A solvent regeneration system and method

Abstract

The present invention provides a solvent regeneration system and method. The system includes a high-pressure regeneration device and a low-pressure regeneration device connected to the outlet of a rich liquid flash tank, and a high-pressure top heat recovery device connected to the high-pressure regeneration device and the low-pressure regeneration device; the high-pressure top heat recovery device includes a heat medium steam tank, a compressor, a condensate tank, and a high-pressure top water medium heat exchanger; the high-pressure top water medium heat exchanger inputs the gas phase at the top of the high-pressure rectification tower after heat exchange into the high-pressure regeneration device; the gas phase outlet of the heat medium steam tank is connected to the reboiler medium inlet of the high-pressure regeneration device and the low-pressure regeneration device through the compressor; the inlet of the condensate tank is connected to the reboiler medium outlet of the high-pressure regeneration device and the low-pressure regeneration device, and its liquid phase takes heat through the high-pressure top water medium heat exchanger and then is mixed with the gas phase at its top and the outlet gas phase of the compressor and input into the heat medium steam tank. The present invention can effectively improve the solvent regeneration separation efficiency and the internal heat utilization efficiency, and thus greatly reduce the solvent regeneration energy consumption.

Description

Technical Field

[0001] The present invention relates to the technical field of solvent regeneration processes, and in particular, to a solvent regeneration system and method. Background Art

[0002] A solvent regeneration system is a process system in petrochemical enterprises for removing acidic gas absorbed by rich amine solution to obtain regenerated lean amine solution. To achieve the separation of solvent and acidic gas solute in the existing solvent regeneration process, a large amount of low-pressure steam is consumed. Although existing processes can utilize the heat of the lean liquid at the bottom of the solvent regeneration tower, the energy-saving method of recovering the heat of the gas at the top of the solvent regeneration tower as the heat source of the reboiler at the bottom through a heat pump is difficult to achieve thermal coupling due to the temperature difference between the top and the bottom of the tower. It not only cannot fully utilize the heat of the high-temperature gas at the top of the tower, but also additionally increases energy consumption (consuming refrigerant medium or electric energy) when cooling and reducing the temperature of the high-temperature gas at the top of the tower to meet the usage requirements at the bottom of the tower. Therefore, how to efficiently recover and utilize the energy in the process while improving the separation efficiency of solvent regeneration has become an important problem faced by the production management of petrochemical enterprises. Summary of the Invention

[0003] The object of the present invention is to provide a solvent regeneration system. Through the thermal coupling design of a high-pressure and a low-pressure dual solvent regeneration tower based on thermodynamic principles, combined with the process of heat recovery by water medium extraction at the top of the tower and steam compression distribution utilization, it can not only effectively improve the separation efficiency of solvent regeneration, but also make the cooling load at the top of the high-pressure tower serve as the heat source of the reboiler at the bottom of the low-pressure tower or in the middle of the tower to achieve thermal coupling of the two towers, effectively improving the internal heat utilization efficiency of the solvent regeneration system, and thus greatly reducing the overall consumption of low-pressure steam in the system and reducing carbon emissions, achieving the optimal energy-saving effect.

[0004] In order to achieve the above object, it is necessary to provide a solvent regeneration system and method for solving the above technical problems.

[0005] In a first aspect, an embodiment of the present invention provides a solvent regeneration system, which includes a rich liquid flash tank, a high-pressure regeneration device and a low-pressure regeneration device connected to the outlet of the rich liquid flash tank, and a high-pressure tower top waste heat recovery device connected to the high-pressure regeneration device and the low-pressure regeneration device;

[0006] The high-pressure top tower waste heat recovery device includes a heat medium steam tank, a compressor, a condensate tank, and a high-pressure top tower water medium heat exchanger; the high-pressure top tower water medium heat exchanger is arranged at the top of the high-pressure rectification tower in the high-pressure regeneration device, and after heat exchange of the top gas phase of the high-pressure rectification tower, it is input into the high-pressure regeneration device; the gas phase outlet of the heat medium steam tank is respectively connected to the reboiler medium inlets of the high-pressure regeneration device and the low-pressure regeneration device through the compressor; the inlet of the condensate tank is respectively connected to the reboiler medium outlets of the high-pressure regeneration device and the low-pressure regeneration device; the liquid phase of the condensate tank takes heat through the high-pressure top tower water medium heat exchanger, and then is mixed with the top gas phase of the condensate tank and the outlet gas phase of the compressor and input into the heat medium steam tank.

[0007] Further, the high-pressure regeneration device includes a high-pressure rectification tower, a high-pressure tower bottom reboiler, a high-pressure tower intermediate reboiler, a high-pressure tower bottom lean amine liquid heat exchanger, a high-pressure tower bottom lean amine liquid cooler, a high-pressure top tower condenser, and a high-pressure top tower reflux tank;

[0008] The feed inlet of the high-pressure rectification tower is connected to the outlet of the rich liquid flash tank through the high-pressure tower bottom lean amine liquid heat exchanger and the rich liquid solvent pump in sequence through pipelines; the bottom liquid phase outlet of the high-pressure rectification tower is connected to the inlet of the lean amine liquid recovery tank through the high-pressure tower bottom lean amine liquid heat exchanger and the high-pressure tower bottom lean amine liquid cooler in sequence through pipelines; the top gas phase outlet of the high-pressure rectification tower is connected to the inlet of the high-pressure top tower reflux tank through the high-pressure top tower water medium heat exchanger and the high-pressure top tower condenser through pipelines; the gas phase outlet and the liquid phase outlet of the high-pressure top tower reflux tank are respectively connected to the inlet of the acid gas recovery device and the reflux inlet of the high-pressure rectification tower.

[0009] Further, the high-pressure tower bottom reboiler and the high-pressure tower intermediate reboiler are respectively arranged at the lower part and the middle part of the high-pressure rectification tower; the medium inlet of the high-pressure tower bottom reboiler is connected to the external heat source outlet; the medium inlet of the high-pressure tower intermediate reboiler is connected to the gas phase outlet of the heat medium steam tank through the compressor, and is used for heating and raising the temperature of the middle extraction reflux liquid and then inputting it into the bottom of the high-pressure rectification tower; the medium outlet of the high-pressure tower intermediate reboiler is connected to the inlet of the condensate tank.

[0010] Further, the low-pressure regeneration device includes a low-pressure rectification tower, a low-pressure tower bottom reboiler, a spare low-pressure tower bottom reboiler, a low-pressure tower intermediate reboiler, a low-pressure tower bottom lean amine liquid heat exchanger, a low-pressure tower bottom lean amine liquid cooler, a low-pressure top tower condenser, and a low-pressure top tower reflux tank;

[0011] The feed inlet of the low-pressure rectification column is connected to the outlet of the rich liquid flash tank through a pipeline successively via the low-pressure bottom lean amine liquid heat exchanger and the rich liquid solvent pump; the bottom liquid phase outlet of the low-pressure rectification column is connected to the inlet of the lean amine liquid recovery tank through a pipeline successively via the low-pressure bottom lean amine liquid heat exchanger and the low-pressure bottom lean amine liquid cooler; the top gas phase outlet of the low-pressure rectification column is connected to the inlet of the low-pressure top reflux tank through a pipeline via the low-pressure top condenser; the gas phase outlet and the liquid phase outlet of the low-pressure top reflux tank are respectively connected to the inlet of the acid gas recovery device and the reflux inlet of the low-pressure rectification column.

[0012] Further, both the low-pressure bottom reboiler and the standby low-pressure bottom reboiler are arranged at the lower part of the low-pressure rectification column; the low-pressure column intermediate reboiler is arranged at the middle part of the low-pressure rectification column; the medium inlet of the standby low-pressure bottom reboiler is connected to the outlet of the external heat source; the medium inlets of the low-pressure bottom reboiler and the low-pressure column intermediate reboiler are connected to the gas phase outlet of the heat medium steam tank via the compressor, and are respectively used for heating and raising the temperature of the bottom drawn reflux liquid and the middle drawn reflux liquid and then inputting them into the bottom of the low-pressure rectification column; the medium outlets of the low-pressure bottom reboiler and the low-pressure column intermediate reboiler are connected to the inlet of the condensate tank.

[0013] Further, the system further includes a distributed control subsystem; the distributed control subsystem includes an optimization controller and a high-pressure tower operation pressure control loop and valve, a high-pressure tower intermediate reboiler heat-carrying medium control loop and valve, a high-pressure top water medium heat exchanger heat-carrying medium flow control loop and valve, a low-pressure tower flow control loop and valve, a low-pressure bottom reboiler heat-carrying medium control loop and valve, and a compressor outlet pressure control loop connected to the optimization controller; the optimization controller outputs the optimal control strategy for the solvent regeneration process in real time based on a preset control optimization model; the optimal control strategy for the solvent regeneration process includes the total feed distribution ratio of the rich amine liquid solvent, the control value of the heat medium medium flow rate, the heat medium medium flow distribution ratio, and the compressor outlet pressure.

[0014] Further, the preset control optimization model is constructed by taking the minimization of the energy cost per unit solvent treatment amount as the optimization objective under preset control constraints; the preset control constraints include the conservation constraint of the total solvent regeneration treatment amount distribution, the constraint between the high-pressure top operation pressure and the compressor inlet pressure, the heat extraction constraint of the high-pressure top working medium, the working medium flow rate constraint, the compressor inlet temperature constraint, the working medium compression enthalpy value constraint, the compression medium flow distribution constraint, the high-pressure tower heating steam consumption constraint, and the low-pressure tower heating steam consumption constraint.

[0015] Further, the objective function of the preset control optimization model is expressed as:

[0016]

[0017] Among them, represents the heat source steam cost of the high-pressure tower reboiler; represents the heat source steam cost of the low-pressure tower reboiler; and respectively represent the power cost and mechanical efficiency; represents the isentropic coefficient of the gas; and respectively represent the compressor inlet pressure and the compressor outlet pressure; and respectively represent the heat source steam flow rate of the high-pressure tower reboiler and the heat source steam flow rate of the low-pressure tower reboiler; and respectively represent the working fluid flow rate and the total processing capacity of the solvent regeneration device; represents the molecular weight of the working fluid; represents the compressor inlet temperature; represents the gas compressibility factor.

[0018] Furthermore, the decentralized control subsystem further includes a low-pressure tower operating pressure control loop and valves, a heat-carrying medium valve for the intermediate reboiler of the low-pressure tower, a condensate tank top pressure control loop and valves, a gas anti-surge control loop and valves, and a condensate tank liquid level control loop and valves.

[0019] In a second aspect, an embodiment of the present invention provides a solvent regeneration method, and the method includes the following steps:

[0020] After the rich amine liquid solvent is subjected to light hydrocarbon flashing through a rich liquid flash tank, the bottom liquid phase of the rich liquid flash tank is pressurized and branched through a rich liquid solvent pump and input into a high-pressure regeneration device and a low-pressure regeneration device for regeneration treatment; the operating pressure of the high-pressure distillation column in the high-pressure regeneration device is greater than the operating pressure of the low-pressure distillation column in the low-pressure regeneration device;

[0021] Using water as the heat transfer medium, the heat of the top gas phase of the high-pressure distillation column is recovered through a high-pressure tower top water heat exchanger, and the steam generated by heat absorption and vaporization is pressurized and lifted by a compressor and then distributed and input into the reboiler medium inlets of the high-pressure regeneration device and the low-pressure regeneration device; the vaporization temperature corresponding to the highest operating pressure at the top of the high-pressure distillation column of the heat transfer medium is not higher than the water vapor condensation temperature inside the high-pressure distillation column top;

[0022] The condensate output from the reboiler medium outlets of the high-pressure regeneration device and the low-pressure regeneration device is collected through a condensate tank for recycling.

[0023] The present application provides a solvent regeneration system and method. Through the system, a high-pressure regeneration device and a low-pressure regeneration device are connected to the outlet of a rich liquid flash tank, and a high-pressure top heat recovery device is arranged between the high-pressure regeneration device and the low-pressure regeneration device. After the rich amine liquid solvent undergoes light hydrocarbon flash evaporation through the rich liquid flash tank and is pressurized and branched through a rich liquid solvent pump and input into the high-pressure regeneration device and the low-pressure regeneration device for regeneration treatment, the high-pressure top water medium heat exchanger in the high-pressure top heat recovery device uses water as the heat medium to exchange heat and recover the top gas phase heat of the high-pressure rectification tower. The steam generated by heat absorption and vaporization is stored in the heat medium steam tank and, after being pressurized and lifted by an internal compressor, is distributed and input to the reboiler medium inlets of the high-pressure regeneration device and the low-pressure regeneration device to provide heat sources, and the condensed water output from the reboiler medium outlets of the high-pressure regeneration device and the low-pressure regeneration device is collected in the internal condensate tank for recycling. Compared with the prior art, this solvent regeneration system, through the thermal coupling design of a high-low pressure dual solvent regeneration tower based on the principles of thermodynamics, combined with the process of heat recovery by water medium heat extraction from the tower top and steam compression and distribution utilization, can not only effectively improve the solvent regeneration separation efficiency, but also use the top cooling load of the high-pressure tower as the reboiler heat source for the low-pressure tower or in the middle of the tower to achieve thermal coupling of the two towers, effectively improving the internal heat utilization efficiency of the solvent regeneration system, thereby greatly reducing the overall low-pressure steam consumption in the system and reducing carbon emissions, achieving the optimal energy-saving effect. Brief Description of the Drawings

[0024] Figure 1 is a schematic structural diagram of the solvent regeneration system in an embodiment of the present invention;

[0025] Figure 2 is a schematic process control diagram of the solvent regeneration system in an embodiment of the present invention;

[0026] Figure 3 is a schematic flow diagram of the solvent regeneration method in an embodiment of the present invention;

[0027] Reference numerals: 1 - rich liquid flash tank, 2 - rich liquid solvent pump, 3 - high-pressure tower bottom reboiler, 4 - high-pressure tower bottom lean amine liquid heat exchanger, 5 - high-pressure tower bottom lean amine liquid cooler, 6 - high-pressure rectifying tower, 7 - high-pressure tower top condenser, 8 - high-pressure tower top reflux drum, 9 - spare low-pressure tower bottom reboiler, 10 - low-pressure tower bottom lean amine liquid heat exchanger, 11 - low-pressure tower bottom lean amine liquid cooler, 12 - low-pressure rectifying tower, 13 - low-pressure tower top condenser, 14 - low-pressure tower top reflux drum, 15 - heat medium steam tank, 16 - compressor, 17 - condensate tank, 18 - high-pressure tower top heat medium heat exchanger, 19 - low-pressure tower bottom reboiler, 20 - low-pressure tower intermediate reboiler, 21 - high-pressure tower intermediate reboiler, 22 - gas anti-surge control loop and valve, 23 - condensate discharge valve, 24 - bypass valve, 25 - liquid level control loop and valve, 26 - high-pressure tower intermediate reboiler heat transfer medium control loop and valve, 27 - low-pressure tower intermediate reboiler heat transfer medium valve, 28 - low-pressure tower reboiler heat transfer medium control loop and valve, 29 - high-pressure tower top heat medium heat exchanger heat transfer medium flow control loop and valve, 30 - compressor outlet pressure control loop, 31 - low-pressure tower flow control loop and valve, 32 - high-pressure tower operating pressure control loop and valve, 33 - low-pressure tower operating pressure control loop and valve, 34 - condensate tank top pressure control loop and valve, 35 - optimization controller, 200 - high-pressure regeneration device, 300 - low-pressure regeneration device, 400 - high-pressure tower top waste heat recovery device. Detailed implementation manners

[0028] In order to make the objectives, technical solutions and beneficial effects of this application clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Obviously, the following described embodiments are part of the embodiments of the present invention and are only used to illustrate the present invention, but not to limit the scope of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0029] The solvent regeneration system provided by the present invention is applicable to separating acid gas from amine solution. The following embodiments will be described in detail by taking the separation and removal of H2S by the highly selective nitrogen-methyl diethanolamine desulfurizer MDEA as an example.

[0030] In one embodiment, as Figure 1As shown, a solvent regeneration system is provided. The system includes a rich liquid flash tank 1, a high-pressure regeneration device 200 and a low-pressure regeneration device 300 connected to the outlet of the rich liquid flash tank 1, and a high-pressure top heat recovery device 400 connected to the high-pressure regeneration device 200 and the low-pressure regeneration device 300. Among them, the rich liquid flash tank 1 is used to flash the rich amine liquid solvent from the upstream, evaporate the dissolved hydrocarbons in the solvent, and input the gaseous hydrocarbons at the top of the rich liquid flash tank 1 into the flare for combustion through the corresponding pipeline. The flashed rich amine liquid solvent at the bottom of the rich liquid flash tank 1 is pressurized by the rich liquid solvent pump 2 and then divided into two streams and respectively input into the high-pressure regeneration device 200 and the low-pressure regeneration device 300 for corresponding solvent regeneration treatment. It should be noted that the feed quantity distribution ratio of the high-pressure regeneration device 200 and the low-pressure regeneration device 300 can be set and adjusted according to actual application requirements.

[0031] Both the high-pressure regeneration device 200 and the low-pressure regeneration device 300 include necessary process equipment such as a distillation column, a bottom reboiler, a bottom lean amine liquid heat exchanger, a bottom lean amine liquid cooler, a top condenser, and a top reflux tank used in the traditional solvent regeneration process. The difference between the two is that the operating pressure of the high-pressure distillation column in the high-pressure regeneration device is greater than the operating pressure of the low-pressure distillation column in the low-pressure regeneration device. And in order to effectively utilize the heat recovered from the top of the high-pressure distillation column, the high-pressure regeneration device additionally adds a high-pressure column intermediate reboiler, and the low-pressure regeneration device additionally adds a low-pressure column intermediate reboiler and a low-pressure bottom reboiler. The original bottom reboiler that needs to provide steam by an external heat source is used as a standby low-pressure bottom reboiler, and the heat sources of the additionally added reboilers in the high-pressure regeneration device and the low-pressure regeneration device both come from the heat recovered from the top of the high-pressure distillation column.

[0032] Specifically, the high-pressure regeneration device 200 includes a high-pressure rectification tower 6, a high-pressure bottom reboiler 3, a high-pressure intermediate reboiler 21, a high-pressure bottom lean amine liquid heat exchanger 4, a high-pressure bottom lean amine liquid cooler 5, a high-pressure top condenser 7, and a high-pressure top reflux drum 8; the low-pressure regeneration device 300 includes a low-pressure rectification tower 12, a low-pressure bottom reboiler 19, a spare low-pressure bottom reboiler 9, a low-pressure intermediate reboiler 20, a low-pressure bottom lean amine liquid heat exchanger 10, a low-pressure bottom lean amine liquid cooler 11, a low-pressure top condenser 13, and a low-pressure top reflux drum 14. In addition, the top pressure control of the high-pressure rectification tower 6 in the high-pressure regeneration device 200 is controlled according to the heat source steam grade provided by the bottom reboiler. For example, when the heat source steam pressure provided is 1.0 MPa, the top pressure is controlled to be 0.5 - 0.7 MPa; when the heat source steam pressure provided is 0.5 MPa, the top pressure is controlled to be 0.3 - 0.4 MPa. The low-pressure rectification tower 12 in the low-pressure regeneration device 300 is an atmospheric distillation column, and the corresponding operating pressure can be set to 0.1 MPa. In this embodiment, considering that in the existing conventional solvent regeneration process flow, the heat source of the low-pressure rectification tower bottom reboiler is 0.35 MPa steam, and a large amount of energy dissipation occurs when 0.5 or 1.0 MPa steam needs to be desuperheated and depressurized before use. By adding a high-pressure rectification tower, this part of the heat source can be utilized. At the same time, by setting the differential pressure control of the two rectification towers, the high-pressure top gas temperature is increased, enabling the normal operation of the high-pressure top water medium heat recovery system, effectively achieving complete thermal coupling between the two towers, greatly improving the heat utilization efficiency, reducing the total separation energy consumption, and improving the separation effect.

[0033] The waste heat recovery device 400 at the high-pressure tower top in this embodiment can be understood as a device that uses water as the heat transfer medium, heats the water medium through the heat at the top of the high-pressure rectification tower in the high-pressure regeneration device to make it steam, compresses it and then sends it to the bottom and middle reboilers in the high-pressure regeneration device 200 and the low-pressure regeneration device 300 as a heat source, and realizes the energy recovery and reuse device in the solvent regeneration system with heat coupling between the high-pressure regeneration device 200 and the low-pressure regeneration device 300. Preferably, the waste heat recovery device 400 at the high-pressure tower top includes a heat medium water steam tank 15, a compressor 16, a condensate tank 17 and a high-pressure tower top water medium heat exchanger 18; the high-pressure tower top water medium heat exchanger 18 is arranged at the top of the high-pressure rectification tower 6 in the high-pressure regeneration device 200, and after heat exchange of the gas phase at the top of the high-pressure rectification tower 6, it is input into the high-pressure regeneration device 200; the gas phase outlet of the heat medium water steam tank 15 is respectively connected to the reboiler medium inlets of the high-pressure regeneration device 200 and the low-pressure regeneration device 300 through the compressor 16; the inlets of the condensate tank 17 are respectively connected to the reboiler medium outlets of the high-pressure regeneration device 200 and the low-pressure regeneration device 300; after the liquid phase of the condensate tank 17 takes heat through the high-pressure tower top water medium heat exchanger 18, it is mixed with the gas phase at the top of the condensate tank 17 and the gas phase at the outlet of the compressor 16 and then input into the heat medium water steam tank 15.

[0034] In practical applications, the heat medium water in the condensate tank 17 is circulated under low pressure to the high-pressure tower top water medium heat exchanger 18 at the top of the high-pressure rectification tower 6 to take heat and vaporize, then enters the heat medium water steam tank 15, and then enters the compressor 16 for compression. The pressurized steam is respectively sent to the high-pressure tower middle reboiler 21, the low-pressure tower middle reboiler 20 and the low-pressure tower bottom reboiler 19 as a heat source through relevant control circuits. After the circulating heat medium water is discharged from the reboilers of the high / low-pressure rectification towers, it is depressurized and enters the condensate tank for taking heat and recycling at the top of the high-pressure rectification tower 6 again. It should be noted that the working medium flow rate used in the high-pressure tower top water medium heat exchanger 18, the outlet pressure of the compressor 16, and the distribution ratio of the working medium among the high-pressure tower middle reboiler 21, the low-pressure tower middle reboiler 20 and the low-pressure tower bottom reboiler 19, etc. can all be set and adjusted according to actual application requirements. In this embodiment, by adding a high-pressure rectification tower, a heat recovery and compression system for heat exchange between the gas and water medium at the top of the high-pressure tower in the traditional solvent regeneration process flow, the remaining heat of the gas at the high-pressure tower top can be effectively recovered.

[0035] In order to ensure that the high-pressure regeneration device can efficiently and reliably achieve solvent regeneration treatment, in this embodiment, it is preferably set that the feed port of the high-pressure rectification tower 6 is connected to the outlet of the rich liquid flash tank 1 through pipelines successively via the high-pressure tower bottom lean amine liquid heat exchanger 4 and the rich liquid solvent pump 2; the bottom liquid phase outlet of the high-pressure rectification tower 6 is connected to the inlet of the lean amine liquid recovery tank (not shown in the figure) through pipelines successively via the high-pressure tower bottom lean amine liquid heat exchanger 4 and the high-pressure tower bottom lean amine liquid cooler 5; the top gas phase outlet of the high-pressure rectification tower 6 is connected to the inlet of the high-pressure tower top reflux tank 8 through pipelines via the high-pressure tower top water medium heat exchanger 18 and the high-pressure tower top condenser 7; the gas phase outlet and the liquid phase outlet of the high-pressure tower top reflux tank 8 are respectively connected to the inlet of the acid gas recovery device (not shown in the figure) and the reflux inlet of the high-pressure rectification tower 6. Meanwhile, the high-pressure tower bottom reboiler 3 and the high-pressure tower intermediate reboiler 21 are respectively arranged at the lower part and the middle part of the high-pressure rectification tower 6; the medium inlet of the high-pressure tower bottom reboiler 3 is connected to the outlet of the external heat source (not shown in the figure); the medium inlet of the high-pressure tower intermediate reboiler 21 is connected to the gas phase outlet of the heat medium steam tank 15 via the compressor 16, and is used for heating and raising the temperature of the reflux liquid taken out from the middle part and then inputting it into the bottom of the high-pressure rectification tower 6; the medium outlet of the high-pressure tower intermediate reboiler 21 is connected to the inlet of the condensate tank 17.

[0036] In the actual solvent regeneration treatment process of the high-pressure regeneration device, when the pressurized rich amine liquid solvent is heated by the high-pressure tower bottom reboiler 3 and then input into the middle part of the high-pressure rectification tower 6 for rectification treatment; during the rectification treatment process, the top gas phase of the high-pressure rectification tower 6 enters the high-pressure tower top reflux tank 8 after heat exchange through the high-pressure tower top water medium heat exchanger 18 and condensation and temperature reduction through the high-pressure tower top condenser 7, and the gas phase of the high-pressure tower top reflux tank 8 enters the acid gas recovery device (acid gas tank) as the raw material of the sulfur regeneration unit, and the liquid phase of the high-pressure tower top reflux tank 8 refluxes to the top of the high-pressure rectification tower 6; meanwhile, a part of the reflux liquid is taken out from the middle part of the high-pressure rectification tower 6 in real time, heated and raised in temperature after heat exchange with the high-pressure tower intermediate reboiler 21 and then enters the bottom of the high-pressure rectification tower 6; the bottom discharge of the high-pressure rectification tower exchanges heat with the feed of the high-pressure regeneration device 200 through the high-pressure tower bottom lean amine liquid heat exchanger 4, and after being cooled by the high-pressure tower bottom lean amine liquid cooler 5, it is output as the lean amine liquid product (regenerated amine solvent) to the lean amine liquid recovery tank.

[0037] Meanwhile, to ensure that the low-pressure regeneration device can efficiently and reliably achieve solvent regeneration treatment, in this embodiment, it is preferably set that the feed inlet of the low-pressure rectification tower 12 is connected to the outlet of the rich liquid flash tank 1 through a pipeline successively via the low-pressure bottom lean amine liquid heat exchanger 10 and the rich liquid solvent pump 2; the bottom liquid phase outlet of the low-pressure rectification tower 12 is connected to the inlet of the lean amine liquid recovery tank (not shown in the figure) through a pipeline successively via the low-pressure bottom lean amine liquid heat exchanger 10 and the low-pressure bottom lean amine liquid cooler 11; the top gas phase outlet of the low-pressure rectification tower 12 is connected to the inlet of the low-pressure top reflux tank 14 through a pipeline via the low-pressure top condenser 13; the gas phase outlet and the liquid phase outlet of the low-pressure top reflux tank 14 are respectively connected to the inlet of the acid gas recovery device (not shown in the figure) and the reflux inlet of the low-pressure rectification tower 12; meanwhile, the low-pressure bottom reboiler 19 and the standby low-pressure bottom reboiler 9 are both arranged at the lower part of the low-pressure rectification tower 12; the low-pressure tower intermediate reboiler 20 is arranged in the middle of the low-pressure rectification tower 12; the medium inlet of the standby low-pressure bottom reboiler 9 is connected to the outlet of the external heat source (not shown in the figure); the medium inlets of the low-pressure bottom reboiler 19 and the low-pressure tower intermediate reboiler 20 are connected to the gas phase outlet of the heat medium steam tank 15 through the compressor 16, respectively used for heating and raising the temperature of the bottom drawn reflux liquid and the middle drawn reflux liquid and then inputting them into the bottom of the low-pressure rectification tower 12; the medium outlets of the low-pressure bottom reboiler 19 and the low-pressure tower intermediate reboiler 20 are connected to the inlet of the condensate tank 17.

[0038] In the solvent regeneration treatment process of the actual low-pressure regeneration device, when the pressurized rich amine liquid solvent is heated by the low-pressure bottom reboiler 19 or the standby low-pressure bottom reboiler 9, it is input into the middle of the low-pressure rectification tower 12 for rectification treatment; during the rectification treatment process, the top gas phase of the low-pressure rectification tower 12 is condensed and cooled by the low-pressure top condenser 13 and then enters the low-pressure top reflux tank 14, and the gas phase of the low-pressure top reflux tank 14 enters the acid gas recovery device (acid gas tank) as the raw material of the sulfur regeneration unit, and the liquid phase of the low-pressure top reflux tank 14 flows back to the top of the low-pressure rectification tower 12; meanwhile, part of the reflux liquid is taken out from the middle and bottom of the low-pressure top reflux tank 14 in real time and exchanges heat and raises the temperature with the corresponding low-pressure tower intermediate reboiler 20 and low-pressure bottom reboiler 19 respectively and then enters the bottom of the low-pressure rectification tower 12; the bottom discharge of the low-pressure rectification tower exchanges heat with the feed of the low-pressure regeneration device 300 through the low-pressure bottom lean amine liquid heat exchanger 10 and is cooled by the low-pressure bottom lean amine liquid cooler 11 and then output as lean amine liquid product to the lean amine liquid recovery tank.

[0039] In this embodiment, a high-pressure regeneration device and a low-pressure regeneration device are connected to the outlet of the rich liquid flash tank, and a high-pressure top heat recovery device is arranged between the high-pressure regeneration device and the low-pressure regeneration device. After the rich amine liquid solvent undergoes light hydrocarbon flashing through the rich liquid flash tank and is pressurized and branched through the rich liquid solvent pump and input into the high-pressure regeneration device and the low-pressure regeneration device for regeneration treatment, the high-pressure top water medium heat exchanger in the high-pressure top heat recovery device uses water as the heat medium to exchange heat and recover the top gas heat of the high-pressure rectification column. The steam generated by heat absorption and vaporization is stored in the heat medium steam tank and, after being pressurized and lifted by the internal compressor, is distributed and input to the reboiler medium inlets of the high-pressure regeneration device and the low-pressure regeneration device to provide heat sources. The condensed water output from the reboiler medium outlets of the high-pressure regeneration device and the low-pressure regeneration device is collected in the internal condensate tank for recycling. The technical solution realizes dual-channel solvent regeneration treatment by constructing high- and low-pressure dual solvent regeneration towers and coupling a heat pump system based on thermodynamic principles. While effectively improving the solvent regeneration efficiency, it also combines the processes of heat recovery by water medium heat extraction from the tower top and steam compression distribution utilization, enabling the top cooling load of the high-pressure tower to serve as the heat source for the reboiler at the middle or bottom of the low-pressure tower to achieve thermal coupling of the two towers. As a result, the heat of the high-pressure top gas is fully utilized, effectively improving the internal heat utilization efficiency of the solvent regeneration system, thereby greatly reducing the overall low-pressure steam consumption in the system and reducing carbon emissions, achieving the optimal energy-saving effect.

[0040] In addition, considering that in the actual solvent regeneration treatment process, the specific settings of the feed volume distribution ratio between the high-pressure regeneration device and the low-pressure regeneration device, the working fluid flow rate used in the high-pressure top water medium heat exchanger, the outlet pressure of the compressor, and the distribution ratio of the working fluid among the intermediate reboilers of the high-pressure tower, the intermediate reboilers of the low-pressure tower, and the bottom reboiler of the low-pressure tower will directly affect the solvent regeneration treatment efficiency of the solvent regeneration system and the heat utilization efficiency within the actual regeneration system. In order to enable the above process control items to be accurately adapted according to the operating conditions of the actual regeneration system, thereby ensuring that the solvent regeneration system can operate continuously and stably and maintain the optimal operating effect, this embodiment preferably sets a distributed control subsystem in the solvent regeneration system for real-time adaptive regulation of various process control items. By adjusting the combination of the distribution ratio of the two raw materials and the flow direction of the heat medium water, and proposing a pressure setting value calculation circuit at the compressor outlet and the condensate recovery tank, the overall energy consumption of the device is further reduced.

[0041] Specifically, as Figure 2As shown in the figure, the decentralized control subsystem includes an optimization controller 35, a high-pressure tower operating pressure control loop and valve 32 connected to the optimization controller 35, a heat carrier medium control loop and valve 26 for the intermediate reboiler of the high-pressure tower, a heat carrier medium flow control loop and valve 29 for the water-medium heat exchanger at the top of the high-pressure tower, a low-pressure tower flow control loop and valve 31, a heat carrier medium control loop and valve 28 for the reboiler at the bottom of the low-pressure tower, and a compressor outlet pressure control loop 30. Among them, the optimization controller 35 outputs the optimal control strategy for the solvent regeneration process in real time based on a preset control optimization model. That is, the optimization controller 35 can be understood as a programmable controller, including a processor, a memory, and a transceiver connected by a bus. The memory stores a regeneration process optimization control program written based on the preset control optimization model. The processor executes the regeneration process optimization control program based on the operation data of the solvent regeneration system obtained in real time by the transceiver to generate the optimal control strategy for the solvent regeneration process, and generates corresponding control instructions accordingly for real-time regulation of the above-mentioned various control loops. The optimal control strategy for the solvent regeneration process includes the total feed distribution ratio of the rich amine liquid solvent, the control value of the heat carrier medium flow rate, the heat carrier medium flow distribution ratio, and the compressor outlet pressure.

[0042] To ensure the simultaneous achievement of the dual goals of energy conservation and consumption reduction and separation efficiency improvement in solvent regeneration, in this embodiment, the optimal regulation target of the decentralized control subsystem is preferably designed as the minimum sum of the heat load costs of the reboilers at the bottom of the high-pressure tower, the heat load costs of the reboilers at the bottom of the low-pressure tower / standby reboilers at the bottom of the low-pressure tower, and the power consumption cost of the compressor. Specifically, the preset control optimization model is constructed by taking the minimum energy cost per unit solvent treatment amount as the optimization target under preset control constraints. The corresponding objective function can be expressed as:

[0043]

[0044] Among them, represents the cost of the heat source steam of the reboiler in the high-pressure tower; represents the cost of the heat source steam of the reboiler in the low-pressure tower; and represent the power cost and mechanical efficiency respectively; represents the gas isentropic coefficient; and represent the compressor inlet pressure and compressor outlet pressure respectively; and represent the heat source steam flow rate of the reboiler in the high-pressure tower and the heat source steam flow rate of the reboiler in the low-pressure tower respectively; and represent the working fluid flow rate and the total processing capacity of the solvent regeneration device respectively; represents the molecular weight of the working fluid; represents the compressor inlet temperature; It represents the gas compressibility factor.

[0045] To ensure that the optimal control strategy obtained by solving based on the above objective function meets the requirements of the actual solvent regeneration scenario, in this embodiment, it is preferably set that the preset control constraints include the following multiple constraint conditions:

[0046] 1) The conservation constraint for the distribution of the total solvent regeneration throughput, which can be understood as the distribution and mass conservation of the total solvent throughput in the solvent regeneration system between the high-pressure regeneration device and the low-pressure regeneration device, is expressed as:

[0047] (1)

[0048] In the formula, represents the total throughput of the solvent regeneration system, in t / h; represents the throughput of the high-pressure regeneration device, in t / h; represents the throughput of the low-pressure regeneration device, in t / h.

[0049] 2) The constraint on the operating pressure of the high-pressure tower top and the compressor inlet pressure, which can be understood as the constraint for determining the operating pressure of the high-pressure tower based on the properties of water vapor according to the steam supply pressure, and then determining the compressor inlet pressure based on the operating pressure of the high-pressure tower, is expressed as:

[0050] (2)

[0051] In the formula, represents the operating pressure of the high-pressure distillation column in the high-pressure regeneration device, in kPa; represents the steam pressure supplied to the reboiler at the bottom of the high-pressure tower, in kPa; represents the compressor inlet pressure, in kPa; represents the relational expression between the operating pressure of the high-pressure tower top and the steam pressure of the reboiler at the bottom of the tower, which can be set according to actual applications.

[0052] 3) The heat extraction constraint for the working medium at the high-pressure tower top, which can be understood as the constraint for calculating the heat extraction amount of the working medium by using the phase change heat of the water vapor in the steam at the high-pressure distillation tower top, is expressed as:

[0053] (3)

[0054] In the formula, represents the heat absorbed by the working medium at the high-pressure distillation tower top, in MJ / h; represents the phase change heat of the water vapor at the high-pressure distillation tower top, in MJ / t; represents the reflux mass ratio of the high-pressure tower; represents the mass fraction of H2S in the rich amine liquid feed; represents the required mass fraction of H2S in the separated lean amine liquid.

[0055] 4) Working medium flow rate constraint, which can be understood as a calculation constraint for calculating the working medium flow rate through the heat extraction of the working medium, is expressed as:

[0056] (4)

[0057] In the formula, represents the working medium flow rate, with the unit of kg / s; represents the heat absorbed by the working medium at the top of the high-pressure rectification column, with the unit of MJ / h; represents the phase change heat of the unit working medium, with the unit of MJ / t.

[0058] 5) Compressor inlet temperature constraint, which can be understood as a constraint that the inlet temperature of the compressor must be equal to the evaporation temperature of the working medium under the low-pressure environment, is expressed as:

[0059] (5)

[0060] In the formula, represents the compressor inlet temperature, with the unit of °C; represents the evaporation temperature of the working medium under the low-pressure environment, with the unit of °C.

[0061] 6) Working medium compression enthalpy value constraint, which can be understood as a calculation constraint for the enthalpy value after the working medium is compressed, is expressed as:

[0062] (6)

[0063] (7)

[0064] In the formula, represents the enthalpy value after the working medium is compressed, with the unit of MJ / h; represents the working medium flow rate, with the unit of kg / s; represents the phase change heat of the unit working medium, with the unit of MJ / t; represents the gas isentropic coefficient; represents the gas compression coefficient; represents 8314 / working medium molecular weight, with the unit of J / (kg·K); represents the compressor inlet temperature, with the unit of K; represents the compressor inlet pressure, with the unit of kPa; represents the compressor outlet pressure, with the unit of kPa; represents the mechanical efficiency; 、 and respectively represent the heat loads of the low-pressure tower reboiler, the low-pressure tower intermediate reboiler, and the high-pressure tower intermediate reboiler, with the unit of MJ / h.

[0065] 7) Compressed medium flow distribution constraint, which is a disjunctive programming constraint and can be understood as the optimization of the flow distribution of the compressed medium to the three reboilers, expressed as:

[0066]

[0067] In the formula, 、 and represent three programming constraint conditions; represents the temperature of the intermediate reboiler of the high-pressure tower, in °C; represents the temperature of the bottom reboiler of the low-pressure tower, in °C; represents the temperature of the intermediate reboiler of the low-pressure tower, in °C; represents the heat transfer temperature difference, taken between 5 and 15 °C; 、 and respectively represent the heat loads of the low-pressure tower reboiler, the intermediate reboiler of the low-pressure tower, and the intermediate reboiler of the high-pressure tower, in MJ / h; represents the unit steam phase change heat of the heat source of the high-pressure tower reboiler, in MJ / t; represents the unit steam phase change heat of the heat source of the low-pressure tower reboiler, in MJ / t; represents the reduced steam amount of the heat source of the high-pressure tower reboiler, in t / h; represents the reduced steam amount of the heat source by the heat coupling of the intermediate reboiler of the low-pressure tower, in t / h; represents the reduced steam amount of the heat source by the heat coupling of the bottom reboiler of the low-pressure tower, in t / h; represents the compressor outlet pressure, in kPa; represents the total reduced steam amount by the heat coupling of the low-pressure tower; represents the relationship between the steam saturation vapor pressure and the phase change temperature.

[0068] 8) High-pressure tower heating steam consumption constraint, which can be understood as the calculation constraint of the heating steam consumption of the high-pressure rectification tower, expressed as:

[0069] (9)

[0070] In the formula, represents the solvent treatment amount of the high-pressure regeneration device, in t / h; represents the steam flow of the heat source of the high-pressure tower reboiler, in t / h; represents the consumption of the heat source of the reboiler per unit treatment amount of the conventional high-pressure tower, in MJ / t; represents the unit steam phase change heat of the heat source of the high-pressure tower reboiler, in MJ / t; represents the reduced steam amount of the heat source of the high-pressure tower reboiler, in t / h.

[0071] 9) The low-pressure tower heating steam consumption constraint can be understood as the calculation constraint of the low-pressure distillation tower heating steam consumption, which is expressed as:

[0072] (10)

[0073] In the formula, It indicates the heat source steam flow rate of the low-pressure tower reboiler, in t / h; Indicates the solvent processing capacity of the low-pressure regeneration device, in t / h; It represents the phase change heat of unit steam of the heat source of the low-pressure tower reboiler, in MJ / t; It indicates the amount of heat source steam reduced by the thermal coupling of the intermediate reboiler in the low-pressure tower, in t / h; It indicates the amount of heat source steam reduced by the thermal coupling of the low-pressure tower bottom reboiler, in t / h; It represents the reboiler heat source consumption per unit processing capacity of a conventional low-pressure tower, in MJ / t.

[0074] By combining the objective function and constraint conditions of the preset control optimization model in the control system, the optimal total feed distribution ratio (total feed distribution ratio of rich amine liquid solvent), working fluid flow (heat medium flow control value), compressor outlet pressure and heat load distribution ratio among the three reboilers (heat medium flow distribution ratio) are calculated in real time, and the optimization results are used as the control set values of the corresponding variables in the distributed control subsystem in combination with the control valve to regulate the corresponding control loop. It should be noted that in actual process operation, if there are engineering and space restrictions, the intermediate reboiler of the high-pressure tower and the intermediate reboiler of the low-pressure tower in the above-mentioned solvent regeneration system can be selectively set. When not set, the corresponding reboiler heat exchange load in the preset control optimization model in the above-mentioned distributed control system can be set to zero.

[0075] At the same time, in order to ensure the comprehensiveness of the control of the solvent regeneration system, the distributed control subsystem also includes Figure 2 The low-pressure tower operating pressure control circuit and valve 33, the low-pressure tower intermediate reboiler heat medium valve 27, the condensate tank top pressure control circuit and valve 34, the gas anti-surge control circuit and valve 22, the liquid level control circuit and valve 25, and the condensate discharge valve 23 and the bypass valve 24 are shown; it should be noted that the low-pressure tower intermediate reboiler heat medium valve 27 here is realized by passive indirect control, and the corresponding heat medium distribution flow is obtained by the difference between the total heat medium flow and the high-pressure tower intermediate reboiler 21 and the low-pressure tower bottom reboiler 19; other control circuits can refer to the relevant control technology in the existing solvent regeneration device or be integrated into the above-mentioned preset control optimization model for coordinated optimization, which will not be described in detail here. In addition, Figure 2In it, ASC (Anti Surge Controller) represents the anti-surge controller, PC represents pressure control, PT represents pressure transmitter, TT represents temperature transmitter, LC represents liquid level control, and FC represents flow control. To facilitate the understanding of the control process of the distributed control subsystem, the following will be described in detail in combination with the actual solvent regeneration process flow:

[0076] The rich amine liquid solvent, which is the feed of the solvent regeneration system, enters the rich liquid flash tank 1. A small amount of light hydrocarbons enter the product dry gas pipeline network from the top of the rich liquid flash tank 1. The liquid phase at the bottom of the rich liquid flash tank 1 is pumped out by the rich liquid solvent pump 2, and its flow rate is controlled by the feed control loop according to the plant scale. Then it is divided into two paths. The first path enters the low-pressure rectification tower 12 through the low-pressure tower bottom lean amine liquid heat exchanger 10, and its flow rate is controlled by the low-pressure tower flow control loop and the valve 31, and the set value comes from the calculated value of the above-mentioned preset control optimization model. The second path enters the high-pressure rectification tower 6 through the high-pressure tower bottom lean amine liquid heat exchanger 4, and its flow rate is passively adjusted by the first path, thereby controlling the ratio of the flow rates of the two paths.

[0077] The gas phase at the top of the high-pressure rectification tower 6 is cooled by the high-pressure tower top water medium heat exchanger 18 and the high-pressure tower top condenser 7 and then enters the high-pressure tower top reflux tank 8. The gas phase at the top of the reflux tank enters the downstream device, and the liquid phase at the bottom of the reflux tank returns to the high-pressure rectification tower 6 as reflux. A high-pressure tower operating pressure control loop and a valve 32 are set at the top of the tower, which is controlled by the gas phase flow valve at the top of the high-pressure tower top reflux tank 8, and the control value is given by the calculation result of the above-mentioned preset control optimization model. A high-pressure tower intermediate reboiler 21 is provided in the middle of the high-pressure rectification tower 6. The heat source of the intermediate reboiler comes from the gas phase at the outlet of the compressor 16, and the flow rate of its heat-carrying medium is controlled by the high-pressure tower intermediate reboiler heat-carrying medium control loop and the valve 26, and the control value is given by the calculation result of the above-mentioned preset control optimization model. A high-pressure tower bottom reboiler 3 is provided at the bottom of the high-pressure rectification tower 6. The heat source of the high-pressure tower bottom reboiler comes from the steam supplied by the external heat source. The bottom discharge of the tower exchanges heat with the feed through the high-pressure tower bottom lean amine liquid heat exchanger 4, and then is cooled by the high-pressure tower bottom lean amine liquid cooler 5 and discharged as the lean liquid product.

[0078] The gas phase at the top of the low-pressure rectification column 12 enters the low-pressure top condenser 13 and is cooled, then enters the low-pressure top reflux drum 14. The gas phase at the top of the low-pressure top reflux drum 14 enters the downstream unit, and the liquid phase at the bottom of the low-pressure top reflux drum 14 is returned as reflux to the low-pressure rectification column 12. A low-pressure column operating pressure control loop and valve 33 are provided at the top of the column, which is controlled by the gas phase flow valve at the top of the low-pressure top reflux drum 14, and the control value is given by the calculation result of the above-mentioned preset control optimization model. A low-pressure tower intermediate reboiler 20 is provided in the middle of the low-pressure rectification column 12. The heat source of the intermediate reboiler comes from the gas phase at the outlet of the compressor 16, and the flow rate of its heat-carrying medium is passively indirectly controlled, which is obtained by the difference between the total flow rate of the heat-carrying medium and the high-pressure tower intermediate reboiler 21 and the low-pressure tower bottom reboiler 19. A spare low-pressure tower bottom reboiler 9 and a low-pressure tower bottom reboiler 19 are provided at the bottom of the low-pressure rectification column 12. The spare low-pressure tower bottom reboiler 9 is in a standby state, and the heat source comes from the steam supplied externally and is not put into use under normal production; the heat source of the low-pressure tower bottom reboiler 19 comes from the gas phase at the outlet of the compressor 16, and the flow rate of its heat-carrying medium is controlled by the low-pressure tower reboiler heat-carrying medium control loop and valve 28, and the control value is given by the calculation result of the above-mentioned preset control optimization model. The bottom discharge of the low-pressure rectification column 12 exchanges heat with the feed through the low-pressure tower bottom lean amine liquid heat exchanger 10, and then is cooled by the low-pressure tower bottom lean amine liquid cooler 11 and used as the lean liquid product.

[0079] The heat-carrying media from the three reboilers, namely the high-pressure tower intermediate reboiler 21, the low-pressure tower intermediate reboiler 20, and the low-pressure tower bottom reboiler 19, enter the condensate tank 17. The top of the tank is connected to the heat medium steam tank 15 by a pipeline. A condensate tank top pressure control loop and valve 34 are provided on this pipeline to control the pressure of the condensate tank 17. A liquid level control loop and valve 25 are provided at the bottom of the condensate tank 17. The liquid phase in the condensate tank 17 first takes heat through the high-pressure top heat exchanger 18 by self-pressure, and then is mixed with the gas phase from the top of the condensate tank 17 and the gas phase returned from the outlet of the compressor 16 and enters the heat medium steam tank 15. A condensate discharge valve 23 is provided at the bottom of the tank. When the compressor is not started, the gas phase outlet in the heat medium steam tank 15 directly enters the downstream through the bypass valve 24. When the compressor is started, this gas phase enters the compressor 16, and the outlet of the compressor is controlled by the control loop 30 for outlet pressure control, and the control value is given by the calculation result of the above-mentioned preset control optimization model. The outlet gas phase of the compressor 16 is divided into two paths. One path is controlled by the gas anti-surge control loop and valve 22 to ensure the stable and safe operation of the compressor. The other path is divided into three parts and enters the three reboilers, namely the high-pressure tower intermediate reboiler 21, the low-pressure tower intermediate reboiler 20, and the low-pressure tower bottom reboiler 19, as the heat source.

[0080] It should be noted that the above-mentioned decentralized control subsystem accesses the devices in the system to read in real time the steam pressure, feed flow rate, feed composition parameters, etc. supplied to the high-pressure regeneration device and the low-pressure regeneration device, and uses them as the input of the preset control optimization model in the optimization controller, so that it aims to minimize the energy cost per unit throughput. Through optimization calculation and solution, the optimal feed ratio of the high-pressure tower to the low-pressure tower (controlling the feed volume of the low-pressure tower), the high-pressure tower pressure, the heat carrier medium flow rate, the compressor outlet pressure, and the heat carrier medium flow rate of the reboiler are given, and they are used as the set values of the corresponding control systems to achieve the optimal operation and stable operation of the process system.

[0081] In the embodiment of the present application, a high-pressure regeneration device and a low-pressure regeneration device are connected to the outlet of the rich liquid flash tank, and a high-pressure tower top waste heat recovery device is arranged between the high-pressure regeneration device and the low-pressure regeneration device. After the rich amine liquid solvent undergoes light hydrocarbon flash evaporation through the rich liquid flash tank and is pressurized and branched through the rich liquid solvent pump and input to the high-pressure regeneration device and the low-pressure regeneration device for regeneration treatment, the high-pressure tower top water medium heat exchanger in the high-pressure tower top waste heat recovery device uses water as the heat medium to exchange heat and recover the top gas phase heat of the high-pressure rectification tower. The steam generated by heat absorption and vaporization is stored in the heat medium steam tank and after being pressurized and lifted by the internal compressor, it is distributed and input to the reboiler medium inlet of the high-pressure regeneration device and the low-pressure regeneration device to provide heat source, and the condensed water output from the reboiler medium outlet of the high-pressure regeneration device and the low-pressure regeneration device is collected in the internal condensate tank for recycling use. And through the technical solution of arranging a decentralized control subsystem to adaptively control the total feed distribution ratio of the rich amine liquid solvent, the heat medium flow control value, the heat medium flow distribution ratio, and the compressor outlet pressure with the goal of minimizing the energy cost per unit solvent throughput, it effectively solves the application defect that the existing solvent regeneration process cannot effectively recover the waste heat at the tower top, resulting in a low internal energy utilization rate of the regenerated solvent system and a high overall energy consumption. Through the thermal coupling design of the high-low pressure dual solvent regeneration tower based on the thermodynamic principle, combined with the tower top water medium heat extraction recovery and steam compression distribution utilization process, it can not only effectively improve the solvent regeneration separation efficiency, but also make the top cooling load of the high-pressure tower serve as the heat source of the reboiler in the low-pressure tower or in the middle of the tower to achieve the thermal coupling of the two towers, effectively improving the internal heat utilization efficiency of the solvent regeneration system, thereby greatly reducing the overall low-pressure steam consumption in the system and reducing carbon emissions. It can also adaptively regulate in real time the rich amine liquid solvent feed distribution ratio, the heat medium flow rate and distribution ratio, and the compressor outlet pressure of the high-low pressure regeneration devices based on the optimization control model to ensure that the solvent regeneration system can operate continuously and stably and maintain the optimal operation effect, thereby significantly reducing the overall energy consumption and achieving the optimal energy-saving effect, and it has significant advantages in terms of process level, device design, and production expansion.

[0082] To verify the actual application effect of the solvent regeneration system provided by the present invention, in this embodiment, the process of desulfurizing and regenerating rich amine liquid (an aqueous solution of MDEA with a molar concentration of 6% and acid gas) into lean amine liquid is taken as an example. Based on the process separation requirement that the content of H2S in the lean amine liquid at the bottom of the distillation column is reduced from 2% (mol) to no higher than 0.1% (mol), a simulation software AspenHYSYS is used to build a regeneration system, and the process of the present invention is compared and verified with the existing process as follows:

[0083] The solvent feed of the rich amine liquid is divided into two streams, and the total feed rate is set to a fixed value. The feed ratio of the high-pressure and low-pressure distillation columns is adjusted so that the heat energy obtained by the heat medium water medium at least meets more than half of the heat load at the bottom of the low-pressure distillation column. And the optimal value of the total heat load required by the process of the present invention is calculated by using an optimizer and compared with the heat load of the original process to verify the energy-saving effect of the process of the present invention. The operating pressure of the high-pressure distillation column is 0.3 - 0.6 MPa, and the operating pressure of the low-pressure distillation column is 0.1 - 0.2 MPa; the flow rate ratio entering the high-pressure distillation column is 50 - 70%, and the flow rate ratio entering the low-pressure distillation column is 30 - 50%; the operating pressure for the heat medium water medium to take heat and vaporize at the top of the high-pressure distillation column is 0.08 - 0.15 MPa, and the vaporization temperature corresponding to the highest heat medium water medium pressure is not higher than the condensation temperature of the water vapor inside the top of the high-pressure distillation column; the low-pressure heat medium water gas phase enters a booster compressor, and the outlet pressure of the compressor is 0.3 - 0.6 MPa, and the condensation temperature corresponding to the lowest pressure is not lower than the temperature of the reboiler at the bottom of the low-pressure distillation column; assuming that the temperatures of the reflux drums at the tops of the high-pressure and low-pressure distillation columns are both 45°C, and the H2S contents of the bottom lean liquid are set to 0.1% and 0.05% (mol) respectively, the operating conditions of each core device are simulated when the total load of the reboiler is the smallest, as shown in Table 1.

[0084] Table 1 Operating conditions of key equipment when the total load of the reboiler is the smallest

[0085]

[0086] As shown in Table 1, under the same separation requirements, compared with the existing mainstream conventional process, the present invention greatly improves the utilization efficiency of the overall energy of the system and reduces energy loss.

[0087] In one embodiment, as Figure 3 shown, a solvent regeneration method is provided, which can be applied to the solvent regeneration system described in any of the above embodiments. The method includes the following steps:

[0088] S11. After subjecting the rich amine liquid solvent to light hydrocarbon flashing through a rich liquid flash tank, the bottom liquid phase of the rich liquid flash tank is pressurized and branched through a rich liquid solvent pump and input into a high-pressure regeneration device and a low-pressure regeneration device for regeneration treatment; the operating pressure of the high-pressure distillation column in the high-pressure regeneration device is greater than the operating pressure of the low-pressure distillation column in the low-pressure regeneration device;

[0089] S12. Using water as the heat transfer medium, the heat of the top gas phase of the high-pressure distillation column in the high-pressure regeneration device is recovered through a high-pressure top water medium heat exchanger. After the steam generated by heat extraction and vaporization is pressurized and lifted by a compressor, it is distributed and input into the reboiler medium inlets of the high-pressure regeneration device and the low-pressure regeneration device; the vaporization temperature of the heat transfer medium corresponding to the highest operating pressure at the top of the high-pressure distillation column is not higher than the condensation temperature of the water vapor inside the high-pressure distillation column top;

[0090] S13. The condensed water output from the reboiler medium outlets of the high-pressure regeneration device and the low-pressure regeneration device is collected through a condensate tank for recycling.

[0091] For the specific limitations of the solvent regeneration method, reference can be made to the limitations of the solvent regeneration system in the above text, and the corresponding technical effects can also be equivalently obtained, which will not be elaborated here. In addition, although the steps in the above flow chart are shown in sequence according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless there is a clear description in this article, the execution of these steps has no strict order limit, and these steps can be executed in other orders.

[0092] In summary, for the solvent regeneration system and method provided in the embodiments of the present invention, the solvent regeneration system realizes connecting a high-pressure regeneration device and a low-pressure regeneration device at the outlet of the rich liquid flash tank, and arranging a high-pressure top heat recovery device between the high-pressure regeneration device and the low-pressure regeneration device. After the rich amine liquid solvent undergoes light hydrocarbon flashing through the rich liquid flash tank, it is pressurized and branched through the rich liquid solvent pump and input into the high-pressure regeneration device and the low-pressure regeneration device for regeneration treatment. In the high-pressure top heat recovery device, the high-pressure top water medium heat exchanger uses water as the heat medium to exchange heat and recover the top gas phase heat of the high-pressure rectification tower, and stores the steam generated by heat absorption and vaporization in the heat medium steam tank. After being pressurized and lifted by the internal compressor, it is distributed and input into the reboiler medium inlets of the high-pressure regeneration device and the low-pressure regeneration device to provide heat sources, and the condensed water output from the reboiler medium outlets of the high-pressure regeneration device and the low-pressure regeneration device is collected in the internal condensate tank for recycling. And by taking the minimization of the energy cost per unit solvent treatment amount as the optimization goal, a distributed control subsystem is arranged to adaptively control the total feed distribution ratio of the rich amine liquid solvent, the heat medium flow control value, the heat medium flow distribution ratio, and the compressor outlet pressure. Through the technical solution of constructing the thermal coupling design of the high-low pressure dual solvent regeneration tower based on the thermodynamic principle, combining the water medium heat extraction recovery at the top of the tower and the steam compression distribution utilization process, the system can not only effectively improve the solvent regeneration separation efficiency, but also make the top cooling load of the high-pressure tower serve as the reboiler heat source of the low-pressure tower or in the middle of the tower to realize the thermal coupling of the two towers, effectively improving the internal heat utilization efficiency of the solvent regeneration system, thereby greatly reducing the overall low-pressure steam consumption in the system and reducing carbon emissions. It can also adaptively adjust the feed distribution ratio of the rich amine liquid solvent, the heat medium flow and distribution ratio, and the compressor outlet pressure of the high-low pressure regeneration devices in real time based on the optimization control model, ensuring that the solvent regeneration system can operate continuously and stably and maintain the optimal operation effect, thereby significantly reducing the overall energy consumption and achieving the optimal energy-saving effect, and having significant advantages in terms of process level, device design, and production expansion, etc.

[0093] Each embodiment in this specification is described in a progressive manner. For the parts that are the same or similar in each embodiment, reference can be made to each other. Each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can refer to the partial description of the method embodiment. It should be noted that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0094] The above-described embodiments merely represent several preferred embodiments of the present application. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and substitutions can be made, and these improvements and substitutions should also be regarded as the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the protection scope of the claims described above.

Claims

1. A solvent regeneration system, characterized in that, The system includes a rich liquid flash tank, a high-pressure regeneration device and a low-pressure regeneration device connected to the outlet of the rich liquid flash tank, and a high-pressure top heat recovery device connected to the high-pressure regeneration device and the low-pressure regeneration device; The high-pressure top heat recovery device includes a heat medium steam tank, a compressor, a condensate tank and a high-pressure top water medium heat exchanger; the high-pressure top water medium heat exchanger is arranged at the top of the high-pressure rectification tower in the high-pressure regeneration device, and inputs the top gas phase of the high-pressure rectification tower into the high-pressure regeneration device after heat exchange; the gas phase outlet of the heat medium steam tank is respectively connected to the reboiler medium inlets of the high-pressure regeneration device and the low-pressure regeneration device through the compressor; the inlet of the condensate tank is respectively connected to the reboiler medium outlets of the high-pressure regeneration device and the low-pressure regeneration device; the liquid phase of the condensate tank takes heat through the high-pressure top water medium heat exchanger and is mixed with the top gas phase of the condensate tank and the outlet gas phase of the compressor and then input into the heat medium steam tank.

2. The solvent regeneration system according to claim 1, wherein The high-pressure regeneration device includes a high-pressure rectification tower, a high-pressure bottom reboiler, a high-pressure middle reboiler, a high-pressure bottom lean amine liquid heat exchanger, a high-pressure bottom lean amine liquid cooler, a high-pressure top condenser and a high-pressure top reflux tank; The feed inlet of the high-pressure rectification tower is connected to the outlet of the rich liquid flash tank through a pipeline in sequence through the high-pressure bottom lean amine liquid heat exchanger and a rich liquid solvent pump; the bottom liquid phase outlet of the high-pressure rectification tower is connected to the inlet of the lean amine liquid recovery tank through a pipeline in sequence through the high-pressure bottom lean amine liquid heat exchanger and the high-pressure bottom lean amine liquid cooler; the top gas phase outlet of the high-pressure rectification tower is connected to the inlet of the high-pressure top reflux tank through a pipeline through the high-pressure top water medium heat exchanger and the high-pressure top condenser; the gas phase outlet and the liquid phase outlet of the high-pressure top reflux tank are respectively connected to the inlet of the acid gas recovery device and the reflux inlet of the high-pressure rectification tower.

3. The solvent regeneration system according to claim 2, characterized in that, The high-pressure bottom reboiler and the high-pressure middle reboiler are respectively arranged at the lower part and the middle part of the high-pressure rectification tower; the medium inlet of the high-pressure bottom reboiler is connected to the outlet of the external heat source; the medium inlet of the high-pressure middle reboiler is connected to the gas phase outlet of the heat medium steam tank through the compressor, and is used for heating and raising the temperature of the middle-drawn reflux liquid and then inputting it into the bottom of the high-pressure rectification tower; the medium outlet of the high-pressure middle reboiler is connected to the inlet of the condensate tank.

4. The solvent regeneration system according to claim 1, wherein The low-pressure regeneration device includes a low-pressure rectification tower, a low-pressure bottom reboiler, a standby low-pressure bottom reboiler, a low-pressure middle reboiler, a low-pressure bottom lean amine liquid heat exchanger, a low-pressure bottom lean amine liquid cooler, a low-pressure top condenser and a low-pressure top reflux tank; The feed inlet of the low-pressure rectification column is connected to the outlet of the rich liquid flash tank through a pipeline successively via the low-pressure bottom lean amine liquid heat exchanger and the rich liquid solvent pump; the bottom liquid phase outlet of the low-pressure rectification column is connected to the inlet of the lean amine liquid recovery tank through a pipeline successively via the low-pressure bottom lean amine liquid heat exchanger and the low-pressure bottom lean amine liquid cooler; the top gas phase outlet of the low-pressure rectification column is connected to the inlet of the low-pressure top reflux tank through a pipeline via the low-pressure top condenser; the gas phase outlet and the liquid phase outlet of the low-pressure top reflux tank are respectively connected to the inlet of the acid gas recovery device and the reflux inlet of the low-pressure rectification column.

5. The solvent regeneration system according to claim 4, wherein Both the low-pressure bottom reboiler and the standby low-pressure bottom reboiler are arranged at the lower part of the low-pressure rectification column; the low-pressure column intermediate reboiler is arranged in the middle of the low-pressure rectification column; the medium inlet of the standby low-pressure bottom reboiler is connected to the outlet of the external heat source; the medium inlets of the low-pressure bottom reboiler and the low-pressure column intermediate reboiler are connected to the gas phase outlet of the heat medium steam tank via the compressor, respectively used for heating and raising the temperature of the bottom withdrawn reflux liquid and the middle withdrawn reflux liquid and then inputting them into the bottom of the low-pressure rectification column; the medium outlets of the low-pressure bottom reboiler and the low-pressure column intermediate reboiler are connected to the inlet of the condensate tank.

6. The solvent regeneration system according to claim 1, wherein The system further includes a distributed control subsystem; the distributed control subsystem includes an optimization controller and a high-pressure tower operation pressure control loop and valve, a high-pressure tower intermediate reboiler heat-carrying medium control loop and valve, a high-pressure tower top water medium heat exchanger heat-carrying medium flow control loop and valve, a low-pressure tower flow control loop and valve, a low-pressure bottom reboiler heat-carrying medium control loop and valve, and a compressor outlet pressure control loop connected to the optimization controller; the optimization controller outputs the optimal control strategy for the solvent regeneration process in real time based on a preset control optimization model; the optimal control strategy for the solvent regeneration process includes the total feed distribution ratio of the rich amine liquid solvent, the control value of the heat medium flow rate, the heat medium flow rate distribution ratio, and the compressor outlet pressure.

7. The solvent regeneration system according to claim 6, wherein The preset control optimization model is constructed by taking the minimization of the energy cost per unit solvent treatment amount as the optimization goal under preset control constraints; the preset control constraints include the conservation constraint of the total solvent regeneration treatment amount distribution, the constraint between the high-pressure tower top operation pressure and the compressor inlet pressure, the heat extraction constraint of the high-pressure tower top working medium, the working medium flow rate constraint, the compressor inlet temperature constraint, the working medium compression enthalpy value constraint, the compression medium flow rate distribution constraint, the high-pressure tower heating steam consumption constraint, and the low-pressure tower heating steam consumption constraint.

8. The solvent regeneration system according to claim 7, characterized in that, The objective function of the preset control optimization model is expressed as: Among them, represents the heat source steam cost of the high-pressure tower reboiler; represents the heat source steam cost of the low-pressure tower reboiler; and represent the power cost and mechanical efficiency respectively; represents the isentropic coefficient of the gas; and represent the compressor inlet pressure and the compressor outlet pressure respectively; and represent the heat source steam flow rate of the high-pressure tower reboiler and the heat source steam flow rate of the low-pressure tower reboiler respectively; and represent the working fluid flow rate and the total treatment capacity of the solvent regeneration unit respectively; represents the molecular weight of the working fluid; represents the compressor inlet temperature; represents the gas compressibility factor.

9. The solvent regeneration system according to claim 6, characterized in that, The distributed control subsystem further includes a low-pressure tower operation pressure control loop and valve, a low-pressure tower intermediate reboiler heat-carrying medium valve, a condensate tank top pressure control loop and valve, a gas anti-surge control loop and valve, and a condensate tank liquid level control loop and valve.

10. A solvent regeneration method, characterized in that Applied to the solvent regeneration system according to any one of claims 1 to 9, the method includes the following steps: After subjecting the rich amine liquid solvent to light hydrocarbon flashing through a rich liquid flash tank, the bottom liquid phase of the rich liquid flash tank is pressurized and branched through a rich liquid solvent pump and input into a high-pressure regeneration device and a low-pressure regeneration device for regeneration treatment; the operating pressure of the high-pressure rectification column in the high-pressure regeneration device is greater than the operating pressure of the low-pressure rectification column in the low-pressure regeneration device; Using water as the heat transfer medium, the heat of the top gas phase of the high-pressure rectification column is recovered through a high-pressure top water medium heat exchanger. After the steam generated by heat extraction and vaporization is pressurized and lifted by a compressor, it is distributed and input into the reboiler medium inlets of the high-pressure regeneration device and the low-pressure regeneration device; the vaporization temperature corresponding to the highest operating pressure at the top of the high-pressure rectification column of the heat transfer medium is not higher than the condensation temperature of water vapor inside the high-pressure rectification column top; The condensate water output from the reboiler medium outlets of the high-pressure regeneration device and the low-pressure regeneration device is collected through a condensate water tank for recycling.

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