DE102007050566A1 - Carbonic raw material e.g. coal, gasifying method, involves using superheated water vapor as gasification agent and energy carrier for gasification reaction at temperature above specified degree Celsius - Google Patents

Abstract

The method involves using a superheated water vapor (3) as a gasification agent and energy carrier for gasification reaction at a temperature above 1000 degree Celsius. The superheated water vapor is provided with a temperature above 1200 degree Celsius and 1400 degree Celsius. A gaseous medium is supplied to the water vapor, which is overheated at high temperature, and supplied to a carburetor (1). The highest temperature in the carburetor lies over the ash dripping point, so that ash (20) is delivered in a liquid state. An independent claim is also included for a device for gasifying a carbonic raw material in a synthesis gas, comprising a carburetor.

Description

The The invention relates to a method and a device for gasification of carbonaceous raw materials, such as coal, other fossil Fuels, biogenic fuels, residues and waste, as well artificial waste.

The known processes for the gasification of carbonaceous raw materials are autothermal, as well as allothermal process. In the autothermal process, the gasification agent is air or oxygen, so that the necessary gasification energy is generated by the incomplete combustion of raw materials. Such processes are relatively simple but have the disadvantage of producing a higher proportion of carbon dioxide (CO ₂ ). Part of the imported raw material is used as fuel and is no longer available for synthesis gas production. Another disadvantage is that when using air as a gasification agent, the synthesis gas produced has a nitrogen content, which significantly lowers its calorific value. The use of pure oxygen is associated with higher operating costs.

State of the art are autothermal fixed bed gasifier (eg British Gas Lurgi type "Application of BGL gasification of solid hydrocarbons for / GCC power generation", Richard A. Olliver et al., Gasification Technologies 2000, San Francisco, 8-11 October 2000 ), or authotherme entrained flow gasifier (eg CHOREN "SunDiesel - made by CHOREN - Experiences and latest developments", Matthias Rudloff, in Synthetic Biofuels, series "Renewable Resources" Volume 25, Agricultural Publishing GmbH, Münster, 2005 ), or as in DE 10 2005 006 305 A1 Furthermore, fluidized bed gasifier (eg the plant in Värnamo - "CHRISGAS Project - Manufacture of a clean hydrogen-rich gas by biomass gasification and hot gas upgrading", L. Waldheim, K. Stahl, L. Gardmark, in Synthetic Biofuels, writing series "Renewable Resources" Volume 25, Agricultural Publishing GmbH, Münster, 2005 ) and many others.

In the allothermal process, the necessary gasification energy is supplied from the outside, so that no additional amount of CO ₂ is produced in the gasifier itself and there is no loss for energy production. Therefore, it is possible to use water vapor as a gasifying agent (endothermic gasification reaction), resulting in a higher concentration of hydrogen (H ₂ ) in the synthesis gas. This is particularly advantageous if the synthesis gas is used for the production of liquid fuels (eg by the Fischer-Tropsch synthesis) or synthetic natural gas (SNG). From the prior art, the fluidized bed gasifier according to the "Güssing principle" is known ( H. Hofbauer, R. Rauch, S. Fürnsinn, Ch. Aichemig, Project report within the framework of the program line Energy Systems of the Future, Federal Ministry of Transport, Innovation and Technology, Vienna 2005 ). The necessary gasification energy is applied by supplying hot sand (950 ° C). The sand preheating is produced by the combustion of used raw material (in this case biomass). In this way, only part of the problems are solved: by separating the combustion and gasification chambers there is no increase in the CO ₂ concentration in the synthesis gas, but valuable raw material is still used as an energy source, which reduces the specific yield. in the DE 102 27 074 A1 also a fluidized bed gasifier with separate combustion chambers is described. The combustion energy is used for the gasification process (heat transfer through the partitions between two chambers) and the combustion gases are discharged separately, without mixing with the product gas from the gasification chamber. The problem of the lower yield due to the combustion of raw material used, as in the first example, remains unresolved.

• – Das Verfahren ist auf die Wirbelschichtvergasung begrenzt, die nicht für die Vergasung von Rohstoffen mit niedrigem Ascheschmelzpunkt (wie bei vielen Sorten von Biomasse, z. B. Stroh usw.) eingesetzt werden kann;
• – Die Dampftemperatur von 800–950°C ist nicht ausreichend um eine vollkommen allotherme Vergasung zu gewährleisten. Daher ist es erforderlich stets eine Menge an Luft zuzumischen, womit wiederum die genannten Probleme mit CO₂ und N₂ Anteil in dem Synthesegas entstehen.
• – Es wurde vorgeschlagen einen hochwertigen rekuperativen Wärmetauscher für die Wasserdampfüberhitzung einzusetzen (auf Inconel 800HT und/oder Haynes HR-120 Basis). Diese Wärmetauscher sind sehr teuer und die Praxis hat gezeigt, dass die Wartung sehr aufwendig und kostenintensiv ist.

A solution to this problem has been sought by exploiting the exhaust gas from the Fischer-Tropsch synthesis, which still has a significant calorific value, for steam superheating to 800-950 ° C and then using this superheated steam as a gasifying agent, as in US Pat WO 2006/043112 A1 described. But that is only a partial solution:

• - The process is limited to fluidised bed gasification, which can not be used for the gasification of low ash melting point raw materials (as with many types of biomass, eg straw, etc.);
• - The steam temperature of 800-950 ° C is not sufficient to ensure a completely allothermal gasification. Therefore, it is always necessary to mix in an amount of air, which in turn causes the aforementioned problems with CO ₂ and N ₂ content in the synthesis gas.
• - It was proposed to use a high quality recuperative heat exchanger for steam overheating (on Inconel 800HT and / or Haynes HR-120 basis). These heat exchangers are very expensive and practice has shown that the maintenance is very expensive and expensive.

The present invention has for its object to develop a gasification process and an apparatus for the gasification of carbonaceous raw materials, which completely eliminates the disadvantages of the prior art. The inventive method is a completely allothermic gasification process that efficient implementation of the raw material and at the same time a real H ₂ / CO ratio in the synthesis gas allows. At the same time, the system remains simple and is well suited for smaller capacities and possible decentralized operation with different feedstocks in order to constantly achieve good cost-effectiveness.

These The object is achieved by a process for the gasification of carbonaceous Raw materials with water vapor as gasification agent and energy source solved, in which the various waste energies for exploited the generation and overheating of water vapor to increase the overall yield and overall efficiency.

According to the invention achieved a completely allothermal gasification by superheated Water vapor both as a gasification agent and as an energy source is used for the gasification reaction and the water vapor used a temperature well above the average gasification temperature having. This is inventively with a steam temperature of at least 1000 ° C, but preferably more as 1200 ° C and more preferably of more than 1400 ° C.

• – Teerbildung ist reduziert und die anfallende Teere sind deutlich kurzkettiger und dadurch dünnflüssiger als bei der Vergasung ohne Dampfüberschuss;
• – Verhältnis H₂/CO im erzeugten Synthesegas ist gleich oder größer als 2, was besonders für eine nachgeschaltete Fischer-Tropsch-Synthese oder SNG-Synthese (synthetischer Erdgas) vorteilhaft ist;
• – Zerstörung von Restteeren im thermischen Cracker ist schneller und vollständiger in einer Atmosphäre mit höherem Dampfanteil.

By using the highly superheated steam as a gasifying agent and energy source you get a high water vapor excess in the carburetor, which is always over 2, more preferably above 3, lies. This excess of steam has many positive effects:

• - Tar formation is reduced and the tars are clearly short-chained and therefore less viscous than in the gasification without excess vapor;
• The ratio H ₂ / CO in the synthesis gas produced is equal to or greater than 2, which is particularly advantageous for downstream Fischer-Tropsch synthesis or SNG synthesis (synthetic natural gas);
• Destruction of residual tar in the thermal cracker is faster and more complete in an atmosphere with higher vapor content.

To In the prior art, it is not possible the high steam temperatures in recuperative heat exchangers and / or boilers. The According to the invention required high temperatures from 1200-1400 ° C, can only be used with regenerative heat exchangers be achieved. Obviously, so far the possible Application of these heat exchangers for one allotherme gasification process not considered, because this would cause significant other problems. The known regenerators have in connection with the inventive allothermal gasification process significant disadvantages, such. B. long heating times, little flexibility for adaptation the gasification process, only a small part (about 10%) of the stored Energy can be exploited, which is why the systems are very expensive. Surprisingly has been shown to be when using bulk regenerators the listed problems are no longer present and thereby in a simple way superheated steam, as is the case for the allotherme Gasification is needed, can be produced.

As bulk regenerators here are preferably from the DE 42 36 619 C2 or from the EP 0 620 909 B1 used known devices. The disclosure of the aforementioned publications is hereby incorporated. The use of such bulk regenerators results in a device that is significantly more efficient than the prior art.

In a preferred process, a synthesis gas having a particularly high H ₂ / CO ratio, which is greater than 2, or even greater than 3, is formed. This makes it possible to directly process the synthesis gas into liquid (CTL - "coal to liquid", BTL - "biomass to liquid"), or gaseous (SNG - "synthetic natural gas") fuels.

In a further preferred method, another gas is supplied to the gasifier together with the steam. This is preferably oxygen or air, if a further increase in temperature in the gasifier is required, or other technical gases (eg H ₂ , CO, CO ₂ , CH ₄ , or a mixture thereof), if an adaptation of the H ₂ / CO ratio is to take place.

There is the possibility to use different carburetor types according to the state of the art. Particularly advantageous is a countercurrent fixed-bed gasifier. Within this reactor, individual zones are formed, in which different temperatures and thus different processes occur. The different temperatures are based on the fact that the respective processes are strongly endothermic and the heat only comes from below. In this way it is best to use the high steam temperatures. Since the highest temperatures prevail in the entry zone of the gasification agent, it is always possible to create the conditions for a liquid ash discharge. This is particularly advantageous in biomass gasification, because the ash melting points, depending on the fuel types and the soil properties, vary greatly. The same problem exists when using different waste materials. Therefore, it is practically impossible according to the prior art in a carburettor type to convert different fuels and to adapt to the market situation. Here it is basically possible to conduct the process so that the resulting ash is discharged in liquid form. If the ash melting point is particularly high, the fuel is small quantities to add to flux. Alternatively, together with the steam, a small amount of oxygen or air (as described above) may be overheated and passed into the gasifier, resulting in a further increase in temperature in the ash discharge zone.

There the pyrolysis gases flow through no further hot zones the tar content in the product gas is relatively high. This tar is mostly not desirable and has the high energy content of the tar a negative impact on process efficiency. That's why the tar, together with the accumulating dust, immediately after the carburetor in a cyclone, particularly preferably in a multi-cyclone, separated and with a suitable pump in the high temperature zone be injected of the carburetor. In special cases can be a suitable electrostatic precipitator for residual tar removal be used.

The synthesis gas is cooled in a gas cooler and the excess water vapor condensed out in a downstream condenser. This reduces the amount of syngas and at the same time increases the proportions of the two most important components, CO and H ₂ . In the condenser, the residual amounts of pollutants (dust, tars, ...) are washed out.

• – die Energie aus dem Gaskühler für die Wasservorwärmung,
• – die Abwärme aus der Weiterverarbeitung des Synthesegases für die Sattdampf-Erzeugung,
• – die chemisch gebundene Energie des Off-Gases für die Dampfüberhitzung, durch Verbrennung oder Mitverbrennung in Schüttgutregeneratoren.

In order to obtain a method with very high energy efficiency, according to the invention all waste energy flows are as far as possible returned to the gasification reactor. For the production of superheated steam as a gasification agent, z. B .:

• - the energy from the gas cooler for water heating,
• The waste heat from the further processing of the synthesis gas for the saturated steam generation,
• - The chemically bound energy of the off-gas for the superheated steam, by combustion or co-combustion in bulk regenerators.

On this way, the resulting waste energy flows from at least one of the following processes in the form of overheated Steam can be recycled into the carburetor, which an increase in efficiency over the prior art allowed.

at Another advantageous method is from the capacitor accumulating condensate again for the production of saturated steam used. In this way, a closed water cycle produced.

at a further advantageous embodiment are at least provided two steam superheating devices in the form of bulk regenerators. In an antiphase operation, this can be a continuous overheating process of the gasification agent can be achieved.

The The invention will be explained in more detail below with reference to the drawings explained.

In 1 a first flow diagram is shown with corresponding device for the gasification of carbonaceous raw material in synthesis gas. The gasification takes place in the basic principle in a state of the art reactor ( 1 ) instead of. For example, in countercurrent gasification, the raw material ( 2 ) into the reactor from above and the gasification agent ( 3 ) from below, so that the gasification agent and the synthesis gas ( 6a ) flow through the reaction space in the opposite direction to the fuel flow.

In the cyclone (preferably multicyclone) ( 4 ), the majority of the tar and the resulting dust from the synthesis gas ( 6a ) and with the pump ( 5 ) back into the high-temperature zone of the carburettor ( 1 ) injected.

The generated synthesis gas ( 6b ) is sent for further processing (final cleaning, cooling, steam condensation) to achieve the necessary end-use quality.

In the bulk regenerator ( 7 ), the saturated steam ( 9 ) overheated to the necessary temperature. At the same time, the bulk regenerator ( 8th ) in the heating phase, that is to say it is charged again with the thermal energy by the combustion of a fuel, preferably an "off-gas" from the downstream process, the combustion gases leaving the system through the chimney ( 10 ). By periodically switching displayed valves ( 11 ) to ( 16 ), a change in the mode of operation of the two bulk regenerators ( 7 ) and ( 8th ). The valves are 11 ) 13 ) and ( 15 ) the bulk regenerator ( 7 ) and the valves ( 12 ) 14 ) and ( 16 ) the bulk regenerator ( 8th ).

Instead of just two bulk regenerators ( 7 ) and ( 8th ) (minimum number for continuous operation) can use 3 or more bulk regenerators to achieve a particularly consistent operation.

2 shows an alternative flow diagram with the injection of a gas, or a gas mixture, into the saturated steam along the arrow ( 17 ). This can be oxygen or air, if a further increase in temperature in the carburetor is required. Thus, the oxygen is mixed with the steam in the bulk regenerators ( 7 ) and ( 8th ) overheated to very high temperature. Already under 10 vol.% Oxygen in the superheated gasification agent ( 3 ) increase the temperature in the ash melting zone significantly. This gives a low-viscosity ash. In addition, this measure can further increase the utilization of carbon, as well as reduce tar formation by increasing the raw gas temperature.

Instead of pure oxygen or air, it will also be possible to add another technical gas or a gas mixture (for example H ₂ , CO, CO ₂ , CH ₄ ...) To the vapor ( 17 ) and in this way to influence the energy balance, as well as the H ₂ / CO ratio in the synthesis gas. With the control valve ( 18 ) regulates the amount of injected gas.

All Features disclosed in the application documents are considered to be essential to the invention as far as they are individually or in combination the prior art are new.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• DE 102005006305 A1 [0003]
• DE 10227074 A1 [0004]
• WO 2006/043112 A1 [0005]
• - DE 4236619 C2 [0011]
• - EP 0620909 B1 [0011]

Cited non-patent literature

• - "Application of BGL gasification of solid hydrocarbons for / GCC power generation", Richard A. Olliver et al., Gasification Technologies 2000, San Francisco, 8-11 October 2000 [0003]
• - CHOREN "SunDiesel - made by CHOREN - experiences and latest developments", Matthias Rudloff, in Synthetic Biofuels, series "Renewable Resources" Volume 25, Agricultural Publishing GmbH, Münster, 2005 [0003]
• - "CHRISGAS Project - Manufacture of a clean hydrogen-rich gas by biomass gasification and hot gas upgrading", L. Waldheim, K. Steel, L. Gardmark, in Synthetic Biofuels, series "Renewable Resources" Volume 25, Agricultural Publishing GmbH, Münster , 2005 [0003]
• - "Energiezentrale Güssing" H. Hofbauer, R. Rauch, S. Fürnsinn, Ch. Aichemig, project report within the framework of the program line energy systems of the future, Federal Ministry of Transport, Innovation and Technology, Vienna 2005 [0004]

Claims (13)

Process for the gasification of carbonaceous raw materials in synthesis gas, characterized in that the gasification is a completely allothermal gasification with water vapor and the superheated steam ( 3 ) is used both as a gasification agent and as an energy source for the gasification reactions and has a temperature above 1000 ° C. A method according to claim 1, characterized in that the overheated Water vapor a temperature above 1200 ° C and especially preferably above 1400 ° C. Process according to Claims 1 and 2, characterized in that a synthesis gas ( 6b ) is formed with a H ₂ / CO ratio above 2. Method according to at least one of the preceding claims, characterized in that the water vapor ( 3 ) is fed to a further gaseous medium which overheats to the same high temperature and the carburetor ( 1 ) is supplied Method according to at least one of the preceding claims, characterized in that the highest temperature in the gasifier ( 1 ) is always above the ash melting point, so that the ash ( 20 ) is discharged in the liquid state. Method according to at least one of the preceding claims, characterized in that the resulting tars and the dust together by means of a cyclone ( 4 ), particularly advantageously by means of a multi-cyclone ( 4 ) are deposited and by means of a pump ( 5 ) back to the carburettor ( 1 ). Method according to at least one of claims 1 to 6, characterized in that the synthesis gas in a gas cooler and then cooled in a condenser is, wherein condensed excess water vapor becomes. Method according to at least one of claims 1 to 7, characterized in that the waste heat, tangible as well as chemical, from the gas cooler and other downstream Components for preheating the water, for the saturated steam generation and overheating, is used. Method according to at least one of claims 1 to 8, characterized in that the resulting condensate from the Condenser of the synthesis gas for saturated steam generation is used and so allows a closed water draw becomes. Device for the gasification of carbonaceous raw materials in synthesis gas, with a gasifier ( 1 ), with superheated steam ( 3 ) both as a gasification agent and as an energy carrier, characterized in that it comprises at least one bulk regenerator ( 7 . 8th ), which overheats the water vapor to a temperature which is above 1000 ° C, preferably above 1200 ° C and more preferably above 1400 ° C. Device according to claim 10, characterized in that a cyclone ( 4 ), preferably a multicyclone ( 4 ), for the separation of tars and dusts from the synthesis gas ( 6a ) is being used. Device according to claims 10 and 11, characterized in that a pump ( 5 ) is used to remove the tars and dust from the cyclone ( 4 ) back into the carburettor ( 1 ) to transport. Device according to at least one of claims 10 to 12, characterized in that at least two bulk regenerators ( 7 . 8th ), at least two of these devices ( 7 . 8th ) are operated in anti-phase.