MXPA97004714A - Process for the obtaining of carbon monoxide and hidrog - Google Patents

Abstract

The present invention is directed to a process for simultaneously obtaining pure carbon monoxide and pure hydrogen in a steam converting plant for the generation of hydrogen or ammonia, having a primary converter, a secondary converter and downstream thereof, a step of CO conversion. A partial gas stream from the synthesis gas stream, which is discharged from the secondary converter having a CO content between 2 and 20 mol% and is at a temperature of 200 to 500 ° C and at a pressure between 15 and 50 bar, it is removed between the secondary converter and the CO conversion stage. The partial gas stream is then cooled to a temperature below 100 ° C, whereby most of the vapor contained in the gas stream is condensed. The remaining crude synthesis gas stream is then guided by means of a multi-stage gas separation plant in which the gaseous components H, residual steam, CH4, CO2 and optionally N2 are separated, either individually or together, of CO The separated gaseous components are then compressed to a pressure that exceeds the pressure in the CO conversion stage, and are recombined to form a mixed gaseous stream. The mixed gaseous stream is then guided to the CO conversion stage of the steam converter, after being heated to a temperature ranging from 200 to 500 ° C. The remaining pure CO fraction is removed in a separate manner, and can optionally be supplied for the added procedure

Description

PROCESS FOR THE OBTAINING OF CARBON MONOXIDE AND HYDROGEN FIELD OF THE INVENTION The invention is based on a process for simultaneously obtaining pure carbon monoxide and hydrogen, by further processing a synthesis gas stream comprising the gaseous components H2, water vapor, CH4, C02, CO and optionally, N2. The present invention results in the use of pure CO, in particular, as a basic material for the synthesis in the production of isocyanate, ethanoic acid or methyl methacrylate.

BACKGROUND OF THE INVENTION There are a number of processes that generate synthesis gases (CO / H2 mixtures) of varying composition from fossil raw materials, for example, for the synthesis of methanol or ammonia. When natural gas is the raw material used, steam reforming is the most widely used process. This process is used at particularly high capacities to supply synthesis gas for the REF: 24863 ammonia plants. Ammonia or natural gas plants provide the highest proportion of ammonia capacity worldwide. The effective synthesis of ammonia at high pressure, requires, as a feed gas, a mixture of N2 / H2 adjusted to be virtually stoichiometric (1: 3). An ammonia synthesis plant is generally closely related, in terms of raw materials and energy, with the upstream converting steam, which must produce exclusively a synthesis gas rich in hydrogen having a corresponding stoichiometric nitrogen content . The entire process is geared toward this goal. The carbon oxides (CO, C02), which are of necessity, present in various stages of the converter process, as a result of the use of natural gas, effectively represent incidental constituents which are undesirable in terms of the objective of the process. The existence of such undesired constituents is remedied in that the CO, which is present in the crude synthesis gas after the reforming process, is catalytically reacted with steam to form H2 in conversion at high temperature and low temperature. As a result, in terms of the objective of the process, the CO is finally reused in the production of hydrogen or ammonia. The C02, which is produced, is a by-product of low energy (low value). Some of the C02 can often be sold as a product, but it generates less market value, which is generally limited regionally, for example, to the beverage industry. The situation is favorable in the sites of the ammonia synthesis plant, where the urea synthesis plants which use C02 as a raw material are also operating. However, in most sites of ammonia plants, considerable proportions of C02 are generally discharged into the atmosphere as surplus, thus adding to environmental pollution. Because ammonia plants are operated economically only at high tonnages, the emission of increasingly large volumes of C02 may result, depending on the plant. In contrast to other gas generation processes based on natural gas, the secondary converter in the ammonia vapor converters is ignited directly with air for combustion, where the nitrogen contained in the air is introduced simultaneously into the gas of synthesis to be produced, the synthesis component for the synthesis of ammonia. In the chemical industry, pure CO is required for the production of ethanoic acid, methyl methacrylates and isocyanates, etc., where compliance with its hydrogen and hydrocarbon contents with the defined specifications is a requirement. A number of processes are known for the production of CO, being its basic structure, for economic reasons, specifically oriented towards CO generation only. In this way, for example, converters can be used, which, in the conversion stage, work towards obtaining the desired CO by means of a proportion of CO / H2, which is adjusted higher, for example, by means of of partial oxidation of natural gas with oxygen. When natural gas undergoes partial oxidation, no steam is used, thus, the amount of hydrogen imported into the synthesis gas is lower when it is used in the ammonia vapor converter. Such a process is described in Berninger (Berninger, R., "Advances in Low-Temperature H2 / C0 Separation", Linde Reports from Techni und issenschaft, 62/88). In this process, natural gas is converted by partial oxidation with oxygen to a CO / H2 / C02 / vapor mixture, relatively rich in CO, from which C02 and steam are subsequently removed in an absorber station. The required purity of hydrogen is 98%. The CO contained in hydrogen is condensed in two stages, by applying low temperatures. Alternatively, the gas separation could be carried out by means of membrane technology or PSA technology (= pressure swing adsorption). The important factor, in order to make possible the use of the technology described, is that nitrogen is not present in the synthesis gas to be separated. An additional process described in Berninger works with a C02 converter, where the natural gas is reacted with C02 instead of with steam, resulting in a synthesis gas richer in carbon (rich in CO). Also, in such processes, by returning C02 from the process steps, which are installed downstream inside the partial oxidation reactor, the proportion of carbon or CO in the product from the partial oxidation reactor is increased, with You aim to obtain as rich a product as possible in CO for the subsequent separation of the gas.

Depending on the hydrogen required in addition to the CO, which will be produced in the relevant site, it is possible, using the technologies described, to adjust the hydrogen / CO ratio in the synthesis gas within certain limits. However, hydrogen always arises in the production of CO, and it must also be frequently discharged into the atmosphere or it can only be used as a combustible gas and not as a raw material. If the pure hydrogen is also to be obtained in addition to the pure CO, it is necessary, for physical reasons, to install a downstream H2 purification fitting, for example using a PSA plant. In Tindall (Tindall, Cre s, "Alternative Technologies to Steam-Methane Reforming", Hydrocarbon Processing, Nov. 1995. P. 75, et seq.), Other alternative processes are described for steam conversion, which have the objective of produce H2 / CO, steam-methane conversion (SMR), optionally combined with a secondary stage of oxygen conversion (SMR / 02R), autothermal conversion (ATR) and thermal partial oxidation (POX). These processes differ in the type of feed gas and the use or lack of use of a catalyst, for example POX, which works without a catalyst. The common characteristic for all processes is that they are capable of generating hydrogen and also CO in the form of a mixture or separately, with the proviso that corresponding gas separation processes are installed downstream. When it is desired to produce CO only, the disadvantages of all these processes is that only a certain proportion of CO / H2 can be adjusted. When CO is produced by itself, a standard reaction for hydrogen always occurs. In addition, a separate simple stage or multi-stage converter is required. The proportion of H2 / CO, which is obtainable and is determined by the process, is as follows for the processes mentioned above: SMR: 3-5; SMR / 02R: 2.5 - 4; ATR: 1.6 - 2.65; POX: 1.6 - 1.8. When the subsequent separation of the gas is carried out, directed towards the CO as the desired product, a hydrogen-rich fraction of generally lower quality always emerges concomitantly. A further disadvantage of the processes that have H2 / C0 ratios in the synthesis gas, which are themselves favorable in terms of CO generation, is that the oxygen, which is expensive, must be used as an oxidant. The POX process, which has the most favorable H2 / CO ratio in terms of CO generation, has the additional disadvantage that soot occurs due to the high partial oxidation temperatures of the natural gas / oxygen mixture, and this reduces the carbon yield, calculated on the natural gas used. The CO / H2 ratio of the synthesis gas from the converter plant can also be displaced in the direction of the CO by recycling C02 from the plant, inside the converter or using C02 imported into the converter. However, due to the reaction equilibrium in the converter, there always remains a hydrogen-rich fraction corresponding to imported C02, which is per se undesirable, and reduces the utilization ratio of natural gas raw material used as feedstock. In US Patent No. 4,836,833, a process is described for the separation of a synthesis gas derived from a converter, in which the two objective components, CO and H2, are separated through semipermeable membranes and a PSA plant. This generates a hydrogen fraction at 99 mol% hydrogen. The CO current generated simultaneously is only 85% pure mol. The process has the disadvantage that the purity of the CO is inadequate for many chemical processes (eg isocyanate production), thus necessitating the installation of an additional stage of downstream preparation for the fraction of 0. In addition, the CO can never be generated as the only product. In European Patent EP 291,857, a process for producing carbon monoxide is described in which C02 and H2 are returned to a reverse gas water conversion reaction, with integrated heat, in which additional carbon monoxide is general. US Patent No. 5,102,645 describes a CO generation process in which a more highly concentrated fraction of CO is generated from a converter, in which a more effective separation of the gas is carried out. The converter comprises a primary and a secondary converter. C02 imported and recycled is passed through the hydrocarbon feed to the primary converter. This primary reaction product is then fed together with the oxygen to a secondary converter, with a fraction of carbon monoxide that is generated in a secondary autothermal reaction. This fraction has a lower hydrocarbon concentration than that discharged from the primary converter. The gas, which is returned from the secondary converter, has a high CO content, such that the subsequent gas separation at low temperature is capable of generating a highly pure fraction of CO at a lower cost. Such interventions, in particular, the recycling of C02 in a conventional ammonia plant, go against the primary objective of generating a fraction of synthesis gas rich in hydrogen, and run the risk of compromising the operation of the ammonia plant. All the described processes interfere in some way with the operation of the converter, such that the continuous operation, which is free of interruption, is no longer possible under the original operating conditions. In Lembeck (Lembeck, M., "The Linde Am onia Concept (LAC)", Linde Reports from Technik und Wissenschaft; 72/1994), an alternative concept for the generation of ammonia is described, which differs from the classical ammonia plant. In particular, a secondary converter, directly ignited with natural gas and air for combustion is supplied and the necessary nitrogen, which is produced separately in an air separation plant and then mixed inside the converter plant for ammonia synthesis, is they operate completely for the generation of hydrogen. In this new concept of ammonia no CO generation is provided, abandoning the generation of pure CO. In German Patent DE 4,236,263, a process for the generation of a high purity hydrogen stream, and a high purity CO stream from a synthesis gas derived from a steam converter is described. The crucial point of this process is the generation of a high purity hydrogen fraction in a PSA plant, downstream of the steam converter, where the exhaust gas stream from the PSA plant is further compressed and is supplied to a membrane separation plant in multiple stages where a pure CO gas stream is obtained. The disadvantages of the process are that the synthesis gas stream to be processed must not contain nitrogen (as in the ammonia plant). A further crucial disadvantage in terms of the generation of high purity CO, is that the pure CO discharged from the membrane separation plant contains virtually all the methane, which is not acceptable, for example, for the production of isocyanate. In order to use such a gas for the production of isocyanate, for example, it is necessary to install an additional, expensive purification step (for example, an additional converter step) in order to bring the concentration of CH4 with the CO to the required specification values of < 50 ppm of the CH4 content. In addition, this process, like all the other processes described, requires the use of a separate converter for the production of CO, and produces a fraction of hydrogen for which a use must be found, when the objective of the process is the generation of CO only. In addition, coke gasification plants are known for the production of pure CO, and these are capable of generating a very pure CO virtually free of hydrogen, with low methane content, through the gasification of coke with C02 and oxygen. These processes, however, have the disadvantage of representing obsolete technology with a high level of handling of solid materials, high costs and manual labor with potentially considerable work difficulties. In addition, oxygen is needed for gasification. A common characteristic for all processes for obtaining pure CO through conversion, partial oxidation with subsequent gas separation (by PSA, low temperature separation, adsorption, etc.), is the orientation of the primary process specifically towards the requirements of the generation of CO and the need for a separating converter plant, to obtain CO, and in addition, the tolerance only of low nitrogen contents, which are derived from natural gas. Hydrogen of generally lower purity inevitably arises - and this can not be prevented from a point of view of the requirement for CO alone - and in most cases can be used only for energy or must even be discharged into the atmosphere. Most of the chemical manufacturing sites, however, already have in their waste electrolysis of NaCl or HCl that supply hydrogen of sufficiently high quality for the hydrogenation. A further disadvantage of the described process is that, without the installation of additional purification steps of fine materials, the generation of pure CO, with the aid of gas separation, is at the expense of the purity of the separated hydrogen such, that using such separation of gas of the prior art, the generation of pure CO and pure hydrogen in parallel, is either impossible or is possible only at a great expense.

BRIEF DESCRIPTION OF THE INVENTION The present invention is directed to a process for simultaneously obtaining pure carbon monoxide and hydrogen by further processing a stream of synthesis gas comprising the gaseous components H2, water vapor, CH4, C02, CO and optionally, N2. In particular, the process of the present invention comprises a process wherein the steps are: a) the elimination between the secondary converter and the stage of conversion of CO, of a partial gas stream of said synthesis gas stream discharged from the secondary converter, which has a CO content of between 2 and 20 mol%, preferably between 5 and 10 mol%, and is at a temperature of 200 to 500 ° C, and at a pressure in the range of 15 to 50 bar, in a steam converting plant for the generation of hydrogen or ammonia, having a primary converter, a secondary coverter and downstream thereof, a stage of CO conversion; b) cooling said partial gas stream to a temperature below 100 ° C, whereby the main part of the vapor contained in said partial gas stream is condensed, resulting in a stream of crude synthesis gas; c) guiding said raw synthesis gas, remaining by means of a multi-stage gas separation plant in which the gaseous H2, waste water, CH4, C02 and optionally N2 components are separated, either individually or together, of the CO; d) the compression of the gaseous components H2, CH4 and optionally N2 from CO, which are separated from the CO, by compressing the gaseous components at a pressure that exceeds the pressure in the CO conversion stage, and are recombined to form a mixed gaseous stream; e) heating said mixed gaseous stream at a temperature of 200 to 500 ° C and supplying said mixed gas stream to the conversion stage of CO of the steam converting plant; and f) the removal of the fraction of pure CO, remaining, in a separate and optionally, supplying said pure remaining fraction of CO for further processing. "Steam converter" in this context is understood to be a plant for the generation of ammonia synthesis gas, or hydrogen, which comprises at least one primary converter, a secondary converter and a CO conversion stage. Therefore, in the process according to the present invention, the CH4 converter of an ammonia plant or of a different steam converting plant, which is mainly oriented towards obtaining hydrogen, is co-used for the obtaining CO, such that a simultaneous generation of CO and hydrogen is conducted in the steam converting plant, without deteriorating the process of generation of ammonia or hydrogen, and no separate converter or other plant should be installed, and used for the obtaining pure CO The object of the invention is therefore to develop a process for the simultaneous and separate acquisition of pure carbon monoxide, without unavoidable hydrogen impurities arising and hydrogen, which has low capital and operating costs. In addition, the process shows an extremely low use of raw material at a high rate of raw material utilization, in terms of natural gas feedstock, calculated on the two target products, CO and hydrogen, and has considerably less impact environmental than the known processes. In addition, the process must adjust the balance of the raw materials of the typical manufacturing sites of chemical products.

DESCRIPTION OF THE DRAWINGS Figure 1 shows a schematic flow diagram of a plant for carrying out the process according to the present invention, which has a conventional steam converting plant, for the generation of ammonia in a main stream, and a CO preparation and separation plant operated in the collateral stream, with the return of the hydrogen-rich waste gases to the main stream, Figure 2 shows a flow chart with a detailed section of the steam converter plant and the parts of the plant for preparing and separating CO of the present invention, which branches off thereof.

DETAILED DESCRIPTION OF THE INVENTION The process according to the present invention covers the following more detailed process steps: a) the partial gas stream cooled below 100 ° C is supplied to a C02 separation stage b) the partial gas stream from from which the CO2 has been removed is guided through a hydrogen separation step in which one or a plurality of hydrogen-rich gas fractions or fractions is / are separated; c) the partial gas stream remaining downstream of the hydrogen separation step is then purified from the traces of C02 and water; d) the partial gas stream from which traces of C02 and water have been removed, is separated in a CO separation stage in a gas stream of pure CO product and a mixture of methane-nitrogen waste gas; e) the hydrogen-rich gas fractions and the nitrogen-methane waste gas mixture are compressed, either separately or together, at a pressure exceeding the pressure in the CO conversion stage of the steam converter, and combine to form a mixed gas stream, with low CO content, free of water; f) the last mixed gas stream is heated to a temperature of 200 to 500 ° C, and is fed to a stage of conversion of CO from the steam converting plant. The heating of the mixed gas stream at temperatures from 200 to 500 ° C, occurs expeditiously in a countercurrent heat exchanger, which is used simultaneously for the cooling of the partial gas stream that is withdrawn between the secondary converter and the stage of CO conversion at temperatures below 100 ° C. In order to separate C02 from the cooled partial gas stream below 100 ° C, the C02 in the C02 separation step is advantageously purified using a potash solution or removed using a C02 selective wash having amines as the selective solvent. A PSA (known) plant (pressure oscillation adsorption plant) can be used as the hydrogen separation stage for the separation of the hydrogen-rich gas fraction or fractions from the C02 free partial stream • The remaining partial flow it is separated in the CO separation step by a low temperature rectification in a gaseous stream of pure CO product and a residual nitrogen-methane gaseous mixture.

In the partial gas stream, which branches between the secondary converter and the CO conversion stage, the process according to the invention is preferably carried out such that the ratio between the main gas volume flow which is additionally guided downstream of the secondary converter and the branched partial flow volume is between 1: 1 and 4: 1. In the process according to the present invention, as a result of the branching of outward transfer of some of the CO upstream of the conversion, hydrogen is lost in the displacement reactors of the CO conversion stage, because less CO It is available for the conversion of CO and water to hydrogen and C02. Therefore, an important complementary characteristic of the process according to the present invention, lies in the fact that the volume of gas CO, which is transferred outwards by means of the partial current, which is, therefore, in deficit in terms of the stoichiometric operation of the CO conversion stage according to the reaction equation CO + H20 - > C02 + H2, is compensated by a slightly increased supply of the natural gas feed material to the primary converter. This only slightly increased supply of natural gas to the primary converter, which ensures the requirement of raw material for the generation of CO, represents an important complementary feature of the invention. This conventional steam converter plant for the generation of ammonia comprises, according to figure 1, the following process steps: natural gas desulfurization 1, primary converter 2 indirectly heated with fuel, secondary converter 3 ignited directly with natural gas and air for combustion, CO 4 converter having the displacement reactor HT 5 and the displacement reactor LT 6, the absorber 7 of C02 and the reactor 8 of methanization. The preheated feeds in the heat exchanger 9, ie the desulfurized natural gas comprising mainly methane, and the steam and air are supplied to the primary converter 2. Further, the primary converter 2 is supplied with the necessary heating gas, and air for combustion for indirect ignition. The hot reaction gases discharged from the primary converter 2 are then guided to the secondary converter 3 which operates autothermally, in which a further catalytic reaction to CO takes place, such that upon discharge from the secondary converter, only one very low methane concentration. The preheated air (oxygen) is likewise supplied to the secondary converter 3. The synthesis gas discharged from the secondary converter 3 is supplied by means of a heat exchanger 10 to the conversion stage 4 of CO having the reactors of displacement 5 and 6, in which the CO is catalytically converted with the steam still present, to C02 and H2 by the reaction of water gas. The C02 is then purified in the absorber 7, and the remaining hydrogen-rich gas is supplied to the methanization stage 8, in which the residual methane is converted with the CO to H2 and C02. The reaction steps described are known in the steam converting plant for ammonia or H2 generation, and consequently constitute the prior art. An essential process step deviating from the prior art now comprises the branching from the product stream 11 of the secondary converter, downstream of the heat exchanger 10, a partial stream of crude synthesis gas 12, comprising mainly H2 , steam, methane, CO, C02 and considerable amounts of nitrogen, which is supplied to a multi-stage CO separation plant 13, and, after compression and heating, the CO-free gas mixture is recombined , remnant, which substantially comprises H2, CH4, and N2, which is the mixed gaseous stream 14, with the main synthesis gas stream 15, which remains after the separation of the partial stream 12, and which flows towards the CO conversion stage 4 The individual gaseous components, water vapor, C02, H2, traces of H20, C02 and N2 in the partial gas stream 12, are separated with the CO according to Figure 2, with the help of individual separation steps, which are known per se. In this way, the hot partial gas stream which is withdrawn from the main stream 11 in a downward direction of the secondary converter 3 and is at a temperature from 200 to 500 ° C is cooled by a heat exchanger 16 countercurrent to the side of the cooling medium, from which the mixed gas stream 14 hits, which is going to be heated and introduced to the conversion stage 4. Most of the vapor contained in the partial stream 12 is condensed in this way. The cooled partial gas stream 12a, from which it has been withdrawn is then guided to a separation stage 17 of C02 in which a selective absorption of C02 into organic amines or a chemisorption takes place in a potassium solution. The loaded potassium solution or the amine solution is supplied to a desorption stage 18 installed downstream, in which the C02 is debugged. The cooled partial stream 12b from which the C02 has been removed is now guided for the separation of hydrogen in a pressure swing adsorption plant 19 (PSA plant) which distributes a plurality of pure hydrogen fractions 20a, 20b , at different pressures. Such PSA plants are conventional components of commercial plants (for example, Linde, Germany). The hydrogen-free partial gas stream 12c, which remains after the PSA plant 19, is compressed (compressor 21), and any traces of CO 2 and steam still present, are removed in the downstream zeolite adsorber column 22. . The gaseous stream 12d present on the discharge from the zeolite adsorber column 22, which now comprises only CO and a mixture of nitrogen / methane waste gas, is supplied to a rectification stage 23 at a low temperature, for processing later. In this process step, the gas stream of CO is separated and compressed at the pressure desired by the user by means of compressor 24. The hydrogen fractions 20 and 20b that arise in the PSA plant 19 and the residual gas mixture 32 of nitrogen / methane separated in the rectification stage 23 at low temperature, are compressed by means of the pressure controlled compressors 25, 26 and 27, at a higher common pressure level, and combined in the return line 28 by the static mixer 29 to form a mixed gas stream 14. The mixed gas stream 14 is reheated in the heat exchanger 6 countercurrently at temperatures from 200 to 500 ° C, as described above and then fed back via the nozzle 30 upstream of the CO conversion stage 4 of the steam converting plant, in that portion 15 which was not circulated outside the gaseous stream 11 of synthesis, unloaded, discharged from the secondary converter 3. Alternatively, the mixed gas stream 14 may also be injected into the converter 4 of CO between the stage 5 of displacement at high temperature and the stage 6 of displacement at low temperature, by means of the line 31. With the exception of the vapor that is separated in the heat exchanger 16 and the CO that arises in the step 18 of desorption, and the stream of pure gas CO obtained in the rectification step 23 at low temperature, therefore, all the gaseous fractions cleaved in the separation plant 13 of CO, are recycled to the mainstream of the steam converting plant. By recirculating outward from the stream 11 of raw synthesis gas, a partial stream 12 corresponding to the volume of CO required, and feedback, virtually free of CO, C02 and water, upstream of or to the converter 4 of CO, the crude synthesis gas is correspondingly exhausted for the CO upstream of the displacement reactors 5 and 6 in the CO converter 4. This results in the discharge of displacement reactors 5 and 6 and consequently a loss of hydrogen during the conversion for which the reaction equation is: CO + H20? C02 + H2 This disadvantage, however, is eliminated, as described below, by the slight increase in the supply of natural gas feed back to the primary converter 2. An expansion valve can be used as an alternative to the nozzle 30. The invention it is further illustrated, but is not intended to be limited by the following examples, in which all parts and percentages are by weight, unless otherwise specified.

EXAMPLES Example 62,000 tons of pure CO p.a. will be produced. with the help of the process according to the invention. The ammonia converter according to Figure 1 has a capacity of ammonia synthesis gas of 110,000 NmVho, having a stoichiometric ratio of N 2 / H 2 of 1: 3. A stream of pure CO gas of 62,000 tons p.a. it will be additionally generated with the help of the process according to the invention. The stream 11 of crude synthesis gas, which is present downstream of the secondary converter 3, has the following composition: H20: 35% vol C02: 4% vol CO: 8% vol N2 vol H2: 35.5% vol. CH4: 2% vol. noble gases 0.5% vol.

It can be seen that the concentration of CO is very low and represents little more than an impurity. It is a particularity of the process according to the present invention that even under these conditions, it is possible to achieve economic generation of pure CO. The stream 11 of crude synthesis gas is then divided into two partial streams 12 and 15, in a ratio of 1: 2 corresponding to the desired volume of pure CO. The larger partial stream 15 of about 140,000 NmVhz of crude synthesis gas, which is at a temperature of 350 ° C and a pressure of 30 bar, is guided in a conventional manner in the direction of the displacement step 5 to high temperature of the ammonia converter, while the second partial current 12 of about 75,000 NmVhora is cooled to 50 ° C in the countercurrent heat exchanger 16. It condenses 95% to 98% of the water contained in the crude synthesis gas. The medium to be heated on the opposite side in the heat exchanger 16 is the mixed gas stream 14 with low CO content, free of water, which is recycled from the separation stage 13 of CO to the ammonia converter. After the partial stream 12 of raw synthesis gas has been cooled, the partial stream 12a with low water content is transferred according to Figure 2 to the scrubber 17 of C02, which operates with the carbonate process of potassium, where the main amount of C02 contained in the crude synthesis gas is eliminated by chemosorption. The loaded potassium solution is thermally regenerated in the desorption stage 18 and the purified C02 is supplied for later use. The partial stream 12b, from which they have now been removed (most of) H20 and C02, is then supplied to the hydrogen PSA plant 19, where virtually complete removal of the hydrogen from the last gas stream. The hydrogen PSA plant 19 distributes a high pressure hydrogen fraction and a low pressure hydrogen fraction 20a and 20b, respectively. The partial stream 12c which remains, after this, now comprises CO, N2, CH4 and traces of noble gases, and still additionally contains traces of C02 and water. The last components are removed from the partial stream 12c in the adsorber stage 22, of zeolite, installed downstream of the hydrogen PSA plant 19. The partial stream 12d, which is present downstream of the zeolite adsorber stage 22, is then supplied to the low temperature rectification stage 23, where the liquefaction / separation of the CO takes place, while the N2 and the CH4 are contained in the gaseous stream 32, which passes over. An essential step now comprises, by means of intermediate compression by means of the compressors 25, 26 and 27, bringing the partial gas streams 20a, 20b to the same pressure level, which exceeds that in the high temperature displacement reactor 5. and 32, which were downloaded from the two separation stages 19 and 23; combining them in the static mixer 29 to form the mixed gas stream 14; bringing the mixed gas stream 14 then to a temperature of about 330 ° C in the countercurrent heat exchanger; and feeding it again and mixing by means of the nozzle 30 into the main synthesis gas stream 15, directly upstream of the CO converter 4 of the ammonia converter. The partial currents 20a, 20b, 32 are compressed to the degree of the insufficiency of pressure of the partial current in question, compared to the pressure of the main stream 15 of synthesis gas, which depends on the operation data of the power plant. PSA 19 and rectification 23 at low temperature, which are incidental to the proposed achievement according to the present invention. The individual stages of the CO separation plant 13, which comprise the scrubber 17 of C02, the plant 19 of hydrogen-PSA, the adsorber stage 22, of zeolite, and the rectification stage 23 at low temperature, are designed and operated such that there are contents in the stream of pure CO, less than 100 ppm of hydrogen and less than 50 ppm of CH4, thereby making it possible to use pure CO, for example, in the production of isocyanate. The detail of the separation steps used is not substantial for the process according to the invention. The process according to the invention can also be carried out in conjunction with a hydrogen generation steam converter, not preparing the hydrogen for an ammonia plant.

The main advantage of the process according to the present invention in all the described modalities lies in the coupling in a synergistic manner of the generation of hydrogen and the generation of pure CO, such as to require only extremely low utilization of materials fossil premiums (natural gas) for the additional preparation of large volumes of pure CO. In a conventionally operated ammonia converter, which has a hydrogen conversion of 100%, the processing of the natural gas takes place according to the following reaction equations: 1. CH4 + H20 - »CO + 3H2 (primary converter 2 + secondary converter 3) 2. CO + H20? C02 + H2 (reactor 5 of displacement HT + reactor 6 of displacement LT) in sum: CH4 + 2 H20 - > C02 + 4 H2 (complete reaction) This means that the ammonia converter produces approximately 4 moles of H2 per mole of CH4.

Now, if some of the CO is transferred upstream of the conversion, and it is separated from the raw synthesis gas, then this results in a loss of hydrogen in the displacement reactors of the CO converter, because less CO is available. for the reaction. However, in order to maintain the stoichiometric ratio N2: H2 of 1: 3 desired for the synthesis of ammonia, this hydrogen deficit must be compensated by an increase in the supply of natural gas to the primary converter 2. However, while in the CO 4 converter, there is a deficit of one mole of H2 in the ammonia synthesis gas for each mole of "lost CO" that results from the generation of pure CO, 4 moles of H can be complemented by a reinforcement of only 1 mole of CH4 inside the primary converter 2. In other words, for the additional generation of pure CO in the steam converter of the ammonia plant, approximately 25% of the natural gas feed material is required, which it could be required, if the CO were to be processed in a separate converter or in another plant for the generation of synthesis gas. This is a very considerable advantage of the process according to the present invention. If this separate converter were operated with a mixture of CH4 / C02, although the carbon balance of this competent achievement of the object of the invention could be improved to some extent, the fundamental advantage of the process according to the invention could remain. The generation according to the invention of pure CO in conjunction with a steam converter for the generation of ammonia or hydrogen, minimizes the use of natural gas, in this way, resources are saved and low operating costs are guaranteed. From an environmental point of view, it is advantageous that the carbon difference between the volume of CO transferred downstream of the secondary converter 3, and the amount of natural gas added to the primary converter 2 as a supplement to offset the hydrogen balance no longer appears as an emission of C02 into the atmosphere from the ammonia plant. In the present example, this means a reduction in CO 2 emissions of approximately 80,000 tons p.a. An additional advantage of process engineering, of the process according to the present invention, is that the ammonia converter and the downstream of the ammonia synthesis of the CO converter 4 are not totally influenced by the obtaining of the CO of according to the present invention, either in terms of volume flow or gas composition. Only the stage 7 of purification of C02 of the steam converter can be operated at a lower capacity, which has an advantageous effect on its steam consumption. The additional advantages of the process according to the invention are that the operating personnel present to operate the ammonia plant or the steam converter, can also monitor the generation of CO, such that no additional labor is needed for the production of CO, thereby further increasing the economy of the process according to the present invention. Although the invention has been described in detail in the foregoing for purposes of illustration, it is understood that such details are solely for that purpose, and that variations may be made herein by those skilled in the art, without departing from the spirit and scope of the invention. the invention, except as this may be limited by the claims.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Having described the invention as above, property is claimed as contained in the following:

Claims (10)

1. A process for simultaneously obtaining pure carbon monoxide and pure hydrogen by further processing a synthesis gas stream comprising the gaseous components H2, water vapor, CH4, C02, CO and optionally N2, characterized the process because it comprises the following steps: a) the withdrawal between the secondary converter and the stage of conversion of CO, of a partial gas stream of said synthesis gas stream discharged from the secondary converter, which has a CO content between 2 and 20% mol, preferably between 5 and 10 mol%, and it is at a temperature from 200 to 500 ° C and at a pressure within the range of 15 to 50 bar, in a steam converter plant for the generation of hydrogen or ammonia, which has a primary converter, a secondary converter and downstream thereof, a stage of CO conversion; b) cooling the partial gas stream to a temperature below 100 ° C, whereby most of the vapor contained in the partial gas stream is condensed, resulting in a stream of crude synthesis gas; c) guiding the raw synthesis gas, remaining by means of a multi-stage gas separation plant, in which the residual H2, H20, CH4, C02 and optionally N2 components are separated, either individually or together, of the CO; d) the compression of H2 gaseous components, CH4, and optionally N2 from CO, which are separated from the CO, by compressing the gaseous components at a pressure that exceeds the pressure in the CO conversion stage and are recombined to form a mixed gas stream. e) heating the mixed gas stream to a temperature of 200 to 500 ° C and supplying the mixed gas stream to the conversion stage of the steam converter plant CO; and f) the removal of the remaining pure CO fraction in a separate and optional manner, supplying the remaining pure CO fraction for further processing.

2. A process according to claim 1, characterized in that: a) the partial gas stream cooled below 100 ° C is supplied to a separation stage of C02 where the C02 is removed; b) the partial gas stream from which the CO2 has been removed is guided through a hydrogen separation step, in which one or a plurality of gas fractions rich in hydrogen are separated; c) the partial gas in which one or a plurality of hydrogen-rich gas fractions that are separated while remaining downstream of the hydrogen separation step, is purified from traces of C02 and water; d) the partial gas stream, where traces of C02 and water have been removed, is separated in a CO separation step into a gas stream of pure CO product and a methane-nitrogen waste gas mixture; e) one or a plurality of hydrogen-rich gas fractions and the methane-nitrogen waste gas mixture are compressed, either separately or together, at a pressure exceeding the pressure in the CO conversion stage, and are combined to form a gaseous stream free of water, mixed, with low CO content; and f) the stream of mixed gas free of water, with low CO content, is heated to a temperature of 200 to 500 ° C and is fed to the CO conversion stage after being mixed with the synthesis gas stream that it remains downstream of the separation of said partial current withdrawn between the secondary converter and the CO compression stage.

3. A process according to claim 2, characterized in that the water-free mixed gaseous stream, with low CO content, is heated to temperature from 200 to 500 ° C in a countercurrent heat exchanger, which is used simultaneously to cool at temperatures below 100 ° C the partial gas stream withdrawn between the secondary converter and the CO conversion stage.

4. A process according to claim 2, characterized in that the CO is purified from the partial stream supplied to the separation stage of C02, using a potash solution.

5. A process according to claim 3, characterized in that the C0 is purified from the partial stream supplied to the CO? Separation stage using a potash solution.

6. A process according to claim 2, characterized in that the C02 is removed from the partial stream supplied to the C02 separation step, using a selective wash with C02 having amines, as the selective solvent.

7. A process according to claim 2, characterized in that the PSA plant is used as the hydrogen separation step to separate one or a plurality of hydrogen-rich gas fractions from the partial stream.

8. A process according to claim 2, characterized in that the stage of separation of CO, in which the partial gas stream in which the traces of C0 and water have been removed, is separated into a gaseous stream of pure CO product and a residual gas mixture of methane-nitrogen, by a rectification plant at low temperature.

9. A process according to claim 1, characterized in that the proportion of the main gaseous volume flow guided further downstream of the secondary converter and the partial gaseous current withdrawn between the secondary converter and the CO conversion stage, is between 1: 1 and 4: 1.

10. A process according to claim 1, characterized in that the volume of the pure CO gas is compensated by an increased supply of the natural gas feed material to the primary converter, according to the reaction equation CO + H20? C02 + H2. SUMMARY OF THE INVENTION The present invention is directed to a process for simultaneously obtaining pure carbon monoxide and pure hydrogen in a steam converting plant for the generation of hydrogen or ammonia, which has a primary converter, a secondary converter and downstream thereof, a step of CO conversion. A partial gas stream of the synthesis gas stream, which is discharged from the secondary converter having a CO content of between 2 and 20 mol% and is at a temperature of 200 to 500 ° C and at a pressure between 15 and 50 bar, is removed between the secondary converter and the conversion stage of'CO. The partial gas stream is then cooled to a temperature below 100 ° C, whereby most of the vapor contained in the gas stream is condensed. The remaining crude synthesis gas stream is then guided by means of a multi-stage gas separation plant in which the gaseous components H2, residual steam, CH4, C02 and optionally N2 are separated, either individually or together, of CO The separated gaseous components are then compressed to a pressure that exceeds the pressure in the CO conversion stage, and are recombined to form a mixed gaseous stream. The mixed gaseous stream is then guided to the CO conversion stage of the steam converter, after being heated to a temperature ranging from 200 to 500 ° C. The remaining pure CO fraction is removed in a separate manner, and may optionally be supplied for further processing.