A denitrification wastewater evaporation and recovery system

Abstract

This utility model discloses a denitrification wastewater evaporation and recovery system, relating to the field of wastewater recovery technology. Its purpose is to improve wastewater treatment efficiency and reduce costs. The proposed technical solution includes a denitrification spray tower, a settling tank, a second-effect evaporation chamber, and a first-effect evaporation chamber. The outlet of the denitrification spray tower is connected to the inlet of the settling tank, and the outlet of the settling tank is connected to the inlet of the second-effect evaporation chamber. The outlet of the second-effect evaporation chamber is connected to both the inlet of the first-effect evaporation chamber and the concentrated liquid inlet of the settling tank. This utility model significantly reduces energy consumption, with a unit steam consumption significantly lower than that of single-effect evaporation, effectively solving the problem of high energy consumption in existing technologies. It also significantly improves the stability and reliability of the system and reduces maintenance difficulty.

Description

Technical Field

[0001] This utility model relates to the field of wastewater recycling technology, specifically to a denitrification wastewater evaporation and recycling system. Background Technology

[0002] With increasingly stringent environmental protection requirements, controlling pollutant emissions has become an urgent issue. Denitrification wastewater is one of the main pollutants generated during the production processes of thermal power plants, chemical plants, and other enterprises. Its low treatment efficiency, high energy consumption, unstable control, and difficult maintenance have long plagued these companies. Currently, most enterprises use mechanical steam recompression evaporators to treat denitrification wastewater, but this method suffers from drawbacks such as high consumption, unstable control, and difficult maintenance. It is also sensitive to voltage requirements, making it difficult to meet practical application needs. Traditional denitrification wastewater treatment methods mainly include chemical precipitation and evaporation crystallization. While chemical precipitation is widely used, it suffers from high operating costs, limited removal rates, and a tendency to cause secondary pollution. Evaporation crystallization, although capable of achieving zero wastewater discharge, has high energy consumption, and the resulting solid waste salts require additional disposal, increasing treatment costs. Furthermore, some emerging treatment technologies, such as ultrafiltration reverse osmosis membrane technology and multi-stage flash evaporation, while improving treatment efficiency to some extent, still suffer from high equipment investment costs and high operating costs. To address the aforementioned issues, there is an urgent need to develop a novel denitrification wastewater recovery system that can effectively reduce energy consumption while ensuring stable operation and ease of maintenance. Simultaneously, the system should possess excellent concentration control capabilities to achieve efficient wastewater treatment and low or zero discharge. This system should be able to fully utilize the resources within the wastewater, realizing the resource-based reuse of water and salt, thereby reducing emissions and conserving freshwater resources.

[0003] Chinese patent application CN111943424A discloses a zero-discharge system and method for desulfurization wastewater. The discharge system includes a pretreatment unit and an evaporation unit. The pretreatment unit reduces the hardness and impurity content of the wastewater to be treated, obtaining pretreated wastewater. The evaporation unit includes a heat source system, a flash evaporation system, and a flue gas evaporation system. The outlet of the heat source system is connected to the inlet of the flash evaporation system, the liquid inlet of the flash evaporation system is connected to the outlet of the pretreatment unit, and the outlet of the flash evaporation system is connected to the inlet of the flue gas evaporation system. The pretreated wastewater enters the flash evaporation system, comes into contact with the heat source provided by the heat source system for countercurrent evaporation, and then undergoes secondary evaporation in the flue gas evaporation system. Although the secondary flash evaporation method used in this scheme improves treatment efficiency, the investment and operating costs of this scheme are relatively high. Utility Model Content

[0004] This invention provides a denitrification wastewater evaporation and recovery system, which aims to effectively improve wastewater treatment efficiency while reducing the cost of the denitrification wastewater evaporation and recovery process.

[0005] The technical solution of this utility model to solve the above-mentioned technical problems is as follows:

[0006] A denitrification wastewater evaporation and recovery system includes a denitrification spray tower, a settling tank, a second-effect evaporation chamber, and a first-effect evaporation chamber. The outlet of the denitrification spray tower is connected to the inlet of the settling tank, the outlet of the settling tank is connected to the inlet of the second-effect evaporation chamber, and the outlet of the second-effect evaporation chamber is connected to the inlet of the first-effect evaporation chamber and the concentrated liquid inlet of the settling tank, respectively.

[0007] Furthermore, the outlet of the settling tank circulating liquid is connected to the inlet of the denitrification spray tower via a circulating pump.

[0008] Furthermore, a plate and frame filter press for removing solid impurities from the denitrification wastewater is installed on the pipeline between the outlet of the settling tank and the inlet of the second-effect evaporation chamber.

[0009] Furthermore, a first condensate storage tank is provided between the plate and frame filter press and the second-effect evaporation chamber. The outlet of the plate and frame filter press is connected to the inlet of the first condensate storage tank, and the outlet of the first condensate storage tank is connected to the inlet of the second-effect evaporation chamber.

[0010] Furthermore, it also includes a first shell-and-tube heat exchanger, a second shell-and-tube heat exchanger, a first material conveying pump, a second material conveying pump, an external steam network, and a condensate recovery device. The material outlet of the second-effect evaporator is connected to the inlet of the first material conveying pump, the outlet of the first material conveying pump is connected to the material inlet of the first shell-and-tube heat exchanger, and the material outlet of the first shell-and-tube heat exchanger is connected to the material inlet of the second-effect evaporator. The material outlet of the first-effect evaporator is connected to the inlet of the second material conveying pump, the outlet of the second material conveying pump is connected to the material inlet of the second shell-and-tube heat exchanger, and the material outlet of the second shell-and-tube heat exchanger is connected to the material inlet of the first-effect evaporator. The steam inlets of both the first and second shell-and-tube heat exchangers are connected to the external steam network, and the condensate outlets of both the first and second shell-and-tube heat exchangers are connected to the condensate recovery device.

[0011] Furthermore, it also includes a second condensate storage tank, a condenser, and a crystallization device. The steam outlet of the second-effect evaporation chamber is connected to the steam inlet of the condenser, the liquid outlet of the condenser is connected to the liquid inlet of the second condensate storage tank, and the waste liquid outlet of the first-effect evaporation chamber is connected to the crystallization device. The crystallization device is used to crystallize the concentrated waste liquid.

[0012] This utility model has the following beneficial effects:

[0013] 1. The system structure of this utility model is compact, the equipment layout is reasonable, the operation is simple, and it is easy to realize automatic control, which reduces the operating cost and solves the problem of high investment costs for some emerging technology equipment such as ultrafiltration reverse osmosis membrane method and multi-stage flash evaporation.

[0014] 2. This utility model replaces the traditional mechanical vapor recompression evaporator by connecting the liquid outlet of the double-effect evaporator with the liquid inlet of the single-effect evaporator or with the concentrated liquid inlet of the settling tank. This significantly reduces energy consumption, and the unit steam consumption is significantly lower than that of single-effect evaporation, effectively solving the problem of high energy consumption in the prior art.

[0015] 3. This utility model achieves automated wastewater circulation treatment by circulating the spray liquid at the bottom of the settling tank and the denitrification spray tower. It eliminates the need for a high-speed rotating steam compressor, significantly improves the stability and reliability of the system, reduces maintenance difficulty, and solves the problems of unstable control and difficult maintenance in the prior art.

[0016] 4. This utility model incorporates a plate and frame filter press and a crystallization device, achieving efficient purification and concentration of wastewater through multi-stage treatment. This effectively improves the overall efficiency of wastewater treatment and solves the problems of low efficiency in traditional chemical precipitation and single evaporation methods.

[0017] 5. This utility model adopts a circulating concentrate method, which allows for human intervention in the concentration according to actual needs, thereby achieving precise control of wastewater concentration, avoiding direct discharge of solid waste salt, and improving the resource utilization efficiency of water and salt. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the denitrification wastewater evaporation and recovery system of this utility model;

[0019] Figure 2 This is a schematic diagram of the wastewater circulation between the denitrification spray tower and the settling tank.

[0020] Figure 3 This is a schematic diagram of the connection structure between the second-effect evaporator and the first-effect evaporator;

[0021] Figures 1 to 3 The reference numerals in the attached drawings represent: 1-Denitrification spray tower, 2-Settling tank, 3-Circulating pump, 4-Plate and frame filter press, 5-First condensate storage tank, 6-Feed pump, 7-Second-effect evaporator, 8-First-effect evaporator, 9-Transfer pump, 10-First shell-and-tube heat exchanger, 11-Second shell-and-tube heat exchanger, 12-Second condensate storage tank, 13-Condenser, 14-First material conveying pump, 15-Second material conveying pump, 16-Crystallization equipment, 17-External steam network, 18-Condensate recovery device, 21-First valve, 22-Second valve, 23-Third valve, 24-Fourth valve, 25-Fifth valve, 26-Sixth valve, 27-Seventh valve, 28-Eighth valve. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0023] In this utility model, the terms "longitudinal," "lateral," "vertical," "upper," "lower," "front," "rear," "left," "right," "top," and "bottom," etc., indicate the orientation or positional relationship based on the appendix. Figure 1 The orientation or positional relationship shown is for the purpose of describing the present invention only, and is not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0024] Please refer to Figure 1-3 This utility model provides a denitrification wastewater evaporation and recovery system, which mainly consists of core components such as a denitrification spray tower 1, a settling tank 2, a double-effect evaporation chamber 7, a first-effect evaporation chamber 8, a second condensate storage tank 12, a condenser 13, and crystallization equipment. The components are connected by reasonable pipelines and set up with supporting equipment to achieve effective treatment and recycling of denitrification wastewater.

[0025] The system includes a denitrification spray tower 1, a settling tank 2, a double-effect evaporator 7, and a single-effect evaporator 8. The outlet of the denitrification spray tower 1 is connected to the inlet of the settling tank 2, and the outlet of the settling tank 2 is connected to the inlet of the double-effect evaporator 7. The outlet of the double-effect evaporator 7 is connected to both the inlet of the single-effect evaporator 8 and the concentrate inlet of the settling tank 2. Denitrification wastewater first enters the denitrification spray tower 1. The denitrification spray tower 1 is equipped with a spraying device. Through sufficient contact between the spray liquid and the waste gas, denitrification and purification are achieved. Simultaneously, the wastewater undergoes a preliminary settling and separation process within the tower. An outlet is located at the bottom of the denitrification spray tower 1, from which the pre-treated wastewater flows out and is transported to the settling tank 2 via pipeline.

[0026] Settling tank 2 is used to receive denitrification wastewater and adjust its pH value by adding calcium hydroxide, controlling the range to 6-8 to prevent internal corrosion damage caused by pH out-of-control conditions. It has an inlet at the top, connected to the outlet of denitrification spray tower 1, to receive wastewater from the tower. Settling tank 2 has a large volume, providing sufficient settling time and space for solid particles in the wastewater. Solid impurities in the wastewater gradually settle to the bottom of the tank under gravity, forming a concentrated liquid; while the relatively clear supernatant remains at the top. The outlet of settling tank 2 continuously transports wastewater meeting concentration standards to the double-effect evaporator 7 through a pipeline, where the wastewater concentration gradually increases. The bottom of the double-effect evaporator 7 is provided with a liquid outlet. The liquid outlet of the double-effect evaporator 7 is connected to the first-effect evaporator 8 through the first valve 21 on the pipeline. The liquid outlet of the double-effect evaporator 7 is connected to the settling tank 2 through the second valve 22 on the pipeline. The liquid outlet of the double-effect evaporator 7 has two flow direction options: one is to open the first valve 21 on the pipeline and close the second valve 22, so that the liquid outlet of the double-effect evaporator 7 is connected to the liquid inlet of the first-effect evaporator 8, and the concentrated wastewater is transported to the first-effect evaporator 8 for further evaporation and concentration; the other is to close the first valve 21 on the pipeline and open the second valve 22, so that the liquid outlet of the double-effect evaporator 7 is connected to the concentrated liquid inlet of the settling tank 2. When the concentration of the wastewater in the double-effect evaporator 7 reaches a certain requirement or according to actual production needs, part of the concentrated liquid can be returned to the settling tank 2 for further settling and separation treatment to further remove any impurities or adjust the composition and concentration of the wastewater. The specific model selection of the pipeline and valve in this embodiment can use commercially available existing technology.

[0027] The outlet of the circulating liquid in the settling tank 2 is connected to the inlet of the denitrification spray tower 1 via a circulating pump 3. To achieve wastewater recycling, a circulating pump 3 is installed at the outlet of the settling tank 2. A third valve 23 is installed on the pipeline between the outlet of the settling tank 2 and the circulating pump 3. The circulating pump 3 provides power for the transport of the circulating liquid, pumping a portion of the supernatant from the upper part of the settling tank 2 back to the denitrification spray tower 1, where it continues to participate in the denitrification and other purification processes as spray liquid. This not only improves the utilization rate of water resources but also maintains the stable concentration and performance of the spray liquid in the denitrification spray tower 1 to a certain extent.

[0028] A plate and frame filter press 4 is installed on the pipeline between the outlet of the settling tank 2 and the inlet of the double-effect evaporation chamber 7 to remove solid impurities from the denitrification wastewater. A fourth valve 24 is installed on the pipeline between the outlet of the settling tank 2 and the plate and frame filter press 4. The plate and frame filter press 4 is a common solid-liquid separation device, consisting of multiple filter plates and frames arranged alternately. Under pressure, solid impurities in the wastewater are trapped on the filter cloth to form a filter cake, while the clarified liquid is discharged through the filter cloth. After preliminary settling in the settling tank 2, the wastewater undergoes deep filtration through the plate and frame filter press 4 before entering the double-effect evaporation chamber 7 to further remove residual fine solid particles, preventing these impurities from entering the subsequent evaporation process and affecting the normal operation of the evaporation equipment and product quality.

[0029] A first condensate storage tank 5 is installed between the plate and frame filter press 4 and the double-effect evaporator 7. The outlet of the filter press 4 is connected to the inlet of the first condensate storage tank 5, and the outlet of the first condensate storage tank 5 is connected to the inlet of the double-effect evaporator 7. The function of the first condensate storage tank 5 is to collect some of the condensate that may be generated during system operation, and it also plays a role in buffering and stabilizing system pressure. The wastewater filtered by the plate and frame filter press 4 enters the first condensate storage tank 5, where it undergoes a brief residence and buffering process before being transported to the double-effect evaporator 7 through pipelines. The top of the double-effect evaporator 7 is equipped with an inlet that is connected to the outlet of the first condensate storage tank 5 to receive the pretreated wastewater.

[0030] It also includes a first shell-and-tube heat exchanger 10, a second shell-and-tube heat exchanger 11, a first material conveying pump 14, a second material conveying pump 15, an external steam network 17, and a condensate recovery device 18. The material outlet of the second-effect evaporator 7 is connected to the inlet of the first material conveying pump 14, the outlet of the first material conveying pump 14 is connected to the material inlet of the first shell-and-tube heat exchanger 10, and the material outlet of the first shell-and-tube heat exchanger 10 is connected to the material inlet of the second-effect evaporator 7. The material outlet of the first-effect evaporator 8 is connected to the inlet of the second material conveying pump 15, the outlet of the second material conveying pump 15 is connected to the material inlet of the second shell-and-tube heat exchanger 11, and the material outlet of the second shell-and-tube heat exchanger 11 is connected to the material inlet of the first-effect evaporator 8. The steam inlets of the first shell-and-tube heat exchanger 10 and the second shell-and-tube heat exchanger 11 are both connected to the external steam network 17. The condensate outlet of the first shell-and-tube heat exchanger 10 and the second shell-and-tube heat exchanger 11 are both connected to the condensate recovery device 18. The first tube heat exchanger 10 consists of multiple heat exchange tubes through which steam is introduced. The first tube heat exchanger 10 provides heat to the wastewater in the double-effect evaporator 7 through heat exchange, causing it to heat up and evaporate. The temperature of the first tube heat exchanger 10 and the second tube heat exchanger 11 is controlled between 60℃ and 80℃. Because it operates under negative pressure, the boiling point of the material is lowered, and temperature control avoids wasting steam.

[0031] The second shell-and-tube heat exchanger 11 provides heat to the wastewater in the first-effect evaporation chamber 8 through heat exchange. The second shell-and-tube heat exchanger 11 also consists of multiple heat exchange tubes. Both the first shell-and-tube heat exchanger 10 and the second shell-and-tube heat exchanger 11 are supplied with live steam for heating through an external steam network 17. The first material transfer pump 14 pumps the wastewater in the second-effect evaporation chamber 7 to the first shell-and-tube heat exchanger 10 for forced circulation to form a gas-liquid mixture. Due to the sudden pressure drop, the material boils violently, the secondary steam separates from the concentrated liquid, the steam is discharged from the top, and the liquid below continues to be heated. After heating, it is sent back to the second-effect evaporation chamber 7, and this cycle repeats, continuously evaporating and concentrating the wastewater. A second material transfer pump 15 is installed between the first-effect evaporation chamber 8 and the second shell-and-tube heat exchanger 11. The function of the second material transfer pump 15 is the same as that of the first material transfer pump 14, ensuring that the concentrated liquid circulates between the first-effect evaporation chamber 8 and the second shell-and-tube heat exchanger 11, achieving efficient evaporation and concentration. When it is necessary to transfer the concentrate in the second-effect evaporator 7 to the first-effect evaporator 8, the transfer pump 9 provides power to ensure that the concentrate can smoothly enter the first-effect evaporator 8.

[0032] A fifth valve 25 is installed on the pipe connecting the material outlet of the second-effect evaporator 7 to the inlet of the first material conveying pump 14. A sixth valve 26 is installed on the pipe connecting the material outlet of the first shell-and-tube heat exchanger 10 to the material inlet of the second-effect evaporator 7. A seventh valve 27 is installed on the pipe connecting the material outlet of the first-effect evaporator 8 to the inlet of the second material conveying pump 15. An eighth valve 28 is installed on the pipe connecting the material outlet of the second shell-and-tube heat exchanger 11 to the material inlet of the first-effect evaporator 8. When it is necessary to heat the second-effect evaporator 7 through the first shell-and-tube heat exchanger 10, the fifth valve 25 and the sixth valve 26 are opened simultaneously for forced circulation. When it is necessary to force circulation to the first-effect evaporator 8 through the second shell-and-tube heat exchanger 11, the seventh valve 27 and the eighth valve 28 are opened simultaneously.

[0033] The system also includes a second condensate storage tank 12, a condenser 13, and a crystallization device 16. The steam outlet of the second-effect evaporator 7 is connected to the steam inlet of the condenser 13, and the liquid outlet of the condenser 13 is connected to the liquid inlet of the second condensate storage tank 12. The waste liquid outlet of the first-effect evaporator 8 is connected to the crystallization device 16, which is used to crystallize the concentrated waste liquid. A steam outlet is provided at the top of the second-effect evaporator 7. The concentration process of the concentrated liquid in the second-effect evaporator 7 generates steam, which can be transported to the condenser 13. The function of the condenser 13 is to condense the steam in the concentrated liquid into liquid water, thereby realizing water recovery. A cooling medium channel is provided inside the condenser 13. Through heat exchange with the cooling medium, the steam entering the condenser 13 is rapidly cooled and condensed. The steam inlet at the top of the condenser 13 is connected to the steam outlet of the second-effect evaporator 7 to receive steam; the liquid outlet at the bottom of the condenser 13 is connected to the liquid inlet of the second condensate storage tank 12 to transport the condensed liquid water to the second condensate storage tank 12 for storage and subsequent reuse. Simultaneously, the concentrated liquid is fed into the first-effect evaporator 8 via the second-effect evaporator 7. After further evaporation and concentration in the first-effect evaporator 8, the concentrated liquid reaches a high concentration. A waste liquid outlet is located at the bottom of the first-effect evaporator 8, and this outlet is connected to the inlet of the crystallization device 16. By controlling conditions such as temperature and concentration, the solute in the waste liquid is precipitated in the form of crystals, achieving minimal wastewater discharge. The crystallization device 16 can use common crystallizers, such as forced circulation crystallizers or evaporative crystallizers, selected according to actual treatment needs and waste liquid characteristics. After crystallization, the crystals are separated from the mother liquor. The crystals can be further recycled or treated, while the mother liquor can be further treated or reused as needed.

[0034] During the operation of the entire denitrification wastewater evaporation and recovery system, the various devices are connected, controlled, and transported through pipelines, valves, pumps, and other means to form an organic whole. This system achieves the complete treatment of denitrification wastewater, from preliminary treatment to deep evaporation and concentration, and then to water recovery and crystallization separation. It achieves the goals of wastewater reduction and resource utilization, while effectively reducing environmental pollution caused by wastewater discharge. The system has a reasonable structure, stable operation, high treatment efficiency and resource recovery rate, and is suitable for various denitrification wastewater treatment and recycling scenarios.

[0035] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A denitrification wastewater evaporation and recovery system, characterized in that, It includes a denitrification spray tower (1), a settling tank (2), a second-effect evaporation chamber (7) and a first-effect evaporation chamber (8). The outlet of the denitrification spray tower (1) is connected to the inlet of the settling tank (2). The outlet of the settling tank (2) is connected to the inlet of the second-effect evaporation chamber (7). The outlet of the second-effect evaporation chamber (7) is connected to the inlet of the first-effect evaporation chamber (8) and the concentrated liquid inlet of the settling tank (2), respectively.

2. The denitrification wastewater evaporation and recovery system according to claim 1, characterized in that, The outlet of the settling tank (2) is connected to the inlet of the denitrification spray tower (1) via a circulating pump (3).

3. The denitrification wastewater evaporation and recovery system according to claim 1, characterized in that, A plate and frame filter press (4) for removing solid impurities from denitrification wastewater is installed on the pipeline between the outlet of the settling tank (2) and the inlet of the double-effect evaporation chamber (7).

4. The denitrification wastewater evaporation and recovery system according to claim 3, characterized in that, A first condensate storage tank (5) is provided between the plate and frame filter press (4) and the second-effect evaporation chamber (7). The outlet of the plate and frame filter press (4) is connected to the inlet of the first condensate storage tank (5), and the outlet of the first condensate storage tank (5) is connected to the inlet of the second-effect evaporation chamber (7).

5. The denitrification wastewater evaporation and recovery system according to claim 1, characterized in that, It also includes a first shell-and-tube heat exchanger (10), a second shell-and-tube heat exchanger (11), a first material conveying pump (14), a second material conveying pump (15), an external steam network (17), and a condensate recovery device (18). The material outlet of the second-effect evaporator (7) is connected to the inlet of the first material conveying pump (14), the outlet of the first material conveying pump (14) is connected to the material inlet of the first shell-and-tube heat exchanger (10), and the material outlet of the first shell-and-tube heat exchanger (10) is connected to the material inlet of the second-effect evaporator (7). The material outlet of the first-effect evaporator (8) is connected to the inlet of the second material conveying pump (15), the outlet of the second material conveying pump (15) is connected to the material inlet of the second shell-and-tube heat exchanger (11), and the material outlet of the second shell-and-tube heat exchanger (11) is connected to the material inlet of the first-effect evaporator (8). The steam inlet of the first tube heat exchanger (10) and the steam inlet of the second tube heat exchanger (11) are both connected to the external steam network (17), and the condensate outlet of the first tube heat exchanger (10) and the second tube heat exchanger (11) are both connected to the condensate recovery device (18).

6. The denitrification wastewater evaporation and recovery system according to claim 1, characterized in that, It also includes a second condensate storage tank (12), a condenser (13), and a crystallization device (16). The steam outlet of the second-effect evaporation chamber (7) is connected to the steam inlet of the condenser (13), the liquid outlet of the condenser (13) is connected to the liquid inlet of the second condensate storage tank (12), and the waste liquid outlet of the first-effect evaporation chamber (8) is connected to the crystallization device (16). The crystallization device (16) is used to crystallize the concentrated waste liquid.

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