Ship waste heat recovery and cooling system for seawater desalination and fuel preheating

Abstract

The invention discloses a ship waste heat recovery and cooling system for seawater desalination and fuel oil preheating, relates to the field of marine diesel engines, and solves the technical problems that an existing ship power device is poor in economical efficiency and heat exchange effect, and marine fresh water storage space is insufficient. The system comprises a cooling unit, a fresh water making unit and a fuel preheating unit, a cooling water outlet of an engine is connected with a water inlet of the cooling unit through a thermostat, a water outlet of the cooling unit is connected with a water inlet of the fresh water making unit, and the heat exchange end of the fuel preheating unit is connected with the heat exchange end of the cooling unit. The heat exchange end of the fuel preheating unit is connected with the heat exchange end of the fresh water making unit, and a water outlet of the cooling unit is connected with a cooling water inlet of the engine through a first fresh water pump. On the basis of engine cooling, low-temperature multi-effect seawater desalination is organically fused into a waste heat recovery system, so that the heat management problem of a ship engine is solved, and the energy consumption of seawater desalination is reduced.

Description

Technical Field

[0001] The present invention relates to the field of marine diesel engines, and more specifically, to a marine waste heat recovery and cooling system for seawater desalination and fuel preheating. Background Art

[0002] When a marine diesel engine is working, the fuel burns in the cylinder, pushing the piston outward to do work. At this time, the marine diesel engine converts the chemical energy of the fuel into the mechanical energy of the piston. In this process, the piston and cylinder in the diesel engine are in direct contact with the flame. If they are not cooled in time, the temperature of the contacted parts will be high, causing the parts to overheat and deform, and the diesel engine will be difficult to work normally. If the cooling is excessive, the heat loss will increase and the overall thermal efficiency will be reduced.

[0003] During the voyage of a ship, the diesel engine of a large ship has huge power and emits a lot of heat. By effectively utilizing the various waste heat generated by the marine engine, it is not only possible to efficiently cool the marine diesel engine, but also to reduce fuel consumption and improve the economy of the ship's power plant. In addition, most of the existing heat exchangers are single-stage cooling, resulting in poor heat exchange effect. If you want to increase the heat exchange effect, you need to increase the heat exchange area, which will cause the heat exchanger to occupy too much space, reduce the cooling utilization rate of seawater, affect the layout of the engine, and increase the power consumption of the pump. At the same time, the fresh water resources on board are relatively scarce, and they are often replenished regularly by corresponding supply ships at sea. The regular replenishment method of supply ships requires huge fresh water storage space and has high purchase costs, which is not very economical. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a ship waste heat recovery and cooling system for seawater desalination and fuel preheating in view of the shortcomings of the existing technology, so as to solve the technical problems of poor economy, poor heat exchange effect and insufficient storage space for marine fresh water of existing ship power units.

[0005] The present invention discloses a waste heat recovery and cooling system for seawater desalination and fuel preheating of a ship, the system comprises a cooling unit, a desalination unit and a fuel preheating unit, the cooling water outlet of the engine is connected to the water inlet of the cooling unit through a thermostat, the water outlet of the cooling unit is connected to the water inlet of the desalination unit, the heat exchange end of the fuel preheating unit is connected to the heat exchange end of the cooling unit, the heat exchange end of the fuel preheating unit is connected to the heat exchange end of the desalination unit, and the water outlet of the cooling unit is connected to the cooling water inlet of the engine through a first fresh water pump.

[0006] As a further improvement, the cooling unit includes a second heat exchange zone, which is a spiral plate heat exchanger. A fresh water outlet and a seawater return port are provided on the outside of the spiral plate heat exchanger. A fresh water inlet 4 connected to the fresh water outlet is provided in the middle of the spiral plate heat exchanger. The cooling water outlet of the engine is connected to the fresh water inlet 4 through a thermostat. A second seawater outlet connected to the seawater return port is provided in the middle of the spiral plate heat exchanger. A first heat exchange zone is provided on the outside of the spiral plate heat exchanger. The first heat exchange zone includes an annular plate and a partition plate. The annular plate is fixedly installed on the outside of the spiral plate heat exchanger, one end of the partition plate is fixedly connected to the outside of the spiral plate heat exchanger, and the other end of the partition plate is fixedly connected to the annular plate. The annular plate is provided with a first seawater outlet on one side of the partition plate, and the annular plate is provided with a seawater inlet on the other side of the partition plate.

[0007] Furthermore, the cooling unit also includes a water-to-air intercooler and an oil cooler, the first seawater outlet is connected to the water inlet of the water-to-air intercooler, the water outlet of the water-to-air intercooler is connected to the water inlet of the oil cooler, the water outlet of the oil cooler is connected to the seawater return port, and the fresh water outlet, the water outlet of the water-to-air intercooler and the water outlet of the oil cooler are all connected to the fresh water making unit.

[0008] Furthermore, the desalination unit includes multiple desalination areas, and the desalination area includes a serpentine condenser, a concentrated seawater collection tank and multiple nozzles, the nozzle is installed on the top of the serpentine condenser, the concentrated seawater collection tank is installed on the bottom of the serpentine condenser, the fresh water outlet, the water outlet of the water-to-air intercooler and the water outlet of the oil cooler are all connected to the nozzle, and the serpentine condenser is connected to the fresh water collection tank.

[0009] Furthermore, the outside of the desalination unit is connected to a first heat exchanger, which is installed outside the desalination area away from the fuel preheating unit, the first heat exchange end inlet of the first heat exchanger is connected to the desalination area, the first heat exchange end outlet of the first heat exchanger is connected to the fresh water collection tank, the second heat exchange end inlet of the first heat exchanger is connected to the external environment through a deep seawater pump, and the second heat exchange end outlet of the first heat exchanger is connected to the external environment.

[0010] Furthermore, a plurality of air outlets are provided above the plurality of desalination zones, the air outlets are connected to gas pipelines, an exhaust port is provided on the gas pipeline away from one end of the fuel preheating unit, and a plurality of air pumps are installed in the gas pipeline.

[0011] Furthermore, the fuel preheating unit includes a fuel preheater, a flue gas heat exchanger, a second heat exchanger, a fourth heat exchanger and a third heat exchanger;

[0012] The exhaust port of the engine is connected to the first heat exchange end inlet of the fourth heat exchanger, the first heat exchange end outlet of the fourth heat exchanger is connected to the second heat exchange end inlet of the flue gas heat exchanger, the second heat exchange end outlet of the flue gas heat exchanger is connected to the first heat exchange end inlet of the third heat exchanger, and the first heat exchange end outlet of the third heat exchanger is in communication with the external environment;

[0013] The fuel delivery end of the engine is connected to the first heat exchange end of the fuel preheater, the second heat exchange end outlet of the fuel preheater is connected to the first heat exchange end inlet of the flue gas heat exchanger, the first heat exchange end outlet of the flue gas heat exchanger is connected to the first heat exchange end inlet of the second heat exchanger, the first heat exchange end outlet of the second heat exchanger is connected to the second heat exchange end inlet of the fuel preheater through a second fresh water pump, the second heat exchange end inlet of the second heat exchanger is connected to a concentrated seawater collection tank, and the second heat exchange end outlet of the second heat exchanger is in communication with the external environment.

[0014] Furthermore, the desalination area near the fourth heat exchanger includes a first serpentine condenser and a plurality of first nozzles, one end of the first serpentine condenser is connected to the outlet of the second heat exchange end of the fourth heat exchanger, and the other end of the first serpentine condenser is connected to the inlet of the second heat exchange end of the fourth heat exchanger;

[0015] The second seawater outlet is connected to the second heat exchange end inlet of the third heat exchanger, and the second heat exchange end outlet of the third heat exchanger is connected to the first nozzle.

[0016] Furthermore, the system also includes a circulation unit, the circulation unit includes a flow-limiting orifice plate, and the thermostat is connected to the engine cooling water inlet through the flow-limiting orifice plate and the first fresh water pump.

[0017] Furthermore, a water temperature sensor is installed at the engine cooling water outlet, and the water temperature of the fresh water coolant flowing through the engine cooling water outlet is obtained by the water temperature sensor. When the water temperature is greater than or equal to a preset water temperature threshold, the ECU turns on the thermostat to allow the fresh water coolant to directly enter the water inlet of the cooling unit from the engine cooling water outlet;

[0018] When the water temperature is lower than a preset water temperature threshold, the ECU closes the thermostat to allow the fresh water coolant to flow from the engine cooling water outlet through the flow limiting orifice plate and then into the engine cooling water inlet.

[0019] Beneficial Effects

[0020] The advantages of the present invention are:

[0021] 1. The present invention is provided with a cooling unit, a desalination unit and a fuel preheating unit, the cooling water outlet of the engine is connected to the water inlet of the cooling unit through a thermostat, the water outlet of the cooling unit is connected to the water inlet of the desalination unit, the heat exchange end of the fuel preheating unit is connected to the heat exchange end of the cooling unit, the heat exchange end of the fuel preheating unit is connected to the heat exchange end of the desalination unit, and the water outlet of the cooling unit is connected to the cooling water inlet of the engine through a first fresh water pump, so that low-temperature multi-effect seawater desalination is organically integrated into the waste heat recovery system on the basis of engine cooling, which not only solves the thermal management problem of the ship engine, but also reduces the energy consumption of seawater desalination.

[0022] 2. The present invention adopts a spiral plate heat exchanger in the cooling unit. During the heat exchange process, the surface seawater enters the spiral plate heat exchanger to cool the fresh water twice, which greatly enhances the heat exchange between fresh water and seawater and improves the cooling efficiency of seawater.

[0023] 3. In the present invention, the surface seawater in the cooling unit is sprayed in the desalination area, and the heat energy of the fuel preheating unit is used to heat the surface seawater in the desalination area to obtain fresh water vapor. The low-temperature seawater is used to cool the low-temperature fresh water vapor, thereby improving the matching of the heat source and the cold source, improving the heat utilization rate, and increasing the desalination output of the desalination system. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the overall structure of the waste heat recovery and cooling system of the present invention;

[0025] Figure 2 It is a cross-sectional view of the first heat exchange area and the second heat exchange area of ​​the present invention.

[0026] Among them: 1-second heat exchange zone, 2-fresh water outlet, 3-seawater reflux port, 4-fresh water inlet, 5-thermostat, 6-second seawater outlet, 7-first heat exchange zone, 8-annular plate, 9-partition plate, 10-first seawater outlet, 11-seawater inlet, 12-water-to-air intercooler, 13-oil cooler, 14-first serpentine condenser, 15-concentrated seawater collection box, 16-fresh water collection box, 17-first heat exchanger, 18-deep seawater pump, 19-gas pipeline, 20-air pump, 21-fuel preheater, 22-flue gas heat exchanger, 23-second heat exchanger, 24-third heat exchanger, 25-fourth heat exchanger, 26-first nozzle, 27-flow limiting orifice, 28-first fresh water pump, 29-second fresh water pump, 30-cooling unit, 31-fresh water unit, 32-fuel preheating unit. DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with the embodiments, but it does not constitute any limitation to the present invention. Any limited number of modifications made by anyone within the scope of the claims of the present invention are still within the scope of the claims of the present invention.

[0028] See also Figure 1-Figure 2 The present invention discloses a waste heat recovery and cooling system for seawater desalination and fuel preheating of a ship, the system comprises a cooling unit 30, a desalination unit 31 and a fuel preheating unit 32, the cooling water outlet of the engine is connected to the water inlet of the cooling unit 30 through a thermostat 5, the water outlet of the cooling unit 30 is connected to the water inlet of the desalination unit 31, the heat exchange end of the fuel preheating unit 32 is connected to the heat exchange end of the cooling unit 30, the heat exchange end of the fuel preheating unit 32 is connected to the heat exchange end of the desalination unit 31, and the water outlet of the cooling unit 30 is connected to the cooling water inlet of the engine through a first fresh water pump 28. The first fresh water pump 28 is used to drive the fresh water coolant after the system is cooled to enter the cooling water inlet of the engine.

[0029] like Figure 2 As shown, the cooling unit 30 includes a second heat exchange area 1, which is a spiral plate heat exchanger. A fresh water outlet 2 and a seawater return port 3 are provided on the outside of the spiral plate heat exchanger. A fresh water inlet 4 connected to the fresh water outlet 2 is provided in the middle of the spiral plate heat exchanger. The cooling water outlet of the engine is connected to the fresh water inlet 4 through a thermostat 5. A second seawater outlet 6 connected to the seawater return port 3 is provided in the middle of the spiral plate heat exchanger. A first heat exchange area 7 is provided on the outside of the spiral plate heat exchanger. The first heat exchange area 7 includes an annular plate 8 and a partition plate 9. The annular plate 8 is fixedly mounted on the outside of the spiral plate heat exchanger. One end of the partition plate 9 is fixedly connected to the outside of the spiral plate heat exchanger. The other end of the partition plate 9 is fixedly connected to the annular plate 8. The annular plate 8 is located on one side of the partition plate 9 and has a first seawater outlet 10. The annular plate 8 is located on the other side of the partition plate 9 and has a seawater inlet 11. Among them, the outermost layer is the first heat exchange area 7, and the inside is the second heat exchange area 1.

[0030] The cooling unit 30 also includes a water-to-air intercooler 12 and an oil cooler 13. The first seawater outlet 10 is connected to the water inlet of the water-to-air intercooler 12, the water outlet of the water-to-air intercooler 12 is connected to the water inlet of the oil cooler 13, the water outlet of the oil cooler 13 is connected to the seawater return port 3, and the fresh water outlet 2, the water outlet of the water-to-air intercooler 12 and the water outlet of the oil cooler 13 are all connected to the fresh water production unit 31.

[0031] At the same time, the surface seawater flows through the seawater inlet 11 into the first heat exchange area 7, and the first heat exchange area 7 cools the high-temperature fresh water coolant. The cooled surface seawater flows out from the seawater outlet and enters the water-to-air intercooler 12, the oil cooler 13, and the second heat exchange area 1 in sequence. The surface seawater exchanges heat with the fresh water coolant in the second heat exchange area 1, and the temperature of the fresh water coolant gradually decreases, while the temperature of the surface seawater gradually increases. When the surface seawater passes through the components in the cooling unit 30 in sequence, a portion of the seawater flows into the desalination area for seawater desalination.

[0032] Low-temperature fresh water is pumped into the engine body through the first fresh water pump 28, and then enters the engine body and supercharger through the water distribution chamber to cool the engine body and supercharger. After the engine body is cooled, the cylinder head is cooled. The fresh water after cooling the cylinder head is mixed with the fresh water after cooling the supercharger, and then the fresh water coolant is discharged from the cooling water outlet of the engine.

[0033] The desalination unit 31 includes a plurality of desalination zones, and the number of desalination zones in this embodiment is 5. The desalination zone includes a serpentine condenser, a concentrated seawater collection tank 15 and a plurality of nozzles, the nozzles are installed at the top of the serpentine condenser, the concentrated seawater collection tank 15 is installed at the bottom of the serpentine condenser, the desalination outlet 2, the water outlet of the water-to-air intercooler 12 and the water outlet of the oil cooler 13 are all connected to the nozzles, and the serpentine condenser is connected to the desalination collection tank 16.

[0034] An air outlet is provided above the desalination zone, and the air outlet is connected to a gas pipeline 19. An exhaust port is provided on the gas pipeline 19 at one end away from the fuel preheating unit 32, and a plurality of air pumps 20 are installed in the gas pipeline 19. The air pump 20 extracts the non-condensable steam from the desalination zone, and the pressures of the desalination zones 1-5 decrease in sequence and are all lower than the normal pressure, and the saturated temperature of water vapor also decreases in sequence, so that the temperature of the desalinated water can be better matched with the pressure.

[0035] The desalination area near the fourth heat exchanger 25 includes a first serpentine condenser 14 and a plurality of first nozzles 26 , one end of the first serpentine condenser 14 is connected to the second heat exchange end outlet of the fourth heat exchanger 25 , and the other end of the first serpentine condenser 14 is connected to the second heat exchange end inlet of the fourth heat exchanger 25 .

[0036] The second seawater outlet 6 is connected to the second heat exchange end inlet of the third heat exchanger 24 , and the second heat exchange end outlet of the third heat exchanger 24 is connected to the first nozzle 26 .

[0037] When the fresh water coolant enters the first heat exchange zone 7 and exchanges heat with the surface seawater in the second heat exchange zone 1, it flows through the nozzle and sprays onto the surface of the serpentine condenser tube. The fresh water inside the serpentine condenser tube flows into the fresh water collection tank 16, and a part of the surface seawater enters the desalination zone 5 away from the fuel preheating unit 32. The surface seawater is cooled and sprayed on the serpentine condenser tube of the desalination zone 5. The high-temperature steam from the previous desalination zone evaporates the surface seawater into water vapor, which is condensed into fresh water in the serpentine condenser tube. A part of the surface seawater sprayed on the surface of the serpentine condenser tube vaporizes into water vapor and enters the first heat exchanger 17. The water vapor exchanges heat with the deep cold seawater, so that the water vapor is condensed into fresh water. The remaining surface seawater will form concentrated seawater due to the reduction of water content and enter the concentrated seawater collection tank 15. For the desalination area 1 close to the fuel preheating unit 32, the heat energy of the fourth heat exchanger 25 is used as a heat source for generating steam for seawater desalination. The relatively high temperature surface seawater flowing through the third heat exchanger 24 flows through the first nozzle 26 of the desalination area 1 and is sprayed on the surface of the serpentine condenser in the desalination area 1. A part of the surface seawater exchanges heat with the high temperature flue gas inside its engine, so that it is vaporized into water vapor at a pressure lower than normal pressure, and then enters the subsequent desalination area for condensation and desalination, and the rest forms concentrated seawater.

[0038] The fuel preheating unit 32 includes a fuel preheater 21, a flue gas heat exchanger 22, a second heat exchanger 23, a fourth heat exchanger 25 and a third heat exchanger 24; the exhaust port of the engine is connected to the first heat exchange end inlet of the fourth heat exchanger 25, the first heat exchange end outlet of the fourth heat exchanger 25 is connected to the second heat exchange end inlet of the flue gas heat exchanger 22, the second heat exchange end outlet of the flue gas heat exchanger 22 is connected to the first heat exchange end inlet of the third heat exchanger 24, and the first heat exchange end outlet of the third heat exchanger 24 is connected to the external environment.

[0039] The fuel delivery end of the engine is connected to the first heat exchange end of the fuel preheater 21, the second heat exchange end outlet of the fuel preheater 21 is connected to the first heat exchange end inlet of the flue gas heat exchanger 22, the first heat exchange end outlet of the flue gas heat exchanger 22 is connected to the first heat exchange end inlet of the second heat exchanger 23, the first heat exchange end outlet of the second heat exchanger 23 is connected to the second heat exchange end inlet of the fuel preheater 21 through the second fresh water pump 29, the second heat exchange end inlet of the second heat exchanger 23 is connected to the concentrated seawater collection tank 15, and the second heat exchange end outlet of the second heat exchanger 23 is connected to the external environment.

[0040] The concentrated seawater in the concentrated seawater collection tank 15 enters the second heat exchanger 23 to exchange heat with the fresh water coolant to reduce the formation of salt crystals. As for the flue gas inside the exhaust manifold, it is discharged by the engine as a heat source for low-temperature multi-effect seawater desalination, enters the fourth heat exchanger 25 to exchange heat with the flue gas after heat exchange, so that the temperature of the fourth heat exchanger 25 of the engine is reduced to ensure the safety of the crew. Then the flue gas enters the flue gas heat exchanger 22 to exchange heat with the fresh water coolant, and the flue gas temperature is further reduced. Then the flue gas exchanges heat with the surface seawater through the third heat exchanger 24, and is finally discharged to the environment.

[0041] In order to preheat the fuel and improve the combustion efficiency of the ship engine, a fuel preheating circuit is set. Considering the safety of the ship during operation, the fuel preheating and the flue gas cannot be directly exchanged. This system recovers the waste heat in the exhaust manifold and concentrated seawater into the fresh water coolant through the fresh water coolant, and then preheats the fuel through the fresh water coolant and the fuel preheater 21. Among them, the second fresh water pump 29 plays the role of driving the fuel preheating circuit.

[0042] A water temperature sensor is installed at the engine cooling outlet, and the water temperature of the fresh water coolant flowing through the engine cooling outlet is obtained through the water temperature sensor. When the water temperature is greater than or equal to a preset water temperature threshold, the water temperature threshold is 70°C, and the ECU turns on the thermostat 5 to allow the fresh water coolant to directly enter the water inlet of the cooling unit 30 from the engine cooling outlet.

[0043] When the water temperature is lower than the preset water temperature threshold, the ECU closes the thermostat 5 to allow the fresh water coolant to flow from the engine cooling outlet through the flow limiting orifice 27 and then flow into the engine cooling inlet. The fresh water mainly goes through the small cycle, and a small amount of fresh water goes through the large cycle. This setting is to allow the fresh water coolant to fully exchange heat with the engine, and then exchange heat with the surface seawater after reaching the water temperature threshold, thereby improving the cooling efficiency of the surface seawater.

[0044] It should be noted that the low-temperature multi-effect seawater desalination process and the fuel preheating process work under the above-mentioned large and small cycles. When the fresh water coolant temperature is greater than 70°C, the energy consumption in the low-temperature multi-effect seawater desalination is lower because the heating of the surface seawater can make the internal air pressure of the desalination area higher, the energy consumption of the air pump 20 is reduced, the desalination effect is better, and the fresh water output is higher.

[0045] The present invention proposes a system for recovering waste heat from ships that integrates low-temperature multi-effect seawater desalination and fuel oil preheating, which utilizes the quality of thermal energy in a cascade manner. The surface seawater is gradually heated after being heated by several heat exchangers of the fuel oil preheating unit 32. The seawater temperatures at the outlets of various heat exchangers are inconsistent. Low-temperature seawater is used to cool low-temperature fresh water vapor, which improves the matching of the heat source and the cold source, improves the heat utilization rate of the heat source, and increases the amount of fresh water produced by the desalination system.

[0046] The above is only a preferred embodiment of the present invention. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the structure of the present invention, which will not affect the effect of the implementation of the present invention and the practicality of the patent.

Claims

1. A ship waste heat recovery and cooling system for seawater desalination and fuel preheating, characterized in that: The system comprises a cooling unit (30), a fresh water unit (31) and a fuel preheating unit (32); the cooling water outlet of the engine is connected to the water inlet of the cooling unit (30) through a thermostat; the water outlet of the cooling unit (30) is connected to the water inlet of the fresh water unit (31); the heat exchange end of the fuel preheating unit (32) is connected to the heat exchange end of the cooling unit (30); the heat exchange end of the fuel preheating unit (32) is connected to the heat exchange end of the fresh water unit (31); and the water outlet of the cooling unit (30) is connected to the cooling water inlet of the engine through a first fresh water pump (28).

2. A ship waste heat recovery and cooling system for seawater desalination and fuel preheating according to claim 1, characterized in that: The cooling unit (30) comprises a second heat exchange area (1), the second heat exchange area (1) being a spiral plate heat exchanger, the outer side of the spiral plate heat exchanger being provided with a fresh water outlet (2) and a seawater return port (3), the middle part of the spiral plate heat exchanger being provided with a fresh water inlet (4) connected to the fresh water outlet (2), the cooling water outlet of the engine being connected to the fresh water inlet 4 via a thermostat (5), the middle part of the spiral plate heat exchanger being provided with a second seawater outlet (6) connected to the seawater return port (3), the spiral plate heat exchanger A first heat exchange area (7) is provided on the outside, and the first heat exchange area (7) comprises an annular plate (8) and a partition plate (9), the annular plate (8) is fixedly mounted on the outside of the spiral plate heat exchanger, one end of the partition plate (9) is fixedly connected to the outside of the spiral plate heat exchanger, and the other end of the partition plate (9) is fixedly connected to the annular plate (8), the annular plate (8) is provided with a first seawater outlet (10) on one side of the partition plate (9), and the annular plate (8) is provided with a seawater inlet (11) on the other side of the partition plate (9).

3. A ship waste heat recovery and cooling system for seawater desalination and fuel preheating according to claim 2, characterized in that: The cooling unit (30) further comprises a water-to-air intercooler (12) and an oil cooler (13); the first seawater outlet (10) is connected to the water inlet of the water-to-air intercooler (12); the water outlet of the water-to-air intercooler (12) is connected to the water inlet of the oil cooler (13); the water outlet of the oil cooler (13) is connected to the seawater return port (3); and the fresh water outlet (2), the water outlet of the water-to-air intercooler (12) and the water outlet of the oil cooler (13) are all connected to the fresh water production unit (31).

4. A ship waste heat recovery and cooling system for seawater desalination and fuel preheating according to claim 3, characterized in that: The desalination unit (31) comprises a plurality of desalination zones, each of which comprises a serpentine condenser, a concentrated seawater collection tank (15) and a plurality of nozzles, wherein the nozzles are mounted on the top of the serpentine condenser, the concentrated seawater collection tank (15) is mounted on the bottom of the serpentine condenser, the fresh water outlet (2), the water outlet of the water-to-air intercooler (12) and the water outlet of the oil cooler (13) are all connected to the nozzles, and the serpentine condenser is connected to the fresh water collection tank (16).

5. A ship waste heat recovery and cooling system for seawater desalination and fuel preheating according to claim 4, characterized in that: The desalination unit (31) is externally connected to a first heat exchanger (17), the first heat exchanger (17) being installed outside a desalination area away from the fuel oil preheating unit (32), the first heat exchange end inlet of the first heat exchanger (17) being connected to the desalination area, the first heat exchange end outlet of the first heat exchanger (17) being connected to a fresh water collection tank (16), the second heat exchange end inlet of the first heat exchanger (17) being connected to an external environment via a deep seawater pump (18), and the second heat exchange end outlet of the first heat exchanger (17) being connected to an external environment.

6. A ship waste heat recovery and cooling system for seawater desalination and fuel preheating according to claim 4, characterized in that: An air outlet is provided above the desalination zone, and the air outlet is connected to a gas pipeline (19). An exhaust port is provided on the gas pipeline (19) at one end away from the fuel preheating unit (32), and a plurality of air pumps (20) are installed in the gas pipeline (19).

7. A ship waste heat recovery and cooling system for seawater desalination and fuel preheating according to claim 4, characterized in that: The fuel preheating unit (32) comprises a fuel preheater (21), a flue gas heat exchanger (22), a second heat exchanger (23), a fourth heat exchanger (25) and a third heat exchanger (24); The exhaust port of the engine is connected to the first heat exchange end inlet of the fourth heat exchanger (25), the first heat exchange end outlet of the fourth heat exchanger (25) is connected to the second heat exchange end inlet of the flue gas heat exchanger (22), the second heat exchange end outlet of the flue gas heat exchanger (22) is connected to the first heat exchange end inlet of the third heat exchanger (24), and the first heat exchange end outlet of the third heat exchanger (24) is in communication with the external environment; The fuel delivery end of the engine is connected to the first heat exchange end of the fuel preheater (21); the second heat exchange end outlet of the fuel preheater (21) is connected to the first heat exchange end inlet of the flue gas heat exchanger (22); the first heat exchange end outlet of the flue gas heat exchanger (22) is connected to the first heat exchange end inlet of the second heat exchanger (23); the first heat exchange end outlet of the second heat exchanger (23) is connected to the second heat exchange end inlet of the fuel preheater (21) through a second fresh water pump (29); the second heat exchange end inlet of the second heat exchanger (23) is connected to a concentrated seawater collection tank (15); and the second heat exchange end outlet of the second heat exchanger (23) is in communication with the external environment.

8. A ship waste heat recovery and cooling system for seawater desalination and fuel preheating according to claim 7, characterized in that: The desalination area near the fourth heat exchanger (25) includes a first serpentine condenser (14) and a plurality of first nozzles (26), one end of the first serpentine condenser (14) is connected to the outlet of the second heat exchange end of the fourth heat exchanger (25), and the other end of the first serpentine condenser (14) is connected to the inlet of the second heat exchange end of the fourth heat exchanger (25); The second seawater outlet (6) is connected to the second heat exchange end inlet of the third heat exchanger (24), and the second heat exchange end outlet of the third heat exchanger (24) is connected to the first nozzle (26).

9. A ship waste heat recovery and cooling system for seawater desalination and fuel preheating according to claim 1, characterized in that: The system also includes a circulation unit, which includes a flow-limiting orifice plate (27). The thermostat (5) is connected to the engine cooling water inlet via the flow-limiting orifice plate (27) and a first fresh water pump (28).

10. A ship waste heat recovery and cooling system for seawater desalination and fuel preheating according to claim 9, characterized in that: A water temperature sensor is installed at the engine cooling outlet, and the water temperature of the fresh water coolant flowing through the engine cooling outlet is obtained through the water temperature sensor. When the water temperature is greater than or equal to a preset water temperature threshold, the ECU turns on the thermostat (5) to allow the fresh water coolant to directly enter the water inlet of the cooling unit (30) from the engine cooling outlet; When the water temperature is lower than a preset water temperature threshold, the ECU closes the thermostat (5) to allow the fresh water coolant to flow from the engine cooling water outlet through the flow limiting orifice (27) and then flow into the engine cooling water inlet.

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