Low-temperature evaporation treatment system for landfill leachate

Abstract

The utility model provides a low-temperature evaporation treatment system for landfill leachate, which comprises a pretreatment unit, a heat treatment unit arranged at the downstream of the pretreatment unit, a multi-effect evaporation crystallization unit arranged at the downstream of the heat treatment unit, and a membrane purification unit arranged at the downstream of the multi-effect evaporation crystallization unit, the multi-effect evaporative crystallization unit comprises a pre-crystallization unit, a plurality of evaporative crystallization units and a separation unit which are connected in sequence; and the membrane purification unit discharges water and salty mud. Solar energy is used as a first-effect heating heat source, and cost is reduced. Membrane concentrated solutions heated by solar energy are gathered and then enter a first-effect separator, the pressure in the first-effect separator is controlled, the membrane concentrated solutions are subjected to flash evaporation, generated secondary steam serves as a second-effect heating heat source, a part of the membrane concentrated solutions subjected to flash evaporation and cooling circulate back to a heat treatment unit, and the other part of the membrane concentrated solutions are recycled. Feeding one part into a subsequent evaporator to be further evaporated and concentrated until carnallite is crystallized; the energy consumption of multi-effect evaporative crystallization is effectively reduced, and the cost is greatly reduced. And the method has a relatively high popularization value.

Description

Technical Field

[0001] The utility model relates to the field of garbage leachate treatment, in particular to a low-temperature evaporation treatment system for garbage leachate. Background Art

[0002] A large number of domestic waste landfills use membrane concentration technology to treat landfill leachate, and the industry provides evaporation crystallization concentration technology for the treatment of membrane concentrated liquid.

[0003] The evaporation crystallization concentration process requires a heat source during the evaporation crystallization process, which is a high-energy consumption process. In order to reduce the energy consumption of the evaporation process, there are two processes in the industry: multi-effect evaporation and MVR evaporation. The multi-effect evaporation process is to use the secondary steam generated by evaporation multiple times to achieve the purpose of energy saving, but this process still requires external heating steam. The MVR process uses a compressor to heat and pressurize the secondary steam for reuse, thereby improving the utilization efficiency of heat, but it requires a certain amount of electricity.

[0004] Due to the special functions of domestic waste landfills, they are generally located in suburban areas, mountainous areas or remote locations. Therefore, if the multi-effect evaporation process is used to treat the landfill leachate membrane concentrate, it is generally difficult to obtain steam supply. If the MVR process is used to treat the landfill leachate membrane concentrate, it requires high energy consumption and high operating costs, and a large amount of power supply capacity needs to be increased. For this reason, we propose a low-temperature evaporation treatment system for landfill leachate to solve the above problems. Utility Model Content

[0005] The utility model provides a low-temperature evaporation treatment system for garbage leachate, which solves the problem that a multi-effect evaporation process needs external heating steam; an MVR process needs to provide a certain amount of electric energy, and a garbage landfill is located in the suburbs, mountainous areas or remote locations, and it is difficult for the multi-effect evaporation process to obtain steam supply, and the MVR process requires high energy consumption and high operating costs.

[0006] In order to solve the above technical problems, the technical solution adopted by the utility model is: a low-temperature evaporation treatment system for landfill leachate, comprising a pretreatment unit, a heat treatment unit is provided downstream of the pretreatment unit, a multi-effect evaporation crystallization unit is provided downstream of the heat treatment unit, a membrane purification unit is provided downstream of the multi-effect evaporation crystallization unit, and the multi-effect evaporation crystallization unit comprises a pre-crystallization unit, a plurality of evaporation crystallization units and a separation unit connected in sequence;

[0007] The membrane purification unit discharges water and salt sludge.

[0008] In a preferred solution, the pretreatment unit includes a softening treatment machine, and a leachate lifting pump and a sludge pump are respectively connected to the softening treatment machine downstream, and the sludge pump is provided with a plate-frame filter press connected thereto, and the other end of the plate-frame filter press is connected to the softening treatment machine;

[0009] The heat treatment unit comprises a plurality of arrays of solar collectors, and the heat treatment unit is connected with the pre-crystallization unit.

[0010] In the preferred solution, the softening machine is provided with a plurality of feed ports, lime milk and sodium carbonate are input from the feed ports of the softening machine, garbage leachate is input from the inlet of the softening machine, and the leachate lifting pump is connected to the heat treatment unit.

[0011] In a preferred embodiment, the pre-crystallization unit includes a first-effect separator and a first-effect circulation pump, and the first-effect separator and the first-effect circulation pump are both connected to the heat treatment unit.

[0012] In a preferred embodiment, the evaporation crystallization unit includes a second-effect heater, a second-effect separator and a circulation pump, which are connected in sequence to form a loop. A second-effect non-condensable gas discharge valve and a second-effect condensate discharge valve are provided on one side of the second-effect heater. The second-effect non-condensable gas discharge valve is connected to the separation unit, the second-effect condensate discharge valve is connected to the membrane purification unit, and the second-effect separator is respectively connected to the second-effect heater and the second-effect separator of the next evaporation crystallization unit.

[0013] In a preferred solution, an efflux pump is provided at the outlet end of the second-effect separator of the last evaporation crystallization unit, and the last second-effect separator forms a loop through the efflux pump, which is also connected to the centrifugal dehydrator of the separation unit.

[0014] In the preferred scheme, the separation unit includes a non-condensable gas condenser, a centrifugal dehydrator and a mother liquor tank. The non-condensable gas condenser is connected to the membrane purification unit, the non-condensable gas condenser is connected to the outside through a vacuum pump, the centrifugal dehydrator discharges salt mud, and the mother liquor tank is connected to the second-effect heater of the last evaporation crystallization unit.

[0015] In a preferred embodiment, the membrane purification unit includes a condensate tank, a condensate purification reverse osmosis membrane group and an intermediate tank. A transfer pump is provided between the condensate tank and the intermediate tank. The intermediate tank is connected to the condensate purification reverse osmosis membrane group through a lifting pump. The condensate purification reverse osmosis membrane group discharges water.

[0016] In the preferred solution, a purification circulation pump is connected to the condensate purification reverse osmosis membrane group, and the purification circulation pump and the condensate purification reverse osmosis membrane group form a loop. A concentrate discharge valve is provided downstream of the condensate purification reverse osmosis membrane group, and the concentrate discharge valve is connected to the softening treatment machine.

[0017] The beneficial effects of the utility model are as follows: firstly, a lime milk softening process is adopted in a softening treatment machine to reduce the hardness of the membrane concentrate of the landfill leachate, so as to avoid scaling and clogging of equipment by scaling substances such as calcium and magnesium in subsequent processes; the membrane concentrate after softening and purification is sent to a heat treatment unit, and an array-type solar collector in the heat treatment unit is composed of a plurality of solar collectors. Relying on the garbage pile of a domestic garbage landfill, solar heaters are distributed on the top of the garbage pile, the slope and other positions to absorb the heat of the solar energy, and the solar energy is used as a single-effect heating heat source to reduce the cost. The membrane concentrate heated by the solar energy is collected and enters the single-effect separator, and the pressure in the single-effect separator is controlled to flash the membrane concentrate, and the secondary steam generated is used as a heating heat source for the second effect. A part of the membrane concentrate after flashing and cooling is circulated back to the heat treatment unit, and a part is sent to a subsequent evaporator for further evaporation and concentration to crystallize the impurities; the energy consumption of multi-effect evaporation and crystallization is effectively reduced, and the cost is greatly reduced. Water that cannot directly meet the standards is purified by the condensate purification reverse osmosis membrane group in the membrane purification unit and then discharged to meet the standards. The resulting membrane concentrate is returned to the pretreatment unit and mixed with the softened membrane concentrate before evaporation and concentration. Compared with the traditional multi-effect evaporation crystallization process, the energy consumption is greatly reduced and has great promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The utility model is further described below in conjunction with the accompanying drawings and embodiments;

[0019] Figure 1 It is a schematic diagram of the principle of the utility model system;

[0020] Figure 2 It is a flow chart of the utility model system;

[0021] Figure 3 This utility model Figure 2 Enlarged view of the pre-processing unit;

[0022] Figure 4 This utility model Figure 2 Enlarged view of the heat treatment unit;

[0023] Figure 5 This utility model Figure 2 Enlarged view of the pre-crystallization unit;

[0024] Figure 6 This utility model Figure 2 Enlarged view of the evaporation crystallization unit;

[0025] Figure 7 This utility model Figure 2 Enlarged view of the middle membrane purification unit;

[0026] In the figure: pretreatment unit 1; softening treatment machine 101; leachate lifting pump 102; sludge pump 103; plate and frame filter press 104; heat treatment unit 2; solar collector 201; pre-crystallization unit 3; first-effect separator 301; first-effect circulation pump 302; evaporation crystallization unit 4; second-effect heater 401; circulation pump 402; second-effect separator 403; second-effect non-condensable gas discharge valve 404; second-effect condensate discharge valve 405; external discharge pump 406; separation unit 5; non-condensable gas condenser 501; vacuum pump 502; centrifugal dehydrator 503; mother liquid tank 504; membrane purification unit 6; condensate tank 601; transfer pump 602; intermediate tank 603; lifting pump 604; purification circulation pump 605; concentrate discharge valve 606; condensate purification reverse osmosis membrane group 607; garbage leachate 7; lime milk 8; sodium carbonate 9. DETAILED DESCRIPTION

[0027] Embodiment 1:

[0028] like Figure 1-7 In the invention, a low-temperature evaporation treatment system for landfill leachate comprises a pretreatment unit 1, a heat treatment unit 2 is arranged downstream of the pretreatment unit 1, a multi-effect evaporation crystallization unit is arranged downstream of the heat treatment unit 2, a membrane purification unit 6 is arranged downstream of the multi-effect evaporation crystallization unit, and the multi-effect evaporation crystallization unit comprises a pre-crystallization unit 3, a plurality of evaporation crystallization units 4 and a separation unit 5 connected in sequence;

[0029] The membrane purification unit 6 discharges water and salt mud. With this structure, the softening process of lime milk 8 is first used in the softening treatment machine 101 to reduce the hardness of the membrane concentrate of the landfill leachate, so as to avoid scaling and clogging of equipment by scaling substances such as calcium and magnesium in the subsequent process; the membrane concentrate after softening and purification is sent to the heat treatment unit 2, and the array solar collector 201 in the heat treatment unit 2 is composed of multiple solar collectors 201. Relying on the garbage pile of the domestic garbage landfill, the solar heater is distributed on the top of the garbage pile, the slope and other positions to absorb the heat of the solar energy. The solar energy is used as a single-effect heating heat source to reduce the cost. The membrane concentrate heated by the solar energy is collected and enters the single-effect separator 301. The pressure in the single-effect separator 301 is controlled to flash the membrane concentrate. The secondary steam generated is used as the heating heat source of the second effect. A part of the membrane concentrate after flashing and cooling is circulated back to the heat treatment unit 2, and a part is sent to the subsequent evaporator for further evaporation and concentration to crystallize the impurities; the energy consumption of multi-effect evaporation and crystallization is effectively reduced, and the cost is greatly reduced. During the evaporation process, pollutants such as ammonia nitrogen and organic matter will evaporate along with the water vapor. Therefore, the water quality of the condensed water from each effect cannot directly meet the standard. It needs to be purified by the condensate purification reverse osmosis membrane group 607 in the membrane purification unit 6 before being discharged in compliance with the standard. The resulting membrane concentrate is then returned to the pretreatment unit 1 and mixed with the softened membrane concentrate before being evaporated and concentrated. Compared with the traditional multi-effect evaporation crystallization process, the energy consumption is greatly reduced.

[0030] In a preferred embodiment, the pretreatment unit 1 includes a softening treatment machine 101, and a leachate lifting pump 102 and a sludge pump 103 are respectively connected to the softening treatment machine 101 downstream, and the sludge pump 103 is provided with a plate-frame filter press 104 connected thereto, and the other end of the plate-frame filter press 104 is connected to the softening treatment machine 101;

[0031] The heat treatment unit 2 includes a plurality of arrays of solar collectors 201, and the heat treatment unit 2 is connected to the pre-crystallization unit 3. With this structure, the landfill leachate membrane concentrate is first softened by the softening treatment machine 101. The equipment adopts the lime milk 8 softening process, that is, lime milk 8 is first used as an alkaline agent for removing magnesium ions. The lime milk 8 also has an adsorption and flocculation effect, which adsorbs and precipitates magnesium ions and part of the macromolecular humic acid in the membrane concentrate. The membrane concentrate precipitated by the lime milk 8 is separated from mud and water in the inclined plate sedimentation tank, and the clear liquid enters the sodium carbonate 9 reaction tank, and the calcium ions in the water are precipitated by carbonate. The precipitate is separated from mud and water after passing through the co-organizer sedimentation tank, and the clear liquid enters the subsequent unit. The bottom mud of the lime milk inclined plate sedimentation tank and the sodium carbonate inclined plate sedimentation tank is pumped out by a pump, and the mud and water are separated by the plate and frame filter press 104. The sludge is transported out for disposal, and the clear liquid is returned to the front end for recycling disposal.

[0032] The interior of the softening machine is divided into five pools, namely the lime milk reaction pool, the lime milk inclined plate sedimentation pool, the sodium carbonate reaction pool, the sodium carbonate inclined plate sedimentation pool, and the softened water temporary storage pool.

[0033] The landfill leachate membrane concentrate treated by the pretreatment unit 1 is mixed with the membrane concentrate from the membrane purification unit 6 and then sent to the heat treatment unit 2 for heating.

[0034] Preferably, in order to prevent scaling from occurring in the heat collecting tubes of the solar collector 201 and affecting heat transfer, the flow rate of the landfill leachate in the heat collecting tubes is controlled at 2-3 m / s.

[0035] In the preferred embodiment, the softening machine 101 is provided with multiple feed ports, lime milk 8 and sodium carbonate 9 are input from the feed ports of the softening machine 101, garbage leachate 7 is input from the inlet of the softening machine 101, and the leachate lifting pump 102 is connected to the heat treatment unit 2.

[0036] In a preferred embodiment, the pre-crystallization unit 3 includes a first-effect separator 301 and a first-effect circulation pump 302, and both the first-effect separator 301 and the first-effect circulation pump 302 are connected to the heat treatment unit 2.

[0037] In the preferred solution, the evaporation crystallization unit 4 includes a second-effect heater 401, a second-effect separator 403 and a circulation pump 402, which are connected in sequence to form a loop, and a second-effect non-condensable gas discharge valve 404 and a second-effect condensate discharge valve 405 are provided on one side of the second-effect heater 401, the second-effect non-condensable gas discharge valve 404 is connected to the separation unit 5, the second-effect condensate discharge valve 405 is connected to the membrane purification unit 6, and the second-effect separator 403 is respectively connected to the second-effect heater and the second-effect separator of the next evaporation crystallization unit 4. With this structure, the landfill leachate heated by solar energy enters the multi-effect evaporation unit, the heating part of the pre-crystallization unit 3 is the solar heat collection unit, and the vapor-liquid separation occurs after flash evaporation in the first-effect separator 301, and the temperature of the liquid phase decreases after flash evaporation, and is recycled back to the heat treatment unit 2 through the first-effect circulation pump 302 for heating and temperature increase, and in this cycle, the vapor phase serves as the heating heat source of the evaporation crystallization unit 4. The pressure of the separators decreases in sequence, that is, the pressure of the first-effect separator 301 is the highest, and the pressure of the last separator is the lowest. The feed amount of the next effect is controlled by the feed valve of each effect. As the pressure decreases in sequence, the feed liquid can be automatically sucked into the next effect by simply controlling the opening of the feed valve. Each effect adopts a forced circulation heating method to form a high-speed turbulent flow of the percolate in the heater tube to prevent scaling on the surface of the heat exchange tube.

[0038] In the preferred solution, an efflux pump 406 is provided at the outlet end of the second-effect separator of the last evaporation crystallization unit 4, and the last second-effect separator forms a loop through the efflux pump 406, and the efflux pump 406 is also connected to the centrifugal dehydrator 503 of the separation unit 5. With this structure, the last second-effect heater provides a high circulation flow rate to ensure that the leachate forms turbulence in the heat exchange tubes of each heater and flushes the surface of the heat exchange tubes, thereby effectively preventing the deposition of scaling substances on the surface of the heat exchange tubes and affecting heat transfer; each separator is an evaporation-separation device, and the garbage leachate heated and heated by each heater enters each evaporation crystallization unit 4 separator and flash evaporates, and the vapor phase is purified by the wire mesh demister on the top of the separator and enters the next heater as a heat source to heat the next wastewater, and the liquid phase is pumped into each heater by the corresponding circulation pump and heated and heated again, and the cycle continues;

[0039] In the preferred solution, the separation unit 5 includes a non-condensable gas condenser 501, a centrifugal dehydrator 503 and a mother liquid tank 504. The non-condensable gas condenser 501 is connected to the membrane purification unit 6. The non-condensable gas condenser 501 is connected to the outside through a vacuum pump 502. The centrifugal dehydrator 503 discharges salt mud. The mother liquid tank 504 is connected to the second-effect heater of the last evaporation crystallization unit 4. According to this structure, the non-condensable gas condenser 501 is a device for condensing and cooling the non-condensable gas extracted from each evaporation crystallization unit 4; the vacuum pump 502 is a device for providing vacuum for each evaporation crystallization unit 4; the external discharge pump 406, the centrifugal dehydrator 503, and the mother liquid tank 504 are devices for solid-liquid separation in the last evaporation crystallization unit 4, and the crystallized salt precipitated in the last evaporation crystallization unit 4 is separated from the system, and the clear liquid is returned to the system to continue evaporation, concentration and crystallization.

[0040] In the preferred embodiment, the membrane purification unit 6 includes a condensate tank 601, a condensate purification reverse osmosis membrane group 607 and an intermediate tank 603. A transfer pump 602 is provided between the condensate tank 601 and the intermediate tank 603. The intermediate tank 603 is connected to the condensate purification reverse osmosis membrane group 607 through a lift pump 604, and the condensate purification reverse osmosis membrane group 607 discharges water. With this structure, the pressure of the separator of the final evaporation crystallization unit 4 is guaranteed by the non-condensable gas condenser 501 and the vacuum pump 502, and the pressure of the vacuum pump 502 is controlled at 5~20 kPa. The percolate flow rate in the heater of each evaporation crystallization unit 4 is controlled at 2~3m / s. The condensate produced by each evaporation crystallization unit 4 may contain a small amount of pollutants such as organic matter and ammonia nitrogen, so the condensate needs to be further purified. Therefore, the membrane purification unit 6 is provided, and the purification circulation pump 605 can increase the flow rate of the membrane surface, flush the membrane surface, and make the membrane more resistant to fouling and clogging, thereby ensuring a more stable operation of the condensate purification reverse osmosis membrane group 607, so that pollutants are less deposited in the membrane. To ensure better pollutant purification efficiency, the head of the lifting pump 604 needs to be between 5 bar and 40 bar. The flow rate of the purification circulation pump 605 is 0.2 to 5 times that of the lifting pump 604.

[0041] In the preferred embodiment, a purification circulation pump 605 is connected to the condensate purification reverse osmosis membrane group 607, and the purification circulation pump 605 forms a loop with the condensate purification reverse osmosis membrane group 607. A concentrated liquid discharge valve 606 is provided downstream of the condensate purification reverse osmosis membrane group 607, and the concentrated liquid discharge valve 606 is connected to the softening treatment machine 101.

[0042] The above embodiments are only preferred technical solutions of the present invention and should not be regarded as limitations of the present invention. The protection scope of the present invention shall be the technical solutions recorded in the claims, including equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. The low-temperature evaporation treatment system for landfill leachate is characterized by: It comprises a pretreatment unit (1), a heat treatment unit (2) is provided downstream of the pretreatment unit (1), a multiple-effect evaporation crystallization unit is provided downstream of the heat treatment unit (2), a membrane purification unit (6) is provided downstream of the multiple-effect evaporation crystallization unit, and the multiple-effect evaporation crystallization unit comprises a pre-crystallization unit (3), a plurality of evaporation crystallization units (4) and a separation unit (5) which are connected in sequence; The membrane purification unit (6) discharges water and salt sludge.

2. The low-temperature evaporation treatment system for landfill leachate according to claim 1 is characterized by: The pretreatment unit (1) comprises a softening treatment machine (101), wherein a leachate lifting pump (102) and a sludge pump (103) are connected to each other at the downstream of the softening treatment machine (101), and the sludge pump (103) is connected to a plate-frame filter press (104), wherein the other end of the plate-frame filter press (104) is connected to the softening treatment machine (101); The heat treatment unit (2) comprises a plurality of arrays of solar collectors (201), and the heat treatment unit (2) is connected to the pre-crystallization unit (3).

3. The low-temperature evaporation treatment system for landfill leachate according to claim 2 is characterized by: The softening machine (101) is provided with a plurality of feed ports, lime milk (8) and sodium carbonate (9) are inputted from the feed ports of the softening machine (101), garbage leachate (7) is inputted from the inlet of the softening machine (101), and the leachate lifting pump (102) is connected to the heat treatment unit (2).

4. The low-temperature evaporation treatment system for landfill leachate according to claim 1 is characterized by: The pre-crystallization unit (3) comprises a first-effect separator (301) and a first-effect circulation pump (302), and both the first-effect separator (301) and the first-effect circulation pump (302) are connected to the heat treatment unit (2).

5. The low-temperature evaporation treatment system for landfill leachate according to claim 1 is characterized by: The evaporation crystallization unit (4) comprises a second-effect heater (401), a second-effect separator (403) and a circulation pump (402). The second-effect heater (401), the second-effect separator (403) and the circulation pump (402) are connected in sequence to form a loop. A second-effect non-condensable gas discharge valve (404) and a second-effect condensate discharge valve (405) are provided on one side of the second-effect heater (401). The second-effect non-condensable gas discharge valve (404) is connected to the separation unit (5), the second-effect condensate discharge valve (405) is connected to the membrane purification unit (6), and the second-effect separator (403) is respectively connected to the second-effect heater and the second-effect separator of the next evaporation crystallization unit (4).

6. The low-temperature evaporation treatment system for landfill leachate according to claim 5 is characterized by: An efflux pump (406) is provided at the outlet end of the second-effect separator of the last evaporation crystallization unit (4). The last second-effect separator forms a loop through the efflux pump (406), and the efflux pump (406) is also connected to the centrifugal dehydrator (503) of the separation unit (5).

7. The low-temperature evaporation treatment system for landfill leachate according to claim 1 is characterized by: The separation unit (5) comprises a non-condensable gas condenser (501), a centrifugal dehydrator (503) and a mother liquid tank (504); the non-condensable gas condenser (501) is connected to the membrane purification unit (6); the non-condensable gas condenser (501) is connected to the outside through a vacuum pump (502); the centrifugal dehydrator (503) discharges salt mud; and the mother liquid tank (504) is connected to the second-effect heater of the last evaporation crystallization unit (4).

8. The low-temperature evaporation treatment system for landfill leachate according to claim 1 is characterized by: The membrane purification unit (6) comprises a condensate tank (601), a condensate purification reverse osmosis membrane group (607) and an intermediate tank (603). A transfer pump (602) is provided between the condensate tank (601) and the intermediate tank (603). The intermediate tank (603) is connected to the condensate purification reverse osmosis membrane group (607) via a lifting pump (604). The condensate purification reverse osmosis membrane group (607) discharges water.

9. The low-temperature evaporation treatment system for landfill leachate according to claim 8 is characterized by: A purification circulation pump (605) is provided in communication with the condensate purification reverse osmosis membrane group (607). The purification circulation pump (605) and the condensate purification reverse osmosis membrane group (607) form a loop. A concentrated liquid discharge valve (606) is provided downstream of the condensate purification reverse osmosis membrane group (607). The concentrated liquid discharge valve (606) is in communication with the softening treatment machine (101).

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