A heat pump drying system and its heating method

Abstract

The present invention belongs to the technical field of flue gas treatment heat pump systems, and specifically relates to a heat pump drying system and a heating method thereof, including an open absorption heat pump unit and a parallel compression heat pump unit. The parallel compression heat pump unit provides the heating amount required for the generator of the open absorption heat pump unit by producing dual-temperature heat energy. The open absorption heat pump unit includes an open adiabatic absorption tower, a high-pressure generator, a low-pressure generator, a first ejector, and a second ejector. The flue gas inlet of the open adiabatic absorption tower is used to introduce the hot and humid flue gas to be treated. A spraying member and a packing layer are arranged in the open adiabatic absorption tower. The spraying member is located above the packing layer, and the packing layer is located above the flue gas inlet. This device can orderly recover and utilize the waste heat and moisture of the flue gas, effectively solving the problems of low efficiency existing in traditional open absorption heat pumps and the inability to recover and utilize the water vapor in the flue gas during the flue gas drying process.

Description

Technical Field

[0001] The present invention belongs to the technical field of flue gas treatment heat pump systems, and in particular relates to a heat pump drying system and a heating method thereof, which can be used for drying hot and wet flue gas and recovering waste heat. Background Art

[0002] In the related prior art, there are generally three methods for treating hot and wet waste gas (flue gas): the first is the flue gas water medium heat exchange system (MGGH), which uses water as a medium to absorb the heat of the high-temperature flue gas before desulfurization through a water circulation method, and is used to heat the clean flue gas after desulfurization, increase the temperature of the clean flue gas, increase the lifting height of the flue gas emission, and reduce the landing concentration of pollutants. The disadvantage of this method is that it cannot achieve the waste gas heat and mass recovery effect. The second is the wet method, that is, the wet tail gas is directly passed into the spray chamber, and the spray water contacts the tail gas for heat exchange; the heat released by the wet tail gas in this process is low in temperature and mixed with pollutants, and cannot be reused, but this method has the effect of dust removal and purification on the tail gas; the third is the indirect heat exchange method, that is, heat exchange is carried out through heat exchange components such as heat exchangers and evaporators of heat pump systems to achieve heat recovery. Compared with the wet method, the temperature of the recovered heat is significantly increased in this method, and its shortcomings are mainly reflected in the fact that the temperature of the heat recovery medium must be reduced to below the dew point temperature.

[0003] At present, the main energy-saving devices for waste heat recovery of hot and wet exhaust gas are wall heat exchangers, closed absorption heat pumps and open absorption heat pumps. The traditional "cooling and condensation method" for recovering latent heat of vaporization, that is, using the "wall heat exchanger + lithium bromide closed absorption heat pump" method, can realize the recovery and utilization of sensible heat and latent heat of hot and wet flue gas, but it has many disadvantages. First, lowering the flue gas temperature to recover waste heat will produce a large amount of sewage, causing secondary environmental disasters, and the cost of later treatment is high; secondly, the reduction of flue gas temperature is not conducive to flue gas emission, and "hanging ice" is formed at the top of the chimney, which has safety hazards; in addition, traditional heat pump products are affected by the fluctuation of heating water temperature in winter, and the heat extraction capacity fluctuates greatly, which seriously affects the waste heat recovery efficiency. In short, traditional latent heat recovery adopts the "cooling and condensation" method, which has a large exergy loss; in addition, during the flue gas condensation process, the condensed water will carry flue gas pollutants (SO2, NOX, dust, etc.), which will become industrial sewage and cause secondary environmental pollution. It can be seen that the traditional cooling and condensation method for treating waste heat and moisture in flue gas has problems such as low energy recovery rate, zero mass recovery rate and secondary disasters of pollutants in hot and wet waste gas.

[0004] Another method is the open absorption heat pump technology. Different from the above methods, it achieves heat transfer through a mass transfer process to recover heat. The advantages of this method are mainly reflected in: (1) The condensation process of water vapor in the humid gas is achieved through the vapor partial pressure difference between the dehumidification solution and the humid gas. Therefore, during the recovery process, the solution temperature does not need to be reduced below the dew point temperature, and the recovered heat temperature is higher; (2) The working fluids used are humid gas and dehumidification solution, both of which are natural working fluids with zero ODP and GWP. The dehumidification solution can also play the role of dust removal and air purification; (3) The open absorption heat pump is a type of absorption heat pump, both of which are heat-driven systems. Low-grade waste heat can be used as the solution regeneration energy to reduce the consumption of primary energy. However, the existing open absorption heat pump technology cannot recover and reuse the water vapor contained in the hot and humid flue gas during the drying process of the hot and humid flue gas. Summary of the Invention

[0005] The purpose of the present invention is to solve the problems existing in the above-mentioned prior art, and to provide a heat pump drying system and its heating method. This device can orderly recover and utilize the waste heat and humidity of hot and humid waste gas, and can effectively solve the problems of low efficiency existing in traditional open absorption heat pumps and the inability to recover the water vapor contained in waste gas (flue gas).

[0006] To achieve the above purpose, one of the purposes of the present invention is to provide a heat pump drying system,

[0007] including an open absorption heat pump unit and a parallel compression heat pump unit. The parallel compression heat pump unit provides the heating required for the generator of the open absorption heat pump unit by producing dual-temperature heat energy;

[0008] The open absorption heat pump unit includes an open adiabatic absorption tower, a high-pressure generator, a low-pressure generator, a first ejector, and a second ejector;

[0009] The flue gas inlet of the open adiabatic absorption tower is used to introduce the hot and humid flue gas to be treated; a spraying member and a packing layer are arranged in the open adiabatic absorption tower. The spraying member is located above the packing layer, and the packing layer is located above the flue gas inlet; the spraying member is used to spray the solution to absorb the water vapor in the hot and humid flue gas to form a dilute solution with a lower concentration, and at the same time release the absorption heat to heat the dilute solution and the flue gas;

[0010] The bottom solution outlet of the open adiabatic absorption tower is divided into two branches;

[0011] The first branch is connected to the solution inlet of the open adiabatic absorption tower through a pump;

[0012] The second branch is respectively connected to the inlets of the high-pressure generator and the low-pressure generator;

[0013] The steam outlet of the high-pressure generator is connected to the working fluid inlet of the second ejector, and the solution outlet of the high-pressure generator is connected to the working fluid inlet of the first ejector;

[0014] The steam outlet of the low-pressure generator is connected to the entrained fluid inlet of the second ejector, and the solution outlet of the low-pressure generator is connected to the entrained fluid inlet of the first ejector;

[0015] The mixed fluid outlet of the second ejector is connected to the condensate storage tank; the mixed fluid outlet of the first ejector is connected to the top solution inlet of the open adiabatic absorption tower, and the solution inlet of the open adiabatic absorption tower is connected to the spraying member.

[0016] As a preferred solution, it further includes a solution heat exchanger;

[0017] The inlet and outlet of the dilute solution channel of the solution heat exchanger are connected to the pipeline between the solution outlet of the open adiabatic absorption tower and the generator inlet;

[0018] The inlet and outlet of the concentrated solution channel of the solution heat exchanger are connected to the pipeline between the mixed fluid outlet of the first ejector and the solution inlet of the open adiabatic absorption tower.

[0019] As a preferred solution, the parallel compression heat pump unit includes a first refrigerant channel and a second refrigerant channel arranged in parallel;

[0020] A first compressor, a high-temperature solution condenser and a first throttling component are sequentially connected in series on the first refrigerant channel;

[0021] Wherein a second compressor, a low-temperature solution condenser and a second throttling component are sequentially connected in series on the second refrigerant channel;

[0022] The refrigerant medium after throttling by the first throttling component and the second throttling component is divided into two paths after absorbing the heat of the external heat source and the heat provided by the open absorption heat pump unit, and respectively enters the first compressor and the second compressor.

[0023] As a preferred solution, it further includes an external heat source evaporator;

[0024] The inlets of the refrigerant channels of the external heat source evaporator are respectively connected to the outlets of the first throttling component and the second throttling component;

[0025] The outlets of the refrigerant channels of the external heat source evaporator are respectively connected to the inlets of the first compressor and the second compressor.

[0026] As a preferred solution, it further includes a solution evaporator; the solution evaporator is located outside the tower body of the open adiabatic absorption tower;

[0027] The inlet and outlet of the solution channel of the solution evaporator are respectively connected to the pump outlet and the solution inlet of the open adiabatic absorption tower;

[0028] The inlet and outlet of the refrigerant channel of the solution evaporator are respectively connected to the refrigerant channel outlet of the external heat source evaporator and the inlets of the first compressor and the second compressor.

[0029] As a preferred solution, it further includes a solution cooler and a steam condenser; the solution cooler is located outside the tower body of the open adiabatic absorption tower;

[0030] The solution cooler includes a solution channel and a medium channel for heat exchange. The inlet of the solution channel of the solution cooler is connected to the pump outlet. The outlet of the solution channel of the solution cooler is connected to the solution inlet of the open adiabatic absorption tower through the solution evaporator. The outlet of the medium channel of the solution cooler is connected to the inlet of the steam condenser, and the inlet of the medium channel is connected to the heating return water pipe;

[0031] The steam condenser is placed inside the condensate storage tank. The steam condenser is used to heat the heating medium passing through it, and at the same time, it condenses the steam in the condensate storage tank. The outlet of the steam condenser is connected to the heating supply water pipe.

[0032] As a preferred solution, the condensate outlet of the condensate storage tank is connected to the industrial make-up water pipe for discharging the internal condensate for industrial make-up water.

[0033] The second object of the present invention is to provide a heating method according to the above heat pump drying system, including the operation steps of the open absorption heat pump unit and the parallel compression heat pump unit;

[0034] Among them, the operation steps of the open absorption heat pump unit include the following steps:

[0035] The concentrated solution generated in the high-pressure generator enters the first ejector as the working fluid to eject the concentrated solution generated in the low-pressure generator. After the mixed concentrated solution at the outlet of the first ejector exchanges heat with the dilute solution from the open adiabatic absorption tower, the mixed concentrated solution at the outlet of the first ejector enters the open adiabatic absorption tower again to absorb and dry the flue gas and becomes a dilute solution, while releasing the absorption heat to heat the dilute solution and the flue gas;

[0036] The water vapor with the first pressure value generated by the high-pressure generator enters the second ejector as the working fluid to eject the water vapor with the second pressure value generated by the low-pressure generator; the mixed water vapor at the outlet of the second ejector releases the condensation heat and is condensed into liquid water;

[0037] The dilute solution flowing out of the open adiabatic absorption tower is divided into two branches. The dilute solution in one branch is used to realize the cascade utilization of the recovered waste heat of the flue gas; the dilute solution in the other branch is preheated by the mixed concentrated solution at the outlet of the first ejector and then enters the generator to absorb heat and generate vapor.

[0038] As a preferred solution, the operation steps of the parallel compression heat pump unit include the following steps:

[0039] The refrigerant working medium of the parallel compression heat pump unit is divided into two paths; among them;

[0040] One path of gaseous refrigerant is compressed by the first compressor into high-pressure and high-temperature superheated refrigerant vapor to complete the compression process with a high compression ratio, and then enters the high-temperature solution condenser to provide the heat required for generation for the high-pressure generator, and the high-pressure generator generates superheated steam with a first pressure value;

[0041] The other path of gaseous refrigerant is compressed by the second compressor into relatively high-pressure and relatively high-temperature superheated refrigerant vapor to complete the compression process with a relatively high compression ratio, and then enters the low-temperature solution condenser to provide the heat required for generation for the low-pressure generator, and the low-pressure generator generates superheated steam with a second pressure value;

[0042] The liquid refrigerant working medium discharged from the high-temperature solution condenser and the low-temperature solution condenser is throttled and depressurized by a throttling component to become refrigerant working medium with the same pressure, and after absorbing heat, it returns to the suction ports of the first compressor and the second compressor to complete the compression process.

[0043] As a preferred solution, the liquid refrigerant working medium discharged from the high-temperature solution condenser and the low-temperature solution condenser is throttled and depressurized by a throttling component to become refrigerant working medium with the same pressure, and after absorbing the heat of the external heat source and recovering the waste heat of the flue gas absorbed by the open absorption heat pump unit, it returns to the suction ports of the first compressor and the second compressor to complete the compression process.

[0044] As a preferred solution, the refrigerant working medium of the parallel compression heat pump unit is a mixed working medium composed of one or more of R32, R290, R600a, and R1234yf.

[0045] As a preferred solution, the circulating solution of the open absorption heat pump unit is a binary non-azeotropic mixed working medium composed of salt and water, and the circulating solution adopts lithium chloride aqueous solution, calcium chloride aqueous solution, lithium bromide solution or potassium formate solution.

[0046] Compared with the prior art, the present invention has at least the following beneficial effects:

[0047] First, the present invention provides a heat pump drying system, which includes an open absorption heat pump unit and a parallel compression heat pump unit. The parallel compression heat pump unit extracts dual-temperature heat energy through a parallel compressor to provide the heating amount required by the generator of the open absorption heat pump unit, thus eliminating the high-temperature heat source heating amount required by the traditional absorption heat pump generator. The solution and water vapor generated by the high-pressure generator are respectively used as the working fluids of the first ejector and the second ejector to eject the solution and water vapor generated by the low-pressure generator, thus eliminating pressure conveying equipment such as solution pumps or compressors. Therefore, this solution realizes a reasonable optimization of the heat pump system structure. Inside the tower body of the open adiabatic absorption tower, the hot and humid flue gas meets the sprayed solution in the packing layer and undergoes heat and mass transfer. The solution recovers the waste heat and moisture carried by the flue gas. The sprayed solution forms a thinner dilute solution by absorbing the water vapor in the flue gas, releases the absorption heat, and heats both the dilute solution and the flue gas simultaneously. The moisture content of the flue gas decreases while the temperature increases. This system has remarkable energy-saving effects, stable and reliable operation, and broad application prospects.

[0048] Second, in this solution, the series design of the solution cooler and the solution evaporator of the open adiabatic absorption tower, and by arranging the solution cooler and the solution evaporator outside the tower body, replaces the structure of setting a water-cooled cooler inside the tower body of the traditional open adiabatic absorption tower, separates the heat and mass transfer processes of the solution absorbing water vapor, and strengthens these two processes respectively.

[0049] Third, the present invention optimizes the heating method of the heat pump system. By combining with the heat pump drying system with the above specific structure, a part of the waste heat of the flue gas recovered by the open absorption heat pump unit is directly heated for hot water supply at one time, and another part is used to improve the heat energy grade and heated for hot water supply at a second time through the parallel compression heat pump unit, thus realizing the cascade heating process of heating water; the waste heat generated by the open absorption heat pump unit can be used as the secondary heat source of the parallel compressor heat pump unit to ensure that the refrigerant at the suction port of the compressor is always in a superheated gas state. Through the drying treatment of the hot and humid flue gas, the recovered moisture from the hot and humid flue gas can be condensed into condensed water for industrial use, significantly reducing the high-temperature heat source heating amount required by the open absorption heat pump, solving the problem of low efficiency existing in the traditional open absorption heat pump, and at the same time realizing the recycling and reuse of the water vapor contained in the flue gas during the drying treatment of the hot and humid flue gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the technical solutions in the embodiments of the invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0051] Figure 1It is a schematic structural diagram of the heat pump drying system of the present invention;

[0052] Markings in the figure: 1. High-pressure generator, 2. Low-pressure generator, 3. First ejector, 4. Solution heat exchanger, 5. Open adiabatic absorption tower, 51. Tower body, 52. Flue gas inlet, 53. Solution inlet, 54. Solution outlet, 55. Flue gas outlet, 6. Pump, 7. Solution cooler, 8. Solution evaporator, 9. Second ejector, 10. Condensate storage tank, 101. Heating return pipe, 102. Heating supply pipe, 103. Industrial make-up water pipe, 11. Steam condenser, 12. First compressor, 13. Second compressor, 14. High-temperature solution condenser, 15. Low-temperature solution condenser, 16. First throttling component, 17. Second throttling component, 18. External heat source evaporator, 181. External heat source side channel, 19. Spraying component, 20. Packing layer. Specific embodiments

[0053] The present invention will be specifically described below through exemplary embodiments. However, it should be understood that, without further elaboration, the elements, structures, and features in one embodiment can also be beneficially combined into other embodiments.

[0054] It should be noted that: Unless otherwise defined, the technical terms or scientific terms used herein should have the ordinary meanings understood by those of ordinary skill in the art to which the present invention pertains. The words such as "a", "an", or "the" used in the specification and claims of the present invention for patent application do not express a limitation of quantity, but rather mean that there is at least one. Words such as "comprising" or "including" indicate that the elements or objects appearing before "comprising" or "including" cover the elements or objects listed after "comprising" or "including" and their equivalents, but do not exclude other elements or objects having the same functions.

[0055] As shown in the figure, this embodiment provides a heat pump drying system, which can be used for waste heat recovery and drying treatment of hot and humid flue gas. It includes the following two parts: an open absorption heat pump unit and a parallel compression heat pump unit. Among them, the open absorption heat pump unit is an open double-effect absorption heat pump unit, which is used to recover the waste heat in the hot and humid flue gas, simultaneously dry the hot and humid flue gas, and recycle the waste heat and moisture in the flue gas. The parallel compression heat pump unit utilizes the waste heat of the absorbed flue gas and the external air heat source, and produces dual-temperature heat energy to provide the required heating amount for the generator of the open absorption heat pump unit. The heat pump system of this solution not only realizes the orderly recovery and utilization of flue gas waste heat and moisture, but also solves the technical problem of low efficiency existing in the existing open absorption heat pump system.

[0056] In a typical embodiment of the present invention, the open absorption heat pump unit includes a high-pressure generator 1, a low-pressure generator 2, a first ejector 3, a second ejector 9, a condensate storage tank 10, a steam condenser 11, a solution heat exchanger 4, a pump 6, a solution evaporator 8, and an open adiabatic absorption tower 5.

[0057] In this solution, the open adiabatic absorption tower 5 includes a tower body 51, on which there are provided a flue gas inlet 52, a solution inlet 53, a solution outlet 54, and a flue gas outlet 55. The flue gas inlet 52 is located at the lower section of the side wall of the tower body 51, and the flue gas outlet 55 is arranged at the top of the tower body 51. The function of the flue gas inlet 52 is to introduce industrial waste gas (hot and humid flue gas) into the tower body 51, and the flue gas flows upward in the tower body 51 and is discharged out of the tower body 51 from the flue gas outlet 55. Inside the tower body 51, there are provided a spraying member 19 and a packing layer 20. Among them, the spraying member 19 is connected to the pipeline of the solution inlet 53. The spraying member 19 includes a spraying pipe and solution spray heads are distributed on the spraying pipe, and the spraying member 19 is located above the packing layer 20. The flue gas inlet 52 is located below the packing layer 20. The solution inlet 53 is located at the upper section of the side wall of the tower body 51, and the solution outlet 54 is located at the bottom of the tower body 51. With such a design, when the flue gas enters the inside of the open adiabatic absorption tower 5 from the flue gas inlet 52, the flue gas passes through the packing layer 20 from bottom to top, while the solution sprayed by the spraying member 19 enters and passes through the packing layer 20 from top to bottom. The flue gas and the sprayed solution meet in the packing layer 20 and heat and mass transfer occur. The solution recovers the waste heat carried in the flue gas and realizes the drying treatment of the flue gas by recovering the residual moisture contained in the flue gas. The sprayed solution forms a dilute solution with a lower concentration by absorbing the water vapor in the flue gas, and at the same time releases the absorption heat to heat both the dilute solution and the flue gas. The moisture content of the treated flue gas decreases while the temperature increases.

[0058] In this solution, the solution outlet 54 of the open adiabatic absorption tower 5 is divided into two branches. Among them, the first branch is connected to the solution inlet 53 of the open adiabatic absorption tower 5 through a pump 6. More specifically, a solution cooler 7 is provided at the outlet of the pump 6. The solution cooler 7 is located outside the tower body 51 of the open adiabatic absorption tower 5. The solution cooler 7 includes a solution channel and a medium channel capable of realizing heat exchange. Among them, the outlet of the pump 6 is connected to the solution channel of the solution cooler 7, and the medium channel of the solution cooler 7 is used to be connected to the external heating water channel. The waste heat of the exhaust gas recovered by the solution in the solution channel is used to preheat the heating medium in the medium channel once. Specifically, the inlet of the medium channel of the solution cooler 7 is connected to the heating return pipe 101, and the outlet of the medium channel of the solution cooler 7 is connected to the heating supply pipe 102.

[0059] In this embodiment, it further includes a solution evaporator 8 which is located outside the tower body 51 of the open adiabatic absorption tower 5. The solution evaporator 8 includes a solution channel and a refrigerant channel. The inlet of the solution channel of the solution evaporator 8 is connected to the outlet of the solution channel of the solution cooler 7, and the outlet of the solution channel of the solution evaporator 8 is connected to the spray member 19 connected to the solution inlet 53 of the open adiabatic absorption tower 5. The refrigerant channel of the solution evaporator 8 is connected to the refrigerant channel of the parallel compression heat pump unit, and is used to heat the refrigerant working medium in the refrigerant channel by the waste heat of the exhaust gas recovered by the solution, so as to realize the full utilization of the recovery of the waste heat of the exhaust gas. In the open adiabatic absorption tower 5 of this solution, a series design of the solution cooler 7 and the solution evaporator 8 is carried out outside the tower body 51, replacing the structure of setting a water-cooled cooler inside the tower body 51 of the traditional open adiabatic absorption tower 5 in the prior art. By separating the heat and mass transfer processes of the solution absorbing water vapor, these two processes are respectively strengthened. In addition, in this solution, a packing layer 20 is provided in the open adiabatic absorption tower 5, which improves the contact time and contact area of the solution absorbing water vapor, thereby further strengthening the heat and mass transfer processes of the solution absorbing water vapor.

[0060] In addition, a solution heat exchanger 4 is provided in the second branch of the solution outlet 54 at the bottom of the open adiabatic absorption tower 5. The function of the solution heat exchanger 4 is to preheat the dilute solution discharged from the open adiabatic absorption tower 5 by the concentrated solution about to enter the open adiabatic absorption tower 5, and then the preheated dilute solution will enter the generator for generation respectively. Specifically, the solution heat exchanger 4 includes a concentrated solution channel and a dilute solution channel. The inlet of the dilute solution channel is connected to the outlet at the bottom of the tower body of the open adiabatic absorption tower 5, and the outlet of the dilute solution channel is respectively connected to the solution inlets of the high-pressure generator 1 and the low-pressure generator 2, and is used to supply the required solution for the high-pressure generator 1 and the low-pressure generator 2. The inlet of the concentrated solution channel is connected to the outlet of the first ejector 3, and is used to send the mixed fluid ejected by the first ejector 3 to the spray member 19 for spraying.

[0061] In this solution, the high-pressure generator 1 includes a solution inlet, a steam outlet and a solution outlet. The steam outlet of the high-pressure generator 1 is connected to the working fluid inlet of the second ejector 9, and the solution outlet of the high-pressure generator 1 is connected to the working fluid inlet of the first ejector 3. The low-pressure generator 2 includes a solution inlet, a steam outlet and a solution outlet. The steam outlet of the low-pressure generator 2 is connected to the entrained fluid inlet of the second ejector 9; the solution outlet of the low-pressure generator 2 is connected to the entrained fluid inlet of the first ejector 3. The first ejector 3 is a liquid-liquid ejector, and the concentrated solution discharged from the high-pressure generator 1 is used as the working fluid to entrain the concentrated solution discharged from the low-pressure generator 2. The second ejector 9 is a steam-steam ejector, and the steam discharged from the high-pressure generator 1 is used as the working fluid to entrain the steam discharged from the low-pressure generator 2.

[0062] In this embodiment, the condensate storage tank 10 includes a steam inlet and a condensate outlet. The condensate storage tank 10 is in a sealed state. The steam inlet of the condensate storage tank 10 is connected to the outlet of the second ejector 9, and the condensate outlet at the bottom of the condensate storage tank 10 is connected to the industrial make-up water pipe 103. A steam condenser 11 is arranged in the condensate storage tank 10. The inlet end of the steam condenser 11 is connected to the outlet of the medium channel of the solution cooler 7. After the solution cooler 7 preheats the heating medium once by recovering the waste heat of the exhaust gas, the steam condenser 11 is used to heat the heating medium for the second time and then send it out. For the waste heat of the exhaust gas recovered by the open-type double-effect absorption heat pump unit, a part of the waste heat of the exhaust gas directly heats the hot water once through the solution cooler 7, and another part of the waste heat of the exhaust gas is heated for the second time by the steam condenser 11 to supply hot water. The heat energy grade is improved through the parallel compression heat pump unit, so as to realize the cascade heating process of the heating water.

[0063] In this embodiment, the outlet of the second ejector 9 is connected to the steam inlet of the condensate storage tank 10, and is used to send the mixed steam discharged from the second ejector 9 into the condensate storage tank 10 for condensation. The steam condensate condensed by the steam condenser 11 can be used as industrial make-up water. That is, the open-type double-effect absorption heat pump unit recovers the waste heat of the exhaust gas and the waste humidity of the exhaust gas recovered during the drying process. The water vapor is concentrated and generated by the high-pressure generator 1 and the low-pressure generator 2. The concentrated water vapor enters the condensate storage tank 10 and condenses into condensate, so as to realize the orderly recovery and utilization of the waste heat and waste humidity of the exhaust gas. The generated condensate realizes industrial make-up water through the industrial make-up water pipe 103, so as to realize the utilization of the waste humidity of the recovered exhaust gas. This solution not only solves the waste heat recovery and drying treatment of the exhaust gas, but also the recovered waste heat can be used for heating the heating water, and at the same time supplies heat to the parallel compression heat pump unit. In addition, the waste humidity of the exhaust gas recovered during the drying process can also be used as industrial make-up water, realizing energy conservation and consumption reduction.

[0064] In this solution, the outlet of the first ejector 3 is connected to the inlet of the concentrated solution channel of the solution heat exchanger 4, and is used to send the mixed solution discharged from the first ejector 3 into the solution inlet 53 of the open-type adiabatic absorption tower 5 through the concentrated solution channel, so as to realize the spray absorption treatment of the exhaust gas through the spray member 19.

[0065] More specifically, the open absorption heat pump unit includes a high-pressure generator 1, a low-pressure generator 2, a first ejector 3, a solution heat exchanger 4, an open adiabatic absorption tower 5, a pump 6, a solution evaporator 8, a second ejector 9, a condensate storage tank 10, and a steam condenser 11. The bottom solution outlet of the open adiabatic absorption tower 5 is divided into two branches. One branch is connected in series with a solution cooler 7, a solution evaporator 8, and a spray member 19 through the pump 6 in sequence. The other branch is connected to the dilute solution channel inlet of the solution heat exchanger 4. The dilute solution channel outlet of the solution heat exchanger 4 is respectively connected to the solution inlets of the high-pressure generator 1 and the low-pressure generator 2. The steam outlet of the high-pressure generator 1 is connected to the working fluid inlet of the second ejector 9. The steam outlet of the low-pressure generator 2 is connected to the entrained fluid inlet of the second ejector 9. The mixed fluid outlet of the second ejector 9 is connected to the steam inlet of the condensate storage tank 10. The bottom concentrated solution outlet of the high-pressure generator 1 is connected to the working fluid inlet of the first ejector 3. The bottom concentrated solution outlet of the low-pressure generator 2 is connected to the entrained fluid inlet of the first ejector 3. The mixed fluid outlet of the first ejector 3 is connected to the spray member 19 in the open adiabatic absorption tower 5 through the concentrated solution channel of the solution heat exchanger 4.

[0066] In this embodiment, the parallel compression heat pump unit extracts dual-temperature heat energy from the flue gas waste heat and the external heat source through parallel compressors to provide heating for the high-pressure generator 1 and the low-pressure generator 2. The parallel compression heat pump unit can adopt the following implementation structure: including a first compressor 12, a second compressor 13, a high-temperature solution condenser 14, a low-temperature solution condenser 15, a first throttling member 16, a second throttling member 17, an external heat source evaporator 18, and a solution evaporator 8. The solution evaporator 8 is a common component for both the parallel compression heat pump unit and the open absorption heat pump unit.

[0067] In this solution, the solution evaporator 8 includes a solution side channel and a refrigerant side channel capable of achieving heat exchange. The solution side channel inlet of the solution evaporator 8 is connected to the solution channel outlet of the solution cooler 7. The solution side channel outlet of the solution evaporator 8 is connected to the solution inlet 53 between the solution evaporator 8 and the open adiabatic absorption tower 5. The refrigerant side channel inlet of the solution evaporator 8 is connected to the refrigerant channel outlet of the external heat source evaporator 18. The refrigerant side channel outlet of the solution evaporator 8 is respectively connected to the suction ports of the first compressor 12 and the second compressor 13. The refrigerant working fluid of the parallel compression heat pump unit can recover the flue gas waste heat absorbed by the open absorption heat pump unit through the solution evaporator 8.

[0068] In this embodiment, the external heat source evaporator 18 includes a refrigerant side channel and an external heat source side channel 181 capable of achieving heat exchange. The inlets of the refrigerant channels of the external heat source evaporator 18 are respectively connected to the outlets of the first throttling member 16 and the second throttling member 17, and the outlet of the refrigerant channel of the external heat source evaporator 18 is connected to the suction ports of the first compressor 12 and the second compressor 13 through the solution evaporator 8. The refrigerant working medium absorbs the high-temperature heat energy in the external environment through the external heat source evaporator 18. The external heat source evaporator 18 is provided with heating quantity by an external heat source. The heat source required by the external heat source side channel 181 can be sourced from low-grade heat sources such as solar energy and industrial waste heat, or can also be sourced from energy sources or heat sources such as fuel, gas or steam. Thus, the above-mentioned energy and heat sources provide heat energy for the refrigerant working medium of the parallel compression heat pump unit.

[0069] Specifically, the first compressor 12 and the second compressor 13 are connected in parallel. The exhaust port of the first compressor 12, the high-temperature solution condenser 14, and the inlet of the first throttling member 16 are connected in series in sequence, wherein the high-temperature solution condenser 14 is built in the high-pressure generator 1 in a sealed state. The exhaust port of the second compressor 13, the low-temperature solution condenser 15, and the inlet of the second throttling member 17 are connected in series in sequence, wherein the low-temperature solution condenser 15 is built in the low-pressure generator 2 in a sealed state. The outlets of the first throttling member 16 and the second throttling member 17 are both connected to the inlet of the refrigerant channel of the external heat source evaporator 18. The outlet of the refrigerant channel of the external heat source evaporator 18 is connected to the inlet of the refrigerant side channel of the solution evaporator 8. The outlet of the refrigerant side channel of the solution evaporator 8 is respectively connected to the suction ports of the first compressor 12 and the second compressor 13.

[0070] The present invention also provides a heating method for a heat pump drying system, including an operating step of an open absorption heat pump unit and an operating step of a parallel compression heat pump unit;

[0071] The operating step of the open absorption heat pump unit includes the following steps:

[0072] The concentrated solution generated in the high-pressure generator 1 enters the first ejector 3 as the working fluid to eject the concentrated solution generated in the low-pressure generator 2. After the mixed concentrated solution at the outlet of the first ejector 3 exchanges heat with the dilute solution from the open adiabatic absorption tower 5, the concentrated solution then enters the open adiabatic absorption tower 5 for spraying to absorb the water vapor in the flue gas to achieve flue gas drying. The concentrated solution becomes a dilute solution while releasing the absorption heat to heat the dilute solution and the flue gas; the water vapor generated by the high-pressure generator 1 enters the second ejector 9 as the working fluid to eject the water vapor generated by the low-pressure generator 2. The mixed water vapor at the outlet of the second ejector 9 releases the condensation heat and is condensed into liquid water. The dilute solution flowing out of the open adiabatic absorption tower 5 is divided into two branches. One branch of the dilute solution is used to realize the cascade utilization of the recovered flue gas waste heat; the other branch of the dilute solution is preheated by the mixed concentrated solution at the outlet of the first ejector 3, and the preheated dilute solution enters the generator to absorb heat and generate.

[0073] In this solution, the concentrated solution generated and discharged in the high-pressure generator 1 of the open double-effect absorption heat pump unit enters the first ejector 3 as the working fluid to eject the concentrated solution generated and discharged in the low-pressure generator 2. After the mixed concentrated solution at the outlet of the first ejector 3 preheats the dilute solution from the open adiabatic absorption tower 5 through the solution heat exchanger 4, it then enters the open adiabatic absorption tower 5 to spray and absorb the water vapor in the flue gas to become a dilute solution and release the absorption heat to heat the dilute solution and the flue gas, and the temperature of the flue gas increases and the moisture content decreases; the dilute solution flowing out of the open adiabatic absorption tower 5 is divided into two branches. One branch of the dilute solution enters the solution heat exchanger 4 to be preheated and then enters the high-pressure generator 1 and the low-pressure generator 2 respectively, and is heated by the high-temperature solution condenser 14 and the low-temperature solution condenser 15 of the parallel compression heat pump unit respectively to realize the cascade heating and concentration generation process of the dilute solution. The water vapor generated by the high-pressure generator 1 enters the second ejector 9 as the working fluid to eject the water vapor generated by the low-pressure generator 2. The mixed water vapor at the outlet of the second ejector 9 enters the condensate storage tank 10 to release the condensation heat and is condensed into liquid water to be used as industrial makeup water, and at the same time, the heating water is reheated for the second time. The other branch of the dilute solution is successively sent to the solution cooler 7 by the pump 6 to preheat the heating water once, and the solution evaporator 8 heats the refrigerant working medium as the low-temperature heat source of the parallel compression heat pump unit to realize the vaporization of the refrigerant working medium.

[0074] The operation steps of the parallel compression heat pump unit include the following steps:

[0075] The refrigerant working medium of the parallel compression heat pump unit is divided into two paths. One path of gaseous refrigerant is compressed by the first compressor 12 to become high-pressure, high-temperature superheated refrigerant vapor to complete the compression process with a high compression ratio, and then enters the high-temperature solution condenser 14 to provide the heat required for the generation in the high-pressure generator 1. The high-pressure generator generates superheated steam with a first pressure value; the other path of gaseous refrigerant is compressed by the second compressor 13 to become relatively high-pressure and relatively high-temperature superheated refrigerant vapor to complete the compression process with a relatively high compression ratio, and then enters the low-temperature solution condenser 15 to provide the heat required for the generation in the low-pressure generator 2. The low-pressure generator generates superheated steam with a second pressure value; the first pressure value is higher than the second pressure value. The refrigerant working medium discharged from the high-temperature solution condenser 14 and the low-temperature solution condenser 15 is throttled and depressurized by a throttling component and then becomes refrigerant working medium with the same pressure. After absorbing the heat of the external heat source, it returns to the suction ports of the first compressor 12 and the second compressor 13 to complete the compression process. In this solution, dual-temperature heat energy is extracted through parallel compressors to provide the heating amount for the high-pressure generator 1 and the low-pressure generator 2, thus eliminating the heating amount of the high-temperature heat source required by the traditional absorption heat pump generator.

[0076] In this solution, in the operation steps of the parallel compression heat pump unit: the refrigerant working medium sequentially passes through the external heat source evaporator 18 to absorb the heat of the external heat source and the solution evaporator 8 to recover the waste heat of the flue gas and becomes low-temperature and low-pressure steam. Part of the gaseous refrigerant working medium is compressed by the first compressor 12 to become superheated steam with high temperature and high pressure to complete the compression process with a high compression ratio, and enters the high-temperature solution condenser 14 to provide the heating amount for the high-pressure generator 1. The high-pressure generator 1 generates superheated steam with a pressure higher than 0.1 MPa. Another part of the gaseous refrigerant working medium is compressed by the second compressor 13 to become superheated steam with a relatively high temperature and relatively high pressure to complete the compression process with a relatively high compression ratio, and enters the low-temperature solution condenser 15 to provide the heating amount for the low-pressure generator 2. The low-pressure generator 2 generates superheated steam with a pressure lower than 0.1 MPa. The liquid refrigerant working media from the high-temperature solution condenser 14 and the low-temperature solution condenser 15 respectively pass through the first throttling component 16 and the second throttling component 17 connected in parallel and then become working media with the same pressure, and then sequentially enter the external heat source evaporator 18 and the solution evaporator 8 to absorb the heat of the external heat source and recover the waste heat of the flue gas in turn.

[0077] In this solution, the circulating solution of the open absorption heat pump unit is a binary azeotropic mixture composed of salt and water. The circulating solution adopts lithium chloride aqueous solution, calcium chloride aqueous solution, lithium bromide solution or potassium formate solution; the refrigerant working medium of the parallel compression heat pump unit is one or two or more of HC or HFC refrigerants such as R32, R290, R600a, R1234yf and other mixed working media composed thereof.

[0078] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with the preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments by using the above-disclosed technical content without departing from the technical solution of the present invention. However, as long as it does not depart from the technical solution content of the present invention, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A heat pump drying system, characterized in that: It comprises an open absorption heat pump unit and a parallel compression heat pump unit, wherein the parallel compression heat pump unit produces dual-temperature heat energy to provide the generator of the open absorption heat pump unit with the required heating amount; The open absorption heat pump unit comprises an open adiabatic absorption tower, a high pressure generator, a low pressure generator, a first ejector and a second ejector; The flue gas inlet of the open-type heat-insulating absorption tower is used to introduce the hot and humid flue gas to be treated; a spraying element and a packing layer are arranged in the open-type heat-insulating absorption tower, the spraying element is located above the packing layer, and the packing layer is located above the flue gas inlet; the spraying element is used to spray a solution to form a dilute solution with a lower concentration by absorbing water vapor in the hot and humid flue gas, and at the same time release absorption heat to heat the dilute solution and the flue gas; The bottom solution outlet of the open adiabatic absorption tower is divided into two branches; The first branch is connected to the solution inlet of the open adiabatic absorption tower through a pump; The second branch is connected to the inlet of the high-pressure generator and the inlet of the low-pressure generator respectively; The steam outlet of the high pressure generator is connected to the working fluid inlet of the second ejector, and the solution outlet of the high pressure generator is connected to the working fluid inlet of the first ejector; The steam outlet of the low-pressure generator is connected to the injection fluid inlet of the second ejector, and the solution outlet of the low-pressure generator is connected to the injection fluid inlet of the first ejector; The mixed fluid outlet of the second ejector is connected to the condensed water storage tank; the mixed fluid outlet of the first ejector is connected to the top solution inlet of the open adiabatic absorption tower, and the solution inlet of the open adiabatic absorption tower is connected to the spraying element.

2. A heat pump drying system according to claim 1, characterized in that: Also includes a solution heat exchanger; The inlet and outlet of the dilute solution channel of the solution heat exchanger are connected to the pipeline between the solution outlet and the generator inlet of the open adiabatic absorption tower; The inlet and outlet of the concentrated solution channel of the solution heat exchanger are connected to the pipeline between the mixed fluid outlet of the first ejector and the solution inlet of the open adiabatic absorption tower.

3. A heat pump drying system according to claim 1 or 2, characterized in that: The parallel compression heat pump unit comprises a first refrigerant channel and a second refrigerant channel arranged in parallel; The first refrigerant channel is provided with a first compressor, a high-temperature solution condenser and a first throttling component in series in sequence; The second refrigerant channel is provided with a second compressor, a low-temperature solution condenser and a second throttling component in series in sequence; The refrigerant medium throttled by the first throttling component and the second throttling component is divided into two paths after absorbing heat from an external heat source and heat provided by the open absorption heat pump unit, and enters the first compressor and the second compressor respectively.

4. A heat pump drying system according to claim 3, characterized in that: Also includes an external heat source evaporator; The inlet of the refrigerant channel of the external heat source evaporator is connected to the outlet of the first throttling component and the outlet of the second throttling component respectively; The outlet of the refrigerant channel of the external heat source evaporator is connected to the inlet of the first compressor and the inlet of the second compressor respectively.

5. A heat pump drying system according to claim 4, characterized in that: Also includes a solution evaporator; The solution evaporator is located outside the tower body of the open adiabatic absorption tower; The inlet and outlet of the solution channel of the solution evaporator are respectively connected to the pump outlet and the solution inlet of the open adiabatic absorption tower; The refrigerant channel inlet and outlet of the solution evaporator are respectively connected to the refrigerant channel outlet of the external heat source evaporator and the inlets of the first compressor and the second compressor.

6. A heat pump drying system according to claim 5, characterized in that: It also includes a solution cooler and a water vapor condenser; the solution cooler is located outside the tower body of the open adiabatic absorption tower; The solution cooler comprises a solution channel and a medium channel for realizing heat exchange, the inlet of the solution channel of the solution cooler is connected to the pump outlet, the outlet of the solution channel of the solution cooler is connected to the solution inlet of the open adiabatic absorption tower via the solution evaporator, the outlet of the medium channel of the solution cooler is connected to the inlet of the water vapor condenser, and the inlet of the medium channel is connected to the heating return pipe; The water vapor condenser is placed inside the condensate storage tank. The water vapor condenser is used to heat the heating medium passing through it and condense the steam in the condensate storage tank. The outlet of the water vapor condenser is connected to the heating drain pipe.

7. A heat pump drying system according to claim 6, characterized in that: The condensed water outlet of the condensed water storage tank is connected to the industrial water supply pipe, which is used to discharge the internal condensed water for industrial water supply.

8. A heating method for a heat pump drying system according to claim 7, characterized in that: The method comprises the steps of operating an open absorption heat pump unit and operating a parallel compression heat pump unit; The operation steps of the open absorption heat pump unit include the following steps: The concentrated solution generated in the high-pressure generator is used as a working fluid to enter the first ejector to eject the concentrated solution generated in the low-pressure generator. After the mixed concentrated solution at the outlet of the first ejector is heat-exchanged with the dilute solution from the open adiabatic absorption tower, the mixed concentrated solution at the outlet of the first ejector enters the open adiabatic absorption tower to absorb moisture and dry the flue gas and turn it into a dilute solution, while releasing absorption heat to heat the dilute solution and the flue gas. The water vapor with a first pressure value generated by the high-pressure generator enters the second ejector as a working fluid to eject the water vapor with a second pressure value generated by the low-pressure generator; the mixed water vapor at the outlet of the second ejector releases condensation heat and is condensed into liquid water; The dilute solution flowing out of the open adiabatic absorption tower is divided into two branches, one of which is used to realize the cascade utilization of the recovered flue gas waste heat; the other branch is preheated by the mixed concentrated solution at the outlet of the first ejector, and then enters the generator to absorb heat and generate.

9. A heating method for a heat pump drying system according to claim 8, characterized in that: The parallel compression heat pump unit operation steps include the following steps: The refrigerant working medium of the parallel compression heat pump unit is divided into two paths; wherein; A gaseous refrigerant is compressed by a first compressor into high-pressure, high-temperature, superheated refrigerant vapor to complete a high compression ratio compression process, and then enters a high-temperature solution condenser to provide heat required for the high-pressure generator to generate superheated water vapor of a first pressure value; The other gaseous refrigerant is compressed by the second compressor into a higher pressure, higher temperature superheated refrigerant vapor to complete a compression process with a higher compression ratio, and then enters the low-temperature solution condenser to provide the low-pressure generator with the heat required for generation, and the low-pressure generator generates superheated water vapor of a second pressure value; The liquid refrigerant discharged from the high-temperature solution condenser and the low-temperature solution condenser becomes a refrigerant of the same pressure after throttling and depressurization by the throttling component and returns to the suction port of the first compressor and the second compressor to complete the compression process after absorbing heat.

10. A heating method for a heat pump drying system according to claim 9, characterized in that: The liquid refrigerant discharged from the high-temperature solution condenser and the low-temperature solution condenser becomes a refrigerant of the same pressure after throttling and reducing the pressure through the throttling component, and after absorbing the heat from the external heat source and recovering the waste heat of the flue gas absorbed by the open absorption heat pump unit, returns to the suction port of the first compressor and the second compressor to complete the compression process.

11. A heating method for a heat pump drying system according to claim 9 or 10, characterized in that: The refrigerant medium of the parallel compression heat pump unit is a mixed medium composed of one or more of R32, R290, R600a, and R1234yf.

12. A heating method for a heat pump drying system according to any one of claims 8 to 10, characterized in that: The circulating solution of the open absorption heat pump unit is a binary non-azeotropic mixed working fluid composed of salt and water, and the circulating solution is a lithium chloride aqueous solution, a calcium chloride aqueous solution, a lithium bromide solution or a potassium formate solution.

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