Pilot-scale experiment system and method for high-valued utilization of fly ash washing byproduct salt

Abstract

The invention relates to the technical field of fly ash treatment, in particular to a fly ash washing byproduct salt high-valued utilization pilot-scale experiment system which comprises a pretreatment system, an ammonium bicarbonate preparation device, an ion exchange device, an RO device, an electrodialysis chemical reactor system and a cooling water system. The pretreatment system is used for removing substances causing damage or performance reduction to membranes in the electrodialysis chemical reactor and the ion exchange device; the ion exchange device is used for carrying out ion exchange, softening the fly ash washing liquid and reducing the content of multivalent ions; the ammonium bicarbonate preparation device is used for preparing an ammonium bicarbonate solution and supplying the ammonium bicarbonate solution to the electrodialysis chemical reactor, and fly ash washing liquid in the raw water tank is softened and then input into an electrodialysis chemical reactor system; the RO system is used for treating fresh water output by the electrodialysis chemical reactor system. According to the invention, configuration of electrodialysis chemical reactor system complete equipment is realized, and hardness removal and high valence ion separation treatment of fly ash washing liquid can be realized.

Description

Technical Field

[0001] The invention belongs to the technical field of fly ash treatment, and particularly relates to a pilot experimental system and method for high-value utilization of fly ash washing by-product salt. Background Art

[0002] Fly ash washing byproduct salts are primarily sodium chloride and potassium chloride. Sodium chloride has low added value, a low external price, and a bleak sales outlook. Sodium carbonate, the primary decalcifying agent for fly ash washing solutions, accounts for a significant portion of operating costs. To reduce operating costs and improve project economics, it is necessary to research the internal recycling of fly ash washing byproduct chloride salts to produce carbonate.

[0003] Sodium carbonate, also known as soda ash, is my country's most important and fundamental chemical raw material, one of the "two alkalis" in the "three acids and two alkalis" formula. It is widely used in a variety of sectors, including building materials, petrochemicals, metallurgy, food, textiles, national defense, and medicine, and holds a crucial position in the national economy.

[0004] The traditional chemical method of producing soda ash is not suitable for the high-value utilization of by-product salts in fly ash washing projects. Electrodialysis technology can realize the conversion of chloride salts to carbonates, and can achieve miniaturized and modular production. Therefore, electrodialysis technology is an effective technical research and development direction for realizing the high-value utilization of by-product salts in fly ash washing projects. However, the fly ash washing liquid obtained from existing fly ash washing projects has the defects of high hardness and high content of multivalent ions, and the electrodialysis treatment effect is poor. The existing technology also lacks a high-value utilization system that can be applied in practice. Therefore, the design of a pilot experimental system that can confirm the technical and economic feasibility of such a new high-value utilization system and be used to evaluate and optimize the process and operation mode of such a scheme has become a technical problem that needs to be solved in the relevant technology research and development. Summary of the Invention

[0005] The purpose of the present invention is to provide a pilot test system for high-value utilization of fly ash water washing by-product salt, which is used to solve the technical problem of how to optimize the process through the pilot test system when the existing technology has defects such as high hardness and high content of multivalent ions in the fly ash water washing liquid.

[0006] The pilot experimental system for high-value utilization of fly ash washing byproduct salts comprises a pretreatment system, an ammonium bicarbonate production unit, an ion exchange unit, an RO unit, an electrodialysis chemical reactor system, and a cooling water system. The pretreatment system removes substances that damage or degrade the membranes in the electrodialysis chemical reactor and the ion exchange unit; the ion exchange unit performs ion exchange to soften the fly ash washing liquid and reduce its polyvalent ion content; the ammonium bicarbonate production unit prepares an ammonium bicarbonate solution for feeding the electrodialysis chemical reactor. The fly ash washing liquid in the raw water tank is softened and then fed into the electrodialysis chemical reactor system; the RO system processes the fresh water output by the electrodialysis chemical reactor system. The concentrated water separated by the RO system is reused with the raw water not fed into the ion exchange unit, and the produced water separated by the RO system is reused as makeup water for the front-end fly ash washing stage.

[0007] Preferably, an ion exchange water production tank and a product water delivery pump are provided at the ion exchange device. The ion exchange water production tank is used to store the ion exchange water output by the ion exchange device, and the product water delivery pump delivers the ion exchange water to the chloride circulation unit of the electrodialysis chemical reactor system.

[0008] Preferably, the RO system includes: an RO high-pressure pump, an RO membrane module, an RO slide, and auxiliary equipment including supporting instruments and valves. The RO fresh water obtained after the fresh water is treated by the RO system is delivered to the outside, and the separated high-concentration solution is recovered and mixed with the raw water before being delivered to the ion exchange device.

[0009] Preferably, the electrodialysis chemical reactor system includes a chloride circulation unit, an ammonium bicarbonate circulation unit, a carbonate circulation unit, an ammonium chloride circulation unit, a chloride fresh water overflow tank, a carbonate overflow tank and an electrodialysis chemical reactor unit; the chloride circulation unit and the ammonium bicarbonate circulation unit each include a circulation tank, a circulation pump and auxiliary equipment including supporting instruments and valves; the ammonium chloride circulation unit and the carbonate circulation unit each include a circulation tank, a product water tank, a circulation pump, an external pump and auxiliary equipment including supporting instruments and valves; fresh water overflows into the chloride fresh water overflow tank and is delivered to the RO system through the external pump.

[0010] Preferably, the pretreatment system includes a raw water tank serving as a fly ash water washing liquid buffer tank, a water feed pump for conveying the chloride solution, and a filter is provided at the outlet of the water feed pump.

[0011] Preferably, the ammonium bicarbonate preparation system includes an ammonium bicarbonate dissolution preparation box and a delivery pump. The ammonium bicarbonate dissolution preparation box is used to dissolve ammonium bicarbonate, and the delivery pump is used to deliver the ammonium bicarbonate solution to the electrodialysis chemical reactor system.

[0012] Preferably, the pilot experimental system for high-value utilization of fly ash washing by-product salt also includes a heat exchanger system, including plate heat exchangers arranged on the chloride circulation side and the ammonium bicarbonate circulation side, which cool the material by circulating cooling water.

[0013] The present invention also provides a pilot experimental method for high-value utilization of fly ash water washing by-product salt, using the above-mentioned pilot experimental system for high-value utilization of fly ash water washing by-product salt, including: sending the fly ash water washing liquid treated by the original water washing liquid purification system of the fly ash water washing into a raw water tank, pressurizing it into an ion exchange device by a raw water pump to remove hardness and multivalent ions in the water, sending the softened fly ash water washing liquid into the ion exchange water production tank as ion exchange water production, and the ion exchange water production pump transports the ion exchange water production to the chloride circulation tank of the electrodialysis chemical reactor system; ammonium bicarbonate is dissolved to form a solution, and is sent into the electrodialysis chemical reactor together with the ion exchange water production to react to generate ammonium chloride solution and carbonate solution.

[0014] Preferably, the ion exchange device utilizes the adsorption and exchange function of the cationic resin to exchange and remove the calcium and magnesium ions in the fly ash water wash liquid; when the ion exchange resin fails, the ion exchange resin is regenerated using a regeneration agent, and the regeneration agent is hydrochloric acid and sodium hydroxide solution. It is first treated with hydrochloric acid and then with sodium hydroxide, and acid-base regeneration is automatically performed according to the system's operating time or the amount of water passing through.

[0015] The present invention has the following advantages:

[0016] 1. The present invention realizes the configuration of an electrodialysis chemical reactor system complete set in the fly ash washing project, and can remove the hardness of the fly ash washing liquid and separate high-valent ions. On the other hand, it can also perform reverse osmosis treatment on the overflowed fresh water and recover the concentrated solution, thereby improving the utilization efficiency of raw materials. The fresh water can be reused in the fly ash washing section as make-up water, saving energy and reducing consumption.

[0017] 2. The present invention has complete configuration and high degree of automation. The device can be used to explore the operating parameters and to judge whether the produced water meets the standards and the stability of the produced water.

[0018] 3. The present invention can be directly grafted onto the existing fly ash washing project production line, and water is taken from the MVR water inlet tank of the fly ash washing production line. The carbonate solution produced in the water can be directly used for decalcification of the fly ash washing liquid. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The present invention is a flow chart of a pilot test system for high-value utilization of by-product salt from fly ash washing. DETAILED DESCRIPTION

[0020] The specific implementation methods of the present invention will be further explained in detail below through the description of embodiments with reference to the accompanying drawings, so as to help those skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention.

[0021] like Figure 1 As shown, the present invention provides a pilot experimental system for high-value utilization of fly ash water washing by-product salt, including a pretreatment system, an ammonium bicarbonate preparation device, an ion exchange device, an RO system, an electrodialysis chemical reactor system, and a cooling water system. The pretreatment system is used to remove substances that damage or degrade the membranes in the electrodialysis chemical reactor and the ion exchange device. For example, surfactants, strong oxidizing substances, ionized high-molecular organic matter, etc., can cause poor performance of the ion exchange membrane and require pretreatment removal; oxidizing substances affect the structure of the membrane and need to be treated in the pretreatment process; if crystallization or scaling occurs in the electrodialysis chemical reactor, it will cause damage to the ion exchange membrane. This is mainly determined by the hardness and multivalent ion content of the fly ash water washing liquid. The ion exchange device is used to perform ion exchange, softening the fly ash water washing liquid and reducing the multivalent ion content. The ammonium bicarbonate preparation device is used to prepare ammonium bicarbonate solution to feed the electrodialysis chemical reactor. The fly ash water washing liquid in the raw water tank is input into the electrodialysis chemical reactor system after softening treatment; the ion exchange device is used to remove substances that damage the electrodialysis chemical reactor and the membrane in the ion exchange device or reduce its performance.

[0022] (1) The pretreatment system includes a raw water tank that serves as a buffer tank for the fly ash water wash, a feed water pump for transporting the chloride solution, and a filter at the outlet of the feed water pump. The filter is sized at 5 microns and is used to filter impurities and particles in the water.

[0023] (2) The ion exchange device is used to further remove residual hardness from the water to ensure the normal operation of the subsequent concentration system and obtain better quality crystallized salt. Two ion exchange devices are used, one for use and one for backup. An ion exchange water tank and a product water delivery pump are set up. The ion exchange water tank is used to store the water output by the ion exchange device, and the product water delivery pump delivers the ion exchange water to the chloride circulation unit of the electrodialysis chemical reactor system.

[0024] The softening principle is to utilize the adsorption and exchange function of cationic resin to remove calcium and magnesium ions in the fly ash water wash. The softening reaction is as follows:

[0025] 2RNa+Ca2+→R2Ca+2Na+

[0026] 2RNa+Mg2+→R2Mg+2Na+

[0027] When ion exchange resin fails, it must be regenerated to restore its exchange capacity. The regeneration agent is hydrochloric acid and sodium hydroxide solution. The regeneration process reaction is as follows:

[0028] R2Ca+2HCl=2RH+CaCl2

[0029] R2Mg+2HCl=2RH+MgCl2

[0030] 2RH+2NaOH=2RNa+H2O

[0031] After the above treatment, the resin can be transformed. The ion exchange is fully automatic and automatically regenerates the acid and alkali according to the system's operating time or the amount of water passing through.

[0032] (3) The ammonium bicarbonate preparation system includes two ammonium bicarbonate dissolution preparation boxes for dissolving ammonium bicarbonate; and one delivery pump for delivering the ammonium bicarbonate solution to the electrodialysis chemical reactor system.

[0033] (4) The electrodialysis chemical reactor system includes an electrodialysis chemical reactor, a chloride solution circulation unit, an ammonium bicarbonate solution circulation unit, a carbonate concentrated water circulation unit, an ammonium chloride concentrated water circulation unit, a cooling and heat exchange unit, etc.

[0034] An electrodialysis chemical reactor consists of alternating cation and anion membranes, forming small water chambers. When raw water enters these chambers, the DC electric field causes ions in the solution to migrate in a targeted manner. The cation membranes allow only cations to pass through, retaining anions; the anion membranes allow only anions to pass through, retaining cations. As a result, a portion of these chambers becomes a freshwater chamber with a low ion content, and the effluent is called freshwater. The adjacent chambers become concentrated water chambers, which are rich in ions, and the effluent is called concentrated water. This allows for material separation and reuse.

[0035] During initial startup, the electrodialysis chemical reactor uses a water purifier to produce pure water, which is slowly filled into the electrodialysis chemical reactor system. Subsequently, chloride solution, ammonium bicarbonate solution, ammonium chloride solution, and carbonate solution are fed into the electrodialysis chemical reactor via their respective circulation pumps, replacing the pure water within the membrane stack. Under the influence of an external DC electric field, chloride and ammonium ions in the water enter concentrating chamber A, forming an ammonium chloride concentrate. Sodium / potassium ions and bicarbonate ions in the water enter concentrating chamber B, where they are then added with alkali to form a carbonate concentrate. These concentrates, circulated by their respective concentration circulation pumps, enter their respective concentrate tanks and are then pumped to downstream systems.

[0036] (5) The chloride circulation unit includes a circulation tank, a circulation pump, and auxiliary equipment including supporting instrument valves. The softened fly ash water wash liquid is sent to the circulation tank and then to the electrodialysis device through the circulation pump. Under the action of the external DC electric field, the sodium / potassium ions and chloride ions in the water enter the corresponding concentrate chambers, forming carbonate solution and ammonium chloride solution respectively. If fresh water overflows into the chloride fresh water overflow tank, it is pumped to the RO system (reverse osmosis membrane system).

[0037] (6) The ammonium bicarbonate circulation unit includes a circulation tank, a circulation pump, and supporting instruments and valves. The ammonium bicarbonate dilution water tank solution is sent to the ammonium bicarbonate circulation tank and then to the electrodialysis device through the circulation pump. Under the action of the external DC electric field, the bicarbonate ions and ammonia ions in the water enter the corresponding concentrate chambers, forming carbonate solution and ammonium chloride solution respectively. Fresh water overflows into the ammonium bicarbonate fresh water overflow tank and is pumped to the ammonium bicarbonate dispensing box for dispensing.

[0038] (7) Ammonium chloride circulation unit, which includes a circulation tank, a product water tank, a circulation pump, an external pump and auxiliary equipment including supporting instruments and valves.

[0039] (8) A carbonate circulation unit, which includes a circulation tank, a product water tank, a circulation pump, an external pump, and auxiliary equipment including supporting instruments and valves. The carbonate that migrates to the concentrate side is pumped into the carbonate concentrate tank by the concentrate circulation pump, where sodium hydroxide is added to adjust the pH to form a carbonate solution. The carbonate overflows from the carbonate circulation tank and is then pumped to the carbonate overflow tank via the external pump to the RO system.

[0040] (9) Heat exchanger system: During the operation of the electrodialysis reactor, the material temperature will rise under the action of the DC electric field. To ensure that the electrodialysis chemical reaction operates within the allowable water temperature range, plate heat exchangers are installed on the chloride circulation side and the ammonium bicarbonate circulation side respectively. The material is cooled by circulating cooling water, so that the electrodialysis operating temperature is maintained at 30-35°C.

[0041] (10) RO system: One reverse osmosis unit with a processing capacity of 300 L / h. The RO system includes an RO high-pressure pump, an RO membrane module, an RO skid, and auxiliary equipment including supporting instruments and valves. The RO fresh water obtained after treatment by the RO system is delivered to the outside, and the separated high-concentration solution is recovered and mixed with the raw water before being transported to the ion exchange unit.

[0042] (11) Pure water system: When the system is first put into operation or in normal operation, the system needs pure water. It is equipped with a pure water machine with a pure water output of 30L / h. The pure water machine has its own water tank and can produce water in real time. It only needs to be connected to the tap water.

[0043] (12) Cooling water system. When the system is running, the membrane stack, water pump and other equipment will generate heat, causing the temperature in the system to rise continuously. To ensure that the system operates efficiently within the specified temperature range, a chiller with a cooling capacity greater than 3.5 kW is equipped. The chiller has its own water tank. The water tank should be filled up when it is first put into use. The water tank can be replenished as needed later according to the water level.

[0044] The present invention also provides a pilot test method for high-value utilization of fly ash washing by-product salt. The pilot test system is applied, and the main process flow is: chloride solution - filter - raw water tank - electrodialysis chemical reactor - reverse osmosis.

[0045] The fly ash wash liquid (chloride solution) treated by the original wash liquid purification system is fed into the raw water tank. The raw water pump pressurizes and feeds it into the ion exchange device to remove hardness and multivalent ions. The softened fly ash wash liquid is then fed into the ion exchange product water tank as ion exchange product water. The ion exchange product water pump then transports the ion exchange product water to the chloride circulation tank of the electrodialysis chemical reactor system. The ammonium bicarbonate dissolves to form a solution, which is then fed into the electrodialysis chemical reactor to react and generate ammonium chloride solution and carbonate solution.

[0046] After optimization of the pilot test system, the control indicators of the inlet water quality of the electrodialysis chemical reactor system can be determined.

[0047] The present invention is described above by way of example in conjunction with the accompanying drawings. It is obvious that the specific implementation of the present invention is not limited to the above-mentioned method. As long as various non-substantial improvements are made using the inventive concept and technical solution of the present invention, or the inventive concept and technical solution are directly applied to other occasions without improvement, they are all within the scope of protection of the present invention.

Claims

1. A pilot test system for high-value utilization of fly ash washing by-product salt, characterized by: The invention comprises a pretreatment system, an ammonium bicarbonate preparation device, an ion exchange device, an RO device, an electrodialysis chemical reactor system and a cooling water system. The pretreatment system is used to remove substances that damage the membranes of the electrodialysis chemical reactor and the ion exchange device or degrade their performance. The ion exchange device is used to perform ion exchange, soften the fly ash water washing liquid and reduce the content of multivalent ions. The ammonium bicarbonate preparation device is used to prepare ammonium bicarbonate solution to feed the electrodialysis chemical reactor. The fly ash water washing liquid in the raw water tank is input into the electrodialysis chemical reactor system after softening treatment. The RO system is used to process the fresh water output by the electrodialysis chemical reactor system. The concentrated water separated by the RO system is reused with the raw water that has not been input into the ion exchange device. The produced water separated by the RO system is reused as the replenishing water for the front-end fly ash water washing section.

2. The pilot test system for high-value utilization of fly ash washing by-product salt according to claim 1 is characterized by: An ion exchange water production tank and a product water delivery pump are provided at the ion exchange device. The ion exchange water production tank is used to store the ion exchange water output by the ion exchange device. The product water delivery pump delivers the ion exchange water to the chloride circulation unit of the electrodialysis chemical reactor system.

3. The pilot test system for high-value utilization of fly ash washing by-product salt according to claim 2 is characterized by: The RO system includes: RO high-pressure pump, RO membrane module, RO slide, and auxiliary equipment including supporting instruments and valves. The RO fresh water obtained after the fresh water is treated by the RO system is delivered to the outside, and the separated high-concentration solution is recovered and mixed with the raw water before being delivered to the ion exchange device.

4. The pilot test system for high-value utilization of fly ash washing by-product salt according to claim 1 is characterized by: The electrodialysis chemical reactor system includes a chloride circulation unit, an ammonium bicarbonate circulation unit, a carbonate circulation unit, an ammonium chloride circulation unit, a chloride fresh water overflow tank, a carbonate overflow tank and an electrodialysis chemical reactor unit; the chloride circulation unit and the ammonium bicarbonate circulation unit each include a circulation tank, a circulation pump and auxiliary equipment including supporting instruments and valves; the ammonium chloride circulation unit and the carbonate circulation unit each include a circulation tank, a product water tank, a circulation pump, an external pump and auxiliary equipment including supporting instruments and valves; fresh water overflows into the chloride fresh water overflow tank and is sent to the RO system through the external pump.

5. The pilot test system for high-value utilization of fly ash washing by-product salt according to claim 1 is characterized by: The pretreatment system includes a raw water tank serving as a fly ash washing liquid buffer tank, a water feed pump for conveying chloride solution, and a filter is provided at the outlet of the water feed pump.

6. The pilot test system for high-value utilization of fly ash washing by-product salt according to claim 1 is characterized by: The ammonium bicarbonate preparation system includes an ammonium bicarbonate dissolution preparation box and a delivery pump. The ammonium bicarbonate dissolution preparation box is used to dissolve ammonium bicarbonate, and the delivery pump is used to deliver the ammonium bicarbonate solution to the electrodialysis chemical reactor system.

7. The pilot test system for high-value utilization of fly ash washing by-product salt according to claim 1 is characterized by: It also includes a heat exchanger system, including plate heat exchangers arranged on the chloride circulation side and the ammonium bicarbonate circulation side, which cool the material through circulating cooling water.

8. A pilot test method for high-value utilization of fly ash washing by-product salt, characterized by: A pilot experimental system for high-value utilization of fly ash washing by-product salts as described in any one of claims 1 to 7 is used, comprising: sending the fly ash washing liquid treated by the original washing liquid purification system of the fly ash washing into a raw water tank, pressurizing it with a raw water pump and sending it to an ion exchange device to remove hardness and multivalent ions in the water, sending the softened fly ash washing liquid into an ion exchange water tank as ion exchange product water, and the ion exchange water pump transports the ion exchange product water to the chloride circulation tank of the electrodialysis chemical reactor system; ammonium bicarbonate is dissolved to form a solution, and is sent into the electrodialysis chemical reactor together with the ion exchange product water to react to generate ammonium chloride solution and carbonate solution.

9. The pilot test method for high-value utilization of fly ash washing by-product salt according to claim 8, characterized in that: The ion exchange device uses the adsorption and exchange function of the cationic resin to exchange and remove the calcium and magnesium ions in the fly ash water wash liquid; when the ion exchange resin fails, it is regenerated using a regeneration agent. The regeneration agent is hydrochloric acid and sodium hydroxide solution. It is first treated with hydrochloric acid and then with sodium hydroxide. The acid-base regeneration is automatically performed according to the system's operating time or the amount of water passing through.

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