A system and method for regenerating hydrogen sulfide and carbon dioxide from MEDA waste liquor

Abstract

The present application relates to the technical field of recycling of organic waste liquid, and particularly relates to a system and method for regenerating hydrogen sulfide and carbon dioxide by using MEDA waste liquid. The system for regenerating hydrogen sulfide and carbon dioxide by using MEDA waste liquid provided by the present application comprises: a MEDA waste liquid tank; a lean-liquid rich-liquid heat exchanger connected with the MEDA waste liquid tank; a regeneration tower connected with a rich-liquid outlet of the lean-liquid rich-liquid heat exchanger; a cooler connected with a gas outlet of the regeneration tower; and a membrane separation device connected with a gas outlet of the cooler; and the membrane separation device is provided with a hydrogen sulfide gas outlet and a carbon dioxide gas outlet. The system and method for regenerating hydrogen sulfide and carbon dioxide by using MEDA waste liquid can remove the dissolved waste gas in the MEDA, realize the recycling of the MEDA solution, and simultaneously produce high-purity hydrogen sulfide and food-grade carbon dioxide products.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of recycling of organic waste liquid, and particularly relates to a system and method for regenerating hydrogen sulfide and carbon dioxide by using MEDA waste liquid. BACKGROUND

[0002] At present, the treatment of MEDA waste liquid is a very tricky problem. Usually, the way of sewage stripping is selected to realize the treatment, but the separated gas cannot be collected and utilized, and the released gas can only be discharged through simple incineration, and the device for treating the waste water and the treatment cost are both high.

[0003] In most cases, carbon dioxide is prepared by high-temperature cracking of limestone, but the carbon dioxide produced by the process needs to be carried out under high temperature and high pressure, has high energy consumption, is harsh to the equipment, has high investment, and the purity of the carbon dioxide itself cannot reach the food grade and has many impurities.

[0004] For hydrogen sulfide, barite is generally used to produce soluble barium salt in industry, and the by-product produced is hydrogen sulfide. The hydrogen sulfide produced by this method has low purity, generally about 70%. At the same time, this method itself has low selectivity and low product yield. SUMMARY

[0005] Therefore, the present application aims to solve the technical problem of providing a system and method for regenerating hydrogen sulfide and carbon dioxide by using MEDA waste liquid, which can remove the dissolved waste gas in MEDA, realize the recycling of MEDA solution, and produce high-purity hydrogen sulfide and food-grade carbon dioxide products.

[0006] The present application provides a system for regenerating hydrogen sulfide and carbon dioxide by using MEDA waste liquid, characterized by comprising:

[0007] a MEDA waste liquid tank;

[0008] a lean-liquid rich-liquid heat exchanger connected with the MEDA waste liquid tank;

[0009] a regeneration tower connected with a rich-liquid outlet of the lean-liquid rich-liquid heat exchanger;

[0010] a cooler connected with a gas outlet of the regeneration tower;

[0011] a membrane separation device connected with a gas outlet of the cooler; the membrane separation device is provided with a hydrogen sulfide gas outlet and a carbon dioxide gas outlet.

[0012] Preferably, the membrane separation device comprises:

[0013] a membrane assembly;

[0014] A pressure reducing valve is arranged at the inlet of the membrane module;

[0015] The membrane module is provided with a permeate gas outlet and an exhaust gas outlet; the permeate gas outlet discharges hydrogen sulfide gas, and the exhaust gas outlet discharges carbon dioxide gas.

[0016] Preferably, the carbon dioxide purification device is further included.

[0017] The carbon dioxide purification device includes:

[0018] A carbon dioxide vaporizer; the carbon dioxide vaporizer is provided with a carbon dioxide raw material inlet and a membrane separation carbon dioxide inlet; the membrane separation carbon dioxide inlet is connected to the exhaust gas outlet of the membrane separation device;

[0019] A carbon dioxide preheater; the vaporization gas inlet of the carbon dioxide preheater is connected to the vaporization gas outlet of the carbon dioxide vaporizer;

[0020] A mixed gas buffer tank; the preheated gas inlet of the mixed gas buffer tank is connected to the preheated gas outlet of the carbon dioxide preheater; the mixed gas buffer tank is used for mixing oxygen and preheated carbon dioxide;

[0021] A two-stage heat exchanger connected to the gas outlet of the mixed gas buffer tank;

[0022] A first electric heater connected to the hot gas outlet of the two-stage heat exchanger;

[0023] A dehydrogenation reactor connected to the gas outlet of the first electric heater; the gas outlet of the dehydrogenation reactor is connected to the hot gas inlet of the two-stage heat exchanger; the cold gas outlet of the two-stage heat exchanger is connected to the hot gas inlet of the carbon dioxide preheater;

[0024] A water cooler connected to the cold gas outlet of the carbon dioxide preheater;

[0025] A dryer, the cold gas inlet of the dryer is connected to the gas outlet of the water cooler;

[0026] A filter connected to the cold gas outlet of the dryer; the gas outlet of the filter is connected to the filtered gas inlet of the carbon dioxide vaporizer;

[0027] A liquefier connected to the cold gas outlet of the carbon dioxide vaporizer;

[0028] A gas-liquid separator connected to the liquid outlet of the liquefier;

[0029] A purification column connected to the outlet of the gas-liquid separator; the outlet of the purification column discharges purified carbon dioxide.

[0030] Preferably, the carbon dioxide purification device further comprises a second electric heater;

[0031] The second electric heater is connected to the non-condensable gas outlet of the purification tower; the gas outlet of the second electric heater is connected to the hot gas inlet of the dryer.

[0032] Preferably, the system further comprises an absorption tower;

[0033] The absorption tower is connected to the hydrogen sulfide gas outlet of the membrane separation device.

[0034] Preferably, the system further comprises a desorption tower;

[0035] The desorption tower is connected to the gas outlet of the absorption tower; the gas discharged from the desorption tower is high-purity hydrogen sulfide gas.

[0036] Preferably, the system further comprises a heat exchanger;

[0037] The heat exchanger is connected to the lean liquid outlet of the regeneration tower;

[0038] The regeneration tower is provided with a steam reboiler.

[0039] The application further provides a method for regenerating hydrogen sulfide and carbon dioxide by using the system described above, comprising the following steps:

[0040] A) The MEDA waste liquid is subjected to lean-liquid rich-liquid heat exchange; the heated rich liquid is heated to 110±5℃ by steam; the salt generated by the reaction of H2S and alcohol amine solution is decomposed to release H2S-containing mixed gas;

[0041] B) After the H2S-containing mixed gas is cooled, it is subjected to membrane separation to obtain hydrogen sulfide gas crude product and carbon dioxide gas crude product.

[0042] Preferably, after obtaining the carbon dioxide gas crude product, the method further comprises purifying the carbon dioxide gas crude product; the specific steps comprise:

[0043] B1) The carbon dioxide gas crude product is mixed with carbon dioxide raw material and vaporized;

[0044] B2) The vaporized carbon dioxide is preheated in a carbon dioxide preheater;

[0045] B3) The preheated carbon dioxide is mixed with oxygen and subjected to heat exchange in a two-stage heat exchanger to 280-350℃;

[0046] B4) The carbon dioxide is heated to 300-350℃ by a first electric heater;

[0047] B5) The carbon dioxide is subjected to dehydrocarbon reaction;

[0048] B6) the product gas after the dehydrocarbon reaction enters the two-stage heat exchanger and the carbon dioxide preheater in turn to exchange heat, and then enters the water cooler to be cooled;

[0049] B7) after drying and filtering, enters the carbon dioxide vaporizer to exchange heat;

[0050] B8) after liquefaction, gas-liquid separation and purification, high-purity carbon dioxide gas is obtained.

[0051] Preferably, after obtaining the hydrogen sulfide gas crude product, the method further comprises: purifying the hydrogen sulfide gas crude product; and the specific steps comprise:

[0052] C1) desulfurizing the hydrogen sulfide gas at 280-360℃ under the condition of zinc oxide;

[0053] C2) resolving the desulfurized hydrogen sulfide gas to obtain high-purity hydrogen sulfide gas.

[0054] The application provides a system for regenerating hydrogen sulfide and carbon dioxide by using MEDA waste liquid, comprising: a MEDA waste liquid tank; a lean- rich liquid heat exchanger connected with the MEDA waste liquid tank; a regeneration tower connected with a rich liquid outlet of the lean- rich liquid heat exchanger; a cooler connected with a gas outlet of the regeneration tower; and a membrane separation device connected with a gas outlet of the cooler; and the membrane separation device is provided with a hydrogen sulfide gas outlet and a carbon dioxide gas outlet. The system and method for regenerating hydrogen sulfide and carbon dioxide by using MEDA waste liquid can remove the dissolved waste gas in MEDA, realize the recycling of MEDA solution, and simultaneously produce high-purity hydrogen sulfide and food-grade carbon dioxide products. BRIEF DESCRIPTION OF DRAWINGS

[0055] Figure 1 A system for regenerating hydrogen sulfide and carbon dioxide by using MEDA waste liquid is provided for an embodiment of the application;

[0056] Figure 2 A structure schematic diagram of a membrane separation device is provided for an embodiment of the application;

[0057] Figure 3 A structure schematic diagram of a carbon dioxide purification device is provided for an embodiment of the application. DETAILED DESCRIPTION

[0058] The technical solutions of the application will be described clearly and completely in combination with the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0059] The application provides a system for regenerating hydrogen sulfide and carbon dioxide by using MEDA waste liquid, comprising:

[0060] a MEDA waste liquid tank;

[0061] a lean- rich liquid heat exchanger connected with the MEDA waste liquid tank;

[0062] a regeneration tower connected with a rich liquid outlet of the lean- rich liquid heat exchanger;

[0063] a cooler connected with a gas outlet of the regeneration tower;

[0064] a membrane separation device connected with a gas outlet of the cooler; the membrane separation device is provided with a hydrogen sulfide gas outlet and a carbon dioxide gas outlet.

[0065] Figure 1 a system diagram for regenerating hydrogen sulfide and carbon dioxide by using MEDA waste liquid provided by an embodiment of the application.

[0066] The system for regenerating hydrogen sulfide and carbon dioxide by using MEDA waste liquid provided by the application comprises a MEDA waste liquid tank. The material, structure and type of the MEDA waste liquid tank are not specially limited in the application, and the MEDA waste liquid tank can store MEDA waste liquid.

[0067] The system for regenerating hydrogen sulfide and carbon dioxide by using MEDA waste liquid provided by the application further comprises a lean- rich liquid heat exchanger connected with the MEDA waste liquid tank. In some embodiments of the application, a waste liquid conveying pump is arranged between the MEDA waste liquid tank and the lean- rich liquid heat exchanger, and is used for conveying the waste liquid in the MEDA waste liquid tank to the lean- rich liquid heat exchanger. The MEDA waste liquid is subjected to heat exchange in the lean- rich liquid heat exchanger. In some embodiments of the application, the waste liquid conveying pump is a centrifugal pump; and the lean- rich liquid heat exchanger is a shell and tube heat exchanger.

[0068] The system for regenerating hydrogen sulfide and carbon dioxide by using MEDA waste liquid provided by the application further comprises a regeneration tower connected with a rich liquid outlet of the lean- rich liquid heat exchanger. The regeneration tower is provided with a steam reboiler. The MEDA waste liquid subjected to heat exchange is heated by the steam reboiler of the regeneration tower, and the mixed acidic gas containing hydrogen sulfide and carbon dioxide in the MEDA rich liquid is discharged from the top of the regeneration tower. The regeneration tower can be any regeneration tower known by those skilled in the art.

[0069] In some embodiments of the application, the system for regenerating hydrogen sulfide and carbon dioxide by using MEDA waste liquid further comprises a heat exchanger. The heat exchanger is connected with a lean liquid outlet of the regeneration tower. The lean liquid from the regeneration tower is cooled by the heat exchanger, and then enters the lean- rich liquid heat exchanger to exchange heat with the MEDA waste liquid in the lean- rich liquid heat exchanger, i.e., to preheat the MEDA waste liquid.

[0070] The system for regenerating hydrogen sulfide and carbon dioxide from MEDA waste liquid also comprises a cooler connected to the gas outlet of the regeneration tower. In some embodiments of the present application, the cooler is a compressor. The separated mixed acid gas of hydrogen sulfide and carbon dioxide is pressurized to 2.5 MPa by the compressor.

[0071] The system for regenerating hydrogen sulfide and carbon dioxide from MEDA waste liquid also comprises a membrane separation device connected to the gas outlet of the cooler; the membrane separation device is provided with a hydrogen sulfide gas outlet and a carbon dioxide gas outlet. The mixed acid gas of hydrogen sulfide and carbon dioxide enters the membrane separation device to realize the separation of hydrogen sulfide gas and carbon dioxide gas.

[0072] In the present application, the membrane separation device can realize the function of permeating hydrogen sulfide molecules and blocking carbon dioxide molecules.

[0073] In some embodiments of the present application, the membrane separation device comprises:

[0074] a membrane assembly;

[0075] A pressure reducing valve is arranged at the inlet of the membrane assembly;

[0076] The membrane assembly is provided with a permeate gas outlet and an exhaust gas outlet; the permeate gas outlet discharges hydrogen sulfide gas, and the exhaust gas outlet discharges carbon dioxide gas.

[0077] Figure 2 The structure diagram of the membrane separation device provided for an embodiment of the present application.

[0078] In the present application, the membrane of the membrane assembly can permeate hydrogen sulfide molecules, but cannot permeate carbon dioxide molecules. The pore size of the membrane of the membrane assembly is 0.6-0.9 nm, the thickness is 1-2 μm, and the working pressure is 0.5-0.7 MPa.

[0079] In some embodiments of the present application, a permeate gas flow meter and a three-way valve are further arranged on the pipeline of the permeate gas outlet of the membrane assembly. They are used to control the exhaust of the permeate gas.

[0080] In some embodiments of the present application, a back pressure valve is further arranged on the pipeline of the exhaust gas outlet of the membrane assembly. It is used to control the exhaust of the exhaust gas.

[0081] In some embodiments of the present application, the membrane separation device is further provided with a protective gas inlet, and a pressure valve is arranged on the pipeline of the protective gas inlet of the membrane separation device, which is used to control the entry of the protective gas into the membrane separation device. The protective gas can be nitrogen.

[0082] The membrane separation device provided by the application can ensure the flux of gas, prevent overpressure of equipment, and reduce energy consumption by the thickness and pore size of the membrane layer. However, the microcrystal morphology of the membrane can make up for the poor selectivity when the flux is large, ensure a large separation factor, and achieve better selectivity and separation effect. The system impurities in the exhaust gas (carbon dioxide gas) are reduced to less than 1%, which basically meets the requirements of industrial-grade carbon dioxide. The permeated gas (hydrogen sulfide gas) is basically free of other impurities (≤0.01%).

[0083] In some embodiments of the application, the system for regenerating hydrogen sulfide and carbon dioxide from MEDA waste liquid further comprises a carbon dioxide purification device; the carbon dioxide purification device is connected to the carbon dioxide gas outlet of the membrane separation device, and is used for purifying carbon dioxide gas, thereby obtaining high-purity carbon dioxide gas (food grade).

[0084] The carbon dioxide purification device comprises:

[0085] A carbon dioxide vaporizer; the carbon dioxide vaporizer is provided with a carbon dioxide raw material inlet and a post-membrane separation carbon dioxide inlet; the post-membrane separation carbon dioxide inlet is connected to the exhaust gas outlet of the membrane separation device;

[0086] A carbon dioxide preheater; the vaporization gas inlet of the carbon dioxide preheater is connected to the vaporization gas outlet of the carbon dioxide vaporizer;

[0087] A mixed gas buffer tank; the preheated gas inlet of the mixed gas buffer tank is connected to the preheated gas outlet of the carbon dioxide preheater; the mixed gas buffer tank is used for mixing oxygen and preheated carbon dioxide;

[0088] A two-stage heat exchanger connected to the gas outlet of the mixed gas buffer tank;

[0089] A first electric heater connected to the hot gas outlet of the two-stage heat exchanger;

[0090] A dehydrogenation reactor connected to the gas outlet of the first electric heater; the gas outlet of the dehydrogenation reactor is connected to the hot gas inlet of the two-stage heat exchanger; the cold gas outlet of the two-stage heat exchanger is connected to the hot gas inlet of the carbon dioxide preheater;

[0091] A water cooler connected to the cold gas outlet of the carbon dioxide preheater;

[0092] A dryer, wherein the cold gas inlet of the dryer is connected to the gas outlet of the water cooler;

[0093] A filter connected to the cold gas outlet of the dryer; the gas outlet of the filter is connected to the filtered gas inlet of the carbon dioxide vaporizer;

[0094] a liquefier connected to the cold gas outlet of the carbon dioxide vaporizer;

[0095] a gas-liquid separator connected to the liquid outlet of the liquefier;

[0096] a purification column connected to the outlet of the gas-liquid separator; the outlet of the purification column discharges purified carbon dioxide.

[0097] Figure 3 A structural schematic diagram of the carbon dioxide purification device provided for an embodiment of the present application.

[0098] In the present application, the carbon dioxide raw material inlet of the carbon dioxide vaporizer is used to input industrial-grade liquid CO2. Specifically, the industrial-grade liquid CO2 coming out of a CO2 storage tank is depressurized to 1.24 MPa / -32℃ through a liquid level control pneumatic valve and then enters the carbon dioxide vaporizer.

[0099] The carbon dioxide vaporizer can be a general commercially available carbon dioxide vaporizer.

[0100] In some embodiments of the present application, the carbon dioxide gas after vaporization enters the carbon dioxide preheater and exchanges heat with the CO2 gas after dehydrocarbon heat exchange, and is preheated to 40℃ / 1.4 MPa.

[0101] The carbon dioxide preheater can be a general commercially available carbon dioxide preheater.

[0102] The mixed gas buffer tank is used for mixing oxygen and preheated carbon dioxide. The buffer tank pressure is controlled at 1.2-1.3 MPa, specifically 1.22 MPa. A buffer tank known to those skilled in the art can be used.

[0103] In some embodiments of the present application, the carbon dioxide purification device further comprises a self-supplying oxygen system. The self-supplying oxygen system comprises a liquid oxygen storage tank, an oxygen temperature control vaporizer and an oxygen buffer tank connected in sequence, and is used to deliver oxygen to the mixed gas buffer tank. The oxygen outlet of the self-supplying oxygen system (i.e. the outlet of the oxygen buffer tank) is connected to the oxygen inlet of the mixed gas buffer tank. Oxygen is used to oxidize carbon monoxide in the gas to carbon dioxide, eliminating carbon monoxide impurities. In the mixed gas buffer tank, the volume ratio of carbon dioxide to oxygen is 2:1.

[0104] The mixed gas discharged from the gas outlet of the mixed gas buffer tank can be pressurized by a compressor and then enter the two-stage heat exchanger. The pressure after pressurization can be 2.5-2.7 MPa, specifically 2.5 MPa.

[0105] In some embodiments of the present application, the two-stage heat exchanger comprises a first-stage heat exchanger and a second-stage heat exchanger. The cold gas inlet of the first-stage heat exchanger is connected to the gas outlet of the mixed gas buffer tank; the cold gas inlet of the second-stage heat exchanger is connected to the hot gas outlet of the first-stage heat exchanger; the hot gas outlet of the second-stage heat exchanger is connected to the first electric heater; the cold gas outlet of the second-stage heat exchanger is connected to the hot gas inlet of the first-stage heat exchanger; and the cold gas outlet of the first-stage heat exchanger is connected to the hot gas inlet of the carbon dioxide preheater. In some embodiments of the present application, the first-stage heat exchanger and the second-stage heat exchanger are heat exchangers known to those skilled in the art, such as shell-and-tube heat exchangers.

[0106]

[0107]

[0108] In some embodiments of the present application, the dehydrocarbon reactor is a gas reactor, which can be commercially available.

[0109] In the present application, the pressurized mixed gas is heated by the two-stage heat exchanger and the dehydrocarbon-purified gas, and the temperature is raised to 280-350℃. The gas is further heated to the working temperature of the catalyst (300-350℃) by the first electric heater, and the deep removal of organic gases such as ethane, propane and propylene is achieved by the dehydrocarbon reactor. Since the impurities in the gas are few, the heat released by the reaction is insufficient to maintain its own heat balance, and the first electric heater is needed to supply heat for the catalytic reaction.

[0110] In some embodiments of the present application, a fine desulfurization reactor is arranged between the first electric heater and the dehydrocarbon reactor. When the sulfide in the mixed gas exceeds the standard, the fine desulfurization reactor is used to deeply remove the sulfur in the gas. The effective recovery of heat is achieved by using a three-stage heat exchanger.

[0111] The fine desulfurization reactor is a desulfurization tower.

[0112] In some embodiments of the present application, the water cooler is a water-cooled cooler, and the dryer is an atmospheric dryer.

[0113] The temperature of the gas from the dehydrocarbon reactor is reduced to 40℃ after heat exchange, preheating and water cooling, and the water is removed to below 20 ppm by the dryer.

[0114] In some embodiments of the present application, the filter is a precision filter.

[0115] The dried CO2 gas is filtered by the precision filter to remove the possible drying agent and catalyst powder.

[0116] ​​The filtered CO2 gas enters a carbon dioxide vaporizer to obtain cold energy from the industrial-grade CO2 raw material, and is further liquefied in a liquefier to obtain CO2 liquid.

[0117] In some embodiments of the present application, the liquefier can be generally commercially available.

[0118] The liquefied CO2 liquid enters a gas-liquid separator.

[0119] The liquid discharged from the gas-liquid separator is transported to a purification column. In some embodiments of the present application, a purification column feed pump is arranged between the gas-liquid separator and the purification column. The liquid discharged from the gas-liquid separator is pumped into the purification column through the purification column feed pump for purification, and food-grade CO2 is obtained from the bottom of the column. Then, after being depressurized to 2.0 MPa, it is stored in a product carbon dioxide storage tank, and then filled into a tank truck or a steel cylinder according to the needs of the user.

[0120] In some embodiments of the present application, the purification column is a rectification column, which can be generally commercially available.

[0121] In some embodiments of the present application, the carbon dioxide purification device further comprises a second electric heater. The second electric heater is connected to the non-condensable gas outlet of the purification column; the gas outlet of the second electric heater is connected to the hot gas inlet of the dryer. The dryer is further provided with a regeneration tail gas outlet, and the discharged gas can be used as regeneration gas and can be discharged.

[0122] In some embodiments of the present application, the system for regenerating hydrogen sulfide and carbon dioxide by using MEDA waste liquid further comprises an absorption tower. The absorption tower is connected to the hydrogen sulfide gas outlet of the membrane separation device. The hydrogen sulfide gas separated by the membrane separation device enters the absorption tower, which can be MEDA lean liquid, specifically, mainly the unused MEDA lean liquid regenerated by the upstream device of the system. The MEDA lean liquid and the hydrogen sulfide gas are reversely contacted to absorb the hydrogen sulfide gas and become rich liquid. In some embodiments of the present application, the absorption tower is a desulfurization tower. In the absorption tower, zinc oxide is used for desulfurization at a medium temperature of 280-360°C to reduce the total sulfur to below 0.1 ppm.

[0123] In some embodiments of the present application, the system for regenerating hydrogen sulfide and carbon dioxide by using MEDA waste liquid further comprises a desorption tower. The desorption tower is connected to the gas outlet of the absorption tower. The gas discharged from the desorption tower is high-purity hydrogen sulfide gas.

[0124] The bottom solution (mainly hydrogen sulfide, MDEA, carbon dioxide, carbon monoxide, hydrocarbons and organic sulfur impurities, etc.) stored in the regeneration tower is heated to 110±5℃ by steam in the reboiler, the salt generated by the reaction of H2S and the alcohol amine solution decomposes to release a mixed gas containing H2S, after the mixed gas containing H2S is released, the solution is desorbed, the MEDA solution is reduced back to the alcohol amine solution, and the solution is cooled through the heat exchanger. The cooled solution can be pumped back to the lean-liquid pump through the lean-liquid pump; or it can be pumped back to the upstream device through the liquid pump. The whole process realizes the purification of H2S through absorption and desorption.

[0125] (HOCH2CH2)2NCH3+H2S→(HOCH2CH2)2CH3NH++SH-(absorption)

[0126] (HOCH2CH2)2CH3NH++SH - →(HOCH2CH2)2NCH3+H2S(desorption)

[0127] In the present application, a small amount of water carried by the raw liquid carbon dioxide and water generated by the dehydrocarbon reaction must be dehumidified and dried before the carbon dioxide is liquefied:

[0128] a. Meet the quality index of water content ≤20ppm of the liquid carbon dioxide product;

[0129] b. Ensure that the carbon dioxide does not block the pipeline and equipment due to the freezing of saturated water in the carbon dioxide gas source at low temperature during the liquefaction and purification process, so that the production cannot continue.

[0130] In order to save energy, fully utilize the residual heat and prolong the operation cycle of the drying agent, the gas after dehydrocarbon is cooled and dehumidified by the dehydrocarbon water cooler, then enters the drying tower, and the trace water in the gas is removed by using the adsorption of the drying agent to the water in the drying tower, so as to ensure that the water content of the dehumidified and dried carbon dioxide raw gas is ≤20ppm. After the drying agent is saturated, it is regenerated by heating to 160℃ using the non-condensable gas at the top of the purification tower and the non-condensable gas in the storage tank, and then it is cooled to room temperature for standby after regeneration is completed. In this way, the drying agent is recycled. The drying tower adopts one standby.

[0131] The present application provides a method for regenerating hydrogen sulfide and carbon dioxide by using the system described above, comprising the following steps:

[0132] A) The MEDA waste liquid is subjected to lean-liquid heat exchange, and the heated rich liquid is heated to 110±5℃ by steam, and the salt generated by the reaction of H2S and the alcohol amine solution decomposes to release a mixed gas containing H2S;

[0133] B) After the mixed gas containing H2S is cooled, membrane separation is carried out to obtain hydrogen sulfide gas crude product and carbon dioxide gas crude product, respectively.

[0134] In step A) :

[0135] In some embodiments of the present application, the temperature of the rich solution after heat exchange with the lean solution is 50-70°C, specifically 60°C.

[0136] In some embodiments of the present application, the heated rich solution is heated to 110°C by steam.

[0137] In some embodiments of the present application, after the decomposition reaction, the obtained lean solution is further subjected to heat exchange and is used in the upstream device.

[0138] In step B) :

[0139] In some embodiments of the present application, the temperature of the H2S-containing gas after cooling is 35-50°C, specifically 40°C.

[0140] In some embodiments of the present application, the purity of the carbon dioxide gas crude product is 99%-99.5%, and the purity of the hydrogen sulfide gas crude product is 95%-99%.

[0141] The carbon dioxide gas crude product after membrane separation mainly contains three types of impurities: one is water (saturated water); two is organic sulfur, a small amount of aldehyde, alcohol, etc., which has a large solubility in liquid carbon dioxide; three is N2, H2, etc.

[0142] After obtaining the carbon dioxide gas crude product, the carbon dioxide gas crude product is further purified.

[0143] The specific steps include:

[0144] B1) The carbon dioxide gas crude product is mixed with carbon dioxide raw material and is vaporized;

[0145] B2) The mixture is preheated in a carbon dioxide preheater;

[0146] B3) The preheated carbon dioxide is mixed with oxygen and is subjected to heat exchange in a two-stage heat exchanger to 280-350°C;

[0147] B4) The mixture is heated to 300-350°C by a first electric heater;

[0148] B5) The mixture is subjected to a dehydrocarbon reaction;

[0149] B6) The product gas after the dehydrocarbon reaction is subjected to heat exchange in the two-stage heat exchanger and the carbon dioxide preheater in sequence, and is then subjected to temperature reduction in a water cooler;

[0150] B7) After drying and filtration, the mixture is subjected to heat exchange in a carbon dioxide vaporizer;

[0151] B8) After liquefaction, the mixture is subjected to gas-liquid separation and purification to obtain high-purity carbon dioxide gas.

[0152] In step B2), the preheating temperature is 30-50°C, specifically 40°C.

[0153] In step B3), before entering the two-stage heat exchanger, the gas is pressurized. The pressure after pressurization is 2.5-2.7 MPa, specifically 2.5 MPa. The gas is then heated to 280°C in the two-stage heat exchanger.

[0154] In step B4), the gas is heated to 330°C by the first electric heater.

[0155] In step B5), the dehydrocarbon reaction is carried out in the presence of a catalyst.

[0156] The catalyst is a dehydrocarbon catalyst containing Pt and / or Pd noble metal, and is subjected to catalytic oxidation with O2 at 260-400°C (as the device operates, the catalyst activity decreases, and the dehydrocarbon temperature needs to be increased) to completely remove non-methane hydrocarbons (such as C2H4, C3H8, C3H6, etc.) and trace amounts of alcohol and aldehyde impurities, ensuring that the total non-methane hydrocarbon content after dehydrocarbon is ≤5 ppm. When the catalytic combustion temperature is low, only part of the methane reacts with oxygen, and through low-temperature distillation in the purification column, the methane content can be ≤20 ppm.

[0157] The reaction equations are as follows:

[0158] 2O2+CH4→CO2+2H2O

[0159] 7O2+2C2H6→4CO2+6H2O

[0160] 5O2+C3H8→3CO2+4H2O

[0161] 9O2+2C3H6→6CO2+6H2O.

[0162] In step B7), the pressure of the dried and filtered carbon dioxide gas is controlled at 2.5-2.7 MPa, such as 2.6 MPa.

[0163] In step B8), the liquefaction temperature is -12 to -9°C, such as -10°C.

[0164] The liquefied cooling medium is liquid ammonia, which evaporates at normal pressure to provide a cooling environment of less than -15°C, thereby liquefying the gaseous carbon dioxide.

[0165] The principle of ammonia cycle refrigeration is that low-pressure gaseous ammonia is compressed to a higher pressure by an ammonia compressor (commonly known as an ice machine), and after oil separation by an oil separator, enters an ammonia cooling condenser, where the gaseous ammonia is condensed into liquid ammonia by water, and is stored in a liquid ammonia storage tank. After pressure reduction by a throttling valve, the liquid ammonia becomes a gas-liquid mixture, the temperature drops, and the gas-liquid mixture enters a liquid ammonia evaporator, where the low-temperature liquid ammonia evaporates into a gas, absorbing heat from the refrigeration object (carbon dioxide gas). The gaseous ammonia after pressure reduction and evaporation enters the ice machine for compression, and the cycle is repeated in the system.

[0166] In some embodiments of the present application, after the purification, the method further comprises heating the produced non-condensable gas and then recycling it to the drying process.

[0167] Generally speaking, the system of the carbon dioxide purification device mainly consists of four basic processes: compression, condensation, throttling expansion and evaporation. Each of the four processes has its own role. Compression: the system does work on the outside, increasing the pressure of ammonia; Condensation: gaseous ammonia is cooled and condensed into liquid ammonia, and heat is discharged to cooling water at a high temperature (e.g. 35℃); Throttling expansion: high-pressure liquid ammonia is reduced in pressure in a throttling valve. Due to the reduction in pressure, the boiling point correspondingly decreases. When the boiling point of the liquid is lower than the temperature at the time, a part of the liquid ammonia will evaporate. When the liquid evaporates, it must absorb heat. However, since the expansion process occurs very quickly, the environment around the throttling valve cannot supply heat in time, so this part of the heat can only be supplied by reducing the internal energy of itself. Therefore, the temperature decreases after throttling, and the expansion becomes a low-temperature gas-liquid mixture; Evaporation: liquid ammonia evaporates into gaseous ammonia, and absorbs heat from the refrigeration object (carbon dioxide gas as the cold energy user) at a low temperature (e.g. -35℃).

[0168] After obtaining the hydrogen sulfide gas crude product, the method further comprises purifying the hydrogen sulfide gas crude product. The specific steps include:

[0169] C1) desulfurizing the hydrogen sulfide gas at 280-360℃ under the condition of zinc oxide;

[0170] C2) resolving the desulfurized hydrogen sulfide gas to obtain high-purity hydrogen sulfide gas.

[0171] In some embodiments of the present application, the desulfurization temperature is 300℃.

[0172] In order to further illustrate the present application, the following embodiments are used to describe in detail a system and method for regenerating hydrogen sulfide and carbon dioxide from MEDA waste liquid provided by the present application, but it should not be understood as limiting the scope of protection of the present application.

[0173] Examples 1-3 (the same steps are repeated three times, respectively denoted as Example 1, Example 2 and Example 3)

[0174] By using the present application Figure 1The system for regenerating hydrogen sulfide and carbon dioxide by using MEDA waste liquid, wherein the membrane separation device adopts the membrane separation device as shown in Figure 2 The carbon dioxide purification device adopts the carbon dioxide purification device as shown in Figure 3 The hydrogen sulfide and carbon dioxide are regenerated.

[0175] The quality of the obtained carbon dioxide product is compared with the national standard, and the result is shown in Table 1.

[0176] Table 1 Comparison of the quality of the food-grade carbon dioxide product of the embodiment of the present application with the national standard

[0177]

[0178]

[0179] The quality of the obtained high-purity hydrogen sulfide product is compared with the national standard, and the result is shown in Table 2.

[0180] Table 2 Comparison of the quality of the high-purity hydrogen sulfide product of the embodiment of the present application with the national standard

[0181]

[0182] The above description of disclosed embodiments enables one skilled in the art to make or use the present application. Numerous modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Therefore, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A system for regenerating hydrogen sulfide and carbon dioxide using MEDA waste liquid, characterized in that, include: MEDA waste liquid tank; A lean-rich liquid heat exchanger connected to the MEDA waste liquid tank; A regeneration tower connected to the rich liquid outlet of the aforementioned rich-lean liquid heat exchanger; A cooler connected to the gas outlet of the regeneration tower; A membrane separation device connected to the gas outlet of the cooler; The membrane separation device includes: a membrane module; a pressure reducing valve is provided at the inlet of the membrane module; the membrane module is provided with a permeate outlet and an exhaust outlet; the permeate outlet discharges hydrogen sulfide gas, and the exhaust outlet discharges carbon dioxide gas. Carbon dioxide purification device; the carbon dioxide purification device includes: A carbon dioxide vaporizer; the carbon dioxide vaporizer is provided with a carbon dioxide feedstock inlet and a post-membrane carbon dioxide inlet; the post-membrane carbon dioxide inlet is connected to the external exhaust outlet of the membrane separation device; A carbon dioxide preheater; the vaporized gas inlet of the carbon dioxide preheater is connected to the vaporized gas outlet of the carbon dioxide vaporizer; A mixed gas buffer tank; the preheated gas inlet of the mixed gas buffer tank is connected to the preheated gas outlet of the carbon dioxide preheater; the mixed gas buffer tank is used for mixing oxygen with preheated carbon dioxide; A two-stage heat exchanger connected to the gas outlet of the mixed gas buffer tank; A first electric heater connected to the hot gas outlet of the two-stage heat exchanger; A dehydrogenation reactor connected to the gas outlet of the first electric heater; the gas outlet of the dehydrogenation reactor connected to the hot gas inlet of the two-stage heat exchanger; the cold gas outlet of the two-stage heat exchanger connected to the hot gas inlet of the carbon dioxide preheater; A water cooler connected to the cold gas outlet of the carbon dioxide preheater; A dryer, wherein the cold gas inlet of the dryer is connected to the gas outlet of the water cooler; A filter connected to the cold gas outlet of the dryer; the gas outlet of the filter is connected to the filtered gas inlet of the carbon dioxide vaporizer; A liquefier connected to the cold gas outlet of the carbon dioxide vaporizer; A gas-liquid separator connected to the liquid outlet of the liquefier; A purification tower is connected to the outlet of the gas-liquid separator; the outlet of the purification tower discharges purified carbon dioxide.

2. The system according to claim 1, characterized in that, The carbon dioxide purification device also includes a second electric heater; The second electric heater is connected to the non-condensable gas outlet of the purification tower; the gas outlet of the second electric heater is connected to the hot gas inlet of the dryer.

3. The system according to claim 1, characterized in that, Also includes: Absorption tower; The absorption tower is connected to the hydrogen sulfide gas outlet of the membrane separation device.

4. The system according to claim 3, characterized in that, Also includes: Analytical tower; The gas outlet of the analytical tower is connected to the gas outlet of the absorption tower; the gas discharged from the analytical tower is high-purity hydrogen sulfide gas.

5. The system according to claim 1, characterized in that, It also includes heat exchangers; The heat exchanger is connected to the lean liquid outlet of the regeneration tower; The regeneration tower is equipped with a steam reboiler.

6. A method for regenerating hydrogen sulfide and carbon dioxide using the system according to any one of claims 1 to 5, comprising the following steps: A) The MEDA waste liquid is subjected to a lean-rich liquid heat exchange. The rich liquid after heating is heated to 110±5℃ with steam. H2S reacts with the salt generated by the alcohol amine solution to release a mixed gas containing H2S. B) After cooling the H2S-containing mixed gas, membrane separation is performed to obtain crude hydrogen sulfide gas and crude carbon dioxide gas, respectively.

7. The method according to claim 6, characterized in that, After obtaining crude carbon dioxide gas, the process further includes: purifying the crude carbon dioxide gas; the specific steps include: B1) The crude carbon dioxide gas and the carbon dioxide raw material are mixed and then vaporized; B2) Preheat in the carbon dioxide preheater; B3) The preheated carbon dioxide is mixed with oxygen and then enters a two-stage heat exchanger to exchange heat to 280~350 ℃; B4) Heated to 300~350℃ by the first electric heater; B5) undergoes a dehydrocarbonization reaction; B6) The product gas after the dehydrogenation reaction enters the two-stage heat exchanger and the carbon dioxide preheater for heat exchange in sequence, and then enters the water cooler for cooling. B7) After drying and filtration, it enters the carbon dioxide vaporizer for heat exchange; B8) After liquefaction, high-purity carbon dioxide gas is obtained through gas-liquid separation and purification.

8. The method according to claim 6, characterized in that, After obtaining crude hydrogen sulfide gas, the process further includes: purifying the crude hydrogen sulfide gas; the specific steps include: C1) The hydrogen sulfide gas is desulfurized under zinc oxide conditions at 280~360℃; C2) The desulfurized hydrogen sulfide gas is analyzed to obtain high-purity hydrogen sulfide gas.

Images