Desulfurization wastewater treatment device and method

Abstract

The invention belongs to the technical field of energy utilization, and relates to a desulfurization wastewater treatment device and method.The device comprises a triple box, a clarification tank, a steam compression device, a multi-stage concentration and evaporation device, an indirect cooling device, a filtering device and a crystallization device. Desulfurization wastewater generated in the wet desulphurization process is fed into a triple box, and is fed into a clarification tank after lime acid-base neutralization, organic sulfur heavy metal removal and flocculation precipitation; part of steam turbine dead steam is fed into a steam compression device to be pressurized and heated, pressurized and heated steam is divided into two parts which are fed into a multi-stage concentration and evaporation device and an absorption type refrigeration device respectively, the steam fed into the multi-stage concentration and evaporation device and desulfurization wastewater from a clarification tank are subjected to indirect heat exchange, and concentration and evaporation of the desulfurization wastewater are achieved; feeding the concentrated desulfurization wastewater into a cooling device, filtering and collecting a solid which is separated out in the cooling process and contains sodium sulfate as a main component by a filtering device, feeding residual liquid into a crystallizing device, crystallizing and evaporating, and collecting a solid which contains sodium chloride as a main component.

Description

Technical Field

[0001] The invention belongs to the technical field of energy utilization, and specifically relates to a desulfurization wastewater treatment device and method. Background Art

[0002] Based on the current reality of raw coal blending in the coal-fired power industry and the increasingly stringent environmental protection requirements for ultra-clean flue gas emissions and wastewater reduction, new challenges have been raised for the efficient and stable operation of desulfurization facilities. Problems such as corrosion and wear, blockage, and excessive chloride ion concentration in desulfurization wastewater that is difficult to handle during the operation of the desulfurization system seriously restrict the efficient operation of the desulfurization device. When the limestone-gypsum wet flue gas desulfurization device is in operation, chlorides and heavy metals in the flue gas are continuously enriched in the absorption tower slurry, affecting the desulfurization efficiency, and thus producing desulfurization wastewater. The desulfurization wastewater produced has a high salt content and is difficult to handle, which has been a technical bottleneck that has plagued the environmental protection work of coal-fired power plants.

[0003] At present, conventional high-salt wastewater treatment methods use MVR, multi-effect evaporation or spray drying. The disadvantages of this method are as follows: 1) The wastewater evaporation process is energy-intensive; 2) The treated crystalline salt is still mixed salt and cannot be sold to obtain a certain degree of economy. Summary of the invention

[0004] In order to overcome the shortcomings of the existing production process, the present invention provides a desulfurization wastewater treatment device and method, which not only reuses part of the turbine exhaust steam of the coal-fired power plant, but also greatly reduces the energy consumption required for the crystallization process of the desulfurization wastewater, and can also achieve high-purity recovery of the crystallized salt, thereby facilitating its application in engineering.

[0005] The technical solution of the present invention:

[0006] A desulfurization wastewater treatment device, comprising a triple tank, a clarifier, a steam compression device, a multi-stage concentration evaporation device, a cooling device, a filtering device, a crystallization device, an absorption refrigeration device, and a condenser;

[0007] The desulfurization wastewater inlet of the triple box is connected to the desulfurization wastewater outlet of the wet desulfurization system, the outlet of the triple box is connected to the inlet of the clarifier, and the outlet of the clarifier is connected to the wastewater inlet of the multi-stage concentration and evaporation device;

[0008] The inlet of the steam compression device is used to receive the exhaust steam of the steam turbine, and the outlet of the steam compression device is respectively connected to the steam inlet of the multi-stage concentration and evaporation device and the absorption refrigeration device;

[0009] The concentrated desulfurization wastewater outlet of the multi-stage concentrating and evaporating device is connected to the concentrated desulfurization wastewater inlet of the cooling device, and the water vapor outlet of the multi-stage concentrating device is connected to the gas inlet of the wet desulfurization system;

[0010] The outlet of the steam-water mixture of the multi-stage condensing and evaporating device and the outlet of the steam-water mixture of the absorption refrigeration device are both connected to the inlet of the condenser; a refrigerant circulation pipeline is arranged between the cooling device and the absorption refrigeration device;

[0011] The outlet of the cooling device is connected to the inlet of the filtering device, the liquid phase outlet of the filtering device is connected to the liquid phase inlet of the crystallization device, and the solid phase outlet of the filtering device is used to discharge the solid phase product;

[0012] The crystallization device is provided with a high-temperature gas inlet, the gas phase product outlet of the crystallization device is connected to the gas phase inlet of the wet desulfurization system, and the solid product outlet of the crystallization device is used to discharge the solid phase product.

[0013] The triple tank is equipped with a neutralization tank, a sedimentation tank and a flocculation tank in sequence.

[0014] The steam compression device is a single-stage high-speed centrifugal blower, a Roots steam compressor, a screw steam compressor or a reciprocating steam compressor. The steam compression device is provided with an auxiliary electric heating device for assisting in heating the compressed steam to a use temperature.

[0015] The multi-stage concentration and evaporation device is a three-effect or four-effect concentration and evaporation device.

[0016] The cooling device is a partition cooler.

[0017] The inlet of the filtering device is provided with a spiral extrusion device, which is used in conjunction with the filtering device to extrude, dehydrate and filter the cooled crystallized salt.

[0018] The absorption refrigeration device is a steam absorption refrigeration device.

[0019] The crystallization device is an OSLO evaporation crystallizer, a DTB evaporation crystallizer or a flue gas bypass crystallization evaporator.

[0020] A method for treating desulfurization wastewater, comprising the following steps:

[0021] (I) Pretreatment stage: The desulfurization wastewater generated by the wet desulfurization system during the wet desulfurization process is sent to a triple tank, which is equipped with a neutralization tank, a sedimentation tank and a flocculation tank in sequence. The desulfurization wastewater is sent to a clarification tank after lime acid-base neutralization, organic sulfur removal of heavy metals, and flocculation and sedimentation;

[0022] (II) Wastewater concentration stage: The desulfurized wastewater from the lower part of the clarifier is sent to a multi-stage concentration and evaporation device, and part of the exhaust steam from the steam turbine is sent to a steam compression device for pressurization and temperature increase. The steam after pressurization and temperature increase is divided into two streams, which are sent to the multi-stage concentration and evaporation device and the absorption refrigeration device respectively. One of the steam sent to the multi-stage concentration and evaporation device is indirectly heat-exchanged with the desulfurized wastewater from the clarifier to achieve concentration and evaporation of the desulfurized wastewater. The concentrated desulfurized wastewater is sent to a cooling device, and the water vapor generated during the evaporation of the wastewater is sent to the wet desulfurization system as make-up water; the other steam sent to the absorption refrigeration device provides a heat source for the refrigerant precipitation of the absorption refrigeration device, and the steam-water mixture generated by cooling the exhaust steam after heat release from the multi-stage concentration and evaporation device and the absorption refrigeration device is sent to the condenser;

[0023] (III) Salt recovery stage: The solid whose main component is sodium sulfate is precipitated during the cooling process. The sodium sulfate is filtered through a filter device, naturally dried and then collected. The remaining liquid after filtration is sent to a crystallization device for direct contact heat exchange with the high-temperature gas input to the crystallization device. The desulfurization wastewater begins to crystallize and evaporate. The main component of the solid product produced during the crystallization and evaporation process is sodium chloride, which is discharged from the solid product outlet and collected. The generated gas phase product is sent to the wet desulfurization system.

[0024] The proportion of lime added in the neutralization box set in the triple box is calculated based on the pH value of the desulfurization wastewater after acid-base neutralization, and the pH value is in the range of 8 to 10.

[0025] The heavy metal desorption material in the sedimentation box of the triple box arrangement is TMT-15.

[0026] The flocculant selected in the flocculation box of the triple box is at least one of ferric chloride, polyferric sulfate or polyaluminium chloride.

[0027] The residence time of the desulfurization wastewater in the clarification tank is not less than 8 hours.

[0028] The operating temperature in the cooling device is set at -20 to 10°C.

[0029] The absorption refrigeration device adopts a steam absorption refrigeration method, and ammonia-water is selected as the refrigerant.

[0030] The evaporation form of the crystallization device is one of spray evaporation and solid adsorption evaporation.

[0031] The high-temperature gas may be air at the outlet of an air preheater, flue gas at the outlet of an induced draft fan, flue gas at the inlet of a dust collector, or a mixture of the flue gas at the outlet of an induced draft fan and the flue gas at the inlet of a dust collector.

[0032] The high temperature gas is used at a temperature between 130 and 300°C. The volume ratio of the high temperature gas to the desulfurized wastewater varies according to the evaporation form of the crystallization device and the high temperature gas use temperature, ranging from 6000 to 20000 Nm 3 / m 3 .

[0033] Beneficial effects of the present invention:

[0034] (1) By reusing the exhaust steam from the steam turbine, the steam used in the concentration and evaporation process of the desulfurization wastewater does not consume latent heat of vaporization, greatly reducing the energy consumption of the entire system.

[0035] (2) Compared with the traditional desulfurization wastewater treatment process, this device can realize the classification and recovery of impurities and greatly improve its added value. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is the process route diagram of the whole set of equipment of the present invention. DETAILED DESCRIPTION

[0037] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0038] Example

[0039] The desulfurization wastewater generated by the wet desulfurization system during the wet desulfurization process is sent to a triple box, which is equipped with a neutralization box, a sedimentation box and a flocculation box in sequence. The desulfurization wastewater is neutralized with lime acid and alkali (pH value is about 9), organic sulfur is detoxified with heavy metals (heavy metal desorption material uses TMT-15), and flocculation and precipitation (flocculant uses ferric chloride) before being sent to a clarifier. The residence time of the desulfurization wastewater in the clarifier is 8 hours; the desulfurization wastewater in the middle and lower part of the clarifier is sent to a multi-stage concentration and evaporation device (using a four-effect concentration and evaporation device), and part of the exhaust steam from the turbine is sent to a steam compression device (using a reciprocating steam compressor) for pressurization and heating to 80°C. The steam after pressurization and heating is divided into two streams, which are respectively sent to a multi-stage concentration and evaporation device and an absorption refrigeration device (using a steam absorption refrigeration device, and ammonia-water is selected as the refrigerant). One of the steam sent to the multi-stage concentration and evaporation device is indirectly heat exchanged with the desulfurization wastewater from the clarifier to achieve concentrated evaporation of the desulfurization wastewater. The concentrated desulfurization wastewater Water is sent to the cooling device (the cooling device adopts a partition cooler, and the temperature inside is controlled at -5°C), and the water vapor generated during the evaporation of the wastewater is sent to the wet desulfurization system as supplementary water; another stream of steam sent to the absorption refrigeration device provides a heat source for the precipitation of the refrigerant of the absorption refrigeration device, and the steam-water mixture generated by cooling the exhaust steam after the multi-stage concentration evaporation device and the absorption refrigeration device releases heat is sent to the condenser; the solid whose main component is sodium sulfate precipitated during the cooling process is filtered by a filtering device, naturally dried and collected, and the remaining liquid after filtration is sent to a crystallization device (using an OSLO evaporation crystallizer, and the volume ratio of 200°C hot air to high-salt wastewater in the crystallization device is 20000Nm3 / m3), and performs direct contact heat exchange with the high-temperature gas input to the crystallization device, and the desulfurization wastewater begins to crystallize and evaporate. The main component of the solid product generated during the crystallization and evaporation process is sodium chloride, which is discharged through the solid product outlet and collected, and the generated gas phase product is sent to the desulfurization system.

[0040] By adopting the above method, the purity of the collected sodium sulfate is greater than 80%, the salt removal rate in high-salt wastewater reaches more than 95%, and the purity of the recovered sodium chloride is greater than 95%, meeting the requirements for industrial salt use.

[0041] The present invention includes but is not limited to this embodiment. It should be pointed out that for ordinary technicians in this field, other methods can be used to make substitutions without departing from the technical principles of the present invention. These substitutions should also be regarded as the protection scope of the present invention.

Claims

1. A desulfurization wastewater treatment device, characterized in that: The desulfurization wastewater treatment device includes a triple tank, a clarifier, a steam compression device, a multi-stage concentration evaporation device, an indirect cooling device, a filtering device, a crystallization device, an absorption refrigeration device, and a condenser; The desulfurization wastewater inlet of the triple box is connected to the desulfurization wastewater outlet of the wet desulfurization system, the outlet of the triple box is connected to the inlet of the clarifier, and the outlet of the clarifier is connected to the wastewater inlet of the multi-stage concentration and evaporation device; The inlet of the steam compression device is used to receive the exhaust steam of the steam turbine, and the outlet of the steam compression device is respectively connected to the steam inlet of the multi-stage concentration and evaporation device and the absorption refrigeration device; The concentrated desulfurization wastewater outlet of the multi-stage concentrating and evaporating device is connected to the concentrated desulfurization wastewater inlet of the cooling device, and the water vapor outlet of the multi-stage concentrating device is connected to the gas inlet of the wet desulfurization system; The outlet of the steam-water mixture of the multi-stage condensing and evaporating device and the outlet of the steam-water mixture of the absorption refrigeration device are both connected to the inlet of the condenser; a refrigerant circulation pipeline is arranged between the cooling device and the absorption refrigeration device; The outlet of the cooling device is connected to the inlet of the filtering device, the liquid phase outlet of the filtering device is connected to the liquid phase inlet of the crystallization device, and the solid phase outlet of the filtering device is used to discharge the solid phase product; The crystallization device is provided with a high-temperature gas inlet, the gas phase product outlet of the crystallization device is connected to the gas phase inlet of the wet desulfurization system, and the solid product outlet of the crystallization device is used to discharge the solid phase product.

2. A desulfurization wastewater treatment device according to claim 1, characterized in that: The triple tank is equipped with a neutralization tank, a sedimentation tank and a flocculation tank in sequence.

3. A method for treating desulfurization wastewater, characterized in that: The method is implemented by using a desulfurization wastewater treatment device as described in any one of claims 1-2, and the specific steps are as follows: (I) Pretreatment stage: The desulfurization wastewater generated by the wet desulfurization system during the wet desulfurization process is sent to a triple tank, which is equipped with a neutralization tank, a sedimentation tank and a flocculation tank in sequence. The desulfurization wastewater is sent to a clarification tank after lime acid-base neutralization, organic sulfur removal of heavy metals, and flocculation and sedimentation; (II) Wastewater concentration stage: The desulfurized wastewater from the lower part of the clarifier is sent to a multi-stage concentration and evaporation device, and part of the exhaust steam from the steam turbine is sent to a steam compression device for pressurization and temperature increase. The steam after pressurization and temperature increase is divided into two streams, which are sent to the multi-stage concentration and evaporation device and the absorption refrigeration device respectively. One of the steam sent to the multi-stage concentration and evaporation device is indirectly heat-exchanged with the desulfurized wastewater from the clarifier to achieve concentration and evaporation of the desulfurized wastewater. The concentrated desulfurized wastewater is sent to a cooling device, and the water vapor generated during the evaporation of the wastewater is sent to the wet desulfurization system as make-up water; the other steam sent to the absorption refrigeration device provides a heat source for the refrigerant precipitation of the absorption refrigeration device, and the steam-water mixture generated by cooling the exhaust steam after heat release from the multi-stage concentration and evaporation device and the absorption refrigeration device is sent to the condenser; (III) Salt recovery stage: The solid whose main component is sodium sulfate is precipitated during the cooling process. The sodium sulfate is filtered through a filter device, naturally dried and then collected. The remaining liquid after filtration is sent to a crystallization device for direct contact heat exchange with the high-temperature gas input to the crystallization device. The desulfurization wastewater begins to crystallize and evaporate. The main component of the solid product produced during the crystallization and evaporation process is sodium chloride, which is discharged from the solid product outlet and collected. The generated gas phase product is sent to the wet desulfurization system.

4. A desulfurization wastewater treatment method according to claim 3, characterized in that: The lime addition ratio in the neutralization box of the triple box is calculated based on the pH value of the desulfurization wastewater after acid-base neutralization, and the pH value is in the range of 8 to 10; the heavy metal desorption material in the sedimentation box of the triple box is TMT-15; the flocculant selected in the flocculation box of the triple box is at least one of ferric chloride, polyferric sulfate or polyaluminium chloride.

5. A desulfurization wastewater treatment method according to claim 3, characterized in that: The residence time of the desulfurization wastewater in the clarification tank is not less than 8 hours.

6. A desulfurization wastewater treatment method according to claim 3, characterized in that: The operating temperature in the cooling device is set at -20 to 10°C.

7. A desulfurization wastewater treatment method according to claim 3, characterized in that: The absorption refrigeration device adopts a steam absorption refrigeration method, and ammonia-water is selected as the refrigerant.

8. A desulfurization wastewater treatment method according to claim 3, characterized in that: The evaporation form of the crystallization device is one of spray evaporation and solid adsorption evaporation.

9. A desulfurization wastewater treatment method according to claim 3, characterized in that: The high-temperature gas may be air at the outlet of an air preheater, flue gas at the outlet of an induced draft fan, flue gas at the inlet of a dust collector, or a mixture of the flue gas at the outlet of an induced draft fan and the flue gas at the inlet of a dust collector.

10. A desulfurization wastewater treatment method according to claim 3, characterized in that: The high temperature gas is used at a temperature between 130 and 300°C. The volume ratio of the high temperature gas to the desulfurized wastewater varies according to the evaporation form of the crystallization device and the high temperature gas use temperature, ranging from 6000 to 20000 Nm 3 / m 3 .

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