DE102006049781A1 - Gasification of organic materials by air, comprises gasifying the organic materials to a raw product gas in a first gasification reactor, separating the coke from the product gas by a cyclone and feeding the coke to a further reactor - Google Patents

Abstract

The gasification of organic materials by air, comprises incompletely gasifying the organic materials to a raw product gas (5) in a first gasification reactor (3), so that a flying coke is obtained with a carbon portion of 30-60%, which is still sufficient to bind the mineral matrix, so that a slagging is prevented, separating the coke from the product gas by a cyclone, feeding the coke to a further reactor, where the coke is further gasified or burned and the emerging ash is taken away, and supplying the emerging gases to the first reactor. The gasification of organic materials by air, comprises incompletely gasifying the organic materials to a raw product gas (5) in a first gasification reactor (3), so that a flying coke is obtained with a carbon portion of 30-60%, which is still sufficient to bind the mineral matrix, so that a slagging is prevented, separating the coke from the product gas by a cyclone, feeding the coke to a further reactor, where the coke is further gasified or burned and the emerging ash is taken away, supplying the emerging gases to the first reactor and continuously supplying a further mineral or inflammable solid material into the further reactor in a quantity of 50 mass.% on the total mass. The separation of the coke from the product gas contained in the gasification of the organic material takes place in a fixed bed. The organic materials have low ash melting point at 300[deg] C. The gasification is carried out at 700-800[deg] C. The gasification is carried out under a pressure of 105> to 106> Pa. The gasification reactor is a Torbed (RTM: High rate gas-solid reactor). The final gasification of the coke takes place by oxygen content sufficient for complete combustion and is carried out in a further reactor with moved fixed bed on rust or in a retort fed by lower push. The gasification of the coke is carried out with fluidization with a reactor and the ash of the coke is separated from the produced gas with a downstream separator. The product gas from the further reactor is fed into the first reactor in raw, hot condition at 500-600[deg] C. The product gas is fed into the process after cooling and cleaning. An independent claim is included for a device for the gasification of organic materials by air.

Description

The The invention relates to a method and a device for gasification of organic substances with low ash melting points below 800 ° C, with the help of air.

In Times of shortage of fossil energy reserves become possibilities sought to tap other source of energy. Here in particular offer organic substances. The energetic potential of plant biomass, especially that of straw, is comparable to that of wood or even bigger. insofar it makes sense to use straw energetically. The following is the Term "straw" synonymous with all organic Substances, in particular all vegetable biomasses with low ash melting points used.

One However, the general problem lies in the low ash melting points, some of which are well below 800 ° C due to the high potassium content can and thus in a conventional firing inevitably to pollution and slagging the plant. This includes all common Straw firing an air grading such that the straw is initially substoichiometric, d. H. is burned with an amount of air that is well below the stoichiometric Air requirement of the complete Combustion of straw lies, leaving an exhaust with combustible Shares is formed, then by adding the remaining air until Burned out to the desired total air combustion becomes. This procedure has now become mature combustion systems for straw guided. The gasification stage can also be designed in several stages.

It is natural to use only the gasification of straw in order to produce in this way a fuel gas that is suitable for power generation by means of gas turbines, gas engines or similar devices. However, this could not be done by the aforementioned combustion systems, even if the addition of burnout air were not required. In the methods known from the prior art, only poorly defined fuel gases can be achieved with a very low calorific value, which is much smaller than 4 MJ / Nm ³ . In addition, in the methods known in the art, the stoichiometrically operated burner muffle is often cooled with water in order to reduce the slagging, which, however, does not lead to unacceptable losses in the efficiency of use only in hot water or steam generation of the considered energy system. Therefore, straw can not be gasified using straw-specific firing systems and omitting the addition of burnout air.

conventional Carburetor systems that are suitable for wood, come just as little for the straw gasification into consideration: with the help of steam gasification Although the gasification of straw succeeds, but this kind of gasification is for Small decentralized power generation plants usually too expensive and too expensive. An air gasification in a fixed bed is for straw not feasible, because a uniform distribution the air passage in the bed Even with woodchips only succeed if previously separated undersized becomes. Therefore it is not to be expected that straw will be distributed so evenly that the air passage over the carburetor is distributed cross-section same. The consequence of an unequal distribution is however, that locally Temperature peaks with the aforementioned slagging problems occur while on In other places, air is so infrequently admitted that it is highest a smoldering comes, which in turn leads to unacceptable tar production of the carburetor leads. Therefore, as a possibility remains cheap air gasification only the implementation of the reaction in the disperse or fluid phase. Again, it is necessary by a corresponding air supply and air distribution to avoid temperature peaks. In fluidized bed process is known that although the longitudinal mixing in the flow direction, So also the backmixing is very good while the cross-mixing is significantly lower. So it's here too to be reckoned with that the air blending is not optimal, the danger temperature peaks is therefore high. One in itself according to the state the technique known possibility in this context is the recirculation of a gasification product gas, which allows two things: On the one hand, the dilution of the Gasification possible Temperature peaks somewhat smoothed second, the aerodynamics of the gasification reactor and the gasification stoichiometry independently vary from each other. However, such a recirculation is very consuming and possibly even impracticable.

It The object of the present invention is a method and a device to cope with what the gasification of straw and other biomass with low ash melting points in the dispersive or fluid phase while avoiding slagging and soiling is possible, too then, if a recirculation of the product gas is not possible or unreasonably difficult.

These The object is achieved by the method and the device according to claims 1 and 13 solved.

developments The invention are set forth in the subclaims.

The inventive method runs two stage, wherein in a first stage a) the organic material or organic substances is incompletely gassed in a first gasification reactor to a crude product gas, so that a Flugkoks obtained with a still high carbon content, preferably from 30% to 60% which is still sufficient to incorporate the mineral matrix so far that a slagging is prevented. In a second stage b) the cokote is carried after the separation of the crude product gas in another reactor where the coke is further gasified or burned and the resulting ash is discharged. The gases produced in this stage are preferably fed to the first gasification reactor. It is essential that the biomass introduced into the first reactor is not completely gasified in the disperse phase with the addition of air. Instead, this gasification reactor is designed with respect to its residence time so that the gasification is driven only to the point at which the majority of the combustible has gone into the product gas, but that the carbon skeleton includes the mineral matrix so far that a slagging not is possible. Nevertheless, the proportion of chemical energy remaining in the cokosh is made usable in the (further) gasification or combustion process itself.

The inventively proposed incomplete gasification (in the first stage of the process) is not pyrolysis, in the known no gasification agent, but only heat is supplied. Thus, the inventive method also differs from that in the DE 199 45 771 C1 described method, in which auxiliary air is supplied to the pyrolysis, so that only the coke content should be reduced. In the present invention, the residence time controlled gasification is performed so far that the carbon contained in the primary solid product is just sufficient to form a carbon matrix which in turn stabilizes the mineral matrix so that no slagging occurs. While in the pyrolysis of biomass, including the oxidizing pyrolysis, a conversion of 70% to 80% is obtained, which is defined as the proportion of the combustible which passes into the gas phase during the pyrolysis, according to the present invention a conversion is sought, significantly above 85%, preferably even well above 90%. In the case of vegetable biomasses with ash contents, in some cases far below 10%, the solid waste, the cokote, should ideally contain 30% to 60% residual carbon.

Preferably if the gasification is carried out at a temperature between 600 ° C and 950 ° C, especially between 700 ° C up to 800 ° C.

According to a further embodiment of the invention, a pressure in the range of 10 ⁵ to 10 ⁶ Pa is set in the gasification.

in the Within the scope of the present invention, it is possible in the further reactor to continuously add more mineral or combustible solids, z. B. but in a proportion of 50% by mass based on the total mass, which is added to the other reactor.

Preferably the gasification of the organic substances takes place in the first stage of the process in a reactor with fluidization, in particular a fluidized bed reactor or a cycloid reactor, more preferably a TORBED reactor.

To a further embodiment of the gasification process coagulated coke released by inertia separation together with the product gas, preferably separated by means of a cyclone. The separation of the Flue coke contained in the gasification of organic matter however, the product gas can also be carried out in a packed bed.

Around to be able to fully exploit the energy content of the flue coke the final one Gasification of the coked (or also combustion) with a sufficient for complete combustion Oxygen content is carried out. It has continued to prove itself the gasification of the coking coke in the further reactor with a moving protective layer perform, preferably on a grate or in a retort equipped with underfeed. The gasification of the coking coke can also be done with a reactor with fluidization carried out be, with the ashes of the coke from a downstream Separator is separated from the generated gas. The product gas off the further reactor is either directly in the raw, raw state, preferably at 500 ° C up to 600 ° C returned to the first reactor or indirectly after cooling and purification.

The Basic components of the device according to the invention are a first Gasification reactor, preferably a fluidized bed reactor or a cycloid reactor is a cyclone for gas / coke separation and another reactor to complete Combustion or gasification of the coking coke.

to advancement the solids from the cyclone to the other reactor serve a rotary valve and / or a conveyor line, which preferably has a further substance addition, for. B. for minerals or other fuels.

Further advantages and embodiments of this invention are illustrated in the single drawing, which inventions a basic structure of device according to the invention shows.

biomass 1 and gasification air 2 become a gasification reactor 3 fed. The gasification takes place in a fluidized, disperse phase, such as in a TORBED reactor. At the outlet of the gasification reactor 3 is then passed through a mechanical or fluid-mechanical separator 4 the incompletely gasified biomass from the then usually to be conditioned and cooled stream of crude gas 5 deposited as far as possible and on the closing organ 6 , For example, a rotary valve and the conveying member 7 a second reactor 8th fed. In this reactor 8th is the incompletely gasified biomass with oxygen, usually atmospheric oxygen 9 , brought in contact. As a result, the residual carbon, from which the still existing burns predominantly consists, implemented, so that only the mineral content of the biomass used, ie the ashes 11 remains. The reactor 8th can be designed as a furnace, but is preferably, in order to keep the temperatures low here as a rule, as a gasifier, so operated in lack of air. In the reactor 8th In addition to the coke from the gasification also other substances 10 be added, for example, residues from the purification of the product gas 5 , but also z. B. other solid fuels or auxiliaries for conditioning the cokce or ash 11 ,

As already mentioned, the calorific value of coking coke should be used in the process. Exergetically useful in this context are the use of the reactor 8th resulting fuel gas, if this is operated in the air-deficient operation as a gasifier, or in any case the sensible heat of the reactor 8th generated gas, whether this is operated as a furnace or as a gasifier. The use of the energy content is done solely by the fact that the hot gas 12 the carburetor 3 recited reciting.

The for the Return of the Product gases required apparatus and process stages are in Individual not shown, in particular, the gas recirculation in hot or cold state of the gas with or without cleaning.

In one embodiment, straw having a residual moisture content of 10% has been introduced which, when dry, has an ash content of 6.5%. This straw is to be converted in the gasifier, such as a cycloid reactor to 95%, ie 95% of the combustible portion is to go into the product gas, so that a coke with 61% ash produced, with the 39% of the combustible material consist of 98% carbon , First of all, it should be noted that the residual chemical energy is not 5%, but 9% of the energy content of the straw, so that its use compared to otherwise 9% more straw consumption is warranted. In the illustrated form of the invention, the coker coke is in the reactor 8th gasified with an air ratio of 50% based on the possible combustion, so that an exhaust gas with up to 35% content of carbon monoxide is formed. This is then found in the product gas of the carburetor as calorific value again. Furthermore, in the example, the ratio 1: 4 (1 kg of lime to 4 kg of coke coke) lime from the product gas cleaning added, so that even at slightly higher temperatures, the slag is at least manageable. On the other hand, it is possible in this way the temperature in the reactor 8th even if it is designed or operated as a furnace, limit it to temperatures not significantly exceeding 800 ° C. Furthermore, in the example considered, the product gas produced in the gasifier is recycled in a slightly cooled, otherwise crude state in a ratio of 1: 1 (as gas 12 ). It follows that a gasification stoichiometry or air ratio of only 25% is sufficient compared with 40% otherwise usual for gasification, so that both the product gas quality with a calorific value of 6.1 MJ / Nm ³ compared to 4 MJ / Nm ³ and a cold gas efficiency of 75% is obtained as a value quite high for an air gasification. In the sense of a reduction of the gasifier stoichiometry and the concomitant improvements in product gas quality and cold gas efficiency is the supply of the exhaust gas of the reactor 8th a particularly suitable measure, since hereby complete sensible heat of at least part of the product gas is available for the process, so that at least to this extent the partial combustion characteristic of the air carburetor can be partially eliminated or reduced.

The process according to the invention can be varied in several ways: During the fixed-bed gasifier, the carburetor used is less than the carburettor used because of the reasons stated above 3 on the other hand, any gasifier can be used, in which the gasification proceeds rapidly in fluid phase, so that in addition to the cycloid reactor and the TORBED reactor, any type of fluidized bed gasifier, in principle, entrained flow gasifier can be used. Also, gasification on a grate or in the rotary kiln are conceivable if this results in a defined, sufficiently short residence time to produce the above-described carbon matrix in the cokote or solid waste product, and on the other hand a sufficient stirring effect is achieved in order to temperature peaks avoid. However, preference is given to using a TORBED reactor. Due to the temperature limitations of the biomasses to be used with their low melting points Flugstromvergaser which work with oxygen as a gasifying agent, rather less suitable. A cyclone as a traffic jam babscheider 4 offers itself due to the simple device design, with mono- and multi-cyclones are equally considered. Alternatively, however, other inertial separators such. B. the bulk layer or Bettabscheider possible. Again, it is not a filtering separator, but an inertial separator, because the separating effect is achieved by the repeated deflection of the dust-laden fluid as it flows through the bed.

The reactor 8th Although explicitly specified by type, but now that the fixed carbon in the fly coke must react in a relatively slow reaction, a grate firing is primarily suitable. Other possible firings work in a mobile fixed bed or with a moving bulk layer. This would be in addition to the rust also a Unterschubfeuerung or more generally a loaded by Unterschub combustion retort. Preference should be paid to the fact that the air is fed from the top of the kiln, so not form in the bottom of embers nest with particularly high temperatures leading to Ver schlackung. The ashes should come out of the reactor 8th Alternatively, another cycloid reactor with a downstream cyclone for the ash deduction would be used.

Claims (15)

Process for the gasification of organic substances which have low ash melting points below 800 ° C, with the aid of air, characterized in that a.) The organic substance or organic substances incompletely in a first gasification reactor ( 3 ) is gasified to a crude product gas so that an aerated coke having a carbon content, preferably from 30% to 60%, is obtained which is still sufficient to incorporate the mineral matrix to prevent slagging; b.) Coke after separation from the crude product gas to another reactor ( 8th ), where the coke is further gasified or burned and the resulting ash ( 11 ) is discharged and the resulting gases ( 12 ) preferably the first gasification reactor ( 3 ). Method according to claim 1, characterized in that that the gasification is carried out at a temperature between 600 ° C and 950 ° C, preferably 700 ° C to 800 ° C is located. A method according to claim 1 or 2, characterized in that the gasification is carried out under a pressure in the range of 10 ⁵ to 10 ⁶ Pa. Method according to one of claims 1 to 3, characterized in that in the further reactor ( 8th ) another mineral or combustible solid ( 10 ) is continuously added, but in particular in an amount of 50% by mass on the total mass. Method according to one of claims 1 to 4, characterized in that the gasification of the organic substances in process step a) in a gasification reactor ( 3 ) takes place with fluidization, preferably in a fluidized bed reactor or a cycloid reactor, further preferably TORBED reactor. Method according to one of claims 1 to 5, characterized in that the coke from the product gas by inertial separation, preferably by means of a cyclone ( 4 ) is separated. Method according to one of claims 1 to 5, characterized that the separation of in the gasification of the organic matter contained coke from the product gas in a packed bed he follows. Method according to one of claims 1 to 7, characterized that the final gasification of coarse coke with a for a complete Combustion sufficient oxygen content occurs. Method according to one of claims 1 to 8, characterized in that the gasification of the coking coke in another reactor ( 8th ) is carried out with a moving bulk layer, preferably on a grid or in a retort fed by underfeed. Method according to one of claims 1 to 8, characterized that the gasification of the coking coke is carried out with a reactor with fluidization and that the ashes of the coke with a downstream separator is separated from the generated gas. Method according to one of claims 1 to 10, characterized in that the product gas from the further reactor ( 8th ) in crude, hot state, preferably at 500 ° C to 600 ° C in the first reactor ( 3 ) is supplied. Process according to claim 11, characterized in that the product gas ( 12 ) is fed into the process after cooling and cleaning. Device for the gasification of organic substances by means of air, characterized in that a first gasification reactor ( 3 ), preferably Example, a fluidized bed reactor or a cycloid reactor, a cyclone ( 4 ) for gas / cokote separation and another reactor ( 8th ) are connected downstream of the complete combustion or gasification of the coke flue. Apparatus according to claim 13, characterized in that the solids from the cyclone ( 4 ) to the further reactor ( 8th ) by means of a rotary valve ( 6 ) and / or a conveying section, which preferably has a further substance addition, can be conveyed. Apparatus according to claim 13 or 14, characterized in that the gas ( 12 ) from the further reactor ( 8th ) via a line in the first gasification reactor ( 3 ) is traceable directly or indirectly via a gas cleaning device.