Waste recovery system and matching method for improving energy efficiency of waste recovery system

Abstract

The invention relates to the technical field of waste recovery, and particularly provides a waste recovery system. The waste recovery system comprises a heat exchanger, a circulating air duct, a multi-stage heat pump unit, a cooling tower heat exchanger and a cooling tower, the cooling tower heat exchanger is communicated with the cooling tower through a circulating water path, the cooling tower is communicated with the outside of the recovery system, and air in the circulating air duct is cooled and condensed through an evaporator step by step to recover waste. After the heat of the air is absorbed by the heat exchanger of the cooling tower, the heat is discharged out of the system through the cooling tower, the condensed air is heated by the condenser step by step and enters the coating machine again for drying, and the high-temperature air and the low-temperature air in the system exchange heat in the heat exchanger. The exhausted waste gas is condensed in the mode that the heat exchanger, the multi-stage heat pump unit and the cooling tower are combined, so that NMP in the waste gas is recycled, the NMP recycling rate is increased, part of heat in the system is taken away through the cooling tower, heat in the system is balanced, it is guaranteed that the heat pump unit operates stably, and the energy efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of waste recycling, and specifically provides a waste recycling system and a matching method for improving the energy efficiency thereof. Background Art

[0002] During the coating process of lithium battery pole pieces, NMP solution (N-methylpyrrolidone) is used to dissolve the adhesive in the pole piece slurry, ensuring uniform distribution of the adhesive on the pole piece and ensuring pole piece quality. However, NMP is an expensive organic solvent. To improve its recycling value and reduce costs, it is generally recovered by condensing the evaporated NMP through a heat pump unit. The air is then reheated and returned to the coater to continue drying the pole piece. However, due to the high drying load of the pole piece coating, the low concentration of NMP solvent in the hot air, and the poor operating stability of the heat pump unit, the recovery process consumes a lot of energy, has low energy efficiency, and has a low recovery rate.

[0003] Accordingly, the art needs a new waste recycling system to solve the problems of poor operating stability and low energy efficiency of the existing NMP recovery system in the battery electrode coating process. Summary of the Invention

[0004] The present invention aims to solve the above technical problems, that is, to solve the problems of poor operating stability and low energy efficiency of the NMP recovery system in the existing battery electrode coating process. The present invention provides a waste recycling system, which includes a heat exchanger, a circulating air duct, a multi-stage heat pump unit, a cooling tower heat exchanger and a cooling tower. The cooling tower heat exchanger and the cooling tower are connected through a circulating water circuit, and the cooling tower is connected to the outside of the recycling system.

[0005] The multi-stage heat pump unit includes an evaporator and a condenser arranged on a refrigerant circulation loop, and the two ends of the circulation air duct are respectively connected to the air inlet and the air outlet of the coating machine, and the heat exchanger, the evaporator and the condenser are sequentially arranged between the air inlet and the air outlet, and the cooling tower heat exchanger is arranged between the air outlet and the condenser, so that the high-temperature air at the air outlet exchanges heat with the low-temperature air through the heat exchanger and then passes through the evaporator step by step to cool and condense the waste to be recovered. After absorbing the heat of the air through the cooling tower heat exchanger, the heat is discharged to the outside of the recovery system through the cooling tower to maintain heat balance. The condensed low-temperature air then passes through the condenser and the heat exchanger step by step to be heated and then enters the air inlet for drying.

[0006] Under the circumstances of adopting the above-mentioned technical scheme, the waste material recovery system of the present invention adopts the mode of combining heat exchanger, multi-stage heat pump unit and cooling tower to condense the exhaust gas to recover the NMP therein, and recycle the heat for drying, thereby improving the recovery efficiency and reducing the energy consumption of the system. Due to the temperature resistance of the existing compressor motor, it is difficult to achieve an ultra-high evaporation temperature. The present invention first exchanges heat with the condensed low-temperature air in the heat exchanger to reduce the temperature before entering the evaporator for condensation, which can reduce the evaporation temperature of the heat pump unit compressor and reduce the cost of the compressor. The inventor found that because the compressor continuously generates heat while the heat required for drying the coating machine is fixed, the heat generated during the closed-loop operation of the recovery system increases, which eventually leads to heat imbalance, making the system unstable and even causing the system to be unable to continue to operate. Therefore, a portion of the heat in the system is removed by the cooling tower to play a role in maintaining the heat balance in the system, ensuring that the heat pump unit always operates smoothly, and improving the energy efficiency of the recovery system. Therefore, the recovery system of the present invention has a better overall condensation effect, more stable operation, high NMP recovery rate, and lower cost.

[0007] In the preferred technical solution of the above-mentioned waste recycling system, the multi-stage heat pump unit includes a first heat pump unit, a second heat pump unit and a third heat pump unit arranged in sequence; the first heat pump unit includes a first compressor, a first evaporator and a first condenser arranged on a first refrigerant circulation loop, the second heat pump unit includes a second compressor, a second evaporator and a second condenser arranged on a second refrigerant circulation loop, the third heat pump unit includes a third compressor, a third evaporator and a third condenser arranged on a third refrigerant circulation loop, and the heat exchanger is arranged between the coater and the first evaporator.

[0008] When the above technical solution is adopted, the three-stage heat pump can keep the three heat pump units within a reasonable temperature rise range, which not only achieves higher energy efficiency but also achieves a balance between energy efficiency and cost. In addition, compared with the two-stage heat pump, the three-stage heat pump can achieve a lower temperature to recover NMP, so the NMP recovery rate is higher.

[0009] In a preferred technical solution of the above waste recycling system, the cooling tower heat exchanger is arranged between the second evaporator and the third evaporator.

[0010] When the above technical solution is adopted, the cooling tower is set between the second heat pump unit and the third heat pump unit, and the air temperature therebetween is not too high or too low. The cooling tower heat exchanger can condense the air only by relying on municipal water, which can prevent the air temperature from being lower than the cooling water temperature, causing the cooling tower to lose its function of cooling the air.

[0011] In the preferred technical solution of the above-mentioned waste recycling system, the multi-stage heat pump unit includes a first heat pump unit, a second heat pump unit and a third heat pump unit arranged in sequence; the first heat pump unit includes a first compressor, a first evaporator and a first condenser arranged on a first refrigerant circulation loop, the second heat pump unit includes a second compressor, a second evaporator and a second condenser arranged on a second refrigerant circulation loop, the third heat pump unit includes a third compressor, a third evaporator and a third condenser arranged on a third refrigerant circulation loop, and the heat exchanger is arranged between the second condenser and the first condenser.

[0012] When the above technical solution is adopted, the three-stage heat pump can keep the three heat pump units within a reasonable temperature rise range, which not only achieves higher energy efficiency but also achieves a balance between energy efficiency and cost. In addition, compared with the two-stage heat pump, the three-stage heat pump can achieve a lower temperature to recover NMP, so the NMP recovery rate is higher.

[0013] In the preferred technical solution of the above-mentioned waste recycling system, the first heat pump unit also includes a first throttle valve arranged on the first refrigerant circulation loop, the second heat pump unit also includes a second throttle valve arranged on the second refrigerant circulation loop, and the third heat pump unit also includes a third throttle valve arranged on the third refrigerant circulation loop.

[0014] When the above technical solution is adopted, the throttle valve blocks the flow of refrigerant through its internal small holes. Working together with the compressor, the system generates high and low pressure areas, ensuring the normal circulation of the refrigerant and playing a throttling and pressure-reducing role. The throttle valve can also control the valve opening according to the change in the refrigerant superheat at the evaporator outlet, thereby adjusting the refrigerant flow entering the evaporator to match the refrigerant flow rate with the evaporator's heat load and ensure sufficient superheat at the compressor intake. The throttle valve not only ensures the cooling effect, but also ensures the stable operation of the system. By precisely controlling the refrigerant flow rate and pressure and rationally adjusting the refrigerant flow rate to avoid excessive or insufficient refrigerant flow, energy waste can be reduced and the energy efficiency ratio of the heat pump system can be improved.

[0015] The present invention also provides a matching method for improving the energy efficiency of a waste recycling system, wherein the waste recycling system includes a heat exchanger, a circulating air duct, a multi-stage heat pump unit, a cooling tower heat exchanger, and a cooling tower, wherein the cooling tower heat exchanger and the cooling tower are connected via a circulating water circuit, and the cooling tower is connected to the outside of the recycling system;

[0016] The multi-stage heat pump unit includes a compressor, an evaporator and a condenser arranged on a refrigerant circulation loop, the two ends of the circulation air duct are respectively connected to the air inlet and the air outlet of the coating machine, the heat exchanger, the evaporator and the condenser are sequentially arranged between the air inlet and the air outlet, and the cooling tower heat exchanger is arranged between the air outlet and the condenser, so that the high-temperature air at the air outlet exchanges heat with the low-temperature air through the heat exchanger and then passes through the evaporator step by step to cool and condense the waste for recycling. After absorbing the heat of the air through the cooling tower heat exchanger, the heat is discharged to the outside of the recovery system through the cooling tower to maintain heat balance. The condensed low-temperature air then passes through the condenser and the heat exchanger step by step to be heated and then enters the air inlet for drying;

[0017] The multi-stage heat pump unit includes a first heat pump unit, a second heat pump unit and a third heat pump unit which are arranged in sequence; the first heat pump unit includes a first compressor, a first evaporator and a first condenser arranged on a first refrigerant circulation loop, the second heat pump unit includes a second compressor, a second evaporator and a second condenser arranged on a second refrigerant circulation loop, and the third heat pump unit includes a third compressor, a third evaporator and a third condenser arranged on a third refrigerant circulation loop; the cooling tower heat exchanger is arranged between the second evaporator and the third evaporator, and the heat exchanger is arranged between the coating machine and the first evaporator and between the second condenser and the first condenser;

[0018] The matching method includes:

[0019] Calculate T1 = (ET1max + (T0 - T5) / 4 + t);

[0020] Calculate the heat exchange temperature difference of the heat exchanger ΔT gas = T0-T1 = T0-(ET1max+(T0-T5) / 4+t);

[0021] Wherein, T0 is the air temperature at the air outlet and the air inlet, ET1max is the maximum limit of the evaporation temperature of the first compressor, T1 is the air temperature in the direction of the air outlet from the heat exchanger to the evaporator, T5 is the air temperature in the direction of the air outlet from the third evaporator, and t is the heat exchange temperature difference; ET1max, T0, T5, and t are set values;

[0022] Calculate the heat exchanger capacity Q of the heat exchanger 气 =m 风 (h0-h1); where h0 and h1 are the enthalpy values ​​of dry air at temperatures T0 and T1 respectively; m 风 is the air mass in the circulating air duct;

[0023] m 风 =Q 风 ρ风 ; where Q 风 is the air volume, ρ 风 is the air density; Q 风 is the set value;

[0024] According to Q 气 Match the heat exchanger with corresponding parameters.

[0025] In the case of adopting the above technical solution, according to the calculated heat exchange capacity Q 气 Select the heat exchanger.

[0026] In the preferred technical solution of the above-mentioned matching method for improving the energy efficiency of the waste recycling system, the matching method further includes:

[0027] Calculate the total temperature rise of the multi-stage heat pump unit ΔT = (T0-T5+2t);

[0028] Calculate the average temperature rise of each heat pump unit △T based on △T 均 =(T0-T5+2t) / 3; wherein, according to the temperature rise of the first heat pump unit ΔT1=CT1-ET1=ΔT 均 Calculate T2;

[0029] According to CT1=T0+t, ET1=T2-t, we can obtain T2=2T0 / 3+T5 / 3+4t / 3; wherein CT1 is the condensing temperature of the first heat pump unit, and ET1 is the evaporating temperature of the first heat pump unit;

[0030] Calculate the heat exchange rate of the first evaporator QE1 = m 风 (h1-h2); where h2 is the enthalpy of dry air at temperature T2;

[0031] The first evaporator, the first condenser and the first compressor are matched with corresponding parameters according to QE1, ET1 and CT1.

[0032] When the above technical solution is adopted, the first evaporator, the first condenser and the first compressor are selected according to the specific values ​​of QE1, ET1 and CT1 obtained by calculation, so as to achieve the optimal system energy efficiency.

[0033] In the preferred technical solution of the above-mentioned matching method for improving the energy efficiency of the waste recycling system, the matching method further includes:

[0034] The heating capacity QC1 of the first compressor is obtained by matching QE1, ET1 and CT1;

[0035] According to QC1=m 风 (h0-h8) gives h8=h0-QC1 / m 风; Wherein, h8 is the enthalpy of dry air at temperature T8, and T8 is the air temperature in the direction of the air outlet from the heat exchanger to the condenser;

[0036] Calculate T3 based on the temperature rise of the second heat pump unit ΔT2 = CT2 - ET2 = ΔT;

[0037] According to T7=T8-△T 气 ,

[0038] CT2=T7+t,ET2=T3-t, so T3=T8-△T 气 +4 / 3t-1 / 3T0+1 / 3T5; wherein CT2 is the condensing temperature of the second heat pump unit, ET2 is the evaporating temperature of the second heat pump unit; T3 is the air temperature in the air outlet direction of the second evaporator; T7 is the air temperature in the air outlet direction of the second condenser;

[0039] Calculate the heat exchange rate of the second evaporator QE2 = m 风 (h2-h3); where h3 is the enthalpy of dry air at temperature T3;

[0040] The second evaporator, the second condenser and the second compressor are matched with corresponding parameters according to QE2, ET2 and CT2.

[0041] When the above technical solution is adopted, the second evaporator, the second condenser and the second compressor are selected according to the specific values ​​of QE2, ET2 and CT2 obtained by calculation, so as to achieve the optimal system energy efficiency.

[0042] In the preferred technical solution of the above-mentioned matching method for improving the energy efficiency of the waste recycling system, the matching method further includes:

[0043] The heating capacity QC2 of the second compressor is obtained by matching QE2, ET2, and CT2;

[0044] According to QC2=m 风 (h7-h6) gives h6=h7-QC2 / m 风 ;

[0045] Wherein, h6 is the enthalpy of dry air at temperature T6, and T6 is the air temperature in the air outlet direction of the third condenser;

[0046] Calculate the heat exchange capacity of the third condenser Qc3 = m 风 (h6-h5); where h5 is the enthalpy of dry air at temperature T5;

[0047] The third evaporator, the third condenser and the third compressor are matched with corresponding parameters according to QE3, ET3 and CT3.

[0048] When the above technical solution is adopted, the third evaporator, the third condenser and the third compressor are selected according to the specific values ​​of QE3, ET3 and CT3 obtained by calculation, so as to achieve the optimal system energy efficiency.

[0049] In the preferred technical solution of the above-mentioned matching method for improving the energy efficiency of the waste recycling system, the matching method further includes:

[0050] The cooling capacity QE3 of the third compressor is obtained according to the matching of QC3, ET3 and CT3;

[0051] According to QE3=m 风 (h4-h5) gives h4=h5+QE3 / m 风 ; Where h4 is the enthalpy of dry air at temperature T4;

[0052] Calculate the heat Q that the cooling tower needs to remove 冷却 =m 风 (h3-h4);

[0053] According to Q 冷却 The cooling tower and the cooling tower heat exchanger are matched with corresponding parameters.

[0054] In the case of adopting the above technical solution, according to the calculated Q 冷却 Sizing cooling towers and cooling tower heat exchangers. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The preferred embodiments of the present invention are described below with reference to the accompanying drawings, in which:

[0056] Figure 1 is a schematic diagram of a waste recycling system of the present invention;

[0057] Figure 2 is a flowchart of the steps of a first embodiment of a matching method for improving energy efficiency of a waste recycling system according to the present invention;

[0058] Figure 3 is a flowchart of the steps of a second embodiment of the matching method for improving the energy efficiency of a waste recycling system of the present invention;

[0059] Figure 4 This is a flowchart of the steps of a third embodiment of the matching method for improving the energy efficiency of a waste recycling system according to the present invention. List of reference numerals: 1. First heat pump unit; 11. First compressor; 12. First evaporator; 13. First condenser; 14. First throttle valve; 2. Second heat pump unit; 21. Second compressor; 22. Second evaporator; 23. Second condenser; 24. Second throttle valve; 3. Third heat pump unit; 31. Third compressor; 32. Third evaporator; 33. Third condenser; 34. Third throttle valve; 41. Cooling tower heat exchanger; 42. Cooling tower; 5. Coating machine; 6. Heat exchanger; 71. Air inlet; 72. Air outlet. DETAILED DESCRIPTION

[0060] Preferred embodiments of the present invention are described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely intended to illustrate the technical principles of the present invention and are not intended to limit the scope of protection of the present invention. Those skilled in the art may adjust these embodiments as needed to suit specific applications. It should be noted that, in the description of the present invention, terms such as "inner" and "outer" indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. This is for ease of description only and does not indicate or imply that the device or component described must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0061] Furthermore, it should be noted that, in the description of the present invention, unless otherwise expressly specified or limited, the term "connection" should be understood in a broad sense. For example, it can mean a fixed connection, a detachable connection, or an integral connection; it can mean a mechanical connection; it can mean a direct connection, an indirect connection through an intermediate medium, or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0062] In order to solve the problems of poor operating stability and low energy efficiency of NMP recovery system in the existing battery electrode coating process, Figure 1 The waste recycling system of the present invention includes a heat exchanger 6, a circulating air duct, a multi-stage heat pump unit, a cooling tower heat exchanger 41 and a cooling tower 42. The cooling tower heat exchanger 41 and the cooling tower 42 are connected through a circulating water circuit, and the cooling tower 42 is connected to the outside of the recycling system;

[0063] The multi-stage heat pump unit includes a compressor, an evaporator and a condenser arranged on a refrigerant circulation loop. The two ends of the circulating air duct are respectively connected to the air inlet 71 and the air outlet 72 of the coating machine. The heat exchanger 6, the evaporator and the condenser are arranged in sequence between the air inlet 71 and the air outlet 72, so that the high-temperature air at the air outlet 72 exchanges heat with the low-temperature air through the heat exchanger 6 and then passes through the evaporator step by step to cool and condense the waste to recover the waste. The cooling tower heat exchanger 41 absorbs the heat of the air and then discharges the heat to the outside of the recovery system through the cooling tower 42 to maintain the heat balance in the system. The condensed low-temperature air is then heated by the condenser and the heat exchanger 6 step by step and then returns to the air inlet 71 for drying.

[0064] The advantages of the above arrangement are that the waste recovery system of the present invention utilizes a combination of a heat exchanger 6, a multi-stage heat pump unit, and a cooling tower 42 to condense the exhaust gas to recover the NMP therein, and recycle the heat for drying, thereby improving recovery efficiency and reducing system energy consumption. Due to the temperature tolerance of existing compressor motors, achieving ultra-high evaporation temperatures is difficult. The present invention first lowers the temperature of the high-temperature air within the system by exchanging heat with the condensed low-temperature air within the heat exchanger 6 before condensing it in the evaporator. This reduces the evaporation temperature of the heat pump unit compressor and reduces compressor costs. The inventors discovered that because the compressor continuously generates heat while the heat required for drying the coating machine is constant, the amount of heat generated during closed-loop operation of the recovery system increases, ultimately leading to a heat imbalance that destabilizes the system and even renders it inoperable. Therefore, the cooling tower 42 removes some of the heat from the system to maintain heat balance within the system, ensuring that the heat pump unit operates smoothly at all times and improving the energy efficiency of the recovery system. Therefore, the recovery system of the present invention achieves better overall condensation efficiency, more stable operation, a high NMP recovery rate, and lowers the cost of the recovery system.

[0065] Reference Figure 1 In one possible embodiment, the waste recovery system of the present invention includes a heat exchanger 6, a circulating air duct, a three-stage heat pump unit, a cooling tower heat exchanger 41, a cooling tower 42 and a collection device. The cooling tower heat exchanger 41 and the cooling tower 42 are connected by a circulating water circuit, and the cooling tower 42 is connected to the outside of the recovery system to discharge excess heat in the system to the outside of the system and maintain the thermal balance in the system.

[0066] Furthermore, the three-stage heat pump unit includes a first heat pump unit 1, a second heat pump unit 2, and a third heat pump unit 3, which are arranged in sequence. The first heat pump unit 1 includes a first compressor 11, a first evaporator 12, a first throttle valve 14, and a first condenser 13, which are arranged on a first refrigerant circulation loop. The second heat pump unit 2 includes a second compressor 21, a second evaporator 22, a second throttle valve 24, and a second condenser 23, which are arranged on a second refrigerant circulation loop. The third heat pump unit 3 includes a third compressor 31, a third evaporator 32, a third throttle valve 34, and a third condenser 33, which are arranged on a third refrigerant circulation loop. Existing two-stage heat pumps require a relatively large temperature rise, resulting in relatively low energy efficiency for each heat pump unit. However, a three-stage heat pump can maintain the three heat pump units within a reasonable temperature rise range, achieving not only higher energy efficiency but also a balance between energy efficiency and cost. Furthermore, compared to a two-stage heat pump, a three-stage heat pump can recover NMP at a lower temperature, resulting in a higher NMP recovery rate. The throttle valve blocks the flow of refrigerant through its internal orifice. Working in conjunction with the compressor, it creates high and low pressure zones in the system, ensuring the proper circulation of the refrigerant and acting as a throttling and pressure reducer. The throttle valve also controls its opening based on changes in the refrigerant superheat at the evaporator outlet, thereby regulating the refrigerant flow entering the evaporator. This ensures that the refrigerant flow matches the evaporator's heat load and provides sufficient superheat at the compressor intake. This ensures both cooling efficiency and stable system operation. By precisely controlling the refrigerant flow and pressure and rationally adjusting the refrigerant flow to avoid excess or insufficient flow, energy waste can be reduced and the energy efficiency of the heat pump system improved.

[0067] Furthermore, the two ends of the circulating air duct are respectively connected to the air inlet 71 and the air outlet 72 of the coating machine. Along the air flow direction, the heat exchanger 6, the first evaporator 12, the second evaporator 22, the cooling tower heat exchanger 41, the third evaporator 32, the third condenser 33, the second condenser 23 and the first condenser 13 are sequentially arranged between the air outlet 72 and the air inlet 71, so that the high-temperature air in the circulating air duct is cooled by the heat exchanger 6, and then gradually passes through the evaporator for cooling and condensation to recover the NMP waste. When the air passes through the cooling tower heat exchanger 41, the cooling tower The heat exchanger 41 discharges the absorbed heat outside the system through the cooling tower 42, maintaining the heat balance of the system so that the recovery system can run more smoothly. The condensed low-temperature air is then heated to the target temperature through the condenser step by step and then re-enters the coater for drying. Among them, the heat exchanger 6 is arranged between the coater 5 and the first evaporator 12 and between the second condenser 23 and the first condenser 13. The low-temperature air and the high-temperature air exchange heat in the heat exchanger 6. The high-temperature air in the heat exchanger 6 is reduced from temperature T0 to T1, and the low-temperature air temperature is heated from T7 to T8.

[0068] Among them, the cooling tower 42 is arranged between the second heat pump unit 2 and the third heat pump unit 3, and the air temperature therebetween is not too high or too low. The cooling tower heat exchanger 41 can condense the air only by relying on municipal water, which can prevent the air temperature from being lower than the cooling water temperature, causing the cooling tower 42 to lose its function of cooling the air.

[0069] The waste recycling system further includes a waste collection device disposed within the circulating air duct for collecting NMP waste precipitated by condensation of air within the circulating air duct. For example, the waste collection device can be a conveyor belt, onto which the NMP waste falls and is then transported out of the circulating air duct. Alternatively, the waste collection device can be a receiving tray suspended within the circulating air duct for receiving the NMP waste.

[0070] As stated in the first paragraph of this section, the above implementation mode is only used to illustrate the principles of the present invention and is not intended to limit the scope of protection of the present invention. Without departing from the principles of the present invention, those skilled in the art can adjust the above structure so that the present invention can be applied to more specific application scenarios.

[0071] In addition, the present invention also provides a matching method for improving the energy efficiency of a waste recycling system. The waste recycling system is the waste recycling system in the above-mentioned embodiment. Through this matching method, the parameters of the heat pump unit and the cooling tower 42 in the recycling system are selected, thereby matching a high-efficiency recycling system that matches the drying capacity of the coating machine, making NMP recovery more energy-efficient.

[0072] Reference Figure 2 Specifically, the matching methods to improve the energy efficiency of waste recycling systems include:

[0073] Step S11: Calculate T1 = (ET1max + (T0 - T5) / 4 + t);

[0074] Step S12: Calculate the heat exchange temperature difference ΔT of the heat exchanger 气 =T0-T1=T0-(ET1max+(T0-T5) / 4+t);

[0075] Wherein, T1 is the air temperature in the direction of air outlet from the heat exchanger 6 to the evaporator, T0 is the air temperature at the air outlet 72 and the air inlet 71, ET1max is the maximum limit of the evaporation temperature of the first compressor 11, T5 is the air temperature in the direction of air outlet from the third evaporator 32, and t is the heat exchange temperature difference; ET1max, T0, T5, and t are all set values, which are selected by those skilled in the art according to actual needs;

[0076] Step S13: Calculate the heat exchanger capacity Q of the heat exchanger 气 =m 风(h0-h1); where h0 and h1 are the enthalpy values ​​of dry air at temperatures T0 and T1 respectively; m 风 is the air quality in the circulating air duct;

[0077] m 风 =Q 风 ρ 风 ; where Q 风 is the air volume, ρ 风 is the air density; Q 风 is a set value, which is selected by those skilled in the art according to the drying requirements of the coater 5;

[0078] Step S14: According to Q 气 Match the heat exchanger with corresponding parameters.

[0079] According to the calculated heat exchange capacity Q of the heat exchanger 6 气 Select a type for heat exchanger 6.

[0080] Reference Figure 3 , step S21: calculating the total temperature rise to be increased by the three-stage heat pump system △T=T0-T5+2t;

[0081] Step S22: Calculate the average temperature rise ΔT of each heat pump unit based on ΔT 均 =(T0-T5+2t) / 3.

[0082] Specifically, △T1=△T2=△T3=△T 均 , where △T1 is the temperature rise of the first heat pump unit, △T2 is the temperature rise of the second heat pump unit, and △T3 is the temperature rise of the third heat pump unit. The temperature rise of the heat pump is directly related to the difficulty of the compressor to perform work, which is also directly related to the operating energy efficiency of the heat pump system. The larger the temperature difference that the heat pump needs to increase, the lower the heat pump efficiency, and the smaller the temperature difference that the heat pump needs to increase, the higher the heat pump efficiency. Therefore, by equalizing the temperature rise of the three heat pump units, the energy efficiency of the three heat pump units is balanced and they can all operate under optimal conditions. Taking T0 = 110℃, T5 = 15℃, and t = 10℃ as an example, the average temperature rise of each heat pump unit in the three-stage heat pump unit is 38.3℃. Under this temperature rise, the heating energy efficiency of the general heat pump system can be greater than 4.0, thereby making the overall energy efficiency of the recovery system higher.

[0083] Step S23: According to ΔT1=CT1-ET1=ΔT 均 Calculate T2; wherein CT1 is the condensing temperature of the first heat pump unit, ET1 is the evaporating temperature of the first heat pump unit; T2 is the air temperature in the outlet direction of the first evaporator 12.

[0084] Specifically, according to CT1=T0+t; ET1=T2-t;

[0085] △T1=CT1-ET1=T0-T2+2t=△T 均 ;

[0086] T0-T2+2t=(T0-T5+2t) / 3;

[0087] Finally, we get T2=2T0 / 3+T5 / 3+4t / 3.

[0088] Step S24: Calculate the heat exchange capacity of the first evaporator QE1 = m 风 (h1-h2); where h2 is the enthalpy of dry air at temperature T2; m 风 It is the air quality in the circulating air duct.

[0089] Step S25: Match the first evaporator, the first condenser, and the first compressor with corresponding parameters for the recovery system according to QE1, ET1, and CT1.

[0090] The first evaporator 12, the first condenser 13 and the first compressor 11 are selected according to the specific values ​​of QE1, ET1 and CT1 obtained by calculation, so as to achieve the optimal system energy efficiency.

[0091] Those skilled in the art can obtain the air enthalpy at the corresponding dry air temperature by looking up the physical properties of air. Since the circulating air has an extremely low moisture content and the NMP it contains is negligible compared to the large change in air enthalpy, it can be treated as dry air for calculating the heat change. It should be noted that the references to air temperature and enthalpy below can be obtained by looking up the table to obtain the dry air enthalpy at the corresponding air temperature or the air temperature at the corresponding dry air enthalpy value, and this will not be further described.

[0092] Reference Figure 4 , further, step S31: according to the calculated QE1, ET1, CT1, the rated operating power W1 of the first compressor and the heating capacity QC1 of the first compressor are obtained by matching through the working condition calculation sheet of the compressor;

[0093] Step S32: According to QC1=m 风 (h0-h8) gives h8=h0-QC1 / m 风 ; Wherein, h8 is the enthalpy of dry air at temperature T8, and T8 is the air temperature in the direction of the heat exchanger 6 outflowing to the condenser;

[0094] Step S33: According to the temperature rise of the second heat pump unit ΔT2=CT2-ET2=ΔT 均 Calculate T2; where CT2 is the condensing temperature of the second heat pump unit, ET2 is the evaporating temperature of the second heat pump unit; T2 is the air temperature in the outlet direction of the second evaporator 22;

[0095] According to CT2 = T7 + t; ET2 = T3 - t;

[0096] T7-T3+2t=(T0-T5+2t) / 3; T7=T8-△T 气 ;

[0097] Finally, we get T3=T8-△T 气 +4 / 3t-1 / 3T0+1 / 3T5;

[0098] Step S34: Calculate the heat exchange capacity of the second evaporator QE2 = m 风 (h2-h3); wherein h3 is the enthalpy of dry air at temperature T3, T3 is the air temperature in the outlet direction of the second evaporator, and T7 is the air temperature in the outlet direction of the second condenser 23;

[0099] Step S35: Match the second evaporator, the second condenser and the second compressor with corresponding parameters for the recovery system according to QE2, ET2 and CT2.

[0100] The second evaporator 22, the second condenser 23 and the second compressor 21 are selected according to the specific values ​​of QE2, ET2 and CT2 obtained by calculation, so as to achieve the optimal system energy efficiency.

[0101] Step S41: According to the calculated QE2, ET2, and CT2, the rated operating power W2 of the second compressor and the heating capacity QC2 of the second compressor are obtained by matching the compressor working condition calculation sheet;

[0102] Step S42: According to QC2=m 风 (h7-h6) gives h6=h7-QC2 / m 风 ; Among them, h6 is the enthalpy value of dry air at temperature T6, T6 is the air temperature in the outlet direction of the third condenser 33, and h7 is the enthalpy value of dry air at temperature T7.

[0103] Step S43: Calculate the heat exchange capacity of the third condenser QC3 = m 风 (h6-h5); where h5 is the enthalpy of dry air at temperature T5;

[0104] Step S44: Match the third evaporator, the third condenser and the third compressor with corresponding parameters for the recovery system according to QE3, ET3 and CT3.

[0105] The third evaporator 32 , the third condenser 33 and the third compressor 31 are selected according to the specific values ​​of QE3 , ET3 and CT3 obtained by calculation, so as to achieve the optimal system energy efficiency.

[0106] Step S51: According to the calculated QE3, ET3, and CT3, the rated operating power W3 of the third compressor and the heating capacity QC3 of the third compressor are obtained by matching the compressor working condition calculation sheet;

[0107] Step S52: According to QE3=m 风 (h4-h5) gives h4=h5+QE3 / m 风 ; Wherein, h4 is the enthalpy of dry air at temperature T4, and T4 is the air temperature in the outlet direction of the cooling tower heat exchanger 41;

[0108] Step S53: Calculate the heat Q that the cooling tower needs to remove 冷却 =m 风 (h3-h4);

[0109] Step S54: According to Q 冷却 Match the cooling tower and cooling tower heat exchanger with corresponding parameters for the recovery system.

[0110] That is, according to the calculated Q 冷却 Select a type for the cooling tower 42 and the cooling tower heat exchanger 41.

[0111] Thus far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art may make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will fall within the scope of protection of the present invention.

Claims

1. A waste recycling system, characterized in that: It includes a heat exchanger, a circulating air duct, a multi-stage heat pump unit, a cooling tower heat exchanger and a cooling tower, wherein the cooling tower heat exchanger and the cooling tower are connected through a circulating water circuit, and the cooling tower is connected to the outside of the recovery system; The multi-stage heat pump unit includes an evaporator and a condenser arranged on a refrigerant circulation loop, and the two ends of the circulation air duct are respectively connected to the air inlet and the air outlet of the coating machine, and the heat exchanger, the evaporator and the condenser are sequentially arranged between the air inlet and the air outlet, and the cooling tower heat exchanger is arranged between the air outlet and the condenser, so that the high-temperature air at the air outlet exchanges heat with the low-temperature air through the heat exchanger and then passes through the evaporator step by step to cool and condense the waste to be recovered. After absorbing the heat of the air through the cooling tower heat exchanger, the heat is discharged to the outside of the recovery system through the cooling tower to maintain heat balance. The condensed low-temperature air then passes through the condenser and the heat exchanger step by step to be heated and then enters the air inlet for drying.

2. The waste recycling system according to claim 1, characterized in that: The multi-stage heat pump unit includes a first heat pump unit, a second heat pump unit and a third heat pump unit arranged in sequence; the first heat pump unit includes a first compressor, a first evaporator and a first condenser arranged on a first refrigerant circulation loop, the second heat pump unit includes a second compressor, a second evaporator and a second condenser arranged on a second refrigerant circulation loop, the third heat pump unit includes a third compressor, a third evaporator and a third condenser arranged on a third refrigerant circulation loop, and the heat exchanger is arranged between the coater and the first evaporator.

3. The waste recycling system according to claim 2, characterized in that: The cooling tower heat exchanger is arranged between the second evaporator and the third evaporator.

4. The waste recycling system according to claim 1, characterized in that: The multi-stage heat pump unit includes a first heat pump unit, a second heat pump unit and a third heat pump unit arranged in sequence; the first heat pump unit includes a first compressor, a first evaporator and a first condenser arranged on a first refrigerant circulation loop, the second heat pump unit includes a second compressor, a second evaporator and a second condenser arranged on a second refrigerant circulation loop, the third heat pump unit includes a third compressor, a third evaporator and a third condenser arranged on a third refrigerant circulation loop, and the heat exchanger is arranged between the second condenser and the first condenser.

5. The waste recycling system according to any one of claims 2 to 4, characterized in that: The first heat pump unit also includes a first throttle valve arranged on the first refrigerant circulation loop, the second heat pump unit also includes a second throttle valve arranged on the second refrigerant circulation loop, and the third heat pump unit also includes a third throttle valve arranged on the third refrigerant circulation loop.

6. A matching method for improving the energy efficiency of a waste recycling system, characterized in that: The waste recovery system includes a heat exchanger, a circulating air duct, a multi-stage heat pump unit, a cooling tower heat exchanger and a cooling tower, wherein the cooling tower heat exchanger and the cooling tower are connected through a circulating water circuit, and the cooling tower is connected to the outside of the recovery system; The multi-stage heat pump unit includes a compressor, an evaporator and a condenser arranged on a refrigerant circulation loop, the two ends of the circulation air duct are respectively connected to the air inlet and the air outlet of the coating machine, the heat exchanger, the evaporator and the condenser are sequentially arranged between the air inlet and the air outlet, and the cooling tower heat exchanger is arranged between the air outlet and the condenser, so that the high-temperature air at the air outlet exchanges heat with the low-temperature air through the heat exchanger and then passes through the evaporator step by step to cool and condense the waste for recycling. After absorbing the heat of the air through the cooling tower heat exchanger, the heat is discharged to the outside of the recovery system through the cooling tower to maintain heat balance. The condensed low-temperature air then passes through the condenser and the heat exchanger step by step to be heated and then enters the air inlet for drying; The multi-stage heat pump unit includes a first heat pump unit, a second heat pump unit and a third heat pump unit which are arranged in sequence; the first heat pump unit includes a first compressor, a first evaporator and a first condenser arranged on a first refrigerant circulation loop, the second heat pump unit includes a second compressor, a second evaporator and a second condenser arranged on a second refrigerant circulation loop, and the third heat pump unit includes a third compressor, a third evaporator and a third condenser arranged on a third refrigerant circulation loop; the cooling tower heat exchanger is arranged between the second evaporator and the third evaporator, and the heat exchanger is arranged between the coating machine and the first evaporator and between the second condenser and the first condenser; The matching method includes: Calculate T1 = (ET1 max +(T0-T5) / 4+t); Calculate the heat exchange temperature difference ΔT of the heat exchanger 气 =T0-T1=T0-(ET1 max +(T0-T5) / 4+t); Wherein, T0 is the air temperature at the outlet and the inlet, ET1 max is the maximum limit of the evaporation temperature of the first compressor, T1 is the air temperature in the direction of the air outlet from the heat exchanger to the evaporator, T5 is the air temperature in the direction of the air outlet from the third evaporator, and t is the heat exchange temperature difference; ET1 max , T0, T5, t are set values; Calculate the heat exchanger capacity Q of the heat exchanger 气 =m 风 (h0-h1); where h0 and h1 are the enthalpy values ​​of dry air at temperatures T0 and T1 respectively; m 风 is the air mass in the circulating air duct; m 风 =Q 风 ρ 风 ; where Q 风 is the air volume, ρ 风 is the air density; Q 风 is the set value; According to Q 气 Match the heat exchanger with corresponding parameters.

7. The matching method for improving the energy efficiency of a waste recycling system according to claim 6, characterized in that: The matching method further includes: Calculate the total temperature rise of the multi-stage heat pump unit ΔT = (T0-T5+2t); Calculate the average temperature rise of each heat pump unit △T based on △T 均 =(T0-T5+2t) / 3; According to the temperature rise of the first heat pump unit ΔT1=CT1-ET1=ΔT 均 Calculate T2; According to CT1=T0+t, ET1=T2-t, we can obtain T2=2T0 / 3+T5 / 3+4t / 3; wherein CT1 is the condensing temperature of the first heat pump unit, and ET1 is the evaporating temperature of the first heat pump unit; Calculate the heat exchange rate of the first evaporator QE1 = m 风 (h1-h2); where h2 is the enthalpy of dry air at temperature T2; The first evaporator, the first condenser and the first compressor are matched with corresponding parameters according to QE1, ET1 and CT1.

8. The matching method for improving the energy efficiency of a waste recycling system according to claim 7, characterized in that: The matching method further includes: The heating capacity QC1 of the first compressor is obtained by matching QE1, ET1 and CT1; According to QC1=m 风 (h0-h8) gives h8=h0-QC1 / m 风 ; Wherein, h8 is the enthalpy of dry air at temperature T8, and T8 is the air temperature in the direction of the air outlet from the heat exchanger to the condenser; According to the temperature rise of the second heat pump unit ΔT2=CT2-ET2=ΔT 均 Calculate T3; According to T7=T8-△T 气 , CT2=T7+t,ET2=T3-t, so T3=T8-△T 气 +4 / 3t-1 / 3T0+1 / 3T5; among them, CT2 is the condensing temperature of the second heat pump unit, ET2 is the evaporating temperature of the second heat pump unit; T3 is the air temperature in the air outlet direction of the second evaporator; T7 is the air temperature in the air outlet direction of the second condenser; Calculate the heat exchange rate of the second evaporator QE2 = m 风 (h2-h3); where h3 is the enthalpy of dry air at temperature T3; The second evaporator, the second condenser and the second compressor are matched with corresponding parameters according to QE2, ET2 and CT2.

9. The matching method for improving the energy efficiency of a waste recycling system according to claim 8, characterized in that: The matching method further includes: The heating capacity QC2 of the second compressor is obtained by matching QE2, ET2, and CT2; According to QC2=m 风 (h7-h6) gives h6=h7-QC2 / m 风 ; Wherein, h6 is the enthalpy of dry air at temperature T6, and T6 is the air temperature in the air outlet direction of the third condenser; Calculate the heat exchange capacity of the third condenser Qc3 = m 风 (h6-h5); where h5 is the enthalpy of dry air at temperature T5; The third evaporator, the third condenser and the third compressor are matched with corresponding parameters according to QE3, ET3 and CT3.

10. The matching method for improving the energy efficiency of a waste recycling system according to claim 9, characterized in that: The matching method further includes: The cooling capacity QE3 of the third compressor is obtained according to the matching of QC3, ET3 and CT3; According to QE3=m 风 (h4-h5) gives h4=h5+QE3 / m 风 ; Where h4 is the enthalpy of dry air at temperature T4; Calculate the heat Q that the cooling tower needs to remove 冷却 =m 风 (h3-h4); According to Q 冷却 The cooling tower and the cooling tower heat exchanger are matched with corresponding parameters.

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