Waste heat recovery system of marine dual-fuel diesel engine

Abstract

The invention relates to a marine dual-fuel diesel engine waste heat recovery system, and relates to the technical field of marine diesel engines, the marine dual-fuel diesel engine waste heat recovery system comprises a first tail gas heat exchange box and a second tail gas heat exchange box which are used for recovering heat of high-temperature tail gas of a diesel engine, and a mixing chamber connected with the first tail gas heat exchange box through a heat exchange assembly is arranged on the side of the first tail gas heat exchange box; the mixing chamber is used for mixing gas fuel and air and preheating mixed gas, a combustion chamber is arranged on the side of the mixing chamber, and a heat return gas box connected with the second tail gas heat exchange box through a heat exchange assembly is arranged on the side of the second tail gas heat exchange box; the system further comprises a wastewater treatment barrel used for treating domestic wastewater on the ship and washing tail gas, and the tail gas of the first tail gas heat exchange box and the tail gas of the second tail gas heat exchange box are input into the wastewater treatment barrel through pipelines. The system can fully recycle waste heat in tail gas of the diesel engine and cooling water, can independently preheat gas fuel and air so as to improve the combustion performance, and is suitable for being used in the dual-fuel diesel engine.

Description

Technical Field

[0001] The invention belongs to the technical field of marine diesel engines, and in particular relates to a waste heat recovery system for a marine dual-fuel diesel engine. Background Art

[0002] When diesel burns in the cylinder, most of the energy is converted into mechanical energy to drive the piston, but a considerable amount of energy is still lost to the cooling water and exhaust in the form of heat energy. This part of heat energy is the main source of diesel engine waste heat. The large amount of diesel engine waste heat emission will have a certain impact on the environment. In order to reduce the emission of diesel engine waste heat and improve energy utilization efficiency, waste heat recovery devices are generally used to convert waste heat into other forms of energy for utilization.

[0003] Dual-fuel marine diesel engines use a high-pressure common rail injection system to inject diesel and gas fuel into the combustion chamber at the same time. During the combustion process, the gas fuel mixes with the air to form a uniform mixture, which is then ignited. Since the calorific value of gas fuel is lower, more air is required to support combustion compared to diesel. Therefore, dual-fuel marine diesel engines require higher intake pressure and temperature during the combustion process. The existing diesel engine waste heat recovery system does not recover heat thoroughly enough. After recovery, there will still be a certain amount of heat in the exhaust gas. At the same time, it is difficult to independently heat the diesel and gas fuel, making it difficult to use in dual-fuel diesel engines. In addition, the existing waste heat recovery system is difficult to treat the exhaust gas accordingly. After the heat of the exhaust gas is recovered, it still needs to enter the washing equipment for corresponding treatment.

[0004] To this end, we provide a marine dual-fuel diesel engine waste heat recovery system to solve the above problems. Summary of the invention

[0005] The purpose of the present invention is to provide a waste heat recovery system for a marine dual-fuel diesel engine in view of the problems of the background technology.

[0006] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0007] A waste heat recovery system for a dual-fuel marine diesel engine comprises a first exhaust gas heat exchange box and a second exhaust gas heat exchange box for recovering heat from high-temperature exhaust gas of a diesel engine. A mixing chamber connected to the first exhaust gas heat exchange box via a heat exchange component is provided on the side of the first exhaust gas heat exchange box, the mixing chamber is used to mix gas fuel and air and preheat the mixed gas, a combustion chamber is provided on the side of the mixing chamber, and a heat recovery gas box connected to the second exhaust gas heat exchange box via a heat exchange component is provided on the side of the second exhaust gas heat exchange box.

[0008] It also includes a wastewater treatment cylinder for treating domestic wastewater on ships and washing exhaust gas. The exhaust gas from the first exhaust gas heat exchange box and the second exhaust gas heat exchange box is input into the wastewater treatment cylinder through a pipeline to heat the wastewater in the wastewater treatment cylinder.

[0009] It also includes a first cooling water heat exchange box and a second cooling water heat exchange box for recovering heat from the high-temperature cooling water of the diesel engine. A heat recovery water tank connected to the first cooling water heat exchange box through a heat exchange component is provided on the side of the first cooling water heat exchange box. A plurality of equally spaced liquid inlet pipes for conveying diesel into the mixing chamber and preheating the diesel are provided through the second cooling water heat exchange box.

[0010] As a further optimization scheme of the present invention, the interior of the wastewater treatment cylinder is provided with a partition plate and is divided into a first treatment chamber, a second treatment chamber and a third treatment chamber; the top of the wastewater treatment cylinder is respectively provided with a wastewater input pipe and a chemical input pipe connected to the first treatment chamber, and the lower end of the side of the wastewater treatment cylinder is provided with a clean water discharge pipe connected to the third treatment chamber.

[0011] As a further optimization solution of the present invention, the partition plate is provided with a through hole for the waste water to pass through, and the bottom of the partition plate is provided with a closing plate which is electrically driven and used to close the through hole.

[0012] As a further optimization scheme of the present invention, a turbine is fixedly provided on the top surface of the first processing chamber, a stirrer is rotatably provided at the bottom of the turbine, and the bottom end of the stirrer extends to the lower end of the second processing chamber.

[0013] As a further optimization scheme of the present invention, an exhaust gas input pipe for receiving exhaust gas output by the first exhaust gas heat exchange box and the second exhaust gas heat exchange box is provided on the side of the turbine, and the exhaust gas sprayed out of the exhaust gas input pipe is used to drive the turbine; an exhaust gas output pipe is provided on the top of the turbine, one end of the exhaust gas output pipe extends to the lower end of the second treatment chamber, and a plurality of aeration holes distributed at equal intervals are provided on the exhaust gas output pipe located in the second treatment chamber; an exhaust gas discharge pipe connected to the second treatment chamber is provided at the middle end of the side of the wastewater treatment cylinder.

[0014] As a further optimization scheme of the present invention, a filter screen and an activated carbon filter element located below the filter screen are respectively provided in the third processing chamber; a hot water input pipe and a hot air input pipe for regenerating the activated carbon filter element are respectively provided between the filter screen and the activated carbon filter element, the hot water input pipe is connected to the heat recovery tank, and the hot air input pipe is connected to the heat recovery gas tank.

[0015] As a further optimization solution of the present invention, the liquid inlet pipe includes a first tube body, a second tube body and a plurality of curved tubes evenly distributed along the circumference connecting the first tube body and the second tube body, and a liquid spray nozzle is installed at the end of the second tube body.

[0016] As a further optimization solution of the present invention, heat transfer fins are provided on the surface of the curved pipe, and a vortex portion is provided at one end of the curved pipe close to the second pipe body.

[0017] As a further optimization scheme of the present invention, a method for recovering waste heat from a marine dual-fuel diesel engine comprises the following steps:

[0018] S1. The high-temperature exhaust gas of the dual-fuel diesel engine flows into the first exhaust gas heat exchange box and the second exhaust gas heat exchange box respectively. The high-temperature exhaust gas in the first exhaust gas heat exchange box preheats the gas fuel and air in the mixing chamber through heat conduction, and the heat of the high-temperature exhaust gas in the second exhaust gas heat exchange box is conducted to the air in the reheating air box;

[0019] S2, the high-temperature cooling water of the dual-fuel diesel engine flows into the first cooling water heat exchange box and the second cooling water heat exchange box respectively. The high-temperature cooling water in the second cooling water heat exchange box preheats the diesel in the liquid inlet pipe after heat conduction, and the heat of the high-temperature cooling water in the first cooling water heat exchange box is conducted to the cold water in the heat return water tank;

[0020] S3. Treat domestic wastewater through a wastewater treatment cylinder. The exhaust gas from the first exhaust gas heat exchange box and the second exhaust gas heat exchange box is transported to the wastewater treatment cylinder. The remaining heat in the exhaust gas is transferred to the wastewater to improve the treatment effect. The exhaust gas is washed with chemical agents in the wastewater. The washed exhaust gas is discharged to the next process. The hot air from the heat recovery box and the hot water from the heat recovery water tank are transported to the wastewater treatment cylinder to regenerate the treatment components.

[0021] The beneficial effects of the present invention are:

[0022] 1. The present invention provides a first exhaust gas heat exchange box, a second exhaust gas heat exchange box, a first cooling water heat exchange box and a second cooling water heat exchange box, so that the system can fully recover the waste heat in the diesel engine exhaust and cooling water, and can independently preheat the gas fuel and air to improve the combustion performance, and is suitable for the use of dual-fuel diesel engines.

[0023] 2. The present invention sets a tail gas input pipe, a tail gas output pipe and a wastewater treatment cylinder, drives the agitator through the tail gas, and fully washes the tail gas with the washing liquid in the wastewater. At the same time, the remaining heat energy in the tail gas is conducted to the domestic wastewater, thereby improving the treatment efficiency and treatment effect of the domestic wastewater, combining the domestic wastewater treatment with the tail gas washing, and making full use of the remaining waste heat in the tail gas.

[0024] 3. The present invention provides a hot water input pipe and a hot air input pipe, and regenerates the activated carbon filter element with hot water and hot air, which can effectively restore the adsorption capacity of the activated carbon, improve the treatment effect of the wastewater treatment cylinder, and make the waste heat of the marine diesel engine be utilized again. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is the overall flow chart of the present invention;

[0026] Figure 2 Schematic diagram of the wastewater treatment cartridge structure of the present invention Figure 1 ;

[0027] Figure 3 Schematic diagram of the wastewater treatment cartridge structure of the present invention Figure 2 ;

[0028] Figure 4 It is a schematic diagram of the structure of the liquid inlet pipe of the present invention.

[0029] In the figure:

[0030] 1. First tail gas heat exchange box; 2. Second tail gas heat exchange box; 3. Mixing chamber; 4. Combustion chamber; 5. Regenerative gas box; 6. Wastewater treatment cylinder; 601. Partition plate; 601a. ​​Closing plate; 602. First treatment chamber; 603. Second treatment chamber; 604. Third treatment chamber; 605. Wastewater input pipe; 606. Reagent input pipe; 607. Turbine; 608. Agitator; 609. Tail gas input pipe; 610. Tail gas output pipe; 611, exhaust gas exhaust pipe; 612, filter screen; 613, activated carbon filter element; 614, hot water input pipe; 615, hot air input pipe; 616, clean water exhaust pipe; 7, first cooling water heat exchange box; 8, second cooling water heat exchange box; 9, hot water return tank; 10, liquid inlet pipe; 1001, first tube body; 1002, second tube body; 1003, elbow; 1004, heat transfer fins; 1005, vortex part; 1006, liquid spray nozzle. DETAILED DESCRIPTION

[0031] The present application is further described in detail below in conjunction with the accompanying drawings. It is necessary to point out here that the following specific implementation methods are only used to further illustrate the present application and cannot be understood as limiting the scope of protection of the present application. Technical personnel in this field can make some non-essential improvements and adjustments to the present application based on the above application content.

[0032] Embodiment 1

[0033] In order to solve the problem that the existing diesel engine waste heat recovery system is not enough to recover heat thoroughly and is difficult to be used in dual-fuel diesel engines, please refer to Figure 1The present invention provides a waste heat recovery system for a dual-fuel diesel engine for a ship, comprising a first exhaust gas heat exchange box 1 and a second exhaust gas heat exchange box 2 for recovering the heat of the high-temperature exhaust gas of the diesel engine. A mixing chamber 3 connected to the first exhaust gas heat exchange box 1 through a heat exchange component is provided on the side of the first exhaust gas heat exchange box 1. The mixing chamber 3 is used to mix gas fuel and air and preheat the mixed gas. A combustion chamber 4 is provided on the side of the mixing chamber 3. A heat recovery gas box 5 connected to the second exhaust gas heat exchange box 2 through a heat exchange component is provided on the side of the second exhaust gas heat exchange box 2. A wastewater treatment cylinder 6 for treating domestic wastewater on a ship and washing the exhaust gas is also included. The exhaust gas of the first exhaust gas heat exchange box 1 and the second exhaust gas heat exchange box 2 is input into the wastewater treatment cylinder 6 through a pipeline to heat the wastewater in the wastewater treatment cylinder 6. It also includes a first cooling water heat exchange box 7 and a second cooling water heat exchange box 8 for recovering the heat of the high-temperature cooling water of the diesel engine. A heat recovery water tank 9 connected to the first cooling water heat exchange box 7 through a heat exchange component is provided on the side of the first cooling water heat exchange box 7. The above heat exchange components can be connected by heat pipe components in the prior art. A plurality of equally spaced liquid inlet pipes 10 for conveying diesel to the mixing chamber 3 and preheating the diesel are provided through the second cooling water heat exchange box 8. The high-temperature exhaust gas in the first exhaust heat exchange box 1 can be used to preheat the gas fuel and air, and the high-temperature cooling water in the second cooling water heat exchange box 8 can be used to preheat the diesel and gas fuel. The temperature of the diesel and gas fuel is increased, the chemical reaction activity is enhanced, and the combustion performance is improved. At the same time, the heat of the remaining high-temperature exhaust gas is collected by the heat recovery gas box 5, and the heat of the remaining high-temperature cooling water is collected by the heat recovery water tank 9. The heat recovery gas box 5 and the heat recovery water tank 9 can be used for other places on the ship where heating is required, and are suitable for waste heat recovery and utilization of marine dual-fuel diesel engines. The dual fuels can be processed independently to improve the combustion effect.

[0034] like Figure 2-Figure 3 As shown, the interior of the wastewater treatment cylinder 6 is provided with a partition plate 601 and is divided into a first treatment chamber 602, a second treatment chamber 603 and a third treatment chamber 604, the partition plate 601 is provided with a through hole for the wastewater to pass through, and the bottom of the partition plate 601 is provided with a closing plate 601a for closing the through hole and electrically driven; the top of the wastewater treatment cylinder 6 is respectively provided with a wastewater input pipe 605 and a drug input pipe 606 connected to the first treatment chamber 602, a turbine 607 is fixedly provided on the top surface of the first treatment chamber 602, and a stirrer 608 is rotatably provided at the bottom of the turbine 607, and the bottom end of the stirrer 608 extends to the lower end of the second treatment chamber 603, a filter screen 612 and an activated carbon filter element 613 located below the filter screen 612 are respectively provided in the third treatment chamber 604, and a clean water discharge pipe 616 connected to the third treatment chamber 604 is provided at the lower end of the side of the wastewater treatment cylinder 6.

[0035] When the wastewater treatment cylinder 6 is in use, domestic wastewater is input into the wastewater treatment cylinder 6 through the wastewater input pipe 605, and chemical agents are input into the wastewater treatment cylinder 6 through the agent input pipe 606, and then the turbine 607 drives the agitator 608 to stir, so that the domestic wastewater and the chemical agents are fully in contact; after a period of time, the closing plate 601a is opened, so that the mixed liquid in the first treatment chamber 602 falls into the second treatment chamber 603, fully absorbs the heat energy of the exhaust gas input from the first exhaust gas heat exchange box 1 and the second exhaust gas heat exchange box 2, and increases the temperature of the mixed liquid. The increase in temperature can improve the treatment efficiency and treatment effect; after a period of time, the closing plate 601a is opened, so that the mixed liquid in the second treatment chamber 603 falls into the third treatment chamber 604, and is adsorbed by the filter net 612 and the activated carbon filter element 613, and the treated water is discharged from the clean water discharge pipe 616.

[0036] like Figure 4 As shown, the liquid inlet pipe 10 includes a first tube body 1001, a second tube body 1002, and a plurality of elbows 1003 evenly distributed along the circumference connecting the first tube body 1001 and the second tube body 1002. A heat transfer fin 1004 is provided on the surface of the elbow 1003 to absorb the heat value of diesel from the high-temperature cooling water in the second cooling water heat exchange box 8. A vortex portion 1005 is provided at one end of the elbow 1003 close to the second tube body 1002. The vortex portion 1005 can destroy the boundary layer and enhance the heat transfer between the diesel and the pipe wall, thereby improving the heat exchange efficiency. A liquid spray nozzle 1006 is installed at the end of the second tube body 1002. When in use, the diesel enters each liquid inlet pipe 10 through the liquid inlet manifold. When flowing through the elbow 1003, it conducts heat with the high-temperature cooling water in the second cooling water heat exchange box 8, and the temperature of the diesel is increased. With the increase in temperature, the evaporation rate of the diesel is accelerated, the atomization quality is improved, and it is helpful to fully mix the fuel and the air, thereby improving the combustion efficiency.

[0037] Embodiment 2

[0038] On the basis of the first embodiment, in order to make full use of the recovered diesel engine waste heat to improve the treatment effect of the wastewater treatment cylinder 6, as shown in FIG. Figure 2 As shown, a tail gas input pipe 609 for receiving the tail gas output from the first tail gas heat exchange box 1 and the second tail gas heat exchange box 2 is provided on the side of the turbine 607, and the tail gas ejected from the tail gas input pipe 609 is used to drive the turbine 607; a tail gas output pipe 610 is provided on the top of the turbine 607, one end of the tail gas output pipe 610 extends to the lower end of the second treatment chamber 603, and a plurality of aeration holes distributed at equal intervals are provided on the tail gas output pipe 610 in the second treatment chamber 603; a tail gas discharge pipe 611 connected to the second treatment chamber 603 is provided at the middle end of the side of the wastewater treatment cylinder 6.

[0039] When in use, the turbine 607 is driven by the high-speed exhaust gas, and the turbine 607 drives the stirrer 608 to rotate. The stirrer 608 stirs the domestic wastewater to make it fully integrated with the chemical agent. The exhaust gas can drive the motor to drive the stirrer 608, and the kinetic energy of the exhaust gas is reasonably utilized to reduce the energy consumption of the entire system; the exhaust gas then enters the wastewater in the second treatment chamber 603 through the exhaust gas output pipe 610, and the exhaust gas is washed by the wastewater. The exhaust gas washing and domestic wastewater treatment share the washing liquid, and the washing liquid in the wastewater is fully in contact with the exhaust gas. The harmful substances in the exhaust gas are dissolved or reacted to generate harmless substances. At the same time, the remaining heat energy in the exhaust gas is conducted to the domestic wastewater, thereby improving the treatment efficiency and treatment effect of the domestic wastewater. The washed exhaust gas is discharged from the system through the exhaust gas discharge pipe 611, and the domestic wastewater treatment is combined with the exhaust gas washing, so as to improve the efficiency and effect of ship waste treatment, reduce pollution to the environment, and reduce the overall energy consumption and carbon emissions of the ship.

[0040] Embodiment 3

[0041] On the basis of the first and second embodiments, in order to solve the problem that the activated carbon filter element 613 in the existing wastewater treatment cylinder 6 is inconvenient to clean, as shown in FIG. Figure 2-Figure 3 As shown, a hot water input pipe 614 and a hot air input pipe 615 for regenerating the activated carbon filter element 613 are respectively provided between the filter screen 612 and the activated carbon filter element 613. The hot water input pipe 614 is connected to the heat recovery tank 9, and the hot air input pipe 615 is connected to the heat recovery tank 5.

[0042] When in use, hot water is first input into the heat recovery tank 9 through the hot water input pipe 614 to spray the activated carbon filter element 613 to remove some organic matter and pollutants adsorbed on the surface of the activated carbon, and then hot air is input into the heat recovery tank 5 through the hot air input pipe 615 to steam heat the activated carbon filter element 613 to deeply decompose and release the adsorbed organic matter and pollutants. The combination of the two can effectively restore the adsorption capacity of the activated carbon, and the waste heat of the marine diesel engine can be utilized again.

[0043] The above-mentioned embodiment only expresses one implementation mode of the present invention, and its description is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A waste heat recovery system for a dual-fuel diesel engine for a ship, comprising a first exhaust gas heat exchange box (1) and a second exhaust gas heat exchange box (2) for recovering heat from high-temperature exhaust gas of a diesel engine, characterized in that: A mixing chamber (3) connected to the first exhaust gas heat exchange box (1) via a heat exchange component is provided on the side of the first exhaust gas heat exchange box (1), the mixing chamber (3) being used to mix gas fuel and air and preheat the mixed gas, a combustion chamber (4) is provided on the side of the mixing chamber (3), and a reheat box (5) connected to the second exhaust gas heat exchange box (2) via a heat exchange component is provided on the side of the second exhaust gas heat exchange box (2); It also includes a wastewater treatment cylinder (6) for treating domestic wastewater on the ship and washing the tail gas, wherein the tail gas from the first tail gas heat exchange box (1) and the second tail gas heat exchange box (2) is input into the wastewater treatment cylinder (6) through a pipeline to heat the wastewater in the wastewater treatment cylinder (6); It also includes a first cooling water heat exchange box (7) and a second cooling water heat exchange box (8) for recovering heat from high-temperature cooling water of the diesel engine. A heat recovery water tank (9) connected to the first cooling water heat exchange box (7) via a heat exchange component is provided on the side of the first cooling water heat exchange box (7). A plurality of liquid inlet pipes (10) for conveying diesel to the mixing chamber (3) and preheating the diesel are provided through the second cooling water heat exchange box (8) at equal intervals.

2. A waste heat recovery system for a marine dual-fuel diesel engine according to claim 1, characterized in that: The wastewater treatment cylinder (6) is provided with a partition plate (601) inside and is divided into a first treatment chamber (602), a second treatment chamber (603) and a third treatment chamber (604); The top of the wastewater treatment cylinder (6) is provided with a wastewater input pipe (605) and a reagent input pipe (606) which are connected to the first treatment chamber (602), and the lower end of the side of the wastewater treatment cylinder (6) is provided with a clean water discharge pipe (616) which is connected to the third treatment chamber (604).

3. A waste heat recovery system for a marine dual-fuel diesel engine according to claim 2, characterized in that: The partition plate (601) is provided with a through hole for waste water to pass through, and the bottom of the partition plate (601) is provided with a closing plate (601a) for closing the through hole and is electrically driven.

4. A waste heat recovery system for a marine dual-fuel diesel engine according to claim 2, characterized in that: A turbine (607) is fixedly provided on the top surface of the first processing chamber (602), and a stirrer (608) is rotatably provided at the bottom of the turbine (607), and the bottom end of the stirrer (608) extends to the lower end of the second processing chamber (603).

5. A waste heat recovery system for a marine dual-fuel diesel engine according to claim 4, characterized in that: A tail gas input pipe (609) for receiving tail gas output from the first tail gas heat exchange box (1) and the second tail gas heat exchange box (2) is provided on the side of the turbine (607), and the tail gas ejected from the tail gas input pipe (609) is used to drive the turbine (607); A tail gas output pipe (610) is provided at the top of the turbine (607), one end of the tail gas output pipe (610) extends to the lower end of the second processing chamber (603), and a plurality of aeration holes distributed at equal intervals are provided on the tail gas output pipe (610) located in the second processing chamber (603); A tail gas discharge pipe (611) connected to the second treatment chamber (603) is provided at the middle end of the side surface of the wastewater treatment cylinder (6).

6. A waste heat recovery system for a marine dual-fuel diesel engine according to claim 2, characterized in that: The third processing chamber (604) is provided with a filter screen (612) and an activated carbon filter element (613) located below the filter screen (612); A hot water input pipe (614) and a hot air input pipe (615) for regenerating the activated carbon filter element (613) are respectively provided between the filter screen (612) and the activated carbon filter element (613); the hot water input pipe (614) is connected to a heat recovery tank (9), and the hot air input pipe (615) is connected to a heat recovery tank (5).

7. A waste heat recovery system for a marine dual-fuel diesel engine according to claim 1, characterized in that: The liquid inlet pipe (10) comprises a first pipe body (1001), a second pipe body (1002), and a plurality of curved pipes (1003) evenly distributed along the circumference connecting the first pipe body (1001) and the second pipe body (1002); a liquid spray nozzle (1006) is installed at the end of the second pipe body (1002).

8. A waste heat recovery system for a marine dual-fuel diesel engine according to claim 7, characterized in that: A heat transfer fin (1004) is provided on the surface of the curved pipe (1003), and a vortex portion (1005) is provided at one end of the curved pipe (1003) close to the second pipe body (1002).

9. A waste heat recovery system for a marine dual-fuel diesel engine according to any one of claims 1 to 8, characterized in that: The waste heat recovery method based on the recovery system comprises the following steps: S1, high-temperature exhaust gas of the dual-fuel diesel engine flows into the first exhaust gas heat exchange box (1) and the second exhaust gas heat exchange box (2) respectively, the high-temperature exhaust gas in the first exhaust gas heat exchange box (1) preheats the gas fuel and air in the mixing chamber (3) through heat conduction, and the heat of the high-temperature exhaust gas in the second exhaust gas heat exchange box (2) is conducted to the air in the heat recovery box (5); S2, the high-temperature cooling water of the dual-fuel diesel engine flows into the first cooling water heat exchange box (7) and the second cooling water heat exchange box (8) respectively, the high-temperature cooling water in the second cooling water heat exchange box (8) preheats the diesel in the liquid inlet pipe (10) after heat conduction, and the high-temperature cooling water in the first cooling water heat exchange box (7) conducts heat to the cold water in the heat recovery water tank (9); S3. Domestic wastewater is treated by a wastewater treatment cylinder (6). The exhaust gas from the first exhaust gas heat exchange box (1) and the second exhaust gas heat exchange box (2) is transported to the wastewater treatment cylinder (6). The remaining heat in the exhaust gas is transferred to the wastewater to improve the treatment effect. The exhaust gas is washed by chemical agents in the wastewater. The washed exhaust gas is discharged to the next process. The hot air from the heat recovery gas box (5) and the hot water from the heat recovery water tank (9) are transported to the wastewater treatment cylinder (6) to regenerate the treatment components.

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