CN110862851A - Method for preparing gas hydrate - Google Patents

Method for preparing gas hydrate Download PDF

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CN110862851A
CN110862851A CN201911294291.9A CN201911294291A CN110862851A CN 110862851 A CN110862851 A CN 110862851A CN 201911294291 A CN201911294291 A CN 201911294291A CN 110862851 A CN110862851 A CN 110862851A
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reactor
gas
hydrate
reaction
storage tank
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张建文
何英伟
辛亚男
时俊宝
杨琪
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Beijing University of Chemical Technology
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Beijing University of Chemical Technology
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    • CCHEMISTRY; METALLURGY
    • C10PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10LFUELS 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
    • C10L3/00Gaseous fuels; Natural gas; Synthetic natural gas obtained by processes not covered by subclass C10G, C10K; Liquefied petroleum gas
    • C10L3/06Natural gas; Synthetic natural gas obtained by processes not covered by C10G, C10K3/02 or C10K3/04
    • C10L3/10Working-up natural gas or synthetic natural gas
    • C10L3/108Production of gas hydrates
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E50/00Technologies for the production of fuel of non-fossil origin
    • Y02E50/30Fuel from waste, e.g. synthetic alcohol or diesel

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  • Oil, Petroleum & Natural Gas (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Abstract

A method for preparing gas hydrate belongs to the field of gas storage and transportation. The tube pass of the reactor adopts an internal spiral groove structure; the shell pass of the reactor adopts a falling film type heat exchange component; after being pressurized by a compressor, gas enters the reactor from a high-pressure gas inlet valve at the bottom of the reactor, fully contacts with low-temperature and high-pressure reaction liquid and undergoes hydration reaction to generate hydrate slurry; the reactor is provided with an internal circulator for adjusting the reaction residence time and the morphology of the hydrate and realizing multiphase separation; after passing through the internal circulator, the hydrate slurry enters an intermediate storage tank for gas-slurry separation, then enters a separator for liquid-solid separation, the separated liquid and gas circulate back to the reaction system, and the separated product is conveyed to a refrigeration house for storage; the exothermic heat of reaction is removed by a refrigeration unit. By the method, the natural gas hydrate, the coal bed gas hydrate, the methane hydrate and the landfill gas hydrate can be conveniently, efficiently and stably generated.

Description

Method for preparing gas hydrate
Technical Field
The invention relates to a method for preparing gas hydrate by a reactor with an internal power field, which belongs to the field of gas storage and transportation and is used for efficiently and stably preparing the gas hydrate, mainly comprising natural gas hydrate, coal bed gas hydrate, biogas hydrate and landfill gas hydrate, thereby improving the comprehensive utilization effect of gases such as natural gas, coal bed gas, biogas, landfill gas and the like.
Background
The energy is the material basis of national economy development and is 'blood' in the social economy development process. The energy and the social economic development are closely related, under the condition that the development speed of China is increasingly accelerated, an energy gap becomes an important factor for restricting the development, and in recent years, the social energy demand of China is increased day by day and becomes the second largest energy consuming country in the world. Although our country has abundant fossil energy and renewable energy, the supply of these energy still cannot meet a large demand. Meanwhile, China faces a situation of serious energy waste, the energy utilization efficiency is low, and the industrial structure is unreasonable. China's coal resources can maintain a self-sufficient state for a long time, but most of petroleum and natural gas need to be imported to meet the current and long-term requirements. The national conditions of China restrict the energy structure, and the development of energy of China in the future faces huge challenges.
Natural gas (including coal bed gas, shale gas, etc.) is an important chemical raw material and clean energy. In the current energy structure of China, natural gas accounts for about 4% of the total energy, and the foreign proportion reaches 20%. China is mainly promoted by the policy of changing coal into gas, and the consumption of natural gas is continuously and rapidly increased. The data show that the natural gas consumption in 2018 in China is 2766 billions of cubic meters, the annual increment exceeds 390 billions of cubic meters, the increment reaches 16.6 percent, and the proportion of the natural gas accounts for nearly 8 percent of the total consumption of primary energy. The domestic natural gas consumption in 2019 is expected to exceed 3000 billions of cubic meters, which is equivalent to an increase of 11.3%.
The conventional natural gas reserves in China are insufficient, and the coal bed gas is the clean energy with the largest resource quantity and the most realistic except the conventional natural gas, is the most important supplement of the conventional natural gas in China, and is the most realistic strategic succeed energy of the conventional natural gas. The development of the coal bed gas can reduce coal mine gas accidents, reduce greenhouse effect caused by methane empty discharge, make up for energy shortage and optimize energy structure in China.
With the increasing exhaustion of fossil energy and the increasing demand of energy consumption, low-carbon clean biogas (biogas) has become a hotspot for research in the field of energy and environment. The biological natural gas is green renewable unconventional natural gas produced by anaerobic fermentation, purification and purification of organic waste raw materials. Agricultural residues such as crop straws, agricultural product processing residues, energy crops and the like in China are rich in resources and are important raw materials for producing the biogas. The development of the biogas industry is brought into the energy development strategy of China, the national energy bureau plans to 2020, and the annual output of biogas in China exceeds 20 billion cubic meters; by 2025, the annual output of the biogas exceeds 150 billion cubic meters, and a new renewable gas industry is formed; by 2030, the annual production of biogas exceeds 300 billionths of cubic meters, with scales at the top of the world. The biogas industry has met with a wide market development opportunity.
The urban domestic garbage yield increases at a rate of 8-10% every year, and the yield is estimated to reach 2.2 x 10 in 20208t/a. In recent years, the number of small and medium-sized landfill sites in small and medium-sized cities, county-level cities, towns and other regions has increased greatly, and it is counted that 1549 seats are provided in 2013, the daily treatment capacity reaches 421776t, and during the landfill process, landfill gas (LFG) is generated by anaerobic digestion of microorganisms, and the annual production capacity is about 1.32 × 1010m3. The landfill gas is a mixed gas generated by degrading organic wastes under the action of anaerobic microorganisms, and the main component of the landfill gas is CH4And CO2About 90-99% of the total volume, and N2、H2Trace gases such as S, toluene and the like and harmful gases are collected and utilized in the landfill gas as the CJJ 133-2009 collection and treatment of landfill gas in the domestic refuse landfill and utilization of engineering technical Specifications are implemented.
The natural gas (including coal bed gas, shale gas and the like), biogas and landfill gas have various utilization purposes, but the utilization of the gas still has some problems, mainly including:
(1) natural gas (including coal bed gas, shale gas and the like) utilization problem
The problem of insufficient building force of the pipe network is as follows: the land area of China is large, the population is large, and the population is scattered, so that the pipe network construction is the primary condition for realizing popularization of the use of natural gas. Although natural gas has achieved a certain effect in recent development and has been widely recognized, there are many people who do not really enjoy the convenience of natural gas because of insufficient pipe network construction strength due to unbalanced regional development and the inability to smoothly transport natural gas.
The problem of entering a pipe network: the coal bed gas and natural gas pipe network is generally constructed by large enterprises in China, monopoly exists in operation, and the coal bed gas produced by other enterprises is difficult to convey by using pipelines. In addition, for the coal bed gas with the methane concentration of less than 90 percent, the coal bed gas can not directly enter a pipeline, and the coal bed gas is required to be dehydrated, desulfurized, purified and the like, so that the methane concentration reaches about 95 percent and then is connected into a pipe network, but the technical requirement is high, and the cost is high.
The problem of waste of energy resources of small-scale gas wells is as follows: for gas wells with small single-well exploitation scale, no matter pipeline transportation, CNG and LNG are high in cost and low in benefit, so that coal bed gas resources cannot be well utilized, and often have to be abandoned, and particularly in the initial development stage, a large amount of coal bed gas is discharged in an empty mode.
The problem of low-concentration gas emission: by 2017, the total gas extraction amount of coal mines in China exceeds 128 billion cubic meters, the usable gas with the concentration of more than 8 percent is about 49 billion cubic meters, and in addition, the gas extracted and discharged by coal mines with the concentration of less than 8 percent is directly emptied by more than 78 billion cubic meters every year, so that not only is the resource waste caused, but also the atmospheric pollution and the greenhouse effect are aggravated.
(2) Problem of utilization of biogas
The biogas is generally developed and utilized as a rural energy source, the comprehensive utilization of resources such as biogas slurry, biogas residue and the like is still in a low layer, the application field is narrow, and the maximum benefit of the biogas is not fully exerted. Most farmers only use the biogas slurry as the organic fertilizer, and the biogas slurry is not fully applied in the aspects of crop seed soaking, pest control, biogas slurry pig raising and disinfection, biogas residue edible fungus production and the like. The mode of a circular economy industrial chain integrating breeding, biogas and planting does not become an important means for developing ecological agriculture and increasing the income of farmers. Although some villages build pools early, the biogas slurry and the biogas residues can be discarded, so that not only is high-quality resources wasted, but also secondary pollution is caused to the environment.
(3) The problem of recycling landfill gas
The main problems of recycling of the landfill gas include that ① geographical distribution of landfill sites in China is relatively dispersed, ② the experience of recycling and utilizing the landfill gas is lacked in utilization of the landfill gas in China, ③ prediction and control technologies in aspects of gas production rate, gas production period and the like of the landfill gas are needed, a landfill process is optimized, the gas production rate and stability of the sites are improved, landfill gas resources and equipment are utilized to the maximum extent, idle or idle running of the equipment is avoided, ④ the technical level of the equipment, energy conversion efficiency and combined utilization efficiency are improved, the integration degree of related technologies needs to be improved, ⑤ the landfill gas utilization in China does not form corresponding industrial foundations and commercial operation modes for reference, and modern landfill gas utilization industry and commercial operation modes need to be established by means of foreign advanced landfill gas utilization industrial experience and commercial operation modes.
In order to better solve the problem of comprehensive utilization of natural gas (including coal bed gas, shale gas and the like), biogas and landfill gas and realize safe, convenient and reliable storage and transportation of the gas so as to meet the requirements of industries and fields of industry, civil use, power generation, vehicle and the like, the patent provides a novel method for preparing gas hydrate for gas storage and transportation.
The hydrate of gas is water molecule and CH4、C2H6、CO2And H2S and other small molecule gases form a non-stoichiometric ice-shaped crystal with a cage-shaped structure under the conditions of specific temperature and pressure, wherein water molecules form a crystal framework by virtue of hydrogen bonds, and holes in the framework are filled with methane, light hydrocarbon or non-light hydrocarbon molecules. Research shows that the natural gas hydrate has considerable gas storage rate, usually 1m3The hydrate can be stored for about 150-180 m3The natural gas of (1). The gas hydrates with different forms can be stored under the conditions of-25 to-10 ℃ and normal pressure, can be efficiently utilized after being gasified, and can realize the safe storage and transportation of gases such as natural gas, coal bed gas, landfill gas, methane and the like. The research of the researchers in the industry finds that the hydrate storage and transportation natural gas technical ratio under the same conditionsThe capital cost of the liquefied petroleum gas storage and transportation technology is reduced by 19 percent, is reduced by 30 percent compared with the capital cost of the compressed natural gas storage and transportation technology, and obviously reduces the storage and transportation cost.
In U.S. patent6,180,843, there is provided a process for preparing natural gas hydrates using a fluidized bed in which natural gas is contacted with water in countercurrent or concurrent flow and the heat of reaction is carried away by excess gas. The sensible heat of the gas is very small, and is only about 2% of the heat of formation of the hydrate. Therefore, the heat transfer mode can only remove a small amount of heat, and correspondingly, the generated hydrate is little, so that the industrial production is difficult to realize.
Gudmundsson (U.S. patent536,893) also proposed a process for the continuous preparation of natural gas hydrates: after being compressed, the natural gas is sprayed into the reactor from the upper part to contact and react with water. In order to increase the reaction contact area, water is sprayed in the form of droplets from the upper part of the reactor and the resulting hydrate is removed from the bottom of the reactor. To remove the heat of reaction, the reactor is provided with a jacket and an internal cooling coil, respectively, resulting in a complicated apparatus. Hydrate removal is problematic because the density of the hydrate is lower than that of water.
Liu's bang et al (CN200610116480.3) have also been studied quite extensively in the preparation of natural gas hydrates, but no commercial examples have been seen. Queen et al (CN200910263068.8) propose a method and a device for efficiently and continuously preparing a natural gas hydrate, but the structure is too complex and easy to block.
Luyiheng and chengyang et al (CN103881775A) propose a system for preparing and recovering energy of coal bed gas hydrate, mainly aiming at energy utilization during extraction of methane hydrate, and do not deeply discuss a method and a device for preparing coal bed gas hydrate. The cooling coil heat removal proposed in this patent remains problematic in terms of efficiency and stable operation. In addition, the apparatus is too complicated, and there are various ways only for the refrigeration system, so that there are some obstacles in terms of industrialization thereof.
The Huanglinji and Zhang Jian (ZL20041000858.7) proposed the preparation of hydrates centered on bubbling and creating suitable conditions of low temperature and high pressure for hydrate formation. In the preparation process, heat transfer, mass transfer and system residence time are difficult to control, the reaction surface is difficult to continue once a hydrate or an ice film is formed on the reaction surface, and continuous production is difficult to realize, so that improvement is needed.
Zhang Jian Wen and Yanglin (ZL201310558066.8) propose to adjust the morphology by taking the bubbling as the center and combining with a crystal adjuster, thereby improving the manufacturing efficiency. The heat transfer, mass transfer and system residence time in the preparation process are difficult to control, and although parallel flow and counter flow process flows are proposed, the production process fluctuates severely and is difficult to control.
Zhang Jian and Xinyaman et al (CN105779049A) propose a method for producing coal bed gas hydrate, the reactor has a simple structure, a shell-and-tube reactor is adopted, reaction mixed liquid flows in a smooth tube, and refrigerant liquid flows outside the smooth tube to remove heat generated by the reaction. For preparing the hydrate in the smooth pipe, because the generation of the hydrate is carried out in a low-temperature and high-pressure environment, in the process of removing reaction heat, the temperature of the inner wall of the reaction pipe is lower than the temperature in the pipe, so that the generation rate of the hydrate at the wall surface is higher, and simultaneously, due to the existence of a speed boundary layer, the hydrate at the wall surface is attached, so that the generation of the hydrate in a reactor is further inhibited, and the equipment cannot continuously and effectively generate the hydrate.
In summary, these techniques have some weaknesses, such as: the method has the advantages of low heat exchange efficiency, complex process, difficult control, unstable and continuous operation and the like, so that the development of a gas hydrate generating method and a gas hydrate generating device which are efficient, stable and applicable to industrial production is needed.
Disclosure of Invention
The invention aims to provide an efficient and stable method for preparing a gas hydrate, which is mainly applied to the field of gas storage and transportation. By the method, the natural gas hydrate, the coal bed gas hydrate, the methane hydrate and the landfill gas hydrate can be conveniently, efficiently and stably generated.
The gas hydrate generation process is a complex dynamic process including fluid flow, heat and mass transfer and other interactions in a multi-phase flow system. Gas hydrate is generated on a contact interface of water and gas, and as the molecular structure of the hydrate does not have chemometrics, the generation process of the hydrate is not a reaction kinetics control process but a process controlled by the conversion of fluid phase to solid phase strictly speaking, and the reaction speed of the hydrate directly determines the production efficiency. For this reason, in a hydrate formation multiphase flow system, the following conditions must be satisfied: (1) fully mixing reaction gas and water; (2) efficient removal of hydrate heat of formation; in order to meet the industrial application, the condition (3) that the reaction system can continuously and stably operate must be met.
The invention has the remarkable innovation that the designed reactor adopts an internal spiral groove structure, and the structure can generate plane secondary flow in the pipe, thereby playing the role of enhancing heat transfer on one hand, and promoting the separation of a gas-water-hydrate multiphase system under the action of an internal force field of a spiral internal groove pipe due to the density difference between gas-liquid-solid components in a hydrate generation system, so that substances with high density such as water in the gas-water-hydrate system are close to the pipe wall, and substances with low density such as hydrate and gas are gathered to the center of the pipe. The process not only promotes heat transfer and mass transfer, but also promotes the separation of a multiphase system, and finally, the method of the invention efficiently and stably produces gas hydrate.
A method for preparing gas hydrate is characterized in that the following devices are applied: the device comprises 2 internal spiral groove reactors, 2 process transformation units, 2 pressure stabilization units, 2 throttle valves, 2 inlet valves, 2 discharge valves, 2 delivery pumps, 1 gas compressor, a separator, an intermediate storage tank, a water storage tank, an additive storage tank, a refrigeration unit, a cold storage unit and a central control system;
A) the inner spiral groove reactors are connected to two ends of the process conversion unit to form a loop, the process conversion unit is composed of a transmitter, a controller and a control valve, parallel and serial operation of the two inner spiral groove reactors is realized, and parallel and countercurrent operation of gas phase and liquid phase in a single inner spiral groove reactor can also be realized;
B) the internal spiral groove reactor, hereinafter referred to as reactor, is composed of five parts: the bottom of the reactor is provided with an air inlet pipe and a water inlet pipe, the lower part of the reactor is provided with an airflow distributor, the middle part of the reactor is a core reaction zone, the upper part of the reactor is provided with an internal circulator, and the top of the reactor is provided with an exhaust valve; the gas inlet at the lower part of the reactor is connected with a gas compressor, and the water inlet is connected with a delivery pump; the middle part of the reactor is a reaction zone and consists of a tube array and a shell pass, reaction mixed liquid is arranged in the tube array, the shell pass is refrigerating liquid, and the middle part of the reactor is provided with a refrigerating liquid inlet and outlet which is connected with a refrigerating unit and adjusts the flow through a valve; the upper part of the reactor is provided with a multiphase separation zone, an internal circulator is arranged to control the reaction residence time, the morphology of the hydrate is adjusted, and the multiphase separation is realized; the upper part and the bottom of the reactor are both provided with a product discharge pipe, wherein the outlet of the upper discharge pipe is connected with the intermediate storage tank through a throttle valve; the top of the reactor is provided with an exhaust valve for adjusting the pressure in the reactor and exhausting gas which is not absorbed by the reaction liquid;
C) the refrigeration unit is provided with five circuits: one path is communicated with the inner spiral groove reactor, the other path is communicated with the other inner spiral groove reactor, the other path is communicated with the intermediate storage tank, the other path is communicated with the water storage tank, and the other path is communicated with the cold storage unit;
D) the reactor is provided with a pressure stabilizing unit for controlling the stability of the pressure in the reactor;
E) the operating pressure of the reactor is 2-9 MPa, and the temperature is 2-12 ℃;
F) the circulation flow of the mixed liquid in the reactor is controlled to be 2-6 m3/h;
G) The ratio of the volume of the cold storage unit to the volume of the reactor is 5 to 6;
H) the reactor forms a water circulation loop through a discharge valve, an intermediate storage tank, a separator, a water storage tank and a delivery pump;
I) the central control system controls the inner spiral tank reactor, the process conversion unit, the refrigeration unit, the delivery pump, the compressor and all valves, monitors all process operation data and synchronously outputs process parameters, wherein the process parameters mainly comprise reaction mixture temperature, delivery pump flow, refrigerant temperature and flow, reactor internal pressure, air inlet flow and the like;
the system is provided with an abnormal alarm system and a protection device so as to ensure the stable and safe operation of the system.
In order to achieve the purpose of the invention, the invention adopts the following technical scheme:
operation 1: before the device is started, the states of all valves are checked to ensure that the states of all valves are normal;
operation 2: starting a delivery pump, filling water into the reactor, and replacing air in the reactor;
operation 3: adding the reaction mixed liquid into a water storage tank, starting a refrigerating unit, supplying chilled water to a cold drain in the water storage tank and an intermediate storage tank, and cooling the water to about 2-12 ℃;
and operation 4: opening a delivery pump and a water inlet valve, adding reaction mixed liquid into the reactor, controlling the liquid level at the top of the reactor to be basically unchanged by controlling the action of a valve and the delivery pump and controlling the liquid level at the top of the reactor to flow to a separator after the water level at the top of the reactor exceeds the outlet of a bypass pipeline and reaches a specified liquid level, collecting hydrate products separated from the hydrate slurry by the separator, flowing the separated water to a water storage tank, and pumping the water in the water storage tank into the reactor by the delivery pump to finally form stable water circulation;
operation 5: starting a refrigeration circulation loop, supplying a refrigerating fluid to the shell pass of the heat exchange section of the reactor, and forming a cold trap at the reaction section;
operation 6: when the temperature of the reaction mixed liquid reaches 2-12 ℃, starting a gas compressor and an air inlet valve to charge gas into the reactor and pressurizing to 2-9 MPa; after the gas passes through the gas flow distributor, a large number of micro-fine bubbles are formed and are in full contact with the reaction mixed liquid in a cold trap of the reaction section, and the gas is violently disturbed, so that the generation of gas hydrate is accelerated;
operation 7: in order to maintain the pressure in the reactor stable, a pressure stabilizing unit is provided. If the pressure is too high, the air inflow is reduced by adjusting the compressor, and an exhaust valve at the top of the reactor is increased; if the pressure is too low, the air inflow is increased by adjusting the compressor, and an exhaust valve at the top of the reactor is reduced;
after the operation of the steps 1-7, stable material circulation is established, and the system is in a stable gas hydrate generation stage.
In order to realize the purpose of the invention, an internal circulator is arranged in the internal spiral groove reactor to adjust the reaction-retention time of hydrate and promote multiphase separation. The technical scheme is as follows:
operation 8: the hydrate flows upwards under the action of buoyancy after being generated, and a buoyancy concentration area is formed by the inner circulator; after the water/slurry is controlled to flow by a guide plate of the internal circulator, the hydrate is concentrated in the slurry at the upper part; the hydrate slurry enters a hydrate enrichment area through a light-phase flow channel, the retention time and the morphology of the hydrate are adjusted, and the gas content of the hydrate is improved;
operation 9: reducing the pressure of the hydrate slurry accumulated by the circulator in the reactor through a throttle valve, flowing into an intermediate storage tank for gas-slurry separation, and allowing the hydrate slurry in the intermediate storage tank to enter a separator for liquid-solid separation to finally obtain a dry hydrate product, collecting the dry hydrate product through a container, and conveying the dry hydrate product to a refrigeration house for long-term storage; recycling the separated unreacted gas; the separated cold water enters a water storage tank, is mixed with fresh water and additives and then is conveyed to the reactor by a conveying pump, so that material circulation is realized, and the cold energy of the material is recovered. The process realizes continuous production of the gas hydrate generation process.
The invention aims at the characteristic of large variation of methane concentration in different gases, and is provided with a process conversion unit and a pressure stabilizing unit, and can realize multi-stage parallel flow and multi-stage countercurrent operation by controlling the connection mode between two internal spiral groove reactors. The technical scheme is as follows:
operation 10: the pressure stabilizing unit is used for controlling so that the hydrate production system maintains stable pressure and the fluctuation of the pressure is reduced;
operation 11: aiming at high-concentration methane gas, the two internal spiral tank reactors are connected in parallel for production through the control of a process conversion unit, so that the generation of gas hydrate is accelerated;
operation 12: aiming at the methane gas with medium and low concentration, the process conversion unit is used for controlling so that the two internal spiral groove reactors can carry out multi-stage countercurrent production, and the method is favorable for accelerating the generation of gas hydrate.
The device of the invention comprises a process transformation unit, a pressure stabilization unit, an inner spiral groove reactor, a delivery pump, a refrigeration unit, a cold storage unit, a heater, a separator, an intermediate storage tank, a water storage tank, an additive storage tank, a gas compressor, a central control system and the like. The method is characterized in that:
the gas hydrate generating reactor adopts an internal spiral groove structure, the structure can generate plane secondary flow centrifugal force to form strong disturbance, the disturbance of the wall surface boundary is enhanced, the cooperation degree between a speed field and a temperature field is enhanced under the action of the plane secondary flow centrifugal force, and the effect of enhancing heat transfer is achieved; meanwhile, the spiral flow of the fluid improves the turbulence degree of the fluid in the pipe, and further enhances heat transfer; due to the density difference between the gas phase, the liquid phase and the solid phase, generated hydrates are gathered at the center of the tube under the action of generated spiral flow and centrifugal force, a water phase with high density moves to the wall surface, the hydrates with low density do not stay at the heat exchange surface of the tube wall, and tiny bubbles are hardly influenced by an internal force field, so that the surface medium is updated and the multiphase system is separated under the condition of the internal force field;
the process conversion unit is connected with the reactor to form a closed loop, and the gas phase and the liquid phase in the reactor form two production processes of parallel flow and countercurrent flow under the action of the process conversion unit; the two reactors form two production processes of series connection and parallel connection under the action of the process conversion unit;
the reactor consists of five parts: the bottom of the reactor is provided with an air inlet pipe and a water inlet pipe, the lower part of the reactor is provided with an airflow distributor, the middle part of the reactor is a reaction area, the upper part of the reactor is provided with an internal circulator, and the top of the reactor is provided with an exhaust valve; the gas inlet at the lower part of the reactor is connected with a gas compressor, a gas flowmeter and a pressure gauge are arranged at the outlet of the compressor, and a water inlet pipe is connected with a delivery pump; the middle part of the reactor is a reaction zone and consists of a tube array and a shell pass, reaction mixed liquid is arranged in the tube array, the shell pass is refrigerating liquid, and the middle part of the reactor is provided with a refrigerating liquid inlet and outlet which is connected with a refrigerating unit and adjusts the flow through a valve; the upper part of the reactor is provided with a multiphase separation zone, and an internal circulator is arranged to adjust the reaction residence time and the morphology of the hydrate so as to realize multiphase separation; the upper part and the bottom of the reactor are both provided with a product discharge pipe, wherein the outlet of the upper discharge pipe is connected with the intermediate storage tank through a throttle valve; the top of the reactor is provided with an exhaust valve for adjusting the pressure in the reactor and exhausting gas which is not absorbed by the reaction liquid;
the middle storage tank is provided with a safety valve and an exhaust pipe, and the lower part of the middle storage tank is provided with a valve and a pipeline which are connected with the separator. The inlet and outlet pipes of the refrigerating fluid in the intermediate storage tank are connected with the cold storage unit and supply the refrigerating fluid to the cold discharge in the tank;
a product discharge port is arranged at the side part of the separator, and a water discharge pipe at the lower part of the separator is connected with a water storage tank; the upper part of the water storage tank is connected with the additive tank, a fresh water inlet pipe is connected with a tap water pipe network, an outlet pipe at the lower part of the water storage tank is connected with a delivery pump, and a refrigerating fluid inlet and outlet pipe of the water storage tank is connected with a refrigerating unit to supply refrigerating fluid to cold discharge in the water storage tank;
the reactor forms a water circulation loop through a discharge valve, an intermediate storage tank, a separator, a water storage tank and a delivery pump;
in order to quickly remove the heat generated by the hydrate, the invention is provided with a refrigeration unit and a cold storage unit for supplementing cold to the shell pass of the reaction section, and the ratio of the volume of the cold storage unit to the volume of the reactor is 5-6. Meanwhile, the shell pass of the reactor related by the invention adopts falling film type heat exchange, the refrigerating fluid flows from top to bottom by being close to the outer wall surface of the reaction tube, the heat transfer efficiency is more than 5 times of that of a shell-and-tube type heat exchange mode, and the removal rate of reaction heat is accelerated;
in order to control the mixing degree of the reaction liquid and simultaneously adjust the morphology of the hydrate, the circulation flow of the reaction mixed liquid is controlled to be 2-6 m3The optimization is 3-5 m3/h;
The pressure stabilizing unit can stabilize the pressure of the production system, reduce the fluctuation of the pressure and stabilize the generation environment of the hydrate;
the central control system controls the reactor, the process conversion unit, the pressure stabilization unit, the refrigeration unit, the cold storage unit, the delivery pump, the compressor and all valves, monitors all process operation data and synchronously outputs process parameters, wherein the process parameters mainly comprise reaction mixture temperature, delivery pump flow, refrigerant temperature and flow, reactor internal pressure, gas inlet flow and the like.
The method of the invention has the following advantages:
1) the gas hydrate reactor adopts an inner spiral groove structure, promotes the separation of a multiphase system and strengthens mass and heat transfer aiming at a hydrate generation system.
2) The shell pass of the reactor adopts a falling film heat exchange mode, and the heat transfer efficiency of falling film heat exchange is more than 5 times of that of a shell-and-tube heat transfer efficiency in an investigation range, so that the rapid removal of hydrate generation heat is facilitated.
3) The multistage forward and reverse circulation operation is realized through the process conversion unit, and the stability and the applicability of the device are improved.
4) And an internal circulator is arranged to realize the adjustment of the residence time of the multiphase system and the adjustment of the morphology of the hydrate.
Drawings
FIG. 1, comparison of heat exchange performance between falling film heat exchange and shell-and-tube heat exchange
FIG. 2, process flow diagram
In the figure: 1-a process transformation unit, 2-an internal spiral groove reactor, 3-an air inlet, 4-a delivery pump, 5-a throttle valve, 6-an exhaust valve, 7-an intermediate storage tank, 8-a refrigeration unit, 9-a cold storage unit, 10-a separator, 11-an additive storage tank, 12-a water storage tank, 13-a gas compressor, 14-a pressure stabilization unit and 15-a central control system.
FIG. 3 is a sectional view of the reactor
In the figure: 16-exhaust valve, 17-internal circulator, 18-shell pass, 19-tube pass, 20-process transformation control unit, 21-gas flow distributor, 22-one-way valve, 23-gas inlet, 24-water inlet, 25-product discharge port, 26-refrigerant liquid outlet, 27-refrigerant liquid inlet, 28-product discharge port, L1-reactor top, L2-reactor upper part, L3-reactor middle part, L4-reactor lower part and L5-reactor bottom.
FIG. 4, Process Change Unit
FIG. 5, pressure stabilization Unit
FIG. 6, fluid flow field in reaction Unit
FIG. 7, hydrate product prepared
FIG. 8, combustion diagram of hydrate product
The specific implementation mode is as follows:
the invention is further illustrated by the examples in connection with the figures. The examples, however, should not be construed as limiting the scope of the claims.
The device comprises a process change control unit 1, an inner spiral groove reactor 2, an air inlet valve 3, a delivery pump 4, a throttle valve 5, an exhaust valve 6, an intermediate storage tank 7, a refrigeration unit 8, a cold storage unit 9, a separator 10, an additive tank 11, a water storage tank 12, a gas compressor 13, a pressure stabilizing unit 14 and a central control system 15.
A) The inner spiral groove reactor 2 is connected to two ends of the process conversion unit 1 to form a loop, the process conversion unit 2 is composed of a transmitter, a controller and a control valve, parallel and serial process operation of two inner spiral groove reactors can be realized, parallel and countercurrent process operation of gas phase and liquid phase in a single inner spiral groove reactor can also be realized, and the logic control chart of the process conversion unit is given by a figure 4;
B) the internal spiral groove reactor is hereinafter referred to as a reactor, and comprises five parts: the lower part of the reactor is provided with an airflow distributor; the bottom of the reactor is provided with an air inlet 23 and a water inlet 24, the air inlet 23 is connected with the compressor 13, and the water inlet 24 is connected with the delivery pump 4; the middle part of the reactor is a reaction zone and consists of a tube array and a shell pass, reaction mixed liquid is arranged in the tube array 19, the shell pass 18 is refrigerating fluid, and the refrigerating fluid flows close to the outer wall surface of the reaction tube from top to bottom; the upper part of the reactor is a multiphase separation zone, and an internal circulator 17 is arranged to adjust the reaction residence time and the morphology of the hydrate so as to realize multiphase separation; the upper part and the bottom of the reactor are both provided with product discharge ports 25 and 28, and the product discharge port 28 is connected with the intermediate storage tank 7; the top of the reactor is provided with an exhaust port 16; the reactor forms a water circulation loop through a discharge valve 5, an intermediate storage tank 7, a separator 10, a water storage tank 12 and a delivery pump 4;
C) the refrigeration unit is provided with five circuits: one path is communicated with the inner spiral groove reactor 2A, the other path is communicated with the other inner spiral groove reactor 2B, the other path is communicated with the intermediate storage tank 7, the other path is communicated with the water storage tank 12, and the other path is communicated with the cold storage unit 9;
D) the reactor is provided with a pressure stabilizing unit 14 for controlling the stability of the pressure in the reactor;
E) the operating pressure of the reactor is 2-9 MPa, and the temperature is 2-12 ℃;
F) the circulation flow of the mixed liquid in the reactor is controlled to be 2-6 m3/h;
G) The ratio of the volume of the cold storage unit 9 to the volume of the reactor 2 is 5-6;
H) the central control system 15 controls the internal spiral tank reactor 2, the process conversion unit 1, the pressure stabilization unit 14, the refrigeration unit 8, the cold storage unit 9, the delivery pump 4, the compressor 13 and various valves, monitors various process operation data and synchronously outputs process parameters, wherein the process parameters mainly comprise the temperature of reaction mixture, the flow rate of the delivery pump, the temperature and the flow rate of refrigerant, the pressure in the reactor, the flow rate of inlet air and the like;
the process shift unit control logic is shown in the following table in conjunction with fig. 4.
Figure BDA0002320071200000121
Figure BDA0002320071200000131
The pressure stabilization unit control logic is shown in the table below in conjunction with fig. 5.
Pressure of Gas compressor control Exhaust valve control
Excessive pressure Reducing compressor frequency Adjustable exhaust valve F7A/B
Too low a pressure Increasing compressor frequency Air exhaust valve F7A/B with small adjustment
Example 1:
starting a refrigerating unit 8 and a cold storage unit 9, supplying refrigerating fluid to a water storage tank 12 and an intermediate storage tank 7, and controlling the temperature of mixed liquid in the reactor 2 to be 6.5 ℃; the central control system 15 and the transfer pump 4 were started, and the SDS reaction mixture solution having a concentration of 300ppm was transferred into the reactor 2 by the transfer pump 4. When the water level at the upper part of the reactor 2 exceeds the top of the internal circulator and reaches the designated liquid level, a throttle valve 5 at the outlet of the by-pass pipe is opened, the opening degree of a valve and the flow of the delivery pump are adjusted, so that the reaction mixed liquid forms a stable water circulation loop through a discharge port 28, an intermediate storage tank 7, a separator 10, a water storage tank 12 and the delivery pump 4; starting a refrigeration unit 8 to supply refrigeration liquid to the shell pass of the reactor 2 to cool the reactor, and controlling the temperature of mixed liquid in the reactor 2 to be stabilized at 6.5 ℃; the gas inlet valve 3 and the gas compressor 13 are opened, the coal bed gas with the methane concentration of 97 percent is introduced into the reactor 2 after the flow of the coal bed gas is adjusted by the compressor 13, and the gas inlet flow is controlled at 80Nm3 /h, controlling the pressure in the reactor to be stabilized at 7.5MPa by the pressure stabilizing unit 14, and controlling the process conversion unit 1 to stabilize the circulation flow of the reaction mixed liquid at 5.0m3H; at the moment, gas hydrate begins to be generated in the reaction tube to form hydrate slurry; the hydrate slurry enters a space between the inner circulator 17 and the wall surface of the reactor through a guide plate at the upper part of the reactor to carry out liquid-solid separation; hydrate slurry gathered at the upper part of the reactor flows into a middle storage tank 7 through a throttle valve 5, gas-slurry separation is carried out in the middle storage tank 7, separated gas is recycled, and the separated slurry flows into a separator 10 for liquid-solid separation; the 'dry' hydrate separated by the separator 10 is simply packaged and then transported to a refrigeration house for storage. The separated liquid flows into a water storage tank 12, is mixed with supplemented fresh water and additives, and then is circulated back to the reactor by a delivery pump 4, so that material circulation is realized, and part of cold energy is recovered; after the reaction, a 'dry' hydrate is obtained, and the gas content in the hydrate reaches 170V/V.
Example 2:
the procedure of example 1 was followed, but the pressure in the reaction column was controlled to 9.0MPa and the temperature of the reaction solution was 5.0 ℃. After the reaction, a 'dry' hydrate is obtained, and the gas content in the hydrate reaches 115.36V/V.
Example 3:
the procedure of example 1 was followed except that the pressure in the reaction column was controlled at 7.5MPa, the gas was landfill gas with a methane concentration of 45%, and the temperature of the reaction solution was 5.0 ℃. After the reaction, a 'dry' hydrate is obtained, and the gas content in the hydrate reaches 88V/V.

Claims (6)

1. A method for preparing gas hydrates, characterized in that the following apparatus is applied: the device comprises 2 internal spiral groove reactors, 2 process transformation units, 2 pressure stabilization units, 2 throttle valves, 2 inlet valves, 2 discharge valves, 2 delivery pumps, 1 gas compressor, a separator, an intermediate storage tank, a water storage tank, an additive storage tank, a refrigeration unit, a cold storage unit and a central control system;
A. the inner spiral groove reactor is connected to two ends of a process conversion unit to form a loop, and the process conversion unit consists of a transmitter, a controller and a control valve; the gas phase and the liquid phase in a single reactor form two production processes of parallel flow and countercurrent flow under the action of a process conversion unit; the two reactors form two production processes of series connection and parallel connection under the action of the process conversion unit;
B. the internal spiral groove reactor, hereinafter referred to as reactor, is composed of five parts: the bottom of the reactor is provided with an air inlet pipe and a water inlet pipe, the lower part of the reactor is provided with an airflow distributor, the middle part of the reactor is a core reaction zone, the upper part of the reactor is provided with an internal circulator, and the top of the reactor is provided with an exhaust valve; the gas inlet at the bottom of the reactor is connected with a gas compressor, and the water inlet is connected with a delivery pump; the middle part of the reactor is a reaction zone and consists of a tube array and a shell pass, reaction mixed liquid is arranged in the tube array, the shell pass is refrigerating liquid, and the middle part of the reactor is provided with a refrigerating liquid inlet and outlet which is connected with a refrigerating unit and adjusts the flow through a valve; the upper part of the reactor is provided with a multiphase separation zone, and an internal circulator is arranged to adjust the reaction residence time and the morphology of the hydrate so as to realize multiphase separation; the upper part and the bottom of the reactor are both provided with a product discharge pipe, wherein the outlet of the upper discharge pipe is connected with the intermediate storage tank through a throttle valve; the top of the reactor is provided with an exhaust valve for adjusting the pressure in the reactor and exhausting gas which is not absorbed by the reaction liquid;
C. the refrigeration unit is provided with five circuits: one path is communicated with the inner spiral groove reactor, the other path is communicated with the other inner spiral groove reactor, the other path is communicated with the intermediate storage tank, the other path is communicated with the water tank, and the other path is communicated with the cold storage unit;
D. the inner spiral groove reactor forms a water circulation loop through a throttle valve, an intermediate storage tank, a separator, a water storage tank and a delivery pump.
2. The method of claim 1, wherein: the operating pressure of the reactor of the equipment is 2-9 MPa, and the temperature is 2-12 ℃.
3. The method of claim 1, wherein: the circulation flow of the mixed liquid in the reactor is controlled to be 2-6 m3/h。
4. The method of claim 1, wherein: the ratio of the volume of the cold storage unit to the volume of the reactor is 5 to 6.
5. The method of claim 1, wherein: the shell pass of the reactor adopts falling film heat exchange, and the refrigerant liquid flows from top to bottom close to the outer wall surface of the reaction tube.
6. The method of claim 1, wherein: the central control system controls the reactor, the process conversion unit, the pressure stabilization unit, the refrigeration unit, the cold storage unit, the delivery pump, the compressor and all valves, monitors all process operation data and synchronously outputs process parameters, wherein the process parameters comprise reaction mixture temperature, delivery pump flow, refrigerant temperature and flow, reactor internal pressure and gas inlet flow.
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