DE102013014042A1 - Process and plant for the at least partial gasification of solid, organic feedstock - Google Patents

Abstract

The invention relates to a process for the at least partial gasification of solid, organic feedstock for the production of synthesis gas, wherein recovered synthesis gas is purified and cooled in a wash column by contact with a washing liquid, wherein the washing liquid is heated by the contact with the synthesis gas, characterized that the heated washing liquid is cooled by means of a heat exchange with a working medium of an organic Rankineanlage (110).

Description

The invention relates to a method and a plant for the at least partial gasification of solid, organic feedstock, in particular of biomass.

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 available from 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 a stoichiometric 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. This forms a synthesis gas, which consists essentially only of 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, the synthesis gas thus produced is brought into contact with coke from the low-temperature gasifier, for example in a quench unit integrated in the high-temperature gasifier or in a quench unit connected downstream of it. 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 syngas, the latter is cooled to about 900 ° C. This causes partial conversion of the carbon dioxide to carbon monoxide.

The carbon monoxide-rich synthesis gas thus produced 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.

Synthesis gas leaving the gasifier is typically cooled to about 200 ° C via an evaporator stage and an economizer stage (heat exchanger stage).

Subsequently, the cooled synthesis gas is typically purified in a wash column, where it is cooled to about 40 ° C. The washing liquid, in particular washing water, is heated in this case, typically to temperatures of about 130 ° C.

In conventional systems, the z. B. so heated wash water filtered, cooled and returned to the wash column.

Cooling devices for cooling the washing water conventionally use air coolers.

A disadvantage of the use of such air cooler is considered that the heat released by the wash water in the context of the system is not available.

If, on the other hand, cooling is carried out by means of a conventional heat exchanger, the result is very difficult to use Low-temperature heat. Another use of such low-temperature heat is associated with relatively high costs.

There is therefore a need for improving the use of heat in the operation of appropriate systems, so that the overall efficiency of such systems can be increased.

Disclosure of the invention

According to the invention, a method and a system are proposed with the features of the independent patent claims. Preferred embodiments are subject of the subclaims and the following description.

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 obtained by smoldering in a low-temperature gasifier. The carbonization gas is then reacted in a high-temperature gasifier by partial oxidation and then partial reduction to a synthesis gas.

According to the invention, in the further conditioning of the synthesis gas produced in a washing column, heat released to the washing liquid is further used as part of an organic Rankine process. This increases the efficiency of the system over conventional solutions. The organic Rankine process is a process for operating steam turbines which differs from a classical Rankine process in that it operates at a lower temperature and pressure gradient. As a result, it is not possible to use water as a working medium. The organic Rankine process uses organic liquids with a lower evaporation temperature than water as the working medium.

According to a preferred embodiment of the invention, the washing liquid is cooled by means of heat exchange in an evaporator of an organic Rankineanlage.

The washing liquid used in the washing column is preferably water. Water is cheap available and easy to handle.

According to a particularly preferred embodiment of the method according to the invention, the synthesis gas in the wash column to about 30 ° C to 50 ° C, in particular about 40 ° C, cooled, wherein the washing liquid in this case at 100 ° C to 140 ° C, in particular to about 130 ° C is heated.

Washing liquid preferably leaves the wash column after it has been heated and is filtered and / or cleaned before or after the heat exchange with the working medium of the organic rank plant and subsequently returned to the wash column for renewed contacting with synthesis gas to be purified. This results in a washing liquid cycle, which increases the overall effectiveness of the system.

It is particularly preferred that the heat exchange takes place in the organic Rankineanlage with evaporation of the working medium of the organic Rankineanlage, being used as the working medium, an organic liquid having an evaporation temperature below the temperature which reaches the washing liquid in the wash column, in particular R507A or R134A or propane or another suitable hydrocarbon is used.

A plant according to the invention preferably comprises a gasifier, a scrubbing column and an organic Rankineanlage. In this case, the carburetor preferably has a low-temperature carburetor, in which a tar-containing carbonization gas can be obtained by smoldering from a solid organic feedstock, and a high-temperature gasifier, in which the carbonization gas can be converted by partial oxidation and partial reduction to synthesis gas.

Advantageous components of an organic Rankineanlage are an evaporator, an expansion turbine, a generator, a condenser and a pump for the transport of the working medium between the respective components, in particular between the condenser and evaporator.

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

1 shows in a schematically simplified representation of a system which is adapted to carry out a method according to the invention.

Embodiment of the invention

A preferred embodiment of a plant according to the invention is in 1 in total with 100 designated. The attachment 100 has a carburetor 102 on, in which in a conventional manner from solid, organic feedstock, so in particular biomass such as wood or corresponding waste, synthesis gas is obtained. The carburetor 102 typically has a low temperature gasifier (not shown in detail) into which the feed and, for example, oxygen is fed. The low-temperature gasifier is set up to blaze the feedstock.

Carbonization gas obtained in the low-temperature gasifier is transferred to the high-temperature gasifier. The high-temperature gasifier is typically formed in two parts, and comprises an oxidation unit and a quench unit. In the oxidation unit, the carbonization gas is partially oxidized with a supplied oxygen-containing gas, resulting in temperatures of, for example, 1400 ° C to 2000 ° C. As a result, a synthesis gas is obtained.

In a downstream quench unit of the gasifier, for example, ground coke from the low-temperature gasifier is reacted endothermically with the synthesis gas. As a result of this endothermic reactions, the gas temperature is cooled in a short time to about 900 ° C, with at least partial reduction occurs.

The resulting gas mixture, which is a carbon monoxide-rich synthesis gas, is then passed through an evaporator 104 and an economizer 106 cooled to about 200 ° C.

Further conditioning of the synthesis gas thus cooled is first carried out in an economizer 106 downstream scrubbing column 108 , Such a scrubber (also called gas scrubber) is a process-engineering device in which the synthesis gas stream is brought into contact with a scrubbing liquid stream in order to take up constituents of the synthesis gas stream in the scrubbing liquid and thus to purify the synthesis gas of undesired constituents.

In the present application, water is preferred as the washing liquid. The following is based on the use of water as a washing liquid.

In the scrubbing column purified synthesis gas can via a line 109 withdrawn from the wash column and fed to other processes.

Due to the contact between the synthesis gas stream and the wash water, the synthesis gas is cooled to about 40 ° C. and the wash water is heated to about 130 ° C.

The thus heated, and contaminated with undesirable synthesis gas components wash water is from the wash column 108 discharged and a heat exchange with a working medium of an organic Rankineanlage 110 subjected.

This heat exchange is advantageously carried out by means of an indirect heat transfer, wherein the washing water stream under spatial separation by means of a heat-permeable wall to an evaporator 112 the organic Rankineanlage 110 is passed.

This occurs, with a suitable choice of the working medium of the organic Rankineanlage, to evaporation of this working medium in the evaporator 112 , The evaporated working fluid becomes an expansion turbine 114 fed, which with a generator 116 cooperates to generate electrical energy. The electrical energy thus generated can via a line 117 be supplied to a suitable use. For example, this electrical energy for stabilizing a power grid and / or for heating z. B. the carburetor 102 be used.

As a particularly suitable working medium of an organic Rankineanlage be mentioned R507A or R134A or propane or other suitable hydrocarbon.

That in the expansion turbine 114 expanded, vaporized working fluid is subsequently placed in a condenser 118 condensed and by means of a pump 120 in the evaporator 112 recycled, resulting in a total of a cycle for the working medium of the organic Rankineanlage.

An organic Rankineanlage or the corresponding organic Rankineprozess is capable of low-temperature heat, as provided by the heated wash water, to be converted into electrical energy in an effective manner. By integrating such an organic Rankineanlage in a gasification plant, the degree of utilization of the supplied fuel, in particular biomass in the form of wood, and the efficiency of the gasification plant can be optimized.

This through the heat exchange with the evaporator 112 cooled wash water can be fed back via a (not shown) line of the wash column (optionally after filtering).

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

• BTL fuels is available from 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 (11)

A process for the at least partial gasification of solid, organic feedstock for the production of synthesis gas, wherein recovered synthesis gas is purified and cooled in a wash column by contact with a washing liquid, wherein the washing liquid is heated by the contact with the synthesis gas, characterized in that the heated washing liquid by means of a heat exchange with a working medium of an organic Rankineanlage ( 110 ) is cooled. A method according to claim 1, characterized in that the washing liquid by means of heat exchange in an evaporator ( 112 ) an organic Rankineanlage ( 110 ) is cooled. Process according to Claim 1 or 2, characterized in that the scrubbing liquid of the scrubbing column ( 108 ) Water is used. Method according to one of the preceding claims, characterized in that the synthesis gas in the wash column ( 108 ) is cooled to about 30 to 50 ° C, in particular about 40 ° C, wherein the washing liquid is heated in this case to 100 to 140 ° C, in particular to about 130 ° C. Method according to one of the preceding claims, characterized in that the heat exchanger ( 108 ) leaving, heated washing liquid before or after the heat exchange with the working medium of the organic Rankineanlage ( 10 ) is filtered and / or cleaned, and then for re-contacting with to be purified synthesis gas in the wash column ( 108 ) is returned. Method according to one of the preceding claims, characterized in that the heat exchange in the organic Rankineanlage ( 110 ) with evaporation of the working medium of the organic Rankineanlage ( 10 ), using as working medium an organic liquid having an evaporation temperature below the temperature which reaches the scrubbing liquid in the scrubbing column, in particular R507A or R134A or propane or another suitable hydrocarbon. Plant suitable for carrying out a process according to any one of the preceding claims with a gasifier ( 102 ), a washing column ( 108 ) and an organic Rankineanlage ( 110 ). Plant according to claim 7, comprising a low-temperature gasifier, in which a tar-containing carbonization gas can be obtained by smoldering from a solid organic feedstock, and a high-temperature gasifier, in which the carbonization gas can be converted by partial oxidation and partial reduction to synthesis gas. Installation according to one of the preceding claims 7 to 8, characterized in that the organic Rankineanlage ( 110 ) as components an evaporator ( 112 ), an expansion turbine ( 114 ), a generator ( 116 ), a capacitor ( 118 ) and a pump ( 120 ) for transporting the working medium between the respective components, in particular between the capacitor ( 118 ) and evaporators ( 112 ), having. Plant according to one of the preceding claims 7 to 9, characterized in that the working medium is an organic liquid having a vaporization temperature below the temperature which the washing liquid in the wash column ( 8th ) is used. Installation according to one of the preceding claims 7 to 10, characterized in that is used as the working medium R507A or R134A or propane or another suitable hydrocarbon.

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