RU2380629C1 - Carbon dioxide liquefaction plant - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: proposed plant comprises radial-flow compressor, pump, steam generator, condenser-evaporator and absorption water-ammonia refrigerator. Proposed pre-cooled carbon dioxide liquefaction process comprises two-stage compression of carbon dioxide in aforesaid radial-flow compressor and pump and chill of aforesaid absorption water-ammonia refrigerator, and steam production in steam generator. The latter process exploits heat resulted from compression of carbon dioxide in aforesaid radial-flow compressor to be fed into absorption water-ammonia refrigerator.

EFFECT: reduced power consumption.

1 dwg

Description

The invention relates to technological lines for liquefying carbon dioxide and may find application in large-scale industries associated with the technology for producing urea.

Known [Reference nitrogen. T.2. - M.: Chemistry, 1969. - 444 p.]. carbon dioxide gas compression unit to a pressure of 15 MPa before feeding it to the urea synthesis unit. They are created on the basis of reciprocating or centrifugal compressors, but can be combined and use different types of compressors, for example, first, for the compression of СО ₂ from 0.1 MPa to 3 MPa, a centrifugal compressor, and then for its final compression from 3 MPa to 15 MPa - piston compressor.

The disadvantages of the known installations are the high specific energy consumption for compression of CO ₂ . When it is compressed in one compressor or group of compressors up to 15 MPa, they amount to 0.135-0.145 kW · h / kg CO ₂ .

The closest in technical essence to the claimed invention, compressor-refrigeration units for liquefying carbon dioxide [Pimenova TF // Production and use of dry ice, liquid and gaseous carbon dioxide. - M .: Light and food industry, 1982. - S.79-80]. When used from gaseous CO ₂ , liquid carbon dioxide can be obtained with an ambient temperature or with a lower temperature, the value of which is determined by the pressure in an isothermal tank designed to collect and store liquid carbon dioxide.

The disadvantages of these settings are:

- obtaining liquid carbon dioxide with an ambient temperature and pressures of 6.0-7.0 MPa, which are lower than the pressure of 15 MPa required for the production of urea;

- obtaining a low-temperature liquid carbon dioxide with a pressure of 1.6-1.8 MPa, which requires additional compression before feeding the urea synthesis reactor.

The technical task of the invention is the installation of carbon dioxide compression, which allows to produce carbon dioxide with the parameters necessary for the production of urea at low energy consumption.

The task is achieved by means of a compressor-pump installation in which gaseous CO _{2 is} first compressed by a centrifugal compressor to 3.0 MPa, condensed by the cold of an absorption water-ammonia refrigeration machine, then compressed by a pump to a pressure of 15 MPa, and then gasified with heat absorption in a regenerative heat exchanger and fed to the urea unit. The compressor-pumping unit corresponding to the claimed invention is characterized not only by the optimal construction of its technological scheme, but also by the use of two sources of cold - an absorption water-ammonia refrigeration machine.

The essence of the proposed technical solution is the installation of carbon dioxide liquefaction, including a centrifugal compressor, pump, steam generator, condenser-evaporator and absorption water-ammonia refrigeration machine, and the process of liquefaction of pre-cooled carbon dioxide is carried out by two-stage compression of carbon dioxide in a centrifugal compressor and pump, as well as cold absorption water-ammonia refrigeration machine and with the simultaneous production of steam in the steam generator by using those carbon dioxide compression rafts in a centrifugal compressor with its supply to an absorption water-ammonia refrigeration machine.

The technological scheme of the compressor-pumping unit for providing high pressure carbon dioxide with the production of urea is shown in the drawing.

The principle of its action is illustrated by the following example.

Example

Gaseous carbon dioxide is supplied at a temperature of 45 ° C in a regenerative heat exchanger 1, in which it is cooled to 24 ° C. There moisture condenses from it, separated in the separator 2. After that, it is compressed in a centrifugal compressor 3 to a pressure of 3 MPa and enters a steam generator 4 with a temperature of 190-200 ° C, in which it is cooled to 140-150 ° C, spending heat on production steam with a temperature of 120-130 ° C. Steam is supplied to a heat-utilizing absorption water-ammonia refrigeration machine 6, and condensate from it is returned to the steam generator 4 by the water pump 5.

Gaseous CO _{2 is} cooled in a recuperative heat exchanger 7 to 35 ° C, and condensed moisture is separated in a separator 8. After that, gaseous carbon dioxide is sent to the drying unit 9 and cooled in a recuperative heat exchanger 10. Then it condenses and is cooled due to the cold boiling ammonia in the condenser -isparitele 11, in which ammonia is supplied from the water-ammonia absorption chiller 6 ammoniacal circulation pump 12. Next, the CO ₂ in the form of the supercooled liquid of low temperature enters the accumulation the tank 13. Carbon dioxide vapors and non-condensable gases from the storage tank 13 are used to regenerate and cool the switching adsorbers of the drying unit 9. At the same time, they are throttled to a pressure of 0.6 MPa through valve 14 and pass through a regenerative heat exchanger 9 and an electric heater 15, which in the regeneration mode of the adsorber of the drying unit is on, and in the cooling mode it is off. After the drying unit 9, carbon dioxide vapors and non-condensable impurities are released into the atmosphere. The liquid low-temperature carbon dioxide from the storage tank 13 is compressed by the pump 16 to a pressure of 15 MPa and, after passing successively three recuperative heat exchangers 10, 7 and 1, is gasified and fed to the urea synthesis column.

The compressor-pumping carbon dioxide plant for providing a high pressure carbon dioxide with a urea production process has lower specific energy consumption compared to the prototype installation, and is also characterized by high reliability. For example, according to the prototype, when compressing carbon dioxide in an amount of 28800 nm ³ / h in a centrifugal compressor to a pressure of 15 MPa, the energy consumption is 7.2 MW, and the unit cost reaches 0.136 kW · h / kg CO ₂ .

In the proposed compressor-pumping carbon dioxide installation, the total energy consumption for compression of CO ₂ in the amount of 28800 nm ³ / h in a turbocharger up to 3 MPa, its drying and condensation in the evaporator of an absorption water-ammonia refrigeration machine and its subsequent compression in the pump up to 15 MPa, after which it Heated and gasified in recuperative heat exchangers, make up 5.5 MW, of which 5.35 MW falls on the turbocharger and 0.15 MW on the pump drive and the operation of the absorption water-ammonia refrigeration machine. The specific energy consumption for the production of CO ₂ with a pressure of 15 MPa will be 0.104 kWh / kg. Thus, energy savings for the production of the same amount of CO ₂ with a pressure of 15 MPa will be about 24% or 1.7 MW.

Claims (1)

Installation of carbon dioxide liquefaction, including a centrifugal compressor, pump, steam generator, condenser-evaporator and absorption water-ammonia refrigeration machine, characterized in that the process of liquefaction of pre-cooled carbon dioxide is carried out by two-stage compression of carbon dioxide in a centrifugal compressor and pump, as well as cold absorption water-ammonia refrigeration machine and with the simultaneous production of steam in a steam generator by using the heat of compression of carbon dioxide in a centrob intermeshing with the compressor being fed to the water-ammonia absorption chiller.

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