JP5601164B2 - Heat supply system and control method thereof - Google Patents

Description

  The present invention relates to an industrial heating system and a control method thereof.

  Generally as a heat supply system, the structure which transmits the heat from a boiler to a target object is known (for example, refer to patent documents 1). In addition, a configuration in which heat of a heat pump medium is transmitted to an object is known. It is known that a heat pump has a relatively high energy utilization efficiency by utilizing heat outside the cycle (heat of a low-temperature heat source).

JP-A-6-249450

  A system using a boiler has a relatively low primary energy efficiency. On the other hand, in a system using a heat pump, if the operating conditions are unstable, there may be a situation where the heat demand cannot be sufficiently met.

  It is an object of the present invention to provide a heat supply system that is stably energy efficient.

According to one aspect of the present invention, an exhaust heat recovery type heat pump that supplies heat to an external device serving as a heat demand section and can input at least part of exhaust heat from an exhaust heat source, a boiler, and an electric heater An auxiliary heat source including at least one of the auxiliary heat source capable of supplying supplementary heat to a low temperature side of the heat pump, and a supply destination of the supplementary heat from the auxiliary heat source, the high temperature side and the low temperature side of the heat pump. And a switching device that switches between the heat supply system and the heat supply system in which switching of the supplementary heat supply destination is performed based on a coefficient of performance of the heat pump .

According to another aspect of the present invention, there is provided a method for controlling a heat supply system including a heat pump and an auxiliary heat source, wherein a supplementary heat supply destination from the auxiliary heat source is set between a high temperature side and a low temperature side for the heat pump. step look including the step of selecting selects said auxiliary heat supply destination in includes a step of calculating for each of the coefficient of performance of the heat pump hot side and a cold side, and comparing the coefficient of performance, and A method for controlling a heat supply system is provided.
A method for controlling a heat supply system including a heat pump and an auxiliary heat source, the step of selecting a supply destination of auxiliary heat from the auxiliary heat source between a high temperature side and a low temperature side for the heat pump, and the heat pump Is set to a full load state or a predetermined partial load state.
Further, a control method of a heat supply system including a heat pump and an auxiliary heat source, including a step of selecting a supply destination of auxiliary heat from the auxiliary heat source between a high temperature side and a low temperature side for the heat pump, When the coefficient of performance in the partial load state is substantially lower than the coefficient of performance in the loaded state, or when the coefficient of performance in the high load state is substantially higher than the coefficient of performance in the low load state within the predetermined operating range, A control method of a heat supply system in which the supplementary heat is supplied to the low temperature side is provided.

  According to this heat supply system and its control method, the supply destination of supplementary heat can be optimized, and the energy efficiency can be stably improved.

It is the schematic which shows one Embodiment. It is a figure which shows an example of the performance curve of the compressor in a heat pump. It is a figure which shows the relationship between the temperature of the low-temperature heat source in a heat pump, and partial load efficiency. It is a figure which shows an example of the relationship between the output of a heat pump, and COP. It is a figure which shows another example of the relationship between the output of a heat pump, and COP.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram illustrating an overview of a heat supply system S1 according to an embodiment.

  As shown in FIG. 1, the heat supply system S <b> 1 includes a heat pump 10 (exhaust heat recovery heat pump) through which a working fluid (first fluid) flows, a boiler (auxiliary heat source, auxiliary heat supply device) 20, and a switching device 30. And a low-temperature heat source device (exhaust heat recovery device, heat recovery device) 50 having a heat storage tank 40, and a control device 70. The control device 70 comprehensively controls the entire system. The configuration of the system S1 can be variously changed according to design requirements.

  In this embodiment, the heat from the heat supply system S1 is supplied to the external device 90 as a heat demand unit. In the present embodiment, the heat pump 10 is an exhaust heat recovery type heat pump that can use at least part of the exhaust heat from the external device 90 (exhaust heat source). In another embodiment, the heat pump 10 can be configured to be able to use at least part of the exhaust heat from other exhaust heat sources other than the external device 90.

  The heat pump 10 is a device that pumps heat from a low-temperature object and applies heat to a high-temperature object by a cycle including evaporation, compression, condensation, and expansion processes. A heat pump generally has the advantage of relatively high energy efficiency and, as a result, relatively low emissions of carbon dioxide and the like. In this embodiment, the heat pump 10 has a heat absorption part, a compression part, a heat radiation part, and an expansion part (all not shown), which are connected via a conduit. In the heat pump 10, the working fluid flows in the conduit. In the present embodiment, the heat pump 10 can heat the heated fluid (second fluid, air, etc.) flowing through the air supply path 15 using the heat of the working fluid.

  In the heat absorption part of the heat pump 10, the working fluid flowing in the conduit (main path) absorbs heat from the heat source outside the cycle. In the present embodiment, the heat absorption part of the heat pump 10 can absorb (recover) the heat (exhaust heat) of the exhaust fluid (exhaust gas, exhaust air) from the external device 90 via the low-temperature heat source device 50. In this embodiment, the heat absorption part of the heat pump 10 includes an evaporator that is thermally connected to the heat radiation part (low temperature heat supply pipe 19) of the low temperature heat source device 50 and in which the working fluid evaporates. The heat of the medium flowing through the heat radiating part of the low-temperature heat source device 50 is absorbed by the heat absorbing part of the heat pump 10. The heat absorption part of the heat pump 10 may be configured to additionally absorb the heat of other heat sources such as the atmosphere.

  The compression unit of the heat pump 10 compresses the working fluid by a compressor or the like. At this time, the temperature of the working fluid usually increases. The compression unit may have a single-stage compression structure or a multistage compression structure that compresses the working fluid into a plurality of stages. The number of stages of compression is set according to the specification of the system S1, and is 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 or more. Among the various compressors such as an axial compressor, a centrifugal compressor, a reciprocating compressor, and a rotary compressor, a compressor suitable for compressing a working fluid is applied. Power is supplied to the compressor. In a compression part having a multistage compression structure, a multiaxial compression structure or a coaxial compression structure can be applied.

  The heat radiating part of the heat pump 10 has a conduit through which the working fluid compressed by the compressing part flows, and gives heat of the working fluid flowing in the conduit (main path) to a heat source (heated fluid) outside the cycle. In the present embodiment, the working fluid from the compression unit of the heat pump 10 flows through the conduit, and the heat from the working fluid is transmitted to the heated fluid that flows through the air supply path 15. The number of heat radiation units is set according to the specification of the system S1, and is 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 or more. In the present embodiment, the heat pump 10 can have a configuration for controlling the flow rate of the working fluid flowing through the heat radiating unit. In this configuration, for example, the heat pump 10 can include a bypass path, a flow rate sensor, a flow path control valve, and the like.

  The expansion part of the heat pump 10 expands the working fluid by a pressure reducing valve or a turbine. At this time, the temperature of the working fluid usually decreases. When a turbine is used, power can be taken out from the expansion section, and the power may be supplied to the compression section of the heat pump 10, for example. As the working fluid used in the heat pump 10, various known heat media such as a fluorocarbon medium (HFC 245fa, R134a, etc.), ammonia, water, carbon dioxide, air, etc. are used according to the specifications and heat balance of the system S1. Used. At least a part of the working fluid flowing through the heat radiating portion of the heat pump 10 may be in a supercritical state.

  The air supply path 15 through which the air heated by the heat pump 10 flows has a conduit through which the fluid to be heated flows, a fluid driving device such as a pump and a blower, a valve for fluid control, a gas processing device such as a filter, and the like as necessary. be able to.

  In the present embodiment, the output temperature of the heated fluid (drying air) from the air supply path 15 can be changed according to the heat demand. The output temperature can be, for example, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, or 200 ° C. or higher.

  In the present embodiment, the external device 90 is, for example, a heating chamber in which a fluid to be heated (second fluid) is supplied and an object is heated. In the present embodiment, the fluid to be heated (second fluid) is air. In the present embodiment, high temperature air heated by at least one of the heat pump 10 and the boiler 20 is supplied to the external device 90. In the external device 90, heat from high-temperature air is transmitted to the object.

  In the present embodiment, in the external device (heating chamber) 90, heat from the heated air is transmitted directly or indirectly to the object. For example, in the external device 90, heated air can directly contact an object. Alternatively, in the external device 90, another substance can be interposed between the heated air and the object.

  In the present embodiment, the heating object is an industrial part or an industrial material. For example, in the external device (heating chamber) 90, at least a part of industrial parts or industrial materials is dried. Alternatively, in the external device 90, at least a part of the industrial part or the industrial material is heat-treated. Sludge, paper, wood, resin, chemicals, chemicals, sand, household waste, industrial waste, crafts, craft materials, electrical parts, electrical equipment, paints, industrial clothing, machine parts, mechanical products, food, foodstuffs Various objects such as food products can be heated. In other embodiments, the fluid to be heated can be air other than drying or a fluid other than air. Examples of the heated fluid other than air include water, compressed water, chemicals, and viscous liquids. In another embodiment, the external device (heating chamber) 90 can include a drying device and / or a heat utilization device other than the drying device.

  The external device 90 includes a fluid inlet portion, a fluid outlet portion, an exhaust route, and a transfer device (not shown) as necessary. In one example, the transfer device can have various forms such as a conveyor, a transport vehicle, and a transport robot. The object to be heated is put into the external device (heating chamber) 90 and taken out from the external device 90 by the transfer device. Alternatively or additionally, the external device 90 may include an output unit having a gate type, a swivel type, or the like for outputting an object after heating. The output part of the heated object can have a mechanism for performing a predetermined process such as a chemical process on the heated object as necessary.

  In the present embodiment, the transfer device can move the heating target in the external device (heating chamber) 90 as necessary. The external device 90 further includes a dehydrating device (not shown) as needed, thereby dehydrating the object. During the dehydration, a flocculant can be added to the object as necessary. Various forms such as a centrifugal type, a pressure type, a pressure type, and a vibration type can be applied to the dehydration depending on the object. Dehydration reduces the volume of the object. Further, the external device 90 can further include a preheating chamber for applying heat to the object before entering the external device 90 as necessary.

  The boiler 20 can supply supplementary heat to the low temperature side or the high temperature side of the heat pump 10. The boiler 20 burns fuel such as oil or gas and heats a heat medium (water or the like) with the combustion heat. Various known forms are applicable as the boiler 20. In another embodiment, an electric heater or other heat device can be used as a supplementary heat supply device instead of or in addition to the boiler 20.

  The low-temperature heat source device 50 as an exhaust heat recovery device includes a heat recovery unit that recovers exhaust heat from the external device 90 (and another heat device (not shown) if necessary), and heat recovered from the heat recovery unit. It has the thermal storage tank 40 which stores at least temporarily, and a thermal radiation part.

  Various forms can be adopted as the heat storage tank 40. In one example, the heat storage tank 40 may have a temperature stratified tank. That is, in the heat storage tank 40, the high temperature heat medium inlet and the high temperature heat medium outlet are arranged at a relatively high position, and the low temperature heat medium inlet and the low temperature heat medium outlet are arranged at a relatively low position. The arrangement positions of the high temperature heat medium inlet and the high temperature heat medium outlet are higher than the arrangement positions of the low temperature heat medium inlet and the low temperature heat medium outlet in the direction of gravity. In the heat storage tank 40, a high temperature region layer composed of a relatively high temperature heat medium is formed at a high position of the tank, and a low temperature region layer composed of a relatively low temperature heat medium is formed at a low position of the tank. In the tank, input / output of the heat medium is performed in a state where mixing of the heat medium having different temperatures is suppressed. A temperature-stratified tank is advantageous in reducing the cost for heat storage. In this example, the heat medium used for exhaust heat recovery is water. That is, in this example, the heat medium is used as a heat transfer medium in the heat recovery unit and is used as a heat storage medium in the heat storage tank 40.

  In other examples, the heat transfer medium and the heat storage medium can be different. Examples of the heat transfer medium include chemicals and viscous liquids in addition to water. Examples of the heat storage medium (heat storage material) include a latent heat storage material in addition to water. Examples of latent heat storage materials include, for example, hydrocarbons such as erythritol and alkanes, wax-based materials (paraffin wax, microcrystalline wax, etc.), sodium acetate, sodium acetate trihydrate, or inorganic hydrate salts as main components. Etc. Other materials such as a sensible heat storage material, a chemical reaction heat storage material, and a heat storage material using a supercritical fluid may be used as the heat storage material.

  The heat recovery unit of the low-temperature heat source device 50 is thermally connected to the exhaust heat recovery pipe (exhaust pipe) 17 through which the exhaust from the external device (heating chamber) 90 (and another heat apparatus) flows, and the exhaust heat recovery pipe. And an endothermic conduit through which the heat medium flows. In another embodiment, the heat recovery unit can be configured to recover exhaust heat from the external device 90 (and another heat device) without going through exhaust.

  The heat radiation unit of the low-temperature heat source device 50 includes a conduit that is thermally connected to the heat absorption unit of the heat pump 10 and through which the heat medium (water) flows. In the present embodiment, heat (exhaust heat) from the external device 90 (and another heat device) is transmitted to the heat medium flowing through the low-temperature heat source device 50. Heat from the heat medium flowing through the heat radiating portion of the low-temperature heat source device 50 is transmitted to the working fluid flowing through the heat absorbing portion of the heat pump 10. That is, the exhaust heat from the heat recovery unit is radiated directly or indirectly from the heat radiating unit toward the heat pump 10. Alternatively, the heat stored in the heat storage tank 40 is radiated from the heat radiating unit. The low-temperature heat source device 50 can include a conduit through which a heat medium flows, a medium driving device such as a pump, a valve for controlling the medium, and the like. The piping configuration can be changed variously.

  A heat exchanger is configured including the heat absorption part of the heat pump 10 and the heat radiation part of the low-temperature heat source device 50. The heat exchanger has a counter-current heat exchange structure in which a low-temperature fluid (a working fluid in the heat absorption part of the heat pump 10) and a high-temperature fluid (a heat medium in the heat dissipation part of the exhaust heat recovery device (50)) flow oppositely. Can have. Alternatively, the heat exchanger may have a parallel flow type heat exchange structure in which a high-temperature fluid and a low-temperature fluid flow in parallel. In this embodiment, various well-known things can be employ | adopted as a heat exchange structure of a heat exchanger. The heat-radiating part conduit and the heat-absorbing part conduit are arranged in contact with or adjacent to each other. For example, the conduit of the heat radiating portion can be disposed on the outer peripheral surface or inside of the conduit of the heat absorbing portion. In the heat exchanger, the heat absorption part of the heat pump 10 absorbs the heat transferred from the heat radiation part of the low-temperature heat source device (exhaust heat recovery device) 50.

  The switching device 30 can switch the supply destination of the supplementary heat from the boiler 20 between the high temperature side and the low temperature side with respect to the heat pump 10. In one example, the switching device 30 may have a mechanism for switching a path through which steam from the boiler 20 flows between a low temperature side or a high temperature side with respect to the heat pump 10. In the present embodiment, piping (for example, exhaust heat recovery piping 17 and low-temperature heat supply piping 19) that is thermally connected directly or indirectly to the heat absorbing portion of the heat pump 10 and piping through which steam from the boiler 20 flows. A thermally connected heat exchange structure is provided. Further, a heat exchange structure in which a pipe (for example, the air supply path 15) that is thermally connected directly or indirectly to the heat radiating portion of the heat pump 10 and a pipe through which steam from the boiler 20 flows is thermally connected. Is provided.

  When the low temperature side is selected by the switching device 30, the fluid flowing in the pipe (for example, the exhaust heat recovery pipe 17, the low temperature heat supply pipe 19) that is thermally connected directly or indirectly to the heat absorption part of the heat pump 10 Heat exchange is performed with the steam from the boiler 20, and supplementary heat from the boiler is supplied to the low temperature side (exhaust heat side) with respect to the heat pump 10. On the other hand, when the high temperature side is selected by the switching device 30, the fluid flowing in the pipe (for example, the air supply path 15) thermally connected directly or indirectly to the heat radiating portion of the heat pump 10 and the steam from the boiler 20. Is exchanged, and supplementary heat from the boiler is supplied to the high temperature side (heat demand side) of the heat pump 10.

  In the present embodiment, by supplying supplementary heat to the low temperature side, the output temperature and / or output heat amount from the low temperature heat source device 50 is improved, and the input temperature and / or input heat amount to the heat pump 10 is improved. . In the heat pump 10, a decrease in the heat input amount may lead to a decrease in COP (Coefficient of Performance). The supplementary heat supply to the low temperature side can at least partially compensate for fluctuations in the energy efficiency of the system S1 when the operating conditions of the heat pump 10 fluctuate. Therefore, in the present embodiment, the system S1 can stably cope with the heat demand even if the operation condition of the heat pump 10 is unstable.

  In this embodiment, the amount of heat supplied to the external device (drying chamber) 90 is improved by supplying supplementary heat to the high temperature side. In the heat pump 10, a decrease in heat input may lead to a decrease in output heat. The supplementary heat supply to the high temperature side can at least partially compensate for fluctuations in the amount of heat supplied to the external device 90 when the operating conditions of the heat pump 10 fluctuate. Also, when the heat demand increases, a supply amount corresponding to the increase can be secured. For example, it can flexibly respond to a relatively high level of heat demand. Therefore, in the present embodiment, the system S1 can stably cope with the heat demand even if the operation condition of the heat pump 10 is unstable.

  FIG. 2 is a diagram illustrating an example of a performance curve of a compressor in a heat pump. FIG. 3 is a diagram showing the relationship between the temperature of the low-temperature heat source and the partial load efficiency in the heat pump. In general, in a heat pump, as shown in FIGS. 2 and 3, the performance curve may change depending on the temperature of a low-temperature heat source. In general, the COP of the heat pump varies depending on the load. In general, in a heat pump, there is a case where the partial load efficiency is higher than the constant load efficiency. That is, there are cases where the overall efficiency is relatively high when the output ratio of the heat pump is lowered. Specifically, when the temperature of the low-temperature heat source is high, that is, when the pressure ratio is small, the partial load efficiency may be relatively high. In the present embodiment, the energy efficiency is improved by controlling the entire system S1 including the partial load operation of the heat pump 10.

  In the present embodiment, the control device 70 can control the operation of the heat pump 10 in a load state between a full load including a partial load state and no load. The control device 70 sets the heat pump 10 to a full load state or a predetermined partial load state according to an operation parameter including the amount of heat on the low temperature side. Moreover, the control apparatus 70 switches the supply destination of supplementary heat based on the coefficient of performance (COP) of the heat pump 10 based on an operation parameter.

  In this embodiment, the system S1 includes heat demand information (required temperature, required flow rate) in the external device 90, output information (temperature, pressure, etc.) of the auxiliary heat source (boiler) 20, and low-temperature heat source information (low-temperature heat source) for the heat pump 10. Sensors for detecting output information (temperature, heat quantity, etc.) from 40, exhaust heat information, etc. in external device 90, respectively, are provided as necessary. The control device 70 can comprehensively control the entire system S1 based on various information.

  In the example of FIG. 4, the COP in the partial load state is substantially lower than the COP in the full load state, or the COP in the high load state is substantially lower than the COP in the low load state within the predetermined operation range. high. In this case, the control device 70 can select the low temperature side of the heat pump 10 as a supplementary heat supply destination, and as a result, energy efficiency can be improved.

  Specifically, in the example of FIG. 4, the effect of switching the auxiliary heat supply destination will be examined below. In one example, the COP when the output is 500 kW is 3.0, and the COP when the output is 250 kW is 1.2. The electrical input is 166.7 kW at 500 kW, 208.3 kW at 250 kW, and the exhaust heat is 333.3 kW at 500 kW and 41.7 kW at 250 kW. In this case, when supplementary heat is supplied to the high temperature side of the heat pump 10, the total primary energy required for the heat pump 10 and the boiler 20 is 798.6 kW. On the other hand, when supplementary heat is supplied to the low temperature side of the heat pump 10, the total primary energy is 740.7 kW. That is, when the COP in the partial load state is substantially lower than the COP in the full load state, or when the COP in the high load state is substantially higher than the COP in the low load state within the predetermined operation range, By selecting the low-temperature side of the heat pump 10 as a supplementary heat supply destination, energy efficiency can be improved.

  In the example of FIG. 5, the COP in the partial load state is substantially higher than the COP in the full load state, or the COP in the high load state is substantially higher than the COP in the low load state within the predetermined operation range. Low. In this case, the control device 70 can select the high temperature side of the heat pump 10 as a supplementary heat supply destination, and as a result, energy efficiency can be improved.

  Specifically, in the example of FIG. 5, the effect of switching the auxiliary heat supply destination will be examined below. In one example, the COP when the output is 500 kW is 3.0, and the COP when the output is 250 kW is 4.0. The electrical input is 166.7 kW at 500 kW, 62.5 kW at 250 kW, and the exhaust heat is 333.3 kW at 500 kW, and 187.5 kW at 250 kW. In this case, when supplementary heat is supplied to the high temperature side of the heat pump 10, the total primary energy required for the heat pump 10 and the boiler 20 is 434.0 kW. On the other hand, when supplementary heat is supplied to the low temperature side of the heat pump 10, the total primary energy is 578.7 kW. That is, when the COP in the partial load state is substantially higher than the COP in the full load state, or when the COP in the high load state is substantially lower than the COP in the low load state within the predetermined operation range, By selecting the high temperature side of the heat pump 10 as the supplementary heat supply destination, energy efficiency can be improved.

  As described above, in the present embodiment, the control device 70 can control the operation of the heat pump 10 in a load state between a full load including a partial load state and no load. According to the present embodiment, the control including the partial load operation of the heat pump 10 and the backup by the boiler 20 can improve the energy efficiency of the entire system S1.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to these embodiment. The numerical value used in the above description is an example, and the present invention is not limited to this. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit of the present invention. The present invention is not limited by the above description, but only by the appended claims.

  S1: heat supply system (heating system), 10: heat pump, 15: air supply path, 17: exhaust heat recovery pipe, 19: low temperature heat supply pipe, 20: boiler (auxiliary heat source), 30: switching device, 40: heat storage Tank, 50: Low-temperature heat source device (exhaust heat recovery device), 70: Control device, 90: External device (heating chamber).

Claims (4)

An exhaust heat recovery type heat pump that supplies heat to an external device as a heat demand section and can input at least part of the exhaust heat from the exhaust heat source;
An auxiliary heat source including at least one of a boiler and an electric heater, the auxiliary heat source capable of supplying supplementary heat to a low temperature side of the heat pump;
A switching device for switching a supply destination of the auxiliary heat from the auxiliary heat source between a high temperature side and the low temperature side with respect to the heat pump ,
The supply destination of the supplementary heat is switched based on the coefficient of performance of the heat pump.
Heat supply system. A method for controlling a heat supply system including a heat pump and an auxiliary heat source,
Wherein the destination of the auxiliary heat from an auxiliary heat source, viewed including the step of selecting between the hot and cold sides for the heat pump,
The step of selecting the auxiliary heat supply destination includes a step of calculating a coefficient of performance of the heat pump for each of a high temperature side and a low temperature side, and a step of comparing the coefficient of performance . A method for controlling a heat supply system including a heat pump and an auxiliary heat source,
Selecting a supply destination of supplementary heat from the auxiliary heat source between a high temperature side and a low temperature side for the heat pump ;
And a step of setting the heat pump to a full load state or a predetermined partial load state . A method for controlling a heat supply system including a heat pump and an auxiliary heat source,
Wherein the destination of the auxiliary heat from an auxiliary heat source, viewed including the step of selecting between the hot and cold sides for the heat pump,
When the coefficient of performance in the partial load state is substantially lower than the coefficient of performance in the full load state, or when the coefficient of performance in the high load state is substantially higher than the coefficient of performance in the low load state in the predetermined operating range A control method of a heat supply system in which the supplementary heat is supplied to the low temperature side .

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