Salt-containing wastewater treatment system based on cold and hot ends of heat pump

Abstract

The invention belongs to the field of wastewater treatment, and particularly relates to a salt-containing wastewater treatment system based on hot and cold ends of a heat pump. The system is provided with the stock solution circulation system and the refrigerant circulation system, the stock solution circulation system can form ice crystals and a concentrated solution through the ice crystal production device, then the ice crystals and the concentrated solution are separated through the solid-liquid separation device, after separation, the stock solution circulation system is divided into the ice crystal circulation system and the concentrated solution circulation system, and the ice crystals are melted into water through the ice crystal circulation system; the concentrated solution circulating system is used for evaporative crystallization and wastewater treatment, and closed-loop flow of heat of a refrigerant is realized. The environment heat energy can be fully utilized, the energy consumption is obviously reduced, and the wastewater treatment efficiency is improved.

Description

Technical Field

[0001] The present application belongs to the technical field of wastewater treatment, and specifically relates to a saline wastewater treatment system based on the hot and cold ends of a heat pump. Background Art

[0002] At present, the full-scale treatment of saline wastewater mainly adopts the "MVR evaporation + evaporator" drying combination process, which has high chemical consumption, easy scaling and high operation and maintenance costs.

[0003] The Chinese utility model patent with application number 2023201755130 discloses a wastewater treatment system that combines freeze concentration with negative pressure vacuum evaporation and crystallization. The system uses the cold source of a heat pump to perform pre-concentration during the ice-making process, and uses the heat source to evaporate and crystallize the concentrated mother liquor. However, the ice crystals produced by the ice-making system and the unfrozen stock liquid flow back to the original storage tank through the ice-making circulation pump. The stock liquid of the above system reaches the eutectic point in the form of gradual enrichment, which causes the output of the ice-making unit to decrease with the increase of the salinity of the raw water. The increase in the salt content of the ice crystals will also cause the water quality compliance rate of the ice-melting unit to decrease, the output of qualified water will be low, and the required treatment system will be bulky. In addition, in the above system, the mother liquor of the original liquid that reaches the eutectic point or the mother liquor of the original liquid that is fully concentrated is sent to the mother liquor storage tank. Since the mother liquor needs to undergo multiple reciprocating cycles of freezing, there will be no mother liquor to evaporate during the multiple cycles. Therefore, the time when its freezing and evaporation can play a role at the same time is seriously mismatched, and it is difficult for the system to effectively utilize the coupled heat. In addition, the cold energy and heat energy of the wastewater treatment process are not effectively recovered, resulting in a continuous cycle of defrosting and ice making for some solutions, causing excessive energy loss and significantly increasing the overall energy consumption. Summary of the invention

[0004] The present application provides a saline wastewater treatment system based on the hot and cold ends of a heat pump, which can fully utilize environmental thermal energy and significantly reduce energy consumption.

[0005] The technical solution of this application is as follows: A saline wastewater treatment system based on the hot and cold ends of a heat pump, comprising a raw liquid circulation system and a refrigerant circulation system; The stock liquid circulation system includes a stock liquid inlet, a low-temperature heat exchanger A, an ice crystal production device and a solid-liquid separation device in order according to the flow direction of the stock liquid. The low-temperature heat exchanger A is a place for low-temperature heat exchange of the stock liquid. The ice crystal production device concentrates the stock liquid crystals after low-temperature heat exchange into a mixture of ice crystals and concentrated liquid and inputs the mixture into the solid-liquid separation device. The solid-liquid separation device is used to separate ice crystals from the concentrated liquid. The raw liquid circulation system is divided into an ice crystal circulation system and a concentrated liquid circulation system at the solid-liquid separation device; The ice crystal circulation system comprises: Low-temperature heat exchanger B is a place where ice crystals melt. After the ice crystals melt into water, they flow into the low-temperature heat exchanger A to perform low-temperature heat exchange with the raw liquid; The concentrated liquid circulation system includes the following steps according to the concentrated liquid circulation direction: Evaporative heat exchanger E, which is the place for concentrated liquid to heat up and exchange heat; The evaporation crystallization device is a place for evaporation crystallization of concentrated liquid, and the evaporation crystallization device has a reaction chamber, a steam outlet and a residue discharge port; the reaction chamber includes a heating layer in zone A and a heating layer in zone B, the heating layer in zone A has a steam inlet and a condensed water outlet, and the condensed water outlet is connected to the evaporation heat exchanger E; the heating layer in zone B has a refrigerant inlet and a refrigerant outlet. The heating layer is an independent space in the reaction chamber, which is used to heat the concentrated liquid in the reaction chamber. The heat source of the heating layer in zone A is steam, and the heating layer in zone B is refrigerant. The steam in the heating layer in zone A flows into the condensed water outlet after releasing heat, and will not flow into the reaction chamber.

[0006] The evaporative heat exchanger C is a heat exchange place for the steam produced during the evaporative crystallization process; a steam inlet pipe and a steam exhaust pipe are respectively provided between the evaporative heat exchanger C and the steam inlet and the steam outlet; The refrigerant circulation system is a closed-loop structure, and the refrigerant circulates through the heat pump compressor, evaporative heat exchanger C, refrigerant inlet, zone B heating layer, refrigerant outlet, evaporative heat exchanger D and low-temperature heat exchanger B, expansion valve, and ice crystal production device; the evaporative heat exchanger D is connected to a cooling tower to restore the refrigerant to ambient temperature.

[0007] Furthermore, a storage tank for storing concentrated liquid is provided between the solid-liquid separation device and the evaporative heat exchanger E. Furthermore, the steam in the steam inlet pipe flows from the evaporative heat exchanger C to the steam inlet, and the steam in the steam exhaust pipe flows from the steam outlet to the evaporative heat exchanger C.

[0008] Furthermore, the steam inlet pipeline is provided with a vacuum pump to keep the evaporative heat exchanger C and the evaporative crystallization device in a negative pressure state.

[0009] Furthermore, the vacuum pressure range of the evaporation crystallization device is 9.106 kPa~19.918 kPa.

[0010] Furthermore, a screw pump is provided between the solid-liquid separation device and the low-temperature heat exchanger B.

[0011] Furthermore, a circulation pump is provided between the cooling tower and the low-temperature heat exchanger B.

[0012] Due to the adoption of the above technical solution, the beneficial effects of this application are as follows: 1. The present application has a raw liquid cycle and a refrigerant cycle, and the ice crystals and concentrated liquid are further divided into two sub-cycles in the raw liquid cycle. The cold end in the present application, that is, the end connected to the ice crystal production device, has the ability to absorb heat after expansion. In the ice crystal production device, the refrigerant absorbs the heat of the wastewater to promote the crystallization of the wastewater, and then obtains the ability to release heat after being compressed by the heat pump compressor. At the hot end, that is, the evaporation crystallization device, it releases heat after entering the B area to promote the evaporation and drying of the concentrated liquid. Finally, after returning to the ambient temperature through the cooling tower, it releases heat again in the low-temperature heat exchanger B to melt the ice crystals. In the circulation process of the refrigerant, its heat absorption and heat release capabilities are fully utilized, which significantly reduces energy consumption.

[0013] 2. The solid-liquid separation device of the present application is the starting point of differentiation, which can separate ice crystals instantly, thereby timely separating the salt and organic matter trapped in the ice crystals, and thus helping to obtain ice crystals with higher purity and concentrated liquid with higher concentration. Ice crystals with higher purity can simplify the subsequent purification process and increase the yield of qualified water; concentrated liquid with higher concentration can improve the efficiency of evaporation and crystallization, improve the efficiency of wastewater treatment, and significantly reduce energy consumption.

[0014] 3. The evaporation crystallization device of the present application is provided with evaporation zones. The heating layer in zone A uses steam as the heating medium with a temperature of 40-50 degrees; the heating layer in zone B uses refrigerant as the heating medium with a temperature of 60-90 degrees. Thus, an evaporation gradient is formed during the evaporation crystallization process, thereby making full use of the latent heat of evaporation, making up for the thermal energy gap of the heat pump, and ensuring the evaporation output under conditions of thermal energy shortage.

[0015] 4. In a preferred embodiment of the present application, a vacuum pump converts the evaporative heat exchanger C and the evaporative crystallization device into a negative pressure environment, and can evaporate the condensed water in the steam into gas under a negative pressure and high temperature environment, which not only helps the recycling of steam, but also can make full use of the latent heat of vaporization of the gas for evaporation. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings described herein are used to provide further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.

[0017] Figure 1 A flow chart of a saline wastewater treatment system based on the hot and cold ends of a heat pump is provided for this application.

[0018] In the attached picture: 110. Low-temperature heat exchanger A; 120. Ice crystal production device; 130. Solid-liquid separation device; 140. Low-temperature heat exchanger B; 150. Screw pump; 210. Vacuum pump; 220. Evaporative heat exchanger C; 230. Evaporative heat exchanger D; 240. Cooling tower; 250. Circulation pump; 260. Evaporative heat exchanger E; 310. Evaporative crystallization device; 320. Storage tank; 410. Heat pump compressor; 420. Expansion valve; 510. Temperature sensor; 520. Residue discharge port. DETAILED DESCRIPTION

[0019] Based on the background technology, the existing saline wastewater treatment system cannot achieve reasonable and effective use of heat. Therefore, this application provides a saline wastewater treatment system based on the hot and cold ends of a heat pump. Figure 1 The salt-containing wastewater treatment system includes a raw liquid circulation system and a refrigerant circulation system.

[0020] The raw liquid circulation system includes a raw liquid inlet, a low-temperature heat exchanger A110, an ice crystal production device 120 and a solid-liquid separation device 130 in sequence according to the flow direction of the raw liquid. The low-temperature heat exchanger A110 is a place for low-temperature heat exchange of the raw liquid. The ice crystal production device 120 concentrates the raw liquid crystals after low-temperature heat exchange into a mixture of ice crystals and concentrated liquid and inputs it into the solid-liquid separation device 130. The solid-liquid separation device 130 is used to separate ice crystals and concentrated liquid.

[0021] The cryogenic concentration method uses the principle that the crystallization process of water molecules repels foreign impurities to obtain relatively pure ice and concentrated liquid. The lower the freezing temperature, the faster the freezing rate, and the faster the crystal branches grow. At this time, the difference in the content of water molecules between the liquid phase and the solid / liquid interface increases, thereby accelerating the migration of water molecules from the liquid phase to the solid / liquid interface. When this rate exceeds the migration rate of salt and organic matter from the solid / liquid interface to the liquid phase, the salt and organic molecules will be wrapped in the ice crystals in the form of tiny liquid droplets. Therefore, in order to obtain high-purity ice crystals, the freezing speed should be as slow as possible, but this will greatly reduce production efficiency. Lowering the refrigeration temperature and increasing the freezing speed will reduce the ice crystal compliance rate, and the existing process cannot effectively solve this problem.

[0022] In the technical solution of the present application, the raw liquid circulation system is divided into an ice crystal circulation system and a concentrated liquid circulation system at the solid-liquid separation device 130. The ice crystal circulation is used to melt ice crystals to produce melt water, and the concentrated liquid circulation evaporates and crystallizes the concentrated liquid and discharges the waste residue, and the heated steam is converted into condensed water when cooled.

[0023] The ice crystal circulation system includes: a low-temperature heat exchanger B140, which is a place for ice crystals to melt. After the ice crystals melt into water, they flow into the low-temperature heat exchanger A110 to perform low-temperature heat exchange with the original liquid. The heat source required for melting ice crystals is the heat possessed by the refrigerant after it passes through the cooling tower 240 in the refrigerant cycle and returns to room temperature. In a preferred embodiment of the present application, a screw pump 150 is provided between the solid-liquid separation device 130 and the low-temperature heat exchanger B140, and the screw pump 150 is used to transfer the ice crystals to the low-temperature heat exchanger B140.

[0024] The concentrated liquid circulation system includes, in order according to the concentrated liquid circulation flow direction: an evaporative heat exchanger E260, which is a place for concentrated liquid heating and heat exchange. It should be noted that the salt content of the concentrated liquid in this application should preferably be twice or more than that of the initial solution or a solution close to saturation. In specific implementation, the condensed water temperature is controlled at about 40°C, and the temperature of the concentrated liquid after solid-liquid separation is relatively low or even negative, so the temperature of the concentrated liquid will increase after the condensed water heat exchange.

[0025] The evaporation crystallization device 310 is a place for evaporation and crystallization of the concentrated liquid. The evaporation crystallization device 310 has a reaction chamber, a steam outlet and a residue discharge port 520. The evaporation crystallization device 310 is equipped with a scraper to discharge the internal salt and residue into the residue discharge port 520. The reaction chamber includes a heating layer in zone A and a heating layer in zone B. The heating layer in zone A has a steam inlet and a condensed water outlet, and the condensed water outlet is connected to the evaporation heat exchanger E260. The heating layer in zone B has a refrigerant inlet and a refrigerant outlet. The heating layer in zone A and the heating layer in zone B are located in a chamber, and have an evaporation order, that is, after the concentrated liquid enters the reaction chamber, it is first evaporated by the heating layer in zone A, and then evaporated by the heating layer in zone B for the second time. The heat source of evaporation in zone A is the heat carried by the steam in the evaporation heat exchanger C220, and the heat source of evaporation and drying in zone B is the heat released by the refrigerant. Based on the above settings, zones A and B form an evaporation gradient due to the different heat sources of the heating layers, thereby improving the evaporation efficiency and the evaporation amount.

[0026] The evaporative heat exchanger C220 is a heat exchange place for the steam produced during the evaporative crystallization process; a steam inlet pipe and a steam exhaust pipe are respectively provided between the evaporative heat exchanger C220 and the steam inlet and the steam outlet; a refrigerant pipe is provided between the evaporative heat exchanger C220 and the refrigerant inlet. In a preferred embodiment of the present application, the steam in the steam inlet pipe flows from the evaporative heat exchanger C220 to the steam inlet, and the steam in the steam exhaust pipe flows from the steam outlet to the evaporative heat exchanger C220. In a specific embodiment of the above embodiment, the steam inlet pipe is provided with a vacuum pump 210 to keep the evaporative heat exchanger C220 and the evaporative crystallization device 310 in a negative pressure state. In a preferred embodiment of the above embodiment, the vacuum degree in the evaporative crystallization device 310 is set to a vacuum pressure range of 9.106kPa~19.918kPa.

[0027] The refrigerant circulation system is a closed-loop structure, and the refrigerant circulates through the expansion valve 420, the ice crystal production device 120, the heat pump compressor 410, the evaporative heat exchanger C220, the refrigerant inlet, the heating layer of the B zone, the refrigerant outlet, the evaporative heat exchanger D230 and the low-temperature heat exchanger B140; the evaporative heat exchanger D230 is connected to the cooling tower 240 to restore the refrigerant to the ambient temperature. The expansion valve 420 is arranged between the low-temperature heat exchanger B140 and the ice crystal production device 120. The refrigerant has the ability to absorb heat after expansion, and absorbs heat from the wastewater in the ice crystal production device 120 to cause it to form ice crystals. The heat pump compressor 410 is a place for heating the refrigerant. The heat pump compressor 410 transports the heated refrigerant to the evaporative heat exchanger C220. The refrigerant exchanges heat with steam in the evaporative heat exchanger C220 and then enters the heating layer of the B zone to release heat. After being pressurized by the heat pump compressor 410, the refrigerant becomes a high-temperature and high-pressure gas and passes through the evaporative heat exchanger C220, the heating layer of zone B, and the evaporative heat exchanger D230 in sequence. Then, it continues to release heat at the low-temperature heat exchanger B140 to become a high-temperature and high-pressure liquid. The liquid passes through the expansion valve 420 and becomes a low-temperature and low-pressure gas-liquid mixed state. It then enters the ice crystal production device 120 to absorb heat and become a gas, and then returns to the heat pump compressor 410 to complete a cycle.

[0028] In the present application, the refrigerant can be an environmentally friendly mixed refrigerant such as R404a, R507, R449A, etc., preferably R404a.

[0029] As a preferred embodiment of the present application, a storage tank 320 for storing concentrated liquid is provided between the solid-liquid separation device 130 and the evaporative heat exchanger E260.

[0030] As a preferred embodiment of the present application, a circulation pump 250 is provided between the cooling tower 240 and the low-temperature heat exchanger B140.

[0031] In the present application, a number of temperature sensors 510 are provided between the pipelines of the system for monitoring the internal temperature of the pipelines.

[0032] Anything not described in this application can be achieved by adopting or drawing on existing technologies.

[0033] The above is only an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims

1. A saline wastewater treatment system based on the hot and cold ends of a heat pump, characterized in that: Including raw liquid circulation system and refrigerant circulation system; The stock liquid circulation system includes a stock liquid inlet, a low-temperature heat exchanger A, an ice crystal production device and a solid-liquid separation device in order according to the flow direction of the stock liquid. The low-temperature heat exchanger A is a place for low-temperature heat exchange of the stock liquid. The ice crystal production device concentrates the stock liquid crystals after low-temperature heat exchange into a mixture of ice crystals and concentrated liquid and inputs the mixture into the solid-liquid separation device. The solid-liquid separation device is used to separate ice crystals from the concentrated liquid. The raw liquid circulation system is divided into an ice crystal circulation system and a concentrated liquid circulation system at the solid-liquid separation device; The ice crystal circulation system comprises: Low-temperature heat exchanger B is a place where ice crystals melt. After the ice crystals melt into water, they flow into the low-temperature heat exchanger A to perform low-temperature heat exchange with the raw liquid; The concentrated liquid circulation system includes the following steps according to the concentrated liquid circulation direction: Evaporative heat exchanger E, which is the place for concentrated liquid to heat up and exchange heat; An evaporation crystallization device is a place for evaporation and crystallization of concentrated liquid, and the evaporation crystallization device has a reaction chamber, a steam outlet and a residue discharge port; the reaction chamber includes a heating layer in zone A and a heating layer in zone B, the heating layer in zone A has a steam inlet and a condensed water outlet, and the condensed water outlet is connected to the evaporation heat exchanger E; the heating layer in zone B has a refrigerant inlet and a refrigerant outlet; The evaporative heat exchanger C is a heat exchange place for the steam produced during the evaporative crystallization process; a steam inlet pipe and a steam exhaust pipe are respectively provided between the evaporative heat exchanger C and the steam inlet and the steam outlet; The refrigerant circulation system is a closed-loop structure, and the refrigerant circulates through the heat pump compressor, evaporative heat exchanger C, refrigerant inlet, zone B heating layer, refrigerant outlet, evaporative heat exchanger D and low-temperature heat exchanger B, expansion valve, and ice crystal production device; the evaporative heat exchanger D is connected to a cooling tower to restore the refrigerant to ambient temperature.

2. A salt-containing wastewater treatment system based on the hot and cold ends of a heat pump according to claim 1, characterized in that: A storage tank for storing concentrated liquid is provided between the solid-liquid separation device and the evaporative heat exchanger E.

3. A salt-containing wastewater treatment system based on the hot and cold ends of a heat pump according to claim 1, characterized in that: The steam in the steam inlet pipe flows from the evaporative heat exchanger C to the steam inlet, and the steam in the steam exhaust pipe flows from the steam outlet to the evaporative heat exchanger C.

4. A salt-containing wastewater treatment system based on the hot and cold ends of a heat pump according to claim 3, characterized in that: The steam inlet pipeline is provided with a vacuum pump to keep the evaporative heat exchanger C and the evaporative crystallization device in a negative pressure state.

5. A salt-containing wastewater treatment system based on the hot and cold ends of a heat pump according to claim 4, characterized in that: The vacuum pressure range of the evaporation crystallization device is 9.106 kPa~19.918 kPa.

6. A salt-containing wastewater treatment system based on the hot and cold ends of a heat pump according to claim 5, characterized in that: A screw pump is provided between the solid-liquid separation device and the low-temperature heat exchanger B.

7. A salt-containing wastewater treatment system based on the hot and cold ends of a heat pump according to claim 1, characterized in that: A circulation pump is provided between the cooling tower and the low-temperature heat exchanger B.

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