CO.SUB.2 .desorption system suitable for limited space in complex sailing region and flexible control method

Abstract

A CO.sub.2 desorption system suitable for limited space in a complex sailing region comprises an exhaust boiler, a compact CO.sub.2 absorber, a compact CO.sub.2 lean-rich liquid heat exchanger, a compact CO.sub.2 desorber, a compact CO.sub.2 rich liquid preheating device, a compact CO.sub.2 rich liquid reboiling pre-desorption device and an intelligent control platform. Further, a global optimization control method for the CO.sub.2 desorption system suitable for limited space in a complex sailing region is further established based through a knowledge and data-driven exhaust extraction flow accurate-prediction model for a heat source of a CO.sub.2 rich liquid preheating device and a steam extraction flow accurate-prediction model for a heat source on an upper section of a CO.sub.2 rich liquid reboiling pre-desorption device to realize flexible control of operation parameters of the desorption system under different operating conditions of an engine.

Claims

1. A CO.sub.2 desorption system suitable for limited space in a complex sailing region, comprising an exhaust boiler, a compact CO.sub.2 absorber, a compact CO.sub.2 lean-rich liquid heat exchanger, a compact CO.sub.2 desorber, a compact CO.sub.2 rich liquid preheating device, a compact CO.sub.2 rich liquid reboiling pre-desorption device and an intelligent control platform, wherein ship exhaust passes through the exhaust boiler to realize waste heat utilization and then enters a ship exhaust scrubber to be purified; the purified ship exhaust further enters the compact CO.sub.2 absorber, CO.sub.2 in the ship exhaust is captured with a composite amine/mixed salt absorbent, the absorbent then turns into CO.sub.2 rich liquid, and 10%-20% of the CO.sub.2 rich liquid is split out to directly flow to a top of the compact CO.sub.2 desorber; remaining non-split CO.sub.2 rich liquid is delivered by a rich liquid delivery pump a into the CO.sub.2 lean-rich liquid heat exchanger to be heated by heat exchange for the first time; after being heated by heat exchange for the first time, the rich liquid is delivered by a rich liquid delivery pump b into Z-shaped bushings of the CO.sub.2 rich liquid preheating device and then comes in contact with an evaporation section of the CO.sub.2 rich liquid preheating device to be heated by heat exchange for the second time, and then the rich liquid enters an upper portion of the CO.sub.2 desorber; all the rich liquid flows through a liquid distributor and packing layers of the CO.sub.2 desorber to reach a bottom of the CO.sub.2 desorber and then circulates to the CO.sub.2 rich liquid reboiling pre-desorption device to be heated by heat exchange for the third time to reach a rich liquid adsorption temperature; semi-rich liquid obtained after the third time of heating is subjected to liquid water vaporization and releases vaporized substances containing a proportion of CO.sub.2, the vaporized substances penetrate through the packing layers by means of a riser in the CO.sub.2 desorber to realize desorption of high-temperature CO.sub.2, the high-temperature CO.sub.2 enters the upper portion of the CO.sub.2 desorber to reversely come in contact with the rich liquid that is heated for the second time to enhance further desorption of the rich liquid, and the semi-rich liquid that is not vaporized after being heated by heat exchange for the third time and the rich liquid obtained after desorption turn into lean liquid.

2. The CO.sub.2 desorption system according to claim 1, wherein the compact CO.sub.2 desorber comprises a demister, a CO.sub.2 split rich liquid distributor, a packing layer, a rich liquid distributor after secondary heating, a packing layer, a riser and the bottom of the CO.sub.2 desorber which are sequentially arranged from top to bottom, and the compact CO.sub.2 rich liquid reboiling pre-desorption device is connected to the bottom of the CO.sub.2 desorber; and a superficial gas velocity of the CO.sub.2 desorber is 0.5-0.8 m/s, packing is one or more selected from MELLAPAK, FLEXIPAC and PALL, a structural parameter of the packing is one or more selected from 500Y, 500X, 250X and 250Y, the number of the packing layers is 2-3, and a total height of the packing layers is 4-8 m.

3. The CO.sub.2 desorption system according to claim 1, wherein the CO.sub.2 rich liquid preheating device comprises an evaporation section and a condensation section, two-phase closed heat-exchange tubes are arranged in the CO.sub.2 rich liquid preheating device, upper portions of the two-phase closed heat-exchange tubes are sleeved with Z-shaped bushings, the evaporation section and the condensation section of the CO.sub.2 rich liquid preheating device are isolated by a partition and located on the upper portions and lower portions of the two-phase closed heat-exchange tubes respectively, a heat-exchange medium in the lower portions of the two-phase closed heat-exchange tubes is heated by a high-temperature heat source, the medium is heated to be evaporated to the upper portions of the two-phase closed heat-exchange tubes to further make full contact with the rich liquid, that is heated by heat exchange for the first time, in the upper portions of the two-phase closed heat-exchange tubes to realize a temperature rise of the rich liquid; and a heat source of the CO.sub.2 rich liquid preheating device is high-temperature exhaust from an outlet of a ship engine, ship exhaust with waste heat being used by the exhaust boiler, steam of the waste boiler, or ship exhaust in front of the scrubber.

4. The CO.sub.2 desorption system according to claim 3, wherein the two-phase closed heat-exchange tubes are configured as trapezoidal spiral structures, the lower portions of the two-phase closed heat-exchange tubes have a diameter of 16-32 mm, the upper portions of the two-phase closed heat-exchange tubes have a diameter of 20-40 mm, the condensation section of the CO.sub.2 rich liquid preheating device accounts for of a bulk length of the two-phase closed heat-exchange tubes, an installation angle of the two-phase closed heat-exchange tube is 10-30, the heat-exchange medium in the two-phase closed heat-exchange tubes is 1-(methoxy) nonafluorobutane or perfluoropentane, and a filling rate of the medium in the two-phase closed heat-exchange tubes is 20%-40%.

5. The CO.sub.2 desorption system according to claim 1, wherein the CO.sub.2 rich liquid reboiling pre-desorption device comprises a rich liquid uniform-distribution section, a heat-exchange section and a pre-desorption section; a liquid distributor is arranged in the rich liquid uniform-distribution section, the heat-exchange section is a main part of the CO.sub.2 rich liquid reboiling pre-desorption device, the pre-desorption section is a detachable pipe provided with a flat cover, and the pipe has a gas outlet located in an upper end of the pipe and a liquid outlet located in a lower end of the pipe and is able to realize gas-liquid separation of secondary steam and hot lean liquid; and a heat source of the CO.sub.2 rich liquid reboiling pre-desorption device is high-temperature exhaust from an outlet of a ship engine, ship exhaust with waste heat being used by the exhaust boiler, steam of the waste boiler, or ship exhaust in front of the scrubber.

6. The CO.sub.2 desorption system according to claim 5, wherein the liquid distributor arranged in the rich liquid uniform-distribution section is a plug-in liquid distributor or a sawtooth overflow distributor; a shell of the heat-exchange section of the CO.sub.2 rich liquid reboiling pre-desorption device is cylindrical and has an upper end and a lower end, the upper end uses the steam of the exhaust boiler as a heat source, the temperature of the steam is 125-155 C., the lower end uses the high-temperature exhaust from the outlet of the ship engine, the ship exhaust with waste heat being used by the exhaust boiler, the steam of the waste boiler, or the ship exhaust in front of the scrubber as a heat source, and the flow of the exhaust is flexibly controlled by means of the intelligent control platform according to an actual condition; and falling-film pipes are vertically arranged in the heat-exchange section of the CO.sub.2 rich liquid reboiling pre-desorption device, the falling-film pipes have a length of 3000 mm, 4000 mm or 6000 mm, a diameter of 28-32 mm and a wall thickness of 2-3 mm, and a center distance between the falling-film pipes is more than twice the diameter of the falling-film pipes.

7. A flexible control method for a CO.sub.2 desorption system suitable for limited space in a complex sailing region, comprising: establishing a knowledge and data-driven exhaust extraction flow accurate-prediction model for a heat source of a CO.sub.2 rich liquid preheating device and a steam extraction flow accurate-prediction model for a heat source on an upper section of a CO.sub.2 rich liquid reboiling pre-desorption device, establishing a global optimization control method for a CO.sub.2 desorption system suitable for limited space in a complex sailing region, and performing operation optimization with an outlet rich liquid temperature of the CO.sub.2 rich liquid reboiling pre-desorption device and energy consumption of the desorption system as constraint indicators; when a ship sails to different regions or an operating condition of the ship fluctuates, implementing accurate prediction of an exhaust extraction flow of the heat source of the CO.sub.2 rich liquid preheating device under different operating conditions by means of the knowledge and data-driven exhaust extraction flow accurate-prediction model for the heat source of the CO.sub.2 rich liquid preheating device; and, implementing accurate prediction of a steam extraction flow of the heat source of the upper portion of the CO.sub.2 rich liquid reboiling pre-desorption device under different operating conditions by means of the steam extraction flow accurate-prediction model for the heat source on the upper section of the CO.sub.2 rich liquid reboiling pre-desorption device in conjunction with operating parameters of the desorption system and quality parameters of extracted steam, so as to minimize the steam extraction flow of the heat source on the upper section of the CO.sub.2 rich liquid reboiling pre-desorption device under the precondition that the outlet rich liquid temperature of the CO.sub.2 rich liquid reboiling pre-desorption device satisfy requirements of the desorption system, thus minimizing energy consumption of the desorption system.

8. The flexible control method according to claim 7, wherein establishing a knowledge and data-driven exhaust extraction flow accurate-prediction model for a heat source of a CO.sub.2 rich liquid preheating device and a steam extraction flow accurate-prediction model for a heat source on an upper section of a CO.sub.2 rich liquid reboiling pre-desorption device comprises the following steps: S1, based on online and historical operation data, establishing a parameter database including physical property parameters of an absorbent, design parameters of a CO.sub.2 lean-rich liquid heat exchanger, the CO.sub.2 rich liquid preheating device and the CO.sub.2 rich liquid reboiling pre-desorption device, inlet and outlet rich liquid temperatures and flows of the CO.sub.2 lean-rich liquid heat exchanger, inlet and outlet rich liquid temperatures and flows of the CO.sub.2 rich liquid preheating device, inlet and outlet rich liquid temperatures and flows of the CO.sub.2 rich liquid reboiling pre-desorption device, inlet and outlet steam temperatures and flows of the CO.sub.2 rich liquid reboiling pre-desorption device, inlet and outlet exhaust temperatures and flows of the CO.sub.2 rich liquid preheating device, and inlet and outlet exhaust temperatures and flows of the CO.sub.2 rich liquid reboiling pre-desorption device; S2, based on the parameter database established in S1, for the CO.sub.2 rich liquid preheating device, analyzing response relations of the inlet rich liquid temperature of the CO.sub.2 rich liquid preheating device (the outlet rich liquid temperature of the CO.sub.2 lean-rich liquid heat exchanger), an inlet rich liquid CO.sub.2 load of the CO.sub.2 rich liquid preheating device (an outlet rich liquid CO.sub.2 load of the CO.sub.2 lean-rich liquid heat exchanger), a lean-rich liquid split fraction, the outlet rich liquid temperature of the CO.sub.2 rich liquid preheating device and an exhaust temperature of the heat source of the CO.sub.2 rich liquid preheating device with an exhaust flow of the heat source of the CO.sub.2 rich liquid preheating device according to a heat-exchange mechanism between different heat sources in the CO.sub.2 rich liquid preheating device and outlet rich liquid of the CO.sub.2 lean-rich liquid heat exchanger and experiential operation knowledge, establishing an exhaust extraction flow model for the heat source of the CO.sub.2 rich liquid preheating device in different sailing regions and operating conditions, modifying the exhaust extraction flow model for the heat source of the CO.sub.2 rich liquid preheating device in conjunction with quality parameters of the heat source and historical data of the outlet rich liquid temperature of the CO.sub.2 rich liquid preheating device, and establishing the knowledge and data-driven exhaust extraction flow accurate-prediction model for the heat source of the CO.sub.2 rich liquid preheating device; wherein, the knowledge and data-driven exhaust t extraction flow accurate-prediction model for the heat source of the CO.sub.2 rich liquid preheating device established in S2 is expressed as:
Q.sub.y1=f.sub.2(T.sub.1,a,b,T.sub.y1)(1) where, Q.sub.y1 is the exhaust flow of the heat source of the CO.sub.2 rich liquid preheating device, T.sub.1 is the outlet rich liquid temperature of the CO.sub.2 lean-rich liquid heat exchanger, T.sub.y1 is the exhaust temperature of the heat source of the CO.sub.2 rich liquid preheating device, a is the outlet rich liquid CO.sub.2 load of the CO.sub.2 lean-rich liquid heat exchanger, and b is the lean-rich liquid split fraction; and S3, based on the parameter database established in S1, for the CO.sub.2 rich liquid reboiling pre-desorption device, analyzing response relations of the outlet rich liquid temperature of the CO.sub.2 rich liquid reboiling pre-desorption device, the outlet rich liquid flow of the CO.sub.2 rich liquid preheating device, the inlet rich liquid flow of the CO.sub.2 rich liquid reboiling pre-desorption device, the inlet rich liquid temperature of the CO.sub.2 rich liquid reboiling pre-desorption device, the inlet rich liquid CO.sub.2 load of the CO.sub.2 rich liquid reboiling pre-desorption device, a steam temperature of the heat source on the upper section of the CO.sub.2 rich liquid reboiling pre-desorption device, and a ship exhaust flow and temperature of a heat source on a lower section of the CO.sub.2 rich liquid reboiling pre-desorption device with a steam flow of the heat source on the upper section of the CO.sub.2 rich liquid reboiling pre-desorption device according to a heat-exchange reboiling mechanism between different heat sources (steam and ship exhaust) in the CO.sub.2 rich liquid reboiling pre-desorption device and outlet rich liquid of the CO.sub.2 rich liquid reboiling pre-desorption device and experiential operation knowledge, establishing a steam flow model for the heat source on the upper section of the CO.sub.2 rich liquid reboiling pre-desorption device, modifying the steam flow model for the heat source on the upper section of the CO.sub.2 rich liquid reboiling pre-desorption device in conjunction with steam parameters of the heat source on the upper section of the CO.sub.2 rich liquid reboiling pre-desorption device, ship exhaust parameters of the heat source on the lower section of the CO.sub.2 rich liquid reboiling pre-desorption device and historical data of the steam flow the heat source on the upper section of the CO.sub.2 rich liquid reboiling pre-desorption device, and establishing the steam extraction flow accurate-prediction model for the heat source on the upper section of the CO.sub.2 rich liquid reboiling pre-desorption device; wherein, the steam extraction flow accurate-prediction model for the heat source on the upper section of the CO.sub.2 rich liquid reboiling pre-desorption device established in S3 is expressed as:
Q.sub.y2=f.sub.2(T.sub.2,Q.sub.C,Q.sub.r,T.sub.r,A.sub.r,T.sub.z,Qx,T.sub.x,Qs)(2) where, Q.sub.y2 is the steam extraction flow of the heat source on the upper section of the CO.sub.2 rich liquid reboiling pre-desorption device, T.sub.2 is the outlet rich liquid temperature of the CO.sub.2 rich liquid reboiling pre-desorption device, Q.sub.C is the outlet rich liquid flow of the CO.sub.2 rich liquid preheating device, Q.sub.r is the inlet rich liquid flow of the CO.sub.2 rich liquid reboiling pre-desorption device, T.sub.r is the inlet rich liquid temperature of the CO.sub.2 rich liquid reboiling pre-desorption device, A.sub.r is the inlet rich liquid CO.sub.2 load of the CO.sub.2 rich liquid reboiling pre-desorption device, T.sub.2 is the steam temperature of the heat source on the upper section of the CO.sub.2 rich liquid reboiling pre-desorption device, Qx is the ship exhaust flow of the heat source on the lower section of the CO.sub.2 rich liquid reboiling pre-desorption device, T.sub.x is the ship exhaust temperature of the heat source on the lower section of the CO.sub.2 rich liquid reboiling pre-desorption device, and Qs is the steam flow of the heat source on the upper section of the CO.sub.2 rich liquid reboiling pre-desorption device.

Description

DESCRIPTION OF THE DRAWINGS

(1) To more clearly describe the technical solutions in the embodiments of the application or in the prior art, drawings used for describing the embodiments of the application or the prior art are briefly described below. Obviously, the drawings in the following description merely illustrate some embodiments of the application, and those skilled in the art can obtain other drawings according to the following ones without creative labor.

(2) FIG. 1 is a flow diagram of a CO.sub.2 desorption system suitable for limited space in a complex sailing region according to the disclosure;

(3) FIG. 2 is a structural diagram of a compact CO.sub.2 desorber according to the disclosure;

(4) FIG. 3 is a structural diagram of a compact CO.sub.2 rich liquid preheating device according to the disclosure;

(5) FIG. 4 is a structural diagram of a compact CO.sub.2 rich liquid reboiling pre-desorption device according to the disclosure;

(6) FIG. 5 is a diagram of the relation between steam temperature and

(7) desorption energy consumption according to the disclosure;

(8) FIG. 6 is a diagram of the relation between the split fraction of rich liquid and desorption energy consumption according to the disclosure; and

(9) FIG. 7 is a diagram of the relation between the temperature difference between an inlet and an outlet of the CO.sub.2 rich liquid preheating device and desorption energy consumption according to the disclosure.

(10) In the FIGS.: 1, engine; 2, exhaust boiler; 3, ship exhaust scrubber; 4, compact CO.sub.2 absorber; 5, compact lean-rich liquid heat exchanger; 6, compact CO.sub.2 desorber; 7-1, delivery pump a; 7-2, delivery pump b; 8, compact t CO.sub.2 rich liquid preheating device; 9, compact CO.sub.2 rich liquid reboiling pre-desorption device; 10, intelligent control platform; 11-1, electric control valve a; 11-2, electric control valve b; 11-3, electric control valve c; 61, demister; 62, CO.sub.2 split rich liquid distributor; 63, rich liquid distributor after secondary heating; 64, packing layer; 65, riser; 66, CO.sub.2 desorber bottom; 81, ship exhaust; 82, evaporation section; 83, condensation section; 84, two-phase closed heat-exchange tube; 85, partition; 86, heat-exchange medium; 87, Z-shaped bushing; 88, rich liquid; 91, rich liquid uniform-distribution section; 91a, plug-in liquid distributor; 92, heat-exchange section; 92a, shell; 92a1, upper end; 92a2, lower end; 92b, falling-fill pipe; 93, pre-desorption section; 93a, gas outlet; 93b, liquid outlet.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(11) The technical solutions in the embodiments of the disclosure will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments. Obviously, the embodiments in the following description are merely illustrative ones and are not all possible ones of the disclosure. All other embodiments obtained by those ordinarily skilled in the art based on the following ones without creative labor should also fall within the protection scope of the disclosure.

Embodiment 1

(12) Referring to FIG. 1, for ship exhaust 81 with a volume of 20000 Nm.sup.3/h, a CO.sub.2 volume concentration of 5% and a temperature of 40 C., the CO.sub.2 desorption system suitable for limited space in a complex sailing region comprises an exhaust boiler 2, a compact CO.sub.2 absorber 4, a compact CO.sub.2 lean-rich liquid heat exchanger 5, a compact CO.sub.2 desorber 6, a compact CO.sub.2 rich liquid preheating device 8, a compact CO.sub.2 rich liquid reboiling pre-desorption device 9 and an intelligent control platform 10.

(13) Referring to FIG. 2, the compact CO.sub.2 desorber 6 comprises a demister 61, a CO.sub.2 split rich liquid distributor 62, a packing layer 64, a rich liquid distributor 63 after secondary heating, a packing layer 64, a riser 65 and a desorber bottom 66 which are sequentially arranged from top to bottom; the CO.sub.2 rich liquid reboiling pre-desorption device 9 is connected to the desorber bottom 66; and the superficial gas velocity of the CO.sub.2 desorber 6 is preferably 0.6 m/s, packing is preferably MELLAPAK, the structural parameter of the packing is preferably 250Y, the number of the packing layers is preferably 2, and the height of the packing layers 64 is preferably 5 m.

(14) Referring to FIG. 3, a heat source of the CO.sub.2 rich liquid preheating device 8 is the ship exhaust 81 in front of a scrubber, and the gas temperature and flow of the heat source are controlled by an electric control valve c 11-3; the CO.sub.2 rich liquid preheating device 8 comprises an evaporation section 82 and a condensation section 83, two-phase closed heat-exchange tubes 84 are arranged in the CO.sub.2 rich liquid preheating device 8, upper portions of the two-phase closed heat-exchange tubes are sleeved with Z-shaped bushings 87, the evaporation section 82 and the condensation section 83 of the CO.sub.2 rich liquid preheating device 8 are isolated by a partition 85 and located on the upper portions and lower portions of the two-phase closed heat-exchange tubes 84 respectively, a heat-exchange medium 86 in the lower portions of the two-phase closed heat-exchange tubes 84 is heated by the high-temperature ship exhaust 81, the heat-exchange medium 86 is preferably 1-(methoxy) nonafluorobutane, the filling rate of the heat-exchange medium 86 is preferably 30%, the heat-exchange medium 86 is heated to be evaporated to the upper portions of the two-phase closed heat-exchange tubes 84 to further make full contact with rich liquid 88, that is heated by heat exchange for the first time, in the Z-shaped bushings 87 on the upper portions of the two-phase closed heat-exchange tubes 84 to realize a temperature rise of the rich liquid 88; and the two-phase closed heat-exchange tubes 84 are preferably configured as trapezoidal spiral structures, the lower portions of the two-phase closed heat-exchange tubes 84 preferably have a diameter of 20 mm, the upper portions of the two-phase closed heat-exchange tubes 84 preferably have a diameter of 25 mm, the condensation section 83 accounts for of the bulk length of the two-phase closed heat-exchange tubes 84, and the installation angle of the two-phase closed heat-exchange tubes 84 is preferably 30.

(15) Referring to FIG. 4, a heat source of the CO.sub.2 rich liquid reboiling pre-desorption device 9 is high-temperature exhaust from an outlet of a ship engine 1, and the gas temperature and flow of the heat source are controlled by an electric control valve a 11-1; the CO.sub.2 rich liquid reboiling pre-desorption device 9 comprises a rich liquid uniform-distribution section 91, a heat-exchange section 92 and a pre-desorption section 93; a liquid distributor is arranged in the rich liquid uniform-distribution section 91, and to lower the structural probability, the liquid distributor is preferably a plug-in liquid distributor 91a; the heat-exchange section 92 is a main part of the CO.sub.2 rich liquid reboiling pre-desorption device 9, and a shell 92a of the heat-exchange section 92 is cylindrical; further preferably, the shell 92a of the heat-exchange section 92 has an upper end 92a1 and a lower end 92a2, the upper end 92al uses steam from the exhaust boiler 2 as a heat source, the temperature of the steam is preferably 135-155 C., the lower end 92a2 uses high-temperature exhaust from the outlet of the ship engine 1 as a heat source, the flow of the exhaust can be intelligently controlled according to the condition of the sailing region, falling-film pipes 92b are vertically arranged in the heat-exchange section 92, outer walls of the falling-film pipes 92b are configured as streamlined spiral unthreaded pipes, inner walls of the falling-film pipes 92b are configured as smooth straight pipes, the falling-film pipes 92b preferably have a length of 3000 mm, a diameter of 32 mm and a wall thickness of 2 mm, and a center distance between the falling-film pipes 92b is 40 mm; and the pre-desorption section 93 is a detachable pipe provided with a flat cover, and the pipe has a gas outlet 93a located in an upper end of the pipe and a liquid outlet 93b located in a lower end of the pipe and is able to realize gas-liquid separation of secondary steam and hot lean liquid.

(16) Monitoring control devices are arranged at an inlet in a front end of the heat-change section 92, a steam inlet and an exhaust inlet of the CO.sub.2 rich liquid reboiling pre-desorption device 9 to monitor in real time the temperature and flow of rich liquid, the temperature and flow of steam, the temperature and flow of exhaust, and other parameters.

(17) Ship exhaust 81 passes through the exhaust boiler 2 to realize waste heat utilization and then enters a ship exhaust scrubber 3 to be purified; the purified ship exhaust 81 further enters the compact CO.sub.2 absorber 4, CO.sub.2 in the ship exhaust is captured with a composite amine/mixed salt absorbent, the absorbent then turns into CO.sub.2 rich liquid, and 10%-20% of the CO.sub.2 rich liquid is split out to directly flow to the top of the CO.sub.2 desorber 6; remaining non-split CO.sub.2 rich liquid is delivered by a rich liquid delivery pump a 7-1 into the CO.sub.2 lean-rich liquid heat exchanger 5 to be heated by heat exchange for the first time; after being heated by heat exchange for the first time, the rich liquid 88 is delivered by a rich liquid delivery pump b 7-2 into the Z-shaped bushings 87 of the CO.sub.2 rich liquid preheating device 8 and then comes in contact with the evaporation section of the CO.sub.2 rich liquid preheating device 8 to be heated by heat exchange for the second time, and then the rich liquid 88 enters an upper portion of the CO.sub.2 desorber 6; the split rich liquid that is not heated sequentially passes through the split rich liquid distributor 62 and the rich liquid distributor 63 after secondary heating, the non-split rich liquid that is heated passes through the rich liquid distributor 63 after secondary heating and then passes through the packing layers 64 to reach the CO.sub.2 desorber bottom 66 and then circulates to the CO.sub.2 rich liquid reboiling pre-desorption device 9 to be heated by heat exchange for the third time to reach a rich liquid adsorption temperature; semi-rich liquid 88 obtained after the third time of heating is subjected to liquid water vaporization and releases a proportion of CO.sub.2 gas, vaporized substances penetrate through the packing layers 64 by means of a riser in the CO.sub.2 desorber 6 to realize desorption of high-temperature CO.sub.2, the high-temperature CO.sub.2 enters the upper portion of the CO.sub.2 desorber 6 to reversely come in contact with the rich liquid 88 that is heated for the second time for further desorption, and the semi-rich liquid 88 that is not vaporized after being heated by heat exchange for the third time and the rich liquid 88 obtained after desorption turn into lean liquid.

(18) In the face of above condition, the heat-exchange area of the CO.sub.2 rich liquid reboiling pre-desorption device provided by the disclosure is only 175 m.sup.2, the heat-exchange area of a traditional hydrocone reboiler is over 220 m.sup.2, and because the CO.sub.2 rich liquid reboiling pre-desorption device has a pre-desorption function, the size of the CO.sub.2 desorber can be reduced by 20%.

Embodiment 2

(19) The flexible control method for a CO.sub.2 desorption system suitable for limited space in a complex sailing region comprises: establishing a knowledge and data-driven exhaust extraction flow accurate-prediction model for a heat source of a CO.sub.2 rich liquid preheating device and a steam extraction flow accurate-prediction model for a heat source on an upper section of a CO.sub.2 rich liquid reboiling pre-desorption device, establishing a global optimization control method for a CO.sub.2 desorption system suitable for limited space in a complex sailing region, and performing operation optimization with an outlet rich liquid temperature of the CO.sub.2 rich liquid reboiling pre-desorption device and energy consumption of the desorption system as constraint indicators; when a ship sails to different regions or an operating condition of the ship fluctuates, implementing accurate prediction of an exhaust extraction flow of the heat source of the CO.sub.2 rich liquid preheating device under different operating conditions by means of the knowledge and data-driven exhaust extraction flow accurate-prediction model for the heat source of the CO.sub.2 rich liquid preheating device; and, implementing accurate prediction of a steam extraction flow of the heat source of the upper portion of the CO.sub.2 rich liquid reboiling pre-desorption device under different operating conditions by means of the steam extraction flow accurate-prediction model for the heat source on the upper section of the CO.sub.2 rich liquid reboiling pre-desorption device in conjunction with operating parameters of the desorption system and quality parameters of extracted steam, so as to minimize the steam extraction flow of the heat source on the upper section of the CO.sub.2 rich liquid reboiling pre-desorption device under the precondition that the outlet rich liquid temperature of the CO.sub.2 rich liquid reboiling pre-desorption device satisfy requirements of the desorption system, thus minimizing energy consumption of the desorption system.

(20) Establishing a knowledge and data-driven exhaust extraction flow accurate-prediction model for a heat source of a CO.sub.2 rich liquid preheating device and a steam extraction flow accurate-prediction model for a heat source on an upper section of a CO.sub.2 rich liquid reboiling pre-desorption device comprises the following steps: S1, based on online and historical operation data, establishing a parameter database including physical property parameters of an absorbent, design parameters of a CO.sub.2 lean-rich liquid heat exchanger, the CO.sub.2 rich liquid preheating device and the CO.sub.2 rich liquid reboiling pre-desorption device, inlet and outlet rich liquid temperatures and flows of the CO.sub.2 lean-rich liquid heat exchanger, inlet and outlet rich liquid temperatures and flows of the CO.sub.2 rich liquid preheating device, inlet and outlet rich liquid temperatures and flows of the CO.sub.2 rich liquid reboiling pre-desorption device, inlet and outlet steam temperatures and flows of the CO.sub.2 rich liquid reboiling pre-desorption device, inlet and outlet exhaust temperatures and flows of the CO.sub.2 rich liquid preheating device, and inlet and outlet exhaust temperatures and flows of the CO.sub.2 rich liquid reboiling pre-desorption device; S2, based on the parameter database established in S1, for the CO.sub.2 rich liquid preheating device, analyzing response relations of the inlet rich liquid temperature of the CO.sub.2 rich liquid preheating device (the outlet rich liquid temperature of the CO.sub.2 lean-rich liquid heat exchanger), an inlet rich liquid CO.sub.2 load of the CO.sub.2 rich liquid preheating device (an outlet rich liquid CO.sub.2 load of the CO.sub.2 lean-rich liquid heat exchanger), a lean-rich liquid split fraction, the outlet rich liquid temperature of the CO.sub.2 rich liquid preheating device and an exhaust temperature of the heat source of the CO.sub.2 rich liquid preheating device with an exhaust flow of the heat source of the CO.sub.2 rich liquid preheating device according to a heat-exchange mechanism between different heat sources in the CO.sub.2 rich liquid preheating device and outlet rich liquid of the CO.sub.2 lean-rich liquid heat exchanger and experiential operation knowledge, establishing an exhaust extraction flow model for the heat source of the CO.sub.2 rich liquid preheating device in different sailing regions and operating conditions, modifying the exhaust extraction flow model for the heat source of the CO.sub.2 rich liquid preheating device in conjunction with quality parameters of the heat source and historical data of the outlet rich liquid temperature of the CO.sub.2 rich liquid preheating device, and establishing the knowledge and data-driven exhaust extraction flow accurate-prediction model for the heat source of the CO.sub.2 rich liquid preheating device; wherein, preferably, the knowledge and data-driven exhaust extraction flow accurate-prediction model for the heat source of the CO.sub.2 rich liquid preheating device established in S2 is expressed as:
Q.sub.y1=f.sub.2(T.sub.1,a,b,T.sub.y1)(1); where Q.sub.y1 is the exhaust flow of the heat source of the CO.sub.2 rich liquid preheating device, T.sub.1 is the outlet rich liquid temperature of the CO.sub.2 lean-rich liquid heat exchanger, T.sub.y1 is the exhaust temperature of the heat source of the CO.sub.2 rich liquid preheating device, a is the outlet rich liquid CO.sub.2 load of the CO.sub.2 lean-rich liquid heat exchanger, and b is the lean-rich liquid split fraction; and S3, based on the parameter database established in S1, for the CO.sub.2 rich liquid reboiling pre-desorption device, analyzing response relations of the outlet rich liquid temperature of the CO.sub.2 rich liquid reboiling pre-desorption device, the outlet rich liquid flow of the CO.sub.2 rich liquid preheating device, the inlet rich liquid flow of the CO.sub.2 rich liquid reboiling pre-desorption device, the inlet rich liquid temperature of the CO.sub.2 rich liquid reboiling pre-desorption device, the inlet rich liquid CO.sub.2 load of the CO.sub.2 rich liquid reboiling pre-desorption device, a steam temperature of the heat source on the upper section of the CO.sub.2 rich liquid reboiling pre-desorption device, and a ship exhaust flow and temperature of a heat source on a lower section of the CO.sub.2 rich liquid reboiling pre-desorption device with a steam flow of the heat source on the upper section of the CO.sub.2 rich liquid reboiling pre-desorption device according to a heat-exchange reboiling mechanism between different heat sources (steam and ship exhaust) in the CO.sub.2 rich liquid reboiling pre-desorption device and outlet rich liquid of the CO.sub.2 rich liquid reboiling pre-desorption device and experiential operation knowledge, establishing a steam flow model for the heat source on the upper section of the CO.sub.2 rich liquid reboiling pre-desorption device, modifying the steam flow model for the heat source on the upper section of the CO.sub.2 rich liquid reboiling pre-desorption device in conjunction with steam parameters of the heat source on the upper section of the CO.sub.2 rich liquid reboiling pre-desorption device, ship exhaust parameters of the heat source on the lower section of the CO.sub.2 rich liquid reboiling pre-desorption device and historical data of the steam flow the heat source on the upper section of the CO.sub.2 rich liquid reboiling pre-desorption device, and establishing the steam extraction flow accurate-prediction model for the heat source on the upper section of the CO.sub.2 rich liquid reboiling pre-desorption device;

(21) wherein, preferably, the steam extraction flow accurate-prediction model for the heat source on the upper section of the CO.sub.2 rich liquid reboiling pre-desorption device established in S3 is expressed as:
Q.sub.y2=f.sub.2(T.sub.2,Q.sub.C,Q.sub.r,T.sub.r,A.sub.r,T.sub.z,Qx,T.sub.x,Qs)(2); where, Q.sub.y2 is the steam extraction flow of the heat source on the upper section of the CO.sub.2 rich liquid reboiling pre-desorption device, T.sub.2 is the outlet rich liquid temperature of the CO.sub.2 rich liquid reboiling pre-desorption device, Q.sub.C is the outlet rich liquid flow of the CO.sub.2 rich liquid preheating device, Q.sub.r is the inlet rich liquid flow of the CO.sub.2 rich liquid reboiling pre-desorption device, T.sub.r is the inlet rich liquid temperature of the CO.sub.2 rich liquid reboiling pre-desorption device, A.sub.r is the inlet rich liquid CO.sub.2 load of the CO.sub.2 rich liquid reboiling pre-desorption device, T.sub.z is the steam temperature of the heat source on the upper section of the CO.sub.2 rich liquid reboiling pre-desorption device, Qx is the ship exhaust flow of the heat source on the lower section of the CO.sub.2 rich liquid reboiling pre-desorption device, T.sub.x is the ship exhaust temperature of the heat source on the lower section of the CO.sub.2 rich liquid reboiling pre-desorption device, and Qs is the steam flow of the heat source on the upper section of the CO.sub.2 rich liquid reboiling pre-desorption device.

(22) The rich liquid flow, the inlet rich liquid temperature and the steam temperature are optimized. Referring to FIG. 5, when the steam temperature is 135 C., the desorption energy consumption may be as high as 4.50 GJ/t CO.sub.2; and when the steam temperature is 150 C., the desorption energy consumption may be as low as 3.57 GJ/t CO.sub.2. Therefore, the steam temperature is set to be 150 C. in this embodiment, and as compared with the case where the steam temperature is set to be 150 C., the energy consumption can be reduced by 20.7%.

(23) Referring to FIG. 6, with the increase of the split fraction of the rich liquid, the CO.sub.2 regeneration heat duty decreases first and then increases; when the split fraction of the rich liquid is 35%, the CO.sub.2 regeneration heat duty is minimum. However, considering that the waste heat of outlet gas of the CO.sub.2 desorber is used to the maximum extent when the split fraction reaches 25% and a further increase in the split fraction of the rich liquid will lead to an increase in the flow of the delivery pumps, which in turn will increase power consumption of the system, the split fraction of the rich liquid is set to be 25% in this embodiment to keep balance between the CO.sub.2 regeneration heat duty and power consumption of a rich liquid split flow pump, and in this case, the CO.sub.2 regeneration heat duty is 2.98 GJ/tCO.sub.2; and compared with a case where the rich liquid split process is not adopted, the CO.sub.2 regeneration heat duty is reduced by 6.9%.

(24) Referring to FIG. 7, under the condition where the split fraction of rich liquid is 25%, 240 C. high-temperature exhaust is extracted from the outlet of the ship engine to be used as a heat source by means of the knowledge and data-driven exhaust extraction flow accurate-prediction model for the heat source of the CO.sub.2 rich liquid preheating device; when the inlet rich liquid temperature of the CO.sub.2 rich liquid reboiling pre-desorption device is increased by 8 C., the desorption energy consumption may be as low as 2.07 GJ/t CO.sub.2, and compared with a case where the high-temperature exhaust of the ship engine is not extracted, the desorption energy consumption is reduced by 25.6%.

(25) Further, operation optimization is performed with the outlet rich liquid temperature of the CO.sub.2 rich liquid reboiling pre-desorption device and energy consumption of the desorption system as constraint indicators; when a ship sails to different regions or an operating condition of the ship fluctuates, accurate prediction of the exhaust extraction flow of the heat source of the CO.sub.2 rich liquid preheating device under different operating conditions is implemented by means of the knowledge and data-driven exhaust extraction flow accurate-prediction model for the heat source of the CO.sub.2 rich liquid preheating device; and accurate prediction of the steam extraction flow of the heat source of the upper portion of the CO.sub.2 rich liquid reboiling pre-desorption device under different operating conditions is implemented by means of the steam extraction flow accurate-prediction model for the heat source on the upper section of the CO.sub.2 rich liquid reboiling pre-desorption device in conjunction with operating parameters of the desorption system and quality parameters of extracted steam, so as to minimize the steam extraction flow of the heat source on the upper section of the CO.sub.2 rich liquid reboiling pre-desorption device under the precondition that the outlet rich liquid temperature of the CO.sub.2 rich liquid reboiling pre-desorption device satisfy requirements of the desorption system. In this way, the ship exhaust is used to the maximum extent to replace part of the steam heat source, thus reducing the desorption energy consumption to be 2.0GJ/t CO.sub.2 or lower.

Comparative Example

(26) For ship exhaust with a volume of 20000 Nm.sup.3/h, a CO.sub.2 volume concentration of 5% and a temperature of 40 C., packing in the desorber of the CO.sub.2 desorption system in Embodiment 1 is IMTP, the number of the packing layers is two, the total height of the packing layers is 10 m, an overall pressure drop of the desorber is as high as 6400 Pa, and rich liquid splitting, utilization of waste heat of ship exhaust, CO.sub.2 rich liquid reboiling desorption and the flexible control method for the CO.sub.2 desorption system suitable for a complex sailing region are not adopted, so the desorption energy consumption of a whole carbon capture system is as high as 4.0 GJ/t CO.sub.2.

(27) Finally, it should be noted that the above embodiments are merely preferred ones of the disclosure and are not intended to limit the disclosure. Although the disclosure has been described in detail with reference to the above embodiments, those skilled in the art can still make amendments to the technical solutions in the above embodiments or make equivalent substitutions to part of the technical features in the embodiments, and any amendments, equivalent substitutions and improvements made based on the spirit and principle of the disclosure should also fall within the protection scope of the claims.