FIELD: gas industry.
SUBSTANCE: invention relates to a method of producing low-carbon ammonia from natural and associated gas by steam-oxygen catalytic conversion, which involves feeding raw natural gas into a heater in which the raw natural gas is heated to temperature of 400 °C, then heated raw natural gas is supplied to the desulphurisation unit, after which the gas purified from sulphur is returned to the heater and heated in it to temperature of 500 °C, and at the outlet is mixed with water vapour supplied with pressure of 3.0 MPa from the outlet of the first stage of the steam turbine with back pressure, after which obtained mixture is fed to autothermal reforming unit, wherein steam generated at autothermal reforming unit with pressure of 10.0 MPa is used to drive two-stage steam turbine with back pressure, which generates electric power for production needs, also, oxygen obtained from atmospheric air is supplied to the autothermal reforming unit, which is preliminary compressed to pressure of 1.5 MPa (g) on an air compressor and supplied to an air separation plant. To drive the air compressor, a gas turbine plant is used, and in the air separation plant, compressed air is dried and subjected to cooling, liquefaction and rectification to obtain oxygen at least 99.5% and nitrogen at least 99.95%, oxygen stream obtained at the air separation unit and directed to the autothermal reforming unit is involved in the process of steam-oxygen conversion using a catalyst, as a result of which a converted gas of the following composition is formed: 50-55 (mol.)% hydrogen, 20-25(mol.)% carbon monoxide, 15-20 (mol.)% water vapour 3-5% CO2 and 1(mol.)% methane, obtained converted gas with temperature of 900 °C gives off heat to generate steam flow supplied to two-stage steam turbine with back pressure, and already with temperature of 350-400 °C is supplied to a unit for two-stage conversion of carbon monoxide with water vapour, as a result of the conversion of carbon monoxide, hydrogen is formed and water vapour is generated, which, after leaving the two-stage conversion unit, is mixed with a steam flow with pressure of 1.0 MPa coming from the second stage of the steam turbine with back pressure, mixed steam is used as heat carrier at amine purification unit of converted gas, wherein the wet converted gas flow with temperature of 200-250 °After conversion of carbon monoxide at the unit of two-stage conversion, it is cooled in the condenser. At that, most of water is condensed, and separated stream of converted gas is supplied to amine treatment unit, where more than 98% of carbon dioxide is separated from it by chemical absorption, and further to short-cycle adsorption unit, in which hydrogen is produced with content of basic substance of not less than 99.95 (mol.)% and stripping gas with hydrogen content of 60-70 (mol.)% is obtained, purified hydrogen from the short-cycle adsorption unit is sent to the ammonia synthesis unit, where it is mixed with nitrogen supplied from the air separation unit at ratio of 3/1, wherein obtained nitrogen-hydrogen mixture is used for synthesis of ammonia without stripping, in the ammonia synthesis unit, after reducing the pressure of the synthesized liquefied ammonia to 0.1 MPa (g), hydrogen and nitrogen dissolved in the liquefied ammonia are extracted, said nitrogen and hydrogen are sent for mixing, to blow-off gas, which comes out of short-cycle adsorption unit, 10% of hydrogen-containing gas coming from the converted gas amine cleaning unit is added to the same gas, obtained by mixing the blowing gas and the hydrogen-containing gas, combined stream contains 90 (mol.)% hydrogen, this stream is fuel for gas turbine plant, hot combustion products from gas turbine plant are divided into two streams, first stream is fed into an organic Rankine cycle unit, where the stream gives off heat to the working medium of the organic Rankine cycle, which drives a turbine, which is a drive of a nitrogen compressor, and the nitrogen compressor compresses low-pressure nitrogen of 0.05 MPa, leaving the air separation unit, and the second flow is supplied to the heater.
EFFECT: use of the proposed method enables to obtain additional energy for a plant used to produce low-carbon ammonia without using energy from third-party sources.
1 cl, 1 dwg
