CN112725048B - Combined dehydration and purification method in coal bed gas utilization process - Google Patents
Combined dehydration and purification method in coal bed gas utilization process Download PDFInfo
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- 239000003245 coal Substances 0.000 title claims abstract description 125
- 230000018044 dehydration Effects 0.000 title claims abstract description 78
- 238000006297 dehydration reaction Methods 0.000 title claims abstract description 78
- 238000000034 method Methods 0.000 title claims abstract description 76
- 238000000746 purification Methods 0.000 title claims abstract description 42
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 127
- 239000007788 liquid Substances 0.000 claims abstract description 52
- 238000001914 filtration Methods 0.000 claims abstract description 41
- 238000000926 separation method Methods 0.000 claims abstract description 39
- 238000001179 sorption measurement Methods 0.000 claims abstract description 28
- 230000006835 compression Effects 0.000 claims abstract description 8
- 238000007906 compression Methods 0.000 claims abstract description 8
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 24
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- 239000003595 mist Substances 0.000 description 7
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- 238000010521 absorption reaction Methods 0.000 description 5
- 239000003463 adsorbent Substances 0.000 description 5
- 238000003795 desorption Methods 0.000 description 5
- 239000000428 dust Substances 0.000 description 5
- 238000010248 power generation Methods 0.000 description 5
- 238000001035 drying Methods 0.000 description 4
- 238000004108 freeze drying Methods 0.000 description 4
- 239000003345 natural gas Substances 0.000 description 4
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- 238000002485 combustion reaction Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000007791 dehumidification Methods 0.000 description 1
- 239000002274 desiccant Substances 0.000 description 1
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- 238000005065 mining Methods 0.000 description 1
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- 230000035699 permeability Effects 0.000 description 1
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- JTJMJGYZQZDUJJ-UHFFFAOYSA-N phencyclidine Chemical class C1CCCCN1C1(C=2C=CC=CC=2)CCCCC1 JTJMJGYZQZDUJJ-UHFFFAOYSA-N 0.000 description 1
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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
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D50/00—Combinations of methods or devices for separating particles from gases or vapours
- B01D50/20—Combinations of devices covered by groups B01D45/00 and B01D46/00
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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
- C10L3/106—Removal of contaminants of water
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Abstract
Discloses a combined dehydration and purification method in the utilization process of coal bed gas, which comprises the following steps: sequentially carrying out liquid water removal and separation treatment, compression treatment, first filtration treatment, first gaseous water removal treatment, second filtration treatment, second gaseous water removal treatment and third filtration treatment on the coal bed gas; finally obtaining the dehydrated and purified coal bed gas. Wherein, a cyclone demister with a gas inlet inclined downwards at an inclination angle of 10-25 degrees is used for liquid water removal and separation treatment, and a freezing dryer and an adsorption dryer are respectively used for first filtration treatment and second filtration treatment. The method can effectively reduce the dew point temperature of the coal bed gas while removing liquid water and gaseous water in the coal bed gas so as to meet the requirements of the subsequent process.
Description
Technical Field
The invention relates to the field of gas dehydration and purification, in particular to a combined dehydration and purification process in a coal bed gas utilization process.
Background
The coal bed gas is associated gas in the processes of coal generation and coal deterioration, the main component of the coal bed gas is methane, the relative density of the coal bed gas to air is 0.554, the permeability of the coal bed gas is 1.6 times of that of the air, and the coal bed gas is difficult to dissolve in water, does not support combustion and cannot maintain respiration. According to different extraction modes, the gas can be divided into ground extraction and underground extraction, the ground extraction is mostly called coal bed gas, and CH of the coal bed gas4The concentration can reach more than 80 percent, the underground extraction is mostly called gas, and CH is CH due to the fact that a large amount of air permeates in the extraction process4The concentration changes from 20 to 80 percent, and a considerable part of directly discharged gas CH4Concentration of<20％。
At present, the coal bed gas is mainly utilized in a power generation, concentration and quality improvement manner. Wherein, the concentration and quality improvement mainly adopts pressure swing adsorption concentration to prepare civil or industrial gas, compressed natural gas, liquefied natural gas and the like.
The extraction and drainage pump station extracts the coal bed gas containing saturated liquid water, and the coal bed gas is required to be dehydrated and purified before being used to meet the requirements of subsequent processes, in particular to a pressure swing adsorption concentration quality improvement method, wherein the separation adsorbent has high requirements on water content, the dew point temperature of the gas is generally required to be lower than-50 ℃, but the existing coal bed gas dehydration process cannot meet the requirements on the dew point temperature of the gas.
If the dehydration method is not suitable, the start-up rate of a generator set is low and the power generation efficiency is low easily in the coal bed gas power generation and utilization process, and the adsorption and separation efficiency is affected by poisoning of a separation adsorbent easily in the coal bed gas pressure swing adsorption, concentration and upgrading utilization process.
The method for solving the problems is to develop a suitable coal bed gas dehydration and purification process technology and ensure that the dehydration effect meets the subsequent utilization requirement.
Coal bed gas dewatering involves the removal of liquid (free) and gaseous water. The liquid water removal is mainly mechanical dehydration, and the method comprises the following steps: cyclone dewatering, wire mesh dewatering and baffle plate dewatering. The method for removing the gaseous water comprises the following steps: low temperature removal method, solvent absorption method, solid adsorption method.
Chinese patent publication No. CN202576373U discloses a dehydration filter device for gas, which comprises a gravity dehydration device and a filter device, wherein the gravity dehydration method can only naturally separate liquid water from gas, and cannot separate and remove gas water.
Chinese patent publication No. CN207412965U discloses a coal mine gas purification treatment device system, which comprises a primary filtering device, a condensation dehydration device, a booster fan, a precision filter and a metering device, which are connected in sequence. The device adopts a gravity dehydration and condensation dehydration combined mode for dehydrating the gas power generation feed gas, but the dehydration efficiency of the device cannot meet the separation requirement of stricter dew point temperature requirement.
Chinese patent application publication No. CN110876880A discloses a combined multi-stage purification apparatus, which comprises a base, a pre-primary filter, a freezing dryer, a three-stage filter, an adsorption dryer, and a post-filter. The treated object is air, the compressed air is used for purification treatment of compressed air, and gaseous saturated water is mainly treated. The desired treatment effect cannot be achieved for a gas containing saturated liquid water.
Chinese patent application publication No. CN110408445A, which discloses a wellhead natural gas dehydration and dehumidification device and method. The device comprises a gas-liquid preseparator, a heat exchanger, a first-stage gas-liquid separator, a throttle pipe, a last-stage gas-liquid separator and control valves on pipelines. The method adopts a multi-stage gas-liquid separation mode to treat the wellhead natural gas, and the removed gas is mainly gaseous condensate which can not remove saturated liquid water and can not meet the removal requirement of the dew point temperature below-50 ℃.
The existing method can be used for dehydrating the coal bed gas, liquid water can be removed only singly, the separation efficiency is generally low (80-85 percent), and gaseous water cannot be removed; gaseous water removal can only remove gaseous water singly and not liquid water. The combined form of the liquid water and the gaseous water removal method is also influenced by low liquid water removal efficiency, so that the gaseous water removal load is increased, and the final dehydration efficiency is influenced. These impact the cost burden on coal bed gas mining and utilization enterprises both technically and economically.
Therefore, for the coal bed gas containing saturated liquid water extracted by the pumping and drainage pump station, a method which can remove both liquid water and gaseous water and has high dehydration efficiency needs to be developed to solve the technical problems, so that the coal bed gas can be suitable for power generation or pressure swing adsorption concentration and purification after dehydration.
Disclosure of Invention
The invention aims to provide a combined dehydration and purification method in the coal bed gas utilization process, which is characterized in that liquid water is firstly removed, the removal efficiency meets the air inlet requirement of a gaseous water removal process, then gaseous water is removed, and the dew point after dehydration can meet the subsequent process requirements of pressure swing adsorption separation and the like.
The invention provides a combined dehydration and purification method in a coal bed gas utilization process, which comprises the following steps:
(1) conveying the coal bed gas to a liquid water removal and separation device to carry out liquid water removal and separation treatment on the coal bed gas to obtain the coal bed gas with liquid water removed;
(2) conveying the coal bed gas treated in the step (1) to a compression device to perform compression treatment on the coal bed gas;
(3) conveying the coal bed gas treated in the step (2) to a first filtering device to perform first filtering treatment on the coal bed gas;
(4) conveying the coal bed gas treated in the step (3) to a first gaseous water removal device to perform first gaseous water removal treatment on the coal bed gas;
(5) conveying the coal bed gas treated in the step (4) to a second filtering device to carry out second filtering treatment on the coal bed gas;
(6) conveying the coal bed gas treated in the step (5) to a second gaseous water removal device to perform second gaseous water removal treatment on the coal bed gas;
(7) conveying the coal bed gas treated in the step (6) to a third filtering device to carry out third filtering treatment on the coal bed gas; finally, the dehydrated and purified coal bed gas is obtained for being conveyed to a subsequent unit for use.
Wherein, the liquid water removing and separating device is a cyclone demister, and a gas inlet of the cyclone demister inclines downwards at an inclination angle of 10-25 degrees.
Wherein, the liquid water in the coal bed gas is removed by more than 95 mass percent through the treatment of the step (1).
A sewage discharge bin is arranged below the cyclone demister, and liquid water obtained by separation is discharged through the sewage discharge bin. The cyclone demister is designed by modifying the liquid water mist drop characteristic by using the separation principle of a cyclone dust collector on dust particles. Conventional cyclones take a horizontal tangential feed, resulting in the presence of an ash ring (or droplet ring) on top. The gas inlet of the cyclone demister is inclined downwards at a certain inclination angle, and the inclination angle ranges from 10 degrees to 25 degrees.
When the cyclone demister works, moisture-containing gas enters the cyclone demister in a straight cutting mode at the wind speed of 16-19m/s, the top cover of the demister is a spiral plate with a certain inclination angle, and the gas inlet is tangent to the straight cylinder and the top cover according to the inclination angle of the top cover. The method effectively eliminates the existence of an ash ring (or a liquid drop ring), increases the axial speed of the gas, strengthens the disturbance of the gas after entering the cone body, and ensures that the flow pattern is more standard, the separation efficiency is higher and the division is clearer when the gas is inverted into an inner rotational flow in the cone body.
Generally, the larger the angle of inclination, the smaller the pressure drop, but the lower the separation efficiency. However, the cyclone demister adopts a small-cone-angle long cone structure, has low inlet air speed and low rotation speed, so the pressure drop is small, the amplification effect is small, the accumulation degree of liquid drop rings can be effectively reduced, the separation efficiency is improved by more than 10 percent, and the separation efficiency of the particle fog drops with the particle size of more than 5 microns can reach more than 95 percent.
The cyclone mist eliminator of the present invention has the configuration shown in FIG. 3.
Through the treatment of the step (1), more than 95% of liquid water in the coal bed gas can be separated and removed, and a large amount of liquid water is prevented from entering a freezing dryer of a gaseous water removal device, so that the following technical problems are avoided: the processing load of the freezing dryer is increased, the gaseous water removal efficiency is reduced, and the pipeline is blocked due to freezing of the gas pipeline, so that the device cannot work normally.
Wherein the compression device comprises a screw compressor. This is a general purpose device that is commercially available from the open market and can be selected based on the actual gas throughput. The purpose of this step is to improve the coal bed gas pressure and meet the requirements of the gas water separation process.
Wherein the first filtering device comprises an oil-water separation filter.
The oil-water separation filter is a general purpose device that is commercially available from the open market, and the device can be selected based on the actual gas throughput. The step is to remove dust and water contained in the gas so as to achieve the aim of purifying the coal bed gas. The step can effectively intercept particle fog drops with the particle size of 3 microns, further remove 5% of residual liquid water after separation of the cyclone demister, and remove the residual liquid water to about 1% of residual liquid water. The oil-water separation filter can prevent residual liquid water from directly entering the freeze dryer, so that the following technical problems are avoided: additionally increase the load that the freezing formula desiccator handled remaining liquid water, freezing formula desiccator gaseous state water desorption efficiency reduces, influences absorption formula desiccator separation efficiency or follow-up pressure swing adsorption separation efficiency, and the gas line freezes simultaneously and blocks up the pipeline and lead to the unable normal work of device.
Wherein, the second filter equipment is including being responsible for filter and high-efficient deoiling filter, perhaps the second filter equipment is including high-efficient deoiling filter.
Wherein, the third filter equipment is including being responsible for filter and high-efficient deoiling filter, perhaps the third filter equipment is including high-efficient deoiling filter.
The main pipe filter and the high-efficiency oil removing filter are all universal equipment and can be purchased from public commercial sources, and the equipment can be selected according to actual gas treatment capacity. The method is used for removing dust and oil contained in the gas so as to achieve the aim of purifying the coal bed gas. Wherein, the filter in the main pipe can effectively intercept particle fog drops of 1 μm, and prevent condensed water generated when the gaseous water removal efficiency of the freezing dryer is reduced or the gas-liquid separation tank of the device is in failure from entering a subsequent system. The high-efficiency oil removal filter can effectively intercept particle fog drops and oil fog drops of 0.01 mu m, and prevent micro oil fog drops brought by the preorder system from entering a subsequent purification system to cause poisoning failure of an adsorbent and influence the separation efficiency of the adsorption dryer or the subsequent pressure swing adsorption separation efficiency.
Wherein the first gaseous water removal device is a freeze dryer.
Wherein the second gaseous water removal device is an adsorption dryer.
The freeze dryer and the adsorption dryer are general-purpose devices, which are commercially available from the public, and the devices can be selected according to the actual gas treatment amount. The dew point of the gas is reduced after the dehydration of the freezing dryer, and the dew point is further reduced after the dehydration of the adsorption dryer, so that the utilization requirement of the subsequent unit is met.
Wherein, the liquid water in the coal bed gas is removed by more than 99 percent by mass through the treatment of the step (3).
Wherein the dehydrated and purified coal bed gas obtained after the treatment in the step (7) has a dew point temperature lower than-50 ℃.
The invention relates to a combined dehydration and purification method in the coal bed gas utilization process, which takes the coal bed gas as a raw material, firstly carries out liquid water removal treatment, then increases the gas pressure through compression and pressurization, enters a filter for filtration treatment, carries out gas water removal treatment on the filtered coal bed gas, and finally sends the coal bed gas to a subsequent unit for utilization after dust removal and oil removal through the filter. The method can effectively reduce the dew point temperature of the coal bed gas while removing liquid water and gaseous water in the coal bed gas so as to meet the requirements of the subsequent process.
The liquid water in the process is removed by the cyclone demister, and the separation efficiency of the particles with the particle size of more than 5 mu m is high and can reach more than 95%.
The gaseous water is removed by adopting a combined dehydration mode of a freezing dryer and an adsorption dryer, so that the dew point temperature is greatly reduced, and the utilization requirements of different coal bed gases can be met.
The multi-stage filtration mode is adopted, and the combined use of various filters is reasonably arranged, so that the treatment requirement of the subsequent process is effectively met, the service life of the device is prolonged, and the cost is saved.
Drawings
FIG. 1 is a flow chart of a combined dehydration and purification method in a coal bed gas utilization process provided by the invention.
Fig. 2 is a flow chart of a method for dehydration and purification by combination of cyclone dehydration and freezing type adsorption drying dehydration in a coal bed gas utilization process according to an embodiment of the present invention.
Fig. 3 is a structural diagram of the appearance of a cyclone demister used in the combined dehydration and purification method in the coal bed gas utilization process provided by the invention.
FIG. 4 is a graph showing the comparison of the efficiency of the cyclone mist eliminator of the present invention with that of a conventional cyclone separator.
FIG. 5 is a graph showing the pressure drop of the cyclone mist eliminator of the present invention compared with that of a conventional cyclone separator
Detailed Description
The present invention will be further described with reference to the following examples, but the present invention is not limited to the following examples. The following methods are all conventional methods unless otherwise specified. The devices or apparatuses are conventional devices or apparatuses unless otherwise specified. The liquid water content is a mass percentage content unless otherwise specified. The gas dew point temperature is the dew point temperature at atmospheric pressure and has the unit of ℃. Wherein, the liquid water content is measured by adopting an adsorption weighing method, and the dew point temperature of the gaseous water is measured by adopting a dew point meter.
Example 1:
fig. 2 shows a process flow of the coalbed methane combined dehydration and purification method of the invention. Wherein, 1 is the coal bed gas, 2 is the coal bed gas whirlwind desorption liquid water step, 3 is the whirlwind dehydration blowdown, 4 is the coal bed gas step after the compression desorption liquid water, 5 is the oil water filtration step, 6 is the freeze drying desorption gaseous water step, 7 is the freeze drying dehydration, the oil water filters, be responsible for and filter and collect the blowdown with high-efficient deoiling, 8 are responsible for the filtration step, 9 is high-efficient deoiling filtration step, 10 is the dry desorption gaseous water step of adsorption, 11 is adsorption drying dehydration, the oil water filters, be responsible for filtering and high-efficient deoiling filters and collects the blowdown, 12 are responsible for the filtration step, 13 is high-efficient deoiling filtration, 14 is the dehydration purification coal bed gas.
The combined dehydration and purification method comprises the following specific steps:
(i) carrying out liquid water separation on the coal bed gas containing saturated liquid water through a cyclone demister to obtain the coal bed gas with the liquid water removed;
in the step, the sewage 3 generated by the separation of the cyclone demister is discharged through a sewage discharging bin;
wherein the coal bed gas pressure of the saturated liquid water is 5kPa, the coal bed gas pressure after the liquid water is removed is 4.4kPa, and the dewatering efficiency of the cyclone demister is 93-94%.
The cyclone mist eliminator of the present invention is shown in FIG. 3, in which: a is cyclone demister body, b is blowdown storehouse, c is gas inlet, d is gas outlet, and e is the drain.
The cyclone demister and the common cyclone separator (model: D) of the inventionIIIType) gas dehydration efficiency versus pressure drop is shown in fig. 4 and 5, as can be seen in fig. 4-5: in the aspect of gas dehydration efficiency, the dehydration efficiency of the DN150 cyclone demister and the dehydration efficiency of the DN400 cyclone demister of the invention show a consistent trend under different gas inlet flow rates, taking the gas inlet flow rate of 18m/s as an example, ordinary DIIIThe dewatering efficiency of the cyclone separator reaches about 84 percent, while the dewatering efficiency of the cyclone demister reaches about 94 percent, and the dewatering efficiency is improved by 10 percent. In the aspect of gas pressure drop after dehydration, the pressure drop after dehydration of the gas of the two cyclone demisters of DN150 and DN400 is obviously lower than that of the gas of the common DIIIPressure drop of gas after dehydration in a cyclone separator, taking the inlet flow rate of 18m/s as an example, ordinary DIIIThe pressure drop of the gas after dehydration of the cyclone separator is about 1.7kPa, while the pressure drop of the gas after dehydration of the cyclone demister is about 0.6kPa, and the pressure drop of the gas after dehydration is reduced by 1.1 kPa.
The dehydration efficiency testing method adopts a mass method to calculate the dehydration separation efficiency, and measures the water content of the inlet end and the water content of the outlet end of the cyclone demister respectively so as to calculate the dehydration efficiency. The water content is measured by a water absorption weighing method, the measuring tube filled with the water absorption drying agent is used for respectively taking gas from the pipeline sampling ports at the inlet end and the outlet end of the cyclone demister under the conditions of the same flow and the same sampling time, and the change of the water absorption is measured, so that the dehydration efficiency is calculated. The pressure drop was measured using a differential pressure gauge.
(ii) (ii) compressing the coal bed gas obtained in the step (i) after liquid water is removed to obtain compressed coal bed gas, wherein the compressed coal bed gas pressure is 650 kPa;
(iii) (iii) passing the compressed coal bed methane obtained in step (ii) through an oil-water separation filter to obtain a first compressed coal bed methane which is further dewatered to obtain liquid water;
in the step, the sewage generated by the oil-water separation filter is collected to a sewage 7 and then is intensively discharged;
(iv) (iv) dehydrating the first filtered and liquid-state water-removed compressed coal bed gas obtained in the step (iii) by using a freeze dryer to obtain a first-stage degassed liquid-state water coal bed gas;
in the step, the sewage generated by the freezing dryer is collected to the sewage 7 and then is intensively discharged;
wherein, the coal bed gas pressure after the first stage dehydration filtration is 630kPa, and the gas dew point temperature is-30 ℃;
(v) filtering the first-stage degassed-state water coal bed gas obtained in the step (iv) by using a main pipe filter to obtain a second filtered degassed-state water coal bed gas;
in the step, the sewage generated by the main pipe filter is collected to the sewage 7 and then is intensively discharged;
(vi) (vi) filtering the second filtered and degassed state water coal bed gas obtained in the step (v) by using a high-efficiency oil removal filter to obtain a third filtered and degassed state water coal bed gas;
in the step, the sewage generated by the high-efficiency oil removal filter is collected to the sewage 7 and then is intensively discharged;
(vii) (vii) dehydrating the third filtered and degassed coal bed gas of water obtained in the step (vi) by an adsorption dryer to obtain a second stage degassed coal bed gas of water;
in the step, the blowdown generated by the adsorption dryer is collected to the blowdown 11 and then is intensively discharged;
wherein the coal bed gas pressure after the second-stage dehydration filtration is 600kPa, and the gas dew point temperature is-70 ℃.
(viii) (viii) filtering the second-stage degassed water coal bed gas obtained in the step (vii) by using a main pipe filter to obtain a fourth filtered degassed water coal bed gas;
in the step, the sewage generated by the main pipe filter is collected to the sewage 11 and then is intensively discharged;
(viii) filtering the fourth filtered and degassed coal bed gas of water obtained in the step (viii) by using a high-efficiency oil removal filter to obtain a fifth filtered and degassed coal bed gas of water, namely the dehydrated and purified coal bed gas 14;
the sewage generated by the high-efficiency oil removal filter in the step is collected to the sewage 11 and then is intensively discharged.
Example 2:
the combined dehydration purification process of this embodiment is substantially the same as that of embodiment 1, and is different from that of embodiment 1 only in that the filtration step after the freeze drying and removal of the gaseous water is only provided with a high-efficiency oil removal filter, and the dew point temperature of the coal bed methane after the dehydration purification of the process is-70 ℃.
Example 3:
the combined dehydration purification process of this embodiment is substantially the same as that of embodiment 1, and is different from that of embodiment 1 only in that the filtration step after the adsorption drying and removal of the gaseous water is only provided with a high-efficiency oil removal filter, and the dew point temperature of the coal bed methane after the dehydration purification of the process is-70 ℃.
Comparative example 1:
the combined dehydration purification process of this comparative example is essentially the same as that of example 1, except that the liquid water removal step is carried out using conventional DIIIThe cyclone type separator has dewatering efficiency of only about 84%. The dew point temperature of the coal bed gas after dehydration and purification by the process is-45 ℃.
Comparative example 2:
the combined dehydration purification process of this comparative example is substantially the same as that of example 1, except that if a freeze dryer is used alone in the gaseous water removal step, the dew point temperature of the coal bed gas after dehydration purification of the process is-30 ℃.
Comparative example 3:
the combined dehydration purification process of this comparative example is substantially the same as that of example 1, except that if an adsorption dryer is used alone in the gaseous water removal step, the dew point temperature of the coal bed gas after dehydration purification of the process is-40 ℃.
Comparative example 4:
the combined dehydration purification process of this comparative example is substantially the same as that of example 1, except that the filtration step before the removal of the gaseous water is not provided with an oil-water filter, and the dew point temperature of the coal bed gas after dehydration purification of the process is-55 ℃, but does not meet the gas inlet requirement of the process for producing Compressed Natural Gas (CNG) by using the gas as the raw material gas.
Comparative example 5:
the combined dehydration purification process of this comparative example is substantially the same as that of example 1, and the only difference is that if only the main pipe filter is provided in the filtration step after the freeze drying and removal of the gaseous water, the dew point temperature of the coal bed gas after the dehydration purification of the process is-70 ℃, but oil mist drops below 0.01 μm cannot be removed, which results in poisoning of the adsorbent used in the adsorption dryer, shortened service life and reduced dehydration separation efficiency of the gaseous water.
Comparative example 6:
the combined dehydration purification process of the comparative example is basically the same as that of example 1, and is different in that if only a main pipe filter is arranged in the filtration step after the adsorption, drying and removal of the gaseous water, the dew point temperature of the coal bed gas after the dehydration purification of the process is-70 ℃, but oil mist drops below 0.01 μm cannot be removed, so that an adsorbent used for the subsequent pressure swing adsorption separation is poisoned, the service life is shortened, and the separation efficiency is reduced.
Claims (6)
1. A combined dehydration and purification method in the utilization process of coal bed gas comprises the following steps:
(1) conveying the coal bed gas to a liquid water removal and separation device to carry out liquid water removal and separation treatment on the coal bed gas;
(2) conveying the coal bed gas treated in the step (1) to a compression device to perform compression treatment on the coal bed gas;
(3) conveying the coal bed gas treated in the step (2) to a first filtering device to perform first filtering treatment on the coal bed gas;
(4) conveying the coal bed gas treated in the step (3) to a first gaseous water removal device to perform first gaseous water removal treatment on the coal bed gas;
(5) conveying the coal bed gas treated in the step (4) to a second filtering device to carry out second filtering treatment on the coal bed gas;
(6) conveying the coal bed gas treated in the step (5) to a second gaseous water removal device to perform second gaseous water removal treatment on the coal bed gas;
(7) conveying the coal bed gas treated in the step (6) to a third filtering device to carry out third filtering treatment on the coal bed gas; finally obtaining the dehydrated and purified coal bed gas for conveying to a subsequent unit for use,
wherein,
the liquid water removing and separating device is a cyclone demister, a gas inlet of the cyclone demister inclines downwards at an inclination angle of 10-25 degrees,
the first filtering device comprises an oil-water separation filter;
the second filtering device comprises a main pipe filter and a high-efficiency oil removing filter;
the third filtering device comprises a main pipe filter and a high-efficiency oil removing filter;
the main pipe filter intercepts particle fog drops with the diameter of 1 mu m, and the high-efficiency oil removal filter intercepts particle fog drops and oil fog drops with the diameter of 0.01 mu m.
2. The combined dehydration and purification method in the coal bed gas utilization process according to claim 1, wherein more than 95 mass% of liquid water in the coal bed gas is removed by the treatment of step (1).
3. The integrated dehydration and purification method in coal bed methane utilization process according to claim 1, wherein said first gaseous water removal device is a freeze dryer.
4. The integrated dehydration and purification method in coal bed methane utilization process according to claim 1, wherein said second gaseous water removal device is an adsorption dryer.
5. The combined dehydration and purification method in the coal bed gas utilization process according to claim 1, wherein more than 99 mass% of liquid water in the coal bed gas is removed by the treatment of step (3).
6. The combined dehydration and purification method in the coal bed gas utilization process according to claim 1, wherein the dehydrated and purified coal bed gas obtained after the treatment of step (7) has a dew point temperature lower than-50 ℃.
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