CN107138025B - Low-temperature methanol washing process for efficiently recycling pressure energy and cold energy - Google Patents
Low-temperature methanol washing process for efficiently recycling pressure energy and cold energy Download PDFInfo
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- CN107138025B CN107138025B CN201710396428.6A CN201710396428A CN107138025B CN 107138025 B CN107138025 B CN 107138025B CN 201710396428 A CN201710396428 A CN 201710396428A CN 107138025 B CN107138025 B CN 107138025B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
- B01D53/1456—Removing acid components
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- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
- B01D53/1425—Regeneration of liquid absorbents
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
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Abstract
The invention belongs to the technical field of energy chemical industry, and discloses low-temperature methanol with high-efficiency recycling of pressure energy and cold energyAnd (5) washing. In the process, methanol rich liquid extracted from the side line of the medium-pressure flash tower and methanol rich liquid at the bottom are subjected to throttling and pressure reduction and then fed into CO2The regeneration tower is adjusted into a newly-added hydraulic turbine for expanding, acting, cooling and depressurizing, then enters a newly-added low-temperature circulating working medium heat exchanger for recovering low-temperature cold energy, and then CO2A regeneration tower; and the most poor methanol and CO in the thermal regeneration tower2Cooling the rich methanol solution at the bottom of the regeneration tower by cooling exchange to the most poor methanol by an advanced newly added precooler, and cooling the CO after heat exchange by a methanol circulating cooler2The methanol rich solution at the bottom of the regeneration tower is firstly added with a low-temperature circulating working medium heat exchanger to recover low-temperature cold energy, and then the most poor methanol and the methanol rich solution are cooled by the rich/poor methanol heat exchanger. The process can obviously recover work and cold energy and has obvious economic benefit.
Description
Technical Field
The invention belongs to the technical field of energy chemical industry, and particularly relates to a low-temperature methanol washing process for efficiently recycling pressure energy and cold energy.
Background
Low temperature methanol scrubbing was a gas purification process developed in the last 50 th century by linde, germany and lurgi. It uses low-temperature methanol as absorption solvent to remove acidic component from raw material gas, so that it can be extensively used in the industries of synthetic ammonia, natural gas desulfurization and urban gas purification, etc. In the synthetic ammonia industry, crude gas from a (coal) gas making unit is subjected to a carbon monoxide shift reaction in a shift unit to maximally convert CO into CO2To produce H-enriched2The conversion gas (wherein the molar concentration of CO is not more than 0.4 percent), then the conversion gas is washed by low-temperature methanol, and the CO in the conversion gas is removed by utilizing the characteristic that the low-temperature methanol has strong dissolving energy on the acid component2And H2Acidic impurities (CO)2Concentration no more than 20ppm, H2The concentration of S is not more than 0.1 ppm; CO removal2Or sent to a urea unit to produce urea or discharged or recycled to produce dry ice and the like, and is rich in H2The acid gas of S is sent to a sulfur production section to produce sulfur or sulfuric acid), and then is subjected to methanation or liquid nitrogen washing unit to remove residual CO and CO2Then (the total content of carbon oxides is not more than 10ppm) an ammonia removal synthesis unit produces liquid ammonia.
Low temperature methanol washingThe main apparatus is H2S absorption tower, CO2Absorption tower, CO2A regeneration tower, a thermal regeneration tower, a methanol-water separation tower and a medium pressure flash tower. Wherein, the absorption tower adopts low-temperature high-pressure operation for enhancing the adsorption effect, and the regeneration tower adopts low-pressure operation because acid gas needs to be desorbed from the rich solution in a boiling state, so that the methanol solvent has the phenomenon of pressure reduction in the circulating process from the lean solution to the rich solution and from the rich solution to the lean solution, such as the methanol solvent is respectively rich in CO from the side line and the bottom of a medium-pressure flash tower2And CO2/H2The methanol of S is decompressed and enters into CO2The tower is regenerated, resulting in a loss of pressure energy. Taking a certain 45 ten thousand tons/year ammonia synthesis device low-temperature methanol washing unit as an example, 108t/h and 206t/h methanol rich liquid are respectively extracted from a side line and the bottom of a medium-pressure flash tower, the methanol rich liquid and the methanol rich liquid are decompressed from 1.42MPag to 0.09MPag, and the pressure difference loss reaches 1.33 MPa. If the pressure energy of the two streams can be recovered or power generation can be carried out or power equipment such as a methanol pump at the lowest grade of the heat regeneration tower can be driven, not only electric energy can be increased and recovered (or power consumption can be saved), but also low-temperature cold energy can be generated, or the low-temperature cold energy can be used for the unit or can be externally transmitted to other sections (such as ammonia synthesis and air separation) so as to reduce the consumption of compressed refrigeration steam of the device. In addition, the existing configuration of the cold exchange process of the low-temperature methanol washing unit is as follows: from CO2The bottom of the lower reabsorption section of the regeneration tower is rich in H2The methanol rich solution of S is cooled with the least lean methanol (415t/h, 100 ℃) from the thermal regeneration tower twice (taking the low-temperature methanol washing section of the 45 ten thousand ton/year ammonia synthesis device as an example, the flow rate is 421t/h, about-25.8 ℃) directly, the least lean methanol is cooled to-7.3 ℃ and is sent to CO2The absorption tower, which is heated to 77.4 ℃ by itself, enters a thermal regeneration tower, which is typically used at high and low temperatures. If the leanest methanol with the temperature of 100 ℃ can be pre-cooled by circulating hot water or circulating water or air, the equivalent cold quantity of about 5279kw at the temperature of-13.1 ℃ to-25.8 ℃ can be replaced, or the refrigeration load of the device is reduced by self-use or transferred to an adjacent cold trap.
Disclosure of Invention
Aiming at the defects of energy loss in the prior art, the invention aims to provide a low-temperature methanol washing process for efficiently recycling pressure energy and cold energy.
The purpose of the invention is realized by the following technical scheme:
a low-temperature methanol washing process for efficiently recycling pressure energy and cold energy comprises the following processing steps:
(1) the methanol rich solution extracted from the side line of the medium-pressure flash tower and the methanol rich solution at the bottom are subjected to throttling and pressure reduction to obtain CO2The regeneration tower is adjusted into a newly-added hydraulic turbine for expanding, acting, cooling and depressurizing, then enters a newly-added low-temperature circulating working medium heat exchanger for recovering low-temperature cold energy, and then CO2A regeneration tower;
(2) the most poor methanol of the thermal regeneration tower and CO after heat exchange of the methanol circulating cooler are carried out2Directly cooling the rich methanol solution at the bottom of the regeneration tower by a rich/poor methanol heat exchanger, adjusting the rich methanol solution to be the most poor methanol, cooling by an advanced newly-added precooler, and cooling by CO after heat exchange by a methanol circulating cooler2The methanol rich solution at the bottom of the regeneration tower is firstly added with a low-temperature circulating working medium heat exchanger to recover low-temperature cold energy, and then the most poor methanol and the methanol rich solution are cooled by the rich/poor methanol heat exchanger.
Furthermore, the newly added liquid power penetration and low-temperature circulating working medium heat exchanger in the step (1) does not influence the methanol rich liquid to enter CO2Temperature and pressure of the regeneration tower, and the like.
Further, the heat load of the precooler additionally arranged in the step (2) is equal to that of the low-temperature circulating working medium heat exchanger so as to ensure that the adjusted methanol rich solution enters a heat regeneration tower and the leanest methanol enters CO2The temperature of the absorption column does not change.
Further, the newly added low-temperature circulating working medium heat exchanger in the step (1) and the step (2) is a cold water heat exchanger at the temperature of 4-10 ℃.
Further, the newly added precooler in the step (2) is a circulating water precooler.
In the adjustment, the low-temperature cold energy displaced by the low-temperature circulating working medium (such as cold water at 10-4 ℃) can be sent out to a synthetic ammonia or air separation unit (or other adjacent cold traps) so as to reduce the refrigeration energy consumption of the synthetic ammonia or the air separation unit. And the recovered pressure energy can be on line in an island power generation mode (wherein a side hydraulic turbine can be used for replacing a motor to be used as the power of the leanest methanol pump of the thermal regeneration tower, and the effective turbine output is basically equivalent to the shaft work of the pump).
The invention is based on the following principle:
(1) throttling is a constant enthalpy and isentropic pressure reduction process, the pressure energy of fluid is consumed in a highly irreversible process, a turbine is used to recover the pressure energy and greatly reduce the temperature of the fluid, and heat is supplemented to raise the temperature when the fluid is recovered to the original throttling outlet state, so that the opportunity is created for outputting cold energy. Therefore, the hydraulic turbine replaces a throttle valve for two purposes, not only the pressure energy of the high-energy fluid is recovered, but also cold energy is created.
(2) In the existing process, the cold exchange between the low-temperature methanol rich solution twice (about-25.8 ℃) and the leanest methanol once (about 100 ℃) is a so-called high effective energy loss process of the second law of thermodynamics, the high irreversible degree enables the cold energy of the methanol rich solution to be seriously degraded and used, even if the leanest methanol is finally cooled to-7.3 ℃, and the temperature difference of the low-temperature end heat exchange is still as high as 18.5 ℃. The most poor methanol is firstly pre-cooled by circulating water and then is exchanged with rich methanol solution for cooling, and the same amount of low-quality energy consumption is used for exchanging high-quality cooling energy (about-13.1 to-25.8 ℃). Therefore, the adjustment is proposed by the principle of 'high energy and high use, low energy and low use' of energy gradual utilization which follows the second law of thermodynamics.
Compared with the prior art, the invention has the following advantages and beneficial effects:
(1) the pressure energy and the high-temperature heat energy of the middle-pressure flash tower side line distillate and the tower bottom distillate which are lost through the throttle valve at present are recovered through a hydraulic turbine, high-quality cold energy which is equal to the output work value is created, and the process which needs a large amount of steam or electric refrigeration for synthesizing ammonia is very beneficial.
(2) The method has the advantages that the circulating water is not consumed, but another benefit is added, so that the method has high benefit.
(3) The invention only adds a hydraulic turbine and a heat exchanger on the pipeline, and can ensure that the related fluid enters the downstream unit by matching with measures such as bypass adjustment and the likeThe parameters of the elements are strictly constant and therefore not on CO2Absorption tower, CO2The operation of the regeneration tower and the thermal regeneration tower has influence, and the yield and the purity of the purified gas of the low-temperature methanol washing unit product can not be influenced naturally.
(4) The three streams (methanol rich liquid and CO distilled from the side line and the bottom of the medium-pressure flash tower) of the invention2The cold output of the methanol rich solution distilled from the bottom of the regeneration tower) is realized by an intermediate circulating medium (such as 4-10 cold water), so that the routes of the medium and the medium are not changed, and the operation is safe and reliable.
Drawings
FIG. 1 is a flow chart of a conventional low temperature methanol wash process of a comparative example of the present invention;
FIG. 2 is a flow chart of the low-temperature methanol washing process for efficiently recycling pressure energy and cold energy in the embodiment of the invention;
the numbering in the figures is as follows: 1-feedstock/syngas heat exchanger; 2-cooling raw material gas ammonia; 3-changing gas-separating tank; 4-feedstock/syngas heat exchanger; 5-H2S, an absorption tower; 6-CO2An absorption tower; 7-CO2An absorption tower intermediate heat exchanger; 8-methanol recycle cooler; 9-H2S, a feeding pump of the absorption tower; 10-medium pressure flash column; 11-H2S, feeding a cooler to the absorption tower; 12-circulating compressor inlet and outlet heat exchanger; 13-recycle compressor feed liquid separation tank; 14-a recycle compressor; 15-circulating the compressor outlet water cooler; 16-an ammonia cooler; 17-a throttle valve; 18-a throttle valve; 19-CO2A regeneration tower; 20-CO2An absorber feed cooler; 21-a thermal regeneration tower feed pump; 22-rich/lean methanol heat exchanger; 23-a thermal regeneration column; 24-prewashing methanol heater; 25-a thermal regeneration tower top water cooler; 26-a thermal regeneration column reboiler; 27-methanol/water fractionation column; 28-methanol/water fractionator reboiler; 29-water/methanol fractionation column bottoms cooler; 30-a hydraulic turbine; 31-low temperature circulating working medium heat exchanger; 32-a hydraulic turbine; 33-low temperature circulating working medium heat exchanger; 34-a low-temperature circulating working medium heat exchanger; 35-circulating water precooler.
Detailed Description
The present invention will be described in further detail with reference to examples and drawings, but the present invention is not limited thereto.
Comparative example
The comparative example is the existing low-temperature methanol washing process, the process flow diagram of which is shown in figure 1, and the specific treatment steps are as follows:
raw material gas (3.0Mpa, 40 ℃) from a conversion unit enters a raw material/synthetic gas heat exchanger 1 and a raw material gas ammonia cooler 2 for cooling, then enters a conversion gas liquid separation tank 3, separated process condensate is sent to a conversion section process condensate stripping tower, gas is mixed with gas from a circulating compressor feeding liquid separation tank 13, and after a small strand of methanol is sprayed, the gas enters a raw material/synthetic gas heat exchanger 4 and then enters H2A pre-washing section of the S absorption tower 5, wherein trace components such as NH in the gas3And HCN is derived from H2Washing and absorbing a small amount of cold methanol in a feeding cooler 11 of the S absorption tower, transferring pre-washed methanol at the bottom of the tower to a thermal regeneration tower 23 for regeneration after heat exchange by a pre-washed methanol heater 24, and arranging a thermal regeneration tower reboiler 26 in the thermal regeneration tower; gas enters H through a gas lift tray2Main absorption section of S absorption tower 5, H in gas2S and CO2Is derived from CO2CO-richness of the absorber 62Methanol is washed and absorbed completely, and then H is enriched2S/CO2The methanol is sent to a medium pressure flash tower 10 for medium pressure flash evaporation. The desulfurized gas at the tower top enters CO2The lower absorption section of the absorption column 6, together with the overhead heat from the thermal regeneration column 23, passes through the shell side of the methanol rich/lean heat exchanger 22 and the CO2The cold lean methanol cooled to-51.7 ℃ on the pipe side of the feed cooler 20 of the absorption tower is subjected to countercurrent absorption, and the middle part of the absorption tower is provided with CO2The intermediate heat exchanger 7 of the absorption tower, the tower top purified gas and the raw material/synthetic gas heat exchanger 4, the raw material/synthetic gas heat exchanger 1 exchange heat and then are sent to a methanation or liquid nitrogen washing unit; CO 222.8Mpa at the bottom of the absorption tower 6 and CO-rich at-22 DEG C2Methanol fraction via H2S absorption tower feed pump 9 sends H2The top of the S absorber 5 serves as an absorbent and the remainder of the methanol flows to the upper flash section of the medium pressure flash column 10. In the packing of the lower flash section of the medium pressure flash column 10, it is rich in H2S/CO2Valuable H in methanol2And a minor proportion of CO2Flash evaporation is carried out, and in order to reduce the total amount of the circulating compressed gas, two flash evaporation gases are mixed and then go upwardsFlows on trays in the lower flash section of the medium pressure flash column 10 and from H2The methanol of the feeding pump at the bottom of the S absorption tower is in countercurrent contact to absorb most of CO2After being led out, the flash evaporation gas sequentially enters the pipe side of an inlet and outlet heat exchanger 12 of the circulating compressor through a circulating compressor 14 and a circulating compressor outlet water cooler 15, and enters a circulating compressor feeding liquid separation tank 13 after cooling the circulating compressor outlet gas; the methanol rich solution extracted from the side line of the medium-pressure flash tower 10 is cooled in an ammonia cooler 16, is decompressed by a throttle valve 18 and is divided into two parts, and the larger part is sent to CO2Low pressure flash section at the top of regeneration column 19, CO2The operating pressure in the upper part of the regeneration column 19 is about 0.12MPa, so that most of the pure CO is obtained2The product is released by flash evaporation; the other rich in CO2Methanol is introduced into CO2Another stream of pure CO is released on the upper tray of the regeneration section of the regeneration tower 192Then methanol is used as a reabsorption medium to flow downwards to absorb the rising CO2Sulfides contained in the gas. H-rich from the bottom of medium pressure flash column 102S/CO2Methanol is decompressed by the throttle valve 17 and then divided into two streams, the larger one of which enters CO2CO of regeneration column 192On the lower packing of the regeneration section, CO2And a small amount of H flashed off simultaneously2S and COS are released, and flash gas flows upwards and in CO2The upper tray of the regeneration section is filled with CO2Methanol reabsorbs sulfide, CO2The gas continues to flow upward through the gas lift tray into the CO2Regeneration tower 19 low pressure flash section, and CO of low pressure flash section2The product is mixed, flows out from the top of the tower, exchanges heat with the raw material to form a product, and is sent to a urea device. From CO2CO of regeneration column 192H-rich in regeneration section2S/CO2Methanol is introduced into CO2The regeneration tower 19 is mainly on the reabsorption section, and simultaneously, another part of methanol from the bottom of the medium-pressure flash tower 10 enters CO after being decompressed by the throttle valve 182The regenerator column 19 is located above the main reabsorption section. CO 22H-rich in the bottom of the lower reabsorption section of the regeneration column 192S methanol is pressurized by a thermal regeneration tower feed pump 21 and contacted with the most lean methanol in the shell side of the methanol recycle cooler 8 and the rich/lean methanol heat exchanger 22After primary heat exchange, the obtained product enters a thermal regeneration tower 23. From CO2Regeneration column feed pump 21 rich in H2S methanol and from H2H-rich in prewashing section of S absorption tower 52S methanol respectively enters the thermal regeneration section of the thermal regeneration tower 23 to be rich in H2The S methanol is completely regenerated through methanol steam stripping, part of the methanol steam comes from a water concentration section at the lower part of the thermal regeneration tower 23, the rest of the methanol steam comes from the top gas of a methanol/water distillation tower 27, the methanol/water distillation tower is provided with a methanol/water distillation tower reboiler 28, and the tower bottom is provided with a water/methanol distillation tower bottom sewage cooler 29 for sewage treatment. The methanol vapor/gas mixture at the top of the thermal regeneration section of thermal regeneration column 23 is subjected to a series of cooling processes to condense the methanol. First, the heating from H is conducted through the shell side of the prewash methanol heater 242Cold prewash rich H of S absorber 52S, after water cooling is carried out on the shell side of a water cooler 25 at the top of the thermal regeneration tower, most of methanol is condensed and enters a reflux section at the bottom of the thermal regeneration tower 23, and the rest uncondensed acid gas is led out from the upper part of the reflux section and is sent to a sulfuric acid device after being cooled; the separated condensate flows back to the reflux section at the bottom of the regenerative tower 23.
Examples
The present example was improved over the comparative example procedure as follows:
(1) h-rich bottoms of medium pressure flash column 102S/CO2Methanol (206t/h, 1.42MPag, -38.4 ℃) enters CO after being throttled by the throttle valve 18 (206t/h, 0.09MPag, -61.4 ℃)2 Regeneration column 19, adjusted to be H-rich at the bottom of medium pressure flash column 102S/CO2Methanol (206t/h, 1.42MPag, -38.4 ℃) is newly added with a hydraulic turbine 32 firstly, after expansion work is done (206t/h, 0.09MPag, -64.7 ℃) is added with a newly added low-temperature circulating working medium (such as cold water at 4-10 ℃) heat exchanger 33, after cold energy is released and heated to be consistent with the temperature before adjustment (206t/h, 0.09MPag, -61.4 ℃) is added with CO2A regeneration column 19. To ensure CO2The operation of the regeneration tower 19 is not affected by this adjustment, and the additional hydraulic turbine 32 and the low-temperature circulating medium cooler 33 are provided with corresponding adjustment measures (such as bypass).
(2) The methanol rich solution extracted from the side line of the medium-pressure flash tower 10 is cooled by an ammonia cooler 16 (108t/h, 1.42MPag-38.4 ℃) and enters a sectionThe stream was throttled by the throttle valve 17 and then fed with CO (108t/h, 0.09MPag, -57.05 ℃ C.)2The regeneration tower 19 is adjusted to be that after the methanol rich solution comes out of the ammonia cooler 16 (108t/h, 1.42MPag-38.4 ℃), a newly added hydraulic turbine 30 is firstly expanded to do work (108t/h, 0.09MPag and 64.7 ℃), a newly added low-temperature circulating working medium (such as cold water at 4-10 ℃) heat exchanger 31 is then added to recover cold energy, and after the cold energy is heated and heated to be consistent with that before adjustment (108t/h, 1.42MPag-57.05 ℃), CO is then added2A regeneration column 19. To ensure CO2The operation of the regeneration tower 19 is not affected, and the newly added hydraulic turbine 30 and the low-temperature circulating working medium heat exchanger 31 are both provided with adjusting measures.
In addition, the ammonia cooler 16 can also be stopped, the methanol rich solution extracted from the side line of the medium-pressure flash tower 10 is made to directly enter the newly added hydraulic turbine 30, not only more work can be done because the fluid temperature is higher, but also the cold output of the downstream low-temperature circulating working medium cooler 31 can be saved (or reduced), and the cold obtained by the turbine can be used by the device (if the cold load of the low-temperature circulating working medium cooler 31 is greater than that of the ammonia cooler 16, the ammonia cooler 16 can be stopped, and if the cold load of the low-temperature circulating working medium cooler 31 is smaller than that of the ammonia cooler 16, the ammonia cooler 16 is provided with a bypass).
(3) From CO2The methanol rich solution at the bottom of the regeneration tower 19 is cooled twice (421t/h to-25.8 ℃) directly with the leanest methanol (415t/h to-100 ℃) from the thermal regeneration tower 23, and is cooled to-7.3 ℃ and then is sent to CO2The absorber feeds cooler 20, which itself is warmed to 77.4 ℃ and feeds thermal regenerator 23. Adjusting to a newly added low-temperature circulating working medium (such as 4-10 cold water) heat exchanger 34 for the second time (421t/h to-25.8 ℃) of the methanol rich solution, and after releasing cold energy and raising the temperature to-13.1 ℃, raising the temperature to 77.4 ℃ through a rich/poor methanol heat exchanger 22 by the original process and then feeding the heat regeneration tower 23; the most poor methanol (415t/h and 100 ℃) is firstly cooled to 88.7 ℃ by a newly added circulating water precooler 35, and then is cooled to-7.3 ℃ by a rich/poor methanol heat exchanger 22 and is sent to CO by the original flow2The absorber feeds a cooler 20. In the adjustment, the cold end heat transfer temperature difference of the rich/lean methanol heat exchanger 22 is reduced from 18.5 ℃ to 5.8 ℃, meanwhile, the heat load is reduced, and the heat is equivalently transferred to the circulating water precooler 35 and the low-temperature circulating working medium heat exchanger 34, so that CO is obtained2The operation of the absorption tower 6 and the thermal regeneration tower 23 is not affected.
Compared with the comparative example, the embodiment adds two hydraulic turbines 30 and 32, three low-temperature circulating working medium heat exchangers 31, 33 and 34 and a circulating water precooler 35. They are arranged on corresponding pipelines and are matched with adjustment measures such as a bypass and the like, so that the operation of the tower is not influenced.
The energy efficiency gains of the examples are shown in tables 1-3, taking a certain 45 ten thousand tons/year ammonia synthesis device low-temperature methanol washing as an example.
TABLE 1 turbine work gains
Calculated based on turbine isentropic expansion efficiency 75%.
TABLE 2 turbine Integrated Cold energy yield
TABLE 3 secondary cold output of rich methanol solution
From the above results it can be seen that:
(1) the tower bottom distillate of the medium-pressure flash tower 10 is decompressed from 1.42MPag to 0.09MPag through a hydraulic turbine, works for 396kW according to 75% of isentropic expansion efficiency, the survey line distillate of the medium-pressure flash tower 10 is decompressed from 1.42MPag to 0.09MPag through a hydraulic turbine, works for 186kW according to 75% of isentropic expansion efficiency, and the total is 582 kW.
(2) Matching with turbo expansion for cooling, respectively harvesting 396kW and 186kW of cold energy at the temperature of-60 ℃ from the tower bottom and a side line distillate of the medium-pressure flash tower 10, and totaling 582 kW; meanwhile, the methanol rich solution is recycled for the second time, and the average cold energy is 5279kw at the temperature of 19 ℃ below zero. The three measures are used for recovering cold energy of 5861kw in total.
The parameters before and after adjustment of the main heat exchange equipment of the present example and the comparative example are shown in table 4.
TABLE 4 parameters before and after adjustment of the main heat exchanger
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.
Claims (1)
1. A low-temperature methanol washing process for efficiently recycling pressure energy and cold energy is characterized by comprising the following processing steps:
(1) the methanol rich solution extracted from the side line of the medium-pressure flash tower and the methanol rich solution at the bottom are subjected to throttling and pressure reduction to obtain CO2The regeneration tower is adjusted into a newly-added hydraulic turbine for expanding, acting, cooling and depressurizing, then enters a newly-added low-temperature circulating working medium heat exchanger for recovering low-temperature cold energy, and then CO2A regeneration tower;
(2) the most poor methanol of the thermal regeneration tower and CO after heat exchange of the methanol circulating cooler are carried out2Directly cooling the rich methanol solution at the bottom of the regeneration tower by a rich/poor methanol heat exchanger, adjusting the rich methanol solution to be the most poor methanol, cooling by an advanced newly-added precooler, and cooling by CO after heat exchange by a methanol circulating cooler2The method comprises the following steps that (1) a newly-added low-temperature circulating working medium heat exchanger is used for recovering low-temperature cold energy for a methanol rich solution at the bottom of a regeneration tower, and then the most poor methanol and the methanol rich solution are subjected to cold exchange through a rich/poor methanol heat exchanger;
the newly-increased liquid power is transparent in the step (1) and the low-temperature circulating working medium heat exchanger does not influence the methanol rich liquid to enter CO2Temperature and pressure parameters of the regeneration tower;
the heat load of the precooler additionally arranged in the step (2) is equal to that of the low-temperature circulating working medium heat exchanger so as to ensure that the adjusted methanol rich solution enters a thermal regeneration tower and the least-lean methanol enters CO2The temperature of the absorption tower is not changed;
the newly added low-temperature circulating working medium heat exchanger in the step (1) and the step (2) is a cold water heat exchanger at the temperature of 4-10 ℃;
the newly added precooler in the step (2) is a circulating water precooler.
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| US20220152549A1 (en) * | 2020-11-17 | 2022-05-19 | Aramco Overseas Company Uk Ltd | Amine absorber configuration |
| CN113532191A (en) * | 2021-07-22 | 2021-10-22 | 华亭煤业集团有限责任公司 | Optimized heat exchange network of low-temperature methanol washing system |
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