RU2233831C2 - Method of production of methanol and plant for realization of this method - Google Patents

Abstract

FIELD: updated methods of production of methanol by direct oxidation of hydrocarbon-containing gas.

SUBSTANCE: proposed method includes delivery of heated hydrocarbon gas and compressed air to mixing unit of reactor which is located in its riding-up portion followed by direct oxidation of hydrocarbon gas, cooling and separation of reaction mixture; after cooling, reaction mixture is separated into waste gases and liquid products; raw methanol is subjected to regeneration at separation of methanol and removal of waste gases; oxidation of hydrocarbon gas is performed at two stages: homogeneous oxidation in tubular portion of reactor and subsequent heterogeneous oxidation in inter-tube portion of reactor with use of two-layer catalyst at temperature of 390-490 C and pressure of 8.0 Mpa; cooling of reaction mixture in performed first in gas-to-gas heat exchanger and then in air cooling apparatus. Plant proposed for realization of this method includes hydrocarbon gas source, reactor for oxidation of methane provided with unit for mixing the compressed air and heated methane before reaction, unit for cooling the mixture before separation, separator for separation of reaction products into waste gases and raw methanol and raw methanol regeneration unit; hydrocarbon gas source is located on complex gas preparation plant; reactor consists of two zones: one zone is reaction zone for homogeneous oxidation and other zone is used for heterogeneous oxidation by means of two-layer catalyst; first layer is metal-containing catalyst for enhancing selectivity and second layer contains Mg, Zn, Ba, Zr for oxidation of formaldehyde; homogeneous reaction is performed in reactor tubes and heterogeneous reaction is performed in inter-tube space of reactor filled with two-layer catalyst ; reactor is provided with multi-channel thermocouple, cooling unit consisting of gas-to-gas heat exchanger and air cooling apparatus which are connected with reactor, complex gas preparation unit and separator connected with raw methanol regeneration unit.

EFFECT: saving of energy; facilitated procedure.

3 cl, 2 dwg, 1 tbl

Description

The present invention relates to the field of organic chemistry, and in particular to a technology for the production of methanol by direct oxidation of a hydrocarbon-containing gas (natural gas).

Natural gas is projected to be a major hydrocarbon resource for the 21st century energy and chemical industries. The main deposits of gas and gas condensate are located in remote areas of the Far North. A sharp drop in gas production in the Russian Federation is due to the fact that large fields such as Urengoyskoye, Yamburgskoye, Medvezhye entered a period of declining production. Replenishment of production is associated with the development of small fuel and energy complex and the development of the shelf of the northern seas, which will be constrained by the lack of transport schemes and inhibitors. The main inhibitor in the fight against hydro-formation in gas production is methanol, the delivery of which to distant fields is a huge cost, several times higher than the price for the purchase of methanol from petrochemical plants.

The creation of small-tonnage methanol production plants by converting natural gas directly to fields as part of integrated gas treatment plants (GPP) would solve the above problems for the gas industry. Given the fact that further growth in gas production will be carried out due to the numerous small fields located in the Far North, this process is gaining priority.

A number of methods are known for converting methane to methanol. The steam conversion of methane to synthesis gas (a mixture of CO and H ₂ ) with its subsequent catalytic conversion to methanol (Karavaev MM, Leonov V.E. et al. Synthetic methanol technology. - Synthetic methanol technology) has wide industrial applications. 1984, pp. 72-125). However, to implement this process, it is necessary: sophisticated equipment, high requirements for gas purity, high energy costs for producing synthesis gas and its purification, a large number of intermediate stages of the process, unprofitability of small and medium-sized plants with a capacity of less than 1000 tons / day.

A known method of producing methanol, including the separate supply of pre-heated to 200-500 ° C hydrocarbon-containing gas under a pressure of 2.5-15 MPa and oxygen-containing gas into the mixing chamber, the subsequent stages of the partial oxidation of methane at an oxygen concentration of 1-4 vol.% With additional introduction reagents (metal oxide catalyst, higher gaseous hydrocarbons or oxygen-containing compounds, a cold oxidizer) into the reaction zone of the reactor, cooling the reaction mixture in a heat exchanger, methanol evolution of liquid reaction products in the separator, the exhaust flow of gaseous reaction products at the reactor entrance (RU 2049086 A). However, the need to use a catalyst or additional reagents and strong heating of the reacting gases leads to a decrease in methanol yield and an increase in the likelihood of soot formation.

A known method for the production of methanol, including the separate supply of a hydrocarbon-containing gas (natural or methane) and an oxygen-containing gas (air or oxygen) to the mixer, the subsequent supply of the mixture to an inert reactor, the gas-phase incomplete oxidation of a hydrocarbon-containing gas in a reactor under a pressure of 1-10 MPa for 2- 1000 seconds, at a temperature of 300-500 ° C in the absence of a catalyst, with an oxygen content of 2-20 vol.%, Methanol evolution in the condenser from the reaction products, return of exhaust reaction gases containing non-reactants ovavshy methane, for mixing with the hydrocarbon-containing source gas into the first reactor and a second reactor connected in series to the first reactor (GB 2,196,335 A). The method provides a high yield of methanol, and 5-15% methane can react at each pass through the reactor, however, a large reaction time limits the methanol productivity of the reactor.

A known method of producing methanol by separate supply and oxidation of a hydrocarbon-containing gas with an oxygen-containing gas at 370-450 ° C, a pressure of 5-20 MPa and a contact time of 0.2-0.222 s in the reactor, with the reaction mixture being cooled to 330-340 ° C With the introduction of methanol into the reactor (SU 1469788 A1) or cooling the reaction mixture without intermediate condensation and separation to 380-400 ° C in the interstage heat exchangers installed in the reactor, after which the reaction mixture enters into 2-3 successive oxidation stages (SU 1336471 A1) . In the first case, the need for additional consumption and re-separation of methanol leads to its inevitable losses, in another case, the installation of additional cooling circuits with the circulation of an additional cooling agent in them is required.

The closest technical solution is the methanol production method (RU 2162460 A), which includes the separate supply of sequentially compressed and heated hydrocarbon-containing gas and compressed oxygen-containing gas to the mixing zones of successive reactors, subsequent gas-phase oxidation of the hydrocarbon-containing gas at an initial temperature of up to 500 ° C, pressure up to 10 MPa and an oxygen content of not more than 8 vol.%, Cooling the reaction mixture after each reaction zone of the reactors by 70-150 ° C through the wall with a cold stream about hydrocarbon-containing gas, quenching the reaction mixture after the last reaction zone by lowering the temperature of the reaction mixture by at least 200 ° C for a time of less than 0.1 of its residence time in the reaction zone, cooling and separating the cooled reaction gas-liquid mixture into exhaust gas and liquid products after each successive reactor, rectification of liquid products with the release of methanol, the supply of exhaust gases to the original hydrocarbon-containing gas or for combustion.

The known method does not provide the necessary rate of heat removal of the reaction, which leads to the need to reduce the degree of conversion of hydrocarbon-containing gas. In addition, even the use of oxygen as an oxidizing agent does not allow to efficiently recycle a hydrocarbon-containing gas due to the rapid increase in its concentration of carbon oxides. At the same time, a significant part of the oxygen supplied is spent on the oxidation of CO to CO ₂ , leading to an additional decrease in the degree of conversion of the initial carbon-containing gas and further overheating of the reaction mixture. In addition, an additional amount of the initial hydrocarbon-containing gas must be burned to provide the stage of rectification of liquid products with steam.

A known installation for the production of methanol, containing a mixing chamber installed in series and connected by pipelines, connected to separate sources of hydrocarbon-containing gas and air or oxygen, an inert material reactor with heating elements for incomplete oxidation of methane in the mixture supplied to the reactor under excess pressure, a condenser and a separator for the separation of methanol from the reaction products, a container for recycled gaseous reaction products with a pipeline for their supply into the original hydrocarbon-containing gas or mixing chamber (GB 2196335 A). However, the long residence time of the reagents in the reactor does not allow for high plant productivity, which makes the process practically inapplicable in an industrial environment.

A known installation for producing methanol, which contains a source of hydrocarbon-containing gas, a compressor and a heater for compressing and heating the gas, a source of oxygen-containing gas with a compressor, sequentially installed reactors with sequentially alternating mixing and reaction zones with pipelines for supplying hydrocarbon-containing gas to the first mixing zone of the reactor and oxygen-containing gas in each mixing zone, recuperative heat exchangers for cooling the reaction mixture through the wall a lump of cold hydrocarbon-containing gas installed near the outlet ends of all reaction zones of the reactor with pipelines for the subsequent supply of heated hydrocarbon-containing gas to a heater, a refrigerator-condenser, a separator for separating exhaust gases and liquid products, followed by methanol separation and a pipeline for supplying exhaust gases to the initial hydrocarbon-containing gas , and a pipeline for supplying waste liquid oxygen-containing products to the first mixing zone of the reactor (RU 2162460 A).

The inability to quickly remove the heat of a high-heat volumetric reaction of hydrocarbon-containing gas oxidation leads to the need to reduce the amount of hydrocarbon-containing gas supplied and, consequently, the degree of conversion of the hydrocarbon-containing gas. In addition, even when using oxygen as an oxidizing agent, it is not possible to efficiently recycle a hydrocarbon-containing gas due to the rapid increase in its concentration of carbon oxides. At the same time, a significant part of the oxygen supplied is spent on the oxidation of CO and CO ₂ , leading to an additional decrease in the degree of conversion of the initial hydrocarbon-containing gas and further overheating of the reaction mixture. The installation also requires the burning of an additional amount of the original hydrocarbon-containing gas to provide steam for the stage of rectification of liquid products. The need to cool the gas-liquid mixture after each reactor for the separation of liquid products and its subsequent heating in front of the next reactor leads to a significant complication of the technological scheme, an increase in units of equipment and additional energy consumption.

The problem is solved in that in the method for producing methanol, which includes sequential supply to the mixing unit located in the acceleration zone of the reactor, compressed air and heated to 390 ° C hydrocarbon gas with a pressure of 8.0 MPa, the acceleration time of the onset of the reaction is 0.5 s, a homogeneous reaction occurs in the tubular part of the reactor, a heterogeneous reaction occurs in a 2-layer catalyst located in the annular part of the reactor, the reaction mixture is cooled in a recuperative gas-gas heat exchanger, the final cooling is the reaction mixture before separation takes place in the gas recovery unit (air-cooling apparatus), in the process of separation of liquid products with the release of methanol and exhaust gas, according to the invention to the complex gas treatment unit.

The required temperature at the inlet to the reactor is provided by heating the gas to a temperature of 390 ° C in a tube furnace, the initial oxygen concentration in front of the reaction zones up to 2.0% by introducing compressed air into the mixing unit of the reactor.

The problem is also solved by the fact that in a plant for producing methanol containing a source of hydrocarbon gas from a complex gas treatment unit, a reactor for oxidizing hydrocarbon gas, consisting of zones of homogeneous oxidation in the tubular part and a zone of heterogeneous oxidation in a 2-layer catalyst located in the annulus of the reactor, the task of the first catalyst layer is to increase the selectivity of the oxidation of methane to methanol on metal-containing catalysts Ni, Co, Fe, the task of the second catalyst layer is times ushenie formaldehyde used for this milder oxidants such as oxides of Mg, Zn, Ba, Zr.

The problem is solved also by the fact that this installation is a pilot plant and due to the contradictions encountered in the literature on the composition of the catalysts, the solution to the problem is achieved by experimental testing of the catalysts, the reactor design allows you to test a wide range of catalysts.

Thus, in the method for producing methanol, hydrocarbon gas from a complex gas treatment unit is subjected to direct oxidation in a reactor where compressed air is supplied, and the reaction is carried out in two stages at a temperature of 390-490 ° C, at 1% conversion, the temperature rises by 47 ° C. and cooling the reaction mixture in the reactor directly at oxygen concentrations up to 2% is not required, since methanol up to 500 ° C remains stable until the final quenching for about 4 s, which determines the distance from the reactor to the heat exchanger-recuperator heat atom.

Moreover, the presence of a stainless steel partition at the outlet of the reactor contributes to the hardening of methanol.

The reaction mixture is cooled in a gas-gas heat exchanger, where the source hydrocarbon gas with a temperature of 20 ° C and a pressure of 8.0 MPa is fed into the annular space as a cooling agent, then the reaction mixture enters the gas air-cooling apparatus. The cooled reaction mixture to 15-25 ° C enters the separator, where dry gas and crude methanol are released.

Raw methanol with a concentration of up to 50% is sent to a methanol recovery unit, where commodity methanol of 95% concentration is obtained, and still bottoms containing a small amount of formaldehyde are sent to a horizontal flare plant for combustion.

The main difference between the method and installation for methanol production is the method of sequential direct oxidation of methane to methanol in one reactor by two methods: homogeneous oxidation in the tubular part and catalytic oxidation in the annulus with the following parameters: temperature 390-490 ° C, pressure 8.0 MPa, time the reaction takes about 2.5 s, the oxygen concentration is up to 2%. To stop the oxidation of methanol, a stainless steel tube sheet is used as a partition, which also serves to secure the tubes of the reactor and to separate the tubular part and the annulus of the reactor.

When using the combined method of oxidizing methane to methanol, the degree of conversion of hydrocarbon gas per one reactor is significantly increased. This, in turn, leads to an increase in methanol yield. The use of this method significantly reduces the amount of equipment and, in turn, facilitates the task of managing the reaction process, its automation and reduces the cost of the installation project, increases the profitability of the process. The application of this methanol production method is facilitated by the fact that in gas and gas condensate fields it is possible to obtain methanol in a relatively simple way, which, in turn, reduces the qualification requirements of service personnel to the level of gas and condensate production operators. Another advantage of this method is that the exhaust gases are returned back to the technological process of the integrated gas treatment unit, without violating the mode of operation and the quality of the commercial gas, since the productivity of the methanol production plant is much lower than the performance of the integrated gas treatment plant, for example, at GPP 10 Bln. ^m3 gas / year increase in the content of nitrogen compounds in the product gas is not more than 0.37% when plant capacity obtaining methano and 6 th. tons / year, which corresponds to the requirements of OST 51.40.-93.

The task of obtaining methanol at low conversions is also facilitated by the installation of the installation in gas condensate plants, where the content of C ₂ + C ₃ in the feed gas reaches 7 vol.%, Which, in turn, contributes to an increase in methanol yield.

This methanol production plant is also distinguished by the fact that it is an environmentally friendly production, where harmful emissions are completely absent.

In the future, the invention is illustrated by specific examples of its implementation and the accompanying drawings, in which:

figure 1 depicts a General view of the installation for methanol;

figure 2 depicts a diagram of the reactor.

Installation for producing methanol contains a reactor 1 (figure 1) for the oxidation of methane directly to methanol. The reactor 1 consists of two zones 2 and 3, one of which, zone 2, designed to conduct a homogeneous gas-phase reaction, is equipped with a device 4 for mixing compressed air and methane and a device 5 with a tubular part, where a homogeneous reaction takes place in the tubes, and zone 3 represents It is an annular space filled with a 2-layer catalyst, where a heterogeneous reaction proceeds. The tubes are mounted in tube boards, which are also a partition for the distribution of flows and contribute to the hardening of methanol. In addition, the reactor 1 is equipped with a multi-channel thermowell 7, which is mounted on a tube plate 6.

The installation also contains a device for cooling the reaction mixture, which is made in the form of a gas-gas heat exchanger 8 and an air cooling apparatus ABO gas 9 connected to the reactor 1. The gas-gas heat exchanger 8 is in communication with the complex gas treatment unit 10, and furnace 11. The cooled reaction mixture is sent to a separator 12, which is connected to a gas treatment unit 10 and a methanol recovery unit 13. The reactor 1 is connected to a compressor 14 for supplying compressed air and a hydrocarbon gas heating furnace 11.

Hydrocarbon natural gas (methane content 92-98%) from the gas dehydration unit passes through a gas-gas heat exchanger 8 (Fig. 1) with a temperature of 10-20 ° C, where the reaction mixture is cooled, and heated to a temperature of 300- 350 ° C, through a heating furnace 11 with a temperature of 390-400 ° C enters the mixing unit 4 of the reactor 1, which also receives compressed air with a temperature of 50 ° C and a pressure of 8.0 MPa from the air compressor 14 in a ratio of up to 2 vol.% oxygen.

In reaction zones 2 and 3, methane is oxidized to methanol, and the reaction mixture with a temperature of up to 500 ° C enters the tube space of the gas-gas heat exchanger 8 and, heating the feed gas to 350 ° C, is sent to the gas air cooler 9, from there it enters the separator 12 with a temperature of 20-25 ° C. Separation of the gas into dry gas and raw methanol takes place in separator 12, then the dry gas is returned to the gas preparation unit 10, and the raw methanol to the methanol recovery unit 13. From the regeneration unit methanol 13 commercial methanol 95% concentration and sent to the methanol park, and still bottoms from the methanol recovery unit 13 is sent to the horizontal flare unit of the complex gas treatment unit 10 for combustion.

An example confirming the feasibility of the proposed method for the production of methanol.

Cold dry natural gas (98% methanol content) from unit 10 with a flow rate of 42,940 kg / h with a pressure of P = 8.0 MPa through a gas-gas heat exchanger 8, where it is heated to 350 ° C, is sent through a heating furnace 11 with a temperature 390-400 ° C into reactor 1, where compressed air is supplied in an amount of 7400 kg / h from compressor 14. The reaction occurs in reactor 1 in reaction zones 2 and 3. The reaction time is up to 2.5 s. Then, the reaction mixture through the gas-gas heat exchanger 8 and the air-cooling apparatus 9 enters the separator 12. The dry gas from the separator in the amount of 48350 kg / h is returned to the unit 10, and the raw methanol in the amount of 1850 kg / h is sent to the regeneration unit methanol 13.

Claims (3)

1. A method of producing methanol, comprising sequentially supplying to the mixing unit of the reactor, which is located in the upper part of the reactor, heated hydrocarbon gas and compressed air, subsequent direct oxidation of the hydrocarbon gas, cooling the reaction mixture and its separation, during which the cooled reaction mixture is separated into waste gases and liquid products, and the regeneration obtained in the process of separation of crude methanol with the release of methanol and exhaust gas, characterized in that the oxidation of hydrocarbon gas is carried out in two stages: homogeneous oxidation in the tubular part of the reactor and subsequent heterogeneous oxidation in the annular part of the reactor using a two-layer catalyst at a temperature of 390-490 ° C and a pressure of 8.0 MPa, and the reaction mixture is cooled first in a gas-gas heat exchanger, then in the gas air cooler. 2. The method according to claim 1, characterized in that in the reaction zones maintain an oxygen concentration of up to 2%, the acceleration time of the onset of the reaction is 0.5 s, the reaction time is 2.5 s, at the maximum temperature at the end of the reaction no more than 490 ° C, which is lower than the temperature of methanol oxidation, which allows not to remove heat from the reaction zone. 3. Installation for producing methanol, containing a source of hydrocarbon gas, a reactor for the oxidation of methane with a unit for mixing compressed air and heated methane before the reaction, a device for cooling the reaction mixture before separation, a separator for separating the reaction products into exhaust gases and raw methanol, block raw methanol regeneration, characterized in that the source of hydrocarbon gas is located at the complex gas treatment unit, the reactor consists of two reaction zones, one of which is a reaction zone For homogeneous oxidation, another zone is a zone for heterogeneous oxidation using a two-layer catalyst, the first layer being a metal-containing catalyst to increase selectivity, and the second layer consisting of oxides Mg, Zn, Ba, Zr for the oxidation of formaldehyde, this homogeneous reaction occurs in tubes reactor, and in the annular part of the reactor filled with a two-layer catalyst, a heterogeneous oxidation of methane to methanol occurs, while the reactor is equipped with a multi-channel thermocouple, a cooling device in the form of a gas-gas heat exchanger installed in series and an air-cooling apparatus connected to a reactor, a complex gas treatment unit, a separator connected to a crude methanol recovery unit.

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