, by any conventional method, the undesirable constituents such as sulfur and ammonia are removed, and the desired fuel gas is obtained

  at low calorific value. This combustible gas contains about 25.3 a.

  of H2, 20.9% CO, 11.1% CO 2, 1.7% CH and 41% N with a gross calorific value of about 6170 J / m. When we speak of low calorific gas, we mean a gas which contains very few constituents with high calorific value such as the

  methane, and relatively high proportions of

  low calorific content, such as H2 and CO.

  The low calorific gas has many applications and, in a preferred embodiment, this gas is mixed with the high calorific gas from the pyrolysis zone, the mixture constituting a calorific gas.

average, about 9300 J / m3.

  In another preferred embodiment, at least a portion of the low calorific gas passes into the heat exchanger 36 which serves to cool the combustible gas fed to the companion product recovery apparatus 34 and which return, warms the gas before its introduction into the burner 52 adjacent the gas turbine 54. It is desirable that the gas is introduced into the burner 52 at a temperature of about

  2050C and a pressure of about 20 bar.

  In the compressor 58, air is compressed at a pressure of about 14 bar absolute; some of that air

  is sent to another air compressor 42 in which its pressure

  is raised to an absolute level of about 28 bar; the compressed air is then mixed in the steam and used in the gasification apparatus 30. It will be noted that the compressor 42 which sends air at high pressures to the gasification apparatus 30 is itself moved

  by the turbine 40, fed by a part of the water vapor pro-

  in the heat exchanger 32. The expanded steam leaving the turbine 40 passes through the condenser 44 and is discharged to the state

of condensate by the pump 46.

  Another part of the compressed air coming from the compressor 58 is sent to the burner 52 for use in the combustion turbine 54 which will produce electrical energy and which

  also propels the compressor 58.

  If desired, part of the water vapor

  in the heat exchanger 32 can be sent in a turbo

  Auxiliary steam engine 60 for additional energy production. The steam leaving the turbine 60 goes into the condensation

  62 and can be discharged in the form of condensate; however, the condensate can also be sent to the heat exchanger 66 for vapor regeneration and recycling of the latter to the turbine 60. The heat exchanger 66 is fed with the pump 64 in flue gas rejected , but still hot, from the

gas turbine 54.

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  It is clear that the invention is in no way limited to the preferred embodiments described above as examples and that one skilled in the art can make

  changes without departing from its scope.

TA B WATER I

  Composition of the coke Test n 1 Temperature of the retort Approximate content. % by weight of coke Moisture Ash Volatile fuels Fixed carbon Total Elemental composition% by weight Carbon Hydrogen Oxygen Nitrogen Sulfur Ashes Other characteristics Moisture equilibrium, Hardgrove roasting Heating value:% by gross weight, J / kg net, J / kg Apparent density (6.5 mm x 0): packed, g / l

1 2

4270 C 482 C

  0.0 12.4, 62.3, 68.8, 3.4, 13.3, 1.0, 12.4, 78.2, 0.0, 19.7, 3.74, 7 3.0 11.8 1.2 0.2, 0.8, 49.1 521 C 0.9.9.8, 9 74.3, O 77.5 2.9 8, 3 1.3 0.3 9.8 9.9, 6

988 11 680 12 056

710 11 420 11 804

780,766

TABLE II

  Properties of oils Properties of oils Test n Elemental composition,% by weight Carbon Hydrogen Oxygen Nitrogen Sulfur Chlorine Ashes Total Retort temperature 81.4 9.3 8.3 0.48 0.43 0.0 0.0 99, 91 , 7 9,1 9,4 0,7 0,2 0,0 0,2, 3, 9 8,7 9,3 0,7 0,2 0,0 0,1 99,9 Gross calorific value, J / kg net, J / kg Density API Primary oil Calculated with C4 components and heavier gas added Drop point, OC Conradson carbon,% by weight Distillation,% by volume 2.5 Viscosity (SUS) 82 C 990C

428 15 082

14,638 14,296

7.9 13.2 7.6 4.5 12.1 9.9

122 123

63 66

14,846

14,099

1.9 6.2 1l14

2 4 7 8 121

TA B L E A U III

  Analyzes of gases Temperature of the retort Test n Component, moles% H2 CO Co2 H2S C1 C2 C2- (ethylene c3 C3_ (propylenec iC4 c4 C5 C6 C7 c8 + Total Average molecular weight Carbon,% by weight Calorific value, calculated

gross, J / m3 -

  net, J / m3 Calculated with raw CO2 and H2S removed, J / m3 net, J / m3

1 2 3

0.8 1.0

18.0 17.3

51.1 42.3

1.7 1.3

16.9 22.0

3.6 4.7

1.9 1.9

1.3 2.2

1.6 3.7

0, 1 0, 1

0.3 2.0

1.0 1.8

0.7 0.6

0, 5 0, 1

0.2 0.0

99.7 101.0

, 9 35.0

, 45.9

19,900 26,600

18,350 to 24,700

41,600 46,000

38,200 37,700

  7.8 18.4 36.4 0.3 24.9 4.4 2.4 1.2 1.6 0.0 1.1 0.7 0.4 0.3 0.1, 0, 6 44 7

24,400

21,600

27,000

* 34,200

e)

Claims (1)

1. A process for gasifying coal by pyrolysis of coal and gasification of coke obtained with the aid of steam and an oxygen-containing gas, characterized in that it comprises the following stages: Pyrolysis particles are pyrolyzed in a pyrolysis zone containing volatile combustible materials by contacting these carbon particles in a non-oxidizing atmosphere with solids for heat transfer at a temperature of 370 to 8150C, preferably from 425 to 5400C, in order to remove virtually all volatile combustible matter forming tars from coal particles and to produce vapors, condensables and coke particles which have been partially removed from volatile volatiles, volatiles remaining in the treated coke particles containing substantially no condensable tarry materials, and the coke particles Partly removed volatiles being practically non-swelling, the coke particles are removed and some of the volatiles are removed from the solids for transfer of heat, vapors and condensables; the coke particles which have been partially removed from the volatiles are transferred to a gasification zone; the coke particles, from which the volatiles have been removed in the gasification zone, are brought into contact with water vapor and an oxygen-containing gas at a temperature of 540 ° to 13,700 ° C., so that volatilizing volatile fuel matter remaining in the coke particles and reacting the carbon of these particles with water vapor, producing a fuel gas substantially free of tar, and ash; and separating the fuel gas substantially free of tar and ashes. The process according to claim 1, further characterized in that, prior to the pyrolysis operation, the coal particles are heated in a drying zone at a temperature of 93 to 3150 ° C. in such a way that eliminate practically all the moisture contained in these particles without eliminating any significant proportion of the volatile fuels contained in these particles of coal. The method of claim 1, further characterized in that the solids for heat transfer in the pyrolysis zone are recycled after being heated in a solids heater. 4. The process as claimed in claim 1, further characterized in that the vapors and condensable gases produced in the pyrolysis zone are separated in a recovery zone so as to form an oil and a gas of high potency. heat. The method of claim 1, further characterized in that: the fuel gas is substantially tar-free from the gasification zone in a heat exchanger, in exchange for heat with water, so as to form water vapor; and a portion of the steam is passed from the heat exchanger to the gasification zone. 6. A process according to claim 5, further characterized in that a further portion of the steam heat exchanger is fed to a steam turbine, which is used to propel a compressor which serves to feed the oxygen-containing gas into the gasification zone. 7. A process according to claim 5, characterized in that another portion of the steam from the heat exchanger is sent to an auxiliary steam turbine which produces electrical energy. 8. Method according to claim 1, characterized in that the fuel gas is sent substantially free of tar from the gasification zone to a recovery facility accompanying products in which the sulfur and ammonia are separated possible, and a clean gas of low calorific value is formed. A process according to claim 8, characterized in that a portion of the low calorific gas from the recovery plant of the accompanying products is mixed with the high calorific gas from the recovery zone, thus forming a gas with calorific value sen. 10. Process according to claim 8, characterized in that a part of the low calorific gas is sent from the recovery plant of the products of accom-   1.0 on a burner, thus forming combustion gases and these combustion gases are sent to a combustion gas turbine   which produces electrical energy.