Method and group of systems for producing synthesis gas

Abstract

A method for producing synthesis gas (2) including the steps of: partial conversion by fermentation of biological reactants (3) to biogas (17) in a biogas system (16), wherein, in addition to the biogas (17), fermentation residues (20) are produced which have a content in carbonaceous and hydrogen-containing components, and feeding of the fermentation residues (20) into a heated fluidized bed reactor (1), in which a synthesis gas (2) is produced from the fermentation residues (20) by gasification.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a 371 National Phase of PCT / EP 2022 / 085907, filed Dec. 14, 2022, which claims priority from German Patent Application No. 10 2021 134 191.4, filed Dec. 22, 2021, both of which are incorporated herein by reference as fully set forth.TECHNICAL FIELD

[0002] The invention relates to a method and a group of systems for producing synthesis gas from carbonaceous and hydrogen-containing reactants by gasification in a fluidized bed reactor.BACKGROUND

[0003] A synthesis gas is a gas mixture which is essentially composed of carbon monoxide (CO) and hydrogen (H2) and which can be used to synthesize other chemical products. In particular, methanol can be synthesized from such a synthesis gas.

[0004] Methanol can in turn be used as an energy source for various purposes. The production of synthesis gas from waste materials from the metallurgical and petrochemical industries is well known. However, there is also an increasing need to produce synthesis gas from biological reactants (biomass), especially as these have a sufficiently high proportion of carbonaceous and hydrogen-containing components due to their organic structure.

[0005] A suitable method for this is the production of synthesis gas in a fluidized bed reactor. In such a fluidized bed reactor, a gaseous fluid flows through the biological material, which is present as a solid bed, forming a fluidized bed in the form of a fluid-solid suspension. The incoming fluid is usually water vapor, air and / or oxygen and the biological reactant is, for example, organic waste, sewage sludge, liquid manure, animal waste or the like.

[0006] In addition, the fluidized bed reactor is heated in order to cause outgassing of the gaseous compounds contained in the biological reactant. As a result, a gas is initially formed which contains hydrogen (H2), methane (CH4), carbon monoxide (CO) and carbon dioxide (CO2) as its main components. Due to its high methane content, this gas is generally suitable for thermal conversion and therefore for generating electricity. However, the proportion of hydrogen and carbon monoxide can also be increased by partial oxidation of the methane content in order to achieve a larger quantity of synthesis gas. In such a partial oxidation, the methane reacts with the oxygen or atmospheric oxygen fed into the fluidized bed reactor, whereby the oxidation is controlled in such a way that no complete conversion of methane to carbon dioxide and water vapor takes place. Instead, the reaction process is interrupted at an early stage in order to produce carbon monoxide and hydrogen.

[0007] Such a method and such a device are known from EP 2 705 121 B1 and DE 10 2004 032 830 A1. A further method and an arrangement for gasifying biomass are known from DE 102 270 74 A1. Further methods and devices in the context of the invention are known from DE 10 2007 006 980 A1, DE 10 2008 032 166 A1, DE 10 2006 022 265 A1, DE 10 2009 039 845 A1, DE 102 58 485 A1, DE 10 2004 045 772 A1, DE 10 2007 012 452 A1, DE 10 2008 036 A1, EP 1 865 046 A1, from the technical article “Choren fuelR from the Carbo-VR gasifier”, Conference Report Biomass Gasification-International Conference Leipzig, October 2003, pages 234 to 238 and from the technical article “The Blue Tower-Hydrogen from Biomass”, Conference Report Biomass Gasification-International Conference Leipzig, October 2003, pages 240 to 249.

[0008] These methods are known in principle. However, in the interests of efficient resource use, efforts are still being made to further improve the field of application and the use of the raw material base of such fluidized bed reactors for the production of synthesis gas. In addition, the product proportions of the synthesis gas are to be optimized with regard to a modified, further use.SUMMARY

[0009] This object is solved by a method and a group of systems having one or more of the features disclosed herein. Preferred variants can be found in the claims, the description and the drawings.

[0010] Accordingly, it is envisaged that the method for producing synthesis gas comprises the following steps:

[0011] Partial conversion by fermentation of biological reactants to biogas in a biogas system, whereby in addition to the biogas, fermentation residues are formed which contain a proportion of carbonaceous and hydrogen-containing components which are no longer broken down further by the microorganisms due to their lignin-containing structure.

[0012] The fermentation residues are fed into a heated fluidized bed reactor, in which a synthesis gas is produced from the fermentation residues by gasification.

[0013] In a particularly preferred variant of the process, the biogas produced in the biogas system is used to heat the fluidized bed reactor.

[0014] The invention thus provides that at least some of the biological reactants are not fed directly into the fluidized bed reactor, but are first fed into a biogas system, whereby such a biogas system uses fermentation processes to produce a biogas from the reactants, which consists to a large extent of methane. The biogas produced in such biogas systems is usually thermally converted directly to generate electricity or fed into the natural gas grid. This is possible because the chemical composition of the biogas largely corresponds to that of natural gas. Such biogas systems are usually found in agricultural areas, as a large number of biological reactants can be put to further use in this way. From an economic point of view, however, such systems can only be operated on the basis of state subsidies, which, however, will soon expire and thus make further use unlikely, at least from an economic point of view.

[0015] However, the invention has recognized that such biogas systems can be coupled extremely effectively with a fluidized bed reactor for producing synthesis gas due to their existing infrastructure. For this purpose, some of the biological reactants are first converted into biogas in the existing biogas system, leaving behind fermentation residues. However, the conversion of the biological reactants is not necessarily complete in this design variant, so that a considerable proportion of carbonaceous and hydrogen-containing components remain in the fermentation residues. These fermentation residues can then in turn be used as reactants in the fluidized bed reactor to produce synthesis gas, while the biogas produced in the biogas system is used to heat the fluidized bed reactor. The conversion of the biological reactants in the biogas system takes place to a degree which, on the one hand, enables a sufficient quantity of biogas to be produced and, on the other hand, leaves a sufficiently high quantity of carbonaceous and hydrogen-containing compounds in the fermentation residues for the production of synthesis gas.

[0016] It should also be borne in mind that biogas systems work most effectively when they can process systems containing sugar, starch or oil as biological reactants. Other reactants such as grasses, residual wood, landscaping material, etc., consist mainly of biopolymer cellulose, hemicellulose and lignin. The conversion of these substances in biogas systems is difficult, as lignin in particular, which protects the system structure against microbial degradation, is hardly digestible for microorganisms. This means that unused reactants also remain in the fermentation residues and have so far had to be disposed of at high cost. Compared to cellulose and hemicellulose, lignin has a very high carbon content, which is advantageous for gasification.

[0017] In a particularly advantageous variant of the process, reactants such as grasses, residual wood, landscaping material and also sewage sludge can be processed directly and fed directly into the fluidized bed reactor as additional biological reactants for the production of synthesis gas.

[0018] Preferably, the biological reactants prepared by drying and pressing are packaged in the form of compacted pellets.

[0019] Ideally, the pellets can be fed into the fluidized bed reactor using a screw conveyor.

[0020] By coupling the fluidized bed reactor with the existing biogas systems, the unfermented residual components of the fermentation residues can be put to further use, resulting in both economic and resource-saving advantages.

[0021] According to one variant of the process, the reactants are only converted in the biogas system to a conversion rate of between 87%, preferably between 20% and 60%. In the context of the invention, a degree of conversion means that only a certain proportion of the maximum possible amount of biogas is actually obtained from the reactant used, in particular in relation to the maximum possible amount of methane.

[0022] According to a further development of the method, at least one heating device is provided for heating the fluidized bed reactor, which has a burner for generating heat, which is operated with a fuel gas which at least partially contains the biogas produced in the biogas system as a component. As previously explained, biogas generally has a high proportion of methane, which corresponds to between 50 and 60% by volume. Other components are water vapor, oxygen, nitrogen, ammonia, hydrogen and hydrogen sulphide. Due to the high methane content, the biogas can therefore be used as a fuel gas, although in principle other components can also be added. These other components can be natural gas, for example, or part of the synthesis gas produced in the fluidized bed reactor. The fuel gas is then burned by oxidation and the heat generated in this way is used to heat the fluidized bed reactor. Here, the at least one heating device is designed to heat the reactor to a temperature of between 600 and 1000 In addition, it is also possible to provide at least two heating devices, which then produce different temperature zones at different housing sections. Based on such an arrangement, at least a first gasification zone with a gasification temperature between 600 and 770° C., preferably between 700 and 770° C., can be generated. A second gasification zone with a second gasification temperature preferably has a temperature between 770 and 1000° C., preferably between 770 and 900° C.

[0023] In a particularly preferred variant of the process, a fluidized bed material can be used to support the formation of a fluidized bed. This fluidized bed material can preferably be in the form of sand.

[0024] In an advantageous variant, the biogas system and the fluidized bed reactor can also be positioned separately from one another. In addition, it is also conceivable that several biogas systems, which are already distributed locally around the fluidized bed reactor, supply a central fluidized bed reactor with biogas and fermentation residues. The biogas produced can also be fed into the existing natural gas grid and extracted via a connection to the fluidized bed reactor. The fermentation residues can be transported to the fluidized bed reactor by tanker, for example.

[0025] According to a further development of the invention, the fuel gas contains the biogas produced in the biogas system in a proportion of between 55% by weight, preferably between 10 and 35% by weight. As already explained above, the further proportions can be formed, for example, from natural gas or synthesis gas.

[0026] In addition, at least one heating device heats the fluidized bed reactor preferably in an allothermal manner. This means that the procedural processes in the fluidized bed are caused solely by the external effect of heat, but without causing chemical changes. For this purpose, it is necessary that the heat generated in the burner is fed to the fluidized bed reactor without the hot exhaust gases from the burner entering the fluidized bed reactor in material terms. This can be made possible, for example, by the hot exhaust gases acting on the fluidized bed in the form of a heat exchanger. In addition, baffle plates can also be provided to increase the surface area acting on the fluidized bed.

[0027] According to a preferred embodiment of the process, the fermentation residues are not the only material with which the fluidized bed reactor is operated.

[0028] Rather, the fermentation residues merely represent a proportion of the biological reactants with which the fluidized bed reactor is operated. In principle, garden waste, green waste, sewage sludge and much more can also be used in the fluidized bed reactor.

[0029] The prerequisite for feeding into the fluidized bed reactor is the processing of fermentation residues, green waste, garden and agricultural waste and sewage sludge. For this purpose, the biological reactant is preferably dried and / or pressed so that a water content of less than 20% can be achieved.

[0030] A further object of the invention is a group of systems for carrying out the method according to the invention with a biogas system for fermenting reactants to biogas and a fluidized bed reactor for producing synthesis gas, wherein the biogas system is connected to the fluidized bed reactor via a first transport device, wherein the first transport device is set up to feed the carbonaceous and hydrogen-containing components of the fermentation residues from the biogas system into the fluidized bed reactor.

[0031] In addition, an advantageous variant of the method may also comprise a second transport device which is adapted to feed biogas from the biogas system into a heating device for heating the fluidized bed reactor.

[0032] In principle, the biogas system and the fluidized bed reactor can thus be arranged close to each other so that the feedstock produced in the biogas system can be processed directly in the fluidized bed reactor. In such a case, it is useful, for example, to provide the second heating device in the form of a simple pipe connection or in the form of a piping system, so that the biogas system can be fed directly into the fluidized bed reactor or into the heating device of the fluidized bed reactor without the interposition of further components. In the context of the invention, such a pipeline system means a pipeline system which is not connected to a municipal natural gas pipeline system, so that apart from the fluidized bed reactor, no or only a few consumers can be operated with the biogas produced. Apart from the fluidized bed reactor, the other possible consumers are only consumers within the group of systems or also consumers in close proximity, e.g. in the area of a connected farm.

[0033] Advantageously, the biological reactant of the fluidized bed reactor is processed so that a fluidizable solid mass with a water content of less than 20 % is achieved.

[0034] For this purpose, in an advantageous variant of the invention, the fermentation residues can be pressed. Preferably, this can be carried out using a belt filter press or a frame filter press or a chamber filter press or a screw press.

[0035] In a particularly advantageous variant of the group of systems, the waste heat from the fluidized bed reactor's exhaust gas washing is used to dry the biological reactants. This can advantageously take place in a belt dryer.

[0036] Garden waste, green waste, sewage sludge and agricultural waste can also be fed into the pressing process and / or the drying process, depending on their water content.

[0037] Preferably, the biological reactant of the fluidized bed reactor is prepared in such a way that the biological reactant can be fluidized. For example, a comminution process can also be used for this purpose.

[0038] Ideally, the biological reactant is compacted into fluidizable pellets after the comminution process.

[0039] In a particularly favorable variant of the process, the group of systems also includes a receiving point and a storage area for biological reactants, such as grasses, residual wood and landscaping material.

[0040] If the biogas system and the fluidized bed reactor are located close to each other, the first transport device can be a conveyor unit that connects the two system components.

[0041] Preferably, the conveyor units are adapted depending on the water content of the reactants. In the case of very wet fermentation residues, for example, this can be an eccentric screw or screw conveyor. In the case of already dried or pressed and processed reactants, conveyor belts are also suitable.

[0042] Of course, the conveyor unit can also be a mobile conveyor unit, e.g. a transport vehicle, truck or similar, which removes the fermentation residues from the biogas system and feeds them to the fluidized bed reactor. Such an arrangement is particularly useful if the fluidized bed reactor and the biogas system are a certain distance apart.

[0043] In such a case, it may also be expedient to provide the first transport device in the form of a mobile conveyor unit, whereby the biogas is then filled into a tank load scale, for example, and transported to the fluidized bed reactor via this.

[0044] Alternatively, the biogas can also be fed into the existing natural gas grid, whereby the fluidized bed reactor is also connected to the natural gas grid and draws its fuel gas from it. In terms of balance, this is also a group of systems.

[0045] In a preferred variant, the synthesis gas is processed into pure hydrogen gas. For this purpose, soot is preferably removed from the synthesis gas, any sulphur compounds present are separated, the carbon monoxide is converted to carbon dioxide and hydrogen by means of a water-gas conversion reaction, the residual water is removed and the carbon dioxide is removed.

[0046] Advantageously, the group of systems also comprises a storage capacity for hydrogen, possibly a connection to a hydrogen grid and a hydrogen filling station for motor vehicles.

[0047] Another object of the invention is the use of reactants only partially converted to biogas by fermentation in a biogas system in a fluidized bed reactor for the production of synthesis gas.

[0048] Advantageously, the biogas produced is used to heat the fluidized bed reactor.

[0049] In a particularly preferred variant, the synthesis gas, which is produced in a group of systems of a biogas system with a fluidized bed reactor for the gasification of biological reactants, is used to obtain pure hydrogen. This is an advantageous way of providing clean hydrogen from biological reactants for the mobility of the future.BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In the following, the invention is explained in more detail using examples of embodiments. It shows:

[0051] FIG. 1 is a process diagram of the group of systems according to the invention, FIG. 2 shows the system combination according to FIG. 1 with alternative transport devices.DETAILED DESCRIPTION

[0052] FIG. 1 shows a group of systems with a fluidized bed reactor 1 for producing synthesis gas 2 from a biological reactant 3. The fluidized bed reactor 1 has a fluidized bed 4, which is formed from the biological reactants 3 and which is also operated with a mixture of steam 5 and air or oxygen 6. In order for a synthesis gas 2 to be formed from the biological reactants 3, the reactants 3 must be fluidizable and have a water content of less than 20%. Steam 5 and air or oxygen 6 are fed into the fluidized bed reactor 1 in such a way that the biological reactant 3 forms a dancing fluidized bed 4, whereby the fluidized bed 4 is simultaneously heated to a high temperature.

[0053] For the purpose of this heating, a heating device 7 in the form of a burner is provided, which is operated with a fuel gas 8 and an air flow 9. This heating device 7 then conducts the heat to the fluidized bed 4 in the form of a heat exchanger arrangement 10, without the exhaust gases generated in the burner entering the fluidized bed reactor 1.

[0054] The generated synthesis gas 2 can be cleaned of solid particles 12 in a first cyclone 11, whereby the solid particles 12 then enter the fluidized bed reactor 1 again. The synthesis gas 2 is then cooled in a heat exchanger arrangement 13, which is operated with cooling water 14. Finally, a further cyclone 15 is provided, which separates the remaining solid particles 12 and leaves the purified synthesis gas 2 behind. Preferably, the waste heat from the heat exchanger arrangement 13 is used to dry the biological reactants 3 in a dryer not shown.

[0055] Furthermore, a biogas system 16 is coupled to the fluidized bed reactor 1, whereby the biogas 17 produced in the biogas system 16 is used as fuel gas 8 in the heating device 7. The fuel gas 8 can also be composed of other combustible gases 19, for example natural gas or the synthesis gas 2 produced in the fluidized bed reactor 1.

[0056] In addition, the fermentation residues 20 produced in the biogas system 16 are used in the fluidized bed 4, whereby further biological reactants 21 may also be provided here. The fermentation residues 20 and the further biological reactants 21 are processed, for example in a chamber filter press, a belt dryer and in a comminution apparatus, which are not shown for the sake of simplicity.

[0057] The biogas system 16 is accordingly designed to produce biogas 17 by fermenting biomass, leaving behind the fermentation residues 20. However, the biomass used is only partially converted into biogas 20 by a targeted control system, so that the remaining fermentation residues 20 continue to have a high proportion of carbonaceous and hydrogen-containing components.

[0058] Due to the fact that the biogas system 16 and the fluidized bed reactor 1 are arranged close to each other, the biogas 17 can, for example, be connected directly to the heating device 7, which is designed as a burner, via a pipeline.

[0059] An alternative embodiment is shown in FIG. 2, where the process diagram basically corresponds to the process diagram shown in FIG. 1. However, here the biogas system 16 is located further away from the fluidized bed reactor 1, so that transport equipment in the form of mobile conveying units 22 or pipelines in the form of the natural gas grid are provided for both the biogas 17 and the fermentation residues 20, which in the example shown are designed as trucks or tanker trucks.

Claims

1. A method for producing synthesis gas (2) comprisingpartially converting by fermenting biological reactants (3) to biogas (17) in a biogas system (16), wherein, fermentation residues (20) are produced having carbonaceous and hydrogen-containing components, andfeeding the fermentation residues (20) into a heated fluidized bed reactor(1).

2. The method according to claim 1, wherein the biogas (17) produced in the biogas system (16) is used for heating the fluidized bed reactor (1).

3. The method according to claim 1, wherein the fermentation residues (20) are processed for feeding into the fluidized bed reactor (1).

4. The method according to claim 1, wherein the biological reactants (3) are converted in the biogas system (16) only to a degree of conversion of between 10 and 80%,5. The method according to claim 1, wherein the biogas system (16) produces biogas (17) in an amount of 20 to 120 m3 per ton of reactants (3).

6. The method according to claim 1, wherein for heating the fluidized bed reactor (1) at least one heating device (7) is provided, which for generating heat has a burner which is operated with a fuel gas (8) which at least partially contains the biogas (17) produced in the biogas system (16) as a component.

7. The method according to claim 6, wherein a proportion of the biogas (17) produced in the biogas system (16) in the fuel gas (8) corresponds to between 5 and 50% by weight.

8. The method according to claim 6, wherein at least one heating device (7) heats the fluidized bed reactor (1) allothermally.

9. The method according to claim 5, wherein the fuel gas (8) comprises further components selected from the group consisting of natural gas, synthesis gas (2), and biogas (17).

10. The method according to claim 1, wherein the fluidized bed reactor (1) is operated with further biological reactants (21) in addition to the fermentation residues (20).

11. A group of systems for carrying out a method according to claim 1, the group of systems comprising: the biogas system (16) for fermenting reactants (3) to biogas (17) and the fluidized bed reactor (1) for producing synthesis gas (2), wherein the biogas system (16) is connected to the fluidized bed reactor (1) via a first transport device, wherein the first transport device is arranged to feed the fermentation residues (20) comprising the carbonaceous and hydrogen-containing component from the biogas system (16) into the fluidized bed reactor (1).

12. The group of systems according to claim 11, further comprising a second transport device set up to feed biogas (17) from the biogas system (16) into a heating device (7) for heating the fluidized bed reactor (1).

13. The group of systems according to claim 11, wherein the fermentation residues (20) are treated before being fed into the fluidized bed reactor (1) so that a water content of the fermentation residues (20) is less than 20%.

14. The group of systems according to one of claim 10, wherein the fermentation residues (20) are processed before being fed into the fluidized bed reactor (1), so that a fluidizable mass of solid material is produced.

15. The group of systems according to claim 12, wherein the second transport device is a pipeline connecting the biogas system (16) to the fluidized bed reactor (1).

16. The group of systems according to claim 10, wherein the first transport device is a conveyor belt and / or a screw conveyor connecting the biogas system (16) to the fluidized bed reactor (1).

17. The group of systems according to claim 12, wherein the first and / or the second transport device is a mobile conveyor unit.

18. The method of claim 1, further comprising providing the reactants (3) to be only partially converted to biogas (17) by fermentation in the biogas system (16) in the fluidized bed reactor (1) to produce synthesis gas (2).

19. The method of claim 1, further comprising using the biogas (17) produced in the biogas system (16) to heat the fluidized bed reactor (1).

20. The method of claim 1, further comprising producing pure hydrogen from the synthesis gas (2) produced in the fluidized bed reactor (1) from the biological reactants (3).

Images