CN115636567A - Sludge drying system based on heat pump and thermodynamic optimization design method thereof - Google Patents
Sludge drying system based on heat pump and thermodynamic optimization design method thereof Download PDFInfo
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Abstract
The invention discloses a sludge drying system based on a heat pump and a thermodynamic optimization design method thereof, wherein in the sludge drying system based on the heat pump, an outlet of a compressor is communicated with an inlet of the compressor through a refrigerant channel of a first condenser, a refrigerant channel of a second condenser, an expansion valve and a refrigerant channel of an evaporator in sequence; in the drying chamber, a sludge inlet is connected with a sludge outlet through a drying conveyor belt, an upper air port is communicated with a middle air port, and the middle air port is communicated with a lower air port; the middle air port is divided into two paths after passing through the air duct of the heat discharger, one path is communicated with the upper air port through the first condensed air duct, and the other path is communicated with the lower air port through the high-temperature side air duct of the sensible heat exchanger, the air duct of the evaporator, the low-temperature side air duct of the sensible heat exchanger and the second condensed air duct in sequence. The method can complete the overall optimization design of the heat pump drying system under the determined operation condition, sludge requirement and structural characteristics.
Description
Technical Field
The invention belongs to the technical field of heat pump application, and particularly relates to a sludge drying system based on a heat pump and a thermodynamic optimization design method thereof.
Background
With the continuous development of economy and society, the total supply of cold and heat energy sources in the traffic field and the industrial, commercial and civil fields is continuously increased year by year, and in consideration of the characteristics of low efficiency and high pollution of the traditional direct combustion type heat supply of primary energy sources, strong demands are put forward on the technical progress and industrial reform in the refrigeration and heating fields in the industrial, commercial and civil fields in modern life.
In the field of distributed drying, a primary energy direct combustion type heat supply method still occupies an absolute leading position, the direct energy utilization efficiency is far less than 100%, and the emission of a large amount of waste gas and waste residues is caused under the condition of distributed combustion, so that the popularization of the heat pump technology in the field has very important energy-saving and environment-friendly significance.
Different from the technical key points of the application backgrounds of the traditional heat pump water heater, the heat pump heating and the like, a heat pump system in the drying field not only needs to rely on a condenser to output heat outwards, but also needs to rely on an evaporator to provide refrigerating capacity for circulating air, so that moisture in the circulating air is separated out, the circulating air is guaranteed to enter a drying chamber in a low-humidity state, the drying effect is guaranteed, and brand-new system optimization design needs to be carried out according to the flow of the heat pump drying system.
In summary, in view of the special requirements of the drying field, the conventional heat pump design methods (heat pump water heater, heat pump heating, etc.) cannot meet the requirements in the drying system, and a new design method is urgently needed.
Disclosure of Invention
The invention aims to provide a sludge drying system based on a heat pump and a thermodynamic optimization design method thereof, so as to solve one or more technical problems. The method provided by the invention can complete the overall optimization design of the heat pump drying system under the determined operation condition, sludge requirement and structural characteristics, find the optimal operation thermodynamic parameters and ensure the lowest energy consumption per ton of sludge in the operation process.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a sludge drying system based on a heat pump, which comprises: the system comprises a compressor, a first condenser, a second condenser, a sensible heat exchanger, an evaporator, an expansion valve, a heat discharger and a drying chamber;
the outlet of the compressor is communicated with the inlet of the compressor through the refrigerant channel of the first condenser, the refrigerant channel of the second condenser, the expansion valve and the refrigerant channel of the evaporator in sequence;
the drying chamber is provided with a sludge inlet, a sludge outlet, an upper air port, a middle air port, a lower air port and a drying conveyor belt; in the drying chamber, the sludge inlet is connected with the sludge outlet through the drying conveyor belt, the upper air port is communicated with the middle air port, and the middle air port is communicated with the lower air port; the middle part wind gap warp divide into two the tunnel behind the wind channel of heat release ware, warp all the way the wind channel of first condensation with the upper portion wind gap is linked together, and another way warp in proper order sensible heat exchanger's high temperature side wind channel the wind channel of evaporimeter the low temperature side wind channel of sensible heat exchanger the wind channel of second condensation with the lower part wind gap is linked together.
The invention further improves the method and also comprises the following steps:
and the water path outlet of the water cooling tower is communicated with the water path inlet of the water cooling tower through the water path channel of the heat discharger.
The invention is further improved in that the drying conveyor belt is arranged in a layered mode.
The invention is further improved in that, in operation:
part of circulating air enters the drying chamber from an upper air port of the drying chamber, passes through a plurality of layers of drying conveyor belts and then reaches a middle air port; the other part of circulating air enters the drying chamber from a lower air port of the drying chamber, passes through a plurality of layers of drying conveyor belts and then reaches a middle air port;
the two parts of circulating air are uniformly fed into the heat discharger to dissipate heat to circulating cooling water after being mixed, the medium-temperature circulating air after heat dissipation is divided into two parts, wherein one part is introduced into the first condenser to absorb the heat of the refrigerant and then returns to an upper air opening of the drying chamber; and the other part of the circulating air firstly passes through the high-temperature side of the sensible heat exchanger to emit partial heat, then is introduced into the evaporator to emit heat and separate out moisture, then passes through the low-temperature side of the sensible heat exchanger again and absorbs the heat at the high-temperature side, and the heated circulating air passes through the second condenser to raise the temperature to reach a high-temperature low-humidity state and finally returns to an air opening at the lower part of the drying chamber.
A further development of the invention is that the medium in the refrigerant channel is R134a.
The invention provides a thermodynamic optimization design method of a sludge drying system based on a heat pump, which comprises the following steps:
acquiring required boundary conditions and working conditions of sludge products, geometric structures of a sludge drying system and structural forms in a drying chamber;
setting the rotating speed of a compressor, the total flow of circulating air, the air volume ratio of an upper layer and a lower layer, the volumetric efficiency and the isentropic efficiency of the compressor, the supercooling degree of a heat pump system, the exhaust pressure of the heat pump system, the suction pressure of the heat pump system, the superheat degree of the heat pump system and the outlet temperature of a low-temperature side after waste heat recovery; based on set conditions, calculating and obtaining the heating capacity and COP of the heat pump system, the circulating air temperature of the two-layer inlet, the water removal capacity of the evaporator, and the temperature, SMER and ton mud energy consumption information after heat exchange of a heat discharger of the drying system;
judging whether the sludge outlet parameters meet the feedforward requirements or not, if not, feeding back and adjusting the rotating speed of the compressor of the heat pump system, increasing a step length from the current value, and continuing to operate; if the dryness of the sludge outlet meets the requirement, judging the energy consumption of each ton of sludge in the system and a preset value, and if the dryness of the sludge outlet is smaller than the preset value, storing all the currently assumed thermodynamic parameters and thermodynamic calculation results as the existing optimal values of the current operation stage; if the temperature of the low-temperature side outlet is larger than or equal to the preset value, skipping the storage step and directly judging whether the temperature of the low-temperature side outlet after waste heat recovery reaches the maximum value, if the temperature of the low-temperature side outlet after waste heat recovery does not reach the maximum value, increasing the temperature of the low-temperature side outlet after waste heat recovery, wherein the increased value is a step length, and continuing to calculate; if the superheat degree of the heat pump system reaches the maximum value, judging whether the superheat degree of the heat pump system reaches the maximum value, if the superheat degree does not reach the maximum value, increasing the superheat degree, wherein the increased value is a step length, and continuing to calculate; if the maximum value is reached, judging whether the suction pressure of the heat pump system reaches the maximum value, if the maximum value is not reached, increasing the suction pressure, wherein the increased value is a step length, and continuing to calculate; if the maximum value is reached, judging whether the air volume ratio of the heat pump system reaches the maximum value, if the maximum value is not reached, increasing the air volume ratio, wherein the increased value is a step length, and continuing to calculate; if the maximum value is reached, judging whether the total air volume of the heat pump system reaches the maximum value, if the maximum value is not reached, increasing the total air volume, wherein the increased value is a step length, and continuing to calculate; and if the maximum value is reached, ending the whole operation process, and finally outputting a result which is the optimal operation state of the system corresponding to the lowest ton of sludge energy consumption in all iterative operation steps.
The invention is further improved in that the boundary conditions of the requirements of the sludge product comprise sludge treatment capacity, sludge inlet moisture content and sludge outlet moisture content; the working condition comprises ambient temperature and ambient humidity; the structural style in the drying chamber comprises the number of drying conveyor belts, air inlet information and air outlet information.
The invention is further improved in that the rotating speed of the compressor comprises a lower rotating speed limit, an upper rotating speed limit and an adjusting step length; the total flow of the circulating air comprises a total air volume lower limit, a total air volume upper limit and an adjusting step length; the two-layer air volume ratio comprises an air volume ratio lower limit, an air volume ratio upper limit and an adjusting step length; the suction pressure of the heat pump system comprises a lower suction pressure limit, an upper suction pressure limit and an adjusting step length; the superheat degree of the heat pump system comprises a lower superheat degree limit, an upper superheat degree limit and an adjusting step length; and the outlet temperature of the low-temperature side after waste heat recovery comprises an outlet temperature lower limit, an outlet temperature upper limit and an adjusting step length.
Compared with the prior art, the invention has the following beneficial effects:
according to the technical scheme provided by the invention, a double-layer parallel drying chamber structure with two inlets and one outlet is innovatively provided, and through structural innovation of the sectional type hot air inlet, the average hot air temperature in the drying chamber is remarkably improved, the air resistance caused in the air flowing process in the drying chamber is effectively reduced, and the power consumption of the circulating fan is greatly reduced.
In the conventional heat pump, an evaporation side (a refrigeration side) and a condensation side (a heating side) are positioned in two different environment areas and respectively exchange heat with different heat exchange media, and the two sides are respectively designed and optimized; the invention provides an optimization design method different from a conventional heat pump system aiming at special working condition requirements in the drying application field, wherein an evaporation side (a refrigeration side) and a condensation side (a heating side) exchange heat with air in the same circulation loop, and the wet air is cooled (water is analyzed) and then heated, so that the method is a strong coupling process and is substantially different from the traditional design optimization scheme. The method provided by the invention can complete the overall optimization design of the heat pump drying system under the determined operation condition, sludge requirement and structural characteristics, find the optimal operation thermodynamic parameters and ensure the lowest energy consumption per ton of sludge in the operation process, and can provide theoretical reference for equipment manufacturers and suppliers.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art are briefly introduced below; it is obvious that the drawings in the following description are some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.
FIG. 1 is a schematic diagram of a heat pump-based sludge drying system provided by the invention;
FIG. 2 is a schematic flow chart of a thermodynamic optimization design method of a sludge drying system according to an embodiment of the present invention;
in the figure, 1, a compressor; 2. a first condenser; 3. a second condenser; 4. a sensible heat exchanger; 5. an evaporator; 6. an expansion valve; 7. a heat release device; 8. and (4) cooling the tower with water.
Detailed Description
In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
The invention is described in further detail below with reference to the accompanying drawings:
referring to fig. 1, a sludge drying system based on a heat pump according to an embodiment of the present invention includes: the system comprises a compressor 1, a first condenser 2, a second condenser 3, an expansion valve 6, an evaporator 5, a sensible heat exchanger 4, a heat discharger 7 and a plurality of conveyor belts of a dryer; the sludge drying system comprises a refrigerant loop, a cooling water loop, a circulating air loop and a sludge conveying channel; the heat pump can be an R134a heat pump.
In the refrigerant loop of the embodiment of the invention, an outlet of a compressor 1 is connected with an inlet of a first condenser 2, an outlet of the first condenser 2 is connected with an inlet of a second condenser 3, an outlet of the second condenser 3 is connected with an inlet of an expansion valve 6, an outlet of the expansion valve 6 is connected with an inlet of an evaporator 5, an outlet of the evaporator 5 is connected with an inlet of the compressor 1, and a circulation loop of the refrigerant is completed;
the cooling water loop of the embodiment of the invention is specially designed for the cooling water loop between the heat discharger 7 and the water cooling tower 8, and the water path inlet and outlet of the heat discharger 7 are respectively connected with the water path inlet and outlet of the water cooling tower 8;
the circulating air loop of the embodiment of the invention is divided into two parallel circulations, wherein, a part of circulating air enters the drying chamber from the upper layer of the drying chamber (the cabin where the drying machine conveyor belt is located), passes through a plurality of layers of drying machine conveyor belts and then reaches the middle outlet position of the drying chamber; another part of circulating air enters the drying chamber from the lower layer of the drying chamber, and also reaches the middle outlet position of the drying chamber after passing through a plurality of layers of drying machine conveyor belts, two parts of circulating air are mixed and then uniformly enter the heat releaser 7 to dissipate heat to circulating cooling water, the intermediate temperature circulating air after heat dissipation is divided into two parts, wherein one part is introduced into the first condenser 2 to absorb the heat of the refrigerant, and then returns to the upper air opening of the drying chamber; the other part firstly discharges partial heat through the high-temperature side of the sensible heat exchanger 4, then is introduced into the evaporator 5 to discharge a large amount of heat, simultaneously separates out a large amount of moisture, then passes through the low-temperature side of the sensible heat exchanger 4 again and absorbs the heat at the high-temperature side, the circulating air after gradual temperature rise passes through the second condenser 3 to raise the temperature to reach a high-temperature low-humidity state, and finally returns to an air opening at the lower end of the drying chamber to finish a circulating loop of the air;
the sludge conveying channel of the embodiment of the invention refers to the whole process of sludge entering and leaving the drying chamber, wherein sludge to be dried enters the sludge conveying belt at the uppermost layer from the sludge inlet of the dryer conveying belt at the uppermost layer, then sequentially flows through each layer of conveying belt and falls to the next layer of conveying belt, and finally flows out from the sludge outlet of the lowermost conveying belt.
The technical scheme provided by the embodiment of the invention has the core invention that one condenser in a conventional heat pump system is split into a first condenser and a second condenser, hot air is divided into two paths, the two paths of hot air are respectively heated by the two condensers, and the two paths of hot air are simultaneously sent into a drying chamber from the upper part and the lower part, so that the special working condition requirements in the drying field can be met.
In a further preferred scheme provided by the embodiment of the invention, a dryer conveyor belt in a drying chamber is divided into an upper part and a lower part, the upper part is a preheating section of sludge, the dryer conveyor belt can comprise 1 to 2 layers of dryer conveyor belts in total for example, and correspondingly depends on high-humidity circulating air which flows through a first condenser 2 and is not subjected to water separation for heating and drying; while the lower half is the main water removal heating section of the sludge, which can comprise 2 layers of dryer conveyor belts in total for example, and correspondingly heats and dries by virtue of low-humidity circulating air which flows through the second condenser 3 and is subjected to water separation.
In a further preferred scheme provided by the embodiment of the invention, the heat pump system adopts the environment-friendly working medium R134a as a working medium so as to provide a higher working temperature range.
In the sludge drying system based on the R134a heat pump provided by the embodiment of the invention, the drying chamber is provided with 3 circulating air inlets and outlets which are respectively arranged at the upper end of the drying chamber, the middle part of the drying chamber and the lower end of the drying chamber; wherein the lower end of the drying chamber is always a circulating air inlet for receiving low-humidity circulating air which flows through the second condenser 3 and is subjected to water separation; in the schematic structural diagram shown in fig. 1, the upper end of the drying chamber is a circulating air inlet for receiving high-humidity circulating air which flows through the first condenser 2 and is not subjected to water separation, and the middle air opening of the drying chamber is a circulating air outlet, and the two parts of circulating air are converged in the middle part and then leave the drying chamber from the middle air opening; in addition, after the upper air opening and the middle air opening of the drying chamber are switched, the high-humidity circulating air which flows through the first condenser 2 and is not subjected to water separation can enter the drying chamber from the middle air opening of the drying chamber, is fully mixed with the circulating air entering from the lower air opening of the drying chamber, flows upwards, flows out of the drying chamber from the upper air opening of the drying chamber, and then returns to the heat discharger 7 to finish the air path circulation.
Referring to fig. 2, a thermodynamic optimization design method for a sludge drying system based on an R134a heat pump according to an embodiment of the present invention includes the following steps:
the method comprises the steps of inputting required boundary conditions (sludge treatment capacity, sludge inlet moisture content, sludge outlet moisture content and the like) of sludge products, working condition conditions (environmental temperature, environmental humidity and the like), a geometric structure of the whole drying system and the like from the beginning, determining a structural form (the number of conveyor belts contained in an upper half part of sludge preheating section, air outlet in the middle of upper air inlet and lower air inlet and the like) specifically adopted in a drying chamber, and then starting design work.
The design method comprises the steps of firstly assuming the rotating speed (including a lower rotating speed limit, an upper rotating speed limit and an adjustment step length) of a heat pump system compressor, then assuming the total flow rate (including a lower total air volume limit, an upper total air volume limit and an adjustment step length) of circulating air, then assuming a two-layer air volume ratio (including a lower air volume ratio limit, an upper air volume ratio limit and an adjustment step length), then assuming the volumetric efficiency and the isentropic efficiency of the heat pump compressor, then assuming the supercooling degree of the heat pump system, then assuming the exhaust pressure of the heat pump system, then assuming the suction pressure (including a lower suction pressure limit, an upper suction pressure limit and an adjustment step length) of the heat pump system, then assuming the superheat degree (including a lower superheat degree limit, an upper superheat degree limit and an adjustment step length) of the heat pump system, then assuming the low-temperature side outlet temperature (including a lower outlet temperature limit, an upper outlet temperature limit and an adjustment step length) after waste heat recovery, then according to all assumed conditions, calculating the heat pump system heat production quantity, COP, two-layer inlet circulating air temperature, evaporator dewatering quantity and other thermodynamic parameters in a circulation heat pump simulation model, then substituting into a drying chamber to calculate the temperature after heat pump system, SMER (SMER energy consumption) and water consumption, judging whether the sludge outlet parameters meet the current requirement of the heat pump, and continuing to increase, if the sludge heat pump system, if the sludge is not meeting the current requirement, continuing to the sludge heat exchanger, and continuing to calculate the sludge heat pump. If the dryness of the sludge outlet meets the requirement, judging the energy consumption of each ton of sludge in the system and a preset value, and if the dryness of the sludge outlet is smaller than the preset value, storing all assumed thermodynamic parameters, thermodynamic calculation results and the like as the existing optimal values of the current operation stage; if the temperature of the low-temperature side outlet after waste heat recovery is greater than or equal to the preset value, skipping the storage step, directly judging whether the temperature of the low-temperature side outlet after waste heat recovery reaches the maximum value, if not, increasing the temperature of the low-temperature side outlet after waste heat recovery, wherein the increased value is a step length, and continuing to calculate; if the superheat degree of the heat pump system reaches the maximum value, further judging whether the superheat degree of the heat pump system reaches the maximum value, if the superheat degree does not reach the maximum value, increasing the superheat degree, wherein the increased value is a step length, and continuing to calculate; if the maximum value is reached, further judging whether the suction pressure of the heat pump system reaches the maximum value, if not, increasing the suction pressure, wherein the increased value is a step length, and continuing to calculate; if the maximum value is reached, further judging whether the air volume ratio of the heat pump system reaches the maximum value, if the maximum value is not reached, increasing the air volume ratio, wherein the increased value is a step length, and continuing to calculate; if the maximum value is reached, further judging whether the total air volume of the heat pump system reaches the maximum value, if not, increasing the total air volume, wherein the increased value is a step length, and continuing to calculate; and if the maximum value is reached, ending the whole operation process, and finally outputting a result which is the optimal operation state of the system corresponding to the lowest ton of mud energy consumption in all iterative operation steps.
In the embodiment of the invention, after thermodynamic parameters such as heating capacity, air outlet temperature and the like are obtained through calculation of a heat pump model, the actual supercooling degree needs to be adjusted by depending on the temperature after heat release by means of the two-section condenser model, and the actual exhaust pressure value is adjusted by depending on the flow of circulating air at two sides. Besides the design idea of a system model, complete calculation work can be finally completed by matching with a part item model, the part item model of each part comprises a compressor three-efficiency model, a condenser model, an evaporator model, a waste heat recovery heat exchanger model, a heat-purging heat exchanger model, a drying chamber heat and mass transfer model and the like, and according to the models of the heat exchangers and the like, the heat exchanger optimization design required to be performed comprises heat-purging heat exchanger optimization design, first condenser and 2 optimization design, evaporator optimization design and waste heat recovery device optimization design. The calculation and optimization design methods of the conventional heat exchanger are adopted in the processes, so that the application of the invention is not repeated.
According to the technical scheme provided by the invention, a double-layer parallel drying chamber structure with two inlets and one outlet is innovatively provided, and through structural innovation of a sectional type hot air inlet, the average hot air temperature in the drying chamber is remarkably improved, the air resistance caused in the air flowing process in the drying chamber is effectively reduced, and the power consumption of a circulating fan is greatly reduced; the structure form that the middle air port and the upper air port of the drying chamber can exchange functions mutually is creatively provided, mode switching between a middle lower air inlet and upper air outlet (pure countercurrent air supply drying is combined with middle single reheating) form and a middle upper air inlet and lower air inlet and middle air outlet (cross-flow air supply is combined with preheating/drying double-section) form can be easily realized in the drying process, and the convenience of mode switching is provided for different sludge types and sludge drying requirements; the thermodynamic optimization design scheme of the R134a heat pump system suitable for the closed sludge drying system is innovatively provided, on the premise of determining the operation condition, the external requirement and the structural size, the optimal operation state corresponding to the lowest ton sludge energy consumption of the whole heat pump drying system can be quickly found by carrying out a plurality of times of iterative calculation in a thermodynamic model, and all thermodynamic parameters in the optimal state are output for reference.
In summary, embodiments of the present invention provide a thermodynamic optimization design method for a sludge drying system based on an R134a heat pump, which is suitable for thermodynamic optimization design of a closed double-layer parallel sludge drying system, and is capable of establishing an effective drying system thermodynamic model on the premise of determining an operation condition, an external requirement, and a structural size, and rapidly finding an optimal operation state corresponding to the lowest ton sludge energy consumption of the whole heat pump drying system through several times of iterative computations in the thermodynamic model, and outputting all thermodynamic parameters in the optimal state, and is capable of performing structural parameter matching and thermodynamic parameter optimization of the heat pump system under special requirements in the drying field, and significantly reducing the operation energy consumption of the sludge heat pump drying system, greatly improving energy consumption efficiency of the drying system, and making an important contribution to energy saving and emission reduction in the drying field.
Finally, it should be noted that: although the present invention has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.
Claims (8)
1. The utility model provides a mud drying system based on heat pump which characterized in that includes: the system comprises a compressor (1), a first condenser (2), a second condenser (3), a sensible heat exchanger (4), an evaporator (5), an expansion valve (6), a heat discharger (7) and a drying chamber;
an outlet of the compressor (1) is communicated with an inlet of the compressor (1) through a refrigerant channel of the first condenser (2), a refrigerant channel of the second condenser (3), an expansion valve (6) and a refrigerant channel of the evaporator (5) in sequence;
the drying chamber is provided with a sludge inlet, a sludge outlet, an upper air port, a middle air port, a lower air port and a drying conveyor belt; in the drying chamber, the sludge inlet is connected with the sludge outlet through the drying conveyor belt, the upper air port is communicated with the middle air port, and the middle air port is communicated with the lower air port; the middle air port is divided into two paths after passing through the air channel of the heat releaser (7), the air channel of the first condensation is communicated with the upper air port, and the other path sequentially passes through the high-temperature side air channel of the sensible heat exchanger (4), the air channel of the evaporator (5), the low-temperature side air channel of the sensible heat exchanger (4), the air channel of the second condensation is communicated with the lower air port.
2. The heat pump based sludge drying system of claim 1, further comprising:
and a water path outlet of the water cooling tower (8) is communicated with a water path inlet of the water cooling tower (8) through a water path channel of the heat release device (7).
3. The heat pump based sludge drying system of claim 1, wherein the drying conveyor belt is layered.
4. The heat pump based sludge drying system of claim 1, wherein in operation:
part of circulating air enters the drying chamber from an upper air port of the drying chamber, passes through a plurality of layers of drying conveyor belts and then reaches a middle air port; the other part of circulating air enters the drying chamber from a lower air port of the drying chamber, passes through a plurality of layers of drying conveyor belts and then reaches a middle air port;
the two parts of circulating air are uniformly mixed and then enter a heat releaser (7) to dissipate heat to circulating cooling water, the medium-temperature circulating air after heat dissipation is divided into two parts, wherein one part is introduced into the first condenser (2) to absorb the heat of a refrigerant and then returns to an upper air opening of a drying chamber; and the other part of the circulating air firstly passes through the high-temperature side of the sensible heat exchanger (4) to emit partial heat, then is introduced into the evaporator (5) to emit heat and separate out moisture, then passes through the low-temperature side of the sensible heat exchanger (4) again and absorbs the heat at the high-temperature side, and the heated circulating air passes through the second condenser (3) to raise the temperature to reach a high-temperature low-humidity state and finally returns to an air opening at the lower part of the drying chamber.
5. The heat pump-based sludge drying system according to claim 1, wherein the medium in the refrigerant channel is R134a.
6. The thermodynamic optimization design method for the sludge drying system based on the heat pump as claimed in claim 1, is characterized by comprising the following steps:
acquiring required boundary conditions and working conditions of sludge products, geometric structures of a sludge drying system and structural forms in a drying chamber;
setting the rotating speed of a compressor, the total flow of circulating air, the air volume ratio of an upper layer and a lower layer, the volumetric efficiency and the isentropic efficiency of the compressor, the supercooling degree of a heat pump system, the exhaust pressure of the heat pump system, the suction pressure of the heat pump system, the superheat degree of the heat pump system and the outlet temperature of a low-temperature side after waste heat recovery; based on set conditions, calculating and obtaining the heating capacity and COP of the heat pump system, the circulating air temperature of the two-layer inlet, the water removal capacity of the evaporator, and the temperature, SMER and ton mud energy consumption information after heat exchange of a heat discharger of the drying system;
judging whether the sludge outlet parameters meet the feedforward requirements or not, if not, feeding back and adjusting the rotating speed of the compressor of the heat pump system, increasing a step length from the current value, and continuing to operate; if the dryness of the sludge outlet meets the requirement, judging the energy consumption of each ton of sludge in the system and a preset value, and if the dryness of the sludge outlet is smaller than the preset value, storing all the currently assumed thermodynamic parameters and thermodynamic calculation results as the existing optimal values of the current operation stage; if the temperature of the low-temperature side outlet is larger than or equal to the preset value, skipping the storage step and directly judging whether the temperature of the low-temperature side outlet after waste heat recovery reaches the maximum value, if the temperature of the low-temperature side outlet after waste heat recovery does not reach the maximum value, increasing the temperature of the low-temperature side outlet after waste heat recovery, wherein the increased value is a step length, and continuing to calculate; if the superheat degree of the heat pump system reaches the maximum value, judging whether the superheat degree of the heat pump system reaches the maximum value, if the superheat degree does not reach the maximum value, increasing the superheat degree, wherein the increased value is a step length, and continuing to calculate; if the maximum value is reached, judging whether the suction pressure of the heat pump system reaches the maximum value, if the maximum value is not reached, increasing the suction pressure, wherein the increased value is a step length, and continuing to calculate; if the maximum value is reached, judging whether the air volume ratio of the heat pump system reaches the maximum value, if the maximum value is not reached, increasing the air volume ratio, wherein the increased value is a step length, and continuing to calculate; if the maximum value is reached, judging whether the total air volume of the heat pump system reaches the maximum value, if the maximum value is not reached, increasing the total air volume, wherein the increased value is a step length, and continuing to calculate; and if the maximum value is reached, ending the whole operation process, and finally outputting a result which is the optimal operation state of the system corresponding to the lowest ton of sludge energy consumption in all iterative operation steps.
7. The method of claim 6, wherein the heat pump-based sludge drying system is designed according to the optimal thermodynamic requirement,
the boundary conditions of the requirement of the sludge product comprise sludge treatment capacity, sludge inlet moisture content and sludge outlet moisture content; the working condition comprises ambient temperature and ambient humidity; the structural style in the drying chamber comprises the number of drying conveyor belts, air inlet information and air outlet information.
8. The thermodynamic optimization design method for the heat pump-based sludge drying system according to claim 6, wherein the compressor rotation speed comprises a lower rotation speed limit, an upper rotation speed limit and an adjustment step length; the total flow of the circulating air comprises a total air volume lower limit, a total air volume upper limit and an adjusting step length; the two-layer air volume ratio comprises an air volume ratio lower limit, an air volume ratio upper limit and an adjusting step length; the suction pressure of the heat pump system comprises a lower suction pressure limit, an upper suction pressure limit and an adjusting step length; the superheat degree of the heat pump system comprises a lower superheat degree limit, an upper superheat degree limit and an adjusting step length; and the outlet temperature of the low-temperature side after waste heat recovery comprises an outlet temperature lower limit, an outlet temperature upper limit and an adjusting step length.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116518600A (en) * | 2023-07-05 | 2023-08-01 | 中建环能科技股份有限公司 | Control method for refrigerating performance of compressor of heat pump low-temperature drying equipment and electronic equipment |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116518600A (en) * | 2023-07-05 | 2023-08-01 | 中建环能科技股份有限公司 | Control method for refrigerating performance of compressor of heat pump low-temperature drying equipment and electronic equipment |
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