DE3112708C2 - Process for generating H 2 and CO-containing gases from fine-grained fuel in the fluidized bed with heat exchangers immersed therein - Google Patents

Abstract

In a method for gasifying carbon-containing particles in a gasification zone operated as a fluidized bed with a gasification agent with indirect heating by a heat exchanger immersed in the fluidized bed and through which a circulating heat transfer fluid flows, the carbon-containing particles are partially gasified; From there they are transferred to a combustion zone operated as a fluidized bed downstream of the gasification zone and burned with air, for example, whereby the heat transfer medium cooled in the gasification zone is fed to a heat exchanger in the combustion zone, where the released heat of combustion is absorbed again and is returned to the heat exchanger of the gasification zone ; The heat transfer fluid flows through another heat exchanger of an additional energy source and the gasification and combustion zone are each supplied with predetermined amounts of carbonaceous particles and reaction gas in order to compensate for a changing supply of thermal energy for gasification and / or a changing demand for product gas wear.

Description

- The heat transfer medium to a part in a further, from an additional, in particular natural Energy source that is not subject to fluctuations in performance, operated heat exchanger is heated, wherein

- The combustion zone heating the heat transfer medium in the other heat exchanger is operated in such a way that the power fluctuations of the further heat exchanger are compensated and the product gas generation is also controlled in the generator.

2. The method according to claim 1, characterized in that the inflow amounts of fuel and Gasification agent can be varied in the gasification zone and the amount of fuel flow into the combustion zone is kept constant by discharging or adding.

3. The method according to claim 2, characterized in that the combustion zone is used as an additional fuel finely divided ballast coal is still supplied.

4. The method according to one or more of claims 1 to 3, characterized in that the in the Gasification zone cooled heat transfer medium flows through the two heat exchangers one after the other.

5. The method according to one or more of claims i to 3, characterized in that the in the Gasification zone cooled heat transfer medium in variable proportions in parallel to the two heat exchangers flows through.

6. The method according to any one of claims 1 to 5, characterized in that the further heat exchanger is heated by solar energy.

The invention relates to a method according to the preamble of claim 1.

One of the main problems with coal gasification is the provision of sufficient quantities of

thermal energy to a Temperuturniveau of about 700 ⁰ C. UOO Various solutions have been described in the generic DE-OS 29 03 985th These are processes in which the supply of gasification heat is essentially constant over time or can easily be kept constant.

It is also known (D. W. Gregg et al., "Solar Energy", 1980, Vol. 24, pages 313 to 321), coal with the help of Gasing solar energy. In this case, a complex technique is required and the problem must be The naturally caused fluctuations in the output of solar energy from other energy sources can be resolved balance.

It is also already known from DE-PS 5 76 134, an additional heating of the reaction zone Make gas generator, preferably by means of electrical heating elements or electrical resistance heating can be done. It is particularly disadvantageous that heating with electrical energy is expensive and from an overall energy point of view, has a very unfavorable degree of efficiency.

In addition, it is already known from DE-OS 26 12 040, focused sunlight from a tower-top solar oven as a heat source in pyrolysis and gasification with steam or CO2 from coal, manure or to use other solid organic wastes in a fluidized state. However, this involves expensive catalysts and a complex device is required. - Steam or CO2 should come through on cloudy days Burning part of the stored generator gas can be heated in order to avoid a shutdown.

Finally, it is known from "Bergbau", 1980, page 56, that solar heat is beneficial for coal gasification Environmentally friendly to use, whereby no energy share from the coal itself is required. That applied However, the method is not disclosed.

The coupling of energy sources with strong fluctuations in output into a conventional gasification process has failed so far because the reactors necessary for the individual sub-processes are not with the necessary flexibility can be coupled with each other.

The object of the invention is now to provide alternatives in a method of the generic type Energy sources that have natural fluctuations in output can be used in the gasification of coal to make and compensate for these fluctuations in performance for a short time in order to use the gas generator with konb5 to be able to operate siant performance; in addition, a gasification process that can be controlled very flexibly is achieved suggested that it could not be influenced despite the different heat generation Heat source enables a higher gas demand to be met.

In a method of the generic type, the object is achieved according to the invention by the characterizing

the features of claim 1 solved

Appropriate further developments are contained in the subclaims.

Helium is particularly suitable as a circulating heat transfer fluid.

As an additional energy source come high-temperature nuclear reactors, solar collectors (»heliostats«), Geothermal storage or fusion reactors, which use the waste heat from high-temperature processes, as well as other energy sources in question, especially those that have power fluctuations, such as at wind energy or tidal currents. - A major advantage of the invention Process consists in its high adaptability to the energy supply of the additional Lnrgiequelle. In this way, previously less usable energy sources or the types of energy can also be used per mnh supply to be exchanged on the energy market. - It is therefore a flexible adaptation of the Gasification process to the respective available thermal energy for the gasification and to the The combination of measures according to the invention makes the demand for product gas possible.

The quantities of carbonaceous particles and reaction gas fed to the gasification zone and the combustion zone are determined according to the demand for product gas and the heat available from the additional energy source. As a rule, the endeavor to operate the gasification zone will result in gas production that is as constant as possible over time, even with a fluctuating supply of additional energy, while at the same time converting the coal used as completely as possible into the overall process. Correspondingly, the amount and residence time of the coal particles in the gasification zone must be controlled according to criteria known per se, with the partially gasified carbon-containing particles reaching the combustion zone being offered in such large quantities that the heat requirement for the gasification reaction beyond the additional energy source is ensured.

Particularly advantageous embodiments of the supply of carbon-containing particles and reaction gas into the Gasification and combustion zones emerge from claims 2 and 3.

If the supply of heat from the additional energy source decreases, the one that is now to be applied as a replacement is used thermal energy for the gasification provided by the fact that, according to the invention, the in the combustion zone transferred mass flow of carbonaceous particles and the amount of combustion gas increase. The heat production in the combustion zone is proportional to the amount fed into it Amount of carbon and, since the reaction rate is very high and proportionally changes the air supply there are practically no delays or dead times in the provision of gasification energy. In this way, z. B. also unexpectedly and quickly occurring cloud formations and the resulting accompanying reductions in energy supply from heliostats are compensated for without this special energy reserves are required.

A preferred mode of operation is independent of the respective power of the additional energy source generate a constant amount of product gas. Then, according to the invention, the same amount of coal must always be used be gassed and. Depending on the performance of the additional energy source, a certain amount of residual coke transferred to the combustion zone and burned there: this has a simultaneous Variation of the flow of carbonaceous particles from the gasification zone to the combustion zone Episode.

Surprisingly, however, it is also possible to keep the combustion zone under very constant operating conditions to operate (volume flow of carbon-containing particles transferred into them and volume of combustion gas) and thereby absorbing power fluctuations of the additional energy source, d. that is, all the time to make full use of the entire energy supply and to start the gasification with the correct amount of gasification energy to ensure the necessary temperature level. This is achieved according to the invention in that the The inflow of carbon-containing particles into the gasification zone and the amount of gasification gas varies will. In this way, by changing the residence time of the carbonaceous particles, the generated Amount of product gas varies and thereby adapted to the energy supply of the additional energy source, nevertheless the combustion in the combustion zone remains just as complete as before, so that the efficiency of the entire system remains constant despite the changed energy supply.

The versatility of the process is advantageously increased by the fact that, according to the invention, the combustion zone in addition, finely divided ballast coal of any origin is added. That way you can in periods of time a little or no supply of energy due to the additional energy source inferior, carbon-containing products are subjected to the fullest possible use of their carbon content, which has a beneficial effect on the usability of the existing coal reserves. The influx of partially gassed carbon-containing particles (residual coke) from the gasification zone into the combustion zone or the inflow at z. B. additional ballast coal in the combustion zone due to the energy requirements of the gasification zone as well as through the supply of thermal energy made available by the additional energy source certainly.

Particularly advantageous ways of using the additional energy source in the best possible way are in the claims 4 and 5 characterized.

A "series connection" according to the invention of the heat carrier flow enables the use of additional Energy sources where the outlet temperatures are insufficient for use in a gasification process are. For example, it has been shown that it would be easier if on a high temperature nuclear reactor to supply energy for coal gasification, the heat transfer fluid heated by it is somewhat lower Exit temperature could have than it is required for direct use in a coal gasification. In In such a case, peak overheating of the heat transfer fluid can occur as a result of the heat demand controlled combustion of the partially gasified carbonaceous particles take place. Especially interesting This method is used when the heat supply from the additional energy source does not only increase in terms of temperature is small, but also fluctuates in terms of quantity, depending on the time.

The "parallel connection" according to the invention of the combustion zone and the additional energy source is you always choose when the temperature is that provided by the additional energy source Heat is sufficiently high and only power fluctuations have to be compensated. In this case, at sufficient heat supply from the additional energy source, the heat production of the combustion zone can be practically reduced to zero by z. B. the carbonaceous ones leaving the gasification zone partially gasified particles are discharged and temporarily stored in the combustion zone for later use will. - A parallel connection is also possible with one that occurs continuously or only intermittently Reduced energy supply from the additional energy source possible; then the residual heating of the heat transfer fluid is thereby achieves that the heat transfer fluid heated in the combustion zone has a corresponding height Temperature, d. that is, the appropriately controlled combustion and admixture with the heat transfer fluid of the additional energy sources in terms of temperature and energy quantity, the remaining requirements of the latter is adjusted.

By using an additional energy source according to the invention with species-specific power fluctuations - which have been explained above - that which can be achieved with the method according to the invention can be achieved Flexibility of adapting to the need for gasification energy with the best possible use of the usable Carbon in the carbonaceous particles are exhausted. - Probably the greatest advantages achieved in a combination with a solar energy source, since on the one hand with such energy sources energy on a sufficiently high temperature level can be provided, but on the other hand the fluctuations in performance are particularly high, which normally results in a considerable amount of technical measures j 20 men leads to the power fluctuations of such in the form of heat storage or the like

To balance energy source to some extent.

Besides an adjustment to the available thermal energy for the gasification process can the method according to a further development of the invention can advantageously be handled in such a way that the volume streams carbonaceous particles fed to the gasification zone and the combustion zone and Reaction gases the respective demand for product gas and the thermal output of the additional energy source be adjusted. In particular, it is thereby possible at any time while avoiding fluctuations to generate a constant or desired amount of usable casting or to increase demand peaks for usable gas at any time cover.

A preferred mode of operation of the process according to the invention is, with a constant output, of the additional energy source to vary the amount of gasification gas. So much for an increase in the amount of product gas is to take place, more carbonaceous particles have to be gasified and therefore more at the same time Energy is made available in the gasification zone; that means that both the fed Amount of carbonaceous particles in the gasification zone as well as the transferred amount of partially gasified carbonaceous particles must be increased in the gasification zone. In contrast, is a lowering of the If the amount of product gas is intended, fewer carbonaceous particles have to be gasified. Here offers alternatively: Either the output of the additional energy source is reduced and at the same time the flow of carbonaceous particles into the gasification zone is reduced, while the amount of into the Combustion zone transferred carbonaceous particles remains constant. This approach also has a The result is a reduction in secondary electricity. Or the performance of the additional energy source will left constant and the flow of carbonaceous particles into the gasification zone is reduced. Depending on the degree of gasification that is established, a defined amount of partially gasified, carbonaceous substances must be used Particles are transferred into the combustion zone. As a result, there is a higher electricity production.

Further advantages and possible applications of the present invention emerge from the following description of exemplary embodiments with reference to the drawings. It shows
F i g. 1 a principle diagram with »parallel connection«,

F i g. 2 shows a representation according to FIG. 1 with "series connection" of the heat transfer medium heater.
In the figures, a gas generator 1 consists of a known, lying, preferably cylindrical container, in the lower half of which two fluidized beds are operated in a trough 2 designed as an inflow base. Heat exchangers 3a and 3b, through which a heat-transferring fluid flows and which operate in a closed heat transfer circuit, are immersed in the fluidized beds. A line 4 continuing from the heat exchanger 36 transports cooled heat transfer fluid to a fan 5 and - according to FIG. 2 - further via an additional energy source 21 to be described later to the heat exchanger 3a which absorbs further heat and from there to the heat exchanger 3b which emits heat. According to FIG. 1, the line 4 divides into two parallel pipelines 4a and 4b. The line 4a leads directly to the heat exchanger 3a and further to the heat exchanger 3b, while the line 4b leads via the additional energy source 21 directly to the heat exchanger 3b

The gas generator 1 has in the area of the one fluidized bed into which the heat exchanger 3b is sunk, an inlet 6 for partially gasified, fine-grained coal or coke, which can be present in the particle size ranges generally known for fluidized-bed processes. Through a further inlet 7, which may be present in the area of the other fluidized bed, into which heat exchanger 3a is sunk, if necessary coal - z. B. cheap ballast coal - are fed in to support the combustion operated in this fluidized bed.

The coal to be partially gasified through inlet 6 leaves the fluidized bed through outlet 8 Gasification zone 9. Outlet 8 is preferably located at the opposite end of the inlet 6 Gasification zone 9 within the gas generator 1, preferably in its bottom area. Since there are fluidized beds Similar to how liquids behave, it comes about by filling the gasification zone with to be gasified Coal through inlet 6 and withdrawal of partially gasified coal through outlet 8 in the longitudinal direction of the gasification zone

automatically to a transport of the carbonaceous particles. The second fluidized bed in the gas generator 1, the combustion zone 10, is in the first line with that through the outlet 8 leaving the gasification zone Remaining amount of coke 11 is applied at one end, while at its opposite end in the longitudinal direction an ash extractor 8a is provided, through which the not to be explained later with the Ash discharged from the flue gas stream is withdrawn. In this second fluidized bed (combustion zone 10) no solids transport from one side to the other is sought; consequently there is no pronounced one Longitudinal concentration gradient.

The gasification zone 9 is via a gas inlet 12, preferably below the inflow base 2, with Gasification agents (reaction gas), such as. B. steam supplied. The gasification agent is before initiation into the gasification zone through a heat exchanger 13, e.g. B. a steam superheater, which on his the other side of the heat transfer fluid leaving the gasification zone and flowing through line 4 is flowed through. It may be advisable to give the heat exchanger 13 a further heat exchanger 14, for. B. a Upstream steam generator, which is thermally connected downstream of the heat exchanger 13 in line 4 is.

It is possible in the heat exchanger 14 z. B. to generate so much steam that a downstream steam turbine 15 can be operated with it first. In this way, the heat transfer fluid flowing in line 4 can be cooled to the most uniform possible inflow temperature to the additional energy source 21 and possibly the combustion zone 10. With a constant, low heat transfer medium inlet temperature, it is possible to operate the additional energy source in a controlled manner. In addition, the fan 5 can thereby be designed as a conventional circulating fan. Since the gasification process only has a fixed and generally known need for gasification agent, in particular water vapor, it is possible with the help of the steam turbine 15 to use additionally generated water vapor and thus to favorably influence the efficiency of the overall process. For example, the steam turbine 15 can be connected via its shaft directly to a generator 15a for generating electrical power. The illustrated cooler t5b and compressor 15c complete the feed water circuit for steam generation.

The raw gases formed in the gasification zone 9 leave this via outlet 9a and can through a Heat exchanger 16, e.g. B. a steam generator, which works in parallel with the heat exchanger 14, can be cooled. The gasification raw gases cooled in this way can be converted into a conversion stage 17 in a manner known per se the desired useful gas 17a are converted. The conversion stage 17 can be a Conversion for the production of synthesis gas with a desired ratio of CO to H2 or a Act methanation to produce methane.

The flue gases produced in the combustion zone 10 become a known per se via outlet 10a Dedusting stage 18 supplied and from there z. B. a gas turbine 19, which has a seated on its shaft Air compressor 20 drives, through soft air (reaction gas) via inlet 20a, preferably in the floor area, the combustion zone 10 is fed.

The coupled into the gasification process thermal energy of the additional energy source 21 is from a and transported the same heat transfer fluid that is also heated in the combustion zone 10. the additional energy source 21 therefore only needs a heat exchanger, the z. B. flowed through by helium and there is no need for intermediate storage which is known to be associated with losses the heat energy released in 21, as z. B. with heliostats for even energy distribution a longer period of time is necessary.

F i g. 2 differs from FIG. 1 only in that now the entire heat transfer fluid one behind the other the additional energy source 21 and the heat exchanger 3a flows through.

The amount of carbonaceous particles fed to the gas generator can be varied in a number of ways, z. B. by weighing the coal charge, with cell wheel metering by setting the speed of the rotary valve or, in the case of pneumatic metering, by weighing the coal charge and via the pressure loss of the pneumatic conveying line or by pulsed conveying at a constant conveying speed. - The gas escaping from the fluidized beds (product gas and flue gas) are z. B. by means of aperture or Gas meters controlled. If these quantities are to remain constant, this can be done with a corresponding Regulation of the feed of carbonaceous particles into the gas generator can be achieved.

Working examples

In a lying gas generator known per se according to FIG. 1, a coal with up to 40 % By weight of volatile components and up to 30% by weight of ash with a maximum of 10% by weight of moisture and a medium grain size of approx. 0.2 to 0.5 mm used. The gas generator consists of a vortex trough with a Length of 48.5 m, with the gasification zone taking up 27.7 m and the combustion zone taking up 20.8 m. Through this a relatively uniform residence time spectrum of the carbon-containing particles is achieved, i. i.e., it acts is not yet a pure, so-called plug flow, but the particle backmixing persists (backmixing) within reasonable limits.

The fluidized bed inside the gas generator has a width of 5.4 m and a height of 2.8 m. The heat exchange area in the gasification section is 3420 m ² , in the combustion section 3700 m ² . The gas generator is divided into two areas by a transverse wall (weir), the gasification zone and the combustion zone. The closed heat transfer circuit operated with helium ests as in the Fi g. 1 or 2 switched. A solar power plant is assumed as an additional energy source, as presented by DW Gregg in "Solar Energy", Vol. 24, pages 313 to 321. The extreme situation that is taken into account is that the solar power plant runs at 100% power and supplies almost all of the thermal energy for the gasification, so that only an insignificant part is burned (example 1). as well as a situation in which the power of the solar power plant

Is 0, so that the entire thermal energy for gasification is provided in the combustion zone must (example 3).

The results given in the table, which are obtained with one and the same gas generator, are of course and show how extremely flexible a gas generator is with the measures according to the invention can be adapted to changing offers of thermal energy by the additional energy source can.

Tabel

Design variant MW For this 2 Parallel connection Series connection 2 ?, 4th % of solar power plants and fluidized bed combustion 63 0 138 Examples 30th 0 66 kg / s 1 Output of the solar power plant ⁰ C 210 146 146 146 Output of the solar power plant m ² 100 900 900 900 Carburetor part kg / s 3420 3420 3420 Helium mass flow kg '. 146 19.3 21.9 15.4 Helium inlet temperature kg / s 900 7.74 10.08 4.05 Heat exchanger surface % 3420 57.1 57.1 57.1 Charcoal input amount NmVs 11.6 41.3 40.9 41.5 Rescoke withdrawal amount o / o 1.08 39.7 39.3 39.8 used water vapor 57.1 59.8 52.2 75.2 Degree of water vapor decomposition kg / s 40.3 Product gas quantity *) kg / s 38.0 104.28 146 146 Degree of gasification kg / s 95 7.74 08/10 4.05 Combustion part NmVs 1.295 1.547 0.932 Helium mass flow m ² 6,935 184 248.5 91.0 Remaining coke input quantity 1.08 3700 3700 3700 Ash withdrawal amount 0.605 (2740) **) (3700) **) (1360) **) Combustion air volume kg / s 13.8 Heat exchanger surface kg / s 3700 16.57 18.81 13.24 kg / s (205) **) 9.92 9.82 9.96 Carbon balance kg / s 6.32 8.54 3.12 C - inserted 10.00 0.33 0.45 0.16 C - gassed **) Product gas composition (dry) in% by volume 9.50 C - burned H 7 52.9% 0.475 C - loss CH ₄ 9.2% 0.025 *) effective heat exchanger surface CO 13.0% H ₂ S 0.1% CO ₂ 24.5% N ₂ 0.3% Sheet drawings

Claims (1)

Patent claims: 1. Process for the production of Hj- and CO-containing gas from fine-grained, carbon-containing fuel, such as coal or coke, which is operated as a fluidized bed gasification zone with steam as Gasifying agent and under indirect heating with the help of a submerged in the fluidized bed, vou a circulating gaseous heat transfer medium through which the heat exchanger is partially gasified is, with the resulting fuel residue from the gasification zone in a downstream of it Combustion zone transferred and burned in an air-powered fluidized bed as well as that The resulting flue gas is discharged and the heat transfer medium cooled in the gasification zone is transferred to a heat exchanger fed into the combustion zone, and the heat transfer medium heated there by the heat of combustion is fed back to the heat exchanger of the gasification zone, characterized in that that