A control method and system using combined sewage and circulating water waste heat

Abstract

The present application relates to the technical field of combined sewage and circulating water waste heat utilization, and is a control method and system for utilizing combined sewage and circulating water waste heat. The present application comprises: detecting the flow and temperature of combined sewage in real time, and calculating the waste heat quantity coefficient of combined sewage according to the detection data; judging the waste heat quantity state of combined sewage according to the calculation result of the waste heat quantity coefficient of combined sewage; when determining that the waste heat quantity state of combined sewage is a lower state, performing secondary recovery on combined sewage and performing tertiary heating on heating return water; and when determining that the waste heat quantity state of combined sewage is a higher state, performing recovery on combined sewage and performing secondary heating on heating return water. The present application introduces the waste heat quantity coefficient of combined sewage, judges whether to utilize an intermediate heat exchanger for secondary recovery of combined sewage waste heat, ensures that heating return water reaches a heating demand temperature, solves the problem of the impact of industrial waste heat source parameter fluctuation on a waste heat utilization system, and improves the operation stability and reliability of a waste heat heating system.

Description

Technical Field

[0001] This invention relates to the field of wastewater discharge and waste heat utilization technology, and in particular to a control method and system for utilizing wastewater discharge and waste heat from circulating water. Background Technology

[0002] During operation, industrial boilers continuously evaporate and concentrate the water inside. If this water is not discharged, it will affect the boiler water quality and heat transfer efficiency. The wastewater is a complex mixture of water from scheduled blowdown, continuous blowdown, condensate, and emergency drainage. Its main components are impurities such as sludge, scale, and mud, with high pH, ​​salinity, alkalinity, and iron content. Most energy plants treat this wastewater before discharging it, releasing it as secondary steam, resulting in resource waste. This water can be used directly, or treated through sedimentation and filtration to supplement other water sources within the plant, or used to recover heat by adding energy recovery devices. Continuous blowdown accounts for the largest proportion of the wastewater, generally controlled below 5%. Due to the high temperature of continuous blowdown wastewater, it is usually first discharged into a continuous blowdown expansion tank. Since the expansion tank is usually connected to a deaerator, its pressure is lower than the steam drum pressure, causing a small portion of the wastewater to vaporize. The majority of the unvaporized wastewater cools to its saturation temperature under the continuous expansion tank pressure before being discharged into a scheduled blowdown expansion tank and then emptied. This results in a significant waste of heat and water, and also causes severe thermal pollution to the environment.

[0003] To address the above issues, research on waste heat recovery and utilization technologies for boiler wastewater has been conducted both domestically and internationally. However, the flow rate and temperature of boiler wastewater fluctuate significantly. Factors such as changes in boiler load, unstable boiler water quality, and inaccurate boiler control system adjustments can all affect the flow rate of the wastewater. Furthermore, changes in boiler load, boiler combustion efficiency, and ambient temperature can also affect the temperature of the wastewater.

[0004] Utility model patent CN221198133U discloses a boiler wastewater waste heat recovery system. This patent recovers waste heat from boiler blowdown and continuous blowdown wastewater for heating the liquid in the gas seal system. However, it does not consider the impact of continuous blowdown flow rate and temperature changes on the waste heat recovery system, nor does it propose a corresponding solution.

[0005] Utility model patent CN220817724U discloses a boiler wastewater waste heat recovery system, which uses continuous and scheduled wastewater collected in a water storage tank to provide a heat source for a lithium bromide unit. However, the temperature of the scheduled wastewater is relatively low, which results in a low COP index when used as a driving heat source for the lithium bromide unit, leading to low waste heat recovery efficiency.

[0006] Invention patent application CN109210523A discloses a boiler wastewater waste heat recovery system. In this invention, the wastewater is flash-evaporated in an expansion tank, and the flash-evaporated steam enters the deaerator. The remaining wastewater is heated to make up for the water. However, the wastewater still has a high temperature after flash evaporation, which leads to the problem of high energy underutilization of waste heat.

[0007] In summary, existing systems and control methods for utilizing waste heat from continuous sewage discharge and circulating water still have some problems. These mainly lie in the low efficiency of waste heat utilization and the failure to consider the impact of changes in sewage flow rate and temperature on the waste heat recovery system. Therefore, it is essential to explore more practical and effective systems and control methods for utilizing waste heat from continuous sewage discharge and circulating water. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention provides a control method and system for utilizing waste heat from continuous sewage discharge and circulating water. The invention primarily introduces a waste heat coefficient for continuous sewage discharge to determine whether an intermediate heat exchanger is needed for secondary recovery of waste heat from the discharge, ensuring that the return water reaches the required temperature for general heating. This solves the problem of fluctuations in industrial waste heat source parameters impacting the waste heat utilization system, and improves the operational stability and reliability of the waste heat heating system.

[0009] The technical means employed in this invention are as follows: A control method utilizing wastewater discharge and waste heat from circulating water includes: The flow rate and temperature of the continuously discharged wastewater are monitored in real time, and the residual heat coefficient of the continuously discharged wastewater is calculated based on the monitoring data. The residual heat status of the continuously discharged wastewater is determined based on the calculation results of the residual heat coefficient. When the residual heat status of the continuous sewage is determined to be low, the continuous sewage is recycled a second time and the heating return water is heated a third time. When the residual heat of the continuously discharged sewage is determined to be at a high level, the continuously discharged sewage is recycled and the heating return water is reheated.

[0010] Furthermore, the residual heat coefficient of the continuously discharged wastewater is calculated. :

[0011] in, This represents the mass proportion of unvaporized wastewater in the continuous discharge expansion tank. The sewage discharge rate is the continuous discharge rate. The initial temperature of the continuously discharged sewage. The temperature after the continuous discharge of sewage drives the lithium bromide absorption heat pump unit.

[0012] Furthermore, the equilibrium point is determined using the residual heat coefficient of the continuously discharged wastewater. Determine the residual heat status of continuously discharged wastewater; when the residual heat coefficient of continuously discharged wastewater... When the wastewater discharge coefficient is low, it is determined that the residual heat of the wastewater is in a low state; when the residual heat coefficient of the wastewater discharge is low... At that time, it was determined that the residual heat of the continuously discharged sewage was at a high level.

[0013] Furthermore, the step of performing secondary recovery of the wastewater and tertiary heating of the heating return water when the residual heat state of the continuously discharged wastewater is determined to be low specifically includes: When the waste heat of the continuous sewage is determined to be at a low level, the continuous sewage is used as the driving heat source of the lithium bromide absorption heat pump unit to heat the absorbent in the generator, thereby achieving the primary recovery of waste heat from the sewage. After the primary recovery is completed, the waste heat is reheated in the intermediate heat exchanger to achieve the secondary recovery of waste heat from the continuous sewage. After the secondary recovery is completed, the waste heat is entered into the fixed discharge expansion tank and treated together with the fixed discharge sewage. The heating return water enters the absorber through the heating water inlet of the lithium bromide absorption heat pump unit to cool the absorbent, achieving primary heating of the heating return water. After primary heating, the heating return water enters the intermediate heat exchanger to exchange heat with the wastewater, achieving secondary heating of the heating return water. After secondary heating, the heating return water enters the condenser to absorb heat, achieving tertiary heating of the heating return water. The heating return water that has undergone tertiary heating enters the heating users' homes to meet their heating needs. The return water that has cooled down after heating is then circulated back into the system for heating.

[0014] Furthermore, when the residual heat state of the continuously discharged wastewater is determined to be high, the continuously discharged wastewater is recycled, and the heating return water is reheated, specifically including: When the waste heat of the continuous sewage is determined to be at a high level, the continuous sewage is used as the driving heat source of the lithium bromide absorption heat pump unit to enter the generator to heat the absorbent, thereby realizing the recovery of waste heat from the sewage. After the recovery is completed, it enters the fixed discharge expansion tank and is treated together with the fixed discharge sewage. The heating return water enters the absorber through the heating water inlet of the lithium bromide absorption heat pump unit to cool the absorbent, achieving primary heating of the heating return water. After primary heating, the heating return water enters the condenser to absorb heat, achieving secondary heating of the heating return water. The secondary heated heating water flows out from the heating water outlet of the lithium bromide absorption heat pump unit and enters the heating users' homes to meet their heating needs. The returned water that has cooled down after heating is recirculated into the system for heating again.

[0015] This invention also provides a control system for utilizing the waste heat from continuous sewage discharge and circulating water, based on a control method for utilizing the waste heat from continuous sewage discharge and circulating water. The system includes: a continuous sewage discharge expansion tank, a lithium bromide absorption heat pump unit, an intermediate heat exchanger, and a stationary sewage discharge expansion tank, wherein: The inlet of the continuous expansion tank is equipped with a mass flow detection device, and the outlet is connected to a lithium bromide absorption heat pump unit. A temperature detection device is installed between the continuous expansion tank and the lithium bromide absorption heat pump unit. The lithium bromide absorption heat pump unit includes a generator, an absorber, a condenser, and an evaporator. One end of the generator is connected to a continuous expansion tank, and the other end is connected to an intermediate heat exchanger. One end of the absorber is a heating water inlet, and the other end is connected to the intermediate heat exchanger and the condenser. The outlet of the condenser is connected to the heating user. One end of the evaporator is a circulating cooling water inlet, which recovers the low-temperature waste heat of the circulating cooling water and re-enters the generator unit's circulating cooling water system through the outlet. The outlet of the intermediate heat exchanger is connected to a continuous expansion tank.

[0016] Compared with the prior art, the present invention has the following advantages: The present invention provides a control method and system for utilizing waste heat from continuous sewage discharge and circulating water. By introducing a waste heat coefficient for continuous sewage discharge, the high and low states of waste heat from continuous sewage discharge are calculated to determine whether to use an intermediate heat exchanger to achieve secondary recovery of waste heat from continuous sewage discharge. This ensures that the return water for heating reaches the general heating demand temperature, avoids the impact of sewage discharge rate and temperature fluctuations on the waste heat utilization system, and improves the operational stability and reliability of the heating system utilizing waste heat from continuous sewage discharge and circulating water. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the control system structure for utilizing continuous sewage discharge and waste heat from circulating water in this invention.

[0019] In the diagram: 1. Continuous discharge expansion tank; 2. Lithium bromide absorption heat pump unit; 21. Generator; 22. Absorber; 23. Condenser; 24. Evaporator; 3. Intermediate heat exchanger; 4. Heating user; 5. Mass flow detection device; 6. Temperature detection device; 7. Fixed discharge expansion tank; 8. Switch valve. Detailed Implementation

[0020] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0023] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0024] like Figure 1 As shown, the present invention provides a control method utilizing continuous wastewater discharge and waste heat from circulating water, comprising: The flow rate and temperature of the continuously discharged wastewater are monitored in real time, and the residual heat coefficient of the wastewater is calculated based on the monitoring data. In a preferred embodiment of the present invention, the residual heat coefficient of the continuously discharged wastewater is calculated. :

[0025] in, The mass ratio of unvaporized wastewater in the continuous discharge expansion tank ranges from 0.8 to 0.9. The sewage discharge rate is 3% to 5%; The initial temperature of the continuously discharged wastewater ranges from 90℃ to 100℃. The temperature after the continuous discharge of wastewater drives the lithium bromide absorption heat pump unit is in the range of 70℃~80℃.

[0026] The residual heat status of the continuously discharged wastewater is determined based on the calculation result of the residual heat coefficient. Specifically, in a preferred embodiment of the invention, the residual heat coefficient of the continuously discharged wastewater is used to determine the equilibrium point. Determine the residual heat status of continuously discharged wastewater; when the residual heat coefficient of continuously discharged wastewater... When the wastewater discharge coefficient is low, it is determined that the residual heat of the wastewater is in a low state; when the residual heat coefficient of the wastewater discharge is low... At that time, it was determined that the residual heat of the continuously discharged sewage was at a high level.

[0027] In implementation, , , , As the equilibrium point, the residual heat coefficient of the continuously discharged wastewater at the equilibrium point is calculated as follows: .

[0028] When the wastewater is determined to be at a low level, it undergoes secondary recovery, and the return water is heated tertiarily. Specifically, in a preferred embodiment of this invention, when the wastewater is determined to be at a low level, it is used as the driving heat source for the lithium bromide absorption heat pump unit 2, entering the generator 21 to heat the absorbent, thus achieving primary recovery of the wastewater's waste heat. After primary recovery, the wastewater temperature drops to 70℃~75℃. The high salt content in the wastewater corrodes the turbine in the steam-water circulation, but has little impact on the lithium bromide unit operating under medium and low pressure conditions, allowing for direct heat exchange between the wastewater and the absorbent, achieving primary recovery of the wastewater's waste heat. After primary recovery, the wastewater enters the intermediate heat exchanger 3 to reheat the return water, achieving secondary recovery of the wastewater's waste heat. After secondary recovery, the wastewater temperature drops to 60℃~65℃. After secondary recovery, the wastewater enters the fixed discharge expansion tank 7 for treatment together with the fixed discharge wastewater. The heating return water enters the absorber 22 through the heating water inlet of the lithium bromide absorption heat pump unit 2 to cool the absorbent, achieving primary heating of the heating return water. After primary heating, the heating return water can be heated by 8℃ to 12℃. After primary heating, the heating return water enters the intermediate heat exchanger 3 to exchange heat with the wastewater, achieving secondary heating of the heating return water. After secondary heating, the heating return water can be heated by 3℃ to 8℃. After secondary heating, the heating return water enters the condenser 23 to absorb heat, achieving tertiary heating of the heating return water. After tertiary heating, the heating return water can be heated by 6℃ to 10℃. The heating return water that has undergone tertiary heating enters the heating user 4 to meet the heating demand. The return water that has cooled down after heating is recirculated into the system for heating again.

[0029] The generator set's circulating cooling water, typically at 25°C to 35°C, is usually cooled by about 5°C via a cooling tower before re-entering the circulating water system to cool the generator set. In this invention, a portion of the circulating cooling water is extracted before entering the cooling tower and used as a low-temperature waste heat coolant in the evaporator of the lithium bromide absorption heat pump unit. This recovers some of the low-temperature waste heat from the circulating cooling water, which is then cooled by about 5°C before re-entering the generator set's circulating cooling water system.

[0030] When the wastewater discharge is determined to be at a high level, the wastewater is recycled, and the heating return water is reheated. In a preferred embodiment of the invention, when the wastewater discharge is determined to be at a high level, the wastewater is used as the driving heat source of the lithium bromide absorption heat pump unit 2 and enters the generator 21 to heat the absorbent, thereby realizing the recovery of wastewater heat. After recovery, the temperature of the wastewater drops to 75℃~80℃. After the recovery is completed, it enters the fixed discharge expansion tank 7 and is treated together with the fixed discharge wastewater. The heating return water enters the absorber 22 through the heating water inlet of the lithium bromide absorption heat pump unit 2 to cool the absorbent, achieving primary heating of the heating return water. After primary heating, the heating return water can be heated by 11℃~16℃. After primary heating, the heating return water enters the condenser 23 to absorb heat, achieving secondary heating of the heating return water. After secondary heating, the heating return water can be heated by about 9℃~13℃, reaching the general heating requirement of 65℃. The heating water that has undergone secondary heating flows out from the heating water outlet of the lithium bromide absorption heat pump unit 2 and enters the heating user 4 to meet the heating demand. The return water that has cooled down after heating is recirculated into the system for heating.

[0031] Before entering the cooling tower, a portion of the circulating cooling water at around 25℃ to 35℃ is extracted and used as a low-temperature waste heat to enter the evaporator cooling medium of the lithium bromide absorption heat pump unit, thus recovering part of the low-temperature waste heat of the circulating cooling water. Generally, after cooling down by about 5℃, it re-enters the circulating cooling water system of the generator unit.

[0032] The above systems and control methods can ensure that the return water is heated to about 65°C or higher, which is the general heating temperature requirement. This avoids the impact of the sewage discharge rate and sewage temperature on the waste heat utilization system and improves the operational stability of the sewage waste heat utilization system.

[0033] This invention also provides a control system for utilizing the waste heat from continuous sewage discharge and circulating water, based on a control method for utilizing the waste heat from continuous sewage discharge and circulating water. The system includes: a continuous sewage discharge expansion tank 1, a lithium bromide absorption heat pump unit 2, an intermediate heat exchanger 3, and a fixed discharge expansion tank 7, wherein: The inlet of the continuous expansion tank 1 is equipped with a mass flow detection device 5, and the outlet is connected to a lithium bromide absorption heat pump unit 2. A temperature detection device 6 is installed between the continuous expansion tank 1 and the lithium bromide absorption heat pump unit 2. The lithium bromide absorption heat pump unit 2 includes a generator 21, an absorber 22, a condenser 23, and an evaporator 24. One end of the generator 21 is connected to the continuous discharge expansion tank 1, and the other end is connected to the intermediate heat exchanger 3. One end of the absorber 22 is a heating water inlet, and the other end is connected to the intermediate heat exchanger 3 and the condenser 23. The outlet of the condenser 23 is connected to the heating user 4. One end of the evaporator 24 is a circulating cooling water inlet, which recovers the low-temperature waste heat of the circulating cooling water and re-enters the generator unit's circulating cooling water system through the outlet. The outlet of the intermediate heat exchanger 3 is connected to the continuous discharge expansion tank 7.

[0034] The boiler continuous wastewater is connected to the inlet of the mass flow rate detection device 5, and the outlet of the mass flow rate detection device 5 is connected to the inlet of the continuous discharge expansion tank 1. The mass flow rate detection device 5 is located before the continuous discharge expansion tank 1 because the wastewater entering the continuous discharge expansion tank is liquid, which facilitates detection. The wastewater outlet of the continuous discharge expansion tank 1 is connected to the inlet of the generator 21 in the lithium bromide absorption heat pump unit 2 through the temperature detection device 6. The wastewater outlet of the generator 21 is connected to the wastewater inlet of the intermediate heat exchanger 3 and the inlet of the fixed discharge expansion tank 7 through switch valves. The wastewater outlet of the intermediate heat exchanger 3 is also connected to the inlet of the fixed discharge expansion tank 7.

[0035] The heating return water first enters through the primary inlet of the absorber 22 in the lithium bromide absorption heat pump unit 2. The heating return water outlet of the absorber 22 is connected to the heating return water inlet of the intermediate heat exchanger 3 and the secondary inlet of the condenser 23 through switch valves. The heating return water outlet of the intermediate heat exchanger 3 is also connected to the secondary inlet of the condenser 23 through switch valves. The heating return water outlet of the condenser 23 is connected to the heating user 4.

[0036] The generator set's circulating cooling water enters through the inlet of evaporator 24 in the lithium bromide absorption heat pump unit and flows out from the outlet of evaporator 24 into the generator set's cooling water circulation system.

[0037] The blowdown rate of boiler continuous wastewater is generally less than 5%, defined as the ratio of wastewater mass flow rate to the boiler's designed steam output. When the boiler equipment is fixed, the blowdown rate can be calculated by monitoring the continuous wastewater mass flow rate. In reality, the blowdown rate of many boilers fluctuates between 3% and 5%, resulting in significant fluctuations in wastewater flow rate. The wastewater first enters the continuous wastewater expansion tank 1. Due to the low pressure within the expansion tank 1, 10% to 30% of the wastewater vaporizes. This vaporized wastewater is typically treated and then used as makeup water in the boiler system's deaerator. The remaining 70% to 90% of the unvaporized wastewater exits from the continuous wastewater expansion tank 1, with a temperature generally fluctuating between 90℃ and 100℃. These fluctuations impact the wastewater waste heat recovery system.

[0038] Example 1 This embodiment focuses on the continuous blowdown of a 350t / h boiler. Mass flow rate detection device 5 and temperature detection device 6 are used to measure and detect the blowdown flow rate and temperature in real time. The measured blowdown flow rate is 10.5t / h, and the blowdown rate of the 350t / h boiler is calculated to be 3.0%. The measured blowdown temperature at the outlet of the continuous blowdown expansion tank 1 is 90℃, the mass ratio of unvaporized wastewater is 0.8, and the flow rate is 8.4t / h. The temperature after the continuous blowdown drives the lithium bromide absorption heat pump unit 2 is set to 70℃. Using the formula for the waste heat coefficient of continuous blowdown, the waste heat coefficient is calculated to be 0.48, which is lower than the equilibrium point of 0.64 for the waste heat coefficient of continuous blowdown, indicating that the waste heat of the continuous blowdown is in a low state.

[0039] In this state, valves 82, 83, and 85 are open, while valves 81 and 84 are closed. The 8.4 t / h 90°C wastewater serves as the driving heat source for the lithium bromide absorption heat pump unit 2, entering the generator 21 for direct heat exchange with the absorbent, achieving primary recovery of wastewater heat. After heating the absorbent, the 8.4 t / h wastewater reaches a temperature of 70°C and exits from the wastewater outlet of the lithium bromide absorption heat pump unit 2. It then enters the intermediate heat exchanger 3 via valve 82 to reheat the return water, achieving secondary recovery of wastewater heat. After heating the return water, the 8.4 t / h wastewater reaches a temperature of 60°C and enters the fixed discharge expansion tank 7 through the wastewater outlet of the intermediate heat exchanger 3 for treatment together with the fixed discharge wastewater.

[0040] 20t / h of 45℃ heating return water enters the absorber 22 through the heating water inlet of the lithium bromide absorption heat pump unit 2 to cool the absorbent, achieving primary heating of the heating return water to a temperature of 53.4℃. Then, after primary heating, the heating return water enters the intermediate heat exchanger 3 through the switch valve 83 to exchange heat with 8.4t / h of 70℃ wastewater, achieving secondary heating of the heating return water to a temperature of 57.6℃. Finally, the heating return water enters the condenser 23 through the switch valve 85 to absorb heat, achieving tertiary heating of the heating return water. Heating water with a temperature of approximately 64.3℃ exits from the heating water outlet of the lithium bromide absorption heat pump unit 2 and enters the heating user 4 to meet the heating demand. After cooling down, the 20t / h of 45℃ heating return water re-enters the heating water inlet of the lithium bromide absorption heat pump unit 2.

[0041] The 35℃ circulating cooling water from the generator set is pumped at a rate of 26.9t / h into the evaporator 24 as the cooling medium before entering the cooling tower. After cooling the medium, the circulating cooling water is cooled by 5℃ and then mixed with the cooled circulating water from the cooling tower before re-entering the circulating water system.

[0042] Example 2 This embodiment focuses on the continuous blowdown of a 350t / h boiler. The flow rate and temperature of the blowdown are measured in real time using a mass flow rate detection device 5 and a temperature detection device 6. The measured flow rate is 17.5t / h, and the blowdown rate of the 350t / h boiler is calculated to be 5%. The measured temperature of the blowdown at the outlet of the expansion tank is 100℃, the mass ratio of unvaporized wastewater is 0.8, and the flow rate is 14t / h. The temperature of the blowdown after driving the lithium bromide absorption heat pump unit 2 is set to 80℃. Using the formula for the waste heat coefficient of the continuous blowdown, the waste heat coefficient is calculated to be 0.8, which is higher than the equilibrium point of 0.64 for the waste heat coefficient of the continuous blowdown, indicating that the waste heat of the continuous blowdown is at a relatively high level.

[0043] In this state, valves 81 and 82 are open, while valves 82, 83, and 85 are closed. 14 t / h of 100°C wastewater, acting as the driving heat source for the lithium bromide absorption heat pump unit 2, enters the generator 21 to directly exchange heat with the absorbent, thus recovering the wastewater's waste heat. After heating the absorbent, the 14 t / h wastewater reaches a temperature of 80°C and enters the fixed discharge expansion tank 7 through valve 81 for treatment together with the fixed discharge wastewater.

[0044] 20t / h of 45℃ heating return water enters the absorber 22 through the heating water inlet of the lithium bromide absorption heat pump unit 2 to cool the absorbent, achieving primary heating of the heating return water to a temperature of 59℃. After primary heating, the heating return water enters the condenser 23 through the switch valve 84 to absorb heat, achieving secondary heating of the heating return water to a temperature of approximately 70℃. Then, the heating water exits from the heating water outlet of the lithium bromide absorption heat pump unit 2 and enters the heating user 4 to meet the heating demand. After the heating cools down, the 20t / h of 45℃ heating return water re-enters the heating water inlet of the lithium bromide absorption heat pump unit 2.

[0045] The 30℃ circulating cooling water from the generator set is pumped at a rate of 44.8t / h into the evaporator 24 as the cooling medium before entering the cooling tower. After cooling the medium, the circulating cooling water is cooled by 5℃ and mixed with the cooled circulating water from the cooling tower before re-entering the circulating water system.

[0046] Example 3 This embodiment focuses on the continuous blowdown of a 350t / h boiler. The flow rate and temperature of the blowdown are measured in real time using a mass flow rate detection device 5 and a temperature detection device 6. The measured flow rate is 14t / h, and the blowdown rate of the 350t / h boiler is calculated to be 4%. The measured temperature of the blowdown at the outlet of the expansion tank is 95℃, the mass ratio of unvaporized wastewater is 0.8, and the flow rate is 11.2t / h. The temperature after the continuous blowdown drives the lithium bromide absorption heat pump unit 2 is set to 75℃. Using the formula for the waste heat coefficient of the continuous blowdown, the waste heat coefficient is calculated to be 0.64, which is equal to the equilibrium point of 0.64, indicating that the waste heat of the continuous blowdown is at a relatively high level.

[0047] In this state, valves 81 and 82 are open, while valves 82, 83, and 85 are closed. 11.2 t / h of 95°C wastewater, acting as the driving heat source for the lithium bromide absorption heat pump unit 2, enters the generator 21 to directly exchange heat with the absorbent, thus recovering the wastewater's waste heat. After heating the absorbent, the 11.2 t / h wastewater reaches a temperature of 75°C and enters the fixed discharge expansion tank 7 through valve 81 for treatment together with the fixed discharge wastewater.

[0048] 20t / h of 45℃ heating return water enters the absorber 22 through the heating water inlet of the lithium bromide absorption heat pump unit 2 to cool the absorbent, achieving primary heating of the heating return water to a temperature of 56.2℃. After primary heating, the heating return water enters the condenser 23 through the switch valve 84 to absorb heat, achieving secondary heating of the heating return water to a temperature of approximately 65.2℃. Then, the heating water exits from the heating water outlet of the lithium bromide absorption heat pump unit 2 and enters the heating user 4 to meet the heating demand. After the heating cools down, the 20t / h of 45℃ heating return water re-enters the heating water inlet of the lithium bromide absorption heat pump unit 2.

[0049] The 30℃ circulating cooling water from the generator set is pumped at a rate of 35.9t / h into the evaporator 24 as the cooling medium before entering the cooling tower. After cooling the medium, the circulating cooling water is cooled by 5℃ and then mixed with the cooled circulating water from the cooling tower before re-entering the circulating water system.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A control method utilizing continuously discharged sewage and waste heat from circulating water, characterized in that, include: The flow rate and temperature of the continuously discharged wastewater are monitored in real time, and the residual heat coefficient of the wastewater is calculated based on the monitoring data. : in, This refers to the mass ratio of unvaporized wastewater in the continuous discharge expansion tank. The sewage discharge rate is the continuous discharge rate. The initial temperature of the continuously discharged sewage. The temperature after the continuous discharge of wastewater drives the lithium bromide absorption heat pump unit; The residual heat status of the continuously discharged wastewater is determined based on the calculation results of the residual heat coefficient. When the residual heat status of the continuous sewage is determined to be low, the continuous sewage is recycled a second time and the heating return water is heated a third time. When the residual heat status of the continuous sewage is determined to be high, the continuous sewage is recycled and the heating return water is reheated. When the waste heat of the continuous sewage is determined to be at a high level, the continuous sewage is used as the driving heat source of the lithium bromide absorption heat pump unit (2) to enter the generator (21) to heat the absorbent, thereby realizing the recovery of waste heat of the sewage. After the recovery is completed, it enters the fixed discharge expansion container (7) and is treated together with the fixed discharge sewage. The heating return water enters the absorber (22) through the heating water inlet of the lithium bromide absorption heat pump unit (2) to cool the absorbent, thus achieving the primary heating of the heating return water. After the primary heating is completed, the heating return water enters the condenser (23) to absorb heat, thus achieving the secondary heating of the heating return water. The heating water that has undergone secondary heating flows out from the heating water outlet of the lithium bromide absorption heat pump unit (2) and enters the heating user (4) to meet the heating demand. The return water that has cooled down after heating is circulated back into the system for heating.

2. The control method for utilizing continuous wastewater discharge and waste heat from circulating water according to claim 1, characterized in that, Determining the equilibrium point using the residual heat coefficient of the continuously discharged wastewater. Determine the residual heat status of continuously discharged wastewater; when the residual heat coefficient of continuously discharged wastewater... When the wastewater discharge coefficient is low, it is determined that the residual heat of the wastewater is in a low state; when the residual heat coefficient of the wastewater discharge is low... At that time, it was determined that the residual heat of the continuously discharged sewage was at a high level.

3. The control method for utilizing continuous wastewater discharge and waste heat from circulating water according to claim 1, characterized in that, The process of secondary recovery of the wastewater and tertiary heating of the return water when the residual heat state of the wastewater is determined to be low includes: When the waste heat of the continuous sewage is determined to be at a low level, the continuous sewage is used as the driving heat source of the lithium bromide absorption heat pump unit (2) to enter the generator (21) to heat the absorbent, thereby realizing the primary recovery of the waste heat of the sewage; after the primary recovery is completed, it enters the intermediate heat exchanger (3) to reheat the return water for heating, thereby realizing the secondary recovery of the waste heat of the continuous sewage; after the secondary recovery is completed, it enters the fixed discharge expansion tank (7) and is treated together with the fixed discharge sewage. The heating return water enters the absorber (22) through the heating water inlet of the lithium bromide absorption heat pump unit (2) to cool the absorbent and achieve the first heating of the heating return water. After the first heating is completed, the heating return water enters the intermediate heat exchanger (3) to exchange heat with the sewage and achieve the second heating of the heating return water. After the second heating is completed, the heating return water enters the condenser (23) to absorb heat and achieve the third heating of the heating return water. The heating return water after the third heating enters the heating user (4) to meet the heating demand. The return water after the heating is cooled down is circulated back into the system for heating.

4. A control system utilizing wastewater discharge and waste heat from circulating water, implemented based on the control method for utilizing wastewater discharge and waste heat from circulating water as described in any one of claims 1-3, characterized in that, include: The system comprises a continuous expansion tank (1), a lithium bromide absorption heat pump unit (2), an intermediate heat exchanger (3), and a fixed expansion tank (7), wherein: The inlet of the continuous expansion tank (1) is equipped with a mass flow detection device (5), and the outlet is connected to a lithium bromide absorption heat pump unit (2). A temperature detection device (6) is provided between the continuous expansion tank (1) and the lithium bromide absorption heat pump unit (2). The lithium bromide absorption heat pump unit (2) includes a generator (21), an absorber (22), a condenser (23), and an evaporator (24). One end of the generator (21) is connected to the continuous discharge expansion tank (1), and the other end is connected to the intermediate heat exchanger (3). One end of the absorber (22) is the heating water inlet, and the other end is connected to the intermediate heat exchanger (3) and the condenser (23). The outlet of the condenser (23) is connected to the heating user (4). One end of the evaporator (24) is the circulating cooling water inlet, which recovers the low-temperature waste heat of the circulating cooling water and re-enters the generator unit's circulating cooling water system through the outlet. The outlet of the intermediate heat exchanger (3) is connected to the fixed discharge expansion tank (7).

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