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INVENTION
Patent of the Russian Federation RU2135454

PROCESSING NATURAL GAS WITH METHANOL PRODUCTION

The name of the inventor: Kochubei VA; Pine of M.H .; Gorkov TN; Kravtsova N.G.
The name of the patent holder: Pine Mikhail Khaimovich
Address for correspondence: 127562, Moscow, ul.Kargopolskaya 12, ap.60, Kornienko E.V.
Date of commencement of the patent: 1998.03.30

The invention relates to the field of chemical technology and can be used in chemical and petrochemical enterprises producing synthetic alcohols, in particular methanol.

The essence of the method consists in the fact that the methanol production method includes the steam-oxygen conversion of natural gas, the utilization of the heat of the synthesis gas, the partial removal of carbon dioxide from it, drying, compression to a pressure of 8.5-9.0 MPa, and methanol synthesis on the low-temperature catalyst in two stages - preliminary flow And the main circulation, with the preliminary stage of synthesis being carried out before drying and compression under the pressure of the steam-oxygen conversion stage, after which the main stage of synthesis is carried out. The synthesis gas is dried by separating the water-methanol fraction. The preliminary synthesis is carried out on a copper-containing catalyst at a space velocity of 2000 to 6500 h ^-1 . The method allows the implementation of energy-saving technology.

DESCRIPTION OF THE INVENTION

The invention relates to the field of chemical technology and can be used in chemical and petrochemical enterprises producing synthetic alcohols, in particular methanol.

A method for processing natural gas to produce methanol is known , which includes heating the process natural gas to 380 ^° -400 ^° C. in a combustion heater, purifying sulfur, mixing with steam, steam reforming in a tube furnace, steam-oxygen conversion in a shaft converter, purifying gas from carbon dioxide , Compression of synthesis gas, synthesis of methanol in shelf columns on a copper-containing catalyst by a circulating method ( Author's certificate SU N 1465410, C 01 B 3/32, 1989 ).

The disadvantage of the method is the high energy intensity of the process.

A method for producing methanol from synthesis gas is known, comprising two stages of methanol synthesis at elevated temperature and pressure, where in the first stage the synthesis is conducted in a flow reactor and in the second stage in a recycle reactor and the volume ratio CO / (H ₂ + CO ₂ ) at the outlet of the second stage reactor is controlled by adding to the gas fed to the second stage an additional gas stream containing excess hydrogen or carbon oxides.

The disadvantage of the method is the considerable energy consumption and low efficiency of using the reacting components of the reaction mixture due to the high solubility of carbon dioxide in methanol when it is condensed after the first stage of the synthesis.

A methanol production process is known which includes steam-oxygen conversion of a hydrocarbon feedstock in a shaft converter to produce a converted gas, heat recovery of the produced gas, partial removal of carbon dioxide from the converted gas mixture to obtain a factorial f defined as (H ₂ -CO ₂ ) / (CO ₂ + CO) of 2.05-2.1, drying out the remaining moisture by freezing and contacting with an alumina gel, compressing the dry gas to a pressure of 8.5-9.0 MPa, and synthesizing methanol in the columnar columns by stepwise gas bypassing on a copper-zinc chromium catalyst at a temperature of 230-250 ^{° C} C by the circulation method ( Analog, RF patent No. 2099320, published in 1997 ).

Disadvantages of the method are increased energy consumption due to the need to compress all fresh synthesis gas to the synthesis pressure and a significant cold expense for condensation of residual moisture from the fresh synthesis gas before the compression stage and at the compression stage.

The claimed invention is directed to the elimination of the above disadvantages and the creation of an economical method for the production of methanol, including the steam-oxygen conversion of natural gas to produce synthesis gas, the utilization of its heat, partial removal of carbon dioxide from the synthesis gas, drying, compression to 8.5-9.0 MPa pressure and methanol synthesis On a low-temperature catalyst, the synthesis being carried out in two stages - a preliminary flow-through under pressure of the steam-oxygen conversion step and a circulating one, with drying and compression being carried out between said stages.

The synthesis gas is dried before compression by separating the water-methanol fraction.

In addition, the preliminary synthesis is carried out on a copper-containing catalyst at a space velocity of 2000-6500 h ^-1 .

The method is carried out by the following examples.

Example 1
Natural gas at a pressure of 1.6 MPa in an amount of 8380 nm ³ / h is subjected to a steam-oxygen conversion process to obtain a 5,100 nm ³ / hour wet converted gas, after utilizing its heat and separating moisture from the synthesis gas at a temperature of 40 ^° C., partially remove carbon dioxide , Obtaining 25725 nm ³ / h of synthesis gas of the following composition, v / v : CO 15.89, CO ₂ 11.55, H ₂ 69.16, H ₂ O 0.43, CH ₄ 1.48, Ar 0.62, N ₂ 0.87 , with factorial 2, 1 . The resulting synthesis gas is separated into two streams, the most of which, after passing the recuperative heat exchanger, is heated to 233 ^° C. by the heat of the reaction mixture after the pre-catalyzed synthesis stage and enters a flow reactor loaded in two layers with a low-temperature copper-containing methanol synthesis catalyst in a volume of 8 m ³ . In the first layer, a synthesis reaction occurs with a simultaneous increase in temperature to 269 ^° C. The reaction mixture after the first layer is mixed with a second, smaller stream of the reaction mixture so that the inlet temperature in the second layer is reduced to 226 ^° C. At the exit from the second catalyst bed, the temperature of the reaction mixture is raised to 257 ^° C and has the following composition, vol% : CO 14.728, CO ₂ 11.764, H ₂ 67.596, H ₂ O 0.718, CH ₃ OH 2.099 . The volumetric rate of methanol synthesis in the precatalysis reactor is 3200 h ^-1 . The reaction mixture is cooled to 5 ^° C. , whereby a 709 kg / h aqueous / methanol mixture is evolved from it with 90% methanol, and the gas is dried, and further 24,000 Nm ³ / h of dry synthesis gas is compressed by the synthesis gas compressor to Pressure of 9.0 MPa and divided into 4 equal streams according to the number of synthesis loops, and then mixed with the gas flow after the circulation compressor and fed to the second synthesis stage, to a column-type column with a catalyst volume of 3.8 m ³ . On the methanol synthesis catalyst placed on five shelves, methanol is synthesized so that, after the synthesis column, the gas has the following composition, vol%: CO 2.24, CO ₂ 4.43, H ₂ 57.15, H ₂ O 1.62, CH ₃ OH 4.03 . The temperature at the exit from the last shelf is 263 ^° C. After cooling in the built-in heat exchanger, the reaction mixture enters the condenser, where it is cooled by recycled water with simultaneous condensation of the water-methanol mixture. The resulting raw methanol contains 20.05% water, the synthesis column for methanol-raw material is 2.816 t / h . After separation of the water-methanol mixture, the circulation gas is divided into two streams, the larger of which flows to the suction of the circulation compressor, and a smaller stream in the form of purge gases is removed from the synthesis cycle. The total capacity of the unit for raw methanol 11.97 t / h with a methanol concentration of 80.53% .

Example 2
Natural gas at a pressure of 1.6 MPa in an amount of 8272 nm ³ / h is subjected to a process of steam-oxygen conversion with the production of 50557 nm ³ / h of wet converted gas, after utilization of its heat and separation of moisture from the synthesis gas at a temperature of 40 ^° C., partially remove carbon dioxide , Thus obtaining 25403 nm ³ / h of synthesis gas of the following composition, v / v: CO 15.89, CO ₂ 11.55, H ₂ 69.16, H ₂ O 0.43, CH ₄ 1.48, Ar 0.62, N ₂ 0.87 , with a factorial equal to 2.1 . The resulting synthesis gas is separated into two streams, the largest of which, after passing the recuperative heat exchanger, is heated to 248 ^° C. by the heat of the reaction mixture after the pre-catalysis synthesis stage and enters a flow reactor loaded in two layers with a low-temperature copper-containing catalyst for methanol synthesis in a volume of 4 m ³ . In the first layer, a synthesis reaction occurs with a simultaneous increase in temperature to 275 ^° C. The reaction mixture after the first layer is mixed with a second, smaller stream of the reaction mixture so that the inlet temperature in the second layer is lowered to 238 ^° C. At the exit from the second catalyst bed, the temperature of the reaction mixture is raised to 262 ^° C and has the following composition, vol.%: CO 15.081, CO ₂ 11.616, H ₂ 67.829, H ₂ O 0.759, CH ₃ OH 1.647 . The volume rate of methanol synthesis in the precatalysis reactor is 6350 h- ¹ . The reaction mixture is cooled to 5 ^° C. , whereby a water-methanol mixture is released from it in an amount of 556 kg / h with an 86.88% methanol content and the gas is dried, and further 24,000 Nm ³ / h of dry synthesis gas is compressed by a syngas compressor to Pressure of 9.0 MPa and divided into 4 equal streams according to the number of synthesis loops, and then mixed with the gas flow after the circulation compressor and fed to the second synthesis stage, to a column-type column with a catalyst volume of 3.8 m ³ . The methanol synthesis catalyst placed on five shelves produces methanol synthesis so that, after the synthesis column, the gas has the following composition, vol%: CO 2.248, CO ₂ 4.42, H ₂ 56.99, H ₂ O 1.59, CH ₃ OH 4.05 . The temperature at the exit from the last shelf is 263.7 ^° C. After cooling in the built-in heat exchanger, the reaction mixture enters the condenser, where it is cooled by recycled water with simultaneous condensation of the water-methanol mixture. The resulting raw methanol contains 19.73% water, the production column of the raw methanol synthesis is 2.817 t / h . After separation of the water-methanol mixture, the circulation gas is divided into two streams, the larger of which flows to the suction of the circulation compressor, and a smaller stream in the form of purge gases is removed from the synthesis cycle. The total capacity of the unit for raw methanol 11.82 t / h with a methanol concentration of 80.57% .

Example 3
The natural gas at a pressure of 1.6 MPa in an amount of 8448 nm ³ / h is subjected to a steam-oxygen conversion process to obtain 51632 nm ³ / h of wet converted gas, after utilizing its heat and separating moisture from the synthesis gas at a temperature of 40 ^° C., carbon dioxide , Thus obtaining 25943 nm ³ / h of synthesis gas of the following composition, v / v: CO 15.89, CO ₂ 11.55, H ₂ 69.16, H ₂ O 0.43, CH ₄ 1.48, Ar 0.62, N ₂ 0.87 , factorial 2, 1 . The resulting synthesis gas is separated into two streams, the larger of which, after passing the recuperative heat exchanger, is heated to a temperature of 224 ^° C. by the heat of the reaction mixture after the pre-catalyzed synthesis stage and enters a flow reactor loaded in two layers with a low-temperature copper-containing catalyst for methanol synthesis in a volume of 12 m ³ . In the first layer, a synthesis reaction occurs with a simultaneous increase in temperature to 266 ^° C. The reaction mixture after the first layer is mixed with a second, smaller stream of the reaction mixture so that the inlet temperature in the second layer is lowered to 219 ^° C. At the exit from the second catalyst bed, the temperature of the reaction mixture is raised to 254 ^° C. and has the following composition, %: CO 14.514, CO ₂ 11.852, H ₂ 67.442, H ₂ O 0.699, CH ₃ OH 2.382 . The volumetric rate of methanol synthesis in the precatalysis reactor is 2162 h ^-1 . The reaction mixture is cooled to 5 ^° C. , whereby a water-methanol mixture is released from it in an amount of 808 kg / hr with 91.31% methanol content and the gas is dried, and further 24000 Nm ³ / h of dry synthesis gas is compressed by the synthesis gas compressor to Pressure of 9.0 MPa and divided into 4 equal streams according to the number of synthesis loops, and then mixed with the gas flow after the circulation compressor and fed to the second synthesis stage, to a column-type column with a catalyst volume of 3.8 m ³ . The methanol synthesis catalyst placed on five shelves produces methanol synthesis so that, after the synthesis column, the gas has the following composition, vol%: CO 2.248, CO ₂ 4.42, H ₂ 56.99, H ₂ O 1.59, CH ₃ OH 4.05 . The temperature at the exit from the last shelf is 262.8 ^° C. After cooling in the built-in heat exchanger, the reaction mixture enters the condenser, where it is cooled by recycled water with simultaneous condensation of the water-methanol mixture. The resulting raw methanol contains 20.25% water, the production column of the raw methanol synthesis is 2.815 t / h . After separation of the water-methanol mixture, the circulation gas is divided into two streams, the larger of which flows to the suction of the circulation compressor, and a smaller stream in the form of purge gases is removed from the synthesis cycle. The total capacity of the methanol plant is 12.068 t / h with a methanol concentration of 80.53% . As can be seen from the examples, in the proposed methanol production process, as compared to the prototype, by 0.9-1.2%, the energy consumption for compressing the synthesis gas to the synthesis pressure is reduced. In addition, the effectiveness of using the reacting components of the reaction mixture in methanol increases with its condensation after the first stage of synthesis and the quality of raw methanol is improved.

CLAIM

1. A method for processing natural gas to produce methanol, which includes steam-oxygen conversion of natural gas to produce synthesis gas, utilization of its heat, partial removal of carbon dioxide from the synthesis gas, drying, compression to a pressure of 8.5 to 9.0 MPa, and methanol synthesis at a low temperature Catalyst, characterized in that the synthesis is carried out in two stages: a preliminary flow-through under pressure of the steam-oxygen conversion step and a main circulation one, where drying and compression are carried out between said stages.

2. The method according to claim 1, characterized in that drying of the synthesis gas is carried out with the separation of the water-methanol fraction.

3. The process of claim 1, wherein the preliminary synthesis is carried out on a copper-containing catalyst at a space velocity of 2000 to 6500 h ^-1 .

print version
Date of publication 11/21/2006

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