WO2004091773A1

WO2004091773A1 - Electrically heated reactor and process for carrying out gas reactions at a high temperature using this reactor

Info

Publication number: WO2004091773A1
Application number: PCT/EP2004/003529
Authority: WO
Inventors: Ernst Gail; Dieter Bathen; Martin Bewersdorf; Michael Rinner; Heiko Mennerich; Robert Weber
Original assignee: Degussa Ag
Priority date: 2003-04-15
Filing date: 2004-04-02
Publication date: 2004-10-28
Also published as: CN100381200C; CN1774291A; ZA200508311B; AU2004229151A1; DE10317197A1

Abstract

The invention relates to an electrically heated reactor (1) for carrying out gas reactions at a high temperature. The reactor comprises a reactor block (2), of one or more monolithic modules (3) of a material which is suitable for an electrical heating, surrounded by a casing (10 to 13), channels (4) extending through the module(s) and being constructed as reaction channels, and a device for passing through or inducing a current in the reactor block. The safety during operation of such a reactor is increased according to the invention in that the casing of the reactor block comprises a double-walled jacket (13) which seals this off gas-tight, and at least one device (14) for feeding an inert gas into the double-walled jacket. The invention also provides a process for carrying out gas reactions at a high temperature, such as the BMA process for the preparation of hydrogen cyanide, using the reactor.

Description

Electrically heated reactor and process for carrying out gas reactions at a high temperature using this reactor

Description:

The invention relates to an electrically heated reactor for carrying out gas reactions at a high temperature, in particular a temperature above 500^aC, wherein the reactor comprises a reactor block of one or more monolithic modules with channels constructed as the reaction space, and the heating takes place by resistance heating or inductive heating.

The invention also relates to a process for carrying out gas reaction at a high temperature, in particular endothermic gas reactions, using this reactor.

Various reactors are known for carrying out reactions in the gas phase which take place in the presence or absence of a catalyst at high temperatures, these usually being endothermic gas phase reactions. The reactors differ, inter alia, in how the energy is transferred to the gas or gas mixture to be reacted, for example by the heat of combustion of a combustible gas by a direct or indirect route or by means of electrical energy.

DE 35 33 385 CI discloses a tubular oven for carrying out gas reactions, in particular for the preparation of hydrogen cyanide by the BMA process: The tubular oven comprises a masonry-lined heating chamber in which ceramic tubes are arranged as reaction spaces. For the heating, electrical heating elements are arranged in parallel with the tubes, and furthermore the_, chamber contains an inner and an outer radiating wall. The heating elements are made of a material which is suitable for resistance heating. Substantial disadvantages of such a tubular oven are its very involved construction and its susceptibility to malfunction, because both the reaction tubes and the heating elements can fracture and accordingly necessitate a shut-down of the installation.

In an effort to reduce the energy requirement of endothermic gas reactions, DE 196 53 991 Al proposed the use of a monolithic counter-current reactor which comprises heating channels and reaction channels running parallel to one another. No suggestion of constructing the monolithic reactor such that the monolith is heated by passing an electric current through can be obtained from this document .

EP 0 684 071 Al discloses a monolithic body with an electrically heated active charcoal structure and devices for passing a fluid product stream through the channels of the monolith. In this reactor, a continuous uninterrupted active charcoal layer heated by passing a current through is located on an electrically non-conductive monolithic inorganic substrate, in particular a ceramic honeycombed body. On opposite sides, the body contains strips of a conductive material as electrodes on the active charcoal structure. Such a reactor can be used in processes for adsorption and desorption of constituents from a fluid product stream. It is expressly pointed out in this document that the monolithic reactor is to be operated at max. 350²C if the medium flowing through is not inert. According to the doctrine of this document, such a reactor is thus not possible if gas reactions are to be carried out at very high temperatures, for example the BMA process, which is carried out at above 1,000²C. One problem of such a reactor is evidently that with the frequent change in temperature the coating scales off . Suggestions as to how such a reactor must be redesigned in order to make it safe to operate for use for gas reactions to be carried out at a high temperature are not to be found in this document.

GB Patent Specification 1 238 468 discloses another type of heating of a reactor for carrying out gas reactions at a high temperature: Two electrodes are "arranged opposite in a tank-like reactor, and for the purpose of heating a current is passed through the catalyst bed of electrically conductive particles arranged in the reactor. The doctrine of WO 02/45837 A2 is a similar fixed bed reactor, wherein the reactor has electrodes standing concentrically inside one another and a fixed bed of electrically conductive material through which a fluid can flow is arranged between these. The BMA process and reforming processes are mentioned as the field of use. While gas reactions can be carried out in a satisfactory manner at a temperature of below 900²C in such a reactor with a fixed bed which is suitable for resistance heating, problems increasingly arise at higher temperatures and in particular in reactions in which hydrogen is present: If the fixed bed, as proposed in this document, comprises a mixture of a conductive and a non-conductive or semi-conductive material, flows can occur in the current conduction.

According to WO 95/21126, a reactor for a gas phase reaction in the presence of a catalyst fixed bed formed from particles can also be heated inductively. In the present Application, an inductive heating is less preferable because of the higher technical outlay, inter alia for the shielding required. According to NL Patent 121 661, hydrogen cyanide can be produced from ammonia and methane at l,600^eC to 2,500^aC if the reaction is carried out in a tubular graphite reactor, preferably in the presence of a diluent gas, such as hydrogen. The reaction temperature required is effected by resistance heating of the graphite tube. The graphite tube is insulated from one end to the other end and surrounded by a conductive casing, which is connected to the tube. The technical difficulties caused by the high operating temperatures make this process not very attractive for a large-scale industrial plant.

In the reactor described in WO 96/15983 for the preparation of hydrogen cyanide by the BMA process, the energy required is also effected by resistance heating or inductive heating of the reaction tubes of graphite used or of a graphite block with bores as reaction channels. Instead of graphite, it is also possible to use other conductive materials or a coating of such materials. Furthermore, the reaction tubes or the bores can be coated with a catalyst. The reactor block containing reaction tubes or reaction channels is surrounded by an insulating layer of aluminium oxide wool and a reactor housing of steel. When such a reactor was used for the preparation of hydrogen cyanide from methane and ammonia, the owner of the protective right encountered considerable safety-relevant problems which stood in the way of further operation of the reactor. This reactor which is already known accordingly has to be improved in several respects in order to render possible safe production of hydrogen cyanide therein.

A further class of reactors which are heated electrically is based on a plasma being produced in the reactor. Such reactors are of little interest for large-scale industrial use because of the high technical outlay. Reactors and processes in which a plasma is produced for heating the gaseous medium are therefore ruled out from further consideration and the scope of protection of the present subject matter of the invention.

The object of the present invention is to provide an improved electrically heatable reactor for carrying out gas reactions safely at a high temperature, in particular a temperature above 500^aC, and preferably above 900²C, with which the disadvantages of the already known reactors described are overcome at least in one point.

A further object relates to providing a reactor with channel-like reaction spaces, which can also be operated safely at a reaction temperature above 900^aC in the presence of hydrogen as a reaction partner.

A further object is to provide a reactor of the generic type which has a simple construction, is not very susceptible to repair work and can be adapted to a desired production capacity in a simple manner.

According to a preferred embodiment of the reactor according to the invention, this should be easy to integrate into an installation for carrying out a gas reaction for the purpose of obtaining a reaction gas and working up of this. If hydrogen is additionally formed as a gas in the gas reaction, in addition to the desired reaction gas, such as, for example, hydrogen cyanide, it should be possible to integrate the reactor into the installation such that the hydrogen can be used in a combined system to increase the profitability of the process for obtaining the reaction gas .

The inventors of the present Application have found that, in contrast to reactors in which the gas reaction takes place in a densely fired ceramic reaction tube, safety problems arise in reactors of a conductive material, such as graphite, because this material and other materials such as are known for resistance heating are not sufficiently gas-tight. Since the insulating materials arranged around the reactor which is operated at a high temperature as a rule likewise are not gas-tight, critical situations may occur if the outer skin of the reactor is damaged or is otherwise not adequately sealed.

It has been found that the problems described can be solved in a simple manner by constructing the reactor casing as a double-walled jacket which is filled with an inert gas or, preferably, through which an inert gas flows. By continuous analysis of the composition of the inert gas flowing through the double-walled jacket it can be ascertained immediately whether a gas is entering the double-walled jacket from the reaction space or whether the double-walled jacket has been damaged from the outside and therefore air is entering. As soon as the composition of the inert gas in the double-walled jacket changes, the expert will take the necessary measures in order to avoid states which are unacceptable in terms of safety.

An electrically heated reactor for carrying out gas reactions at a high temperature has been found, comprising a reactor block, of one or more monolithic modules of a material which is suitable for resistance heating or inductive heating, surrounded by a casing, channels constructed as the reaction space which extend from one to the opposite side of the reactor block, in each case a device for feeding and removing a gaseous medium into/out of the channels and at least two electrodes, connected to a power source and the reactor block, for passing a current through the reactor block or a device for inducing a current in the reactor block, which is characterized in that the casing of the reactor block comprises a double-walled jacket which seals this off gas-tight, with at least one device for feeding an inert gas into the double-walled jacket.

The subclaims of the electrically heated reactor relate to preferred embodiments thereof and include installations into which the reactor is integrated. The double-walled jacket particularly preferably has a device for feeding in an inert gas and a further device for removing the same, so that the inert gas can flow through the double-walled jacket .

The invention will be explained in more detail with reference to figures 1 to 4 :

Figure 1 shows a diagram of a section through an electrically heatable reactor with a reactor block comprising four monolithic modules, and a multi-layered casing including a double-walled jacket according to the invention through which an inert gas flows . Figure 2 shows a longitudinal section through a reactor block of eight monolithic modules, the channels arranged in parallel which are constructed as reaction spaces each extending through all the modules.

Figure 3 shows a cross-section through a monolithic module and reveals the reaction channels running perpendicular to the diagram.

Figure 4 shows a diagram of an installation in which gaseous feed substances are reacted in a reactor according to the invention, a valuable substance of the reaction gas is converted into a secondary product, a further valuable substance, namely a combustible gas, is freed from residual gases and then burned in a fuel cell, and the current thereby obtained is used for heating the reactor according to the invention.

The reactor (1) shown in figure 1 comprises a reactor block (2) of several monolithic modules (3) arranged one above the other, through which a plurality of parallel reaction channels (4) extend. A reactor block can have one or more monolithic modules, but it particularly preferably comprises, as shown in figure 1 and in figure 2, several modules arranged one above the other, the reaction channels extending through all the modules . The number of modules arranged one above the other depends on the duration of reaction required for the gas or gas mixture to be reacted, and the desired capacity of the reactor. An increase in capacity is possible by adding one or more modules to a reactor block and at the same time increasing the flow rate of the gas to be reacted. In principle, several modules arranged one above the other or modules arranged in parallel side by side can be arranged to form a reactor block. The cross-section of the modules can be substantially arbitrary. Modules with a circular, rectangular or hexagonal cross-section are particularly suitable. The height of an individual module likewise can be freely chosen. In the case of circular modules, the ratio of the diameter to the height is in general in the range from 0.5 to 5, preferably in the range from 1 to 4.

Each monolithic module comprises at least one, but preferably many reaction channels, which extend from one side of the module to the opposite side. The channels are preferably arranged parallel to one another. However, another arrangement, for example such a one in which several tubes run at an angle to one another, is not ruled out.

According to one embodiment, in which several modules of the same construction are arranged one above the other, centring and therefore passage through of the channels (4) is effected by, for example, guide pins (16) or a specific design of the lower and upper edge zones of each module in the sense of engaging in one another in accordance with the tongue and groove principle. To ensure contacting which is as uniform and flat as possible between the individual modules, the boundary surfaces lying on one another should be constructed to be as smooth as possible.

According to an alternative embodiment of the reactor block, modules arranged one above the other are in contact with one another not directly but via a sealing element lying in between. This sealing element can be electrically conductive or insulating and is constructed such that the gas mixture emerging from the channels of a first module can enter into the channels of a second module arranged opposite. For example, the sealing element is constructed such that it has bores corresponding to the modules. According to one alternative, the sealing element is constructed as a coating between two modules. An electrically conductive coating can be produced e.g. by application of a paste of e.g. graphite particles or/and metal particles in a suspension medium, the particles preferably being nanoparticles . Suitable metal particles are made e.g. of elements of the 8th and 1st sub-group of the periodic table and alloys thereof. The sealing element expediently has a melting point above the operating temperature . After coating and arranging the modules one above the other, the suspension medium is evaporated by heating.

For the preferred resistance heating of the reactor block, suitably constructed electrodes (8 and 8')/ supplied with current via the current feed lines (9) , are located on opposite sides. In the embodiment shown in figure 1, the monolithic modules lie immediately one above the other, so that the current flows through all the modules and thereby heats the block. If the modules have a circular cross- section, it is expedient to arrange the electrodes on the top and bottom module, the electrodes being constructed annularly or in the form of plates with channel openings. In the case of a rectangular cross-section of the modules, it is usual to construct the electrodes in plate form. The electrodes must be in close contact with the corresponding surface of the contacted module. This is possible, for example, by pressure contact by means of a spring or by the intrinsic weight of several modules arranged one on top of the other. It may be expedient to arrange a coating of a conductive material between the electrodes and the contacted modules, in order to ensure a better contact. If a reactor block is constructed from several modules with insulating sealing elements arranged in between, each monolithic module must be equipped with corresponding electrodes and current feed lines or have suitable contacting elements between a first module and an adjacent module. One embodiment in which individual modules or groups of modules are supplied with current, it is possible to run a specific temperature profile in the reactor block.

The electrodes are expediently made of an electrode material of high heat stability which is conventional in technical circles, for example an electrode graphite.

The choice of material for the monolithic modules is of particular importance. By the choice of material, which can be a uniform substance or a substance mixture, it is possible to obtain modules of such specific resistance with which the desired reaction temperatures are easily obtainable by an ohmic resistance heating. The modules are thus made of an electrically conductive material with a specific resistance of greater than 1 μΩ-m up to about or even above 1,000 μΩ-m, in particular greater than 10 μΩ-m and particularly preferably 15 to 100 μΩ-m. The specific resistances stated relate to the complete material. The specific resistance of the module increases with the number of channels, because the effective cross-section decreases.

Examples of suitable materials for the modules are graphite, carbon black, carbides and nitrides, in particular those of silicon and titanium. By combination of such substances with a non-conductive or semi-conductive material, the specific resistances can be increased further if the mixtures are very homogeneous and sintered together well .

The reactor block is surrounded substantially completely by a casing, this also serving as thermal insulation. The thermal insulation comprises one or more layers, the choice of substance for the insulating layer depending on the desired temperature range. In the embodiment in figure 1 given by way of example, the reactor block has a three- layered casing, namely an insulating layer 1, 2 and 3 (10, 11, 12) . The choice of material for the insulating layers and the thickness of the layers depend on the coefficients of expansion of the materials chosen and the temperature profile aimed for within the thermal insulation. According to a preferred embodiment, the insulating layer 1 is a flexible material, for example a graphite fibre or mineral fibre nonwoven or a fibre mat of such materials, with which the coefficients of expansion both of the reactor block and of the insulating layer 2 can be taken into account and therefore no fractures occur. The insulating layers 2 and 3 can have been produced from known thermally insulating materials, including lightweight stones and vacuum shaped stones. A device for radiation shielding (7 and 7') is expediently located on the entry side and the exit side of the channels of the reactor block.

An element of the reactor which is essential to the invention is that the casing of the reactor block has a double-walled jacket, which seals this off gas-tight, of a material which is impermeable to gases. This double-walled jacket (13) has at least one device (14) for feeding in an inert gas, and preferably a further device (15) for removing the same . These devices are arranged on the double-walled jacket such that a constant pressure can be held inside the double-walled jacket, or such that an inert gas can flow uniformly through the entire double-walled jacket. It is not essential that the double-walled jacket is located as the outermost reactor wall on the insulating layers lying underneath, rather the double-walled jacket can also be located between two insulating layers.

It has been found that the material from which the modules are produced as a rule is not completely gas-tight, so that gas can leak through the side wall of the modules. This leakage of gas presents considerable risks if the gas or gas mixture .comprises combustible and/or toxic gases. Since the reactor according to the invention is designed for carrying out gas reactions, in particular endothermic gas reactions, such as reforming processes and the BMA process for the preparation of hydrogen cyanide, the reaction gas also comprises hydrogen. Since the materials used to produce the thermally insulating casing of the reactor block as a rule have a high porosity, these substances also are not gas-tight. The double-walled jacket according to the invention thus on the one hand acts as a diffusion barrier, and on the other hand increases the safety of the plant, since even if the outer wall of the double-walled jacket is damaged, atmospheric oxygen cannot come into contact directly with the reaction gas which has passed through the insulation and generate an explosive gas mixture .

According to a preferred embodiment of the invention, the composition of the inert gas emerging from the double- walled jacket is monitored continuously, so that damage to the double-walled jacket - whether to the inner wall or the outer wall - can be detected and an appropriate measure to avoid damage can be taken. Safer operation of the reactor is possible by the feature according to the invention. Instead of passing an inert gas through the double-walled jacket, it is also possible to keep an inert gas under an increased or reduced pressure in the double-walled jacket and to monitor the pressure. Since in this embodiment it cannot be ascertained directly whether the inner side or the outer side of the double-walled jacket is damaged, this embodiment is less preferable.

According to a further embodiment of the reactor, a gas diffusion barrier of a gas-tight material is located directly on the reactor block or on one of the further insulating layers of the casing lying inside. An additional safety gain is achieved by such a gas diffusion barrier, which can be either a closed metal casing or a tight coating.

According to a specific embodiment, the double-walled jacket according to the invention is constructed such that the inner wall has the function of the gas diffusion barrier and the outermost wall of the reactor simultaneously is the outer wall of the double-walled jacket.

The monolithic modules as a rule comprise a plurality of continuous channels. According to a particularly preferred embodiment, the diameter of the channels is in the range from 2 to 20 mm, preferably in the range from 3 to 10 mm. It is an advantage of the reactor according to the invention that very many channels can be arranged in a narrow space and the space/time yields of the gas reactions to be carried out using this reactor are in each case very high. Reactors which are already known and in which the reactions are carried out in ceramic tubes, heating taking place either electrically or by combustion of a combustible gas, have a considerably lower space/time yield.

If the gas reaction is to be carried out in the presence of a catalyst, it is expedient to coat the channels of the modules with an active catalyst. The catalyst to be used depends on the gas reaction aimed for. In reforming processes, oxidic catalysts are accordingly preferably used, and in the BMA process for the preparation of hydrogen cyanide catalysts from the series consisting of platinum, platinum compounds, platinum-gold alloys and nitrides of lightweight metals, in particular aluminium nitride, it also being possible for the nitrides to have been formed in situ from the corresponding metals and the nitrogen formed from ammonia in the reaction.

A reactor for operating the BMA process on an industrial scale comprises, for example, 4 - 10 modules arranged one above the other, the height of which is 25 cm and the diameter of which 46 cm and which have 2,200 bores (= channels) with a width of 5 mm.

In addition to the high space/time yield, a further advantage of the reactor according to the invention is that the reactor block has a simple construction and comprises no individual ceramic tubes which are susceptible to fracture. The invention also relates to an installation for the preparation and further processing of a gas which, in addition to the reactor according to the invention, additionally comprises a device for working up the reaction gas. Such an installation can also comprise a heat exchanger, in which the gases to be employed or a gas mixture is preheated by the reaction gas emerging from the reactor before entry into the reactor . The heat exchanger can be constructed in accordance with the regenerative or the recuperative principle.

The device for working up the reaction gas depends decisively on the composition thereof and on the target products of the valuable substances produced from individual constituents of the reaction gas. If the reactor according to the invention is used for carrying out the BMA process for the preparation of hydrogen cyanide, the device for working up and further processing of the reaction gas mixture includes an absorption of the hydrogen cyanide in an aqueous medium or a condensation of the hydrogen cyanide. By absorption of the hydrogen cyanide from the reaction gas in an alkali metal or alkaline earth metal hydroxide solution, an alkali metal cyanide or alkaline earth metal cyanide solution, such as, in particular, sodium cyanide or calcium cyanide solution, such as are conventional in mining in leaching processes for obtaining gold, can be obtained. After absorption of the hydrogen cyanide, a gas which predominantly comprises hydrogen remains and can be fed, directly or after further purification, to further uses, including a fuel cell for the purpose of providing electricity. In the case of condensation of the reaction gas, liquid hydrogen cyanide, which can be used for the preparation of further secondary products, can be obtained in a manner known per se. Figure 4 shows an installation which has the abovementioned features and is suitable in a particular manner for carrying out the BMA process. The installation comprises the reactor (1) according to the invention, a heat exchanger (17) for preheating the gases (18 and 19) to be reacted, and a line (20) for the preheated gas mixture, which is reacted in the reactor (1) . The reaction gas which leaves the reactor passes via a line (21) into the heat exchanger (17) in order to release some of the heat there. The partly cooled reaction gas passes via a line (22) into the working up device (23) . The auxiliary substances required for the working up, for example an alkali metal or alkaline earth metal hydroxide solution in the case of the preparation of an alkali metal or alkaline earth metal cyanide from a reaction gas comprising HCN, are fed in via line (25) . The reaction products from the working up of the reaction gas comprising hydrogen cyanide, that is to say an alkali metal cyanide or alkaline earth metal cyanide solution or liquid hydrogen cyanide, is discharged from the system via line (24) . The gas which remains from the working up, the main constituent of which is hydrogen, is separated into a hydrogen stream (28) and a residual gas stream (29) in a device (27) for purification of the gas. The purified hydrogen stream passes into a fuel cell (30) , in which it is burned to give water, it being possible for the water formed to be recycled via a line (31) into the working up stage (23) . The electricity obtained in the fuel cell is fed via an electric line (32) to the electrically heatable reactor. In the closed system shown, a large portion of the energy required for carrying out the endothermic gas reaction is obtained by combustion of the hydrogen in a fuel cell. Such an embodiment is advantageous in particular if there is no other possible use for the hydrogen formed as a by-product. The reactor according to the invention and an installation comprising this can be used, as already referred to above, in processes for carrying out gas reactions at high temperatures, in particular endothermic reactions at more than 500^aC, and in particular more than 900²C. If the gas reaction is a pure pyrolysis, the gas to be pyrolysed or a gas mixture comprising this is fed to the reactor. In the case of gas reactions in which at least two gases are reacted with one another, at least the gases to be reacted are fed to the reactor, and if required the gas mixture can additionally comprise gases which are inert under the reaction conditions. The process can be carried out in the presence or in the absence of an active catalyst, depending on the reaction type.

According to a particularly preferred embodiment of the process according to the invention, ammonia and a lower hydrocarbon, in particular methane, are reacted in the presence of a suitable catalyst for the BMA process at 1,100 to 1,200²C to give hydrogen cyanide and hydrogen.

A further process relates to reforming processes, in which a combustible substance, such as methanol, is converted into hydrogen and C0₂ in the presence of steam and the hydrogen can be fed to a fuel cell to obtain electrical energy. Reference symbols Reactor Reactor block Monolithic module Channels (reaction space) Gas entry (gas mixture to be reacted) Gas exit (reaction mixture) , 7' Radiation shielding , 8 'Electrodes (annular) Current feed 0 Insulating layer 1 Insulating layer 2 Insulating layer 3 Tank wall (double-walled jacket) Inert gas feed Inert gas removal Guide pin Heat exchanger Gas feed (gas 1) Gas feed (gas 2) Gas mixture exit Reaction gas line into 17 Reaction gas line out of 17 Device for working up Feed for auxiliary substances Discharge of reaction products Line to device 27 Device for separation of the gas Combustion line (H ) Residual gas discharge Fuel cell Water line Current feed line from fuel cell to reactor

Claims

Patent claims :

1. Electrically heated reactor (1) for carrying out gas reactions at a high temperature, comprising a reactor block (2), of one or more monolithic modules (3) of a material which is suitable for resistance heating or inductive heating, surrounded by a casing (10 to 13), channels constructed as the reaction space which extend from one to the opposite side of the reactor block, in each case a device for feeding and removing a gaseous medium (5 and 6) into/out of the channels and at least two electrodes (8, 8'), connected to a power source and the reactor block, for passing a current through the reactor block or a device for inducing a current in the reactor block, characterized in that the casing of the reactor block comprises a double- walled jacket (13) which seals this off gas-tight and at least one device (14) for feeding an inert gas into the double-walled jacket.

2. Electrically heated reactor according to claim 1, characterized in that the double-walled jacket has a device for removal (15) of the inert gas, this preferably being connected to a device for gas analysis.

3. Electrically heated reactor according to claims 1 or 2 , characterized in that the reactor block comprises several monolithic modules arranged directly or at a distance by means of a sealing element one above the other or side by side and the channels are arranged such that a gaseous medium fed in on one side of the reactor block can flow through all the modules and emerge on the opposite side of the reactor block.

4. Electrically heated reactor according to one of claims 1 to 3, characterized in that between the modules are arranged sealing elements of an electrically insulating material, the channel exits of a first module lie opposite the channel entries of an adjacent module and the sealing elements have corresponding channel openings .

5. Electrically heated reactor according to claim 4, characterized in that each heated module has two electrodes for passing a current through .

6. Electrically heated reactor according to one of claims 1 to 5, characterized in that the thermally insulating casing comprises one or more thermally insulating layers and a gas diffusion barrier.

7. Electrically heated reactor according to claim 6, characterized in that the gas diffusion barrier is a gas-tight coating or a densely fired ceramic or vitreous material.

8. Electrically heated reactor according to one of claims 1 to 7, characterized in that the modules are made of a conductive material with a specific resistance of greater than 1 μΩ-m, in particular greater than 10 μΩ-m and particularly preferably 15 to 50 μΩ-m.

9. Electrically heated reactor according to one of claims 1 to 8, characterized in that the channels at least partly have a catalytically active coating.

0. Electrically heated reactor according to one of claims 1 to 9, characterized in that a device for radiation shielding (7, 7') is arranged on both sides of the reactor block at which the channels enter or exit.

11. Electrically heated reactor according to one of claims 1 to 10, characterized in that the modules are made of insulating graphite and the electrodes are made of electrode graphite, wherein the electrodes are constructed annularly or in the form or perforated plates in the case of cylindrical modules and in plate form in the case of parallelepipedal modules.

12. Electrically heated reactor according to one or more of claims 1 to 11, characterized in that it is integrated into an installation which comprises a device for working up (23) the gaseous medium emerging from the reactor (reaction gases) , the device for removal of the gaseous medium being connected via a gas line (21) to the device for working up.

13. Electrically heated reactor according to one of claims 1 to 12, characterized in that it is integrated into an installation which comprises a heat exchanger (17) , through which the gaseous medium to be reacted is passed for the purpose of heating before feeding thereof into the channels of the reactor and through which the reaction gas removed from the reactor is passed for the purpose of cooling.

14. Electrically heated reactor according to one of claims 1 or 13, characterized in that it is integrated into an installation which comprises a device for working up (23) the gaseous medium emerging from the reactor (= reaction gas) , separating off of a combustible gas (29) contained therein, and additionally a fuel cell (30) for combustion of the combustible gas, the fuel cell being connected as a power source for heating the reactor (1) .

15. Process for carrying out gas reactions at a high temperature, in particular endothermic reactions at a temperature of more than 500²C, wherein at least two gases to be reacted with one another are passed through a reactor at an effective reaction temperature in the presence or absence of a catalyst, characterized in that the gas reaction is carried out in a reactor according to one or more of claims 1 to 14.

16. Process according to claim 15, characterized in that the gas reaction is the formation of hydrogen cyanide and hydrogen from ammonia and a lower hydrocarbon, in particular methane (BMA process) .

17. Process according to claim 15, characterized in that it is a reforming process, hydrogen being obtained from a combustible substance, such as methanol.

18. Process according to claim 15 or 16, characterized in that hydrogen is separated off from the reaction gas, and is burned with air in a fuel cell, electrical energy being obtained, and the electrical energy obtained is used for heating the reactor.