FI84203C - FOERFARANDE OCH ANORDNING FOER BEHANDLING AV BRAENSLE I EN FOERGASAR- ELLER FOERBRAENNINGSANLAEGGNING. - Google Patents

Description

84203

METHOD AND APPARATUS FOR FUEL TREATMENT IN FUEL OR GASIFICATION PLANTS

ADJUSTMENT OF MEASURES FOR BEHANDLING AV BRÄNSLE I EN FÖRGASAR- ELLER FÖRBRÄNNINGSANLÄGGNING

The present invention relates to a method of treating a carbonaceous fuel in a fluidized bed gasification or combustion process to increase the carbon efficiency in the process.

5

The present invention also relates to an apparatus for treating carbonaceous fuel fed to a fluidized bed reactor in a gasification or combustion process, to increase the carbon efficiency in the process. The fluidized bed reactor according to the invention 10 comprises a reactor chamber and a particle separator connected to the upper part of the reactor chamber, which is connected to the gas purifier via a degassing opening. The particle separator is connected to the lower part of the reactor chamber via a circulating mass return pipe.

15

It is known that, for example, in fluidized bed gasification plants, it is difficult to make the gasification reactions go far enough. The gas generated in the carburetor always carries out some of the carbon 20 of the injected fuel as fine dust. This fine coal dust is of the coke type and has a rather low reactivity. In other words, the coal dust generated is difficult to gasify. The amount of this carbon dust escaped depends not only on the reactivity of the fuel itself, but also greatly on the grain size of the fuel.

Peat is an example. When the peat is fed to the fluidized bed gasifier in the form of pellets with a grain size of 5-25 mm, 98 to 99.5% of the carbon contained in the peat is easily gasified. Correspondingly, when non-granulated milled peat is used as fuel, this carbonization of the carbon contained in the peat decreases to 75-85%.

5 When fine coal dust is separated from the gases and returned to the carburetor, the carbon efficiency does not substantially increase, as this coke dust has such a low reactivity that it does not have time to gasify before it flies out of the carburetor again.

10

Making finely divided fuel into pellets is expensive and known methods of making pellets require a lot of electricity or separate additives to form pellets. In addition, there are always 15 material losses in these processes.

According to Finnish publication FI 77688, it is known to prepare straw briquettes by mixing fly ash as a binding material with substantially dry straw material and pressing the mixture using a pressure sufficient to bring the mixture to a temperature of at least 75 ° C. According to the method, the binding effect of fly ash is achieved by pressure and temperature. The compression treatment takes place in an extrusion machine, from which cut 5 25 - 20 cm logs are made.

According to the Finnish patent FI 62678, it is known to compress peat into pellets by the suction trolley method without artificial drying. The energy used to compact the material raises the temperature of the pellets. The pellets are cooled by air blowing.

According to Finnish patent publication FI 76592, it is known to treat a fuel, such as peat, by pressurizing and heating it in a heat exchanger with a preheated liquid or combustible fuel. After cooling, the treated product is compressed into balls of the desired shape.

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It is an object of the present invention to provide an improved method for improving the carbon efficiency of fuel fed to fluidized bed reactors.

It is a particular object of the present invention to provide a more advantageous and simpler method for treating and granulating carbonaceous fuels than known methods.

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The process according to the invention is characterized in that the fuel is heated to 150-400 ° C by mixing hot bed material or circulating mass so that sticky surfaces are formed on the surface of the fuel due to the partial pyrolysis of the volatile organic portion in the fuel. The heated fuel is then rapidly cooled by mixing a substance colder than the heated fuel so that the finely divided fuel forms coarser granular fuel fractions.

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The device according to the invention is characterized in that the device comprises - a mixing chamber connected to a fuel supply connection and a hot material supply connection for supplying hot circulating mass and / or hot bed material to the mixing chamber, raising the fuel temperature to 150-400 eC, and - a cooling chamber connected to the mixing chamber, having an inlet connection for conducting a substance colder than the heated fuel to the cooling chamber and one for supplying granulated fuel to the reactor chamber in the cooling chamber.

The treatment according to the invention provides a simply granular fuel with a residence time in the combustion or gasification process which is long enough. One of the advantages to be achieved according to the invention is an increase in the efficiency of the process.

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The composition of solid fuels can be described by the following breakdown: - solid carbon 5 - volatile organic compounds - water - ash (inorganic fraction)

When the fuel is heated, the water in the fuel starts to evaporate. As the temperature of the fuel is further raised, gaseous and liquid fractions begin to form from the organic portion. This conversion of the organic volatile fraction into liquid and vaporous fractions is known as pyrolysis. Pyrolysis is defined as those reactions in which the longer hydrocarbon chains in the fuel are cleaved into shorter ones. On the other hand, some fuels contain waxy, tar-like heavy hydrocarbon residues with a low melting point of about 100 to 400 ° C.

20 When the fuel is heated, sticky surfaces are obtained on the surface of the fuel which tend to adhere to each other and form larger fuel particles.

It will be appreciated that when such a heated, sticky and tarry material is rapidly cooled while suitably stirring the material, a granular material is formed. The fuel granules formed become quite strong because they are "glued" to each other with organic waxes or silicon.

Typically, the fuel temperature must be raised to about 150 to 400 ° C. The required temperature depends on the fuel, its water content and the total reaction pressure.

The necessary heating of the fuel can be done by mixing e.g. hot bed material from the hot fluidized bed or hot circulating material from the circulating fluidized bed in a suitable manner so that the required fuel temperature is reached.

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Rapid cooling of the heated and sticky fuel is preferably accomplished by mixing a colder material. Such a suitable substance is, for example, chilled fuel fly ash preferably obtained from the process. In this case, in addition, any carbon or coke particles in the ash are made to bind to the fuel into larger particles. The coarser coke particles remain longer in the carburetor, for example, and have time to gasify in a known manner.

Cooling can also be performed with the circulating mass entering the return pipe from the particle separator. A portion of the circulating mass is cooled, e.g. in a heat exchanger, and then mixed with the heated fuel. By adjusting the temperature or amount of circulating mass used to cool the heated fuel, the desired cooling effect or and granulation is obtained.

Sorbents added to the combustion or gasification process can also be used as a refrigerant. For example, it is advantageous to supply Ca- or Mg-containing substances to the carburetor in connection with the fuel supply in order to separate the sulfur contained in the fuel from the gases.

Cooling can also be accomplished by adding to the fuel a suitable amount of unheated fuel that adheres to the sticky particles while cooling the mixture. Thus, only a portion of the fuel needs to be heated to effect granulation.

Cooling is preferably performed in a fluidized bed, whereby the sticky particles adhere to the bed material and cool rapidly, forming a granular substance. The fluidizing space 35 does not require agitators or other moving members to adhere to the sticky particles that would be susceptible to wear.

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According to the invention, the cooled granular fuel does not adhere to the feed nozzles and can be easily fed evenly into the combustion chamber.

The invention will now be described in more detail with reference to the accompanying schematic drawings, in which Figure 1 shows an embodiment of the invention and Figure 2 shows another embodiment of the invention.

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Figure 1 shows a circulating mass type fluidized bed reactor 1 comprising a reactor chamber 2 and a particle separator 3 connected thereto. The particle separator is connected to the top of the reactor chamber. At the top of the particle separator there is a degassing opening 6 and at the bottom there is a return pipe 7 separated from the circulating mass. The second gas purifier is provided with a clean gas outlet 10 and a fly ash outlet pipe 11.

In one embodiment of the invention shown in Fig. 25, the separated circulating mass return pipe 7 is connected both to the lower part of the combustion chamber with a joint 12 and to a separate mixing chamber 14 with a connection 13. Fuel is fed to the mixing chamber via one 15. In the mixing chamber, the temperature of the fuel is raised by means of the circulating mass to obtain a granular composition.

One of the mixing chambers 14 leads to an adjacent cooling chamber 16, to which colder fly ash is introduced from the fly ash outlet pipe 11 by a connection 17. A part of the fly ash can be removed from the process directly to one 18. From the cooling chamber, the granular fuel-circulating mixture is led through 19 to the lower part of the combustion chamber.

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In the embodiment according to Figure 1, fuel, such as milled peat, is thus fed into a mixing chamber 14, where hot circulating pulp particles are mixed at the same time. Sticky surfaces are formed in the fuel, which allow the fine fuel particles to adhere both to each other and to the larger particles in the fuel mixture. The sticky fuel-circulating mass mixture is led to a cooling chamber 16, where it is rapidly cooled by the colder fly ash particles added thereto. The mixture is stirred at the same time to form a granular mixture which is fed to the reactor chamber 2.

Unheated fuel can also be used to cool the fuel-circulating mixture in the cooling chamber. 15

In the embodiment of Figure 2, the fuel introduced into the mixing chamber 14 through the joint 15 is heated directly from the reactor chamber 2 through the bed material introduced through the joint 20. Cooling in the cooling chamber 16 is performed in this embodiment with a cooled circulating mass. At least part of the circulating mass is led from the circulating mass return pipe 7 to the heat exchanger 21 to cool the circulating mass. A portion of the circulating pulp can be fed directly to the reactor chamber 2 without conventional cooling.

The embodiments shown in Figures 1 and 2 can, of course, be modified e.g. by using part of the circulating mass tube 7 to heat the fuel in the mixing chamber 14 and another part of the circulating mass to be cooled and used for cooling in the cooling chamber 16. It is also conceivable to heat the fuel directly then with fly ash or even some process input such as lime.

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The invention is not intended to be limited to the embodiments shown by way of example, but can be modified and applied within the scope of the inventive idea defined by the claims.

Claims (12)

A process for treating carbonaceous fuel prior to a gasification or combustion process in a reactor with conventional fluidized bed or circulating fluidized bed for increasing the useful power of the coal in the process, characterized in that the fuel is heated to 150-400 ° C. by incorporating hot bed material or circulating mass into it, such that by a partial pyrolysis of the volatile organic combustion portion of the fuel, sticky surfaces are formed on the surface of the fuel particles, whereupon the fuel is rapidly cooled by incorporating in this mixed material which is cooler than the heat. , So that fine-grained fuel forms coarser grain-shaped fuel fractions. Process according to Claim 1, characterized in that the fuel consists of milling or other atomized biofuel. 3. A method according to claim 1, characterized in that the fuel is cooled by incorporating cooled circulating mass in this. 25 4. A process according to claim 1, characterized in that the fuel is cooled by incorporating cooled ash from the fuel. 30 Process according to Claim 1, characterized in that the fuel is cooled by incorporating unheated fuel in it. 6. A process according to claim 1, characterized in that the fuel is cooled by incorporating in it absorbent which is used to remove sulfur from the fuel. Process according to claim 1, characterized in that the fuel is cooled in a fluidized state. i3 84203 Apparatus for treating carbonaceous fuel to be fed into a fluidized bed reactor in a gasification or combustion process for increasing the utility of the coal in the process, the fluidized bed reactor (1) comprising a reactor chamber (2) and a particle separator (3) connected to the upper part of the reactor chamber, which is connected by a gas outlet opening (6) to a gas purifier (9) and through a circulating mass return pipe (7) and / or a duct (12) with the bottom of the reactor chamber part, characterized in that the device comprises a mixing chamber (14) which is connected to a fuel feed line (15) and a hot material feed line (13,20) to feed hot circulating mass and / or hot bed material in the mixing chamber, to raise the fuel temperature to 150-400 ° C, and a cooling chamber (16) adjacent to the mixing chamber, said cooling chamber having an inlet duct (17 , 22) for feeding materials colder than the heated fuel to the cooling chamber and a channel (19) for feeding the fuel granulated into the cooling chamber to the reactor gun. Device according to claim 8, characterized in that the inlet duct (17) for the cooler material connected to the cooling chamber is connected to the gas ash (9) outlet (11) for the fly ash to guide the fly ash to the cooling chamber. 10. Device according to claim 9, characterized in that a heat exchanger (8) is arranged between the gas outlet opening (6) in the particle separator (3) and the gas purifier (9). 11. Device according to claim 8, characterized in that the cooler material inlet duct (22) connected to the cooler material is connected to a heat exchanger (21) connected to the circulating mass feed pipe (7) for conducting. the cooled circulating mass via the duct (22) and the heat exchanger (21) into the cooling chamber.