Hydrocarbon conversion plant and operating method thereof

Abstract

The invention relates to a hydrocarbon conversion plant and an operating method thereof. Proposed is a hydrocarbon conversion plant comprising a supply line for a steam-gas mixture flow which allows for the division of said steam-gas mixture flow into a main steam-gas mixture flow which is fed into a steam reforming apparatus and an additional steam-gas mixture flow which is fed into an additional steam reforming apparatus. More particularly, the supply line for a steam-gas mixture flow allows for the division of the steam-gas mixture flow such that the ratio of the volumetric flow rate of the main steam-gas mixture flow to the volumetric flow rate of the additional steam-gas mixture flow is from 90:10 to 81:19. Converted gas from the steam reforming apparatus and from the additional steam reforming apparatus is fed into a catalytic hydrocarbon converter which is configured to allow for the discharge of at least a portion of the flow of converted gas into a heat exchange loop of the additional steam reforming apparatus. Also proposed is an operating method of the claimed plant. The technical result is that of making it possible to modernize existing plants with the aim of increasing the productivity thereof, as well as to increase the service life of equipment, relax the requirements with respect to the equipment used, permit flexibility in the regulation of the operation of the plant, simplify the process flow while maintaining a high degree of methane conversion, and reduce hydraulic losses along a natural gas reforming path.

Description

[0001] HYDROCARBON CONVERSION PLANT AND ITS OPERATING METHOD

[0002] Field of technology

[0003] The proposed invention relates to a hydrocarbon conversion plant and its operating method. The present invention can be used in any known technological processes in which it is necessary to obtain hydrogen from natural gas, in particular, in the production of ammonia at chemical industry plants.

[0004] Prior art

[0005] From the book [1] Safety precautions in the production, storage and transportation of ammonia [Text] / M. I. Vedernikov. - Moscow: Chemistry, 1978, it is known that the process of obtaining synthetic ammonia consists of obtaining the initial gas mixture, consisting mainly of nitrogen and hydrogen (synthesis gas), purifying the nitrogen-hydrogen mixture, compressing it and synthesizing ammonia on a catalyst.

[0006] Conversion of hydrocarbon gases is the most common and economical method of producing hydrogen for ammonia synthesis.

[0007] One of the main methods of natural gas processing is the method of steam-oxygen-air conversion of methane in shaft converters.

[0008] The gas mixture obtained by converting natural gas contains 54% hydrogen and up to 22% carbon monoxide.

[0009] Process gas for ammonia synthesis is obtained in large installations for two-stage steam-air catalytic conversion of natural gas.

[0010] In such a plant, natural gas under a pressure of 1 MPa passes through a separator, where heavy hydrocarbons are separated, is compressed by a compressor to 4 MPa and mixed with a nitrogen-hydrogen mixture (synthesis gas) pumped by the compressor.

[0011] The resulting gas mixture is heated to 400°C and fed to a desulphurization unit, where organosulfur compounds are reduced to hydrogen sulphide by the hydrogen contained in the gas mixture on a cobalt-molybdenum catalyst.

[0012] The hydrogen sulfide is then absorbed in an apparatus loaded with an absorbent mass based on zinc oxide.

[0013] The resulting purified natural gas contains no more than 1 mg / m3 3 sulfur, mixed with water vapor having a pressure of 4 MPa and a temperature of 350-400°C until the volume ratio of steam: gas is 4:1.

[0014] SUBSTITUTE SHEET (RULE 26) The steam-gas mixture is heated to 500°C in the convection and radiation chambers of the tubular furnace and fed into the reaction tubes, which contain the nickel catalyst (top-down feed).

[0015] The catalyst converts hydrocarbon gases with water vapor.

[0016] The converted gas, containing 8-10% residual methane, leaves the reaction tubes at a temperature of about 800°C and enters the second-stage shaft methane converter, where the conversion of residual methane with steam and atmospheric oxygen occurs on a nickel catalyst.

[0017] Before being fed into the converters, the air is cleaned in a filter and fed under a pressure of about 3.5 MPa to be heated to 500°C.

[0018] From the second stage methane converter, the converted gas under a pressure of about 2.9 MPa and a temperature of 960°C enters the waste heat boiler to produce water vapor by utilizing its heat and for further processing.

[0019] The disadvantage of the known technical solution is the low productivity of the plant and the insufficiently deep degree of methane conversion, which is expressed in the increased content of residual methane in the converted gas. In the known plant, an additional heat exchanger is required to cool the converted gas, and the heat of the converted gas is also inefficiently used.

[0020] From document [2], patent EP2384308B1, published on 15.04.2015, a method for producing hydrogen from natural gas is known, which uses a combination of a steam reforming unit and a gas-heated reforming unit.

[0021] The purified hydrocarbon stream is mixed with steam from the pipeline, the mixture is heated in a chimney and sent to a pre-reformer where it reacts adiabatically over a bed of nickel catalyst to form a pre-reformer gas mixture.

[0022] After preliminary reforming, the gas mixture is heated in the flue and divided into two streams.

[0023] The first stream (about 30% by volume) of the gas mixture is mixed with additional steam from the pipeline and sent to the pipe section of the gas-fired reforming unit, which contains a nickel catalyst.

[0024] The second stream (about 70% by volume) of the gas mixture is fed into a plurality of steam reforming unit tubes containing a nickel catalyst. As a result, the gas mixture

[0025] SUBSTITUTE SHEET (RULE 26) is converted into crude synthesis gas containing hydrogen, carbon monoxide, carbon dioxide and water vapor.

[0026] This raw syngas is sent to the shell side of the gas-fired reformer where it is used to heat the first gas mixture stream as it passes over the particulate catalyst.

[0027] The gas mixture obtained after passing through the first stream of the gas-heated reforming unit is combined with the raw synthesis gas collected from the intertube space of the gas-heated reforming unit, resulting in a raw synthesis gas mixture.

[0028] The volume percentage of pre-reformed gas fed to the steam reformers (second stream) and gas-fired reformers (first stream) can vary in the range from 10:90 to 90:10.

[0029] The disadvantage of the known technical solution is also the low productivity of the plant, the insufficiently deep degree of methane conversion, i.e. the increased content of residual methane in the converted gas, as well as the complexity of the process flow diagram, since an additional steam reforming unit (pre-reforming unit) is required in order to achieve the required level of methane conversion, as well as a heat exchanger for cooling the resulting mixture of raw synthesis gas.

[0030] From the information source [3] PJSC Dorogobuzh "Reconstruction of the ammonia unit with an increase in productivity up to 2100 tons per day", published on the Internet at https: / / www.acron.ru / upload / iblock / 2a2 / Proekt-OVOS-_otsenka- vozdeystviya-na-okruzhayushchuyu-sredu_-tekstovaya-chast_-prilozheniya-po-obektu- _Rekonstruktsiya-agregata-ammiaka-s-uvelicheniem-proizvoditelnosti-do-2100-tonn-v-sutki_.pdf, an installation is known in which the process of steam-air conversion of natural gas is carried out in two stages (a two-stage conversion unit for natural gas), as well as a design solution - a three-stage conversion unit for natural gas.

[0031] The well-known process of steam-air conversion of natural gas, which is carried out in two stages, is described below.

[0032] Natural gas conversion (primary reforming)

[0033] SUBSTITUTE SHEET (RULE 26) In the coils of the convection and transition zones of the primary reforming furnace, the steam-gas mixture is heated and directed into reaction tubes, in which steam conversion of natural gas is carried out on a nickel catalyst.

[0034] Heat is supplied to maintain the endothermic reaction of steam reforming of natural gas by means of flue gases generated during combustion of fuel gas.

[0035] After the reaction tubes, the converted gas enters the secondary reforming reactor through the transfer manifold.

[0036] Natural gas conversion (secondary reforming)

[0037] In the secondary reforming reactor, steam-air conversion of the methane remaining in the converted gas is carried out on a nickel catalyst by interaction with steam and atmospheric oxygen.

[0038] Steam-air conversion of methane is carried out without heat supply.

[0039] The converted gas from the secondary reforming reactor enters two parallel waste heat boilers, in which high-pressure steam is produced by utilizing the heat of the gas.

[0040] The disadvantage of classical two-stage steam reforming is the high cost of the first stage of conversion, due to the need to use a large number of tubes operating at a noticeable pressure drop and high temperature. These tubes must have high heat resistance and scale resistance.

[0041] The three-stage natural gas conversion plant disclosed in the above source [3] operates as follows.

[0042] In the known installation, natural gas after the desulphurization stage is divided into two streams:

[0043] - the first stream (~14% of the total natural gas stream) is mixed in the steam / gas mixing unit with medium-pressure steam and fed to the KRES reforming reactor-heat exchanger for recuperative conversion of natural gas;

[0044] - the second, main flow (~86% of the total flow of natural gas) is mixed with medium-pressure steam in the steam / gas mixing unit, followed by steam reforming of natural gas in the primary reforming furnace.

[0045] Natural gas conversion (primary reforming)

[0046] SUBSTITUTE SHEET (RULE 26) In the coils of the convection and transition zones of the primary reforming furnace, the main flow of the steam-gas mixture is heated and directed to the reaction tubes, in which steam conversion of natural gas is carried out on a nickel catalyst.

[0047] Heat is supplied to maintain the endothermic reaction of steam reforming of natural gas by means of flue gases generated during combustion of fuel gas.

[0048] After the reaction tubes, the converted gas enters the secondary reforming reactor through the transfer manifold.

[0049] Natural gas conversion (secondary reforming)

[0050] The converted gas from the primary reforming furnace is sent to the existing secondary reforming reactor, where steam-air conversion of the methane remaining in the converted gas is carried out on a nickel catalyst by interaction with steam and oxygen from the process air.

[0051] Steam-air conversion of methane is carried out without the supply of heat, since when the converted gas is mixed with air, partial combustion of combustible components occurs with an increase in the temperature of the gas mixture.

[0052] The converted gas from the secondary reforming reactor is directed to the inter-tube space of the KRES heat exchanger reactor.

[0053] The KRES reforming reactor-heat exchanger performs steam reforming of natural gas over a nickel catalyst.

[0054] The heat required for the endothermic steam reforming reaction of methane is supplied by the reformed gas after the secondary reforming reactor.

[0055] In the lower part of the inter-tube space of the KRES reforming reactor-heat exchanger, the converted gas is mixed with the converted gas from the secondary reforming reactor and fed into two parallel-operating waste heat boilers, in which high-pressure steam is produced by utilizing the heat of the gas.

[0056] The cooled convertible gas is sent to a high-temperature carbon monoxide converter.

[0057] Thus, in the known three-stage plant, the initial natural gas is divided into a first stream and a second (main) stream. The first stream is fed to the KRES reforming reactor-heat exchanger. The second stream is fed to the primary reforming furnace, the secondary reforming reactor and into the intertube space of the KRES reactor-heat exchanger for heating the tubes containing the first stream. Then both streams are mixed in

[0058] SUBSTITUTE SHEET (RULE 26) the lower part of the inter-tube space of the KRES reforming reactor-heat exchanger and is sent to the waste heat boilers.

[0059] The disadvantages of the three-stage installation known from source [3] include:

[0060] 1. Increased content of residual methane in the converted gas sent to waste heat boilers due to the need to mix the second (main) stream of converted gas from the secondary reforming reactor and the converted gas of the first stream, which undergoes only one reforming (in the KRES reforming heat exchanger reactor) and, accordingly, cannot achieve a deep degree of methane conversion;

[0061] 2. Increased heat exchange surface in the KRES reforming reactor-heat exchanger due to low temperature head in heat exchange reforming, caused by the need for maximum possible heating of the converted gas of the first stream due to the need to obtain the lowest possible residual methane content in the converted gas before the waste heat boilers.

[0062] 3. Excessive combustion temperature of the second (main) stream of converted gas with air in the secondary reforming reactor due to the need to dose nitrogen air for the converted gas obtained from the first stream and not passing through the secondary reforming reactor.

[0063] 4. Complex technological scheme of the plant due to the need to organize mixing of both flows in the lower part of the inter-tube space of the KRES reforming reactor-heat exchanger - the first flow located in the tubes of the KRES reforming heat exchanger, and the main (second) flow coming from the secondary reforming reactor. Also in this plant there is a need to cool the resulting mixed flow, since the cooled second flow is mixed with the hot converted gas of the first flow, which leads to an increase in the temperature of the mixed flow.

[0064] As the closest analogue of the present invention, one can choose document [4], patent RU2053957C1, published on 10.02.1996, from which a method for converting hydrocarbons by steam reforming is known, including dividing the purified steam-gas mixture into two parallel streams, feeding one stream into the first catalytic primary reforming apparatus, and the second into the second catalytic primary reforming apparatus, combining the streams from the first and second

[0065] SUBSTITUTE SHEET (RULE 26) apparatuses, mixing the latter with an oxidizer and feeding the resulting flow to the adiabatic secondary reforming stage with subsequent passing of the resulting product through a second primary reforming apparatus for indirect heat exchange with the steam-gas mixture, removal of the resulting product, characterized in that the indirect heat exchange of the product from adiabatic secondary reforming with the steam-gas mixture in the second primary reforming apparatus is carried out in a direct flow, the initial purified steam-gas mixture before being divided into two flows is subjected successively to indirect heating and partial catalytic reforming countercurrent to the product from the adiabatic reforming stage, previously passed through the second primary reforming apparatus.

[0066] The above analogue has the following disadvantages:

[0067] 1. Lack of flexibility in the process flow diagram in terms of the load on heat exchange reforming and the required steam generation, which is especially important for the reconstruction of existing production facilities.

[0068] 2. Significant pressure drop along the heating converted gas line, which leads to a decrease in the productivity of the ammonia unit for the finished product.

[0069] 3. Reduction of the temperature of the converted gas before the waste heat boilers, which leads to a decrease in steam production.

[0070] 4. Complexity of the process flow diagram, since an additional steam reforming unit (partial catalytic reforming unit) is required in order to achieve the required level of methane conversion, and it is also necessary to ensure the passage of heated converted gas from the secondary reforming unit (adiabatic reforming unit) through the heat exchange circuits of the second primary reforming unit and the partial catalytic reforming unit, where the converted gas is cooled to 603.3°C, which leads to the need to heat it in a heater before feeding it to the waste heat boiler.

[0071] 4. High requirements for heat resistance of the equipment due to the high heating temperature of the converted gas (over 1024°C) leaving the secondary reforming apparatus.

[0072] Disclosure of invention

[0073] SUBSTITUTE SHEET (RULE 26) The objective of the present invention and the technical result is to provide the possibility of modernizing existing installations in order to increase their productivity.

[0074] Additional technical results are:

[0075] - increasing the service life of equipment;

[0076] - reduction of requirements for the equipment used;

[0077] - flexibility of regulation of the installation operation;

[0078] - simplification of the process flow diagram while maintaining a high degree of methane conversion;

[0079] - reduction of hydraulic losses along the natural gas reforming line.

[0080] In order to solve the above-mentioned problem and achieve the technical result, a hydrocarbon conversion plant is proposed, comprising: a steam reforming apparatus, an additional steam reforming apparatus equipped with a heat exchange circuit, a converter for the catalytic conversion of hydrocarbons, designed with the possibility of feeding air and converted gas into it, a line for feeding a steam-gas mixture flow, which allows the steam-gas mixture flow to be divided into a main flow of the steam-gas mixture, which is fed into the steam reforming apparatus, and an additional flow of the steam-gas mixture, which is fed into an additional steam reforming apparatus, wherein the steam reforming apparatus and the additional steam reforming apparatus are designed with the possibility of feeding converted gas into the converter for the catalytic conversion of hydrocarbons,wherein the converter for catalytic conversion of hydrocarbons is designed with the possibility of diverting at least part of the converted gas flow into the heat exchange circuit of an additional steam reforming apparatus, characterized in that the line for feeding the steam-gas mixture flow makes it possible to divide the steam-gas mixture flow in such a way that the ratio of the volumetric flow rate of the main steam-gas mixture flow to the volumetric flow rate of the additional steam-gas mixture flow is from 90: 10 to 81: 19.

[0081] SUBSTITUTE SHEET (RULE 26) In the preferred embodiment, the ratio of the volumetric flow rate of the main flow of the steam-gas mixture to the volumetric flow rate of the additional flow of the steam-gas mixture is from 90: 10 to 85: 15.

[0082] The above-mentioned features make it possible to modernize existing installations in order to increase their productivity. The ratio of the volumetric flow rate of the main flow to the volumetric flow rate of the additional flow, which is from 90: 10 to 81: 19, more preferably from 90: 10 to 85: 15, makes it possible to ensure the highest productivity of the installation and the deepest degree of methane conversion.

[0083] In a preferred embodiment, the converter for catalytic conversion of hydrocarbons is connected to a line for removing the first stream of converted gas from the converter for catalytic conversion of hydrocarbons and a line for removing the second stream of converted gas from the converter for catalytic conversion of hydrocarbons, wherein the line for removing the first stream of converted gas allows directing the first stream of converted gas to a steam generation apparatus, and the line for removing the second stream of converted gas allows directing the second stream of converted gas to a heat exchange circuit of an additional steam reforming apparatus.

[0084] The above features additionally increase the possibilities of upgrading existing installations in order to increase their productivity. The withdrawal of the converted gas leaving the converter for catalytic conversion of hydrocarbons along two lines: the first flow withdrawal line and the second flow withdrawal line, allows to preset or regulate during operation the amount of hot converted gas that is sent to the heat exchange circuit of the steam generation apparatus, and the amount of hot converted gas that is sent to the heat exchange circuit of the additional steam reforming apparatus. The hot first flow in the steam generation apparatus gives up part of its heat to generate steam, which is used to provide energy to devices used in the process of obtaining ammonia.The hot second stream gives up part of its heat for heating and primary steam conversion of an additional stream of steam-gas mixture, allowing for greater production of synthesis gas while maintaining a low residual methane content at the outlet of the heat exchange reforming.

[0085] SUBSTITUTE SHEET (RULE 26) In this way, it is possible to ensure flexible control of hot flows, which allows for simultaneous increase in synthesis gas production while maintaining low residual methane content, providing energy to the necessary devices, reducing requirements for the equipment used and increasing its service life by eliminating critical operating modes.

[0086] The converted gas exiting the converter for catalytic conversion of hydrocarbons can be either immediately discharged via two separate lines, or via one line, which is then divided into two lines. The choice of one of the specified options depends on the design of the elements of the modernized installation and the possibility of changing the existing piping.

[0087] The steam reforming apparatus may be any apparatus (furnace) known from the prior art that allows steam reforming (steam methane reforming (SMR), catalytic conversion of hydrocarbons in the presence of steam).

[0088] The converter for catalytic conversion of hydrocarbons may be any converter for catalytic conversion of hydrocarbons known from the prior art that allows obtaining converted gas by catalytic conversion of methane of natural gas.

[0089] The steam generation device is intended for obtaining water steam by utilizing the heat of converted gas. Any device known from the prior art that allows obtaining steam, which can then be used as an energy source, can be used, in particular, this can be a waste heat boiler. In the present invention, there can be either one waste heat boiler or several waste heat boilers. Preferably, they are installed in series.

[0090] The lines for feeding or diverting flows may be any known means used for feeding or diverting flows, such as pipes or connections of pipes and shut-off and control valves, designed with the possibility of feeding or diverting flows, respectively. The said lines may be equipped with known means for regulating the volumetric flow rate of flows, separating flows, measuring the pressure and temperature of flows.

[0091] In a preferred embodiment, a line for removing a first stream of converted gas from a converter for catalytic conversion of hydrocarbons and a line for removing a second stream of converted gas from a converter for catalytic conversion

[0092] SUBSTITUTE SHEET (RULE 26) and hydrocarbons are designed in such a way that the ratio of the volumetric flow rate of the first stream of converted gas to the volumetric flow rate of the second stream of converted gas can be adjusted.

[0093] This allows for even greater flexibility in regulating the plant operation to increase its productivity and to regulate directly during operation the amount of hot converted gas that is sent to the heat exchange circuit of the steam generation apparatus and the amount of hot converted gas that is sent to the heat exchange circuit of the additional steam reforming apparatus. This allows for an additional increase in the service life of the equipment used to obtain ammonia by eliminating critical modes of its operation.

[0094] In a preferred embodiment, the line for feeding the steam-gas mixture flow is designed with the possibility of regulating the ratio of the volumetric flow rate of the main steam-gas mixture flow to the volumetric flow rate of the additional steam-gas mixture flow.

[0095] This allows for even greater flexibility in regulating the operation of the plant to increase its productivity and to regulate directly during operation the amount of steam-gas mixture flow that is sent to the steam reforming apparatus and the amount of steam-gas mixture flow that is sent to the additional steam reforming apparatus. This allows for an additional increase in the service life of the equipment used to obtain ammonia by eliminating critical modes of its operation.

[0096] In a preferred embodiment, the line for removing the first stream of converted gas from the converter for catalytic conversion of hydrocarbons is designed in such a way that the first stream of converted gas after the steam generation apparatus can be directed: for further processing or to an additional steam generation apparatus and then for further processing.

[0097] This allows for even greater flexibility in regulating the plant operation to increase its productivity. If the output from the steam generator is too hot for further processing, it can be sent to an additional steam generator before further processing so that its thermal energy can be used to power the devices used

[0098] SUBSTITUTE SHEET (RULE 26) in the process of obtaining ammonia. This allows for an additional increase in the service life of the equipment used to obtain ammonia by eliminating critical modes of its operation.

[0099] In a preferred embodiment, the line for removing the second stream of converted gas from the converter for catalytic conversion of hydrocarbons is designed in such a way that the second stream of converted gas after the heat exchange circuit of the additional steam reforming apparatus can be directed: for further processing or to a steam generation apparatus and / or to an additional steam generation apparatus and then for further processing, or to a heat exchanger for heating an additional stream of steam-gas mixture before feeding it to an additional steam reforming apparatus, then to a steam generation apparatus and / or to an additional steam generation apparatus and then for further processing.

[0100] This allows for even greater flexibility in regulating the plant operation to increase its productivity. If the output stream from the heat exchange circuit of the additional steam reformer is too hot for further processing, it can be sent to a heat exchanger before further processing so that its thermal energy can be used to heat an additional flow of steam-gas mixture, which will ensure deeper conversion of methane and lower metal consumption of the heat exchange reformer, as well as to steam generation devices to provide energy to devices used in the process of obtaining ammonia.

[0101] In a preferred embodiment, the first converted gas flow outlet line and the second converted gas flow outlet line are connected in such a way that the first converted gas flow and the second converted gas flow are combined before being fed for further processing.

[0102] This allows obtaining a flow of converted gas of a given temperature to increase the service life of equipment used to obtain ammonia by eliminating critical operating modes.

[0103] In a preferred embodiment, the hydrocarbon catalytic conversion converter is a shaft converter, the steam reformer is a tubular steam reformer, and the additional steam reformer is a tubular converter.

[0104] SUBSTITUTE SHEET (RULE 26) In the present invention, any converters and steam reforming devices known from the state of the art, which are used for the conversion of hydrocarbons that are already present in the installation, can be used. At the same time, the above-mentioned particular variants represent the simplest and most effective devices.

[0105] A shaft converter or shaft-type converter is a cylindrical apparatus with a lid, which has a refractory lining and is filled with a nickel catalyst.

[0106] The tube furnace contains tubes filled with nickel catalyst that are heated by burning fuel.

[0107] The tubular converter contains tubes filled with a nickel catalyst, which are heated by a heat exchange circuit.

[0108] Also, in order to solve the above-mentioned problem and achieve the technical result, a method is proposed for operating the above-mentioned hydrocarbon conversion unit in any manner, including the following operations: feeding a steam-gas mixture flow, dividing the steam-gas mixture flow into a main flow, which is fed to a steam reforming apparatus, and an additional flow, which is fed to an additional steam reforming apparatus, feeding converted gas from the steam reforming apparatus and the additional steam reforming apparatus to a converter for catalytic conversion of hydrocarbons, feeding air to the converter for catalytic conversion of hydrocarbons, removing at least a portion of the converted gas flow into a heat exchange circuit of an additional steam reforming apparatus, characterized in that the ratio of the volumetric flow rate of the main steam-gas mixture flow to the volumetric flow rate of the additional steam-gas mixture flow is from 90: 10 to 81: 19.

[0109] In a preferred embodiment, the ratio of the volumetric flow rate of the main flow of the steam-gas mixture to the volumetric flow rate of the additional flow of the steam-gas mixture is from 90:10 to 85:15.

[0110] SUBSTITUTE SHEET (RULE 26) In a preferred embodiment, a first stream of converted gas and a second stream of converted gas are removed from the converter for catalytic conversion of hydrocarbons, wherein the first stream of converted gas is sent to a steam generation apparatus, and the second stream of converted gas is sent to the heat exchange circuit of an additional steam reforming apparatus.

[0111] In a preferred embodiment, the ratio of the volumetric flow rate of the first converted gas stream to the volumetric flow rate of the second converted gas stream is from 10:90 to 90:10, preferably from 15:85 to 85:15, preferably from 20:80 to 80:20, more preferably from 70:30 to 90:10, more preferably from 80:20 to 90:10.

[0112] This allows generating the required amount of steam to provide the unit with energy while maintaining the plant's ammonia productivity, and also ensuring the same pressure drop in both flows: the first and second, which leads to an increase in the ammonia unit's productivity for the finished product, as well as to an increase in the temperature of the converted gas before the steam generation apparatus, to an increase in the steam generation in them and a decrease in hydraulic losses along the natural gas reforming path.

[0113] In a preferred embodiment, the first stream of converted gas after the steam generation apparatus is directed: for further processing or to an additional steam generation apparatus and then for further processing.

[0114] In a preferred embodiment, the second stream of converted gas after the heat exchange circuit of the additional steam reforming apparatus is directed: for further processing or to a steam generation apparatus and / or to an additional steam generation apparatus and then for further processing, or to a heat exchanger for heating the additional stream of steam-gas mixture before feeding it to the additional steam reforming apparatus, then to a steam generation apparatus and / or to an additional steam generation apparatus and then for further processing.

[0115] In a preferred embodiment, the first converted gas stream and the second converted gas stream are combined before being fed for further processing.

[0116] SUBSTITUTE SHEET (RULE 26) In a preferred embodiment, the air supplied to the converter for catalytic conversion of hydrocarbons has a temperature of 420-560°C, preferably 450-520°C, and the ratio of the volumetric flow rate of the converted gas supplied to the converter for catalytic conversion and the said air is selected so that the converted gas exiting the converter for catalytic conversion of hydrocarbons has a ratio of (H2+CO) / N2 equal to 3.0-3.05.

[0117] The above ratio (H2+CO) / N2 equal to 3.0-3.05 corresponds to the stoichiometric indicator of the ammonia synthesis reaction and ensures the most efficient use of reagents without wasting them.

[0118] In a preferred embodiment, the steam-gas mixture comprises a mixture of natural gas purified from sulfur and steam, wherein the volume ratio of natural gas to steam is 1:3.0-3.9, preferably 1:3.2-3.7, preferably 1:3.35-3.6, more preferably 1:3.4.

[0119] Compared with known methods, where the said ratio is higher, for example 1:4, the above-mentioned ratio of natural gas to steam makes it possible to reduce hydraulic loads on the devices included in the installation and to increase the service life of the devices included in the installation.

[0120] In a preferred embodiment, the steam-gas mixture has a temperature of 350-560°C, preferably 480-520°C, and a pressure of 26-45 atm, preferably 35-37 atm.

[0121] In a preferred embodiment, the converted gas exiting the steam reforming apparatus and the additional steam reforming apparatus has a temperature of 780-860°C, preferably 790-820°C, and a pressure of 26-39 atm., preferably 32-34 atm.

[0122] In a preferred embodiment, the converted gas exiting the converter for catalytic conversion of hydrocarbons has a temperature of 910-1000°C, preferably 960-990°C, and a pressure of 26-38 atm., preferably 31-33 atm.

[0123] In a preferred embodiment, the converted gas leaving the heat exchange circuit of the additional steam reforming apparatus has a temperature of 550-850°C, preferably 600-700°C.

[0124] The above-mentioned modes additionally allow to increase the service life of the equipment used for obtaining ammonia by eliminating critical modes of its operation.

[0125] SUBSTITUTE SHEET (RULE 26) Brief description of drawings

[0126] The drawings are presented for a better understanding of the invention, however, it will be obvious to a person skilled in the art that the disclosed invention is not limited to the embodiments shown therein.

[0127] Fig. 1 is a schematic view of a natural gas conversion plant according to a first embodiment of the present invention.

[0128] Fig. 2 shows a schematic view of a natural gas conversion plant in accordance with a second (best) embodiment of the present invention.

[0129] Variants of implementation of the invention. The best embodiment

[0130] Description of the process flow diagram of the proposed two-stage steam-air conversion plant for natural gas with parallel steam converters.

[0131] After compression, natural gas is mixed with a stream of hydrogen-containing gas so that the hydrogen content in the mixture is about 5%.

[0132] The mixture is heated to 350-400°C, preferably to 370°C, and fed into a desulphurization reactor loaded with an aluminum-cobalt-molybdenum catalyst, where the hydrogenation of sulphur compounds present in the natural gas to H2S occurs.

[0133] The gas mixture then enters adsorbers loaded with zinc absorbent, where H2S is absorbed to form zinc sulfide.

[0134] Natural gas purified from sulfur is mixed with a process steam flow in a volume ratio of 1:3.4, after which it is heated in a heat exchanger (heat-utilizing equipment unit (HUE)) and the resulting steam-gas mixture flow is fed under pressure to the hydrocarbon conversion unit. In this case, an additional steam-gas mixture flow sent to the heat exchange reforming circuit can be withdrawn before the main flow is heated in the HUE zone in order to maintain the existing heat load on the steam-gas mixture heating coil.

[0135] The steam-gas mixture flow is fed to the hydrocarbon conversion unit via line 100 for feeding the steam-gas mixture flow, including sections 100a, 101a, 102a, 102b.

[0136] Line 100 for feeding a flow of steam-gas mixture allows dividing the flow of steam-gas mixture into a main flow 101 of steam-gas mixture moving along section 101a, and an additional flow 102 of steam-gas mixture moving along sections 102a, 102b. Line 100 for feeding a flow of steam-gas mixture allows

[0137] SUBSTITUTE SHEET (RULE 26) regulate the ratio of the volumetric flow rate of the main flow 101 of the steam-gas mixture to the volumetric flow rate of the additional flow 102 of the steam-gas mixture using valve V-102a

[0138] The main flow 101 of the steam-gas mixture is directed through section 101a to the R-101a steam reforming apparatus (tubular steam reforming furnace), and the additional flow 102 of the steam-gas mixture is directed through section 102a to the H-102a heat exchanger, where it is heated, and then through section 102b enters the additional R-102b steam reforming apparatus (tubular converter), equipped with an H-102b heat exchange circuit, where steam conversion of the steam-gas mixture occurs and converted gas is obtained.

[0139] From the R-101a steam reformer, the converted gas is fed via line 101б to the R-101b converter for catalytic conversion of hydrocarbons (shaft converter). From the additional R-102b steam reformer, the converted gas is also fed via line 102c to the R-101b converter for catalytic conversion of hydrocarbons, where heated process air is also fed via line 200. The streams entering via lines 101б and 102с can either enter the R-101b converter separately or be combined in section 103 and enter the R-101b converter together.

[0140] In the upper part of the R-101b converter for catalytic conversion of hydrocarbons, in the free space above the catalyst bed, a portion of the mixture of both converted gas flows entering via line 101b and line 102c burns with an increase in temperature. With this temperature, the hot flow passes through a bed of loaded nickel catalyst, in which the conversion of methane residual after steam reforming occurs with the formation of H2, CO and CO2. The ratio of the volumes of converted gas and process air ensures a ratio of H2+CO) / N2 equal to 3.0-3.05 at the outlet of the shaft converter, which corresponds to the stoichiometric indicator of the ammonia synthesis reaction.

[0141] In the tubular steam reforming furnace (R-101a steam reforming unit), the endothermic steam reforming process occurs due to the heat released during fuel combustion, and in the tubular converter (additional R-102b steam reforming unit), due to the utilization of heat from the converted gas stream removed from the R-101b converter for the catalytic conversion of hydrocarbons.

[0142] SUBSTITUTE SHEET (RULE 26) In both R-101a and R-102b units, the reaction tubes are loaded with a nickel catalyst, and primary reforming is carried out in them - steam reforming (catalytic conversion of hydrocarbons in the presence of steam), and in the R-101b converter for catalytic conversion of hydrocarbons (shaft converter), secondary reforming is carried out - catalytic conversion of hydrocarbons.

[0143] The R-101b converter for catalytic conversion of hydrocarbons is connected to a line 111 for withdrawing the first stream of converted gas, which includes sections Illa, 111b, 111c, and a line 112 for withdrawing the second stream of converted gas, which includes sections 112a, 112b, 112c, 112d, 112e.

[0144] The line 111 for removing the first stream of converted gas from the converter for catalytic conversion of hydrocarbons and the line 112 for removing the second stream of converted gas from the converter for catalytic conversion of hydrocarbons are designed in such a way that the ratio of the volumetric flow rate of the first stream of converted gas to the volumetric flow rate of the second stream of converted gas can be adjusted using valves V-lllc, V-112c, V-112e.

[0145] The first stream of converted gas is sent via section 111a to the steam generation apparatus G-111a (waste heat boiler), from which via section 111b it enters an additional steam generation apparatus G-lllb (waste heat boiler). In both steam generation apparatuses, the heat of the hot converted gas is utilized to provide energy to devices used in the process of obtaining ammonia, and then via section 111c it enters for further processing via line 113.

[0146] The second stream of converted gas is sent through section 112a to heat exchange circuit H-102b of additional steam reforming apparatus R-102b, where its thermal energy is used to heat additional stream 102 of steam-gas mixture, which will provide deeper conversion of methane. Then the second stream of converted gas is fed through section 112b to heat exchanger H-102a to heat additional stream 102 of steam-gas mixture before it is fed to additional steam reforming apparatus R-102b. The second stream of converted gas is then fed through section 112c and section 112d to the additional apparatus G-lllb for generating steam, and then it enters section 111c, in which both streams (the first and the second) are combined before being fed for further processing through line 113. Depending on the temperature of the second stream in section 112c, part of the second stream or the entire second stream can be directed through section 112e, bypassing the additional apparatus G-lllb.

[0147] SUBSTITUTE SHEET (RULE 26) steam generation, which will allow it to immediately enter line 113, in which both streams (the first and the second) will be combined before being fed for further processing.

[0148] Section 112d, 112e may be a bypass line already present on the modernized plant, which simplifies the insertion of line 112 for the second converted gas flow into it. Bypass line 112d, 112e is designed with the possibility of regulating the ratio of the volumetric flow rate of the flow entering through line 112d to the volumetric flow rate of the flow entering through line 112e using valve V-112e.

[0149] The operating modes of the declared installation and its method of operation, as well as the results obtained, are presented in the table below.

[0150] SUBSTITUTE SHEET (RULE 26) Table

[0151]

[0152]

[0153]

[0154] The following advantages are achieved by implementing the present invention:

[0155] 1. It provides the possibility of upgrading existing installations in order to increase their productivity. The technological scheme is simplified, while maintaining a deep degree of methane conversion.

[0156] 2. Flexible control of hot flows is provided, which allows for simultaneous achievement of a high degree of methane conversion, provision of energy to the necessary devices, reduction of requirements for the equipment used and increase of its service life by eliminating critical operating modes.

[0157] 3. A deep degree of methane conversion is achieved, which allows obtaining converted gas ready for further processing with a methane content of 0.20-0.21 vol. %, using a simpler process flow diagram than in known analogues. In particular, without the need to use preliminary reforming devices, as well as additional flow heaters on the line between the secondary reforming device (shaft converter) and the steam generation device.

[0158] 4. The converted gas formed in the shaft converter has an optimal ratio for subsequent ammonia synthesis (H2+CO) / N2 ~ 3. Moreover, this ratio is achieved at lower temperatures of the process in the shaft converter than in known analogues.

[0159] 5. Due to the fact that the target process indicators for residual methane content and the (H2+CO) / N2 ratio are achieved at lower temperatures, the equipment required to implement such a process has a longer service life and can be made from steels with a smaller range of requirements.

[0160] The described embodiment examples are given solely for illustrative purposes. It will be obvious to a specialist that other embodiments are possible without changing the essence of the invention.

[0161] Conventional designations on drawings:

[0162] 100 - line for feeding the steam-gas mixture flow

[0163] 101 - main flow of steam-gas mixture

[0164] SUBSTITUTE SHEET (RULE 26) 102 - additional flow of steam-gas mixture

[0165] 100a - section of line 100 for feeding a flow of steam-gas mixture for separation into the main and additional flows

[0166] 101a - section of line 100 for feeding a flow of steam-gas mixture, through which the main flow of steam-gas mixture enters the R-101a steam reforming apparatus

[0167] 102a - section of line 100 for feeding a flow of steam-gas mixture, through which an additional flow of steam-gas mixture enters the heat exchanger H-102a

[0168] 102Ь - section of line 100 for feeding a flow of steam-gas mixture, through which an additional flow of steam-gas mixture enters an additional R-102b steam reforming apparatus

[0169] R-101a - steam reformer

[0170] R-102b - Additional steam reformer

[0171] H-102Ь - heat exchange circuit of additional steam reforming apparatus

[0172] 101Ь - line for feeding converted gas from the R-101a steam reformer to the R-101b converter for catalytic conversion of hydrocarbons

[0173] 102c - line for feeding converted gas from the additional R-102b steam reformer to the R-101b converter for catalytic conversion of hydrocarbons

[0174] 103 - line in which the streams coming from lines 101b and 102c are combined before being fed to the R-101b converter for the catalytic conversion of hydrocarbons

[0175] R- 101Ь - converter for catalytic conversion of hydrocarbons

[0176] 200 - Air supply line to the R-101b converter for catalytic conversion of hydrocarbons

[0177] 111 - line for the removal of the first stream of converted gas from the R-101b converter for the catalytic conversion of hydrocarbons

[0178] 111a - section of line 111 for removing the first flow of converted gas, through which the converted gas enters the apparatus Gl 11a for generating steam

[0179] 111b - section of line 111 for the first flow of converted gas, through which the converted gas enters the additional apparatus Gl l lb for generating steam

[0180] 111c - section of line 111 for removing the first stream of converted gas, through which the converted gas is fed for further processing through line IZ.

[0181] 112 - line for the withdrawal of the second stream of converted gas from the R-101b converter for catalytic conversion of hydrocarbons

[0182] SUBSTITUTE SHEET (RULE 26) 112a - section of line 112 for the second flow of converted gas, through which the converted gas enters the heat exchange circuit H-102b of the additional apparatus R-102b of the steam reforming

[0183] 112Ь - section of line 112 for the second flow of converted gas, through which the converted gas enters the heat exchanger H-102a

[0184] 112c - section of line 112 for removing the second stream of converted gas, through which the converted gas enters the bypass line 112d, 112e, designed with the possibility of regulating the ratio of the volumetric flow rate of the stream entering through line 112d to the volumetric flow rate of the stream entering through line 112e

[0185] 112d - section of line 112 for the withdrawal of the second flow of converted gas, through which the converted gas enters the additional apparatus Gl l lb for generating steam

[0186] 112e - section of line 112 for the second flow of converted gas, through which the converted gas enters line IZ bypassing the additional apparatus Gl 11Ь for generating steam

[0187] H-102a - heat exchanger for heating additional flow 102 of steam-gas mixture before feeding it to additional apparatus R-102Ь of steam reforming

[0188] V-102a - valve for regulating the volumetric flow rate of the steam-gas mixture in section 102a

[0189] V-112c - valve for regulating the volumetric flow rate of converted gas in section 112c

[0190] V-112e - valve for regulating the volumetric flow rate of converted gas in section 112e

[0191] V-111c - valve for regulating the volumetric flow rate of converted gas in section 111c

[0192] Gl 11a - steam generating apparatus

[0193] Gl l lb - additional steam generation device

[0194] IZ - a line in which the first stream of converted gas and the second stream of converted gas are combined before being fed for further processing

[0195] SUBSTITUTE SHEET (RULE 26)

Claims

Invention formula 1. A hydrocarbon conversion plant comprising: a steam reforming apparatus, an additional steam reforming apparatus equipped with a heat exchange circuit, a converter for catalytic conversion of hydrocarbons configured to feed air and converted gas thereto, a line for feeding a steam-gas mixture flow that allows the steam-gas mixture flow to be divided into a main steam-gas mixture flow that is fed to the steam reforming apparatus, and an additional steam-gas mixture flow that is fed to the additional steam reforming apparatus, wherein the steam reforming apparatus and the additional steam reforming apparatus are configured to feed converted gas to the converter for catalytic conversion of hydrocarbons, wherein the converter for catalytic conversion of hydrocarbons is configured to divert at least a portion of the converted gas flow into the heat exchange circuit of the additional steam reforming apparatus, characterized in thatthat the line for feeding the flow of the steam-gas mixture allows the flow of the steam-gas mixture to be divided in such a way that the ratio of the volumetric flow rate of the main flow of the steam-gas mixture to the volumetric flow rate of the additional flow of the steam-gas mixture is from 90: 10 to 81: 19., 2. The installation according to paragraph 1, characterized in that the line for feeding the flow of steam-gas mixture allows the flow of steam-gas mixture to be divided in such a way that the ratio of the volumetric flow rate of the main flow of steam-gas mixture to the volumetric flow rate of the additional flow of steam-gas mixture is from 90: 10 to 85:

15.

3. The installation according to paragraph 1, characterized in that the converter for catalytic conversion of hydrocarbons is connected to a line for removing the first stream of converted gas from the converter for catalytic conversion of hydrocarbons and a line for removing the second stream of converted gas from the converter for catalytic conversion of hydrocarbons, wherein SUBSTITUTE SHEET (RULE 26) the line for removing the first stream of converted gas allows the first stream of converted gas to be directed to the steam generation apparatus, the line for removing the second stream of converted gas allows the second stream of converted gas to be directed to the heat exchange circuit of the additional steam reforming apparatus.

4. The installation according to paragraph 3, characterized in that the line for removing the first stream of converted gas from the converter for catalytic conversion of hydrocarbons and the line for removing the second stream of converted gas from the converter for catalytic conversion of hydrocarbons are designed in such a way that the ratio of the volumetric flow rate of the first stream of converted gas to the volumetric flow rate of the second stream of converted gas can be adjusted.

5. The installation according to paragraph 1, characterized in that the line for feeding the flow of steam-gas mixture is designed with the possibility of regulating the ratio of the volumetric flow rate of the main flow of steam-gas mixture to the volumetric flow rate of the additional flow of steam-gas mixture.

6. The installation according to paragraph 4, characterized in that the line for removing the first stream of converted gas from the converter for catalytic conversion of hydrocarbons is designed in such a way that the first stream of converted gas after the steam generation apparatus can be directed: for further processing or to an additional steam generation apparatus and then for further processing.

7. The installation according to paragraph 6, characterized in that the line for removing the second stream of converted gas from the converter for catalytic conversion of hydrocarbons is designed in such a way that the second stream of converted gas after the heat exchange circuit of the additional steam reforming apparatus can be directed: for further processing or to a steam generation apparatus and / or to an additional steam generation apparatus and then for further processing, or to a heat exchanger for heating an additional stream of steam-gas mixture before feeding it to an additional steam reforming apparatus, then to the apparatus SUBSTITUTE SHEET (RULE 26) steam generation and / or into an additional steam generation apparatus and then for further processing.

8. The installation according to paragraph 7, characterized in that the line for removing the first stream of converted gas and the line for removing the second stream of converted gas are connected in such a way that the first stream of converted gas and the second stream of converted gas are combined before being fed for further processing.

9. The installation according to paragraph 1, characterized in that the converter for catalytic conversion of hydrocarbons is a shaft converter, the steam reforming apparatus is a tubular steam reforming furnace, and the additional steam reforming apparatus is a tubular converter.

10. A method for operating a hydrocarbon conversion plant according to any one of paragraphs 1-9, comprising the following operations: feeding a steam-gas mixture flow, dividing the steam-gas mixture flow into a main flow, which is fed to a steam reforming apparatus, and an additional flow, which is fed to an additional steam reforming apparatus, feeding converted gas from the steam reforming apparatus and the additional steam reforming apparatus to a converter for catalytic conversion of hydrocarbons, feeding air to the converter for catalytic conversion of hydrocarbons, removing at least a portion of the converted gas flow into a heat exchange circuit of the additional steam reforming apparatus, characterized in that the ratio of the volumetric flow rate of the main steam-gas mixture flow to the volumetric flow rate of the additional steam-gas mixture flow is from 90:10 to 81:

19.

11. The method according to paragraph 10, characterized in that the ratio of the volumetric flow rate of the main flow of the steam-gas mixture to the volumetric flow rate of the additional flow of the steam-gas mixture is from 90: 10 to 85:

15. SUBSTITUTE SHEET (RULE 26) 12. The method according to paragraph 10, characterized in that a first stream of converted gas and a second stream of converted gas are removed from the converter for catalytic conversion of hydrocarbons, wherein the first stream of converted gas is sent to a steam generation apparatus, and the second stream of converted gas is sent to the heat exchange circuit of an additional steam reforming apparatus.

13. The method according to claim 12, characterized in that the ratio of the volumetric flow rate of the first stream of converted gas to the volumetric flow rate of the second stream of converted gas is from 10:90 to 90:10, preferably from 15:85 to 85:15, preferably from 20:80 to 80:20, more preferably from 70:30 to 90:10, more preferably from 80:20 to 90:

10.

14. The method according to paragraph 12, characterized in that the first stream of converted gas after the steam generation apparatus is directed: for further processing or to an additional steam generation apparatus and then for further processing.

15. The method according to paragraph 14, characterized in that the second stream of converted gas after the heat exchange circuit of the additional steam reforming apparatus is sent: for further processing or to a steam generation apparatus and / or to an additional steam generation apparatus and then for further processing, or to a heat exchanger for heating the additional stream of steam-gas mixture before feeding it to the additional steam reforming apparatus, then to the steam generation apparatus and / or to an additional steam generation apparatus and then for further processing.

16. The method according to paragraph 15, characterized in that the first stream of converted gas and the second stream of converted gas are combined before being fed for further processing.

17. The method according to paragraph 10, characterized in that the air supplied to the converter for catalytic conversion of hydrocarbons has a temperature of 420-560°C, preferably 450-520°C, and the ratio of the volumetric flow rate of the converted gas supplied to the converter for catalytic conversion and the said air is selected such that SUBSTITUTE SHEET (RULE 26) The converted gas leaving the hydrocarbon catalytic converter had a ratio of (H2+CO) / N2 equal to 3.0-3.

05.

18. The method according to claim 10, characterized in that the steam-gas mixture contains a mixture of natural gas purified from sulfur and steam, wherein the volume ratio of natural gas to steam is 1:3.0-3.9, preferably 1:3.2-3.7, preferably 1:3.35-3.6, more preferably 1:3.

4.

19. The method according to paragraph 10, characterized in that the steam-gas mixture has a temperature of 350-560°C, preferably 480-520°C, and a pressure of 26-45 atm., preferably 35-37 atm.

20. The method according to paragraph 10, characterized in that the converted gas exiting the steam reforming apparatus and the additional steam reforming apparatus has a temperature of 780-860°C, preferably 790-820°C, and a pressure of 26-39 atm., preferably 32-34 atm.

21. The method according to paragraph 10, characterized in that the converted gas exiting the converter for catalytic conversion of hydrocarbons has a temperature of 910-1000°C, preferably 960-990°C, and a pressure of 26-38 atm., preferably 31-33 atm.

22. The method according to paragraph 10, characterized in that the converted gas leaving the heat exchange circuit of the additional steam reforming apparatus has a temperature of 550-850°C, preferably 600-700°C. SUBSTITUTE SHEET (RULE 26)

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