Heat exchange system reusing drainage heat

Abstract

To provide a heat exchange system reusing waste water heat, usable even in waste water of such poor water quality that a metal heat exchanger cannot be used, operable in just proportion according to a waste water amount, and constructible at low cost as a whole.SOLUTION: A pretreatment device 100 for removing solids, impurities, and the like contained in wastewater discharged from, for example, a poultry processing step 500 as a cold water / hot water use process in a factory, a primary-side heat exchange device 200 for performing heat exchange between treated wastewater from which solids have been removed and a refrigerant, and a secondary-side heat exchange device 200 for performing heat exchange between raw water supplied to a water temperature adjustment means 310 such as a chiller or a boiler and recovered exhaust heat are provided, and an operation is performed based on a water level in a water storage tank 210 of the primary-side heat exchange device 300.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a heat exchange system that utilizes the heat contained in wastewater discharged from a specific cold water / hot water use process (e.g., a food processing process) that uses cold water or hot water to generate cold water or hot water to be used in that cold water / hot water use process. More specifically, the present invention relates to a heat exchange system that reuses wastewater heat, which can be constructed inexpensively and exhibits high heat exchange capacity even if the water quality is poor. [Background technology]

[0002] Cooling water and heated water used in factories are made from industrial water or other raw materials, which are cooled or heated in chillers or boilers for use within the factory. However, the electricity and fuel consumed for cooling and heating purposes impose an environmental burden. Therefore, from the perspectives of energy conservation and environmental protection, it is preferable to recover and reuse the heat contained in wastewater discharged from factories, etc. (wastewater heat).

[0003] In most industrial wastewater heat exchange systems, cold or hot wastewater discharged from a factory is stored in a water tank, and a throw-in heat exchanger is immersed in the tank to exchange heat between the heat in the wastewater and the refrigerant circulating inside the heat exchanger.

[0004] Typically, throw-in heat exchangers are made of metal, so there is a risk that chemical components in wastewater will corrode them and cause their performance to deteriorate. For this reason, there are restrictions on the water quality that can be used, and wastewater with a quality that exceeds the restrictions is not used for heat exchange. Instead, the water is improved to a quality that meets wastewater standards at a water treatment facility within the factory before being discharged outside. In addition, solids contained in wastewater will adhere to the heat exchanger, so the heat exchanger needs to be cleaned regularly or irregularly.

[0005] As an example of a process using cold / hot water, in the chicken cutting process, 0°C cooling water generated in a chiller is used to cool the processing plant and wash away blood generated during cutting, and cold wastewater is discharged at 2 to 3°C. In the chicken pre-processing process, 80°C hot water generated in a boiler is used to remove feathers and sterilize the surface of birds before processing, and hot wastewater is discharged at 60°C.

[0006] These cold and hot wastewaters are useful for pre-cooling and pre-heating the raw water supplied to chillers and boilers. However, because they contain a large amount of chemical components and suspended solids, there is a risk of corrosion and clogging in metal immersion heat exchangers, and therefore heat recovery is not performed.

[0007] Patent Documents 1 and 2 describe a waste heat recovery technology in which waste heat is recovered from warm wastewater discharged from facilities that use hot water, such as bathrooms, washrooms, and kitchens, and the recovered waste heat is used to heat water supply. However, this technology is intended for use with less polluted wastewater and cannot be applied to the chicken processing process exemplified above.

[0008] In addition, because the amount of wastewater discharged from factories varies depending on the manufacturing process within the factory, a heat exchange system that uses this type of wastewater as a heat source must operate appropriately according to the amount of wastewater. To achieve this, it is necessary to measure the amount of wastewater and determine the operating status of the system.

[0009] Generally, the capacity of drainage pipes is designed to have a sufficient cross section relative to the designed drainage volume, so the water level in the pipe is almost never full. Devices for measuring the flow rate in a drainage pipe that is not full are available on the market, but they are expensive. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 5-99501 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-42539 Summary of the Invention [Problem to be solved by the invention]

[0011] Therefore, the object of the present invention is to provide a heat exchange system for recycling wastewater heat that can be constructed inexpensively overall and can be used even with wastewater of such poor quality that a metal heat exchanger cannot be used, and that can operate just enough depending on the amount of wastewater. [Means for solving the problem]

[0012] In order to solve the above problems, the present invention provides a heat exchange system in which raw water as industrial water is converted into used water at a predetermined temperature for use in a food processing process or the like by a water temperature adjusting means such as a chiller or a boiler, and wastewater heat contained in used wastewater discharged from the processing process is reused, The system is characterized by comprising a pretreatment device that removes solids from used wastewater discharged from the processing step, a water storage tank, a water pump that supplies treated wastewater from which solids have been removed by the pretreatment device into the water storage tank, a corrosion-resistant primary side heat exchanger that is immersed in the treated wastewater in the water storage tank while being included in a part of a refrigerant circulation circuit including a refrigerant circulation pump, a secondary side heat exchanger that performs heat exchange between the refrigerant circulating in the primary side heat exchanger and the raw water that is supplied to the water temperature adjustment means, a first water level gauge that measures the water level in the pretreatment device, a second water level gauge that measures the water level in the water storage tank, and control means that controls the operation of the water supply pump and / or the refrigerant circulation pump based on measurement signals from at least the first water level gauge and the second water level gauge.

[0013] In the present invention, it is preferable to use a resin heat exchanger as the primary heat exchanger.

[0014] In the present invention, it is preferable that a plate heat exchanger is used as the secondary heat exchanger.

[0015] According to a preferred embodiment of the present invention, the pretreatment device includes a wire mesh receiving basket that initially receives the wastewater, an upstream partition wall that separates floating matter that has passed through the receiving basket from the wastewater, and a downstream partition wall that separates sediments in the wastewater that have passed below the upstream partition wall from the wastewater, and the wastewater that has passed through the downstream partition wall is supplied to the water storage tank as the treated wastewater by the water supply pump.

[0016] The control means is characterized in that it drives the water pump and the refrigerant circulation pump when the water level in the pretreatment device and the water level in the water storage tank are both equal to or higher than a predetermined level.

[0017] The present invention also includes an embodiment in which the system further includes a water thermometer that measures the temperature of the treated wastewater in the water storage tank, and the control means drives the water supply pump and the refrigerant circulation pump when the water level in the pretreatment device and the water level in the water storage tank are both above a predetermined level and the temperature of the treated wastewater in the water storage tank is below a first threshold temperature or above a second threshold temperature. [Effects of the Invention]

[0018] According to the present invention, a wastewater heat exchange system is provided that can be used even with wastewater of such poor quality that a metal heat exchanger cannot be used, can operate just enough depending on the amount of wastewater, and can be constructed inexpensively overall.

[0019] In addition, by using the cold and hot energy recovered from this wastewater heat exchange system to cool and heat raw water, it is possible to reduce the electricity and fuel consumed by chillers and boilers. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a schematic diagram showing an embodiment of a wastewater heat exchange system according to the present invention. [Figure 2] 1 is a perspective view showing an example of a resin heat exchanger preferably used in the present invention. [Figure 3]4 is a flowchart illustrating the operation of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] Next, an embodiment of the present invention will be described with reference to FIGS. 1 to 3, but the present invention is not limited to this.

[0022] Referring to Figure 1, this heat exchange system for reusing wastewater heat (hereinafter simply referred to as the heat exchange system) basically comprises a pretreatment device 100 that removes solids and impurities contained in wastewater (wastewater) discharged from, for example, a chicken processing process 500 as a cold / hot water use process within a factory, a primary side heat exchange device 200 that exchanges heat between the treated wastewater from which the solids have been removed and a refrigerant (heat medium), and a secondary side heat exchange device 300 that exchanges heat between raw water as industrial water supplied to water temperature adjustment means 310 such as a chiller or boiler and the recovered waste heat.

[0023] In the chicken processing process 500, in the chicken cutting process, cooling water at, for example, 0°C produced in a chiller is used to cool the processing plant and wash away blood generated during cutting, and cold wastewater is discharged at, for example, 2 to 3°C. In addition, in the chicken pre-treatment process, hot water at, for example, 80°C produced in a boiler is used to remove feathers from birds and sterilize their surfaces before processing, and hot wastewater is discharged at, for example, 60°C.

[0024] These cold and hot wastewaters are useful for pre-cooling (pre-cooling) and pre-heating (pre-heating) raw water supplied to chillers and boilers, but because they contain a large amount of chemical components and suspended solids, they may cause corrosion or clogging in a throw-in type heat exchanger. Therefore, the present invention is equipped with a pre-treatment device 100.

[0025] The pretreatment device 100 is equipped with a solid removal means 110 that first receives wastewater (cold wastewater / warm wastewater) in the pretreatment tank 101, an upstream partition wall 120 that separates floating matter that has passed through the solid removal means 110 from the wastewater, a downstream partition wall 130 that separates sediments in the wastewater that has passed through the lower part of the upstream partition wall 120, a water supply pump P1 as water supply means 140 that supplies wastewater that has overflowed the downstream partition wall 130 to the water storage tank 210 of the primary side heat exchange device 200, and a water level gauge 150 that measures the water level in the treated tank 103 in which the water supply pump P1 is installed.

[0026] The solid matter removal means 110 used in the pretreatment device 100 is preferably a wire mesh basket which is available at low cost, but may be changed as desired depending on the amount and type of solid matter.

[0027] The upstream partition wall 120 is installed only at the upper part of the pretreatment tank 101 as a barrier to contain floating matter within the limited water surface of the pretreatment tank 101, but a permeable screen may also be placed at the bottom depending on the type of solid matter.

[0028] In contrast, the downstream partition wall 130 is a partition plate that separates the interior of the pretreatment tank 101 into the settling tank 102 and the treated tank 103, and the supernatant wastewater from which the sediment has been separated overflows the downstream partition wall 130 and flows into the treated tank 103. Although not shown, it is preferable to install a water vent with a plug at the bottom of the settling tank 102 to allow the water to be drained to the outside in order to remove the substances that have settled in the settling tank 102.

[0029] The primary side heat exchange device 200 includes a water storage tank 210 for storing treated wastewater (hereinafter simply referred to as wastewater) supplied from the pretreatment device 100 by a water supply pump P1, a primary side heat exchanger 220 for exchanging heat between the wastewater in the water storage tank 210 and a refrigerant, a blower device (blower) 230 having a compressor P2 for blowing compressed air into a perforated pipe (not shown) located below the primary side heat exchanger 220 to generate air bubbles, a water level gauge 240 for measuring the water level in the water storage tank 210, and a water thermometer (not shown) for measuring the water temperature in the water storage tank 210.

[0030] The primary heat exchanger 220 is immersed in the treated wastewater in the water storage tank 210 while being included in a refrigerant circulation circuit 201 having a refrigerant circulation pump P3 as the refrigerant circulation means 160.

[0031] The primary heat exchanger 220 is a heat exchanger that is corrosion-resistant and not susceptible to corrosion by chemical components in the wastewater, and may be made of metal as long as it is treated to be corrosion-resistant, but in the present invention, a resin heat exchanger is used. An example of this is described with reference to FIG.

[0032] This resin heat exchanger 221 is preferably a planar heat exchanger having multiple heat exchange tubes 224 connected in parallel between a first end tube 222 on the refrigerant inlet side and a second end tube 223 on the refrigerant outlet side.

[0033] Each heat exchange tube 224 is connected to a first end pipe 222 and a second end pipe 223. In this embodiment, the refrigerant is supplied to the first end pipe 222 by operating the refrigerant circulation pump P3, passes through each heat exchange tube 224, flows toward the second end pipe 223, exchanges heat with the wastewater, and is returned from the second end pipe 223 to the refrigerant circulation circuit 201. Water, antifreeze, etc. may be used as the refrigerant.

[0034] The heat exchange tubes 224 may be flexible synthetic resin tubes, such as polyethylene tubes. As an example, the heat exchange tubes 224 are tubes with a diameter of 6 mm and a length of 3.8 m, and 117 of them are arranged parallel to each other at regular intervals between the end tubes 222 and 223 by beam members 225, and appear to be a single sheet. Therefore, this resin heat exchanger 221 is sometimes called a heat exchange sheet or a sheet-like heat exchanger.

[0035] This planar resin heat exchanger 221 can also be rolled up, so in this embodiment, as shown in Figure 1, the planar resin heat exchanger 221 is rolled up in a spiral shape and stored in a basket to form a unit.

[0036] In this example, three resin heat exchangers 221 are installed, but the number of installed devices may be selected arbitrarily depending on the temperature and flow rate of the wastewater. Also, although each resin heat exchanger 221 is connected in parallel to the refrigerant circulation circuit 201, they may be connected in series in some cases.

[0037] The secondary-side heat exchange device 300 includes a heat exchanger 302 that exchanges heat between the primary-side refrigerant in the primary-side refrigerant circulation circuit 201 and raw water supplied to a water temperature adjustment means 310 such as a chiller or a boiler from a raw water supply circuit 301 having a water pump P4. Industrial water, river water, etc. may be used as the raw water.

[0038] As described above, depending on the purpose of use, the raw water is cooled to, for example, 0°C by a chiller, or heated to, for example, 80°C by a boiler, and then supplied to, for example, the chicken processing process 500.

[0039] A plate-type heat exchanger, which is inexpensively available, is preferably used for the heat exchanger 302 of this secondary heat exchange device 300, but this may be changed depending on the temperature and type of refrigerant in the resin heat exchanger 220.

[0040] The heat exchange system also includes a control unit 400 that controls the operation of the entire system. The control unit 400 may be implemented by a microcomputer, a personal computer, or the like.

[0041] The control unit 400 appropriately controls the water pump P1, compressor P2, refrigerant circulation pump P3, etc. based on measurement signals from water level gauges 150, 240, water thermometers (not shown), etc., so that the wastewater heat exchange system can be operated efficiently.

[0042] Raw water is supplied to water temperature adjustment means 310 by water pump P4, cooled to, for example, 0°C by a chiller, and sent to the chicken cutting process in chicken processing process 500. In the case of the chicken pre-processing process, the raw water is heated to, for example, 80°C by a boiler and used to remove feathers from birds and sterilize their surfaces before processing.

[0043] Referring to the flowchart of FIG. 3, in step ST1, cold wastewater at, for example, about 2°C after the chicken cutting process or warm wastewater at, for example, about 60°C after the chicken pre-treatment process flows into pre-treatment tank 101, where solids and impurities contained in the wastewater (cold wastewater / warm wastewater) are removed.

[0044] In step ST2, the control unit 400 determines whether the water level in the pre-treatment tank 101 is higher than the set value. If the result in step ST2 is NO, meaning that the water level in the pre-treatment tank 101 is lower than the set value, the process proceeds to step ST3, where the water pump P1, compressor P2, and refrigerant circulation pump P3 are stopped, and the process returns to step ST1.

[0045] If the result in step ST2 is YES and the water level in the pretreatment tank 101 is higher than the set value, the control unit 400 operates the water supply pump P1 in step ST4 to supply the treated wastewater to the water storage tank 210, and determines in step ST5 whether the water level in the water storage tank 210 is higher than the set value.

[0046] If the result of step ST5 is NO, meaning that the water level in the water storage tank 210 is lower than the set value, the process proceeds to step ST6, where the compressor P2 and the refrigerant circulation pump P3 are stopped, and the process returns to step ST4.

[0047] If the result in step ST5 is YES and the water level in the water tank 201 is higher than the set value, the control unit 400 operates the compressor P2 and the refrigerant circulation pump P3 in step ST7, and then returns to step ST1.

[0048] In this way, by operating the water supply pump P1, compressor P2, refrigerant circulation pump P3, and water supply pump P4, heat exchange occurs between the wastewater (e.g., cold wastewater at 2°C / warm wastewater at 60°C) and the refrigerant in the primary side heat exchanger 220, and heat exchange occurs between the refrigerant after heat exchange and the raw water supplied to the water temperature adjustment means 310 in the secondary side heat exchanger 302.

[0049] In addition, in an embodiment further including a water thermometer (not shown) for measuring the temperature of the treated wastewater in the water storage tank 201, the control unit 400 drives the water supply pump P1, compressor P2 and refrigerant circulation pump P3 when the water level in the pre-treatment tank 101 and the water level in the water storage tank 201 are both above a predetermined level, and when the treated wastewater in the water storage tank 201 is cold wastewater and its water temperature is below a first threshold temperature, or when it is warm wastewater and its water temperature is above a second threshold temperature.

[0050] In this way, according to the present invention, a wastewater heat exchange system is provided that can be used even with wastewater of such poor quality that a metal heat exchanger cannot be used, can operate just enough depending on the amount of wastewater, and can be constructed inexpensively overall.

[0051] In addition, by using the cold and hot energy recovered from this wastewater heat exchange system to cool and heat raw water, it is possible to reduce the electricity and fuel consumed by chillers and boilers.

[0052] Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the description of the above embodiments. Modifications or improvements made to the above embodiments by those skilled in the art are also included in the technical scope of the present invention. [Explanation of symbols]

[0053] 100 Pretreatment device 102 Settling tank 103 Treated tank 110 Solid removal means 120 Upstream partition wall 130 Downstream partition wall 140 Water Pump 150 Water level gauge 200 Primary side heat exchange device 201 Primary refrigerant circulation circuit 210 Water Tank 220 Primary heat exchanger 221 Resin heat exchanger 230 Blower 240 Water level gauge 300 Secondary side heat exchange device (secondary side heat exchanger) 301 Raw water supply circuit 310 Water temperature control means such as chillers / boilers 400 control section 500 Cold / hot water process (chicken processing)

Claims

1. A heat exchange system in which raw industrial water is converted into used water at a predetermined temperature for use in a food processing process or the like by a water temperature adjusting means such as a chiller or boiler, and wastewater heat contained in used wastewater discharged from the processing process is reused, a water pump that supplies treated wastewater from which solids have been removed by the pretreatment device into the water storage tank; a corrosion-resistant primary heat exchanger that is immersed in the treated wastewater in the water storage tank while being included in a part of a refrigerant circulation circuit including a refrigerant circulation pump; a secondary heat exchanger that performs heat exchange between the refrigerant circulating in the primary heat exchanger and the raw water that is supplied to the water temperature adjustment means; a first water level gauge that measures the water level in the pretreatment device; a second water level gauge that measures the water level in the water storage tank; and control means that controls operation of the water pump and / or the refrigerant circulation pump based on measurement signals from at least the first water level gauge and the second water level gauge.

2. 2. The heat exchange system for reusing wastewater heat according to claim 1, wherein a resin heat exchanger is used as the primary heat exchanger.

3. 3. The heat exchange system for reusing wastewater heat according to claim 1, wherein a plate heat exchanger is used as the secondary heat exchanger.

4. The heat exchange system for reusing wastewater heat as described in claim 1, characterized in that the pretreatment device includes a wire mesh receiving basket that initially receives the wastewater, an upstream partition wall that separates floating matter that passes through the receiving basket from the wastewater, and a downstream partition wall that separates sediments in the wastewater that pass below the upstream partition wall from the wastewater, and the wastewater that passes through the downstream partition wall is supplied to the water storage tank by the water supply pump as the treated wastewater.

5. 2. The heat exchange system for reusing wastewater heat as described in claim 1, wherein the control means drives the water supply pump and the refrigerant circulation pump when the water level in the pretreatment device and the water level in the water storage tank are both above a predetermined level.

6. A heat exchange system for reusing wastewater heat as described in claim 1, further comprising a water thermometer for measuring the temperature of the treated wastewater in the water storage tank, and wherein the control means drives the water supply pump and the refrigerant circulation pump when the water level in the pretreatment device and the water level in the water storage tank are both above a predetermined level and the temperature of the treated wastewater in the water storage tank is below a first threshold temperature or above a second threshold temperature.

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