A method for recycling underground coal synthesis gas produced water

Abstract

The present invention relates to a method for recycling produced water from underground coal synthesis gas, comprising: recovering heat from synthesis gas from an underground gasifier having a temperature higher than 200°C, cooling the temperature to about 110°C, and then entering a main three-phase separator for water-oil-gas three-phase separation; the liquid discharged from the liquid phase of the main three-phase separator is throttled and depressurized to 0.3MPa and then separated by a third three-phase separator; the liquid in the liquid phase of the third three-phase separator is sent to a rough treatment system for cooling, sedimentation, aeration, degradation, and separation processes, and then injected into the underground gasifier after being pressurized in multiple stages; the present invention has the advantage of multi-stage treatment and utilization.

Description

Technical Field

[0001] The invention belongs to the technical field of underground coal synthesis gas produced water reuse, and in particular relates to an underground coal synthesis gas produced water reuse method. Background Art

[0002] Underground coal gasification is the process of converting physical coal mining into chemical gas extraction through the in-situ transformation of coal underground. Underground coal gasification has outstanding advantages such as short process, high safety, environmental friendliness, and good investment economy. It is highly valued by countries around the world and is an important supplement to coal mining and utilization technology.

[0003] Underground coal gasification will produce a lot of water during the high-temperature gasification process, and the synthesis gas will contain more than half of the water vapor at a high temperature of up to 200°C. In the production process of the underground gasifier, a large amount of oxygen (or oxygen-enriched air or air) and water need to be injected. If the water produced in the high-temperature synthesis gas is recycled, the amount of raw water required by the gasifier will be greatly reduced.

[0004] However, the water and groundwater produced during the underground high-temperature coal gasification process have complex compositions, mainly containing various phenols, ammonia nitrogen, sulfide, coal gas, dust and other components. In addition, the produced water contains a lot of calcium, magnesium, sodium, potassium, chloride ions, bicarbonate and other salts. Therefore, a method for recycling underground coal synthesis gas produced water that can be processed and utilized in multiple stages is needed. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for recycling underground coal synthesis gas produced water with multi-stage treatment and utilization.

[0006] The technical solution of the present invention is as follows:

[0007] A method for recycling underground coal synthesis gas produced water comprises the following steps:

[0008] S1: The synthesis gas from the underground gasifier with a temperature higher than 200°C is cooled to 110°C after heat recovery, and then enters the main three-phase separator for water, oil and gas three-phase separation;

[0009] S2: The liquid discharged from the liquid phase of the main three-phase separator is throttled and depressurized to 0.3MPa and then separated by the third three-phase separator. The liquid phase of the third three-phase separator is sent to the rough treatment system for cooling, sedimentation, aeration, degradation, separation process, and then injected into the underground gasifier after multi-stage pressurization;

[0010] S3: The gas discharged from the gas phase of the main three-phase separator enters the water scrubber for cooling and oil removal. The gas after cooling and oil removal enters the synthesis gas purification system for purification and discharge;

[0011] S4: The liquid discharged from the liquid phase of the water washing tower is throttled to 0.3MPa and then separated by the first three-phase separator. The water discharged from the liquid phase of the first three-phase separator is cooled to 40°C by an air cooler and then enters the sewage purification system. The water is purified by the sewage purification system through PH adjustment, filtration, sedimentation, biochemical treatment, aeration, degradation, adsorption, and separation, and then pressurized to 3.5MPa by a medium-pressure pump and sent to the top of the water washing tower.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] 1. The present invention realizes the rough purification of the liquid of underground coal synthesis gas through the third three-phase separator and the rough treatment system and then reinjects it, thereby realizing the liquid treatment and reuse of underground coal synthesis gas;

[0014] 2. The present invention uses a first three-phase separator, an air cooler and a sewage purification system to achieve the treatment and purification of the water discharged from the water washing tower liquid phase, thereby achieving liquid treatment and reuse of the water washing tower liquid phase, thereby achieving multi-stage treatment and utilization;

[0015] In summary, the present invention has the advantages of multi-stage processing utilization.

[0016] Furthermore, the gas discharged from the gas phase of the first three-phase separator and the gas discharged from the gas phase of the third three-phase separator are mixed, cooled once, separated twice, compressed and cooled twice, and after three separations, mixed with the gas cooled and deoiled in step S3 and then transported to the synthesis gas purification system.

[0017] Furthermore, the gas discharged from the gas phase of the first three-phase separator and the gas discharged from the gas phase of the third three-phase separator are mixed and then separated for the second time by the second three-phase separator, and the gas phase of the second three-phase separator is compressed and cooled for the second time before being transported to the synthesis gas purification system, and the liquid discharged from the liquid phase of the second three-phase separator and the liquid discharged from the liquid phase of the third three-phase separator are mixed and then transported to the rough treatment system.

[0018] Furthermore, the inlet of the main three-phase separator is sequentially provided with a main cooler, a first cooler, and a main mixer through a pipeline, and the liquid phase outlet of the main three-phase separator is sequentially connected with a first throttle valve, a third three-phase separator, and a rough treatment system through a pipeline;

[0019] The gas phase outlet of the main three-phase separator is connected to a water washing tower, a main throttle valve connected to the liquid phase outlet of the water washing tower, a first three-phase separator, a first air cooler connected to the liquid phase outlet of the first three-phase separator, and a sewage purification system in sequence through a pipeline, and the sewage purification system is connected to the water washing tower through a pipeline;

[0020] The gas phase outlet of the water washing tower is connected to a second mixer.

[0021] Furthermore, a first mixer is connected to the liquid phase outlet of the third three-phase separator, and the first mixer is connected to the third air cooler, the first sewage treatment unit, and the high-pressure pump in sequence through a pipeline.

[0022] Furthermore, the sewage purification system includes an auxiliary mixer connected to the first air cooler, and a main sewage treatment unit connected to the liquid phase outlet of the auxiliary mixer, and the main sewage treatment unit is connected to the medium pressure pump and the water washing tower in sequence through pipelines.

[0023] Furthermore, the gas phase outlet of the first three-phase separator is connected to the third mixer, the main air cooler, the second three-phase separator, the compressor connected to the gas phase outlet of the second three-phase separator, the second air cooler, and the two-phase separator in sequence through a pipeline, and the gas phase outlet of the two-phase separator is connected to the second mixer.

[0024] Furthermore, the gas phase outlet of the third three-phase separator is connected to the third mixer, and the liquid phase of the second three-phase separator is connected to the first mixer. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the pipeline structure of the present invention.

[0026] In the figure, main mixer SAT-100, first cooler E-101, main cooler E-100, main three-phase separator V-100, first throttle valve VLV-101, third three-phase separator V-103, first mixer MIX-101, third air cooler AC-103, first sewage treatment unit X-101, high-pressure pump P-106, water washing tower T-100, medium-pressure pump P-100, main throttle valve VLV-100, first three-phase separator V-101, first air cooler AC-101, auxiliary mixer TEE-100, main sewage treatment unit X-100, third mixer MIX-100, main air cooler AC-100, second three-phase separator V-102, compressor K-100, second air cooler AC-102, two-phase separator V-104, second mixer MIX-102. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] like Figure 1As shown, a method for recycling underground coal synthesis gas produced water comprises the following steps:

[0029] S1: The synthesis gas from the underground gasifier with a temperature higher than 200°C is cooled to 110°C after heat recovery. The temperature of the synthesizer of the underground gasification line can fluctuate around 110°C, and then enters the main three-phase separator V-100 for water, oil and gas three-phase separation;

[0030] S2: The liquid discharged from the liquid phase of the main three-phase separator V-100 is throttled and depressurized to 0.3MPa and then separated by the third three-phase separator V-103. The liquid of the liquid phase of the third three-phase separator V-103 is sent to the rough treatment system for cooling, sedimentation, aeration, degradation, separation process, and then injected into the underground gasifier after multi-stage pressurization;

[0031] S3: The gas discharged from the gas phase of the main three-phase separator V-100 enters the water washing tower T-100 for cooling and deoiling. The gas after cooling and deoiling enters the synthesis gas purification system for purification and discharge;

[0032] S4: The liquid discharged from the liquid phase of the water washing tower T-100 is throttled to 0.3MPa and then separated by the first three-phase separator V-101. The water discharged from the liquid phase of the first three-phase separator V-101 is cooled to 40°C by the first air cooler AC-101 and then enters the sewage purification system. The temperature of the water discharged from the liquid phase of the first three-phase separator V-101 after cooling by the first air cooler AC-101 can fluctuate around 40°C. The water is purified by the sewage purification system through PH adjustment, filtration, sedimentation, biochemical treatment, aeration, degradation, adsorption, and separation, and then pressurized to 3.5MPa by the medium-pressure pump P-100 and sent to the top of the water washing tower T-100. The gas discharged from the gas phase of the first three-phase separator V-101 and the gas discharged from the gas phase of the third three-phase separator V-101 are mixed with the gas discharged from the gas phase of the third three-phase separator V-101. The gas discharged from the gas phase of the phase separator V-103 is mixed, cooled once, separated twice, compressed and cooled twice, and after three separations, it is mixed with the gas that has been cooled and deoiled in step S3 and then transported to the synthesis gas purification system. The gas discharged from the gas phase of the first three-phase separator V-101 and the gas discharged from the gas phase of the third three-phase separator V-103 are mixed and passed through the second three-phase separator V-102 for secondary separation, and the gas phase of the second three-phase separator V-102 is compressed and cooled twice and then transported to the synthesis gas purification system. The liquid discharged from the liquid phase of the second three-phase separator V-102 and the liquid discharged from the liquid phase of the third three-phase separator V-103 are mixed and then sent to the rough treatment system.

[0033] Through the above steps, the utilization rate of produced water can be achieved to be greater than 95%, and the impurity components in the synthesis gas can be effectively reduced through the water washing tower T-100, so as to achieve the purposes of dust reduction, oil removal and temperature reduction. The problem that coal tar may block the bottom of the water washing tower and sewage is difficult to recycle and reuse is effectively solved, so that the synthesis gas can meet the requirements of the subsequent treatment process. The two-stage sewage circulation treatment process of roughly purifying the produced water of the underground gasification furnace synthesis gas and finely purifying the sewage of the water washing tower is adopted, which effectively reduces the treatment process and difficulty. At the same time, the amount of recyclable and recycled water is 600t / h, which greatly reduces the consumption of raw water.

[0034] In this embodiment, if Figure 1 As shown, the inlet of the main three-phase separator V-100 is sequentially provided with a main cooler E-100, a first cooler E-101, and a main mixer SAT-100 through a pipeline, the liquid phase outlet of the main three-phase separator V-100 is sequentially connected to the first throttle valve VLV-101, the third three-phase separator V-103, and a rough treatment system through a pipeline, the gas phase outlet of the main three-phase separator V-100 is sequentially connected to a water washing tower T-100, the main throttle valve VLV-100 connected to the liquid phase outlet of the water washing tower T-100, the first three-phase separator V-101, the first air cooler AC-101 connected to the liquid phase outlet of the first three-phase separator V-101, and a sewage purification system through a pipeline, the sewage purification system is connected to the water washing tower T-100 through a pipeline, and the gas phase outlet of the water washing tower T-100 is connected to the second mixer MIX-102;

[0035] When in use, the main mixer SAT-100 is used to mix the synthesis gas of the underground gasifier, and the main cooler E-100 and the first cooler E-101 are used to physically cool the synthesis gas of the underground gasifier with a temperature higher than 200°C to about 110°C to prevent the synthesis gas of the underground gasifier from being too high. The main three-phase separator V-100 is used to separate the synthesis gas of the underground gasifier at one level, and the separated gas enters the water scrubber T-100 for purification, and the synthesis gas of the underground gasifier that has passed through the water scrubber T-100 is discharged into the synthesis gas purification system after passing through the second mixer MIX-102;

[0036] The liquid discharged from the liquid phase outlet at the bottom of the water washing tower T-100 is throttled and depressurized by the main throttle valve VLV-100, so that the liquid is depressurized to 0.3MPa and then passes through the first three-phase separator V-101 to separate the oil, water and gas. The separated liquid is cooled by the first air cooler AC-101 and then enters the sewage purification system, thereby achieving liquid purification of the water washing tower T-100 and conveying the purified liquid to the water washing tower T-100, thereby achieving water recycling and greatly reducing the consumption of raw water.

[0037] The liquid discharged from the liquid phase of the main three-phase separator V-100 passes through the first throttle valve VLV-101 to achieve throttling and pressure reduction of the liquid, and is then separated at the second level by the third three-phase separator V-103. The separated liquid is processed by the rough treatment system and then reinjected, thereby realizing the recycling of the liquid and greatly reducing the consumption of raw water.

[0038] In this embodiment, the rough treatment system includes a first mixer MIX-101 connected to the liquid phase outlet of the third three-phase separator V-103. The first mixer MIX-101 is connected to the third air cooler AC-103, the first sewage treatment unit X-101, and the high-pressure pump P-106 in sequence through pipelines. The first sewage treatment unit X-101 is a prior art and will not be described in detail. The third air cooler AC-103 is used to cool the liquid in the liquid phase of the third three-phase separator V-103, and the first sewage treatment unit X-101 is used to perform sedimentation, aeration, degradation, and separation processes on the cooled liquid. Finally, the high-pressure pump P-106 is used to perform multi-stage pressurized reinjection of the purified liquid.

[0039] In this embodiment, the sewage purification system includes an auxiliary mixer TEE-100 connected to the first air cooler AC-101, and a main sewage treatment unit X-100 connected to the liquid phase outlet of the auxiliary mixer TEE-100. The main sewage treatment unit X-100 is connected to the medium-pressure pump P-100 and the water washing tower T-100 in sequence through pipelines. The main sewage treatment unit X-100 is a prior art, so it is not repeated here. The dirty oil in the liquid cooled by the first air cooler AC-101 is separated by the auxiliary mixer TEE-100, and the liquid from which the dirty oil is separated enters the main sewage treatment unit X-100. The main sewage treatment unit X-100 performs pH adjustment, filtration, sedimentation, biochemical treatment, aeration, degradation, adsorption, and separation treatment on the liquid from which the dirty oil is separated. The treated liquid is injected back into the water washing tower T-100 through the medium-pressure pump P-100.

[0040] In this embodiment, the gas phase outlet of the first three-phase separator V-101 is connected to the third mixer MIX-100, the main air cooler AC-100, the second three-phase separator V-102, the compressor K-100 connected to the gas phase outlet of the second three-phase separator V-102, the second air cooler AC-102, and the two-phase separator V-104 in sequence through pipelines, and the gas phase outlet of the two-phase separator V-104 is connected to the second mixer MIX-102; when in use, the main air cooler AC-100 is used to cool the gas discharged from the gas phase outlet of the first three-phase separator V-101, and the second three-phase separator V-102 is used to achieve secondary separation, and then the compressor K-100 is used to compress the gas discharged from the gas phase outlet of the second three-phase separator V-102, and finally the two-phase separator V-104 is used to achieve tertiary separation.

[0041] In this embodiment, the gas phase outlet of the third three-phase separator V-103 is connected to the third mixer MIX-100, and the liquid phase of the second three-phase separator V-102 is connected to the first mixer MIX-101; when in use, the gas at the gas phase outlet of the third three-phase separator V-103 and the gas at the gas phase outlet of the first three-phase separator V-101 are mixed through the third mixer MIX-100 to ensure the recovery of the underground gasification furnace synthesis gas, and the liquid discharged from the liquid phase outlet of the second three-phase separator V-102 and the liquid discharged from the liquid phase outlet of the third three-phase separator V-103 are mixed through the first mixer MIX-101, thereby ensuring the recovery and utilization of water and greatly reducing the consumption of raw water.

[0042] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for recycling underground coal synthesis gas produced water, comprising the following steps: S1: The synthesis gas from the underground gasifier with a temperature higher than 200°C is cooled to 110°C after heat recovery, and then enters the main three-phase separator for water, oil and gas three-phase separation; S2: The liquid discharged from the liquid phase of the main three-phase separator is throttled and depressurized to 0.3MPa and then separated by the third three-phase separator. The liquid phase of the third three-phase separator is sent to the rough treatment system for cooling, sedimentation, aeration, degradation, and separation processes, and then injected into the underground gasifier after multi-stage pressurization; S3: The gas discharged from the gas phase of the main three-phase separator enters the water scrubber for cooling and oil removal. The gas after cooling and oil removal enters the synthesis gas purification system for purification and discharge; S4: The liquid discharged from the liquid phase of the water washing tower is throttled to 0.3MPa and then separated by the first three-phase separator. The water discharged from the liquid phase of the first three-phase separator is cooled to 40°C by the first air cooler and then enters the sewage purification system. The water is purified by the sewage purification system through PH adjustment, filtration, sedimentation, biochemical treatment, aeration, degradation, adsorption, and separation, and then pressurized to 3.5MPa by a medium-pressure pump and sent to the top of the water washing tower.

2. The method for recycling underground coal synthesis gas produced water according to claim 1, characterized in that: The gas discharged from the gas phase of the first three-phase separator and the gas discharged from the gas phase of the third three-phase separator are mixed, cooled once, separated twice, compressed and cooled twice, and after three separations, mixed with the gas cooled and deoiled in step S3 and then transported to the synthesis gas purification system.

3. A method for recycling underground coal synthesis gas produced water according to claim 2, characterized in that: The gas discharged from the gas phase of the first three-phase separator and the gas discharged from the gas phase of the third three-phase separator are mixed and then passed through the second three-phase separator for secondary separation, and the gas phase of the second three-phase separator is compressed and secondarily cooled before being transported to the synthesis gas purification system, and the liquid discharged from the liquid phase of the second three-phase separator and the liquid discharged from the liquid phase of the third three-phase separator are mixed before being transported to the rough treatment system.

4. The method for recycling underground coal synthesis gas produced water according to claim 3, characterized in that: The inlet of the main three-phase separator is sequentially provided with a main cooler, a first cooler, and a main mixer through a pipeline, and the liquid phase outlet of the main three-phase separator is sequentially connected with a first throttle valve, a third three-phase separator, and a rough treatment system through a pipeline; The gas phase outlet of the main three-phase separator is connected to a water washing tower, a main throttle valve connected to the liquid phase outlet of the water washing tower, a first three-phase separator, a first air cooler connected to the liquid phase outlet of the first three-phase separator, and a sewage purification system in sequence through a pipeline, and the sewage purification system is connected to the water washing tower through a pipeline; The gas phase outlet of the water scrubber is connected to a second mixer.

5. The method for recycling underground coal synthesis gas produced water according to claim 4, characterized in that: The rough treatment system includes a first mixer connected to the liquid phase outlet of the third three-phase separator, and the first mixer is connected to the third air cooler, the first sewage treatment unit, and the high-pressure pump in sequence through pipelines.

6. A method for recycling underground coal synthesis gas produced water according to claim 5, characterized in that: The sewage purification system comprises an auxiliary mixer connected to the first air cooler, and a main sewage treatment unit connected to the liquid phase outlet of the auxiliary mixer. The main sewage treatment unit is connected to a medium-pressure pump and a water washing tower in sequence through pipelines.

7. A method for recycling underground coal synthesis gas produced water according to claim 6, characterized in that: The gas phase outlet of the first three-phase separator is connected to the third mixer, the main air cooler, the second three-phase separator, the compressor connected to the gas phase outlet of the second three-phase separator, the second air cooler, and the two-phase separator in sequence through a pipeline, and the gas phase outlet of the two-phase separator is connected to the second mixer.

8. The method for recycling underground coal synthesis gas produced water according to claim 7, characterized in that: The gas phase outlet of the third three-phase separator is connected to the third mixer, and the liquid phase of the second three-phase separator is connected to the first mixer.

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