Method for treating tail gas of dual-fuel ship engine

Abstract

The invention discloses a dual-fuel ship engine tail gas treatment method, and relates to the technical field of ship engine tail gas treatment.According to the method, in the dual-fuel tail gas treatment process, a mixer is used for preposed pretreatment, necessary conditions for a catalytic reduction reaction are provided for an SCR reactor, and an ASC reactor can prevent ammonia from corroding follow-up equipment; therefore, collaborative purification and synchronous removal are achieved, the purification efficiency is larger than 90%, meanwhile, the escape amount is smaller than 5 ppm, and the high-standard emission requirement is met; and on the basis of dynamic regulation and control of temperature and reducing agent flow, tail gas characteristics of the dual-fuel engine under different loads are adapted, and meanwhile, the reaction speed and the catalyst efficiency are in an efficient state through temperature control, so that tail gas treatment of the dual-fuel system is met.

Description

Technical Field

[0001] This invention relates to the field of marine engine exhaust gas treatment, and particularly to a method for treating exhaust gas from a dual-fuel marine engine. Background Technology

[0002] With increasingly stringent ship emission regulations, ammonia, as a carbon-neutral fuel, is being gradually applied to ship power systems, forming a dual-fuel system with diesel to balance power performance and environmental requirements. Due to its advantages in both fuel economy and emissions, it will be more widely used in the shipping industry in the future.

[0003] However, dual-fuel combustion produces complex exhaust gases, mainly nitrogen oxides. The main sources are diesel combustion and ammonia oxidation; unreacted ammonia. Ammonia is a byproduct of incomplete combustion of fuel or its excessive introduction as a reducing agent, posing risks of equipment corrosion and secondary pollution. Particulate matter (PM) mainly originates from incomplete combustion of diesel fuel. Existing ship exhaust gas treatment technologies (such as commonly used SCR and EGR) are difficult to adapt to the complex emission characteristics of both ammonia and diesel fuels, thus a targeted and efficient treatment method is urgently needed. Summary of the Invention

[0004] The purpose of this invention is to provide a method for treating exhaust gas from a dual-fuel marine engine, in order to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for treating exhaust gas from a dual-fuel marine engine, comprising the following steps: S1. Exhaust gas collection and mixer pretreatment: flue gas and denitrification reducing agent are introduced into the mixer in a preset ratio to react and generate vaporized ammonia, and the vaporized ammonia is mixed with the exhaust gas. S2. The main reactor undergoes denitrification treatment. The mixed tail gas enters the main reactor and is then processed by a vanadium-based catalyst. and Transform into and Furthermore, by controlling the feed rate of the denitrification reducing agent, so that... and The molar ratio is maintained within a preset range to prevent ammonia escape; S3, ASC reactor for deep purification; an ASC reactor is connected at the tail end of the mixer to remove unreacted gas from the exhaust gas. Further catalytic reaction generates Meanwhile, the exhaust gas is adsorbed and purified before being discharged from the ship's chimney. In step S2, a temperature control module is introduced to adjust the temperature based on the exhaust gas temperature so that the main reactor is kept at a preset temperature, thereby allowing the reduction reaction to proceed at a preset efficiency.

[0006] Preferably, in step S1, the exhaust gas from the ship's engine enters the mixer through the exhaust pipe. The denitrification reducing agent is a urea solution. The urea solution is precisely controlled by the PLC control unit at a preset injection dosage, with an injection accuracy controlled within ±2%. It enters the mixer through the atomizing nozzle of the urea spray gun. The urea spray gun has an adjustable angle of 0-15°, which can dynamically adjust the injection direction according to the flow field distribution in the mixer to ensure that the urea solution uniformly covers the exhaust gas flow section.

[0007] Preferably, a buffer chamber is provided at the front end of the mixer's flue gas inlet. The buffer chamber is equipped with a flow sensor, a temperature probe, and an ammonia concentration probe for real-time monitoring of the exhaust gas flow rate, initial exhaust gas temperature, and initial ammonia concentration. The concentration data is synchronously transmitted to the PLC control unit, providing real-time configuration parameters for the injection volume of the urea solution and the temperature control of the mixer.

[0008] Preferably, the mixer is equipped with multiple layers of baffles made of corrosion-resistant stainless steel, with an anti-dust coating on the surface. The baffles are arranged in a staggered pattern to ensure that the exhaust gas and the atomized urea solution have sufficient contact and collision, promoting the hydrolysis of the urea solution. On the other hand, the waste heat of the exhaust gas itself is used to promote ammonia vaporization. At the same time, the flow field is disturbed by the baffle to achieve uniform mixing of ammonia and exhaust gas, with a mixing uniformity of ≥95%. The buffer chamber is equipped with a heating module, which pressurizes and heats the exhaust gas after recovering waste heat from the ship's chimney. A temperature sensor and an ammonia concentration probe are installed at the mixer outlet to monitor the temperature and ammonia concentration of the pretreated exhaust gas in real time. If the temperature is lower than 280℃, the heating module will raise the exhaust gas temperature to 280-300℃ to ensure the ammonia vaporization effect. If the ammonia concentration is abnormal, it will be fed back to the urea control unit to adjust the injection volume in real time.

[0009] Preferably, in step S2, the vanadium-based catalyst is filled inside the main reactor. The vanadium-based catalyst adopts a honeycomb structure with a specific surface area ≥300m² / g. The catalyst is filled in multiple layers, and a guide plate is set between each catalyst layer to ensure that the mixed airflow passes through the catalyst layer uniformly. At the same time, the main reactor has a built-in backflushing system to periodically backflush the catalyst layer to remove the dust accumulated on the catalyst surface.

[0010] Preferably, the main reactor maintains an optimal reaction temperature of 280-450°C through a temperature control module to maximize the activity of the vanadium-based catalyst and achieve a denitrification efficiency of 90%-95%. When the tail gas temperature is below 280°C, the built-in electric heating device in the main reactor is activated to quickly raise the reaction temperature to the optimal range. When the tail gas temperature is above 450°C, the reactor cooling bypass is opened to introduce a small amount of cooled purified tail gas to prevent the vanadium-based catalyst from deactivating at high temperatures.

[0011] Preferably, in the main reactor, the reaction process is a selective catalytic reduction reaction, and its core reaction formula is as follows: Meanwhile, an ammonia concentration sensor is installed in the main reactor to monitor the inlet and outlet in real time. Concentration and ammonia concentration; the flow rate of urea solution is adjusted by a PLC control unit in conjunction with monitoring parameters, so that... and The molar ratio is precisely maintained within the range of 0.85–1.15.

[0012] Preferably, the inner wall of the ASC reactor is provided with a catalyst layer, which is composed of a noble metal Pt-Pd alloy and metal oxides. It is composed of a composite material with a precious metal loading controlled at 0.1%–0.3% and a metal oxide as a co-catalyst. The ASC reactor adopts a wall-flow structure, and the exhaust gas flows through the catalyst wall to increase the contact area.

[0013] Preferred, unreacted It is catalytically oxidized in the ASC reactor, and the main reaction formula is as follows: Meanwhile, trace amounts of VOCs in the exhaust gas are oxidized and decomposed under the action of a precious metal catalyst. and ; Trace particulate matter in the exhaust gas is trapped by the filtration effect of the wall-flow structure and simultaneously oxidized and decomposed by the catalyst layer, further reducing particulate matter emissions. Trace amounts in exhaust gas The derivatives, under the action of metal oxide catalysts, are converted into stable sulfates, which adhere to the catalyst surface and are periodically removed by a backflushing system.

[0014] Preferably, the ASC reactor and the backflushing system in the main reactor are connected by a common-source diversion pipeline.

[0015] The technical effects and advantages of this invention are as follows: 1. The method for treating exhaust gas from dual-fuel ship engines achieves synergistic purification and simultaneous removal of exhaust gases during the dual-fuel exhaust gas treatment process. Purification efficiency >90%, while The escape rate is less than 5 ppm, meeting the high standard emission requirements.

[0016] 2. The method for treating exhaust gas from a dual-fuel marine engine is based on dynamic control of temperature and reducing agent flow rate, adapting to the exhaust gas characteristics of the dual-fuel engine under different loads, effectively ensuring a thorough reaction, while temperature control keeps the reaction rate and catalyst efficiency at a high level.

[0017] 3. This dual-fuel marine engine exhaust treatment method utilizes a mixer as a pretreatment stage to provide the necessary conditions for the catalytic reduction reaction in the SCR reactor, thereby improving the efficiency of the downstream reaction. The ASC reactor can further reduce... To minimize the amount of ammonia escaping and prevent ammonia from corroding downstream equipment. Attached Figure Description

[0018] Figure 1 This is a flowchart of the method for treating exhaust gas from a dual-fuel marine engine according to the present invention; Figure 2 This is a schematic diagram of the overall real-time system of the dual-fuel ship engine exhaust gas treatment method of the present invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] This invention provides, for example Figures 1 to 2 The method for treating exhaust gas from a dual-fuel marine engine, as shown, includes the following steps: S1. Exhaust gas collection and mixer pretreatment: flue gas and denitrification reducing agent are introduced into the mixer in a preset ratio to react and generate vaporized ammonia, and the vaporized ammonia is mixed with the exhaust gas. S2. The main reactor undergoes denitrification treatment. The mixed tail gas enters the main reactor and is then processed by a vanadium-based catalyst. and Transform into and Furthermore, by controlling the feed rate of the denitrification reducing agent, so that... and The molar ratio is maintained within a preset range to prevent ammonia escape; S3, ASC reactor for deep purification; an ASC reactor is connected at the tail end of the mixer to remove unreacted gas from the exhaust gas. Further catalytic reaction generates Meanwhile, the exhaust gas is adsorbed and purified before being discharged from the ship's chimney. In step S2, a temperature control module is introduced to adjust the temperature based on the exhaust gas temperature so that the main reactor is kept at a preset temperature, thereby allowing the reduction reaction to proceed at a preset efficiency.

[0021] Preferably, in step S1, the exhaust gas from the ship's engine enters the mixer through the exhaust pipe. The denitrification reducing agent is a urea solution. The urea solution is precisely controlled by the PLC control unit at a preset injection dosage, with an injection accuracy controlled within ±2%. It enters the mixer through the atomizing nozzle of the urea spray gun. The urea spray gun has an adjustable angle of 0-15°, which can dynamically adjust the injection direction according to the flow field distribution in the mixer to ensure that the urea solution uniformly covers the exhaust gas flow section.

[0022] Preferably, a buffer chamber is provided at the front end of the mixer's flue gas inlet. The buffer chamber is equipped with a flow sensor, a temperature probe, and an ammonia concentration probe for real-time monitoring of the exhaust gas flow rate, initial exhaust gas temperature, and initial ammonia concentration. The concentration data is synchronously transmitted to the PLC control unit, providing real-time configuration parameters for the injection volume of the urea solution and the temperature control of the mixer.

[0023] Preferably, the mixer is equipped with multiple layers of turbulence, made of corrosion-resistant stainless steel, and coated with an anti-dust-accumulation coating. The turbulence plates are arranged in a staggered pattern, which allows the exhaust gas to fully contact and collide with the atomized urea solution, promoting the hydrolysis of the urea solution. On the other hand, the waste heat of the exhaust gas itself is used to promote ammonia vaporization. At the same time, the flow field is disturbed by the baffle to achieve uniform mixing of ammonia and exhaust gas, with a mixing uniformity of ≥95%. The buffer chamber is equipped with a heating module, which pressurizes and heats the exhaust gas after recovering waste heat from the ship's chimney. A temperature sensor and an ammonia concentration probe are installed at the mixer outlet to monitor the temperature and ammonia concentration of the pretreated exhaust gas in real time. If the temperature is lower than 280℃, the heating module will raise the exhaust gas temperature to 280-300℃ to ensure the ammonia vaporization effect. If the ammonia concentration is abnormal, it will be fed back to the urea control unit to adjust the injection volume in real time.

[0024] Preferably, in step S2, the vanadium-based catalyst is filled inside the main reactor. The vanadium-based catalyst adopts a honeycomb structure with a specific surface area ≥300m² / g. The catalyst is filled in multiple layers, and a guide plate is set between each catalyst layer to ensure that the mixed airflow passes through the catalyst layer uniformly. At the same time, the main reactor has a built-in backflushing system to periodically backflush the catalyst layer to remove the dust accumulated on the catalyst surface.

[0025] Preferably, the main reactor maintains an optimal reaction temperature of 280-450°C through a temperature control module to maximize the activity of the vanadium-based catalyst and achieve a denitrification efficiency of 90%-95%. When the tail gas temperature is below 280°C, the built-in electric heating device in the main reactor is activated to quickly raise the reaction temperature to the optimal range. When the tail gas temperature is above 450°C, the reactor cooling bypass is opened to introduce a small amount of cooled purified tail gas to prevent the vanadium-based catalyst from deactivating at high temperatures.

[0026] Preferably, in the main reactor, the reaction process is a selective catalytic reduction reaction, and its core reaction formula is as follows: Meanwhile, an ammonia concentration sensor is installed in the main reactor to monitor the inlet and outlet in real time. Concentration and ammonia concentration; the flow rate of urea solution is adjusted by a PLC control unit in conjunction with monitoring parameters, so that... and The molar ratio is precisely maintained within the range of 0.85–1.15.

[0027] Preferably, the inner wall of the ASC reactor is provided with a catalyst layer, which is composed of a noble metal Pt-Pd alloy and metal oxides. It is composed of a composite material with a precious metal loading controlled at 0.1%–0.3% and a metal oxide as a co-catalyst. The ASC reactor adopts a wall-flow structure, and the exhaust gas flows through the catalyst wall to increase the contact area.

[0028] Preferred, unreacted It is catalytically oxidized in the ASC reactor, and the main reaction formula is as follows: Meanwhile, trace amounts of VOCs in the exhaust gas are oxidized and decomposed under the action of a precious metal catalyst. and ; Trace particulate matter in the exhaust gas is trapped by the filtration effect of the wall-flow structure and simultaneously oxidized and decomposed by the catalyst layer, further reducing particulate matter emissions. Trace amounts in exhaust gas The derivatives, under the action of metal oxide catalysts, are converted into stable sulfates, which adhere to the catalyst surface and are periodically removed by a backflushing system.

[0029] Preferably, the ASC reactor and the backflushing system in the main reactor are connected by a common-source diversion pipeline.

[0030] Working principle: When the fuel is diesel and the engine is in Tier III mode, the V1 valve opens, the SCR system starts, and the diesel exhaust gas enters the exhaust pipe through the exhaust gas box and the V1 valve.

[0031] Urea solution enters the urea pumping station system from the urea daily use tank. The urea pumping station system consists of filters, urea pumps, flow sensors, proportional valves, etc. Meanwhile, Sensors detect the concentration of exhaust gas and feed the collected signals back to the SCR control system. Temperature sensors in the SCR and ASC reactors transmit the monitored temperatures to the SCR control system. The SCR control system calculates the urea injection rate based on the feedback concentration and temperature signals, and adjusts the opening of the proportional valve to match the required urea injection rate. The urea solution is atomized by the urea spray gun and injected into the mixer. The atomized urea solution mixes with the exhaust gas... The product is generated through pyrolysis, hydrolysis, and thorough mixing within the mixer. .

[0032] Compressed air enters the SCR reactor and ASC reactor under the control of the SCR control system via flow sensors, pressure sensors, solenoid valves, etc. When the differential pressure sensors in the SCR reactor and ASC reactor detect that the pressure difference between the inlet and outlet of the equipment exceeds the set value, the SCR control system starts the soot blowing program. The soot blowing device blows away the dust and deposits adsorbed on the surface of the catalyst block, so as to maintain the good activity of the catalyst.

[0033] The mixed waste gas reaches the reactor through a waste gas pipeline. The reactor contains multiple layers of denitrification catalyst. The waste gas undergoes a reduction reaction with the denitrification catalyst, thereby removing the nitrogen from the waste gas. .

[0034] The exhaust gas enters the ASC reactor through the pipeline, and the unreacted gas... Catalytic oxidation in the ASC reactor and To prevent ammonia escape, the exhaust gas is further purified to meet emission requirements. The purified exhaust gas enters the main unit's booster through the V2 valve before being discharged.

[0035] When the fuel is ammonia and the engine is in Tier III mode, the V1 valve opens, the SCR system starts, and the ammonia exhaust gas enters the exhaust pipe through the exhaust gas box and the V1 valve.

[0036] Urea solution enters the urea pumping station system from the urea daily use tank. At the same time, the NOx sensor detects the concentration of exhaust gas and feeds back the collected signal to the SCR control system. The temperature sensors of the SCR reactor and ASC reactor transmit the monitored temperature to the SCR control system. The SCR control system calculates the supply amount of urea injection based on the feedback concentration signal and temperature, and adjusts the opening of the proportional valve to match the required urea injection amount (when the fuel is ammonia, the required urea amount is lower than that of diesel fuel). After being atomized by the urea spray gun, it is sprayed into the mixer. The atomized urea solution and NOx in the exhaust gas are pyrolyzed, hydrolyzed, and fully mixed in the mixer to generate NH3. Its subsequent treatment reaction process is the same as that of diesel. This enables the entire system to achieve synergistic purification and simultaneous removal of exhaust gases during the dual-fuel exhaust gas treatment process. Purification efficiency >90%, while The escape rate is less than 5 ppm, meeting high emission standards; and based on dynamic control of temperature and reducing agent flow, it is adapted to the exhaust gas characteristics of dual-fuel engines under different loads; the mixer is used as a pretreatment to provide the necessary conditions for the catalytic reduction reaction of the SCR reactor, while the ASC reactor can avoid ammonia corrosion of subsequent equipment.

[0037] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for treating exhaust gas from a dual-fuel marine engine, characterized in that, Includes the following steps: S1. Exhaust gas collection and mixer pretreatment: flue gas and denitrification reducing agent are introduced into the mixer in a preset ratio to react and generate vaporized ammonia, and the vaporized ammonia is mixed with the exhaust gas. S2. The main reactor undergoes denitrification treatment. The mixed tail gas enters the main reactor and is then processed by a vanadium-based catalyst. and Transform into and Furthermore, by controlling the feed rate of the denitrification reducing agent, so that... and The molar ratio is maintained within a preset range to prevent ammonia escape; S3 and ASC reactors provide deep purification; An ASC reactor is connected at the tail end of the mixer to process unreacted gas in the exhaust gas. Further catalytic reaction generates Meanwhile, the exhaust gas is adsorbed and purified before being discharged from the ship's chimney. In step S2, a temperature control module is introduced to adjust the temperature based on the exhaust gas temperature so that the main reactor is kept at a preset temperature, thereby allowing the reduction reaction to proceed at a preset efficiency.

2. The method for treating exhaust gas from a dual-fuel marine engine according to claim 1, characterized in that, In step S1, the exhaust gas from the ship's engine enters the mixer through the exhaust pipe. The denitrification reducing agent is a urea solution. The urea solution is precisely controlled by the PLC control unit at a preset injection dosage, with an injection accuracy controlled within ±2%. It enters the mixer through the atomizing nozzle of the urea spray gun. The urea spray gun has an adjustable angle of 0-15°, which can dynamically adjust the injection direction according to the flow field distribution in the mixer to ensure that the urea solution uniformly covers the exhaust gas flow section.

3. The method for treating exhaust gas from a dual-fuel marine engine according to claim 2, characterized in that, A buffer chamber is provided at the front end of the mixer's flue gas inlet. The buffer chamber is equipped with a flow sensor, a temperature probe, and an ammonia concentration probe for real-time monitoring of the exhaust gas flow rate, initial exhaust gas temperature, and initial ammonia concentration. The concentration data is synchronously transmitted to the PLC control unit, providing real-time configuration parameters for the injection volume of the urea solution and the temperature control of the mixer.

4. The method for treating exhaust gas from a dual-fuel marine engine according to claim 3, characterized in that, The mixer is equipped with multiple layers of turbulence, made of corrosion-resistant stainless steel, and coated with an anti-dust-accumulation coating. The turbulence plates are arranged in a staggered pattern to ensure that the exhaust gas and the atomized urea solution have sufficient contact and collision, promoting the hydrolysis of the urea solution. On the other hand, the waste heat of the exhaust gas itself is used to promote ammonia vaporization. At the same time, the flow field is disturbed by the baffle to achieve uniform mixing of ammonia and exhaust gas, with a mixing uniformity of ≥95%. The buffer chamber is equipped with a heating module, which pressurizes and heats the exhaust gas after recovering waste heat from the ship's chimney. A temperature sensor and an ammonia concentration probe are installed at the mixer outlet to monitor the temperature and ammonia concentration of the pretreated exhaust gas in real time. If the temperature is lower than 280℃, the heating module will raise the exhaust gas temperature to 280-300℃ to ensure the ammonia vaporization effect. If the ammonia concentration is abnormal, it will be fed back to the urea control unit to adjust the injection volume in real time.

5. The method for treating exhaust gas from a dual-fuel marine engine according to claim 4, characterized in that, In step S2, a vanadium-based catalyst is filled inside the main reactor. The vanadium-based catalyst adopts a honeycomb structure with a specific surface area ≥300m² / g. The catalyst is filled in multiple layers, and a guide plate is set between each catalyst layer to ensure that the mixed airflow passes through the catalyst layer uniformly. At the same time, the main reactor has a built-in backflushing system to periodically backflush the catalyst layer to remove the dust accumulated on the catalyst surface.

6. The method for treating exhaust gas from a dual-fuel marine engine according to claim 5, characterized in that, The main reactor maintains an optimal reaction temperature of 280-450°C through a temperature control module to maximize the activity of the vanadium-based catalyst and achieve a denitrification efficiency of 90%-95%. When the tail gas temperature is below 280°C, the built-in electric heating device in the main reactor is activated to quickly raise the reaction temperature to the optimal range. When the tail gas temperature is above 450°C, the reactor cooling bypass is activated to introduce a small amount of cooled purified tail gas to prevent the vanadium-based catalyst from deactivating at high temperatures.

7. The method for treating exhaust gas from a dual-fuel marine engine according to claim 6, characterized in that, In the main reactor, the reaction process is a selective catalytic reduction reaction, and its core reaction formula is as follows: Meanwhile, an ammonia concentration sensor is installed in the main reactor to monitor the inlet and outlet in real time. Concentration and ammonia concentration; The flow rate of urea solution is adjusted by a PLC control unit in conjunction with monitoring parameters, so that... and The molar ratio is precisely maintained within the range of 0.85–1.

15.

8. The method for treating exhaust gas from a dual-fuel marine engine according to claim 5, characterized in that, The inner wall of the ASC reactor is provided with a catalyst layer, which is composed of a noble metal Pt-Pd alloy and metal oxides. It is composed of a composite material with a precious metal loading controlled at 0.1%–0.3% and a metal oxide as a co-catalyst. The ASC reactor adopts a wall-flow structure, and the exhaust gas flows through the catalyst wall to increase the contact area.

9. A method for treating exhaust gas from a dual-fuel marine engine according to claim 8, characterized in that, Unresponsive It is catalytically oxidized in the ASC reactor, and the main reaction formula is as follows: Meanwhile, trace amounts of VOCs in the exhaust gas are oxidized and decomposed under the action of a precious metal catalyst. and ; Trace particulate matter in the exhaust gas is trapped by the filtration effect of the wall-flow structure and simultaneously oxidized and decomposed by the catalyst layer, further reducing particulate matter emissions. Trace amounts in exhaust gas The derivatives, under the action of metal oxide catalysts, are converted into stable sulfates, which adhere to the catalyst surface and are periodically removed by a backflushing system.

10. A method for treating exhaust gas from a dual-fuel marine engine according to claim 9, characterized in that, The ASC reactor and the backflushing system in the main reactor are connected by a common source and separate pipeline.

Images