DE1240829B - Device for the production of pure hydrogen - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

COIb

A ^z

German class: 12 i- 1/18

COIB-

Number: 1 240 829

File number: A 44374IV a / 12 i

Filing date: October 23, 1963

Opened on: May 24, 1967

3/5 6 D

The invention relates to a device for obtaining pure hydrogen by reaction or thermal decomposition of gaseous hydrogen compounds on a hot catalyst Hydrogen and residual gases and separation of the hydrogen by means of diffusion.

Such a device is e.g. B. from US A patent 2516974 known. This device has a boiler with two zones, only the first of which is filled with catalyst, wherein in the latter one closed on one side and with a collecting line that runs through the second zone in a gas-tight manner connected diffusion tubes made of hydrogen-permeable material are embedded. The first zone is a transfer pipe for the preheated starting gases coming from the second zone connected in such a way that they flow through the catalyst material, wash around the diffusion tubes and withdraw through the second zone as residual gas again, being connected to the pipe walls with the output gases guided through this second zone are in indirect heat exchange.

Both zones merge directly into one another, and the feed pipe for the starting gases is passed through the second zone in a gas-tight manner, pulls outside the two zones to the first zone and opens in the latter. Since in this device also the collecting line connected to the diffusion tubes does not have a large surface, but leads directly to the outside, the starting gases are only preheated by the hot exhaust gases in the second zone, while making use of the heat of the diffused Hydrogen is not possible. Such a use was also in the case of the known device unnecessary, as this should not be used as a useful product for the production of hydrogen, but the hydrogen, who diffuses through the walls of the diffusion tubes, inside the diffusion tubes with a Oxidant is burned. The resulting combustion heat covers the heat demand for the endothermic conversion or thermal decomposition of the working gases.

Further devices of this type, in which hydrogen diffuses selectively or preferably through a hydrogen-permeable wall and is withdrawn as useful or by-product, are e.g. Known, for example, from U.S. Patents 1,951,280 and 2,637,625. In these externally heated devices, for example, the hydrogen generated in a catalyst bed is conducted through diffusion tubes arranged in this bed into a collecting line and is drawn off in a device for recovery during the reaction
of pure hydrogen

Applicant:

Public company Brown, Boveri & Cie.,

Baden (Switzerland)

Representative:

Dr.-Ing. E. Sommerfeld, patent attorney,

Munich 23, Dunantstr. 6th

Named as inventor:

Dr. Wilfried Fischer, Neuenhof, Aargau

(Switzerland)

Claimed priority:

Switzerland of October 8, 1963 (12343)

gen, but they do not allow the heat of the discharged gases to be transferred to the output gases.

It is the object of the invention to provide such a known device according to the United States patent 2,516,974 in such a way that it enables the production of pure hydrogen with optimal thermal Efficiency and a small ratio of surface to volume allowed.

Another object of the invention is to provide a device of the type mentioned, in which, as in the known devices, the hydrogen formed as a reaction product already during the reaction is separated from the other gases and by removing hydrogen during the Reaction both the chemical equilibrium is shifted to the side of the reaction products as well as the rate of reaction is increased.

The device according to the invention is opposite to the device according to the United States patent 2 516 974 characterized in that both zones are separated by a wall and a residual gas discharge pipe out of the first zone in a gas-tight manner through the second zone to the outside, while this second zone has an open feed pipe for the starting gases and the transfer pipe to the catalyst zone in the second zone as well open in such a way that in this zone the

709 587/524

Starting gases circulate around the hydrogen collection and residual gas discharge lines, which have a large surface area.

The construction of the device according to the invention makes it possible to use the hydrogen entrained amount of heat, which in many practical cases, z. B. also in the implementation of Hydrocarbons with water vapor make up the predominant part of the heat of the reaction gases, to use to preheat the working gases and thus in connection with the compact Construction of the device to enable a very high thermal efficiency to be achieved, so that the catalyst zone only needs to be heated from the outside to a lesser extent than the known ones Devices.

The invention will be explained in more detail with reference to the drawings.

Fig. 1 shows, partly in section, an elevation of one Embodiment of the invention;

F i g. FIG. 2 shows a cross section of the device of FIG.

In Fig. 1 is an embodiment of the invention Device shown for the production of pure hydrogen by converting methane with water vapor to hydrogen and carbon oxides. The gas mixture consisting of methane and water vapor flows through the pipe 1 into the Heat exchanger space 2, where it is preheated and from where it passes through the pipe 3 into the adjacent Reaction chamber 4 arrives. In the exemplary embodiment shown, the heat exchanger space and the reaction space are one above the other in the interior of a cylindrical one Vessel 5 arranged. The vessel 5, which is thermally insulated from the atmosphere, has an inner housing wall 6 made of stainless steel, thermal insulation 7 made of fireclay and an outer cladding 8 Sheet steel on. The electrical heating winding 9 and its connections are used to heat the reaction chamber 4 to a power source are not shown.

A part of the reaction space 4 is provided with a suitable for the conversion of methane with water vapor Catalyst 10 filled, for example a commercially available nickel catalyst in the form of sintered Chunks or grains. In the reaction space 4 are also, preferably in an axial position, hydrogen-permeable Metal pipes 11, for example made of a palladium alloy pipes attached. The upper ends of the tubes 11 are closed, while their lower ends enter the collecting channel 12 flow out. In order to have the largest possible area of hydrogen-permeable metal in the reaction space, i. H. if possible To be able to accommodate many tubes 11, the tubes lie against one another and are closed by soldering summarized a pipe wall.

The hydrogen generated by the conversion of methane and water vapor on the catalyst diffuses through the tubes 11, is collected in the channel 12 and flows over a greater length through the heat exchanger chamber outflow line 13 to the point of consumption. The implementation Residual gases produced, mainly carbon oxides, are collected in the discharge line 14 and discharged in this through the heat exchanger space 2. Give the two drain lines 13 and 14 this transfers heat to the gases flowing in through line 1 to be converted. The the collecting channel delimiting walls, the pipe 3 and the drain lines 13 and 14 are expediently made Made of stainless steel.

F i g. 2 shows a cross section of the device along the section line designated AA in FIG. 1 through the reaction space 4. The electrical heating coil 9 is embedded in the thermal insulation. By

ίο the pipeline 1 flows the gases to be converted in the establishment; The generated hydrogen or the residual gases flows through the discharge line 13 or 14 from the facility. With 3 the tube is referred to, through which the gases to be converted from Get the heat exchanger chamber into the reaction chamber. At 11 are the hydrogen-permeable metal pipes denotes through which the generated hydrogen diffuses. The pipes are each to a pipe wall summarized, the space surrounding the tubes being filled with the catalyst material 10 is.

For the sake of clarity, FIG. 1 and 2 the hydrogen-permeable pipes are not drawn to scale. To achieve a large surface area, it is advantageous to choose a small pipe diameter and to arrange the pipe walls formed by lining up and soldering pipes only at a small distance from one another. Instead of the tube walls shown, another hollow body arrangement with a large, hydrogen-permeable surface can also be used, for example an arrangement with zigzag-shaped curved hollow lamellas made of palladium sheet.
Dimensions are given as an example.

To generate about 1000 liters of hydrogen per hour, the device of FIG. 1 and 2 3501 methane and 700 g of water vapor supplied per hour. The reaction space 4 in FIG. 1 has a volume of about 30 dm ³ , of which about 12 dm ^{3 are taken up} by the pipes 11 with hydrogen-permeable walls. These tubes are made of palladium, have a diameter of 5 mm and a wall thickness of 0.1 mm. Their total surface is about 10 m ² . The reaction chamber is brought to a temperature of approximately 700 ° C. by the electrical heater 9. About 1000 l of pure hydrogen can then be withdrawn through the outlet line 13, while the residual gases flowing through the outlet line 14 contain _{65 mol percent CO, 30 mol percent CO 2} , a few mol percent H ₂ and 1 mol percent CH _4. Since the residual gases contain flammable gases, they can be used to heat the reaction space, for example by providing a gas heater next to or instead of the electrical heater.

During the reaction by removing the hydrogen from the reaction space, the chemical Equilibrium on the side of the reaction products, d. H. to move to the hydrogen side and to increase the reaction rate, it is advantageous to use the hydrogen-permeable Metal pipes to suck out diffusing hydrogen with a pump. Another way to achieve it the same goal is to keep the total pressure in the reaction space so high that the Partial pressure of hydrogen in the reaction space is greater than 1 atm. This makes it possible that the Hydrogen through the hydrogen permeable

Walls of the pipes diffuses, even if there is atmospheric pressure inside the pipes.

The forced removal of hydrogen during the reaction advantageously achieves that at the same temperature and the same pressure a percentage lower content to be converted Gases in the reaction gases and thus a more complete conversion results, or that during The temperature of the reaction can be lowered if the content to be reacted is the same as a percentage Gases in the reaction gases is allowed. A major advantage of the facility is that that the hydrogen is withdrawn directly from the reaction zone. In addition, the combined generation offers and separation of hydrogen considerable, thanks to the compact and thermally favorable design given advantages.

The advantages of the device according to the invention for generating pure hydrogen can be summarized with the aid of the thermal efficiency. The device is supplied _{with gases with a calorific value of A 1} to be converted per unit of time and per unit of volume. Furthermore, the heat of reaction Q _R and the amount of heat Q _T , which is necessary to maintain the desired temperature, are supplied to the device. The latter amount of heat in the steady state is equal to the amount of heat that is lost to the outside through heat conduction and heat radiation. Finally, let A _{2 be} the calorific value of the hydrogen escaping per unit of time and volume. The thermal efficiency of the device is then given by

^η K + Qr + Qt "

By removing hydrogen from the reaction zone according to the invention, the chemical equilibrium is shifted to the side of the reaction products. If a fixed proportion of the gases to be converted is permitted in the reaction gases, then, as stated, the reaction temperature can be set lower, as a result of which Q _T becomes smaller and thus the efficiency η becomes greater.

By removing hydrogen from the reaction zone according to the invention, the reaction rate is increased, ie A ₁ , A ₂ and Q _R are increased by the same factor, while Q ₇ remains the same. This also increases the efficiency //.

Because of the compact design of the device according to the invention, in which the heat of reaction Q _R and the amount of heat Q _T required to maintain the desired temperature are required in the same place, the surface-to-volume ratio is small. So that too is

Ratio ^ ^r small and thus the efficiency η

OV

Claims (1)

Claim: Device for the production of pure hydrogen by conversion or thermal decomposition from gaseous hydrogen compounds on a hot catalyst to hydrogen and Residual gases and separation of the hydrogen by diffusion, which has two zones, from in which only the first one can be heated from the outside and is filled with a catalyst, in which the latter one on one side closed and connected to a collecting line which passes through the second zone in a gas-tight manner Diffusion body made of hydrogen-permeable material are embedded, and to which one of the second zone coming transfer pipe for the preheated output gases connected in this way is that these flow through the catalyst material, wash around the diffusion body and withdraw through the second zone as residual gas again, being connected to the pipe walls with the output gases passed through this second zone are in indirect heat exchange, characterized in that both zones are separated by a wall and a residual gas discharge pipe from the first zone is gas-tight is led through the second zone to the outside, while this second zone is an open mouth Has feed pipe for the starting gases and the transfer pipe to the catalyst zone in the second zone also opens openly in such a way that the output gases are one in this zone Rinse hydrogen collection and residual gas discharge lines with large surface areas. Considered publications:
U.S. Patents Nos. 1,951,280, 2,516,974,
637 625. 1 sheet of drawings 709 587/524 5. 67 © Bundesdruckerei Berlin