CN104358627B - Boat diesel engine NOx and SOx associating emission reduction device and control method - Google Patents

Abstract

The invention provides a marine diesel engine NOx and SOx joint emission reduction device and control method. In the non-nitrogen oxide emission control area, working in the non-EGR mode, the exhaust gas from the exhaust manifold drives the turbine to do work, drives the compressor to compress the air, and enters the engine through the scavenging box to participate in combustion; when the ship is in the nitrogen oxide emission control When sailing in the region, it works in EGR mode, part of the exhaust gas is drawn from the exhaust manifold, through cooling and washing, the temperature is lowered and the particles and SOx are removed, and then it is pressurized by the EGR fan and mixed with fresh air to reduce the NOx of the engine The generation and emissions meet IMO's Tier III standards for NOx emissions; when in sulfur emission control areas or ports, work in the scrubbing mode, and the exhaust gas is desulfurized by the scrubbing and desulfurization device and then discharged into the atmosphere, meeting IMO's requirements for the sulfur content of ship fuel; In non-sulfur emission control areas and non-port areas, it works in non-scrubbing mode, and the exhaust gas is directly discharged into the ambient atmosphere.

Description

Marine diesel engine NOx and SOx combined emission reduction device and control method

technical field

The present invention relates to a ship exhaust pollutant emission control device, in particular to a joint control device and control method for marine diesel engine NOx and SOx to meet the International Maritime Organization (IMO) regulations on ship exhaust pollutant emission.

Background technique

In order to reduce ship operating costs, ocean transport ships use high-sulfur heavy oil, and the NOx and SOx produced by engine combustion have caused serious harm to the marine atmosphere and port environment.

IMO and developed countries such as Europe and the United States have imposed strict restrictions on NOx and SOx emissions in ship engine exhaust.

At present, commonly used NOx emission reduction measures mainly include in-machine emission reduction measures and out-of-machine emission reduction measures. The internal emission reduction measures are through certain methods, such as delaying fuel injection in the cylinder, improving the fuel injection law, reducing the intake air temperature, spraying water in the cylinder, etc., to change the combustion in the cylinder, reduce the generation of NOx in the cylinder, and finally reduce the NOx of the engine Emissions: Off-machine NOx reduction measures are mainly SCR post-treatment technology, which uses reducing agents to reduce NOx in the exhaust pipe of diesel engines and turn them into harmless N ₂ , ultimately reducing engine NOx emissions. Relatively speaking, the above-mentioned internal emission reduction measures are relatively easy to implement, but the emission reduction effect is limited; the external emission reduction SCR technology has a good emission reduction effect and can meet the NOx emission requirements of IMO, but the post-processing device is bulky, reducing the number of ships. The effective space of the SCR, while the operation and maintenance costs of the SCR are also relatively high.

As an effective NOx emission reduction measure for diesel engines, Exhaust Gas Recirculation (EGR) technology draws a part of the exhaust gas from the exhaust manifold, goes through the process of cooling down and removing particles, enters the engine scavenging box, and then distributes it to each cylinder of the engine Participate in combustion, because the recirculated exhaust gas contains a certain amount of CO ₂ and H ₂ O, which reduces the specific heat of the working medium in the engine cylinder, and at the same time the recirculated exhaust gas reduces the oxygen concentration in the cylinder, reduces the engine combustion temperature, and thus reduces EGR technology is a promising NOx emission control technology for marine diesel engines because it can meet IMO's Tier III emission standards for NOx, and its volume and cost are much smaller than SCR systems.

Ship SOx emission reduction technologies mainly include the use of low-sulfur fuel oil and exhaust gas scrubbing technology. Relatively speaking, it is more convenient to use low-sulfur fuel oil, and the changes to the ship are small. It can meet the IMO requirements for the sulfur content of ship fuel oil. The use of low-sulfur fuel has problems such as low viscosity, poor lubricity, and easy wear, which will cause certain damage to the engine, and low-sulfur fuel will produce a large amount of CO ₂ during the refining process, which will intensify the global warming effect.

As an effective method approved by IMO to remove SOx from ship exhaust gas, the exhaust gas scrubbing technology cleans the exhaust gas produced by burning low-quality high-sulfur heavy oil to remove SOx and meet the IMO requirements on fuel sulfur content. The operation cost of exhaust gas scrubbing is low, but the scrubbing device also has the problem of large volume and certain costs for operation and maintenance.

At present, the research and treatment of ship exhaust NOx and SOx are carried out separately, that is, two sets of different equipment are used to treat NOx and SOx respectively. This exhaust gas series treatment method has huge equipment volume and high back pressure, which has a great impact on the normal operation of the engine, and the equipment investment and operation costs are very high.

So far, there is no integrated treatment device for NOx and SOx emitted by marine diesel engines at home and abroad, which can reduce the size and cost of emission control equipment and reduce emission reduction while meeting IMO's requirements for NOx and SOx emissions. The impact of equipment on ship operating costs and effective space.

Contents of the invention

The purpose of the present invention is to provide a method that can effectively improve the combustion conditions of the engine, reduce the combustion temperature in the cylinder, reduce the NOx generation of the diesel engine and remove the SOx in the exhaust gas, realize the simultaneous reduction of _NOx and SOx in the engine exhaust gas, and meet the requirements of IMO regulations. Marine diesel engine NOx and SOx combined emission reduction device for limiting NOx and SOx emissions from marine diesel engines. The object of the present invention is also to provide a control method of a marine diesel engine NOx and SOx combined emission reduction device.

The marine diesel engine NOx and SOx combined emission reduction device of the present invention comprises the intake system connected between the exhaust manifold connected with the exhaust pipe of the diesel engine and the scavenging box connected with the intake pipe of the oil engine, the intake system The system includes a turbine connected to the exhaust manifold, a compressor driven by the turbine, an air intercooler connected between the outlet of the compressor and the scavenging box, the exhaust manifold connected to the exhaust pipe of the diesel engine and the diesel engine An EGR system is also connected between the scavenging air tanks connected to the intake pipe of the intake pipe, and the EGR system includes a pre-washer connected to the exhaust manifold through a second one-way stop valve, an EGR cooler connected after the pre-washer, and a The EGR scrubber behind the EGR cooler, the EGR droplet catcher connected behind the EGR scrubber, the outlet of the EGR droplet catcher is connected to the fan, and the outlet of the fan is connected to the scavenging box through the third one-way stop valve, so The air intake system also includes a compressed air bypass passage connected between the compressor outlet and the exhaust manifold and includes a first one-way stop valve. A waste gas bypass line is arranged between the turbine inlet and outlet. The waste gas bypass pipe The fourth one-way stop valve is set on the road, the waste gas bypass pipeline is connected to the waste heat boiler, and the waste heat boiler is connected to the waste gas scrubber through a three-way valve or directly connected to the atmosphere.

Marine diesel engine NOx and SOx combined emission reduction device of the present invention can also comprise:

1. An air droplet catcher between the air intercooler and the scavenging air box.

2. The pre-scrubber and EGR scrubber adopt a one-stage or multi-stage spray tower structure, or a packed tower structure.

The control method of marine diesel engine NOx and SOx combined emission reduction device of the present invention is:

Including non-EGR mode and EGR mode;

When the ship is sailing in a non-nitrogen oxide emission control area, the engine is running in non-EGR mode, the second and third one-way stop valves in the EGR system are closed, the exhaust gas of the diesel engine is completely passed into the turbine through the exhaust manifold, and the compressed air passes through the air center The cooler cools down, enters the droplet collector, enters the scavenging air box, and then enters the diesel engine through the intake pipe to participate in combustion; the first one-way stop valve in the compressed air bypass passage is closed, and when the engine is working under high load, the turbine exhaust gas is turned on. The fourth one-way stop valve in the bypass passage bypasses excess exhaust gas;

When the ship is navigating in the nitrogen oxide emission control area, the engine is running in EGR mode, and the second and third one-way stop valves in the EGR system are opened, and most of the exhaust gas of the diesel engine is still passed into the turbine; the rest of the exhaust gas flows into the turbine through the second one-way stop valve. In the EGR system, the temperature of the exhaust gas is reduced by the exhaust gas prewashing device and part of the particles are removed, and then the temperature of the exhaust gas is reduced by the EGR cooler, and then enters the EGR scrubber to remove particles and SOx in the exhaust gas, and then the water droplets carried by the exhaust gas are eliminated by the water droplet catcher, and the exhaust gas passes through The EGR fan pressurizes, enters the scavenging box through the third one-way stop valve and mixes with the pressurized fresh air from the intake passage, and the mixture passes through the intake pipe and enters the engine to participate in combustion, reducing the generation and emission of NOx in the engine; EGR In mode, the fourth one-way stop valve in the turbine waste gas bypass passage is closed, and the first one-way stop valve in the compressed air bypass passage is opened, and the compressor supplies part of the compressed air to the turbine;

The exhaust gas scrubber is divided into two operating modes: non-scrubbing mode and scrubbing mode. When the ship is sailing in the non-sulfur emission control area and non-port area, the non-recirculating exhaust gas passes through the three-way valve after recovering energy from the waste heat boiler. The exhaust gas bypass channel is directly discharged into the ambient atmosphere; when the ship is sailing in the sulfur emission control area or the port area, the non-recirculated exhaust gas, after recovering energy through the waste heat boiler, passes through the three-way valve, and flows into the exhaust gas scrubber through the exhaust gas scrubbing and desulfurization channel. , wash off the SOx and particles, remove the water droplets by the demister at the top of the washing device, and discharge it into the ambient atmosphere; when the ship's exhaust gas washing device is repaired or fails, the exhaust gas will be directly discharged into the waste gas bypass passage through the three-way valve. Atmospheric Environment.

Aiming at the deficiencies of the existing marine diesel engine emission control technology, the present invention proposes a method and device for combined removal of NOx and SOx from marine diesel engines, which can effectively improve the combustion conditions of the engine, reduce the combustion temperature in the cylinder, and reduce the NOx of the diesel engine Generate and remove SOx in exhaust gas, realize simultaneous reduction of _NOx and SOx in engine exhaust gas, and meet IMO regulations on NOx and SOx emissions from marine diesel engines. The main features of the technical solution of the present invention are reflected in:

The marine diesel engine NOx and SOx emission control device of the present invention includes a diesel engine system, an EGR device and an exhaust gas cleaning device attached to the diesel engine system. The EGR device is connected to the exhaust manifold and the scavenging air box, and is provided with a one-way stop valve, an exhaust gas prewashing device, an EGR cooler, an EGR scrubber and an EGR blower. The exhaust gas cleaning device is connected with the exhaust outlet of the waste heat boiler through a three-way valve.

In the diesel engine system, a water droplet catcher is added after the air intercooler.

In the diesel engine system, a turbine waste gas bypass passage is added to communicate with the turbine inlet and outlet.

In the diesel engine system, a compressed air bypass passage is added to communicate with the compressor outlet and the turbine inlet.

In the diesel engine system, the non-recirculating exhaust gas passes through the waste heat boiler, then passes through the three-way valve, or goes to the exhaust gas cleaning device for washing or is directly discharged into the atmosphere.

In the combined emission reduction device, the exhaust gas prewashing device, EGR scrubber and exhaust gas scrubbing device adopt a one-stage or multi-stage spray tower structure, or adopt a packed tower structure.

The main features of the marine diesel engine NOx and SOx joint emission reduction control method of the present invention are:

The marine diesel engine with EGR device is divided into two working modes, non-EGR mode and EGR mode.

Non-EGR mode: When the ship is sailing in a non-nitrogen oxide emission control area, the engine runs in a non-EGR mode, that is, the one-way stop valve in the EGR passage is closed, and the EGR device is not put into operation; at this time, the exhaust gas of the diesel engine passes through the exhaust manifold and all It enters the turbine, works to drive the compressor to work, compresses fresh air, and the compressed air passes through the air intercooler to cool down, enters the water droplet collector, removes the water droplets contained in it, enters the scavenging air box, and then enters the diesel engine through the intake pipe to participate in combustion; In non-EGR mode, the one-way stop valve in the compressed air bypass passage is closed, and when the engine is working under high load, the one-way stop valve in the turbine waste gas bypass passage is opened to bypass excess exhaust gas.

EGR mode: When the ship is sailing in the nitrogen oxide emission control area, the engine runs in the EGR mode, that is, the one-way stop valve in the EGR passage is opened, and the EGR device is put into operation; at this time, most of the exhaust gas of the diesel engine is still passed into the turbine; the rest of the exhaust gas passes through the single Flow into the EGR channel through the stop valve, reduce the temperature of the exhaust gas and remove some particles through the exhaust gas prewashing device, then reduce the temperature of the exhaust gas through the EGR cooler, enter the EGR scrubber to remove particles and SOx in the exhaust gas, and then eliminate the particles and SOx carried by the exhaust gas by the water droplet trap Water droplets and exhaust gas are pressurized by the EGR fan, enter the scavenging box through the one-way stop valve, and mix with the pressurized fresh air from the intake passage. The mixed gas enters the engine through the intake pipe to participate in combustion, reducing the generation of engine NOx and Emission volume: In EGR mode, the one-way stop valve in the turbine exhaust bypass passage is closed, and the one-way stop valve in the compressed air bypass passage is opened, and the compressor supplies part of the compressed air to the turbine.

In EGR mode, the recirculated exhaust gas flow rate (that is, the EGR rate) is adjusted through the EGR fan, so that the NOx emission of the engine can meet the requirements of IMO Tier III under different engine operating conditions.

The one-way stop valve in the turbine exhaust bypass passage is opened in non-EGR mode, which is used to bypass excess exhaust gas from the diesel engine and improve engine efficiency.

The one-way stop valve in the compressed air bypass channel is opened in EGR mode, which is used to supplement part of the compressed air to the turbine and increase the output power of the turbine.

According to whether the exhaust gas scrubber works, the marine diesel engine system is divided into two operating modes, non-scrubbing mode and scrubbing mode.

Non-scrubbing mode: When the ship is sailing in a non-sulfur emission control area and a non-port area, the non-recirculating exhaust gas is directly discharged into the ambient atmosphere through the waste gas bypass passage through the three-way valve after recovering energy through the waste heat boiler.

Scrubbing mode: When a ship is navigating in a sulfur emission control area or a port area, the non-recirculating exhaust gas, after recovering energy through the waste heat boiler, passes through the three-way valve, flows into the exhaust gas scrubbing device through the exhaust gas scrubbing and desulfurization passage, and washes off the SOx and The particles are discharged into the ambient atmosphere after the water droplets are removed by the demister at the top of the washing device.

When the ship exhaust gas scrubber is repaired or fails, the exhaust gas will be directly discharged into the atmosphere through the waste gas bypass passage through the three-way valve.

Compared with the prior art, the present invention has the advantages of:

1. A kind of marine diesel engine NOx and SOx combined emission reduction system that the present invention adopts meets the relevant IMO emission standards for ships that are about to be implemented, that is, both the emission control area and the non-emission control area can meet the IMO relevant NOx and fuel oil sulfur content requirements Require.

2. Compared with the SCR combined exhaust gas scrubbing technical solution, the marine diesel engine NOx and SOx combined emission reduction system adopted by the present invention is small in size, saves the effective space of the ship, has low investment and operating costs, and has little impact on the engine.

3. Before the recirculated exhaust gas enters the engine combustion chamber, it passes through the scrubber and demister to remove SO _X and most of the particles in the exhaust gas, so that the exhaust gas is purified, reducing the particle content entering the diesel engine cylinder, and avoiding engine wear. At the same time, the combustion conditions are significantly improved. By adjusting the engine parameters, the power, economic performance and emission performance of the diesel engine can be improved.

4. After the recirculation exhaust gas is washed, the temperature can be reduced, which increases the intake air volume of the engine and can ensure the engine power.

5. The recirculated low-temperature exhaust gas contains CO ₂ and water vapor. After entering the engine, the content of CO ₂ and water vapor in the working fluid in the cylinder is increased, the oxygen concentration in the cylinder is reduced, and the specific heat of the working fluid in the cylinder is increased. The combustion temperature is reduced, thereby reducing the amount of NO _X produced.

6. Since a set of devices is used to simultaneously remove NOx and SOx in the exhaust gas of the engine, the volume and weight of the device of the present invention are significantly smaller than the sum of the volume and weight of the devices for desulfurization and denitrification respectively, and the operation and maintenance costs are much smaller .

Description of drawings

Fig. 1 is a schematic diagram of a marine diesel engine NOx and SOx combined emission reduction system of the present invention.

detailed description

The present invention will be described in detail below with reference to FIG. 1 .

The marine exhaust NOx and SOx combined emission reduction system of the present invention is suitable for marine power plants, which have: a diesel engine 1, an exhaust manifold 3 connected to the diesel engine 1 through an exhaust pipe 2, and an exhaust manifold 3 arranged on the intake passage. The air intercooler 15 and the droplet catcher 16 are connected to the turbine 12 of the exhaust manifold 3, and the compressor 13 arranged on the intake passage; the intake passage communicates with the outlet of the compressor 13 and the scavenging box 17, including Air intercooler 15 and water droplet collector 16; turbine waste gas bypass passage containing one-way stop valve 11 is directly connected to turbine 12 inlet and waste heat boiler 19 inlet; compressed air bypass passage including one-way stop valve 14 is directly connected to compressed air The outlet of the machine 13 and the inlet of the turbine 12; the exhaust gas scrubbing and desulfurization passage and the waste gas bypass passage controlled by the three-way valve 20.

The EGR device includes: an EGR passage connecting the exhaust manifold 3 and the scavenging air box 17, a one-way stop valve 4 arranged on the EGR passage for controlling the opening of EGR and the flow direction of the exhaust gas; arranged on the EGR passage for preliminary cooling Exhaust gas pre-washing device 5 for pre-washing the exhaust gas; it is installed on the EGR passage, after the exhaust gas pre-washing device 5, it is used to cool the EGR exhaust gas EGR cooler 6; after the EGR cooler 6, it is used for washing the EGR exhaust gas A scrubber 7 for particles and SOx; behind the scrubber 7, a water drop catcher 8 for trapping water droplets in the scrubbed EGR exhaust gas; an EGR blower 9 arranged in the EGR passage for supercharging the EGR exhaust gas; setting In the EGR passage, the one-way stop valve 10 is used to control the opening and closing of the EGR passage and the flow direction of the exhaust gas.

The EGR system of the present invention is divided into two working modes, non-EGR mode and EGR mode.

Non-EGR mode: When the ship is running in a non-nitrogen oxide emission control area, the engine runs in a non-EGR mode, that is, the one-way stop valve 4 and 10 in the EGR passage are closed, and the EGR device is not put into operation; at this time, the exhaust gas of the diesel engine 1 passes through the exhaust The air manifold 3 is all connected to the turbine 12, expands in the turbine 12 to do work, drives the compressor 13 to work, the compressor 13 compresses fresh air, the compressed air passes through the air intercooler 15 to cool down, enters the water droplet collector 16, and removes all Contains water droplets, enters the scavenging air box 17, and then enters the diesel engine 1 through the intake pipe 18, and participates in combustion; in the non-EGR mode, the one-way stop valve 14 in the compressed air bypass passage is closed, and when the engine is working at a high load, the exhaust gas volume of the diesel engine Excess, open the one-way stop valve 11 in the turbine waste gas bypass passage, bypass the excess waste gas, and improve engine efficiency.

EGR mode: when the ship is running in the nitrogen oxide emission control area, the engine runs in the EGR mode, that is, the one-way stop valves 4 and 10 in the EGR passage are opened, and the EGR device is put into operation; at this time, most of the exhaust gas of the diesel engine 1 is still passed into the turbine 12 The rest of the exhaust gas flows into the EGR passage through the one-way stop valve 4, passes through the exhaust gas prewashing device 5, reduces the temperature of the exhaust gas and removes some particles, passes through the EGR cooler 6, reduces the temperature of the exhaust gas, enters the EGR scrubber 7, and removes particles and SOx in the exhaust gas , and then the water droplet catcher 8 eliminates the water droplets carried by the exhaust gas, pressurized by the EGR fan 9, passes through the one-way stop valve 10, enters the scavenging air box 17, and mixes with the pressurized fresh air coming from the intake passage B, mixing The gas passes through the intake pipe 18 and enters the ship's two-stroke diesel engine 1 to participate in combustion, reducing the generation and emission of NOx from the engine; in EGR mode, because the EGR passage is opened, part of the exhaust gas is diverted, so that the flow of exhaust gas flowing through the turbine 12 is insufficient, and it is closed at this time The one-way stop valve 11 in the turbine waste gas bypass passage opens the one-way stop valve 14 in the compressed air bypass passage at the same time, and the compressor 13 supplies part of the compressed air to the turbine 12 to increase the output power of the turbine 12. In the EGR mode, the recirculated exhaust gas flow rate (that is, the EGR rate) is adjusted through the EGR fan 9 in the EGR passage, so that the NOx emission of the engine can meet the requirements of IMO Tier III under different engine operating conditions.

The one-way stop valve 11 in the turbine waste gas bypass passage is opened in the non-EGR mode and closed in the non-EGR mode, and the airflow direction is from the exhaust manifold 3 to the waste heat boiler 19 .

The one-way stop valve 14 in the compressed air bypass passage is closed in the non-EGR mode and opened in the EGR mode, and the airflow direction is from the outlet of the compressor 13 to the inlet of the turbine 12 .

The one-way stop valves 4 and 10 in the EGR passage are closed in non-EGR mode and opened in EGR mode, and the airflow directions are from the exhaust manifold 3 to the exhaust gas prewashing device 5 and from the EGR fan 9 to the scavenging air box 17 respectively.

According to whether the exhaust gas washing device 21 is put into operation, the marine diesel engine system is divided into two operating modes, a non-washing mode and a washing mode.

Non-scrubbing mode: When the ship is navigating in non-sulfur emission control areas and non-port areas, the non-recirculating exhaust gas is discharged into the ambient atmosphere through the waste gas bypass passage through the three-way valve 20 after recovering energy through the waste heat boiler 19 .

Scrubbing mode: When a ship is navigating in a sulfur emission control area or a port area, the non-recirculated exhaust gas, after recovering energy through the waste heat boiler 19, passes through the three-way valve 20, flows into the exhaust gas scrubber 21 through the exhaust gas scrubbing and desulfurization passage, and washes off the exhaust gas. Among them, SOx and particles are discharged into the ambient atmosphere after the demister at the top of the washing device removes water droplets.

When the exhaust gas scrubber of the ship is maintained or fails, the exhaust gas passes through the three-way valve 20 and is directly discharged into the atmosphere through the exhaust gas bypass passage.

Claims (4)

1. null1. boat diesel engine NOx and SOx combines emission reduction device，It is included between exhaust manifold and the scavenging air box being connected with the air inlet pipe of diesel engine that the exhaustor with diesel engine is connected the gas handling system being connected，Described gas handling system includes the turbine being communicated to exhaust manifold、By turbo-driven compressor、The air intercooler being connected between blower outlet and scavenging air box，It is characterized in that: between the scavenging air box that the air inlet pipe of the exhaust manifold being connected with the exhaustor of diesel engine and diesel engine is connected, be also connected with egr system，Described egr system includes the waste gas prewashing device being connected by the second unidirectional stop valve with exhaust manifold、It is connected to the cooler for recycled exhaust gas after waste gas prewashing device、It is connected to the EGR scrubber after cooler for recycled exhaust gas、It is connected to the EGR water droplet catcher behind EGR scrubber，The outlet connecting fan of EGR water droplet catcher，The outlet of blower fan is connected with scavenging air box by the 3rd unidirectional stop valve，Described gas handling system also includes the compressed air bypass comprising the first unidirectional stop valve being connected between blower outlet and exhaust manifold，Between turbine is imported and exported, exhaust gas bypass pipeline is set，4th unidirectional stop valve is set on exhaust gas bypass pipeline，Exhaust gas bypass pipeline connects waste heat boiler，Connect exhaust gas scrubber by three-way valve after waste heat boiler or directly connect air.
2. Boat diesel engine NOx and SOx the most according to claim 1 combines emission reduction device, it is characterized in that: arrange air water droplet catcher between in atmosphere between cooler and scavenging air box.
3. Boat diesel engine NOx and SOx the most according to claim 1 and 2 combines emission reduction device, it is characterized in that: described waste gas prewashing device and EGR scrubber use one or more levels spray column structure, or use packed tower structure.
4. 4. a control method for boat diesel engine NOx and the SOx associating emission reduction device described in claim 1, is characterized in that:

   Including non-EGR mode and EGR mode；

   When boats and ships navigate by water in non-discharged nitrous oxides control zone, electromotor operates in non-EGR mode, close second and third unidirectional stop valve in egr system, the waste gas of diesel engine is all passed through turbine by exhaust manifold, compressed air is lowered the temperature through air intercooler, enters water droplet catcher, enters scavenging air box, again by air inlet pipe, enter diesel engine and participate in burning；The first unidirectional stop valve in compressed air bypass is closed, and when high engine load works, opens the 4th unidirectional stop valve in turbine exhaust bypass, bypasses unnecessary waste gas；

   When boats and ships navigate by water in discharged nitrous oxides control zone, electromotor operates in EGR mode, opens second and third unidirectional stop valve in egr system, and diesel engine major part waste gas is still passed through turbine；Remaining waste gas flows into egr system by the second unidirectional stop valve, reduce EGT through waste gas prewashing device and remove partial particulate, EGT is reduced again through cooler for recycled exhaust gas, enter EGR scrubber and remove granule and SOx in waste gas, the water droplet that waste gas carries is eliminated again by water droplet catcher, waste gas is pressurizeed by EGR blower fan, scavenging air box and the pressurised fresh air mixing come by intake channel is entered through the 3rd unidirectional stop valve, gaseous mixture passes through air inlet pipe, enter electromotor and participate in burning, reduce generation and the discharge capacity of electromotor NOx；Under EGR mode, the 4th unidirectional stop valve in turbine exhaust bypass is closed, and opens the first unidirectional stop valve in compressed air bypass, compressor supplements Partial shrinkage air to turbine；

   Exhaust gas scrubber is divided into non-washing mode and two kinds of operational modes of washing mode, when boats and ships navigate by water in non-sulphur emissions control zone and non-port area, the waste gas of non-recirculated, after waste heat boiler recovers energy, through three-way valve, exhaust gas bypass path it is directly discharged into ambient air；When boats and ships navigate by water in sulphur emissions control zone or port area, the waste gas of non-recirculated, after waste heat boiler recovers energy, through three-way valve, by waste gas washing desulphurization path inflow exhaust gas wash mill, wherein SOx and granule are sloughed in washing, after water droplet removed by exhaust gas scrubber top demister, enter ambient air；When exhaust gas scrubber keeps in repair or breaks down, waste gas, through three-way valve, is directly discharged into atmospheric environment by exhaust gas bypass path.