High pressure liquid gas injection system and method for in-situ dewatering of stockpiled waste

Abstract

This invention discloses a high-pressure liquid-gas injection system and method for in-situ dehydration treatment of existing waste. The system uses a mobile liquid-gas injection device and a sealed reverse filter layer to form a cylindrical space of a specific length at a designated depth within the existing waste. This cylindrical space is connected to the outside environment only through a central injection pipe and radially through the waste. Liquid and gas are injected into this cylindrical space via a pressurization device, the liquid-gas injection device, and the central injection pipe. The injected liquid and gas enter the cylindrical space through the central injection pipe and then radially into the existing waste through well openings and the reverse filter layer. By injecting air and ammonia nitrogen removal agents through the high-pressure liquid-gas injection system of this invention, pore water in the existing waste can be displaced, the concentration of odorous gases such as ammonia can be reduced, and aerobic degradation can be promoted. After pretreatment, the moisture content of the waste in situ is reduced, and the odor concentration is suppressed for a long time.

Description

Technical Field

[0001] This invention relates to a liquid-gas injection system, and to the field of in-situ remediation technology for landfills, specifically to a high-pressure liquid-gas injection system and method for in-situ dehydration treatment of existing waste. Background Technology

[0002] Food waste landfills have large amounts of liquid and gas accumulation, and there are problems such as high liquid level in the pile, high water content of the waste, and high odor concentration, which makes the landfill excavation, screening and treatment project very difficult.

[0003] To reduce the difficulty of landfill excavation and remediation projects and eliminate safety and environmental risks during the remediation process, in-situ pretreatment is usually carried out before remediation. Currently, the in-situ pretreatment technology used in landfill excavation and remediation projects generally involves injecting air into the landfill through a manhole (1) to quickly displace odors, with a treatment time of 7-10 days. Theoretical research, laboratory experiments, and engineering practice show that this technology currently has the following three problems: 1) The existing technology has a short treatment time. Simply injecting air and extracting landfill gas is insufficient to transform the anaerobic degradation environment in the landfill into an aerobic degradation environment within 7-10 days. Therefore, the main odorous gases such as ammonia and hydrogen sulfide in the landfill are only temporarily displaced during the injection and extraction process, and their concentrations quickly return to a high level within one day after the pretreatment stops; 2) The existing technology usually connects the manhole head of the manhole (1) directly to the blower equipment, injecting air into the landfill through the entire manhole. Under the designed airflow, it is difficult to form a high injection pressure within the manhole, and the air pressure decays rapidly along the path, with an influence radius of less than 5. m) It is difficult to reduce the moisture content of the garbage through the displacement effect of gas pressure. The moisture content of the treated garbage is usually higher than 40%, resulting in poor screening effect of excavated garbage; 3) At present, the well pipe 1 installed in the project only wraps a layer of nylon mesh around the well wall or fills the whole section with crushed stone as a filter structure. Since there are large pore channels between the well wall and the crushed stone filter layer or garbage, some of the air will be lost along the large pore channels of the well wall after it is ejected from the well pipe through hole, and will not enter the garbage, resulting in a large pressure loss. This is also one of the reasons for the small influence radius. Through indoor large model well pipe 1 air injection test, the inventor found that when a single layer of crushed stone is used as the filter structure, when the air injection pressure in the well is 28 kPa, the maximum air pressure measured by the monitoring well 10.7 meters away from the well pipe is only 16 kPa.

[0004] In summary, existing technologies generally suffer from poor odor suppression, low gas injection pressure, and large pressure loss in the filter layer, which makes it impossible to achieve safe excavation and efficient screening of waste. Summary of the Invention

[0005] To address the problems existing in the background technology, this invention provides a high-pressure liquid-gas injection system and method for in-situ dehydration treatment of existing waste. This invention addresses the issues of short odor suppression time, low injection pressure, and large pressure loss in the filter layer in existing technologies. By utilizing a specially designed segmented liquid-gas injection system and a segmented liquid-gas injection method for existing waste, it solves the problems of existing technologies, achieving high-pressure liquid-gas injection, in-situ reduction of waste moisture content, and effective odor suppression, thus achieving excellent technical results.

[0006] The technical solution adopted in this invention is:

[0007] I. A high-pressure liquid-gas injection system for in-situ dehydration treatment of existing waste:

[0008] The system includes a well casing, a mobile liquid-gas injection device, a sealed reverse filter layer, a pressurizing device, and a liquid-gas injection device. The well casing is vertically installed in the pre-treated stock waste, and several openings are evenly spaced on the casing wall. The mobile liquid-gas injection device is coaxially installed inside the well casing. The depth of the mobile liquid-gas injection device is adjustable to perform segmented in-situ dehydration treatment of the stock waste. The sealed reverse filter layer is installed between the outer wall of the well casing and the stock waste. The pressurizing device and the liquid-gas injection device are both located outside the well casing and are connected to the mobile liquid-gas injection device.

[0009] The mobile liquid-gas injection device includes two sealing devices, two central injection pipes, two plugs, and a connecting pipe. The two sealing devices are coaxially arranged in the well casing from top to bottom. Each sealing device includes an outer shell and a rubber bladder. The outer shell includes two caps and is coaxially fitted into the well casing. The rubber bladder is located between the two caps, with both ends located inside the two caps to form a single unit. The two central injection pipes are coaxially inserted into the centers of the two outer shells and the rubber bladder, spaced apart from each other. The two ends of the central injection pipes are located on the outer part of the outer shell of their respective sealing devices. The top end of the upper central injection pipe is connected to the liquid-gas injection device, and the bottom end of the upper central injection pipe is connected to the space between the two sealing devices. Both ends of the lower central injection pipe are plugged by plugs to seal the lower sealing device. The top and bottom ends of the upper outer shell and the top end of the lower outer shell are provided with pressure ports. The top end of the upper rubber bladder is connected to the pressure charging device through the pressure port. The two rubber bladders are connected to each other through the pressure port and the connecting pipe.

[0010] The mobile liquid-gas injection device also includes two connecting steel wire ropes, two lifting steel wire ropes, and a hand-cranked hoist. The hand-cranked hoist is located directly above the well pipe. The upper outer side of the upper central injection pipe is symmetrically equipped with first lifting rings on both sides. The hand-cranked hoist is connected to the two first lifting rings through the lower ends of the two lifting steel wire ropes. The lower outer side of the upper central injection pipe and the upper outer side of the lower central injection pipe are both equipped with second lifting rings. The second lifting rings of the two central injection pipes are connected to each other through connecting steel wire ropes. The hand-cranked hoist drives the two sealing devices to move up and down inside the well pipe.

[0011] The top and bottom of the well casing are sealed. When the two rubber bladders inflate and press tightly against the inner wall of the well casing, the processing area between the two sealing devices forms a space that communicates with the external environment only through the central injection pipe in the upper sealing device and the opening of the well casing.

[0012] The pressurizing device is connected to the rubber bladder located above through the pressurizing pipe and the pressurizing port. The pressurizing device injects water or air through the pressurizing port, the pressurizing pipe and the connecting pipe in sequence to make the two rubber bladders expand and stick tightly to the inner wall of the well pipe. The two rubber bladders contract by depressurizing.

[0013] The liquid-gas injection device includes a liquid injection pump and a gas injection pump. The liquid injection pump and the gas injection pump are connected to the top of the central injection pipe above through a liquid-gas delivery pipe. The liquid injection pump or the gas injection pump injects ammonia-removing nitrogen bacteria solution or air into the treatment area between the two sealing devices through the central injection pipe. The ammonia-removing nitrogen bacteria solution or air passes through the opening of the well pipe and the sealed reverse filter layer in sequence and enters the existing waste.

[0014] The sealed filter layer includes a nylon mesh and several layers of sealed filler. The nylon mesh is wrapped around the outer wall of the well pipe. Each layer of sealed filler is buried along the length of the well pipe on the outside of the well pipe and the nylon mesh. Each layer of sealed filler includes a low-permeability bentonite layer and a high-permeability gravel soil layer. The bentonite layer and the gravel soil layer are alternately buried along the length of the well pipe.

[0015] In the sealing packing layers on the outside of the well casing, the bentonite layer is located at the top and the gravel layer is located at the bottom.

[0016] The thickness of each layer of crushed stone soil is the same as the length of the treatment area formed between the two sealing devices of the mobile liquid-gas injection device.

[0017] II. A treatment method for a high-pressure liquid-gas injection system used for in-situ dehydration of existing waste:

[0018] When the mobile liquid-gas injection device is moved, the pressure is released by the pressurizing device to cause the rubber bladders of the two sealing devices to contract. Then, the treatment area between the two sealing devices is moved from top to bottom to several preset heights by a hand-cranked hoist. When it moves to the side of the gravel and soil layer of the sealing filler layer, the movement stops. The pressurizing device is then used to pressurize the rubber bladders of the two sealing devices to expand them and press them tightly against the inner wall of the well pipe. Then, the ammonia nitrogen removal agent solution is injected by the injection pump. It is then transported sequentially through the central injection pipe, the opening of the well pipe in the treatment area, the nylon mesh, and the gravel and soil layer to the existing waste around the treatment area, so as to inject ammonia nitrogen removal microorganisms into the existing waste and create a deodorizing microbial environment. Then, the mobile liquid-gas injection device is taken out. At this time, the gas injection pump uses liquid-gas... The delivery pipe connects directly from the top of the well pipe to the inside of the well pipe. Air is injected into the existing waste through an air injection pump to provide oxygen for the ammonia-removing microorganisms in the waste. Then, a mobile liquid-gas injection device is placed again, and the treatment area between the two sealing devices is moved from top to bottom to the side of the gravel and soil layer at multiple preset heights. Ammonia-removing bacteria solution is injected through a liquid injection pump, and high-pressure air is injected through an air injection pump to displace the pore water in the pores of the existing waste through high pressure, thereby reducing the in-situ moisture content of the existing waste. For the bottom gravel and soil layer of the existing waste, only the ammonia-removing bacteria solution is injected under high pressure, without high-pressure air injection to displace the pore water, in order to form a low-permeability buffer layer to prevent odor from escaping upwards.

[0019] The beneficial effects of this invention are:

[0020] This invention utilizes a mobile liquid-gas injection device and a multi-layer sealed reverse filter layer to create a cylindrical treatment area of ​​a specific length at a designated depth within a vertical well casing. The liquid-gas injection device, placed outside the vertical well casing, is connected to the mobile device via a central injection pipe, injecting liquid and gas into the sealed spaces at both ends. The injected liquid and gas enter the cylindrical space through the liquid-gas injection pipe of the mobile device. By injecting high-pressure air through the segmented liquid-gas injection system of this invention, leachate in the pores of the waste can be displaced, reducing the moisture content of the waste in situ. Furthermore, by injecting ammonia-removing nitrogen-reducing bacterial solution through the same system, anaerobic microbial metabolism can be inhibited, and an aerobic degradation environment can be strengthened, achieving long-term suppression of odor concentration after pretreatment. Therefore, this invention solves the problems of short odor suppression time, low injection pressure, and large pressure loss in the reverse filter layer, achieving the goals of high-pressure liquid-gas injection, in-situ reduction of waste moisture content, and effective odor suppression, enabling safe excavation and efficient screening of waste. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the high-pressure liquid-gas injection system for in-situ dehydration treatment of existing waste according to the present invention;

[0022] Figure 2This is a schematic diagram of the mobile liquid-gas injection device of the present invention;

[0023] Figure 3 This is a schematic diagram of the mobile liquid-gas injection device of the present invention being inserted into a vertical well casing;

[0024] Figure 4 This is a flowchart illustrating the implementation of the in-situ dehydration treatment method for existing waste according to the present invention.

[0025] Figure 5 This is a schematic diagram of the layered high-pressure injection of ammonia nitrogen removal bacterial agent solution in this invention;

[0026] Figure 6 This is a schematic diagram of the gas injection steps for the entire section of well casing 1 in this invention;

[0027] Figure 7 This is a schematic diagram of the layered high-pressure gas injection steps in this invention;

[0028] Figure 8 This is a plan view of the field test area according to an embodiment of the present invention;

[0029] Figure 9 This is a comparison chart of air pressure data for different forms of mobile high-pressure injection devices according to embodiments of the present invention;

[0030] Figure 10 This is a graph showing the changes in ammonia and hydrogen sulfide concentrations in a waste pile according to an embodiment of the present invention.

[0031] In the diagram: 1. Well casing; 11. Opening; 2. Mobile liquid-gas injection device; 21. Sealer; 211. Pressurization port; 212. Outer shell; 213. Rubber bladder; 22. Central injection pipe; 23. Plug; 24. Connecting pipe; 25. Pressurization pipe; 26. Liquid-gas delivery pipe; 27. First lifting ring; 28. Second lifting ring; 29. ​​Connecting wire rope; 3. Sealed reverse filter layer; 31. Nylon mesh; 32. Sealed packing layer; 321. Bentonite layer; 322. Crushed stone layer; 4. Lifting wire rope; 5. Hand-cranked hoist; 6. Pressurization device; 7. Liquid-gas injection device; 71. Liquid injection pump; 72. Gas injection pump; 8. Air; 9. Existing waste; 10. Ammonia nitrogen removal agent solution; 12. Pore water. Detailed Implementation

[0032] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0033] like Figure 1 , Figure 2 and Figure 3 As shown, in an embodiment of the present invention, a high-pressure liquid-gas injection system for in-situ dehydration treatment of existing waste is provided. The system includes a well pipe 1, a mobile liquid-gas injection device 2, a sealed reverse filter layer 3, a pressurizing device 6, and a liquid-gas injection device 7. The well pipe 1 is vertically installed in the pre-treated existing waste 9, and a plurality of openings 11 are evenly spaced on the pipe wall. The mobile liquid-gas injection device 2 is coaxially installed inside the well pipe 1. The depth of the mobile liquid-gas injection device 2 is adjustable to perform segmented in-situ dehydration treatment of the existing waste 9. The sealed reverse filter layer 3 is installed between the outer wall of the well pipe 1 and the existing waste 9. The pressurizing device 6 and the liquid-gas injection device 7 are both located outside the well pipe 1 and are connected to the mobile liquid-gas injection device 2.

[0034] The mobile liquid-gas injection device 2 includes two sealing devices 21, two central injection pipes 22, two plugs 23, and a connecting pipe 24. The two sealing devices 21 are coaxially arranged from top to bottom within the well casing 1. Each sealing device 21 includes a housing 212 and a rubber bladder 213. The housing 212 includes two caps and is coaxially fitted within the well casing 1. The rubber bladder 213 is located between the two caps, with both ends located within the two caps, forming a single unit. The length of the inflatable rubber bladder 213 of the sealing device 21 is 1.2 to 1.8 meters. The two central injection pipes 22 are coaxially inserted through the centers of the two housings 212 and the rubber bladder 213, spaced apart from each other. The two ends of the central injection pipes 22 are located on the outer portion of the housing 212 of their respective sealing devices 21. The two sealing devices 21... The use of an open, hollow tube instead of a connected perforated tube reduces pressure loss. The top of the upper central injection tube 22 is connected to the liquid-gas injection device 7, and the bottom of the upper central injection tube 22 is connected to the space between the two sealing devices 21. Both ends of the lower central injection tube 22 are sealed by plugs 23, thus sealing the lower sealing device 21. The inner diameter of the central injection tube 22 is not less than 1 / 2 of the inner diameter of the vertical well pipe 1. The top and bottom of the upper outer shell 212 and the top of the lower outer shell 212 are provided with a pressurization port 211. The top of the upper rubber bladder 213 is connected to the pressurization device 6 through the pressurization port 211. The two rubber bladders 213 are connected to each other through the pressurization port 211 and the connecting pipe 24. The pressurization device 6 is a hydraulic pump or an air compressor.

[0035] The mobile liquid-gas injection device 2 also includes two connecting steel wire ropes 29, two lifting steel wire ropes 4, and a hand-cranked hoist 5. The hand-cranked hoist 5 is located directly above the well pipe 1. The upper outer side of the upper central injection pipe 22 is symmetrically provided with first lifting rings 27. The hand-cranked hoist 5 is connected to the two first lifting rings 27 through the lower ends of the two lifting steel wire ropes 4. The lower outer side of the upper central injection pipe 22 and the upper outer side of the lower central injection pipe 22 are both provided with second lifting rings 28. The second lifting rings 28 of the two central injection pipes 22 are connected to each other by connecting steel wire ropes 29. The size of the space between the two sealing devices 21 can be adjusted by changing the length of the connecting steel wire ropes 29. The height of the space is the same as the thickness of the single layer of crushed stone soil 322 in the sealed reverse filter layer 3, which is generally 1 to 3 meters. The two sealing devices 21 are moved up and down inside the well pipe 1 by the hand-cranked hoist 5.

[0036] The top and bottom of the well casing 1 are sealed. When the two rubber bladders 213 inflate and adhere tightly to the inner wall of the well casing 1, the processing area between the two sealing devices 21 forms a space that communicates with the external environment only through the central injection pipe 22 in the upper sealing device 21 and the opening 11 of the well casing 1. The rubber bladders 213 expand when inflated, gradually widening the distance between the two sealing devices 21. Therefore, the second lifting ring 28 of the connecting wire rope 29 needs to be fixed to the central injection pipe 22, preventing the central injection pipe 22 from moving. The length of the inflated rubber bladders 213 shortens, causing the upper sealing device 21 to move upwards and the lower sealing device 21 to move downwards.

[0037] The pressurizing device 6 is connected to the upper rubber bladder 213 via the pressurizing pipe 25 and the pressurizing port 211. Water or air is injected sequentially through the pressurizing port 211, the pressurizing pipe 25, and the connecting pipe 24, causing the two rubber bladders 213 to inflate and adhere tightly to the inner wall of the well casing 1. Depressurization causes the two rubber bladders 213 to contract. After expansion, the rubber bladders 213 seal against the inner wall of the well casing 1, ensuring that the treatment area between the two sealing devices 21 is only connected to the external environment through the central injection pipe 22 and the opening 11 of the well casing 1. Depressurization of the pressurizing device 6 causes the pressurized and inflatable rubber bladders 213 to contract. After contraction, they can move within the well casing 1 under the traction of the wire rope 4 and the hand-cranked hoist 5.

[0038] The liquid-gas injection device 7 includes a liquid injection pump 71 and an air injection pump 72. Both pumps are connected to the top of the central injection pipe 22 via a liquid-gas delivery pipe 26. The liquid injection pump 71 or the air injection pump 72 injects ammonia-removing bactericidal solution 10 or air 8 into the treatment area between the two sealing devices 21 through the central injection pipe 22. The ammonia-removing bactericidal solution 10 or air 8 passes sequentially through the opening 11 of the well pipe 1 and the sealed reverse filter layer 3 into the stock waste 9. By supplying the ammonia-removing bactericidal solution 10 or air 8 to the treatment area between the two sealing devices 21 through the liquid-gas injection device 7, a greater pressure is generated compared to directly injecting water or air into the well pipe 1 at the same flow rate, due to the relatively small space of the treatment area. This allows the ammonia-removing bactericidal solution 10 and air 8 to flow further within the stock waste 9, generating greater water or air pressure within the stock waste 9. This greater air pressure can displace the pore water 12 in the pores of the stock waste 9.

[0039] The sealed filter layer 3 includes a nylon mesh 31 and several layers of sealed packing material 32. The nylon mesh 31 wraps around the outer wall of the well pipe 1. Each layer of sealed packing material 32 is buried along the length of the well pipe 1 on the outside of the well pipe 1 and the nylon mesh 31. Each layer of sealed packing material 32 includes a low-permeability bentonite layer 321 and a high-permeability gravelly soil layer 322. The bentonite layer 321 and the gravelly soil layer 322 are alternately buried along the length of the well pipe 1 to prevent pressure loss of liquid and gas pressure along the outer wall of the vertical well pipe 1, and to prevent clogging of the vertical well pipe 1. The radial width of the sealed filter layer 3 is 0.1 meters. The thickness of each layer of bentonite 321 is 1 to 1.5 meters, and the thickness of each layer of gravelly soil 322 is 1 to 3 meters. The porosity of the gravelly soil layer 322 is not less than 0.4. The mesh size of the filter mesh 31 is equal to the average particle size d of the sealed packing material layer 32. 50 1.5 to 2.0 times that.

[0040] During system installation, a vertical well is first drilled in the existing waste 9. Then, nylon mesh 31 is wrapped around the well pipe 1 and then the well pipe 1 is lowered vertically. The lower part of the well pipe 1 is an open section with an opening 11, which is buried in the existing waste 9. Then, a layer of sealed filler 32 is filled between the well pipe 1 and the existing waste 9. Liquid and gas injection operations are carried out into the existing waste 9 through the opening 11.

[0041] In the sealing packing layers 32 outside the well casing 1, the bentonite layer 321 is the uppermost layer, and the gravelly soil layer 322 is the lowermost layer. The thickness of each gravelly soil layer 322 is the same as the length of the treatment area formed between the two sealing nozzles 21 of the mobile liquid-gas injection device. The mobile liquid-gas injection device 2 and the sealing filter layer 3 work together. The gravelly soil layer 322 and the treatment area are basically the same length, so that when the treatment area moves to the side of the gravelly soil layer 322, a relatively closed space is formed between the two sealing nozzles 21, the gravelly soil layer 322, and the two bentonite layers 321 above and below it. This prevents gas from escaping along the outer wall of the well casing 1 and ensures that high water or gas pressure can be generated in the relatively closed space.

[0042] When the mobile liquid-gas injection device 3 operates inside the vertical well casing 1, the upper and lower sealing devices 21 are aligned with the bentonite layer 321, and the space between the upper and lower sealing devices is aligned with the gravel layer 322. At this time, the space between the upper and lower sealing devices 21 and the gravel layer 322 form a relatively closed cavity. When the liquid-gas injection device 7 is opened to inject liquid and gas into the space between the upper and lower sealing devices 21 through the central injection pipe 22, the liquid and gas enter this cavity from the central injection pipe and then seep radially into the existing waste 9 around the gravel layer 322. After a certain layer of existing waste 9 has been processed, the mobile liquid-gas injection device 2 is moved along the vertical well casing 1 to the depth of the next waste layer to be processed, and the existing waste 9 at that depth is processed. Since the volume of this cavity formed by the space between the upper and lower sealing devices 21 and the gravel layer 322 is significantly smaller than the internal volume of the entire vertical well casing 1, a higher pressure condition will be formed under the same injection volume of liquid and gas. Because of the presence of bentonite layers 321 above and below each layer of gravelly soil 322, the liquid and gas flowing out from the opening 11 will not flow upward or downward along the large pore channels of the outer wall of the vertical well pipe 1, which can ensure that the liquid and gas pressure can be effectively transmitted radially.

[0043] The treatment method of the high-pressure liquid-gas injection system for in-situ dehydration of existing waste according to the present invention is as follows:

[0044] First, based on the monitoring results of the moisture content and odor concentration in the stock waste 9, when the moisture content is higher than 30% or the hydrogen sulfide concentration is higher than 20ppm, the mobile liquid-gas injection device 2 needs to be moved in the vertical well pipe 1 to the depth of the stock waste 9 for pretreatment. When the mobile liquid-gas injection device 2 moves, the pressure is released by the pressurizing device 6, causing the rubber bladders 213 of the two sealing devices 21 to contract. Then, the treatment area between the two sealing devices 21 is moved from top to bottom to multiple preset heights by the hand-cranked hoist 5. When it moves to the side of the gravel and soil layer 322 of the sealing packing layer 32, it stops moving. The pressurizing device 6 presses the rubber bladders 213 of the two sealing devices 21 to expand and press them tightly against the inner wall of the well pipe 1. Then, the ammonia nitrogen removal agent solution 10 is injected by the injection pump 71. Then, it is transported sequentially through the central injection pipe 22, the opening 11 of the well pipe 1 in the treatment area, the nylon mesh 31, and the gravel and soil layer 322 to the existing waste 9 around the treatment area, so as to treat the existing waste 9. Injecting ammonia-removing microorganisms and creating a deodorizing microbial environment can inhibit anaerobic microbial metabolism and odor concentration. Then, the mobile liquid-gas injection device 2 is removed. At this time, the air injection pump 72 is directly connected from the top of the well pipe 1 to the inside of the well pipe 1 through the liquid-gas delivery pipe 26. Air 8 is injected into the well pipe 1 into the stock garbage 9 through the air injection pump 72 to provide oxygen for the ammonia-removing microorganisms in the stock garbage 9. Then, the mobile liquid-gas injection device 2 is put back in, and the treatment area between the two sealing devices 21 is moved from top to bottom to the side of the gravel soil layer 322 at multiple preset heights. High-pressure air 8 is injected again through the air injection pump 72. During high-pressure air injection, the air pressure of the outlet section of the mobile liquid-gas injection device 2 is not lower than 10. The pressure is kPa to displace the pore water 12 in the pores of the existing waste 9, thereby reducing the in-situ moisture content of the existing waste 9. At the same time, it provides an aerobic environment for ammonia nitrogen removal microorganisms and quickly removes ammonia nitrogen from the pore water 12 through stripping. The in-situ moisture content of the waste is the ratio of the mass of water contained in a unit volume of waste to the total mass at the original location of the waste. For the lowest layer of gravel soil 322 of the existing waste 9, only the ammonia nitrogen removal agent solution 10 is injected under high pressure, without high pressure air injection to displace the pore water 12, so as to form a low-permeability buffer layer to prevent odor from escaping upward. This makes the existing waste 9 within the depth range of the well pipe 1 and the lower 2-4 meters of the excavated waste layer a low-permeability buffer layer, preventing the odor in the underlying waste layer from escaping upward to the existing waste 9 that has undergone in-situ dehydration and deodorization treatment.

[0045] like Figure 4 , Figure 5 , Figure 6 and Figure 7 As shown, in specific implementation, the present invention employs a high-pressure liquid-gas injection method for in-situ dehydration treatment of existing waste, including a sequentially performed layered high-pressure liquid injection step, a full-section gas injection step, and a layered high-pressure gas injection step, as detailed below:

[0046] 1) After a layered high-pressure injection process, a mobile liquid-gas injection device 2 is used to inject ammonia-removing bacterial agent solution 10 into the existing waste 9 layer by layer from top to bottom under high pressure, creating a deodorizing microbial environment and removing ammonia nitrogen contained in the pore water 12, as follows:

[0047] like Figure 6 As shown, the length of the outflow section of the mobile liquid-gas injection device 2 is adjusted according to the thickness of the first layer of gravel and soil 322. Then, the mobile liquid-gas injection device 2 is placed in the vertical well pipe 1. The steel wire rope 4 is moved to the depth of the first layer of gravel and soil 322 by the hand-cranked hoist 5. The outflow section is aligned with the gravel and soil 322. The pressurizing device 6 is used to pressurize the expansion rubber bladder 213 of the mobile liquid-gas injection device 2 to make it expand, blocking the channel along the inner wall of the vertical well pipe 1. The outflow section and the gravel and soil 322 form a relatively closed space, which is connected to the surrounding environment only through the central injection pipe 22 and the existing garbage 9. The ammonia nitrogen removal agent solution 10 is injected into the outflow section through the central injection pipe 22 by the liquid-gas injection device 7 until the designed dosage is reached, creating a deodorizing microbial environment.

[0048] The injection volume and concentration of ammonia-removing bactericidal agent solution 10 are shown in the following formula:

[0049]

[0050] in, Q t The amount of solution required to inject per unit thickness of waste 9 (in m³) 3 ); π is pi; R is the radius of influence of the vertical well pipe 1 (in meters); n is the porosity of the stock waste 9; S r The saturation level of existing waste (9). λ t The concentration of the ammonia nitrogen removal agent solution 10 is expressed in kg / L. λ The preset concentration of the ammonia nitrogen removal agent solution 10 is (in kg / L); the injection pressure of the ammonia nitrogen removal agent solution 10 is 150~180 kPa; the density of the pore water 12 in the existing waste 9 can usually be taken as 1000 kg / m³. 3 .

[0051] like Figure 7 As shown, the pressurization device 6 depressurizes, retracts the sealing device 21 of the mobile liquid-gas injection device 2, and moves the mobile liquid-gas injection device 2 sequentially to several underlying gravel soil layers 322 along the vertical well pipe 1, repeating the above operation.

[0052] 2) After the entire section of air injection, air 8 is injected into the existing waste 9 through the vertical well pipe 1 to provide oxygen for the ammonia nitrogen removal bacteria, accelerate the ammonia nitrogen removal efficiency, and improve the ammonia nitrogen removal effect, as follows:

[0053] Take out the mobile liquid-gas injection device 2 from the vertical well pipe 1, connect the liquid-gas injection device 7 directly to the wellhead of the vertical well pipe 1, turn on the liquid-gas injection device 7 and inject air 8 into the stock garbage 9 through the entire open section of the vertical well pipe 1 to provide oxygen for the ammonia nitrogen removal microorganisms and accelerate the ammonia nitrogen removal rate of the microorganisms; the injection pressure in the vertical well pipe 1 during injection is 1~2 kPa.

[0054] 3) After the layered high-pressure air injection step, the mobile liquid-gas injection device 2 injects air 8 into the stock garbage 9 in layers from top to bottom under high pressure. This displaces the pore water 12 in the pores of the stock garbage 9, reducing the moisture content of the garbage. At the same time, it further removes ammonia nitrogen through stripping, enhancing the deodorization effect, as follows:

[0055] like Figure 6 As shown, the length of the outflow section of the mobile liquid-gas injection device 2 is adjusted according to the thickness of the first layer of gravelly soil 322. Then, the mobile liquid-gas injection device 2 is placed into the vertical well pipe 1. The steel wire rope 4 is moved to the depth of the first layer of gravelly soil 322 by the hand-cranked hoist 5, and the outflow section is aligned with the gravelly soil 322. The inflation system 6 is used to inflate the expansion rubber bladder 213 of the mobile liquid-gas injection device 2 to seal the channel along the inner wall of the vertical well pipe 1. The outflow section is aligned with the gravelly soil 322. 22 forms a relatively enclosed space, connected to the surrounding environment only through the central injection pipe 22 and the existing waste 9. High-pressure air 8 is injected into the outflow section through the central injection pipe 22 via the liquid-gas injection system 7. This high-pressure air displaces the pore water 12 in the existing waste 9 until the in-situ moisture content of the existing waste 9 within the treated depth range is reduced to below 30%. The displaced pore water 12, under the action of air pressure, will first move horizontally away from the well pipe 1, and then move downwards under gravity. The ammonia-removing bacteria will affect a wider area along with the movement of the pore water 12, further enhancing the deodorization effect.

[0056] like Figure 7As shown, the pressurization device 6 depressurizes, retracts the sealing device 21 of the mobile liquid-gas injection device 2, and moves the mobile liquid-gas injection device 2 sequentially to the next gravel-soil layer 322 along the vertical well pipe 1, repeating the operation. This continues until the last gravel-soil layer 322 at the bottom of the vertical well pipe 1 is reached. No high-pressure gas injection is performed on the waste layer corresponding to the last gravel-soil layer 322. The pore water 12 displaced by the overlying waste flows downwards to this layer, resulting in a high water content and rich ammonia-removing microorganisms. This waste layer acts as a temporary buffer layer, preventing odors from the lower waste layer from escaping upwards to the existing waste 9 in the pretreatment area, thus extending the odor suppression time in the pretreatment area. During high-pressure gas injection, the gas pressure in the outlet section of the mobile liquid-gas injection device 2 and the space within the gravel-soil layer is not lower than 10 kPa. The moisture content of the waste in the pretreatment area can be obtained by burying a moisture content sensor or by sampling and testing. When the in-situ moisture content of the waste does not decrease to 30% or below, the above steps can be repeated and the air injection volume can be increased to increase the air pressure in the space between the outlet section of the mobile liquid-gas injection device 2 and the gravel layer 322.

[0057] The high-pressure liquid-gas injection system of the present invention utilizes a specially designed mobile liquid-gas injection device 2 and a sealed reverse filter layer 3 to solve the problems of low injection pressure, small gas pressure influence radius, and high in-situ moisture content of pretreated waste in the prior art. By using a special operation procedure that combines injection of ammonia nitrogen removal agent solution with high-pressure gas injection, the problem of short odor suppression time is solved.

[0058] To verify the beneficial effects of the technical solution adopted in this invention, a field test was conducted in an excavation and screening remediation project at a landfill in Hainan. For example... Figure 8The diagram shows the layout of the test area, with a total of 5 injection wells (ZQ-1, 2, 3, 4, 5), 4 drainage wells, and 6 monitoring wells (JC-1, 2, 3, 4, 5, 6). The distance between injection and drainage wells is 8 meters, and the distance between similar wells is 16 meters. The pre-treated waste layer in this test is 6 meters thick. To suppress odor concentration long-term and prevent odor from migrating from the bottom waste to the test area, the injection and drainage wells are designed to be 9 meters deep, using the 6-9 meter buried waste layer as a buffer. Two monitoring wells are installed at each monitoring point, with depths of 2 meters and 5 meters respectively, and a moisture content sensor and a gas concentration sensor are buried there. The injection well has a borehole diameter of 300mm. Well casing 1 is made of 100mm diameter galvanized steel pipe, with 0.2 meters protruding above the surface. No holes are drilled 1 meter below the surface. Holes with a diameter of 10mm are drilled from 1 meter to 7.5 meters below the surface, arranged in a staggered pattern with 8 rows of holes spaced 10cm apart. The 0.5 meters above the bottom of the well is designated as a sedimentation section and remains un-drilled. The bottom of the well is sealed with plug 23. The drilled section of the injection well casing is covered with a layer of 10-mesh nylon mesh 31. Bentonite layer 321 and gravel layer 322 are layered between the galvanized steel pipe and the existing waste 9 to form a multi-layered sealed filter layer 3. First, a 2-meter layer of gravel is filled at the bottom. Then, layers of filling are added in layers, each 1 meter thick for bentonite and 2 meters thick for gravel. The bentonite layer 321 is 1 meter below the surface of well casing 1. To test the injection pressure of the outflow section, pore pressure sensors were embedded in each layer of gravelly soil 322, allowing for simultaneous testing of air and water pressure. The drainage wells used De90 specification high-density polyethylene (HDPE) pipes. No holes were drilled 2 meters below the surface, while the remaining sections were perforated with 10mm diameter holes in four rows, spaced 10cm apart, arranged in a staggered pattern. The bottom of the wells was sealed with plugs 23. The space between the drainage wells and the existing waste 9 was filled with in-situ waste, and a bentonite layer 321 was used for sealing 2 meters below the surface. The mobile liquid-gas injection device 2 used in this field test had a single sealing device 21 with a length of 1.8 meters, and the length of the outflow section was adjusted to 2 meters based on the thickness of the gravelly soil layer 322.

[0059] The landfill is preparing for excavation and remediation, while aerobic pretreatment projects are being carried out simultaneously in other areas. The depth of the gas injection wells used in these areas is different from that in the test area. The depth of the gas injection wells in other areas is 6 meters. They all use De90 specification high-density polyethylene (HDPE) pipes. The well body and the nine sections of existing waste are filled with waste, and the ground is sealed with high-density polyethylene (HDPE) film.

[0060] To prevent the test area from affecting the surrounding area, a ring of eight extraction wells was drilled 8 meters away from the test well to block odors. The wells were all 9 meters deep and had the same structure as the extraction wells in the test area.

[0061] In specific implementation, the present invention underwent two sets of experiments, as follows:

[0062] Experiment 1, to verify the magnitude of the gas injection pressure generated in the outflow section of well casing 1 under different gas injection methods, employed three gas injection methods: full-section gas injection of well casing 1, the mobile liquid-gas injection device 2 proposed in this invention, and a liquid-gas injection device with the outflow section replaced by an open-hole pipe. For each gas injection method, the gas injection flow rate was sequentially increased from 50 m³ / h. 3 / h gradually increased to 300m 3 / h, the air pressure of the flow section is measured by a pore pressure sensor buried in the gravelly soil layer 322.

[0063] Experiment 2 involved treating the waste in the experimental area using the in-situ dehydration pretreatment method for existing waste proposed in this invention. The operation steps are as follows:

[0064] a) Connect the central injection pipe 22 of the mobile liquid-gas injection device 2 to the injection pump 71 via the liquid-gas delivery pipe 26, and then place it into the injection well pipe 1. Move it from top to bottom, placing the mobile liquid-gas injection device 2 sequentially at several designated locations at depths of 1-3 meters, 4-6 meters, and 7-9 meters (at which depth, only the upper sealing device 21 is used for sealing at a depth of 7 meters) for layered high-pressure injection. The amount of ammonia nitrogen removal bacterial agent solution 10 injected at each depth is 108m³. 3 The injection rate is 3m 3 / h, injection pressure is 150kPa.

[0065] b) Depressurize the mobile liquid-gas injection device 2 and remove it from the injection well. Connect the liquid-gas delivery pipe 26 directly to the injection well head. Simultaneously, switch the liquid-gas injection device 7 to a centrifugal fan and inject gas into the existing waste 9 through the entire injection well at a rate of 120 m³ / s. 3 / h, lasting for 2 days.

[0066] c) Reconnect the central injection pipe 22 of the mobile liquid-gas injection device 2 to the liquid-gas delivery pipe 26, then place it into the injection well pipe 1 and move it from top to bottom. Place the mobile liquid-gas injection device 2 at depths of 1-3 meters and 4-6 meters respectively, with an injection rate of 200 m³ / s. 3 The injection rate is 15 kPa / min, and the injection is stopped when the water cut sensor readings at the corresponding depths of four or more monitoring wells are no greater than 30% and remain basically stable.

[0067] The in-situ aerobic pretreatment process of the present invention was carried out for a total of 8 days, including a) a layered high-pressure liquid injection step for 2 days, b) a full-section gas injection step for 2 days, and c) a layered high-pressure gas injection step for 4 days.

[0068] like Figure 9As shown, the data graph shows the change of gas pressure in the outflow section with flow rate under different gas injection methods. At the same gas injection flow rate, the gas pressure in the outflow section of the mobile liquid-gas injection device 2 proposed in this invention is about 1.5 to 3.5 times that of the liquid-gas injection device with an open pipe in the outflow section, and 2.3 to 6.0 times that of the full-section gas injection of the well pipe 1.

[0069] Table 1 shows a comparison of the moisture content of garbage at different depths obtained by monitoring wells through moisture content sensors before and after in-situ dehydration pretreatment. Before treatment, the average moisture content of garbage at depths of 2 meters and 5 meters in the test area was 46.5% and 46.0%, respectively. After in-situ dehydration pretreatment using the method proposed in this invention, the average moisture content of garbage at burial depths of 2 meters and 5 meters decreased to 27.8% and 30.0%, respectively.

[0070] Table 1

[0071]

[0072] like Figure 10 The figure shows the changes in methane and hydrogen sulfide concentrations over time in the test area after treatment. After treatment, the methane and hydrogen sulfide concentrations were reduced by more than 80%, and four days after the pretreatment, the methane concentration was below 5% and the hydrogen sulfide concentration was below 5 ppm. In contrast, in other areas using the traditional full-section gas injection method (well 1), the methane concentration rose to 28.7% and the hydrogen sulfide concentration rose to 114.9 ppm on the second day after the gas injection treatment was stopped. During excavation, deodorizing fog cannons were required to prevent the spread of odor.

[0073] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-pressure liquid-gas injection system for in-situ dehydration treatment of existing waste, characterized in that: The system includes a well casing, a mobile liquid-gas injection device, a sealed reverse filter layer, a pressurizing device, and a liquid-gas injection device. The well casing is vertically installed in the stock waste and has several evenly spaced openings on its wall. The mobile liquid-gas injection device is coaxially installed inside the well casing. The depth of the mobile liquid-gas injection device is adjustable to perform segmented in-situ dehydration treatment of the stock waste. The sealed reverse filter layer is installed between the outer wall of the well casing and the stock waste. The pressurizing device and the liquid-gas injection device are both located outside the well casing and are connected to the mobile liquid-gas injection device. The mobile liquid-gas injection device includes two sealing devices, two central injection pipes, two plugs, and a connecting pipe. The two sealing devices are coaxially arranged in the well casing from top to bottom. Each sealing device includes an outer shell and a rubber bladder. The outer shell includes two caps and is coaxially fitted in the well casing. The rubber bladder is located between the two caps, with its two ends located inside the two caps respectively. The two central injection pipes are coaxially inserted through the centers of the two outer shells and the rubber bladder, and are spaced apart from each other. The two ends of the central injection pipes are located outside the outer shell of their respective sealing devices. The top end of the upper central injection pipe is connected to the liquid-gas injection device, and the bottom end of the upper central injection pipe is connected to the space between the two sealing devices. Both ends of the lower central injection pipe are plugged by plugs to seal the lower sealing device. The top and bottom ends of the upper outer shell and the top end of the lower outer shell are provided with pressure ports. The top end of the upper rubber bladder is connected to the pressure charging device through the pressure port. The two rubber bladders are connected to each other through the pressure port and the connecting pipe. The sealed filter layer includes a nylon mesh and several layers of sealed filler. The nylon mesh is wrapped around the outer wall of the well pipe. Each layer of sealed filler is buried along the length of the well pipe on the outside of the well pipe and the nylon mesh. Each layer of sealed filler includes a bentonite layer and a gravel layer, which are alternately buried along the length of the well pipe.

2. The high-pressure liquid-gas injection system for in-situ dehydration treatment of existing waste according to claim 1, characterized in that: The mobile liquid-gas injection device also includes two connecting steel wire ropes, two lifting steel wire ropes, and a hand-cranked hoist. The hand-cranked hoist is located directly above the well pipe. The upper outer side of the upper central injection pipe is symmetrically equipped with first lifting rings on both sides. The hand-cranked hoist is connected to the two first lifting rings through the lower ends of the two lifting steel wire ropes. The lower outer side of the upper central injection pipe and the upper outer side of the lower central injection pipe are both equipped with second lifting rings. The second lifting rings of the two central injection pipes are connected to each other through connecting steel wire ropes. The hand-cranked hoist drives the two sealing devices to move up and down inside the well pipe.

3. The high-pressure liquid-gas injection system for in-situ dehydration treatment of existing waste according to claim 1, characterized in that: The top and bottom of the well casing are sealed. When the two rubber bladders inflate and press tightly against the inner wall of the well casing, the processing area between the two sealing devices forms a space that communicates with the external environment only through the central injection pipe in the upper sealing device and the opening of the well casing.

4. The high-pressure liquid-gas injection system for in-situ dehydration treatment of existing waste according to claim 1, characterized in that: The pressurizing device is connected to the rubber bladder located above through the pressurizing pipe and the pressurizing port. The pressurizing device injects water or air through the pressurizing port, the pressurizing pipe and the connecting pipe in sequence to make the two rubber bladders expand and stick tightly to the inner wall of the well pipe. The two rubber bladders contract by depressurizing.

5. The high-pressure liquid-gas injection system for in-situ dehydration treatment of existing waste according to claim 1, characterized in that: The liquid-gas injection device includes a liquid injection pump and a gas injection pump. The liquid injection pump and the gas injection pump are connected to the top of the central injection pipe above through a liquid-gas delivery pipe. The liquid injection pump or the gas injection pump injects ammonia-removing nitrogen bacteria solution or air into the treatment area between the two sealing devices through the central injection pipe. The ammonia-removing nitrogen bacteria solution or air passes through the opening of the well pipe and the sealed reverse filter layer in sequence and enters the existing waste.

6. The high-pressure liquid-gas injection system for in-situ dehydration treatment of existing waste according to claim 1, characterized in that: In the sealing packing layers on the outside of the well casing, the bentonite layer is located at the top and the gravel layer is located at the bottom.

7. The high-pressure liquid-gas injection system for in-situ dehydration treatment of existing waste according to claim 1, characterized in that: The thickness of each layer of crushed stone soil is the same as the length of the treatment area formed between the two sealing devices of the mobile liquid-gas injection device.

8. The treatment method of the high-pressure liquid-gas injection system for in-situ dehydration treatment of existing waste according to any one of claims 2-7, characterized in that, include: When the mobile liquid-gas injection device is moved, the pressure is released by the pressurizing device to cause the rubber bladders of the two sealing devices to contract. Then, the treatment area between the two sealing devices is moved from top to bottom to multiple preset heights by a hand-cranked hoist. When it moves to the side of the gravel and soil layer of the sealing filler layer, the movement stops. The pressurizing device is used to pressurize the rubber bladders of the two sealing devices to expand them and make them fit tightly against the inner wall of the well pipe. Then, the ammonia nitrogen removal agent solution is injected by the injection pump. Then, it is transported sequentially through the central injection pipe, the opening of the well pipe in the treatment area, the nylon mesh, and the gravel and soil layer to the existing garbage around the treatment area, so as to inject ammonia nitrogen removal microorganisms into the existing garbage and create a deodorizing microbial environment. Then, the mobile liquid-gas injection device is taken out. At this time, the air injection pump is directly connected to the well pipe from the top of the well pipe through the liquid-gas delivery pipe. The air injection pump injects air into the existing garbage into the well pipe to provide oxygen for the ammonia nitrogen removal microorganisms in the existing garbage. Then, the mobile liquid-gas injection device is placed again, and the treatment area between the two sealing devices is moved from top to bottom to the side of the gravel and soil layer at multiple preset heights. The ammonia-removing bactericidal agent solution is injected through the liquid injection pump, and air is injected through the air injection pump to displace the pore water in the pores of the existing waste through high air pressure, thereby reducing the in-situ moisture content of the existing waste. For the bottom layer of gravel and soil of the existing waste, only the ammonia-removing bactericidal agent solution is injected, and no air is injected to displace the pore water, so as to form a buffer layer to prevent the odor from escaping upward.

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