System and process for producing synthesis gas from carbonaceous solids and slurries

Abstract

The present invention relates to a multistage process and to a system for producing synthesis gas from carbonaceous solids and slurries. The process comprises the pyrolysing of the carbonaceous solids and slurries with exclusion of air to form a solid carbon carrier carbonizate and a pyrolysis gas; the oxidizing of the separated pyrolysis gas with incoming oxygen, and the contacting of the carbon carrier carbonizate with the oxidized pyrolysis gas.

Description

[0001] System and process for producing synthesis gas from carbonaceous solids and sludges

[0002] The present invention relates to a multi-stage process and a system for producing synthesis gas from carbonaceous solids and sludges. The process comprises pyrolyzing the carbonaceous solids and sludges in the absence of air to form a solid carbon carrier carbonate and a pyrolysis gas; oxidizing the separated pyrolysis gas in the presence of oxygen; and contacting the carbon carrier carbonate with the oxidized pyrolysis gas and optionally with other reaction gases, in particular carbon dioxide (CO2) and water vapor (H2O).

[0003] Synthesis gas consists of the active components carbon monoxide (CO) and hydrogen (H2) and is an indispensable reactant for a wide range of chemical syntheses. For example, hydroformylations, methanol, and Fischer-Tropsch syntheses are carried out using synthesis gas as a reactant. Synthesis gas can, in principle, be obtained from solid or liquid reactants. Coal gasification is the most important method of production from solid materials; in this process, coal is reacted with oxygen and steam to form a mixture of CO and H2. Crude oil distillates, for example, can be used to produce synthesis gas from liquid feedstocks. Here, low-boiling or high-boiling fractions are converted after desulfurization by reaction with steam using the steam reforming process.Another, more sustainable, and potentially more environmentally friendly process is the production of syngas using organic waste or residues. In principle, these processes can be produced on an industrial scale, but the extraction processes based on waste-derived materials still have disadvantages. For example, gasification processes based on waste-derived materials have stringent fuel quality requirements in the form of specific materials, ash softening temperatures, particle sizes, or specified grain shapes. Long-term stable processes could usually only be reliably carried out using high-quality and expensive wood chips from woody biomass. Deviations from these specifications lead to a decline in the available syngas quality, for example, in the form of a higher tar content in the syngas.Non-convertible particles and heteroatom-containing compounds, for example based on sulfur or halogen atoms, in the biological reactants also make it difficult or impossible to achieve sufficient quality in the synthesis gases produced.

[0004] The patent literature also contains a wide variety of approaches to producing synthesis gas.

[0005] For example, DE 10 2011 051 906 A1 describes a process for the gasification of coal or carbon-containing materials in a fluidized bed gasification reactor, wherein a gasification agent containing carbon dioxide and / or water vapor is blown into the gasification reactor under pressure in the lower part of the gasification reactor by means of a feed device, wherein the gasification material is introduced into the gasification reactor under pressure above the fluidized bed, wherein the gasification of the gasification materials with the gasification agents takes place by discontinuously igniting a plasma which rotates step by step in the fluidized bed around the central axis of the reactor shell and which rotates step by step following the stress field, and dust-laden raw gas is withdrawn from the top and bottom product (ash) is withdrawn from the bottom of the gasification reactor.

[0006] Furthermore, DE 10 2007 062 413 B3 describes a process for the reprocessing of COi-containing exhaust gases in a multi-stage reduction process, wherein the COi-containing exhaust gas is passed in countercurrent to a solid mass flow comprising a circulating bulk material and thermally decomposable organic mass through a number of zones into a pressure equalization zone and is converted into pyrolysis gases, wherein in the flow direction of the solid mass flow a. in a fuel gas generation stage at 250°C-700°C the organic mass is thermally decomposed under reducing conditions into short-chain hydrocarbons, hydrogen and carbon monoxide to produce coke and residue, and b. in an intermediate stage the coke is oxidized at rising temperature, wherein the carbon monoxide produced is sucked off countercurrent to the solid mass flow in the direction of the fuel gas generation stage, wherein c.in a carbon monoxide production stage at 800 - 600°C, remaining coke residues are converted into carbon monoxide with the carbon dioxide of the exhaust gas under adjustment of pressure and temperature according to the Boudouard equilibrium, and d. the CO2-containing exhaust gas is introduced into a cooling stage which follows the carbon monoxide production stage in the flow direction of the solid mass flow and in which the resulting slag as residue and the bulk material in the CO2 flow stream are cooled to below 100°C and discharged, and e. the bulk material is returned to the cycle after removal from the cooling stage.

[0007] Against this background of the prior art, the object of the invention is therefore to provide an improved process for producing synthesis gas and an improved system for carrying out this improved process. In particular, the process according to the invention is intended to enable the production of synthesis gas from a wide variety of carbon-containing feedstocks with low levels of impurities, particularly tar.

[0008] This object of the invention is achieved by a method having the features specified in claim 1 and by a system having the features specified in claim 9. Preferred developments of the invention are specified in the associated subclaims, the following description and the drawing. Accordingly, the invention provides a method for producing synthesis gas, wherein the method comprises at least the steps: a) providing a carbon-containing sludge or solid; b) pyrolyzing the carbon-containing sludge or solid in the absence of air at a temperature of greater than or equal to 600°C and less than or equal to 1200°C to form a solid carbon carrier carbonizate and a pyrolysis gas, wherein the pyrolysis gas is separated from the carbon carrier carbonizate during or after the pyrolysis;c) oxidizing the separated pyrolysis gas in the presence of oxygen in a temperature range of greater than or equal to 1000°C and less than or equal to 1600°C to obtain an oxidized pyrolysis gas; d) contacting the carbon carrier carbonizate from process step b) with the oxidized pyrolysis gas from process step c) in a temperature range of greater than or equal to 800°C and less than or equal to 1500°C to obtain the synthesis gas.

[0009] It was found that the multi-stage process, which uses an oxidation step, can cover a broad range of feedstocks comprising different carbonaceous materials and also different physical product specifications with minimal requirements. By specifically adapting the process parameters in the individual steps, consistently high synthesis gas quality can be achieved. In particular, the tar content in the synthesis gas can be reduced to almost any desired residual amount. This is particularly important because the resulting tar fraction represents a significant and limiting factor in state-of-the-art gasification processes. Tars consist of long-chain, sometimes harmful, aliphatic or aromatic hydrocarbons, which complicate product gas purification and analysis and have a severely negative impact on process stability.By connecting the process steps according to the invention in series, particularly the long-chain hydrocarbons produced in conventional gasifiers can be broken down within the specified temperature ranges. Therefore, no or only marginal amounts of tar are formed in this sequence. This greatly simplifies the purification of the gas, including the removal of other components such as acidic gases. In addition, state-of-the-art gasification processes often produce PAH-contaminated biomass carbonates, the further utilization of which is limited. The proposed process, within the specific temperature ranges, enables the production of a virtually PAH-free carbonate.Through the optional use of CO2 as an additional oxidant in the gasification reactor, captured CO2 from carbon capture and storage facilities, for example, can be converted into economically valuable products. The process can also be modified so that the composition of the product gas can be flexibly adapted to the requirements of various downstream processes by adding additional steam to the gasification reactor or downstream water gas shift reactors. Furthermore, the targeted addition of additional process additives during carbonization can access an additional quantity of starting materials for conversion without negatively impacting the quality of the available synthesis gas. These additional substances cannot be converted to high quality using state-of-the-art processes.The process according to the invention therefore makes it possible to obtain both a high-quality synthesis gas and a high-quality carbonizate from a wide range of feedstocks.

[0010] The process according to the invention is a process for producing synthesis gas. Synthesis gas, as defined by the invention, is a gas mixture whose main components, with the largest molar proportions, are carbon monoxide and hydrogen. The quantitative ratios of the two gas components can vary, and other gases may also be present in the gas mixture in smaller quantities.

[0011] The process comprises process step a), the provision of a carbon-containing sludge or solid. The carbon carriers in this process are feedstocks / residues such as woody biomass, residual forest wood and landscape maintenance wood, herbaceous biomass, straw, miscanthus, waste wood, food scraps, market waste and industrial residues from food and feed production such as pomace or shells. In principle, all types of combustible, carbon-containing materials can be used in the process, including, for example, fossil feedstocks (coal, residues from the petrochemical industry) or anthropogenic waste (plastic and biomass-containing waste fractions from domestic waste, commercial waste, industry and end-of-life vehicle processing). Feedstocks with different water contents can be used in the process. Preferably, however, the water content can be less than 50 wt.%, more preferably less than 25 wt.-% and more preferably less than 15 wt.%. The feedstock can be in the form of a loose powder bed, in the form of pellets or granules, as a slurry, or in the form of irregularly shaped particles. The feedstock can preferably have an average particle size of less than or equal to 10 cm, preferably less than or equal to 5 cm, and more preferably less than or equal to 2.5 cm. Particle size is understood to be the longest dimension within the feedstock particle.

[0012] The process comprises process step b), pyrolyzing the sludge or solid in the absence of air at a temperature of greater than or equal to 600°C and less than or equal to 1200°C to form a solid carbon carrier carbonizate and a pyrolysis gas, wherein the pyrolysis gas is separated from the carbon carrier carbonizate during or after pyrolysis. The pyrolyzing of the feedstock represents a heat treatment of the carrier, wherein in this step the molecular composition of the feedstock is at least partially destroyed without the active addition of further reaction gases. The treatment in the specified temperature range essentially results in water and gaseous degradation products being expelled from the feedstock in the form of a pyrolysis gas. The pyrolysis gas therefore contains the degradation products of the feedstock that are volatile under these process conditions.These gaseous degradation products can be aliphatic or aromatic hydrocarbons, their heterocyclic compounds, or generally volatile degradation compounds such as ammonia or hydrogen sulfide, which are volatile in this temperature range. What remains is a carbon carrier carbonate depleted of these degradation products, which essentially comprises carbon and non-volatile, inorganic components, for example in the form of salts. The treatment duration in this step depends on the type and size of the carrier used and can, for example, be longer than 15 minutes, longer than 30 minutes, or longer than 1 hour. During the heat treatment, the gaseous reaction products are separated from the carbonate continuously or at irregular intervals from the treatment chamber, for example, a pyrolysis reactor.It is also possible that the pyrolysis gas is only separated from the carbonate remaining in the reactor at the end of the process step.

[0013] The process comprises process step c), oxidizing the separated pyrolysis gas in the presence of oxygen at a temperature range of greater than or equal to 1000°C and less than or equal to 1600°C to obtain an oxidized pyrolysis gas. The separated pyrolysis gas is mixed with oxygen and oxidized within the specified temperature range. The oxidation reaction can also be carried out by continuously supplying oxygen to the pyrolysis gas. Preferably, the oxidation of the pyrolysis gas can involve burning the pyrolysis gas in a flame with the addition of oxygen. The oxygen can be supplied for oxidation as atmospheric oxygen or in the form of specific oxygen-containing gas mixtures.The oxygen content can vary; preferably, the molar oxygen content upon oxygen addition can be greater than or equal to 30 mol% and less than or equal to 100 mol%, more preferably greater than or equal to 50 mol% and less than or equal to 100 mol%, and furthermore preferably greater than or equal to 75 mol% and less than or equal to 100 mol%. The amount of oxygen supplied for oxidation can, for example, be 1:1 based on the volume of the pyrolysis gas. During this process step, any long-chain organic hydrocarbon compounds present in the pyrolysis gas are essentially oxidized to carbon dioxide and water. Any hetero compounds present are also oxidized and can, for example, be removed by optional purification steps. After this step, the pyrolysis gas can be free of carbon compounds with more than one C atom.

[0014] The process comprises process step d), contacting the carbon carrier carbonate from process step b) with the oxidized pyrolysis gas from process step c) at a temperature range of greater than or equal to 800°C and less than or equal to 1500°C to obtain the synthesis gas. During this step, the carbonate from process step a) is contacted with the oxidized pyrolysis gas. This produces a very high-quality synthesis gas and further conditions the carbonate. In this step, the oxidized pyrolysis gas is reduced at the carbon of the carbonate, and the components CO2 and H2O are converted to CO and H2. The porous structure of the coke can be specifically influenced by the temperature and duration of the reactions on the particle surface.

[0015] In a preferred characteristic of the process, complete oxidation of the separated pyrolysis gas can be carried out in process step c). To obtain a very high-quality synthesis gas with a very low tar content and very low levels of unwanted gas admixtures, it has proven particularly advantageous to oxidize all compounds in the pyrolysis gas within this process step. Complete oxidation of the pyrolysis gas occurs in cases where at least 99.5 wt.%, preferably at least 99.9 wt.%, and more preferably 100 wt.% of the organic compounds in the pyrolysis gas have been converted to carbon dioxide and water. For this purpose, the process gas fed into this step can preferably have an oxygen content of greater than or equal to 95 mol.%.

[0016] In a further preferred embodiment of the process, an oxidized pyrolysis gas at the end of process step c) can have an oxygen concentration of greater than or equal to 0.25 vol.% and less than or equal to 5.0 vol.%. To ensure controlled and reproducible oxidation of the pyrolysis gas, conducting the process via the residual oxygen content at the end of this process step has proven particularly suitable. After carrying out this step with an oxygen concentration in this range, the oxidized pyrolysis gas is guaranteed to no longer contain any tars. In addition, the oxidized pyrolysis gas (= CO2 + H2O + O2) is particularly advantageously prepared for the subsequent conversion step with this oxygen concentration.A sufficient initial amount of oxygen is present to achieve immediate and subsequent complete conversion of the oxidized pyrolysis gas (= CO2 + H2O + O2) upon contact with the carbon into synthesis gas through oxidative reactions of the gas with the carbon carrier carbonate and the resulting energy input. This can increase the synthesis gas yield or contribute to an overall faster or more complete conversion. Higher oxygen concentrations can be disadvantageous, as they would banish too much solid carbon, thus leaving insufficient solid carbon carrier available for the complete conversion of the oxidized pyrolysis gas into synthesis gas. Furthermore, the reaction chamber could overheat, causing process and material-related problems, for example, in the form of ash melting or thermal damage to the reactor materials.Preferably, an oxidized pyrolysis gas at the end of process step c) can have an oxygen concentration of greater than or equal to 0.3 vol.% and less than or equal to 3.0 vol.%, further preferably of greater than or equal to 0.5 vol.% and less than or equal to 1.0 vol.%.

[0017] In a further preferred characteristic of the process, the carbonaceous sludge or solid can have an ash content, determined according to DIN EN ISO 18122, of greater than or equal to 0 wt.% and less than or equal to 50 wt.%. The process according to the invention can also be used to process feedstocks that can only be converted insufficiently using the processes known in the prior art. The process presented here can be characterized in particular by the fact that even very ash-containing feedstocks can be efficiently utilized over long plant operating times. The ash content of the feedstocks can preferably be greater than or equal to 0.01 wt.% and less than or equal to 30 wt.%, more preferably greater than or equal to 0.1 wt.% and less than or equal to 20 wt.%, and further preferably greater than or equal to 0.2 wt.% and less than or equal to 10 wt.%. The ash content is determined based on the dry matter according to the method specified above.

[0018] In a preferred embodiment of the process, the carbonaceous sludge or solid can have a minimum permissible calorific value (dry), determined according to DIN EN ISO 18125, of greater than or equal to 10 MJ / kg and less than or equal to 30 MJ / kg. The process according to the invention can be carried out very energy-efficiently even with organic starting materials that have only a moderate energy content. These substances can be converted into high-quality synthesis gases. The calorific value can preferably be greater than or equal to 12 MJ / kg and less than or equal to 25 MJ / kg, and more preferably greater than or equal to 15 MJ / kg and less than or equal to 20 MJ / kg. The calorific value is determined based on the dry substance using the method specified above.

[0019] In a further preferred embodiment of the process, in process step a) prior to pyrolysis, an additive containing alkali or alkaline earth ions can be added to the carbonaceous sludge or solid. By adding auxiliary substances in the form of alkali or alkaline earth salts, the process can also process other feedstocks that would otherwise be inaccessible to the process due to their thermal properties. For example, the addition of lime to the carbon carrier prior to pyrolysis can promote catalytic cracking of tars and the binding of acid-forming gases. Furthermore, these additives can lead to an increase in the ash softening temperature, which can prevent operational disruptions in pyrolysis. In addition to the synthesis gas, carbonates can also be obtained, which, due to their quality properties, can potentially serve as adsorbents or pigments.The carbonates can, for example, also be stored in geogenic deposits as part of Biochar Carbon Removal (BCR) for the permanent binding of CO2 or used as an additive in processes for the production of material products such as cement or concrete.

[0020] In a preferred feature of the process, pure oxygen can be used for oxidation in process step c). For efficient and rapid oxidation of the pyrolysis gas, reaction with pure oxygen has proven particularly advantageous. Tar-free product gases can be obtained very quickly. For this purpose, the pyrolysis gas can preferably be contacted with an amount of at least 50%, more preferably at least 100%, of pure oxygen, based on the volume of the pyrolysis gas, within this step.

[0021] In a further preferred embodiment of the process, process step b) can be carried out in a temperature range of greater than or equal to 800°C and less than or equal to 1200°C. The temperature range specified above has proven particularly suitable for the controlled and largely tar-free processing of organic residues. Pyrolysis takes place within short process times, while ensuring the most uniform possible pyrolysis of very differently structured organic materials. Within this temperature range, only very few unwanted gases or gas compounds, such as halogens or hydrogen halides, are formed or expelled from the organic material, so that the purest and most suitable pyrolysis gas possible can be obtained within short process times. Lower temperatures can lead to significantly longer process times and only insufficient pyrolysis of the organic material.Higher temperatures can unintentionally increase the general spectrum of available pyrolysis gases.

[0022] Within a further preferred aspect of the process, process step b) can be carried out in a rotary tube reactor. Obtaining the most defined pyrolysis gas possible and the most suitable carbon carrier carbonate possible is not trivial. The inhomogeneity of most organic substances requires that the boundary conditions during pyrolysis be selected such that the inhomogeneities in the starting material are uniformed so that only small amounts of undesirable by-products are produced. To meet these requirements and to obtain high-quality pyrolysis gas from a variety of otherwise unsuitable materials, the use of a rotary tube reactor has proven particularly suitable. Without being bound by theory, the particular suitability probably arises from the fact that the organic material is pyrolyzed uniformly by this type of reactor during pyrolysis.The movement prevents temperature peaks and improves and evens out the heat input into the organic material. Using this type of reactor allows pyrolysis to be carried out faster and / or at lower temperatures. The latter can improve the energy balance of the overall process.

[0023] In a further preferred embodiment of the process, process step d) can be carried out in a temperature range of greater than or equal to 950°C and less than or equal to 1200°C. For the production of a synthesis gas with a very high proportion of hydrogen and carbon monoxide, further contacting of the oxidized pyrolysis gas with the carbonizate in the specified temperature range has proven particularly advantageous.

[0024] Within a preferred aspect of the process, process step d) can be carried out in a fluidized-bed reactor or a moving-bed reactor. A reaction environment in the form of a fluidized-bed reactor or a moving-bed reactor has proven particularly suitable for reacting the carbonate with the oxidized pyrolysis gas. Uniform H2 / CO2 ratios are achieved even within long process times or with unfavorable starting materials. Furthermore, the use of these two reactor types leads to a significant homogenization of the reaction in cases where additional process agents are added in this step. In summary, high-quality synthesis gas compositions can be obtained in a controlled manner with low energy consumption and within short process times.

[0025] In a preferred embodiment of the process, process step c) can be carried out in a temperature range of greater than or equal to 1000°C and less than or equal to 1200°C. This temperature range has proven particularly effective for rapid and complete oxidation of the pyrolysis gas with a very low tar content in the oxidized pyrolysis gas. Tar-free product gases can be obtained as a function of the contact time and the oxygen content.

[0026] Furthermore, the invention relates to a system for producing synthesis gas, the system comprising at least: i) a pyrolysis reactor configured to pyrolyze a carbon-containing solid or sludge in the absence of air at a temperature of greater than or equal to 800°C and less than or equal to 1200°C and to separate a resulting pyrolysis gas from a remaining, solid carbon carrier carbonate; ii) an oxidation reactor configured to oxidize a pyrolysis gas with the supply of oxygen at a temperature of greater than or equal to 1000°C and less than or equal to 1200°C; iii) a synthesis gas reactor configured to contact an oxidized pyrolysis gas with the carbon carrier carbonate at a temperature of greater than or equal to 950°C and less than or equal to 1500°C.

[0027] Using this system, high-quality synthesis gases and high-quality carbonizates can be produced from a wide variety of carbon-containing solids and sludges. Compared to existing systems, the feedstocks can be subject to significantly less restrictive specifications regarding their physical / chemical properties. This allows a wide variety of different carriers, even those with varying properties, to be safely converted into flexibly applicable synthesis gases. The carbonizates produced by the system can also find other uses, for example, in pigments, in cement production, or as a carbon source in reduction processes in metallurgy. The system is also so flexible that, if desired, additional process steps can easily be added to produce specifically modified end products.These additional system options include, for example, water gas shift reactors, which can specifically modify the composition of the synthesis gas. For further advantages of the system according to the invention, explicit reference is made to the advantages mentioned in the area of ​​the process according to the invention.

[0028] The system comprises a pyrolysis reactor designed to pyrolyze a carbonaceous solid or sludge under air-tight conditions at a temperature of greater than or equal to 800°C and less than or equal to 1200°C, and to separate the resulting pyrolysis gas from a remaining solid carbon carrier carbonate. A closed reactor can be used for pyrolysis, which prevents the ingress of air or oxygen. The reactor can have a solids feed and a discharge for the resulting pyrolysis gas. Furthermore, the reactor can also include mechanical recirculation of the feedstock.

[0029] The system comprises an oxidation reactor configured to oxidize a pyrolysis gas under oxygen supply at a temperature of greater than or equal to 1000°C and less than or equal to 1200°C. The oxidation reactor can be designed in the form of a burner, for example in the form of an oxy-fuel burner, and have a common supply of a gas mixture of pyrolysis gas and an oxygen-containing gas. However, it is also possible for both gases to be supplied to the burner from separate sources to carry out the oxidation. The burner has a sufficient residence time of the gases in the hot zone to ensure complete combustion of the long-chain products from the pyrolysis gas. The system comprises a reactor configured to contact an oxidized pyrolysis gas with the carbon carrier carbonizate at a temperature of greater than or equal to 950°C and less than or equal to 1500°C.This reactor can be the same as the reactor used for component i), but it doesn't have to be. For example, it may be appropriate to maintain two reactors at different temperatures and to carry out further contacting of the oxidized pyrolysis gas in an independent reactor. In this way, the system can also be operated continuously.

[0030] In a preferred embodiment of the system, the individual reactors can represent separate reaction chambers in different reactors, with the pyrolysis reactor being a rotary tube reactor and the synthesis gas reactor iii) being selected from the group consisting of a fluidized bed reactor or a moving bed reactor. In order to achieve the most controllable overall conversion possible, even with organic starting materials that vary greatly in their properties, it has proven particularly suitable to carry out the individual steps in separate, suitable reaction chambers. High-quality synthesis gases with a very low tar content and a precisely controllable H2 / CO ratio can be obtained from a wide variety of different, even inhomogeneous, starting materials.In addition, this determination can also reduce the proportion of unwanted foreign gases, particularly in the form of nitrogen, hydrogen halides or sulphur-containing gases.

[0031] Within a preferred aspect of the system, i) the pyrolysis reactor can be configured to pyrolyze a carbonaceous solid or sludge under vacuum at a temperature of greater than or equal to 800°C and less than or equal to 1200°C; ii) the oxidation reactor can be configured to oxidize a pyrolysis gas under oxygen supply at a temperature of greater than or equal to 1000°C and less than or equal to 1200°C; and iii) the synthesis gas reactor can be configured to contact an oxidized pyrolysis gas with the carbon carrier carbonizate at a temperature of greater than or equal to 950°C and less than or equal to 1250°C. Designing the individual reactors for these narrow temperature ranges can lead to a system that can provide high synthesis gas output with low investment costs.

[0032] The invention also provides for the use of a system according to the invention for producing synthesis gas. The specific design of the system allows for processes to be implemented in which the individual process stages within individual system components can be precisely tailored to the feedstock in question. Many different raw material sources can be used, or the properties of the produced synthesis gases and / or carbonates can be specifically adjusted. This results in a flexible structure and process for producing high-quality synthesis gas.

[0033] Examples and embodiments of the present invention will be described by way of example with reference to Figures 1-3:

[0034] Figure 1 shows schematically the sequence of the method according to the invention;

[0035] Figure 2 shows schematically a structure of a system according to the invention;

[0036] Figure 3 shows a diagram with the concentration curve of individual product components of a reaction according to the invention.

[0037] Figure 1 schematically shows the sequence of the process 10 according to the invention. In the first process step a) 11, a carbon-containing solid or sludge is provided from which synthesis gas is to be obtained. A wide variety of different carbon carriers can be processed using the multi-stage process presented here. In particular, it is possible for the process 10 to be operated over long periods of time without undesired substances, such as tars, accumulating in the system or in the synthesis gas. In an optional process step 15, further substances, such as salts, can be added to the feedstock. This can increase the range of processable feedstocks. In a second process step b) 12, the feedstock is pyrolyzed under the exclusion of air and subjected to heat. The feedstock is converted into a pyrolysis gas and a solid carbonate.At the end of the step, the pyrolysis gas is withdrawn continuously or intermittently and subjected to a further process step c) 13. Within this process step, the pyrolysis gas is oxidized, preferably completely oxidized, in the presence of oxygen. Complete oxidation can involve the complete conversion of the higher-molecular-weight hydrocarbons present in the pyrolysis gas to carbon dioxide. The oxidized pyrolysis gas is contacted with the carbonizate under the influence of heat in a further process step d) 14. This results in, in particular, in a synthesis gas with a higher carbon monoxide and hydrogen content. Optionally, the composition of the synthesis gas can be further modified in one or further optional process steps 16. Alternatively, the synthesis gas can also leave the process 10 without further conditioning.In summary, a high-quality, tar-free or very low-tar synthesis gas and a high-quality carbonizate are provided, which can be used in a wide variety of chemical reactions and in various industrial sectors.

[0038] Figure 2 schematically shows a structure of a system 20 according to the invention. The first process step a) 11, for providing the carbon-containing solid or sludge, can take place within a pyrolysis reactor 21. The material can, for example, be layered or filled into the pyrolysis reactor 21 continuously, semi-continuously, or batchwise. The pyrolysis reactor 21 can have mechanical means for circulating the solid. Furthermore, the pyrolysis reactor 21 is provided with seals and / or valves and / or locks, which enable gas-tight operation of the pyrolysis reactor 21. In addition, the pyrolysis reactor 21 has a gas discharge for separating the resulting pyrolysis gas 19 from the resulting carbonizate 17. The pyrolysis is carried out in process step b) 12 at elevated temperatures. For this purpose, the pyrolysis reactor 21 is also provided with one or more heating options.The products of process step b) are the pyrolysis gas 19 and the carbonate 17. The pyrolysis gas 19 is subjected to oxidative treatment in a further process step c) 13. This can take place, for example, in an oxidation reactor 22 in the form of an oxyfuel burner 22 with the addition of an oxidizing gas, for example oxygen. Pure oxygen can preferably be used in this step, which leads to complete oxidation of the separated pyrolysis gas 19. In particular, any tars or long-chain hydrocarbons present in the separated pyrolysis gas 19 are completely converted to carbon dioxide or carbon monoxide. The oxidized pyrolysis gas is then contacted again with the carbonate 17, which is converted accordingly to the treated carbonate 18. This conversion can take place in a further reactor 14 or in the previously used pyrolysis reactor 21.It is also possible for the oxidized pyrolysis gas to be further conditioned and its composition adjusted in an optional stage 16 (not shown), for example by reaction with steam. The final reaction of the oxidized pyrolysis gas with the carbonizate 17 produces a synthesis gas 23, which can be used as such. The synthesis gas 23 can be used in chemical reactions, for example for the production of liquid fuels. The treated carbonizate 18 can be used, for example, as a pigment. In the system 20 according to the invention, high-quality synthesis gases 23 can be produced over long periods of time. The process is particularly low in tar, delivers very uniform synthesis gases, can also be operated with less suitable feedstocks, and enables continuous process control.

[0039] Figure 3 shows a diagram with the concentration curve of individual product components of a reaction according to the invention. The concentration curves of selected components in the synthesis gas reactor are shown. The measurement was carried out using a wood gas analyzer from Eheim. The reaction was carried out on charcoal that was generated by a pyrolysis step according to the invention. The reaction took place at a temperature of 1200°C. The charcoal was heated to the target temperature at a rate of 5 K / min under nitrogen. After a holding time of 90 minutes, water and carbon dioxide were added to the charcoal (marked by the 1 in the diagram). The 2 in the diagram marks the end of the holding time.Using an artificial flue gas consisting of CO2 and H2O, as occurs after complete oxidation of the pyrolysis gas with pure oxygen and a small residual oxygen content (= CO2 + H2O + O2), complete conversion to CO and H2 was demonstrated. This diagram shows the concentration curve of the relevant process gases. After the start of the supply of carbon dioxide and water vapor, only hydrogen and carbon dioxide are detected in the product gas stream. The supplied gases are therefore completely converted into the desired products. Only a very low methane concentration is measurable, thus hardly any hydrocarbons are produced. The increase in carbon dioxide concentration observed over the course of the test period is due to the fact that the charcoal introduced into the reactor is consumed during the reduction process, meaning that there is gradually no longer enough solid material available for complete carbon dioxide conversion.Of course, under continuous reaction conditions such an effect will not occur.

Claims

Patent claims 1. A process for producing synthesis gas (23), comprising at least the steps of: a) providing (11) a carbonaceous sludge or solid; b) pyrolyzing (12) the sludge or solid in the absence of air at a temperature of greater than or equal to 600°C and less than or equal to 1200°C to form a solid carbon carrier carbonate (17) and a pyrolysis gas (19), wherein the pyrolysis gas (19) is separated from the carbon carrier carbonate during or after the pyrolysis; c) oxidizing (13) the separated pyrolysis gas (19) with the addition of oxygen in a Temperature range of greater than or equal to 1000°C and less than or equal to 1600°C to obtain an oxidized pyrolysis gas; d) contacting (14) the carbon carrier carbonizate (17) from process step b) (12) with the oxidized pyrolysis gas from process step c) (13) in a temperature range of greater than or equal to 800°C and less than or equal to 1500°C to obtain the synthesis gas (23).

2. The method according to claim 1, wherein in process step c) (13) a complete oxidation of the separated pyrolysis gas (19) is carried out.

3. The process according to claim 1 or 2, wherein an oxidized pyrolysis gas at the end of process step c) (13) has an oxygen concentration of greater than or equal to 0.25 vol.% and less than or equal to 5.0 vol.%.

4. Process according to one of the preceding claims, wherein the carbonaceous sludge or solid has an ash content, determined according to DIN EN ISO 18122, of greater than or equal to 0 wt.% and less than or equal to 50 wt.%.

5. Process according to one of the preceding claims, wherein the carbonaceous sludge or solid has a minimum permissible calorific value (dry), determined according to DIN EN ISO 18125, of greater than or equal to 10 MJ / kg and less than or equal to 30 MJ / kg.

6. Method according to one of the preceding claims, wherein in method step c) (13) pure oxygen is used for oxidation.

7. Method according to one of the preceding claims, wherein the method step b) (12) is carried out in a temperature range of greater than or equal to 800°C and less than or equal to 1200°C.

8. Method according to one of the preceding claims, wherein the method step b) (12) is carried out in a rotary tube reactor.

9. Method according to one of the preceding claims, wherein the method step d) (14) is carried out in a temperature range of greater than or equal to 950°C and less than or equal to 1200°C.

10. Process according to one of the preceding claims, wherein process step d) (14) is carried out in a fluidized bed reactor or a moving bed reactor.

11. Method according to one of the preceding claims, wherein the method step c) (13) is carried out in a temperature range of greater than or equal to 1000°C and less than or equal to 1200°C.

12. System (20) for producing synthesis gas (23), comprising at least i) a pyrolysis reactor (21) designed to pyrolyze a carbon-containing solid or sludge in the absence of air at a temperature of greater than or equal to 800°C and less than or equal to 1200°C and to separate a resulting pyrolysis gas (19) from a remaining, solid carbon carrier carbonate (17); ii) an oxidation reactor (22) configured to oxidize a pyrolysis gas (19) with the supply of oxygen at a temperature of greater than or equal to 1000°C and less than or equal to 1200°C; iii) a synthesis gas reactor configured to contact an oxidized pyrolysis gas with the carbon carrier carbonate (17) at a temperature of greater than or equal to 950°C and less than or equal to 1250°C.

13. System according to claim 12, wherein the individual reactors represent separate reaction spaces in different reactors, wherein the pyrolysis reactor (21) is a rotary tube reactor and the synthesis gas reactor iii) is selected from the group consisting of fluidized bed reactor or moving bed reactor.

14. System according to claim 12 or 13, wherein i) the pyrolysis reactor (21) is configured to pyrolyze a carbonaceous solid or sludge in the absence of air at a temperature of greater than or equal to 800°C and less than or equal to 1200°C; ii) the oxidation reactor (22) is configured to oxidize a pyrolysis gas (19) in the presence of oxygen at a temperature of greater than or equal to 1000°C and less than or equal to 1200°C; and iii) the synthesis gas reactor is configured to contact an oxidized pyrolysis gas with the carbon carrier carbonizate (17) at a temperature of greater than or equal to 950°C and less than or equal to 1250°C.

15. Use of a system (20) according to one of claims 12 to 14 for producing synthesis gas (23).

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