A sludge drying device and method driven by low-grade waste heat

Abstract

The present invention discloses a sludge drying system driven by low-grade waste heat, which includes a sludge dryer, an absorption refrigeration cycle system and a second-type absorption heat pump cycle system; a fan is connected to the gas outlet of the sludge dryer, and the sludge dryer, the refrigeration evaporator of the absorption refrigeration cycle system, the fan and the heat pump absorber of the second-type absorption heat pump cycle system are sequentially and cyclically connected to form an air circulation loop; the cooling capacity of the refrigeration evaporator comes from the absorption refrigeration cycle system, and the heat of the heat pump absorber comes from the second-type absorption heat pump cycle system; the waste heat carrier is gradually cooled by passing through the refrigeration reboiler of the absorption refrigeration cycle system and the heat pump reboiler of the second-type absorption heat pump cycle system in sequence. The present invention realizes the dehumidification of air through the absorption refrigeration cycle, realizes the heating of air through the second-type absorption heat pump, and the waste heat carrier passes through the absorption refrigeration cycle system and the second-type absorption heat pump cycle system in sequence to realize the hierarchical utilization of low-grade heat sources.

Description

Technical Field

[0001] The present invention relates to a sludge drying device and method driven by low-grade waste heat, belonging to the technical field of sludge drying. Background Art

[0002] Sludge drying is a commonly used sludge treatment method. Usually, an external heat source is used to heat the sludge, so that the water in the sludge evaporates, and finally dried sludge is formed. In the sludge drying process of the prior art, a large amount of heat energy is consumed, and the economy is relatively low. For a Chinese patent with the publication number CN217025736U, the publication date of July 22, 2022, and the name of "a sludge heat pump drying system with waste heat recovery of a ring-tube reheater", through the auxiliary adjustment of a heat pipe waste heat recovery device and a plate heat exchanger, after the dried circulating air passes through the heat pipe, the latent heat of vaporization of water vapor and the sensible heat of air in the hot and humid gas can be recovered. At the same time, the recovered heat is used to reheat the circulating air after cooling and dehumidification, and then the heat of industrial wastewater is recovered again. Finally, it is heated again through the condenser of the system, and the heated circulating air re-enters the drying chamber to dry the sludge. Although this sludge heat pump drying system can recover most of the heat energy, the steam and wastewater after heat recovery still contain low-grade heat energy, and these low-grade heat energies cannot be fully recovered and utilized. Summary of the Invention

[0003] The purpose of the present invention is to provide a sludge drying device and method driven by low-grade waste heat, which reduces the energy consumption cost of sludge drying through the hierarchical utilization of low-temperature waste heat by an absorption heat pump.

[0004] In the first aspect, the present invention provides a sludge drying device driven by low-grade waste heat, adopting the following technical solution: A sludge drying device driven by low-grade waste heat includes a sludge dryer, an absorption refrigeration cycle system, and a second-type absorption heat pump cycle system; a fan is connected to the gas outlet of the sludge dryer, and the sludge dryer, the refrigeration evaporator of the absorption refrigeration cycle system, the fan, and the heat pump absorber of the second-type absorption heat pump cycle system are sequentially connected in a cycle to form an air circulation loop; the cooling capacity of the refrigeration evaporator comes from the absorption refrigeration cycle system, and the heat of the heat pump absorber comes from the second-type absorption heat pump cycle system; the waste heat carrier is gradually cooled through the refrigeration reboiler of the absorption refrigeration cycle system and the heat pump reboiler of the second-type absorption heat pump cycle system in sequence.

[0005] Based on the above implementation scheme, the high-temperature and high-humidity air flowing out of the sludge dryer first passes through the refrigeration evaporator in the absorption refrigeration cycle. Taking the circulating medium as ammonia water for example, ammonia evaporation in the refrigeration evaporator generates cooling capacity, the high-temperature and high-humidity air is cooled into low-temperature saturated wet air, and the condensed water is separated out; the low-temperature saturated wet air then enters the heat pump absorber in the second type of absorption heat pump cycle. Taking the circulating medium as ammonia water for example, water in the heat pump absorber absorbs ammonia and releases a large amount of heat, and the low-temperature saturated wet air is heated and raised to high-temperature and low-humidity air, and then enters the sludge dryer to dry the sludge; among them, the low-grade waste heat provides heat for the refrigeration reboiler at the bottom of the refrigeration rectification tower in the absorption refrigeration cycle system, effectively utilizing the waste heat, and the low-grade waste heat also provides heat for the reboiler at the bottom of the heat pump rectification tower in the second type of absorption heat pump cycle system, further effectively utilizing the waste heat.

[0006] The above scheme realizes the dehumidification of air through the absorption refrigeration cycle, significantly reducing the power consumption compared with the traditional drying method; and realizes the heating of air through the second type of absorption heat pump, increasing the air temperature and the absorption potential of water vapor, which is beneficial to reducing the air circulation volume and thus reducing the fan power consumption. The low-grade waste heat is used as the heat source of the refrigeration cycle reboiler and the heat pump cycle reboiler in turn, realizing the hierarchical utilization of low-grade heat sources and being beneficial to reducing energy consumption.

[0007] Among them, the waste heat carrier can be flue gas or hot water, mainly providing heat for the system. The waste heat carrier flows through the refrigeration reboiler, the heat pump reboiler, the heat pump evaporator and the air regenerator in turn, and its temperature drops after four heat releases

[0008] Combined with the first aspect, in some embodiments of the first aspect, the absorption refrigeration cycle system includes a refrigeration evaporator, a refrigeration absorber, a refrigeration rectification tower and a refrigeration condenser connected in a cycle, and the refrigeration reboiler is connected to the bottom of the refrigeration rectification tower; the second type of absorption heat pump cycle includes a heat pump absorber, a heat pump rectification tower and a heat pump evaporator connected in a cycle, and the heat pump reboiler is connected to the bottom of the heat pump rectification tower; the waste heat carrier flows through the heat pump reboiler and then through the heat pump evaporator.

[0009] Based on the above implementation solutions and the above devices, in the absorption refrigeration cycle system, the mixed vapor of the light-component refrigerant and the solvent generated after the solution in the bottom reboiler of the intermediate-cooling rectification tower is heated by the waste heat carrier enters the refrigeration rectification tower. The dilute solution of the heavy-component refrigerant flows out at the bottom. The mixed vapor is rectified in the refrigeration rectification tower. The refrigerant vapor at the top of the tower enters the refrigeration evaporator to evaporate and generate cooling capacity. The refrigerant flowing out of the refrigeration evaporator then enters the refrigeration absorber and is absorbed by the dilute solution to generate a concentrated solution, which then enters the refrigeration rectification tower, and so on in a cycle. And based on the above devices, in the second-type absorption heat pump cycle system, the bottom reboiler of the heat pump rectification tower generates mixed vapor at the top after being heated by the waste heat carrier, and the dilute solution flows out at the bottom. After the mixed vapor is rectified, the refrigerant vapor at the top of the tower enters the heat pump evaporator to further absorb the heat in the waste heat carrier, causing the refrigerant to evaporate under high pressure. The vapor coming out directly enters the heat pump absorber to absorb and release a large amount of heat at a higher absorption pressure to heat the air. The concentrated solution obtained by absorption enters the heat pump rectification tower, and so on in a cycle. In summary, the waste heat carrier flows through the heat pump reboiler and then through the heat pump evaporator, and the low-grade heat source is further utilized in a graded manner.

[0010] In some embodiments of the first aspect, a refrigeration regenerator is provided between the refrigeration absorber and the refrigeration reboiler. The refrigerant inlet and outlet of the refrigeration regenerator are respectively connected to the bottom outlet of the refrigeration absorber and the feed inlet of the refrigeration rectification tower. The heat medium inlet and outlet of the refrigeration regenerator are respectively connected to the outlet of the refrigeration reboiler at the bottom of the refrigeration rectification tower and the feed inlet of the refrigeration absorber. A refrigeration throttle valve is provided on the pipeline of the refrigerant outlet of the refrigeration regenerator. A refrigeration solution pump is provided on the pipeline of the heat medium inlet of the refrigeration regenerator.

[0011] Based on the above implementation solutions, by setting the refrigeration regenerator, the concentrated solution at the bottom outlet of the refrigeration absorber is preheated by the higher-temperature stream at the outlet of the refrigeration reboiler and then enters the refrigeration rectification tower, which can further improve the energy utilization rate and save energy consumption.

[0012] In some embodiments of the first aspect, a heat pump regenerator is provided between the heat pump absorber and the heat pump reboiler. The heat medium inlet and outlet of the heat pump regenerator are respectively connected to the outlet of the heat pump reboiler at the bottom of the heat pump rectification tower and the feed inlet of the heat pump absorber. The refrigerant inlet and outlet of the heat pump regenerator are respectively connected to the bottom outlet of the heat pump absorber and the feed inlet of the heat pump rectification tower. A heat pump throttle valve is provided on the pipeline of the refrigerant outlet of the heat pump regenerator. A heat pump solution pump is provided on the pipeline of the heat medium inlet of the heat pump regenerator.

[0013] Based on the above implementation solutions, by setting the heat pump regenerator, the concentrated solution at the bottom outlet of the heat pump absorber is preheated by the higher-temperature stream at the outlet of the heat pump reboiler and then enters the heat pump rectification tower, which can further improve the energy utilization rate and save energy consumption.

[0014] In some embodiments of the first aspect, the absorption refrigeration cycle system further includes a refrigeration condenser, which is connected between the refrigeration rectification column and the refrigeration absorber; the second type of absorption heat pump cycle further includes a heat pump condenser, which is connected between the heat pump rectification column and the heat pump evaporator.

[0015] In some embodiments of the first aspect, an expansion valve is provided on the pipeline between the refrigeration condenser and the refrigeration evaporator; a refrigerant pump is provided on the refrigerant pipeline between the heat pump condenser and the heat pump evaporator.

[0016] In some embodiments of the first aspect, an air recuperator is provided on the air circulation loop between the fan and the heat pump absorber. After the waste heat carrier passes through the second type of absorption heat pump cycle system, it then enters the air recuperator to be cooled.

[0017] Based on the above implementation scheme, the heat of the waste heat carrier is further utilized to preheat the air, realizing the deep hierarchical utilization of low-grade heat sources. The waste heat discharge temperature can be reduced to below 40°C, which can further improve the energy utilization rate and save energy consumption.

[0018] In some embodiments of the first aspect, a condensate collector is connected to the bottom of the refrigeration evaporator, and the condensed water cooled by the refrigeration evaporator flows into the condensate collector.

[0019] In the second aspect, the present invention provides a sludge drying method driven by low-grade waste heat, adopting the following technical solution: a sludge drying method driven by low-grade waste heat, where the waste heat carrier drives the absorption refrigeration cycle system to generate cold in the refrigeration evaporator, and this cold is used to cool the air at the outlet of the sludge dryer and condense water vapor; the waste heat carrier also drives the second type of absorption heat pump cycle system to generate heat in the heat pump absorber, and this heat is used to heat the air at the inlet of the sludge dryer; at the same time, the waste heat carrier is gradually cooled through the absorption refrigeration cycle system and the second type of absorption heat pump cycle system.

[0020] Based on the above implementation scheme, the high-temperature and high-humidity air flowing out of the sludge dryer is cooled into low-temperature saturated wet air by the refrigeration evaporator of the absorption refrigeration cycle, and then blown into the air recuperator by the fan for preheating. The condensed water cooled by the refrigeration evaporator flows into the condensate collector. The preheated air then enters the sludge dryer to dry the sludge after being heated to high-temperature and low-humidity air by the heat pump absorber of the second type of absorption heat pump cycle. The waste heat carrier can be flue gas or hot water, mainly providing heat for the system. The waste heat carrier flows through the refrigeration reboiler, the heat pump reboiler, the heat pump evaporator, and the air recuperator in sequence, and its temperature is reduced to slightly higher than the ambient temperature after four heat releases and then discharged, and the waste heat resources carried by it are fully utilized.

[0021] In combination with the second aspect, in some embodiments of the second aspect, after the waste heat carrier flows through the second type of absorption heat pump cycle system, it enters the air recuperator to cool down, and at the same time, the air recuperator heats the air before entering the inlet of the sludge dryer.

[0022] In the absorption refrigeration cycle system, the waste heat carrier heats the refrigeration reboiler, and the generated mixed vapor enters the refrigeration rectification tower for rectification. The dilute solution hot fluid at the bottom of the refrigeration reboiler flows into the refrigeration recuperator to exchange heat with the concentrated solution from the bottom of the refrigeration absorber. The pure refrigerant obtained after passing through the refrigeration rectification tower is condensed by the refrigeration condenser, depressurized by the expansion valve, and enters the refrigeration evaporator to evaporate to produce a refrigeration effect, cooling the hot and humid air from the sludge dryer. The evaporated refrigerant vapor enters the refrigeration absorber and contacts the dilute solution that has been cooled by the refrigeration recuperator and depressurized by the refrigeration throttle valve to undergo an absorption reaction. The heat released during the absorption process is taken away by the cooling water. The concentrated solution at the bottom of the refrigeration absorber is heated and then pressurized by the refrigeration solution pump and enters the refrigeration recuperator to exchange heat with the dilute solution, and then enters the refrigeration reboiler to complete the cycle.

[0023] In the second type of absorption heat pump cycle system, the waste heat carrier flowing out of the refrigeration reboiler heats the heat pump reboiler and the heat pump evaporator in sequence. The mixed vapor generated at the top of the heat pump reboiler enters the heat pump rectification tower for rectification, and the dilute solution hot fluid at the bottom is pressurized by the heat pump solution pump and flows into the heat pump recuperator to exchange heat with the concentrated solution from the bottom of the heat pump absorber. The pure refrigerant obtained after passing through the heat pump rectification tower is condensed by the heat pump condenser, pressurized by the refrigerant pump, and enters the heat pump evaporator to evaporate, absorbing the low-grade heat in the waste heat carrier. The evaporated refrigerant vapor enters the heat pump absorber and contacts the dilute solution that has been heated by the heat pump recuperator to undergo an absorption reaction. The heat released during the absorption process heats the air from the air recuperator, which can increase the air temperature, thereby increasing its saturation humidity and improving the ability to absorb water vapor. The high-temperature concentrated solution at the bottom of the heat pump absorber enters the heat pump recuperator to exchange heat with the dilute solution, and then enters the heat pump reboiler after being depressurized by the heat pump throttle valve to complete the cycle. Description of the Drawings

[0024] Figure 1 It is a schematic diagram of a low-grade waste heat-driven sludge drying device according to an embodiment of the present invention.

[0025] In the figure: 1 - Absorption refrigeration cycle system; 2 - Second - type absorption heat pump cycle system; 3 - Sludge dryer; 4 - Fan; 5 - Air regenerator; 6 - Condensate collector; 11 - Refrigeration absorber; 12 - Refrigeration evaporator; 13 - Expansion valve; 14 - Refrigeration condenser; 15 - Refrigeration rectification tower; 16 - Refrigeration reboiler; 17 - Refrigeration regenerator; 18 - Refrigeration throttle valve; 19 - Refrigeration solution pump; 21 - Heat pump absorber; 22 - Heat pump evaporator; 23 - Refrigerant pump; 24 - Heat pump condenser; 25 - Heat pump rectification tower; 26 - Heat pump reboiler; 27 - Heat pump regenerator; 28 - Heat pump throttle valve; 29 - Heat pump solution pump. Specific implementation mode

[0026] The following further clarifies the present invention in conjunction with the attached drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. After reading the present invention, various equivalent modifications made by those skilled in the art fall within the scope defined by the appended claims of the present invention.

[0027] As Figure 1 shown, the low - grade waste heat - driven sludge drying device of this embodiment includes an absorption refrigeration cycle system 1, a second - type absorption heat pump cycle system 2, and a sludge dryer 3.

[0028] A fan 4 is connected to the gas outlet of the sludge dryer 3. The sludge dryer 3, the refrigeration evaporator 12 of the absorption refrigeration cycle system 1, the fan 4, and the heat pump absorber 21 of the second - type absorption heat pump cycle system 2 are sequentially and cyclically connected to form an air circulation loop.

[0029] The absorption refrigeration cycle system 1 includes a refrigeration evaporator 12, a refrigeration absorber 11, and a refrigeration rectification tower 15 that are cyclically connected. A refrigeration reboiler 16 is connected to the bottom of the refrigeration rectification tower 15; A heat - refrigeration regenerator 17 is provided between the refrigeration absorber 11 and the refrigeration reboiler 16. The refrigerant inlet and outlet of the refrigeration regenerator 17 are respectively connected to the bottom of the refrigeration absorber 11 and the top of the refrigeration rectification tower 15. The heat - medium inlet and outlet of the refrigeration regenerator 17 are respectively connected to the refrigeration reboiler 16 at the bottom of the refrigeration rectification tower 15 and the top of the refrigeration absorber 11; A refrigeration throttle valve 18 is provided on the pipeline of the refrigerant outlet of the refrigeration regenerator 17; A refrigeration solution pump 19 is provided on the pipeline of the heat - medium inlet of the refrigeration regenerator 17. The absorption refrigeration cycle system 1 further includes a refrigeration condenser 14, and the refrigeration condenser 14 is connected between the refrigeration rectification tower 15 and the refrigeration absorber 11; An expansion valve 13 is provided on the pipeline between the refrigeration condenser 14 and the refrigeration evaporator 12.

[0030] The second type of absorption heat pump circulation system 2 includes a heat pump absorber 21, a heat pump distillation tower 25 and a heat pump evaporator 22 that are cyclically connected, and a heat pump reboiler 26 is connected to the bottom of the heat pump distillation tower 25; a heat pump reheater 27 is provided between the heat pump absorber 21 and the heat pump reboiler 26, and the heat medium inlet and outlet of the heat pump reheater 27 are respectively connected to the heat pump reboiler 26 at the bottom of the heat pump distillation tower 25 and the top of the heat pump absorber 21, and the refrigerant inlet and outlet of the heat pump reheater 27 are respectively connected to the bottom of the heat pump absorber 21 and the top of the heat pump distillation tower 25; a heat pump throttle valve 28 is provided on the refrigerant outlet pipeline of the heat pump reheater 27; a heat pump solution pump 29 is provided on the heat medium inlet pipeline of the heat pump reheater 27. The second type absorption heat pump circulation system 2 also includes a heat pump condenser 24 , which is connected between the heat pump distillation tower 25 and the heat pump evaporator 22 . A refrigerant pump 23 is provided on the refrigerant pipeline between the heat pump condenser 24 and the heat pump evaporator 22 .

[0031] The cooling capacity of the refrigeration evaporator 12 comes from the absorption refrigeration cycle system 1, and the heat of the heat pump absorber 21 comes from the second type absorption heat pump cycle system 2. The bottom of the refrigeration evaporator 12 is connected to a condensed water collector 6, and the condensed water cooled by the refrigeration evaporator 12 flows into the condensed water collector 6. The waste heat carrier is cooled step by step through the refrigeration reboiler 16 of the absorption refrigeration cycle system 1 and the heat pump reboiler 26 of the second type absorption heat pump cycle system 2. The waste heat carrier flows through the heat pump reboiler 26 and then flows through the heat pump evaporator 22. An air regenerator 5 is provided on the air circulation loop between the fan and the heat pump absorber 21. After the waste heat carrier passes through the second type absorption heat pump cycle system 2, it enters the air regenerator 5 for cooling.

[0032] The low-grade waste heat driven sludge drying system of this embodiment also includes a cooling water flow (not shown in the drawings) for cooling. Specifically, the cooling water can flow in parallel into the condenser, refrigeration condenser 14, refrigeration absorber 11, and heat pump condenser 24 in the refrigeration distillation tower 15 and the heat pump distillation tower 25 to take away the heat released by the corresponding equipment and control the temperature of these equipment to be within the normal temperature range.

[0033] The low-grade waste heat driven sludge drying system of this embodiment is a closed sludge drying system based on an absorption refrigeration cycle system 1 and a second-type absorption heat pump cycle system 2. Figure 1As shown, the waste heat carrier flue gas or hot water flows through the refrigeration reboiler 16, the heat pump reboiler 26, the heat pump evaporator 22, and the air recuperator 5 in sequence and then leaves the system. The high-temperature and high-humidity air (relative humidity nearly 100%) flowing out of the sludge dryer 3 flows into the refrigeration evaporator 12 in the absorption refrigeration cycle system 1 and is cooled to a lower temperature (<15°C). The water vapor in the air condenses into droplets and flows into the condensate collector 6. The water vapor content in the low-temperature saturated air after condensation is very low. Subsequently, it is pumped into the air recuperator 5 by the fan 4 to exchange heat with the waste heat carrier and is preliminarily heated to 40 - 50°C, and then enters the heat pump absorber 21 to be heated by the high-temperature heat (>85°C) generated by the second-class absorption heat pump. The heated high-temperature and low-humidity air enters the sludge dryer 3 to fully exchange heat with the sludge and absorb the water vapor in the sludge, generating high-temperature and high-humidity gas to continue the cycle.

[0034] In Figure 1 In the absorption refrigeration cycle system on the left: The solution heated by the waste heat carrier generates a mixed vapor of refrigerant and solvent at the top of the refrigeration reboiler 16, and a dilute solution of refrigerant flows out at the bottom. After the mixed vapor is rectified by the refrigeration rectification tower 15, the liquid phase at the top of the tower flows back to the refrigeration reboiler 16 through the first reflux pipeline. The pure refrigerant vapor at the top of the tower enters the refrigeration condenser 14 to be condensed into a liquid state, and then is depressurized by the expansion valve 13 and enters the refrigeration evaporator 12 to evaporate and generate cold, cooling the high-temperature and high-humidity air entering the refrigeration evaporator 12. The refrigerant vapor flowing out of the refrigeration evaporator 12 then enters the refrigeration absorber 11 and is absorbed by the dilute solution. The concentrated solution obtained at the bottom of the refrigeration absorber 11 is pressurized by the refrigeration solution pump 19 and enters the refrigeration reboiler 16 to be heated after being preheated by the refrigeration recuperator 17. The dilute solution at the bottom of the refrigeration reboiler 16 enters the refrigeration recuperator 17 to release heat, and then the pressure is reduced by the refrigeration throttle valve 18, and then enters the refrigeration absorber 11 to absorb the vapor from the refrigeration evaporator 12. Ammonia and water, or other absorption refrigeration working fluid pairs can be used as the refrigerant and solvent.

[0035] In Figure 1In the second type of absorption heat pump cycle system on the right side, the solution heated by the waste heat carrier generates mixed vapor at the top of the heat pump reboiler 26 and the weak solution flows out at the bottom. After the mixed vapor is rectified in the heat pump rectification tower 25, the liquid phase at the bottom of the tower flows back to the heat pump reboiler 26, and the pure refrigerant vapor at the top of the tower enters the heat pump condenser 24 and is cooled to room temperature, and then is pressurized by the refrigerant pump 23 and pumped into the heat pump evaporator 22 to further absorb the heat in the waste heat carrier, causing the refrigerant to evaporate under high pressure. The vapor coming out of the heat pump evaporator 22 directly enters the heat pump absorber 21. At this time, the absorption pressure is relatively high, and heat is released during the absorption of the refrigerant by the weak solution. Therefore, the heat pump absorber 21 will generate a relatively high temperature (>85°C) to heat the air flowing through the heat pump absorber 21. The concentrated solution at the bottom of the heat pump absorber 21 first exchanges heat with the weak solution entering the heat pump absorber 21 through the heat pump recuperator 27, and then enters the heat pump rectification tower 25 after being depressurized by the heat pump throttle valve 28. After rectification, almost pure refrigerant vapor is obtained at the top of the tower, and the dilute refrigerant solution at the bottom of the tower flows into the heat pump reboiler 26 through the second reflux pipeline. The weak solution at the bottom of the heat pump reboiler 26 is pressurized by the heat pump solution pump 29 and enters the heat pump recuperator 27, where it absorbs waste heat from the concentrated solution and then enters the heat pump absorber 21 to absorb the vapor. Ammonia and water or other absorption refrigeration working fluid pairs can be used as the refrigerant and solvent.

[0036] In summary, the closed sludge drying device using the absorption refrigeration cycle and the second type of absorption heat pump cycle can achieve deep recovery of low-grade heat sources, and at the same time use the recovered heat to dry the sludge, thereby reducing the energy consumption and operating costs of the enterprise for sludge treatment.

[0037] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A sludge drying device driven by low-grade waste heat, characterized in that, Comprising: A sludge dryer (3), an absorption refrigeration cycle system (1) and a second type of absorption heat pump cycle system (2); A fan (4) is connected to the gas outlet of the sludge dryer (3), and the sludge dryer (3), the refrigeration evaporator (12) of the absorption refrigeration cycle system (1), the fan (4) and the heat pump absorber (21) of the second type of absorption heat pump cycle system (2) are sequentially connected in a cycle to form an air circulation loop; The cooling capacity of the refrigeration evaporator (12) comes from the absorption refrigeration cycle system (1), and the heat of the heat pump absorber (21) comes from the second type of absorption heat pump cycle system (2); The waste heat carrier is gradually cooled through the refrigeration reboiler (16) of the absorption refrigeration cycle system (1) and the heat pump reboiler (26) of the second type of absorption heat pump cycle system (2) in sequence.

2. The sludge drying device driven by low-grade waste heat according to claim 1, wherein: The absorption refrigeration cycle system (1) includes a refrigeration evaporator (12), a refrigeration absorber (11) and a refrigeration rectification tower (15) connected in a cycle, and the refrigeration reboiler (16) is connected to the bottom of the refrigeration rectification tower (15); The second type of absorption heat pump cycle system (2) includes a heat pump absorber (21), a heat pump rectification tower (25) and a heat pump evaporator (22) connected in a cycle, and the heat pump reboiler (26) is connected to the bottom of the heat pump rectification tower (25); The waste heat carrier flows through the heat pump reboiler (26) and then through the heat pump evaporator (22).

3. The sludge drying device driven by low-grade waste heat according to claim 2, wherein: A heat refrigeration regenerator (17) is provided between the refrigeration absorber (11) and the refrigeration reboiler (16). The refrigerant inlet and outlet of the refrigeration regenerator (17) are respectively connected to the bottom outlet of the refrigeration absorber (11) and the feed inlet of the refrigeration rectification tower (15), and the heat medium inlet and outlet of the refrigeration regenerator (17) are respectively connected to the outlet of the refrigeration reboiler (16) at the bottom of the refrigeration rectification tower (15) and the feed inlet of the refrigeration absorber (11); A refrigeration throttle valve (18) is provided on the pipeline of the refrigerant outlet of the refrigeration regenerator (17); A refrigeration solution pump (19) is provided on the pipeline of the heat medium inlet of the refrigeration regenerator (17).

4. The sludge drying device driven by low-grade waste heat according to claim 2, wherein: A heat pump regenerator (27) is provided between the heat pump absorber (21) and the heat pump reboiler (26). The heat medium inlet and outlet of the heat pump regenerator (27) are respectively connected to the outlet of the heat pump reboiler (26) at the bottom of the heat pump rectification tower (25) and the feed inlet of the heat pump absorber (21), and the refrigerant inlet and outlet of the heat pump regenerator (27) are respectively connected to the bottom outlet of the heat pump absorber (21) and the feed inlet of the heat pump rectification tower (25); A heat pump throttle valve (28) is provided on the pipeline of the refrigerant outlet of the heat pump regenerator (27); A heat pump solution pump (29) is provided on the pipeline of the heat medium inlet of the heat pump regenerator (27).

5. The sludge drying device driven by low-grade waste heat according to claim 2, characterized in that: The absorption refrigeration cycle system (1) further includes a refrigeration condenser (14), and the refrigeration condenser (14) is connected between the refrigeration rectification tower (15) and the refrigeration absorber (11); The second type of absorption heat pump cycle system (2) further includes a heat pump condenser (24), and the heat pump condenser (24) is connected between the heat pump rectification tower (25) and the heat pump evaporator (22).

6. The sludge drying device driven by low-grade waste heat according to claim 5, wherein: An expansion valve (13) is provided on the pipeline between the refrigeration condenser (14) and the refrigeration evaporator (12); a refrigerant pump (23) is provided on the refrigerant pipeline between the heat pump condenser (24) and the heat pump evaporator (22).

7. The sludge drying device driven by low-grade waste heat according to claim 1, wherein: An air regenerator (5) is provided on the air circulation loop between the fan and the heat pump absorber (21). After the waste heat carrier passes through the second type of absorption heat pump cycle system (2), it then enters the air regenerator (5) to be cooled down.

8. The sludge drying device driven by low-grade waste heat according to claim 1, characterized in that: The bottom of the refrigeration evaporator (12) is connected to a condensate collector (6), and the condensate cooled by the refrigeration evaporator (12) flows into the condensate collector (6).

9. A sludge drying method driven by low-grade waste heat, characterized in that: The waste heat carrier drives the absorption refrigeration cycle system (1) to generate cooling capacity in the refrigeration evaporator (12), and the cooling capacity is used to cool the air at the outlet of the sludge dryer and condense water vapor; the waste heat carrier also drives the second type of absorption heat pump cycle system (2) to generate heat in the heat pump absorber (21), and the heat is used to heat the air at the inlet of the sludge dryer; at the same time, the waste heat carrier is gradually cooled down through the absorption refrigeration cycle system (1) and the second type of absorption heat pump cycle system (2).

10. The sludge drying method driven by low-grade waste heat according to claim 9, characterized in that: After the waste heat carrier flows through the second type of absorption heat pump cycle system (2), it then enters the air regenerator (5) to be cooled down, and at the same time, the air regenerator (5) heats the air before entering the inlet of the sludge dryer (3).

Images