DE858543C - Process for the production of nitrogen oxide-free synthesis gases - Google Patents

Description

(WiGBl. P. 175)

ISSUED DECEMBER 8, 1952

H 5620 IVb I is i

The invention relates to the purification of gases, in particular to the removal of nitrogen oxide from nitrogenous gases. In particular, the invention relates to the manufacture of substantially nitrogen oxide-free synthesis gases for the production of ammonia.

In the manufacture of synthetic ammonia in technology, hydrogen and nitrogen are used usually produced by separate processes, but these gas components can also be used in one Surgery to be obtained. In whatever way the gas components are generated, it is always necessary, the various impurities, such as carbon and sulfur compounds, ζ. Β. To remove carbon dioxide, carbon dioxide, sulfur dioxide and hydrogen sulfide. These well-known Synthesis gas generating processes have given good results, and synthetic ammonia is off this gas has been produced in acceptable yield.

In the production and purification of .Synthesegase and the ammonia obtained therefrom you are encountered difficulties in operation in that small amounts of impurities in the gas mixture attack the equipment. In particular, it has been found that the presence of even very slight Amounts of nitrogen oxide excessive corrosion especially in the compressors, pipes, valves and the like.

So far, the nitrogen oxide has been eliminated by liquefying the synthesis gases with or were subjected without washing the gas components with liquid nitrogen. Yet these procedures are very expensive, as both the facility and

the operating costs are very high. Furthermore, the removal of nitrogen oxide by absorption in Other liquid media considered, however, could be effective or satisfactory means and Paths cannot be found.

The object of the present invention is now to provide synthesis gases for use in the ammonia: - to produce synthesis that is essentially nitrogen oxide-free are.

ίο Another object of the invention is the production of nitrogen, which is essentially free of nitrogen oxide.

Another object of the present invention is the production of gas mixtures which in the contain essential nitrogen oxide-free nitrogen.

Another object of the present invention is the production of a hydrogen-nitrogen mixture, which is essentially free of nitrogen oxide. Another object of the present invention is a process for removing nitrogen oxide from nitrogen.

Another object of the present invention is a method for removing nitrogen oxide. the end Hydrogen-nitrogen mixtures.

Another object of the present invention is a process for the simultaneous production of a Mixture of hydrogen and nitrogen, which is essentially free of nitrogen oxide.

Further objects of the present invention will become apparent from the description given below and emerge from the drawing.

In general, the objects of the present invention are achieved in that the synthesis gases, the contain any, but usually small, amounts of undesirable nitric oxide, with a volume of hydrogen be treated, which is at least equal to the existing nitrogen oxide and preferably is in excess of the latter. The treatment is carried out at elevated temperature and under pressure in Runs in the presence of a catalyst, so that the hydrogen turns the nitrogen oxide into nitrogen and water reduced.

In particular, it has been found that the gas components can be treated at any of the various stages in their manufacture. In nitrogen production z. For example, hydrogen can be added to the nitrogen after and / or during its production in any suitable manner in sufficient quantity that its volume is equal to or greater than that of the nitrogen oxide present, after which the mixture is then passed over a suitable catalyst which Reduction of the NO to N ₂ and water, or nitrogen generated by the combustion of a hydrocarbon with air can be passed directly over a suitable catalyst, the reduction of the NO present by reaction with the small amount of hydrogen generated by the combustion of the hydrocarbon gases. is generated. However, even in the latter case, it has been considered advisable to add hydrogen in order that at least an amount equivalent to that of nitrogen oxide is certain to be present in the gas.

If, for example, synthesis gases are to be produced for the catalysis of ammonia, the NO present in the nitrogen can be removed by the methods described above before mixing with the necessary hydrogen, or all of the _{hydrogen required for NH 3} catalysis can be mixed with the nitrogen and this Mixture can then only be passed through a catalyst, which brings about the reduction of the NO to nitrogen and water.

After the nature and purpose of the present invention has generally been indicated, let us now a more detailed description of a preferred embodiment with reference to the appended Drawing given, which represents a scheme, which the process for the production of an im shows essential nitrogen-oxide-free nitrogen-hydrogen mixture.

It has been found that .. that for the production of the gas components for an ammonia synthesis system, the preferred method is the simultaneous production of nitrogen and hydrogen. Referring to the drawings, this preferred method includes a furnace 14 through which a number of catalyst tubes 15 filled with a catalyst 16 pass. The furnace 14 is equipped with gas burners 17 which are mounted vertically one above the other along the side of the furnace. The furnace and tubes are heated by the gas burners 17, which burners can be regulated so that they produce a flue gas mixture which contains nitrogen, carbon dioxide, a small amount of nitric oxide and usually some O ₂ (1 ° / ₀ to 4 ° / ₀ ) and leaves the oven at 19. The tubes 15 in the furnace are heated to a temperature at which a mixture of natural gas and steam, which is ^{introduced into the collecting tube 20 for example at 20 0} and flows through the raw ice, is converted into hydrogen, carbon dioxide and carbon dioxide by the catalyst 16 or is split. This mixture leaves the apparatus through collecting pipe 21.

The flue gas mixture, which flows out at 19, can be heated by a boiler 22, a cooler 24 and then passed into a compressor 25 where it is brought under sufficient pressure is driven out at 25 ° and pressed into the manifold 20 with the natural gas and steam will. Mixed with the latter, it is then passed through the catalyst tubes 15 into which the reduction of the nitrogen oxide present takes place through the production of hydrogen. The gas mixture flows, as described above and indicated by the arrow at 21 °, out through manifolds 21. It is now a gas mixture which is very suitable for ammonia synthesis. This introduction of the flue gas from the burners of the hydrogen furnace enables the process to be simplified for the production of synthesis gases for an ammonia plant.

In the above procedure, high pressure steam was used to operate the compressor 25. The introduction of the high pressure steam is indicated by the arrow at 25 ^s . Furthermore, the Lower

pressurized steam leaving the compressor 25 at 25 °, used as a source of steam for the can 15 of the furnace 14. But he can also go through with those from 21 Pipe 26 coming gases mixed and used to cool them. This arrangement means a saving for the whole system. The steam for the compressor can be in the exhaust gases heated boiler 22 can be generated, and further steam, as indicated at 37, can be supplied, to be mixed with the natural gas to be introduced into the manifold 20.

The method described above is advantageous because the use of the nitrogen-containing flue gas makes possible a larger excess of steam in the converter and this steam of better Quality, which in turn is due to the further cooling that the Pipes require incoming nitrogen in the system. In reality, the pipes provide a heating device for the nitrogen, which is the use of "first class steam" to cool them down on the CO converter temperature allowed, creating a larger one, very desirable for the conversion Excess steam is generated. Of course, during the production of the hydrogen in the Pipes that reduce NO and thus produce the desired synthesis gas.

In most cases it is desirable to convert the carbon dioxide contained in the hydrogen produced to carbon dioxide before the hydrogen is used in a process such as ammonia synthesis. This can be achieved in that the hydrogen containing the carbon oxide is passed through a CO converter containing a suitable catalyst with an added excess steam. It is known that a substantial excess of steam must be added to obtain an effective implementation, and that the temperature on the vorteilhaftesten point must usually be about 350 to 400 ⁰ maintained. It can happen that a sufficient amount of steam to lower the temperature is much too high to achieve an efficient conversion of the CO and steam to CO ₂ and hydrogen in an economical manner. After the reaction, it is customary to add the nitrogen necessary to maintain the 3: i mixture.

The method described above for generating the starting gases for an ammonia synthesis plant has been cited to apply the improved and novel removal technique of NO from nitrogenous gases. The removal of NO from nitrogenous Gases is for the operation of a plant in which the nitrogen is compressed and / or in a to corrosion tilting apparatus is of great importance. The problem of corrosion is particular Difficult to control in ammonia synthesis as high pressure compressors are used must be and the cylinders, pistons and seals of the same, even if only slightly attacked, present serious operational difficulties. Further corrosion problems occur in the pipelines, through which the nitrogen is passed, and especially in the valves regulating these pipes on.

In the foregoing process, the use of a catalyst has been emphasized as necessary to bring about a practical conversion. The catalyst which has been found suitable and preferred for reducing the NO by H ₂ by the method described here is nickel on a slide support. Other catalysts contemplated by the present invention are supported nickel such as corundum oak, asbestos, pumice stone, aluminum oxide or the like, oxides of iron group metals alone or mixed with aluminum oxide, chromium oxide and the like. It becomes natural in each case the catalyst chosen which is most effective in the operation in question. For example, activated catalysts can be used or prepared with hydraulic cement or catalysts in various shapes, such as tubular, spherical, or conglomerates, etc. Or pre-reduced catalysts can also be used.

Let us now consider the process for the production of essentially nitrogen oxide-free nitrogen according to the invention explained in more detail using the following example.

90 example

According to the arrangement illustrated in the drawing, a nitrogen-hydrogen mixture essentially freed from NO was obtained in that the flue gases, which had previously been used to heat the cans of the hydrogen furnace containing the gs catalyst, were passed down through the cans themselves. According to the method, the flue gases exiting the furnace, which were analyzed to contain between 80 to 100 parts nitrogen oxide per million gas parts, were first passed through a compressor and then returned to the top of the furnace catalyst tubes. After mixing with steam and natural gas, which are to be converted into hydrogen, CO and CO ₂ within the tubes, the entire mixture was at a space velocity of about 400, that is 400 liters of gas per 1 liter of catalyst per hour, and one at the outlet pressed up to about 871 ⁰ increasing temperature by the catalyst contained in the tubes. The catalyst used consisted of nickel on a slide support. The exit gas when analyzed showed a total amount of nitric oxide of less than 1 part per million. This reduction in the nitrogen oxide content prevents corrosion of the equipment and ensures that ammonia synthesis proceeds smoothly.

In the example above, the space velocity has been matched to the working temperature, what is necessary to obtain the most favorable working conditions.

Claims (4)

PATENT CLAIMS: i. Process for the production of nitrogen oxide-free and suitable for ammonia synthesis Synthesis gases, characterized in that a mixture of hydrocarbon gas, water vapor and combustion gases which are the combustion products of hydrocarbon gas and air and are rich in nitrogen, but contain nitric oxide, through a catalyst layer underneath such temperature and pressure conditions is passed that the nitrogen oxide contained in the gases reduced by means of the hydrogen originally present or simultaneously generated therein will. 2. The method according to claim i, characterized by carrying out the reduction in the in the catalyst layer arranged in the combustion zone under the action of the combustion gases developed heat in this zone. 3. The method according to claim 1 or 2, characterized in that the combustion of Hydrocarbon gas and air produced in a furnace are compressed and flue gases Hydrocarbon gases and steam are added to these compressed flue gases and that the gas mixture is then passed through a catalyst in an array of tubes contained in this furnace and caused by the combustion of the hydrocarbon-air mixture generated heat is heated in such a way that gases with a high hydrogen and nitrogen content, but free of nitrogen oxide. 4. The method according to claim 1, 2 or 3, characterized in that the catalyst from Nickel is made on a carrier material. 1 sheet of drawings © 5551 11.52