System for treating desulfurization wastewater

Abstract

The utility model relates to a system for treating desulfurization wastewater. The system comprises a pretreatment unit, a concentration tower, a heat exchanger, a drying tower, an air preheater and a first trap, the system disclosed by the utility model is high in automation degree, the scaling and blocking problems of equipment pipelines are small, the concentration of chloride ions in utilized flue gas is low, and the investment and operation cost is relatively low.

Description

Technical Field

[0001] The present disclosure relates to the field of water treatment, and in particular, to a system for treating desulfurization wastewater. Background Art

[0002] Power plant desulfurization wastewater originates from the limestone-gypsum wet flue gas desulfurization process. This wastewater has a complex chemical composition, including supersaturated sulfites, sulfates, grease, organic matter (COD), fluoride, high concentrations of suspended solids, and heavy metal ions such as As, Hg, and Pb.

[0003] The desulfurization wastewater treatment system is a crucial component of the wet flue gas desulfurization process in coal-fired power plants. Treating and discharging desulfurization wastewater ensures stable and reliable operation of the desulfurization unit. Due to factors such as the desulfurization unit, coal type, process water, and operating conditions, the complex composition of desulfurization wastewater presents significant challenges for wastewater treatment.

[0004] During the treatment process, the desulfurization wastewater extraction, pre-sedimentation, dosing reaction, clarification and sludge discharge links have their own division of labor and influence each other. It is necessary to carry out relevant technical management work from a systematic perspective to solve the problems existing in operation.

[0005] The difficulties and challenges of zero-emission treatment of membrane desulfurization wastewater include: (1) Complex wastewater composition: Desulfurization wastewater contains a large amount of suspended solids, chloride ions, sulfate ions, calcium ions, etc. These substances may cause corrosion and scaling to equipment, pipelines and membrane components during the treatment process, affecting the treatment effect; (2) High wastewater treatment cost: The treatment of desulfurization wastewater requires multiple process steps, including pretreatment, membrane concentration, evaporation crystallization, etc. These steps require a large amount of energy and chemicals, so the treatment cost is relatively high; (3) The solid waste generated during the wastewater treatment process is difficult to treat: The solid waste generated during the membrane desulfurization wastewater treatment process mainly includes crystallized salt and sludge, etc. These wastes are difficult to dispose of. If they are directly landfilled, they may cause secondary pollution to the environment; (4) The maintenance and management of wastewater treatment equipment is difficult: Membrane desulfurization wastewater treatment equipment needs to be cleaned and maintained regularly. If improperly maintained, it may affect the treatment effect and equipment life. At the same time, the failure rate of the equipment is also relatively high, and management and maintenance need to be strengthened. Compared with the membrane desulfurization wastewater treatment system, the desulfurization wastewater treatment system using flue gas has low pretreatment requirements and relatively low investment and operating costs, but there are problems such as easy scaling and chloride ions entering the flue gas and enrichment. Utility Model Content

[0006] The purpose of the present disclosure is to provide a system for treating desulfurization wastewater, which has a high degree of automation, a small problem of scaling and clogging of equipment pipelines, a controllable chloride ion concentration in the utilized flue gas, and low investment and operating costs.

[0007] In order to achieve the above object, the present disclosure provides a system for treating desulfurization wastewater, the system comprising a pretreatment unit, a concentration tower, a heat exchanger, a drying tower, an air preheater and a first collector;

[0008] The outlet of the air preheater is connected to the inlet of the desulfurization tower through a low-temperature flue gas pipeline;

[0009] The inlet of the air preheater is connected to the high-temperature flue gas pipeline;

[0010] The pretreatment unit is provided with a wastewater inlet and a pretreated water outlet;

[0011] The wastewater inlet is connected to the wastewater outlet of the desulfurization tower;

[0012] The concentration tower is provided with a low-temperature flue gas inlet, a first flue gas outlet, a first outlet and a first inlet;

[0013] The drying tower is provided with a high-temperature flue gas inlet, a second flue gas outlet and a liquid inlet;

[0014] The heat exchanger is provided with a refrigerant inlet, a refrigerant outlet, a heat medium inlet and a heat medium outlet;

[0015] The refrigerant inlet of the heat exchanger is connected to the pretreated water outlet of the pretreatment unit; the refrigerant outlet is connected to the first inlet of the concentration tower; the heat medium inlet is connected to the first outlet of the concentration tower; the heat medium outlet is connected to the liquid inlet of the drying tower;

[0016] The low-temperature flue gas inlet and the first flue gas outlet of the concentration tower are respectively connected to the low-temperature flue gas pipeline;

[0017] The high-temperature flue gas inlet and the second flue gas outlet of the drying tower are respectively connected to the high-temperature flue gas pipeline;

[0018] The inlet of the first collector is connected to the first smoke outlet and is used to capture liquid discharged from the first smoke outlet;

[0019] The gas outlet of the first collector is connected to the low-temperature flue gas pipeline.

[0020] Optionally, the pretreatment unit includes a first reaction tank, a second reaction tank, a third reaction tank, a clarifier and a filter that are sequentially connected;

[0021] The filter is connected to the pre-treated water outlet;

[0022] The system further comprises a dosing unit, which comprises a lime dosing box, a caustic soda dosing box, a magnesium agent dosing box, an organic sulfur dosing box, a flocculant dosing box, and an acid dosing box;

[0023] The outlet of the lime dosing box, the outlet of the caustic soda dosing box and the outlet of the magnesium agent dosing box are respectively connected to the first reaction tank through dosing pumps;

[0024] The outlet of the organic sulfur dosing tank is connected to the second reaction tank via a dosing pump;

[0025] The outlet of the flocculant dosing box is connected to the third reaction tank via a dosing pump;

[0026] The outlet of the acid dosing tank is connected to the clarification tank via a dosing pump;

[0027] The filter comprises a multi-microfiltration filter and / or an ultrafiltration filter.

[0028] Optionally, a circulation pump is provided in the concentration tower;

[0029] The inlet of the circulation pump is connected with the first inlet and the bottom of the concentration tower.

[0030] Optionally, more than two layers of spray assemblies are provided in the concentration tower, and the spray assembly includes a distribution main pipe and multiple distribution branch pipes connected to the outlet of the distribution main pipe, and each outlet of the distribution branch pipe is provided with a nozzle; the outlet of the circulation pump is connected to the inlet of the distribution main pipe.

[0031] Optionally, the system further comprises a second collector for capturing liquid discharged from the second smoke outlet;

[0032] The inlet of the second collector is connected to the second smoke outlet;

[0033] The gas outlet of the second collector is connected to the high-temperature flue gas pipeline.

[0034] Optionally, the system further comprises a stabilization tank;

[0035] The inlet of the stabilization tank is connected to the heat medium outlet;

[0036] The outlet of the stabilization tank is connected to the liquid inlet;

[0037] An agitator is provided in the stabilization tank.

[0038] Optionally, the system further includes a dust collector; the dust collector is arranged downstream of the air preheater, the inlet of the dust collector is connected to the outlet of the air preheater, and the outlet of the dust collector is connected to the low-temperature flue gas pipeline.

[0039] Optionally, a rotary atomizer is provided in the drying tower, the inlet of the rotary atomizer is connected to the liquid inlet of the drying tower, and the outlet of the rotary atomizer is connected to the second flue gas outlet.

[0040] Optionally, the system further comprises a first booster fan and / or a second booster fan;

[0041] The gas inlet of the first booster fan is connected to the low-temperature flue gas pipeline;

[0042] The gas outlet of the first booster fan is connected to the low-temperature flue gas inlet;

[0043] The gas outlet of the second booster fan is connected to the high-temperature flue gas inlet;

[0044] The gas inlet of the second booster fan is connected to the high-temperature flue gas pipeline.

[0045] Optionally, the heat exchanger is a plate-and-frame heat exchanger and / or a tube-and-tube heat exchanger.

[0046] Through the above technical solution, the system disclosed in the present invention utilizes low-temperature flue gas and high-temperature flue gas to perform direct contact heat exchange in the concentration tower and the drying tower respectively, to concentrate and reduce the wastewater and to dry and solidify it. The low-temperature flue gas and the high-temperature flue gas after gas-liquid contact are returned to the low-temperature flue gas pipeline and the high-temperature flue gas pipeline; the system disclosed in the present invention has a high degree of automation, little problem of scaling and clogging of equipment pipelines, a low chloride ion concentration in the utilized flue gas, and low investment and operating costs.

[0047] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following detailed description, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings:

[0049] Figure 1 It is a schematic diagram of a system for treating desulfurization wastewater according to an embodiment of the present disclosure.

[0050] Description of Reference Numerals

[0051] 1 first booster fan 8 first collector

[0052] 2 Second booster fan 9 stabilization tank

[0053] 3 desulfurization tower 10 drying tower

[0054] 4 Wastewater collection tank 11 Second collector

[0055] 5 pre-treatment units 12 dust collectors

[0056] 6 heat exchangers 13 chimneys

[0057] 7 Concentration tower 14 Air preheater DETAILED DESCRIPTION

[0058] The following describes the specific embodiments of the present disclosure in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure and are not intended to limit the present disclosure.

[0059] like Figure 1 As shown, the present disclosure provides a system for treating desulfurization wastewater, the system comprising a pretreatment unit 5, a concentration tower 7, a heat exchanger 6, a drying tower 10, an air preheater 14 and a first collector 8;

[0060] The outlet of the air preheater 14 is connected to the inlet of the desulfurization tower through a low-temperature flue gas pipeline;

[0061] The inlet of the air preheater 14 is connected to the high-temperature flue gas pipeline;

[0062] The pretreatment unit 5 is provided with a wastewater inlet and a pretreated water outlet;

[0063] The wastewater inlet is connected to the wastewater outlet of the desulfurization tower;

[0064] The concentration tower 7 is provided with a low-temperature flue gas inlet, a first flue gas outlet, a first outlet and a first inlet;

[0065] The drying tower 10 is provided with a high-temperature flue gas inlet, a second flue gas outlet and a liquid inlet;

[0066] The heat exchanger 6 is provided with a refrigerant inlet, a refrigerant outlet, a heat medium inlet and a heat medium outlet;

[0067] The refrigerant inlet of the heat exchanger 6 is connected to the pretreated water outlet of the pretreatment unit 5; the refrigerant outlet is connected to the first inlet of the concentration tower 7; the heat medium inlet is connected to the first outlet of the concentration tower 7; the heat medium outlet is connected to the liquid inlet of the drying tower 10;

[0068] The low-temperature flue gas inlet and the first flue gas outlet of the concentration tower 7 are respectively connected to the low-temperature flue gas pipeline;

[0069] The high-temperature flue gas inlet and the second flue gas outlet of the drying tower 10 are respectively connected to the high-temperature flue gas pipeline;

[0070] The inlet of the first collector 8 is connected to the first smoke outlet and is used to capture the liquid discharged from the first smoke outlet;

[0071] The gas outlet of the first collector 8 is connected to the low-temperature flue gas pipeline.

[0072] In the present disclosure, the pretreated effluent of the pretreatment unit enters the heat exchanger through the refrigerant inlet of the heat exchanger, contacts the effluent of the concentration tower entering the heat exchanger through the heat medium inlet, exchanges heat to increase the temperature, and then is discharged through the refrigerant outlet, and then enters the concentration tower through the first inlet, contacts the low-temperature flue gas for heat exchange to achieve concentration, and the concentrated effluent enters the heat exchanger through the heat medium inlet, and contacts the pretreated effluent entering the heat exchanger through the refrigerant inlet as a heat medium. On the one hand, heat is exchanged with the pretreated effluent to increase its temperature, and on the other hand, the temperature of the concentrated effluent is reduced to avoid scaling of subsequent pipelines; the cooled effluent is discharged through the heat medium outlet and enters the next treatment step.

[0073] In the present disclosure, the first collector is used to capture the liquid discharged from the first flue gas outlet and separate the salt mist therein. The separated low-temperature flue gas is transported to the low-temperature flue gas pipeline through a pipeline and then passed into the desulfurization tower. The liquid flows back to the drying tower due to gravity.

[0074] According to one embodiment of the present disclosure, the pretreatment unit 5 includes a first reaction tank, a second reaction tank, a third reaction tank, a clarifier and a filter which are sequentially connected;

[0075] The filter is connected to the pre-treated water outlet;

[0076] The system further comprises a dosing unit, which comprises a lime dosing box, a caustic soda dosing box, a magnesium agent dosing box, an organic sulfur dosing box, a flocculant dosing box, and an acid dosing box;

[0077] The outlet of the lime dosing box, the outlet of the caustic soda dosing box and the outlet of the magnesium agent dosing box are respectively connected to the first reaction tank through dosing pumps;

[0078] The outlet of the organic sulfur dosing tank is connected to the second reaction tank via a dosing pump;

[0079] The outlet of the flocculant dosing box is connected to the third reaction tank via a dosing pump;

[0080] The outlet of the acid dosing box is connected to the clarification tank through a dosing pump;

[0081] The effluent from the third reaction tank passes through a clarifier and a filter for solid-liquid separation, and the outlet of the filter is the pre-treated water outlet;

[0082] Preferably, in order to promote contact and improve treatment effect, a stirrer is respectively provided in the first reaction tank, the second reaction tank and the third reaction tank.

[0083] According to one embodiment of the present disclosure, pH probes are provided in the first reaction tank, the second reaction tank, the third reaction tank, and the clarification tank to measure the pH value of the liquid therein, and treatment agents are added according to the test results.

[0084] According to one embodiment of the present disclosure, the filter may be a multi-media filter, which may include a microfiltration filter and / or an ultrafiltration filter, for example, a sand filter tank, and the specific structure of the filter is conventional in the art.

[0085] According to one embodiment of the present disclosure, a circulation pump is provided in the concentration tower 7; the inlet of the circulation pump is connected to the first inlet and the bottom of the concentration tower 7, and the liquid flow entering the concentration tower through the first inlet and the liquid in the concentration tower enter the circulation pump for further concentration, thereby achieving full circulation of the liquid in the concentration tower and improving the concentration efficiency.

[0086] In order to further heat exchange and concentrate the wastewater in the concentration tower, according to one embodiment of the present disclosure, more than two layers of spray components are provided in the concentration tower 7, and the spray components include a distribution main pipe and a plurality of distribution branches connected to the outlet of the distribution main pipe, and each outlet of the distribution branch pipe is provided with a nozzle; the outlet of the circulation pump is connected to the inlet of the distribution main pipe; the material of the spray pipe can be 2507, for example; the wastewater leaves the heat exchanger through the refrigerant outlet, and then enters the circulation pump through the first inlet, and enters the spray system after internal circulation, and is sprayed and distributed through multiple nozzles, and contacts with the low-temperature flue gas for concentration treatment, thereby further improving the efficiency of concentration and heat exchange. The concentrated liquid settles in the concentration tower and then enters the circulation pump through the inlet of the circulation pump for circulation and concentration.

[0087] According to one embodiment of the present disclosure, the system further comprises a second trap 11;

[0088] The inlet of the second collector 11 is connected to the second smoke outlet;

[0089] The gas outlet of the second collector 11 is connected to the high-temperature flue gas pipeline;

[0090] Among them, the second collector 11 is used to capture the flue gas from the second flue gas outlet of the drying tower 10, separate the salt mist therein, and transport the separated high-temperature flue gas to the high-temperature flue gas pipeline through a pipeline. The liquid flows back to the concentration tower due to gravity.

[0091] According to one embodiment of the present disclosure, the second collector 11 is disposed inside the drying tower 10 .

[0092] According to one embodiment of the present disclosure, the droplet content at the gas outlet of the first collector 8 is less than 150 mg / Nm³.

[0093] According to one embodiment of the present disclosure, the droplet content at the gas outlet of the second collector 11 is less than 150 mg / Nm³.

[0094] According to one embodiment of the present disclosure, a rotary atomizer is provided in the drying tower 10, the inlet of the rotary atomizer is connected to the liquid inlet of the drying tower 10, and the outlet of the rotary atomizer is connected to the second flue gas outlet. The rotary atomizer is used to fully contact the input liquid with the high-temperature flue gas to perform crystallization and solidification treatment, thereby realizing the treatment of desulfurization wastewater.

[0095] According to one embodiment of the present disclosure, the liquid inlet flow rate of the rotary atomizer is above 0.6 m / s, and the flow rate can be adjusted by using an electric valve, which is a V-shaped ceramic-lined wear-resistant ball valve; the pressure is below 0.2 MPa, and the rotation speed is above 1000 rpm.

[0096] According to one embodiment of the present disclosure, the system further comprises a first booster fan 1 and / or a second booster fan 2;

[0097] The gas inlet of the first booster fan 1 is connected to the low-temperature flue gas pipeline, and is used to extract low-temperature flue gas from the low-temperature flue gas pipeline and enter the concentration tower to perform heat exchange and concentration on the liquid therein;

[0098] The gas outlet of the first booster fan 1 is connected to the low-temperature flue gas inlet;

[0099] The gas outlet of the second booster fan 2 is connected to the high-temperature flue gas inlet;

[0100] The gas inlet of the second booster fan 2 is connected to the high-temperature flue gas pipeline, and is used to extract high-temperature flue gas from the upstream high-temperature flue gas pipeline and enter the drying tower to dry and solidify the liquid therein.

[0101] According to one embodiment of the present disclosure, the temperature of the gas inlet of the first booster blower 1 is 85-120°C.

[0102] According to an embodiment of the present disclosure, the gas inlet temperature of the second booster blower 2 is 300-400°C.

[0103] According to one embodiment of the present disclosure, the system further comprises a stabilization tank 9 for settling the liquid entering therein and removing solid impurities;

[0104] The inlet of the stabilization tank 9 is connected to the heat medium outlet;

[0105] The outlet of the stabilization tank 9 is connected to the liquid inlet, and a feed pump can be provided between the outlet of the stabilization tank 9 and the liquid inlet of the drying tower 10 to transport the liquid in the stabilization tank to the drying tower;

[0106] The stabilization tank 9 is provided with an agitator for fully mixing the suspended solids in the stabilization tank.

[0107] According to one embodiment of the present disclosure, the system further includes a dust collector 12, which is used to remove dust from the flue gas; the dust collector 12 is arranged downstream of the air preheater 14, the inlet of the dust collector 12 is connected to the outlet of the air preheater 14, and the outlet of the dust collector 12 is connected to the low-temperature flue gas pipeline.

[0108] According to one embodiment of the present disclosure, a temperature probe is provided in the stabilization tank 9 for measuring the temperature of the material in the stabilization tank.

[0109] According to one embodiment of the present disclosure, the type of the heat exchanger 6 is conventional in the art, for example, it can be a plate and frame heat exchanger and / or a tube heat exchanger.

[0110] According to one embodiment of the present disclosure, the system further includes a chimney, the desulfurization tower is connected to the chimney, and the exhaust gas generated in the desulfurization tower is passed into the chimney and discharged.

[0111] According to one embodiment of the present disclosure, the system further includes a wastewater collection tank, the inlet of the wastewater collection tank is connected to the desulfurization tower, and the outlet of the wastewater collection tank is connected to the pretreatment unit 5.

[0112] According to a specific embodiment of the present disclosure, a method for treating desulfurization wastewater using the system of the present disclosure includes:

[0113] (1) The desulfurization wastewater generated by the desulfurization tower 3 is tested for water quality and then passed into the wastewater collection tank 4, and then sent to the pretreatment unit 5 for dosing pretreatment;

[0114] (2) The outlet water of the pretreatment unit enters the heat exchanger 6 through the refrigerant inlet of the heat exchanger, and exchanges heat with the outlet water of the concentration tower entering the heat exchanger 6 from the heat medium inlet to increase the temperature. Then, the outlet water enters the concentration tower 7 through the refrigerant inlet for concentration. The water is distributed through the circulation pump and the multi-layer spraying system in the concentration tower 7, and directly exchanges heat with the flue gas extracted from the low-temperature flue gas pipeline by the first booster fan 1 (the temperature of the gas inlet is 85-120°C) for evaporation and concentration. Then, the water enters the heat exchanger through the heat medium inlet and is finally discharged through the hot coal outlet to achieve the concentration of the desulfurization wastewater. The liquid at the first flue gas outlet of the concentration tower 7 is captured and separated by the first collector 8, and the obtained flue gas is passed into the low-temperature flue gas pipeline and then transported to the desulfurization tower 3 for treatment. The obtained liquid flows back to the concentration tower by gravity, and the droplet content of the gas outlet of the first collector 8 is less than 150mg / Nm³. The desulfurization tower 3 is connected to the chimney 13 to discharge the waste gas generated by the desulfurization tower 3.

[0115] (3) The effluent discharged through the heat medium outlet enters the stabilization tank 9 for sedimentation to remove solid particles, and is then sent to the drying tower 10 through the feed pump for direct heat exchange with the high-temperature flue gas extracted from the high-temperature flue gas pipeline by the second booster fan 2 (gas inlet temperature is 300-400°C). The liquid at the second flue gas outlet of the drying tower 10 is captured and separated by the second collector 11, and the obtained flue gas is sent back to the high-temperature flue gas pipeline. The liquid flows back to the drying tower by gravity, and the droplet content at the gas outlet of the second collector 11 is less than 150 mg / Nm³;

[0116] A rotary atomizer is provided in the drying tower. The liquid inlet flow rate of the rotary atomizer is above 0.6m / s, the pressure is below 0.2MPa, and the rotation speed is above 1000 rpm.

[0117] (4) The high-temperature flue gas in the high-temperature flue gas pipeline passes through the air preheater 14 to reduce the temperature, then enters the dust collector 12 to remove dust, and enters the low-temperature flue gas pipeline to realize the circulation of flue gas.

[0118] The system disclosed herein utilizes low-temperature flue gas and high-temperature flue gas to perform direct contact heat exchange in a concentration tower and a drying tower, respectively, to concentrate and reduce the wastewater and to dry and solidify it. By lowering the temperature of the concentrated liquid, the supersaturation of CaSO4 therein is reduced, making it in a stably dissolved state, thereby avoiding scaling and clogging in the pipeline; and by capturing the liquid in the flue gas, the chlorine concentration in the flue gas is reduced.

[0119] The preferred embodiments of the present disclosure are described in detail above in conjunction with the accompanying drawings. However, the present disclosure is not limited to the specific details of the above embodiments. Within the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the scope of protection of the present disclosure.

[0120] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0121] In addition, the various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A system for treating desulfurization wastewater, characterized in that: The system includes a pretreatment unit (5), a concentration tower (7), a heat exchanger (6), a drying tower (10), an air preheater (14) and a first collector (8); The outlet of the air preheater (14) is connected to the inlet of the desulfurization tower through a low-temperature flue gas pipeline; The inlet of the air preheater (14) is connected to the high-temperature flue gas pipeline; The pretreatment unit (5) is provided with a wastewater inlet and a pretreated water outlet; The wastewater inlet is connected to the wastewater outlet of the desulfurization tower; The concentration tower (7) is provided with a low-temperature flue gas inlet, a first flue gas outlet, a first outlet and a first inlet; The drying tower (10) is provided with a high-temperature flue gas inlet, a second flue gas outlet and a liquid inlet; The heat exchanger (6) is provided with a refrigerant inlet, a refrigerant outlet, a heat medium inlet and a heat medium outlet; The refrigerant inlet of the heat exchanger (6) is connected to the pretreated water outlet of the pretreatment unit (5); the refrigerant outlet is connected to the first inlet of the concentration tower (7); the heat medium inlet is connected to the first outlet of the concentration tower (7); the heat medium outlet is connected to the liquid inlet of the drying tower (10); The low-temperature flue gas inlet and the first flue gas outlet of the concentration tower (7) are respectively connected to the low-temperature flue gas pipeline; The high-temperature flue gas inlet and the second flue gas outlet of the drying tower (10) are respectively connected to the high-temperature flue gas pipeline; The inlet of the first collector (8) is connected to the first smoke outlet and is used to capture liquid discharged from the first smoke outlet; The gas outlet of the first collector (8) is connected to the low-temperature flue gas pipeline.

2. The system according to claim 1, wherein: The pretreatment unit (5) comprises a first reaction tank, a second reaction tank, a third reaction tank, a clarifier and a filter which are connected in sequence; The filter is connected to the pre-treated water outlet; The system further comprises a dosing unit, which comprises a lime dosing box, a caustic soda dosing box, a magnesium agent dosing box, an organic sulfur dosing box, a flocculant dosing box, and an acid dosing box; The outlet of the lime dosing box, the outlet of the caustic soda dosing box and the outlet of the magnesium agent dosing box are respectively connected to the first reaction tank through dosing pumps; The outlet of the organic sulfur dosing tank is connected to the second reaction tank via a dosing pump; The outlet of the flocculant dosing box is connected to the third reaction tank via a dosing pump; The outlet of the acid dosing tank is connected to the clarification tank via a dosing pump; The filter comprises a multi-microfiltration filter and / or an ultrafiltration filter.

3. The system according to claim 1, wherein: A circulation pump is provided in the concentration tower (7); The inlet of the circulation pump is connected to the first inlet and the bottom of the concentration tower (7).

4. The system according to claim 3, characterized in that The concentration tower (7) is provided with more than two layers of spraying components, the spraying components including a distribution main pipe and a plurality of distribution branch pipes connected to the outlet of the distribution main pipe, each outlet of the distribution branch pipe is provided with a nozzle; the outlet of the circulation pump is connected to the inlet of the distribution main pipe.

5. The system according to claim 1, wherein: The system further comprises a second collector (11) for collecting liquid discharged from the second smoke outlet; The inlet of the second collector (11) is connected to the second smoke outlet; The gas outlet of the second collector (11) is connected to the high-temperature flue gas pipeline.

6. The system according to claim 1, wherein: The system further comprises a stabilization tank (9); The inlet of the stabilization tank (9) is connected to the heat medium outlet; The outlet of the stabilization tank (9) is connected to the liquid inlet; A stirrer is provided in the stabilization tank (9).

7. The system according to claim 1, wherein: The system further comprises a dust collector (12); the dust collector (12) is arranged downstream of the air preheater (14), the inlet of the dust collector (12) is connected to the outlet of the air preheater (14), and the outlet of the dust collector (12) is connected to the low-temperature flue gas pipeline.

8. The system according to claim 1, wherein: A rotary atomizer is provided in the drying tower (10), the inlet of the rotary atomizer is connected to the liquid inlet of the drying tower (10), and the outlet of the rotary atomizer is connected to the second flue gas outlet.

9. The system according to claim 1, wherein: The system further comprises a first booster fan (1) and / or a second booster fan (2); The gas inlet of the first booster fan (1) is connected to the low-temperature flue gas pipeline; The gas outlet of the first booster fan (1) is connected to the low-temperature flue gas inlet; The gas outlet of the second booster fan (2) is connected to the high-temperature flue gas inlet; The gas inlet of the second booster fan (2) is connected to the high-temperature flue gas pipeline.

10. The system according to claim 1, wherein: The heat exchanger (6) is a plate-and-frame heat exchanger and / or a tube-and-tube heat exchanger.

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