FR2529221A1 - METHOD AND APPARATUS FOR GASIFICATION USING COAL, COKE OR THE LIKE - Google Patents

Abstract

A process and equipment for the gasification of coal, coke or the like in a fluid bed in equipment according to the fluidised surge process are described, having a gasification reaction chamber in which the raw material for gasification is held in a fluidised state, and having a combustion chamber arranged underneath the gasification reaction chamber, characterised in that a part of the gas generated is introduced together with an oxygen-containing gas into the combustion chamber for combustion and that the gas produced is passed into the gasification reaction chamber, located above the combustion chamber, and is used as fluidising gas.

Description

 The present invention relates to an improved method and apparatus for producing combustible gas from coal, coke or the like.

 In view of the recent circumstances surrounding the critical energy problem, the reuse of coal energy, for example, has been studied around the world.

 Due to the solid form of coal as an energy source, liquefaction or gasification of coal has been in high demand by suppliers and users who have experienced the ease of handling oil and gas as well as their forms leaving no solid residue during use or after use during the period of reliance on oil and gas and there was an urgent need to establish the necessary techniques.

 If the necessary techniques for liquefaction or gasification of coal were developed, very significant economic effects would be obtained since the conventional energy supply routes or the final equipment forming the sites of use could be used without considerable modifications of these tracks or this equipment.

 Under these conditions, technical studies concerning the liquefaction and gasification of coal were undertaken and there was a great deal of information concerning the results of studies or proposals.

 Known coal gasification techniques have been broadly divided into methods of the fixed bed type, the fluidized bed type, the bent bed type and other methods. All of these methods have a serious problem regarding how to dispose of the residue left after the gasification of coal, i.e. ash, and the goal of finding a solution to this problem is now an important question. occupying a prominent position in coal gasification techniques.

 The present invention relates to a gasification furnace of the fluidized bed type.

 Although it is known that in the gasification of coal by means of a fluidized bed, the conduct of the reactions at high temperatures has the effect of increasing the speed of the reaction of gasification of coal and of improving the yield of the gasification, it is also known that troubles are caused by the ash resulting from the gasification. More particularly, when the temperature of the gasification reaction approaches the melting point of the ash, the melting of the ash begins and it vitrifies on the distribution plate and the surface of the walls in the gasification furnace, thus giving rise to the problems. As a result of scorification. As a result, it was considered difficult to carry out the gasification of coal at temperatures ~ above 1000 C in ordinary gasification furnaces of the fluidized bed type.

 In the case of the Winkler process currently used in the form of gasification furnaces of the fluidized bed type, the temperature of the gasification reaction is between 900 and 1000 μb, with the result that not only the yield of gasification per revolution is low, but still tar, phenol, etc. are produced in large quantities due to the low reaction temperature.

 The increase in the gasification yield is based on a solution used to reduce to zero or to a low level the slagging disorders and it has been proposed, as a gasification process to prevent the slagging disorders, a gasification process with a fluidized bed in which the ash produced is positively agglomerated until a given particle size or a given particle weight is reached and then the ash is discharged outside the system.

This process removes the agglomerated ash from the groove below the fluidized bed while carrying out the gasification reaction at a temperature close to the melting point of the ash and a typical example of this process is the so-called "U-gas" process. implemented by the firm
IGT in America. To now describe this process, the pulverized coal arriving from a hopper 7 is introduced into a gasification furnace 1 with ash agglomeration by a known type of conveyor means, for example a screw or belt conveyor so that the coal is mixed with air or oxygen or water vapor arriving separately through a pipe9 and gasified.

The resulting raw gas is introduced into a washing tower 6 through a first stage cooler 2, a second stage cyclone 3, a third stage cyclone 4 and a second stage cooler 5 and the gas produced is supplied by a pipeline. 16. In the figure, the references 11, 13 and 14 designate water supply pipes and the reference 15 designates a flow pipe. The unreacted pulverized coal and the ash which have been collected by the second stage and third stage cyclones 3 and 4 are brought back to the lower part of the gasification furnace 1 by a pipe 12. An inclined distribution plate 17 is arranged in the lower part of the gasification furnace 1 and the distribution plate 17 also serves as an injector for the gas introduced. In addition, air or oxygen is introduced into the gasification furnace 1 by a pipe. 10 so that, in addition to the gasification reaction, the formation of an ash agglomeration progresses while the ash is maintained in a fluidized state and that a given agglomeration of ash is formed for discharge from the bottom.

 However, as this method uses two fluid supply lines, namely line 9 for air or oxygen and water vapor introduced mainly for the gasification of pulverized coal and line 10 for air or the oxygen introduced mainly for the fluidization of the pulverized coal and the ash, it can be said, for each of the pipes, that any change in the flow rate of the fluid substances has an influence on the fluidized state of the powdered material and the temperature gasification in the agglomeration gasification furnace 1 and the adjustment operations of the two pipes become very complicated.

 From the point of view of the actual operation, the method of introducing the gasifying agent and the mechanism for discharging the ash are important and the conventional methods are disadvantageous in the following points.

 FIG. 2 shows by way of example the apparatus described in Japanese patent publication NO 52-126404.

This device allows localized heating inside the fluidized bed, so that the individual ash particles are fused into coarser particles and are continuously removed from the interior of the bed.

A dry distilled carbonization product 24 is introduced into a fluidized bed oven 21 and steam 25 is injected from bottom to top through an inclined distribution plate 23 of the perforated plate type in the lower part of the oven and by a pipe 26 for discharging the ash formed in the central part of the distribution plate 23, thus fluidizing the carbonization product. In addition, a gasifying agent 22 comprising oxygen is injected by nozzles 27 so that the portions surrounding the nozzles are transformed into combustion zones and the ash is melted and agglomerated. Thus, the agglomerated ash 29 , arriving in the state of particles large enough to overcome the upward pushing force exerted by the steam 25 is cooled and solidified by the steam 25 and the ash in large particles falls and is discharged through the discharge pipe 26.

 Although this process removes any localized heating on the distribution plate 23 and prevents the ash from melting, the temperature of the distribution plate 23 is lowered to a temperature level which causes the adhesion of the coal and it is impossible to directly use coal as a raw material. Thus, it is necessary to use a carbonization product which has been subjected beforehand to a certain heat treatment and which does not present any danger of adhesion.

 As a result, not only must a thermal cracking furnace be used in addition to the gasification furnace, but also there are drawbacks in that operation for a long time results in the molten ash sticking to the anterior ends of the nozzles. , thus giving rise to so-called slagging disorders; and that the oxygen-containing gas 22 and the water vapor 23 are injected separately into the gasification furnace, thereby making it very difficult to control the temperature inside the gasification furnace.

 The inventors have carried out various studies with a view to preventing these slagging disorders and have discovered a gasification process and apparatus in which instead of using in the lower portion of the gasification oven a perforated plate which must be a resistant element heat and tends to cause a scorification disadvantage, part of the gas produced is burned in a combustion chamber situated below the gasification furnace so as to introduce the resulting combustion gas as a fluidizing gas into the gasification furnace and gasifying coal, coke or the like starting material in this way, and the resulting ash is agglomerated so as to discharge the agglomerated ash arrived at a given size (or at a given weight) outside the system through the combustion chamber.

In the accompanying drawings:
Figures 1 and 2 are schematic diagrams for explaining prior techniques relating to the gasification of coal.

 Figures 3 and 4 are schematic diagrams for explaining the gasification techniques according to the invention.

 A method and an apparatus according to the invention, although they are an extremely simplified method and apparatus which does not require complicated control of fluids as in the case of the so-called "U-gas" method and which does not require either 'addition to the device .as.

similar element such as an inclined distribution plate, are particularly excellent in that the speed of the gasification reaction is increased and also the treatment capacity per unit volume of the reaction chamber is increased.

 The present invention will now be described with reference to the accompanying drawings.

 FIG. 3 is a block diagram for the gasification of materials essentially comprising coal, coke or a similar material (which will be referred to hereinafter as coal). A pulverized material for gasification having a particle size of several sm is introduced continuously into a gasification furnace 32 from a hopper 31 per year csmm type of conveyor means such as a screw feeder. n the gasification furnace 32, the particles of starting material are formed in the form of a fluidized bed by a fluidizing gas and the interior temperature of the bed is adjusted with a lower temperature limit chosen.

at about 2000C below the melting point of the ash in the starting material. The temperature in the gasification furnace 32 is regulated by controlling the quantities of the gasification gases, that is to say air or oxygen and water vapor, which are introduced through a line 33 In this case, the gasification gases to be introduced must preferably be such that the water vapor / oxygen volume ratio is less than 3.

 The ash produced as a result of the progress of the gasification reaction is subjected to an agglomeration magnification action carried out inside the fluidized bed so that the resulting ash agglomerate, of spheroid or granular shape, falls into a hopper 35 through a combustion chamber 34.

When the gasification reaction system is operated for a high pressure process, the resulting ash agglomerate is transferred to a lower hopper 36 and then discharged to the outside of the system.

 Furthermore, the gas produced in the gasification furnace 32 is passed through the top of the furnace in a cyclone 37 to remove fine substances such as unreacted carbon and then the gas is introduced into a tower 38 for purifying the gas for removal of dust, NOx, SOx, etc. Then, the gas is kept in a gas tank 40 after passing through a compressor 39.

 The fine substances separated by the cyclone 37 are brought back through a line 41 to the gasification furnace 32 and are subjected again, together with the starting material, to the gasification reaction.

 Furthermore, part of the product gas stored in the gas tank 40 is introduced into the combustion chamber 34 by a pipe 42 and also oxygen or an oxygen-containing gas is introduced into the combustion chamber 34 by a way 43 to burn the first gas to produce a fluidizing gas. With regard to the combustion conditions in the combustion chamber 34, the combustion is adjusted so that the flow speed in the groove formed between the gasification furnace 32 and the combustion chamber 34 becomes greater than the terminal speed of the powdered material flowing in the gasification furnace 32.

 As part of the produced gas is burned in the combustion chamber 34, the amount of the fluidizing gas can be adjusted very easily.

 The results of various tests have shown that although it has been recognized that the ash can be satisfactorily agglomerated by adjusting the temperature of the fluidizing gas to about 100 C below the melting point of the ash, depending on the steam / oxygen ratio and the quality of the starting coal, this obviously cannot be mentioned at the same time and generally a satisfactory operation can be ensured by adjusting the temperature in the interval between the melting point of the ash and a temperature around 2000C below the melting point of the ash.

 With regard to the method of introduction of the gasification agent and the prevention of slagging disorders which are particularly important from the operational point of view, the desired effects can be obtained using a method such as that shown in the figure. 4.

 More particularly, in FIG. 4, the raw material arriving via a pipe 51 is put in the form of a fluidized bed in a gasification furnace 53 by the fluidizing gas injected from bottom to top by a groove 55 and the material is gasified by the mixture of oxygen or air and water vapor introduced by nozzles 52. Each nozzle 52 for supplying a gasification agent projects into the oven 53 through its wall so as to prevent the formation of a hot spot with a high concentration of gasifying agent near the wall.

 If such a hot spot forms near the wall, the ash in the charcoal is melted and sticks to the nozzle, causing scorification disorders. the molten ash on the front end of the nozzles 52 is removed by devices 54 such as pneumatic hammers or vibrators.

 The ash thus removed has a high density compared to that of coal and it falls through the groove 55 in a lower hopper.

 Obviously, the devices 54 are operated such as pneumatic hammers or vibrators so as to prevent the molten ash from becoming larger than the inside diameter of the groove 55.

 As regards the material used for the gasification agent injection nozzles 52, they should preferably be formed from a heat-resistant alloy such as stainless steel having impact-resistant and tensile properties. to prevent the molten ash from sticking to the nozzles. (your temperature of introduction of the gasification agent is of the order of 1500C and the nozzles themselves are cooled).

 In addition, in order to prevent the lower part of the oven from heating up and beyond the melting point of the ash, cooling pipes 56 are buried in the wall of the oven in its lower part and a cooling medium such as Water, steam or nitrogen gas is introduced into the cooling pipes 56 so as to prevent the melting of the ash or the adhesion and growth of the molten ash.

 Although it is desirable to connect the raw material supply pipe 51 to the lowest possible part of the furnace so as to decompose the tar formed as a by-product during the thermal decomposition of the coal and to reduce the amount of pulverized charcoal which disperses in the unreacted state, If the charcoal is introduced into the conical portion, the charcoal introduced into the conical portion will not be completely distributed due to stagnation and there is the danger of causing coking disorder in this portion. In addition, it would not make sense to place the pipe 51 for supplying raw material below the pipe 52 (33) bringing the gasification agent and in the final analysis the the most advantageous method consists in connecting the pipe 51 to the portion situated just above the conical portion, or the portion of rising side wall.

 Although the positions of the pipe 52 (33) bringing the gasifying agent are preferably chosen below the raw material supply pipe 51 so as to connect them to the lowest possible portion of the oven for the reasons mentioned above , if their positions are too close to the vicinity of the throat, there is the danger of producing a hot spot in the vicinity of the throat and, as a consequence, of slagging disorders. As a result, the pipe 52 (33) should preferably be connected to substantially middle positions on the slope of the conical portion. In this case, by projecting the discharge ends of the pipe 52 (33) into the furnace through the furnace wall, it is possible to prevent the slag from melting from the surface of the wall on the ends of unloading and grow there.

 The supply pipe 41 for recovered charcoal must be connected to the lower part of the oven, preferably to the portion of the oven situated below the pipe 33 (52) so as to increase as much as possible the period of time during which the coal is retained inside the gasification furnace.

 The temperature of the surface of the wall of the oven at the forge 55 and that of the conical portion of the bottom of the oven are adjusted according to the quantity of the cooling agent introduced into the cooling pipes 56.

When the starting material is a carbon coking dobby, the temperature interval must be such that the lower limit is the maximum temperature causing the coking (about 7000C) and that the upper limit is the temperature of de-boiling at this time. ash contained in the starting material.

 From the above description, it will be seen that the use of the method and of the apparatus according to the invention has the advantage of remarkably simplifying the operation compared to the method of the prior art, due to the fact that the temperature and the flow movement inside a gasification furnace are regulated independently of each other.

 Some examples are shown below showing the effects of the present invention.

Examples
Coal gasification is carried out using different types of combustion promoting gases for introduction into the combustion chamber.

raw material used
Heskisson (ordinary coal)
Particle size 3 mm or less
Heating capacity 29,335 kJ / kg
Softening temperature
ash 1 1750C
Melting temperature
ash 1 2500C
Elemental analysis (dry weight,%)
Carbon 7.72
hydrogen 4.6
Nitrogen 1.72
Oxygen 9.4
Sulfur 0.42
Ash 9.06
Introduction temperatures
Raw material 25 C
Gasification agent 1500C
Air (oxygen) from the
combustion 25 @
Operating temperatures
Gasification furnace 1,175 C
Combustion chamber 1 2O00C
Operating pressure 1471 Pa
Chamber gas Amount of gas required
of combustion for the gasification furnace
Type Quantity Steam
Oxygen water kit
Nm3 / h Nm3 / h Nm3 / h
Case 1 Air 26.0t 38.48 32.94
Case 2 Oxygen 14.10 46.18 36.21
Composition of dry gas produced (%)
H2 N2 CH4 CO CO2
Case 1 22.61 35.32 3.55 22.91 15.61
Case 2- 41.02 0.6 2.81 30.07 25.50

Claims (7)

 1 - A process for the gasification of coal or a similar material, comprising the steps according to which  the raw materials (31) comparing coal, coke or the equivalent, as well as oxygen or air and water vapor (33) are introduced into a gasification reaction chamber (32 ) and the coal is gasified in a fluidized state; and  a part of the gas which has been produced is injected (42) into the gasification reaction chamber, together with an oxygen-containing gas (43), into a combustion chamber (34) located below the gasification reaction chamber, the gas is burnt in the combustion chamber and the resulting gas is used as the fluidizing gas in the gasification reaction chamber.  2 - A gasification process according to claim 1, characterized in that one maintains in a lower part of the gasification reaction chamber (32) a temperature lower than the melting point of the ash produced in the reaction chamber gasification,  3 - A gasification process according to claim 1, characterized in that one chooses a gas flow speed in a groove of the gasification reaction chamber greater than the terminal speed of the particulate matter flowing at inside the gasification reaction chamber.  4 - An apparatus usable for the gasification of coal or a similar material, characterized in that it comprises  - a gasification reaction chamber (32; 53),  - means (31; 51) for introducing into said chamber raw materials comprising coal, coke or the like  - means (33; 52) for introducing into said chamber oxygen or air and water vapor  - a combustion chamber (34) situated below the gasification reaction chamber so as to use, as a common constituent of the fuel in this chamber, part of a gas produced in the gasification reaction chamber, the gasification reaction chamber (32;; 53) and the combustion chamber (34) being connected to each other by a vertical groove (55).  5 - An apparatus according to claim 4, characterized in that the means for introducing into the gasification reaction chamber (53) of oxygen or air and water vapor comprise nozzles (52) which protrude into said chamber (53) through its wall.  6 - An apparatus according to claim 5, characterized in that it comprises means (54) for vibrating said nozzles.  7 - A gasification device according to one of claims 4 to 6, characterized in that it further comprises a cooling means (56) disposed in a lower part of the gasification reaction chamber.