Waste gas treatment system and method suitable for dual-fuel main engine ship

Abstract

The waste gas treatment system comprises a cavity communicated with a flue, the interior of the cavity is divided into a heat exchange cavity and a reaction cavity through a vertical partition plate, and the reaction cavity is divided into a first catalytic reaction chamber and a second catalytic reaction chamber through a horizontal partition plate; an ammonia spraying device is mounted at the top of the second catalytic reaction chamber, a heat exchanger is mounted in the heat exchange cavity, a thermal medium inlet of the heat exchanger is communicated with the waste gas inlet, a thermal medium outlet of the heat exchanger is communicated with a gas inlet of the first catalytic reaction chamber, and a cold source inlet of the heat exchanger is communicated with a gas outlet of the second catalytic reaction chamber; a cold source outlet of the heat exchanger is communicated with the waste gas outlet. According to the device, heat exchange, heating and catalytic reaction are integrated, the occupied space of the device is reduced, a small amount of HC left in tail gas can be fully decomposed by arranging the first catalytic reaction chamber with the heating device, the waste gas is fully decomposed by arranging the second catalytic reaction chamber, and the treatment efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of ship exhaust gas treatment, and particularly to an exhaust gas treatment system and method applicable to ships with dual-fuel main engines. Background Art

[0002] With the increasingly strict requirements of the International Maritime Organization (IMO) for ship emissions, ship exhaust gas treatment technology has become the focus of the industry. Dual-fuel main engines (diesel + LNG or diesel + methanol) have gradually become an important choice for ship power due to their low carbon emissions and fuel flexibility. However, when the dual-fuel main engine switches fuels, the NOx concentration in the exhaust gas will change, and traditional exhaust gas treatment technologies are difficult to adapt to this dynamic change, resulting in unstable treatment effects. In addition, traditional treatment processes mainly focus on improving the engine group and the supporting external exhaust gas circulation system, and the treatment effects are average and cannot meet the increasingly strict exhaust gas emission standards. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide, in view of the deficiencies of the prior art, an exhaust gas treatment system applicable to ships with dual-fuel main engines that is reasonably designed, simple in structure, stable in operation, low in maintenance cost.

[0004] Another technical problem to be solved by the present invention is to provide, in view of the deficiencies of the prior art, an exhaust gas treatment method that dynamically adjusts the treatment process according to the fuel type (diesel, LNG, methanol) to ensure stable exhaust gas treatment effects.

[0005] To achieve the above object, the present invention adopts the following technical solutions: An exhaust gas treatment system applicable to ships with dual-fuel main engines, characterized in that the system includes a cavity communicated with a flue. The cavity is divided into a heat exchange chamber and a reaction chamber by a vertical partition. An exhaust gas inlet is provided at the bottom of the heat exchange chamber, and an exhaust gas outlet is provided at the top of the heat exchange chamber. A heat exchanger is installed in the heat exchange chamber. The reaction chamber is divided into a first catalytic reaction chamber equipped with a CO catalyst layer and a second catalytic reaction chamber equipped with an SCR catalyst layer by a horizontal partition. A spray ammonia device is installed at the top of the second catalytic reaction chamber. Ventilation holes for communicating adjacent chambers are installed on the vertical partition and the horizontal partition; the heat medium inlet of the heat exchanger is communicated with the exhaust gas inlet, the heat medium outlet of the heat exchanger is communicated with the air inlet of the first catalytic reaction chamber, the cold source inlet of the heat exchanger is communicated with the air outlet of the second catalytic reaction chamber, and the cold source outlet of the heat exchanger is communicated with the exhaust gas outlet; The spray ammonia device includes a horizontally arranged spray ammonia pipe and a plurality of nozzles arranged side by side along the spray ammonia pipe. The nozzles are arranged on the spray ammonia pipe inside the flue. One end of the spray ammonia pipe is fixed on the inner wall of the flue, and the other end of the spray ammonia pipe extends out of the flue and is connected with an ammonia inlet pipe. A regulating valve for adjusting the liquid ammonia injection amount is installed on the ammonia inlet pipe.

[0006] The technical problem to be solved by the present invention can also be achieved by the following technical solution. The first catalytic reaction chamber is provided with a heating chamber and a CO catalytic reaction chamber. The heating chamber is arranged on the inlet side of the CO catalytic reaction chamber, and a heating device is installed in the heating chamber.

[0007] The technical problem to be solved by the present invention can also be achieved by the following technical solution. The heating device is an electric heater.

[0008] The technical problem to be solved by the present invention can also be achieved by the following technical solution. Flange structures connected to the flue are provided at the waste gas inlet and the waste gas outlet of the cavity.

[0009] The technical problem to be solved by the present invention can also be achieved by the following technical solution. The system further includes a controller, an NH3 on-line analyzer, and a NOx concentration sensor installed on the waste gas inlet pipeline. The NOx concentration sensor and the NH3 on-line analyzer are signal-connected to a regulating valve through the controller to ensure efficient reduction of NOx.

[0010] The technical problem to be solved by the present invention can also be achieved by the following technical solution. A cold fluid bypass pipeline for avoiding the risk of over-temperature is provided between the cold source inlet and the cold source outlet of the heat exchanger, and the reserved opening is adjusted orderly through real-time monitoring of the system temperature.

[0011] The technical problem to be solved by the present invention can also be achieved by the following technical solution. Both the CO catalyst layer and the SCR catalyst layer are provided with several layers of base nets. The surface of the base net of the CO catalyst layer is coated with a platinum material layer or a palladium material layer, and the surface of the base net of the SCR catalyst layer is coated with a vanadium-based material layer or an iron-based material layer. The catalyst adopts noble metals and vanadium-based or iron-based materials, and can adapt to the treatment requirements of different NOx concentrations and HC left over from incomplete combustion.

[0012] An exhaust gas treatment method for an exhaust gas treatment system of a ship using the above-mentioned dual-fuel main engine is characterized in that the method is as follows: The exhaust gas is discharged from the ship's main engine, enters the exhaust gas inlet of the catalytic reaction integrated machine through the flue, enters the hot medium inlet of the heat exchanger from the exhaust gas inlet, is discharged from the hot medium outlet of the heat exchanger, enters the heating chamber, is heated by the heating device, then enters the CO catalytic reaction chamber, and the HC is reduced to carbon dioxide (CO2) and water (H2O) through the catalyst material layer coated with platinum or palladium on the surface of the chamber. Then it enters the second catalytic reaction chamber, where a chemical reaction occurs with the urea solution sprayed by the ammonia injection device. Under the action of the catalyst material layer coated with vanadium-based or iron-based on the surface of the second catalytic reaction chamber, the NOx is reduced to nitrogen and water, and the reacted nitrogen is discharged through the cold source inlet and the cold source outlet of the heat exchanger.

[0013] The technical problem to be solved by the present invention can also be achieved by the following technical solution. In this method, the injection amount of urea solution is dynamically adjusted according to the NOx concentration in the waste gas. The specific adjustment method is as follows: When the NOx concentration ≤ 30 ppm, the opening degree of the regulating valve is controlled at 30% - 45%; When 30 ppm < NOx concentration < 50 ppm, the opening degree of the regulating valve is controlled at 45% - 60%; When 50 ppm ≤ NOx concentration < 80 ppm, the opening degree of the regulating valve is controlled at 60% - 80%; When 80 ppm ≤ NOx concentration < 100 ppm, the opening degree of the regulating valve is controlled at 80% - 95%; When the NOx concentration ≥ 100 ppm, the opening degree of the regulating valve is controlled at 95% - 100%; This can better ensure the waste gas treatment effect.

[0014] Compared with the prior art, the present invention integrates heat exchange, heating and catalytic reaction by setting a heat exchange chamber, a first catalytic reaction chamber and a second catalytic reaction chamber in a cavity, reducing the occupied space of the device. By setting the first catalytic reaction chamber with a heating device, a small amount of HC remaining in the tail gas can be fully decomposed. By setting the second catalytic reaction chamber, the waste gas can be fully decomposed, improving the treatment efficiency. The heat of the gas path is recycled by the heat exchanger, improving the system operation efficiency and reducing the tail gas emission temperature. By setting sensors and controllers, the injection amount of urea solution can be dynamically adjusted according to the NOx concentration in the waste gas, improving the automation of the system.

[0015] The waste gas treatment system and method of the present invention are applicable to the ship application scenarios (humid, corrosive, shaking), applicable to dual-fuel main engine ships, and can dynamically adjust the treatment process according to the fuel type (diesel, LNG, methanol) to ensure stable waste gas treatment effect. Adopting the integrated technology of HC catalysis and SCR, the overall exhaust concentration of NOx + HC after treatment meets the increasingly stringent IMO emission standards compared with the inlet concentration. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is the schematic diagram of the waste gas treatment method applicable to dual-fuel main engine ships of the present invention; Figure 2 It is the structural diagram of the waste gas treatment system applicable to dual-fuel main engine ships of the present invention; Figure 3 It is for Figure 1 the left view; Figure 4 It is for Figure 1 the top view.

[0017] In the figure: 1 - flue, 2 - NOx concentration sensor, 3 - heat exchanger, 4 - heater, 5 - CO catalyst layer, 6 - ammonia injection device, 7 - SCR catalyst layer, 8 - cavity, 9 - heat exchange cavity, 10 - heating cavity, 11 - CO catalytic reaction cavity, 12 - second catalytic reaction chamber. Detailed implementation manners

[0018] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0019] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0020] Referring to Figures 1-4 , an exhaust gas treatment system applicable to a ship with a dual-fuel main engine, the system includes a cavity 8 communicated with the flue 1, the bottom of the cavity 8 is provided with an exhaust gas inlet, the top of the cavity is provided with an exhaust gas outlet, the cavity 8 is separated into a heat exchange cavity 9 and a reaction cavity by a vertical partition, the reaction cavity is separated into a first catalytic reaction chamber equipped with a CO catalyst layer and a second catalytic reaction chamber 12 equipped with an SCR catalyst layer by a horizontal partition, ventilation holes communicating adjacent chambers are installed on the vertical partition and the horizontal partition, an ammonia injection device 6 is installed on the top of the second catalytic reaction chamber 12, a heat exchanger 3 is installed in the heat exchange cavity 9, the heat medium inlet of the heat exchanger 3 is communicated with the exhaust gas inlet, the heat medium outlet of the heat exchanger 3 is communicated with the air inlet of the first catalytic reaction chamber, the cold source inlet of the heat exchanger 3 is communicated with the air outlet of the second catalytic reaction chamber, the cold source outlet of the heat exchanger 3 is communicated with the exhaust gas outlet, the heat exchanger 3 is inclined along the axis of the flue to realize the cross-flow of the flue gas, and better heat exchange can be achieved. Both the CO catalyst layer 5 and the SCR catalyst layer 7 are provided with several layers of base nets, the surface of the base net of the CO catalyst layer is coated with a platinum material layer or a palladium material layer, and the surface of the base net of the SCR catalyst layer is coated with a vanadium-based material layer or an iron-based material layer; The ammonia injection device 6 includes a horizontally arranged ammonia injection pipeline and several nozzles arranged side by side along the ammonia injection pipeline, the nozzles are arranged on the ammonia injection pipeline in the flue, one end of the ammonia injection pipeline is fixed on the inner wall of the flue, the other end of the ammonia injection pipeline extends out of the flue and is connected with an ammonia inlet pipeline, and a regulating valve for adjusting the liquid ammonia injection amount is installed on the ammonia inlet pipeline.

[0021] The first catalytic reaction chamber is provided with a heating chamber 10 and a CO catalytic reaction chamber 11. The heating chamber 9 is arranged on the inlet side of the CO catalytic reaction chamber 11. A heating device is installed in the heating chamber 9, and the heating device 4 is an electric heater.

[0022] Flange structures connected to the flue are provided at the exhaust gas inlet and the exhaust gas outlet of the cavity, facilitating quick and convenient installation.

[0023] The system further includes a controller, an NH3 online analyzer, and a NOx concentration sensor 2 installed on the exhaust gas inlet pipeline. The NOx concentration sensor 2 and the NH3 online analyzer are signal-connected to the regulating valve through the controller.

[0024] A cold fluid bypass pipeline to avoid the risk of over-temperature is provided between the cold source inlet and the cold source outlet of the heat exchanger 3.

[0025] Exhaust gas is discharged from the ship's main engine, enters the exhaust gas inlet of the catalytic reaction integrated machine through the flue, enters the hot medium inlet of the heat exchanger 3 from the exhaust gas inlet, is discharged from the hot medium outlet through the heat exchanger 3, enters the heating chamber 9, is heated by the heating device 4, then enters the CO catalytic reaction chamber 11, and passes through the catalyst material layer with platinum or palladium coated on the surface of this chamber to reduce HC to carbon dioxide (CO2) and water (H2O). Then it enters the second catalytic reaction chamber 12, where it undergoes a chemical reaction with the urea solution sprayed down by the ammonia injection device 6. Under the action of the catalyst material layer with vanadium-based or iron-based coated on the surface in the second catalytic reaction chamber 12, NOx is reduced to nitrogen (N2) and water (H2O). The reacted nitrogen is discharged through the cold source inlet and the cold source outlet of the heat exchanger 3. In this method, the injection amount of the urea solution is dynamically adjusted according to the NOx concentration in the exhaust gas. The specific adjustment method is as follows: When the NOx concentration ≤ 30 ppm, the opening degree of the regulating valve is controlled at 30% - 45%; When 30 ppm < NOx concentration < 50 ppm, the opening degree of the regulating valve is controlled at 45% - 60%; When 50 ppm ≤ NOx concentration < 80 ppm, the opening degree of the regulating valve is controlled at 60% - 80%; When 80 ppm ≤ NOx concentration < 100 ppm, the opening degree of the regulating valve is controlled at 80% - 95%; When the NOx concentration ≥ 100 ppm, the opening degree of the regulating valve is controlled at 95% - 100%. Here, the opening degree of 100% of the regulating valve refers to the state where the regulating valve is fully opened.

[0026] The function of the HC catalytic and selective catalytic reduction unit (SCR) integrated reactor in the present invention is to remove NOx components and HC components from the tail gas. The selective catalytic reduction denitration technology is the most widely used denitration technology in the world. It has no by-products, does not form secondary pollution, has a simple device structure, and has a high removal efficiency (up to more than 95%), reliable operation, and is easy to maintain. The main working principle of the SCR technology is to mix NH3 and the NOx-containing waste gas evenly and then pass them through a reactor filled with a special catalyst. NOx and NH3 undergo a reduction reaction in the reactor to generate N2 and H2O. The denitration catalyst is generally placed in multiple orders to reduce the system resistance. The HC catalyst selects a noble metal catalyst, which can effectively decompose HC in the engine tail gas under the reaction temperature environment.

[0027] When the fuel is diesel, LNG, methanol, or their combination, the control system of the waste gas treatment device adjusts the urea injection amount according to the NOx inlet concentration to ensure that the overall exhaust concentration of NOx + HC after treatment meets the IMO or other relevant emission standards.

[0028] Dynamic adjustment function: The device is equipped with a NOx concentration sensor and a fuel type identification system, which can monitor the NOx concentration and fuel type in the waste gas in real time, and dynamically adjust the urea injection amount and the catalyst working state through the control system to ensure stable treatment effect.

[0029] The control of the ammonia injection amount will be real-time controlled by the NOx and NH3 online analyzers.

[0030] As mentioned above, it is only the preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. An exhaust gas treatment system suitable for dual-fuel main engine ships, characterized in that: The system is installed in the middle of the flue, and includes a cavity communicated with the flue, wherein a heat exchange cavity and a reaction cavity are separated by a vertical partition, an exhaust gas inlet is provided at the bottom of the heat exchange cavity, an exhaust gas outlet is provided at the top of the heat exchange cavity, a heat exchanger is installed in the heat exchange cavity, and the reaction cavity is separated by a horizontal partition into a first catalytic reaction chamber equipped with a CO catalyst layer and a second catalytic reaction chamber equipped with an SCR catalyst layer, an ammonia injection device is installed on the top of the second catalytic reaction chamber, and vents communicating with adjacent chambers are installed on the vertical partition and the horizontal partition; the heat medium inlet of the heat exchanger is communicated with the exhaust gas inlet, the heat medium outlet of the heat exchanger is communicated with the air inlet of the first catalytic reaction chamber, the cold source inlet of the heat exchanger is communicated with the air outlet of the second catalytic reaction chamber, and the cold source outlet of the heat exchanger is communicated with the exhaust gas outlet; The ammonia spraying device comprises a horizontally arranged ammonia spraying pipeline and a plurality of nozzles arranged side by side along the ammonia spraying pipeline, wherein the nozzles are arranged on the ammonia spraying pipeline in the flue, one end of the ammonia spraying pipeline is fixed on the inner wall of the flue, and the other end of the ammonia spraying pipeline extends out of the flue and is connected to an ammonia inlet pipeline, and a regulating valve for adjusting the liquid ammonia injection amount is installed on the ammonia inlet pipeline.

2. The exhaust gas treatment system suitable for dual-fuel main engine ships according to claim 1, characterized in that: The first catalytic reaction chamber is provided with a heating chamber and a CO catalytic reaction chamber. The heating chamber is provided at the inlet side of the CO catalytic reaction chamber, and a heating device is installed in the heating chamber.

3. The exhaust gas treatment system suitable for dual-fuel main engine ships according to claim 2, characterized in that: The heating device is an electric heater.

4. The exhaust gas treatment system for a dual-fuel main engine ship according to claim 1, characterized in that: Flange structures connected to the flue are provided at the exhaust gas inlet and the exhaust gas outlet.

5. The exhaust gas treatment system for a dual-fuel main engine ship according to claim 1, characterized in that: The system also includes a controller and a NOx concentration sensor installed on the exhaust gas intake pipe. The NOx concentration sensor is connected to the regulating valve signal through the controller.

6. The exhaust gas treatment system for a dual-fuel main engine ship according to claim 1, characterized in that: A cold fluid bypass pipeline is provided between the cold source inlet and the cold source outlet of the heat exchanger to avoid the risk of overheating.

7. The exhaust gas treatment system for a dual-fuel main engine ship according to claim 1, characterized in that: The CO catalyst layer and the SCR catalyst layer are both provided with several layers of base mesh. The surface of the base mesh of the CO catalyst layer is coated with a platinum material layer or a palladium material layer, and the surface of the base mesh of the SCR catalyst layer is coated with a vanadium-based material layer or an iron-based material layer.

8. An exhaust gas treatment method using the exhaust gas treatment system applicable to a dual-fuel main engine ship according to any one of claims 1 to 7, characterized in that: The method is as follows: the exhaust gas is discharged from the ship main engine, enters the exhaust gas inlet of the catalytic reaction integrated machine through the flue, enters the heat medium inlet of the heat exchanger from the exhaust gas inlet, is discharged from the heat medium outlet of the heat exchanger, enters the heating chamber, is heated by the heating device, enters the CO catalytic reaction chamber, and is reduced to carbon dioxide (CO2) and water (H2O) through the catalyst material layer coated with platinum or palladium on the surface of the chamber, and then enters the second catalytic reaction chamber, reacts chemically with the urea solution sprayed from the ammonia spraying device in the second catalytic reaction chamber, and NOx is reduced to nitrogen and water under the action of the vanadium-based or iron-based catalyst material layer coated on the surface of the second catalytic reaction chamber. The nitrogen after the reaction is discharged through the cold source inlet and the cold source outlet of the heat exchanger.

9. A waste gas treatment method according to claim 8, characterized in that: In this method, the injection amount of urea solution is dynamically adjusted according to the NOx concentration in the exhaust gas. The specific adjustment method is: When NOx concentration is ≤30ppm, the opening of the regulating valve is controlled at 30%-45%; When 30ppm<NOx concentration<50ppm, the opening of the regulating valve is controlled at 45%-60%; When 50ppm≦NOx concentration<80ppm, the opening of the regulating valve is controlled at 60%-80%; When 80ppm≦NOx concentration<100ppm, the opening of the regulating valve is controlled at 80%-95%; When the NOx concentration is ≧100ppm, the opening of the regulating valve is controlled at 95%-100%.

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