Waste gas and waste heat utilization system and method of marine dual-fuel engine

Abstract

The invention discloses a waste gas and waste heat utilization system and method for a marine dual-fuel engine. The waste gas and waste heat utilization system comprises an exhaust collecting pipe, a scavenging collecting pipe, a turbine, a gas compressor, an ICER system, a power turbine, a generator, a waste heat boiler and an evaporator. The power turbine technology and the ICER technology are combined and adopted, waste heat energy in waste gas is recycled, meanwhile, emission of NOx in the waste gas is reduced, and according to different operation working conditions, switching is conducted between a waste gas recirculation power generation mode and a waste gas bypass power generation mode, so that waste heat utilization maximization is achieved. According to the invention, the emission of NOx is reduced, the marine engine is ensured to meet the requirements of ship emission regulations, and two different switchable application modes, namely an exhaust gas recirculation power generation mode and an exhaust gas bypass power generation mode, are provided for different operation working conditions of a main engine; two waste heat utilization modes including power turbine power generation and waste gas heat exchange after acting are achieved, waste heat energy is fully utilized, the maximum utilization of waste heat of a main engine under all working conditions is achieved, the comprehensive heat efficiency is improved, and the ship operation economical efficiency is improved.

Description

Technical Field

[0001] The present invention relates to an operating system of a marine low-speed diesel engine, and particularly to a waste gas and waste heat utilization system and method for a marine dual-fuel engine, belonging to the technical field of marine diesel engines. Background Art

[0002] In view of the increasingly strict regulations on ship emissions, in order to meet the requirements, it is urgent to use new fuel engines. At present, heavy-duty dual-fuel main engines are the main power of large ships, and their energy conservation and emission reduction are particularly important. Ship waste heat recovery belongs to the secondary utilization of thermal energy, which is to improve the fuel thermal efficiency and meet the rigid index requirements of EEDI (Energy Efficiency Design Index for Ships). The intelligent control exhaust gas recirculation (ICER) technology is to introduce the exhaust gas after cooling and purification treatment into the cylinder again, reduce the oxygen content, increase the working medium heat capacity, reduce the combustion rate and combustion temperature, so as to achieve the effect of reducing Nox emissions.

[0003] At present, the engine and computer-aided engineering technologies have become mature, and the improvement space for optimizing the engine structure or in-cylinder combustion to reduce ship energy consumption is very limited. And the existing application of ICER technology is generally to reduce NOx emissions, but the waste gas energy in the ICER system is wasted in vain. Therefore, how to achieve ship energy conservation and emission reduction through waste heat recovery and combustion regulation has become a technical problem in this field. Summary of the Invention

[0004] The purpose of the present invention is to provide a waste gas and waste heat utilization system and method for a marine dual-fuel engine, which can recover part of the heat in the waste gas while adopting the ICER technology to reduce NOx emissions, so as to improve the comprehensive thermal efficiency and reduce the operating cost.

[0005] To achieve the above purpose, on the one hand, the present invention provides a waste gas and waste heat utilization system for a marine dual-fuel engine, which is connected to a dual-fuel main engine and includes an exhaust manifold, a scavenging manifold, a turbine, a compressor, an ICER system, a power turbine, a generator, a waste heat boiler and an evaporator;

[0006] The exhaust manifold is connected to the exhaust gas outlet of the dual-fuel main engine, the scavenging manifold is connected to the inlet of the dual-fuel main engine, the turbine and the compressor are coaxially connected, the inlet of the turbine is connected to the exhaust manifold, the outlet is connected to the waste heat boiler, the inlet of the compressor sucks in fresh air, the outlet is connected to the scavenging manifold and is connected to the inlet of the turbine through a third valve group, the power turbine is coaxially connected to the generator, the inlet is connected to the exhaust manifold through a first valve group, and the outlets are respectively connected to the ICER system through a second valve group and to the waste heat boiler through a fourth valve group. The outlet of the ICER system is connected to the scavenging manifold. The evaporator is arranged in the waste heat boiler for heat exchange to obtain the waste heat of the exhaust gas.

[0007] The exhaust gas generated by the dual-fuel main engine is introduced into the exhaust manifold. A part of the exhaust gas drives the generator to generate electricity through the power turbine, and then enters the ICER system for treatment, and then is mixed with fresh air and re-enters the dual-fuel main engine to form an exhaust gas utilization loop. Another part of the exhaust gas enters the turbine to drive the compressor to compress fresh air, and the exhausted gas comes out and enters the waste heat boiler, and the waste heat recovery is completed by heat exchange with the evaporator to form a waste heat utilization loop.

[0008] In another aspect, the present invention provides a method for utilizing the exhaust gas and waste heat of a marine dual-fuel engine, which combines the power turbine technology and the ICER technology to recover the waste heat energy in the exhaust gas and at the same time reduce the NOx emission in the exhaust gas. According to different operating conditions, it switches between the exhaust gas recirculation power generation mode and the exhaust gas bypass power generation mode to maximize the waste heat utilization.

[0009] Preferably, the exhaust gas recirculation power generation mode includes: opening the first valve group and the second valve group, closing the fourth valve group. The exhaust gas from the exhaust manifold enters the power turbine to drive the generator to generate electricity. The exhausted gas after power generation enters the ICER system for treatment, and then is mixed with fresh air and then enters the dual-fuel main engine for combustion.

[0010] The exhaust gas bypass power generation mode includes: opening the first valve group and the fourth valve group, closing the second valve group, stopping the operation of the ICER system. The exhaust gas from the exhaust manifold enters the power turbine to drive the generator to generate electricity. The exhausted gas after power generation enters the waste heat boiler and exchanges heat with the evaporator (0) to complete the waste heat utilization.

[0011] Preferably, the third valve group is a cylinder bypass valve, which is opened in the exhaust gas recirculation power generation mode to keep the operating point of the compressor basically unchanged.

[0012] Preferably, when the ICER system fails or under the low load condition of TIER II, the first valve group is closed.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0014] Firstly, the present invention adopts the ICER technology to reduce the NOx emissions and ensure that the marine engine meets the requirements of the ship emission regulations. Secondly, the present invention utilizes the power turbine to recover part of the heat in the exhaust gas, improving the overall thermal efficiency. Moreover, for different operating conditions of the main engine, different application modes are provided, realizing two waste heat utilization methods including power turbine power generation and heat exchange of the exhaust gas after work in the waste heat boiler, fully utilizing the waste heat energy of the dual-fuel main engine and achieving the maximization of waste heat utilization of the main engine under all operating conditions.

[0015] In summary, by combining the power turbine with the ICER system, the present invention not only reduces the pollutant emissions, but also fully converts the exhaust gas energy into electric energy and heat energy, realizing energy conservation and emission reduction. Brief Description of the Drawings

[0016] Figure 1 It is the system schematic diagram of the present invention.

[0017] In the figure, 1 - dual-fuel main engine, 2 - exhaust manifold, 3 - turbine, 4 - compressor, 5 - scavenging manifold, 6 - power turbine, 7 - ICER system, 8 - generator, 9 - waste heat boiler, 10 - evaporator, 11 - air, 101 - first valve group, 102 - second valve group, 103 - third valve group, 104 - fourth valve group. Detailed Embodiments

[0018] The preferred embodiments of the present invention will be described in detail below in conjunction with the drawings to more clearly understand the structure and usage process of the present invention, but the protection scope of the present invention cannot be limited thereby.

[0019] The present invention is used for the exhaust gas and waste heat utilization of a marine dual-fuel engine; it adopts the power turbine technology to recover the heat in the exhaust gas and improve the thermal efficiency of the main engine. At the same time, it adopts the ICER technology to reduce the NOx emissions in the exhaust gas; and corresponding application modes are proposed for this system, including the exhaust gas recirculation power generation mode (ICER-GE) and the exhaust gas bypass power generation (EGB-GE) mode, so that the system energy can be efficiently utilized.

[0020] Embodiment

[0021] Refer to Figure 1As shown in the figure, the exhaust gas and waste heat utilization system of the marine dual-fuel engine described in the present invention is connected to the dual-fuel main engine 1, and includes an exhaust manifold 2, a scavenging manifold 5, a turbine 3, a compressor 4, an ICER system 7, a power turbine 6, a generator 8, a waste heat boiler 9, and an evaporator 10.

[0022] The exhaust manifold 2 is connected to the exhaust gas outlet of the dual-fuel main engine 1, and the scavenging manifold 5 is connected to the inlet of the dual-fuel main engine 1. The turbine 3 and the compressor 4 are coaxially connected. The inlet of the turbine 3 is connected to the exhaust manifold 2, and the outlet of the turbine 3 is connected to the waste heat boiler 9. The inlet of the compressor 4 sucks in fresh air, and the outlet is connected to the scavenging manifold 5 and is connected to the inlet of the turbine 3 through a third valve group 103. The power turbine 6 is coaxially connected to the generator 8. The inlet of the power turbine 6 is connected to the exhaust manifold 2 through a first valve group 101, and the outlet is respectively connected to the ICER system 7 through a second valve group 102 and to the waste heat boiler 9 through a fourth valve group 104. The evaporator 10 is arranged in the waste heat boiler 9 for heat exchange to obtain waste heat of the exhaust gas. The outlet of the ICER system 7 is connected to the scavenging manifold 5.

[0023] The operation process of the system is as follows:

[0024] The exhaust gas generated by the dual-fuel main engine 1 is first introduced into the exhaust manifold 2, and the exhaust gas is divided into two parts:

[0025] One part of the exhaust gas drives the generator 8 to generate electricity through the power turbine 6, and then enters the ICER system 7 for washing and dehumidification treatment. The treated exhaust gas is then mixed with the fresh air from the compressor 4, and then re-enters the dual-fuel main engine 1 to form a loop. This part of the exhaust gas completes a waste heat utilization before entering the ICER system 7.

[0026] Another part of the exhaust gas enters the turbine 3 to drive the compressor 4 to compress fresh air to ensure the normal operation of the dual-fuel main engine 1; the exhaust gas coming out of the turbine 3 enters the waste heat boiler 9, and through heat exchange with the evaporator 10, the waste heat recovery after power generation is completed, and the exhaust gas after heat exchange is discharged to the atmosphere.

[0027] The third valve group 103 is a cylinder bypass valve. The third valve group 103 can be opened in the intelligent control exhaust gas recirculation (ICER) mode to make up for the power reduction of the turbocharger, so as to keep the working point of the compressor 4 basically unchanged.

[0028] When the ICER system fails or under the TIER II low load condition, the first valve group 101 can be closed.

[0029] The present invention provides two operation method modes for waste gas and waste heat utilization. According to different system operation conditions, the operation mode is switched to maximize the waste heat utilization rate. Please refer to Figure 1 .

[0030] I. Inlet Gas Recirculation for Electricity Generation (ICER-GE) mode -

[0031] Open the first valve group 101 and the second valve group 102, close the fourth valve group 104, and operate the Inlet Gas Recirculation for Electricity Generation (ICER-GE) mode; the high-temperature and high-pressure waste gas from the exhaust manifold 2 enters the power turbine 6, drives the generator 8 to generate electricity, and the used waste gas enters the ICER system 7 for washing and dehumidification treatment, and then is mixed with the fresh air from the compressor 4 and enters the cylinder of the dual-fuel main engine 1 for combustion. While the power turbine 6 utilizes the waste gas energy to generate electricity, the normal operation of the ICER system 7 ensures that the dual-fuel main engine 1 meets the TIER III waste gas emission standard.

[0032] II. Exhaust Gas Bypass for Electricity Generation (EGB-GE) mode -

[0033] Open the first valve group 101 and the fourth valve group 104, close the second valve group 102, stop operating the ICER system 7, and operate the Exhaust Gas Bypass for Electricity Generation (EGB-GE) mode; the high-temperature and high-pressure waste gas from the exhaust manifold 2 enters the power turbine 6, drives the generator 8 to generate electricity, and the waste gas after power generation enters the waste heat boiler 9, where it exchanges heat with water in the evaporator 10 to generate domestic steam, completing the final waste heat utilization. In the Exhaust Gas Bypass for Electricity Generation (EGB-GE) mode, the load of the dual-fuel main engine 1 is relatively high, but it still meets the TIER II emission standard.

[0034] It should be understood that in practical applications, corresponding control strategies are respectively proposed for different operation modes of the dual-fuel main engine, so that the system can achieve high energy efficiency and low emissions in each operation mode, improving economic benefits.

[0035] The above is only the preferred embodiment of the present invention. It must be pointed out that all equivalent modifications, changes and corrections made by those skilled in the art according to the content of the present invention application should fall within the protection scope of the present invention.

Claims

1. An exhaust gas and waste heat utilization system for a marine dual-fuel engine, characterized in that, The described waste gas and waste heat utilization system is connected to a dual-fuel main engine (1), and includes an exhaust manifold (2), a scavenging manifold (5), a turbine (3), a compressor (4), an ICER system (7), a power turbine (6), a generator (8), a waste heat boiler (9), and an evaporator (10). The exhaust manifold (2) is connected to the waste gas outlet of the dual-fuel main engine (1), the scavenging manifold (5) is connected to the inlet of the dual-fuel main engine (1), the turbine (3) and the compressor (4) are coaxially connected. The inlet of the turbine (3) is connected to the exhaust manifold (2), and the outlet is connected to the waste heat boiler (9). The inlet of the compressor (4) sucks in fresh air, and the outlet is connected to the scavenging manifold (5) and is connected to the inlet of the turbine (3) through a third valve group (103). The power turbine (6) is coaxially connected to the generator (8), the inlet is connected to the exhaust manifold (2) through a first valve group (101), and the outlet is respectively connected to the ICER system (7) through a second valve group (102) and to the waste heat boiler (9) through a fourth valve group (104). The outlet of the ICER system (7) is connected to the scavenging manifold (5). The evaporator (10) is arranged in the waste heat boiler (9) for obtaining waste heat from the exhaust gas through heat exchange. The waste gas generated by the dual-fuel main engine (1) is introduced into the exhaust manifold (2). A part of the waste gas drives the generator (8) to generate electricity through the power turbine (6), and then enters the ICER system (7) for treatment, and then is mixed with fresh air and re-enters the dual-fuel main engine (1) to form a waste gas utilization loop. Another part of the waste gas enters the turbine (3) to drive the compressor (4) to compress fresh air, and the exhausted waste gas enters the waste heat boiler (9) to complete waste heat recovery through heat exchange with the evaporator (10) to form a waste heat utilization loop.

2. A method for utilizing the exhaust gas and waste heat of a marine dual-fuel engine implemented by the system according to claim 1, characterized in that By combining the power turbine technology and the ICER technology, the waste heat energy in the waste gas is recovered, and at the same time, the emission of NOx in the waste gas is reduced. According to different operating conditions, it is switched between the waste gas recirculation power generation mode and the waste gas bypass power generation mode to maximize waste heat utilization.

3. The method for utilizing exhaust gas and waste heat of a marine dual-fuel engine according to claim 2, characterized in that The described waste gas recirculation power generation mode includes: opening the first valve group (101) and the second valve group (102), closing the fourth valve group (104). The waste gas from the exhaust manifold (2) enters the power turbine (6), drives the generator (8) to generate electricity, and the exhausted waste gas after power generation enters the ICER system (7) for treatment, and then is mixed with fresh air and enters the dual-fuel main engine (1) for combustion. The described waste gas bypass power generation mode includes: opening the first valve group (101) and the fourth valve group (104), closing the second valve group (102), stopping the operation of the ICER system (7). The waste gas from the exhaust manifold (2) enters the power turbine (6), drives the generator (8) to generate electricity, and the exhausted waste gas after power generation enters the waste heat boiler (9) to perform heat exchange with the evaporator ((1)0) to complete waste heat utilization.

4. The method for utilizing exhaust gas and waste heat of a marine dual-fuel engine according to claim 3, characterized in that The third valve group (103) described above is a cylinder bypass valve, which is opened in the waste heat recovery power generation mode to keep the operating point of the compressor (4) basically unchanged.

5. The method for utilizing exhaust gas and waste heat of a marine dual-fuel engine according to claim 3, characterized in that, When a failure occurs in the ICER system (7) or under the TIER II low load condition, the first valve group (101) is closed.

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