DE102013015536A1 - Process and plant for the at least partial gasification of solid, organic feedstock - Google Patents

Abstract

The invention relates to a method for the at least partial gasification of solid organic feedstock (A), in which a tar-containing carbonization gas is recovered from the feedstock (A) in a low-temperature gasifier (1) by smoldering, and the carbonization gas (B) is subsequently ( 2) is reacted by partial oxidation and then partial reduction to a synthesis gas (D), whereby in a cooling device (30) provided downstream of the high-temperature gasifier (2) the synthesis gas is cooled such that alkalis present in the synthesis gas remain in the gaseous phase, and Coke particles already present in the synthesis gas are no longer sticky, and a coarse fraction of coke particles from the synthesis gas is deposited in a cyclone device (4) downstream of the cooling device (30), a fine fraction of the coke particles passing the cyclone device (4) with the synthesis gas.

Description

The invention relates to a method and a plant for the at least partial gasification of solid organic feedstock, in particular of biomass, with a low-temperature gasifier and a high-temperature gasifier.

State of the art

Processes for the production of synthesis gas from solid organic feedstock, also referred to for short as gasification processes, are known. Advantageously, coal or biomass are used as starting material for such processes. In biomass gasification processes, for example, used wood and forestry wood or so-called energy wood, but also agricultural residues such as straw or chaff are used.

By gasification of biomass to synthesis gas with downstream process steps (so-called Biomass to Liquids method, BTL), for example, synthetic biofuel can be obtained, the well-known in its physicochemical properties gas-to-liquids (GTL) and coal-to- Liquids (CTL) fuels is similar. An example of a plant for the production of BTL fuels is at Kiener, C. and Bilas, I .: Synthetic biofuel of the second generation. World's first commercial BTL production plant. Energy 2.0, July 2008, pp. 42-44 , shown.

Methods and systems for the at least partial gasification of solid organic feed are also for example EP 0 745 114 B1 . DE 41 39 512 A1 and DE 42 09 549 A1 known. The present application relates in this case to such processes or plants which have a low-temperature gasifier and a high-temperature gasifier, as explained below. Compared with other methods, these allow, inter alia, a lower consumption of feedstock and have a higher cold gas efficiency.

In a low-temperature gasifier, the feedstock, such as biomass, by partial gasification with a gasification agent at temperatures between about 300 ° C and 600 ° C to coke (in the case of biomass so-called biococ) and carbonization reacted. The implementation is referred to in this application as "smoldering". Smoldering is known to be characterized by substoichiometric oxygen supply and thus incomplete combustion at a comparatively low temperature.

The carbonization gas is then transferred into a combustion chamber of the high-temperature gasifier and there with an oxygen-containing gas, for example with more or less pure oxygen, but also with air and / or oxygen-containing exhaust gases, eg. B. from gas turbines or internal combustion engines, partially oxidized. By this oxidation released heat causes a temperature increase to 1200 ° C to 2000 ° C, for example 1400 ° C. Under such conditions, aromatics, tars and oxo compounds contained in the carbonization gas are completely decomposed. As a result, a synthesis gas is formed, which essentially only contains carbon monoxide, hydrogen, carbon dioxide and water vapor. The synthesis gas can also be referred to as (synthesis) raw gas at this point.

In a further stage, for example in a quench unit integrated in the high-temperature gasifier or in a downstream unit, the synthesis gas produced in this way can be brought into contact with coke from the low-temperature gasifier. The coke can be previously treated separately (eg by grinding and sifting) and then introduced into the quench unit. By endothermic reactions between coke and synthesis gas (so-called chemical quench) the latter is cooled to a target temperature of about 900 ° C. This also causes partial conversion of the carbon dioxide to carbon monoxide.

The carbon monoxide-rich synthesis gas produced in this way can then be further conditioned. The conditioning includes, for example, a further cooling, a dedusting, a compression and / or the separation of residual carbon dioxide.

The conditioning comprises in particular the separation of residual coke from the synthesis gas. This is accomplished in practice by means of a cyclone and a downstream filter. The thus separated residual coke is then cooled in cooling screws and discharged via a container lock from the pressure chamber. A portion of the residual coke is introduced via container locks back into the pressure chamber and passed through a dense phase conveyance to the burner (Hochtemperaturvergaser).

During the cooling of the synthesis gas, however, there is a condensation of alkalis on the residual coke, so that not all the residual coke can be recycled to avoid too much alkali concentration in Hochtemperaturvergaser. In conventional systems, therefore, a portion of the alkali-loaded residual coke is removed from the system or discarded.

By this partial non-use of residual coke, however, the efficiency of the system is reduced overall.

There is therefore a need for improvements in the operation of corresponding plants, in particular for a possibility of more effective utilization of residual coke.

Disclosure of the invention

According to the invention, a method and a plant for the at least partial gasification of solid organic feedstock, in particular of biomass with a low-temperature gasifier and a high-temperature gasifier with the features of the independent claims are proposed. Preferred embodiments are subject of the subclaims and the following description.

Advantages of the invention

The invention is based on a known process for the at least partial gasification of solid organic feedstock, for example biomass. From the feedstock a tar-containing carbonization gas is recovered in a low-temperature gasifier by smoldering, as explained above. The carbonization gas is then reacted in a high-temperature gasifier by partial oxidation and then partial reduction to a synthesis gas and further processed downstream of the high-temperature gasifier in appropriate treatment facilities.

The synthesis gas is cooled after leaving the Hochtemperaturvergasers first in a cooling device to a temperature of about 600-800 ° C. The cooling takes place according to the invention in such a way, d. H. to a temperature such that a substantial proportion (in particular at least% by weight 10%,% by weight 20%, 30%, 40%, 50%, 60%, 70%, 80% or 90%) of the synthesis gas existing alkalis remain in the gaseous phase, but coke particles are already no longer sticky. At higher temperatures, although a large proportion of the alkalis in the gaseous phase, the stickiness of the coke particles is too pronounced, which can lead to problems in further handling.

The actual temperature to which it is cooled may depend on the composition of the feed and / or environmental conditions. To set a suitable temperature can be used on empirical values. It is also conceivable to provide corresponding sensors or measuring devices which detect the phase of the alkalis or the stickiness of the coke particles, and give the detected values to a control device, via which the temperature can be set.

The invention is characterized in that a coarse fraction of coke particles is separated from the synthesis gas in a cyclone device provided downstream of the high-temperature gasifier and the cooling device, a fine fraction of the coke particles passing through the cyclone device with the synthesis gas. The fine fraction of coke particles leaves with the synthesis gas containing the gaseous alkalis, the cyclone device and can be removed from the system. The coarse fraction of the coke particles, which is substantially alkali-free, can be recycled to the high temperature gasifier.

According to a particularly preferred embodiment of the method according to the invention, the synthesis gas passing through the cyclone device is further cooled in a cooler provided downstream of the cyclone device. The coke particles of the fine fraction present in the synthesis gas in this case have, for example, diameters of 0.1 to 10 .mu.m. During further cooling, the alkalis also present in the synthesis gas condense on the surface of these coke particles. Hereby, a targeted separation of the alkalis takes place on the particles of the fine fraction, which passes through the cyclone device with the synthesis gas stream. The particles of the fine fraction are particularly suitable for alkali deposition, since they have a relatively large surface area with relatively low mass. As a result, a relatively large surface area is available for the condensation, the calorific value loss being relatively low.

According to a preferred embodiment of the method, the coarse fraction of the coke particles, in particular taking advantage of gravity, transferred in a buffer tank and then in a vertically arranged standpipe, wherein the height of the standpipe is selected so that in its lower part sufficient for fluidization pressure is provided to allow dense phase conveying and to ensure the entry of the coke thereby provided in the high-temperature gasifier. The diameter of the standpipe is chosen so that bridging of the coke particles of the coarse fraction can be avoided.

In a particularly advantageous manner, the lowest part of the standpipe can be formed with a further reduced diameter, whereby an increase in the flow velocity can be provided, so that the required for the dense phase fluidization fluidization is ensured only in this lowermost region of the standpipe.

The existing in the buffer tank or in the standpipe residual coke acts as a pressure barrier, so that from the bottom of the standpipe in the Hochtemperaturvergaser recirculated coke can be promoted under a suitable delivery pressure. Compared with the pressure in the cyclone device prevails in the lowest part of the standpipe preferably an overpressure of about 0.2 to 1 bar.

Conveniently, recycle of coke over the buffer vessel and standpipe is performed at a temperature substantially equal to the temperature in the cyclone device. As a result, coke can be recycled to the high temperature gasifier at a very high temperature, whereby the efficiency of the gasification is improved accordingly, for example, 0.5% to 1%.

The invention will be further explained with reference to the attached figures, which show preferred embodiments of the invention.

Brief description of the drawings

1 shows a plant which is adapted to carry out a method according to the invention, in a schematic representation.

Embodiment of the invention

In 1 a system is shown which is set up to carry out a method according to the invention and has a total of 10 is designated. The attachment 10 includes a low temperature carburetor 1 and a high temperature carburetor 2 ,

In the low temperature carburetor 1 For example, an input material, for example biomass such as wood or corresponding waste, can be fed in (as explained above) by means of an arrow 11 illustrated). About a line 12 For example, oxygen can be fed. The low temperature carburetor 1 is designed to blaze the solid organic feedstock A. For this purpose, the low-temperature carburetor 1 externally, for example with waste heat from the high-temperature gasifier 2 , to a suitable temperature, for example 300 ° C to 600 ° C, heated. In a start-up phase of the system can also start-up burner of the high-temperature gasifier 2 be used.

About a line 13 can from the low temperature carburetor 1 a Schwelgas B and discharged into the high-temperature gasifier 2 be transferred. The high temperature carburetor 2 is formed in two parts. It comprises an oxidation unit 21 and a quenching unit 22 , In the oxidation unit 21 the carbonization B is partially oxidized with an oxygen-containing gas supplied, resulting in, for example, temperatures of 1,400 ° C to 2,000 ° C. As a result, a synthesis gas is obtained. In this synthesis gas contained coke particles have due to the high temperature on a strong stickiness. That at the exit of the high-temperature gasifier 2 obtained synthesis gas becomes a cooler 30 fed, and there, for example, cooled to a temperature of 600 to 800 ° C.

This temperature is chosen so that present in the synthesis gas alkalis remain in a substantial proportion in the gaseous phase, and in the synthesis gas contained coke particles have no more stickiness.

After this cooling device, the synthesis gas of a cyclone device 4 fed where a coarse fraction of the residual coke in a buffer tank 15 is separated, while the synthesis gas, which among other things receives a fine fraction of coke particles (for example, with diameters of 0.1-10 microns) and gaseous alkalis, via a line 17 another cooling device 19 is supplied.

In the cooling device 19 the synthesis gas is cooled in such a way, for example, to temperatures of 100 ° C to 200 ° C, so that the alkalis on the particles of the fine fraction of the coke particles condense. This contaminated with alkalies residual coke z. B. by means of (not shown) wet gas scrubbing from the syngas stream.

The coarse fraction of the residual coke, which is substantially free of alkalis, passes, as mentioned, by gravity into the buffer tank 15 and then into a below the buffer tank 15 vertically arranged standpipe 25 , The diameter of the standpipe is chosen so that bridging of the coke particles can be avoided. Preferred diameters of the standpipe here are 300 mm to 1,000 mm.

The height h of the standpipe, for example 5 to 50 meters, is selected such that a sufficiently large pressure build-up is achieved during fluidization of the coke particles present in the lowermost part of the standpipe, so that dense phase conveying by means of a suitable conveying gas (inert gas, For example, CO2) can be operated. Such dense phase conveying represents a particularly effective form of conveying the coke back into the high-temperature gasifier. The lowest part 25a of the standpipe 25 is formed by a reduction in diameter so that here the flow rate of the supplied gas for the fluidization is sufficient, but not for the larger cross-section above.

The promotion of the coke from the standpipe 25 to the high-temperature gasifier via a line 30 , which for example via a valve 32 , Can be acted upon by a conveying gas. It is preferred that the promotion takes place at the temperature level of the cyclone device. This means that the recirculated coke, when returned to the high temperature gasifier, is at substantially the same temperature as during its separation in the cyclone device 4 having.

The plant shown thus is able to auszuschleusen targeted alkalis from the residual coke to be returned.

It is also able to recycle high-temperature residual coke into the high-temperature gasifier, thereby increasing overall gasification efficiency. Such a system can be provided in a very cost-effective manner. The system has no mechanical moving parts, and is therefore compared to conventional solutions very reliable and low maintenance. The efficiency of the carburetor is increased over conventional solutions, since a smaller proportion of coke must be discarded.

The illustrated components cyclone device 4 , Buffer tank 15 and standpipe 25 may also be provided further downstream in the system, for example, downstream of the cooling device 19 , In this case, however, eliminates the advantage of effective heat recovery and targeted Alkalaliausschleusung. The advantage of reliability by absence or minimization of the number of moving parts is retained.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 0745114 B1 [0004]
• DE 4139512 A1 [0004]
• DE 4209549 A1 [0004]

Cited non-patent literature

• Kiener, C. and Bilas, I .: Synthetic biofuel of the second generation. World's first commercial BTL production plant. Energy 2.0, July 2008, pp. 42-44 [0003]

Claims (7)

Process for the at least partial gasification of solid organic feedstock (A), in which from the feedstock (A) in a low-temperature gasifier ( 1 ) by smoldering a tar-containing carbonization gas is obtained, and the carbonization gas (B) then in a high-temperature gasifier ( 2 ) is converted by partial oxidation and then partial reduction to a synthesis gas (D), characterized in that in a downstream of the high-temperature gasifier ( 2 ) provided cooling device ( 30 ) the synthesis gas is cooled to a temperature at which the alkalis present in the synthesis gas at least partially remain in the gaseous phase, and coke particles present in the synthesis gas are no longer sticky, and which is present in a downstream of the cooling device ( 30 ) provided cyclone device ( 4 ) a coarse fraction of coke particles is separated from the synthesis gas, wherein a fine fraction of the coke particles, the cyclone device ( 4 ) with the synthesis gas. A method according to claim 1, characterized in that the synthesis gas passing through the cyclone means is located in a downstream of the cyclone means ( 4 ) provided cooler ( 19 ) is cooled. Method according to one of the preceding claims, characterized in that the coarse fraction of the coke particles deposited in the cyclone device into the high temperature gasifier ( 2 ) is returned. A method according to claim 3, characterized in that the coarse fraction of the coke particles in particular under application of gravity in a buffer tank ( 15 ) and then in a vertically arranged standpipe ( 25 ), wherein the height of the standpipe is selected so that in the lowermost part of the standpipe sufficient for fluidizing pressure can be provided to initiate a dense phase current promotion and the entry of the thus provided coke in the high-temperature gasifier ( 2 ) to ensure. Method according to one of the preceding claims 3 or 4, characterized in that the diameter of the standpipe is selected so that bridging of the coke particles is avoided. Method according to one of the preceding claims 3 to 5, characterized in that the recycling of coke via the buffer container ( 15 ) and the standpipe ( 25 ) is carried out at a temperature substantially equal to the temperature in the cyclone device ( 4 ) corresponds. An installation set up for carrying out a method according to any one of the preceding claims, comprising a low-temperature gasifier ( 1 in which by smoldering a tar-containing carbonization gas can be obtained from a solid organic feedstock and a high-temperature gasifier, in which the carbonization gas can be converted by partial oxidation and then partial reduction to a synthesis gas, wherein downstream of the high-temperature gasifier a cooling device ( 30 ), which cools the synthesis gas leaving the high-temperature gasifier in such a way that alkalis present in the synthesis gas remain in a gaseous state, with coke particles already present in the synthesis gas no longer being tacky, and a downstream cooling device ( 30 ) provided cyclone device ( 4 ), by means of which a coarse fraction of coke particles from the synthesis gas is deposited, wherein a fine fraction of the coke particles passes through the cyclone means with the synthesis gas.

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