Sewage waste heat comprehensive utilization system and treatment method thereof

Abstract

The invention discloses a sewage waste heat comprehensive utilization system and a treatment method thereof. The system comprises three functional units, namely a preheating unit, a sewage temperature raising unit and a sewage waste heat heating unit. In the preheating unit, sewage is preliminarily preheated through reuse water or reclaimed water in a plant to achieve primary recovery of waste heat, then in the sewage temperature raising unit, secondary recovery of waste heat is conducted on the reuse water or the reclaimed water through a heat pump evaporator to achieve multi-stage utilization of energy, heat exchange and temperature raising are conducted on the sewage in a condenser through the recovered energy, and the heat exchange efficiency is improved. The temperature of the sewage is increased; in addition, a sewage waste heat heating unit is arranged to recycle waste heat of recycled water or reclaimed water, so that heating return water of a user is heated, and sewage waste heat heating is achieved. Therefore, the sewage waste heat energy utilization rate can be increased through multi-stage energy recovery, the sewage waste heat is turned into wealth, and meanwhile the problems of low-temperature operation of the biological pool in winter and plant building heating requirements are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sewage treatment and renewable energy utilization, and in particular to a sewage waste heat comprehensive utilization system suitable for a sewage treatment plant and a treatment method thereof. BACKGROUND

[0002] In northern China, the winter climate is cold, and the influent temperature of the sewage treatment plant is often lower than 10℃, even close to the freezing point. The microbial flora relied on by the biochemical treatment process of sewage, especially the key reactions of nitrification and denitrification, will significantly reduce the biological activity when the temperature is lower than 12℃, resulting in a decrease in sewage treatment efficiency and difficulty in meeting the water quality standards.

[0003] To solve this problem, the prior art has proposed various schemes for heating sewage. For example, some schemes use coal or gas boilers to directly heat sewage or process media. Although this method can effectively increase the water temperature, it has problems such as high energy consumption, high operating cost, and large emissions of carbon dioxide and pollutants. Other schemes use heat pump technology, such as the sewage heating water source heat pump system disclosed in Chinese Invention Patent CN119958142A, which uses the waste heat of treated reclaimed water to heat raw sewage, making progress in energy efficiency and environmental protection.

[0004] However, the inventors have realized that such heat pump-based heating schemes are relatively single-functioned, usually focusing only on solving the heat preservation problem of the biochemical tank, and failing to consider the overall energy demand of the sewage plant. For example, sewage treatment plants are also major energy consumers, especially in winter, when office buildings, workshops and other buildings in the plant area also have huge heating demands. Currently, plant heating relies on municipal heat networks or independent coal / gas boilers, which undoubtedly further increases the operating cost and carbon emissions of the sewage treatment plant. On the other hand, in the existing sewage waste heat recovery process, the utilization of energy is often not sufficient, there is a phenomenon of "high quality and low use" or waste heat being directly discharged and wasted, and energy maximization utilization is not achieved. Therefore, it is necessary to propose a new technical scheme to solve the problems in the prior art. SUMMARY

[0005] The present application provides a sewage waste heat comprehensive utilization system and a treatment method thereof to solve the problem of insufficient energy utilization in existing sewage waste heat recovery, which makes it difficult to cover the energy demand of the sewage plant as much as possible.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical scheme:

[0007] On the one hand, the present application provides a sewage waste heat comprehensive utilization system, comprising:

[0008] The preheating unit includes a preheater, which is equipped with a sewage pipeline and a recycled water pipeline. The inlet end of the sewage pipeline is connected to the primary sedimentation tank, and the inlet end of the recycled water pipeline is connected to the recycled warm water tank. The preheater is used to realize heat exchange and temperature increase of the sewage by the recycled water.

[0009] The wastewater heating unit includes a wastewater heating heat pump unit, which comprises a first compressor, a first condenser, a first expansion valve, and a first evaporator connected in sequence. The first condenser has a wastewater inlet and a wastewater outlet. The wastewater inlet is connected to the outlet end of the wastewater pipeline, and the wastewater outlet is connected to a biological tank. The first evaporator has a recycled water inlet and a recycled water outlet. The recycled water inlet is connected to the outlet end of the recycled water pipeline, and the recycled water outlet is connected to a recycled cold water tank.

[0010] The wastewater waste heat heating unit includes a wastewater source heat pump unit, which includes a second compressor, a second condenser, a second expansion valve, and a second evaporator connected in sequence. The second condenser has a heating return water inlet and a heating supply water outlet. The heating return water inlet is connected to the user's heating return water outlet, and the heating supply water outlet is connected to the user's heating water inlet. The second evaporator has a greywater inlet and a greywater outlet. The greywater inlet is connected to a greywater tank, and the greywater outlet is connected to a reused cold water tank.

[0011] Furthermore, in the above technical solution, the wastewater heating unit also includes a wastewater bypass disposed between the wastewater inlet and the wastewater outlet of the first condenser. A regulating valve is provided on the wastewater bypass, and a mixing pipe section is formed at the end of the wastewater bypass. The wastewater outlet of the first condenser is connected to the mixing pipe section to ensure uniform mixing.

[0012] Furthermore, the regulating valve is an electric regulating valve, which is communicatively connected to the controller; a temperature sensor is installed in the biological tank, which is communicatively connected to the controller, which is configured to compare the temperature signal obtained from the temperature sensor with a reference temperature signal, and output an opening adjustment control signal to the electric regulating valve based on the comparison result.

[0013] Furthermore, the wastewater heating heat pump unit is used to recover the waste heat carried by the recycled water discharged from the preheater through refrigerant circulation, and to exchange heat and raise the temperature of the wastewater fed into the first condenser; the refrigerant outlet of the first compressor is connected to the refrigerant inlet of the first condenser, and the first compressor is used to send the compressed and heated refrigerant into the first condenser; the refrigerant outlet of the first condenser is connected to the refrigerant inlet of the first expansion valve, and the first condenser is used to exchange heat between the heated refrigerant and the wastewater flowing into it to raise the temperature of the wastewater; the refrigerant outlet of the first expansion valve is connected to the refrigerant inlet of the first evaporator, and the first expansion valve is used to throttle and reduce the pressure of the refrigerant after heat exchange and cooling; the refrigerant outlet of the first evaporator is connected to the refrigerant inlet of the first compressor, and the first evaporator is used to exchange heat between the recycled water discharged from the preheater and the refrigerant to recover the waste heat carried by the recycled water discharged from the preheater.

[0014] Furthermore, the wastewater source heat pump unit is used to recover the waste heat carried by the greywater discharged from the greywater tank through refrigerant circulation, and to exchange heat and raise the temperature of the heating return water fed into the second condenser; the refrigerant outlet of the second compressor is connected to the refrigerant inlet of the second condenser, and the second compressor is used to send the compressed and heated refrigerant into the second condenser; the refrigerant outlet of the second condenser is connected to the refrigerant inlet of the second expansion valve, and the second condenser is used to exchange heat between the heated refrigerant and the heating return water flowing into it, thereby raising the temperature of the heating return water; the refrigerant outlet of the second expansion valve is connected to the refrigerant inlet of the second evaporator, and the second expansion valve is used to throttle and reduce the pressure of the refrigerant after heat exchange and cooling; the refrigerant outlet of the second evaporator is connected to the refrigerant inlet of the second compressor, and the second evaporator is used to exchange heat between the greywater discharged from the greywater tank and the refrigerant to recover the waste heat carried by the greywater.

[0015] Furthermore, the user-end heating return water outlet is connected to the heating return water inlet via a third water pump; the greywater outlet of the greywater tank is connected to the greywater inlet of the second evaporator via a fourth water pump.

[0016] Furthermore, the primary sedimentation tank's raw wastewater outlet is connected to a filtration device, and the filtration device's outlet is connected to the inlet of the wastewater pipeline via a first water pump; the recycled water outlet of the reused warm water tank is connected to the inlet of the recycled water pipeline via a second water pump.

[0017] On the other hand, this application provides a wastewater waste heat comprehensive treatment method based on the above-mentioned wastewater waste heat comprehensive utilization system, including the following steps:

[0018] S1: Raw wastewater preheating: The recycled water from the reuse warm water tank and the raw wastewater from the primary sedimentation tank are sent into the preheater for heat exchange to achieve raw wastewater preheating.

[0019] S2: Raw sewage is heated by sending the preheated raw sewage into the first condenser of the sewage heating heat pump unit, and the recycled water discharged from the preheater is sent into the first evaporator. The refrigerant is circulated through the sewage heating heat pump unit to recover the waste heat carried by the recycled water and use it to heat the raw sewage. The heated raw sewage is then sent into the biological tank.

[0020] S3: Wastewater waste heat heating. The greywater in the greywater tank is sent to the second evaporator of the wastewater source heat pump unit, and the heating return water discharged from the user end is sent to the second condenser. The refrigerant is circulated through the wastewater source heat pump unit to recover the waste heat carried by the greywater and use it to heat exchange and raise the temperature of the heating return water. The heated heating return water is then sent to the heating water inlet at the user end.

[0021] Further in the above technical solution, in step S2, a sewage bypass is set between the sewage inlet and sewage outlet of the first condenser of the sewage heating heat pump unit, an electric regulating valve is set on the sewage bypass, and the electric regulating valve is communicatively connected to the controller; and a temperature sensor communicatively connected to the controller is set in the biological tank; the controller obtains the real-time temperature value of the sewage in the biological tank through the temperature sensor, and compares the real-time temperature value with a reference temperature value. If the real-time temperature value is less than the reference temperature value, the controller controls the electric regulating valve to increase its opening.

[0022] Compared with the prior art, this application has at least the following beneficial effects:

[0023] 1. Based on further analysis and research of existing technical problems, this application recognizes that current wastewater waste heat recovery suffers from insufficient energy utilization and difficulty in covering the energy needs of wastewater treatment plants as much as possible. Therefore, this application provides a comprehensive wastewater waste heat utilization system, comprising three functional units: a preheating unit, a wastewater temperature raising unit, and a wastewater waste heat heating unit. In the preheating unit, wastewater is preheated using recycled water or greywater to achieve primary waste heat recovery. Then, in the wastewater temperature raising unit, wastewater is recovered a second time using a heat pump evaporator, achieving multi-stage energy utilization. The recovered energy is used to heat the wastewater in the condenser, raising its temperature. Furthermore, this application also incorporates a wastewater waste heat heating unit to recover and utilize the wastewater from recycled water or greywater to raise the temperature of the user's heating return water, achieving wastewater waste heat heating. Therefore, this application can improve the energy utilization rate of wastewater waste heat through multi-stage energy recovery, turning wastewater waste heat into a valuable resource, while simultaneously solving the problem of low-temperature operation of biological treatment ponds in winter and the heating needs of plant buildings.

[0024] 2. This application includes a wastewater bypass and an electric regulating valve installed between the wastewater inlet and outlet of the first condenser. This pipeline structure allows for precise mixing of wastewater that has only undergone preliminary heating in the preheater with high-temperature wastewater that has undergone deep heating in the first condenser. By dynamically adjusting the mixing ratio through the controller, the temperature of the mixed wastewater entering the biological tank can be precisely stabilized at 12°C. The system does not need to heat all the wastewater flow to the maximum temperature. Instead, it concentrates the limited heat energy to heat a portion of the wastewater and then mixes it to reach the target temperature, thus achieving on-demand heating and maximizing energy savings.

[0025] 3. This application makes full use of the plant's existing recycled water and greywater as a heat source, without relying on expensive fossil fuels or municipal heating, reducing dependence on external energy and significantly reducing operating costs; in addition, the heating and warming process of this system is combustion-free and has no exhaust emissions, making it cleaner and more environmentally friendly than traditional gas boiler heating solutions, achieving near-zero carbon emission heating. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. It should be understood that the specific shapes and structures shown in the drawings should not generally be regarded as limiting conditions for implementing this application. For example, based on the technical concepts disclosed in this application and the exemplary drawings, those skilled in the art are able to easily make conventional adjustments or further optimizations to the addition / reduction / classification, specific shapes, positional relationships, connection methods, and size ratios of certain units (components).

[0027] Figure 1 This is a schematic diagram of the process flow of the wastewater waste heat comprehensive utilization system provided in this application in one embodiment. Detailed Implementation

[0028] The present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] In the description of this application: unless otherwise stated, "a plurality of" means two or more. The terms "first," "second," etc., in this application are intended to distinguish the objects referred to and do not have any special meaning in terms of technical connotation (e.g., they should not be construed as an emphasis on importance or order). Expressions such as "including," "comprising," and "having" also mean "not limited to" (certain units, components, materials, steps, etc.).

[0030] This application provides a wastewater waste heat comprehensive utilization system. This system, through the cooperation of a preheating unit, a wastewater temperature raising unit, and a wastewater waste heat heating unit, transforms the wastewater waste heat from the wastewater treatment plant into a valuable resource, achieving resource recovery and utilization. Simultaneously, it solves the problem of low-temperature operation of the biological treatment tank in winter and meets the heating needs of the plant's buildings. The following detailed description of the wastewater waste heat comprehensive utilization system and its treatment method, with reference to specific embodiments, is provided.

[0031] Example 1

[0032] This embodiment provides a wastewater waste heat comprehensive utilization system. See [link / reference] Figure 1 The system mainly consists of three functional units: a preheating unit, a sewage temperature raising unit, and a sewage waste heat heating unit.

[0033] I. Preheating Unit

[0034] The preheating unit includes a preheater, within which parallel sewage and recycled water pipelines are installed, exchanging heat between the two media. The inlet of the sewage pipeline is connected to the primary sedimentation tank of the sewage treatment plant to receive raw sewage. The inlet of the recycled water pipeline is connected to a reclaimed water tank or a recycled warm water tank within the plant to receive recycled or reclaimed water. The preheater utilizes the heat from the recycled or reclaimed water to preheat the raw sewage.

[0035] In one specific embodiment, raw wastewater (approximately 7°C) is discharged from the primary sedimentation tank and first passes through a filtration device (such as an ultrafine screen) to remove impurities that may clog subsequent heat exchange equipment. The filtered wastewater is then pumped by a first water pump to the wastewater pipeline of the preheater. Simultaneously, reclaimed water (approximately 12°C) from a warm water tank with a higher temperature is pumped by a second water pump to the reclaimed water pipeline of the preheater. Inside the preheater, the two water streams exchange heat indirectly, with the warmer reclaimed water transferring heat to the cooler wastewater, achieving preliminary preheating of the wastewater (to approximately 10°C). This process requires no external energy and is the first stage of energy recovery in the system, reducing the heat load on subsequent heat pump units. The preheated wastewater then enters the wastewater warming unit, while the cooled reclaimed water enters the next stage of waste heat recovery.

[0036] II. Wastewater Heating Unit

[0037] The wastewater warming unit is the core unit for ensuring the effectiveness of biochemical treatment, and mainly includes a wastewater warming heat pump unit. The wastewater warming heat pump unit comprises a first compressor, a first condenser, a first expansion valve, and a first evaporator, which are connected sequentially through pipes to form a refrigerant circulation loop. Specifically: the first condenser has a wastewater inlet and a wastewater outlet. The wastewater inlet is connected to the outlet of the preheater's wastewater pipeline to receive the preheated wastewater, and its outlet is connected to the biological treatment tank to transport the finally heated wastewater to the biochemical treatment stage. The first evaporator has a recycled water inlet and a recycled water outlet. The recycled water inlet is connected to the outlet of the preheater's recycled water pipeline to receive recycled water that has released some heat. Its recycled water outlet is connected to the recycled cold water tank to discharge the thoroughly cooled recycled water. The working principle of this wastewater warming heat pump unit is as follows:

[0038] 1. Heat absorption process: The recycled water (temperature about 9°C) from the preheater and which has been initially cooled enters the first evaporator. In the first evaporator, the low-temperature liquid refrigerant absorbs the residual heat in the recycled water and evaporates into low-temperature, low-pressure steam, thereby further cooling the recycled water before it is discharged into the recycled cold water pool (temperature drops to 7°C).

[0039] 2. Compression and Heat Release Process: The low-temperature, low-pressure refrigerant vapor from the first evaporator is drawn into and compressed by the first compressor, becoming high-temperature, high-pressure vapor, which then enters the first condenser. Inside the first condenser, the high-temperature refrigerant vapor releases heat to the preheated wastewater from the preheater, condensing itself into a high-temperature liquid. The wastewater absorbs heat and its temperature rises to approximately 17°C. The wastewater, heated by the first condenser, is then mixed with the preheated wastewater from the wastewater bypass and discharged into the biological treatment tank to maintain a stable water temperature of 12°C within the tank.

[0040] 3. Throttling process: The high-temperature and high-pressure liquid refrigerant flowing out of the first condenser is throttled and depressurized by the first expansion valve, and becomes a low-temperature and low-pressure gas-liquid mixture again. It returns to the first evaporator to complete one refrigeration cycle and re-enters the next cycle to realize heat transfer.

[0041] Furthermore, considering the difference between the inlet and outlet water temperatures of the condenser in the wastewater warming heat pump unit and the process treatment temperature, this application installs an electric flow regulating valve at the condenser inlet. The opening of the flow regulating valve is controlled by the unit's outlet water temperature to achieve overall system temperature balance. Specifically, a wastewater bypass is configured for the wastewater warming unit, with its two ends connected between the wastewater inlet and outlet of the first condenser, respectively. A valve, preferably an electric regulating valve, is installed on the wastewater bypass. Simultaneously, a mixing pipe section is formed at the end of the wastewater bypass, and the wastewater outlet of the first condenser is connected to the mixing pipe section to ensure uniform mixing.

[0042] To achieve precise control, a temperature sensor is installed inside the biological treatment tank, and this sensor is communicatively connected to a controller. The controller is also communicatively connected to an electric regulating valve. The controller receives the biological treatment tank water temperature signal from the temperature sensor in real time, compares it with an internally preset reference temperature signal (e.g., 12°C), and outputs an opening adjustment control signal to the electric regulating valve based on the comparison result. If the actual temperature is lower than the reference temperature, the controller reduces the opening of the electric regulating valve, allowing more wastewater to flow through the first condenser and be heated. If the actual temperature reaches or exceeds the reference temperature, the controller increases the opening of the electric regulating valve, allowing some wastewater to bypass and pass directly through, avoiding overheating.

[0043] In one specific embodiment, the first condenser can heat wastewater from 10°C to 17°C. However, to maintain the treatment effect of the biological treatment tank, the wastewater temperature in the tank only needs to be stably maintained at 12°C. Heating all the wastewater to 17°C, while ensuring the temperature meets the standard, would result in excessive consumption of thermal energy resources, which does not conform to the principle of energy-saving optimization. Therefore, this application provides a wastewater bypass and an electric regulating valve between the wastewater inlet and outlet of the first condenser. This pipeline structure allows for precise mixing of wastewater that has only undergone preliminary heating in the preheater (e.g., 10°C) with high-temperature wastewater (17°C) that has been deeply heated by the first condenser. By dynamically adjusting the mixing ratio through a controller, the temperature of the mixed wastewater finally entering the biological treatment tank can be precisely stabilized at 12°C.

[0044] Taking a single biological treatment tank as an example, the wastewater to be treated is processed through an ultrafine screen and then pumped to a plate heat exchanger for preheating, assuming a flow rate of 1656 m³ / h and a temperature of 10℃. The preheated wastewater is then divided into two streams: one stream, with a flow rate of 1139.6 m³ / h (10℃), passes through an electric flow regulating valve and directly bypasses the wastewater to the condenser outlet; the other stream, with a flow rate of 516.4 m³ / h, enters the heat pump unit condenser and is heated to 17℃. At the condenser outlet, these two streams of wastewater are mixed again and then jointly transported to the biological tank. This mixing process achieves both thermal and mass balance.

[0045] Heat balance: 516.4 m³ / h × 17℃ + 1139.6 m³ / h × 10℃ = 1656 m³ / h × 12.89℃.

[0046] Mass balance: 516.4 m³ / h + 1113.6 m³ / h = 1656 m³ / h.

[0047] Therefore, in practical applications, the opening degree of the electric flow regulating valve can be controlled by the condenser outlet temperature of the heat pump unit. When the outlet water temperature of the heat pump unit is higher than the set value, the opening degree of the flow regulating valve can be determined by comparing the inlet water temperature and the output heating capacity of the unit, thus realizing intelligent automatic mixing.

[0048] Therefore, the intelligent wastewater mixing operation strategy adopted in this application can maximize the temperature range of wastewater using limited heat. That is, the system does not need to heat all the wastewater flow to the highest temperature, but instead concentrates limited heat energy to heat a portion of the wastewater, and then mixes it to reach the target temperature. This is equivalent to using the same amount of heat energy to heat more wastewater, significantly improving heat utilization efficiency and maximizing system energy efficiency. Simultaneously, it achieves on-demand heating, maximizing energy savings. Furthermore, this closed-loop water temperature control ensures stable water temperature in the biological tank, providing the most suitable environment for nitrifying and denitrifying bacteria and aerobic microorganisms, fundamentally guaranteeing the efficiency and effectiveness of wastewater treatment in winter.

[0049] III. Wastewater Waste Heat Heating Unit

[0050] The wastewater waste heat heating unit is used to recover waste heat from greywater to increase the temperature of the plant's heating return water, thus achieving plant heating. Its core component is a wastewater source heat pump unit, preferably a screw-type wastewater source heat pump unit. This unit includes a second compressor, a second condenser, a second expansion valve, and a second evaporator, which are connected sequentially through pipelines to form a refrigerant circulation loop. Specifically: the second condenser has a heating return water inlet and a heating supply water outlet. The heating return water inlet is connected to the user's heating return water outlet via a pipeline to receive heating return water. The heating supply water outlet is connected to the user's heating water inlet via a pipeline to output heated heating supply water. The second evaporator has a greywater inlet and a greywater outlet. The greywater inlet is connected to a greywater tank via a pipeline to receive greywater from the plant area. The greywater outlet is connected to a recycled cold water tank via a pipeline to discharge the greywater after heat extraction.

[0051] The working principle of this wastewater source heat pump unit is similar to that of a wastewater temperature-raising heat pump unit, including a heat absorption process in the second evaporator, a compression and heat release process in the second compressor and second condenser, and a refrigerant throttling process in the second expansion valve. Specifically: Greywater (approximately 12°C) from the plant's greywater tank is pumped to the second evaporator by a fourth water pump. In the second evaporator, the refrigerant absorbs the residual heat from the greywater and evaporates. The resulting refrigerant vapor is compressed by the second compressor and enters the second condenser. In the second condenser, the high-temperature refrigerant releases heat to the heating return water from the user end (driven by a third water pump, with a heating return water temperature of approximately 37°C). The heated heating return water is then sent to the user end for heating (the heating supply water temperature at the user end is approximately 47°C). The refrigerant, having released heat, returns to the second evaporator after being throttled by the second expansion valve, starting a new cycle. The greywater, having extracted heat, drops to approximately 7°C and is discharged into the reuse cold water tank, serving as a stable cold source for the system.

[0052] Since the preheater and wastewater heating heat pump unit in this system involve the inlet and outlet of raw wastewater, anti-corrosion design was carried out for the preheater and wastewater heating heat pump unit.

[0053] In one specific embodiment, the preheater employs a custom-designed wide-channel plate heat exchanger, primarily comprising a frame made of low-carbon steel, corrugated heat transfer plates machined and die-cast, and system sealing components. To meet corrosion resistance requirements, the heat transfer plates of the plate heat exchanger are made of 316 stainless steel. In practical applications, the preheater can be combined with a skid-mounted container to form a skid-mounted preheater unit. This skid-mounted container has an overall protection rating of at least IP54, providing dustproof, waterproof, rustproof, corrosion-resistant, and thermal insulation properties.

[0054] The heat exchange tubes of the wastewater temperature-raising heat pump unit in this application are made of acid and alkali resistant B10 tubes, the tube sheet is made of 316L stainless steel composite tube sheet, and the water chamber is made of 316L stainless steel.

[0055] In one specific embodiment, the evaporator of the wastewater warming heat pump unit is a falling film shell-and-tube low-temperature acid and alkali corrosion resistant evaporator. The heat exchange tubes in the evaporator are made of acid and alkali corrosion resistant BO4 material or higher, the tube sheet of the evaporator is made of acid and alkali corrosion resistant lining material or 316L stainless steel, and the water chamber is made of 316L stainless steel. Similarly, the condenser of the wastewater warming heat pump unit is an acid and alkali corrosion resistant wastewater shell-and-tube condenser. The heat exchange tubes are made of acid and alkali corrosion resistant BO4 material or higher, the tube sheet is made of acid and alkali corrosion resistant lining material or 316L stainless steel, and the water chamber is made of 316L stainless steel. The refrigerant used in the unit is environmentally friendly refrigerant R134A. The compressor is a customized large-capacity, low-pressure-ratio centrifugal compressor with an energy efficiency ratio of over 13.

[0056] Overall, the wastewater waste heat utilization system provided in this application can bring the following technical effects:

[0057] 1. Significantly improves wastewater treatment efficiency and stability: Through precise and stable heat compensation, the problem of inhibited microbial activity caused by low wastewater temperature in northern winters is completely solved, ensuring the efficient operation of the biological system (especially the nitrification / denitrification process) and guaranteeing that the effluent quality meets the standards stably.

[0058] 2. High energy efficiency and energy saving: The system realizes the cascade utilization of energy. For example, the preheating unit first recovers the waste heat from the sewage, and then the heat pump unit realizes secondary recovery. In addition, the main energy input of this system is electricity, but compared with the traditional gas boiler heating and municipal heating scheme, this application can achieve energy saving and energy saving through heat pump technology and waste heat recovery.

[0059] 3. Low operating costs and outstanding economic benefits: This application makes full use of the plant's existing recycled water and greywater as heat sources, eliminating the need to rely on expensive fossil fuels or municipal heating, reducing dependence on external energy sources and significantly lowering operating costs.

[0060] 4. Clean, environmentally friendly, and low-carbon emission reduction: The heating and warming process of this system involves no combustion and no exhaust emissions, making it cleaner and more environmentally friendly than traditional gas boiler heating solutions, achieving near-zero carbon emission heating.

[0061] 5. This system integrates two major functions: sewage heating and user heating. It also achieves unattended operation and optimized operation through an automatic control system, which improves management efficiency and reduces labor costs.

[0062] Therefore, the wastewater waste heat utilization system provided in this application is not only a waste heat recovery system, but also a comprehensive solution that can simultaneously improve wastewater treatment efficiency, reduce overall energy consumption, and create economic and environmental benefits.

[0063] Example 2

[0064] Based on the wastewater waste heat comprehensive utilization system provided in Embodiment 1 above, this embodiment provides a wastewater waste heat comprehensive treatment method based on the wastewater waste heat comprehensive utilization system. The treatment method includes a wastewater temperature raising method and a wastewater waste heat heating method.

[0065] I. The wastewater heating method includes the following steps:

[0066] First, the recycled water from the reused warm water tank and the raw sewage from the primary sedimentation tank are sent to the preheater for heat exchange to preheat the raw sewage. Then, the preheated raw sewage is sent to the first condenser of the sewage heating heat pump unit, and the recycled water discharged from the preheater is sent to the first evaporator. The refrigerant is circulated through the sewage heating heat pump unit to recover the waste heat carried by the recycled water and use it to heat the raw sewage. The heated raw sewage is then sent to the biological tank.

[0067] To achieve on-demand heating and maximize energy savings, a wastewater bypass can be installed between the wastewater inlet and outlet of the first condenser. An electric regulating valve is installed on the bypass, and a temperature sensor is placed inside the biological treatment tank. Both the temperature sensor and the electric regulating valve are communicatively connected to a controller. The controller receives the biological treatment tank water temperature signal from the temperature sensor in real time, compares it with an internally preset reference temperature signal (e.g., 12°C), and outputs an opening adjustment control signal to the electric regulating valve based on the comparison result. If the actual temperature is lower than the reference temperature, the controller reduces the opening of the electric regulating valve, allowing more wastewater to flow through the first condenser and be heated. If the actual temperature reaches or exceeds the reference temperature, the controller increases the opening of the electric regulating valve, allowing some wastewater to pass directly through the bypass, avoiding overheating.

[0068] II. Wastewater waste heat heating method includes the following steps:

[0069] The greywater from the greywater tank is sent to the second evaporator of the sewage source heat pump unit, and the heating return water discharged from the user end is sent to the second condenser. The refrigerant is circulated through the sewage source heat pump unit to recover the waste heat carried by the greywater and use it to heat exchange and raise the temperature of the heating return water. The heated heating return water is then sent to the heating water inlet at the user end.

[0070] Compared with traditional wastewater heating solutions, this application utilizes the waste heat from recycled water and greywater within the plant, achieving a fundamental shift from "consuming fossil fuels" to "recovering our own energy." This significantly reduces operating costs, provides substantial environmental benefits, and the heat pump's energy efficiency ratio is far higher than that of a boiler, resulting in high energy utilization efficiency.

[0071] Furthermore, compared with the wastewater heating system provided by Chinese invention patent CN119958142A, this application differs fundamentally from the wastewater heating route described therein. The specific analysis is as follows: CN119958142A uses greywater as the low-grade heat source of the water source heat pump. In the greywater heat exchanger, it exchanges heat with cold intermediate water, releasing waste heat. The cold intermediate water is then sent to the evaporator to transfer heat to the heat pump refrigerant. The refrigerant condenses and releases heat after passing through a throttling valve, forming hot intermediate water. This hot intermediate water is then pumped from the condenser to the wastewater heat exchanger via a circulating pump, exchanging heat with the raw water to raise its temperature to above 12°C. The heated raw water is then returned to the fine-grinding tank and discharged into the biological treatment pond. Therefore, this technical solution recovers the waste heat of treated greywater through a heat pump unit and uses refrigerant to transfer heat, directly heating raw wastewater from 8°C to above 12°C. The wastewater heating route in this application includes wastewater preheating followed by wastewater heating. Before the wastewater enters the heat pump, it is heated by heat exchange using existing, higher-temperature recycled water within the plant. This initial heating process does not consume electricity. Because the preheating unit undertakes part of the heating task, the total heat load of the entire system is split, which significantly reduces the initial load of the subsequent wastewater heating heat pump unit (because the heat pump only needs to raise the wastewater from 10°C to 12°C, instead of from 7°C to 12°C; the heating range is smaller, the required work is reduced, and the power consumption is significantly lower). While achieving the same heating effect, this application can select a smaller capacity, lower-cost heat pump model, reducing the initial investment cost of the system. Therefore, this "free preheating + high-efficiency heat pump heating" tiered heating combination scheme provided by this application can significantly improve energy efficiency and reduce operating costs. Furthermore, this application incorporates wastewater bypasses at the condenser inlet and outlet of the wastewater heating heat pump unit, along with electrically operated regulating valves, constructing a "sewage heating intelligent mixing strategy." By adjusting the opening of the electrically operated regulating valves, the mixing ratio of high-temperature and low-temperature water can be precisely controlled, thereby providing the biological treatment tank with an extremely stable 12°C influent. Moreover, this "sewage heating intelligent mixing strategy" gives the system strong adaptability, enabling it to accommodate changes in wastewater flow or temperature. Therefore, compared to CN119958142A, this application offers significant advantages in energy efficiency, operating costs, temperature control, and resistance to load shocks through free preheating at the heat pump front end and precise mixing at the back end, reducing energy consumption. Furthermore, this system can also achieve wastewater heating combined with wastewater waste heat heating, not only meeting the wastewater treatment needs in winter but also simultaneously satisfying the heating requirements of the plant area during winter, maximizing the utilization of wastewater waste heat resources and achieving energy conservation and consumption reduction.

[0072] Furthermore, compared with the wastewater waste heat recovery device disclosed in Chinese invention patent CN102927685A (which recovers treated wastewater at 20-30°C) and the automatic waste heat recovery system for heating disclosed in Chinese invention patent CN102287861A (which recovers steam condensate at 70-90°C), this application is applicable to the wastewater waste heat recovery and utilization of wastewater treatment plants in northern winters. It uses recycled water and greywater at 12°C as the heat source for the heat pump, realizing the reuse of its own energy according to local conditions. The heat source is stable and not directly affected by the external climate, avoiding the problem of heat pump efficiency reduction in winter. In addition, this application performs preliminary preheating of wastewater before it enters the heat pump, realizing multi-stage energy utilization, and achieves on-demand heating through intelligent control, so that the comprehensive energy efficiency ratio of the system reaches the highest level and the overall energy efficiency of the system is improved. Furthermore, this application addresses both the "process temperature increase" and "plant area heating" requirements through a single system, ensuring the stability and efficiency of the core processes of the wastewater treatment plant while reducing the economic cost of plant area heating, thus supporting the low-carbon and zero-carbon construction of wastewater treatment plants in northern regions.

[0073] The technical features of the above embodiments can be combined in any way (as long as there is no contradiction in the combination of these technical features). For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described; these embodiments not explicitly written should also be considered to be within the scope of this specification.

[0074] The present application has been described in a relatively specific and detailed manner above through general descriptions and specific embodiments. It should be understood that, based on the technical concept of the present application, several conventional adjustments or further innovations can be made to these specific embodiments; however, as long as they do not depart from the technical concept of the present application, the technical solutions obtained by these conventional adjustments or further innovations also fall within the protection scope of the claims of the present application.

Claims

1. A wastewater waste heat comprehensive utilization system, characterized in that, include: The preheating unit includes a preheater, which is equipped with a sewage pipeline and a recycled water pipeline. The inlet end of the sewage pipeline is connected to the primary sedimentation tank, and the inlet end of the recycled water pipeline is connected to the recycled warm water tank. The preheater is used to realize heat exchange and temperature increase of the sewage by the recycled water. The wastewater heating unit includes a wastewater heating heat pump unit, which comprises a first compressor, a first condenser, a first expansion valve, and a first evaporator connected in sequence. The first condenser has a wastewater inlet and a wastewater outlet. The wastewater inlet is connected to the outlet end of the wastewater pipeline, and the wastewater outlet is connected to a biological tank. The first evaporator has a recycled water inlet and a recycled water outlet. The recycled water inlet is connected to the outlet end of the recycled water pipeline, and the recycled water outlet is connected to a recycled cold water tank. The wastewater waste heat heating unit includes a wastewater source heat pump unit, which includes a second compressor, a second condenser, a second expansion valve, and a second evaporator connected in sequence. The second condenser has a heating return water inlet and a heating supply water outlet. The heating return water inlet is connected to the user's heating return water outlet, and the heating supply water outlet is connected to the user's heating water inlet. The second evaporator has a greywater inlet and a greywater outlet. The greywater inlet is connected to a greywater tank, and the greywater outlet is connected to a reused cold water tank.

2. The wastewater waste heat comprehensive utilization system according to claim 1, characterized in that, The wastewater heating unit also includes a wastewater bypass located between the wastewater inlet and the wastewater outlet of the first condenser. A regulating valve is installed on the wastewater bypass, and a mixing pipe section is formed at the end of the wastewater bypass. The wastewater outlet of the first condenser is connected to the mixing pipe section to ensure uniform mixing.

3. The wastewater waste heat comprehensive utilization system according to claim 2, characterized in that, The regulating valve is an electric regulating valve, and the electric regulating valve is communicatively connected to the controller; A temperature sensor is installed in the biological tank. The temperature sensor is communicatively connected to the controller. The controller is configured to compare the temperature signal obtained from the temperature sensor with a reference temperature signal, and output an opening adjustment control signal to the electric regulating valve based on the comparison result.

4. The wastewater waste heat comprehensive utilization system according to claim 1 or 3, characterized in that, The wastewater heating heat pump unit is used to recover the waste heat carried by the recycled water discharged from the preheater through refrigerant circulation, and to heat the wastewater sent into the first condenser. The refrigerant outlet of the first compressor is connected to the refrigerant inlet of the first condenser, and the first compressor is used to send the compressed and heated refrigerant into the first condenser. The refrigerant outlet of the first condenser is connected to the refrigerant inlet of the first expansion valve. The first condenser is used to exchange heat between the heated refrigerant and the sewage flowing into it, thereby raising the temperature of the sewage. The refrigerant outlet of the first expansion valve is connected to the refrigerant inlet of the first evaporator. The first expansion valve is used to throttle and reduce the pressure of the refrigerant after heat exchange and cooling. The refrigerant outlet of the first evaporator is connected to the refrigerant inlet of the first compressor. The first evaporator is used to exchange heat between the reclaimed water discharged from the preheater and the refrigerant in order to recover the waste heat carried by the reclaimed water discharged from the preheater.

5. The wastewater waste heat comprehensive utilization system according to claim 1 or 3, characterized in that, The wastewater source heat pump unit is used to recover the waste heat carried by the greywater discharged from the greywater tank through refrigerant circulation, and to exchange heat and raise the temperature of the heating return water sent into the second condenser. The refrigerant outlet of the second compressor is connected to the refrigerant inlet of the second condenser, and the second compressor is used to send the compressed and heated refrigerant into the second condenser; The refrigerant outlet of the second condenser is connected to the refrigerant inlet of the second expansion valve. The second condenser is used to exchange heat between the heated refrigerant and the heating return water flowing into it, thereby raising the temperature of the heating return water. The refrigerant outlet of the second expansion valve is connected to the refrigerant inlet of the second evaporator. The second expansion valve is used to throttle and reduce the pressure of the refrigerant after heat exchange and cooling. The refrigerant outlet of the second evaporator is connected to the refrigerant inlet of the second compressor. The second evaporator is used to exchange heat between the greywater discharged from the greywater pool and the refrigerant in order to recover the waste heat carried by the greywater.

6. The wastewater waste heat comprehensive utilization system according to claim 5, characterized in that, The user-end heating return water outlet is connected to the heating return water inlet via a third water pump; the greywater outlet of the greywater tank is connected to the greywater inlet of the second evaporator via a fourth water pump.

7. The wastewater waste heat comprehensive utilization system according to claim 1, characterized in that, The primary sedimentation tank's raw wastewater outlet is connected to a filtration device, and the filtration device's outlet is connected to the inlet of the wastewater pipeline via a first water pump. The recycled water outlet of the recycled hot water tank is connected to the inlet of the recycled water pipeline via a second water pump.

8. A treatment method based on the wastewater waste heat comprehensive utilization system according to claim 1, characterized in that, Includes the following steps: S1: Raw wastewater preheating: The recycled water from the reuse warm water tank and the raw wastewater from the primary sedimentation tank are sent into the preheater for heat exchange to achieve raw wastewater preheating. S2: Raw sewage is heated by sending the preheated raw sewage into the first condenser of the sewage heating heat pump unit, and the recycled water discharged from the preheater is sent into the first evaporator. The refrigerant is circulated through the sewage heating heat pump unit to recover the waste heat carried by the recycled water and use it to heat the raw sewage. The heated raw sewage is then sent into the biological tank. S3: Wastewater waste heat heating. The greywater in the greywater tank is sent to the second evaporator of the wastewater source heat pump unit, and the heating return water discharged from the user end is sent to the second condenser. The refrigerant is circulated through the wastewater source heat pump unit to recover the waste heat carried by the greywater and use it to heat exchange and raise the temperature of the heating return water. The heated heating return water is then sent to the heating water inlet at the user end.

9. The treatment method based on the wastewater waste heat comprehensive utilization system according to claim 8, characterized in that, In step S2, a wastewater bypass is set between the wastewater inlet and wastewater outlet of the first condenser of the wastewater temperature-raising heat pump unit, an electric regulating valve is set on the wastewater bypass, and the electric regulating valve is communicatively connected to the controller; and a temperature sensor communicatively connected to the controller is set in the biological tank. The controller obtains the real-time temperature value of the wastewater in the biological tank through the temperature sensor, and compares the real-time temperature value with the reference temperature value. If the real-time temperature value is less than the reference temperature value, the controller controls the electric regulating valve to increase the opening degree.

Images