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INVENTION
Patent of the Russian Federation RU2099320
METHOD OF OBTAINING METHANOL
The name of the inventor: Pine M.H . ; Lobanovskaya A.L .; Kharkov TV
The name of the patent owner: Pine Mikhail Khaimovich
Address for correspondence:
Date of commencement of the patent: 1995.06.21
The invention relates to the chemical industry, in particular to a process for producing methanol from a carbonaceous feedstock. SUMMARY OF THE INVENTION consists in a process for producing methanol comprising a steam-oxygen conversion of a hydrocarbon feedstock, recovering a portion of carbon dioxide from the converted gas, and synthesizing methanol from carbon oxides and hydrogen, in which the feedstock is pre-sated to a volume ratio of steam: gas 0.4-0.7, The conversion is carried out at a vapor-gas mixture temperature at the inlet to the converter of 260-300 ° C, a vapor-to-gas ratio of 2.2-2.8 and a pressure of 2.0 MPa, removal of carbon dioxide is carried out by a single-stage washing with a monoethanolamine solution until Factorial f = 2.05-2.2, followed by drying and compression of the reaction mixture to a pressure of 8.5-9.5 MPa with feeding to the synthesis stage.
DESCRIPTION OF THE INVENTION
The invention relates to the chemical industry, in particular to the process for producing methanol from a hydrocarbon feedstock.
A method for producing methanol is known in which a feed gas mixture for the synthesis of methanol is produced by converting a hydrocarbon feedstock with steam, mixing the feedstock with a recycle gas leaving the reaction system and fed to the converter inlet at the pressure that the produced gas has, i.e., without Additional compression. In the reaction zone, all the raw materials are subjected to partial oxidation with oxygen, primary conversion, resulting in a gas mixture for the synthesis of methanol with a ratio of reagents close to the stoichiometric. The primary conversion is carried out at an absolute pressure of> 55 bar above the catalyst contained in pipes heated externally by a gas which, moving out of the secondary conversion zone, moves countercurrently to the primary conversion reaction mixture.
In a preferred embodiment, steam is introduced into the hydrocarbon feed stream fed to the converter until saturation, and excess steam is removed from the converted gas by direct contact with cold water. This method ensures that there is no need to use high pressure steam in the system to remove it from the converted gas. See, for example, European Patent No. 0329292A2, cl. C 07 C 29/15, 1989).
The main drawback of this method is the high energy intensity of the process.
A method for producing methanol is also known, comprising the production of a gas containing hydrogen and carbon monoxide by partially combusting a carbonaceous substance, converting the carbon monoxide contained in the gas obtained in the first stage to carbon dioxide and hydrogen by reacting it with steam, separating a portion of the carbon dioxide From the gas obtained in the second stage, the reaction of the remaining gaseous carbon dioxide and hydrogen to form methanol, drying the product obtained (see, for example, French Application No. 2,288,722, class C 07 C 31/04, 1976 prototype).
The main disadvantage of this method is the insufficiently high purity of the target product and high energy costs.
A method for producing methanol is known, which involves the conversion of natural gas or oil by steam at 600-1000 ° C and a pressure of 8-53 atm. In the presence of a nickel catalyst, the reduction of carbon oxides by hydrogen to methanol at 215-450 ° C and a pressure of 70-300 atm in the presence of an aluminum-zinc-copper or aluminum-zinc chromium catalyst, separating the methanol formed, recycling the unreacted mixture as purging gases in part Or completely to the conversion stage, the mixture is hydrogenated at a temperature of 180-200 ° C and a feed rate of 100-300 × 10 3 h -1 in the presence of a catalyst composition, Nickel oxide 32-40; Aluminum oxide 47-57; Calcium oxide 3-21, followed by pre-hydrogenation at a temperature of 250-450 ° C and a feed rate of 10 50 × 10 3 h -1 in the presence of a catalyst composition, Nickel oxide 23-26; Aluminum oxide 43-49; Magnesium oxide 13-17; Calcium oxide 6-13; Barium oxide 0.6-1.2, and a separation of 40-70 vol. Hydrogen by means of a palladium membrane (see, for example, USSR copyright certificate No. 829609, class C 07 C 31/04, 1981 analog).
The main drawback of this method is the high energy intensity of the process, as well as the need to use expensive catalysts and palladium membranes for post-cleaning the gas mixture of methanol synthesis.
The aim of the invention is to develop a method for producing methanol having a low energy intensity, ensuring the absence of harmful emissions and obtaining methanol of superior quality of the brand "AA".
The object is achieved by a process for producing methanol, comprising a steam-oxygen conversion of natural gas, recovering a portion of the carbon dioxide of their converted gas, and synthesizing methanol from carbon oxides and hydrogen, in which the feedstock is pre-saturated to a volume ratio of steam to gas of 0.4 to 0.7 By spraying with a gas condensate heated to 150-170 ° C., the conversion is carried out at the temperature of the vapor-gas mixture at the inlet to the converter equal to 260-300 ° C., the volume ratio of steam: gas equal to 2.2-2.8 and a pressure of 2.0 MPa , The removal of carbon dioxide is carried out by a single-stage washing with a solution of monoethanolamine to obtain the factorial f 2.05-2.2, followed by drying and compression of the reaction mixture to a pressure of 8.5-9.5 MPa with the supply of the gas mixture to the synthesis stage, which is carried out in shelf Columns with stepwise gas bypassing at a temperature of 220-270 o C, pressure 8.5-9.5 MPa on a low-temperature copper-containing catalyst.
The essence of the invention lies in the fact that the developed technology provides significant energy savings in natural gas and oxygen, as well as additional production of steam in the circuit having a pressure of 27 atm.
In addition, the methanol produced in the process has the highest quality and corresponds to the "AA" grade due to the methanol synthesis stage at a pressure of 90 atm.
According to the invention, the hydrocarbon feedstock is pre-sated with a heated gas condensate circulating in the system. This makes it possible to use the low-potential heat of the converted gas and reduce the consumption of process steam.
The steam-oxygen conversion of the hydrocarbon feedstock is carried out in a shaft converter, where the conversion takes place at a low volume ratio of steam: gas and the temperature of the vapor-gas mixture at the converter inlet. This saves process steam at the process and saves heat, that is, the optimal thermal regime of the conversion process and low specific energy consumption.
The removal of carbon dioxide from the converted gas mixture is carried out with a 8-12% aqueous solution of monoethanolamine (MEA) until the factorial f is obtained 2.05-2.1. At the same time, heat savings are achieved for the regeneration of the MEA solution.
Regeneration of a saturated solution of monoethanolamine is carried out by contacting with a heated gas condensate circulating in the system.
After removing a portion of the carbon dioxide, the gas mixture is dried by freezing the main remaining moisture and further condensing the gas and contacting the alumina gel.
This makes it possible to provide the compression required for dry gas with the required condensation.
Synthesis of methanol is carried out in the columnar columns, using stepwise gas bypassing in equal parts for each column of the column.
This allows us to conduct the process in the optimal temperature regime, which ensures the maximum yield of methanol-raw material and the production of high-quality methanol-rectificate, corresponding to the brand "AA", with a mass fraction of methanol of not less than 99.9%
Then the gas mixture is compressed to a pressure of 8.5-9.5 MPa, which is necessary for carrying out the process of methanol synthesis on a copper-containing catalyst and ensures the production of high-quality methanol and the production of methanol-rectificate of the brand "AA".
The figure shows the scheme of the process for the production of methanol, which contains the following symbols: PP steam superheated, Mo saturated steam, VNN water, non-aerated, VAP water, deaerated, MEA monoethanolamine, water VO circulating.
The method according to the scheme is carried out as follows
The initial natural gas from the network at a pressure of 2.0 MPa enters the saturator 1, where it is saturated with water vapor contained in the gas condensate to a volume ratio of steam: natural gas equal to 0,4: 0,7, due to the heat of the circulating gas condensate from Scrubber 6.
Then the gas-vapor mixture is heated in the heat exchanger 2 by the converted gas from the recovery boiler 5, mixed with superheated steam and fed to the mixer 3 of the methane converter.
The starting oxygen from the network is compressed in the compressor 16 to a pressure of 2.0 MPa, mixed with superheated steam acting as a protective vapor, and supplied to the mixer 3 of the methane converter. The total volume ratio of steam: natural gas in mixer 3 is 2.2-2.8. After the mixer 3, the steam-gas-oxygen mixture enters the methane converter 4, where a gas-oxygen conversion of natural gas takes place on the nickel catalyst to a residual methane content of 0.6-1.1 vol. On dry gas. The temperature of the converted gas at the exit from the methane converter 4 is 870-920 ° C.
Then the converted gas enters the recovery boiler 5, where the saturated steam with a pressure of 2.7-3.0 MPa is produced by the heat. After the recovery boiler 5, the converted gas is cooled in a heat exchanger 2 by a vapor-gas mixture, then in a scrubber cooler 6 by a circulating gas condensate and in a heat exchanger 7 with recycled water to a temperature of 40 ° C.
The cooled converted gas after the heat exchanger 7 enters the separator 8 to cool the condensed moisture and enters the monoethanolamine gas purification section 9 where one part of the carbon dioxide is removed to one stage until the factorial f [(H 2 -CO 2 ) / (CO 2 + CO)] equal to 2.05-2.2, necessary for the synthesis of methanol.
The purified converted gas is then sent to the adsorber 10 for drying, where residual moisture is removed from it, after which the gas is compressed in the compressor 11 to a pressure of 9.0 MPa and fed to the columnar methanol synthesis column with stepwise bypass. In column 12 on a copper-zinc chromium catalyst at a temperature of 230-250 ° C and a pressure of 9.0 MPa, methanol is synthesized to produce raw methanol.
Further, raw methanol is fed to the rectification section 13 to produce commercial methanol-rectificate of the brand "AA".
The unheated nutrient water necessary for steam generation in the recovery boiler 5 is heated in the heat exchanger 14 by the circulating gas condensate leaving the saturator 1, deaerated in the deaerator 15, reheated in the heat exchanger 17 and fed to the recovery boiler 5.
The gas condensate circulation circuit is as follows. In the scrubber cooler 6, the flow of cooled gas condensate entering the reflux is heated by the converted gas and at the outlet of the scrubber 6 is connected to the gas condensate released in the scrubber from the converted gas. The outflow with a temperature of 165-170 o C is divided into two streams. One stream, which is 1/3 of the total, is fed to the saturation of natural gas in the saturator 1 and to the heating of the feedless, non-aerated water in the heat exchanger 14.
A second stream of 2/3 of the total is fed to heat the feed deaerated water in the heat exchanger 14 and to regenerate the monoethanolamine solution in the purification section 9. Then, both cooled streams are mixed and fed to the scrubber cooler 6.
Example. Natural gas of the following composition, vol. CO 2 0.04; N 2 0.8; Ar 0.75; CH 4 95.5; C 2 H 6 1.81; C 3 H 8 0.74; C 4 H 10 0.29; C 5 H 12 0.07, with a temperature of 0 ° C, at a pressure of 2.0 MPa in an amount of 7788 nm 3 / h enters the saturator, where, passing through the nozzle, irrigated with a hot condensate at a temperature of 170 ° C, is saturated with water vapor up to Steam: gas ratio is 0.65.
After saturation, the vapor-gas mixture is heated in the heat exchanger to 290 ° C, mixed with the process superheated steam to the steam: gas ratio of 2.48 and fed to the annular space of the gas-oxygen mixer. The steam-oxygen mixture is fed into the mixer tube space with the ratio of pairs: oxygen 0.47.
The amount of oxygen is 5297 nm 3 / h.
The total steam: natural gas ratio at the outlet from the mixer is 2.8.
In the mine converter a steam-oxygen conversion of methane occurs on the nickel catalyst GIAP-8. The amount of converted gas at the output of the converter is 4563.5 nm 3 / h, the temperature is 870 ° C.
The heat of the hot converted gas is utilized to produce saturated vapor at a pressure of 2.7 MPa, to heat the vapor-gas mixture after saturation. The final utilization of heat takes place in a scrubber cooler, where the gas condensate used for the process of saturation and regeneration of monoethanolamine is heated.
The converted gas enters a single-stage carbon dioxide purification unit. At the outlet from the purification section, the ratio of the components, i.e. the factorial of the gas, is (H 2 CO 2 ) / (CO 2 + CO) 2.11.
Then the converted gas is dried from moisture and in an amount of 24000 nm 3 / h at a pressure of 1.6 MPa is compressed to a pressure of 9.0 MPa and enters the methanol synthesis section.
Synthesis of methanol is carried out on a copper-containing catalyst in shelf columns with stepwise gas bypassing.
The raw methanol obtained is fed to the rectification section, where methanol-rectificate of the grade "AA" is produced in the amount of 8.44 t / h and the corresponding specification is 113-05-494-85. Comparative with the known method data on the effectiveness of the claimed methanol production process are shown in the table.
CLAIM
A process for producing methanol comprising a steam-oxygen conversion of natural gas, recovering a portion of carbon dioxide from the converted gas, and synthesizing methanol from carbon oxides and hydrogen, characterized in that the feedstock is pre-sated to a volume ratio of steam / gas of 0.4 0.7 by irrigation heated to 150 170 o With gas condensate, the conversion is carried out at the temperature of the vapor-gas mixture at the inlet to the converter of 260-300 ° C, the volume ratio of vapor / gas 2.2 2.8, and the pressure of 2 MPa, the removal of carbon dioxide is carried out by a single-stage washing with monoethanolamine solution up to Obtaining the factorial f 2.05 2.2, followed by drying and compression of the reaction mixture to a pressure of 8.5 9.5 MPa with the supply of the gas mixture to the synthesis stage, which is carried out in the shelf columns with stepwise gas bypassing at 220-270 ° C., pressure 8 , 5 9.5 MPa on a low-temperature copper-containing catalyst.
print version
Date of publication 07.04.2007gg
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