CN112077128A

CN112077128A - Water washing treatment system and method for fly ash

Info

Publication number: CN112077128A
Application number: CN202011060375.9A
Authority: CN
Inventors: 周海明; 陈志刚; 周天睿
Original assignee: Sinochem Zhejiang Membrane Industry Development Co Ltd
Current assignee: Sinochem Zhejiang Membrane Industry Development Co Ltd
Priority date: 2020-09-30
Filing date: 2020-09-30
Publication date: 2020-12-15

Abstract

The invention provides a system and a method for treating fly ash by water washing. The flying ash washing treatment system comprises a flying ash washing unit and a washing water treatment unit, wherein the flying ash washing unit is used for washing flying ash, the washing water treatment unit is used for carrying out innocent treatment on washing water generated by the flying ash washing, the flying ash washing unit comprises a multi-stage washing device and a multi-stage dehydration device which are in one-to-one correspondence, the washing device is used for washing the flying ash, the dehydration device is used for separating a mixture of the flying ash and the washing water into plaster and the washing water, and the washing devices and the dehydration devices at different stages are connected with each other in a reverse washing mode. The fly ash washing treatment system can realize the fly ash washing dechlorination and the zero discharge of the fly ash washing water.

Description

Water washing treatment system and method for fly ash

Technical Field

The invention belongs to the field of waste incineration fly ash disposal, and relates to a fly ash washing treatment system and method.

Background

The household garbage incineration fly ash refers to the collected matters of a flue gas purification system generated by household garbage incineration and bottom ash settled at the bottom of a flue and a chimney, and is referred to as fly ash in the text. The fly ash is a hazardous waste which has both heavy metal hazard characteristics and persistent organic toxicity hazard characteristics to the environment.

Currently, common methods for fly ash disposal are: (1) after proper disposal, the waste enters a hazardous waste landfill for final disposal; (2) curing and stabilizing, such as cement curing, asphalt curing, melt curing technology, chemical agent curing and stabilizing, and the products after curing and stabilizing treatment, such as meeting leaching toxicity standards or recycling standards, can enter a common landfill for landfill treatment or recycling; and (3) performing resource utilization by using the cement kiln to cooperatively treat the fly ash.

At present, the land supply is increasingly tense, and a large amount of land is occupied regardless of the landfill according to the hazardous waste or the solidification stabilization landfill. The conventional cement kiln co-processing fly ash technology or the limit addition amount is not more than 3 per thousand due to too high salt content in the fly ash, so that the co-processing fly ash amount of the cement kiln is greatly reduced; or the common water washing fly ash technology is adopted to elute the salt in the fly ash into the waste water, and finally the mixed salt is evaporated and crystallized, and the pollutants are transferred into the mixed salt.

The existing fly ash washing treatment system has the following defects: 1. the water consumption is large when washing; 2. the fly ash washing sludge is dehydrated by adopting a belt type vacuum filter press, the dehydration effect is poor, the water content of the discharged sludge is high, and the energy consumption of the subsequent drying device is increased; 3. the operation cost is extremely high; 4. the washing water treatment adopts a simple chemical-adding precipitation filtration process, can not completely remove harmful substances in the wastewater, and the subsequent salt separation process can only produce mixed salt with more impurities and needs to treat the mixed salt according to hazardous wastes.

Therefore, there is still a need in the art for a fly ash water-washing treatment system that has low water consumption, good dewatering effect, low operating cost, and can completely remove harmful substances in wastewater and obtain crystalline salts meeting the requirements of industrial byproducts.

Disclosure of Invention

In order to solve the problems, the invention provides a fly ash washing treatment system. The fly ash washing treatment system comprises a fly ash washing unit and a washing water treatment unit, wherein the fly ash washing unit comprises a multi-stage washing device and a multi-stage dehydration device. The washing water treatment unit preferably comprises an adjusting reaction tank, a solid-liquid separation device, a reaction sedimentation tank, a gypsum reaction tank, a gypsum separation device, a softening device and a multi-stage membrane device. The fly ash washing unit can ensure that the salt in the fly ash is completely eluted, greatly improve the fly ash amount of the cement kiln co-processing, and simultaneously reduce the water consumption of washing. According to the method, the sodium sulfate and sodium carbonate are combined to be added with the chemicals for decalcification, so that the operation cost is reduced, meanwhile, gypsum is byproduct, the fly ash washing water is subjected to advanced treatment through a multi-stage membrane technology, impurities in the washing water are removed, the fly ash washing water can be evaporated and crystallized to obtain qualified finished salt, and the resource utilization is completely realized.

Particularly, the invention provides a fly ash washing treatment system, which comprises a fly ash washing unit and a washing water treatment unit, the fly ash washing unit is used for washing fly ash, the washing water treatment unit is used for performing innocent treatment on washing water generated by washing fly ash, the flying ash washing unit comprises a multi-stage washing device and a multi-stage dehydration device which are in one-to-one correspondence, the washing device is used for washing flying ash, the dewatering device is used for separating the mixture of the fly ash and the washing water into the plaster and the washing water, the washing device comprises a feed inlet, a water inlet, a discharge outlet, a stirring device and an optional mud scraping device, the dewatering device comprises a feed inlet, a discharge outlet and a filtrate outlet, the discharge outlet of each stage of washing device is respectively connected with the feed inlet of the same stage of dewatering device, and the washing devices and the dewatering devices at different stages are mutually connected in a backwashing mode.

In one or more embodiments, the fly ash water wash unit includes at least a tertiary water wash device and a dewatering device.

In one or more embodiments, the feed inlet of the first stage washing device is used for receiving fly ash to be washed, the feed inlets of the other stages of washing devices are respectively connected with the discharge outlet of the previous stage dewatering device and used for receiving plaster discharged by the previous stage dewatering device, the water inlet of the last stage washing device is used for receiving initial washing water, the water inlets of the other stages of washing devices are respectively connected with the filtrate outlet of the next stage dewatering device and used for receiving washing water discharged by the next stage dewatering device, the filtrate outlet of the first stage dewatering device is connected with the washing water treatment unit and used for discharging final washing water, and the discharge outlet of the last stage dewatering device is used for discharging final plaster.

In one or more embodiments, the water wash device is a water wash tank, and/or the dewatering device is a decanter centrifuge.

In one or more embodiments, the washing water treatment unit comprises a regulation reaction tank, a solid-liquid separation device, a reaction sedimentation tank, a gypsum reaction tank, a gypsum separation device, a softening device and a multi-stage membrane device which are connected in sequence, wherein the regulation reaction tank is used for stabilizing the quality of the washing water produced by the fly ash washing unit, the solid-liquid separation device is used for separating and regulating solid particles and liquid in the material discharged by the reaction sedimentation tank, the reaction sedimentation tank is used for removing heavy metals and partial calcium ions in the liquid produced by the solid-liquid separation device, the gypsum reaction tank is used for further removing calcium ions in the liquid discharged by the reaction sedimentation tank and generating gypsum, the gypsum separation device is used for separating solid particles and liquid in the material discharged by the gypsum reaction tank, the softening device is used for softening the liquid produced by the gypsum separation device, and the multi-stage membrane device is used for further softening suspended matters in the liquid discharged by the removing device, Residual heavy metal ions and sulfate ions.

In one or more embodiments, the solid-liquid separation device is a decanter centrifuge.

In one or more embodiments, the reaction sedimentation tank comprises a feed inlet, a dosing port, a water outlet, a sludge outlet and a stirring device, preferably, the reaction sedimentation tank comprises a mixing zone, a reaction zone and a sedimentation zone, the mixing zone comprises the feed inlet, the stirring device and an optional dosing port, the reaction zone comprises the stirring device and an optional dosing port, and the sedimentation zone comprises the water outlet and the sludge outlet.

In one or more embodiments, the gypsum separation device is a decanter centrifuge.

In one or more embodiments, the softening device comprises a softening sedimentation tank and an optional softening water production tank, the softening sedimentation tank comprises a feed inlet, a dosing port, a water outlet, a sludge outlet and an agitation device, the softening water production tank comprises a water inlet and a water outlet, preferably, the softening sedimentation tank comprises a mixing zone, a reaction zone and a sedimentation zone, the mixing zone comprises the feed inlet, the agitation device and the optional dosing port, the reaction zone comprises the agitation device and the optional dosing port, and the sedimentation zone comprises the water outlet and the sludge outlet.

In one or more embodiments, the multi-stage membrane device includes a material separation membrane and an ion separation membrane.

In one or more embodiments, the water wash water treatment unit further comprises an evaporative partial salt crystallization device for producing sodium chloride crystalline monosalt and potassium chloride crystalline monosalt, the evaporative partial salt crystallization device being connected to the multi-stage membrane device.

In one or more embodiments, the evaporative salt crystallization apparatus includes a mechanical vapor recompression evaporative crystallization assembly, a cooling crystallization assembly, and optionally an influent holding tank.

The invention also provides a method for washing treatment of fly ash, which comprises the following steps:

(1) and (4) sending the fly ash into a fly ash washing unit, and washing by adopting a multi-stage reverse washing mode.

In one or more embodiments, the method further comprises the steps of:

(2) introducing the washing water produced by the fly ash washing unit into a regulating reaction tank, and optionally adding a flocculating agent;

(3) introducing the material discharged from the regulating reaction tank into a solid-liquid separation device for solid-liquid separation;

(4) introducing the filtrate produced by the solid-liquid separation device into a reaction sedimentation tank, and adding a pH regulator to precipitate heavy metals and partial calcium ions in the liquid;

(5) introducing the supernatant of the reaction sedimentation tank into a gypsum reaction tank, adding sodium sulfate to precipitate calcium ions in the liquid and generate gypsum;

(6) introducing the materials discharged from the gypsum reaction tank into a gypsum separation device for solid-liquid separation;

(7) introducing the filtrate produced by the gypsum separation device into a softening device for softening water;

(8) and introducing the softened water produced by the softening device into a multi-stage membrane device to remove suspended matters, residual heavy metal ions and sulfate ions in the softened water.

In one or more embodiments, the method further comprises the steps of:

(9) and (3) introducing the filtrate produced by the multistage membrane device into an evaporation salt separation crystallization device to generate sodium chloride crystal salt and potassium chloride crystal salt.

In one or more embodiments, the method is performed using a fly ash water-wash treatment system according to any embodiment of the invention.

Drawings

FIG. 1 is a schematic structural diagram of a fly ash washing treatment system of the present invention, wherein the reference numerals are as follows: 1-first-stage water washing tank, 2-first-stage centrifuge, 3-second-stage water washing tank, 4-second-stage centrifuge, 5-third-stage water washing tank, 6-third-stage centrifuge, 7-reuse water tank, 8-regulation reaction tank, 9-filtrate centrifuge, 10-reaction sedimentation tank, 11-gypsum reaction tank, 12-gypsum centrifuge, 13-softening sedimentation tank, 14-softening water production tank, 15-multi-stage membrane device and 16-evaporation salt separation crystallization device.

FIG. 2 is a schematic diagram of the structure of a water washing tank of the fly ash water washing treatment system of the present invention.

FIG. 3 is a schematic structural diagram of a reaction settling tank of a fly ash washing treatment system according to the present invention.

FIG. 4 is a schematic structural diagram of a multi-stage membrane device of a fly ash washing treatment system according to the present invention.

Detailed Description

To make the features and effects of the present invention comprehensible to those skilled in the art, general description and definitions are made below with reference to terms and expressions mentioned in the specification and claims. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

The theory or mechanism described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, i.e., the present invention may be practiced without limitation to any particular theory or mechanism.

All features defined herein as numerical ranges or percentage ranges, such as amounts, amounts and concentrations, are for brevity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to cover and specifically disclose all possible subranges and individual numerical values (including integers and fractions) within the range.

Herein, unless otherwise specified, the ratio refers to a mass ratio, the percentage refers to a mass percentage, and the part refers to a mass part.

In this context, for the sake of brevity, not all possible combinations of features in the various embodiments or examples are described. Therefore, the respective features in the respective embodiments or examples may be arbitrarily combined as long as there is no contradiction between the combinations of the features, and all the possible combinations should be considered as the scope of the present specification.

The fly ash washing treatment system comprises a fly ash washing unit and a washing water treatment unit. The fly ash water washing unit is used for washing the fly ash with water so as to elute partial salt and pollutants in the fly ash into water washing water. The washing water treatment unit is used for performing harmless treatment on washing water and optionally performing resource utilization on impurities in the washing water. An exemplary fly ash water-wash treatment system is configured as shown in FIG. 1.

The fly ash washing unit typically comprises a washing device and a dewatering device. The water washing device is used for washing the fly ash. The dewatering device is used for separating the mixture of the fly ash and the water washing water into the stucco and the water washing water. Herein, stucco has the conventional meaning in the art and refers to the solid residue obtained after dewatering a mixture of fly ash and wash water, containing fly ash and a certain amount of water.

In the invention, the water washing device comprises a feed inlet, a water inlet, a discharge outlet, a stirring device and an optional mud scraping device. The feed inlet of the washing device is used for receiving fly ash or plaster, and the water inlet of the washing device is used for receiving washing water. The inlet and outlet of the water wash apparatus are typically located in the upper portion of the water wash apparatus. The discharge of the washing apparatus for discharging the mixture of fly ash and washing water is usually arranged at the bottom of the washing apparatus. The stirring device is arranged inside the washing device and used for stirring materials in the washing device. Herein, the structure of the stirring device is not particularly limited, and may be a stirring device commonly used in the art, for example, a stirrer. In the present invention, whether or not the sludge scraping device needs to be installed in the water washing device can be determined according to the scale of the project, the scale of the amount of water, and the form of the water washing device. The mud scraping device is usually arranged at the bottom of the washing device and used for turning over materials deposited in the washing device to avoid hardening of the bottom of the washing device. Herein, the structure of the mud scraping device is not particularly limited, and may be a mud scraping device commonly used in the art, for example, a mud scraper. The water wash apparatus may also include a rinse port and/or a vent port. The water washing device may be, for example, a water washing tank. The configuration of the water wash tank may be conventional in the art. The water washing tank suitable for the present invention may be, for example, the water washing tank shown in fig. 2, the top of the water washing tank is provided with a feed inlet, a water inlet, a flushing port and a vent port, the inside of the water washing tank is provided with a stirrer, and the bottom of the water washing tank is provided with a discharge port.

In the invention, the dehydration device comprises a feed inlet, a filtrate outlet and a discharge outlet. The dewatering device can be one commonly used in the art for dewatering stucco, such as a centrifuge, plate and frame dewaterer, filter, or the like. In a preferred embodiment, the dewatering device is a horizontal screw centrifuge. The invention discovers that the horizontal screw centrifuge is used for solid-liquid separation, the dehydration effect is good, and the operation is simple. The feed inlet of the dewatering device is used for receiving the mixture of the fly ash and the washing water, and can be arranged at the top or the side of the dewatering device; when the dewatering device is a horizontal decanter centrifuge, the feed opening is usually arranged laterally. The feed inlet of the dewatering device is connected with the discharge outlet of the washing device. The filtrate outlet of the dewatering device is used for discharging washing water, and the discharge port of the dewatering device is used for discharging plaster. The filtrate outlet and discharge of the dewatering device are usually arranged at the bottom of the dewatering device. It will be appreciated by those skilled in the art that the water wash separated by the dewatering device may still contain some amount of solid impurities.

In a preferred embodiment of the invention, the fly ash washing unit comprises a plurality of washing devices and a number of dewatering devices equal to the number of washing devices. Herein, when the fly water washing unit includes N water washing devices and N dehydration devices (N is an integer of 2 or more), each water washing device is referred to as a first-stage to N-stage water washing device, each dehydration device is referred to as a first-stage to N-stage dehydration device, and the water washing devices and the dehydration devices of the same stage number correspond one-to-one. For example, when the fly ash water-washing unit includes three water-washing devices and three dehydration devices, the three water-washing devices are referred to as a primary water-washing device, a secondary water-washing device, and a tertiary water-washing device, respectively, and the three dehydration devices are referred to as a primary dehydration device, a secondary dehydration device, and a tertiary dehydration device, respectively. Herein, the number of stages of the water washing device and the dewatering device is used to indicate the correspondence and connection between the water washing device and the dewatering device, and is described in detail below. In some embodiments, the fly ash water wash unit of the present invention comprises at least two water wash devices and at least two dewatering devices; preferably, the fly ash water wash unit of the present invention comprises at least three water wash devices and at least three dewatering devices.

In the invention, the discharge ports of the water washing devices of all stages are respectively connected with the feed port of the dewatering device of the same stage. In a preferred embodiment of the invention, the water washing devices and the dewatering devices of different stages are connected with each other in a backwashing manner, wherein backwashing means that the fly ash sequentially enters the water washing devices of different stages according to the stage sequence of the water washing devices, and the washing water sequentially enters the water washing devices of different stages in a reverse sequence according to the stage sequence of the water washing devices, namely, in the invention, a feed inlet of one-stage water washing device is used for receiving the fly ash to be washed, feed inlets of other water washing devices of different stages are respectively connected with a discharge outlet of a previous-stage dewatering device and are used for receiving the plaster discharged by the previous-stage dewatering device, a water inlet of the last-stage water washing device is used for receiving the initial washing water, water inlets of other water washing devices of different stages are respectively connected with a filtrate outlet of a next-stage dewatering device and are used for receiving the washing water discharged by the next-stage dewatering device, and a filtrate outlet of the one-, Connected with the water washing and water processing unit, and the discharge port of the final stage dehydration device is used for discharging the final plaster. The method adopts a multi-stage backwashing mode, preferably at least three-stage backwashing mode to carry out washing dechlorination on the fly ash, obviously reduces the using amount of washing water, reduces the water content of the plaster and improves the removal rate of chloride ions in the fly ash, for example, the three-stage backwashing mode is adopted for washing, and the mass ratio of the washing water to the fly ash can be controlled to be (2-3): 1, the water content of the three-stage washing plaster is less than 40 percent, the chloride ion is less than 1 percent, and the removal rate of the chloride ion in the fly ash is more than 90 percent.

In the present invention, it is understood that the washing water used in each stage of the washing apparatus is the washing water discharged from the next stage of the dewatering apparatus, in addition to the washing water used in the last stage of the washing apparatus (i.e., the first washing water). The source of the washing water for the final-stage washing apparatus is not particularly limited and may be from various conventional water supply apparatuses or pipes. In some embodiments, the fly ash wash unit of the present invention comprises a reuse water basin, and the wash water for the last stage wash unit is from the reuse water basin. The stucco discharged from the final dewatering apparatus (i.e., the final stucco) can be transported, stored, and/or processed (e.g., dried) in a manner conventional in the art, for example, the discharge outlet of the final dewatering apparatus can be connected to a screw conveyor to transport the stucco out.

In the present invention, unless otherwise specified, when connected, the units, and the devices (for example, between the outlet of the water washing device and the inlet of the dewatering device, between the inlet of the water washing device and the filtrate outlet of the dewatering device, between the inlet of the water washing device and the outlet of the dewatering device, and between the filtrate outlet of the dewatering device and the water washing water treatment unit) may be connected by pipes; pumps may be provided on each pipe or at the outlet of each device (e.g., filtrate outlet of dewatering device, discharge of water washing device) as needed to facilitate transport of material in the pipe. The pump suitable for use in the present invention is not particularly limited, and may be, for example, a lift pump or the like.

In some preferred embodiments, as shown in fig. 1, the fly ash washing unit comprises three washing apparatuses (i.e., a primary washing apparatus, a secondary washing apparatus, and a tertiary washing apparatus) and three dewatering apparatuses (i.e., a primary dewatering apparatus, a secondary dewatering apparatus, and a tertiary dewatering apparatus); the fly ash sequentially enters a first-stage washing device, a second-stage washing device and a third-stage washing device, and washing water sequentially enters the third-stage washing device, the second-stage washing device and the first-stage washing device; the upper part of each water washing device is provided with a feed inlet and a water inlet, the bottom of each water washing device is provided with a discharge outlet, and a stirring device (such as a stirrer) is arranged in each water washing device, and a mud scraping device (such as a mud scraper) is preferably arranged in each water washing device; each water washing device is preferably a water washing tank; the upper part or the side surface of each dewatering device is provided with a feed inlet, and the bottom of each dewatering device is provided with a filtrate outlet and a discharge outlet; each dewatering device is preferably a centrifuge, more preferably a decanter centrifuge; the feed inlet of the first-level washing device is a feed inlet of fly ash to be washed; the water inlet of the first-stage water washing device is connected with the filtrate outlet of the second-stage dehydration device through a pipeline; the discharge hole of the primary water washing device is connected with the feed inlet of the primary dewatering device through a pipeline, and a pump (such as a lift pump) is preferably arranged at the discharge hole of the primary water washing device; the filtrate outlet of the primary dewatering device is connected with a washing water treatment unit; the feed inlet of the secondary water washing device is connected with the discharge outlet of the primary dewatering device through a pipeline; the water inlet of the second-stage water washing device is connected with the filtrate outlet of the third-stage dehydration device through a pipeline; the discharge hole of the secondary washing device is connected with the feed inlet of the secondary dewatering device through a pipeline, and a pump (such as a lift pump) is preferably arranged at the discharge hole of the secondary washing device; the discharge hole of the second-stage dehydration device is connected with the feed inlet of the third-stage washing device through a pipeline; the water inlet of the third-stage water washing device is the water inlet of the initial water washing water; preferably, the fly ash washing unit comprises a reuse water tank, a water inlet of the third-stage washing device is connected with the reuse water tank through a pipeline, and a water outlet of the reuse water tank is preferably provided with a pump (such as a lift pump); the discharge hole of the third-stage water washing device is connected with the feed inlet of the third-stage dehydration device through a pipeline, and a pump (such as a lift pump) is preferably arranged at the discharge hole of the third-stage water washing device; preferably, the fly ash washing unit comprises a screw conveyor, and a discharge port of the three-stage dehydration device is connected with the screw conveyor.

The pH of the fly ash water washing water is usually up to more than 12, and the fly ash water washing water contains a large amount of fly ash suspended substances and a large amount of calcium ions and heavy metal ions, and the fly ash water washing water needs to be subjected to membrane treatment and salt separation crystallization after water treatment to remove the impurities. Thus, the water wash water treatment unit typically comprises one or more reaction devices, filtration devices, evaporation devices and/or crystallization devices. The reaction apparatus is used for adding a reagent (for example, a pH adjusting agent, a precipitating agent, etc.) to water washed with water to carry out a reaction. The reaction apparatus may be, for example, a reaction cell, a reaction tank, or the like. The filtering device is used for filtering out solids in the water washing water. The evaporation device is used for concentrating the washing water and/or recovering pure water. The crystallization device is used for separating out the crystallized salt in the water washing water.

In a preferred embodiment of the invention, the water washing water treatment unit comprises a regulating reaction tank, a solid-liquid separation device, a reaction sedimentation tank, a gypsum reaction tank, a gypsum separation device, a softening device and a multi-stage membrane device.

In the invention, the regulating reaction tank is a container for receiving the washing water produced by the fly ash washing unit. In the invention, the regulating reaction tank is used for stabilizing the water quality of the washing water, namely, the washing water generated by washing the fly ash in different batches is collected and mixed with each other to ensure uniform water quality, so that the subsequent water treatment device is prevented from being influenced by severe change of the water quality. The type of the conditioning reaction tank suitable for use in the present invention is not particularly limited, and may be, for example, a conditioning tank known in the art. Herein, the regulation tank has a meaning well known in the art, and means a tank for regulating the amount or quality of water provided before a subsequent wastewater treatment facility in order to allow the wastewater treatment facility to normally operate without being affected by a peak flow rate or concentration change of wastewater in the wastewater treatment. The regulating reaction tank is provided with a water inlet and a discharge hole. The regulating reaction tank has a water inlet connected to the fly ash washing unit (specifically, to the filtrate outlet of the dewatering device) for receiving the washing water from the fly ash washing unit, and the water inlet is usually disposed at the upper part of the regulating reaction tank. In embodiments where the fly ash wash unit comprises a plurality of dehydration means, the water inlet of the conditioning reaction tank is connected to the filtrate outlet of the primary dehydration means. The discharge port of the regulating reaction tank is used for discharging materials in the regulating reaction tank, and the discharge port is usually arranged at the bottom of the regulating reaction tank. In some embodiments, the conditioning reaction tank further comprises a dosing port for receiving a pharmaceutical agent, typically disposed in an upper portion of the conditioning reaction tank. A certain amount of flocculating agent, such as Polyacrylamide (PAM), can be added through a medicine adding port of the adjusting reaction tank so as to improve the separation effect of the subsequent solid-liquid separation device. In some embodiments, the regulating reaction tank is also internally provided with a stirring device and/or a mud scraping device for stirring the materials in the regulating reaction tank and turning over the materials deposited in the regulating reaction tank respectively. In the invention, the washing water treatment unit can also comprise one or more medicine adding devices for adding medicine to devices (such as an adjusting reaction tank, a reaction sedimentation tank, a gypsum reaction tank and a softening sedimentation tank) needing medicine according to the needs, and the medicine adding ports of the devices needing medicine adding are connected with the medicine outlet ports of the corresponding medicine adding devices through pipelines. Herein, the dosing device may be, for example, a dosing metering pump, and the corresponding drug outlet of the dosing device is an outlet of the dosing metering pump.

In the invention, the solid-liquid separation device is used for separating and adjusting solid particles and liquid in the material discharged from the reaction tank. The solid-liquid separation device comprises a feed inlet, a filtrate outlet and a discharge outlet. The solid-liquid separation device may be any of various common solid-liquid separation devices for separating solid particles from liquid, and may be, for example, a centrifuge, a plate-and-frame dehydrator, a filter, or the like. In a preferred embodiment, the solid-liquid separation device is a horizontal screw centrifuge. The feed inlet of the solid-liquid separation device is used for receiving materials discharged by the regulating reaction tank and can be arranged at the top or the side surface of the solid-liquid separation device; when the solid-liquid separation device is a horizontal screw centrifuge, the feed port is usually provided at the side. The feed inlet of the solid-liquid separation device is connected with the discharge outlet of the regulating reaction tank. The filtrate outlet of the solid-liquid separation device is used for discharging separated liquid, and the discharge hole of the solid-liquid separation device is used for discharging separated solid. The filtrate outlet and the discharge outlet of the solid-liquid separation device are usually arranged at the bottom of the solid-liquid separation device. In a preferred embodiment, the discharge port of the solid-liquid separation device is connected with the feed port of the water washing device of the fly ash water washing unit so as to realize the purification treatment and recycling of solid impurities. In embodiments where the fly ash washing unit comprises a tertiary washing device, the discharge outlet of the solid-liquid separation device is preferably connected to the feed inlet of the secondary washing device. The solid content of the washing water generated by the fly ash washing unit is extremely unstable, and the solid content of the filtrate can be effectively controlled by arranging the regulating reaction tank and the solid-liquid separation device in the washing water treatment unit, so that the working efficiency and the stability of the subsequent washing water treatment device are guaranteed.

In the invention, the reaction sedimentation tank is used for adding a medicament into the liquid separated by the solid-liquid separation device to carry out reaction so as to remove heavy metals and partial calcium ions in the solution. The reaction sedimentation tank comprises a feed inlet, a dosing port, a water outlet, a sludge outlet, a stirring device and an optional sludge scraping device. And a feed inlet of the reaction sedimentation tank is connected with a filtrate outlet of the solid-liquid separation device and is used for receiving the liquid separated by the solid-liquid separation device. In the present invention, the agent added to the reaction sedimentation tank is mainly a pH adjuster, usually an acid solution such as hydrochloric acid. It can be understood that the washing water generated by washing the fly ash is strongly alkaline, and some heavy metals (such as aluminum and zinc) can be dissolved in water in an ionic form under the strongly alkaline condition, so that the pH of the solution needs to be adjusted to 9-10 by using acid, the heavy metals are precipitated in the form of oxides or hydroxides, and meanwhile, partial calcium ions are separated out due to the change of the pH. The reaction sedimentation tank may be a reaction sedimentation tank commonly used for water treatment, and may be, for example, a reaction sedimentation tank including a mixing zone, a reaction zone, and a sedimentation zone. In the present invention, the configurations of the mixing zone, the reaction zone and the precipitation zone of the reaction precipitation tank may be conventional in the art. An exemplary reaction settling tank is shown in fig. 3. The mixing zone, the reaction zone and the precipitation zone are connected in sequence. The upper part or the side surface of the mixing area is provided with a feed inlet, and the mixing area is optionally provided with a dosing port. And a feed inlet of the mixing zone is connected with a filtrate outlet of the solid-liquid separation device and is used for receiving liquid separated by the solid-liquid separation device. The dosing port of the mixing zone is for receiving a medicament. The mixing area is internally provided with a stirring device and used for stirring the materials in the mixing area. The reaction zone is optionally provided with a dosing port. The reaction zone is internally provided with a stirring device for stirring the materials in the reaction zone. The settling zone comprises a water outlet and a sludge outlet. The effluent of the settling zone is connected with a subsequent gypsum reaction tank through a pipeline. Inside the settling zone, a mud scraper, such as a mud scraper, may be provided. The inside of the settling zone can be provided with an inclined plate and a sludge hopper. The inclined plate and the sludge hopper have meanings well known in the art herein. In some embodiments, the sludge outlet of the reaction sedimentation tank is connected with the regulation reaction tank through a sludge pump.

In the invention, the gypsum reaction tank is used for adding a medicament into the effluent of the reaction sedimentation tank for reaction so as to remove calcium ions in the solution and generate gypsum. In the invention, the medicament added into the reaction sedimentation tank is mainly sodium sulfate. In the gypsum reaction tank, calcium ions in the solution are mainly converted into calcium sulfate, so that the precipitate is removed. The gypsum reaction tank may be a reaction tank commonly used for water treatment. The gypsum reaction tank comprises a water inlet, a discharge port and a drug adding port. The water inlet of the gypsum reaction tank is connected with the water outlet of the reaction sedimentation tank. The discharge port of the gypsum reaction tank is connected with a subsequent gypsum separation device. The method adopts a sodium sulfate and sodium carbonate combined dosing mode to decalcify, adds sodium sulfate into a gypsum reaction tank, adds sodium carbonate into a subsequent softening device, reduces the operation cost, produces gypsum as a byproduct, and separates and removes introduced sulfate ions by using a subsequent multistage membrane device.

In the invention, the gypsum separation device is used for separating solid particles and liquid in the material discharged from the gypsum reaction tank. The gypsum separating device comprises a feed inlet, a filtrate outlet and a discharge outlet. The gypsum separating device can be various common solid-liquid separating devices for separating solid particles and liquid, such as a centrifuge, a plate-and-frame dehydrator, a filter and the like. In a preferred embodiment, the gypsum separation device is a horizontal decanter centrifuge. The feed inlet of the gypsum separating device is connected with the water outlet of the gypsum reaction tank, is used for receiving materials discharged by the gypsum reaction tank, and can be arranged at the top or the side surface of the gypsum separating device; when the gypsum separation plant is a horizontal decanter centrifuge, the feed opening is usually arranged at the side. The filtrate outlet of the gypsum separating device is used for discharging separated liquid, and the discharge port of the gypsum separating device is used for discharging separated solid. The filtrate outlet and the discharge opening of the gypsum separation unit are usually arranged at the bottom of the gypsum separation unit. The filtrate outlet of the gypsum separating device is connected with the water inlet of the subsequent softening device. The discharge port of the gypsum separation device can be externally connected with a gypsum storage yard.

In the invention, the softening device is used for reducing the hardness of water and removing calcium ions in the water. The softening device may be an apparatus for softening water as is conventional in the art. The softening device comprises a water inlet and a water outlet, wherein the water inlet is connected with a filtrate outlet of the gypsum separation device, and the water outlet is connected with a water inlet of the multi-stage membrane device. In some embodiments, the softening device comprises a softening settling tank. The softening sedimentation tank comprises a feed inlet, a dosing port, a water outlet, a mud outlet, a stirring device and an optional mud scraping device. The feed inlet of the softening sedimentation tank is connected with the filtrate outlet of the gypsum separation device. The softening and settling tank is used for adding softening agents (such as sodium carbonate and sodium hydroxide) into the liquid separated by the gypsum separation device to react so as to further remove calcium ions in the solution. The softening settling tank may be a reaction settling tank commonly used for water treatment, and may be, for example, a reaction settling tank including a mixing zone, a reaction zone, and a settling zone. The mixing zone, the reaction zone and the precipitation zone are connected in sequence. The upper part or the side surface of the mixing area is provided with a feed inlet, and the mixing area is optionally provided with a dosing port. And a feed inlet of the mixing zone is connected with a filtrate outlet of the solid-liquid separation device and is used for receiving liquid separated by the solid-liquid separation device. The dosing port of the mixing zone is for receiving a medicament. The mixing area is internally provided with a stirring device and used for stirring the materials in the mixing area. The reaction zone is optionally provided with a dosing port. The reaction zone is internally provided with a stirring device for stirring the materials in the reaction zone. The settling zone comprises a water outlet and a sludge outlet. Inside the settling zone, a mud scraper, such as a mud scraper, may be provided. The inside of the settling zone can be provided with an inclined plate and a sludge hopper. The effluent of the settling zone is connected with a subsequent multi-stage membrane device or a softening water producing pool through a pipeline. In some embodiments, the sludge outlet of the softening sedimentation tank is connected with the conditioning reaction tank through a sludge pump.

In some embodiments, the softening device comprises a softening settling tank and a softening product water tank. In the invention, the softening water producing tank is a container for receiving the water discharged from the softening sedimentation tank. The softening water producing pool is used for stabilizing the quality of liquid entering the subsequent multi-stage membrane device. The type of softened water producing basin suitable for use in the present invention is not particularly limited and may be, for example, a conditioning basin as is known in the art. The softening water producing tank is provided with a water inlet and a water outlet. The water inlet of the softening water producing tank is connected with the water outlet of the softening sedimentation tank and is used for receiving the water outlet of the softening sedimentation tank. The inlet of the softened water producing tank is usually arranged at the upper part of the softened water producing tank. The water outlet of the softening water producing tank is used for discharging materials in the adjusting reaction tank. The water outlet of the softening water producing tank is usually arranged at the bottom of the softening water producing tank. The water outlet of the softening water producing tank is connected with the multi-stage membrane device.

In the invention, the multi-stage membrane device is used for further removing suspended matters, residual heavy metal ions and sulfate ions in the liquid. In the text, a membrane device (i.e. a membrane separation device) has the meaning known in the art and refers to a device which performs a separation operation using a filtration membrane. A multistage membrane device refers to a membrane device comprising a plurality of separation membranes. A multi-stage membrane device suitable for use in the present invention may be a multi-stage membrane device as known in the art. The multistage membrane apparatus of the present invention preferably comprises a material separation membrane and an ion separation membrane. The material separation membrane has a pore diameter less than 0.05 μm, and can be used for solid-liquid separation, such as tubular ultrafiltration membrane or ceramic ultrafiltration membrane. The ion separation membrane mainly has the function of separating divalent ions and heavy metal ions in water, and a nanofiltration membrane, such as a modified nanofiltration membrane resistant to organic matters and salt tolerance, can be adopted. In the invention, the material separation membrane is used for removing residual fine suspended matters in the wastewater, and then the ion separation membrane is used for removing residual heavy metal ions and sulfate ions. The multi-stage membrane device comprises a water inlet, a concentrated water outlet and a filtrate outlet. The water inlet of the multi-stage membrane device is connected with the water outlet of the softening device. The concentrated water outlet of the multi-stage membrane device is connected with the water inlet of the softening device. The filtrate outlet of the multi-stage membrane device is connected with the evaporation salt separation crystallization device. The invention adopts a multi-stage membrane device to carry out grading treatment on the washing water, and finally realizes the complete removal of impurities in the washing water. An exemplary multi-stage membrane apparatus is shown in fig. 4, and includes an ultrafiltration membrane, a filter, a high-pressure pump, and a nanofiltration membrane.

According to the invention, the washing water is treated by adopting a multi-stage membrane, so that impurity ions in the water can be almost completely removed, calcium ions in the wastewater are reduced to below 50mg/L, heavy metal ions are reduced to below 0.1mg/L, sulfate ions are also reduced to below 100mg/L, monovalent salt in the wastewater is mainly used, the salt separation difficulty of subsequent crystallization is reduced, further, the crystalline sodium salt formed by the subsequent salt separation crystallization can be ensured to meet the index requirement of the superior product of the refined industrial salt in the national standard industrial salt (GB/T5462-2015), and the separated potassium salt can meet the standard of the superior product in the national standard potassium chloride (GB6549-2011) class II. The qualified sodium chloride can be used as an industrial raw material in the printing and dyeing industry or the chlor-alkali industry and the like. The qualified potassium chloride can be used as industrial raw materials of potassium hydroxide, potassium sulfate, potassium nitrate and the like.

In some embodiments, the water wash water treatment unit of the fly ash water wash treatment system of the present invention further comprises an evaporative salt separation crystallization device. The evaporation salt separation crystallizing device is used for producing sodium chloride crystal monosalt and potassium chloride crystal monosalt. The feed inlet of the evaporation salt separation crystallization device is connected with the filtrate outlet of the multi-stage membrane device. In the invention, the evaporative salt separation crystallization device can be an evaporative salt separation crystallization device which is commonly used for water treatment, for example, a multi-effect evaporative crystallization device, and preferably, the evaporative salt separation crystallization device is an evaporative salt separation crystallization device capable of producing sodium chloride crystal monosalt and potassium chloride crystal monosalt. In some embodiments, the evaporative salt crystallization device comprises a mechanical vapor recompression evaporative crystallization component (MVR mechanical compression evaporative crystallization component) and a cooling crystallization component, and the mechanical vapor recompression evaporative crystallization and cooling crystallization processes are respectively adopted to produce sodium chloride crystal salt and potassium chloride crystal salt. Herein, the mechanical evaporation recompression evaporation crystallization component refers to a structure or a device for realizing evaporation crystallization through mechanical evaporation recompression, and the cooling crystallization component refers to a structure or a device for realizing cooling crystallization. Those skilled in the art can determine the mechanical vapor recompression evaporative crystallization assembly and cooling crystallization assembly suitable for use in the present invention based on the crystallization principles of sodium chloride and potassium chloride. According to the difference of the crystallization phase diagrams of sodium chloride and potassium chloride, the saturated concentration of sodium chloride has little change with the temperature, and the saturated concentration of potassium chloride has obvious change with the temperature. Therefore, the invention realizes the high-temperature evaporative crystallization of sodium chloride by utilizing the MVR mechanical compression evaporative crystallization component, and realizes the cooling crystallization of potassium chloride by utilizing the cooling crystallization component. The invention adopts sodium chloride MVR evaporation crystallization and potassium chloride cooling crystallization, and can produce qualified sodium chloride and potassium chloride crystal salt.

In some embodiments, the evaporative salt separation crystallization apparatus of the present invention comprises an MVR mechanical compression evaporative crystallization apparatus and a cooling crystallization apparatus in series. The MVR mechanical compression evaporative crystallization device suitable for use in the present invention may be one known in the art that produces sodium chloride. The cooling crystallization device suitable for the present invention may be a cooling crystallization device known in the art that can produce potassium chloride. In the invention, the condensate generated by the evaporation salt separation crystallization device can be recycled to the reuse water pool for cyclic utilization.

In some embodiments, the evaporative salt separation crystallization device further comprises a water inlet regulating reservoir, wherein a water inlet of the water inlet regulating reservoir is connected with a filtrate outlet of the multi-stage membrane device, and a water outlet of the water inlet regulating reservoir is connected with a subsequent component (such as an MVR mechanical compression evaporation assembly) of the evaporative salt separation crystallization device.

In a preferred embodiment, the fly ash washing treatment system of the invention carries out multi-stage (for example, three-stage) water chlorine elution on fly ash, then the fly ash enters a final-stage dehydration device, the sludge discharged from the final-stage dehydration device can enter a cement kiln for cooperative treatment after being dried, and the filtrate of the first-stage dehydration device enters a regulation reaction tank; the filtrate in the regulating reaction tank enters a reaction sedimentation tank after being filtered again by a solid-liquid separation device, removing heavy metal and partial calcium ions in the filtrate by adding a water treatment agent, feeding the water produced in the reaction sedimentation tank into a gypsum reaction tank, adding sodium sulfate into the gypsum reaction tank to react to generate gypsum, then the fly ash is dehydrated by a gypsum separation device, the dehydrated filtrate enters a softening sedimentation tank, the supernatant after hard removal and softening enters a multi-stage membrane device, the water produced by the multi-stage membrane device enters an evaporation salt separation crystallization device, the condensate produced by the evaporation salt separation crystallization device enters a reuse water tank for recycling, the high-purity NaCl crystal monosalt produced by the evaporation salt separation crystallization device can be considered to be sold as raw salt or snow-melting agent products in the chlor-alkali industry, and the high-purity KCl crystal monosalt can be considered to be industrial raw materials such as potassium hydroxide, potassium sulfate, potassium nitrate and the like, so that the full resource utilization of the fly ash is realized. The water washing treatment system for the fly ash can realize the water washing dechlorination of the fly ash, meet the requirement of the cement kiln for cooperatively treating the fly ash and realize the zero discharge of the water washing water of the fly ash.

Compared with the existing fly ash washing treatment system, the fly ash washing treatment system has the following advantages:

1. according to the invention, through a three-stage backwashing process, the water-ash ratio of water washing can be controlled to be 2-3: 1.

2. the existing fly ash washing treatment system adopts a belt type vacuum filter press to dehydrate fly ash washing sludge, the dehydration effect is poor, the water content of the discharged sludge is high, and the energy consumption of the subsequent drying device is increased; the invention adopts the horizontal screw centrifuge to carry out solid-liquid separation, has good dehydration effect and simple operation.

3. The decalcification is carried out by adopting a sodium sulfate and sodium carbonate combined dosing mode on a fly ash washing project for the first time in the fly ash washing industry. The invention adopts the sodium sulfate and sodium carbonate combined dosing mode to carry out decalcification, thereby greatly reducing the operating cost. In the invention, more than 90% of calcium ions can be removed by sodium sulfate, and the rest less than 10% of calcium ions are removed by sodium carbonate. The cost of the medicament can be saved by about 80 percent.

4. The washing water of the existing fly ash washing treatment system adopts a simple chemical-adding, precipitating and filtering process, so that harmful substances in the waste water cannot be completely removed, and the subsequent salt separation process can only generate mixed salt with more impurities and needs to be treated according to dangerous waste; according to the invention, the multi-stage membrane device is adopted to treat the washing water, so that calcium ions in the washing water can be reduced to below 50mg/L, heavy metal ions can be reduced to below 0.1mg/L, sulfate ions can be reduced to below 50mg/L, impurities in the washing water can be almost completely removed, and the subsequent salt separation crystallization device can be ensured to reliably and stably separate qualified crystal salt.

The fly ash washing treatment system can realize the washing dechlorination of the fly ash so as to meet the requirement of the cooperative treatment of the fly ash in the cement kiln, solve the problem of insufficient capability of the cooperative treatment of the fly ash in the cement kiln due to high salt content of the fly ash, realize the zero discharge of the water washing of the fly ash, solve the problems of poor purity and low quality of evaporative crystalline salt and only can be used as hazardous waste for treatment, and realize the full resource utilization of the fly ash. The high-purity NaCl crystal monosalt generated by the fly ash washing treatment system can be considered to be sold as raw material salt or snow-melting agent products in the chlor-alkali industry, and the high-purity KCl crystal monosalt can be considered to be industrial raw materials such as potassium hydroxide, potassium sulfate, potassium nitrate and the like, so that the fly ash is completely recycled.

The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present disclosure, and that any devices and structures similar or equivalent to those described herein may be used in the present disclosure. The reagents used in the examples are, unless otherwise indicated, commercially available. The equipment and process conditions used in the examples were conventional unless otherwise specified.

Example of the apparatus

The present apparatus embodiment specifically describes a fly ash washing treatment system according to the present invention with reference to fig. 1. As shown in fig. 1, the fly ash washing membrane treatment system comprises a fly ash washing unit and a washing water treatment unit, wherein the fly ash washing unit comprises a first-level washing tank 1, a first-level centrifuge 2, a second-level washing tank 3, a second-level centrifuge 4, a third-level washing tank 5, a third-level centrifuge 6 and a reuse water tank 7, and the washing water treatment unit comprises an adjusting reaction tank 8, a filtrate centrifuge 9, a reaction sedimentation tank 10, a gypsum reaction tank 11, a gypsum centrifuge 12, a softening sedimentation tank 13, a softening water production tank 14, a multi-level membrane device 15 and an evaporation salt separation crystallization device 16.

Each washing tank (the first-stage washing tank 1, the second-stage washing tank 3 and the third-stage washing tank 5) comprises a feed inlet, a water inlet, a washing port and a vent port which are arranged on the upper part of the washing tank, a discharge port arranged at the bottom of the washing tank and a stirring machine arranged in the washing tank, and the structure is shown in figure 2. Each centrifuge (first-level centrifuge 2, second-level centrifuge 4, third-level centrifuge 6, filtrate centrifuge 9, gypsum centrifuge 12) is a horizontal decanter centrifuge, comprising a feed inlet arranged on the side of the centrifuge and a filtrate outlet and a discharge outlet arranged at the bottom of the centrifuge. The three-stage backwashing system is composed of a first-stage water washing tank 1, a first-stage centrifuge 2, a second-stage water washing tank 3, a second-stage centrifuge 4, a third-stage water washing tank 5 and a third-stage centrifuge 6, fly ash sequentially enters the first-stage water washing tank 1, the second-stage water washing tank 3 and the third-stage water washing tank 5, water for washing sequentially enters the third-stage water washing tank 5, the second-stage water washing tank 3 and the first-stage water washing tank 1, and initial water for washing comes from a reuse water pool 7. The feed inlet of the first-level washing tank 1 is a feed inlet of the fly ash to be washed. The water inlet of the first-stage washing tank 1 is connected with the filtrate outlet of the second-stage centrifuge 4 through a pipeline. The discharge hole of the first-level water washing tank 1 is connected with the feed inlet of the first-level centrifugal machine 2 through a pipeline. A lifting pump is arranged at the discharge port of the first-stage water washing tank 1. The filtrate outlet of the primary centrifuge 2 is connected with the regulating reaction tank 8. The feed inlet of the second-stage water washing tank 3 is connected with the discharge outlet of the first-stage centrifugal machine 2 through a pipeline. The water inlet of the second-stage water washing tank 3 is connected with the filtrate outlet of the third-stage centrifuge 6 through a pipeline. The discharge hole of the second-stage water washing tank 3 is connected with the feed inlet of the second-stage centrifuge 4 through a pipeline. A lifting pump is arranged at the discharge port of the second-stage washing tank 3. The discharge hole of the second-stage centrifuge 4 is connected with the feed inlet of the third-stage washing tank 5 through a pipeline. The water inlet of the third-stage washing tank 5 is the water inlet of the initial washing water. The water inlet of the third-stage washing tank 5 is connected with the reuse water pool 7 through a pipeline. A lifting pump is arranged at the water outlet of the reuse water tank 7. The discharge hole of the third-stage washing tank 5 is connected with the feed inlet of the third-stage centrifuge 6 through a pipeline. A lifting pump is arranged at the discharge port of the third-stage washing tank 5.

The primary centrifuge 2, the adjusting reaction tank 8, the filtrate centrifuge 9, the reaction sedimentation tank 10, the gypsum reaction tank 11, the gypsum centrifuge 12, the softening sedimentation tank 13, the softening water production tank 14, the multistage membrane device 15 and the evaporation salt separation crystallization device 16 are sequentially connected.

The upper part of the regulating reaction tank 8 is provided with a water inlet and a medicine feeding port, the bottom is provided with a discharge port, and a stirrer and a mud scraper are arranged in the regulating reaction tank. The water inlet of the regulating reaction tank 8 is connected with the filtrate outlet of the primary centrifuge 2 through a pipeline. The medicine adding port of the regulating reaction tank 8 is connected with the outlet of the medicine adding metering pump through a pipeline. The discharge port of the regulating reaction tank 8 is connected with a lift pump, and the outlet of the lift pump is connected with the feed port of the filtrate centrifuge 9 through a pipeline.

The filtrate centrifuge 9 is a horizontal screw centrifuge, the side surface of which is provided with a feed inlet, and the bottom of which is provided with a filtrate outlet and a discharge outlet. The feed inlet of the filtrate centrifuge 9 is connected with the discharge outlet of the regulating reaction tank 8 through a pipeline. The filtrate outlet of the filtrate centrifuge 9 is connected with the reaction sedimentation tank 10 through a pipeline. The discharge hole of the filtrate centrifuge 9 is connected with the feed inlet of the second-stage washing tank 3 through a pipeline.

The structure of the reaction sedimentation tank 10 is shown in fig. 3, and comprises a mixing zone, a reaction zone and a sedimentation zone which are connected in sequence. The side surface of the mixing area is provided with a feed inlet, and the upper part is provided with a dosing port. The upper part of the reaction zone is provided with a dosing port. The mixing zone and the reaction zone are internally provided with stirrers. The side surface of the settling zone is provided with a water outlet, and the bottom of the settling zone is provided with a sludge outlet. A mud scraper is arranged in the settling zone. The feed inlet of the reaction sedimentation tank 10 is connected with the filtrate outlet of the filtrate centrifuge 9 through a pipeline. The dosing port of the reaction sedimentation tank 10 is connected with the outlet of the dosing metering pump through a pipeline. The water outlet of the reaction sedimentation tank 10 is connected with the water inlet of the gypsum reaction tank 11 through a pipeline. The sludge outlet of the reaction sedimentation tank 10 can be connected with the adjusting reaction tank 8 through a sludge pump.

The upper side of the gypsum reaction tank 11 is provided with a water inlet, a drug adding port and a discharge port, and a stirrer is arranged in the gypsum reaction tank. The water inlet of the gypsum reaction tank 11 is connected with the water outlet of the reaction sedimentation tank 10 through a pipeline. The drug adding port of the gypsum reaction tank 11 is connected with the outlet of the drug adding device through a pipeline. The discharge port of the gypsum reaction tank 11 is connected with a lift pump, and the outlet of the lift pump is connected with the feed port of the gypsum centrifuge 12 through a pipeline.

The gypsum centrifuge 12 is a horizontal decanter centrifuge, with a feed inlet on the side and a filtrate outlet and a discharge outlet on the bottom. The feed inlet of the gypsum centrifuge 12 is connected with the discharge outlet of the gypsum reaction tank 11 through a pipeline. The filtrate outlet of the gypsum centrifuge 12 is connected with a softening and precipitating tank 13 through a pipeline. The discharge port of the gypsum centrifuge 12 is a finished product gypsum output port.

The upper part of the softening sedimentation tank 13 is provided with a feed inlet and a dosing port, the side surface is provided with a water outlet, the bottom is provided with a mud outlet, and a stirrer and a mud scraper are arranged in the softening sedimentation tank. The inlet of the softening and precipitating tank 13 is connected with the filtrate outlet of the gypsum centrifuge 12 through a pipeline. The dosing port of the softening sedimentation tank 13 is connected with the outlet of the dosing metering pump through a pipeline. The sludge outlet of the softening sedimentation tank 13 is connected with the adjusting reaction tank 8 through a sludge pump. The water outlet of the softening sedimentation tank 13 is connected with the water inlet of the softening water production tank 14 through a pipeline. The softening reservoir 14 has a water inlet and a water outlet.

The multi-stage membrane device 15 is provided with a water inlet, a concentrate outlet and a filtrate outlet. The structure of the multi-stage membrane device is shown in fig. 4, and comprises an ultrafiltration membrane, a filter, a high-pressure pump and a nanofiltration membrane. The water inlet of the multi-stage membrane device 15 is connected with the water outlet of the softening water producing pool 14 through a pipeline by a water inlet pump. The concentrated water outlet of the multi-stage membrane device 15 is connected with the feed inlet of the softening and precipitating tank 13. The filtrate outlet of the multi-stage membrane device 15 is connected with the water inlet regulating reservoir of the evaporation salt separation crystallizing device 16.

The evaporation salt separation crystallizing device 16 comprises a water inlet adjusting tank, a sodium chloride MVR mechanical compression evaporation crystallizing component and a potassium chloride cooling crystallizing component. The condensate outlet of the evaporation salt separation crystallizing device is connected with the reuse water tank 7.

Example of application of the device

The application example of the device utilizes the fly ash washing treatment system of the device example to carry out fly ash washing treatment and harmless treatment of washing water, and the specific working process is as follows:

(1) conveying the fly ash to a first-stage water washing tank 1 for water washing treatment, and then sequentially passing the fly ash through a first-stage centrifuge 2, a second-stage water washing tank 3, a second-stage centrifuge 4, a third-stage water washing tank 5 and a third-stage centrifuge 6; washing water comes from a reuse water tank 7, enters a three-stage washing tank 5 through lifting for washing, and is discharged into an adjusting reaction tank 8 from a first-stage centrifuge 2; the water inflow of each batch is 0.6m³The ash feeding amount is 0.2 ton, and the ash feeding water-ash ratio is about 3: 1;

(2) when the solid content of washing water entering the regulating reaction tank 8 is large, adding a flocculating agent PAM into the regulating reaction tank 8, wherein the adding amount of the PAM is adjustable according to the fly ash component and is generally 0.5-3 ppm, lifting the filtrate of the regulating reaction tank 8 to a filtrate centrifuge 9 by using a water pump, and enabling sludge generated by the filtrate centrifuge 9 to enter a secondary washing tank 3;

(3) filtrate generated by the filtrate centrifuge 9 sequentially passes through a reaction sedimentation tank 10, a gypsum reaction tank 11 and a gypsum centrifuge 12, hydrochloric acid is added into the reaction sedimentation tank 10 to adjust the pH value to 9-10 so as to remove part of amphoteric heavy metal ions, and sodium sulfate is added into the gypsum reaction tank to generate gypsum;

(4) filtrate generated by the gypsum centrifuge 12 sequentially passes through a softening sedimentation tank 13, a softening production water tank 14 and a multi-stage membrane device 15, and sodium carbonate and sodium hydroxide are added into the softening sedimentation tank 13 to remove residual calcium ions;

(5) the water produced by the multi-stage membrane device 15 enters an evaporation salt separation crystallization device 16 to produce qualified sodium chloride crystal salt, potassium chloride crystal salt and condensate;

(6) the condensate generated by the evaporation salt separation crystallizing device 16 enters a reuse water tank 7 for reuse, the high-purity NaCl crystalline monosalt generated by the evaporation salt separation crystallizing device 16 can be sold as raw material salt or snow-melting agent products in the chlor-alkali industry, and the high-purity KCl crystalline monosalt can be used as industrial raw materials such as potassium hydroxide, potassium sulfate, potassium nitrate and the like, so that the full resource utilization of the fly ash is realized.

The experimental results of the application example of the device for carrying out the fly ash washing treatment and the harmless treatment of the washing water are as follows:

1. verifying the three-stage washing process flow, the water-cement ratio design value and the washing dechlorination effect

The water inflow of each batch is 0.6m³The ash inlet amount is 0.2 ton, and the ash inlet water-ash ratio is about 3: 1, the result shows that the water content of the plaster after three-stage water washing is less than 38%, the chlorine content is less than 1%, and the removal rate of the fly ash chloride ions is more than 90%. The water content and chlorine content of the fly ash (raw ash) to be washed with water and the stucco after the third-stage washing are shown in table 1. The existing washing device is adopted for washing the fly ash, water with the mass 4-6 times that of the fly ash is needed, and the water consumption is large. In the prior art, a belt type vacuum filter press is adopted to dehydrate the fly ash water washing sludge, and the water content of the dehydrated plaster is generally 40-45%.

Table 1: water content and chlorine content of raw ash and plaster

Batch number	Chlorine content of raw ash	Chlorine content of plaster	Removal rate of chloride ion	Water content of raw ash	Water content of plaster
						1	14.7785％	0.7134％	92.56％	4.30％	37.87％
2	25.1175％	0.8576％	94.99％	8.74％	37.79％
						3	26.1284％	0.7989％	95.47％	7.11％	37.27％
4	19.3221％	0.5086％	96.32％	11.20％	36.53％
						5	19.8129％	0.5145％	96.50％	15.74％	37.46％
6	14.7599％			1.87％	33.87％
						7	14.0037％			7.45％	32.82％
8	24.5748％	0.7161％	95.73％	8.1％	37.25％
						9	23.0797％	0.6807％	95.55％	6.11％	37.84％
10	13.6385％	0.5756％	93.72％	6.92％	37.47％
						11	13.2753％	0.6109％	92.86％	3.03％	37.48％

2. Verifying the centrifugal separation effect of a filtrate centrifuge

The solid content (SS) of the filtrate discharged from the primary centrifuge 2 and the filtrate separated by the filtrate centrifuge 9 was measured, and the results are shown in table 2. As can be seen from Table 2, the solid content of the filtrate discharged from the primary centrifuge 2 was very unstable, ranging from 1335.6mg/L to 76226.8mg/L, and the solid content of the filtrate centrifuged by the filtrate centrifuge 9 was significantly reduced.

The above results indicate that the filtrate (washing water) produced by the fly ash washing unit contains solid particle impurities with different contents, and if the filtrate directly enters wastewater treatment facilities such as a reaction tank, the filtrate is not beneficial to the normal operation of the wastewater treatment facilities. According to the invention, the solid-liquid separation device (such as the filtrate centrifuge 9) is arranged in front of the reaction sedimentation tank, so that the solid content of the filtrate is effectively controlled, and the working efficiency and stability of the subsequent washing water treatment device are ensured. In addition, the regulating reaction tank is arranged in front of the solid-liquid separation device, and different batches of washing water with different solid contents are firstly converged into the regulating reaction tank, so that the regulating reaction tank plays a role in stabilizing water quality. And the regulating reaction tank is also provided with a chemical adding port, when the fly ash with small particle size remains in the washing water, PAM can be added through the chemical adding port of the regulating reaction tank to be converted into particles with larger particle size, and then the particles are separated and removed through a solid-liquid separation device.

Table 2: the solid content of the filtrate discharged from the first-stage centrifuge and the filtrate separated by the filtrate centrifuge

3. Analyzing the raw ash component and the plaster component to know the change rule of the raw ash component and the plaster component

The components of the raw ash and the stucco discharged from the three-stage centrifuge were measured, and the results are shown in tables 3 and 4.

As can be seen from tables 3 and 4, the raw ashes of different batches vary greatly in terms of their components, with chlorine content ranging from 14 to 26%, water content ranging from 2 to 15%, and contents of sodium, potassium, calcium and various heavy metals varying from one another. For the raw ashes with large component differences, after the fly ash water-washing treatment system is adopted for treatment, the chlorine content of the plaster is reduced to below 1 percent, and the water content is reduced to below 38 percent, which shows that the fly ash water-washing treatment system has wide applicability and can treat the raw ashes with different components.

Table 3: composition analysis (Total analysis) of raw Ash and mortar

Table 4: composition analysis of raw Ash and stucco (routine analysis and heavy metals)

4. Analyzing the water quality after the treatment of the multi-stage membrane device and determining the effect of the membrane device

The results of the examination of the quality of the washing water (raw water) in the control reaction tank 8 and the water produced by the multistage membrane device 15 are shown in table 5.

As can be seen from the table 5, after the advanced treatment of the multi-stage membrane, the calcium ions in the wastewater are reduced to be below 50mg/L, the heavy metal ions are reduced to be below 0.1mg/L, and the sulfate ions are also reduced to be below 100mg/L, so that the multi-stage membrane device ensures that the wastewater is mainly made of monovalent salt, the subsequent salt separation crystallization difficulty is reduced, and the purity of the salt separation crystallization product can reach the standard.

It can be seen that through the multi-stage membrane treatment, the dissolved substances contained in the produced water of the multi-stage membrane device are mainly sodium ions, potassium ions and chloride ions, and impurity ions are almost completely removed, so that high-purity sodium chloride crystals and potassium chloride crystals can be obtained through subsequent salt separation crystallization, the crystallized sodium salt formed through the subsequent salt separation crystallization can meet the index requirements of national industrial salt GB/T5462-2015 refined industrial salt superior products (Table 6), and the separated potassium salt can meet the national standard potassium chloride (GB6549-2011) class II superior product standard (Table 7).

Table 5: quality of raw water and water produced by multi-stage membrane device

Table 6: national standard 'Industrial salt' GB/T5462-2015 refined industrial salt superior index

Table 7: national standard potassium chloride (GB6549-2011) II-class superior product index

Claims

1. A fly ash washing treatment system is characterized by comprising a fly ash washing unit and a washing water treatment unit, wherein the fly ash washing unit is used for washing fly ash, the washing water treatment unit is used for performing innocent treatment on washing water generated by washing the fly ash, the fly ash washing unit comprises a one-to-one correspondence multi-stage washing device and a multi-stage dehydration device, the washing device is used for washing the fly ash, the dehydration device is used for separating a mixture of the fly ash and the washing water into plaster and the washing water, the washing device comprises a feed inlet, a discharge outlet and a filtrate outlet, the discharge outlet of each stage of washing device is respectively connected with the feed inlet of the same stage of dehydration device, and the washing devices and the dehydration devices at different stages are connected with each other in a backwashing manner, preferably, the fly ash washing unit comprises at least a tertiary washing device and a dewatering device.

2. A fly ash water washing treatment system as claimed in claim 1, wherein the feed inlet of the first stage water washing device is for receiving fly ash to be washed, the feed inlets of the other stages of water washing devices are respectively connected to the discharge outlet of the previous stage water removal device for receiving the stucco discharged from the previous stage water removal device, the water inlet of the last stage water washing device is for receiving the initial water washing water, the water inlets of the other stages of water washing devices are respectively connected to the filtrate outlet of the next stage water removal device for receiving the water washing water discharged from the next stage water removal device, the filtrate outlet of the first stage water removal device is connected to the water washing water treatment unit for discharging the final water washing water, and the discharge outlet of the last stage water removal device is for discharging the final stucco.

3. A fly ash water-washing treatment system as claimed in claim 1, wherein the water-washing device is a water-washing tank and/or the dewatering device is a decanter centrifuge.

4. The fly ash washing treatment system of claim 1, wherein the washing water treatment unit comprises a regulation reaction tank, a solid-liquid separation device, a reaction sedimentation tank, a gypsum reaction tank, a gypsum separation device, a softening device and a multi-stage membrane device which are connected in sequence, the regulation reaction tank is used for stabilizing the quality of the washing water produced by the fly ash washing unit, the solid-liquid separation device is used for separating solid particles and liquid in the material discharged by the regulation reaction tank, the reaction sedimentation tank is used for removing heavy metals and partial calcium ions in the liquid produced by the solid-liquid separation device, the gypsum reaction tank is used for further removing calcium ions in the liquid discharged by the reaction sedimentation tank and generating gypsum, the gypsum separation device is used for separating solid particles and liquid in the material discharged by the gypsum reaction tank, and the softening device is used for softening the liquid produced by the gypsum separation device, the multistage membrane device is used for further removing suspended matters, residual heavy metal ions and sulfate ions in the liquid discharged by the softening device.

5. The fly ash water-wash treatment system of claim 4, wherein the fly ash water-wash treatment system has one or more of the following features:

the solid-liquid separation device is a horizontal screw centrifuge;

the reaction sedimentation tank comprises a feed inlet, a dosing port, a water outlet, a mud outlet and a stirring device, preferably, the reaction sedimentation tank comprises a mixing zone, a reaction zone and a sedimentation zone, the mixing zone comprises the feed inlet, the stirring device and an optional dosing port, the reaction zone comprises the stirring device and an optional dosing port, and the sedimentation zone comprises the water outlet and the mud outlet;

the gypsum separation device is a horizontal screw centrifuge;

the softening device comprises a softening sedimentation tank and an optional softening water production tank, the softening sedimentation tank comprises a feed inlet, a dosing port, a water outlet, a sludge outlet and a stirring device, the softening water production tank comprises a water inlet and a water outlet, preferably, the softening sedimentation tank comprises a mixing zone, a reaction zone and a sedimentation zone, the mixing zone comprises the feed inlet, the stirring device and the optional dosing port, the reaction zone comprises the stirring device and the optional dosing port, and the sedimentation zone comprises the water outlet and the sludge outlet;

the multistage membrane device comprises a material separation membrane and an ion separation membrane.

6. A fly ash water-washing treatment system according to claim 4, wherein the water-washing water treatment unit further comprises an evaporative salt-splitting crystallization device for producing sodium chloride crystalline mono-salt and potassium chloride crystalline mono-salt, the evaporative salt-splitting crystallization device being connected to the multi-stage membrane device.

7. The fly ash water wash treatment system of claim 6, wherein the evaporative salt crystallization device comprises a mechanical vapor recompression evaporative crystallization assembly, a cooling crystallization assembly, and optionally a surge tank.

8. A method for washing treatment of fly ash, which is characterized by comprising the following steps:

9. The method of claim 8, further comprising the steps of:

10. The method of claim 8, further comprising the steps of: