WO2024023586A1

WO2024023586A1 - Process for recovering methane from hot process gas when reacting carbon-containing post-consumer materials

Info

Publication number: WO2024023586A1
Application number: PCT/IB2023/050664
Authority: WO
Inventors: Alfred Edlinger
Original assignee: Radmat Ag
Priority date: 2022-07-26
Filing date: 2023-01-26
Publication date: 2024-02-01

Abstract

The invention relates to a process for recovering methane from hot process gas when reacting carbon-containing post-consumer materials, in particular wood chips, biomass, waste fractions, post-consumer plastics, post-consumer solvents, shredder light fraction, post-consumer wood, post-consumer tyres and the like, the process comprising at least the following steps: pyrolysis and optionally partial gasification of the carbon-containing post-consumer materials using hot process gas to form synthesis gas containing CO and H₂, wherein the carbon-containing post-consumer materials are added in an amount that leads to the formation of carbon black; catalytic methanation of the synthesis gas to form methane.

Description

Process for producing methane from hot process gas by converting carbon-containing waste materials

The present invention relates to a method for obtaining methane from hot process gas by converting carbon-containing waste materials, in particular wood chips, biomass, waste fractions, waste plastics, waste solvents, shredder light fraction, waste wood, old tires and the like, as well a device for utilizing process gas by converting waste materials and forming synthesis gas, in particular for carrying out the method according to the invention.

With the help of renewable energy sources, significant amounts of hydrogen can be obtained through electrolysis of water as a climate-neutral fuel, although the utilization of the hydrogen and its storage are problematic. In particular, hydrogen cannot be fed into existing gas pipeline networks due to its embrittling effect on metallic gas pipes, which would, however, represent the most economical use of hydrogen and a significant contribution to overcoming dependencies on various raw material suppliers. The methanation of hydrogen is therefore increasingly becoming the focus of private and municipal energy suppliers in connection with the use of renewable energy sources such as wind power in particular and the problem inherent in wind power in particular of storing the energy generated by wind power.

At the same time, chemically contaminated solids such as dust, dry sludge and sludge from the chemical industry, metallurgy, agriculture, municipal and industrial waste management etc. and in particular combustion dust, grinding dust, steelworks dust, sewage sludge, animal meal, shredder light fraction, waste wood, old tires, battery scrap, old plastic, old solvents and the like, due to the high inorganic and organic pollutant content as well as the large specific surface area and the high chemical content Reaction potential with the environment represents a major environmentally relevant problem. The processing of small solid particles is the subject of a variety of technologies. The applicant of the present invention recently proposed a device and a method in Austrian patent application A 0010/2021 for converting such waste materials into synthesis gas. Synthesis gas consists of CO and H2 and would therefore generally be suitable for conversion to methane.

The catalytic methanation of hydrogen according to Sabatier has been known in the state of the art for some time. The methanation takes place according to the reaction equations

CO + 3H ₂ -> CH ₄ + H ₂ O respectively

_CO2 + _4H2 -> _CH4 + _2H2O .

It is clear from these reaction equations that methanation requires a high proportion of hydrogen in addition to carbon monoxide or carbon dioxide. At the same time, these reactions, although exothermic, still require temperatures of 300 ° C to 700 ° C in order to provide the necessary activation energy. The conversion of synthesis gas to methane and water in the sense of the Sabatier methanation described above and known in the prior art now fails because the ratio of carbon f to hydrogen f in the synthesis gas is too high (C: H = 1: 2) and Therefore, even with optimal catalysis, the reaction takes place for stoichiometric reasons in such a way that CO2 is formed in significant quantities. However, the CO2 is difficult to separate from H2, which calls into question the economic viability of methanation. Simply adding hydrogen to the synthesis gas would provide a remedy here, but does not appear to make sense due to the high use of hydrogen.

It is therefore the object of the present invention to provide a method with which the methanation of synthesis gas from the pyrolysis of the mentioned waste materials using hot process gas is achieved without the addition of hydrogen that is foreign to the process and in which an overall optimal use of the starting materials is achieved.

To solve this problem, according to the invention, a method of the type mentioned at the beginning comprises at least the following steps:

Pyrolysis and, if necessary, partial gasification of the carbon-containing waste materials with hot process gas to form synthesis gas containing CO and H2, the carbon-containing waste materials being added in an amount that leads to the formation of soot, catalytic methanation of the synthesis gas to form methane.

The addition of the old substances in an amount that leads to the formation of soot means in this context Invention that, compared to the waste materials, the process gas is only added in an amount at which no free oxygen and no CO2 are present in the resulting synthesis gas during the pyrolysis and partial gasification of the waste materials. In other words, the process gas is added substoichiometrically with respect to the conversion to synthesis gas. The formation of soot preferably takes place to such an extent that the carbon f of the carbon-containing waste materials is produced as soot to an extent between at least 30% and 70%, preferably between 40% and 60% and particularly preferably between 45% and 55%.

The soot formation to be aimed at in the context of the present invention is adjusted in terms of control technology due to the composition of the carbon-containing waste materials used in the process according to the invention, which is not always exactly known, and due to the equally changing composition of the process gas used. The target variable here is the desired ratio of CO to H2 in order to subsequently carry out methanation according to the formula

CO + 3H ₂ -> CH ₄ + H ₂ O.

Because the carbon-containing waste materials are added in excess, which results in unclean pyrolysis of the carbon-containing waste materials, soot is formed. As a result, carbon falls out of the gas phase as a solid and is thereby relatively depleted, so that the hydrogen content in the synthesis gas increases compared to the gaseous carbon content. In this way, soot formation can increase the ratio of carbon f to hydrogen f in the Reduce the gas phase to up to 1:4 (C:H=1:4) and even below, so that the stoichiometric conditions for the Sabatier reaction are met without the addition of hydrogen that is foreign to the process. At the same time, the exergy of process gases from various sources can be used to recycle and dispose of problematic waste materials. Overall, the result is a process in which valuable heat from exhaust gases is used, waste materials are disposed of and valuable fuel gas is formed in the form of methane suitable for use in gas pipeline networks. Because synthesis gas can be used for methanation, the additional electrolytic production of hydrogen can be dispensed with, which results in enormous savings in electrical energy compared to the conventional synthesis of methane. Of course, hydrogen from the hydrolysis of water using renewable energy sources can still be added to the synthesis gas. In addition, conventional methanation starts from synthesis gas of H2 and CO2 and/or CO, with CO2 and/or CO being present in excess. Consequently, in the state of the art, the resulting gas mixture of CH4, CO2 and H2O must be separated in a complex manner in order to obtain CH4 in pure form. The process according to the invention works without excess gaseous carbon species, since the excess carbon fraction precipitates out of the gas phase as soot and is separated.

By appropriately adjusting the process parameters with regard to the C/H ratio, the method according to the invention can also be used to produce a gas mixture of CH4 and H2. Furthermore, homologues of CH4 such as ethane or propane as well as ethylene and acetylene can also be produced. For the production of ethane or propane as well as ethylene and acetylene as well as other higher-chain hydrocarbons It is also conceivable to use O2 to adjust the process parameters. This leads to the formation of CO at the expense of the soot content, so that higher-chain hydrocarbons such as ethane, ethyne, ethane or precursors for methanol synthesis or precursors for Fischer-Tropsch synthesis also become accessible. The formation of methane can preferably also take place under an increased pressure of preferably 2 bar to 5 bar.

The parameters of the pyrolysis are selected according to the invention so that the hot process gas is used for pyrolysis at temperatures of 1800 ° C to 2400 ° C, preferably 1900 ° C to 2300 ° C, more preferably 2000 ° C to 2200 ° C and particularly preferably 2100 ° C of the carbon-containing waste materials is used and the superstoichiometric addition of the carbon-containing waste materials is carried out to such an extent that the synthesis gas is obtained during pyrolysis and, if necessary, partial gasification at temperatures of 450 ° C to 800 ° C. In this way, at temperatures of the hot process gas of 1800°C to 2400°C, the old materials are reliably pyrolyzed and partially gasified, as well as those that are harmful to the environment

(organic) contaminants are eliminated and when a quantity of carbon-containing waste materials is added, which leads to a reduction in the temperature during the formation of the synthesis gas during pyrolysis to temperatures of 450 ° C to 800 ° C, the carbon content of the carbon-containing waste materials becomes a significant part converted into soot, so that a synthesis gas with a C:H ratio of at least 1:4 is obtained. The person skilled in the art understands that the carbon in the synthesis gas is present as CO. For the catalytic methanation, the synthesis gas enriched with hydrogen due to the soot formation is optionally cooled. The synthesis gas is preferably subjected to a drying step to remove water vapor in order to avoid the undesirable reverse reaction

CH ₄ + H ₂ O -> CO + 3 H ₂ should be held back. According to a preferred embodiment of the present invention, this can be done by condensing excess water vapor, but in a particularly preferred manner the drying step is carried out by bringing the synthesis gas into contact with quicklime (CaO). Excess water vapor is chemistored according to the reaction equation

CaO + H ₂ O -> Ca (OH) ₂ is removed from the synthesis gas, whereby the slaked lime formed (Ca (OH) ₂ ) also chemically neutralizes and binds any sulfur species (H ₂ S, COS, SO ₂ ) present in the synthesis gas. This also applies to halogens and halides that may be contained in the synthesis gas.

According to a preferred embodiment of the present invention, the catalytic methanation of the synthesis gas takes place in a fluidized bed of nickel-containing steelworks dust, preferably at temperatures of 300 ° C to 500 ° C, more preferably at a temperature of 400 ° C. The catalysis of the Sabatier reaction to form methane from CO and H ₂ is carried out as standard with nickel catalysts; the use of nickel-containing steelworks dust, especially from stainless steel production, is considered particularly advantageous because these dusts have an enormous surface area, which ensures optimal catalysis is achieved. The soot formed must be captured to meet various legal requirements. In connection with the present invention, the preferred procedure is such that the soot formed during pyrolysis is in a filter, e.g. B. Deep bed filter, with a filter column made of graphite, coke, and / or steel bodies, in particular balls, is separated.

In the course of the process according to the invention, the filter becomes increasingly loaded with soot, so that the filter must be regenerated at some point. According to a preferred embodiment of the present invention, the soot in the filter is converted into water gas containing CO2 and H2 by preferably inductive heating of the filter column with the addition of water vapor. This frees the filter from the solid soot and thus makes it ready for further separation of soot (carbon black).

A particularly advantageous process results in a preferred embodiment of the present invention when, after a water-gas shift reaction, CO2 is separated from H2 by alkaline scrubbing and separated H2 is added to the synthesis gas for methanation. In this way, by simply adding water vapor to the heated filter column, valuable hydrogen is formed, which in turn can be used to increase the relative hydrogen content of the synthesis gas for catalytic methanation.

The process according to the invention is preferred for the elimination of solid components from the stream of synthesis gas formed during pyrolysis and optionally partial gasification or from the methane formed further developed in such a way that solid components are separated off by means of a gas cyclone and/or bag filter connected to the fluidized bed and are preferably returned to the fluidized bed.

When using halogenated starting materials, such as PVC (polyvinyl chloride), the corresponding acid anhydrides are formed in the synthesis gas, which represent an environmental problem. For this reason, according to a preferred embodiment of the present invention, the carbon-containing waste materials are added to separate halogens, alkalis and/or alkaline earths. Halogens, such as bromides, are often found in carbon-containing waste materials as flame-retardant additives in plastics and the like and are neutralized by the addition of alkalis and/or alkaline earths and can be separated as solids. Sulfur compounds such as H2S or COS are completely bound by the zinc content of the steelworks dust preferably used for catalysis. The use of old tires as a waste material can be seen as advantageous in this context, since old tires contain ZnO as a vulcanization accelerator.

The device according to the invention for utilizing process gas by converting waste materials and forming synthesis gas and for carrying out the method according to the invention comprises at least: a riser pipe formed along an axial direction and arranged vertically, a supply line for the process gas opening into the riser pipe and a feed pipe connected to the riser pipe subsequent exhaust gas treatment system for the synthesis gas and a feeding device for the waste materials with at least one projecting into the riser pipe over a defined length Delivery pipe, wherein the at least one delivery pipe has an open end opening into the riser pipe and the supply line opens into the riser pipe in the axial direction below the open end, so that process gas entering the riser pipe from the supply line can flow around the at least one delivery pipe, and is according to the invention, characterized in that the exhaust gas treatment system has at least one filter for separating soot from the synthesis gas, the at least one filter being connected to a supply line for water vapor and being heatable.

In this way, the device according to the invention allows waste materials to be converted or recycled, in particular wood chips, biomass, waste fractions, old tires, old solvents, food leftovers, used oils, used plastics, shredder light fraction, waste wood, old tires and the like, to be flowed around with hot process gas to heat, whereby pyrolysis and, depending on the intensity of the heating, partial decomposition of the used materials into synthesis gas takes place in the at least one delivery pipe. The defined length of the at least one delivery pipe is between 40 cm and 200 cm, depending on the specific design described below. As a result of the pyrolysis, gases are formed from the waste materials in the delivery pipe, which cause the waste materials introduced by the feeding device to be loosened and thrown explosively out of the delivery pipe and into the riser pipe. The waste materials comminuted in this way end up in fine particles with a piece size of less than 1.5 mm effective diameter and with a relatively large surface area in the gas stream of the process gas in the riser pipe, which flows around the at least one delivery pipe from below at high speed and flows further up the riser pipe and the crushed waste materials. As a result of this and the large amounts of heat provided by the process gas, the waste materials are pyrolyzed and, if necessary, partially gasified. In this way, hydrogen and carbon monoxide (water gas, also known as synthesis gas) are formed from waste gas (process gas) and waste materials, which means that waste materials can be disposed of profitably and at the same time the waste heat from a wide range of combustion processes can be used. To carry out the process according to the invention, the used substances are added in an amount that leads to the formation of soot, so that complete conversion to synthesis gas does not occur. The process gas is therefore added substoichiometrically in relation to the conversion to synthesis gas. As a result, soot is formed from the excess carbon added, which leads to a relative enrichment of hydrogen compared to carbon in the synthesis gas. This in turn enables the Sabatier reaction to form methane from carbon monoxide and hydrogen in a later step. What is essential in the device according to the invention is that the exhaust gas treatment system has at least one filter for separating soot from the synthesis gas, wherein the at least one filter is connected to a supply line for water vapor and can be heated. This makes it possible to separate soot from the synthesis gas stream.

Due to the possibility of adding water vapor and the ability to heat the filter, the filter can be regenerated by converting the soot into water gas containing CO2 and H2 using a water gas shift reaction. The hydrogen f obtained in a simple manner can, as already mentioned in connection with the process according to the invention, in turn be used to positively influence the C:H ratio in the synthesis gas for the methanation of hydrogen f. A suitable and advantageous configuration of the filter with regard to the regeneration of the filter results when the at least one filter is formed by a filter column made of graphite, coke, steel bodies, in particular spheres, and / or steel fleece and an induction device is arranged surrounding the filter column is, as corresponds to a preferred embodiment of the present invention. The components of the filter column mentioned can be coupled to an induction field in a known effective manner and the filter column can thereby be heated relatively evenly right down to its interior in order to convert the soot, together with the added water vapor, into CO and H2. In the subsequent water gas shift reaction, CO2 and H2 are formed with an increased hydrogen content, since CO2 and H2 are formed from CO and H2O through rearrangement.

In order to be able to maintain the operation of the device according to the invention or the method according to the invention without interruption despite the need for regeneration of the filter, the invention is further developed according to a preferred embodiment in such a way that at least two filters are arranged parallel to one another and can be flowed through alternately with synthesis gas. This makes it possible to always leave one filter in filter mode and to remove soot from the other filter by preferably inductively heating the filter column and adding water vapor, thereby releasing CO2 and H2. As already described in connection with the method according to the invention, the CO2 can be washed out of the stream of CO2 and H2 by means of an alkaline wash in order to obtain hydrogen that is as pure as possible, with which the C/H ratio of the synthesis gas can be further shifted towards hydrogen fs moved can be used to promote the Sabatier reaction to form methane.

While it appears possible in principle to divert the synthesis gas and the soot suspended therein from the riser pipe using a single exhaust pipe and to feed it alternately to the at least two filters through, for example, a three-way valve, it is provided according to a preferred embodiment of the present invention, that at least two exhaust pipes open out at the axially upper end of the riser pipe, each of which is connected to a filter and which can be individually shut off by at least one shut-off device, with preferably two exhaust pipes opening out which can be shut off alternately by a common shut-off device. This means that a separate exhaust pipe is provided from the riser pipe for each filter. Such an exhaust pipe can be shut off with a shut-off device corresponding to the diameter of such an exhaust pipe, thereby avoiding small valves and thus blockages of the valves with soot. If, as is preferred, two exhaust pipes open out, which can be shut off alternately by a common shut-off device, the shut-off device can be designed as a flap, which only has to be moved back and forth between the outlets of the exhaust pipes in order to shut off one exhaust pipe at a time to divert the flow of synthesis gas to the other exhaust pipe.

In order to further promote the Sabatier reaction from the hydrogen-enriched synthesis gas, the present invention is preferably further developed in such a way that a reactor is connected in a gas-tight manner to the at least one filter, in which the synthesis gas is mixed with nickel-containing steelworks dust Fluidized bed forms, preferably at temperatures of 300 ° C to 500 ° C, more preferably at a temperature of 400 ° C. The catalysis of the Sabatier reaction to form methane from CO and H2 is carried out as standard with nickel catalysts. The use of nickel-containing steelworks dust, especially from stainless steel production, is particularly advantageous because these dusts have an enormous surface area, which results in optimal catalysis becomes .

In order to standardize the fluidized bed and to bring the reactants into as close spatial contact as possible with one another, the present invention is further developed according to a preferred embodiment of the present invention in such a way that the reactor is at least partially penetrated axially by a rotor with a plurality of radially directed rods and the synthesis gas can be introduced through the rods.

Preferably, the reactor has cooling fins between the rods of the rotor that project radially inwards through a wall of the reactor, through which a cooling medium can flow, preferably water, thermal oil, ionic liquids and/or tin melt, in order to remove excess heat from the exothermic Sabatier reaction to be able to derive from the reactor.

According to a preferred embodiment of the present invention, the reactor has an exhaust for methane formed in the fluidized bed, with the exhaust preferably opening into a cyclone separator for separating off dust.

Advantageously, the invention can also be developed in such a way that the device has a plurality of reactors in series in order to maintain the reaction equilibrium To shift the direction of the methane yield and the undesirable reverse reaction

CH ₄ + H ₂ O -> CO + 3 H ₂ should be held back. Here, condensation of excess water vapor preferably takes place between the reactors arranged in series, but in a particularly preferred manner excess water vapor is removed by bringing the synthesis gas into contact with quicklime (CaO). Excess water vapor is chemistored according to the reaction equation

In order to ensure particularly efficient heat transfer in the feeding device, the feeding device is preferably formed by a plurality of delivery pipes projecting radially or tangentially into the riser pipe, the delivery pipes preferably being directed obliquely upwards with respect to the axial direction. According to this preferred

In this embodiment, a plurality of conveying pipes are provided as the feeding device, so that for a certain throughput of waste materials, there are smaller amounts of waste materials in each individual conveying pipe of the feeding device. This leads to faster and more intensive heating and thus to very efficient pyrolysis and partial gasification Waste materials and at the same time leads to more efficient cooling of the

gas flow. The preferred orientation of the delivery pipes obliquely upwards results in an advantageous introduction of the pyrolyzed and partially gasified waste materials into the riser pipe in relation to the flow direction of the process gas in the riser pipe, by promoting the occurrence of turbulence in the riser pipe, which results in intense heat - and material exchange occurs in the riser pipe. The defined length of the delivery pipes in this preferred embodiment is between 40 cm and 120 cm.

According to a preferred, alternative embodiment of the present invention, the feeding device is formed by a delivery pipe which projects into the riser pipe in the axial direction, in particular concentrically, at a lower end of the riser pipe. This embodiment is to be regarded as advantageous in terms of the space-saving design without delivery pipes opening into the riser pipe from the side and in terms of the flow-efficient introduction of the pyrolysed waste materials into the riser pipe. In addition, with a certain diameter of the riser pipe, the defined length over which the delivery pipe projects into the riser pipe can be longer than with the above-described radial or tangential configuration of the delivery pipes, so that in turn a very effective heat transfer to the waste materials in the delivery pipe takes place. The defined length of the delivery pipes in this preferred embodiment is between 40 cm and 200 cm. In this embodiment, the conveyor pipe points with its open end directly in the direction of the axis of the riser pipe, so that the pyrolyzed waste materials ejected from the conveyor pipe are thrown into the flow direction of the gas stream of the process gas for partial gasification. According to a preferred embodiment of the present invention, the conveyance of the waste materials through the at least one conveyor pipe is accomplished in terms of apparatus in that the at least one conveyor pipe has a conveyor device at an end facing away from the open end, preferably in the form of one in the conveyor pipe arranged screw conveyor, a piston slide and/or a thick flow pump. The type of conveyor device can be selected depending on the type of starting materials, and it can preferably also be provided that the conveyor device is removably fixed at the end facing away from the open end, whereby the conveyor device is removed when the waste materials to be recycled change and can be exchanged.

However, it is preferred that the at least one conveyor pipe has a conveyor device at an end facing away from the open end in the form of a screw conveyor arranged in the conveyor pipe, the screw conveyor having a central shaft which is hollow and hollow for introducing inert gas into the conveyor screw process gas, hydrogen and/or methane can flow through. Methane, which behaves inertly in the environment prevailing in the riser pipe, as well as other gases that are beneficial and/or inert in this environment and in relation to the Sabatier reaction to be promoted, such as H2, CO and N2, are well suited to promoting the old materials. The introduction of hydrogen f in turn increases the proportion of hydrogen f in the synthesis gas formed, as is the object of the present invention. On the other hand, the waste materials can be pyrolyzed by introducing hot process gas into the screw conveyor, which significantly reduces the conveying work required to operate the screw. Further This preferred embodiment enables the

The screw conveyor is burned out at certain intervals by blowing in hot process gas and without conveying old materials, which means that caking that has developed over time can be removed.

The method according to the invention is assessed below using the model substance polyethylene as an existing substance.

Example 1 :

Bio-natural gas is burned as a process gas according to the following reaction equation:

CH ₄ + 2 0 ₂ -> C0 ₂ + 2 H ₂ 0 (at lambda = 1)

When using 1 kg of methane and 4 kg of O2, 2.75 kg or 62.5 mol of CO2 + 2.25 kg or 125 mol of H2O are formed as process gas with a temperature of approximately 2000°C. This process gas is now used to pyrolyze and partially gasify around 3.4 kg of polyethylene (model substance), producing around 2.92 kg of carbon as soot. Approximately 1.92 kg of methane can be formed in the reactor from the remaining gas phase. This means that 1 kg of bio-methane produces approximately 2 kg of synthetic methane. From the 2.92 kg of soot, 1.09 kg of H2 can be formed through regeneration using 9.07 kg of H2O:

C + H ₂ O -> CO + H ₂ CO + H ₂ O -> CO ₂ + H ₂

The invention is explained in more detail below using an exemplary embodiment shown in the drawing. In this 1 shows a sectional view of an axially lower region of a device according to the invention for carrying out the method according to the invention, FIG. 2 shows a sectional view of a device according to the invention with a shut-off element, FIG. 3 shows a filter arrangement in the sense of the present invention and FIG.

In Figure 1, the device according to the invention is designated by reference number 1. The device 1 comprises a riser pipe 3 which is formed along an axial direction or flow direction 2 and is arranged vertically. The axial extension is also symbolized by the longitudinal axis designated by reference symbol 4. The riser pipe 3 is lined on the inside with a refractory material, preferably made of graphite, Magcarbon (for example Magcarbon R 94A1 Horn & Co. Group) and/or SiC. 5 denotes a supply line for the process gas that opens into the riser pipe 3. The waste materials are fed into the delivery pipe 9 via a feeding device 7. In the embodiment shown in FIG. 1, the feeding device 7 is formed by a screw conveyor 6 accommodated in the conveying pipe, to which the waste materials intended for the production of the synthesis gas are fed laterally from the feeding device 7. The screw conveyor 6 rotates around a hollow shaft 8, via which process gas, hydrogen, water vapor and/or methane can be introduced into the screw conveyor 6. The process gas, which is injected via the supply line 5, flows around the delivery pipe 9 along the route L. The length L can be between 40 cm and 200 cm depending on the requirements for the pyrolysis of the waste materials. The designation “E/R” in Figure 1 stands for the supply of educt/reactant. The designation “M/H2/PG” stands for the supply of methane and hydrogen and/or process gas. The designation "PG 1800/2400" stands for the supply of process gas at temperatures of 1800 ° C to 2400 ° C.

In Figure 2 and the other figures, identical or corresponding elements are provided with the same reference symbols. In Figure 2, the riser pipe 3 and the delivery pipe 9 extending therein can again be seen. The feeding device 7 is shown in simplified form in FIG. At the axially upper end 3a of the delivery pipe 9, two exhaust pipes 10 and 11 open out of the delivery pipe 9, the two exhaust pipes 10 and 11 each being connected to a filter (not shown in FIG. 2) for separating soot. The exhaust pipes 10 and 11 can be alternately closed or opened via a flap 12, which forms a shut-off device, in that the flap 12 can be pivoted back and forth in the direction of the double arrow 13. In this way, the exhaust pipes 10 and 11 and thus the subsequent filters can be alternately supplied with synthesis gas and soot suspended therein in order to separate the soot from the gas. Already at positions 14, water vapor can be added to the synthesis gas emerging from the riser pipe 3 to regenerate the subsequent filter. The designation “E/R” in Figure 2 also stands for the supply of educt/reactant.

3 now shows two mutually parallel filters 15a and 15b, which can be alternately supplied with synthesis gas containing soot via the exhaust line 16 and the three-way valve 17 or also via the exhaust lines 10 and 11 from FIG. The filters 15a and 15b are filtered and regenerated in such a way that, in a first phase, synthesis gas containing soot flows through the filter 15b to separate soot is, for which the induction device 18b is switched off.

In this way, the soot accumulates in the filter 15b, which is preferably formed essentially from a filter column 19b made of graphite, coke, steel balls and/or steel fleece in a housing 20b. At the filter outlet 21b, soot-cleaned synthesis gas containing carbon monoxide and enriched hydrogen is obtained, which is used for the Sabatier reaction to form methane. In this phase, the water vapor valve 22 is closed. At the same time, the filter 15a is separated from the synthesis gas stream by closing the exhaust gas valve 23. The induction device 18a is activated to heat the filter column 19a, whereby carbon monoxide and hydrogen are obtained by the simultaneous addition of water vapor through the water vapor valve 24. When the regeneration of the filter 15a is completed and the filter 15b is saturated with soot, the filter 15b is regenerated in the same way with water vapor through the water vapor valve 22 and the action of the induction device 18b and the filter 15a is used for filtering.

The reactor for carrying out the Sabatier reaction is provided with the reference number 26 in FIG. The reactor 26 is connected in a gas-tight manner to the two filters 15a and 15b and contains a fluidized bed 27 made of synthesis gas with nickel-containing steelworks dust at temperatures of 300 ° C to 500 ° C. In the stoichiometric conditions prevailing due to the relative enrichment of hydrogen, methane is formed in an exothermic reaction according to one of the reaction equations listed above. The synthesis gas is introduced via the perforated rods 28, optionally with adjustable gas nozzles, of the rotor 33. To cool the reactor

26 and to stabilize and mix the fluidized bed

27, the reactor 26 also has cooling fins 29, which Wall 30 of the reactor 26 passes through and a cooling medium such as water, thermal oil, ionic liquids and / or tin melt flows through it. At an axially upper end, paddles knock down 31 nickel dust particles. Methane and water vapor are drawn off at the outlet 32 of the reactor 26. Nickel-containing catalyst dust collects at an axially lower end 34 of the reactor 26 and can be recycled from there into the fluidized bed 27. If the catalyst dust is inactivated, for example by sulfur loading, it is removed and replaced or supplemented with fresh or regenerated dust. The designation “SG” in Figure 4 stands for the supply of synthesis gas.

Claims

Patent claims:

1. Process for obtaining methane from hot process gas by converting carbon-containing waste materials, in particular wood chips, biomass, waste fractions, waste plastics, waste solvents, shredder light fraction, waste wood, waste tires and the like, comprising at least the following steps:

Pyrolysis and, if necessary, partial gasification of the carbon-containing waste materials with hot process gas to form synthesis gas containing CO and H2, the carbon-containing waste materials being added in an amount that leads to the formation of soot, catalytic methanation of the synthesis gas to form methane, the hot process gas being added Temperatures of 1800°C to 2400°C, preferably 1900°C to 2300°C, more preferably 2000°C to 2200°C and particularly preferably 2100°C are used for pyrolysis and possibly partial gasification of the carbon-containing used materials and the addition of the carbon-containing ones Existing materials are used to such an extent that the synthesis gas is produced during pyrolysis and, if necessary, partial gasification at temperatures of 450°C to 800°C.

2. The method according to claim 1, characterized in that the synthesis gas is subjected to a drying step, preferably by bringing the synthesis gas into contact with quicklime.

3. The method according to claim 1 or 2, characterized in that the catalytic methanation of the synthesis gas takes place in a fluidized bed of nickel-containing steelworks dust, preferably at temperatures of 300 ° C to 500 ° C, more preferably at a temperature of 400 ° C.

4. The method according to claim 1, 2 or 3, characterized in that the soot formed during the pyrolysis and possibly partial gasification is in a filter, e.g.

Deep bed filter, with a filter column made of graphite, coke and / or steel bodies, in particular balls, is separated.

5. The method according to claim 4, characterized in that the soot in the filter is converted into water gas containing CO and H2 by preferably inductive heating of the filter column with the addition of water vapor.

6. The method according to claim 5, characterized in that after a water gas shift reaction, CO2 is separated from H2 by alkaline scrubbing and separated H2 is added to the synthesis gas for methanation.

7. The method according to any one of claims 3 to 6, characterized in that solid components are separated off by means of a gas cyclone and/or bag filter connected to the fluidized bed and are preferably returned to the fluidized bed.

8. The method according to any one of claims 1 to 7, characterized in that alkalis and / or alkaline earths are added to the carbon-containing waste materials to separate halogens.

9. Device (1) for recycling process gas by converting waste materials and forming synthesis gas and for obtaining methane from hot process gas by converting carbon-containing waste materials, in particular wood chips, biomass, waste fractions, waste plastics, waste solvents, shredder light fraction, waste wood, waste tires and the same, in particular for carrying out the method according to one of claims 1 to 8, the device at least comprising: a riser pipe (3) formed along an axial direction (4) and arranged vertically, a supply line (5) for the process gas opening into the riser pipe (3). and an exhaust gas treatment system for the synthesis gas connected to the riser pipe (3) and a feeding device (7) for the used materials with at least one delivery pipe (9) projecting into the riser pipe (3) over a defined length (L), wherein the at least one delivery pipe ( 9) has an open end opening into the riser pipe (3) and the supply line (5) opens into the riser pipe (3) in the axial direction below the open end, so that the at least one delivery pipe (9) from the supply line (5) Process gas entering the riser pipe (3) can be flowed around, characterized in that the exhaust gas treatment system has at least one filter (15a, 15b) for separating soot from the synthesis gas, the at least one filter (15a, 15b) having a supply line for water vapor Connection is made and can be heated.

10. Device (1) according to claim 9, characterized in that the at least one filter (15a, 15b) is formed by a filter column (19a, 19b) made of graphite, coke, steel balls and / or steel fleece and an induction device (18a , 18b) is arranged surrounding the filter column (19a, 19b).

11. Device (1) according to claim 9 or 10, characterized in that at least two filters (15a, 15b) are arranged parallel to one another and can be alternately flowed through with synthesis gas.

12. Device (1) according to claim 9, 10 or 11, characterized in that at the axially upper end (3a) of the riser pipe

(3) at least two exhaust pipes (10, 11) open out, each of which is connected to a filter (15a, 15b) and which can be individually shut off by at least one shut-off element (12), with preferably two exhaust pipes (10, 11) opening out can be blocked alternately by a common shut-off device (12).

13. Device (1) according to one of claims 9 to 12, characterized in that a reactor (26) is connected in a gas-tight manner to the at least one filter (15a, 15b), in which the synthesis gas forms a fluidized bed with nickel-containing steelworks dust, preferably at temperatures from 300°C to 500°C, more preferably at a temperature of 400°C.

14. Device (1) according to claim 13, characterized in that the reactor (26) is axially at least partially penetrated by a rotor (33) with a plurality of radially directed rods (28) and the synthesis gas can be introduced through the rods (28).

15. Device (1) according to claim 14, characterized in that the reactor (26) has cooling fins (29) projecting radially inwards through a wall (30) of the reactor (26) between the rods (28) of the rotor (33). through which a cooling medium can flow, preferably water, thermal oil, ionic liquids and/or tin melt.

16. Device (1) according to claim 13, 14 or 15, characterized in that the reactor (26) has an outlet (32) for methane formed in the fluidized bed (27), wherein Preferably the extractor (32) for separating dust opens into a cyclone separator.

17. Device (1) according to one of claims 9 to 16, characterized in that the feeding device is formed by a plurality of delivery tubes (9) projecting radially or tangentially into the riser tube (3), the delivery tubes (9) preferably being in relation to are directed obliquely upwards in the axial direction.

18. Device (1) according to one of claims 9 to 16, characterized in that the feeding device is formed by a delivery pipe (9) projecting into the riser pipe (3) in the axial direction, in particular concentrically, at a lower end of the riser pipe (3). is.

19. Device (1) according to claim 17 or 18, characterized in that the at least one conveyor pipe (9) has a conveyor device (6) at an end facing away from the open end, preferably in the form of a screw conveyor (6) arranged in the conveyor pipe, a piston valve and/or a thick flow pump.

20. Device (1) according to claim 19, characterized in that the at least one conveyor pipe (9) has a conveyor device (6) in the form of a conveyor screw (6) arranged in the conveyor pipe (9) at an end facing away from the open end, wherein the screw conveyor (6) has a central shaft (8) which is hollow in order to introduce inert gas into the screw conveyor (6) and through which process gas, hydrogen and/or methane can flow.