DE102006050603A1 - Gasifying biomass comprises compression in a crammer screw press, processing in a shredder screw press and partial combustion in a gasification chamber - Google Patents

Abstract

Gasifying biomass comprises compressing the biomass into a gas-impermeable plug in a crammer screw press, feeding the biomass under pressure into a shredder screw press and heating it to 200-250[deg] C by supplying steam and/or oxygen before or after emergence from the press, mixing the biomass with oxygen in a gasification chamber to effect partial combustion at about 900[deg] C, filtering the resulting gas and passing it through a catalytic unit to render residual pollutants harmless. An independent claim is also included for apparatus for gasifying biomass as above.

Description

The The invention relates to a process for the gasification of biomass with continuous feed, subsequent comminution and gas cleaning as well as a facility for implementation this procedure.

It gives fixed bed process, stationary and circulating fluidized bed processes for the gasification of biomass or Brown coal.

• • Gleichmäßige Temperaturverteilung auf Grund der großen Wärmekapazität der im Wirbelbett befindlichen Teilchen, die meist aus Sand oder anderem Material bestehen. und
• • gute Durchmischung der Vergasungskomponenten (Luft-Dampf) und der der Pyrolyse und Vergasungsprodukte.

Common today are so-called fluidized bed and entrained flow processes. In the fluidized bed process, comminuted biomass (lignite) is transported to a reactor, which is gasified there by oxygen or air added at 800 ° C. to 1000 ° C. from below. If the particles are very small and the gasification process at the upper end of the reactor is largely completed, this is called a stationary fluidized bed. If, however, the gasification process is only partially completed, as in the case of larger particles, the gasified particles are separated by a cyclone, separated and then transported back into the gasification process. This process is called circulating fluidized bed process. The particles are transferred in a hot bed by the up-flowing gasification agent in a combustible gas. Typical features of the reactor are:

• • Uniform temperature distribution due to the large heat capacity of the particles in the fluidized bed, which are usually made of sand or other material. and
• • good mixing of the gasification components (air-steam) and of the pyrolysis and gasification products.

At the Air flow method, however, are oxygen or air with the too Gasifying product entered simultaneously and usually gassed at about 1400 ° C.

The in the most recent Time known, currently operated pilot plants for biomass In the field of entrainment gasification, for example, the "Carbo V-method "the Choren and in the field of fluidized bed a plant in "Güssing" of the Vienna University of Technology and Austrian Energy and the heat pipe reformer of the TU Munich. A another pilot plant in operation, but with one completely different concept, the stepped reforming is "Blue Tower "by DTM The experimental stage also includes the "AER process" and fluidized bed gasification the Institute "circumspection" of the Fraunhofergesellschaft. All these systems work without pressure in a decentralized work step and with conventional, very expensive gas cleaning, the immediate cooling mandatory after gasification. The research center Karlsruhe used an existing pilot plant with flystream pressure gasification of the Fa. Future Energy (Freiberg / Saxony). This is a previously by pyrolysis produced carbon-tar mixture in quasi-liquid form entered. In addition to the atmospheric There are still plants operating at pressures of 20-30 working bar. These include the Värnamo CFB Project and the stationary Fluidized bed in Tampere. An overview of the mentioned plant technologies is in relevant literature [resp. on the Internet sites of the plant operators} to find.

• a) Der Biomasseeintrag: Die üblicherweise zur Beschickung druckaufgeladener Vergaser genutzten Druckschleusen (Look-Hopper) sind sehr teuer und verlieren beim Schleusvorgang so genanntes Schleusengas (z.B. N₂). Dadurch wird die Effizienz der Gesamtanlage bei kleiner Schüttdichte der Biomasse stark verringert.
• b) Die Heißgasreinigung: Die Reinigung des erzeugten Synthesegases aus der thermochemischen Umwandlung von Biomasse wurde zwar technisch, nicht aber wirtschaftlich gelöst. Zum Einhalten der von den anschließenden Konversionsanlagen geforderten Grenzwerte für die Weiterverarbeitung werden hauptsächlich Crackstufen zum Entfernen von Teer, entweder innerhalb des Reaktors oder in einem separaten Reaktor verwendet. Diese Reaktion findet bei ähnlichen Temperaturen wie bei der Vergasung statt. Alternativ besteht die Möglichkeit, Waschsysteme zu verwenden. Dazu muss das das heiße Gas vor dem Waschen abgekühlt werden. Diese bewährten Technologien sind zwar für die Gasreinigung grundsätzlich geeignet, haben jedoch, wie bereits erwähnt, sowohl unter energetischen als auch unter Kostengesichtspunkten große Nachteile.

However, the systems mentioned here are only in the pilot or experimental stage and already have some serious shortcomings and errors. Decisive critical points are:

• a) The biomass entry: The pressure locks normally used to charge supercharged carburetors (look-hopper) are very expensive and lose so-called lock gas (eg N ₂ ) during the lock process. As a result, the efficiency of the entire system is greatly reduced with low bulk density of the biomass.
• b) Hot gas purification: The purification of the generated synthesis gas from the thermochemical conversion of biomass was solved technically, but not economically. In order to comply with the limits for further processing required by the subsequent conversion plants, cracker stages are mainly used to remove tar, either inside the reactor or in a separate reactor. This reaction occurs at temperatures similar to gasification. Alternatively, it is possible to use washing systems. For this, the hot gas must be cooled before washing. Although these proven technologies are generally suitable for gas purification, they have, as already mentioned, great disadvantages both in terms of energy and cost.

Particles are usually deposited on candle filters made of ceramic or sintered metals. The operating temperature of these filters is in a reducing atmosphere due to their material properties a maximum of 650 ° C. The removal of sulfur from coal or oil gasification plants takes place at ambient temperatures temperature with the aid of a chemical or a physical sorbent instead. In various pilot and demonstration plants mostly lime is used as bed material for this purpose.

Ammonia, cyanide and halogens are turning into big ones Investments basically just washed out. This is the cleaning problem in the water management postponed.

On the state of the art biomass gasification and purification technology was detailed at a symposium that took place from 27.-28. September 2001 in Oberhausen took place, reports. Particularly interesting is a summary from dr. Nußbauer. He comes to the conclusion that, in terms of performance, smaller Facilities far too expensive, modern, but large technically not mature. He calls, however, an exception; the wood-fired power plant Sydkraft in Sweden. It became, however, as later mentioned is shut down for cost reasons several years ago.

It there are hundreds, maybe even thousands of releases about that Topic gasification of biomass. At the biennial Conference "Biomass for Energy and Industry " EU is about it again in detail reported. The result: too little practical, too expensive and too complicated. Above all, the entire logistics are missing, from the choice of suitable Plants, their preparation and storage to cost-effective Implementation into electricity and fuels such as gasoline and diesel. As already mentioned, is almost always only talk about wood, although you know that there are hardly any potentials of this in Western Europe.

Also the Commission in Brussels has determined that it u. a. for power generation from biomass There is no major biomass gasification project around the world today has given. An exception was, as already mentioned, the plant in Vänamo, the after overcoming greater technical difficulties for at least two months is. But that had its price.

In order to not already at a relatively high temperature condensing tar gases In this case, the wood was gassed at over 1,000 ° C. To ash agglomerations to avoid (which is easy at this temperature) and around a uniform temperature distribution To reach, one has the applied here circulating fluidized bed Sand added as heat transfer. That led to relatively high pressure losses in the carburetor. Furthermore, the and discharging the sand very complicated. The plant might have for one Continuous operation can be made suitable. But this did not happen. That had economic Reasons. The technology used was namely too expensive and too complicated and therefore has not been followed up. One had got up mostly already existing technical elements supported and not to realize a fundamentally new technical concept tries.

As already mentioned, has never been a commercially larger facility for the gasification of Biomass built.

• • Die Biomasse wurde meistens bei Atmosphärendruck in den Vergaser transportiert. Entsprechend groß sind das Volumen des Vergasungsraumes und somit die Kosten.
• • Bei Druckvergasung wird dagegen abwechselnd jeweils aus einem von zwei Behältern über Schleusen die Biomasse in den Reaktor transportiert. Trotz erheblich kleineren Volumens des Reaktors fallen infolge der Schleusen erhebliche Zusatzkosten an.

This had the following reasons:

• • The biomass was mostly transported to the carburetor at atmospheric pressure. Correspondingly large are the volume of the gasification space and thus the costs.
• • In pressure gasification, on the other hand, the biomass is transported alternately from one of two containers via sluices to the reactor. Despite much smaller volume of the reactor fall due to the locks considerable additional costs.

The So far, many negative experiences with biomass gasification and gas cleaning have shown that the technique used apparently was not suitable, an economic and technical to achieve reasonable success.

Therefore the invention has the object, a device for gasification and to create biomass gas purification, which (A) built compact is, (B) inexpensive in big Quantities can be produced, (C) is simply constructed, (D) a low susceptibility and (E) is environmentally friendly.

The Points (A) and (B) are then fulfilled when a fast throughput occurs. You can do that with high temperatures, by means of a big one surface of the reaction mixture or biomass and by increased pressure to reach.

Because of the inherently predetermined ash melting point and for chemical-thermodynamic reasons, a temperature of about 900 ° C. can not normally be significantly exceeded. Want On the other hand, to achieve the largest possible surface area, it is advantageous to disassemble the lignocellulose or biomass (also lignite) into their elemental components, the fiber elements. With grasses they have a length of only 2 mm and a diameter of 25 μ.

A simple construction according to point (C.) is given when the required process steps up narrowest space in one unit immediately after one another.

A low susceptibility to interference according to point (D) is given when the system is electronically easily monitored can be and the process as possible subject to slight fluctuations in its parameters.

environmental Protection according to point (E). should be with as possible be associated with low costs. In previously conventional gasification systems that is not the case. Rather, the gas cleaning is the main cost factor, which should definitely be avoided and therefore new solutions necessary are.

The object underlying this invention is achieved by the features characterized in claim 1. She is going through the in 1 and 2 shown illustration additionally clarified.

Biomass entry and gasification:

So far, it has been customary to transport energy carriers such as biomass by means of pressure locks (lock-hopper systems) in the pressurized carburetor. This is expensive and requires a lot of space. In addition, the necessary reservoirs must be filled with pure nitrogen at every replenishment for safety reasons. Idealist therefore a continuous entry, as in 1 and 2 is shown. Thereafter, briquettes made from stems are first coarsely crushed and then compacted by means of a stuffing screw. It forms a graft, which, if necessary, then crushed by a so-called tuber breaker again. In this form, the biomass then enters a single-screw or twin-screw extruder, to which additional hot steam is added at a pressure of about 30 bar and about 220 ° C. The purpose of the plug is that the superheated steam can not escape backwards to the point of entry.

by virtue of the strong warming the biomass softens its lignin (lignin is the "putty" between the fibers). By shearing can the fibers are then easily separated from each other. That will be included Single-shaft extruders achieved through so-called paddles, the less serve the transport but have the purpose, the conveyed to be mixed thoroughly (as is usual, for example, in the animal feed industry). This creates great Shearing forces. Due to the softened lignin fibers can then easily be separated from each other. For twin screw extruders are such measures unnecessary. However, they are more expensive than single-screw extruders.

The Operation of the entry system can be represented as follows: The biomass is first so compacted by a plug screw that a gas-impermeable plug arises. This is possible, because the biomass is easily deformable. The graft will then, if necessary, called by a cutting knife, also Knollenbrecher, finely chopped.

The Material then passes in a shredding screw.

alternative would it be possible, to get along without a stuffing screw and tuber breaker, if you have the Biomass gradually by adding oxygen and water vapor heated starting at, for example, 100 ° C, then 140 ° C until in the extruder a temperature of about 200 to 250 ° C and a Pressure has reached about 25-30 bar and then by high shear forces in the Extruder check is crushed as explained below. This leads to a significant reduction in costs.

The Biomass is at the beginning of this snail by adding water vapor or pure oxygen (or a combination of both components) heated to a temperature of about 200 to 250 ° C at a pressure of about 25-30 bar.

While oxygen and water vapor to heat the biomass whereby the lignin ("putty" between the Vegetable fibers), the biomass is replaced by the oxygen additionally partially chemically decomposed (especially the epidermis and the Nodien with grasses).

Due to the very high shear forces, for example, with single-shaft extruders through various in the Slug built-in so-called paddle (shear elements) are generated, there is a separation of the fibers from each other and further comminution of chemically decomposed biomass. The fibers of grasses (C4 reed plants, which are preferably used), for example, have a diameter of only 25 micrometers and are about 2 mm long, resulting in a very large surface area.

In front End of the snail is added so much water sprayed around, that at subsequent Adding the for the gasification of necessary oxygen is not for self-ignition Entry into the gasification chamber comes.

In addition, can one saturated Add water vapor (which does not condense). This leads in addition to greater divergence of the "explosive mixture", if significant Pressure difference between the exit of the biomass at the end of the extruder and the gasification chamber is made. Because then at the end of the slug biomass and oxygen are homogeneously mixed with each other uniformly, it comes subsequently in the combustion chamber to a homogeneous "explosion" (optimal partial combustion) at about 900 ° C, similar to with an explosive (complete Combustion).

alternative it is natural also possible, to add the oxygen separately only within the combustion chamber.

The Gasification runs in fractions of a second ("explosion gasification") the plant (by a factor of 100-500 compared to the usual Technology).

immediate Thereafter, the gas purification for technical reasons 900 ° C instead, how later even closer explained becomes.

Around to meet these requirements, are metallic membrane filters that stabilize on grids welded is needed.

Description of the membrane filter:

In collaboration with the industry, a high-temperature filter has been developed that is suitable for gasification purposes up to 1,000 ° C. It consists of a thin membrane, the surface of which has up to 40% 1-3 μm openings (s. 4 ). This results in spite of these small dimensions, an extremely low pressure loss, which is greater by 1-2 orders of magnitude with ceramic filters. In addition, the chemical resistance is sufficient in contrast to ceramic filters.

In the new filter several lined filter membranes of this type are arranged concentrically to each other (s. 5 and 6 ). This creates a very large surface in the smallest of spaces. For a filter of 1 m length, 0.8 m ⌀ and 4 filter bodies (without insulation) suitable for industrial purposes, this is at least 6 m ² .

by virtue of the thin one Membrane and very smooth surface you can the filter cake already at low pressure difference very remove easily.

This Filter can be manufactured industrially user-specific. However, as we have learned from the manufacturer, it is a matter of the principal, for to determine an order important parameters beforehand to be determined.

at same size of the filter pores and use of particulate matter from biomass gasification processes is the cheapest Diameter 1-3 μm. This is 10 times smaller than the average pore size of comparable ceramic Exhaust filter. The optimal slot dimensions and arrangement the openings can first finally determined and the appropriate membrane are manufactured, if the grain distribution of dust of biomass is known. This must be different Masks are written with different designs or layouts, different film types of different thickness for testing purposes to obtain.

Previously, existing films were purchased (or silicon wafers etched down to the desired thickness) and perforated with lithographic methods, just as masks for ion projection lithography (so-called stencil masks) are produced. That is, the processes (coating of the Si wafer, mask exposure, high aspect ratio plasma etching of the structures) for producing such thin perforated silicon films are known. Experience from stencil mask development ha ben shown that the silicon is very brittle and with the required film thickness of only a few microns (microns) is very difficult to handle.

It Therefore, attempts were made with metallic and thus more ductile materials made. It was possible, the perforations by laser make. It soon turned out that this was a dead end was. The required feature sizes of 1 μm to 3 μm were simply not nearly enough reachable.

therefore was trying to similar the processes those used in microelectronics. Here it is important that the material during plasma etching with fluorine- or chlorine-containing process gases a volatile compound enters, which can then be easily pumped out. Come in addition to silicon therefor nor titanium, tantalum, zirconium, niobium, hafnium, tungsten chromium etc. as well also aluminum in question, the latter probably for lack of durability falls away at the desired high temperatures.

From The aim of the form was an ideal filter that a very has low pressure drop, can be easily cleaned and one so big Passage area has that as possible low pressure losses occur.

This is a whole new technique that unlike filter candles Sintered metal or ceramic is very space-saving. Also suitable they are at much higher Temperature load (up to 1000 ° C in a reducing atmosphere) compared to usual Filters suitable under the same conditions only up to 500-600 ° C are. That's the special thing about these new filters.

The gas purification based on these filters runs in three stages, such as 5 - 7 shows.

Detailed description of filter level 1:

The filter stage 1 is designed as a redundant system with two filters. These two filters are operated alternately, whereby the cleaning takes place in each case in the "off-line" filter 5 as well as in Table 2, the principle of this filter unit is shown

The Total filter consists (as already mentioned) of several concentric mutually arranged cylindrical filter units. As soon as the preset maximum differential pressure when "on-line" filter is reached, the gas flow passed on the second identical filter and the previous "on-line" filter by the Inlet valve separated from the gas stream.

Of the The ash is discarded by creating a pressure difference between filter cake and filter membrane.

Under circumstances it is possible, that at sufficiently fast generation of the pressure difference .DELTA.p, the filter stage 1 to operate only with a filter. This reduces the Number of valves on only one exhaust valve for the ash discharge. This is a major simplification of the filter system and is also with associated with significant cost savings.

Such a filter is very compact. For the same performance it is one Magnitude smaller than corresponding filters with ceramic candles. Besides, they are The new membrane filters are chemically more resistant than conventional ones Ceramic candles. Ceramic has the disadvantage that at high temperature Alkalis slowly penetrate into them and thereby their melting point decreases, which at the same time leads to a loss of strength.

Detailed description filter level 2:

construction and the operation ("on-live", "off-line") are identical the ash filter. Only difference: Located on the filter membrane an artificial one Applied filter cake, which consists mainly of dolomite and to neutralize the acid gases, cleavage of tar compounds and binding of the halogens. To achieve this is a temperature from 900 ° C optimal.

The gas is supplied to one of two parallel stage 2 filters. In 6 as well as in Table 3, the principle of this filter unit or filter stage 2 is shown.

The lime or dolomite layer, consisting of fine particles, is transferred to the meme via a gas stream bran applied. As it flows through this layer harmful gases such as HCl and H ₂ S are chemically bound. Hydrogen chloride and hydrogen sulfide react with calcium oxide to form calcium chloride and calcium sulfide.

When saturation of the filter by HCl and H ₂ S occurs, these components can be measured at the filter outlet. From a still to be determined concentration of the filter cake must be replaced.

at Presence of sufficient quantities of alkalis (natural or artificial added) you can probably do without the second filter stage, (i.e., filter stage 1 replaces filter stage 2). This leads to a additional considerable cost savings.

The Filterstufe 3 is similar to the filter stages 1 and 2, but instead of 2 only one strand (see. 7 ). Here is located on the membrane, a layer of finest nickel particles of about 20-50 μ size, which are applied by means of a gas as a means of transport and then sintered. The advantage: the volume or surface of this catalyst layer is several hundred times smaller than usual with the same effect. The effective surface per filter unit, the total only a volume of z. B. 0.7 m ³ is even 6-10 m ^{2 in} size and thus at the same power many times smaller than usual in catalysts. As a result, all remaining hydrocarbons, especially methane and possibly still existing tar gases, completely converted into CO and H ₂ , for which also a temperature of 900 ° C is optimal.

Of the Reason: The gas must (as already with the upstream two Double filtering) through very fine pores. This will find an intense Contact between the gas and catalyst surface instead, which is common Catalysts in this form does not take place.

In addition, the nickel catalyst converts all nitrogen compounds such as ammonia (NH ₃ ) and hydrogen cyanide (HCN) into atmospheric nitrogen. The synthesis gas treated in this way is then so pure that it can be used for synthesis purposes or for combustion in gas turbines.

In Table 4 summarizes what impurities in which filter stage are removed from the synthesis gas.

• (1) Kompakte Einschleusung der Biomasse mittels Stopfschnecke;
• (2) schnelle momentane Erwärmung durch Druckerhöhung mit. Wasserdampf;
• (3) gleichzeitige Erweichung des Lignins (der „Kitt" der die Zellstofffasern zusammenhält);
• (4) anschließende Scherung und Trennung der Pflanzenfasern.
• (5) Zugabe kleinerer Mengen Sauerstoff und Dampf (Dampf, der nicht mehr kondensiert aufgrund konstanter Temperatur);
• (6) Verringerung des Druckes um ca. 1-5 bar bei Eintritt der Fasern in den Vergasungsraum und dadurch bedingt; explosionsartiges Auseinandertreiben und Vergasung der Pflanzenfasern;
• (7) keine vorherige Temperaturabsenkung des erzeugten Gases bei Gasturbinen notwendig und
• (8) kompakte, sehr Kosten günstige Gasreinigung an Stelle der sonst üblichen, sehr aufwendigen chemischen Gaswäsche.

Advantages of the method according to the invention are:

• (1) Compact introduction of the biomass by means of plug screw;
• (2) rapid instantaneous heating by pressure increase with. Steam;
• (3) simultaneous softening of the lignin (the "putty" that holds the pulp fibers together);
• (4) subsequent shearing and separation of the plant fibers.
• (5) adding smaller amounts of oxygen and steam (vapor that no longer condenses due to constant temperature);
• (6) reducing the pressure by about 1-5 bar when the fibers enter the gasification chamber and thereby conditional; explosive dispersal and gasification of plant fibers;
• (7) no previous temperature reduction of the gas generated in gas turbines necessary and
• (8) compact, very cost-effective gas cleaning instead of the usual, very expensive chemical gas scrubbing.

Of the special advantage is that the steps from 1-10 immediately after one another in a confined space and thereby the entire system by one Many times smaller and cheaper is considered usual. These This method is especially good for small, decentralized systems suitable, which are therefore mounted in containers and mass produced can. This makes production even cheaper many times over. Because these units are all the same, unlike large-scale facilities only once approval from the authorities necessary. That saves time and further costs. It is even possible, if necessary, larger systems to build by adding several smaller facilities to a larger unit assembles. The decentralized application has it In addition, the advantage of combined heat and power apply. That's great Plants, because of the distance between producer and user (too high heat loss the lines), not possible. In addition, can you have such facilities (because they are all the same) simply with the same Operate remote control. Another advantage is that of the rural Room in the way is economically revitalized.

By the gas cleaning at a temperature of 900 ° C is no previous temperature reduction of the gas generated, especially for Gas turbines necessary.

Thereby an efficiency is achieved that is similar to that of natural gas operated turbines.

Of the The invention is described below with reference to the description a preferred embodiment described in more detail. Show it:

1 a schematic diagram of a biomass pressure gasification plant with hot gas purification;

2 a detailed view of defibration and lignin liquefaction;

3 a principle of purification of the raw synthesis gas;

4 Section of a 10μ thick perforated titanium foil (scanning electron micrographs);

5 a schematic diagram of a filter stage 1 (ash filter);

6 a schematic diagram of a filter stage 2 (alkaline catalyst and chemical filter) and

7 a schematic diagram of a filter stage 3 (nickel catalyst).

In the 1 illustrated biomass pressure gasification plant with hot gas cleaning has a reservoir ( 1 ) on. There the coarsely shredded briquettes made from stalks are evenly packed into a stuffing screw ( 2 ) introduced in the conveying direction (P). According to the invention, this stuffing screw ( 3 ) by means of a drive ( 2 ) the biomass is continuously compressed, so that at the outlet of the plug screw in the compression zone ( 4 ) forms a gas-impermeable plug, which has the purpose that the later preferably added hot steam ( 11 ) And gases not opposite to the direction of discharge to the input point can escape. It is then passed through a cutting knife wheel ( 5 ), a so-called tuber breaker, with the help of a drive ( 6 ) again crushed. The comminuted biomass then passes into a screw extruder ( 7 ). The extruder screw ( 8th ) is with a drive ( 9 ) Mistake. It consists of an arrangement of different conveying elements ( 10 ) and shear elements ( 12 ). The propulsion and the further compression of the biomass takes place here first by the conveyor elements ( 10 ). According to the invention, shortly after the inlet of the screw extruder ( 7 ) the biomass in conveying direction (Q) by adding water vapor ( 11 ) or pure oxygen (or a combination of both components) to a temperature of up to about 250 ° C at a pressure of about 25-30 bar heated. Due to the strong warming of the biomass by water vapor and oxygen softens its lignin (the "putty" between the fibers) .In addition, the biomass is partially chemically decomposed by the oxygen.Through shearing, the fibers can then be easily separated from each other.Within the screw extruder ( 7 ) by the shear elements ( 12 ), so-called paddles achieved, which serve less to transport, but have the purpose to strongly mix the conveyed. This results in large shear forces. The fibers have a diameter of only 25 microns after separation and are about 2 mm long. This creates a very large surface.

According to the invention, shortly before the exit into the screw extruder ( 7 ) saturated or superheated steam ( 13 ) was added. This leads due to the resulting, larger volume to a drift apart of the fiber-vapor mixture.

At the exit of the extruder screw ( 8th ), the oxygen required for gasification ( 15 ) was added. There, biomass and oxygen are uniformly mixed together, and then it comes in the gasification chamber ( 16 ) to a homogeneous "explosion" (optimal partial combustion) at about 900 ° C. In order to prevent self-ignition before the "explosion mixture" enters the gasification chamber, before the addition of oxygen ( 15 ) additionally tiny amounts of water ( 14 ) sprayed all around.

Alternatively, it is also possible to use oxygen ( 15a ) separately added only within the combustion chamber. However, the mixture is then inhomogeneous and therefore gasses more unevenly with the known disadvantages.

The Gasification runs both cases in fractions of a second ("explosion gasification") is the plant (by a factor of 100-500 compared to the usual Technology).

After gasification, a mixture of synthesis gas and ash ( 17 ), that upwards flows. However, when the temperature exceeds a certain level, the ash becomes liquid. This liquid ash ( 18 ) can then down into a disposal container ( 20 ) expire.

According to the invention, from the synthesis gas ( 22 ) at a temperature of about 900 ° C in the filters ( 21 ) the filter stage 1 (detail X) removes the solids and in the filters ( 30 ) of filter stage 2 (detail Y) absorbs the halogen compounds and sour gases. The resulting filtrate ( 28 ) is stored in a disposal container ( 20 ). In it, by adding oxygen ( 19 ) Sulfite converted to sulfate.

Subsequently, in the catalyst ( 33 ) of filter stage 3 (detail Z) completely converts the remaining hydrocarbons and any remaining tar gases into CO and H ₂ . In addition, there is a conversion of all nitrogen compounds in atmospheric nitrogen. The result is a pure synthesis gas. The gas purification from the synthesis gas ( 22 ) to pure synthesis gas ( 35 ) by means of filter stages 1 (detail X), 2 (detail Y) and 3 (detail Z) are in 5 - 7 explained in more detail.

In 2 (Detail A) is once again in 1 According to the invention described, continuous biomass entry with the plug screw ( 3 ), the compaction zone of biomass ( 4 ), the tuber-breaker ( 5 ) with drive ( 6 ), shown enlarged. It also shows a part of the screw extruder ( 7 ) with an extruder screw ( 8th ) powered by a drive ( 9 ) and from an arrangement of different conveying and shearing elements ( 10 . 12 ) consists. The addition of water vapor ( 11 ) or pure oxygen (or a combination of both components) up to about 250 ° C at the beginning of the extruder screw ( 8th ) serves, as already mentioned, the softening of the lignin.

4 shows according to the invention as an example a perforated titanium foil produced by lithography and plasma etching technique. The minimal openings on the underside of the film (dark rectangles in the left picture) correspond to the original openings in the paint; during the etching process, the paint is also etched and gives way back and with it the etch front, creating an oblique edge in the etched material (gray area between dark openings and bright untouched top of the film). The dimensions of in

4 shown membrane are shown in Table 1. Table 1: Diagram of the membrane 1st pattern slit membrane filter Scale: 1: 1,750 Thickness of the membrane 5 μm below above slot width 2 μm 3 μm slot length 10 μm 12 μm

In 5 is the filter stage 1 (detail X) as a redundant system with two filters ( 21 ), which are operated alternately, wherein in each case the "off-line" filter takes place the cleaning.

The filter baskets ( 23 ) consist according to the invention of several concentrically arranged cylindrical filter units.

In the "on-line" filter (shown on the left), the synthesis gas ( 22 ) through the opened valves ( 24 ) and is displayed in the filter basket ( 23 ), so that a purified of solids synthesis gas ( 29 ) after the first filter stage. The increasing filter cake layer thickness on the filter membrane creates a pressure difference. Once the preset maximum differential pressure is reached in the "on-line" filter, the gas stream is passed according to the invention to the second identical filter and the previous "on-line" filter separated by the inlet valve from the gas stream. The "on-line" filter then goes into the "off-line" mode shown on the right. Here are the shut-off valves ( 25 ) closed. There is no gas flow here. Due to the activated pressure difference Δp ( 26 ) the filter cake falls off and the filtrate ( 28 ) passes through the open flap (valve) for the Filtrataustrag ( 27 ) in a disposal container ( 20 ) (s. 1 ). Then the shut-off valves ( 25 ) and the filter goes online again.

Table 2: Illustration of the functioning of filter stage 1

The in 6 shown construction and the operation ("on-line", "off-line") of the filter stage 2 (detail Y) with two filters ( 30 ) is essentially identical to that of filter stage 1. The purified of solids synthesis gas ( 29 ) flows in the "on-line" filter (shown on the left) through the open valves ( 24 ) and is displayed in the filter basket ( 23 ) filtered. The result is a prepurified synthesis gas ( 32 ) after the 2nd filter stage. In the "off-line" mode shown on the right, the shut-off valves ( 25 ) also closed.

The difference to the filter stage 1 is that on the filter membrane on the filter basket ( 23 ) is an artificially applied filter cake. This consisting of fine particles of lime or dolomite layer according to the invention via a gas stream ( 31 ) is applied to the membrane. The predominantly made of dolomite filter cake serves to absorb the acid gases and halogen compounds and the cleavage of possibly still existing Teergase at a temperature of about 900 ° C. As it flows through this layer harmful gases such as HCl and H ₂ S are chemically bound. Hydrogen chloride and hydrogen sulfide react with calcium oxide to form calcium chloride and calcium sulfide. Due to the pressure difference Δp ( 26 ), calcium chloride and calcium sulfide precipitate as filtrate ( 28 ) over the open flap (valve) ( 27 ). When saturation of the filter by HCl and H ₂ S occurs, these components can be measured at the filter outlet. From a concentration still to be determined, the filter cake must be replaced in good time.

Table 3: Illustration of the functioning of filter stage 2

In the 7 Filter stage 3 shown has a similar structure to filter stages 1 and 2 but instead of 2 contains only one strand, the nickel catalyst ( 33 ). Here is located according to the invention on the membrane ( 34 ) a layer of finest nickel particles of about 20-50 μ size, through which the pre-purified synthesis gas ( 32 ) flows after the filter stage 2. There, all remaining hydrocarbons, especially methane and possibly still existing tar gases are completely converted into CO and H ₂ at a temperature of about 900 ° C.

In addition, all nitrogen compounds, such as ammonia (NH ₃ ) and hydrogen cyanide (HCN) are converted into atmospheric nitrogen. The resulting pure synthesis gas ( 35 ) can be used either for combustion in gas turbines or for synthesis purposes (production of gasoline or diesel).

Table 4: Overview of the removed impurities in the 3 filter stages

1

reservoir

2

drive stuffing screw

3

stuffing screw

4

compression zone the biomass

5

lump breaker (Schneidmesserrad)

6

drive Schneidmesserrad

7

Screw extruder

8th

extruder screw

9

drive extruder screw

10

conveying elements to advance the biomass

11

Steam up to approx. 250 ° C or pure oxygen (or combination)

12

shearing elements for defibration

13

saturated or overheated Steam

14

encore tiny amounts of water

15

oxygen for gasification

15a

alternative Oxygen addition for Verg.

16

gasification chamber (about 900 ° C)

17

synthesis gas and ashes

18

procedure liquid ash

19

encore of oxygen for Conversion of sulphite into sulphate

20

disposal containers

21

filter Filter stage 1 (ash filter) - Detail X

22

synthesis gas

23

filter basket

24

Shut-off valves open

25

Shut-off valves closed

26

Pressure difference Δp for filtrate discharge

27

flap (Valve) opened for filtrate discharge

28

filtrate to the collection container

29

from Solids purified synthesis gas

30

filter the filter stage 2 (halogen and sour gas absorber) - detail Y

31

gas flow for the Renewal of the lime dolomite layer

32

prepurified synthesis gas

33

nickel catalyst the filter level 3 - detail Z

34

membrane with layer of the finest nickel particles

35

pure Synthesis gas (about 900 ° C)

Claims (22)

Process for the gasification of biomass with continuous feed, subsequent comminution and gas purification, characterized in that (a) the biomass is fed to a plug screw and thereby continuously compressed so that a gas-impermeable plug is formed, whereby steam and gases can not escape opposite to the conveying direction, (b) the biomass is either continuously fed under pressure to a shredder screw and gradually heated from 100 ° C to about 200-250 ° C by the addition of steam or pure oxygen or a combination of both, (c) or Biomass shortly after the inlet of the fiberizing screw by adding water vapor or pure oxygen or a combination of both heated to a temperature of about 200-250 ° C and brought to a pressure of about 25-30 bar, (d) that by the heating of the lignin contained in the biomass (putty between the plant fibers) erweic ht or becomes liquid, (e) that the biomass (in particular the epidermis and the nodes of grasses) is additionally partially chemically decomposed by the supplied oxygen, (f) that the shearing forces generated by the shearing elements of the defibration screw, the biomass fibers separate from each other and Epidermis sheath and nodules are also comminuted due to the embrittlement by the oxygen, (g) that just before the exit into the screw extruder water vapor is added, resulting in (h) that at the extruder outlet the oxygen required for the gasification of the biomass is added and whereby both mix uniformly with each other and are then fed to a combustion chamber, so that it is at 900 ° C to a homogeneous "explosion" (optimal partial combustion) comes, (i) or that the oxygen required for gasification is added separately within the combustion chamber, whereby the mixture is then inhomogeneous and therefore gassed unevenly, (j ) that the supply of biomass (or the gasification mixture) can be carried into the gasification chamber by one or an arrangement of several extruders, (k) that the resulting gas at 900 ° C by a high-temperature filter (metallic membrane filter) out and this in several Stages is cleaned, and (l) that the gas at the end of a kataly passes through table device, the remaining pollutants are rendered harmless. Method according to claim 1, characterized in that that after compaction of the biomass the graft by a tuber breaker (Cutting knife) is finely crushed. Method according to claim 1 or 2, characterized in addition to the addition of oxygen in addition tiny amounts of water sprayed all around become, with it a Selbstentzündung of the "explosion mixture" before entering into the gasification chamber is prevented. Method according to one of claims 1 to 3, characterized that for the gas cleaning used high-temperature filters made of a thin membrane exists whose area up to 40% 1-3 μm big openings having. Method according to one of claims 1 to 4, characterized that uses as a high-temperature filter more cylindrical membrane be arranged concentrically with each other and with wire mesh relined which creates a large surface in the smallest of spaces. Method according to one of claims 1 to 5, characterized that the filter stage 1 is designed as a redundant system with two filters and these two filters are operated alternately, each one in the "off-line" filter the cleaning takes place and that as soon as the preset maximum differential pressure achieved at the "on-line" filter is, the gas stream passed to a second identical filter and the previous "on-line" filter through Inlet valve is separated from the gas stream and that the discharge of the Filtrats by creating a pressure difference between filter cake and filter membrane takes place. Method according to one of claims 1 to 6, characterized that at sufficiently fast generation of the pressure difference .DELTA.p, the filter stage 1 can only be operated with a filter, where the number the valves on only one outlet valve for Filtrataustrag reduced. Method according to one of claims 1 to 7, characterized characterized in that construction and operation filter stage 2 ("on-line", "off-line") identical to the ash filter (Filter level 1) and that the difference is merely that on the filter membrane an artificially applied via a gas stream, is made of fine particles existing filter cake, preferably consists of dolomite and to neutralize the acid gases, cleavage the tar gases and absorption of the halogen compounds serves and at saturation the filter is replaced. Method according to one of claims 1 to 8, characterized that in the presence of sufficient amounts of alkalis (naturally present or artificial admitted) can be dispensed with the second filter stage. Method according to one of claims 1 to 9, characterized in that the filter stage 3 is constructed similar to the filter stages 1 and 2 and contains only one strand, and that there is a layer of finest nickel particles of about 20-50 μ size on the membrane, which are applied by means of a gas as a means of transport and then sintered, that the volume or the surface of this catalyst layer with the same effect several hundred times smaller than usual and thereby all remaining hydrocarbons, especially methane and possibly still existing tar gases, completely in CO and H _{2 are} converted. Method according to one of claims 1 to 10, characterized in that the gas flows through very fine pores in the nickel catalyst, as a result of which takes place an intensive contact between the gas and catalyst surface and wherein the nitrogen compounds, such as ammonia (NH ₃ ) and hydrocyanic acid (HCN ) are converted into atmospheric nitrogen. Plant for carrying out the process for the gasification of biomass with continuous feed, subsequent comminution and gas purification according to one of claims 1 to 11, characterized (α) by a plug screw ( 3 ), which is supplied to the biomass and thereby continuously compressed so that a gas-impermeable graft is formed, whereby steam and gases can not escape opposite to the conveying direction, (β) in a screw extruder ( 7 ) by a shredding screw ( 8th ), to which the biomass is either supplied continuously under pressure, and in which the biomass is gradually heated by the addition of water vapor or pure oxygen or a combination of both from 100 ° C to about 200-250 ° C, or the biomass short after the inlet of the screw extruder ( 7 ) by adding steam ( 11 ) or pure oxygen or a combination of both heated to a temperature of about 200-250 ° C and brought to a pressure of about 25-30 bar, wherein (in both cases) - by heating the contained in the biomass Lignin (putty between the plant fibers) softens or becomes liquid, - the biomass (in particular the epidermis shell and the nodules of grasses) is additionally partially chemically decomposed by the supplied oxygen, - which is separated by the shearing elements ( 12 ) of the shredding screw ( 8th ) sheared shear forces that separate biomass fibers from each other and epidermis and nodes are also comminuted due to the embrittlement by the oxygen, - just before the exit into the screw extruder ( 7 ) additionally water vapor ( 13 ), which leads to a drifting apart of the fiber-vapor mixture due to the resulting larger volume, and wherein - at the outlet of the screw extruder ( 7 ) the oxygen required for gasification ( 15 ) of the biomass is added, (γ) through a combustion chamber ( 16 ), which is either the evenly mixed biomass-oxygen mixture is supplied, so that it comes at about 900 ° C to a homogeneous "explosion" (optimal partial combustion), or alternatively the necessary for gasification oxygen ( 15a ) only within the combustion chamber ( 16 ) is added separately, whereby the mixture is however then inhomogeneous and therefore gassed more unevenly, (δ) by an extruder ( 7 ) or an array of multiple extruders ( 7 ), by the biomass (or the gasification mixture) of the gasification chamber ( 16 ), (ε) by high-temperature filter (metallic membrane filter) through which the resulting gas is passed at 900 ° C and thereby purified in several stages, and (ζ) by a catalytic device ( 33 ), in which at the end the remaining pollutants in the passing gas are rendered harmless. Plant according to claim 12, characterized by a tuber breaker (a cutting knife) ( 5 ), through which the graft is finely comminuted after compaction of the biomass. Plant according to claim 12 or 13, characterized by a device ( 14 ), by the addition of oxygen in addition tiny amounts of water are sprayed around with it, so that a self-ignition of the "explosion mixture" before entering the gasification chamber ( 16 ) is prevented. Plant according to one of claims 12 to 14, characterized through for the gas cleaning used high-temperature filters made of a thin membrane consisting of their area up to 40% 1-3 μm big openings having. Installation according to one of claims 12 to 14, characterized in that the high-temperature filter consists of a plurality of cylindrical membranes ( 23 ), which are arranged concentrically to each other and lined with wire mesh, creating a large surface area in a confined space. Installation according to one of claims 12 to 16, characterized in that the filter stage 1 (detail X) as a redundant system with two filters ( 21 ) and these two filters are operated alternately, wherein in each case in the "off-line" filter cleaning takes place and that as soon as the preset maximum Differential pressure in the "on-line" filter is reached, the gas flow passed to a second filter of the same design and the previous "online" filter is separated by an inlet valve from the gas stream and that the discharge of the filtrate ( 28 ) by generating a pressure difference Δp ( 26 ) takes place between filter cake and filter membrane. Installation according to one of claims 12 to 17, characterized in that at sufficiently fast generation of the pressure difference Δp, the filter stage 1 (detail X) only one filter is provided, wherein the number of valves ( 24 . 25 ) to an outlet valve ( 27 ) reduced for Filtrataustrag. Installation according to one of claims 12 to 18, characterized in that the construction and the operation filter stage 2 ("on-line", "off-line") (detail Y) are identical to the ash filter (filter stage 1) and that the difference therein only There is an artificial presence on the filter membrane via a gas flow ( 31 ) is applied, consisting of fine particles filter cake, which preferably consists of dolomite and serves to neutralize the acid gases, cleavage of the tar gases and absorption of the halogen compounds and is replaced at saturation of the filter. Installation according to one of claims 12 to 19, characterized that only one gas filter stage is provided, if sufficient (Naturally existing or artificial added) amounts of alkalis are available, so that on the second filter stage can be omitted. Installation according to one of claims 12 to 20, characterized in that the filter stage 3 (detail Z) is constructed similar to the filter stages 1 and 2, and contains only one strand, and that on the membrane ( 34 ) is a layer of finest nickel particles of about 20-50 μ size, which are applied by means of a gas as a means of transport and then sintered that the volume or the surface of this catalyst layer with the same effect several hundred times smaller than usual and thus all the rest Hydrocarbons, especially methane and possibly existing tar gases, are completely converted to CO and H ₂ . Installation according to claim 21, characterized in that the nickel catalyst has the finest pores through which the gas flows, wherein intensive contact between the gas and catalyst surface takes place, and wherein the nitrogen compounds, such as ammonia (NH ₃ ) and hydrogen cyanide (HCN) in atmospheric nitrogen being transformed.