CN116020252A - Alcohol amine method energy-saving acid gas desulfurization process based on low-temperature absorption-heat pump rectification - Google Patents
Alcohol amine method energy-saving acid gas desulfurization process based on low-temperature absorption-heat pump rectification Download PDFInfo
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Abstract
The invention discloses an alcohol amine method energy-saving acid gas desulfurization process based on low-temperature absorption-heat pump rectification, which is characterized in that on the basis of the existing alcohol amine method desulfurization process, the rich liquid at the bottom of a flash tank is pumped into a lean-rich liquid heat exchange system, and the rich liquid at the bottom of the other part of flash tank is separated by a flow dividing system and enters a heat recovery heat exchanger, and enters a rectifying tower system for separation after heat exchange with a high-temperature gas stream; the high-temperature gas phase material flow is formed by compressing a gas phase extracted from the top of a rectifying tower by a compressor; the normal temperature absorbent liquid phase material flow is cooled by a cold recovery heat exchanger and a chilled water cooler through low temperature gas extracted from the top of the absorption tower before entering the absorption tower. The process fully recovers the cold energy of the low-temperature purified gas after absorption, and recycles the gas phase heat of the tower top, and reduces the operation cost by 14-28% and the comprehensive energy consumption by 25-33% compared with the prior alcohol amine desulfurization under the condition of meeting the same product purity and separation requirements.
Description
Technical Field
The invention relates to a desulfurization process, in particular to an alcohol amine method energy-saving acid gas desulfurization process based on low-temperature absorption-heat pump rectification, which is applied to the links of acid gas desulfurization processes such as natural gas purification, petrochemical industry, metal smelting, power generation of coal-fired power plants and the like.
Background
In the fields of natural gas purification, petrochemical industry, metal smelting, coal-fired power plant power generation and the like, sulfur-containing gas is directly used as a chemical raw material or fuel, so that the problems of environmental pollution, low combustion heat value, corrosion of pipeline equipment and the like are caused. It is necessary to perform the acid gas desulfurization treatment. The existing alcohol amine desulfurization process has higher energy consumption. Therefore, the energy consumption of the desulfurization process is reduced, and the carbon dioxide emission is further reduced, so that the desulfurization process has very important social benefit and environmental protection benefit.
The prior acid gas alcohol amine method desulfurization process (Zhang Hao, which utilizes Aspen Hysys to simulate the processes of acid water stripping, dry gas, liquefied hydrocarbon desulfurization and solvent regeneration, energy chemical industry, volume 37 of 2016, 3 rd) is based on the following basic principle, and the absorbent absorbs H in acid gas under the conditions of pressurization and normal temperature 2 S and other acidic components, and then separating out the acidic components in the rich liquid under the conditions of decompression and temperature rise, so that the absorbent can be regenerated and recycled. Specifically, the conventional alcohol amine desulfurization process is shown in fig. 1: raw material gas S1 (temperature: 40 ℃ C. To 45 ℃ C., pressure: 1000kPa to 1400kPa, flow: 11000N m) 3 /h～12000N m 3 And/h) from the bottom of the absorption column B1 into the absorption column B1, the gas phase stream from bottom to top, the normal temperature absorbent liquid phase stream (temperature: 35-40 ℃, pressure: 2000kPa to 2200kPa, flow rate: 20t/h to 40 t/h) S14 (lean solution) enters from the top of the absorption tower B1 from top to bottom. Countercurrent contact of the gas phase stream and the absorbent liquid phase stream, H 2 The S and other acidic components are absorbed by the absorbent in the process, rich liquor S2 is formed at the bottom of the tower, and S15 gas reaching the standard is purified and enters the next working procedure.
The rich liquid S2 is extracted from the bottom of the absorption tower B1, is decompressed (pressure drop: 760 kPa) by a decompression valve B4 to form a material flow S3, and enters a flash tank B3 (temperature: 52-55 ℃ and pressure: 240 kPa), light components S4 such as dissolved and entrained hydrocarbons in the rich liquid S2 are flashed out, and then collected to enter the next working procedure. Pumping the rich liquid S5 at the bottom of the flash tank B3 into a lean and rich liquid heat exchange system B5, preheating (temperature: 95-98 ℃) to form a material flow S7, separating in a rectifying tower B2, leading acid gas out of the top of the rectifying tower B2, introducing the acid gas into a condensation cooler, and finally introducing the acid gas into a reflux tank, and carrying out high-concentration H through a reflux pump 2 The acidic substance such as S is extracted as a product S9 for the next process. The lean solution S8 at the bottom of the rectifying tower enters a lean-rich solution heat exchange system B5 to be cooled to form a stream S6 (the temperature is 68-72 ℃), the stream S6 enters a lean solution supplementing system B8 to be mixed with supplementing water S10 and MDEA solvent S11 to form a stream S12 (the mass concentration of MDEA in the S12 is maintained between 30-35% through supplementing water and MDEA), the stream S12 is pumped by a feed pump B6 to form a stream S13, the stream S13 is conveyed to pass through a circulating water cooler B7 to form a stream S14, and finally the stream S14 enters the top of the absorbing tower for recycling. Wherein the reboiler at the bottom of the rectifying tower provides a source of heat for the whole process flow.
The existing acid gas alcohol amine desulfurization process also faces the following problems and challenges:
1) In how to improve the absorption efficiency, intensive research is required in terms of enhanced absorption: the existing alcohol amine desulfurization process adopts normal temperature absorption, the temperature of the absorber (barren solution) entering a tower is controlled above 25 ℃, and the problems of large recycling amount of the absorber (barren solution), low concentration of rich solution at the bottom of the tower and low mass transfer efficiency in the absorption process exist.
2) In the solvent regeneration process, a simple rectification stripping mode is still adopted, the gas phase stream at the top of the tower is directly cooled by circulating water, and a large amount of circulating water is consumed while the heat in the system is wasted. The rectification stripping operation accounts for 60% -70% of the energy consumption in the whole desulfurization process, and how to improve the process and reduce the energy consumption of the system is also a problem to be solved urgently.
3) In actual industrial production, the acid-containing substances have strong corrosiveness, so that pipelines and equipment involved in the desulfurization process are all faced with problems of corrosion, blockage and the like in the long-term operation process.
Disclosure of Invention
The invention provides a novel energy-saving process for acid gas desulfurization, which is developed based on a low-temperature solvent-cold recovery absorption technology and a rectification tower top gas phase compression-heat recovery technology. Under the same separation requirement, the absorption efficiency of the absorption unit is improved, the comprehensive energy consumption of the whole desulfurization process is reduced, the running cost of the system is reduced, and the double-carbon strategy falling to the ground is facilitated.
The aim of the invention can be achieved by the following technical scheme:
an alcohol amine method energy-saving acid gas desulfurization process based on low-temperature absorption-heat pump rectification is characterized in that raw material gas enters from bottom to top of an absorption tower, normal-temperature absorbent liquid phase material flow enters from top to bottom of the absorption tower, countercurrent contact is performed, rich liquid is formed at the bottom of the absorption tower, the rich liquid is depressurized by a depressurization valve and enters a flash tank, the rich liquid at the bottom of the flash tank is pumped into a lean-rich liquid heat exchange system for preheating and then enters a rectification tower for separation, and acid gas enters a condensation cooler and a reflux tank from the top of the rectification tower and contains high-concentration H 2 S, acid substances are extracted as products; the lean solution at the bottom of the rectifying tower enters a lean-rich solution heat exchange system for cooling and then enters a lean solution supplementing system for mixing with supplementing water and MDEA solvent to form a material flow, a normal-temperature absorbent liquid-phase material flow is formed by a feed pump and a circulating water cooler and enters the top of an absorption tower for recycling; the rich liquid at the bottom of the flash tank is pumped into a lean-rich liquid heat exchange system, and the rich liquid at the bottom of the flash tank is separated by a flow dividing system and enters a heat recovery heat exchanger to be subjected to heat exchange with a high-temperature gas phase stream and then enters a rectifying tower system for separation; the high-temperature gas phase material flow is formed by compressing a gas phase extracted from the top of a rectifying tower by a compressor; the normal temperature absorbent liquid phase material flow is cooled by a cold recovery heat exchanger and a chilled water cooler through low temperature gas extracted from the top of the absorption tower before entering the absorption tower.
In order to further achieve the object of the present invention, preferably, the rich liquid entering the heat recovery heat exchanger accounts for 5% -10% of the rich liquid exiting the flash tank.
Preferably, the raw material gas mainly comes from dry gas generated in the refining process of sulfur-containing petroleum and sulfur-containing natural gas, and the main components of the raw material gas are except H 2 S, in addition to H 2 、CO 2 、CH 4 、C 2 、C 3 、C 4 And C 5 A gas; the temperature of the raw material gas is 40-45 ℃, the pressure is 1000-1400 kPa, and the flow is 11000N m 3 /h～12000N m 3 /h。
Preferably, the high-temperature gas phase flow is decompressed through a second decompression valve after heat exchange through a heat exchanger, cooled by a condenser and enters a reflux tank for gas-liquid separation, wherein the high-temperature gas phase flow contains high-purity H 2 The acidic component of S is collected and the liquid phase material is returned to the rectifying column as a reflux.
Preferably, the pressure drop of the second pressure reducing valve is 100-150kp; the condenser is cooled to 48-50 ℃.
Preferably, the lean solution at the bottom of the rectifying tower enters a lean-rich solution heat exchange system and is cooled to 46-53 ℃; the cooled lean solution is mixed with additional water and additional solvent MDEA in a lean solution additional system, and is conveyed to a circulating water cooler through a feed pump to be cooled to the temperature of 32-35 ℃, then enters a cold recovery heat exchanger to be further cooled to the temperature of 28-31 ℃ by low-temperature purified gas, and is cooled to the temperature of 15-18 ℃ by a chilled water cooler.
Preferably, the top pressure of the rectifying tower is 175+/-10 kPa, the bottom pressure of the rectifying tower is 205+/-10 kPa, and the molar reflux ratio is 0.6-0.8.
Preferably, the pressure of the low temperature absorbent liquid phase stream is 2000kPa to 2200kPa, and the flow rate is 17t/hr to 30t/hr.
Preferably, the temperature of the flash tank is 42-44 ℃ and the pressure is 240-250 kPa.
Preferably, the rich liquid is extracted from the bottom of the absorption tower, depressurized by a first depressurization valve and enters a flash tank, and the rich liquid is dissolved and the entrained hydrocarbon light components are collected after being flashed off.
Compared with the prior art, the invention has the following advantages and beneficial effects:
1) The invention develops a low-temperature solvent-cold recovery absorption technology. By the application of the technology, the circulating dosage of the absorbent (lean solution) is reduced by 23-30%, the concentration of the rich solution is increased by 28-40%, and the absorption mass transfer efficiency is greatly improved. And meanwhile, the high-grade cold energy is recycled, so that the consumption of circulating cooling water is reduced, and the energy consumption and the running cost are saved.
2) The invention combines the characteristics of the prior alcohol amine desulfurization process, develops a rectification tower top gas phase compression-heat recovery technology, ensures that the heat of the tower top gas phase material flow is fully recycled by optimizing and determining key process parameters such as rich liquor split ratio, greatly reduces the energy consumption in the acid gas desulfurization process, and achieves the aim of improving the comprehensive energy utilization rate of the whole process.
3) Through the development of the two technologies, the novel acid gas desulfurization process can reduce the running cost by 14-28% and the comprehensive energy consumption by 25-33% under the condition of meeting the same product purity and separation requirements.
Drawings
FIG. 1 is a flow chart of a prior alcohol amine desulfurization process.
The figure shows: b1-absorption tower, B2-rectifying tower, B3-flash tank, B4-reducing valve, B5-lean-rich liquid heat exchanger, B6-feed pump, B7-circulating water cooler and B8-lean liquid supplementing system
Fig. 2 is a flow chart of an alcohol amine method energy-saving acid gas desulfurization process based on low-temperature absorption-heat pump rectification.
The figure shows: the system comprises a B1-absorption tower, a B2-first pressure reducing valve, a B3-flash tank, a B4-split system, a B5-lean-rich liquid heat exchanger, a B6-feed pump, a B7-circulating water cooler, a B8-cold energy recovery heat exchanger, a B9-chilled water cooler, a B10-lean liquid supplementing system, a B11-rectifying tower, a B12-compressor, a B13-heat recovery heat exchanger, a B14-second pressure reducing valve, a B15-reflux cooler and a B16-reflux tank.
Detailed Description
For a better understanding of the present invention, reference will now be made to the following description of embodiments of the invention, taken in conjunction with the accompanying drawings and examples.
Based on the existing alcohol amine method, a new energy-saving acid gas desulfurization process based on a low-temperature solvent-cold recovery absorption technology and a rectification tower top gas phase compression-heat recovery technology is developed. The raw material gas of the invention mainly comes from dry gas and sulfur-containing natural gas generated in the refining process of sulfur-containing petroleum, and the main components thereof are used for removing H 2 S, in addition to H 2 、CO 2 、CH 4 、C 2 、C 3 、C 4 And C 5 Hydrocarbon material, H 2 The mole fraction of the acid component with S as the main component accounts for 5-15%.
The alcohol amine method energy-saving acid gas desulfurization process flow based on low-temperature absorption-heat pump rectification is shown in figure 2, wherein the related process parameters are the preferred parameters of the invention, and can be properly adjusted according to the raw material gas.
Raw material gas S1 (temperature: 40 ℃ C. To 45 ℃ C., pressure: 1000kPa to 1400kPa, flow: 11000N m) 3 /hr.～12000N m 3 From the bottom of absorber column B1 into absorber column B1, the vapor phase stream from bottom to top, low temperature absorber liquid phase stream at 15 to 18 ℃ (pressure: 2000kPa to 2200kPa, flow rate: 17 t/hr.) to 30 t/hr.) S18 (lean solution) enters from the top of the absorption column B1 from the top down. Countercurrent contact of feed gas and absorbent liquid stream, with H 2 The acid component with S as main component is absorbed by the absorbent liquid phase material flow, and rich liquid S2 is formed at the bottom of the tower; the low-temperature gas S19 reaching the purification standard passes through the cold recovery heat exchanger B8 to transfer cold to the absorbent S16 (lean solution). The rich liquid S2 is extracted from the bottom of the absorption tower B1, is depressurized (pressure drop: 760 kPa) by a first depressurization valve B2, forms a material flow S3, enters a flash tank B3 (temperature: 42-44 ℃ and pressure: 240-250 kPa), is dissolved in the rich liquid, and is flashed out of entrained hydrocarbon light components S4, and is collected to enter the next working procedure. The flow S5 at the bottom of the flash tank B3 is divided into two flows (the flow of S21 accounts for the flow of S5 and is controlled to be 5% -10%) by a flow dividing system B4 (generally a flow regulating valve),the material flow S6 enters a lean-rich liquid heat exchanger B5, and after preheating (the temperature is 100-102 ℃), a material flow S7 is formed and enters a rectifying tower B11 for separation; the material flow S21 and the high-temperature gas phase material flow S9 are preheated (the temperature is 152-155 ℃) by a heat recovery heat exchanger B13 to form a material flow S22, and the material flow S22 enters a rectifying tower system B11 for separation; the high-temperature gas phase stream S9 is formed by extracting a stream S8 from the top of a rectifying tower B11 and then compressing the stream S8 by a compressor B12 (compression ratio: 1.5-1.7); the high-temperature gas-phase stream S9 enters a heat recovery heat exchanger B13 and exchanges heat with the stream S21 to cool to form a stream S23 (the temperature is 101-104 ℃), then the stream S23 is decompressed (the pressure drop is 95-105 kPa) by a second decompression valve B14 to form a stream S24, the stream S24 is cooled (the temperature is 48-50 ℃) by a reflux cooler B15 to form a stream S25, the stream S25 is decompressed and enters a reflux tank B16 to carry out gas-liquid separation, and high-purity H is obtained 2 S27, and the like, is sent to the next step, and the liquid phase substance S26 is returned as a reflux to the rectifying column B11 (the top pressure: 175.+ -.10 kPa, the bottom pressure: 205.+ -.10 kPa, and the molar reflux ratio: 0.6 to 0.8). Wherein the reboiler at the bottom of the rectifying tower provides a source of heat for the whole process flow.
The lean solution S10 at the bottom of the rectifying tower enters a lean-rich solution heat exchanger B5 to be cooled (the temperature is 46-53 ℃) to form a stream S11, then the stream S11 is mixed with a water supplementing stream S12 and a solvent supplementing MDEA stream S13 in a lean solution supplementing system B10 to form a stream S14 (the mass concentration of MDEA in S12 is maintained to be 30-35% through supplementing water and MDEA), the stream S14 is conveyed by a feed pump B6 to form a stream S15, the stream S15 is firstly cooled (the temperature is 32-35 ℃) by a circulating water cooler B7 to form a stream S16, the stream S16 then enters a cold recovery heat exchanger B8 to be further cooled (the temperature is 28-31 ℃) by low-temperature purified gas S19, and finally is cooled to the temperature of 15-18 ℃ by a 7 ℃ chilled water cooler B9 to enter the top of the absorbing tower for recycling.
The process shown in fig. 2 is significantly improved over the process shown in fig. 1 by:
1) In FIG. 2, the absorbent liquid-phase stream (lean solution) S18 adopts a low-temperature process of 15-18 ℃, which can reduce the operation temperature of the whole absorption unit and is beneficial to improving H 2 S absorption efficiency, improves H in rich liquor 2 The concentration of S is such that,therefore, the recycling amount of the liquid-phase material flow (lean solution) of the absorbent can be reduced, and the power consumption of pump body conveying of the whole system and the steam consumption of the rectification unit for desulfurization and regeneration are reduced;
2) The cold energy recovery heat exchanger B8 is introduced into the absorption unit, so that the high-grade cold energy in the absorption tail gas S19 can be fully recovered and utilized, and the use amount of circulating water and chilled water is further reduced;
3) Compared with the rectification operation in fig. 2, the technology of 'rectification tower top gas phase compression-heat recovery' is developed, and after the rectification tower top gas phase material flow is compressed by a compressor B12 (with the heat insulation efficiency of more than 75 percent), heat is conveyed into the rectification tower by a heat recovery heat exchanger B13, so that the comprehensive energy consumption of the rectification operation is reduced.
The absorbent (lean liquid) of the process is cooled to about 15-18 ℃ and then enters the tower body from the top of the absorption tower. The low-temperature absorption strategy is adopted, so that the operating temperature of the absorption tower is reduced, the consumption of the absorbent is reduced, the absorption efficiency is improved, and the aim of strengthening the absorption process is fulfilled.
Before the absorbent (lean solution) enters the absorption tower, a cold recovery heat exchanger and a chilled water cooler are added, wherein the cold recovery heat exchanger is used for fully recovering the cold of high-grade low-temperature purified gas, so that the purposes of saving cooling circulating water and chilled water are achieved. Whereas the subsequent addition of a chilled water cooler is added to cool the absorbent (lean liquid) further to 15-18 c. The purposes of saving energy, reducing consumption and reducing the later operation cost are achieved through high-grade cold energy recovery.
When the technology of the invention is applied to the technology of 'rectifying tower top gas phase compression-heat recovery', H in the feed material flow of the rectifying tower 2 The S and other components account for less than 10 percent, the heat provided by the vapor phase compression of the tower top effluent is limited, and the split ratio of the rich liquid at the bottom of the flash tank to two streams is preferably controlled to be 5-10 percent. The heat recovery and utilization of the gas phase material flow at the top of the tower greatly reduce the energy consumption in the acid gas desulfurization process, and improve the comprehensive energy utilization rate of the whole process.
Example 1
As shown in fig. 2, an alcohol amine method energy-saving acid gas desulfurization process based on low-temperature absorption-heat pump rectification: h-containing H with 7% mole fraction 2 S acid raw material gas S1 (temperature: 43 ℃ C., pressure: 1200 kPa), at a feed rate of 11210Nm 3 The// h is led into the absorption tower B1 from the bottom of the absorption tower B1; the lean solution S18 (temperature: 15 ℃ C., pressure: 2060 kPa) containing MDEA was fed into the absorption column at a feed rate of 17590kg/h from the top of the absorption column B1 at a mass fraction of 32%. Bottom H of absorption tower 2 The rich liquid S2 with the mole fraction of 4.42% enters a first pressure reducing valve B2 (pressure drop: 760 kPa) to be treated to form a stream S3, then enters a flash tank B3 (temperature: 42.5 ℃ C., pressure: 240 kPa) to be treated, light components S4 such as dissolved and entrained hydrocarbons in the rich liquid are flashed out, the stream S5 obtained after the flash tank B3 treatment enters a split system B4 to be separated, and the separated liquid-phase stream S5 is divided into two liquid-phase streams (stream S6 and stream S21) through the split system B4, wherein the mass ratio of the stream S21 is 8%. The material flow S6 enters a lean-rich liquid heat exchanger B5, is preheated to 101 ℃ to form a material flow S7, and then enters a rectifying tower B11 for separation; the material flow S21 exchanges heat with a high-temperature gas-phase material flow S9 from the top of the rectifying tower B11 compressed by the compressor B12 through the heat recovery heat exchanger B13, and a material flow S22 formed after the material flow S21 is preheated to 154 ℃ enters the rectifying tower B11 for separation; the gas stream S8 at the top of the rectifying tower is led out from the top of the rectifying tower, is heated to 164 ℃ by a compressor B12 (compression ratio is 1.57) to form a high-temperature gas stream S9, enters a heat recovery heat exchanger B13, exchanges heat with a stream S21 to cool down to form a stream S23, then forms a stream S24 by a second pressure reducing valve B14 (pressure drop: 100 kPa), and then forms a stream S25 by a reflux cooler B15, the temperature of which is reduced to 50 ℃ to enter a reflux tank B16 to form a product S27 (H) 2 The S mole fraction was 92% and the temperature was 49.6%). The common medium water vapor (the temperature is 148 ℃ and the pressure is 450 kPa) is taken as a heat source to enter a rectifying tower reboiler, and the feeding amount is 1316kg/h; in the rectification process, the operating pressure of the tower top is 175kPa, and the operating pressure of the tower bottom is 205kPa. The temperature of the rich liquid S10 at the bottom of the rectifying tower is 123 ℃, the rich liquid is cooled to 53 ℃ by a lean-rich liquid heat exchanger B5 to form a material flow S11, and then the material flow S11 is mixed with the supplementing water S12 and the MDEA supplementing solvent S13 by a lean liquid supplementing system B10 to form a material flow S14, and the material flow S14 is treated by waterAnd supplementing MDEA to enable the mass fraction of the MDEA in S14 to reach 32%, processing the material flow S14 through a feed pump B6 to form a material flow S15, cooling the material flow S14 to 35 ℃ in a first step through a circulating water cooler B7, further cooling the material flow S to 31 ℃ in a cold recovery heat exchanger B8 by low-temperature purified gas S19, and finally cooling the material flow S to 15 ℃ through a 7 ℃ chilled water cooler B9 to form a lean solution S18, and entering the top of an absorption tower to realize recycling. The electricity consumption and the steam consumption of the process are converted into standard coal, the coal consumption is 135.43kgce per hour, and the operation cost is 590.79 yuan per hour (this).
Comparative example 1
As shown in fig. 1, a prior alcohol amine desulfurization process: h-containing H with 7% mole fraction 2 S acid raw material gas S1 (temperature: 43 ℃ C., pressure: 1200 kPa), at a feed rate of 11210Nm 3 Introducing the// h from the bottom of the absorption tower B1 into the absorption tower; a32% by mass of a lean solution (temperature: 38 ℃ C., pressure: 2100 kPa) S14 containing MDEA was fed into the absorption column from the top of the absorption column B1 at a feed rate of 23000 kg/h. Bottom H of absorption tower 2 The rich liquid S2 with the mole fraction of 3.45% enters a pressure reducing valve B4 (pressure drop: 760 kPa) to form a material flow S3, the material flow S3 enters a flash tank B3 (temperature: 52 ℃ and pressure: 240 kPa) to be separated, and a separated liquid-phase material flow S5 is preheated to 98 ℃ by a lean-rich liquid heat exchanger B5 to form a material flow S7, and the material flow S7 enters a rectifying tower B2. The common medium steam (the temperature is 148 ℃ and the pressure is 450 kPa) is taken as a heat source to enter a rectifying tower reboiler, and the feeding amount is 1980kg/h; in the rectification process, the operating pressure of the tower top is 175kPa, the operating pressure of the tower bottom is 205kPa, and the distillate S9 (H) 2 The S mole fraction was 92% and the temperature was 47.6%) was taken as product. The temperature of the rich solution S8 at the bottom of the rectifying tower is 123 ℃, the rich solution is cooled to 70 ℃ through a lean-rich solution heat exchanger B5 to form a material flow S6, then the supplemented water S10 and the MDEA supplemented solvent S11 are mixed in a lean solution supplementing system B8 to form a material flow S12, the mass fraction of MDEA in the S12 reaches 32% through supplementing water and MDEA, the material flow S12 is conveyed through a feed pump B6 to form a material flow S13, the material flow S13 is further cooled to 38 ℃ through a circulating water cooler B7 to form a lean solution S14, and the lean solution S14 is sent into an absorption tower B1 for recycling. The electricity consumption and the steam consumption of the process are converted into standard coal, and the standard coal is measured in each hour192.06kgce was consumed. The running cost per hour is 689.76 yuan (this).
Example 2
As shown in fig. 2, an alcohol amine method energy-saving acid gas desulfurization process based on low-temperature absorption-heat pump rectification: h-containing H with a mole fraction of 10% 2 S acid raw material gas (temperature: 43 ℃ C., pressure: 1200 kPa) S1 at a feed rate of 11210Nm 3 Introducing the// h from the bottom of the absorption tower B1 into the absorption tower; the lean solution (temperature: 15 ℃ C., pressure: 2060 kPa) S18 containing MDEA was fed at a feed rate of 23070kg/h from the top of the absorption column B1 to the absorption column. Bottom H of absorption tower 2 The rich liquid S2 with the mole fraction of 4.94% enters a first pressure reducing valve B2 (pressure drop: 760 kPa) to be treated to form a stream S3, then enters a flash tank B3 (temperature: 43 ℃ C., pressure: 240 kPa) to be treated, and the separated liquid-phase stream S5 is divided into two liquid-phase streams (stream S6 and stream S21) by a separation system B4, wherein the stream S21 accounts for 8%. The material flow S6 enters a lean-rich liquid heat exchange system B5, is preheated to 101 ℃ and then enters a rectifying tower system B11 for separation; the material flow S21 and a high-temperature gas phase material flow S9 of which the top of the rectifying tower B11 is compressed by a compressor B12 are preheated to 154 ℃ by a heat recovery heat exchanger B13 to form a material flow S22, and the material flow S22 enters a rectifying tower system B11 for separation; the gas stream S8 at the top of the rectifying tower is led out from the top of the rectifying tower, is heated to 163 ℃ through a compressor (compression ratio is 1.57) B12 to form a high-temperature gas stream S9, enters a heat recovery heat exchanger B13 to exchange heat with a stream S21 to cool down to form a stream S23, then passes through a second pressure reducing valve B14 (pressure drop: 100 kp) to form a stream S24, passes through a reflux cooler B15 to reduce the temperature to 50 ℃ to form a stream S25, and enters a reflux tank B16 to form a product S27 (H) 2 The S mole fraction was 92% and the temperature was 49.6%). The common medium water vapor (the temperature is 148 ℃ and the pressure is 450 kPa) is taken as a heat source to enter a rectifying tower reboiler, and the feeding amount is 1788kg/h; in the rectification process, the operating pressure of the tower top is 175kPa, and the operating pressure of the tower bottom is 205kPa. The temperature of the rich solution S10 at the bottom of the rectifying tower is 123 ℃, the rich solution is cooled to 50 ℃ through a lean-rich solution heat exchanger B5 to form a material flow S11, and then the material flow S14 is formed after the material flow S11 is mixed with the supplementing water S12 and the MDEA supplementing solvent S13 through a lean solution supplementing system B10, and the mass fraction of the MDEA in the S14 is up toTo 32%. The material flow S14 is firstly processed by a feed pump B6 to form a material flow S15, then is cooled to 35 ℃ in the first step by a circulating water cooler B7, then enters a cold recovery heat exchanger B8 to be further cooled to 32 ℃ by low-temperature purified gas S19, finally is cooled to 15 ℃ by a 7 ℃ chilled water cooler B9 to form a lean solution S18, and enters the top of an absorption tower to realize cyclic utilization. The electricity consumption and the steam consumption of the process are converted into standard coal, and the standard coal consumption is 184.24kgce per hour. The running cost per hour is 715.58 yuan (this).
Comparative example 2
As shown in fig. 1, a prior alcohol amine desulfurization process: h-containing H with a mole fraction of 10% 2 S acid raw material gas S1 (temperature: 43 ℃ C., pressure: 1200 kPa), at a feed rate of 11210Nm 3 Introducing the// h from the bottom of the absorption tower B1 into the absorption tower; the lean solution (temperature: 38 ℃ C., pressure: 2100 kPa) S14 containing MDEA was fed into the absorption column at a feed rate of 30010kg/h from the top of the absorption column B1, in a mass fraction of 32%. Bottom H of absorption tower 2 The rich liquid S2 with the mole fraction of 3.87% enters a pressure reducing valve B4 (pressure drop: 760 kPa) to form a material flow S3, the material flow S3 enters a flash tank B3 (temperature: 54.7 ℃ and pressure: 240 kPa) to be separated, and a separated liquid-phase material flow S5 is preheated to 98 ℃ by a lean-rich liquid heat exchanger B5 to form a material flow S7, and the material flow S7 enters a rectifying tower B2. The common medium water vapor (the temperature is 148 ℃ and the pressure is 450 kPa) is taken as a heat source to enter a rectifying tower reboiler, and the feeding amount is 2594kg/h; in the rectification process, the operating pressure at the top of the column was 175kPa, the operating pressure at the bottom of the column was 205kPa, and the distillate at the top of the column (H 2 S mole fraction 92%, temperature 48.67%) S9 was taken as product. The temperature of the rich solution S8 at the bottom of the rectifying tower is 123 ℃, the rich solution is cooled to 70 ℃ through a lean-rich solution heat exchanger B5 to form a material flow S6, then a certain amount of water S10 and an MDEA replenishing solvent S11 are supplemented and mixed in a lean solution replenishing system B8 to form S12, and the mass fraction of the MDEA in the S12 is up to 32% through the replenishing of the water and the MDEA. The material flow S12 is conveyed by a feed pump B6 to form a material flow S13, the material flow S13 is further cooled to 38 ℃ by a circulating water cooler B7 to form a lean solution S14, and the lean solution S14 is conveyed into an absorption tower B1 for recycling. The electricity consumption and the steam consumption of the process are converted into standard coal, and the standard coal consumption is 251.62kgce per hour. Cost of operation per hour 892.70 yuan(￥)。
Example 3
As shown in fig. 2, an alcohol amine method energy-saving acid gas desulfurization process based on low-temperature absorption-heat pump rectification: h-containing H with 13% mole fraction 2 S acid raw material gas (temperature: 43 ℃ C., pressure: 1200 kPa) S1 at a feed rate of 11210Nm 3 Introducing the// h from the bottom of the absorption tower B1 into the absorption tower; the lean solution (temperature: 15 ℃ C., pressure: 2060 kPa) S18 containing MDEA was fed into the absorption column at a feed rate of 28050kg/h from the top of the absorption column B1 at a mass fraction of 32%. Bottom H of absorption tower 2 The rich liquid S2 with the mole fraction of 5.26% enters a first pressure reducing valve B2 (pressure drop: 760 kPa) to be treated to form a stream S3, and then enters a flash tank B3 (temperature: 43.4 ℃ C., pressure: 240 kPa) to be treated, and the separated liquid-phase stream S5 is divided into two liquid-phase streams (stream S6 and stream S21) by a dividing system B4, wherein the stream S21 accounts for 8%. The material flow S6 enters a lean-rich liquid heat exchange system B5, is preheated to 101 ℃ and then enters a rectifying tower system B11 for separation; the material flow S21 and a high-temperature gas phase material flow S9 of which the top of the rectifying tower B11 is compressed by a compressor B12 are preheated to 154 ℃ by a heat recovery heat exchanger B13 to form a material flow S22, and the material flow S22 enters a rectifying tower system B11 for separation; the gas stream S8 at the top of the rectifying tower is led out from the top of the rectifying tower, is heated to 164 ℃ by a compressor (compression ratio is 1.57) B12 to form a high-temperature gas stream S9, enters a heat recovery heat exchanger B13 to exchange heat with a stream S21 to cool down to form a stream S23, then passes through a second pressure reducing valve B14 (pressure drop: 100 kPa) to form a stream S24, passes through a reflux cooler B15 to reduce the temperature to 50 ℃ to form a stream S25, and enters a reflux tank B16 to form a product S27 (H) 2 The S mole fraction was 92% and the temperature was 49.6%). The common medium steam (temperature is 148 ℃ and pressure is 450 kPa) is taken as a heat source to enter a rectifying tower reboiler. The feeding amount is 2157kg/h; in the rectification process, the operating pressure of the tower top is 175kPa, and the operating pressure of the tower bottom is 205kPa. The temperature of the rich solution S10 at the bottom of the rectifying tower is 123 ℃, the rich solution is cooled to 53 ℃ through a lean-rich solution heat exchanger B5 to form a material flow S11, and then the material flow S14 is formed after the material flow S11 is mixed with the supplementing water S12 and the MDEA supplementing solvent S13 through a lean solution supplementing system B10, and the mass fraction of the MDEA in the S14 is up to 32% through supplementing water and MDEA. Stream S14 is processed by feed pump B6The resultant flow S15 is cooled to 35 ℃ in the first step by a circulating water cooler B7, then enters a cold recovery heat exchanger B8, is further cooled to 29 ℃ by low-temperature purified gas S19, finally is cooled to 15 ℃ by a 7 ℃ chilled water cooler B9 to form lean solution S18, and enters the top of an absorption tower to realize cyclic utilization. The electricity consumption and the steam consumption of the process are converted into standard coal, and the standard coal consumption is 222.72kgce per hour. The running cost per hour is 850.59 yuan (this).
Comparative example 3
As shown in fig. 1, a prior alcohol amine desulfurization process: h-containing H with 13% mole fraction 2 S acid raw material gas S1 (temperature: 43 ℃ C., pressure: 1200 kPa), at a feed rate of 11210Nm 3 Introducing the// h from the bottom of the absorption tower B1 into the absorption tower; a32% by mass of a lean solution (temperature: 38 ℃ C., pressure: 2100 kPa) S14 containing MDEA was fed into the absorption column from the top of the absorption column B1 at a feed rate of 40000 kg/h. Bottom H of absorption tower 2 The rich liquid S2 with the mole fraction of 3.78% enters a pressure reducing valve B4 (pressure drop: 760 kPa) to form a material flow S3, the material flow S3 enters a flash tank B3 (temperature: 54.5 ℃ and pressure: 240 kPa) to be separated, and a separated liquid-phase material flow S5 is preheated to 98 ℃ by a lean-rich liquid heat exchanger B5 to form a material flow S7, and the material flow S7 enters a rectifying tower B2. The common medium steam (the temperature is 148 ℃ and the pressure is 450 kPa) is taken as a heat source to enter a rectifying tower reboiler, and the feeding amount is 3413kg/h; in the rectification process, the operating pressure at the top of the column was 175kPa, the operating pressure at the bottom of the column was 205kPa, and the distillate at the top of the column (H 2 S mole fraction 92%, temperature 49.8%) S9 was taken as product. The temperature of the rich solution S8 at the bottom of the rectifying tower is 123 ℃, the rich solution is cooled to 70 ℃ through a lean-rich solution heat exchanger B5 to form a material flow S6, then a certain amount of water S10 and an MDEA replenishing solvent S11 are supplemented and mixed in a lean solution replenishing system B8 to form S12, and the mass fraction of the MDEA in the S12 is up to 32% through the replenishing of the water and the MDEA. The material flow S12 is conveyed by a feed pump B6 to form a lean solution S13, the lean solution S13 is further cooled to 38 ℃ by a circulating water cooler B7 to form a lean solution S14, and the lean solution S14 is sent into an absorption tower B1 for recycling. The electricity consumption and the steam consumption of the process are converted into standard coal, and the standard coal consumption is 331.06kgce per hour. The running cost per hour is 1189.43 yuan (this).
The comparison of the process and performance parameters of the above examples and comparative examples is shown in table 1, and it can be seen from table 1 that in the process of acid gas desulfurization, compared with the conventional acid gas desulfurization process, the new low-temperature energy-saving alcohol amine desulfurization process is adopted, and the new process can reduce the operation cost by 14% -28% and the comprehensive energy consumption by 25% -33% under the condition of meeting the same product purity and separation requirements.
In Table 1, the standard coal consumption is obtained by adding the power consumption and the steam consumption in the process after being folded into the standard coal consumption; the cost is obtained by adding the costs of circulating water, chilled water, electricity and steam in the process.
The low-temperature energy-saving alcohol amine desulfurization process has the following advantages:
1) The invention creatively develops the technology of low-temperature absorption and cold recovery. By the application of the technology, the circulating dosage of the absorbent (lean solution) is reduced by 23-30%, the concentration of the rich solution is increased by 28-40%, and the absorption mass transfer efficiency is greatly improved. And meanwhile, the high-grade cold energy is recycled, so that the consumption of circulating cooling water is reduced, and the energy consumption and the running cost are saved.
2) The invention combines the characteristics of the traditional alcohol amine desulfurization process, develops a rectification tower top gas phase compression heat recycling technology, ensures that the heat of a tower top gas phase material flow is fully recycled by optimizing and determining key process parameters such as rich liquor split ratio, greatly reduces the energy consumption in the acid gas desulfurization process, and achieves the aim of improving the comprehensive energy utilization rate of the whole process.
3) Through the development of the two technologies, under the condition of meeting the same product purity and separation requirements, the novel acid gas desulfurization process can reduce the operation cost by 14-28%, and the comprehensive energy consumption is reduced by approximately 25-33%.
TABLE 1 comparative examples of the process of the invention and comparative examples of the conventional desulfurization process and the comparative conditions
Table 1 data energy saving rate calculation mode:
wherein c is the energy saving rate, Q 1 For standard coal consumption in comparative example, Q 2 The standard coal consumption in the examples was determined.
Table 1 data cost savings ratio calculation mode:
where w is the cost savings rate, P 1 For the cost in the comparative example, P 2 Is the cost in the embodiment.
The above embodiments are merely examples for clearly illustrating the present invention and are not limiting on the embodiments of the present invention. Various modifications or alterations may also be made by those skilled in the art based on the foregoing description. It is not necessary here nor is it exhaustive of all embodiments. Any modification, equivalent replacement, improvement, etc. which are within the spirit and principle of the present invention are included in the protection scope of the present invention as set forth in the claims.
Claims (10)
1. An alcohol amine method energy-saving acid gas desulfurization process based on low-temperature absorption-heat pump rectification is characterized in that raw material gas enters from bottom to top of an absorption tower, normal-temperature absorbent liquid phase material flow enters from top to bottom of the absorption tower, countercurrent contact is performed, rich liquid is formed at the bottom of the absorption tower, the rich liquid is depressurized by a depressurization valve and enters a flash tank, the rich liquid at the bottom of the flash tank is pumped into a lean-rich liquid heat exchange system for preheating and then enters a rectification tower for separation, and acid gas enters a condensation cooler and a reflux tank from the top of the rectification tower and contains high-concentration H 2 S, acid substances are extracted as products; the lean solution at the bottom of the rectifying tower enters a lean-rich solution heat exchange system for cooling and then enters a lean solution supplementing system for mixing with supplementing water and MDEA solvent to form a material flow, a normal-temperature absorbent liquid-phase material flow is formed by a feed pump and a circulating water cooler and enters the top of an absorption tower for recycling; characterized in that the flash tankThe rich liquid at the bottom is pumped into a lean-rich liquid heat exchange system to be separated by a diversion system, and the rich liquid at the bottom of the other part of flash tank enters a heat recovery heat exchanger to be subjected to heat exchange with a high-temperature gas phase material flow and then enters a rectifying tower system to be separated; the high-temperature gas phase material flow is formed by compressing a gas phase extracted from the top of a rectifying tower by a compressor; the normal temperature absorbent liquid phase material flow is cooled by a cold recovery heat exchanger and a chilled water cooler through low temperature gas extracted from the top of the absorption tower before entering the absorption tower.
2. The alcohol amine method energy-saving acid gas desulfurization process based on low-temperature absorption-heat pump rectification as claimed in claim 1, wherein the rich liquid entering the heat recovery heat exchanger accounts for 5% -10% of the rich liquid exiting the flash tank.
3. The alcohol amine method energy-saving acid gas desulfurization process based on low temperature absorption-heat pump rectification as claimed in claim 1, wherein the raw material gas mainly comes from dry gas generated in the refining process of sulfur-containing petroleum and sulfur-containing natural gas, and the main components of the raw material gas are except H 2 S, in addition to H 2 、CO 2 、CH 4 、C 2 、C 3 、C 4 And C 5 A gas; the temperature of the raw material gas is 40-45 ℃, the pressure is 1000-1400 kPa, and the flow is 11000N m 3 /h～12000N m 3 /h。
4. The alcohol amine method energy-saving acid gas desulfurization process based on low-temperature absorption-heat pump rectification as claimed in claim 1, wherein the high-temperature gas stream is subjected to heat exchange by a heat exchanger, then is decompressed by a second decompression valve, cooled by a condenser and enters a reflux tank for gas-liquid separation, and the high-purity H is contained in the gas-liquid separation process 2 The acidic component of S is collected and the liquid phase material is returned to the rectifying column as a reflux.
5. The alcohol amine method energy-saving acid gas desulfurization process based on low-temperature absorption-heat pump rectification as claimed in claim 4, wherein the pressure drop of the second pressure reducing valve is 100-150kp; the condenser is cooled to 48-50 ℃.
6. The alcohol amine method energy-saving acid gas desulfurization process based on low-temperature absorption-heat pump rectification as claimed in claim 1, wherein the lean solution at the bottom of the rectification tower enters a lean-rich solution heat exchange system and is cooled to 46-53 ℃; the cooled lean solution is mixed with additional water and additional solvent MDEA in a lean solution additional system, and is conveyed to a circulating water cooler through a feed pump to be cooled to the temperature of 32-35 ℃, then enters a cold recovery heat exchanger to be further cooled to the temperature of 28-31 ℃ by low-temperature purified gas, and is cooled to the temperature of 15-18 ℃ by a chilled water cooler.
7. The alcohol amine method energy-saving acid gas desulfurization process based on low-temperature absorption-heat pump rectification as claimed in claim 1, wherein the top pressure of the rectification column is 175+/-10 kPa, the bottom pressure is 205+/-10 kPa, and the molar reflux ratio is 0.6-0.8.
8. The alcohol amine process energy-saving acid gas desulfurization process based on low temperature absorption-heat pump rectification according to claim 1, wherein the pressure of the low temperature absorbent liquid phase stream is 2000kPa to 2200kPa, and the flow rate is 17t/hr to 30t/hr.
9. The alcohol amine method energy-saving acid gas desulfurization process based on low-temperature absorption-heat pump rectification as claimed in claim 1, wherein the temperature of the flash tank is 42-44 ℃ and the pressure is 240-250 kPa.
10. The alcohol amine method energy-saving acid gas desulfurization process based on low-temperature absorption-heat pump rectification as claimed in claim 1, wherein the rich liquid is extracted from the bottom of the absorption tower, is depressurized by a first depressurization valve and enters a flash tank, and the dissolved and entrained hydrocarbon light components in the rich liquid are collected after being flashed off.
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