Catalytic cracking fractionation and absorption stabilization system, and energy saving method thereof

Patent metadata

Field	Value
Publication number	US-10246650-B2
Application number	US-201415524614-A
Country	US
Kind code	B2
Filing date	Dec 12, 2014
Priority date	Nov 12, 2014
Publication date	Apr 2, 2019
Grant date	Apr 2, 2019

Abstract

The present invention provides a catalytic cracking fractionation and absorption-stabilization system, and energy saving method thereof; the present invention is to arrange a waste heat refrigerator of the main fractionating tower, a waste heat refrigerator of rich gas and a waste heat refrigerator of stabilizer in a catalytic cracking fractionation and absorption-stabilization system so as to utilize low temperature waste heat at the top of a main fractionating tower, rich gas, stable gasoline, intermediate heat exchange flow of an absorber of the system as a refrigerator driving heat source; in order to cool naphtha and circulating gasoline to a low temperature lower than 40° C., control low temperature operations of the absorber and reduce the heat load of a desorber and a stabilizer, and the heat extracted by the refrigerators is cooled by cooling water with a higher temperature so as to reduce the consumption of the cooling water. In addition, developed residual pressure generating units and waste heat generating units coordinate to convert medium and low pressure of the dry gas and low-grade waste heat of other products in the system into electric energy that can be conveyed into a grid, therefore the electricity consumption of a dry gas compressor can be supplemented, and the operation cost of the system is reduced to the minimum.

First claim

What is claimed is:

1. A catalytic cracking fractionation and absorption-stabilization system of an oil refinery, wherein heat is extracted from the top of a main fractionating tower ( 1 ) by a first waste heat refrigerator ( 3 ) to serve as a refrigerator driving heat source after heat extraction so as to cool naphtha; rich gas ( 28 ) at the top of the main fractionating tower enters into a compressor for compression, the compressed rich gas is mixed with rich gasoline ( 30 ) discharged from the bottom of an absorber and desorbed gas ( 31 ) discharged from the top of a desorber to form a mixture, and the mixture enters into a gas-liquid separation tank ( 8 ) to reduce the phase splitting temperature therein after being cooled in a second waste heat refrigerator ( 7 ); a diesel oil tower ( 2 ) is arranged on the siding of the main fractionating tower ( 1 ), after the diesel oil discharged from the bottom of the diesel oil tower ( 2 ) exchanges heat with a diesel oil heat exchanger ( 11 ), the residual waste heat is used for generating power by a waste heat generator; in an absorption-stabilization system, two absorber intermediate heat exchangers ( 21 ) serially connected are arranged on each side edge of an absorber ( 9 ) and are serially connected with a third waste heat refrigerator ( 14 ) that is driven by the waste heat of the stable gasoline by pipelines so as to extract the heat discharged by the absorber in time during absorption and control low temperature absorption of the absorber; a residual pressure generator is connected to the top of a reabsorber ( 10 ) to generate power by the medium and low residual pressure of dry gas ( 32 ) at the top; a liquid phase at the bottom of a stabilizer ( 18 ) preheats the feedstock by a feedstock heat exchanger and is entered into the third waste heat refrigerator, a part of the discharge is extracted as product gasoline ( 34 ), and the other part enters into the third waste heat refrigerator to be refrigerated and cooled and returns to the top of the absorber from the third waste heat refrigerator to serve as circulating gasoline ( 35 ); and the residual pressure generator and the third waste heat generator generate electricity which is respectively conveyed into a grid by electric wires, and the power supply used by the compressor is led out from the grid by an electric wire.

2. An energy saving method for the catalytic cracking fractionation and absorption-stabilization system of the oil refinery according to claim 1 , wherein a catalytic cracking reaction product ( 23 ) and rich diesel oil ( 24 ) returning from the bottom of the reabsorber ( 10 ) enter into the main fractionating tower ( 1 ) for oil cutting according to different boiling point ranges, heat is extracted from top oil gas ( 25 ) by a waste heat refrigerator ( 3 ) of the main fractionating tower to serve as a refrigerator driving heat source, the top oil gas enters into a naphtha tank ( 4 ) after being cooled within the temperature ranges from 40 to 80° C., the liquid phase in the tank is naphtha, a part of the naphtha returns to the tower as backflow, the other part of the naphtha is cooled by the waste heat refrigerator ( 3 ) of the main fractionating tower, and naphtha ( 26 ) is cooled within the temperature ranges from solidifying point to 40° C. and then enters into the top of the absorber ( 9 ); the rich gas ( 28 ) is discharged from the naphtha tank ( 4 ) and is pressurized to 0.1 to 3 MPa in a compressor ( 6 ) to produce electricity which is led out by a compressor power supply ( 39 ) from a grid ( 22 ), and the compressed rich gas is mixed with the rich gasoline ( 30 ) at the bottom of the absorber and the desorbed gas ( 31 ) at the top of a desorber ( 15 ); a mixed gas-liquid phase enters into the third waste heat refrigerator ( 7 ) of rich gas to exchange heat within the temperature ranges from solidifying point to 40° C., the rich gas separated by the gas-liquid separation tank ( 8 ) enters into the absorber ( 9 ) from the bottom, the operating pressure of the absorber ( 9 ) is within the pressure ranges from 0.8 to 2.6 Mpa, the naphtha and the circulating gasoline at the top mainly absorb C3, C4 components in the rich gas, and the two absorber intermediate heat exchangers ( 21 ) serially connected on the side edge of the tower extract heat from the siding so as to keep the low temperature absorption of the absorber at the temperature ranges from 5 to 80° C.; light components containing the gasoline enter into the reabsorber ( 10 ) and are absorbed by a circulating diesel oil, the operating pressure of the reabsorber ( 10 ) is within the pressure ranges from 0.8 to 2.6 Mpa, the dry gas ( 32 ) is pressurized by a residual pressure generator ( 13 ) to the atmospheric pressure to be discharged, and the residual pressure generator ( 13 ) generates electricity which is conveyed into a grid ( 22 ) by a power supply ( 38 ) of residual pressure power generation; diesel oil containing rich gasoline components is discharged from the bottom of the reabsorber ( 10 ), exchanges heat with diesel oil ( 27 ) through the diesel oil heat exchanger ( 11 ) to be heated within the temperature ranges from 150 to 250° C., and is circulated to the top of the main fractionating tower ( 1 ) as rich diesel oil ( 24 ); the diesel oil tower is arranged on the siding of the main fractionating tower ( 1 ), light components are removed from the liquid phase extracted from the side of the main fractionating tower by the refining of the diesel oil tower ( 2 ), after the diesel oil ( 27 ) extracted from the bottom of the diesel oil tower ( 2 ) is cooled within the temperature ranges from 80 to 150° C. by the heat exchange with the diesel oil heat exchanger ( 11 ), with the temperature still in said range, the diesel oil can be used as the waste heat source of a waste heat generator ( 12 ), the generated electricity is conveyed into the grid ( 22 ) by a power supply ( 37 ) of waste heat power generation to supplement the power consumption, the diesel oil is cooled to 40° C. after heat extraction, a part of the diesel oil is circulated to the reabsorber, and the rest part is extracted as product diesel oil ( 33 ).

Assignees

• Univ Tianjin
• Pei Yang National Distillation Tech Corporation Limited

Inventors

• Sui Hong
• Han Zhen
• Li Xingang
• Li Jingyi

Classifications

• C10G7/02

  Stabilising gasoline by removing gases by fractioning · CPC title

• C10G2400/02

  Gasoline · CPC title

• C10G7/00

  Distillation of hydrocarbon oils · CPC title

• C10G11/00

  Catalytic cracking, in the absence of hydrogen, of hydrocarbon oils (cracking in direct contact with molten metals or salts C10G9/34) · CPC title

• F01K27/00

  Plants for converting heat or fluid energy into mechanical energy, not otherwise provided for · CPC title