RU2720813C1 - Gas processing cluster - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention relates to a gas processing cluster intended for additional processing of methane-hydrogen fraction (MHF). A cluster consists of a methane liquefaction unit and liquefied natural gas (LNG) storage unit. MHF is supplied to methane liquefaction unit, from where liquefied methane is supplied to reservoirs of LNG storage unit. Then, LNG is pumped out as a commercial product, uncondensed part of MHF from methane liquefaction unit in form of hydrogen-bearing gas (HBG) is subjected to methane purification in additional HBG purification unit, after which purified hydrogen is successively supplied to an additional hydrogen liquefaction unit, which includes an ortho-para-converter of hydrogen, and into reservoirs of an additional unit for storing liquefied hydrogen. Further, liquefied hydrogen is pumped out in the form of a commercial product, the stripping gas from reservoirs of the LNG storage unit and the tail gas from the additional purification unit HBG is diverted to the gas processing works fuel system and / or recycled.

EFFECT: technical result consists in development of gas processing cluster, which ensures processing of cheap by-product of gas- and petrochemical processes – MHF – into valuable commodity products in the form of LNG and liquefied hydrogen.

10 cl, 4 dwg, 4 tbl

Description

The gas processing cluster is designed for additional processing of the methane-hydrogen fraction (IMF) of the units of oil and gas chemical complexes and can be used in the oil refining, petrochemical and gas chemical industries.

One of the characteristic non-commodity technological flows of modern large-capacity gas and petrochemical plants that perform thermal and catalytic destruction of hydrocarbons, for example, pyrolysis, cracking and dehydrogenation units of light and heavy hydrocarbon fractions, is the IMF, which is separated from the target fractions. So, for example, in pyrolysis plants in the production of monomers: ethylene and propylene, 0.05-0.19 t of IMF is produced per 1 ton of raw material, depending on the type of feedstock. According to the plan for the development of oil and gas chemistry of the Russian Federation, by 2030 it is necessary to bring the processing of raw materials for the production of monomers to 55.7 million tons / year, which requires the creation of six large production clusters near large existing sources of petrochemical raw materials (Bikchurina A.R. the development of pyrolysis complexes / A.R. Bikchurina, I.V. Tsivunina // Bulletin of the Technological University. - 2015. - No. 9 (19). - P. 137-139). At the same time, taking the IMF average yield of 0.1 t / t of raw materials, its associated production will amount to 5.5 million tons / year, which raises the question of the effective use of this product.

Currently, the IMF is mainly used as fuel for power plants directly at petrochemicals and thermal power plants. However, at the price of marketable fuel gas at the level of 8-10 rubles / kg, this is an irrational use of resources, since hydrogen is currently predominantly produced by an expensive catalytic method due to the interaction of water vapor with methane at a temperature of 700-1000 ℃. It is more efficient to process the IMF with separate production of methane and hydrogen, and use commercial fuel gas for the fuel needs of gas and petrochemical enterprises. In addition, the IMF of gas-chemical processes is a mixture of methane and hydrogen, practically free of impurities, which significantly reduces the costs of its processing due to the lack of costs for preparatory cleaning procedures. The growing demand for liquefied hydrogen and liquefied natural gas (LNG) will allow the IMF processing to achieve the maximum realization of the product potential of this fraction.

A known method for the simultaneous production of at least one gaseous product, as well as a product consisting mainly of liquid methane, from an initial mixture consisting mainly of hydrogen, carbon monoxide and methane, where the initial mixture is divided into several fractions in a device for low-temperature gas separation, while the methane fraction having commercial purity is discharged in the form of a liquid after low-temperature gas separation, and preferably, after additional cooling, it is accumulated in the form of liquefied methane in an intermediate tank (patent RU 2456517 C2, IPC F25J 3/02, filed March 11, 2003). 2008, published on July 20, 2012). The disadvantages of the invention are:

- the inability to regulate the quality of marketable products due to the limitation of the composition of the resulting LNG due to the equilibrium between the liquid and gas phases;

- the lack of liquefaction of the resulting hydrogen due to the need for post-treatment, which limits its product potential.

A known method of hydrogen evolution from a gas mixture containing hydrogen and methane obtained by thermal decomposition of methane, which consists in passing this mixture in an adsorption step under increased pressure through an adsorbent bed, while releasing pure hydrogen for subsequent external use, in reducing the pressure in the stage desorption and separation of adsorbed components such as hydrogen and methane, a hydrogen-methane mixture is obtained by methane pyrolysis, from which pure hydrogen is extracted in the stage of adsorption at a pressure of 0.5-2.0 MPa, and in the stage of desorption, the pressure is first reduced to 0, 1 MPa and a substandard hydrogen fraction is isolated, which is returned to the adsorber inlet, and then, to complete the desorption stage, the pressure is lowered to a lower level of 0.010-0.005 MPa and a fraction containing predominantly methane is returned to the feed stream fed to pyrolysis, which allows to obtain additional hydrogen (patent RU 2466 928 C2, IPC C01B 3/56, B01D 53/047, announced December 24, 2009, published November 20, 2011). The disadvantages of the invention are:

- the lack of preliminary purification of hydrogen from methane by low-temperature gas-liquid processes, significantly increasing the load on the capital and material-intensive sites of adsorption purification when hydrogen is extracted from the IMF processes of oil and gas chemistry containing 30-70% (mass.) methane;

- the complexity of the implementation in an industrial environment of the return of a substandard hydrogen fraction extracted at the desorption stage and having a variable pressure (from 0.5-2.0 MPa to 0.1 MPa) at the inlet of the adsorber at a pressure of incoming raw materials of 0.5-2.0 MPa;

- the complexity of the implementation in industrial conditions of the return to the pyrolysis of the methane fraction with an admixture of hydrogen isolated at the desorption stage with a variable pressure from 0.1 MPa to 0.01-0.005 MPa.

A known method of removing hydrogen and nitrogen from a methane-containing gas by distillation and LNG production, including the stage of low-temperature liquefaction and distillation separation; at the stage of low-temperature liquefaction, the methane-rich gas containing hydrogen and nitrogen enters the refrigeration chamber and is cooled by mixing with an agent that supplies the necessary amount of cold to liquefy the methane component in the refrigeration chamber; at the distillation separation stage, the stream after the low-temperature liquefaction stage enters the distillation column, from the top of which hydrogen, nitrogen and a small amount of carbon monoxide are discharged, and the liquid phase from the lower part of the distillation column is returned to the refrigeration chamber for supercooling, and LNG having a hydrogen content is obtained not more than 500 ppm, nitrogen content not more than 2% and carbon monoxide not more than 2% (patent for invention CN 104513680 A, IPC C10L 3/10, F25J 3/02, F25J 5/00, F25J 1/02, claimed September 30, 2013, published April 15, 2015). The disadvantages of the invention are:

- a high content of impurities in the LNG, due to the equilibrium between the liquid and gas phases in the process of liquefying natural gas in a distillation column and a refrigerating chamber;

- low quality of the resulting gas mixture of hydrogen, nitrogen and carbon monoxide, suitable for use only as low-calorie fuel or raw materials for subsequent hydrogen extraction.

                 When creating the invention, the task was to develop a gas processing cluster, which provides the processing of a cheap by-product of gas and petrochemical processes - the IMF - into valuable commodity products.

                The problem is solved due to the fact that the gas processing cluster consists of a methane liquefaction unit and an LNG storage unit, the IMF is fed to a methane liquefaction unit, from where the liquefied methane enters the reservoirs of the LNG storage unit, LNG is pumped out as a commercial product, the non-condensed part of the IMF from the liquefaction unit methane in the form of a hydrogen-containing gas (WGH) is purified from methane in an additional WGH purification unit, after which the purified hydrogen is subsequently fed to an additional hydrogen liquefaction unit, including, among other things, an ortho-para-hydrogen converter, and to the tanks of the additional liquefied hydrogen storage unit , then the liquefied hydrogen is pumped out as a commercial product, the stripping gas from the tanks of the LNG storage unit and the tail gas from the additional purification unit of the LNG are diverted to the fuel system of the gas processing cluster and / or recycled. This solution makes it possible to obtain liquid methane and hydrogen, which are expensive on world markets, from a cheap by-product, the IMF, by separation into technically pure gaseous methane and hydrogen.

An additional unit for purification of the second-line gas may be a methane short-cycle adsorption system (CCA), consisting of at least two alternately working adsorbers, while in one adsorber adsorption purification of the second-line gas from methane at high pressure is provided, purified hydrogen is fed to an additional hydrogen liquefaction unit, and in another adsorber at this time, the adsorbent is regenerated at low pressure, leading to the desorption of methane with its pumping and / or blowing.

Also, an additional VGU purification unit can be a system of at least two alternately operating freezer separators, while in one separator-freezer gas is throttled with the deposition of frozen solid methane, the residual methane content in the gas is captured by an adsorbent layer in the upper part of the separator -freezer, purified hydrogen is fed to an additional hydrogen liquefaction unit, and in the other separator-freezer at this time, the accumulated solid methane is thawed, pumped and / or purged, and the adsorbent is regenerated.

It is advisable in the methane liquefaction unit, the liquefaction process is carried out in one step using a nitrogen refrigeration cycle or stepwise using a nitrogen refrigeration cycle combined with a mixed refrigerant cycle and / or with a propane and / or propylene refrigeration cycle and / or with ethane and / or ethylene refrigeration cycle, which ensures the variability of the unit on various refrigerants.

It is useful to ensure the processing of gaseous raw materials containing impurities undesirable for liquefaction processes, and to improve the quality of LNG and liquefied hydrogen obtained, the gas processing cluster should be supplemented with a feed gas purification unit, which will allow regulating the quality indicators of commercial products.

It is useful to supplement the gas processing cluster with the calorie content control unit of LNG, which provides for the injection of liquefied hydrocarbon gases, propane and / or ethane into the LNG in the amount necessary to fulfill the requirements for the commercial product to ensure the required calorific value of commercial LNG.

It is also useful to combine the IMF of various plants and / or directly oil and gas chemical complexes before supplying methane to the liquefaction unit, which makes the gas processing cluster an independent enterprise, which is part of the oil and gas chemical cluster and receives raw materials from its various objects.

It is useful in case of using the CCA system of methane for adsorbent regeneration with variable pressure to equalize the pressure in the receiver, forming tail gas, and tail gas can be implemented as a component of commercial fuel gas supplied to gas distribution networks, after mixing with commercial natural gas in concentrations that allow minimize the effect of hydrogen corrosion, which expands the range of commercial products of the gas processing cluster.

It is advisable, when using a system of at least two freezer separators, to thaw solid methane in freezer separators by LNG flow from the reservoirs of the LNG storage unit with a recycle of the liquid mixed stream into the tanks, which will reduce the amount of tail gas generated at the gas processing cluster.

In figures 1-4 presents a schematic diagram of several possible embodiments of the inventive gas processing cluster:

- FIG. 1 - a gas processing cluster with an additional unit for purification of WASH using the methane CCA method and supplying stripping gas from the tanks of the LNG storage unit and tail gas from an additional unit for purification of WASH in the fuel system of the gas processing plant;

- FIG. 2 - a gas processing cluster with an additional unit for purification of WASH using the CCA method of methane and supply of stripping gas from the tanks of the storage unit of LNG and tail gas from the additional block of purification of WASH for recycling;

- FIG. 3 - gas processing cluster with an additional unit for purification of WASH by freezing methane, melting solid methane and recycling the liquid mixture stream into the tanks of the LNG storage unit;

- FIG. 4 - a gas processing cluster with an additional unit for purification of WASH by freezing methane, melting solid methane and recycle the liquid mixture stream into the tanks of the LNG storage unit and the stripping gas from the tanks of the LNG storage unit;

using the following notation:

1-11 - pipeline;

100 - methane liquefaction unit;

200 - LNG storage unit;

301 - additional unit for purification of hydrogen-containing gas (CCA method of methane);

302 - an additional unit for purification of hydrogen-containing gas (methane freezing method);

400 - an additional unit for liquefying hydrogen;

500 - an additional unit for storing liquefied hydrogen;

600 - fuel system.

The gas processing cluster of FIG. 1, operates as follows. The IMF is sent via pipeline 1 to the methane liquefaction unit 100, where it is liquefied by any known method. Liquefied methane through pipeline 2 enters the reservoir of the LNG 200 storage unit, from where LNG is pumped through pipeline 3 in the form of a commercial product. At the same time, the stripping gases generated during storage of liquefied methane from the tanks of the LNG storage unit 200 are discharged via line 4 to the fuel system 600.

The non-condensed part of the IMF in the form of SHG is fed to an additional purification unit of the SHG 301, where adsorption purification of the SHG from methane is provided at high pressure. Purified hydrogen via line 6 first enters an additional hydrogen liquefaction unit 400, including, but not limited to, an ortho-para-hydrogen converter. From the additional hydrogen liquefaction unit 400, liquefied hydrogen is supplied via line 8 to the tanks of the additional liquefied hydrogen storage unit 500 for further shipment through line 9 as a commercial liquefied hydrogen. The stripped hydrogen generated during storage of liquefied hydrogen via pipeline 11 from the tanks of the additional liquefied hydrogen storage unit 500 is returned for recycling to the hydrogen liquefaction unit 400. The tail gas formed after equalizing the adsorbent regeneration gas pressure in the receiver is sent through pipeline 7 from the additional purification unit VSG 301 to the fuel system 600.

The circuit of FIG. 2 is distinguished by the return of stripping gases from the tanks of the LNG storage unit 200 and tail gas from the additional purification unit of the LNG 301 through pipelines 4 and 7, respectively, to recycling for mixing with the original IMF.

The gas processing cluster of FIG. 3 and FIG. 4, includes an additional purification unit, 30G, where the incoming gas 5 is throttled to precipitate frozen solid methane and adsorbent residual methane, to obtain purified dry gas for further liquefaction in an additional hydrogen liquefaction unit 400. The thawed methane formed during thawing of the separator-freezer is piped 10 is diverted to the LNG storage unit 200. The circuit of FIG. 4 is distinguished by the return of stripping gases from the tanks of the LNG 200 storage unit through pipeline 4 to a recycling unit for mixing with the original IMF.

Tables 1-4 show material balances for each of the embodiments of the inventive gas processing cluster according to the diagrams in FIG. 1-4 with the production of ethylene pyrolysis units with a capacity of 2.8 million tons / year for ethylene and propane dehydrogenation plants with a capacity of 1.5 million tons / year for propylene from the initial IMF in the amount of 0.6579 million tons / year.

Thus, the claimed invention solves the problem of developing a gas processing cluster that provides the processing of a cheap by-product of gas and petrochemical processes - IMF - into valuable commodity products in the form of LNG and liquefied hydrogen.

Claims (10)

1. A gas processing cluster consisting of a methane liquefaction unit and a liquefied natural gas (LNG) storage unit, a methane-hydrogen fraction (IMF) is fed to a methane liquefaction unit, from where the liquefied methane is delivered to the tanks of the LNG storage unit, LNG is pumped out as a commercial product, characterized in that the non-condensed part of the IMF from the methane liquefaction unit in the form of a hydrogen-containing gas (WASH) is subjected to methane purification in an additional Wash purification unit, after which the purified hydrogen is subsequently fed to an additional hydrogen liquefaction unit, including, but not limited to, an ortho-para converter hydrogen, and into the tanks of the additional unit for storing liquefied hydrogen, then liquefied hydrogen is pumped out as a commercial product, the stripping gas from the tanks of the LNG storage unit and tail gas from the additional unit for cleaning the LNG are removed to the fuel system of the gas processing cluster and / or returned for recycling. 2. The cluster according to claim 1, characterized in that the additional unit for cleaning the WASH is a system of short-cycle adsorption (CCA) of methane, consisting of at least two alternately working adsorbers, while in one adsorber provide adsorption purification of WASH from methane at high pressure, purified hydrogen is fed to an additional hydrogen liquefaction unit, and in the other adsorber at this time, the adsorbent is regenerated at low pressure, leading to the desorption of methane with its pumping and / or blowing off. 3. The cluster according to claim 1, characterized in that the additional cleaning unit for the WASH is a system of at least two alternately working separators-freezers, while in one separator-freezer gas is throttled with the deposition of frozen solid methane, the methane content remaining in equilibrium in gas is captured by an adsorbent layer in the upper part of the freezer separator, purified hydrogen is fed to an additional hydrogen liquefaction unit, and in the other freezer separator, the accumulated solid methane is thawed, pumped and / or purged, and the adsorbent is regenerated. 4. The cluster according to claim 1, characterized in that in the methane liquefaction unit, the liquefaction process is carried out in one step using a nitrogen refrigeration cycle or stepwise using a nitrogen refrigeration cycle combined with a mixed refrigerant cycle and / or with propane and / or propylene refrigeration a cycle and / or with an ethane and / or ethylene refrigeration cycle. 5. The cluster according to claim 1, characterized in that the gas processing cluster is supplemented with a feed gas purification unit. 6. The cluster according to claim 1, characterized in that the gas processing cluster is supplemented with an LNG calorie control unit. 7. The cluster according to any one of claims 1 to 6, characterized in that the IMF of various plants and / or directly oil and gas chemical complexes are combined before being fed to the methane liquefaction unit. 8. The cluster according to claim 2, characterized in that the regeneration gas of the adsorbent with variable pressure is subjected to pressure equalization in the receiver, forming a tail gas. 9. The cluster of claim 8, characterized in that the tail gas is sold as a component of commercial fuel gas supplied to the gas distribution network, after mixing with commercial natural gas in concentrations that minimize the effect of hydrogen corrosion. 10. The cluster according to claim 3, characterized in that the thawing of solid methane in the separator-freezers is carried out by the flow of LNG from the tanks of the LNG storage unit with a recycle of the liquid mixed stream into the tanks.

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