WO2018166865A1

WO2018166865A1 - Method and installation for creating and preparing a synthesis gas mixture

Info

Publication number: WO2018166865A1
Application number: PCT/EP2018/055612
Authority: WO
Inventors: Evgeni Gorval
Original assignee: Thyssenkrupp Industrial Solutions Ag; Thyssenkrupp Ag
Priority date: 2017-03-14
Filing date: 2018-03-07
Publication date: 2018-09-20
Also published as: DE102017204208A1; EA201992148A1

Abstract

The present invention relates to a method for creating and preparing a synthesis gas mixture for preparing ammonia, in which a starting gas mixture containing hydrocarbons and vapour is converted to a raw synthesis gas mixture in an autothermic reformer (49) by means of oxygen. After further preparation, said raw synthesis gas mixture is fed to at least one ammonia synthesis (15, 45), wherein only a partial flow (48) of the starting gas mixture is fed to the autothermic reformer (49), while a further partial flow (32) of the starting gas mixture is fed to a primary reformer (33) and then to the secondary reformer (20), and the gas mixture created in these primary and secondary reformers is, after further preparation as appropriate, also fed to an ammonia synthesis (15, 45), wherein the synthesis gas mixture (44) is brought to a higher pressure, which corresponds to the ammonia synthesis pressure, wherein only after the increase in pressure is further nitrogen fed to the synthesis gas mixture from at least one line (14, 57) before the synthesis gas mixture is fed to the ammonia synthesis. One advantage of this method is that the load on all process units between the secondary reformer and main synthesis, including the process air compressor and synthesis gas compressor, is enormously reduced. Compared to a variant with only one autothermic reformer, one advantage, in addition to other advantages, of the combination according to the invention with the primary reformer is for example that the heat in the flue gas duct of the primary reformer can be utilised.

Description

Process and plant for the production and treatment of a sudese gas mixture

The present invention relates to a process for the production and preparation of a synthesis gas mixture for the production of ammonia, in which a hydrocarbon-containing starting gas mixture is converted in an autothermal reformer (ATR) by means of steam and oxygen in a Rohsynthesegasgemisch, which optionally supplied after further treatment at least one ammonia synthesis reactor is, wherein supplying only a partial stream of the starting gas mixture to the autothermal reformer, while supplying a further partial stream of the starting gas mixture to a primary reformer and the gas mixture produced there, optionally after further, known per se, treatment steps also supplies a Ammoniaksynthesereaktor.

In the case of existing ammonia plants, there are bottlenecks in the area of various plant components which prevent a desired increase in capacity. These are in particular the primary reformer, the secondary reformer, the process air compressor, the CGyWäsche, the synthesis gas compressor and the ammonia synthesis reactor. The circumvention of these bottlenecks requires expensive measures. There are different concepts from different providers for the economic transformation and renewal of existing plants (so-called "revamp").

From DE 100 55 818 Al a process for the catalytic production of ammonia from a nitrogen-hydrogen mixture is known in which natural gas passes together with an oxygen-rich gas in an autothermal reformer, where at temperatures in the range of 900 ° C to 1200 ° C, a pressure of 40 to 100 bar and in the presence of a cracking catalyst produces a crude synthesis gas, wherein this crude synthesis gas is withdrawn from the autothermal reformer, cooled, passes through a catalytic conversion to convert CO to H ₂ and a converted synthesis gas with an H ₂ content of at least 55 vol.% and a CO content of at most 8 vol.%, whereby the converted synthesis gas is subjected to a multistage gas purification to remove CO ₂ , CO and CH ₄ and an N ₂ Generates H ₂ mixture, which is fed to an ammonia synthesis for the catalytic production of ammonia. In this known method, only an autothermal reformer is provided for reforming and the ammonia synthesis takes place at only one pressure level. The liquid nitrogen is also used after the air separation plant before the synthesis gas compressor for nitrogen scrubbing, with all inert (argon and methane) and all 0 ₂ -containing components (CO, C0 ₂ , H ₂ 0) are washed out and with the necessary ratio H ₂ : N _{2 is set} equal to 3: 1. The fresh make-up gas prior to synthesis thus contains only N ₂ and H ₂ . EP 1339641 B1 describes a process for the synthesis of ammonia at two pressure levels. Here, the production of ammonia from fresh synthesis gas, which contains in addition to the reactants hydrogen and nitrogen inert constituents, successively in different synthesis systems, wherein produced in all synthesis systems in each case from a portion of the synthesis gas ammonia and a part thereof is discharged and each subsequent synthesis system a higher Pressure than the previous synthesis system.

In WO 2016/198487 AI also a multi-pressure process for the production of ammonia is described in which a starting gas mixture comprising hydrogen, nitrogen, water, methane, optionally argon, carbon monoxide and carbon dioxide is prepared by reforming hydrocarbons, wherein the reforming in an autothermal reformer takes place, which is operated with pure oxygen or with oxygen-enriched air or with air.

The document EP 0 522 744 A2 discloses a process for the production and preparation of a synthesis gas mixture having the features mentioned in the introduction. In this known method, the conversion of a first partial stream of the starting gas mixture takes place in a primary reformer and a downstream secondary reformer, while a second partial stream of the starting gas mixture is first processed in a Vorreformer and then in an autothermal reformer. Thereafter, both partial streams are combined with each other and it then follows the addition of a nitrogen-containing stream with the gas mixture further nitrogen is supplied. However, this nitrogen-containing stream is a circulating gas, which is recycled from the ammonia synthesis after removal of a product stream and which consequently contains only a smaller proportion of nitrogen and also a larger proportion of hydrogen and carbon monoxide, carbon dioxide and optionally methane. Only after this addition of the recycle gas is an increase in pressure before the synthesis gas is fed to an ammonia synthesis.

Another method for the production and preparation of a synthesis gas mixture for the production of ammonia is known from US 2011/0297886 AI. In this known method, a natural gas is divided into two partial streams, wherein the first partial stream is fed to an autothermal reformer, which is supplied with an oxygen-enriched stream from an air separation plant. The second partial flow is fed to a primary steam reformer, which, however, is not followed by a secondary reformer. Both partial streams are combined after the primary reformer and then further processed by a CO shift and a pressure swing adsorption and then the treated gas mixture further nitrogen from the air separation plant is supplied. This synthesis gas mixture is fed to an ammonia synthesis reactor. A pressure increase of the gas mixture is not described in this document. The lack of a secondary reformer after the primary reformer has the disadvantage in this known method that the entire nitrogen required for ammonia production must be produced in the air separation plant. The object of the present invention is to provide a process for the production and preparation of a synthesis gas mixture for the production of ammonia having the features of the aforementioned type, which allows an increase in capacity of an ammonia plant bypassing or significantly weakening the abovementioned bottlenecks ,

Another concern of the present invention is to efficiently integrate an air separation plant into the revamping operations of an existing ammonia plant.

The solution of the aforementioned object provides a process for the production and preparation of a synthesis gas mixture for the production of ammonia of the type mentioned above with the features of claim 1.

According to the invention, the synthesis gas mixture is brought to an elevated pressure which corresponds to the ammonia synthesis pressure and only after the pressure increase the synthesis gas mixture from at least one line further nitrogen before the synthesis gas mixture enters a one- or multi-stage ammonia synthesis.

The solution according to the invention has the advantage over the known processes that the expensive synthesis gas compressor is thereby relieved.

If it is mentioned in the present application that the synthesis gas mixture after the pressure increase "additional" nitrogen, then it is meant that it is preferably a supply of nitrogen in the form of fresh gas from outside the plant and not in shape If one adds to the "make-up" gas a recycle gas, which is recirculated from the reactor, this contains nitrogen, but also other constituents such as, inter alia, hydrogen, wherein the exact composition of the circulating gas would probably have to be determined analytically, so that the addition of circulating gas is unsuitable to set a targeted for the ammonia synthesis stoichiometric ratio of hydrogen to nitrogen of 3: 1 targeted. Further nitrogen from "outside the plant" thus means in this context that this nitrogen originates from outside the actual plant for the production of ammonia and thus not from the recycle gas.If this nitrogen is produced for example in an air separation plant, this air separation plant can of course be installed on the be positioned in the same area as the plant for the production of ammonia This variant is therefore encompassed by the invention.

Preferably, according to a development of the process according to the invention, further nitrogen is carried out with a purity of at least 60%, preferably with a purity of at least 80 %, more preferably with a purity of at least 90%, particularly preferably with a purity of at least 95% after the pressure increase of the synthesis gas mixture.

Preferably, a first partial stream fed to the primary reformer is branched off from a line containing the hydrocarbons and steam and leads the remaining partial stream of this gas mixture to the autothermal reformer.

Preferably, in the variant using a primary reformer, the gas mixture leaving the primary reformer is fed to a secondary reformer.

In this preferred variant of the method according to the invention, a primary reformer and a secondary reformer are thus provided in addition to the autothermal reformer. The secondary reformer can be operated, for example, with enriched air. The use of the secondary reformer has the advantage, in comparison to the method known from US 2011/0297886 AI, that not all the nitrogen required for ammonia production has to be produced in an air separation plant. Rather, in this preferred variant of the present invention, the preferably significantly larger part of the nitrogen is obtained by supplying the process air to the secondary reformer, in which the oxygen contained in the air reacts with additional methane from the starting gas mixture, while the nitrogen contained in the process air subsequently available for ammonia synthesis.

According to a preferred development of the invention, the crude synthesis gas stream treated in the autothermal reformer and the crude synthesis gas stream treated in the primary reformer are combined, and then a combined treatment of these gas streams takes place before they are fed to an ammonia synthesis reactor. The combining is preferably carried out before the CO conversion, more preferably before the cooling section, i. immediately after leaving the ATR and from the secondary reformer.

According to a preferred embodiment of the invention, the joint preparation of these gas streams comprises at least one step in which a CO conversion and / or a CGyWäsche and / or a methanation take place.

If the production of ammonia is a so-called multi-pressure process, then according to a preferred development of the invention, the treated synthesis gas stream is fed to at least one synthesis gas compressor where it is compressed to an increased pressure Pi, which is higher than the initial pressure, then to a first synthesis unit ("Once "Through" or "GT 'ammonia synthesis, usually comprising a gas preheating, an ammonia converter (this optionally comprising a plurality of catalyst beds with a gas intermediate cooling), a gas cooling, an ammonia condensation and an ammonia deposition), wherein the Gas stream is compressed after the ammonia deposition in the multi-pressure process by means of a further compression stage or another synthesis gas compressor to a pressure p ₂ , which is higher than the pressure Pi and this gas stream is then a second synthesis unit ("cyclic ammonia synthesis, also usually comprising a gas preheating, an ammonia converter (this comprising optionally a plurality of catalyst beds with a gas intermediate cooling), a gas cooling, a NH ₃ condensation and an ammonia deposition) supplied.

If, however, it is a variant of the ammonia synthesis with only one pressure level, then, according to a preferred embodiment of the invention, the treated synthesis gas stream at least one synthesis gas compressor are fed there compressed to an elevated pressure and then fed to one or more ammonia synthesis reactors.

According to a preferred embodiment of the invention, the synthesis gas mixture brought to an elevated pressure before it is fed to the cyclic ammonia synthesis and / or before it is supplied in the multi-pressure variant of a GT ammonia synthesis, in each case via a line further nitrogen.

According to a development of the invention, it is particularly advantageous if the additional nitrogen introduced is produced in an air separation plant and then liquefied and pumped to the pressure Pi or p ₂ .

The nitrogen flowing through the secondary reformer is added, for example, between a second and a third synthesis gas compressor stage of the GT ammonia synthesis, which can be carried out at a pressure Pi in the order of about 100 bar. By contrast, the nitrogen from the air separation plant is preferably pumped directly to the pressure p _{2 of} the circulatory ammonia synthesis of about 200 bar and is thus guided past the synthesis gas compressor. However, some of the nitrogen from the air separation plant can be added to the OT ammonia synthesis to increase the ammonia yield. Preferably, unlike in the prior art according to DE 100 55 818 Al methane is not removed in the gas cleaning, but it even creates additional methane in the methanation unit. The fresh gas before the ammonia synthesis thus contains, besides nitrogen and hydrogen, also the argon and methane gases, which are inert in relation to the ammonia synthesis, and possibly helium.

An existing air separation plant is preferably modernized so far that the products 0 ₂ and N _{2 are} almost pure and in liquid form, the argon is preferably separated.

According to the invention, an autothermal reformer is provided in parallel with the existing primary reformer and optionally secondary reformer, preferably with pure oxygen from the Air separation plant can be operated. The liquid oxygen is pumped to the working pressure of the autothermal reformer, for example, about 40 bar and then evaporated, the cold of the liquid oxygen is used.

The starting gas mixture, for example natural gas, is usually mixed with steam before it is introduced into the autothermal reformer or primary reformer. Since both an autothermal reformer and a primary reformer are used in the process of the present invention, the natural gas-steam mixture for the autothermal reformer may advantageously be diverted from the main stream directed into the primary reformer only before the primary reformer. In this way, one obtains two piping systems, each with at least one reformer, in which the reforming process takes place in parallel and you can use the previously generated natural gas-steam mixture in both parallel piping systems. It is advantageous to bring both Rohsynthesegasstrom after reforming in the autothermal reformer or in the primary reformer and secondary reformer together again and then process together in further process steps. This treatment can comprise, for example, CO conversion and / or CO ₂ scrubbing and / or methanation.

The liquid nitrogen from the air separation plant is preferably pumped to the final synthesis pressure of, for example, about 200 bar and mixed with the fresh gas only after the synthesis gas compressor. The cold of the supercritical nitrogen can be used.

Part of the ammonia can be formed by the OT ammonia synthesis between the compression stages of a syngas compressor (typically between the second and third stages). Optionally, a portion of the nitrogen from the air separation plant after the second compression stage of the synthesis gas compressor is added to the make-up gas to optimize the gas composition prior to OT ammonia synthesis.

Part of the oxygen is added to the secondary reformer to reduce the residual methane content so that the methane residue after the secondary reformer and after the autothermal reformer is approximately equal. This is advantageous for the economy of the process, since a lower methane residue leads to higher ammonia production.

In the method according to the invention, the distribution of the gas is new compared to the aforementioned known solutions. One advantage is, among other things, the massive relief of all process units between the secondary reformer and the main synthesis, including the process air compressor and the synthesis gas compressor. Compared to a variant with the reforming in only one autothermal reformer, an advantage of the combination according to the invention with the primary reformer is that the heat in the flue gas channel of the primary reformer can be used. Thus, the preheating of the inlet streams for the autothermal reformer in the flue gas channel of the primary reformer is possible.

According to a preferred embodiment of the invention, it is such that the supplied additional nitrogen from the air separation plant brought by at least one pump to the intended ammonia synthesis pressure and then via a line immediately before the circulatory ammonia synthesis or partially before the OT Ammonia synthesis is supplied.

A preferred embodiment of the invention provides that both the autothermal reformer and the secondary reformer oxygen is supplied, which was obtained in an air separation plant.

A preferred embodiment of the invention provides that the secondary reformer process air is supplied, which was preferably previously brought by means of a compressor to an elevated pressure and / or by means of a heat exchanger, preferably in the flue gas duct of the primary reformer, was preheated.

The process air can be additionally mixed with oxygen from outside, which was obtained in an air separation plant, and this oxygen-enriched air can be supplied to the secondary reformer.

The present invention furthermore relates to a process for the production of ammonia, in which the preparation of the ammonia is carried out using a synthesis gas mixture produced and prepared in the manner described above.

According to a preferred embodiment of the invention, a synthesis gas mixture is first generated in this process for the production of ammonia, which contains the gases hydrogen and nitrogen in a ratio H ₂ : N ₂ greater than 3 and this superstoichiometric synthesis gas mixture is then prior to introduction into the ammonia synthesis reactor added more nitrogen. This additional nitrogen was preferably produced in an air separation plant.

In the process according to the invention, the ammonia synthesis can be carried out either at only one pressure level or alternatively it can be a multi-pressure process.

The present invention further relates to a plant for the production and processing of a synthesis gas mixture for the production of ammonia, in which a hydrocarbon-containing starting gas mixture is converted in an autothermal reformer by means of steam and oxygen / air in a Rohsynthesegasgemisch, which supplied after further treatment at least one ammonia synthesis reactor is, according to the invention, this plant in addition to at least one autothermal reformer at least one primary reformer and further comprises at least one secondary reformer downstream of the primary reformer in the flow path.

According to a further preferred development of the system according to the invention, the autothermal reformer and the secondary reformer are arranged in mutually parallel piping systems, wherein the respective output lines of autothermal reformer and secondary reformer lead in a common conduit system for synthesis gas, preferably before the CO conversion tion.

According to a further preferred development of the system according to the invention, this comprises at least one CO conversion and / or at least one CGy wash and / or at least one methanation device, which are arranged in the common synthesis gas line system downstream of autothermal reformer and secondary reformer.

The present invention further relates to a plant for the production of ammonia comprising a plant for the production and processing of a synthesis gas mixture of the type described above, this plant further comprises according to the invention at least one of the autothermal reformer and the primary reformer and optionally the secondary reformer in the flow downstream ammonia synthesis reactor. In particular, in a multi-pressure process, these may also be two or more ammonia synthesis reactors, which operate at different pressures.

Hereinafter, the present invention will be explained in more detail with reference to two embodiments with reference to the accompanying drawings. Showing:

Figure 1 is a simplified schematic flow diagram of a first exemplary system according to the invention;

Figure 2 is a schematically simplified flow diagram of a second exemplary system according to the invention according to an alternative variant of the present invention.

Hereinafter, a first possible embodiment of the present invention will be explained in more detail with reference to FIG. The illustration shows a simplified flow diagram of an exemplary plant according to the invention for the production and preparation of a synthesis gas mixture and for the subsequent production of ammonia from this synthesis gas mixture. In an air separation plant 10 argon is separated and liquid nitrogen from the air separation plant 10 is fed via line 11 to a pump 12 and there brought to a pressure of for example about 200 bar, heated in a heat exchanger 13 and then on the Line 14 fed to the cycle gas before it is fed to a cyclic ammonia synthesis 15.

The liquid oxygen from the air separation plant 10 is fed via the line 16 to a pump 17, brought there to a higher pressure of for example about 40 bar, then evaporated in an evaporator 18 and a part of the gaseous oxygen is then via the line 19 of the process air the line 24 mixed before the enriched air is supplied to a secondary reformer 20.

The system supplied process air is compressed in the process air compressor 21, passes via the line 22 in a device 23 for preheating the process air, where it is heated and is then fed via line 24 to a secondary reformer 20.

The natural gas is supplied via a compressor 25 and the line 26 of the system, then in a heat exchanger 27, preferably in the flue gas duct of the primary reformer, heated to a temperature of, for example, about 380 ° C, desulfurized in a corresponding device 28, then flows through the line 29, where an admixture of steam takes place, then through another heat exchanger 30 in the flue gas duct of the primary reformer, where the gas is heated, for example up to about 480 ° C to 600 ° C and then leaves this heat exchanger 30 via line 31, where then a Dividing the natural gas / steam mixture into two partial streams takes place, of which a partial stream is supplied via the line 32 to the primary reformer 33. In the primary reformer 33, the reaction of the hydrocarbons with the water vapor takes place to form a synthesis gas mixture which contains carbon monoxide and hydrogen as main components.

In steam reforming, methane usually reacts with water vapor in the primary reformer according to the following reaction equations (1) and (3):

CH ₄ + H ₂ O 3 CO + 3 H ₂ (1)

Since no complete conversion of the methane takes place in the primary reformer 33, the crude synthesis gas mixture leaving the primary reformer 33 is fed via the line 34 to the above-described secondary reformer 20, in which by the supply of air or oxygen methane to carbon monoxide and Hydrogen according to the reaction equation (1) and (3) and partially the following reaction equation (2) is reacted.

2 CH ₄ + 0 ₂ ^ 2 CO + 4 H ₂ (2)

The synthesis gas mixture leaving the secondary reformer 20 is then cooled, generating steam, and is supplied via the line 35 to a CO conversion 36. This cooling is called "waste heat recovery" (WHR), in which the gas gives off the heat to water, which then evaporates, so that the gas is cooled and heat is recovered. The so-called CO conversion, also referred to as the water gas shift reaction, is used to reduce the carbon monoxide content in the syngas and generate additional hydrogen. It is an exothermic equilibrium reaction which follows the reaction equation (3) given below:

CO + H ₂ 0 C0 ₂ + H ₂ (3)

Following the CO conversion 36, a C0 ₂ scrubber 37 is provided to remove the C0 ₂ from the synthesis gas mixture.

Following the C0 ₂ scrubbing, the synthesis gas flows through a device for methanation in which carbon monoxide or carbon dioxide react at elevated temperatures according to the reaction equations (4) and (5) reproduced below with hydrogen to give methane and water:

CO + 3 H ₂ -> CH ₄ + H ₂ O (4)

C0 ₂ + 4 H ₂ -> CH ₄ + 2 H ₂ 0 (5)

After methanation, the educt gases hydrogen and nitrogen are present in the generated synthesis gas mixture in a superstoichiometric ratio of more than 3: 1, that is, it contains more hydrogen in the gas mixture relative to nitrogen than is needed for the ammonia synthesis reaction. Via the line 39, the synthesis gas mixture then enters the synthesis gas compressor, where it can operate, for example, with two compression stages 40 and 41 connected in series and an increase in pressure to, for example, 100 bar takes place in two stages. As long as the water content in the fresh gas is too high (water deactivates the catalyst in the ammonia converter), the water is separated after each pressure increase, as exemplified by a device 42 is shown. This can be done both by the condensation and by other methods known in the art. Thereafter, the fresh gas enters the OT (once through) - ammonia synthesis 15, consisting of the gas preheating, an ammonia converter (possibly several catalyst beds with a gas intercooling), a gas cooling, an ammonia condensation and ammonia deposition). After the ammonia separation, the remaining gas mixture is compressed in the two-pressure process shown in FIG. 1 in a further compressor stage 43 to a higher pressure of, for example, about 200 bar, and then via conduit 44 to a second ammonia synthesis , the circuit ammonia synthesis 45 supplied, also consisting of the gas preheating, ammonia converter (several catalyst beds with a gas intercooling), gas cooling, ammonia condensation and ammonia deposition. In this cycle ammonia synthesis, a further ammonia synthesis takes place at a higher pressure level. From the two ammonia syntheses 15 and 45, the ammonia is removed as a product via the lines 46 and 47, respectively. In order to change the ratio of hydrogen to nitrogen in the direction of 3: 1, denn the supplied via the line 39 synthesis gas mixture indeed contains hydrogen in excess, - the fresh gas before the first ammonia synthesis 15, the OT-ammonia synthesis, via the from the line 14 branching branch 57 further nitrogen can be supplied. The remaining nitrogen from the line 14 opens before the second ammonia synthesis, the circulation ammonia synthesis, in the line 44. From the cyclic ammonia synthesis 45, the ammonia is removed as a product via the line 47. So that the methane and argon which are inert for the synthesis of ammonia and, if appropriate, helium do not accumulate in the recycle gas, part of the gas - the so-called purge gas - is removed via line 53 after synthesis 45 and before the admixing of the fresh gas. To compensate for the pressure losses in the synthesis cycle, the gas mixture is fed via line 54 to a further compressor or a further compressor stage 55, in this brought to a required for the reaction of increased pressure and then via the return lines 56, 44 and after the Adding fresh gas and nitrogen from the line 14, the circuit ammonia synthesis 45 supplied so that you can lead unreacted starting materials in the circulation and bring in the ammonia synthesis reactor again to react.

It has already been stated above that only a branched-off first partial flow of the natural gas / vapor mixture is introduced via the branch line 32 into the primary reformer. The second partial stream is fed to the branch 48 via the line 48 an autothermal reformer 49, which oxygen is supplied via a diverted from the line 19 partial flow 19 a. Autothermal reforming is a combination of steam reforming and partial oxidation to optimize efficiency. In this case, a hydrocarbon such as natural gas can be reformed. By combining steam reforming with partial oxidation, the advantage of oxidation, which provides thermal energy, adds to the advantage of steam reforming, which results in higher hydrogen yield. The air and water supply must be precisely metered here. The crude synthesis gas mixture leaving the autothermal reformer 49 via the line 50 then contains approximately the same proportion of residual methane as the synthesis gas mixture leaving the secondary reformer 20 via the line 35. The two gas streams are best after the cooling section before the CO conversion at the branch 51 Vereinen and the combined synthesis gas stream can then be introduced into the CO conversion 36. After the combination, the combined synthesis gas stream from the lines 50 and 35 can thus be further treated together and finally fed to the ammonia syntheses 15 and 45.

The peculiarity of the method according to the invention thus lies in the fact that the process gas stream, that is, the natural gas / steam mixture is divided into two partial streams, of which a partial stream via the branch line 32 for reforming a primary reformer 33 is fed, while the other partial flow over the second branch line 48 is reformed in the autothermal reformer 49, wherein the two partial streams are then reunited after the respective reforming at the branch 51 and thereafter treated together in the further process.

A further advantage of the method according to the invention is that the liquid nitrogen from the air separation plant 10 is pumped to the final synthesis pressure of, for example, about 200 bar (with significantly less energy expenditure compared with the compression of the gaseous nitrogen to the same pressure) and then via the line 14 bypassing the synthesis gas compressor 40 is mixed with fresh gas, which flows through the line 44 for cyclic ammonia synthesis 45, so that the synthesis gas compressor is relieved. The cold of the supercritical nitrogen is used beforehand.

Hereinafter, a second possible embodiment of the present invention will be explained in more detail with reference to FIG. The illustration shows a simplified flow diagram according to a second alternative variant of an exemplary plant according to the invention for the production of ammonia. In this variant, the synthesis of the ammonia takes place at only one pressure level. Large areas of the plant scheme agree with the embodiment previously described with reference to FIG.

In the variant of the system shown in FIG. 2, the system parts designated by the reference numerals 10 to 50, which have already been explained above with reference to FIG. 1, are present in the same form, so that their function will not be described again here, but instead The above comments on Figure 1 reference is made.

As long as the water content in the fresh gas is too high (water deactivates the catalyst in the ammonia converter), the water is separated after each pressure increase, as exemplified by a device 42 is shown. This can be done both by the condensation and by other methods known in the art. In the last compressor stage 43, the fresh gas is compressed to the synthesis pressure of, for example, about 200 bar and then fed via the line 44 of the cyclic ammonia synthesis 45, in which the ammonia synthesis takes place. In order to produce the stoichiometric ratio of hydrogen to nitrogen = 3: 1 necessary for the reaction, since the synthesis gas mixture supplied via the line 52 contains hydrogen in an excess, the gas mixture is supplied via the line 14 prior to the cyclic ammonia synthesis 45 fed additional nitrogen. For this purpose, the nitrogen line 14 opens into the line 44, which leads the synthesis gas mixture. From the cyclic ammonia synthesis 45, the ammonia is removed as a product via line 47. So that the methane and argon which are inert for the ammonia synthesis and, if appropriate, helium do not accumulate in the recycle gas, a portion of the gas - the so-called purge gas - is removed via the line 53 after the synthesis 45 and before the admixing of the fresh gas. In order to compensate for the pressure losses in the synthesis cycle, the gas mixture is fed via line 54 to a further compressor or a further compressor stage 55, in this brought to an elevated pressure required for the reaction and then via the return lines 56, 44 and after the admixing of the fresh gas and the nitrogen from the line 14, the circulation ammonia synthesis 45 is supplied so that you can lead unreacted starting materials in the circulation and bring in the ammonia synthesis reactor again to react. It has already been stated above that only a branched first partial flow of the natural gas / steam mixture is introduced via the branch line 32 into the primary reformer. After the branching off, the second partial stream is fed via the line 48 to an autothermal reformer 49, to which oxygen is supplied via a partial stream diverted from the line 19. The crude synthesis gas mixture leaving the autothermal reformer 49 via the line 50 then contains approximately the same proportion of residual methane as the synthesis gas mixture leaving the secondary reformer 20 via the line 35. The two gas streams are best combined after the cooling section before the CO conversion at the branch 51 and the combined synthesis gas stream can then be introduced into the CO conversion 36. After unification, the combined synthesis gas stream from lines 50 and 35 can thus be further treated together and finally fed to the cyclic ammonia synthesis 45.

The peculiarity of the method according to the invention is thus that the process gas stream, that is, the natural gas / steam mixture is divided into two streams, of which a partial stream via the branch line 32 for reforming a primary reformer 33 and then a secondary reformer is fed during the Other partial flow is reformed via the second branch line 48 in the autothermal reformer 49, wherein the two partial flows are then reunited after the respective reforming at the branch 51 and subsequently treated together in the further process.

A further advantage of the method according to the invention is that the liquid nitrogen from the air separation plant 10 is pumped to the final synthesis pressure of, for example, about 200 bar (with significantly less energy expenditure compared with the compression of the gaseous nitrogen to the same pressure) and then via the line 14 bypassing the synthesis gas compressor 40 is mixed with fresh gas, which flows via the line 44 for cyclic ammonia synthesis 45. The cold of the supercritical nitrogen is used beforehand.

LIST OF REFERENCES

10 air separation plant

11 nitrogen line (liquid)

12 nitrogen pump

13 nitrogen preheating

14 nitrogen line (gaseous)

15 "Once Through" or OT ammonia synthesis, consisting of a gas preheating, ammonia converter (possibly several catalyst beds with a gas intercooling), gas cooling, ammonia condensation and ammonia separation

16 oxygen line (liquid)

17 oxygen pump

18 oxygen evaporator

19 Oxygen line (gaseous) 19a Oxygen partial stream (gaseous)

20 secondary reformers

21 process air compressor

22 line for process air

23 preheating process air

24 line for process air

25 compressor for natural gas

26 pipe for natural gas

27 Preheating natural gas before desulphurisation

28 Desulfurization equipment

29 pipe for natural gas

30 preheating natural gas / steam mixture

31 Pipeline for natural gas / steam

32 branch line for partial flow Primary reformer Partially reformed synthesis gas line after the primary reformer Line for crude synthesis gas after cooling down to secondary reformer CO conversion C0 ₂ scrubber Methanation device Fresh gas line First compression stage of synthesis gas compressor Second stage compression of the synthesis gas compressor Separate water separator Further compressor stage (s) Cond Circulation ammonia synthesis, consisting of gas preheating, ammonia converter (several catalyst beds with gas intercooling), gas cooling, ammonia condensation and separation Conduction for ammonia (liquid) Conduction for ammonia (liquid) Line for second partial stream autothermal reformer Line for crude synthesis gas Combination of crude synthesis gas to secondary reformer and autothermal reformer Purge gas line Return line Compressor (stage) Return line Branch pipe for nitrogen

Claims

claims

1. A process for the production and preparation of a synthesis gas mixture for the production of ammonia, in which a hydrocarbon and vapor-containing starting gas mixture is converted in an autothermal reformer (49) by means of oxygen in a Rohsynthesegasgemisch which at least one ammonia synthesis (15, 45) is supplied in which only one substream (48) of the starting gas mixture is fed to the autothermal reformer (49) while another substream (32) of the starting gas mixture is fed to a primary reformer (33) and the gas mixture produced in the primary reformer is likewise fed to an ammonia synthesis (15, 45), characterized in that bringing the synthesis gas mixture (44) to an elevated pressure, which corresponds to the ammonia synthesis pressure and only after the pressure increase the synthesis gas mixture from at least one line (14, 57) further nitrogen before the synthesis gas mixture in a single or multi-stage Ammonia synthesis gela depends.

2. Method according to claim 1, characterized in that the gas mixture produced in the primary reformer (33) is subsequently fed to a secondary reformer (20).

3. The method according to any one of claims 1 or 2, characterized in that one feeds the additional nitrogen as a fresh gas from outside the plant and not in the form of a circulating gas.

4. The method according to any one of claims 1 to 3, characterized in that further nitrogen having a purity of at least 60%, preferably with a purity of at least 80%, more preferably with a purity of at least 90%, more preferably with a purity of at least 95% feeds.

5. The method according to any one of claims 1 to 4, characterized in that a first, the primary reformer (33) and optionally then the secondary reformer (20) supplied partial stream (32) from a gas mixture containing the hydrocarbons and steam containing line (31) branches off and the remaining portion (48) of this gas mixture to the autothermal reformer (49) supplies.

6. The method according to any one of claims 1 to 5, characterized in that the ammonia synthesis (15, 45) comprises a gas preheating before the reaction in an ammonia converter, and a subsequent gas cooling, an ammonia condensation and an ammonia separation.

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7. The method according to claim 6, characterized in that the ammonia synthesis takes place in an ammonia converter with a plurality of catalyst beds, wherein a gas intermediate cooling is provided.

8. The method according to any one of claims 2 to 7, characterized in that one combines in the autothermal reformer (49) treated Rohsynthesegasstrom (50) and in the secondary reformer (20) treated Rohsynthesegasstrom (35) and then a common treatment of these gas streams takes place before they are fed to an ammonia synthesis (15, 45).

9. The method according to claim 8, characterized in that the combined treatment of these gas streams comprises at least one step in which a CO conversion (36) and / or a CGyWäsche (37) and / or a methanation (38).

10. The method according to any one of claims 8 or 9, characterized in that the processed synthesis gas stream at least one synthesis gas compressor (40, 41) is supplied there is compressed to an elevated pressure Pi, which is higher than the outlet pressure, then a first ammonia synthesis (15), preferably comprising a gas preheating, an ammonia converter, optionally with a plurality of catalyst beds and with a gas intermediate cooling, a gas cooling, an ammonia condensation and an ammonia deposition, wherein then the Ammonia synthesis (15) leaving product gas mixture is compressed by means of at least one further compression stage (43) to a pressure p ₂ , which is higher than the pressure Pi and this gas stream (44) after admixing the nitrogen from the line (14) then a second ammonia synthesis (45), also preferably comprising a gas preheating, an ammonia converter, optionally with meh Reren catalyst beds and with a gas intercooling, a gas cooling, ammonia condensation and ammonia deposition, is supplied.

11. The method according to any one of claims 1 to 10, characterized in that the supplied additional nitrogen in an air separation plant (10) was generated.

12. The method according to claim 11, characterized in that the supplied additional nitrogen from the air separation plant (10) by means of at least one compressor or a pump (12) brought to the intended ammonia synthesis pressure and then via a line (14) or 57 the Gas mixture immediately before the ammonia synthesis (45) or in each case before the ammonia synthesis (15, 45) is supplied.

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13. The method according to any one of claims 2 to 12, comprising, characterized in that both the autothermal reformer (49) and the secondary reformer (20) oxygen is supplied, which was obtained in an air separation plant (10).

14. The method according to any one of claims 2 to 13, characterized in that the

Secondary reformer (20) process air is supplied, which was previously brought by means of a compressor (21) to an elevated pressure which is higher than the outlet pressure and which has been preheated by means of at least one heat exchanger (23).

15. A process for the production of ammonia, characterized in that the preparation of the ammonia is carried out using a synthesis gas mixture produced and treated by a process according to any one of claims 1 to 14.

16. A process for the production of ammonia according to claim 15, characterized in that in this a synthesis gas mixture is produced which contains the gases hydrogen and nitrogen in a ratio H ₂ : N ₂ of greater than 3 and this superstoichiometric synthesis gas mixture either after at least one compression stage a synthesis gas compressor (40, 41), or if it has almost synthesis pressure, before the introduction into the ammonia synthesis, further nitrogen is mixed.

17. A process for the production of ammonia according to any one of claims 15 or 16, characterized in that in this process the ammonia synthesis is carried out at only one pressure level.

18. The method according to any one of claims 15 or 16, characterized in that the

Ammonia synthesis is carried out at two or more pressure levels.

19. Plant for the production and preparation of a synthesis gas mixture for the production of

Ammonia, wherein a starting gas mixture containing hydrocarbons and steam in an autothermal reformer (49) is converted by means of oxygen into a Rohsynthesegasgemisch, which after further processing at least one ammonia synthesis (15, 45), preferably for carrying out a method according to one of the claims 1 to 14, characterized in that the system in addition to at least one autothermal reformer (49) at least one primary reformer (33) u sowieweiterhin at least one primary reformer (33) downstream in the flow secondary reformer (20).

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20. Plant according to claim 19, characterized in that the autothermal reformer (49) and the secondary reformer (20) are arranged in mutually parallel conduit systems, wherein the respective output lines of autothermal reformer and secondary reformer lead in a common conduit system for synthesis gas.

21. Installation according to one of claims 19 or 20, characterized in that it comprises at least one CO conversion (36) and / or at least one C0 ₂ scrubbing (37) and / or at least one means for methanation (38), which in the common synthesis gas manifold downstream of autothermal reformer (49) and secondary reformer (20).

22. A plant for the production of ammonia comprising a plant for the production and processing of a synthesis gas mixture according to one of claims 19 to 21, characterized in that it further comprises at least one of the autothermal reformer (49) and the primary reformer (33) and the secondary reformer (20) in the flow path downstream ammonia synthesis (15, 45), each preferably comprising a gas preheating, at least one ammonia converter with one or more catalyst beds, optionally with a gas intermediate cooling, a gas cooling, an ammonia condensation and a ammonia deposition.

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