CN113209779B - Solvent/hydration combined gas separation process without pressurization - Google Patents
Solvent/hydration combined gas separation process without pressurization Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
- B01D53/1456—Removing acid components
- B01D53/1475—Removing carbon dioxide
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
- B01D53/1418—Recovery of products
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
- B01D53/1425—Regeneration of liquid absorbents
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
- B01D53/18—Absorbing units; Liquid distributors therefor
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L3/00—Gaseous fuels; Natural gas; Synthetic natural gas obtained by processes not covered by subclass C10G, C10K; Liquefied petroleum gas
- C10L3/06—Natural gas; Synthetic natural gas obtained by processes not covered by C10G, C10K3/02 or C10K3/04
- C10L3/10—Working-up natural gas or synthetic natural gas
- C10L3/101—Removal of contaminants
- C10L3/102—Removal of contaminants of acid contaminants
- C10L3/104—Carbon dioxide
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L3/00—Gaseous fuels; Natural gas; Synthetic natural gas obtained by processes not covered by subclass C10G, C10K; Liquefied petroleum gas
- C10L3/06—Natural gas; Synthetic natural gas obtained by processes not covered by C10G, C10K3/02 or C10K3/04
- C10L3/10—Working-up natural gas or synthetic natural gas
- C10L3/108—Production of gas hydrates
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
- Y02C20/00—Capture or disposal of greenhouse gases
- Y02C20/40—Capture or disposal of greenhouse gases of CO2
Abstract
The invention discloses a solvent/hydration combined gas separation process and a system without pressurization. Under the condition of no need of pressurization, the method can realize the recovery of acid gas and separate and produce methane-rich gas meeting the power generation standard, and organically combine the environmental management and the waste gas recycling process. Compared with the prior art, the process and the system can economically and efficiently treat CO 2 High concentration recovery and CH achievement 4 And N 2 The high-efficiency separation of the process has the advantages that the energy in the process is reasonably utilized, and the energy consumption is greatly reduced; the whole process is environment-friendly and reliable, and has good economic benefit.
Description
Technical Field
The invention relates to the technical field of gas separation, in particular to a solvent/hydration combined gas separation process and system without pressurization, and especially relates to CO 2 The capture and the resource recycling of pollutants.
Background
The application of the thermal oil recovery method technology makes an important contribution to realizing high and stable yield of the thick oil, but also causes some adverse factors, such as the appearance of a large amount of secondary gas. Because the secondary gas contains a large amount of N 2 、CO 2 And the secondary gas cannot be directly utilized, other processes can be affected due to improper treatment, and energy waste and environmental pollution can be caused due to direct discharge, so that the significance of harmless treatment of the secondary gas is great. If also useful gas components such as CO can be recovered therefrom 2 And CH 4 When CO is present 2 When reaching a certain concentration, the oil can be used as the oil displacement gas to be injected back into the well for oil displacement, and when CH is generated 4 The enrichment to a certain concentration can be used for generating electricity or used for other purposes.
Currently, pressure swing adsorption and adsorption/cryogenic rectification are the primary methods for recovering CH in the separation of such gases 4 With CO 2 The process of (1). In order to realize the separation of the three gas components, the Pressure Swing Adsorption (PSA) process utilizes the difference of the adsorption capacity of the gas components on different adsorption materials to realize the separation of the components, and the pressure swing adsorption process in the actual operation process needs at least nine steps, namely: a final pressure increasing process, an adsorption process, a forward pressure reducing process, an even pressure reducing process, a reverse pressure reducing process, a flushing regeneration process, a vacuumizing process, an even pressure increasing process and a replacement process. The single adsorption tower is intermittent operation, and in order to make the operation of the pressure swing adsorption process smoother and continuous, the pressure swing adsorption operation must be more than 2 pressure swing adsorption towers, and the more the number of the adsorption towers, the more stable and continuous the operation.
The low-temperature rectification method is characterized in that raw material gas enters a rectification tower after being pressurized and cooled to the temperature of saturated liquid, vapor-liquid contact is carried out for multiple times in each tower plate or filler by utilizing the boiling point difference of different gas components to realize gas separation, more volatile components are evaporated when heat is absorbed, and more difficultly volatile components are condensed when mixed steam absorbs cold, so that separation is realized.
However, in the actual operation process, the pressure swing adsorption method has low investment relative to the low temperature rectification method, the operation is simple, the treatment cost is low, and the method is widely applied, but in the actual application, repeated pressurization and depressurization are needed, the process energy consumption is high, and the adsorbent is sensitive to heavy hydrocarbon, water and other components in the raw material gas, and the adsorption performance of the adsorbent can be reduced after long-term use, so that the water component and the heavy hydrocarbon component in the raw material gas need to be fully removed to ensure the normal operation of the adsorbent in the pressure swing adsorption method which is widely used at present, however, the energy consumption of raw material gas dehydration is very high, and the operation is not convenient.
Hydrate gas separation technique using the temperature at which different gases form hydratesThe pressure conditions are different. During the hydration separation process in the mixed gas, the molecules which are easy to generate hydrate preferentially enter the hydrate phase, the enrichment degree of the molecules in the hydrate phase is gradually increased along with the time, and the concentration of the molecules in the residual gas phase is gradually reduced, so that the gas mixture entering the hydration system is separated from the gas phase in the hydration phase. For fireflooding oilfield gas, the main raw material component is CH 4 、CO 2 And N 2 While for the sII type hydrate, CH, formed by the mixed gas of the three-component gas in a pure water system 4 With CO 2 Occupying a small cage, N 2 Occupying a large cage, and if the three components need to be separated in a hydrate method, the required flow is very complicated and difficult to realize. But CO 2 Easily soluble in alcohol amine solution (MEA, MDEA, etc.) by adding CO 2 Removing by flux method to leave CH which is easy to separate by hydration 4 And N 2 。
At present, the recovery of fireflood oilfield gas is mainly characterized in that no related new process patent is available for recovering and treating oilfield secondary gas, only CN 203750379U provides a new loading and unloading device on adsorption tower equipment in a process of recovering oilfield associated gas by a pressure swing adsorption method, and the operation design optimization is carried out on a unit (adsorption tower) in the traditional pressure swing adsorption.
In addition, CN 108722135A which is an invention for utilizing a hydration method for acid gas recovery adopts a hydration method to separate CO 2 And H 2 The solvent is further removed after the mixed acid gas of S, the method may have process leak, the decomposed hydrate is low pressure (< 0.2 MPa), the hydrate enters into a high-pressure absorption tower without pressurization treatment, and the solvent for absorption adopts conventional alcohol amine solution, so the absorption effect may not be ideal in practical application. Especially, as the development of new unconventional energy sources is well progressed, the supply of energy markets is greatly enriched, and the exploitation economy of thick oil becomes more important, new economic recovery processes need to be explored for the recovery of secondary gas in oil fields. In this patent, CH is used to realize the actual operation of oil field 4 With CO 2 To reduce gas separation and recovery operationsAs a cost of implementation, a solvent/hydration combination process and system is proposed that does not require pressurization.
Disclosure of Invention
In order to make up the defects of the prior art, the invention provides a solvent/hydration combined gas separation process and a system without pressurization, which can realize full CO utilization by a solvent method 2 While recovering, the economic and energy-saving hydrate method is utilized to separate CH meeting the power generation requirement of the gas turbine 4 The gas integrates the concept of energy conservation and emission reduction into the chemical production process. Compared with the prior art, the process and the system can economically and efficiently carry out CO-containing treatment in a system without pressurization 2 、N 2 And CH 4 The secondary gas of the oil field is recycled, so that the energy in the process is reasonably utilized, and the energy consumption is greatly reduced; the whole process is environment-friendly and reliable, and has good economic benefit.
The technical scheme of the invention is as follows.
A pressurization-free solvent/hydration combined gas separation process is characterized in that a gas phase discharged from the top of a solvent absorption tower can reach the pressure condition of a hydration reaction without pressurization after heat exchange of a gas cooler and pressure regulation of a throttle valve; solvent/water in the present invention means solvent absorption and hydration separation.
The method comprises the following specific steps: the separation device is adopted to carry out the solvent/hydration combined gas separation process without pressurization, and the solvent absorption method is adopted to remove CO 2 Cooling the raw material gas from the top of the solvent absorption tower to the hydration reaction temperature by a gas cooler, regulating the pressure by a throttle valve, then feeding the raw material gas into a hydration reactor, cooling the raw material gas and the accelerator solution decomposed by a hydration decomposer by an additive cooler, and then performing the hydration reaction, wherein the main gas phase component participating in the hydration reaction is CH 4 The component remaining in the gas phase being mainly N 2 The hydrate slurry is pumped to a hydrate decomposer, and the decomposed product is subjected to gas-liquid separation in the hydrate decomposer, so that rich CH is separated 4 The gas is used for generating electricity or other purposes, the liquid is an accelerator solution and is added with additivesAfter being cooled by the cooler, the cooled mixture is circulated back to the hydrate reactor to participate in the hydration reaction, and the subsequent CH is separated without pressurization compared with the traditional pressure swing adsorption 4 And N 2 In other words, the separation operation can be carried out directly without repressurization to the adsorption pressure.
Further, the separation device comprises a solvent absorption tower, a solvent regeneration tower, a hydration reactor, a hydrate decomposer, a solvent cooler, a lean liquid pump, a rich liquid pump, a lean/rich liquid heat exchanger, a reboiler, a gas cooler, a throttle valve, a hydrate slurry pump and an additive cooler;
further, the solvent absorption tower is respectively connected with a gas cooler, a solvent cooler, a rich liquid pump and a pretreated fireflood oilfield gas pipeline; the top of the solvent regeneration tower is divided into two parts, one part is connected with the heat exchange part of the hydration decomposer, the other part is connected with the lean/rich liquid heat exchanger, the two parts of the bottom of the solvent regeneration tower are connected with one part of the lean/rich liquid heat exchanger, and the other part is connected with the reboiler and circulated back into the solvent regeneration tower; the gas cooler is connected with the hydrate reactor;
further, the hydrate reactor is respectively connected with a slurry circulating pump and an additive cooler;
further, the bottom of the hydrate decomposer is respectively connected with a solvent regeneration tower, a slurry circulating pump and an additive cooler;
further, the solvent cooler is respectively connected with the solvent absorption tower and the barren liquid pump; the lean liquid pump is respectively connected with the solvent cooler and the lean/rich liquid heat exchanger; the rich liquid pump is respectively connected with the solvent absorption tower and the lean/rich liquid heat exchanger; the lean/rich liquid heat exchanger is respectively connected with a tower top feeding plate, a lean liquid pump and a rich liquid pump at the bottom of the solvent regeneration tower; the reboiler is connected with the bottom of the solvent regeneration tower; the hydrate slurry pump is respectively connected with the hydration reactor and the hydrate decomposer; the additive cooler is respectively connected with the hydration reactor and the hydrate decomposer.
Further, the pressure of the solvent absorption tower is 0.6MPa-2MPa, and preferably 1.2MPa; the 1.2MPa pressure is chosen here because the subsequent hydration reaction is facilitated by the increased absorption pressure, which takes into account the 600kPa pressure of the subsequent hydration reaction, in order to avoid additional pressurization and heat exchange of the system. The hydration reactor pressure is between 0.7MPa and 1.3MPa, preferably 0.8MPa.
Further, the pre-treated fireflood oilfield gas line needs to be fed from the bottom of the solvent absorption tower so as to ensure that the gas is fully contacted with the lean solution.
Further, the solvent absorption tower is a vapor-liquid mass transfer device and is selected from a plate tower and a packed tower; preferably selecting a plate tower, wherein a liquid distributor is arranged at the top of the tower for spraying, and a liquid redistributor is arranged in the middle of the tower for strengthening mass transfer; the solvent absorption tower is a vapor-liquid mass transfer device, particularly a plate tower and a packed tower, preferably the plate tower, the top of the tower is sprayed with a liquid device, and the middle of the tower is provided with a liquid redistributor to strengthen mass transfer. The vapor-liquid ratio of the solvent absorption tower is 3-60, preferably 5.8, the loss of the gas phase carried out from the top of the solvent absorption tower is related to the vapor-liquid ratio and the temperature during absorption, and the larger vapor-liquid ratio is not considered to be suitable for reducing the part of liquid carried out by gas.
Furthermore, the solvent regeneration tower is a vapor-liquid mass transfer device, particularly a plate tower and a packed tower, the plate tower is preferably convenient to maintain and disassemble, and instruments for monitoring the temperature are arranged at feeding and discharging tower plates. The gas phase discharged from the top of the solvent regeneration tower is a high-temperature material flow and is used for providing heat for the hydration decomposition of the hydrate decomposer, the material flow providing a heat source is not limited to the material flow at the top of the solvent regeneration tower, preferably the hot material flow at the top of the solvent regeneration tower, the heat source for the hydration thermal decomposition can be derived from the waste heat of lean liquid after heat exchange with rich liquid, normal-temperature air is used as a hydration decomposition heat source, and the like, if the material flow is placed in a more complex upstream and downstream system, the decomposition heat can be derived from hot material flows in other processes, the temperature of the hot material flow flowing out from the top of the tower is about 120 ℃, and after heat exchange with low-temperature hydrate in the hydrate decomposer, the moisture in the hot material flow is condensed and recovered.
Further, the gas cooler is connected with a gas phase at the top of the solvent absorption tower and a throttle valve feeding hole; the throttle valve is respectively connected with the feeding port of the hydration reactor and the gas cooler.
Furthermore, the hydrate reactor is provided with an additional additive feeding port to supplement the loss of the additive brought out by the gas phase in the operation process, wherein the loss brought out by the additive feeding port is small, the main component of the additive feeding port is free water, the system cannot be greatly influenced in the short-time operation, and the additive feeding port needs to be intermittently supplemented with the additive in the long-time operation process.
The hydrate reactor contains a small amount of water in the gas phase discharge at the top of the absorption tower, however, in the hydrate reaction system, water is one of raw materials for forming hydrate, and the water serving as trace water does not influence the gas phase feed serving as the hydration reaction, for example, in other separation systems, such as pressure swing adsorption method, low temperature rectification method and other processes, the operation can be greatly influenced by the content of the trace water, for example, the effective adsorption of the gas phase on the adsorbent can be reduced by the increase of the water component in the pressure swing adsorption, and even the adsorbent loses the adsorption effect; in cryogenic rectification, because of the high freezing point of water (0 degrees centigrade), water forms ice when other gas components are separated by cooling, and heat and mass transfer of the fluid is hindered because of the temperature below 0 degrees centigrade.
Further, the tower top removed CO through the solvent absorption tower 2 Gas and regenerated CO-rich 2 The gas contains a small amount of moisture which is carried out by the gas and needs to be analysed for consideration when entering the next hydrate reactor.
Further, the heat transfer component inside the hydrate decomposer should be a device with high heat transfer efficiency, specifically a finned heat exchange assembly, a threaded pipe heat exchanger or a coil heat exchanger, preferably a finned coil heat exchanger, so that a gas phase heat source is not considered to be directly used to improve the gas release effect, firstly, a harmless high-temperature gas source is lacked, and secondly, the released gas needs to be utilized, the use of the gas stripping scheme of the patent such as CN 08722135A can indeed reduce the partial pressure of the released gas, accelerate the decomposition but other introduced sources are not beneficial to subsequent operation, and in addition, the gas can also reduce the partial pressure of water, so that the water content in the gas is improved, and the subsequent operation is not beneficial.
Further, a hydrate slurry pump or other conveying devices are arranged between the outlet part of the bottom of the hydrate reactor and the inlet of the hydrate decomposer, wherein the hydrate slurry pump is a preferable solid-liquid fluid conveying device.
Furthermore, more than one heat exchanger device is arranged between the inlet part of the hydrate reactor circulating additive and the outlet of the hydrate decomposer to cool the decomposed accelerator solution, wherein in order to reduce the energy consumption of the system and not use a cold source generated in public works, air cooling, circulating cooling water utilization or air cooling and water cooling combination is recommended to further cool the circulating barren solution.
The hydrate additive is an aqueous solution of a quaternary ammonium salt or an aromatic compound, and specifically may be a solution of an additive such as Tetrahydrofuran (THF) solution, tetrabromobutylammonium bromide (TBAB) solution, tea polyphenol, catechin, isooctyl glucoside, or cyclopentane, and water.
Compared with the prior art, the invention has the advantages that:
1) The quantity of equipment is reduced, and in order to realize the continuous stable output of adsorbed gas, the device quantity of present pressure swing adsorption technology is 10 molecular sieve adsorption towers, and contains many corollary equipment such as vacuum pump and booster compressor, and the device is various.
2) Compared with the pressure swing adsorption process widely applied at present, particularly the hydrate method separation step, the energy consumption of binary gas separation is reduced.
3) The investment of the whole system is lower than that of the pressure swing adsorption process.
Drawings
FIG. 1 is a schematic diagram of a solvent/hydrate combination gas separation process and system flow provided by the present invention.
The components in the figures are numbered: 1. the system comprises a solvent regeneration tower 2, a hydration reactor 3, a hydrate decomposer 4, a solvent cooler 5, a lean liquid pump 6, a rich liquid pump 7, a lean/rich liquid heat exchanger 8, a reboiler 9, a gas cooler 10, a throttle valve 11, a hydrate slurry pump 12 and an additive cooler 13.
Detailed Description
The solvent/hydrate combination gas separation process and system of the present invention will be described in detail with reference to the accompanying drawings, which are not intended to limit the invention.
The invention provides a solvent/hydration combined gas separation process, which comprises a solvent absorption tower 1, a solvent regeneration tower 2, a hydration reactor 3, a hydrate decomposer 4, a solvent cooler 5, a lean solution pump 6, a rich solution pump 7, a lean/rich solution heat exchanger 8, a reboiler 9, a gas cooler 10, a throttle valve 11, a hydrate slurry pump 12 and an additive cooler 13. The solvent absorption tower 1 is respectively connected with a gas cooler 10, a rich liquid pump 7 and a pretreated fireflood oilfield gas pipeline; the top of the solvent regeneration tower 2 is divided into two parts, one part is connected with a heat exchange part of the hydration decomposer, the other part is connected with a lean/rich liquid heat exchanger 8, the two parts of the bottom of the solvent regeneration tower 2 are connected with one part of the lean/rich liquid heat exchanger 8, and the other part is connected with a reboiler 9 and circulates back into the solvent regeneration tower 2; the hydrate reactor 3 is respectively connected with a throttle valve 11, a slurry circulating pump 12 and an additive cooler 13; the bottom of the hydrate decomposer 4 is respectively connected with the solvent regeneration tower 2, the slurry circulating pump 12 and the additive cooler 13; the solvent cooler 5 is respectively connected with the solvent absorption tower 1 and the barren liquor pump 6; the lean liquid pump 6 is respectively connected with the solvent cooler 5 and the lean/rich liquid heat exchanger 8; the rich liquid pump 7 is respectively connected with the solvent absorption tower 1 and the lean/rich liquid heat exchanger 8; the lean/rich liquid heat exchanger 8 is respectively connected with the tower bottom of the solvent regeneration tower 2 and the tower top feeding plate, the lean liquid pump 6 and the rich liquid pump 7; the reboiler 9 is connected with the bottom of the solvent regeneration tower 2; the gas cooler 10 is connected with a gas phase at the top of the solvent absorption tower 1 and a feed inlet of a throttle valve 11; the throttle valve 11 is respectively connected with a feed inlet of the hydration reactor 3 and the gas cooler 10; the hydrate slurry pump 12 is respectively connected with the hydration reactor 3 and the hydrate decomposer 4; the additive cooler 13 is connected to the hydration reactor 3 and the hydrate decomposer 4, respectively.
The flow in the solvent/hydration combined gas separation process of the present invention can be divided into two sections, a solvent absorption section and a hydration separation section, which are specifically described as follows: the fireflood oilfield gas from the pre-treatment (without dehydration) enters the solvent absorption tower 1 and passes through the barren liquor pump 6The lean solution after heat exchange in the pressurizing and solvent cooler 5 is in gas-liquid contact in a countercurrent manner in the solvent absorption tower 1, so that CO in the raw material gas 2 Contact with solvent to remove CO 2 Cooling the raw material gas from the top of the solvent absorption tower 1 through a gas cooler 10 to the hydration reaction temperature, regulating the pressure through a throttle valve 11, then feeding the raw material gas into a hydration reactor 3, cooling the accelerator solution decomposed by a hydration decomposer 4 through an additive cooler 13, and then carrying out the hydration reaction, wherein the main gas phase component participating in the hydration reaction is CH 4 The component remaining in the gas phase being mainly N 2 Can be directly discharged after reaching the standard or collected for other uses, the other gases and the accelerant solution form hydrate slurry after hydration reaction, the hydrate slurry is sent to the hydrate decomposer 4 through the hydrate slurry pump 12, the decomposed product is subjected to gas-liquid separation in the hydrate decomposer 4, thereby separating out rich CH 4 The gas is used for power generation or other purposes, and the liquid is an accelerant solution which is cooled by the additive cooler 13 and then circulated back to the hydrate reactor to participate in the hydration reaction. Absorb CO 2 The rich solution is delivered to a lean/rich solution heat exchanger 8 through a rich solution pump 7, exchanges heat with the lean solution regenerated in the solvent regeneration tower 2 and then enters the upper part of the solvent regeneration tower 2, and the rich solution is separated into rich CH in the regeneration tower 2 after absorbing the heat provided by a reboiler 4 The gas and the high-temperature barren solution, the high-temperature barren solution exchanges heat with the rich solution pumped by the rich solution pump 7 through the barren/rich solution heat exchanger 8, and then the barren solution is conveyed to the solvent cooler 5 through the barren solution pump to be cooled and then enters the solvent absorption tower 1.
Example 1
Certain fireflood oilfield gas pretreatment exploitation gas quantity Q =1000Nm 3 H, pressure 1.2MPa, wherein CH 4 Volume fraction of 11.6%, CO 2 Volume fraction of 15.8% and N 2 The volume fraction was 72.6%, and the three component gas was treated using the treatment system shown in fig. 1. The hydrate decomposer is internally provided with a coil pipe to increase the heat exchange area of the hot material flow and the hydrate slurry, and the coil pipe is provided with fins to increase the heat transfer coefficient to improve the decomposition effect of the hydrate slurry.
The operating conditions and treatment effects during the treatment were as follows: the operating conditions of the solvent absorption tower are as follows: at 40 deg.C and 1.2MPaThe steam ratio was 4.5, the number on the trays was 20, the trays being a common sieve tray column. The operating conditions of the solvent regeneration tower are as follows: the temperature is 120 ℃, the pressure is 0.2MPa, the number of the tower plates is 20, and the tower plates are sieve plate towers. The gas phase discharge at the top of the solvent regeneration column is 96.82% CO 2 CO of the entire absorption System 2 The recovery rate is up to 96%, and the oil can be directly pressurized and injected back into the oil field to displace oil after the pressurization and dehydration operation. The operating conditions of the hydrate reactor are: the temperature is 5 ℃, the pressure is 1.1MPa, the hydrate accelerant is THF with the molar content of 6 percent, and the circulating volume of the accelerant solution is 164.6m 3 H, in a hydrated system containing THF, CH 4 Hydrates with THF are more likely to form. The gas component at the top of the solution absorption tower is CH 4 13.7％，N 2 The content is 85.6 percent and a small amount of CO 2 The hydrate slurry after the hydration reaction is conveyed to a hydrate decomposer, and the operating conditions of the hydrate decomposer are as follows: the temperature is 20 ℃, the pressure is 0.2MPa, and the heat source for decomposition is rich in CO from a solvent regeneration tower 2 Gas phase, flow rate 164.6Nm 3 H, gas phase discharge CH at the top of the hydrate decomposer 4 Concentration 33.91%, N 2 The concentration was 65.92%. The separated methane-rich gas can meet the lowest heat value of the gas turbine power generation gas, the secondary gas of the fire-driving oil field which is directly combusted is utilized and converted into electric energy, and simultaneously, the high-purity CO recovered by a solvent method is utilized 2 And the oil is recycled to the production gas well to be used as production oil displacement.
The gas phase at the top of the regeneration tower is used as the heat source of the hydrate decomposer, so that the process reduces the need of a condenser at the top of the regeneration tower to recover liquid carried by the gas phase compared with the traditional regeneration tower, and the hydrate decomposer plays a role in condensing the gas phase at the top of the regeneration tower.
The three gases separated are shown in table 1: wherein is rich in CO 2 The gas is the molar concentration composition of gas phase discharge at the top of the regeneration tower and is rich in CH 4 Gas is a gas dry-based molar composition enriched in a hydrate phase and is N-rich 2 The gas is the gas phase which flows out from the top of the hydrate reactor and does not participate in the hydration reaction. Unit CO of solvent absorption method 2 The recovery energy consumption is 8.428kWh kmol -1 Unit CH of hydrate method 4 The recovery energy consumption is 8.850kWh kmol -1 Compared with the pressure swing adsorption system for separating the three components by activated carbon adsorption, the total energy consumption of the pressure swing adsorption system is about 86 percent, but the energy consumption can be reduced by the novel adsorbent.
Table 1 table of molar concentrations of three-component gases separated in example 1
Example 2
The same feed gas composition as in example 1, the operating conditions for the solvent absorber column were: the temperature is 40 ℃, the pressure is 1.2MPa, the liquid-vapor ratio is 4.5, the number of the tower plates is 20, and the tower plates are common sieve plate towers. The operating conditions of the solvent regeneration tower are as follows: the temperature is 120 ℃, the pressure is 0.2MPa, the number of the tower plates is 20, and the tower plates are sieve plate towers. The gas phase discharge at the top of the solvent regeneration column is 96.82% CO 2 CO of the entire absorption System 2 The recovery rate is up to 96%, and the oil can be directly pressurized and injected back into the oil field to displace oil after the pressurization and dehydration operation. The difference is that a pure water system without an accelerant is adopted in a hydrate reactor for hydration reaction, the hydration pressure is 7MPa, the temperature is 2 ℃, and the circulation quantity of an aqueous solution is 132.6m 3 H is used as the reference value. After the absorption is finished, the material flow entering the hydrate reactor is pressurized to 7MPa, and under the system, multi-stage compression and interstage heat exchange and pressure stabilization force are needed to be increased, so that a hydrate phase CH passes through 4 The recovery rate is improved by 12 percent. However, at the same time N 2 The hydrate phase was also increased by 10%. The overall energy consumption of the system is increased by 124% due to the need for gas phase pressurization and cryogenic cooling at the top of the absorber column, and the system CH 4 Less than 25% of the concentration recovered, under which conditions CH is present in the hydration separation system 4 The concentration does not reach the calorific value of the lowest gas entering the gas turbine for power generation, if the pure water hydrate system is continuously used for concentration, at least two stages of hydration are needed, but the recovery rate is obviously reduced at the moment, and the traditional pressure swing adsorption cannot compete.
Table 2 table of molar concentrations of the three-component gases isolated in example 2
Embodiment example 3
The operating conditions of the solvent absorber column, identical to the feed gas composition of example 1, were: the temperature is 40 ℃, the pressure is 1.2MPa, the liquid-vapor ratio is 4.5, the number of the tower plates is 20, and the tower plates are common sieve plate towers. The operating conditions of the solvent regeneration tower are as follows: the temperature is 120 ℃, the pressure is 0.2MPa, the number of the tower plates is 20, and the tower plates are sieve plate towers. The gas phase discharge at the top of the solvent regeneration column is 96.82% CO 2 CO of the entire absorption System 2 The recovery rate is up to 96%, and the oil can be directly pressurized and injected back into the oil field to displace oil after the pressurization and dehydration operation. Except that the operating conditions of the hydrate were changed, the pressure was 1.3MPa and the temperature was 7 ℃. The hydrate accelerator is THF with the molar content of 6 percent, and the circulating amount of the accelerator solution is 164.6m 3 The system energy consumption is increased by 1.2 percent under the condition of the system, and the system CH 4 The recovery rate is improved by 10 percent, but the CH in the methane-rich gas is recovered 4 The concentration is reduced to 28.52 percent, the minimum heating value of the combustible gas used for generating power by a gas turbine cannot be met, and if further hydration separation is carried out under the system, a first stage hydration separation operation needs to be additionally arranged on the top of a hydrate decomposer of the system to meet the actual operation requirement.
Table 3 table of molar concentrations of three-component gases separated in example 3
EXAMPLES example 4
The same composition as that of the feed gas in example 1 was applied except that the operating conditions of the absorption column were changed to 600kPa, and the vapor-liquid ratio, the temperature conditions, and the number of trays and the type of trays in the absorption column were kept constant. The operating conditions of the solvent regeneration tower are as follows: at a temperature of 120 ℃ and a pressure of0.2MPa, and the number of the tower plates and the type of the tower plates are kept unchanged. The gas phase discharge at the top of the solvent regeneration column was 94.42% CO 2 CO of the entire absorption System 2 The recovery rate reaches 91.5 percent; after energy recovery, the oil can be directly pressurized and then injected back into the oil field to drive oil. Compared with the hydrate reactor of the example 1, the temperature is 5 ℃, the pressure operation condition is 800kPa 2 The absorption effect is reduced, the energy consumption of the absorption system is reduced by 20 percent, and CH enriched in a hydration phase in a hydration reactor 4 Concentration of 32.43% CO 2 The recovery rate is 90.5%, and the total energy consumption of the system is reduced by about 8%. Separated rich CH 4 The minimum heat value for power generation of the gas turbine can be satisfied.
Table 4 table of molar concentrations of the three-component gases separated in example 4
The above examples of the present invention are merely examples for clearly illustrating the present invention and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. This need not be, nor should it be exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.
Claims (1)
1. A pressurization-free solvent/hydration combined gas separation process is characterized in that the pressurization-free process refers to the condition that the pressure of a hydration reaction can be achieved without pressurization after the gas phase discharge at the top of a solvent absorption tower (1) is subjected to heat exchange by a gas cooler (10) and pressure regulation by a throttle valve (11);
the method comprises the following specific steps: adopts a separation device to carry out a solvent/hydration combined gas separation process without pressurization and a solvent absorption method to remove CO 2 The raw material gas is cooled to the hydration reaction temperature from the top of the solvent absorption tower (1) through a gas cooler (10), and then is adjusted through a throttle valve (11)Enters a hydration reactor (3) after being pressed, is cooled by an additive cooler (13) with an accelerator solution decomposed by a hydrate decomposer (4) and then undergoes hydration reaction, and the main gas phase component participating in the hydration reaction is CH 4 The component remaining in the gas phase being mainly N 2 Directly discharging the gas after reaching the standard or collecting the gas for other uses, forming hydrate slurry after the hydration reaction of the rest gas and the accelerator solution, sending the hydrate slurry to a hydrate decomposer (4) through a hydrate slurry pump (12), and carrying out gas-liquid separation on decomposed products in the hydrate decomposer (4) so as to separate out the rich CH 4 The gas is used for power generation or other purposes, the liquid is an accelerant solution, is cooled by an additive cooler (13) and then is circulated back to the hydration reactor to participate in the hydration reaction, and the subsequent CH is separated without pressurization compared with the traditional pressure swing adsorption 4 And N 2 In other words, the separation operation can be directly carried out without increasing the pressure to the adsorption pressure;
the separation device comprises a solvent absorption tower (1), a solvent regeneration tower (2), a hydration reactor (3), a hydrate decomposer (4), a solvent cooler (5), a lean solution pump (6), a rich solution pump (7), a lean/rich solution heat exchanger (8), a reboiler (9), a gas cooler (10), a hydrate slurry pump (12) and an additive cooler (13);
the solvent absorption tower (1) is respectively connected with a gas cooler (10), a solvent cooler (5), a rich liquid pump (7) and a pretreated fireflood oilfield gas pipeline; the top of the solvent regeneration tower (2) is divided into two parts, one part is connected with the heat exchange part of the hydrate decomposer (4), the other part is connected with the lean/rich liquid heat exchanger (8), the two parts of the bottom of the solvent regeneration tower (2) are connected with one part of the lean/rich liquid heat exchanger (8), and the other part is connected with a reboiler (9) and circulates back into the solvent regeneration tower (2); the gas cooler (10) is connected with the hydration reactor (3);
the hydration reactor (3) is respectively connected with a slurry circulating pump (12) and an additive cooler (13);
the bottom of the hydrate decomposer (4) is respectively connected with the solvent regeneration tower (2), the slurry circulating pump (12) and the additive cooler (13);
the solvent cooler (5) is respectively connected with the solvent absorption tower (1) and the barren liquor pump (6); the lean liquid pump (6) is respectively connected with the solvent cooler (5) and the lean/rich liquid heat exchanger (8); the rich liquid pump (7) is respectively connected with the solvent absorption tower (1) and the lean/rich liquid heat exchanger (8); the lean/rich liquid heat exchanger (8) is respectively connected with a tower top feeding plate, a lean liquid pump (6) and a rich liquid pump (7) at the bottom of the solvent regeneration tower (2); the reboiler (9) is connected with the bottom of the solvent regeneration tower (2); the hydrate slurry pump (12) is respectively connected with the hydration reactor (3) and the hydrate decomposer (4); the additive cooler (13) is respectively connected with the hydration reactor (3) and the hydrate decomposer (4);
the pressure of the solvent absorption tower is 0.6MPa-2MPa; the pressure of the hydration reactor is 0.7MPa-1.3MPa;
the solvent absorption tower (1) is vapor-liquid mass transfer equipment and is selected from a plate tower and a packed tower; the top of the tower is sprayed by a liquid device, and the middle part of the tower is provided with a liquid redistributor for strengthening mass transfer; the operation vapor-liquid ratio of the solvent absorption tower (1) is 3-60;
the solvent regeneration tower (2) is vapor-liquid mass transfer equipment, in particular a plate tower and a packed tower; the gas phase discharged from the top of the solvent regeneration tower (2) is a high-temperature material flow and is used for providing heat for the hydration decomposition of the hydrate decomposer (4);
also comprises a throttle valve (11); the throttle valve (11) is respectively connected with a feed inlet of the hydration reactor (3) and the gas cooler (10);
the heat transfer component inside the hydrate decomposer (4) is a finned heat exchange assembly, a threaded pipe heat exchanger or a coil pipe heat exchanger;
a hydrate slurry pump is arranged between the outlet part at the bottom of the hydration reactor (3) and the inlet of the hydrate decomposer;
more than one heat exchanger device is arranged between the inlet part of the circulating additive of the hydration reactor (3) and the outlet of the hydrate decomposer;
the hydrate additive is a quaternary ammonium salt or aromatic compound aqueous solution.
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