JP5339193B2 - Exhaust gas heat recovery device - Google Patents

Description

  The present invention relates to an exhaust gas heat recovery device that preheats feed water to a boiler using exhaust gas from a boiler.

  Conventionally, as disclosed in Patent Document 1 below, steam that includes a boiler and a heat pump, uses a heat pump for heating in a relatively low temperature range to water as a medium to be heated, and uses a boiler for heating in a relatively high temperature range A supply system has been proposed. Specifically, in this steam supply system, a heat pump is disposed on the upstream side and a boiler is disposed on the downstream side with respect to the flow direction of the water to be heated. The heat pump draws heat from the atmosphere and preheats the water supplied to the boiler. In this way, the water that is the medium to be heated rises in temperature by heat exchange with the refrigerant of the heat pump, and is then supplied to the boiler and vaporized.

  On the other hand, an economizer that preheats water supplied to the boiler using exhaust gas from the boiler is also known. In this case, water supplied to the boiler is preheated with exhaust gas in an economizer and then supplied to the boiler and evaporated.

JP 2006-308164 A (Claim 1, paragraph numbers 0018, 0019, FIG. 1)

  In any of the above-described methods, there is room for improvement in the thermal efficiency of the entire steam supply system. In particular, when the feed water temperature is high, the conventional economizer cannot sufficiently heat the feed water. That is, if high temperature drain is returned from the steam using equipment to the water supply tank to the boiler and heat recovery is performed, the water in the water supply tank rises in temperature due to the high temperature drain, and the water supply temperature may become considerably higher than normal temperature However, in that case, the conventional economizer has not been able to sufficiently heat the feed water.

  The problem to be solved by the present invention is to realize an exhaust gas heat recovery device capable of efficiently heating the feed water to the boiler even when the feed water temperature is relatively high.

The present invention has been made to solve the above problems, and the invention according to claim 1 includes a heat pump configured by sequentially connecting a compressor, a condenser, an expansion valve, and an evaporator in an annular shape, The evaporator is a heat exchanger with exhaust gas from the boiler, the condenser is a heat exchanger with water supply to the boiler, and the evaporator is provided in the boiler flue, An economizer is provided on the upstream side of the exhaust gas flow with respect to the evaporator, and water supplied to the boiler is supplied to the boiler through the economizer after being passed through the condenser, and the economizer is The exhaust gas heat recovery device is an exhaust gas sensible heat recovery unit, and the evaporator is an exhaust gas latent heat recovery unit .

  According to the first aspect of the present invention, heat can be pumped up from the exhaust gas of the boiler using the heat pump, and heating of the feed water to the boiler can be effectively achieved. By using a heat pump that draws heat from the exhaust gas of the boiler, it is possible to heat relatively high-temperature water supply.

According to the first aspect of the present invention, a heat pump is used in combination with an economizer, and more effective heat recovery can be achieved by disposing the exhaust gas flow downstream of the economizer and upstream of the water supply from the economizer. it can.

Furthermore, in the invention according to claim 2 , in the evaporator, the refrigerant of the heat pump is caused to flow from the downstream side to the upstream side of the exhaust gas flow from the boiler, and in the condenser, the refrigerant of the heat pump is the flows from the downstream side of the water supply to the boiler to the upstream side, in the economizer, the water supply to the boiler, according to claim 1, characterized in that flows to the upstream side from the downstream side of the exhaust gas flow from said boiler The exhaust gas heat recovery device.

According to the invention of claim 2 , in the evaporator of the heat pump, the refrigerant and the exhaust gas are opposed to each other, in the condenser of the heat pump, the refrigerant and the water supply are opposed to each other, and in the economizer, the water supply and the exhaust gas are opposed to each other. Thus, heat recovery can be achieved more efficiently.

  According to the present invention, even when the feed water temperature is relatively high, the feed water to the boiler can be efficiently heated.

It is the schematic which shows the use condition of Example 1 of the waste gas heat recovery apparatus of this invention. It is the schematic which shows the use condition of Example 2 of the waste gas heat recovery apparatus of this invention.

  Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. However, the exhaust gas heat recovery apparatus of the present invention is not limited to the configuration of the following embodiment, and can be changed as appropriate.

  FIG. 1 is a schematic view showing a usage state of Embodiment 1 of the exhaust gas heat recovery apparatus of the present invention. The exhaust gas heat recovery device of the present embodiment is a device that uses the heat pump 1 to heat up the exhaust gas from the boiler 2 and heats the feed water to the boiler 2.

  The boiler 2 is supplied with water from the water supply tank 3 via the water supply path 4. A water supply pump 5 is provided in the water supply path 4, and the presence or absence of water supply to the boiler 2 is switched depending on whether or not the water supply pump 5 is activated. The water supply tank 3 is appropriately supplied with water from the make-up water channel 6 and maintained at a desired water level. The replenishment water channel 6 to the water supply tank 3 is provided with a pure water device or a soft water device (not shown), and pure water or soft water is supplied to the water supply tank 3.

  The water supplied to the boiler 2 is vaporized by the boiler 2. The steam from the boiler 2 is sent to one or a plurality of various steam utilizing devices 7 via a steam header (not shown) as required. Drain generated in the steam using device 7 is returned to the water supply tank 3 through a steam trap 8 and a drain recovery path 9.

  In the boiler 2, fuel is burned in order to heat and vaporize the feed water, and the exhaust gas is discharged to the outside through the flue 10. The exhaust gas heat recovery device attempts to preheat water supplied to the boiler 2 by the heat pump 1 using the heat of the exhaust gas passing through the flue 10.

  The heat pump 1 is configured by sequentially connecting a compressor 11, a condenser 12, an expansion valve 13, and an evaporator 14 in an annular shape. The compressor 11 compresses the refrigerant into a high-temperature and high-pressure gas. The vaporized refrigerant from the compressor 11 is sent to the condenser 12. The condenser 12 condenses and liquefies the vaporized refrigerant from the compressor 11. The liquefied refrigerant from the condenser 12 is sent to the expansion valve 13. The expansion valve 13 allows the liquefied refrigerant from the condenser 12 to pass therethrough, thereby reducing the pressure and temperature of the refrigerant. The evaporator 14 evaporates the refrigerant from the expansion valve 13.

  The compressor 11 may be driven by an electric motor, but may be driven by a steam engine. The steam engine is a device that generates power using steam, and is, for example, a screw-type steam engine. The steam engine is driven by steam from the boiler 2 as one of the steam utilization devices 7.

  The condenser 12 will be described in more detail. The condenser 12 according to the present embodiment is a heat exchanger having a refrigerant flow path 15 and a water flow path 16, and performs heat exchange without mixing the refrigerant and water. The refrigerant from the compressor 11 passes through the refrigerant flow path 15 of the condenser 12 and is sent to the expansion valve 13. On the other hand, water from the water supply tank 3 passes through the water flow path 16 of the condenser 12 and is supplied to the boiler 2. Therefore, while the water from the water supply tank 3 passes through the condenser 12, it takes heat from the refrigerant and is heated. On the contrary, the refrigerant from the compressor 11 is cooled by water supplied to the boiler 2 while passing through the condenser 12.

  The evaporator 14 will be described in more detail. The evaporator 14 of the present embodiment is a refrigerant flow path 17 provided in the flue 10 and exchanges heat without mixing the refrigerant and the exhaust gas. At this time, the evaporator 14 may be configured as a unit including a cylindrical body constituting a part of the flue 10 and a refrigerant flow path 17 provided in the cylindrical body. Moreover, the refrigerant flow path 17 provided in the flue 10 can be comprised similarly to various conventionally well-known economizers, such as making it meander suitably in the flue 10. FIG.

  By the way, although the refrigerant | coolant used for the heat pump 1 is not ask | required in particular, In order to enable heating of comparatively high temperature water supply, it is preferable to use R-245fa, for example. However, the refrigerant used in the heat pump 1 is not limited to such a fluorocarbon refrigerant, but may be other refrigerants such as water.

  Since it is the above structures, the exhaust gas from the boiler 2 passes the evaporator 14 of the flue 10, and is discharged | emitted outside. The exhaust gas is cooled by the refrigerant while passing through the evaporator 14, and the volume is reduced. On the other hand, the refrigerant from the expansion valve 13 is warmed and vaporized by the exhaust gas while passing through the evaporator 14. Thereafter, the refrigerant is sent to the condenser 12 in a state of high temperature and high pressure in the compressor 11. In the condenser 12, water having a temperature lower than that of the refrigerant is passed, so that the feed water to the boiler 2 is heated by the heat of the refrigerant, while the refrigerant is cooled by the feed water and sent to the expansion valve 13.

  Thus, according to the exhaust gas heat recovery apparatus of the present embodiment, heat can be pumped up from the exhaust gas using the heat pump 1 to heat the feed water to the boiler 2. At this time, by using the heat pump 1, heating of relatively high temperature water supply can be achieved. That is, when the drain is recovered from the steam utilization device 7 to the water supply tank 3, the water in the water supply tank 3 is heated by the high-temperature drain as compared with the case where the drain is not recovered to the water supply tank 3, May reach up to about 80 ° C. Even in such a case, according to the exhaust gas heat recovery apparatus of the present embodiment, further heating of the feed water can be realized.

  FIG. 2 is a schematic view showing a usage state of the second embodiment of the exhaust gas heat recovery apparatus of the present invention. The exhaust gas heat recovery apparatus according to the second embodiment basically has the same configuration as that of the first embodiment. Therefore, in the following description, the differences between the two will be mainly described, and corresponding portions will be described with the same reference numerals.

  The exhaust gas heat recovery apparatus according to the second embodiment further includes an economizer 18 in addition to the heat pump 1 according to the first embodiment. At this time, an economizer 18 is preferably provided in the flue 10 of the boiler 2 on the upstream side of the exhaust gas flow from the evaporator 14. In addition, the water supply to the boiler 2 is preferably supplied to the boiler 2 through the condenser 12 and then through the economizer 18. By using the heat pump 1 together with the economizer 18 and disposing the exhaust gas flow downstream of the economizer 18 and upstream of the water supply relative to the economizer 18, more effective heat recovery can be achieved.

  In the second embodiment, the economizer 18 is an exhaust gas sensible heat recovery unit, and the evaporator 14 is basically an exhaust gas latent heat recovery unit. However, part or all of the evaporator 14 may be a sensible heat recovery unit depending on circumstances.

  Moreover, in FIG. 2, although the evaporator 14 is installed on the economizer 18 in the flue 10 of the boiler 2, the treatment of the condensed water from the exhaust gas is taken into consideration in the place where the evaporator 14 is installed. The flue 10 may be directed downward and the exhaust gas may flow downward from above. Thereby, the condensed water produced in the evaporator 14 can be dropped downward. Then, the exhaust gas after passing through the evaporator 14 turns upward and is discharged to the outside.

  In the evaporator 14, the refrigerant of the heat pump 1 is caused to flow from the downstream side to the upstream side of the exhaust gas flow from the boiler 2. In the condenser 12, the refrigerant of the heat pump 1 is the boiler 2. It is good to comprise so that it may flow from the downstream of the feed water to the upstream. That is, it is preferable that the refrigerant and the exhaust gas are counterflowed in the evaporator 14 of the heat pump 1 and the refrigerant and feed water are counterflowed in the condenser 12 of the heat pump 1. Further, in the second embodiment, in the economizer 18, the water supply to the boiler 2 is preferably flowed from the downstream side to the upstream side of the exhaust gas flow from the boiler 2. That is, in the economizer 18, it is preferable that the water supply and the exhaust gas are opposed to each other. If comprised in this way, heat exchange will be made efficiently and heat recovery efficiency can be improved. Other configurations and controls are the same as those in the first embodiment, and thus description thereof is omitted.

DESCRIPTION OF SYMBOLS 1 Heat pump 2 Boiler 3 Water supply tank 4 Water supply path 7 Steam utilization apparatus 9 Drain collection path 10 Flue 11 Compressor 12 Condenser 13 Expansion valve 14 Evaporator 18 Economizer

Claims (2)

A heat pump comprising a compressor, a condenser, an expansion valve and an evaporator sequentially connected in an annular manner;
The evaporator is a heat exchanger with exhaust gas from the boiler,
The condenser is a heat exchanger for supplying water to the boiler ,
In the boiler flue, the evaporator is provided, and an economizer is provided on the upstream side of the exhaust gas flow from the evaporator,
After the water supply to the boiler is passed through the condenser, the economizer is passed through and supplied to the boiler ,
The exhaust gas heat recovery apparatus , wherein the economizer is an exhaust gas sensible heat recovery unit, and the evaporator is an exhaust gas latent heat recovery unit. In the evaporator, the refrigerant of the heat pump is caused to flow from the downstream side to the upstream side of the exhaust gas flow from the boiler,
In the condenser, the refrigerant of the heat pump is caused to flow from the downstream side to the upstream side of the water supply to the boiler,
The exhaust gas heat recovery apparatus according to claim 1 , wherein in the economizer, water supplied to the boiler flows from a downstream side to an upstream side of an exhaust gas flow from the boiler.

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