WO2016037494A1

WO2016037494A1 - Method for separating mixed gas by hydrate process

Info

Publication number: WO2016037494A1
Application number: PCT/CN2015/079428
Authority: WO
Inventors: 李小森; 陈朝阳; 夏志明; 徐纯刚; 张郁; 吕秋楠; 颜克凤
Original assignee: 中国科学院广州能源研究所
Priority date: 2014-09-12
Filing date: 2015-05-21
Publication date: 2016-03-17
Also published as: CN104289083A; CN104289083B

Abstract

A method for separating mixed gas by a hydrate process. Gas hydration reaction and gas dissociation are sequentially and alternately carried out in the same reactor, so that the formation heat and decomposition heat of a hydrate are coupled and utilized. The method comprises the following steps: a, preparation of a slurry separation system; b, gas hydration reaction; c, gas dissociation; d, after the gas dissociation ends, the concentration of a promoter, and the content, pressure and temperature of a pure promoter hydrate solid in the slurry of the reactor are restored to the state at the end of step a; and repeating steps b and c to complete separation of a mixed gas hydrate in the next cycle.

Description

Method for separating mixed gas by hydrate method

Technical field:

The invention relates to the field of mixed gas separation technology, in particular to a method for separating mixed gas by a hydrate method.

Background technique:

At present, the mixed gas separation technology is a very common chemical unit process in modern industrial production, and is widely used in various fields of production and life. Common gas separation methods include cryogenic rectification, chemical absorption (adsorption), physical adsorption (absorption), membrane separation, etc., various methods in product purity, separation efficiency, separation energy consumption, equipment investment, operating process, environmental compatibility Each has its own advantages and disadvantages.

Gas hydrate separation technology is a new gas separation technology developed in the past ten years. It is mainly based on the temperature and pressure conditions of different guest molecules to form hydrates. By controlling the temperature and pressure conditions in the hydrate formation process, The hydrate-forming guest component is enriched in the hydrate phase and separated from the other mixture components. Compared with the traditional separation method, the hydrate separation technology has mild separation operation conditions, simple separation process and equipment, clean and environmental protection, no need for pretreatment of gas, strong technical applicability, and high product pressure after separation. In the past ten years, a large number of hydrate gas separation studies have been carried out at home and abroad. The research system involves flue gas (CO ₂ /N ₂ ), IGCC synthesis gas (CO ₂ /H ₂ ) and natural gas (CO ₂ /CH ₄ ). Separation and capture of CO ₂ , coalbed methane (CH ₄ /N ₂ ), biogas (CH ₄ /CO ₂ ), landfill gas (CH ₄ /CO ₂ ) and biomass gas (CH ₄ /H ₂ S) The separation and purification of CH ₄ in the refinery, the desulfurization of the refinery and the light hydrocarbons of the oil field (methane/ethane/propane) and the separation and recovery of hydrogen.

But so far, there is no real industrial application of hydrate gas separation technology at home and abroad. The main reasons are as follows: (1) The gas hydrate separation pressure is relatively high, the equipment investment is large, and the operation cost is high. Although the development of hydrate formation promoters such as tetrabutylammonium bromide (TBAB), tetrahydrofuran (THF), and cyclopentane (CP) can significantly reduce the hydrate separation pressure, the addition of these accelerators can significantly reduce the hydrate storage. The gas volume leads to a decrease in the separation capacity per unit volume of the equipment; more serious is that these accelerator hydrates are formed and decomposed in large quantities, resulting in a large amount of hydrate formation and decomposition heat load, resulting in a significant increase in separation energy consumption. (2) The separation device is difficult to amplify and has high energy consumption. Hydrate separation processes involve hydrate formation heat, decomposition heat, gas-liquid mass transfer, and multiphase flow, which directly affect hydrate separation costs, especially in large separations. Gas, liquid and solid three-phase heat transfer, mass transfer and multiphase flow in the device are difficult. For the rapidly forming hydrate in the separation system, when the hydrate solid amount reaches 30-40% by weight or more of the total hydrate slurry, these fine hydrate-containing slurries are easily gelled, resulting in heat transfer and transmission in the separation system. It is difficult to transport and flow the hydrate slurry; more seriously, these hydrate gels contain 60-70% by weight of aqueous solution, and a large amount of aqueous solution is alternately cooled and heated in the hydrate formation and decomposition system, resulting in separation energy consumption. Significantly increased. Therefore, research and invention of a new gas hydrate separation method, to solve the above-mentioned gas hydrate separation energy consumption, large-scale device heat transfer and flow difficulties and other difficult issues are particularly important and key.

Summary of the invention:

The object of the present invention is to provide a method for separating a mixed gas by a hydrate method with simple separation process and simple equipment, low separation energy consumption and easy industrial amplification, and solves the problem of high energy consumption for gas hydrate separation and difficulty in heat transfer and flow of large devices. problem.

The present invention is achieved by the following technical solutions:

A method for separating a mixed gas by a hydrate method, wherein gas hydration reaction and gas analysis are alternately performed in the same reactor, including the following steps:

a. Separation slurry system preparation: adding an aqueous solution containing an accelerator to the reactor, cooling, forming a pure accelerator hydrate solid, controlling the formation amount of the pure accelerator hydrate solid, and forming a pure accelerator in the final solid-liquid mixed slurry The promoting dose of the hydrate solids and the promoting dose of the dissolution in the slurry reach a predetermined ratio, and the mass concentration of the solid pure accelerator hydrate in the slurry may not exceed 40% by weight;

b. Gas hydration reaction: under the adiabatic heat preservation condition of the reactor, the pre-cooled mixed gas to be separated is introduced into the solid-liquid mixed slurry, and the pressure is increased to increase the pressure in the reactor to the accelerator+gas mixed hydrate. The phase equilibrium pressure is above, and at the same time, the mixed gas to be separated is sufficiently contacted with the above-mentioned solid-liquid mixed slurry, and the hydrate-forming component in the mixed gas to be separated is mixed with the accelerator generating accelerator + gas to mix the hydrate solid, and discharged. The hydrate formation heat raises the temperature of the slurry to above the equilibrium temperature of the pure promoter hydrate phase, so that the pure accelerator hydrate solids in the slurry decompose and absorb heat; the remaining gas is continuously discharged from the top of the reactor; and the intake and exhaust are controlled by The gas rate controls the pressure in the reactor to maintain pressure stability and the continuous progress of the separation process; the promoter + gas mixed hydrate solids are continuously formed in the reactor, and the pure accelerator hydrate solids are continuously decomposed until the pure accelerator hydrate The solid is completely or partially converted into a promoter + gas mixed hydrate solid; the gas entering and exiting the reactor is measured in real time. Difference in volume, determine hydration The amount of accelerator + gas mixed hydrate solids formed during the reaction, thereby controlling the ratio of pure accelerator hydrate solids converted to accelerator + gas mixed hydrate solids;

c. Gas analysis: When the hydration reaction is completed, close the intake and exhaust valves of the reactor, open the hydrate analysis exhaust valve, exhaust and reduce the pressure to the equilibrium pressure of the accelerator + gas mixed hydrate phase to promote The agent + gas mixed hydrate solid decomposes, releasing the gaseous product continuously discharged from the other outlet of the top of the reactor, while absorbing heat during decomposition, causing the temperature to drop below the equilibrium temperature of the pure promoter hydrate phase, and the pure promoter hydrate is formed. The hydrate is released to form heat; the promoter + gas mixed hydrate is continuously decomposed, and the pure accelerator hydrate is continuously formed until the promoter + gas mixed hydrate is completely or partially converted into a pure accelerator hydrate;

d. After the gas analysis is completed, the accelerator concentration in the reactor slurry, the pure accelerator hydrate solid content, the pressure, the temperature, and the like are restored to the state at the end of the step a; the steps b and c are repeated to complete the next round of the mixed gas. Hydrate separation.

In the step b gas hydration reaction, the formation of the accelerator + gas mixed hydrate solid and the decomposition of the pure accelerator hydrate solid are simultaneously coupled in the same slurry system, and the pure accelerator hydrate solid is continuously converted into the accelerator + Gas mixed hydrate solid, using pure accelerator hydrate solid decomposition heat absorption, compensating accelerator + gas mixed hydrate solid heat generation, at the same time, pure accelerator hydrate solid decomposition release accelerator compensation due to accelerator + gas mixed hydration The concentration of the promoter in the solution caused by the formation of the substance is lowered, so that the concentration and temperature of the promoter in the slurry remain substantially unchanged.

This is because the molar generation heat of the pure accelerator hydrate solid and the accelerator + gas mixed hydrate solid is not much different, and the accelerator + gas mixed hydrate solid generates the heat released and the heat absorbed by the pure accelerator hydrate is absorbed into the heat. The coupling is balanced and the temperature in the reactor is always stable. At the same time, the accelerator + gas mixed hydrate solids in the reactor are continuously formed, so that the concentration of the accelerator in the slurry is reduced, and the solid accelerator hydrate solid is continuously decomposed, so that the concentration of the accelerator in the slurry is increased, and the accelerator + gas mixed hydrate is increased. The formation rate of the solid and the pure accelerator hydrate solid decomposition rate are controlled by the coupling of the heat of formation and the heat of decomposition, and the two are basically equivalent, so the concentration of the promoter in the slurry in the reactor is also always in a stable state.

In the step c gas analysis process, the accelerator + gas mixed hydrate solid decomposition and the pure accelerator hydrate solid formation are simultaneously coupled in the same slurry system, and the accelerator + gas mixed hydrate solid is continuously converted into a pure accelerator hydrate. Solid, using pure accelerator hydrate solids to form heat, compensating accelerator + gas mixed hydrate solid decomposition endotherm, accelerator + gas mixed hydrate decomposition and absorption of heat and pure The hydrate generated by the hydrate reaches the heat coupling equilibrium, and the temperature in the reactor is always in a stable state; at the same time, the promoter of the pure accelerator hydrate solid formation compensates for the solid decomposition of the accelerator+gas mixed hydrate. The concentration of the promoter in the solution is increased so that the concentration of the promoter in the solution remains substantially unchanged.

During the gas analysis process of the step c, the promoter + gas mixed hydrate solid in the reactor is continuously decomposed, so that the concentration of the promoter in the slurry is increased, and the solid promoter hydrate solid is continuously generated, so that the concentration of the accelerator in the slurry is reduced. Small, accelerator + gas mixed hydrate solid decomposition and pure accelerator hydrate solids formation rate is controlled by the coupling of its decomposition heat and heat of formation, the two are basically equivalent, so the concentration of the accelerator in the slurry in the reactor is always at stable state.

The reactor may be connected in parallel by two or more hydrate reactors, each of which is switched between the hydration reaction stage and the gas analysis stage to achieve continuous separation of the mixed gas.

The accelerator includes a macromolecular alkane having a liquid state at normal temperature and pressure or a chlorofluorocarbon having a C atom number of at least 5, an oxygen-containing heterocyclic compound dissolved in water, a quaternary ammonium salt, a phosphonium salt, and a phosphonium salt. The accelerator can lower the gas hydrate formation pressure and increase the gas hydrate formation temperature.

The promoter is selected from one of the following or a mixture thereof: cyclopentane, neopentane, cyclohexane, methylcyclopentane, methylcyclohexane, fluorinated cyclopentane, fluorinated neopentane, tetrahydrofuran , 1,4-dioxane, acetone, quaternary ammonium salt, cerium salt, cerium salt.

The quaternary ammonium salt is one of the compounds of the formula (I) or a mixture thereof:

Wherein: R ₁ , R ₂ , R ₃ , R ₄ represent an alkyl group having 1 to 5 carbon atoms, and X ^— represents a halogen ion or a hydroxide ion or a nitrate ion or a phosphate ion or a hydrogencarbonate ion or an acetic acid. Root ion or propionate ion.

The promoter is preferably one of or a mixture thereof: tetrabutylammonium fluoride, tetrabutylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium nitrate, tetrabutylammonium phosphate, tetraisoamyl fluoride Ammonium, tetraisoamylammonium chloride, tetraisoamylammonium bromide, tetrahydrofuran.

The accelerator-containing aqueous solution has a promoter concentration of 5% to 60%, preferably 20% to 40%.

The aqueous solution containing an accelerator may also be added with a conventional gas solubilizing agent or a conventional surfactant such as lauryl sulfate or dodecylsulfonate to increase the gas dissolution rate and the hydration reaction rate.

The predetermined ratio of the promoting dose of the pure accelerator hydrate solid formed in the final solid-liquid mixed slurry in step a to the promoted dose in the slurry is from 0.5 to 2.0, preferably from 0.8 to 1.2.

The separation method of the hydrate mixed gas, in the hydration reaction stage, in order to improve the dispersion effect of the gas in the solution and increase the gas-liquid contact area, the conventional bubbling technique and the jet mixing technique can be applied to the present invention to increase the hydration reaction rate. .

The invention has the following advantages:

(1) The method can realize the coupling and utilization of hydrate formation and decomposition heat. The separation process basically does not require external cooling and heating, and the energy balance of the whole process can be achieved, which can save a lot of energy, and the temperature of the whole separation process and the accelerator in the solution. The concentration remains stable and the separation operation is stable;

(2) The heat transfer in the hydrate formation and decomposition process is carried out at a micro-scale in the slurry system, and the heat transfer efficiency is high, which avoids the defects that the traditional heat exchanger has poor heat transfer effect and the heat transfer equipment is complicated;

(3) The hydration reaction and the analytical reaction are carried out in the same reactor, and the transportation of a large amount of hydrate slurry between the hydration reactor and the analytical reactor is not required in the conventional separation process, thereby saving a large amount of transportation energy;

(4) Large separation capacity, simple hydrate separation solution, low price, no regeneration, no pollution, low gas pretreatment requirements, and strong adaptability;

(5) Compared with the existing refrigeration cycle technology, the invention has the advantages of high coupling utilization efficiency, no additional heat transfer process and equipment, low investment and operation cost, and the like. In summary, the present invention utilizes a pure accelerator hydrate decomposition endothermic coupling accelerator + gas mixed hydrate to generate heat in the gas hydration reaction stage, and the concentration of the compensation accelerator is lowered; in the gas analysis stage, the pure promoter hydrate is used to form thermal coupling promotion. The agent + gas mixed hydrate decomposes the endothermic heat, offsets the increase of the accelerator concentration, automatically achieves the coupling balance of the heat and the concentration of the accelerator in the separation process; realizes the perfect coupling utilization of the hydrate formation and decomposition heat, and the separation process basically does not require external cooling and Heating, the basic energy balance can be achieved in the whole process, the temperature of the separation process and the concentration of the accelerator in the solution remain stable, the separation operation is good, the heat transfer efficiency is high, the hydrate slurry transport is not required, the separation process and equipment are simple, the operation is convenient, and Low consumption, low cost, easy to achieve industrialization and automated production, wide range of applications, not only for flue gas (CO ₂ /N ₂ ), IGCC synthesis gas (CO ₂ /H ₂ ), biomass synthesis gas (CO ₂ / ₂ H), natural gas (CO ₂ / CH _4), coalbed methane gas mixture of CO ₂ industrial continuous separation, but is also applicable to coal Gas (CH ₄ / N _2), methane (CH ₄ / CO _2), landfill gas (CH ₄ / CO ₂₎ gas and the biomass (CH ₄ / H ₂ S) in CH ₄ separation and purification, refinery Separation and purification of light hydrocarbons (methane/ethane/propane) and hydrogen separation and recovery in oil and gas, petrochemical, biochemical, metallurgical and other fields, economic and social benefits Significantly, the future market has broad prospects.

BRIEF DESCRIPTION OF THE DRAWINGS:

1 is a schematic diagram of the principle of heat and mass coupling technology in the separation process of the present invention (taking A+B mixed gas as an example);

_{2 is} a schematic view showing a process flow for separating CO _{2 in a} CO ₂ +H ₂ mixed gas by using tetrabutylammonium bromide as a promoter;

Among them 1, mixed gas pre-cooler, 2, mixed gas intake control valve, 301, 302, intake valve, 401, 402, bubble generator, 5, insulation layer, 6, cooling jacket, 701, 702, slurry Phase zone, 801, 802, gas phase zone, 901, 902, demister, 1001, 1002, CO ₂ gas exhaust gas regulating valve, 1101, 1102, H ₂ gas exhaust gas regulating valve, 1201, 1202, shut-off valve , 1301, 1302, reactor.

detailed description:

The following is a further description of the invention and is not to be construed as limiting.

Example 1: The method for separating mixed gas by the hydrate method, and the principle of internal heat and mass coupling technology in the separation process

As shown in Fig. 1, the A+B mixed gas is taken as an example to illustrate the hydrate phase change and the hydrate formation, the decomposition heat coupling and the accelerator concentration coupling in the separation process of the present invention, and A is a component which is easy to form a hydrate, B. It is difficult to form a component of a hydrate. At the beginning of the hydrate reaction stage, the reactor is a solid-liquid mixed slurry composed of a pure accelerator hydrate solid and an aqueous solution containing an accelerator, and the ratio of the promoted dose of the pure accelerator hydrate solid to the promoted dose dissolved in the slurry may be It is determined by controlling the solid accelerator hydrate solid concentration generated in the solution; when the A+B mixed gas is injected into the reactor for inflation and pressure, the hydrate-forming component A and the accelerator forming accelerator are easily formed in the mixed gas. A mixed hydrate solid, B component which is difficult to form or does not form hydrate is discharged from the top to control the reactor pressure stability; Accelerator + A mixed hydrate solids generate hydrate formation heat, resulting in elevated temperature in the reactor When the temperature rises to pure accelerator hydration At the decomposition temperature of the solid, the pure accelerator hydrate decomposes, releasing the promoter to form a new accelerator + gas mixed hydrate solid, while absorbing heat, promoting +A mixed hydrate formation heat and pure accelerator hydration The decomposition heat of the material reaches the equilibrium of the coupling, and the temperature of the solution is basically unchanged. At the same time, the pure accelerator hydrate is continuously decomposed to compensate for the decrease of the accelerator concentration in the solution caused by the formation of the accelerator + A mixed hydrate, thereby ensuring the concentration of the promoter in the entire hydration reaction stage. The coupling equilibrium is maintained; until the pure accelerator hydrate is fully or partially converted to the accelerator + A mixed hydrate. After the hydration reaction is completed, the intake air is stopped, the exhaust valve is opened, and the exhaust gas is depressurized. The accelerator + A mixed hydrate is decomposed in the reactor to release the A gas, and the decomposition reaction absorbs heat, resulting in a decrease in the temperature inside the reactor, and the pure accelerator hydrates. The formation of matter, the release of hydrate formation heat, the compensation accelerator + A mixed hydrate decomposition heat, the two reach the coupling equilibrium, the solution temperature is basically unchanged; at the same time, the accelerator + A mixed hydrate is continuously decomposed to compensate for the formation of pure accelerator hydrate The resulting concentration of the promoter in the solution is reduced, thereby ensuring that the concentration of the promoter remains in equilibrium throughout the gas analysis stage; until the promoter + A mixed hydrate is fully or partially converted to the pure accelerator hydrate.

Example 2: Separation of feed gas CO ₂ + H ₂

As shown in Fig. 2, the system for separating the mixed gas is composed of two

identical reactors

1301 and 1302 in parallel. In normal operation, one is used as a hydration reactor and the other is used as a gas resolver. To ensure the continuity of the separation process. The raw material gas is a CO ₂ +H ₂ mixed gas (molar percentage of 40 mol% CO ₂ and 60 mol% H ₂ ), and the aqueous solution of the accelerator is used as a mass percentage of 21.5 wt% of tetrabutylammonium bromide (TBAB). ) an aqueous solution. Before the start of separation, a certain amount of 21.5 wt% TBAB solution is injected into the

reactors

1301 and 1302 through the

shutoff valves

1201 and 1202, respectively, and the cooling water inlet and outlet valves of the reactor cooling jacket 6 are opened to cool the TBAB solution in the reactor. Below 280.5K, pure TBAB hydrate solids are formed, and the mass concentration of TBAB hydrate in the slurry is controlled to 30% by weight. At this time, the amount of TBAB of pure TBAB hydrate solids formed in the solid-liquid mixed slurry and the amount of dissolved TBAB in the slurry are obtained. The ratio of 1.0 is closed, and the cooling water inlet and outlet valves of the reactor cooling jacket 6 are closed.

In the following, the reactor 1301 is used as a hydration reactor, and the reactor 1302 is used as a gas analyzer as an example to illustrate the normal separation operation: after the CO ₂ +H ₂ mixed gas is pre-cooled to 281.5 K by the mixed gas precooler 1 mixing the intake air adjusting valve 2 controls the flow of 100mol / h, opening the inlet valve 301 to the reactor was pressurized to 1301 1.5-2.0MPa inflated, while closing the CO ₂ rich gas exhaust valve 1001, open the exhaust gas rich H ₂ The regulating valve 1101 controls the exhaust rate to maintain the pressure of the reactor at 1.5-2.0 MPa. During the aeration process, the mixed gas is dispersed into the fine liquid bubbles through the bubble generator 401 into the slurry region 701, and is sufficiently contacted with the solution to generate TBAB+CO _{2 .} Mixing the hydrate solids, releasing the hydrate formation heat, raising the temperature of the reactor slurry zone 701 to about 282.5K, at which time the pure TBAB hydrate solids in the slurry decomposes and absorbs heat, compensating for the solid formation of the TBAB+CO ₂ mixed hydrate. heat, a reactor such as good heat insulating effect the insulation layer 5, the temperature in the reactor remains substantially constant at about 282.5K, simultaneously, the solid pure hydrate of TBAB TBAB decomposed released into solution by compensating the TBAB + CO ₂ mixture solid dihydrate The resulting solution to reduce the concentration of TBAB in the solution remains substantially constant concentration of TBAB; separation process, difficult to hydrate forming gas H ₂ converge zone 801, a demister 901 after removing mist, H-enriched _{2 The} gas exhaust gas regulating valve 1101 controls continuous discharge, the flow rate of the H ₂ rich gas is 70 mol/h, the molar content of CO _{2 in the} H ₂ -rich gas is 17 mol%, and the molar content of H _{2 is} 83 mol%. As the hydration separation process progresses, the TBAB + CO ₂ mixed hydrate solids are continuously formed, and the pure TBAB hydrate solids are continuously decomposed until the pure TBAB hydrate solids are fully or partially converted into TBAB + CO ₂ mixed hydrate solids.

While the reactor 1301 performs the above hydration reaction, the reactor 1302 switches to perform the CO ₂ analysis reaction. After the last round of hydration reaction is completed in the reactor 1302, the mixed gas intake valve 302 and the H ₂ rich gas exhaust gas regulating valve 1102 are closed, and the mixed gas is stopped by the bubble generator 402 to open the CO ₂ -rich gas exhaust. The regulating valve 1002, the pressure in the exhaust gas pressure reducing reactor 1302 is 0.3 to 0.5 MPa, and the TBAB+CO ₂ mixed hydrate solid in the reactor slurry region 702 is decomposed by pressure reduction, releasing CO ₂ to form CO ₂ bubbles, and collecting. in the top of the reactor gas space 802, in addition to the Mo continuously discharged through a demister 902, the CO ₂ rich exhaust gas control regulating valve 1101, the CO ₂ rich gas flow 30mol / h, CO ₂ -rich gas CO ₂ in mole percent The fractional content is 95 mol%, the H ₂ molar percentage is 5 mol%, and the recovery rate of CO ₂ in the separation process reaches 70%. The absorption heat of decomposition of TBAB+CO ₂ mixed hydrate during solid decomposition causes the solution temperature to decrease from 282.5K to 280.5K. At this time, pure TBAB hydrate solids are formed, and hydrate is released to form thermal compensation TBAB+CO ₂ mixed hydrate solid decomposition. Heat, the two reached a coupling equilibrium, the temperature in the solution remained basically stable; at the same time, the TBAB consumed by the pure TBAB hydrate solids compensated for the increase of the TBAB concentration in the solution due to the solid decomposition of the TBAB+CO ₂ mixed hydrate, so that the solution The concentration of TBAB remained essentially unchanged; the pure TBAB hydrate solids formed continuously, and the TBAB+CO ₂ mixed hydrate solids continued to decompose until the TBAB+CO ₂ mixed hydrate solids were completely or partially converted to pure TBAB hydrate solids.

After the completion of the previous round of separation, the reactor 1301 switches to the gas analysis reaction, and the reactor 1302 switches to perform the hydration reaction, thereby ensuring that the separation process is continuously performed.

Example 3: Separation of raw material gas CO ₂ +H ₂

As shown in Fig. 2, the system for separating the mixed gas is composed of two

identical reactors

1301 and 1302 in parallel. In normal operation, one is used as a hydration reactor and the other is used as a gas resolver. To ensure the continuity of the separation process. The raw material gas is a CO ₂ +H ₂ mixed gas (molar percentage of 40 mol% CO ₂ and 60 mol% H ₂ ), and the accelerator aqueous solution is used as a mass percentage of 20 wt% of tetrabutylammonium bromide (TBAB). Aqueous solution. Before the start of separation, a certain amount of 20 wt% TBAB solution is injected into the

reactors

1301 and 1302 through the

shutoff valves

1201 and 1202, respectively, and the cooling water inlet and outlet valves of the reactor cooling jacket 6 are opened, and the TBAB solution in the reactor is cooled to Below 280K, pure TBAB hydrate solids are formed, and the mass concentration of TBAB hydrate in the slurry is controlled to 40% by weight. At this time, the ratio of the amount of TBAB of pure TBAB hydrate solids formed in the solid-liquid mixed slurry to the amount of dissolved TBAB in the slurry At 1.2, the cooling water inlet and outlet valves of the reactor cooling jacket 6 are closed.

In the following, the reactor 1301 is used as a hydration reactor, and the reactor 1302 is used as a gas analyzer as an example to illustrate the normal separation operation: the CO ₂ +H ₂ mixed gas is pre-cooled to 281 K by the mixed gas precooler 1 and mixed. an intake air regulating valve 2 controls the flow of 100mol / h, opening the inlet valve 301 to the reactor was pressurized to 1301 1.5-2.0MPa inflated, while closing the CO ₂ rich gas exhaust valve 1001, open the enriched H ₂ gas exhaust conditioning The valve 1101 controls the exhaust rate to maintain the pressure of the reactor at 1.5-2.0 MPa. During the aeration process, the mixed gas is dispersed into the fine liquid bubbles through the bubble generator 401 into the slurry region 701, and is sufficiently contacted with the solution to form a TBAB+CO ₂ mixture. The hydrate solids release the hydrate formation heat, and the temperature of the reactor slurry region 701 is raised to about 282K. At this time, the pure TBAB hydrate solid in the slurry decomposes and absorbs heat, and compensates for the solid generation heat of the TBAB+CO ₂ mixed hydrate. For example, the thermal insulation effect of the reactor insulation layer 5 is good, and the temperature in the reactor is basically kept at about 282K. At the same time, the TBAB released from the solid decomposition of the pure TBAB hydrate enters the solution to compensate for the solid formation of the TBAB+CO ₂ mixed hydrate. The concentration of TBAB in the solution is reduced, so that the concentration of TBAB in the solution remains substantially unchanged; during the separation process, H ₂ which is not easy to form hydrate converges in the gas phase region 801, and after removing the water mist through the demister 901, the H ₂ rich gas is obtained. The exhaust gas regulating valve 1101 controls continuous discharge, the flow rate of the H ₂ rich gas is 72 mol/h, the molar content of CO _{2 in the} H ₂ -rich gas is 18 mol%, and the molar content of H _{2 is} 82 mol%. As the hydration separation process progresses, the TBAB + CO ₂ mixed hydrate solids are continuously formed, and the pure TBAB hydrate solids are continuously decomposed until the pure TBAB hydrate solids are fully or partially converted into TBAB + CO ₂ mixed hydrate solids.

While the reactor 1301 performs the above hydration reaction, the reactor 1302 switches to perform the CO ₂ analysis reaction. After the last round of hydration reaction is completed in the reactor 1302, the mixed gas intake valve 302 and the H ₂ rich gas exhaust gas regulating valve 1102 are closed, and the mixed gas is stopped by the bubble generator 402 to open the CO ₂ -rich gas exhaust. The regulating valve 1002, the pressure in the exhaust gas pressure reducing reactor 1302 is 0.3 to 0.5 MPa, and the TBAB+CO ₂ mixed hydrate solid in the reactor slurry region 702 is decomposed by pressure reduction, releasing CO ₂ to form CO ₂ bubbles, and collecting. in the top of the reactor gas space 802, in addition to the Mo continuously discharged through a demister 902, the CO ₂ rich exhaust gas control regulating valve 1101, the CO ₂ rich gas flow 28mol / h, CO ₂ -rich gas CO ₂ in mole percent The fractional content was 96.5 mol%, the H ₂ molar percentage was 3.5 mol%, and the recovery of CO ₂ in the separation process reached 67.6%. The absorption heat of decomposition of TBAB+CO ₂ mixed hydrate during solid decomposition causes the solution temperature to decrease from 282K to 280K. At this time, pure TBAB hydrate solids are formed, and hydrate is released to form thermal compensation TBAB+CO ₂ mixed hydrate solid decomposition heat. The two have reached the coupling equilibrium, and the temperature in the solution is basically stable. At the same time, the TBAB consumed by the pure TBAB hydrate solids compensates for the increase of the TBAB concentration in the solution due to the solid decomposition of the TBAB+CO ₂ mixed hydrate, so that the TBAB in the solution The concentration remained essentially unchanged; the pure TBAB hydrate solids continued to form, and the TBAB + CO ₂ mixed hydrate solids continued to decompose until the TBAB + CO ₂ mixed hydrate solids were fully or partially converted to pure TBAB hydrate solids.

Example 4: Separation of flue gas CO ₂ + N ₂

Separation process and equipment Similar to Figure 2, the system for separating the mixed gas consists of two

identical reactors

1301 and 1302 in parallel. In normal operation, one is used as a hydration reactor and the other is used as a gas analyzer. The two switches to run to ensure the continuity of the separation process. The raw material gas is a CO ₂ +N ₂ mixed gas (molar percentage of 40 mol% CO ₂ and 60 mol% N ₂ ), and the accelerator aqueous solution used is 40 wt% of tetrabutylammonium chloride (TBAC). Aqueous solution. Before the start of separation, a certain amount of 40 wt% TBAC solution is injected into the

reactors

1301 and 1302 through the

shutoff valves

1201 and 1202, respectively, and the cooling water inlet and outlet valves of the reactor cooling jacket 6 are opened, and the TBAC solution in the reactor is cooled to Below 282.5K, a pure TBAC hydrate solid is formed, and the mass concentration of TBAC hydrate in the slurry is controlled to 30% by weight. At this time, the amount of TBAC of pure TBAC hydrate solid formed in the solid-liquid mixed slurry and the amount of TBAC dissolved in the slurry are At a ratio of 0.8, the cooling water inlet and outlet valves of the reactor cooling jacket 6 are closed.

In the following, the reactor 1301 is used as a hydration reactor, and the reactor 1302 is used as a gas analyzer as an example to illustrate the normal separation operation: after the CO ₂ + N ₂ mixed gas is pre-cooled to 282.5 K by the mixed gas precooler 1 The mixed air intake adjusting valve 2 controls the flow rate to be 100 mol/h, opens the intake valve 301 to inflate the reactor 1301 to 1.5-2.0 MPa, and simultaneously closes the CO ₂ rich gas exhaust valve 1001 to open the N ₂ -rich gas exhaust. The regulating valve 1101 controls the exhaust rate to maintain the pressure of the reactor at 1.5-2.0 MPa. During the aeration process, the mixed gas is dispersed into the fine liquid bubbles through the bubble generator 401 into the slurry region 701, and is sufficiently contacted with the solution to form TBAC+CO _{2 .} Mixing the hydrate solids, releasing the hydrate formation heat, raising the temperature of the reactor slurry region 701 to about 284K, at which time the pure TBAC hydrate solids in the slurry decomposes and absorbs heat, compensating for the heat generation of the TBAC+CO ₂ mixed hydrate solids. For example, the thermal insulation effect of the reactor insulation layer 5 is good, and the temperature in the reactor is basically maintained at about 284K. At the same time, the TBAC released by the solid decomposition of the pure TBAC hydrate enters the solution to compensate for the solid formation of the TBAC+CO ₂ mixed hydrate. The concentration of TBAC in the solution is reduced, so that the concentration of TBAC in the solution remains substantially unchanged; during the separation process, N ₂ which is not easy to form hydrate converges in the gas phase region 801, and after removing the water mist through the demister 901, the N ₂ rich The gas exhaust gas regulating valve 1101 controls continuous discharge, the N ₂ -rich gas flow rate is 70 mol/h, the CO ₂ molar percentage in the N ₂ -rich gas is 18.6 mol%, and the N ₂ molar percentage is 81.4 mol%. As the hydration separation process progresses, the TBAC+CO ₂ mixed hydrate solids are continuously formed, and the pure TBAC hydrate solids are continuously decomposed until the pure TBAC hydrate solids are fully or partially converted to the TBAC + CO ₂ mixed hydrate solids.

While the reactor 1301 performs the above hydration reaction, the reactor 1302 switches to perform the CO ₂ analysis reaction. After the last round of hydration reaction is completed in the reactor 1302, the mixed gas intake valve 302 and the N ₂ -rich gas exhaust gas regulating valve 1102 are closed, and the mixed gas is stopped by the bubble generator 402 to open the CO ₂ -rich gas exhaust. The regulating valve 1002, the pressure in the exhaust gas pressure reducing reactor 1302 is 0.3 to 0.5 MPa, and the TBAC+CO ₂ mixed hydrate solid in the reactor slurry region 702 is decomposed by pressure reduction, releasing CO ₂ to form CO ₂ bubbles, and collecting. in the top of the reactor gas space 802, in addition to the Mo continuously discharged through a demister 902, the CO ₂ rich exhaust gas control regulating valve 1101, the CO ₂ rich gas flow 30mol / h, CO ₂ -rich gas CO ₂ in mole percent The fractional content is 90 mol%, the N ₂ molar percentage is 10 mol%, and the recovery rate of CO ₂ in the separation process is 67.5%. The TBAC+CO ₂ mixed hydrate absorbs decomposition heat during solid decomposition, which causes the solution temperature to decrease from 284K to 282.5K. At this time, pure TBAC hydrate solids are formed, and hydrate is released to form thermal compensation TBAC+CO ₂ mixed hydrate solid decomposition heat. The two have reached the coupling equilibrium, and the temperature in the solution is basically stable. At the same time, the TBAC consumed by the pure TBAC hydrate solids compensates for the increase of the concentration of TBAC in the solution caused by the solid decomposition of the TBAC+CO ₂ mixed hydrate, so that the solution is in the solution. The TBAC concentration remained essentially unchanged; pure TBAC hydrate solids were continuously formed and the TBAC + CO ₂ mixed hydrate solids continued to decompose until the TBAC + CO ₂ mixed hydrate solids were fully or partially converted to pure TBAC hydrate solids.

Example 5: Separation and capture of CO ₂ in natural gas (CO ₂ /CH ₄ ), coalbed methane (CH ₄ /N ₂ ), biogas (CH ₄ /CO ₂ ), landfill gas (CH ₄ /CO ₂ ) And separation and purification of CH ₄ in biomass gas (CH ₄ /H ₂ S), refinery gas and oil field light hydrocarbon (methane / ethane / propane) and hydrogen separation and recovery

Referring to Example 2 or 3 or 4, the promoter is selected from one of the following or a mixture thereof: cyclopentane, neopentane, cyclohexane, methylcyclopentane, methylcyclohexane, fluorinated cyclopentane, Fluorinated neopentane, tetrahydrofuran, 1,4-dioxane, acetone, quaternary ammonium salt, cerium salt, cerium salt; the content of the aqueous solution of the promoter varies between 5% and 60%, and all can be obtained well. The separation effect.

The detailed description above is a detailed description of the possible embodiments of the present invention, which is not intended to limit the scope of the invention, and the equivalents and modifications of the present invention should be included in the scope of the patent. in.

Claims

A method for separating a mixed gas by a hydrate method, characterized in that gas hydration reaction and gas analysis are alternately performed in sequence in the same reactor, comprising the following steps:

a. Separation slurry system preparation: adding an aqueous solution containing an accelerator to the reactor, cooling, forming a pure accelerator hydrate solid, controlling the formation amount of the pure accelerator hydrate solid, and forming a pure accelerator in the final solid-liquid mixed slurry The promoting dose of the hydrate solids and the promoting dose of the dissolution in the slurry reach a predetermined ratio; the mass concentration of the solid pure accelerator hydrate in the slurry does not exceed 40% by weight;

b. Gas hydration reaction: under the adiabatic heat preservation condition of the reactor, the pre-cooled mixed gas to be separated is introduced into the solid-liquid mixed slurry, and the pressure is increased to increase the pressure in the reactor to the accelerator+gas mixed hydrate. The phase equilibrium pressure is above, and at the same time, the mixed gas to be separated is sufficiently contacted with the above-mentioned solid-liquid mixed slurry, and the hydrate-forming component in the mixed gas to be separated is mixed with the accelerator generating accelerator + gas to mix the hydrate solid, and discharged. The hydrate formation heat raises the temperature of the slurry to above the equilibrium temperature of the pure promoter hydrate phase, so that the pure accelerator hydrate solids in the slurry decompose and absorb heat; the remaining gas is continuously discharged from the top of the reactor; and the intake and exhaust are controlled by The gas rate controls the pressure in the reactor to maintain pressure stability and the continuous progress of the separation process; the promoter + gas mixed hydrate solids are continuously formed in the reactor, and the pure accelerator hydrate solids are continuously decomposed until the pure accelerator hydrate The solid is completely or partially converted into a promoter + gas mixed hydrate solid;

c. Gas analysis: When the hydration reaction is completed, close the intake and exhaust valves of the reactor, open the hydrate analysis exhaust valve, exhaust and reduce the pressure to the equilibrium pressure of the accelerator + gas mixed hydrate phase to promote The agent + gas mixed hydrate solid decomposes, releasing the gaseous product continuously discharged from the other outlet of the top of the reactor, while absorbing heat during decomposition, causing the temperature to drop below the equilibrium temperature of the pure promoter hydrate phase, and the pure promoter hydrate is formed. The hydrate is released to form heat; the promoter + gas mixed hydrate is continuously decomposed, and the pure accelerator hydrate is continuously formed until the promoter + gas mixed hydrate is completely or partially converted into a pure accelerator hydrate;

d. After the gas analysis is completed, the accelerator concentration in the reactor slurry, the pure accelerator hydrate solid content, the pressure, and the temperature are restored to the state at the end of the step a; the steps b and c are repeated to complete the next round of mixed gas hydrate separation. .
The method for separating a mixed gas by the hydrate method according to claim 1, wherein The reactor may be connected in parallel with two or more reactors, each of which is switched between the hydration reaction stage and the gas analysis stage.
The method for separating a mixed gas by the hydrate method according to claim 1 or 2, wherein the accelerator comprises a macromolecular alkane having a liquid state at normal temperature and normal pressure or a chlorofluorocarbon having a C atom number of at least 5. An oxygen-containing heterocyclic compound dissolved in water, a quaternary ammonium salt, a phosphonium salt, or a phosphonium salt.
The method for separating a mixed gas by the hydrate method according to claim 3, wherein the accelerator is selected from one of the following or a mixture thereof: cyclopentane, neopentane, cyclohexane, methylcyclopentane , methylcyclohexane, fluorinated cyclopentane, fluorinated neopentane, tetrahydrofuran, 1,4-dioxane, acetone, quaternary ammonium salt, phosphonium salt, phosphonium salt, the quaternary ammonium salt is One of the compounds of the formula (I) or a mixture thereof:

Wherein: R 1 , R 2 , R 3 , R 4 represent an alkyl group having 1 to 5 carbon atoms, and X - represents a halogen ion or a hydroxide ion or a nitrate ion or a phosphate ion or a hydrogencarbonate ion or an acetic acid Root ion or propionate ion.
The method for separating a mixed gas by the hydrate method according to claim 4, which is characterized by being selected from one of the following or a mixture thereof: tetrabutylammonium fluoride, tetrabutylammonium chloride, tetrabutylammonium bromide, Tetrabutylammonium nitrate, tetrabutylammonium phosphate, tetraisoamyl ammonium fluoride, tetraisoamyl ammonium chloride, tetraisoamylammonium bromide, tetrahydrofuran.
The method for separating a mixed gas by the hydrate method according to claim 1 or 2, wherein the accelerator-containing aqueous solution has a promoter concentration of 5% to 60% by mass.
The method for separating a mixed gas by the hydrate method according to claim 6, wherein the accelerator-containing aqueous solution has a promoter concentration of 20% to 40% by mass.
The method for separating a mixed gas by the hydrate method according to claim 1 or 2, wherein the aqueous solution containing an accelerator is added with a conventional gas solubilizing agent or a conventional surfactant.
The method for separating a mixed gas by the hydrate method according to claim 1 or 2, wherein in the final solid-liquid mixed slurry in the step a, a promoting amount of the pure promoter hydrate solid is formed and the slurry is dissolved in the slurry. The predetermined ratio of the promoted dose of the solution is from 0.5 to 2.0.
The method for separating a mixed gas by the hydrate method according to claim 9, wherein a predetermined ratio of a promoting dose of the pure accelerator hydrate solid to the promoted dose of the dissolved solid in the final solid-liquid mixed slurry in the step a is It is 0.8 to 1.2.