Solvent regeneration system and method

Abstract

The invention provides a solvent regeneration system and method. The system comprises a high-pressure regeneration device and a low-pressure regeneration device which are connected with an outlet of a pregnant solution flash tank, and a high-pressure tower top waste heat recovery device connected with the high-pressure regeneration device and the low-pressure regeneration device, the high-pressure tower top waste heat recovery device comprises a heating medium water vapor tank, a compressor, a condensed water tank and a high-pressure tower top water medium heat exchanger; the high-pressure tower top water medium heat exchanger exchanges heat of the gas phase at the top of the high-pressure rectifying tower and inputs into the high-pressure regeneration device; a gas phase outlet of the heating medium water vapor tank is connected with reboiler medium inlets of the high-pressure regeneration device and the low-pressure regeneration device through a compressor; an inlet of the condensed water tank is connected with reboiler medium outlets of the high-pressure regeneration device and the low-pressure regeneration device, and a liquid phase of the condensed water tank is mixed with a top gas phase and an outlet gas phase of the compressor after being heated by the high-pressure tower top water medium heat exchanger and is input into the heating medium water vapor tank. The solvent regeneration separation efficiency and the internal heat utilization efficiency can be effectively improved, and then the solvent regeneration energy consumption is greatly reduced.

Description

Technical Field

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

[0002] The solvent regeneration system is a process system used in petrochemical enterprises to remove the acid gas absorbed by the rich amine liquid to obtain the regenerated lean amine liquid. The existing solvent regeneration process consumes a large amount of low-pressure steam to achieve the separation of solvent and acidic gas solutes. Although the existing process can realize the utilization of 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 by a heat pump as the heat source of the reboiler at the bottom of the tower is limited by the temperature difference between the top and the bottom of the tower and is difficult to achieve thermal coupling. Not only can the heat of the high-temperature gas at the top of the tower not be fully utilized, but when the high temperature at the top of the tower is cooled and cooled to meet the use requirements of the bottom of the tower, additional energy consumption (consumption of refrigerant or electricity) is increased. Therefore, how to efficiently recycle and utilize the energy in the process while improving the solvent regeneration separation efficiency has become an important problem faced by the production management of petrochemical enterprises. Summary of the invention

[0003] The purpose of the present invention is to provide a solvent regeneration system, which constructs a thermal coupling design of a high-low pressure dual solvent regeneration tower based on thermodynamic principles, combines the tower top water medium heat recovery and steam compression distribution utilization process, not only can effectively improve the solvent regeneration separation efficiency, but also can make the tower top cooling load of the high-pressure tower serve as the heat source of the reboiler of the low-pressure tower or the middle of the tower to realize the double-tower thermal coupling, effectively improve the internal heat utilization efficiency of the solvent regeneration system, and then greatly reduce the overall low-pressure steam consumption in the system and reduce carbon emissions, so as to achieve the best energy-saving effect.

[0004] In order to achieve the above objectives, it is necessary to provide a solvent regeneration system and method in response to the above technical problems.

[0005] In a first aspect, an embodiment of the present invention provides a solvent regeneration system, the system comprising 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 tower top waste heat recovery device includes a heat medium water vapor tank, a compressor, a condensate tank and a high-pressure tower top water medium heat exchanger; the high-pressure tower top water medium heat exchanger is arranged at the top of the high-pressure distillation tower in the high-pressure regeneration device, and the top gas phase of the high-pressure distillation tower is input into the high-pressure regeneration device after heat exchange; the gas phase outlet of the heat medium water vapor tank is connected to the reboiler medium inlet of the high-pressure regeneration device and the low-pressure regeneration device respectively 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 respectively; the liquid phase of the condensate tank 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 water vapor tank after taking heat through the high-pressure tower top water medium heat exchanger.

[0007] Further, the high-pressure regeneration device includes a high-pressure distillation 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 tower top condenser and a high-pressure tower top reflux tank;

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

[0009] Furthermore, 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 distillation tower; the medium inlet of the high-pressure tower bottom reboiler is connected to the outlet of the external heat source; the medium inlet of the high-pressure tower intermediate reboiler is connected to the gas phase outlet of the heat medium water vapor tank through the compressor, and is used to heat exchange and heat up the middle produced reflux liquid and then input it into the bottom of the high-pressure distillation 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 tower distillation device comprises a low-pressure distillation 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 tower top condenser and a low-pressure tower top reflux tank;

[0011] The feed inlet of the low-pressure distillation tower is connected to the outlet of the rich liquid flash tank through a pipeline in sequence through the low-pressure tower bottom reboiler / the standby low-pressure tower bottom reboiler, the low-pressure tower bottom lean amine liquid heat exchanger and the rich liquid solvent pump; the bottom liquid phase outlet of the low-pressure distillation tower is connected to the inlet of the lean amine liquid recovery tank through a pipeline in sequence through the low-pressure tower bottom lean amine liquid heat exchanger and the low-pressure tower bottom lean amine liquid cooler; the top gas phase outlet of the low-pressure distillation tower is connected to the inlet of the low-pressure tower top reflux tank through a pipeline through the low-pressure tower top condenser; the gas phase outlet and liquid phase outlet of the low-pressure tower top reflux tank are respectively connected to the inlet of the acid gas recovery device and the reflux inlet of the low-pressure distillation tower.

[0012] Furthermore, the low-pressure tower bottom reboiler and the spare low-pressure tower bottom reboiler are both arranged at the lower part of the low-pressure distillation tower; the low-pressure tower intermediate reboiler is arranged in the middle part of the low-pressure distillation tower; the medium inlet of the spare low-pressure tower bottom reboiler is connected to the outlet of the external heat source; the medium inlet of the low-pressure tower bottom reboiler and the low-pressure tower intermediate reboiler are connected to the gas phase outlet of the heat medium water vapor tank through the compressor, and are respectively used to heat exchange and heat up the bottom produced reflux liquid and the middle produced reflux liquid and then input them into the bottom of the low-pressure distillation tower; the medium outlet of the low-pressure tower bottom reboiler and the low-pressure tower intermediate reboiler is connected to the inlet of the condensate tank.

[0013] Furthermore, the system also includes a distributed control subsystem; the distributed control subsystem includes an optimization controller and a high-pressure tower operating pressure control loop, a high-pressure tower intermediate reboiler heat carrier control loop, a high-pressure tower top water-medium heat exchanger heat carrier flow control loop, a low-pressure tower flow control loop, a low-pressure tower bottom reboiler heat carrier control loop and a compressor outlet pressure control loop connected to the optimization controller; the optimization controller outputs an 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 a total feed distribution ratio of rich amine liquid solvent, a heat carrier flow control value, a heat carrier flow distribution ratio and a compressor outlet pressure.

[0014] Furthermore, the preset control optimization model is constructed by taking minimizing the energy cost per unit solvent processing volume as the optimization goal under preset control constraints; the preset control constraints include conservation constraints on the total solvent regeneration processing volume distribution, constraints on the high-pressure tower top operating pressure and the compressor inlet pressure, constraints on the heat extraction of the working fluid at the high-pressure tower top, constraints on the working fluid flow rate, constraints on the compressor inlet temperature, constraints on the compression enthalpy of the working fluid, constraints on the compressed medium flow distribution, constraints on the high-pressure tower heating steam consumption, and constraints on the low-pressure tower heating steam consumption.

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

[0016]

[0017] Where α represents the heat source steam cost of the high-pressure tower reboiler; β represents the heat source steam cost of the low-pressure tower reboiler; γ and η represent the power cost and mechanical efficiency respectively; k represents the gas isentropic coefficient; p1 and p2 represent the compressor inlet pressure and compressor outlet pressure respectively; F hps and F lps They 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; F medium and F unit They represent the working fluid flow rate and the total processing capacity of the solvent regeneration device respectively; R represents the working fluid molecular weight; T1 represents the compressor inlet temperature; and Z represents the gas compression coefficient.

[0018] Furthermore, the distributed control subsystem also includes a low-pressure tower operating pressure control loop, a low-pressure tower intermediate reboiler heat carrier control loop, a condensate tank top pressure control loop, a gas anti-surge control loop and a condensate tank liquid level control loop.

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

[0020] After the rich amine liquid solvent is flashed with light hydrocarbons by a rich liquid flash tank, the bottom liquid phase of the rich liquid flash tank is input to a high-pressure regeneration device and a low-pressure regeneration device through a rich liquid solvent pump pressurization branch for regeneration treatment; the operating pressure of the high-pressure distillation tower in the high-pressure regeneration device is greater than the operating pressure of the low-pressure distillation tower in the low-pressure regeneration device;

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

[0022] 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 condensed water tank for recycling.

[0023] The present application provides a solvent regeneration system and method, through which the outlet of the rich liquid flash tank is connected to a high-pressure regeneration device and a low-pressure regeneration device, 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 flashes light hydrocarbons through the rich liquid flash tank, it is pressurized and branched into the high-pressure regeneration device and the low-pressure regeneration device for regeneration treatment through the rich liquid solvent pump. The high-pressure tower top water medium heat exchanger in the high-pressure tower top waste heat recovery device uses water as a heat medium to exchange heat and recover the top gas phase heat of the high-pressure distillation tower, and the steam generated by heat extraction and vaporization is stored in a heat medium water vapor tank and, after being pressurized and lifted by an internal compressor, is distributed and input to the reboiler medium inlet of the high-pressure regeneration device and the low-pressure regeneration device to provide a 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 an internal condensate tank for recycling. Compared with the existing technology, the solvent regeneration system, through the thermal coupling design of high- and low-pressure dual solvent regeneration towers based on thermodynamic principles, combined with the top water medium heat recovery and steam compression distribution utilization process, can not only effectively improve the solvent regeneration and 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 the middle of the tower to achieve dual-tower thermal coupling, effectively improve 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 best energy-saving effect. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0026] Figure 3 Schematic diagram of the solvent regeneration method in an embodiment of the present invention;

[0027] Figure 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 liquid cooler, 6-high-pressure distillation tower, 7-high-pressure tower top condenser, 8-high-pressure tower top reflux tank, 9-spare low-pressure tower reboiler, 10-low-pressure tower bottom lean amine liquid heat exchanger, 11-low-pressure tower bottom lean liquid cooler, 12-low-pressure distillation tower, 13-low-pressure tower top condenser, 14-low-pressure tower top reflux tank, 15-heat medium water vapor tank, 16-compressor, 17-condensate tank, 18-high-pressure tower top water 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 circuit and valve, 2 3- condensate discharge valve, 24- bypass valve, 25- liquid level control circuit and valve, 26- heat medium control circuit and valve of intermediate reboiler of high-pressure tower, 27- heat medium valve of intermediate reboiler of low-pressure tower, 28- heat medium control circuit and valve of reboiler of low-pressure tower, 29- heat medium flow control circuit and valve of water-medium heat exchanger at the top of high-pressure tower, 30 compressor outlet pressure control circuit, 31 low-pressure tower flow control circuit and valve, 32 high-pressure tower operating pressure control circuit and valve, 33 low-pressure tower operating pressure control circuit and valve, 34 condensate tank top pressure control circuit and valve, 35 optimization controller, 200- high-pressure regeneration device, 300- low-pressure regeneration device, 400- waste heat recovery device at the top of high-pressure tower. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and beneficial effects of the present application clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. Obviously, the embodiments described below are part of the embodiments of the present invention and are only used to illustrate the present invention, but are not used to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] The solvent regeneration system provided by the present invention is suitable for separating acidic gas in amine solution. The following embodiment takes the separation and removal of H2S by the highly selective nitrogen methyl diethanolamine desulfurizer MDEA as an example for detailed description.

[0030] In one embodiment, 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 tower top waste heat recovery device 400 connected to the high-pressure regeneration device 200 and the low-pressure regeneration device 300; wherein 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 fire cabinet through the corresponding pipeline for combustion, and 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 to 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 amount 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] The high-pressure regeneration device 200 and the low-pressure regeneration device 300 both include necessary process equipment such as a distillation tower, 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 a conventional solvent regeneration process. The difference between the two is that the operating pressure of the high-pressure distillation tower in the high-pressure regeneration device is greater than the operating pressure of the low-pressure distillation tower in the low-pressure regeneration device, and in order to achieve effective utilization of the heat recovered from the top of the high-pressure distillation tower, the high-pressure regeneration device additionally adds a high-pressure tower intermediate reboiler, and the low-pressure regeneration device additionally adds a low-pressure tower intermediate reboiler and a low-pressure bottom reboiler, and the original bottom reboiler that requires steam to be provided by an external heat source is used as a spare bottom reboiler, and the heat sources of the additional reboilers of the high-pressure regeneration device and the low-pressure regeneration device are all from the heat recovered from the top of the high-pressure distillation tower.

[0032] Specifically, the high-pressure regeneration device 200 includes a high-pressure distillation tower 6, a high-pressure tower bottom reboiler 3, a high-pressure tower intermediate reboiler 21, a high-pressure tower bottom lean amine liquid heat exchanger 4, a high-pressure tower bottom lean amine liquid cooler 5, a high-pressure tower top condenser 7 and a high-pressure tower top reflux tank 8; the low-pressure tower distillation device 300 includes a low-pressure distillation tower 12, a low-pressure tower bottom reboiler 19, a spare low-pressure tower bottom reboiler 9, a low-pressure tower intermediate reboiler 20, a low-pressure tower bottom lean amine liquid heat exchanger 10, a low-pressure tower bottom lean amine liquid cooler 11, a low-pressure tower top condenser 13 and a low-pressure tower top reflux tank 14. In addition, the top pressure of the high-pressure distillation tower 6 in the high-pressure regeneration device 200 is controlled according to the level of the heat source steam provided by the bottom reboiler. For example, when the pressure of the heat source steam provided is 1.0MPa, the top pressure is controlled to be 0.5-0.7MPa, and when the pressure of the heat source steam provided is 0.5MPa, the top pressure is controlled to be 0.3-0.4MPa; and the low-pressure distillation tower 12 in the low-pressure regeneration device 300 is a normal pressure operating distillation tower, and the corresponding operating pressure can be set to 0.1MPa. This embodiment takes into account that in the existing conventional solvent regeneration process, the heat source of the reboiler at the bottom of the low-pressure distillation tower is 0.35MPa steam, and 0.5 or 1.0MPa steam is needed to reduce the temperature and pressure before reuse, resulting in a large amount of energy dissipation. By adding a high-pressure distillation tower, this part of the heat source can be utilized. At the same time, by setting the differential pressure control of the two distillation towers, the temperature of the high-pressure tower top gas is increased, so that the high-pressure tower top water medium heat extraction and heat recovery system can operate normally, effectively realizing 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 high-pressure tower top waste heat recovery device 400 in this embodiment can be understood as using water as a heat medium, converting the heat at the top of the high-pressure distillation tower in the high-pressure regeneration device into steam by heating the water medium, and then compressing it and sending it to the bottom of the tower and the reboiler in the tower in the high-pressure regeneration device 200 and the low-pressure regeneration device 300 for use as a heat source, and realizing an energy recovery and reuse device in the solvent regeneration system that thermally couples the high-pressure regeneration device 200 and the low-pressure regeneration device 300. Preferably, the high-pressure tower top waste heat recovery device 400 includes a heat medium water vapor 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 distillation tower 6 in the high-pressure regeneration device 200, and the top gas phase of the high-pressure distillation tower 6 is input into the high-pressure regeneration device 200 after heat exchange; the gas phase outlet of the heat medium water vapor tank 15 is connected to the reboiler medium inlet of the high-pressure regeneration device 200 and the low-pressure regeneration device 300 respectively through the compressor 16; the inlet of the condensate tank 17 is connected to the reboiler medium outlet of the high-pressure regeneration device 200 and the low-pressure regeneration device 300 respectively; the liquid phase of the condensate tank 17 is heated by the high-pressure tower top water medium heat exchanger 18, and then mixed with the top gas phase of the condensate tank 17 and the outlet gas phase of the compressor 16 and input into the heat medium water vapor tank 15.

[0034] In actual application, 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 distillation tower 6 to obtain heat and vaporize, then enter the heat medium water vapor tank 15, and then enter the compressor 16 for compression, and the pressurized steam is respectively passed to the high pressure tower intermediate reboiler 21, the low pressure tower intermediate reboiler 20 and the low pressure tower bottom reboiler 19 through the relevant control loop for use as a heat source, and the circulating heat medium water is discharged from the reboiler of the high / low pressure distillation tower, and then decompressed and enters the liquid storage tank to prepare for entering the high pressure distillation tower 6 again for heat extraction and circulation. It should be noted that the working fluid flow rate used by the high pressure tower top water medium heat exchanger 18, the outlet pressure of the compressor 16, and the distribution ratio of the working fluid between the high pressure tower intermediate reboiler 21, the low pressure tower intermediate reboiler 20 and the low pressure tower bottom reboiler 19 can all be set and adjusted according to actual application requirements. This embodiment can effectively recover the residual heat of the high-pressure tower top gas by adding a high-pressure distillation tower, a high-pressure tower top gas-water medium heat recovery and compression system to the traditional solvent regeneration process.

[0035] In order to ensure that the high-pressure regeneration device can efficiently and reliably realize the solvent regeneration treatment, the present embodiment preferably arranges the feed port of the high-pressure distillation tower 6 to be connected to the outlet of the rich liquid flash tank 1 through a pipeline in sequence through the high-pressure tower bottom reboiler 3, 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 distillation tower 6 is connected to the inlet of the lean amine liquid recovery tank (not shown in the figure) through a pipeline in sequence through 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 distillation tower 6 is connected to the inlet of the high-pressure tower top reflux tank 8 through a pipeline through 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 distillation tower 6. At the same time, 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 distillation 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 water vapor tank 15 through the compressor 16, which is used to heat exchange and heat up the middle produced reflux liquid and then input it into the bottom of the high-pressure distillation 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 process of the high-pressure regeneration device, after the pressurized rich amine liquid solvent is heated by the high-pressure tower bottom reboiler 3, it is input into the middle of the high-pressure distillation tower 6 for distillation treatment; during the distillation treatment process, the top gas phase of the high-pressure distillation tower 6 enters the high-pressure tower top reflux tank 8 after heat exchange by the high-pressure tower top water medium heat exchanger 18 and condensation and cooling by 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 sulfur regeneration unit raw material , the liquid phase of the high-pressure tower top reflux tank 8 refluxes to the top of the high-pressure distillation tower 6; at the same time, part of the reflux liquid is extracted from the middle of the high-pressure distillation tower 6 in real time, and then enters the bottom of the high-pressure distillation tower 6 after heat exchange with the high-pressure tower intermediate reboiler 21 to increase the temperature; the bottom discharge of the high-pressure distillation tower is heat exchanged with the high-pressure regeneration device 200 feed through the high-pressure tower bottom lean amine liquid heat exchanger 4, and is output to the lean amine liquid recovery tank as a lean amine liquid product (regenerated amine solvent) after cooling through the high-pressure tower bottom lean amine liquid cooler 5.

[0037] At the same time, in order to ensure that the low-pressure regeneration device can efficiently and reliably realize the solvent regeneration treatment, the present embodiment preferably arranges the feed port of the low-pressure distillation tower 12 to be connected to the outlet of the rich liquid flash tank 1 through a pipeline in sequence through the low-pressure tower bottom reboiler 19 / the standby low-pressure tower bottom reboiler 9, the low-pressure tower bottom lean amine liquid heat exchanger 10 and the rich liquid solvent pump 2; the bottom liquid phase outlet of the low-pressure distillation tower 12 is connected to the inlet of the lean amine liquid recovery tank (not shown in the figure) through a pipeline in sequence through the low-pressure tower bottom lean amine liquid heat exchanger 10 and the low-pressure tower bottom lean amine liquid cooler 11; the top gas phase outlet of the low-pressure distillation tower 12 is connected to the inlet of the low-pressure tower top reflux tank 14 through a pipeline through the low-pressure tower top condenser 13; the gas phase outlet and the liquid phase outlet of the low-pressure tower top reflux tank 14 are respectively connected to the acid gas recovery device (Figure (not shown in the figure) inlet is connected to the reflux inlet of the low-pressure distillation tower 12; at the same time, the low-pressure tower bottom reboiler 19 and the spare low-pressure tower bottom reboiler 9 are both arranged at the lower part of the low-pressure distillation tower 12; the low-pressure tower intermediate reboiler 20 is arranged in the middle of the low-pressure distillation tower 6; the medium inlet of the spare low-pressure tower bottom reboiler 9 is connected to the outlet of the external heat source (not shown in the figure); the medium inlet of the low-pressure tower bottom reboiler 19 and the low-pressure tower intermediate reboiler 20 is connected to the gas phase outlet of the heat medium water vapor tank 15 through the compressor 16, and is respectively used to heat the bottom produced reflux liquid and the middle produced reflux liquid and then input them into the bottom of the low-pressure distillation tower 12 after heat exchange and temperature increase; the medium outlet of the low-pressure tower bottom reboiler 19 and the low-pressure tower intermediate reboiler 20 is connected to the inlet of the condensate tank 17.

[0038] In the solvent regeneration process of the actual low-pressure regeneration device, after the pressurized rich amine liquid solvent is heated by the low-pressure tower bottom reboiler 19 or the spare low-pressure tower bottom reboiler 9, it is input into the middle of the low-pressure distillation tower 12 for distillation treatment; during the distillation treatment process, the top gas phase of the low-pressure distillation tower 12 is condensed and cooled by the low-pressure tower top condenser 13 and then enters the low-pressure tower top reflux tank 14, and the gas phase of the low-pressure tower top reflux tank 14 enters the acid gas recovery device (acid gas tank) as the sulfur regeneration unit raw material, and the low-pressure tower top reflux The liquid phase of the tank 14 refluxes to the top of the low-pressure distillation tower 12; at the same time, part of the reflux liquid is extracted in real time from the middle and bottom of the low-pressure tower top reflux tank 14, and is respectively heat exchanged with the corresponding low-pressure tower intermediate reboiler 20 and low-pressure tower bottom reboiler 19 to heat up before entering the bottom of the low-pressure distillation tower 12; the bottom discharge of the low-pressure distillation tower is heat exchanged with the low-pressure regeneration device 300 through the low-pressure tower bottom lean amine liquid heat exchanger 10, and is output to the lean amine liquid recovery tank as a lean amine liquid product after cooling through the low-pressure tower bottom lean amine liquid cooler 11.

[0039] The embodiment provides a method of 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 tower top waste heat recovery device between the high-pressure regeneration device and the low-pressure regeneration device. After the rich amine liquid solvent passes through the rich liquid flash tank for light hydrocarbon flashing, 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. 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 for heat exchange to recover the top gas phase heat of the high-pressure distillation tower, and stores the steam generated by heat vaporization in the heat medium water vapor tank and, after being pressurized and lifted by the internal compressor, distributes it to the reboiler medium inlet of the high-pressure regeneration device and the low-pressure regeneration device to provide a heat source, and the high The technical solution is to collect the condensed water output from the reboiler medium outlet of the high-pressure regeneration device and the low-pressure regeneration device into the internal condensate tank for recycling. The high- and low-pressure dual solvent regeneration towers are constructed based on thermodynamic principles and coupled with the heat pump system to realize dual-path solvent regeneration treatment, which effectively improves the solvent regeneration efficiency. At the same time, the top cooling load of the high-pressure tower is used as the heat source of the reboiler of the low-pressure tower or the middle of the tower by combining the tower top water medium heat recovery and steam compression distribution utilization process to realize dual-tower thermal coupling, so that the heat of the high-pressure tower 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 best energy-saving effect.

[0040] In addition, considering the feed distribution ratio of the high-pressure regeneration device and the low-pressure regeneration device in the actual solvent regeneration process, the working fluid flow rate used by the water-medium heat exchanger at the top of the high-pressure tower, the outlet pressure of the compressor, and the specific setting of the distribution ratio of the working fluid between the intermediate reboiler of the high-pressure tower, the intermediate reboiler 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 in the actual regeneration system. In order to enable the above-mentioned 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, and further reduces the overall energy consumption of the device by adjusting the two-way raw material distribution ratio and the combination of the heat medium water flow direction, and proposing a pressure set value calculation loop at the compressor outlet and the condensate recovery tank.

[0041] Specifically, Figure 2As shown, the distributed control subsystem includes an optimization controller 35 and a high-pressure tower operating pressure control loop 32, a high-pressure tower intermediate reboiler heat medium control loop 26, a high-pressure tower top water medium heat exchanger heat medium flow control loop 29, a low-pressure tower flow control loop 31, a low-pressure tower bottom reboiler heat medium control loop 28 and a compressor outlet pressure control loop 30 connected to the optimization controller 35; wherein, the optimization controller 35 outputs the optimal control strategy of the solvent regeneration process in real time based on the 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 through a bus, and the memory stores a regeneration process optimization control program written based on the preset control optimization model, and the processor executes the regeneration process optimization control program based on the operating data of the solvent regeneration system obtained in real time by the transceiver to generate the optimal control strategy of the solvent regeneration process, and generates corresponding control instructions for real-time regulation of the above-mentioned control loops; the optimal control strategy of the solvent regeneration process includes 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.

[0042] In order to ensure that the dual goals of energy saving and consumption reduction of solvent regeneration and improvement of separation efficiency are achieved at the same time, this embodiment preferably designs a preset control optimization model by minimizing the sum of the heat load cost of the reboiler at the bottom of the high-pressure distillation tower, the heat load cost of the auxiliary reboiler at the bottom of the low-pressure distillation tower, and the power consumption cost of the compressor as the optimal control target of the decentralized control subsystem; specifically, the preset control optimization model is constructed by minimizing the energy cost per unit solvent processing volume under the preset control constraints as the optimization target, and the corresponding objective function can be expressed as:

[0043]

[0044] Where α represents the heat source steam cost of the high-pressure tower reboiler; β represents the heat source steam cost of the low-pressure tower reboiler; γ and η represent the power cost and mechanical efficiency respectively; k represents the gas isentropic coefficient; p1 and p2 represent the compressor inlet pressure and compressor outlet pressure respectively; F hps and F lps They 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; F medium and F unit They represent the working fluid flow rate and the total processing capacity of the solvent regeneration device respectively; R represents the working fluid molecular weight; T1 represents the compressor inlet temperature; and Z represents the gas compression coefficient.

[0045] In order to ensure that the optimal control strategy obtained based on the above objective function meets the actual solvent regeneration scenario requirements, the preset control constraints preferably include the following constraints:

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

[0047] F unit =F htin +F ltin (1)

[0048] In the formula, F unit Indicates the total processing capacity of the solvent regeneration system, t / h; F htin Indicates the processing capacity of the high-pressure regeneration device, t / h; F ltin Indicates the processing capacity of the low-pressure regeneration device, t / h.

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

[0050] p hto ≤h(p supply ),p1≤p hto (2)

[0051] In the formula, p hto Indicates the operating pressure of the high-pressure distillation tower in the high-pressure regeneration device, in kPa; p supply It represents the steam pressure supplied to the reboiler at the bottom of the high-pressure tower, in kPa; p1 represents the compressor inlet pressure, in kPa; h(·) represents the relationship between the operating pressure at the top of the high-pressure tower and the steam pressure at the bottom of the tower reboiler, which can be set according to the actual application.

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

[0053]

[0054] In the formula, Q hthi It indicates the heat absorbed by the working fluid at the top of the high-pressure distillation tower, in MJ / h; q htla It represents the phase change heat of water vapor at the top of the high-pressure distillation tower, in MJ / t; r htr Indicates the reflux mass ratio of the high-pressure tower; c 0 Indicates the mass fraction of H2S in the rich amine feed; c ps Indicates the mass fraction requirement of H2S in the separated lean amine liquid.

[0055] 4) Working fluid flow constraint, which can be understood as the calculation constraint of calculating the working fluid flow by taking heat from the working fluid, expressed as:

[0056] F medium ≤Q hthi / q medium / 3.6 (4)

[0057] In the formula, F medium Indicates the working fluid flow rate, in kg / s; Q hthi It indicates the heat absorbed by the working fluid at the top of the high-pressure distillation tower, in MJ / h; q medium It represents the phase change heat per unit working fluid, and its unit is MJ / t.

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

[0059] T1=T lpst (5)

[0060] Where, T1 represents the compressor inlet temperature, in °C; T lpst Indicates the evaporation temperature of the working fluid under low pressure environment, in degrees Celsius.

[0061] 6) The working fluid compression enthalpy constraint can be understood as the enthalpy calculation constraint after the working fluid is compressed, which is expressed as:

[0062]

[0063] Q htho =Q hthoa +Q hthob +Q hthoc (7)

[0064] In the formula, Q htho Indicates the enthalpy value of the working fluid after compression, in MJ / h; F medium Indicates the working fluid flow rate in kg / s; q medium represents the phase change heat per unit working fluid, in MJ / t; k represents the gas isentropic coefficient; Z represents the gas compressibility coefficient; R represents 8314 / working fluid molecular weight, in J / (kg.K); T1 represents the compressor inlet temperature, in K; p1 represents the compressor inlet pressure, in kPa; p2 represents the compressor outlet pressure, in kPa; η represents the mechanical efficiency; Q hthoa , Q hthob and Q hthoc They represent the heat loads of the low-pressure tower reboiler, the low-pressure tower intermediate reboiler and the high-pressure tower intermediate reboiler respectively, and the unit is MJ / h.

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

[0066]

[0067] In the formula, Y1, Y2 and Y3 represent three planning constraints; T hpmrb Indicates the temperature of the intermediate reboiler of the high-pressure tower, in °C; T lprb Indicates the temperature of the low-pressure tower bottom reboiler, in °C; T lpmrb It indicates the temperature of the reboiler in the low-pressure tower, in °C; ΔT indicates the heat transfer temperature difference, which is between 5 and 15 °C; Q hthoa , Q hthob and Q hthoc Respectively represent the heat load of the low-pressure tower reboiler, the low-pressure tower intermediate reboiler and the high-pressure tower intermediate reboiler, in MJ / h; q hps It represents the phase change heat of unit steam of the heat source of the high-pressure tower reboiler, in MJ / t; q lps It represents the phase change heat of unit steam of the heat source of the low-pressure tower reboiler, in MJ / t; F Δhps Indicates the reduced amount of heat source steam in the high-pressure tower reboiler, in t / h; F Δlpsb Indicates the amount of heat source steam reduced by thermal coupling in the intermediate reboiler of the low-pressure tower, in t / h; F Δlpsc It indicates the amount of heat source steam reduced by the thermal coupling of the low-pressure tower bottom reboiler, in t / h; p2 indicates the compressor outlet pressure, in kPa; F Δlps It represents the total amount of steam reduced by thermal coupling of the low-pressure tower; g(·) represents the relationship between the saturated vapor pressure of steam and the phase change temperature.

[0068] 8) The high-pressure tower heating steam consumption constraint can be understood as the high-pressure distillation tower heating steam consumption calculation constraint, which is expressed as:

[0069]

[0070] In the formula, F htin Indicates the solvent processing capacity of the high-pressure regeneration device, in t / h; F hps Represents the heat source steam flow rate of the high-pressure tower reboiler, in t / h; ω htsc Indicates the heat source consumption of the reboiler per unit processing capacity of the conventional high-pressure tower, in MJ / t; q hps It represents the phase change heat of unit steam of the heat source of the high-pressure tower reboiler, in MJ / t; F Δhps Indicates the reduction in the amount of heat source steam in 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]

[0073] In the formula, Flps Indicates the heat source steam flow rate of the low-pressure tower reboiler, in t / h; F ltin Indicates the solvent processing capacity of the low-pressure regeneration device, in t / h; q lps It represents the phase change heat of unit steam of the heat source of the low-pressure tower reboiler, in MJ / t; F Δlpsb Indicates the amount of heat source steam reduced by thermal coupling in the intermediate reboiler of the low-pressure tower, in t / h; F Δlpsc Indicates the amount of heat source steam reduced by thermal coupling of the low-pressure tower bottom reboiler, in t / h; ω ltsc 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 optimized 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 loop 33, the low-pressure tower intermediate reboiler heat carrier control loop 27, the condensate tank top pressure control loop 34, the gas anti-surge control loop 22, the condensate tank level control loop 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 carrier control loop 27 is realized by passive indirect control, and the corresponding heat carrier distribution flow is obtained by the difference between the total heat carrier flow and the high-pressure tower intermediate reboiler 21 and the low-pressure tower bottom reboiler 19; other control loops 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 2 ASC (AntiSurge Controller) stands for anti-surge controller, PC stands for pressure control, PT stands for pressure transmitter, TT stands for temperature transmitter, LC stands for liquid level control, and FC stands for flow control. In order to facilitate the understanding of the control process of the distributed control subsystem, the following is a detailed description combined with the actual solvent regeneration process:

[0076] The solvent regeneration system feeds rich amine liquid solvent into the rich liquid flash tank 1, and a small amount of light hydrocarbons enters the product dry gas pipeline network through 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 scale of the device; then it is divided into two paths, the first path enters the low-pressure distillation tower 12 through the lean amine liquid heat exchanger 10 at the bottom of the low-pressure tower, and its flow rate is controlled by the low-pressure tower flow control loop and 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 distillation tower 6 through the lean amine liquid heat exchanger 4 at the bottom of the high-pressure tower, and its flow rate is passively regulated by the first path, thereby controlling the ratio of the two flow rates.

[0077] The gas phase at the top of the high-pressure distillation tower 6 is cooled by the high-pressure tower top water medium heat exchanger 18 and the high-pressure tower top cooler 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 distillation tower 6 as reflux; the high-pressure tower operating pressure control loop and 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. An intermediate reboiler 21 is set in the middle of the high-pressure distillation tower 6. The heat source of the intermediate reboiler comes from the gas phase at the outlet of the compressor 16. The flow rate of its heat carrier medium is controlled by the heat carrier medium control loop and valve 26 of the high-pressure tower intermediate reboiler, and the control value is given by the calculation result of the above-mentioned preset control optimization model. A reboiler 3 is set at the bottom of the high-pressure distillation tower 6, and the heat source of the reboiler comes from the steam supplied by the external heat source; the bottom discharge of the tower is heat-exchanged with the feed through the high-pressure tower bottom lean amine liquid heat exchanger 4, and then cooled by the high-pressure tower bottom lean amine liquid cooler 5 as a lean liquid product.

[0078] The gas phase at the top of the low-pressure distillation tower 12 is cooled by the low-pressure tower top condenser 13 and enters the low-pressure tower top reflux tank 14. The gas phase at the top of the low-pressure tower top reflux tank 14 enters the downstream device, and the liquid phase at the bottom of the low-pressure tower top reflux tank 14 returns to the low-pressure distillation tower 12 as reflux. A low-pressure tower operating pressure control loop and valve 33 are set at the top of the tower, which is controlled by the gas phase flow valve at the top of the low-pressure tower top reflux tank 14, and the control value is given by the calculation result of the above-mentioned preset control optimization model. An intermediate reboiler 20 is set in the middle of the low-pressure distillation tower 12. The heat source of the intermediate reboiler comes from the gas phase at the outlet of the compressor 16. The heat carrier flow rate is passively and indirectly controlled, which is obtained by the difference between the total heat carrier flow rate and the intermediate reboiler 21 of the high-pressure tower and the reboiler 19 at the bottom of the low-pressure tower. The bottom of the low-pressure distillation tower 12 is provided with a spare low-pressure tower bottom reboiler 9 and a low-pressure tower bottom reboiler 19. The spare low-pressure tower bottom reboiler 9 is in a standby state, and its heat source comes from the steam supplied from the outside, and it 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 its heat carrier flow is controlled by the low-pressure tower reboiler heat carrier 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 distillation tower 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 as a lean liquid product.

[0079] The heat-carrying medium from the high-pressure tower intermediate reboiler 21, the low-pressure tower intermediate reboiler 20, and the low-pressure tower bottom reboiler 19 enters the condensate tank 17, and the tank top is connected to the heat medium water vapor tank 15 by a pipeline. The pipeline is provided with a pressure control loop and a valve 34 to control the pressure of the condensate tank 17. The bottom of the condensate tank 17 is provided with a liquid level control loop and a valve 25. The liquid phase in the condensate tank 17 first passes through the high-pressure tower top heat exchanger 18 to extract heat by self-pressure, and then mixes 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 water vapor tank 15. The tank bottom is provided with a drain valve 23. The gas phase outlet in the heat medium water vapor tank 15 directly enters the downstream through the valve 24 when the compressor is not started. When the compressor is started, the gas phase enters the compressor 16, and the outlet pressure of the compressor outlet is controlled by the control loop 30, and its 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 of which is controlled by a gas anti-surge control loop and a valve 22 to ensure smooth and safe operation of the compressor, and the other is divided into three parts and enters the high-pressure tower intermediate reboiler 21, the low-pressure tower intermediate reboiler 20, and the low-pressure tower bottom reboiler 19 as heat sources.

[0080] It should be noted that the above-mentioned distributed control subsystem is connected to the device in the system to read the steam pressure, feed flow and feed composition parameters supplied to the high-pressure regeneration device and the low-pressure regeneration device in real time, and use it as the input of the preset control optimization model in the optimization controller, so that it can minimize the energy cost per unit processing volume. Through optimization calculation and solution, the optimal high-pressure tower and low-pressure tower feed ratio (control the low-pressure tower feed amount), high-pressure tower pressure, heat carrier flow, compressor outlet pressure and reboiler heat carrier flow are given, and used as the set value of the corresponding control system to achieve 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 at 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 flashes light hydrocarbons through the rich liquid flash tank, it is pressurized and branched to the high-pressure regeneration device and the low-pressure regeneration device for regeneration treatment through the rich liquid solvent pump. 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 for heat exchange to recover the top gas phase heat of the high-pressure distillation tower, and the steam generated by heat extraction vaporization is stored in the heat medium water vapor tank and, after being pressurized and lifted by the internal compressor, it is distributed to the reboiler medium inlet of the high-pressure regeneration device and the low-pressure regeneration device to provide a 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, and the distributed control subsystem is arranged with the minimization of the energy cost per unit solvent processing amount as the optimization goal 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 pressure The technical solution of reducing the outlet pressure of the compressor effectively solves the application defect that the existing solvent regeneration process cannot effectively recover the waste heat from the top of the tower, resulting in low energy utilization rate inside the regeneration solvent system and high overall energy consumption. By constructing a thermal coupling design of high- and low-pressure dual solvent regeneration towers based on thermodynamic principles, combined with the tower top water medium heat recovery and steam compression distribution and 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 of the low-pressure tower or the middle of the tower to realize double-tower thermal coupling, effectively improve 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 control the rich amine liquid solvent feed distribution ratio, heat medium flow and distribution ratio and compressor outlet pressure of the high and low pressure regeneration device in real time based on the optimization control model, ensuring that the solvent regeneration system can operate continuously and stably and maintain the optimal operating effect, thereby significantly reducing the overall energy consumption and achieving the optimal energy-saving effect. It has significant advantages in terms of process level, device design and expansion.

[0082] In order to verify the practical application effect of the solvent regeneration system provided by the present invention, this embodiment also takes the process flow of desulfurization regeneration of rich amine liquid (MDEA aqueous solution with a molar concentration of 6% and acid gas) into lean amine liquid 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 tower is reduced from 2% (mol) to no more than 0.1% (mol), the simulation software AspenHYSYS is used to build a regeneration system, and the process of the present invention is compared with the existing process for the following simulation verification:

[0083] The rich amine liquid solvent feed is divided into two streams, and the total feed amount is set to a fixed value. The feed ratio of the high-pressure and low-pressure distillation towers is adjusted so that the thermal energy obtained by the heat medium water medium can meet at least more than half of the thermal load at the bottom of the low-pressure distillation tower. The optimal value of the total thermal load required for the process of the present invention is calculated by using an optimizer and compared with the thermal 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 tower is 0.3-0.6MPa, and the operating pressure of the low-pressure distillation tower is 0.1-0.2MPa; the flow rate entering the high-pressure distillation tower accounts for 50-70%, and the flow rate entering the low-pressure distillation tower accounts for 30-50%; the operating pressure of the heat medium water medium taking heat and vaporizing at the top of the high-pressure distillation tower is 0.08-0.15MPa, and the vaporization temperature corresponding to the maximum heat medium water medium pressure is not higher than the condensation temperature of water vapor in the top of the high-pressure distillation tower; the low-pressure heat medium water vapor phase enters the booster for compression, the compressor outlet pressure is 0.3-0.6MPa, and the condensation temperature corresponding to the lowest pressure is not lower than the reboiler temperature at the bottom of the low-pressure distillation tower; assuming that the temperature of the reflux tank at the top of the high and low-pressure distillation towers is 45°C, and the H2S content of the lean liquid at the bottom of the tower is set to 0.1% and 0.05% (mol) respectively, the simulation obtains the operation status of each core equipment when the total load of the reboiler is the minimum, as shown in Table 1.

[0084] Table 1 Operation status of key equipment when the total reboiler load is minimum

[0085]

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

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

[0088] S11, after flashing the light hydrocarbons of the rich amine liquid solvent through the rich liquid flash tank, the bottom liquid phase of the rich liquid flash tank is input to the high-pressure regeneration device and the low-pressure regeneration device through the rich liquid solvent pump pressurization branch for regeneration treatment; the operating pressure of the high-pressure distillation tower in the high-pressure regeneration device is greater than the operating pressure of the low-pressure distillation tower in the low-pressure regeneration device;

[0089] S12, using water as a heat medium, recovering the gas phase heat at the top of the high-pressure distillation tower in the high-pressure regeneration device through a water-medium heat exchanger at the top of the high-pressure tower, and pressurizing and lifting the steam generated by heat extraction and vaporization through a compressor, and then distributing and inputting it to the reboiler medium inlet of the high-pressure regeneration device and the low-pressure regeneration device; the vaporization temperature of the heat medium corresponding to the highest operating pressure at the top of the high-pressure distillation tower is not higher than the condensation temperature of the water vapor in the top of the high-pressure distillation tower;

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

[0091] For the specific definition of the solvent regeneration method, please refer to the definition of the solvent regeneration system above, and the corresponding technical effects can also be obtained equivalently, which will not be repeated here. In addition, although the various steps in the above flow chart are displayed in sequence according to the instructions of the arrows, these steps are not necessarily performed in the order indicated by the arrows. Unless otherwise clearly stated in this article, there is no strict order restriction for the execution of these steps, and these steps can be performed in other orders.

[0092] In summary, an embodiment of the present invention provides a solvent regeneration system and method, wherein the solvent regeneration system realizes connecting a high-pressure regeneration device and a low-pressure regeneration device at the outlet of a rich liquid flash tank, and arranging a high-pressure tower top waste heat recovery device between the high-pressure regeneration device and the low-pressure regeneration device. After the rich amine liquid solvent flashes light hydrocarbons through the rich liquid flash tank, it is pressurized and branched and input into the high-pressure regeneration device and the low-pressure regeneration device for regeneration treatment through the rich liquid solvent pump. 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 for heat exchange to recover the top gas phase heat of the high-pressure distillation tower, and stores the steam generated by heat vaporization in a heat medium water vapor tank and, after being pressurized and lifted by an internal compressor, distributes it to the reboiler medium inlet of the high-pressure regeneration device and the low-pressure regeneration device to provide a heat source, and collects the condensed water output from the reboiler medium outlet of the high-pressure regeneration device and the low-pressure regeneration device into an internal condensate tank for recycling, and arranges a distributed control subsystem for automatic The technical scheme is adapted to control the total feed distribution ratio of rich amine liquid solvent, the heat medium flow control value, the heat medium flow distribution ratio and the compressor outlet pressure. The system constructs a thermal coupling design of high- and low-pressure dual solvent regeneration towers based on thermodynamic principles, and combines the tower top water medium heat recovery and steam compression distribution utilization process. It can not only effectively improve the solvent regeneration separation efficiency, but also make the tower top cooling load of the high-pressure tower serve as the reboiler heat source of the low-pressure tower or the middle of the tower to achieve double-tower thermal coupling, effectively improve 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 control the rich amine liquid solvent feed distribution ratio, heat medium flow and distribution ratio and compressor outlet pressure of the high and low pressure regeneration device in real time based on the optimization control model, ensuring that the solvent regeneration system can operate continuously and stably and maintain the optimal operating effect, thereby significantly reducing the overall energy consumption and achieving the optimal energy-saving effect. It has significant advantages in terms of process level, device design and expansion.

[0093] Each embodiment in this specification is described in a progressive manner, and the same or similar parts of each embodiment can be directly referred to each other, and 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 be referred to the partial description of the method embodiment. It should be noted that the technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, all possible combinations of the technical features in the above-mentioned embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0094] The above-mentioned embodiments only express several preferred implementation modes of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in the technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention, 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 based on the protection scope of the claims.

Claims

1. A solvent regeneration system, characterized in that: The system comprises 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; The high-pressure tower top waste heat recovery device includes a heat medium water vapor tank, a compressor, a condensate tank and a high-pressure tower top water medium heat exchanger; the high-pressure tower top water medium heat exchanger is arranged at the top of the high-pressure distillation tower in the high-pressure regeneration device, and the top gas phase of the high-pressure distillation tower is input into the high-pressure regeneration device after heat exchange; the gas phase outlet of the heat medium water vapor tank is connected to the reboiler medium inlet of the high-pressure regeneration device and the low-pressure regeneration device respectively 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 respectively; the liquid phase of the condensate tank 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 water vapor tank after taking heat through the high-pressure tower top water medium heat exchanger.

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

3. The solvent regeneration system according to claim 2, characterized in that: 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 distillation tower; the medium inlet of the high-pressure tower bottom reboiler is connected to the outlet of the external heat source; the medium inlet of the high-pressure tower intermediate reboiler is connected to the gas phase outlet of the heat medium water vapor tank through the compressor, and is used to heat the middle produced reflux liquid and then input it into the bottom of the high-pressure distillation tower after heat exchange and temperature increase, and is used to heat the middle produced reflux liquid and then input it into the bottom of the high-pressure distillation tower after heat exchange and temperature increase; the medium outlet of the high-pressure tower intermediate reboiler is connected to the inlet of the condensate tank.

4. The solvent regeneration system according to claim 1, characterized in that: The low-pressure tower distillation device comprises a low-pressure distillation 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 tower top condenser and a low-pressure tower top reflux tank; The feed inlet of the low-pressure distillation tower is connected to the outlet of the rich liquid flash tank through a pipeline in sequence through the low-pressure tower bottom reboiler / the standby low-pressure tower bottom reboiler, the low-pressure tower bottom lean amine liquid heat exchanger and the rich liquid solvent pump; the bottom liquid phase outlet of the low-pressure distillation tower is connected to the inlet of the lean amine liquid recovery tank through a pipeline in sequence through the low-pressure tower bottom lean amine liquid heat exchanger and the low-pressure tower bottom lean amine liquid cooler; the top gas phase outlet of the low-pressure distillation tower is connected to the inlet of the low-pressure tower top reflux tank through a pipeline through the low-pressure tower top condenser; the gas phase outlet and liquid phase outlet of the low-pressure tower top reflux tank are respectively connected to the inlet of the acid gas recovery device and the reflux inlet of the low-pressure distillation tower.

5. The solvent regeneration system according to claim 4, characterized in that: The low-pressure tower bottom reboiler and the spare low-pressure tower bottom reboiler are both arranged at the lower part of the low-pressure distillation tower; the low-pressure tower intermediate reboiler is arranged in the middle part of the low-pressure distillation tower; the medium inlet of the spare low-pressure tower bottom reboiler is connected with the outlet of the external heat source; the medium inlet of the low-pressure tower bottom reboiler and the low-pressure tower intermediate reboiler are connected with the gas phase outlet of the heat medium water vapor tank through the compressor, and are respectively used to heat exchange and heat up the bottom produced reflux liquid and the middle produced reflux liquid and then input them into the bottom of the low-pressure distillation tower; the medium outlet of the low-pressure tower bottom reboiler and the low-pressure tower intermediate reboiler is connected with the inlet of the condensate tank.

6. The solvent regeneration system according to claim 1, characterized in that: The system also includes a distributed control subsystem; the distributed control subsystem includes an optimization controller and a high-pressure tower operating pressure control loop, a high-pressure tower intermediate reboiler heat carrier control loop, a high-pressure tower top water medium heat exchanger heat carrier flow control loop, a low-pressure tower flow control loop, a low-pressure tower bottom reboiler heat carrier control loop and a compressor outlet pressure control loop connected to the optimization controller; the optimization controller outputs an 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 a total feed distribution ratio of rich amine liquid solvent, a heat carrier flow control value, a heat carrier flow distribution ratio and a compressor outlet pressure.

7. The solvent regeneration system according to claim 6, characterized in that: The preset control optimization model is constructed by taking minimizing the energy cost per unit solvent processing volume as the optimization goal under the preset control constraints; the preset control constraints include the conservation constraint of the total solvent regeneration processing volume distribution, the high-pressure tower top operating pressure and the compressor inlet pressure constraint, the high-pressure tower top working fluid heat extraction constraint, the working fluid flow constraint, the compressor inlet temperature constraint, the working fluid compression enthalpy constraint, the compressed medium flow 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: Where α represents the heat source steam cost of the high-pressure tower reboiler; β represents the heat source steam cost of the low-pressure tower reboiler; γ and η represent the power cost and mechanical efficiency respectively; k represents the gas isentropic coefficient; p1 and p2 represent the compressor inlet pressure and compressor outlet pressure respectively; F hps and F lps They 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; F medium and F unit They represent the working fluid flow rate and the total processing capacity of the solvent regeneration device respectively; R represents the working fluid molecular weight; T1 represents the compressor inlet temperature; and Z represents the gas compression coefficient.

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

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 comprises the following steps: After the rich amine liquid solvent is flashed with light hydrocarbons by a rich liquid flash tank, the bottom liquid phase of the rich liquid flash tank is input to a high-pressure regeneration device and a low-pressure regeneration device through a rich liquid solvent pump pressurization branch for regeneration treatment; the operating pressure of the high-pressure distillation tower in the high-pressure regeneration device is greater than the operating pressure of the low-pressure distillation tower in the low-pressure regeneration device; Using water as a heat medium, the gas phase heat at the top of the high-pressure distillation tower is recovered through a water-medium heat exchanger at the top of the high-pressure tower, and the steam generated by heat vaporization is pressurized and lifted by a compressor, and then distributed and input to the reboiler medium inlet of the high-pressure regeneration device and the low-pressure regeneration device; the vaporization temperature of the heat medium corresponding to the highest operating pressure at the top of the high-pressure distillation tower is not higher than the condensation temperature of the water vapor in the top of the high-pressure distillation tower; 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 condensed water tank for recycling.

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