JP2017089973A - Waste heat recovery system and cogeneration system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a waste heat recovery system capable of effectively enhancing waste heat recovery amount and facilitating work for removing unburned oil.SOLUTION: A waste heat recovery system 1 includes a first stage hot water boiler 2 and a second stage hot water boiler 3. The first stage hot water boiler 2 has a finned tube through which second exhaust gas G2 discharged from an exhaust gas boiler 12 is caused to pass, recovers waste heat of the second exhaust gas G2 and discharges third exhaust gas G3 having a condensation prevention temperature enabling prevention of condensation of unburned oil included in the second exhaust gas G2. The second stage hot water boiler 3 includes a tube without fins through which the third exhaust gas G3 is caused to pass, recovers waste heat of the third exhaust gas G3 and discharges fourth exhaust gas G4 having a temperature lower than the condensation prevention temperature.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a waste heat recovery system and a cogeneration system for recovering exhaust heat of exhaust gas exhausted from an engine power generation system.

  In an engine power generation system that generates power by combustion of an engine, the exhaust heat of exhaust gas exhausted from the engine power generation system is recovered by an exhaust gas boiler to construct a cogeneration system. In the exhaust gas boiler, steam or the like is produced by exhaust heat recovered from the exhaust gas. In addition, a heat exchanger (economizer) that preheats water to the exhaust heat steam boiler is placed downstream of the exhaust gas flow of the exhaust gas boiler, and further exhaust heat recovery is performed by this heat exchanger. There is also.

  As such an exhaust gas boiler, for example, there is one disclosed in the can structure of an exhaust heat recovery boiler of Patent Document 1. In the can structure of this exhaust heat recovery boiler, a large number of water pipes are inserted into the exhaust gas passage, and the side wall defining the exhaust gas passage is constituted by a water cooling wall and a casing wall located downstream of the water cooling wall. doing. Further, by using the water cooling wall and the casing wall in combination, the thermal expansion of the side wall due to the temperature change of the exhaust gas is suppressed, and the can body having a simple configuration can be formed.

Japanese Patent No. 2842190

  By the way, the exhaust gas exhausted from the engine power generation system includes moisture and unburned oil such as a lubricant discharged without being burned. In particular, unburned oil is in a gaseous state in an environment above a specific temperature, but condenses in an environment below a specific temperature, and accumulates on the inner wall surface of the heat exchanger through which exhaust gas passes. The Therefore, in the conventional heat exchanger, the exhaust heat of exhaust gas is recovered only until the temperature at which the unburned oil does not condense, for example, a temperature of about 120 to 140 ° C. Therefore, in order to increase the recovery amount of exhaust heat, it is necessary to recover exhaust heat to a temperature lower than the temperature at which unburned oil is condensed. However, in this case, it is not easy to remove unburned oil accumulated on the inner wall surface of the heat exchanger through which the exhaust gas passes.

  The present invention has been made in view of such problems, and it is intended to provide a waste heat recovery system and a cogeneration system that can effectively increase the amount of exhaust heat recovered and facilitate the removal of unburned oil. It was obtained as.

One aspect of the present invention is a waste heat recovery system disposed on the downstream side of an exhaust gas boiler that recovers exhaust heat of a first exhaust gas exhausted from an engine power generation system that generates power by combustion of an engine,
A first stage hot water boiler that recovers exhaust heat of the second exhaust gas exhausted from the exhaust gas boiler;
A second-stage hot water boiler that recovers exhaust heat of the third exhaust gas exhausted from the first-stage hot water boiler;
The first stage hot water boiler has a finned tube that allows the second exhaust gas to pass through, recovers exhaust heat of the second exhaust gas, and prevents condensation of unburned oil contained in the second exhaust gas. It is configured to exhaust the third exhaust gas above the condensation prevention temperature,
The second stage hot water boiler has a finless tube that allows the third exhaust gas to pass through, collects exhaust heat of the third exhaust gas, and exhausts the fourth exhaust gas lower than the condensation prevention temperature. Is in the waste heat recovery system.

Another aspect of the present invention is an engine power generation system that generates power by combustion of an engine;
An exhaust gas boiler for recovering exhaust heat of the first exhaust gas exhausted from the engine power generation system;
A first stage hot water boiler for recovering exhaust heat of the second exhaust gas exhausted from the exhaust gas boiler;
A second-stage hot water boiler that recovers exhaust heat of the third exhaust gas exhausted from the first-stage hot water boiler;
Between the engine power generation system and the exhaust gas boiler, a catalyst for decomposing unburned oil contained in the first exhaust gas is disposed,
The first stage hot water boiler has a finned tube that allows the second exhaust gas to pass through, recovers exhaust heat of the second exhaust gas, and prevents condensation of unburned oil contained in the second exhaust gas. It is configured to exhaust the third exhaust gas above the condensation prevention temperature,
The second stage hot water boiler has a finless tube that allows the third exhaust gas to pass through, collects exhaust heat of the third exhaust gas, and exhausts the fourth exhaust gas lower than the condensation prevention temperature. Is in the cogeneration system.

The waste heat recovery system is disposed downstream of the exhaust gas boiler and further recovers exhaust heat of the exhaust gas exhausted from the exhaust gas boiler. The waste heat recovery system uses an appropriate combination of a first-stage hot water boiler having a finned tube and a second-stage hot water boiler having a finless tube, thereby improving the amount of exhaust heat recovered and attaching unburned oil. This is to achieve both trouble avoidance.
Here, from the viewpoint of clarifying the explanation, the exhaust gas exhausted from each element is the exhaust gas exhausted from the engine power generation system as the first exhaust gas, the exhaust gas exhausted from the exhaust gas boiler as the second exhaust gas, and the first stage hot water boiler. The exhaust gas discharged from the third exhaust gas is represented as a third exhaust gas, and the exhaust gas exhausted from the second stage hot water boiler is represented as a fourth exhaust gas.

  The recovery of the exhaust heat of the second exhaust gas by the first stage hot water boiler is performed within a range where the temperature of the third exhaust gas is equal to or higher than the condensation prevention temperature at which condensation of unburned oil contained in the third exhaust gas can be prevented. In the first stage hot water boiler, the heat transfer efficiency from the exhaust gas to the heat recovery medium can be increased by recovering the exhaust heat using the finned tube. In addition, exhaust heat recovery using a finned tube is performed only within a range where the temperature of the third exhaust gas is equal to or higher than the condensation prevention temperature, and unburned oil is condensed on heat transfer fins that are difficult to clean. Adhesion can be prevented.

Further, the recovery of the exhaust heat of the third exhaust gas by the second stage hot water boiler is performed until the temperature of the fourth exhaust gas becomes lower than the condensation prevention temperature. And in the second stage hot water boiler, by collecting exhaust heat using a finless tube, there is no heat transfer fin that is difficult to wash, and the unburned oil adhering to the tube can be easily washed Can do.
Therefore, according to the waste heat recovery system, the amount of exhaust heat recovered can be effectively increased, and unburned oil can be easily removed.

  Note that the unburned oil means that the lubricating oil or the like used in the engine in the engine power generation system remains in the first exhaust gas without being burned together with the fuel in the engine.

In the cogeneration system, a catalyst for decomposing unburned oil contained in the first exhaust gas is disposed between the engine power generation system and the exhaust gas boiler.
And, by removing most of the unburned oil contained in the first exhaust gas with the catalyst, the amount of unburned oil reaching the waste heat recovery system by the first stage hot water boiler and the second stage hot water boiler is reduced. Can do. Thereby, the adhesion amount of unburned oil to the finless tube of the second stage hot water boiler can be reduced.

Explanatory drawing which shows the waste heat recovery system arrange | positioned with respect to the engine electric power generation system and exhaust gas boiler concerning Embodiment 1. FIG. Explanatory drawing which expands and shows the waste heat recovery system concerning Embodiment 1. FIG. BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing which shows schematically the structure of the 1st stage | paragraph hot water boiler concerning Embodiment 1. FIG. BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing which shows roughly the structure of the 2nd stage warm water boiler concerning Embodiment 1. FIG.

A preferred embodiment according to the above-described waste heat recovery system and cogeneration system will be described with reference to the drawings.
(Embodiment 1)
As shown in FIG. 1, the waste heat recovery system 1 is disposed downstream of an exhaust gas boiler 12 that recovers exhaust heat of the first exhaust gas G1 exhausted from an engine power generation system 11 that generates power by combustion of the engine. . The waste heat recovery system 1 uses the exhaust heat of the first stage hot water boiler 2 that recovers the exhaust heat of the second exhaust gas G2 exhausted from the exhaust gas boiler 12 and the third exhaust gas G3 that is exhausted from the first stage hot water boiler 2. A second-stage hot water boiler 3 to be recovered is provided.

As shown in FIGS. 2 and 3, the first stage hot water boiler 2 has a finned tube 21 that allows the second exhaust gas G2 to pass through. The exhaust gas from the second exhaust gas G2 is recovered and the second exhaust gas is recovered. The third exhaust gas G3 having a condensation prevention temperature capable of preventing the unburned oil contained in G2 from being condensed is exhausted. The second stage hot water boiler 3 has a finless tube 31 through which the third exhaust gas G3 passes, recovers the exhaust heat of the third exhaust gas G3, and exhausts the fourth exhaust gas G4 lower than the condensation prevention temperature. It is configured as follows.
For convenience, the exhaust gas passing through the boilers 12, 2, 3 of the exhaust gas boiler 12, the first stage hot water boiler 2, and the second stage hot water boiler 3 are referred to as the first exhaust gas G 1, the second exhaust gas G 2, the third exhaust gas G 3, and This is expressed as the fourth exhaust gas G4.

Hereinafter, the waste heat recovery system 1 and the cogeneration system 10 of this embodiment will be described in further detail.
As shown in FIGS. 1 and 2, the waste heat recovery system 1 is disposed on the downstream side of the exhaust gas boiler 12 and further recovers exhaust heat of the exhaust gas exhausted from the exhaust gas boiler 12. The waste heat recovery system 1 is a combination of a first stage hot water boiler 2 having a finned tube 21 and a second stage hot water boiler 3 having a finless tube 31.

  The engine power generation system 11 performs power generation by a generator using rotational force generated by combustion of a fuel mixture in an engine such as a stationary gas engine or a stationary diesel engine. In the engine power generation system 11, a cogeneration system that collects exhaust heat (thermal energy) of exhaust gas generated by engine combustion and exhaust water (thermal energy) of cooling water that is heated when the engine is cooled is constructed. Is done. Exhaust heat of the exhaust gas is used for water vaporization by the exhaust gas boiler 12 and warm water temperature rise by the waste heat recovery system 1, and exhaust heat of the cooling water is used as a heat source for air conditioning.

As shown in FIG. 1, in this embodiment, a cogeneration system 10 is formed using an exhaust heat recovery system 1. The cogeneration system 10 includes an engine power generation system 11, a catalyst 13, an exhaust gas boiler 12, a first stage hot water boiler 2, and a second stage hot water boiler 3.
The catalyst 13 is disposed between the engine exhaust port 112 in the engine power generation system 11 and the air supply port 121 of the exhaust gas boiler 12 and volatilizes in the first exhaust gas G1 exhausted from the engine power generation system 11. It has the function of decomposing unburned oil. The catalyst 13 is configured using a noble metal such as platinum, palladium, or rhodium.

  The catalyst 13 removes most of the unburned oil contained in the first exhaust gas G1, so that the unburned oil reaches the waste heat recovery system 1 using the first stage hot water boiler 2 and the second stage hot water boiler 3. The amount can be reduced. Thereby, the adhesion amount of the unburned oil to the finless tube 31 of the second stage hot water boiler 3 can be reduced.

As shown in FIG. 1, the exhaust gas boiler 12 of this embodiment is an exhaust gas steam boiler that generates steam by using exhaust gas. A first exhaust gas G1 of 300 ° C. or higher is supplied from the engine power generation system 11 to the air supply port 121 of the exhaust gas boiler 12, and is about 160 ° C. (within a range of 150 to 170 ° C.) from the exhaust port 122 of the exhaust gas boiler 12. The second exhaust gas G2 is exhausted. Steam produced by the exhaust gas boiler 12 is used in various processes such as a factory.
The exhaust gas boiler 12 can be an exhaust gas hot water boiler that raises the temperature of the water using the exhaust gas. Also in this case, the temperature of the second exhaust gas G2 is in the range of 150 to 170 ° C.

The first stage hot water boiler 2 and the second stage hot water boiler 3 are heat exchangers that heat the hot water W used in the absorption chiller 6 to a predetermined temperature by the exhaust heat of the second exhaust gas G2 and the third exhaust gas G3. . The absorption refrigerator 6 is sometimes called an absorption chiller / heater.
As shown in FIGS. 2 and 3, the first stage hot water boiler 2 includes a container (not shown) through which the second exhaust gas G2 circulates and a plurality of finned tubes 21 arranged in parallel in the container. Have. The air supply port 22 and the exhaust port 23 in the first stage hot water boiler 2 are provided at positions facing each other, and the plurality of finned tubes 21 are in the direction in which the air supply port 22 and the exhaust port 23 are opposed to each other. It is arrange | positioned along the direction orthogonal to. The hot water W used in the absorption refrigerator 6 flows through the plurality of finned tubes 21 via the hot water inlet 24 and the hot water outlet 25. Then, when the second exhaust gas G2 flows through the container of the first stage hot water boiler 2 and the hot water W flows through the finned tube 21, the exhaust heat of the second exhaust gas G2 flows through the finned tube 21 into the hot water W. Is transmitted to.

  As shown in FIGS. 2 and 4, the second stage hot water boiler 3 includes a container (not shown) through which the third exhaust gas G3 circulates, and a plurality of finless tubes 31 arranged in parallel in the container. Have. In the second stage hot water boiler 3, the air supply port 32 and the exhaust port 33 are provided at positions facing each other, and the plurality of finless tubes 31 are opposed to the air supply port 32 and the exhaust port 33. It arrange | positions along the direction orthogonal to a direction. Hot water W used in the absorption chiller 6 flows through the plurality of finless tubes 31 through the hot water inlet 34 and the hot water outlet 35. When the third exhaust gas G3 flows through the container of the second stage hot water boiler 3 and the hot water W flows through the finless tube 31, the exhaust heat of the third exhaust gas G3 is transferred to the hot water W via the finless tube 31. Is transmitted to.

As shown in FIG. 3, the finned tube 21 in the first stage hot water boiler 2 is formed by providing a plurality of heat transfer fins 212 on the outer periphery of the tube 211. Therefore, the first stage hot water boiler 2 has good heat transfer efficiency, can be formed compactly, and the manufacturing cost per unit amount of exhaust heat is inexpensive. On the other hand, as shown in FIG. 4, the finless tube 31 in the second stage hot water boiler 3 is formed of a tube 311 having no heat transfer fins. is there. Further, since the second stage hot water boiler 3 uses the finless tube 31, even if unburned oil accumulates on the outer peripheral surface of the tube 311, the unburned oil may not easily block the inside of the container. it can. However, when the finless tube 31 is used, the heat transfer efficiency is poor, the apparatus is enlarged, and the manufacturing cost per unit amount of exhaust heat is also expensive.
The amount of exhaust heat recovered by the first-stage hot water boiler 2 and the amount of exhaust heat recovered by the second-stage hot water boiler 3 are determined according to restrictions on the arrangement space of the waste heat recovery system 1 in factories, capital investment budgets, etc. It can be set appropriately.

As shown in FIG. 1, the waste heat recovery system 1 includes a main exhaust pipe 41, a main damper 51, a bypass exhaust pipe 42, a bypass damper 52, and the like in addition to the first stage hot water boiler 2 and the second stage hot water boiler 3. ing. The main exhaust pipe 41 is connected to the exhaust port 122 of the exhaust gas boiler 12. In the main exhaust pipe 41, the first stage hot water boiler 2 and the second stage hot water boiler 3 of the first stage hot water boiler 2 located downstream of the flow of the third exhaust gas G3 are arranged in series. ing.
Here, FIGS. 1 and 2 show a state in which a part of the main exhaust pipe 41 is disposed between the first-stage hot water boiler 2 and the second-stage hot water boiler 3. The first stage hot water boiler 2 and the second stage hot water boiler 3 may be directly connected without passing through a part of the main exhaust pipe 41.

As shown in FIG. 2, the main damper 51 is provided in the main exhaust pipe 41 in the vicinity of the air supply port 121 of the exhaust gas boiler 12 and in the main exhaust pipe 41 in the vicinity of the exhaust port 33 of the second stage hot water boiler 3. Has been placed. The main damper 51 is rotatable in the main exhaust pipe 41. The bypass exhaust pipe 42 is branched from the main exhaust pipe 41 in the vicinity of the air inlet 121 of the exhaust gas boiler 12, and is connected to the main exhaust pipe 41 located in the vicinity of the exhaust outlet 33 of the second stage hot water boiler 3. . The bypass exhaust pipe 42 bypasses the first exhaust gas G1 supplied to the exhaust gas boiler 12 without passing through the exhaust gas boiler 12, the first stage hot water boiler 2, and the second stage hot water boiler 3. The bypass damper 52 is rotatably disposed in the bypass exhaust pipe 42.
As shown in FIG. 1, the main exhaust pipe 41 is connected to a chimney 43 for exhausting the fourth exhaust gas G4 after the exhaust heat is recovered to the atmosphere.

  When performing maintenance on the exhaust gas boiler 12, the first stage hot water boiler 2, and the second stage hot water boiler 3, the main exhaust pipe 41 is closed by the main damper 51 and the bypass exhaust pipe 42 is opened by the bypass damper 52. Thus, the first exhaust gas G1 can be exhausted to the chimney 43 and the like without passing through the exhaust gas boiler 12, the first stage hot water boiler 2, and the second stage hot water boiler 3 by using the bypass exhaust pipe 42.

  The first stage hot water boiler 2 and the second stage hot water boiler 3 are connected in parallel with a hot water pipe 61 that circulates the hot water W used in the absorption chiller 6 between the absorption chiller 6. The hot water pipe 61 is connected to the first stage hot water boiler 2 via the hot water inlet 24 and the hot water outlet 25 of the first stage hot water boiler 2, and the hot water inlet 34 and the hot water outlet 35 of the second stage hot water boiler 3 Is connected to the second stage hot water boiler 3. The hot water piping 61 connected to the hot water inlets 24 and 34 of the hot water boilers 2 and 3 is provided with a hot water pump 62 for circulating the hot water W between the absorption refrigerator 6 and the hot water boilers 2 and 3. Has been.

The condensation temperature of the unburned oil contained in the exhaust gas varies depending on the type of oil used in the engine in the engine power generation system 11. The condensation prevention temperature is set as a temperature higher than the condensation temperature of the unburned oil, and can be a predetermined temperature selected from a temperature range of 110 to 140 ° C. Thereby, it is possible to prevent various unburned oils from adhering to the finned tube 21 in the first stage hot water boiler 2. In this embodiment, the condensation prevention temperature is set as 120 ° C.
In the waste heat recovery system 1 of this embodiment, the temperature of the third exhaust gas G3 exhausted from the first stage hot water boiler 2 is set appropriately for the heat recovery amount from the second exhaust gas G2 and the third exhaust gas G3 to the hot water W. By carrying out the step, the temperature is kept above the condensation prevention temperature.

  The absorption refrigerator 6 is an evaporator that evaporates the refrigerant to produce cold water by heat of vaporization, an absorber that absorbs the refrigerant into the absorbing solution, a regenerator that concentrates the absorbing solution and separates the absorbing solution from the vapor refrigerant, and It has a pseudo-condenser that condenses the vapor refrigerant. The hot water W can be used in the regenerator.

In the waste heat recovery system 1, the exhaust heat recovery of the second exhaust gas G2 by the first stage hot water boiler 2 can prevent the temperature of the third exhaust gas G3 from condensing unburned oil contained in the third exhaust gas G3. It is performed within the range above the condensation prevention temperature. In the first stage hot water boiler 2, the heat transfer efficiency from the second exhaust gas G2 to the hot water W used in the absorption refrigerator 6 can be increased by collecting the exhaust heat using the finned tube 21. . In addition, the exhaust heat recovery using the finned tube 21 is performed only within a range where the temperature of the third exhaust gas G3 is equal to or higher than the condensation prevention temperature, and unburned oil is applied to the heat transfer fins 212 that are difficult to clean. Condensation and adhesion can be prevented.
The temperature of the third exhaust gas G3 can be monitored using a thermometer arranged at the exhaust port 23 of the first stage hot water boiler 2.

  Further, the recovery of the exhaust heat of the third exhaust gas G3 by the second stage hot water boiler 3 is performed until the temperature of the fourth exhaust gas G4 becomes lower than the condensation prevention temperature. In the second stage hot water boiler 3, exhaust heat is recovered using the finless tube 31, so that there is no heat transfer fin that is difficult to clean, and unburned oil adhered to the outer peripheral surface of the tube 311. Can be easily washed by high-pressure washing or the like.

  Therefore, according to the waste heat recovery system 1 and the cogeneration system 10 of the present embodiment, it is possible to effectively increase the amount of exhaust heat recovered and facilitate the removal of unburned oil.

(Embodiment 2)
In this embodiment, as a method for designing the waste heat recovery system 1, a method for setting the heat transfer area of the finned tube 21 of the first stage hot water boiler 2 will be described.
In setting the heat transfer area of the finned tube 21, a calculation formula used for designing the heat transfer area of a general heat exchanger can be used.

  Specifically, the heat exchange amount Q of the first-stage hot water boiler 2 is calculated using the heat transfer rate K of the first-stage hot water boiler 2, the heat transfer area A of the finned tube 21, and the logarithm average temperature difference ΔTm. = K · A · ΔTm. Here, the heat exchange amount Q is the temperature of the second exhaust gas G2 at the air supply port 22 of the first stage hot water boiler 2, the temperature of the third exhaust gas G3 at the exhaust port 23 of the first stage hot water boiler 2, and the second exhaust gas G2. And the specific heat of the second exhaust gas G2. The heat transfer rate K is calculated using the material, thickness, and shape of the finned tube 21, the flow rate of the second exhaust gas G 2, and the flow rate of the hot water W. The logarithmic average temperature difference ΔTm is the temperature of the second exhaust gas G2 at the air supply port 22 of the first stage hot water boiler 2, the temperature of the third exhaust gas G3 at the exhaust port 23 of the first stage hot water boiler 2, and the finned tube 21. The temperature of the warm water W at the warm water inlet 24 and the temperature of the warm water W at the warm water outlet 25 of the finned tube 21 are calculated.

The heat transfer area A is obtained by substituting the heat exchange amount Q, the heat passage rate K, and the logarithmic average temperature difference ΔTm obtained by the above calculation into an equation of A = Q / (K · ΔTm).
Thus, the amount of exhaust heat recovered by the first stage hot water boiler 2 can be set appropriately by appropriately obtaining the heat transfer area A of the first stage hot water boiler 2. And it becomes easy to keep the temperature of the 3rd exhaust gas G3 exhausted from the 1st stage warm water boiler 2 more than condensation prevention temperature.
Further, the amount of exhaust heat recovered by the second stage hot water boiler 3 can be appropriately set according to the temperature of the fourth exhaust gas G4, which is the final temperature for recovering exhaust heat.
In this embodiment, the configuration of the waste heat recovery system 1 is the same as that of the first embodiment.

  The present invention is not limited only to the embodiments, and can be applied to further different embodiments without departing from the scope of the invention.

DESCRIPTION OF SYMBOLS 1 Waste heat recovery system 10 Cogeneration system 11 Engine power generation system 12 Exhaust gas boiler 13 Catalyst 2 First stage hot water boiler 3 Second stage hot water boiler 21 Finned tube 31 Finless tube 6 Absorption type refrigerator 61 Hot water piping

Claims (4)

A waste heat recovery system disposed on the downstream side of the flow of the first exhaust gas of an exhaust gas boiler that recovers exhaust heat of the first exhaust gas exhausted from an engine power generation system that generates power by combustion of the engine,
A first stage hot water boiler that recovers exhaust heat of the second exhaust gas exhausted from the exhaust gas boiler;
A second-stage hot water boiler that recovers exhaust heat of the third exhaust gas exhausted from the first-stage hot water boiler;
The first stage hot water boiler has a finned tube that allows the second exhaust gas to pass through, recovers exhaust heat of the second exhaust gas, and prevents condensation of unburned oil contained in the second exhaust gas. It is configured to exhaust the third exhaust gas above the condensation prevention temperature,
The second stage hot water boiler has a finless tube that allows the third exhaust gas to pass through, collects exhaust heat of the third exhaust gas, and exhausts the fourth exhaust gas lower than the condensation prevention temperature. Waste heat recovery system.   The waste heat recovery system according to claim 1, wherein the condensation prevention temperature is a predetermined temperature selected from a temperature range of 110 to 140 ° C. The first-stage hot water boiler and the second-stage hot water boiler heat the hot water used in the absorption chiller to a predetermined temperature by exhaust heat of the second exhaust gas and the third exhaust gas,
The waste according to claim 1 or 2, wherein a warm water pipe for circulating the warm water between the first stage hot water boiler and the second stage warm water boiler is connected in parallel with the absorption refrigerator. Heat recovery system. An engine power generation system that generates power by combustion of the engine;
An exhaust gas boiler for recovering exhaust heat of the first exhaust gas exhausted from the engine power generation system;
A first stage hot water boiler for recovering exhaust heat of the second exhaust gas exhausted from the exhaust gas boiler;
A second-stage hot water boiler that recovers exhaust heat of the third exhaust gas exhausted from the first-stage hot water boiler;
Between the engine power generation system and the exhaust gas boiler, a catalyst for decomposing unburned oil contained in the first exhaust gas is disposed,
The first stage hot water boiler has a finned tube that allows the second exhaust gas to pass through, recovers exhaust heat of the second exhaust gas, and prevents condensation of unburned oil contained in the second exhaust gas. It is configured to exhaust the third exhaust gas above the condensation prevention temperature,
The second stage hot water boiler has a finless tube that allows the third exhaust gas to pass through, collects exhaust heat of the third exhaust gas, and exhausts the fourth exhaust gas lower than the condensation prevention temperature. Cogeneration system.

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