AU2018330243B2

AU2018330243B2 - Conversion reactor and management of method

Info

Publication number: AU2018330243B2
Application number: AU2018330243A
Authority: AU
Inventors: Tim BÖLTKEN; Robin DÜRRSCHNABEL; Phillip ENGELKAMP; Peter Pfeifer; Paolo Piermartini
Original assignee: Ineratec GmbH
Current assignee: Ineratec GmbH
Priority date: 2017-09-08
Filing date: 2018-08-22
Publication date: 2023-12-14
Anticipated expiration: 2038-08-22
Also published as: EP3678767C0; EP3678767A1; CL2020000476A1; ES2954324T3; DE102017120814A1; BR112020004350A2; WO2019048236A1; EP3678767B1; AU2018330243A1

Abstract

The invention relates to a pressure- and temperature-resistant reactor for preparing syngas in a reverse CO conversion, in which gases containing CO2 are converted under high pressure with the aid of hydrogen into a syngas mixture (CO and H2), and relates to a method for preparing a syngas mixture using said reactor.

Description

Conversion reactor and management of method

Technical Field

The invention relates to a pressure- and heat-resistant reactor for producing synthesis gas in a reverse CO conversion in which a pressurized conversion of C02-containing gases into a synthesis gas mixture (CO and H 2 ) is carried out by means of hydrogen and also to a process for producing a synthesis gas mixture using this reactor.

Background

Reactors in which C02 is reacted with H 2 are known from the prior art, and the following may be mentioned by way of example:

W02013135706A1 describes a flow reactor in which carbon monoxide (CO) is formed as product with electric heating at temperatures up to 1300°C.

US20090313886A1describes the use of a heliostat for heating a C02 stream from recycling, which is introduced together with other offgases from fuel synthesis into a RWGS (reverse water gas shift) reactor.

The reactors are typically made of steel. Due to the presence of carbon-containing starting materials and/or products, soot is formed as undesirable by-product at high temperatures and/or pressures. The formation of soot on the steel surfaces leads to carburization and destruction of the steel. However, an input of heat is necessary for the endothermic reaction of the starting materials C02 and H 2 to give a synthesis gas mixture. A high pressure is likewise necessary, especially in the FT (Fischer-Tropsch) synthesis and methanation or methanol-dimethyl ether synthesis, since in these downstream processes the synthesis gas mixture is used as starting material.

Many reactors and processes for producing synthesis gas of the prior art consume a large quantity of energy and require complicated purification of the products for further use and/or multistage processes and a corresponding reactor structure.

In the multistage processes, the starting materials are, in order to achieve a very high yield, passed a number of times over a catalyst and/or by-products are removed a number of times from the product mixture. However, both adversely affect the economics of the overall process. Accordingly, in single-stage processes the starting materials are passed only once over a catalyst and/or by-products are removed only once from the product mixture.

20408023_1 (GHMatters) P45869AU00

Summary and Description

The present invention provides a reactor which addresses at least some of the disadvantages of the prior art or provides an attractive alternative. In particular, it may have very few or no separation stages and soot formation in the reactor may be largely minimized or avoided. Furthermore, the reactor may allow optimal utilization of the resources, both in respect of energy and also the starting materials. The reactor may also be produced and operated both as large-scale reactor and also as microstructure. Vertical erection and utilization of the reactor may also be possible. Furthermore, the reactor may have the technical prerequisites for being operated using different starting materials and be able to be used for different reactions.

The present invention also provides a process for producing synthesis gas which addresses at least some of the disadvantages of the prior art or provides an attractive alternative. In particular, the process may allow recycling and avoid the production of soot in the RWGS reactor. Advantages of recycling are a high degree of utilization of the carbon containing species/compounds in the overall process. In particular, the offgases here can be recycled to a Fischer Tropsch synthesis (FT synthesis). Furthermore, the process may be able to be operated in an energy-saving manner. The product fluid from the reactor should, after removal of water, be able to be used directly for an FT synthesis or for methane methanol and/or dimethyl ether production, i.e. the reaction conditions in the reactor should make it possible to set an optimal ratio of the individual components of the product fluid for further use.

In a first aspect, disclosed herein is a pressure- and heat-resistant reactor for producing synthesis gas in a reverse CO conversion, having at least the following components:

- at least two fluid-tight feed conduits for at least two different starting fluids, where the first starting fluid is an essentially C02-containing fluid, thus referred to as C02 starting fluid, and the second starting fluid is an essentiallyH 2-containing fluid, thus referred to as H 2 starting fluid;

- at least one fluid-tight discharge conduit for the synthesis gas or synthesis gas mixture as product;

- at least one heating zone, with at least a subregion of the at least second feed conduit for the second starting fluid being arranged in the heating zone;

- at least two recuperative countercurrent heat exchange zones, with subregions of the at least two feed conduits being arranged in both countercurrent heat exchange zones, and

- at least one reaction zone having at least one catalyst in a catalyst bed;

20408023_1 (GHMatters) P45869AU00 wherein the first C02 starting fluid feed conduit is arranged in a subregion directly next to the synthesis gas product discharge conduit.

The process of reaction of the C02 with H 2 to give CO and H 2 0 is referred to as reverse water gas conversion, reverse CO conversion or "reverse water gas shift" RWGS.

For the purposes of the present invention, pressure-resistant means that both the reactor of the invention and also the entire apparatus for carrying out the process of the invention is stable up to pressures of 50 bar and more, advantageously for pressures of 0.1-40 bar, particularly advantageously 1-30 bar.

For the purposes of the invention, temperature-stable means that the reactor of the invention and the apparatus for carrying out the process of the invention are stable up to temperatures of 1100°C or more, advantageously 50-1000°C, particularly advantageously -950°C, in particular 100C-900°C. A zone in the context of the invention is a region, e.g. a region of the reactor, which is a part of the whole perceptible from the outside, with the zone differing from its surroundings or adjacent zones according to a particular criterion. A heating zone is, for example, a region in which the temperature of a particular content is increased.

For the purposes of the invention, the expression "containing essentially" a material X means that this material X is present in an amount of at least 50%, advantageously 60, 65, , 75%, particularly advantageously 80%, 85%, 90%, in particular 91, 92, 93, 94, 95, 96, 97, 99% or more, in a mixture or composition.

In one alternative, the reactor is pressure-resistant up to a pressure of at least 10 bar, advantageously at least 20 bar, particularly advantageously at least 30 bar or more, and heat-resistant up to at least 500°C, advantageously at least 700°C, particularly advantageously up to at least 900°C or more.

In one embodiment, the first C02 starting fluid feed conduit is arranged in a subregion directly next to the synthesis gas product discharge conduit.

For the purposes of the invention, the expression "directly next to" means that two zones or subregions are arranged directly adjacent to one another separated only by a material delimitation, e.g. at least one conduit wall or reactor wall.

The reaction zone in which the RWGS reaction takes place is thus itself a heat exchanger operating in countercurrent. The starting materials are fed in outside the reaction zone in countercurrent, and thus flow in the opposite direction to the products of the reaction in the reaction zone. The introduction of the fresh C02 through a separate feed conduit avoids the Bosch reaction (reaction of C02 with 2H 2 to give C and 2H 2 0).

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The catalyst is arranged in the reaction zone, in the virtually isothermal region, opposite to the direction of the inflowing starting fluids in order to maximize the temperature and minimize the space requirement. Minimization of the space requirement is achieved by the high reaction rate according to the invention at high temperature. The maximization of the temperature allows a high reaction conversion since the target reaction, i.e. the RWGS, is an endothermic reaction.

As a result, the reactor can, in one alternative, also be arranged and operated upright, i.e. vertically, and/or be installed in a container. This means that the catalyst and thus the reaction zone are arranged above the product discharge conduit.

In one alternative, as large-scale reactor (fig. 1), one feed conduit, optionally the outer feed conduit, is a dead-end single tube or a bundle of tubes having in each case a concentric interior structure of the feed conduits described here with reaction zone, heat exchange zone and heater. Since the smallest stream is the freshly introduced C02, this is introduced centrally in the inner tube (smallest available cross section), i.e. in the first starting feed conduit. In this alternative, the first starting feed conduit, in the engineering system, has a diameter of (about) 2-20 mm, advantageously 3-15 mm, particularly advantageously 4 12 mm.

Around this tube, the catalyst is arranged in the form of pellets (size about 0.1-15 mm, advantageously 0.5-10 mm, particularly advantageously 1-5 mm, in diameter) in the reaction zone on top of an inert bed having a similar particle diameter. The material for the inert bed is selected from among SiC (crushed material), YSZ, silica, A1 20 3 , CeO2 or ZrO 2 and mixtures/combinations thereof, advantageously A12 03 and/or SiC. The catalyst is a primarily Ni-based system, thus Ni-containing catalysts for conversion of the starting material into a synthesis gas mixture. The catalyst advantageously contains 2-25% of Ni on A1 20 3 .

The outer tube, the second starting feed conduit, in which fresh H 2 is conveyed has, in this alternative, a diameter of not more than about 100 mm, advantageously 2.5-100 mm, particularly advantageously 10-80 mm, in particular 15-60 mm. In setting the diameter, care is taken to ensure that the flow velocities in the resulting outer cylindrical gap, in the central tube and in the inner cylindrical gap are approximately equal.

The heating zone is (about) 10-50 cm long, advantageously 15-45 cm, in particular 20 cm long, in this alternative. The heating zone is a third heat exchange zone for the second starting fluid, or for an optional third starting fluid.

The reaction zone with catalyst feed is, in this alternative, (about) 25 cm long, advantageously 10-50 cm, particularly advantageously 15-40 cm, in particular 20-30 cm, and the inert bed, advantageously composed of SiC orAl 2O 3 , is, in this alternative, (about) 50 cm long, advantageously 25-100 cm, particularly advantageously 35-75 cm, in particular 40

20408023_1 (GHMatters) P45869AU00 cm, and is held in place by a filter element at the lower end. The reaction zone is a second heat exchange zone for the first and second starting fluids, or for an optional third starting fluid.

The length here is the extension of a region or a zone parallel to the conduits (feed conduit and/or discharge conduit).

The filter element can be a porous shaped body or else a perforated plate made of highly inert steel/high-temperature steel or ceramic (see materials of the reactor or else the inert bed).

The relatively small diameters of the concentric tubes allow good heat input and a small wall thickness of the outer pressure-bearing dead-end tube, with the position of the catalyst being intended to permit a very high temperature. Although the use of the bed material underneath the catalyst layer increases the pressure drop, it reduces the risk of blockage of the reactor by soot in the cooling zone. This results from an increase in heat transfer due to the particles of the bed of inert material, which additionally reduces the total length of the reactor and makes installation in containers possible. In one alternative, the heat exchange can also be improved by means of so-called flow guide elements instead of the inert bed, or the catalyst can be held in position thereby. Flow guide elements are by definition specific regularly structured packing elements/guide plates which increase mixing in a fluid space. Possible materials of the flow guide elements are identical to the listing of the reactor materials and the inert bed. Supporting the entire bed of material (catalyst and inert bed) by means of a filter element in the relatively cool zone of the reactor is likewise simpler from materials-technical points of view due to improved heat exchange.

In the large-scale reactor, at least three manifolds serve to distribute the separate feed streams and product streams. To increase the heat input, a conductive, inert material (e.g. a bed of SiC) or flow elements can also likewise be installed in the outer cylindrical gap (second feed conduit) in order to increase the heat input from the outside. Such a reactor is depicted by way of example in fig. 1.

In one variant, the reactor can also comprise microstructured plates (fig. 2) instead of concentric tubes. To increase the heat input, the microstructure is characterized by an analogous construction, but in this case by channels and/or hollow spaces which are arranged next to and/or above one another in the and/or between the plates. The manifolds are necessary for scaling the reactor system. A microstructure assists the construction in the case of separate introduction of fresh H 2 . Such a reactor is shown by way of example in fig. 2.

In one embodiment, at least two of the above-described reactors are assembled for parallel operation. In the case of the large-scale reactor, at least two of the above-described,

20408023_1 (GHMatters) P45869AU00 concentrically arranged feed conduits including reaction zone, heat exchange zone and heater form a tube bundle. In the alternative of microstructures, at least two of the above described constructions are assembled for parallel operation (fig. 3A and 3B).

The reactor of the invention has a reactor shell in one embodiment. Such a reactor shell can also encompass the above-described tube bundles or assembled microstructured constructions. In this alternative, the shell has the manifolds described. Distribution of the starting materials and collection of the products to the individual feed conduits or from the individual discharge conduits advantageously occurs within the shell (fig. 3A and 3B).

The catalyst is for thermodynamic reasons advantageously arranged in the hottest part of the reactor. This part of the reactor, namely the reaction zone, in which heat has to be supplied due to the reaction of C02 with H 2 to give CO and H 20, is heated either electrically or by combustion of residual gases from the synthesis step.

In one embodiment, the heating device is configured as combustion heating or electric heating.

In the case of combustion heating, the combustion heating takes place outside the pressure-bearing dead-end single tube or a bundle of tubes (fig. 1). It can occur homogeneously or catalytically. In the alternative of the reactor made up of microstructured plates (fig. 2), the combustion reaction is carried out in separate plates which are arranged alternately with the reactor plates. In the case of combustion heating, the combustion is supplied with combustion gas and residual gas for the purposes of energy utilization through at least one separate feed conduit. Combustion air or residual gas can optionally be mixed in at a number of positions along the reaction zone (see also fig. 2). The residual gas is the offgases from the FT synthesis, thus the abovementioned recycled gas.

A uniform temperature over the catalyst is ensured by the distributed introduction of the residual gas or the combustion air.

In the case of electric heating, preference is given to direct heating of the reaction gases for the purpose of minimizing heat transfer losses and the size of the heated zone. To avoid long heating-up times and thus the risk of further soot formation, the use of so-called capillary heaters is particularly suitable. These comprise advantageously ceramic capillaries which are arranged next to one another and have a tubular, square or other cross section, each with an interior resistance wire. Further resistance wires here are, in electrical terms, advantageously connected in series. The fluid here flows in parallel through the adjacent capillaries. The small gap between ceramic capillary and resistance wire in the order of 1 mm results in a high heat flow into the fluid. The introduction of electric energy into the individual pressure-bearing dead-end reaction tubes is effected through temperature-resistant feed throughs in the direct vicinity of the heater (fig. 1, 1-1). Suitable capillary heaters are

20408023_1 (GHMatters) P45869AU00 described in EP 2 926 623 B1. The connection of the capillary heaters in a tube bundle made up of a plurality of tubes can be in series or in parallel outside the reaction space (to ambient temperature). In addition, to reduce the heating power at the capillary heater, the external environment (external heating) of the pressure-bearing dead-end tube or a bundle of tubes can be provided with supplementary heating in order to reduce the heat losses to the surroundings. To reduce the heat losses, temperatures of only about 300-500°C are required in the surroundings, which overall reduces the requirements for heat resistance of the regions of the manifolds of the reactor.

The reactor advantageously comprises essentially of steel, in particular the interior surfaces of the reaction zone and the feed conduits. Steel having a low activity, for example Alloy 800 H/HT, Inconel CA 602 or Inconel 693, is used. These steels can be deactivated if necessary by coating with water glass, tin plating or treatment with aluminum.

In one embodiment, the second feed conduit contains not only H 2, but also steam (H2 0), advantageously from the cooling of an FT synthesis, and/or offgases from an FT synthesis containing H 2 , CO, C02, CH 4, CxHy.

The feed conduits advantageously have passivating layers (Al, Sn and/or water glass) in the heating-up zone of the FT offgas/steam stream and also in the reaction zone in the RWGS reactor in order to avoid carburization of the steel.

In addition or as an alternative, the second starting fluid can also contain the product of a WGS reaction. A WGS reaction is a so-called water gas shift reaction in which CO is reacted with H 2 0 to give C02 and H 2 . This aftertreatment of the FT offgas has been found to be advantageous for reducing soot formation, since it results in the CO partial pressure at the inlet of the RWGS reactor being lower.

In a further embodiment, the reactor has at least one further feed conduit in addition to the first starting feed conduit containing essentially C02 and the second starting feed conduit containing essentially H 2. This at least one further starting feed conduit contains steam H 20, advantageously from the cooling of an FT synthesis, and/or offgases from an FT synthesis containing H 2 , CO, C02, CH 4 , CxHy and/or the product of a WGS reaction. This further starting feed conduit has the same course as the second starting feed conduit.

In general, i.e. independently of which of the above-described variants of the reactor of the invention has been established, the separate introduction of fresh C02 allows a reduction in the partial pressure of carbon-containing components in the feed conduit for hydrogen and thus results in a reduced risk of soot formation during heating up. Finally, recycle gas, which itself has a certain potential for soot formation, can be present in the feed conduit for hydrogen. The term recycle gas is used to refer to the offgases from the FT synthesis.

20408023_1 (GHMatters) P45869AU00

Thus, a further starting fluid feed conduit having at least in each case three subregions is present in this alternative, with each of these subregions being arranged in at least the two recuperative countercurrent heat exchange zones and the heating zone.

In a further embodiment, steam reforming in which CH 4 is reacted with H 2 0 to give CO and H 2 takes place in parallel to the RWGS reaction in the reaction zone. The reactor is thus a reactor for RWGS and steam reforming.

The invention further provides a process for producing synthesis gas using the inventive reactor as described above.

Here, a fluid containing essentially C02 or comprising thereof is used as a first starting material and essentially H 2 , optionally also offgas from an FT synthesis and optionally steam and/or the product of a WGS reaction, is used as second starting fluid. Freshly introduced hydrogen can, but does not have to, be supplied separately. In the case of joint introduction, it is combined/mixed with the offgas/steam mixture.

Due to the high potential, in particular of the second feed fluid at pressures of from 5 to bar, there is formation of soot on the steel surfaces and the associated carburization and destruction of the steel in the heating zone. The addition of water in the second starting material prevents or decreases these negative effects.

There is thus a maximization of the product yield of CO and minimization of CH 4 formation, in particular due to a favorable position of the thermodynamic equilibrium at high temperature. A high pressure in the RWGS reactor in principle worsens the yield of CO and increases accordingly possible CH 4 and soot formation. However, pressure is required in the syntheses, e.g. 10-30 bar in the FT synthesis, > 5 bar in methanation and > 30 bar in the methanol/dimethyl ether synthesis. H 2 can already be produced under pressure from water by electrolysis, and C02 can easily be compressed. For this reason, the moisture-containing synthesis gas is not compressed according to the invention. As a result of the subsequent condensation of moisture, the process achieves a high volume flow of useful synthesis gas.

A characteristic of the invention is the single-stage RWGS which is carried out in the reactor. Likewise, the steam reforming carried out in parallel in the same reaction zone in one variant is advantageous.

In the process, the first starting fluid is conveyed in countercurrent to the discharge of the product directly next to the discharge conduit for the product through a first recuperative heat exchange zone and subsequently through a second recuperative heat exchange zone directly next to the catalyst to the reaction zone.

Furthermore, in one embodiment the second starting fluid is conveyed through the first

20408023_1 (GHMatters) P45869AU00 and second recuperative heat exchange zones to the heating zone and conveyed through these onto the reaction zone. The heating zone thus represents a third heat exchange zone for the second starting fluid.

In the first recuperative heat exchange zone in the flow direction of the starting materials, the inflowing starting gas mixture fluid is heated to at least 400°C or above, advantageously to from 600 to 800°C, between the exiting product fluid and the inflowing feed gas mixture. For reasons of stability of the material, the temperature in the reaction zone is, in one alternative, subjected to an upper limit of not more than 950°C, advantageously from 800 to 900°C, in the reaction of the C02.

As a result of the single-stage RWGS process in the reactor with countercurrent flow and with advantageously electric heating located directly in the fluid region upstream of the reaction zone and the preceding heat exchange zones using nickel catalysts, no heat losses take place at the required high temperature level between, for example, an external high temperature heat exchanger and the actual RWGS reactor. Because of their known heat resistance at 900°C, nickel systems are among the few catalysts which allow a single-stage process. The reactor designed is critical for this.

A WGS reaction can optionally be used for converting CO into C02 with the aid of the steam produced in the cooling of the FT synthesis in order to reduce the risk of soot formation due to a high proportion of CO in the feed to the RWGS stage. The use of an optional WGS reactor for the conversion of CO from the residual gas (offgas) from the FT synthesis utilizing high-pressure steam from the cooling of the FT synthesis reduces soot formation or the amount of water consequently required in the heating-up zones of the reactor of the invention.

In contrast to the use of a reformer which has to operate at relatively high temperatures and also has the objective of removing CH 4 from the FT product or producing as much CO as possible before the RWGS stage, the strategy followed according to the invention is to use part of the steam to react CO intermediately in the WGS and keep CH 4 in the FT residual gas. This has the advantage that by-product formation of CH 4 is lower (and thus less recycling is required in the overall process) because of the thermodynamic boundary conditions in the RWGS reaction and the C02 formed is converted back into CO in the RWGS reaction zone, without soot formation occurring beforehand.

Water is removed from the synthesis gas by condensation after leaving the reactor of the invention. The water is, in particular, removed in order to protect the FT catalyst. However, "substantial" removal of the water is sufficient, and thus 100% removal of the water is not necessary. Reduction of the water content to 0% therefore does not have to be carried out since some residual moisture, in the range from 0.01% to 5%, advantageously from 0.01 to

20408023_1 (GHMatters) P45869AU00

1%, promotes the formation of relatively long-chain hydrocarbons in the FT synthesis. Relatively long-chain hydrocarbons in this context are hydrocarbons having a carbon chain length of at least 5 carbon atoms.

The synthesis gas is fed to a single-stage FT synthesis, the offgas of which and also the steam produced in which from the cooling thereof can be used as second starting fluid in the reactor of the invention. After removal of the water by condensation, the synthesis gas produced as product in the reactor of the invention can be reused directly in the single-stage FT synthesis. Owing to the process procedure and the process conditions in the process of the invention, a single-stage FT synthesis is sufficient, i.e. multiple passage of the synthesis gas over a catalyst with multiple removal of products from the respective FT reactor stage is not necessary according to the invention.

Offgas from the FT synthesis is introduced together with heated water from the cooling of the FT synthesis and optionally separately from C02 supplied freshly to the process into the RWGS reactor and mixed up to directly before the catalyst bed. The water used for cooling the FT synthesis is heated in the FT reactor by heat transfer and advantageously transformed into the vapor phase; the steam produced in this way is particularly advantageously under pressure, so that high-pressure steam is introduced into the RWGS reactor. All gases are subsequently under pressure. The steam reduces the activity of the FT offgas in respect of soot formation and carburization of steel. The addition of C02, on the other hand, would again increase the activity in respect of soot formation. This is particularly necessary when high pressures are employed.

A molar ratio of C0 2 :CO:H 2 :H 20:CH 4 of 0.5-2:0.1-0.5:1-2:0.5-1.5:0.05-0.2, advantageously 0.75-1.5:0.15-0.3:1.2-1.6:0.75-1.25:0.08-0.15, particularly advantageously 1:0.2:1.4:1:0.1, is employed in the reaction zone in the process of the invention. A conversion of C02 of about 40% is achieved as a result. The addition of water, however, virtually completely prevents the formation of soot and/or carburization of steel in the heating-up of the reaction mixture and in the catalyst zone (reaction zone).

At the same time, an H 2 :CO molar ratio of about 2, which is, for example, approximately optimal for the FT synthesis, is produced using the relatively very low initial H 2 :CO2 ratio of 1.4. Higher proportions of H 2 in order to increase the conversion result in a disproportionate increase in CH 4 formation and increase the H 2 :CO ratio to significantly above 3.

A simplified process flow diagram without depiction of the RWGS reactor details and without depiction of heat exchangers for preheating the two separate starting streams by means of the exiting product gas is shown in fig. 4.

The process and reactor concept is, according to the invention, a largely autothermal and single-stage process procedure for all stages of the process.

20408023_1 (GHMatters) P45869AU00

Unreacted C02 is either looped through in the synthesis or rarely is reacted completely in the synthesis. For this reason, the unreacted process offgas is separated off and recirculated to the RWGS stage, optionally part is discharged in order to prevent accumulation of inert gases or harmful gases. Here, the separate introduction of the freshly fed-in C02 and, in an alternative, that of the freshly fed-in H 2 into the RWGS reactor and mixing of the two reactants into the mixture of process steam and recycle stream is advantageous.

The overall compact construction and production of process steam at high pressure level in the FT synthesis, which is sufficient to utilize the steam in respect of energy and material in the RWGS stage, is advantageous.

Numerous tests using various conditions have already been carried out on a laboratory system/pilot plant scale. Without use of steam, tremendous soot formation was already observed in the heating-up zone (above 500°C) when using a pure starting material comprising of C02 and H 2 . The steel Alloy 800 H was attacked. Although coating with water glass reduced carburization of the steel, soot formation was not influenced. The addition of steam finally enabled soot formation to be prevented completely. However, at a molar ratio of H 2 :CO2 of 2, this increased the H 2 :CO ratio in the possible temperature window to above 4, which is no longer usable for syntheses. Finally, a process simulation to determine closed materials circuits was carried out for appropriate compositions of the FT residual gas and the recycle streams were tested and validated in the RWGS laboratory system.

Fig. 5 shows a series of measurements for C0 2:CO:H 2 :H 20:CH 4of 1:0.2:1.4:1:0.1. Yield (Y) and conversion (X) of the respective materials are reported. Above about 800°C, methane from the starting material is converted. All measurement points attain approximately the thermodynamic equilibrium conditions (EC).

Fig. 6 shows the H 2 /CO ratio achieved at the outlet from the RWGS stage for a comparison between C0 2 :CO:H 2:H 2 0:CH 4 of 1:0.2:1.4:1:0.1 (corresponding to 5.8 ml/min of H 2 0) and a slightly higher (7.3 ml/min of H 20) and slightly lower (4.3 ml/min of H 2 0) water mass stream under otherwise constant conditions. At the temperature of 820°C over the catalyst, the target ratio for the FT synthesis can be established. Above the ratio indicated, soot formation is reduced and the composition corresponds to the equilibrium condition.

Legends:

Figure 1 1-1: Electric connections for heater 1-2: Heating zone, represents a third heat exchange zone, in countercurrent to the heater, for the second starting fluid containing essentially H 2 and optionally steam and/or FT offgas; 1-3: Heater

20408023_1 (GHMatters) P45869AU00

1-4: Reaction zone with catalyst, corresponds to the second heat exchange zone; 1-5: First heat exchange zone for second starting fluid outside and first starting fluid inside; an inert bed is also arranged underneath the catalyst in this zone; 1-6: Second starting fluid, fresh H 2 , optionally steam and/or FT offgas; 1-7: Product; 1-8: Feed conduit for first starting fluid

Figure 2: 2-1: Plates of the stack sequence for the combustion heating, electric heating can be used as an alternative; 2-2: Plates of the stack sequence for the RWGS reactor; 2-3: RWGS catalyst; 2-4: Combustion catalyst; 2-5: Countercurrent heat exchange; 2-6: First starting fluid; 2-7: Second starting fluid; 2-8: Third starting fluid containing FT offgas and/or H 20; 2-9: Synthesis gas, product of the RWGS reaction; 2-10: Combustion air for the combustion heating; 2-11: FT offgas, as fuel for the combustion heating.

Figure 3: 3-1: reactors according to the invention (for example as per fig. 1) collected into tube bundles; 3-2: Reactor shell 3-3: Second starting fluid, fresh H 2 , optionally steam and/or FT offgas; 3-4: Product; 3-5: Feed conduit for first starting fluid.

Figure 4: 4-1: First starting fluid, containing essentially C0 2 ; 4-2: Fresh H 2 (second starting fluid, optionally in admixture with H 2 0 and FT offgas or product gas from the WGS); 4-3: RWGS (with separate starting inlets for starting fluid 1 and 2); 4-4: Condensation of H 20; 4-5: Discharge of H 2 0; 4-6: Single-stage FT synthesis, conversion 60-80%; 4-7: Introduction of H 2 0 for cooling the FT synthesis;

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4-8: Discharge of the cooling water as steam; 4-9: Isolation of FT products; 4-10: FT products; 4-11: Residual gas containing H 2 , CO, C02, CH 4 , CxHy; 4-12: Optional WGS; 4-13: Introduction of FT offgas and also product from WGS and optionally mixture with H 2 ; 4-14: Offgas from the FT synthesis as optional fuel gas for heating the RWGS.

It is to be understood that, if any prior art is referred to herein, such reference does not constitute an admission that the prior art forms a part of the common general knowledge in the art, in Australia or any other country.

In the claims which follow and in the preceding description of the disclosure, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the disclosure.

20408023_1 (GHMatters) P45869AU00

Claims

1. A pressure- and heat-resistant reactor for producing synthesis gas in a reverse CO conversion, having at least the following components:

- at least two fluid-tight feed conduits for at least two different starting fluids, where the first starting fluid is an essentially C0 2-containing fluid and the second starting fluid is an essentiallyH2-containing fluid;

- at least one fluid-tight discharge conduit for the synthesis gas as product;

- at least two recuperative countercurrent heat exchange zones, with subregions of the at least two feed conduits being arranged in both countercurrent heat exchange zones,and

- at least one reaction zone having at least one catalyst in a catalyst bed;

wherein the first C02 starting fluid feed conduit is arranged in a subregion directly next to the synthesis gas product discharge conduit

2. The reactor as claimed in claim 1, wherein the reactor is pressure-resistant up to a pressure of at least 10 bar, preferably at least 20 bar, particularly preferably at least 30 bar or more, and is temperature-resistant up to at least 500°C, preferably at least 700°C, particularly preferably up to at least 900°C or more.

3. The reactor as claimed in claims 1 or 2 comprising a reaction zone which is heatable by combustion heating or electric heating.

4. The reactor as claimed in any of the preceding claims, wherein at least one further starting fluid feed conduit having at least three subregions is present, with in each case one of these subregions being arranged in the two recuperative countercurrent heat exchange zones and the heating zone.

5. The reactor as claimed in any one of the preceding claims for steam reforming.

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6. A process for producing synthesis gas using a reactor as claimed in any of claims 1 5.

7. The process as claimed in claim 6, wherein a first starting fluid containing essentially C02 or comprising thereof is used and a mixture of H 2 and offgas from a Fischer Tropsch synthesis is used as second starting fluid.

8. The process as claimed in claim 6 or 7, wherein the second starting fluid contains water, optionally steam.

9. The process as claimed in any one of claims 6 or 7, wherein a single-stage reverse water gas shift is carried out in the reactor as claimed in any of claims 1-5.

10. The process as claimed in one of claims 6 or 7, wherein steam reforming is carried out in the reactor.

11. The process as claimed in any one of claims 6 or 7, wherein the first starting fluid is conveyed in countercurrent to the discharge of the product directly next to the discharge conduit for the product through a first recuperative heating zone and subsequently through a second recuperative heating zone directly next to the catalyst to the reaction zone.

12. The process as claimed in any one of claims 6 or 7, wherein the second starting fluid is conveyed through the first and second recuperative heat exchange zone to the heating zone and through this onto the reaction zone.

13. The process as claimed in any one of claims 6 or 7, wherein the second starting fluid passes through a water gas shift stage upstream of a conducting reactor as claimed in any of claims 1-5.

14. The process as claimed in any one of claims 6 or 7, wherein water is at least partially removed from the synthesis gas by condensation after leaving the reactor.

15. The process as claimed in any one of claims 6 or 7, wherein the synthesis gas is fed to a single-stage Fischer-Tropsch synthesis, the offgas from which is used together with H 2 0 as second starting fluid in a reactor as claimed in any of claims 1-5.

16. The process as claimed in any one of claims 6 or 7, wherein a molar ratio of

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C0 2:CO:H 2 :H 20:CH 4 of 0.5-1:0.1-0.5:1-2:0.5-1.5:0.05-0.2 is used in the reaction zone.

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