FR2465776A1 - PROCESS AND INSTALLATION FOR GASIFYING SOLID CARBON SUBSTANCES - Google Patents

Abstract

THE PRESENT INVENTION CONCERNS A PROCESS AND A PLANT FOR THE GASIFICATION OF SOLID CARBON SUBSTANCES. THE PROCESS CONSISTS OF BURNING THE RESIDUAL COKE COMING 38 FROM THE GASING REACTOR 14 IN A FLUIDIZED LAYER 40, IN WHICH ARE FLOODED THE HEATING SURFACES OF THE DECOMPOSITION OVEN 26 AND A STEAM GENERATOR 46 SUPPLYING A TURBINE, 58 OF THE HANDLER. COMBUSTION IN THE FLUIDIZED LAYER BEING CONDUCTED BETWEEN APPROXIMATELY 800 AND 950C. THUS A QUASI-SELF-ENERGY SUFFICIENCY OF THE LIGNITE GASING SYSTEM IS OBTAINED, INDEPENDENT OF VARIATIONS IN THE CARBON CONTENT OF THE RESIDUAL COKE AT THE OUTLET OF THE GAZEIFICATION REACTOR.

Description

The invention relates to a method and an installation for gasification

  solid carbonaceous substances, in particular lignite, using a gasification agent containing hydrogen, in which a part of the methane contained in the gaseous product is decomposed in a decomposition or cracking apparatus, with addition of water vapor, to get 1 '

  a gasification agent containing hydrogen, the

  of decomposition being heated at least to a preponderant extent by the heat of combustion of the

  residual coke formed during gasification.

  By German patent application 1,796,050.8, it is known in the gasification of coal, in particular of lignite, to burn residual coke to cover

  the heat requirements of the gasification process.

  In a coal gasification-hydrogenation plant according to German Patent Application 2,704,465,

  we proceed by using the residual coke to heat

  Iron the decomposition furnace in which hydrogen is produced for gasification. It is necessary that the decomposition furnace can be heated either directly by residual coke or by gas

  formed by gasification of the residual coke. The disad-

  the latter solution is that it requires

  an additional installation for gasification

  residual coke. However, difficulties can arise when directly heating the decomposition furnace by the heat of combustion of the

  residual coke, for example, especially if the

  In ash is high, it is to be expected difficulties in the combustion chamber due to the melting of ash. In addition, there is a risk of fouling at the downstream contact surfaces

  which results in a corresponding decrease in

is lying.

  The object of the invention is to improve a process of the type defined above so that the decomposition or cracking furnace is heated particularly advantageously, appropriate to the nature of the residual coke. Technical means and equipment

  implemented remaining reduced. It must be

  you can, even if the residual coke has bad

combustion qualities.

  To solve this problem, the invention proposes to

  gasification in a fluidized layer, burning

  ler the residual coke in a fluidized bed furnace, and dissipate the heat directly into the fluidized combustion bed, transmitting it at least to partial regions of the heating surfaces

of the decomposition apparatus.

  The gasification, on the one hand, and the combustion of the residual coke, on the other hand, are harmonized with each other. Since the residual coke comes from a fluidized bed reactor, it ensures, a priori, the

  conditions necessary for the maintenance of a fireplace

  fluidized, for example granulometry and

  granulometric scale. The fluidized bed hearth allows an extremely compact construction which, in

  comparison of other households, leads to investment

  less heat loss. The construction

  In particular, the collection of the tubes from the tubular decalcifying furnace directly plunges into the fluidized bed and thus, in comparison with the usual flue gas combustion fires, very large

  heat transfer coefficients. It is possible

  It is advantageous to conduct combustion in the fluidized bed at temperatures between 800 and 950.degree. C., preferably between 850 and 9500.degree. These temperatures are particularly advantageous for the process of steam reforming ("reforming") which takes place in the decomposition furnace. The good thermal transmission within the layer

  fluidized also has the effect that it reigns

  fluidized bed temperature

  practically uniform, so we do not have to

  to doubt overheating in partial regions of the tubular decomposition furnace. Another advantage lies in the fact that the fluidized layer hearth does not require high combustion qualities of the residual coke. This is particularly the case for

  the ash content of the residual coke, which may

  significant differences as a result of changes in the rate of gasification of the coal introduced. Under the construction collected, the installation finally requires less investment than an apparatus of

classic type.

  Other features and advantages of the invention

  will emerge from the following description made in

  relation with the annex drawing which represents, as an example of execution, the schematic diagram under

  block form of a gasification plant-

hydrogenation of lignite.

  The lignite 11 is dried in a dryer 12 and introduced

  in the fluidized bed reactor 14. The gasification agent, mainly formed of H2 and supplied by the pipe 16, also serves to maintain the layer

  fluidized. The reaction is carried out exothermically

In the equation:

C + 22 -2> CH4

  The gaseous mixture that comes from the reactor 14, and which still contains in particular hydrogen in

  excess, arrives by a pipe 17 and after cooling

  in a heat exchanger 18, to a device 20

  in which it is freed of solid particles.

  In another apparatus 22 the separation of

  undesirable gaseous constituents, for example CO2.

  Downstream thereof an apparatus 23 serves to separate CH4 and H2, and optionally CO. Part of the methane

  (CH4) arrives via a pipe 24, to a decomposition furnace

  or cracking 26, after having undergone at 28 a steam additon from a pipe 29, so that the endothermic reaction takes place in the decomposition furnace 26:

CH4 + H2O- 3 H2 + CO

  The gaseous mixture obtained, consisting essentially of H 2, CO, CH 4, H 2 O and Co 2, arrives via a pipe 30

  and a heat exchanger 32, in which it is cooled

  said by yielding heat to the methane-steam mixture which arrives at the decomposition furnace 26 through the pipe 27, to an apparatus 33 in which, with the addition of water vapor, the CO fraction of the gaseous mixture is converted

  en-Co2, which is then removed by washing, from the

  usual in a device 34 arranged downstream. From the apparatus 33, the mixture, mainly formed of H2, arrives through the pipe 16 as a reagent and agent of

  fluidization at the fluidized bed reactor 14.

  The residual coke formed in the reactor 14 and which, with a gasification rate of 50 or 60%, for example,

  still contains significant amounts of C, is chas-

  reactor 14 operating under an overpressure; if necessary, it is cooled to a temperature allowing its handling, in a cooler 36

  following the reactor 14. It arrives, as indicated

  by the dashed line 38, to a focus 40 in which it is burned within a fluidized layer

  whose upper limit is approximately 42.

  Combustion air, serving at the same time as a fluid

  disation, is brought by a pipe 44. The decomposition furnace

  position 26, which is generally in the form of a tubular furnace, is located within

  the fluidized layer. In this one is furthermore

  placed the steam generator 46 preceded by a preheat

  48 heated by the exit gases of the diaper

  fluidized 40, the water supply being designated 50.

  Downstream of the steam generator 46 is provided a sur-

  driver 52 heated by the combustion gases of the fluidized bed furnace. Steam, which for example has a

Z465176

  pressure of 110 bar and a temperature of 5350C,

  by a pipe 54 to a turbine 58 causing a general

  By means of the extraction pipe 29 of the turbine, steam, for example having a pressure of about 40 to 50 bar and a temperature of about 4000.degree.

  brought to the apparatus 28 in which the mixing is carried out.

  ge with methane, before the introduction of the mixture

  thus formed in the tubular decomposition furnace 26.

  In addition, there is provided at the turbine outlet a sampling pipe 60, through which the

  steam at a pressure of about 5 bar and at a temperature of

  of 1700C is brought to dryer 12 where lignite

is initially dried.

  The hydrogen separated in the apparatus 23 can be brought back by a pipe 61 directly to the pipe 16, and

  there to the fluidized bed reactor 14.

  The outlet gas of the fluidized bed furnace 40 arrives via a pipe 62 to a separation cleaner 63, and after separation of the materials

  residuals, possibly released into the atmosphere.

  From the turbine 58 can from other pipes of

  sample. Steam generated in the combustion chamber

  fluidized 40 and the electrical energy generated in

  generator 56 are sufficient, if the installation is con-

  venably designed, to cover all the energy needs

of it.

  Of course, we can still imagine other devices that complete the installation. Thus, the CO separated in the separator 23 could be converted with addition of water vapor to CO2, and the hydrogen thus released could also be conveyed as

  gasification agent in the reactor 14.

  If the amount of residual coke is not quite enough to cover the heat requirements

  fluidized bed, it is possible to

  without difficulty, the rest of these needs by other fuels fed to the fluidized bed,

for example raw lignite

  Although the present invention has been described in

  with a particular type of installation, it does not

is not limited.

Claims (7)

  1 - Process for the gasification of solid carbonaceous substances, in particular of lignite, with the use of a gasification agent containing hydrogen,   in which a decomposition apparatus is decomposed   a portion of the methane contained in the gaseous product, with the addition of water vapor, to obtain the gasification agent containing hydrogen, the decomposition apparatus being heated at least to a preponderant extent by the heat of   combustion of the residual coke formed during the gasification   characterized in that the gasification is effected   cation in a fluidized layer, preferably in excess pressure, that the residual coke is burned in a fluidized bed furnace, and that the heat is dissipated, directly   in the fluidized bed of combustion, in the trans-   putting at least partial areas of surfaces   heating the decomposition apparatus.   2 - Process according to claim 1, characterized in that the combustion is conducted in the fluidized bed at temperatures between 800 and   950 ° C, preferably between 850 and 95 ° C.   3 - Installation for the implementation of the process   according to one of claims 1 and 2, comprising a   fluidized bed reactor, a methane decomposition furnace, and apparatus for generating and / or superheating water vapor, characterized in that   it comprises a fluidized bed furnace (40) capable of   being fed by the residual coke from the gasification reactor (14), and in which   at least partial regions of the heating surfaces   fage of the decomposition furnace (26).   4 - Installation according to claim 3, characterized   in that the steam generator (46) and the superheater (52) are disposed within and / or above the fluidized bed in the combustion gases.   - Installation according to one of the claims   3 and 4, characterized in that the steam generator   is disposed in the region of the combustion gases.   6 - Installation according to one of the claims   3-5, characterized in that at least   of the heat transfer surfaces of the genera-   of steam (46) are arranged within the neck. fluidized.   7 - Installation according to one of the claims   3 to 6, characterized in that a superheater (52), following the steam aenerator (46) can be heated by the combustion gases.   8 - Installation according to one of the claims   3-7, characterized in that it comprises a   it can be heated by the exit gas.