Heat pump sludge drying system

Abstract

The present invention provides a heat pump sludge drying system, which includes an absorption heat pump, a sludge dryer, a cooling tower, a first circulation pipeline and a second circulation pipeline; the absorption heat pump includes a heat absorption part and a heat release part, and the sludge dryer includes a circulation air duct, a condenser, an evaporator and a sludge conveying mechanism; the circulation air duct passes through the condenser, the evaporator and the sludge conveying mechanism, and the sludge conveying mechanism is arranged between the air outlet of the condenser and the air inlet of the evaporator; the first circulation pipeline passes through the heat release part and the condenser, and the condenser is used to transfer the heat in the first circulation pipeline to the circulation air duct; the second circulation pipeline passes through the heat absorption part, the evaporator and the cooling tower, and the evaporator is used to transfer the heat in the circulation air duct to the second circulation pipeline. Compared with the prior art, the present invention provides heat for the sludge dryer through the absorption heat pump, and recovers the heat of the second heat exchange medium output by the evaporator through the absorption heat pump, improving the efficiency of sludge drying.

Description

Technical Field

[0001] The present invention relates to the field of sludge drying, and particularly to a heat pump sludge drying system. Background Art

[0002] At present, with the continuous development of society, the sewage treatment volume and sludge production across the country increase year by year. With the gradual tightening of environmental protection policies, the sludge generated after the treatment of domestic wastewater and industrial wastewater needs to be properly treated. Sludge drying is an important means to achieve sludge reduction, harmlessness, and resource utilization. Existing sludge dryers mainly include a compressor, a condenser, a throttling element, an evaporator, and a circulation fan for forming a circulating air flow; when air flows through the condenser, it is heated, and then flows through the sludge, and the moisture in the sludge is transferred to the air; subsequently, the air containing moisture is transported to the evaporator, the air is cooled, and the moisture in the air is condensed into liquid water, thereby reducing the moisture content in the air; finally, the air from which moisture has been removed is transported back to the condenser for reheating, thus forming a cycle to dry the sludge. However, the existing sludge dryers have the disadvantages of relatively small heating capacity and low energy utilization efficiency, resulting in low sludge drying efficiency. Summary of the Invention

[0003] Based on this, the purpose of the present invention is to provide a heat pump sludge drying system with a large heating capacity and high energy utilization efficiency to improve the drying efficiency of the sludge drying system.

[0004] The heat pump sludge drying system of the present invention includes an absorption heat pump, a sludge dryer, a cooling tower, a first circulation pipeline, and a second circulation pipeline; the absorption heat pump includes a heat absorption part for absorbing heat and a heat release part for releasing heat, and the sludge dryer includes a circulation air duct, a condenser, an evaporator, and a sludge conveying mechanism;

[0005] The circulation air duct is also provided with a circulation fan for circulating air in the circulation air duct; the circulation air duct passes through the condenser, the evaporator, and the sludge conveying mechanism, and the sludge conveying mechanism is arranged between the air outlet of the condenser and the air inlet of the evaporator;

[0006] The first circulation pipeline is used to accommodate a first heat exchange medium, and a first circulation pump is arranged on the first circulation pipeline for circulating the first heat exchange medium in the first circulation pipeline; the first circulation pipeline passes through the heat release part and the condenser, and the condenser is used to transfer the heat in the first circulation pipeline to the circulation air duct;

[0007] The second circulation pipeline is used to accommodate a second heat exchange medium. A second circulation pump is provided on the second circulation pipeline, and the second circulation pump is used to circulate the second heat exchange medium in the second circulation pipeline; the second circulation pipeline passes through the heat absorption part, the evaporator and the cooling tower, and the input end of the cooling tower is connected to the output end of the heat absorption part, and the input end of the evaporator is connected to the output end of the cooling tower; the evaporator is used to transfer the heat in the circulation air duct to the second circulation pipeline.

[0008] Further, it further includes a controller, a first flow meter, a second flow meter and a first temperature sensor. The first flow meter is arranged on the first circulation pipeline, the second flow meter is arranged on the second circulation pipeline, and the first temperature sensor is arranged at the air outlet of the condenser; the controller is electrically connected to the absorption heat pump, the circulation fan, the sludge conveying mechanism, the first circulation pump, the second circulation pump, the first flow meter, the second flow meter and the first temperature sensor;

[0009] The first flow meter is used to detect the flow rate of the first heat exchange medium in the first circulation pipeline and convert it into a first flow detection signal and send it to the controller;

[0010] The second flow meter is used to detect the flow rate of the second heat exchange medium in the second circulation pipeline and convert it into a second flow detection signal and send it to the controller;

[0011] The first temperature sensor is used to detect the air outlet temperature of the condenser and convert it into a first temperature detection signal and send it to the controller;

[0012] During the startup process, the controller is used to:

[0013] Control the second circulation pump to start, so that the second heat exchange medium forms a circulation in the second circulation pipeline;

[0014] When the value of the received second flow detection signal reaches the corresponding set value, control the first circulation pump to start;

[0015] When the value of the received first flow detection signal reaches the corresponding set value, control the absorption heat pump and the circulation fan to start;

[0016] When the received first temperature detection signal reaches the set value, control the sludge conveying mechanism to start.

[0017] Further, there are multiple sludge dryers, and the first circulation pump is a variable-frequency circulation pump;

[0018] During the startup process, the controller is further configured to obtain the number n of sludge dryers to be started.

[0019] When n = 1 and the value of the second flow rate detection signal received by the controller reaches the set value, the controller is configured to control the first circulation pump to increase to the first set frequency fs1.

[0020] When n = 2 and the value of the second flow rate detection signal received by the controller reaches the set value, the controller is configured to control the first circulation pump to increase to the second set frequency fs2.

[0021] When n = 3 and the value of the second flow rate detection signal received by the controller reaches the set value, the controller is configured to control the first circulation pump to increase to the third set frequency fs3.

[0022] Wherein, the first set frequency fs1 < the second set frequency fs2 < the third set frequency fs3.

[0023] Furthermore, there are multiple sludge dryers.

[0024] The controller is further configured to obtain the maximum value Ts of the outlet air temperature set values of the condensers of each sludge dryer max , and control the temperature T of the first heat exchange medium output by the heat release part of the absorption heat pump according to the maximum value Ts of the outlet air temperature set values max , so that T out > Ts out + X1; where X1 is a preset first temperature difference value. max

[0025] Furthermore, a regulating valve is provided at the first heat exchange medium input end of each condenser, and each regulating valve is electrically connected to the controller; the controller is further configured to perform PID control on the opening degree of the corresponding regulating valve according to the deviation of the actual outlet air temperature of the condenser from the outlet air temperature set value.

[0026] Furthermore, it further includes a controller and a first heat exchange medium replenishing device, and the first heat exchange medium replenishing device includes a first heat exchange medium storage tank, a first heat exchange medium replenishing pump and a pressure sensor;

[0027] The input end of the first heat exchange medium replenishing pump is connected to the first heat exchange medium storage tank, and the output end of the first heat exchange medium replenishing pump is connected to the first circulation pipeline;

[0028] The pressure sensor is arranged on the first circulation pipeline and is electrically connected to the controller; the pressure sensor is used to detect the pressure of the first circulation pipeline and transmit the pressure detection signal to the controller;

[0029] The controller is electrically connected to the first heat exchange medium makeup pump, and the controller is used to control the first heat exchange medium makeup pump according to the received pressure detection signal.

[0030] Further, the output end of the first heat exchange medium makeup pump is connected between the output end of the condenser and the input end of the heat release part.

[0031] Further, the first heat exchange medium makeup device further includes a buffer tank connected to the output end of the first heat exchange medium makeup pump.

[0032] Further, a check valve is provided at the output end of the first heat exchange medium makeup pump, and the first heat exchange medium makeup pump is connected to the first circulation pipeline and the buffer tank through the check valve.

[0033] Further, the first heat exchange medium is water; a softened water device is further included, and the input end and the output end of the softened water device are respectively connected to a water source and the first heat exchange medium storage tank.

[0034] Further, a liquid storage tank for collecting the cooled heat exchange medium is provided below the cooling tower;

[0035] A controller and a second heat exchange medium makeup device are further included. The second heat exchange medium makeup device includes a second heat exchange medium makeup pipeline, a second heat exchange medium makeup valve and a liquid level sensor. The output end of the second heat exchange medium makeup pipeline is connected to the liquid storage tank. The second heat exchange medium makeup valve is arranged on the second heat exchange medium makeup pipeline, and the liquid level sensor is arranged in the liquid storage tank;

[0036] The second heat exchange medium makeup valve and the liquid level sensor are respectively electrically connected to the controller. The liquid level sensor is used to detect the liquid level in the liquid storage tank and transmit a liquid level detection signal to the controller. The controller is used to control the opening degree of the second heat exchange medium makeup valve according to the received liquid level detection signal.

[0037] Further, the first circulation pump is arranged between the output end of the condenser and the input end of the heat release part, and the second circulation heat pump is arranged between the output end of the cooling tower and the input end of the evaporator.

[0038] Further, there are multiple first circulation pumps, and the first circulation pumps are connected in parallel with each other;

[0039] There are multiple second circulation pumps, and the second circulation pumps are connected in parallel with each other.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] 1. The absorption heat pump provides heat for the sludge dryer, and the heat of the second heat exchange medium output by the evaporator is recovered by the absorption heat pump, improving the heating capacity and energy utilization rate, thereby improving the efficiency of sludge drying;

[0042] 2. Multiple sludge dryers are set up to make more full use of the heat provided by the absorption heat pump to further improve the efficiency of sludge drying;

[0043] 3. A first heat exchange medium replenishing device is set up to keep the pressure of the first circulation pipeline within the normal range and ensure the normal operation of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a schematic diagram of the overall structure of the heat pump sludge drying system of the present invention;

[0045] Figure 2 It is a schematic diagram of the structure of the dryer of the heat pump sludge drying system of the present invention;

[0046] Figure 3 It is a schematic diagram of the circuit structure of the heat pump sludge drying system of the present invention.

[0047] In the figure: 10. Absorption heat pump; 11. Heat absorption part; 12. Heat release part; 20. Sludge dryer; 211. First temperature sensor; 22. Condenser; 23. Evaporator; 24. Circulation fan; 25. Sludge conveying mechanism; 30. Cooling tower; 31. Liquid storage tank; 32. Heat exchange fan; 41. First circulation pump; 42. First flow meter; 51. Second circulation pump; 52. Second flow meter; 60. Softening water device; 71. First heat exchange medium storage; 72. First heat exchange medium replenishing pump; 73. Buffer tank; 74. Pressure sensor; 81. Second heat exchange medium replenishing pipeline; 82. Second heat exchange medium replenishing valve; 83. Liquid level sensor; C. Controller. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0048] The following are specific embodiments of the present invention. In combination with the accompanying drawings, the technical solutions of the present invention are further described, but the present invention is not limited to these embodiments.

[0049] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0050] It should be noted that when an element is referred to as "fixed to" another element, it can be directly on the other element or there may also be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time.

[0051] Currently, with the continuous development of society, the sewage treatment volume and sludge production across the country are increasing year by year. With the gradual tightening of environmental protection policies, the sludge generated after the treatment of domestic wastewater and industrial wastewater needs to be properly treated. Sludge drying is an important means to achieve sludge reduction, harmlessness, and resource utilization. Existing sludge dryers mainly include a compressor, a condenser, a throttling element, an evaporator, and a circulation fan for forming a circulating air flow; when air flows through the condenser, it is heated, and then it flows through the sludge, and the moisture in the sludge is transferred to the air; subsequently, the air containing moisture is transported to the evaporator, the air is cooled, and the moisture in the air is condensed to form liquid water, thereby reducing the moisture content in the air; finally, the air from which the moisture has been removed is transported back to the condenser for reheating, thus forming a cycle to dry the sludge. However, the sludge dryers of the existing technology have the disadvantages of relatively small heating capacity and low energy utilization rate, resulting in low efficiency of sludge drying.

[0052] To solve the above technical problems, the present invention provides a heat pump sludge drying system, as Figure 1 and Figure 2 shown. The heat pump sludge drying system includes an absorption heat pump 10, a sludge dryer 20, a cooling tower 30, a first circulation pipeline, and a second circulation pipeline. Specifically, the absorption heat pump 10 further includes a heat absorption part 11 for absorbing heat and a heat release part 12 for releasing heat. The sludge dryer 20 includes a circulation air duct, a condenser 22, an evaporator 23, and a sludge conveying mechanism 25.

[0053] A circulation fan 24 is further provided on the circulation air duct. The circulation fan 24 is used to make the air circulate in the circulation air duct; the circulation air duct passes through the condenser 22, the evaporator 23, and the sludge conveying mechanism 25, and the sludge conveying mechanism 25 is arranged between the air outlet of the condenser 22 and the air inlet of the evaporator 23.

[0054] The first circulation pipeline is used to accommodate a first heat exchange medium. A first circulation pump 41 is provided on the first circulation pipeline. The first circulation pump 41 is used to make the first heat exchange medium circulate in the first circulation pipeline; the first circulation pipeline passes through the heat release part 12 and the condenser 22, and the condenser 22 is used to transfer the heat in the first circulation pipeline to the circulation air duct 21.

[0055] The second circulation pipeline is used to accommodate the second heat exchange medium. A second circulation pump 51 is provided on the second circulation pipeline, and the second circulation pump 51 is used to make the second heat exchange medium circulate in the second circulation pipeline; the second circulation pipeline passes through the heat absorption part 11, the evaporator 23 and the cooling tower 30. The input end of the cooling tower 30 is connected to the output end of the heat absorption part 12, and the input end of the evaporator 23 is connected to the output end of the cooling tower 30. A heat exchange fan 32 for making the second heat exchange medium exchange heat with air is provided on the cooling tower 30. By adjusting the rotation speed of the heat exchange fan 32, the temperature of the second heat exchange medium output from the cooling tower 30 can be adjusted; the evaporator 23 is used to transfer the heat in the circulation air duct 21 to the second circulation pipeline.

[0056] The working principle of the present invention is as follows:

[0057] 1. In the first circulation pipeline: The first heat exchange medium in the first circulation pipeline is heated by the heat release part 12 and then transported to the condenser 22. The first heat exchange medium releases heat in the condenser 22, increasing the temperature of the air flowing through the condenser 22; the first heat exchange medium flowing through the condenser 22 is transported back to the heat release part 12, and the heat release part 12 heats the first heat exchange medium again, thus forming a cycle.

[0058] 2. In the second circulation pipeline: The second heat exchange medium in the second circulation pipeline is cooled by the heat absorption part 11 and the cooling tower 30 and then transported into the evaporator 23. The second heat exchange medium absorbs heat in the evaporator 23, reducing the temperature of the air flowing through the evaporator 23; the second heat exchange medium flowing through the evaporator 23 is transported back to the heat absorption part 11 and the cooling tower 30, and the heat absorption part 11 and the cooling tower 30 cool the second heat exchange medium again, thus forming a cycle.

[0059] 3. In the circulation air duct: The air is heated by the condenser 22 and then transported to the sludge conveying mechanism 25. The sludge on the sludge conveying mechanism 25 is heated by the air, and the moisture in the sludge forms water vapor and separates from the sludge. The water vapor and the air are jointly transported to the evaporator 23; the temperature of the evaporator 23 is relatively low, and the water vapor is cooled by the evaporator 23 to form liquid water and then discharged from the circulation air duct. Thus, the water vapor is separated from the air, and the separated air is transported to the condenser 22 for reheating, thereby forming a cycle of air in the circulation air duct.

[0060] 4. In the absorption heat pump 10: Under the action of the input high-temperature heat source, the heat of the heat absorption part 11 is recovered and transferred to the heat release part 12, thereby increasing the temperature of the first heat exchange medium flowing through the heat release part 12 and reducing the temperature of the second heat exchange medium flowing through the heat absorption part 11; the absorption heat pump 10 improves the energy utilization rate by recovering heat from the heat absorption part 11 and transferring the recovered heat to the heat release part 12.

[0061] In a preferred embodiment, both the first heat exchange medium and the second heat exchange medium are water; in other embodiments, the first heat exchange medium and the second heat exchange medium may also be heat-conducting oil. In a preferred embodiment, the absorption heat pump 10 is a lithium bromide absorption heat pump, using natural gas as the high-temperature heat source to transfer the heat of the heat absorption part 11 to the heat release part 12; in other embodiments, the absorption heat pump 10 may also be an ammonia-water absorption heat pump.

[0062] The structure of the heat pump sludge drying system of the present invention is relatively complex. To facilitate the automatic startup of the device, in a preferred embodiment, as Figures 1 - 3 shown, it further includes a controller C, a first flowmeter 42, a second flowmeter 52, and a first temperature sensor 211. The first flowmeter 42 is arranged on the first circulation pipeline, the second flowmeter 52 is arranged on the second circulation pipeline, and the first temperature sensor 211 is arranged at the air outlet of the condenser 22; the controller C is electrically connected to the absorption heat pump 10, the circulation fan 24, the sludge conveying mechanism 25, the first circulation pump 41, the second circulation pump 51, the first flowmeter 42, the second flowmeter 52, and the first temperature sensor 211.

[0063] The first flowmeter 42 is used to detect the flow rate of the first heat exchange medium in the first circulation pipeline and convert it into a first flow rate detection signal and send it to the controller C; the second flowmeter 52 is used to detect the flow rate of the second heat exchange medium in the second circulation pipeline and convert it into a second flow rate detection signal and send it to the controller C; the first temperature sensor 211 is used to detect the air outlet temperature of the condenser 22 and convert it into a first temperature detection signal and send it to the controller C.

[0064] During the startup process:

[0065] The controller C is used to control the second circulation pump 51 to start, so that the second heat exchange medium forms a circulation in the second circulation pipeline;

[0066] When the value of the second flow rate detection signal received by the controller C reaches the corresponding set value, it indicates that the second circulation pipeline can provide sufficient cooling capacity for the sludge dryer 20, can prevent the sludge dryer 20 from overheating, and can ensure the safe operation of the sludge dryer 20. At this time, the controller C is used to control the startup of the first circulation pump 41;

[0067] The controller C is used to control the absorption heat pump 10 and the circulation fan 24 to start when the value of the first flow rate detection signal received reaches the corresponding set value, so as to heat the first heat exchange medium in the first circulation pipeline and transfer the heat in the first circulation pipeline to the circulation air duct through the condenser 22;

[0068] The controller C is used to control the sludge conveying mechanism 25 to start when the received first temperature detection signal reaches the corresponding set value, so as to convey the sludge into the sludge dryer 20 and start drying the sludge.

[0069] In order to improve the production capacity of sludge drying, in a preferred embodiment, there are multiple sludge dryers 20, and the first circulation pump 41 is a variable-frequency circulation pump; during the startup process, the controller C is further used to obtain the number n of sludge dryers 20 to be started; when n = 1 and the value of the second flow signal received by the controller C reaches the set value, the controller C is used to control the first circulation pump 41 to increase to the first set frequency fs1; when n = 2 and the value of the second flow signal received by the controller C reaches the set value, the controller C is used to control the first circulation pump 41 to increase to the second set frequency fs2; when n = 3 and the value of the second flow signal received by the controller C reaches the set value, the controller C is used to control the first circulation pump 41 to increase to the third set frequency fs3; where the first set frequency fs1 < the second set frequency fs2 < the third set frequency fs3.

[0070] Thus, when the number of sludge dryers 20 to be started is larger, the first circulation pump 41 increases to a higher frequency, so that the first heat exchange medium in the first circulation pipeline can be adjusted to a suitable flow rate as soon as possible; the frequency increase process of the first circulation pump 41 can be continuously increased to the corresponding set frequency, or can be stepped up to the corresponding set frequency. It can be understood that the set frequencies are obtained through calculation or experimental testing, and the set frequencies can include not only the first set frequency fs1, the second set frequency fs2, and the third set frequency fs3. When the number of sludge dryers 20 to be started exceeds 3, the set frequencies also include the corresponding fourth set frequency fs4, the fifth set frequency fs5, etc.

[0071] In actual production, each sludge dryer 20 may be drying different types of sludge at the same time, or in different drying stages. Therefore, there will be differences in the set temperatures of each sludge dryer 20; in order to enable each sludge dryer 20 to reach the corresponding outlet air temperature set value, in a preferred embodiment, the controller C is further used to obtain the maximum value Ts of the outlet air temperature set values of the condensers 22 of each sludge dryer 20 max and control the temperature T of the first heat exchange medium output by the heat release part 12 of the absorption heat pump 10 according to the maximum value Ts of the outlet air temperature set value max so that T out > Ts out max+X1, where X1 is a preset first temperature difference; heat loss occurs during the process of heat transfer from the heat release part 12 to the air flowing through the condenser 22, resulting in the actual outlet air temperature of the condenser 22 of the sludge dryer 20 being lower than the first heat exchange medium temperature T output by the heat release part 12 of the absorption heat pump 10 out , so it is necessary to make the temperature T of the heat exchange medium output by the heat release part 12 of the absorption heat pump 10 out be greater than the maximum value Ts of the outlet air temperature setting values of the condensers 22 of each sludge dryer 20 max , and T out > Ts max +X1, where X1 is a preset first temperature difference value, X1 is greater than the temperature reduction value caused by heat loss during the process of heat transfer from the heat release part 12 to the air flowing through the condenser 22, and the value of X1 can be obtained through experiments or calculations.

[0072] It can be understood that the outlet air temperature of each condenser 22 can be adjusted by adjusting the flow rate of the first heat exchange medium flowing through each condenser 22; therefore, in a preferred embodiment, regulating valves are provided at the first heat exchange medium input ends of each condenser 22, and each regulating valve is electrically connected to the controller C. The controller C is also used to control the opening degree of the corresponding regulating valve according to the outlet air temperature setting value of each condenser 22. For any sludge dryer, when the difference between the outlet air temperature setting value of the condenser 22 and the temperature difference of the first heat exchange medium input into the condenser 22 is large, the controller C controls the regulating valve to adjust to a smaller opening degree to reduce the flow rate of the first heat exchange medium flowing through the condenser 22, thereby reducing the heat exchange amount between the condenser 22 and the air and reducing the outlet air temperature of the condenser 22 to the set value; similarly, when the difference between the outlet air temperature setting value of the condenser 22 and the temperature difference of the first heat exchange medium input into the condenser 22 is small, the controller C controls the regulating valve to adjust to a larger opening degree to increase the flow rate of the first heat exchange medium flowing through the condenser 22, thereby increasing the heat exchange amount between the condenser 22 and the air and increasing the outlet air temperature of the condenser 22 to the set value.

[0073] When the difference in the outlet air temperature setting values of the condensers 22 between each sludge dryer 20 is large, in the sludge dryer 20 with a smaller outlet air temperature setting value, the difference between the outlet air temperature setting value of the condenser 22 and the temperature difference of the first heat exchange medium input into the condenser 22 is large, resulting in a large fluctuation in the actual outlet air temperature of the condenser 22, which affects the sludge drying effect; therefore, in a preferred embodiment, the controller C performs PID control on the opening degree of the regulating valve at the inlet of the condenser 22 according to the deviation of the actual outlet air temperature of the condenser 22 from the outlet air temperature setting value, so as to reduce the flow rate fluctuation of the first heat exchange medium flowing through the condenser 22, thereby reducing the fluctuation of the outlet air temperature of the condenser 22.

[0074] In a preferred embodiment, each regulating valve is a proportional regulating valve to improve the accuracy of flow regulation. In a specific embodiment, the output voltage corresponding to the opening degree of 0 - 100% of the proportional regulating valve is 0 - 10V; during the startup process of the device, after the fan is turned on for 20s, the proportional regulating valve starts to regulate; after the device is shut down, the proportional regulating valve closes. When the controller C performs PID regulation on the regulating valve, the regulation amplitude does not exceed the set regulation amplitude. During the PID regulation process, if the first temperature sensor 211 used to obtain the outlet air temperature of the condenser 22 fails, the regulating valve maintains the current opening degree. If the temperature of the first circulation pipeline is too high, it will cause the absorption heat pump 10 to overheat and affect the normal operation of the absorption heat pump 10; therefore, in a preferred embodiment, the controller C is also used to control the temperature T of the first heat exchange medium output by the heat release part 12 of the absorption heat pump 10 out , so that T out < T'; where T' is the safety temperature threshold of the heat release part 12, which can be set according to the performance of the absorption heat pump 10, and X1 < T'.

[0075] During the operation of the device, if the first heat exchange medium in the first circulation pipeline evaporates or leaks, it will cause the pressure in the first circulation pipeline to decrease and affect the normal operation of the device; in order to supplement the first heat exchange medium to the first circulation pipeline to keep the first circulation pipeline at an appropriate pressure, in a preferred embodiment, it further includes a first heat exchange medium replenishing device, and the first heat exchange medium replenishing device includes a first heat exchange medium storage tank 71, a first heat exchange medium replenishing pump 72 and a pressure sensor 74; the input end of the first heat exchange medium replenishing pump 72 is connected to the first heat exchange medium storage tank 71, and the output end of the first heat exchange medium replenishing pump 72 is connected to the first circulation pipeline; the pressure sensor 74 is arranged on the first circulation pipeline and is electrically connected to the controller C; the pressure sensor 74 is used to detect the pressure of the first circulation pipeline and transmit the pressure detection signal to the controller C; the controller C is used to control the first heat exchange medium replenishing pump 72 to replenish water to the first circulation pipeline according to the received pressure detection signal. Specifically, when the pressure detected by the pressure sensor 74 is lower than the set value, the controller C controls the first heat exchange medium replenishing pump 72 to start; when the pressure detected by the sensor 74 reaches the set value, the controller C controls the first heat exchange medium replenishing pump 72 to close.

[0076] The temperature of the first heat exchange medium stored in the first heat exchange medium storage tank 71 is relatively low. In order to reduce the influence of the process of replenishing the first heat exchange medium on the temperature of the first heat exchange medium output by the heat release part 12, thereby reducing the fluctuation of the outlet air temperature of the condenser 22, in a preferred embodiment, the output end of the first heat exchange medium replenishing pump 72 is connected between the output end of the condenser 22 and the input end of the heat release part 12.

[0077] In order to reduce the water pressure fluctuation in the first circulation pipeline and enable the equipment to operate safely and stably, in a preferred embodiment, the first heat exchange medium replenishing device further includes a buffer tank 73 connected to the output end of the first heat exchange medium replenishing pump 72. A buffer airbag is provided in the buffer tank 73. When the pressure in the first circulation pipeline drops, the buffer airbag expands under the action of the pressure difference, thereby discharging the first heat exchange medium in the buffer tank 73 into the first circulation pipeline until the pressure in the buffer tank 73 is balanced with that in the first circulation pipeline; when the pressure in the first circulation pipeline rises, the buffer airbag contracts under the action of the pressure difference, thereby enabling the first heat exchange medium in the first circulation pipeline to flow into the buffer tank 73 until the pressure in the buffer tank 73 is balanced with that in the first circulation pipeline.

[0078] In order to prevent the pressure drop caused by the reverse flow of the first heat exchange medium in the first circulation pipeline from the first heat exchange medium replenishing pump 72, in a preferred embodiment, a check valve is provided at the output end of the first heat exchange medium replenishing pump 72, and the first heat exchange medium replenishing pump 72 is connected to the first circulation pipeline and the buffer tank 73 through the check valve.

[0079] If the first heat exchange medium is hard water, due to the high concentration of calcium and magnesium ions in hard water, it is easy to cause scaling in the pipeline and each heat exchanger, affecting the heat exchange efficiency; therefore, in a preferred embodiment, a softened water device 60 is further included. The input end and the output end of the softened water device 60 are respectively connected to the water source and the first heat exchange medium storage tank 71; an ion exchange resin is provided in the softened water device 60. The hard water from the water source flows through the ion exchange resin, and the calcium and magnesium ions in the hard water are adsorbed by the ion exchange resin and then converted into softened water, and then output to the first heat exchange medium storage tank 71.

[0080] A liquid storage tank 31 for collecting the cooled second heat exchange medium is provided below the cooling tower 30. If the liquid level in the liquid storage tank 31 is too low, it will cause the cooling tower 30 to be unable to effectively transport the cooled second heat exchange medium to the evaporator 23, which will not only affect the sludge drying effect but also affect the safe operation of the sludge dryer 20; therefore, in a preferred embodiment, a second heat exchange medium replenishing device is further included. The second heat exchange medium replenishing device includes a second heat exchange medium replenishing pipeline 81, a second heat exchange medium replenishing valve 82, and a liquid level sensor 83. The output end of the second heat exchange medium replenishing pipeline is connected to the liquid storage tank 31. The second heat exchange medium replenishing valve 82 is provided on the second heat exchange medium replenishing pipeline 81, and the liquid level sensor 83 is provided in the liquid storage tank 31; the second heat exchange medium replenishing valve 82 and the liquid level sensor 83 are respectively electrically connected to the controller C. The liquid level sensor 83 is used to detect the liquid level in the liquid storage tank 31 and transmit the liquid level detection signal to the controller C. The controller C is used to control the opening degree of the second heat exchange medium replenishing valve 82 according to the received liquid level detection signal, so as to maintain the liquid level in the liquid storage tank 31 within a set range.

[0081] To prevent the high-temperature first heat exchange medium from affecting the first circulation pump 41, in a preferred embodiment, the first circulation pump 41 is arranged between the output end of the condenser 22 and the input end of the heat release part 12. The temperature of the first heat exchange medium in this part of the first circulation pipeline is relatively low, which is beneficial to reducing the influence of high temperature on the first circulation pump 41.

[0082] To reduce the distance between the second circulation pump 51 and the liquid storage tank 31 of the cooling tower 30 to ensure the normal operation of the second circulation water pump 51, in a preferred embodiment, the second circulation water pump 51 is arranged between the output end of the cooling tower 30 and the input end of the evaporator 23; it can be understood that the output end of the cooling tower 30 is the output end of the liquid storage tank 31.

[0083] To prevent the failures of the first circulation pump 41 and the second circulation pump 51 from affecting the operation of the entire sludge drying system, in a preferred embodiment, there are multiple first circulation pumps 41, and the first circulation pumps 41 are connected in parallel with each other. When one or more of the first circulation pumps 41 fail, the heat exchange medium in the first circulation pipeline can still be circulated through the other first circulation pumps 41; there are also multiple second circulation pumps 51, and the second circulation pumps 51 are connected in parallel with each other. Similarly, when one or more of the second circulation pumps 51 fail, the heat exchange medium in the second circulation pipeline can still be circulated through the other second circulation pumps 51.

[0084] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0085] 1. The absorption heat pump is used to provide heat for the sludge dryer, and the heat of the second heat exchange medium output by the evaporator is recovered by the absorption heat pump, improving the heat production and energy utilization rate, thereby improving the efficiency of sludge drying;

[0086] 2. Multiple sludge dryers are arranged to make more full use of the heat provided by the absorption heat pump to further improve the efficiency of sludge drying;

[0087] 3. A first heat exchange medium replenishing device is arranged to keep the pressure of the first circulation pipeline within the normal range and ensure the normal operation of the equipment.

[0088] The above-described embodiments only represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A heat pump sludge drying system, characterized in that: It includes an absorption heat pump (10), a sludge dryer (20), a cooling tower (30), a first circulation pipeline and a second circulation pipeline; the absorption heat pump (10) includes a heat absorption part (11) for absorbing heat and a heat release part (12) for releasing heat, and the sludge dryer (20) includes a circulation air duct, a condenser (22), an evaporator (23) and a sludge conveying mechanism (25); A circulation fan (24) is further provided on the circulation air duct, and the circulation fan (24) is used to make air circulate in the circulation air duct; the circulation air duct passes through the condenser (22), the evaporator (23) and the sludge conveying mechanism (25), and the sludge conveying mechanism (25) is arranged between the air outlet of the condenser (22) and the air inlet of the evaporator (23); The first circulation pipeline is used to accommodate a first heat exchange medium, and a first circulation pump (41) is arranged on the first circulation pipeline, and the first circulation pump (41) is used to make the first heat exchange medium circulate in the first circulation pipeline; the first circulation pipeline passes through the heat release part (12) and the condenser (22), and the condenser (22) is used to transfer the heat in the first circulation pipeline to the circulation air duct; The second circulation pipeline is used to accommodate a second heat exchange medium, and a second circulation pump (51) is arranged on the second circulation pipeline, and the second circulation pump (51) is used to make the second heat exchange medium circulate in the second circulation pipeline; the second circulation pipeline passes through the heat absorption part (11), the evaporator (23) and the cooling tower (30), and the input end of the cooling tower (30) is connected to the output end of the heat absorption part (11), and the input end of the evaporator (23) is connected to the output end of the cooling tower (30); the evaporator (23) is used to transfer the heat in the circulation air duct to the second circulation pipeline.

2. The heat pump sludge drying system according to claim 1, characterized in that: It further includes a controller (C), a first flow meter (42), a second flow meter (52) and a first temperature sensor (211), the first flow meter (42) is arranged on the first circulation pipeline, the second flow meter (52) is arranged on the second circulation pipeline, and the first temperature sensor (211) is arranged at the air outlet of the condenser (22); the controller (C) is electrically connected to the absorption heat pump (10), the circulation fan (24), the sludge conveying mechanism (25), the first circulation pump (41), the second circulation pump (51), the first flow meter (42), the second flow meter (52) and the first temperature sensor (211); The first flow meter (42) is used to detect the flow rate of the first heat exchange medium in the first circulation pipeline and convert it into a first flow rate detection signal and send it to the controller (C); The second flowmeter (52) is used to detect the flow rate of the second heat exchange medium in the second circulation pipeline and convert it into a second flow detection signal for sending to the controller (C); The first temperature sensor (211) is used to detect the air outlet temperature of the condenser (22) and convert it into a first temperature detection signal for sending to the controller (C); During the startup process, the controller (C) is used for: Controlling the second circulation pump (51) to start, so that the second heat exchange medium forms a circulation in the second circulation pipeline; When the value of the received second flow detection signal reaches the corresponding set value, controlling the first circulation pump (41) to start; When the value of the received first flow detection signal reaches the corresponding set value, controlling the absorption heat pump (10) and the circulation fan (24) to start; When the received first temperature detection signal reaches the set value, controlling the sludge conveying mechanism (25) to start.

3. The heat pump sludge drying system according to claim 2, wherein: There are multiple sludge dryers (20), and the first circulation pump (41) is a variable frequency circulation pump; During the startup process, the controller (C) is further used to obtain the number n of the sludge dryers (20) to be started; When n = 1 and the value of the second flow detection signal received by the controller (C) reaches the set value, the controller (C) is used to control the first circulation pump (41) to be increased to the first set frequency fs1; When n = 2 and the value of the second flow detection signal received by the controller (C) reaches the set value, the controller (C) is used to control the first circulation pump (41) to be increased to the second set frequency fs2; When n = 3 and the value of the second flow detection signal received by the controller (C) reaches the set value, the controller (C) is used to control the first circulation pump (41) to be increased to the third set frequency fs3; Wherein, the first set frequency fs1 < the second set frequency fs2 < the third set frequency fs3.

4. The heat pump sludge drying system according to claim 2, wherein: There are multiple sludge dryers (20); The controller (C) is further configured to obtain the maximum value Ts of the outlet air temperature set value of the condenser (22) of each sludge dryer (20). max And based on the maximum value Ts of the outlet air temperature set value max control the temperature T of the first heat exchange medium output by the heat release part (12) of the absorption heat pump (10), out such that T out > Ts max + X1; where X1 is a preset first temperature difference value.

5. The heat pump sludge drying system according to claim 4, wherein: A regulating valve is provided at the first heat exchange medium input end of each condenser (22), and each regulating valve is electrically connected to the controller (C); the controller (C) is further used to perform PID control on the opening degree of the corresponding regulating valve according to the deviation of the actual air outlet temperature of the condenser (22) relative to the air outlet temperature set value.

6. The heat pump sludge drying system according to claim 1, wherein: It further includes a controller (C) and a first heat exchange medium replenishing device, and the first heat exchange medium replenishing device includes a first heat exchange medium storage tank (71), a first heat exchange medium replenishing pump (72) and a pressure sensor (74); The input end of the first heat exchange medium replenishing pump (72) is connected to the first heat exchange medium storage tank (71), and the output end of the first heat exchange medium replenishing pump (72) is connected to the first circulation pipeline; The pressure sensor (74) is disposed on the first circulation pipeline and is electrically connected to the controller (C); the pressure sensor (74) is used to detect the pressure of the first circulation pipeline and transmit a pressure detection signal to the controller (C). The controller (C) is electrically connected to the first heat exchange medium replenishing pump (72), and the controller (C) is used to control the first heat exchange medium replenishing pump (72) according to the received pressure detection signal.

7. The heat pump sludge drying system according to claim 6, wherein: The output end of the first heat exchange medium replenishing pump (72) is connected between the output end of the condenser (22) and the input end of the heat release part (12).

8. The heat pump sludge drying system according to claim 6, wherein: The first heat exchange medium replenishing device further includes a buffer tank (73) connected to the output end of the first heat exchange medium replenishing pump (72).

9. The heat pump sludge drying system according to claim 8, wherein: A check valve is provided at the output end of the first heat exchange medium replenishing pump (72), and the first heat exchange medium replenishing pump (72) is connected to the first circulation pipeline and the buffer tank (73) through the check valve.

10. The heat pump sludge drying system according to claim 6, wherein: The first heat exchange medium is water; It further includes a softened water device (60), and the input end and the output end of the softened water device (60) are respectively connected to a water source and the first heat exchange medium storage tank (71).

11. The heat pump sludge drying system according to claim 1, wherein: A liquid storage tank (31) for collecting the cooled heat exchange medium is provided below the cooling tower (30); It further includes a controller (C) and a second heat exchange medium replenishing device. The second heat exchange medium replenishing device includes a second heat exchange medium replenishing pipeline (81), a second heat exchange medium replenishing valve (82) and a liquid level sensor (83). The output end of the second heat exchange medium replenishing pipeline is connected to the liquid storage tank (31). The second heat exchange medium replenishing valve (82) is provided on the second heat exchange medium replenishing pipeline (81), and the liquid level sensor (83) is provided in the liquid storage tank (31); The second heat exchange medium replenishing valve (82) and the liquid level sensor (83) are respectively electrically connected to the controller (C). The liquid level sensor (83) is used to detect the liquid level in the liquid storage tank (31) and transmit a liquid level detection signal to the controller (C). The controller (C) is used to control the opening degree of the second heat exchange medium replenishing valve (82) according to the received liquid level detection signal.

12. The heat pump sludge drying system according to claim 1, wherein: The first circulation pump (41) is disposed between the output end of the condenser (22) and the input end of the heat release part (12), and the second circulation pump (51) is disposed between the output end of the cooling tower (30) and the input end of the evaporator (23).

13. The heat pump sludge drying system according to claim 1, wherein: The first circulation pumps (41) include a plurality of them, and the first circulation pumps (41) are connected in parallel with each other; The second circulation pumps (51) include a plurality of them, and the second circulation pumps (51) are connected in parallel with each other.

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