Thermal energy efficient utilization system and control method of multiple heat exchange units

Abstract

The present invention proposes a system and control method for efficiently utilizing heat energy of multiple heat exchange units. The control method acquires the heat exchange efficiency of each heat exchange unit by collecting the operating parameters of each heat exchange unit and acquiring the output balance parameters of the entire heat exchange system. The operating state of each heat exchange unit under different operating parameter conditions is simulated, and the optimal control parameters are calculated to control the operation of each heat exchange unit so that the entire heat exchange system can operate in the most efficient state and can operate stably without human intervention. The control method can be applied to existing heat exchange equipment without increasing equipment investment and has strong applicability.

Description

Technical Field

[0001] The invention belongs to the field of printing and dyeing equipment, and in particular relates to a multi-heat exchange unit heat energy efficient utilization system and a control method. Background Art

[0002] The printing and dyeing industry uses a lot of heat and water in the production process. For example, the washing process of pre-treatment and the soap washing process of printing / dyeing require the use of steam to heat the washing tank to above 85 degrees Celsius to meet the needs of the production process. A large amount of waste hot water (the temperature can reach 70-75 degrees Celsius) is generated during the washing process. If this waste hot water is discharged directly, it will cause a lot of energy waste, and the high waste water temperature will bring a heavy burden to the wastewater treatment department.

[0003] In order to reduce energy consumption and solve the problem of excessive wastewater temperature in the wastewater treatment department, heat exchange units are usually used to recycle the heat energy of high-temperature wastewater from washing, which is used to heat clean water to obtain hot water and also reduce the temperature of the wastewater. Large-scale printing and dyeing enterprises are generally equipped with multiple heat exchange units according to the source, quantity, type, etc. of waste hot water. However, the coordinated operation and control of multiple heat exchange units are relatively complicated. The main reasons are as follows: First, the total water output of multiple units is limited. Under normal circumstances, there are many sources of hot water in printing and dyeing factories, such as hot water recycled by steam condensation, hot water for compressor cooling, and cooling water for concentrated dilute alkali. These hot waters, together with the hot water exchanged, constitute the source of hot water for production in printing and dyeing enterprises. It is generally required that the total amount of these hot waters cannot be greater than the production demand. That is, the amount of clean water in the heat exchange unit is limited and depends on factors such as changes in production demand and changes in peripheral hot water. Second, the discharge temperature of waste hot water needs to meet the standard. While utilizing the heat of waste water, the heat exchange unit also plays an important role in cooling the waste water. The joint operation of multiple units requires strict control of the operating status of each unit to ensure that the wastewater discharge temperature is minimized while maximizing the heat exchange efficiency.

[0004] When there are more than two heat exchange units, facing complex and changeable production conditions, relying solely on manual control of the operation modes of each unit is difficult to achieve the optimal operating state of each unit, and cannot meet the requirements of stable and balanced production operations. In addition, the intensity of manual monitoring and scheduling is extremely high. Summary of the invention

[0005] The present invention aims to solve the technical problem that existing enterprises rely on manual control of the operation of multiple heat exchange units, making it difficult to improve the heat exchange efficiency. The present invention proposes a system and a control method for efficiently utilizing heat energy of multiple heat exchange units, which obtains the optimal operating parameters of each heat exchange unit through data monitoring and calculation, so that each heat exchange unit operates in the optimal state.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A heat energy efficient utilization system of multiple heat exchange units, comprising a hot water storage tank, a master control module and n heat exchange modules, wherein n is an integer greater than or equal to 2, the heat exchange module comprising a heat exchange unit for heat exchanging clean water with waste hot water, a waste hot water tank and a PLC controller, the heat exchange unit is provided with a clean water inlet, a waste water inlet, a clean water outlet and a waste water outlet, the waste water inlet is connected to the waste hot water tank, and the clean water outlet is connected to the hot water storage tank.

[0008] Preferably, the hot water storage tank is provided with an external hot water inlet and a main water supply outlet.

[0009] Preferably, a liquid level gauge is provided in the hot water storage tank.

[0010] Preferably, flow meters and temperature sensors are provided on the clean water inlet, waste water inlet, clean water outlet and waste water outlet of the heat exchange unit.

[0011] Preferably, the master control module includes a data server and a master controller.

[0012] The present invention also provides a control method for a multi-heat exchange unit heat energy efficient utilization system, comprising the following steps:

[0013] (1) Collect parameters and obtain the output-output balance parameters of the entire heat exchange system

[0014] Collect the real-time water flow rate V of the total water supply outlet of the hot water storage tank 总出 , Real-time flow rate V of external hot water inlet 外 , calculate the total amount of water discharged into the hot water storage tank by all heat exchange modules,

[0015] V 总进 =V 总出 -V 外

[0016] Introducing the correction parameter K to V 总进 Make corrections, then

[0017] V 总进 '=V 总进 *K

[0018] (2) Obtaining the heat exchange efficiency of each heat exchange unit

[0019] The operating parameters of each heat exchange unit are uploaded to the data server through the PLC controller at a regular interval, and the relationship between the heat exchange efficiency of each heat exchange unit and the set operating parameters is obtained through analysis and calculation;

[0020] Query and analyze the relationship between the heat removal ratio x and the heat exchange efficiency η in different time periods, fit the slope equation η=a*x+b, and obtain the values ​​of a and b;

[0021] (3) Obtaining the optimal control parameters

[0022] The master control system analyzes the operating data of each heat exchange unit, simulates the operating status of each heat exchange unit under different operating parameter conditions, and calculates the optimal control parameters to control the operation of each unit.

[0023] Preferably, the calculation method of the correction parameter K in step (1) is as follows:

[0024] Set the appropriate operating liquid level height range of the hot water storage tank to standard liquid level H0, high level H1 and low level H2, and record the current water level of the hot water tank as H.

[0025]

[0026] Preferably, the operating parameters uploaded by each heat exchange unit in step (2) include:

[0027] Clean water inlet meter Q 清

[0028] Wastewater inlet meter number Q 污

[0029] Clean water inlet temperature t 清进

[0030] Clean water discharge temperature t 清出

[0031] Wastewater inlet temperature t 污进

[0032] Wastewater discharge temperature t 污出

[0033] Record time

[0034] The definitions of heat removal ratio x and heat exchange efficiency η are as follows:

[0035] x=(Q 清1 -Q 清2 ) / (Q 污1 -Q 污2 )

[0036] η=((Q 清1 -Q 清2 )*(t 清出均 -t 清进均 )) / ((Q 污进均 -Q 污出均 )*(t 污出均 -t 清进均 ))

[0037] Where Q 清1 , Q 清2Q is the total number of clean water meters in the start and end periods of a unit time; 污1 , Q 污2 is the total number of wastewater meters in the start and end periods of unit time; t 清出均 ,t 清进均 are the average outlet and inlet temperatures of clean water per unit time, respectively; t 污出均 ,t 污进均 are the average inlet temperature and average outlet temperature of the wastewater per unit time respectively.

[0038] Preferably, the optimal control parameters of each unit in step (3) are calculated by the following steps:

[0039] (3.1) Assume that there are n heat exchange units, n is an integer greater than or equal to 2, and the fresh water inflow of each unit is L(x), then the total fresh water inflow of the system is L = L(1) + L(2) + L(3) ... + L(n) = V 总进 '=V 总进 *K;

[0040] Then the heat removal ratio of this heat exchange unit is X(x) = L(x) / Q(x), where Q(x) is the wastewater inlet flow rate. The heat exchange efficiency η(x) of the heat exchange unit is calculated.

[0041] η(x)=a(x)*(L(x) / Q(x))+b(x)

[0042] Then the fresh water outlet temperature of the heat exchange unit is t(x)=η(x) / X(x)*(t 污 (x)-t0)+t0, where t 污 (x) is the wastewater inlet temperature, t0 is the clean water inlet temperature;

[0043] (3.2) Calculate the average outlet water temperature of all heat exchange units,

[0044] T 均 =(L(1)*t(1)+L(2)*t(2)+L(3)*t(3)...+L(n)*t(n)) / L

[0045] Under the general condition of L = Vtotal output * K, calculate the clean water outlet temperature T corresponding to different clean water inlet volumes of each unit. 均 When T reaches the maximum value, the X(x) value of each heat exchange unit is given, and the water inlet flow control parameters of the heat exchange unit are set accordingly.

[0046] Preferably, the method further includes step (4), wherein the main controller repeats step (3) according to a set time interval to adjust the water inlet flow rate of the heat exchange unit.

[0047] Compared with the prior art, the advantages and positive effects of the present invention are:

[0048] The heat energy efficient utilization system of multiple heat exchange units of the present invention monitors the amount of high-temperature wastewater generated in the system, the flow rate of external hot water and the total hot water consumption in real time, and adjusts the flow rate of clean water input into different heat exchange units in real time, thereby maintaining the liquid level balance of the hot water storage tank and ensuring water for production; at the same time, it monitors parameters such as the flow rate of wastewater transported to the wastewater pool by different heat exchange modules, the outlet temperature of wastewater, and the operating efficiency of the heat exchange units. The above-mentioned control method is used to adjust the operating parameters of each heat exchange unit through the main controller, thereby maximizing the overall heat exchange efficiency of the heat exchange module, reducing the average outlet temperature of the discharged wastewater, and maintaining efficient and stable operation of the entire multiple heat exchange unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is a structural schematic diagram of a heat energy efficient utilization system of a multi-heat exchange unit of the present invention;

[0050] Figure 2 is a control flow chart of the control method of the present invention;

[0051] In the above figures: 1. hot water storage tank; 11. external hot water inlet; 12. main water supply outlet; 2. master control module; 21. data server; 22. master controller; 3. heat exchange module; 31. heat exchange unit; 32. waste water tank; 33. PLC controller; 34. clean water inlet; 35. waste water inlet; 36. clean water outlet; 37. waste water outlet; 38. high temperature waste water inlet. DETAILED DESCRIPTION

[0052] In order to better understand the present invention, a detailed description is given below in conjunction with the accompanying drawings and embodiments.

[0053] Embodiment 1:

[0054] like Figure 1As shown, a heat energy efficient utilization system of multiple heat exchange units includes a hot water storage tank 1, a master control module 2 and a plurality of heat exchange modules 3. The heat exchange module 3 includes a heat exchange unit 31 for heat exchange between clean water and waste hot water, a waste hot water tank 32 and a PLC controller 33. The heat exchange unit 31 is provided with a clean water inlet 34, a waste water inlet 35, a clean water outlet 36 and a waste water outlet 37. The clean water inlet 34, waste water inlet 35, clean water outlet 36 and waste water outlet 37 of the heat exchange unit 31 are all provided with electronic flow meters and temperature sensors, which are electrically connected to the PLC controller 33. The clean water and waste water flow rates of the clean water inlet 34, waste water inlet 35, clean water outlet 36 and waste water outlet 37 are transmitted to the PLC controller 33 in real time through the electronic flow meters. The temperature sensor detects the temperature of the clean water and waste water at the clean water inlet 34, waste water inlet 35, clean water outlet 36 and waste water outlet 37 and transmits it to the PLC controller 33, and the PLC controller 33 transmits it to the master control module 2.

[0055] The waste water pool 32 is used to temporarily store waste water from the washing tank, etc. The water inlet of the waste water pool 32 is provided with a high-temperature waste water inlet 38, and the water outlet of the waste water pool 32 is connected to the waste water inlet 35 of the heat exchange unit 31. The waste water outlet 37 of the heat exchange unit 31 is connected to the waste water treatment and discharge system, and the waste water after heat exchange is discharged after being treated and qualified. The clean water inlet 34 of the heat exchange unit 31 is connected to the clean water source, and normal temperature clean water is introduced; the hot water outlet of the heat exchange unit 31 is connected to the hot water storage tank 1, and the clean water after heat exchange is input into the hot water storage tank 1 for storage.

[0056] The hot water storage tank 1 is provided with an external hot water inlet 11 and a main water supply outlet 12, and both the external hot water inlet 11 and the main water supply outlet 12 are provided with an electronic flow meter electrically connected to the main control module 2, which can detect the real-time flow rate V of the external hot water delivered to the hot water storage tank 1 in real time. 外 And the total real-time water supply V of the total production water supply end 总出 The hot water storage tank 1 is provided with a digital liquid level meter, which can detect the liquid level H in the hot water storage tank 1 in real time and transmit it to the master control module 2 .

[0057] The master control module 2 includes a data server 21 and a master controller 22. The data server 21 is communicated with the PLC controller 33 of each heat exchange module 3, and is used to store the operating parameters of each heat exchange module 3 and perform calculations, and transmit the calculation results to the master controller 22. The master controller 22 controls the operation of the heat exchange group 31 in each heat exchange module 3.

[0058] The heat energy efficient utilization system of multiple heat exchange units 31 of the present invention monitors the amount of high-temperature wastewater generated in the system, the flow rate of external hot water and the total hot water consumption in real time, and adjusts the clean water flow rate input into different heat exchange units 31 in real time, thereby maintaining the liquid level balance of the hot water storage tank 1 and ensuring water for production; at the same time, it monitors the wastewater flow rate, wastewater outlet temperature, operating efficiency of the heat exchange unit 31 and other parameters transported to the wastewater pool 32 by different heat exchange modules 3, and adjusts the operating parameters of each heat exchange unit through the main controller 22, including the clean water inlet and the wastewater hot water inlet, so as to maximize the overall heat exchange efficiency of the heat exchange module 3, reduce the average outlet temperature of the discharged wastewater, and keep the entire multiple heat exchange unit in efficient and stable operation.

[0059] Embodiment 2:

[0060] A control method for a multi-heat exchange unit heat energy efficient utilization system comprises the following steps:

[0061] (1) Collect parameters and obtain the output-output balance parameters of the entire heat exchange system

[0062] The digital level meter in the hot water tank accurately measures the change data of the tank liquid level, and the electronic flow meter at the total water supply outlet of the hot water tank detects the water supply flow V in real time. 总出 , the electronic flow meter at the inlet of external hot water detects the flow rate V of external hot water in real time 外 The above data is transmitted to the master control module in real time. The total amount of water V discharged from all heat exchange modules into the hot water storage tank is calculated. 总进 ,

[0063] V 总进 =V 总出 -V 外

[0064] In order to eliminate the problem of unstable control system caused by large instantaneous flow changes, the correction parameter K is introduced to V 总进 Make corrections, then

[0065] V 总进 '=V 总进 *K

[0066] The calculation method of the correction parameter K is as follows:

[0067] Set the appropriate operating liquid level height range of the hot water storage tank to standard liquid level H0, high level H1 and low level H2, record the current water level of the hot water tank as H, and then modify the parameter K to calculate by the following formula:

[0068]

[0069] (2) Obtaining the heat exchange efficiency of each heat exchange unit

[0070] Different heat exchange units have different heat exchange efficiencies due to their own parameter differences, water supply conditions, and heat exchange methods. The system needs to obtain the heat exchange efficiency of each heat exchange unit under different operating conditions, and reasonably control the unit operating parameters according to the changes in the operating efficiency of each heat exchange unit, so as to ensure the total water inflow V 总进 On the basis of stability, the heat exchange efficiency of each unit can be maximized.

[0071] The specific operating efficiency of each heat exchange unit is obtained by analyzing and calculating the operating data of the heat exchange unit within a certain period of time. The acquisition method is as follows:

[0072] The operating parameters of each heat exchange unit are uploaded to the data server through the PLC controller at a regular interval. The data server analyzes and calculates the relationship between the heat exchange efficiency of each heat exchange unit and the set operating parameters;

[0073] The operating parameters uploaded by each heat exchanger group include:

[0074] Clean water inlet meter number Q 清

[0075] Wastewater inlet meter number Q 污

[0076] Clean water inlet temperature t 清进

[0077] Clean water discharge temperature t 清出

[0078] Wastewater inlet temperature t 污进

[0079] Wastewater discharge temperature t 污出

[0080] Record time

[0081] By querying the heat exchange data over a period of time and performing analytical calculations, the relationship between the heat exchange efficiency of the heat exchange unit and the set operating parameters can be obtained.

[0082] Introduce two parameters:

[0083] x: Clean water ratio, which means the ratio of the total clean water intake to the waste hot water intake within the unit operating time.

[0084] η: Heat exchange efficiency, which indicates the total heat exchange efficiency of the heat exchange unit during this time period.

[0085] By definition, we can conclude that:

[0086] x=(Q 清1 -Q 清2 ) / (Q污1 -Q 污2 )

[0087] η=((Q 清1 -Q 清2 )*(t 清出均 -t 清进均 )) / ((Q 污进均 -Q 污出均 )*(t 污出均 -t 清进均 ))

[0088] Where Q 清1 , Q 清2 Q is the total number of clean water meters in the start and end periods of a unit time; 污1 , Q 污2 is the total number of wastewater meters in the start and end periods of unit time; t 清出均 ,t 清进均 are the average outlet and inlet temperatures of clean water per unit time, respectively; t 污出均 ,t 污进均 are the average inlet temperature and average outlet temperature of the wastewater per unit time respectively.

[0089] By querying and analyzing the relationship between the heat removal ratio x and the heat exchange efficiency η in different time periods, a series of X and η values ​​can be obtained. By using a two-dimensional coordinate system to depict the above values, it can be found that the heat removal ratio X and the heat exchange coefficient η can be approximated as a straight line distribution when the X value is small (such as less than 1.2). The straight line can be represented by the slope equation η=a*x+b. Based on the series of X and η values ​​queried, the two parameters a and b of the slope equation are obtained by using data fitting, linear regression, least squares method, etc.

[0090] (3) Obtaining the optimal control parameters

[0091] The master control system analyzes the operating data of each heat exchange unit, simulates the operating status of each heat exchange unit under different operating parameter conditions, and calculates the optimal control parameters to control the operation of each unit.

[0092] The optimal control parameters of each unit are calculated through the following steps:

[0093] (3.1) Assume that there are n heat exchange units, n is an integer greater than or equal to 2, and the fresh water inflow of each unit is L(x), then the total fresh water inflow of the system is L = L(1) + L(2) + L(3) ... + L(n) = V 总进 '=V 总进 *K;

[0094] The wastewater inlet flow rate of each heat exchange unit can be obtained by reading the digital flow meter on the wastewater inlet. The wastewater inlet flow rate is set to Q(x).

[0095] Then the heat removal ratio of this heat exchange unit is X(x)=L(x) / Q(x).

[0096] (3.2) According to the slope curve equation, calculate the heat exchange efficiency η(x) of the heat exchange unit,

[0097] η(x)=a(x)*(L(x) / Q(x))+b(x)

[0098] Then the fresh water outlet temperature of the heat exchange unit is t(x)=η(x) / X(x)*(t 污 (x)-t0)+t0, where t 污 (x) is the wastewater inlet temperature, t0 is the clean water inlet temperature;

[0099] (3.3) Calculate the average outlet water temperature of all heat exchange units. According to the fresh water flow rate L(x) and outlet water temperature t(x) of each heat exchange unit, calculate the total fresh water outlet temperature T of the system. 均 ,

[0100] T 均 =(L(1)*t(1)+L(2)*t(2)+L(3)*t(3)...+L(n)*t(n)) / L

[0101] (3.4) Using the exhaustive algorithm, when L = V 总进 *K, calculate the clean water outlet temperature T corresponding to different clean water inlet volumes (i.e. different heat removal ratios) of each unit. 均 When T 均 When the maximum value is reached, the X(x) value of each heat exchange unit is given, and the water inlet flow control parameters of the heat exchange unit are set accordingly.

[0102] (3.5) The master controller sends the water inlet flow control parameters to the PLC controller of each heat exchange module, and the PLC controller controls the operation of the unit according to the instructions.

[0103] (4) The master controller repeats step (3) according to the set time interval to adjust the water inlet flow of the heat exchange unit so that the entire system maintains a stable operation state.

[0104] The control method of the heat energy efficient utilization system of multiple heat exchange units described above acquires the heat exchange efficiency of each heat exchange unit by collecting the operating parameters of each heat exchange unit and obtaining the output-output balance parameters of the entire heat exchange system. The operating state of each heat exchange unit under different operating parameter conditions is simulated, and the optimal control parameters are calculated to control the operation of each heat exchange unit so that the entire heat exchange system can operate in the most efficient state and can operate stably without human intervention. The control method can be applied to existing heat exchange equipment, has strong practicality, and has a wide range of applications.

[0105] The above description is only a preferred embodiment of the present invention and does not limit the present invention in other forms. Any technician familiar with the profession may use the technical content disclosed above to change or modify it into an equivalent embodiment with equivalent changes and apply it to other fields. However, any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A control method for a multi-heat exchange unit heat energy efficient utilization system, characterized in that: The steps include: (1) Collect parameters and obtain the output-output balance parameters of the entire heat exchange system Collect the real-time water flow rate V of the total water supply outlet of the hot water storage tank 总出 , Real-time flow rate V of external hot water inlet 外 , calculate the total amount of water discharged into the hot water storage tank by all heat exchange modules, V 总进 =V 总出 -V 外 Introducing the correction parameter K to V 总进 Make corrections, then V 总进 '=V 总进 *K (2) Obtaining the heat exchange efficiency of each heat exchange unit The operating parameters of each heat exchange unit are uploaded to the data server through the PLC controller at a regular interval, and the relationship between the heat exchange efficiency of each heat exchange unit and the set operating parameters is obtained through analysis and calculation; Query and analyze the relationship between the heat removal ratio x and the heat exchange efficiency η in different time periods, fit the slope equation η=a*x+b, and obtain the values ​​of a and b; (3) Obtaining the optimal control parameters The master control system analyzes the operating data of each heat exchange unit, simulates the operating status of each heat exchange unit under different operating parameter conditions, and calculates the optimal control parameters to control the operation of each unit; The calculation method of the correction parameter K in step (1) is as follows: Set the appropriate operating liquid level height range of the hot water storage tank to standard liquid level H0, high level H1 and low level H2, and record the current water level of the hot water tank as H. The operating parameters uploaded by each heat exchange unit in step (2) include: Clean water inlet meter Q 清 Wastewater inlet meter number Q 污 Clean water inlet temperature t 清进 Clean water discharge temperature t 清出 Wastewater inlet temperature t 污进 Wastewater discharge temperature t 污出 Record time The definitions of heat removal ratio x and heat exchange efficiency η are as follows: x=(Q 清1 -Q 清2 ) / (Q 污1 -Q 污2 ) η=((Q 清1 -Q 清2 )*(t 清出均 -t 清进均 )) / ((Q 污进均 -Q 污出均 )*(t 污出均 -t 清进均 )) Where Q 清1 , Q 清2 Q is the total number of clean water meters in the start and end periods of a unit time; 污1 , Q 污2 The total number of wastewater meters in the start and end periods of a unit time; t 清出均 ,t 清进均 They are the average outlet water temperature and the average inlet water temperature of the clean water per unit time respectively; t 污出均 ,t 污进均 are the average inlet temperature and average outlet temperature of wastewater per unit time respectively; The optimal control parameters of each unit in step (3) are calculated by the following steps: (3.1) Assume that there are n heat exchange units, n is an integer greater than or equal to 2, and the fresh water inflow of each unit is L(x), then the total fresh water inflow of the system is L = L(1) + L(2) + L(3) ... + L(n) = V 总进 '=V 总进 *K; Then the heat removal ratio of this heat exchange unit is X(x) = L(x) / Q(x), where Q(x) is the wastewater inlet flow rate. Calculate the heat exchange efficiency η(x) of the heat exchange unit. η(x)=a(x)*(L(x) / Q(x))+b(x) Then the fresh water outlet temperature of the heat exchange unit is t(x)=η(x) / X(x)*(t 污 (x)-t0)+t0, where t 污 (x) is the wastewater inlet temperature, t0 is the clean water inlet temperature; (3.2) Calculate the average outlet water temperature of all heat exchange units, T 均 =(L(1)*t(1)+L(2)*t(2)+L(3)*t(3)...+L(n)*t(n)) / L When L=V 总进 *K, calculate the clean water outlet temperature T corresponding to the different clean water inlet volume of each unit 均 When T reaches the maximum value, the X(x) value of each heat exchange unit is given, and the water inlet flow control parameters of the heat exchange unit are set accordingly.

2. The control method of the heat energy efficient utilization system of multiple heat exchange units according to claim 1 is characterized in that: The method further comprises step (4), wherein the master controller repeats step (3) according to a set time interval to adjust the water inlet flow rate of the heat exchange unit.

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