阅读说明：本技术 一种高效复合式低温甲醇洗co2回收塔 (Efficient composite low-temperature methanol-washing CO2Recovery tower ) 是由 高维平 高铭鸿 于 2021-08-02 设计创作，主要内容包括：一种高效复合式低温甲醇洗CO-(2)回收塔,针对酸性气低温甲醇洗工艺中富甲醇液CO-(2)、H-(2)S的分离,发明一种高效复合式低温甲醇洗CO-(2)回收塔,取消氮气气提；本发明有两种方案,方案一,对新建装置,把富甲醇液CO-(2)分离所用的原H-(2)S浓缩塔和氮气气提塔及绝大部分冷量和热量换热回收过程高效集成在一个塔内完成；方案二,对老装置改造,把原富甲醇液CO-(2)分离所用的氮气气提塔及一部分冷量和热量换热回收过程高效集成在一个塔内完成；本发明特点：(1)解决国内外大多数企业采用低温甲醇洗所面临的大量CO-(2)排放问题,回收高纯CO-(2)气体；(2)取消气提所用氮气,回收全部冷量和热量,减少生产成本；(3)减少流体输送,降低运行费用；(4)简化工艺流程,极大节省建设投资；(5)在全球推广,每年可减少上亿吨CO-(2)排放,对环境治理价值无限。(Efficient composite low-temperature methanol-washing CO 2 A recovery tower for the methanol-rich liquid CO in the low-temperature methanol washing process of the acid gas 2 、H 2 Separation of S, the invention relates to a high-efficiency combined low-temperature methanol CO washing method 2 A recovery tower is adopted, and nitrogen gas stripping is cancelled; the invention has two schemes, namely, a scheme I, for a newly-built device, methanol-rich liquid CO is introduced 2 Separation of the original H used 2 The S concentration tower, the nitrogen stripping tower and most of cold and heat exchange recovery processes are efficiently integrated in one tower; scheme II, old devices are reformed, and original methanol-rich liquid CO is treated 2 The nitrogen stripping tower used for separation and part of the cold and heat exchange recovery process are efficiently integrated in one towerForming; the invention is characterized in that: (1) solves the problem that most enterprises at home and abroad adopt a large amount of CO faced by low-temperature methanol washing 2 Problem of discharge, recovery of high purity CO 2 A gas; (2) the nitrogen used by gas stripping is eliminated, and the whole cold and heat are recovered, so that the production cost is reduced; (3) the fluid conveying is reduced, and the operating cost is reduced; (4) the process flow is simplified, and the construction investment is greatly saved; (5) can reduce billions of tons of CO annually after being popularized all over the world 2 Discharge and has unlimited environmental treatment value.)

1. Efficient composite low-temperature methanol-washing CO₂A recovery tower, an absorption washing tower in the low-temperature acid gas methanol washing process generates two strands of methanol-rich washing liquid, wherein one strand contains CO₂The other part of the methanol-rich liquid contains CO₂、H₂The methanol-rich liquid of S needs to be treated with CO in the two methanol-rich liquids₂、H₂Separating S to obtain poor methanol solution for cyclic use, CO₂The separation original process flow diagram is shown in figure 1; the invention aims at CO in methanol-rich liquid₂The invention provides a high-efficiency compound low-temperature methanol CO washing method₂The recovery column provides two schemes: scheme I, the technological process is shown as attached figure 2, and the efficient compound type low-temperature methanol CO washing method is used for washing CO₂The recovery tower structure is shown in figure 3, and the low-temperature methanol is used for washing methanol-rich liquid CO₂Separation of the original H used₂The S concentration tower, the nitrogen stripping tower and most of cold and heat exchange recovery processes are efficiently integrated into one CO₂The process is completed in a recovery tower; scheme II, the technological process is shown in figure 4, and the efficient compound type low-temperature methanol CO washing process is carried out₂The recovery tower structure is shown in figure 5, and the low-temperature methanol is used for washing methanol-rich liquid CO₂The original nitrogen stripping tower used for separation and part of cold and heat exchange recovery process are efficiently integrated into one CO₂Is finished in the recovery towerAnd (4) obtaining.

2. Efficient composite low-temperature methanol-washing CO₂Recovery column, methanol scrubbing of CO at low temperature₂In the separation process, H is₂S, a concentration tower, a nitrogen stripping tower and most of cold and heat exchange recovery processes are efficiently integrated into one tower, and a built-in heat exchanger is arranged in the tower, so that cold and heat material flows are subjected to step heat exchange in the built-in heat exchanger according to the temperature level; in the internal heat exchanger, the methanol-rich liquid in the tower flows from top to bottom through the tube pass, and absorbs the heat of the methanol-poor liquid in the shell pass in the process, and CO dissolved in the methanol-rich liquid₂Continuously gasify.

3. Efficient composite low-temperature methanol-washing CO₂Recovery column, methanol scrubbing of CO at low temperature₂During the separation process, the original H is retained₂S concentration tower, reforming or replacing nitrogen stripping tower in original flow, arranging heat exchanger in tower, replacing heat exchanger in tower, allowing methanol-rich liquid in tower to flow from top to bottom, absorbing heat of methanol-poor liquid in shell side, and dissolving CO in methanol-rich liquid₂Continuously gasify.

4. The efficient composite low temperature methanol CO scrubber of claims 1-3₂Recovery column in which CO₂A steam raising pipe is arranged in the built-in heat exchanger in the recovery tower, and the top of the steam raising pipe is higher than the upper pipe plate of the built-in heat exchanger by a certain distance; the top of the steam lift pipe is provided with a liquid-proof umbrella, and the liquid on the upper tube plate of the heat exchanger passes through the tube pass of the heat exchanger.

5. The efficient composite low temperature methanol CO scrubber of claims 1-3₂Recovery tower, washing CO with high-efficiency combined low-temperature methanol₂The recovery tower is internally provided with efficient structured packing.

6. The efficient composite low temperature methanol CO scrubber of claims 1-3₂The recovery tower is cancelled, and the nitrogen gas stripping is cancelled to separate CO₂By heat recoveryCO separation by heating and stripping₂。

7. The efficient composite low temperature methanol CO scrubber of claims 1-3₂Recovery tower in which CO is washed with high-efficiency combined low-temperature methanol₂An auxiliary reboiler is arranged at the bottom of the recovery tower.

Technical Field

The invention relates to purification of coal gas in coal chemical industry, gas purification in ammonia and urea synthesis industry and a method for purifying the sameThe process of purifying city gas, etc. the shift gas produced in the process needs to be purified to separate out qualified H₂And CO₂Generally, low-temperature methanol washing and liquid nitrogen washing processes are adopted, and CO is generated in the low-temperature methanol washing process₂、H₂The methanol-rich liquid of S is obtained by adding CO in the methanol-rich liquid₂、H₂S is separated out to obtain the lean methanol liquid for recycling.

Background

Since the development of the low-temperature methanol washing technology, the low-temperature methanol washing technology has remarkable advantages in the aspect of acid gas absorption and the like, so that the low-temperature methanol washing technology is widely applied to the absorption and removal of acid gas in the chemical industry and plays an important role in the desulfurization and decarburization of shift gas. In 1954, Lurgi company in Germany firstly establishes a first set of industrialized low-temperature methanol washing device in Sasol company in south Africa, and is popularized and applied all over the world in the later period; the low-temperature methanol washing technology is widely applied to a Lurgi process and a Linde process, and is widely applied to the purification of coal gas in the coal chemical industry, the purification of gas in the synthetic ammonia industry and the urea industry, the purification of urban gas and the like on the basis of 2 processes. In a large-scale synthetic ammonia plant which is built in the 70 th century of 20 th in China and takes coal and residual oil as raw materials, low-temperature methanol is adopted as an absorbent for gas purification, the low-temperature methanol is widely applied in the later period, and at present, hundreds of devices in China adopt low-temperature methanol washing for purifying converted gas.

The acid gas generally contains H₂、CO₂、H₂S、N₂、Ar、CO、CH₄、COS、H₂O, etc., wherein H₂、CO₂Is high in content of (H)₂S and other components with low content, but obtaining H with certain purity₂And CO₂For the synthesis of NH₃And urea, etc., H must be removed₂And CO₂Separating to obtain purity meeting the process requirement, and adopting low-temperature methanol washing and low-temperature liquid nitrogen washing processes; two washing liquids are generated in a low-temperature methanol washing absorption washing tower, wherein one washing liquid contains CO₂The other stream of the methanol-rich liquid contains CO₂、H₂The methanol-rich liquid of S needs to be treated with CO in the two methanol-rich liquids₂、H₂S is separated out to obtain the lean methanol liquid for recycling. Aiming at CO in methanol-rich liquid₂The original process flow is shown as figure 1, and CO is separated₂Separated out by three towers, and CO is adopted₂Desorption (T202 column), H₂Concentrating S (T203 tower), and stripping with nitrogen (T207 tower), wherein the T203 tower and the T207 tower are stripped with nitrogen, and stripping nitrogen and CO extracted from gas₂At the top of T203 tower with CO₂+N₂The mixture is extracted in the form of mixture, and discharged after cold recovery and water washing, and the CO is used as CO for a device producing 30 ten thousand tons of urea annually₂+N₂CO emitted in the form of a mixture₂The amount of the CO is as high as 12 ten thousand tons, great waste is caused, and the CO is discharged in such a way₂Greenhouse gases, have a severe impact on the environment.

At present, the process flow of the low-temperature methanol washing process used by most enterprises is shown as the attached figure 1, and the low-temperature methanol washing process is also deeply researched domestically and is continuously perfected, but some problems exist, and the first problem to be solved urgently is that a large amount of CO is needed to be solved₂The invention can solve the two problems and benefit the offspring generation.

The absorption process of the gas, which is advantageous at low temperatures and high pressures, is an exothermic process, in which the heat released by the absorption of the gas should be removed as far as possible to reduce the absorption temperature and to ensure that the temperature of the absorbent and the gas entering the absorption column is as low as possible; the desorption process of the dissolved components in the absorption liquid is favorable at high temperature and low pressure, is a heat absorption process, and needs to provide certain heat for desorbing the dissolved components in the absorption liquid; the cold and heat quantity required in the absorption and desorption processes of the low-temperature methanol washing of the shift gas can be optimally matched for heat exchange, and the cold and heat quantity in the process can be fully recovered to reduce the input of the cold and heat quantity of public works so as to achieve the purposes of energy conservation and consumption reduction.

Disclosure of Invention

The invention develops a high-efficiency composite low-temperature methanol CO washing method₂The recovery tower adopts the process flow shown in the attached figure 2 for a newly built device according to the scheme I of the invention, and the high-efficiency combined type low-temperature methanol washing CO is carried out₂The structure of the recovery tower T203r is shown in figure 3, which is used for washing methanol-rich liquid CO with low-temperature methanol₂Separation of the original H used₂The S concentration tower T203, the nitrogen stripping tower T207 and most of cold and heat exchange recovery processes are efficiently integrated in one tower T203r to complete, and nitrogen stripping is omitted; for old device transformation, the second scheme of the invention is adopted, and the process flow shown in the attached figure 4 is adopted, so that the high-efficiency compound low-temperature methanol CO washing process is realized₂The structure of the recovery tower T207r is shown in figure 5, which is used for washing methanol-rich liquid CO with low-temperature methanol₂The original nitrogen stripping tower T207 used for separation and a part of cold and heat exchange recovery process are efficiently integrated in one tower T207r to complete, and nitrogen stripping is cancelled.

The invention is characterized in that: (1) solves the problem that most enterprises at home and abroad adopt a large amount of CO faced by low-temperature methanol washing₂Problem of discharge, recovery of high purity CO₂Gas, this CO₂Can be sold as a product or used for producing CO₂The downstream products achieve the purposes of saving energy, reducing consumption and improving economic benefits, reduce the emission of a large amount of greenhouse gases, have great social benefits and benefit the offspring generations; (2) recovering all cold and heat in the low-temperature methanol washing process, and recovering CO through the heat₂The desorption provides enough energy, the nitrogen used by gas stripping is eliminated, a large amount of nitrogen is saved, the cold energy is recovered, the input of the cold energy and the heat energy of public works is reduced, and the production cost is reduced; (3) the conveying of the fluid is reduced, the power consumption of a pump used for conveying the fluid is saved, and the operating cost is reduced; (4) the flow and liquid level regulation control instrument and the fluid conveying pipeline are reduced, the production operation and control are convenient, the process flow is simplified, and the construction investment is saved; (5) if the invention can be popularized and applied all over the world, billions of tons of CO can be reduced every year₂The emission of (2) creates unlimited value for the health development of the world.

The technical scheme of the invention is as follows:

the technical scheme of the invention is divided into two situations, wherein the first scheme is suitable for newly building a low-temperature methanol washing device, and the second scheme is aimed at the transformation of a low-temperature methanol washing old device. (the newly-built device can also adopt a scheme II but the investment is more, and the old device can also adopt a scheme I but the investment for reconstruction is more but the operation cost is reduced after the reconstruction.)

The first scheme is as follows:

aiming at the newly-built low-temperature methanol washing device, a scheme I is adopted, wherein CO is obtained₂The separation process is shown in figure 2, and the high-efficiency combined low-temperature methanol washing CO is performed₂The recovery tower T203r is shown in the attached figure 3, and the invention is characterized in that:

1. handle H₂The S concentration tower T203 and the nitrogen stripping tower T207 are integrated into one tower, which is called as an efficient combined type low-temperature methanol washing CO₂The recovery tower is numbered as T203r, and integrates most of cold and heat exchange recovery processes in the tower to be completed;

2. three high-efficiency built-in heat exchangers are arranged in the T203r tower, so that the cold and hot material flows realize cascade heat exchange according to the temperature level; in the internal heat exchanger, the methanol-rich liquid in the tower flows from top to bottom in the tube pass, in the process, the heat from the methanol-poor liquid at the bottom of the methanol heat regeneration tower in the shell pass is absorbed, and CO dissolved in the methanol-rich liquid₂The gas is continuously gasified, the process is actually a falling film evaporation process, the heat transfer coefficient is large, the heat transfer efficiency is high, the heat exchange area required by cold and heat recovery is reduced, the equipment structure is more compact, and the equipment and construction investment are saved;

3. high purity CO is extracted from the top of the T203r tower₂The gas is compressed and cooled after cold energy recovery, and the CO is obtained₂Can be sold as a product or used for producing CO₂The downstream product of (1);

4. the method is characterized in that the original plate type structure is replaced by the high-efficiency structured packing in a T203r tower, the high-efficiency structured packing is divided into 6 sections, the heights of the sections are different, and the high-efficiency structured packing depends on the separation requirements of the sections and the required theoretical plate number, the requirements on the temperature distribution of the tower and the structural size and the separation efficiency of the used high-efficiency structured packing;

scheme II:

aiming at the transformation of the low-temperature methanol washing old device, a scheme II is adopted, the original equipment is fully utilized so as to save the transformation investment, and CO is used₂The separation process is as shown in the figure4, high-efficiency combined low-temperature methanol washing of CO₂The structure of the recovery tower T207r is schematically shown in figure 5, and high purity CO can be recovered by only partial reconstruction₂The invention cancels the nitrogen gas stripping, reduces the reconstruction investment and the production cost, and has the key points as follows:

5. retention of H₂S concentration tower T203, nitrogen used for stripping of T203 is eliminated, and two CO streams are extracted from the top of the T203 tower₂After the gas is mixed, the gas is sent to a subsequent heat exchanger for recovering cold energy, and then CO is sent₂A compression condensation packaging system;

6. the structure of the nitrogen stripping tower T207 shown in figure 5 is modified or replaced, and the structure is called as high-efficiency combined type low-temperature methanol CO washing₂The number of the recovery tower is T207r, a methanol-rich liquid extraction pump P205 is added, the position number of a heat exchanger E210 of original nitrogen stripping tower T207 tower bottom extraction liquid and methanol-poor liquid at the bottom of a methanol thermal regeneration tower is changed into E210A, and the recovery tower is used; the extraction position of the E210A methanol-rich liquid is a liquid collecting plate above a filler at the C section of the T207r tower, the methanol-rich liquid returns to a gas-liquid distributor below the extraction plate of the T207r tower after heat exchange, and the bottom liquid of the T207r tower is directly sent to a methanol thermal regeneration tower through an original pump P204;

7. arranging a high-efficiency built-in heat exchanger E210B at one position in a T207r tower, in the built-in heat exchanger E210B, enabling methanol-rich liquid in the tower to move from top to bottom in a tube pass, absorbing heat of a shell pass from E210A methanol-poor liquid in the process, and dissolving CO in the methanol-rich liquid₂The gas is continuously gasified, the process is actually a falling film evaporation process, the heat transfer coefficient is large, the heat transfer efficiency is high, the heat exchange area required by cold and heat recovery is reduced, the equipment structure is more compact, and the equipment and construction investment are saved;

8. high purity CO is extracted from the top of the T203 tower₂The gas, after recovering cold, is compressed, condensed and packaged in a system, the CO₂Can be sold as a product or used for producing CO₂The downstream product of (1);

9. the method is characterized in that an original plate type tower structure is replaced by high-efficiency structured packing in a T207r tower, the high-efficiency structured packing is divided into 3 sections, the heights of the sections are different, and the requirements on the separation requirements of the sections, the number of required theoretical plates, the temperature distribution of the tower and the like are met, and the structural size and the separation efficiency of the used high-efficiency structured packing are also met;

the first scheme and the second scheme have the common points that:

10. the method is characterized in that steam raising tubes are arranged in built-in heat exchangers in the towers T203r and T207r, when a steam phase rising in the towers passes through the heat exchangers, most of the steam raising tubes go away from the steam raising tubes, the tops of the steam raising tubes are higher than the upper tube plates of the heat exchangers by a certain distance, liquid-proof umbrellas are arranged at the tops of the steam raising tubes, and liquid on the upper tube plates of the heat exchangers directly goes away from the steam raising tubes without going away from the steam raising tubes, so that the pressure drop of steam-liquid phase fluid in the towers flowing through the built-in heat exchangers is reduced, the flooding in the heat exchange process is prevented, and the height of the heat exchange tubes and the liquid level on the upper tube plates provide flowing power for the liquid in the towers to exchange heat through the tube passes;

11. efficient structured packing is adopted in the T203r and T207r towers to replace the original plate tower structure, so that more gas-liquid contact area is provided, the mass and heat transfer efficiency is enhanced, the height of the towers is reduced, the operation elasticity of the towers is improved, the liquid holdup of methanol in the towers is reduced, and the consumption of methanol in the production process is reduced;

12. eliminating CO separation by nitrogen stripping₂A large amount of nitrogen is saved, so that the production cost is greatly reduced;

13. an auxiliary reboiler E210C is arranged at the bottoms of T203r and T207r, and heating steam is used for efficient combined low-temperature methanol washing of CO during driving₂The recovery tower provides initial heat, when the methanol thermal regeneration tower is opened and qualified poor methanol liquid is extracted from the bottom of the tower, the poor methanol liquid can enter the high-efficiency composite low-temperature methanol CO washing tower₂The recovery tower exchanges heat with liquid in the tower, and the high-efficiency combined type low-temperature methanol CO washing method is realized₂The recovery tower provides heat, the heat load of the auxiliary reboiler E210C is continuously reduced at the moment, and the high-efficiency composite low-temperature methanol CO washing method is used for washing₂95% of the heat required by the recovery tower is provided by recovering the heat of the methanol-poor liquid extracted from the bottom of the thermal methanol regeneration tower, and CO is recovered while the heat of the methanol-poor liquid is recovered₂The cold energy in the recovery tower is used for cooling the poor methanol liquid from about 98 ℃ to about-58 ℃ initially, and the poor methanol liquid returns to the absorption washing tower for recycling, and CO is recycled₂The methanol-rich liquid in the recovery tower is processed in a T203r tower from the initial temperature of-60 ℃ after flash evaporationScheme one) or T203 and T207r tower (scheme two), the temperature gradually rises, the temperature reaches about 80 ℃ already when the methanol-rich liquid at the bottom of the T203r or T207r tower comes out, and the methanol-rich liquid at the bottom of the T203r or T207r tower contains CO₂About 0.3wt% of the total amount of the methanol can be directly purified by a methanol-removing thermal regeneration tower; after the normal operation, the auxiliary reboiler E210C only plays a role in adjusting the heat load so as to ensure that CO in the produced liquid at the bottom of the T203r or T207r tower₂The content meets the process requirements;

14. the operating pressure of the T203r tower is about 0.190MPa (a), and the operating pressure of the T207r tower is about 0.280MPa (a);

15. the tower diameter is determined by the production capacity, and the tower internals and other ancillary structures and dimensions can be designed according to the process, equipment tooling, installation and operational controls.

Drawings

FIG. 1: low-temperature methanol washing methanol-rich liquid CO₂Separating the original process flow schematic diagram;

FIG. 2 is a drawing: low-temperature methanol washing methanol-rich liquid CO₂A process flow diagram of the 2-tower after the separation is improved;

FIG. 3: efficient composite low-temperature methanol-washing CO₂A schematic drawing of recovery column T203 r;

FIG. 4 is a drawing: low-temperature methanol washing methanol-rich liquid CO₂A process flow diagram of the 3-tower with improved separation;

FIG. 5: efficient composite low-temperature methanol-washing CO₂Recovery column T207r schematic.

Detailed Description

The following are illustrated by way of example:

for the low-temperature methanol washing device for annual production of 30 ten thousand tons of urea, the temperature, pressure, composition and flow of two streams of methanol-rich liquid from the low-temperature methanol washing absorption washing section and methanol-poor liquid from the methanol thermal regeneration tower section are shown in Table 1.

If the device is newly built, the process flow shown as the scheme I in the attached figure 2 is adopted, and the high-efficiency compound low-temperature methanol CO washing is carried out₂The stream data of the recovery column T203r are shown in Table 2; the operation pressure of the tower top is 0.19MPa (a); the packing in the T203r tower is divided into 6 sections, and the theoretical plate number required by each section for separation is as follows: the number of A-segment theoretical plates is more than or equal to 29, and the number of B-segment theoretical plates is more than or equal to4, the number of C-section theoretical plates is more than or equal to 12, the number of D-section theoretical plates is more than or equal to 5, the number of E-section theoretical plates is more than or equal to 3, and the number of F-section theoretical plates is more than or equal to 3; the method adopts special efficient structured packing SZJCBW-500Y, the inner diameter ID =1600mm of a T203r tower, the inner diameters of shells E210A, E210B and E209 are 1600mm, the length of a heat exchange tube is 6000mm, the heat exchange tube adopts DN25 tubes, and the heat exchange area is 949m²The steam lift pipe adopts DN200 pipe, and the detailed structure of the tower body, the tower internals and the built-in heat exchanger needs to be designed according to the mechanical design specification.

If the old device is modified, the scheme II is adopted, the existing equipment is fully utilized, the process flow shown in the attached figure 4 is used, and the efficient compound low-temperature methanol CO washing is carried out₂The recovery column T207r is shown in FIG. 5, and T207r is combined with the column T203 to complete the high purity CO₂The data of the streams entering and exiting the T207r column are shown in Table 3, stream line number<37>For high purity CO extracted from the second plate at the top of the T203 column₂A gas; the T207r packing is divided into 3 sections, and the number of theoretical plates required by each section for separation is as follows: the number of A-segment theoretical plates is more than or equal to 5, the number of B-segment theoretical plates is more than or equal to 3, and the number of C-segment theoretical plates is more than or equal to 3; the method is characterized in that a specially-made efficient structured packing SZJCBW-500Y is adopted, the internal diameter ID =1600mm of a T207r tower, a heat exchanger E210A is used, and the heat exchanger is an E210 heat exchanger of the original process; the internal heat exchanger E210B has the shell inner diameter of 1600mm, the heat exchange tube length of 6000mm and the heat exchange area of 949m²The heat exchange tube adopts DN25 tube, and the heat exchange area is 949m²The steam lift pipe adopts DN200 pipe, and the detailed structure of the tower body, the tower internals and the built-in heat exchanger needs to be designed according to the mechanical design specification.

Table 1: acid gas low-temperature methanol washing into CO₂Separation system logistics data

Table 2: in-out efficient composite low-temperature methanol CO washing₂Stream data of the recovery column T203r

The material flow numbers and names are shown in figure 3

Continuing with Table 2: in-out efficient composite low-temperature methanol CO washing₂Stream data of the recovery column T203r

The material flow numbers and names are shown in figure 3

Table 3: in-out efficient composite low-temperature methanol CO washing₂Data on stream from the recovery column T207r

The stream numbers and names are shown in figure 5.