WO2014008995A1

WO2014008995A1 - Method for the gasification of carbonaceous feedstock

Info

Publication number: WO2014008995A1
Application number: PCT/EP2013/001973
Authority: WO
Inventors: Thomas Heidrich; Gerald GAUBE; Dirk BAUERSFELD
Original assignee: Linde Aktiengesellschaft
Priority date: 2012-07-11
Filing date: 2013-07-04
Publication date: 2014-01-16
Also published as: DE102012013670A1

Abstract

The invention relates to a method for the gasification of carbonaceous feedstock, in particular biomass. According to the invention, in order to cool and/or heat the system components used for the gasification, i.e. in particular gasification reactors and/or pyrolysis gas lines, a molten salt is used.

Description

description

Process for the gasification of carbonaceous feedstocks

The invention relates to a process for the gasification of carbonaceous

Feedstocks, in particular of biomass.

Such gasification processes are e.g. used for the production of fuel gas from water- and ballast-containing organic matter, such as coal, municipal and industrial sludges, wood and biomass, municipal and industrial waste and refuse, and waste products, residues and other. They can be energetic

Utilization of biomass and wood of cyclically cultivated agricultural areas, in particular recultivated mining areas and thus for the design of carbon dioxide neutral conversion of natural fuels into mechanical and thermal energy and for the beneficial disposal of municipalities, commercial, agricultural and industrial waste, other organic waste, residues, by-products and waste products are used.

The state of the art is characterized by a large number of proposals and practical applications for the energetic use of plants and organic waste up to the waste from municipalities, commerce, industry and agriculture. A carried out in November 1981 by the nuclear research facility Jülich GmbH

Seminar summarizes the state of the art of thermal gas generation from biomass, d. H. The degassing and degassing together, which still largely characterizes the state of the art today (Report of the Nuclear Research Facility Jülich - JülConf-46). Accordingly, combustion, degasification and gasification processes, individually or in combination, determine the state of the art with the following objectives: Production of combustion gas as a thermal energy source for steam generation

Combustion, - production of high-calorific solid and liquid fuels, such as coke, charcoal and liquid, oily tars, through carbonization, de-and

Gasification, - production of fuel gas while avoiding solid and liquid

Fuels through complete gasification.

In the gasification process, the process control decides whether the liquid and large molecular weight Schwelprodukte obtained or also by Oxidation be gasified.

The oldest type of gasification is the gasification in a fixed bed, whereby fuel and gasification are moved in countercurrent to each other. These processes achieve the highest possible gasification efficiency with the lowest possible oxygen demand. The disadvantage of this type of gasification is that the fuel gas and all known liquid carbonization products are contained in the gasification gas. In addition, this type of gasification requires lumpy fuel. The gasification in the fluidized bed, known as Winkler gasification, eliminated this lack of fixed bed gasification as much as possible, but not completely. In the

Gasification of bituminous fuels is z. B. not always the necessary tarryness of the gasification gas, as required for the application of the gas as fuel for internal combustion engines, achieved. In addition, the oxygen consumption is significantly higher due to the higher average temperature level in the process control over the fixed bed gasification. In addition, the temperature level of the Winkler gasification has the effect that a large part of the

carbon is not converted into fuel gas, but in the form of dust and, bound to the ash, is discharged from the process again. This lack of gasification technology can be combined with the

High temperature aviation gasification process usually above the

Melting point of the ash work, be avoided. The price for this is further increasing oxygen demand and decreasing gasification efficiency, although the organic substance is almost completely converted into fuel gas. The causes are in the high temperature level of these gasification processes, which have the consequence that a large part of the fuel heat is converted into physical enthalpy of the fuel gas.

Although the production of charcoal and oily tars can help to meet fuel and fuel needs in developing countries, the processes that produce smoldering products are, above all else

Fixed bed carburetors, which operate on the countercurrent principle, from the perspective of

Environmental pollution always under criticism. This applies in particular to the resulting aqueous gas condensates and production-related impurities associated with tar production. DC and

Fluidized bed gasification processes allow the generation of approximately tar-free combustion and synthesis gases. It is becoming apparent that these processes, because of their environmental friendliness, belong to the future, in particular because it is also possible to produce liquid basic substances such as methanol, fuels such as gasoline, but also protein, via known synthesis processes in this way from biomass. The transition to such production targets and the planned cyclical production of biomass for the energetic and possibly material use is associated with the demand for efficient, environmentally friendly processes, suitable for biomass of different quality and different origin as well as industrially feasible also in less developed countries.

Although fixed bed gasifiers with DC or dual fuel technology ensure nearly tar-free gasification, these methods do not meet current and future requirements in terms of performance-related end-use and environmental protection. How to achieve

Power plants based on processes for the combustion or gasification of biomass today energy efficiencies - based on the potential technical work - between 20 and 30%. But also the Flugstrom- and

Fluidized bed gasification processes have their specific shortcomings. Thus, the entrained flow gasification processes operate at high temperatures, usually above the

Melting point of the inorganic constituents of solid substances intended for gasification. The advantage of this process is that the inorganic fraction of the fuels leaves the gasification process as vitrified, elution-resistant slag. The price for this, however, is high exergetic losses, which usually occur during the cooling of the gasification gas in the context of the required gas purification.

On the other hand, fluidized-bed gasification processes, as is known, are not always capable of controlling the use of the gasification gas as fuel, e.g. In

Gas turbines and gas engines to ensure necessary tar-free. In addition, they are characterized by incomplete conversion of carbon.

The company CHOREN has developed a technology with which a tarry-free synthesis gas is first produced in a multi-stage process. After purification and conditioning, the synthesis gas can be converted into a liquid hydrocarbon mixture (BTL) by the Fischer-Tropsch synthesis. In the following, the individual process stages of the so-called Carbo-V process, which is described, for example, in EP 0745 114 B1, are briefly presented:

a) In a first process stage, the biomass is in a

Low-temperature gasifier (LTG) by partial combustion with a

Gasification agent at temperatures between 400 Ό and 500 "Ό converted to biocokes and carbonization .The carbonization gas is then in the

Combustion chamber of a high-temperature gasifier (HTG) partially oxidized with pure oxygen. The heat released by this oxidation heats the carbonization gas to temperatures above 1400Ό. In these conditions, aromatics, tars and oxo compounds contained in carbonization are completely decomposed. It forms a gas that consists essentially of CO, H2, C02 and water vapor. In a third process step, the ground biocok is blown into the hot gas stream from the combustion chamber. Due to the energy-consuming (endothermic) reaction between biokoks and combustion gas, the gas temperature drops within fractions of a second to about 900 "C (" chemical quenching ").

b) The crude gas is cooled, dedusted and freed in a gas scrubbing of chlorides, salt-like constituents and other water-soluble impurities. The dust from the filter is returned to the combustion chamber and at the prevailing very high temperatures to liquid slag

melted. The solidified on the cooler wall of the carburetor slag forms a glassy coating, the lining of the

High temperature gasifier (HTG) before the high temperatures of the

Combustion chamber protects. At the boundary layer to the gas space flows liquid slag and is converted by quenching in a water bath to an eluierfesten granules.

After gas scrubbing, the synthesis gas contains only CO, H2 and C02 except traces of other substances. Catalytic water gas shift reaction sets the ratio between H2 and CO for the requirements of the Fischer-Tropsch reaction. After further purification steps (eg washing out C02 and S compounds), aliphatic hydrocarbons are built up from the pure synthesis gas on the Fischer-Tropsch catalyst. In the described methods for high-temperature gasification and low-temperature gasification in sole or combined form problems may occur with respect to the temperature of the gasification reactors. Also in the transfer of pyrolysis gas from the low-temperature gasification to

High-temperature gasification can lead to temperature-related problems. Specifically, the problem situation is as follows:

1. High-temperature gasification (general): In the field of high-temperature gasification, a separate protection of the gas is often used

Carburetor shrouds are required against aggressive media and hot temperatures. This can be realized by a lining or a water-cooled cooling screen or a combination of both. The temperature of the cooling water is below the optimum temperature for the operation of the gasification due to the limitation of the vapor pressure. A heat-insulating coating (lining) between the cooling screen and the reaction space is necessary. The coating allows only a limited temperature gradient when starting up. This makes starting up time-consuming. The lining has a very limited shelf life and must be replaced regularly. This restricts the achievable operating hours.

Damage in the pressure jacket leads to the ingress of water into the reaction chamber, which may result in water vapor explosions.

2. Low-temperature gasification (general): In the area of low-temperature gasification, the carburetor jacket can be designed for the expected temperatures and media. The problem here, however, is in hot spots, for which a design is not possible. Hot spots or reverse flow from the high-temperature gasifier lead to the design temperature being exceeded. The uneven temperature distribution across the container acts on the bearings of the paddle shaft and causes increased wear. Heat losses via the container wall must be compensated by an increased oxidation of carbon, which reduces the efficiency. 3. Pyrolysis gas line (Carbo-V method):

In the Carbo-V process, the pyrolysis gas produced in the low-pressure gasifier is transported via the pyrolysis gas line to the high-temperature gasifier. Experiences from the operation of a beta plant show the following two problems: a) Deposits of pyrolysis coke and tar: To prevent deposits, oxygen was introduced into the pyrolysis gas line in the beta plant, whereby overheating was achieved. In addition to safety problems, the procedure could not be sufficiently tested. The pyrolysis gas is teergesättigt. The tars condense on the inner

Surface of the tube and lead in extreme cases to the closure.

b) Backflow of hot gasification gas from the high temperature gasifier:

In this type of backflow, material failure (loss of

Containment). To avoid this scenario, the entire system is currently relaxed in the torch in suspected backflow. A restart is difficult and time consuming. Return flow from the high-temperature gasifier leads to exceeding the design temperature.

Object of the present invention is to provide a comparison with the prior art improved temperature of the gasification available.

The stated object is achieved in that system components used in the gasification are tempered by means of a molten salt. The system components, in particular the reactor jacket of the gasification reactor and / or pyrolysis gas-carrying lines, are cooled or heated by heat exchange with the molten salt as needed. In a preferred embodiment of the invention, the carburetor jacket of a

Tempered high-temperature gasification reactor by means of the molten salt. For this purpose, for example, the usually provided water cooling jacket can be replaced by a salt cooling jacket. According to another variant, the carburetor jacket of a

Low temperature gasification reactor tempered by the molten salt. For this, e.g. a salt cooling jacket can be attached to the low temperature gasification reactor. As a result, a homogenization of the temperature can be achieved.

A combined temperature control of high and low temperature reactor is possible. For this purpose, separate or combined molten salt circuits can be provided. In a succession of low-temperature gasification reactor and high-temperature gasification reactor as in the Carbo-V process is in accordance with a particularly preferred embodiment of the invention leading from the low temperature reactor to the high temperature reactor for the transport of pyrolysis

Pyrolysis gas line tempered by the molten salt. This embodiment is based on the consideration to provide a heat tracing means of the molten salt to avoid the condensation of tar. The determining temperature of the pipe surface of the pyrolysis gas line is in the temperature of the molten salt.

After a development of the inventive concept is by the

High temperature gasification reactor heated molten salt used for controlling the temperature of the pyrolysis gas line and the low-temperature gasification reactor. The Salzschmelzkreisläufe are so interconnected that in the

High temperature gasification reactor heated salt is then passed over the jacket of the pyrolysis gas line and the low-temperature gasification reactor. This also results in an increased efficiency of gasification, as less biomass must be oxidized to maintain the temperature.

Another embodiment provides that the molten salt is used to warm the system parts when starting.

In addition, the molten salt can also be used as thermal energy storage for the

Restart will be used after a failure.

The invention offers a whole series of further advantages, of which only a few are mentioned below by way of example: The Temperierungsmethode allows a simple and robust construction of Kühlbzw. Heating devices, whereby inexpensive materials can be used.

Moreover, this method offers low mechanical wear. The efficiency can be compared to conventional tempering, e.g. by cooling water, be increased considerably. It also has a favorable effect that the cooling system can be designed for low pressure. In addition, all safety issues related to the design temperature are solved for different scenarios.

Claims

claims

1. A process for the gasification of carbonaceous feedstocks, in particular of biomass, characterized in that used in the gasification

Plant components are tempered by means of a molten salt.

2. The method according to claim 1, characterized in that the carburetor jacket of a high-temperature gasification reactor is tempered by means of the molten salt.

3. The method according to claim 1 or 2, characterized in that the

Carburetor jacket of a low-temperature gasification reactor is tempered by means of the molten salt.

4. The method according to any one of claims 1 to 3, characterized in that a leading from a low-temperature reactor to a high-temperature reactor for the transport of pyrolysis gas pyrolysis gas is tempered by means of the molten salt.

5. The method according to claim 4, characterized in that by the

High temperature gasification reactor heated molten salt is used for controlling the temperature of the pyrolysis gas line and the low-temperature gasification reactor.

6. The method according to any one of claims 1 to 5, characterized in that the molten salt is used to warm the system parts when starting.

7. The method according to any one of claims 1 to 6, characterized in that the molten salt is used as a heat energy storage for restarting after a failure.