Integrated ship exhaust gas desulfurization, denitrification and decarbonization treatment method

Abstract

The invention discloses an integrated ship waste gas desulfurization, denitrification and decarburization treatment method which comprises the following steps: A) low NOx combustion: an air / fuel staged low NOx combustor is adopted, a low-oxygen reduction area is formed at the downstream of a primary flame area by accurately controlling the feeding proportion and position of air and fuel, and when a fuel product passes through the area, the low-oxygen reduction area is formed at the downstream of the primary flame area; the generated NOx can be partially reduced into N2; b) flue gas pretreatment: carrying out pretreatment on low-NOx combustion flue gas to remove large-particle substances and impurities in the low-NOx combustion flue gas; d) decarburization treatment; and E) purifying and drying the tail gas by an adsorption method: treating the decarbonized flue gas, and further removing residual pollutants, compared with the prior art, the method can efficiently remove pollutants, and is low in economic cost, environment-friendly and simple and convenient to operate.

Description

Technical Field

[0001] The invention relates to the field of ship exhaust gas treatment, and in particular to a method for treating exhaust gas for desulfurization, denitration and decarbonization. Background Art

[0002] As global environmental awareness increases, countries are increasingly stringent in controlling ship emissions. The International Maritime Organization (IMO) has formulated a series of ship emission standards, requiring ships of all countries to comply with these standards when they are on the high seas and at ports. According to Annex VI of the International Convention for the Prevention of Pollution from Ships (MARPOL Convention), sulfur oxides (SO x ) and nitrogen oxides (NO x ) Emissions must be strictly controlled to reduce harm to the environment and human health.

[0003] During operation, ships will emit a large amount of SO, especially when burning heavy fuel oil and diesel. x and NO x After these pollutants enter the atmosphere, they will generate sulfuric acid and nitric acid through chemical reactions, forming acid rain. Acid rain will not only pollute the soil and water bodies, but also corrode buildings and infrastructure, leading to reduced agricultural production and damage to forests. In addition, SO x and NO x They are also precursors of fine particulate matter such as PM2.5. Long-term exposure to these pollutants will increase health risks such as respiratory diseases and cardiovascular diseases.

[0004] At the same time, the global pressure to respond to climate change has also prompted the shipping industry to pay attention to carbon emissions. Carbon dioxide (CO2) is the main greenhouse gas, and its emissions are closely related to the fuel combustion process. The shipping industry is one of the important sources of global CO2 emissions, especially the CO2 emissions from ocean voyages and large cargo ships. The accumulation of CO2 exacerbates the greenhouse effect, leading to global warming, which in turn triggers a series of ecosystem imbalances and extreme weather phenomena.

[0005] In the existing technology, the desulfurization, denitrification and decarbonization of ship exhaust gas mainly rely on the following solutions: 1. Fuel improvement: Use low-sulfur fuel or desulfurized fuel to replace high-sulfur fuel to reduce SOx emissions from the source. This method significantly reduces sulfur oxides produced during combustion by changing the type of fuel used by ships. Low-sulfur fuel refers to marine fuel oil with a sulfur content lower than the prescribed standard. This fuel can effectively reduce SOx emissions. However, the supply of low-sulfur fuel is limited and the price is high, resulting in increased ship operating costs; 2. Wet desulfurization: Wet scrubbing technology is used to spray alkaline solution through the scrubber to react with SOx in the exhaust gas to generate sulfate, thereby removing SOx. This technology uses alkaline solution (such as sodium hydroxide solution or seawater) to react chemically with SOx in the exhaust gas to generate harmless sulfate or calcium sulfate. The advantage of wet desulfurization is high reaction efficiency and can effectively remove SOx in the exhaust gas, but its disadvantages are that the equipment is bulky, the installation and maintenance costs are high, and the treated waste liquid needs to be further treated to avoid secondary pollution; 3. Selective catalytic reduction (SCR): By adding a reducing agent (such as ammonia or urea) to the exhaust gas, NOx is reduced to nitrogen and water under the action of a catalyst. SCR technology is an efficient denitrification method that can achieve efficient reduction of NOx at a relatively low temperature (300-400°C). The type and performance of the catalyst play a decisive role in the efficiency of the SCR system, but the catalyst is easily contaminated and fails, and needs to be replaced and maintained regularly, which increases the operating cost of the system; 4. Selective non-catalytic reduction (SNCR): The reducing agent is directly injected into the high-temperature exhaust gas to reduce NOx to nitrogen and water without the need for a catalyst. The operating temperature range of SNCR technology is relatively high (850-1100°C), and no expensive catalyst is required. The equipment structure is relatively simple, but due to the lack of catalyst assistance, its denitrification efficiency is relatively low, usually only 30-50% NOx removal rate can be achieved, which is difficult to meet strict emission standards; 5. Carbon capture and decarbonization: Ship operations have the special characteristics of being offshore, constantly moving, and having variable operating conditions. Factors such as the space occupied, energy consumption, technical maturity, amount of ship modification, and investment costs of different carbon capture methods will restrict the choice of ship carbon capture methods. At present, carbon capture technologies mainly include pre-combustion capture, oxygen-enriched combustion, post-combustion capture, biomass capture, and direct air capture. Pre-combustion capture, oxygen-enriched combustion, and post-combustion capture are relatively mature, while biomass energy capture and direct air capture are relatively new technologies.

[0006] Although the existing technology has achieved desulfurization, denitrification and decarbonization of ship exhaust gas to a certain extent, it still has the following defects: 1. High cost of fuel improvement: The price of low-sulfur fuel is significantly higher than that of high-sulfur fuel, which leads to a significant increase in ship operating costs. Although fuel improvement is effective in reducing SOx emissions, the increase in fuel costs will bring economic pressure to shipping companies, especially in a market environment with large fluctuations in fuel prices, making it difficult to maintain long-term economic feasibility; 2. Complex wet desulfurization equipment: The wet scrubber is large in size, occupies limited space on the ship, and has high installation and maintenance costs. The complexity of the equipment increases the difficulty of operation and maintenance, and requires professional technicians to operate and maintain it. In addition, the waste liquid generated during the washing process needs to be treated to prevent secondary pollution to the marine environment, which further increases operating costs and environmental pressures; 3. Difficulty in maintaining the SCR system: The SCR system relies on the high efficiency of the catalyst, but the catalyst is easily contaminated and fails, and needs to be replaced and regenerated regularly. The failure of the catalyst may be accelerated by the accumulation of pollutants such as sulfur, lead, and vanadium, which not only increases the frequency and cost of maintenance, but may also cause system downtime, affecting the normal operation of the ship. The price of the catalyst is high, and the replacement process is complicated, requiring the ship to be stopped for operation, which affects the operating efficiency of the ship; 4. Low SNCR efficiency: In the absence of a catalyst, the denitrification efficiency of SNCR is low, usually only 30-50% of NOx can be removed, making it difficult to meet increasingly stringent emission standards. Although the equipment investment and operating costs of the SNCR system are low, due to its low efficiency, it often needs to be combined with other technical means to meet compliant emission requirements, which increases the complexity and overall cost of the system. In addition, the optimal operating temperature range of SNCR is narrow, and precise temperature control is required to achieve the best effect, which increases the difficulty of operation and management; 5. The amount of carbon capture modification and investment cost are large: H2 produced by pre-combustion capture technology can be used as ship fuel, but it is necessary to develop ship hydrogen fuel engines, solve problems such as ship hydrogen fuel engine application, H2 leakage and safety technology, and carry out overall power system design modification and equip some necessary reaction tanks and systems. The amount of modification and investment cost are huge, but there is great potential for development in ships using LNG and H2 mixed fuels to produce hydrogen from fuel. Oxygen-enriched combustion is greatly restricted by technology and equipment. Its application on board requires relevant modifications or upgrades to the ship's engine structure, system and materials. It is also necessary to solve the problem of low-cost oxygen production technology and complex process equipment. It is currently difficult to implement and has few application opportunities. Biomass energy capture is a negative emission technology that captures CO2 from the combustion or conversion of biofuels, but it still faces technical, economic and social challenges and is still in the research and development and demonstration stage. The significant advantage of direct air capture technology is that it is not restricted by the type and geographical location of emission sources, eliminating the infrastructure challenges involved in deploying CCUS applications in and near residential areas, but there is still a high cost constraint. Summary of the invention

[0007] The purpose of the present invention is to solve the problems in the prior art and to propose a treatment method for integrated ship exhaust gas desulfurization, denitrification and decarbonization, which can solve at least one of the above technical problems.

[0008] To achieve the above object, the present invention proposes a treatment method for integrated ship exhaust gas desulfurization, denitrification and decarbonization, comprising the following steps: A) Low NOx combustion: using air / fuel staged low NO x The burner forms a low oxygen reduction zone downstream of the primary flame zone by precisely controlling the ratio and position of air and fuel. When the fuel products pass through this zone, the NO generated is x Will be partially reduced to N2; B) Flue gas pretreatment: Pre-treat low NOx combustion flue gas to remove large particles and impurities; C) Desulfurization treatment: The pretreated flue gas is introduced into the desulfurization reactor, and seawater is sprayed to react with SOx in the flue gas to generate sulfate; D) Decarbonization treatment: The flue gas treated with desulfurization is brought into contact with an alcohol amine solution, and the CO2 in the flue gas is dissolved in the solution to form an alcohol amine solution containing CO2. Then, the CO2 is desorbed from the alcohol amine solution by reducing the pressure or heating to obtain pure CO2 gas. The CO2 in the alcohol amine solution is released by heating or distillation to turn the solution into pure alcohol amine again. Finally, the obtained pure CO2 gas is compressed for easy storage and transportation; E) Purification of dry tail gas by adsorption: The decarbonized flue gas is treated to further remove residual pollutants.

[0009] Preferably, in the B) flue gas pretreatment step, a filter or dust collector is used to remove large particles and impurities, and large particles and heavy metal impurities in the exhaust gas are removed by physical separation.

[0010] Preferably, in the desulfurization treatment C), fresh seawater is filtered through a filter to remove impurities and then introduced into an absorption tower via a centrifugal pump.

[0011] Preferably, in the C) desulfurization treatment, the Flakt-Hydro process is used to utilize the natural alkalinity of seawater for desulfurization. The process mainly includes a flue gas system, a seawater supply and exhaust system, and a seawater recovery system. After dust removal and cooling, the flue gas is sent to the absorption tower from the bottom of the tower through the flue, and is reversely contacted and mixed with pure seawater evenly sprayed from the top of the tower. The seawater absorbs SO2 in the flue gas to generate sulfite ions. The purified flue gas is heated by a heat exchanger and sent to the decarbonization device through the flue. The main structure of the seawater recovery system is an aeration tank. The acidic seawater from the absorption tower and the alkaline seawater discharged from the condenser are fully mixed in the aeration tank. At the same time, an appropriate amount of compressed air is blown into the tank through the aeration system to convert the sulfite in the seawater into stable and harmless sulfate, while releasing CO2 to raise the pH of the seawater to above 6.5, and then it is discharged into the sea after reaching the standard.

[0012] Preferably, in the A) low NOx combustion step, a primary flame zone is first formed, and combustion close to the theoretical air amount can ensure flame stability; the reducing agent is mixed at a certain distance downstream of the primary flame to form a secondary flame. In this zone, the generated NO x The reducing agent is reduced to N2; the graded air is sent into the third stage to complete the burnout stage, and the reducing agent is one or more of ammonia, urea, CH, and HCN.

[0013] Preferably, in the step E) of purifying and drying the tail gas by adsorption, activated carbon adsorption or zeolite is used to remove residual pollutants, and drying is performed to obtain the final purified gas.

[0014] Preferably, the zeolite is 5A or 13X zeolite.

[0015] Preferably, a monitoring and control step is also included. During the whole process, online monitoring equipment is used to monitor the exhaust gas composition in real time, and the processing parameters of each link are adjusted through the control system to ensure the desulfurization, denitrification and decarbonization effects.

[0016] Preferably, the online monitoring equipment includes a gas analyzer, a particulate matter monitor and a flow meter to monitor the concentrations of SOx, NOx, particulate matter and other pollutants in the exhaust gas in real time; the control system automatically adjusts the spraying amount of the spray device, the amount of reducing agent added and the temperature and pressure parameters in the reactor by collecting and analyzing the monitoring data to ensure the efficient desulfurization and denitrification reactions, and performs early warning and fault handling as needed.

[0017] Beneficial effects of the present invention: 1. Efficient removal of pollutants: The low NO x The combustion technology uses innovative staged air supply and fuel injection methods to form multiple flame zones in the furnace, effectively reducing NO x The specially designed low oxygen reduction zone uses NH3, CH, HCN and other reducing agents to efficiently convert the generated NO x Reducing to N2 while maintaining combustion stability and high burnout rate. Compared with traditional technologies, this technology not only significantly improves denitrification efficiency, but also reduces environmental pollution; Low economic cost: The operation process of this method is simple, the required equipment is relatively small, and the operating cost is low. Since seawater desulfurization has no desulfurization agent cost, the process equipment is relatively simple, and there is no subsequent desulfurization product treatment and disposal, its investment and operating costs are relatively low, reducing the economic burden of ship operators. Secondly, the recycling of alcohol amine solution reduces long-term operating costs. At the same time, the captured CO2 can be recycled as a carbon resource; Environmentally friendly: The seawater desulfurization technology in this method innovatively uses pure seawater as an absorbent, utilizing the natural alkalinity of seawater to reduce the use of desulfurizers, and is environmentally friendly. The soluble salts in seawater are used to absorb and convert SOx, and the generated sulfite ions are further converted into sulfates. The entire process is environmentally friendly, and no secondary pollution is generated during the waste gas treatment process, which has good environmental benefits. Easy to operate: The system structure of this method is simple, easy to maintain and operate. Through the application of automatic control system, intelligent management of the processing process is realized, manual intervention is reduced, operation complexity and error rate are reduced, and system reliability and operation efficiency are improved.

[0018] The features and advantages of the present invention will be described in detail through embodiments in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The present invention is a process flow chart of a treatment method for integrated ship exhaust gas desulfurization, denitrification and decarbonization. DETAILED DESCRIPTION

[0020] The present invention provides a treatment method for integrated ship exhaust gas desulfurization, denitrification and decarbonization, comprising the following steps: A) Low NOx combustion: using air / fuel staged low NO x The burner forms a low oxygen reduction zone downstream of the primary flame zone by precisely controlling the ratio and position of air and fuel. When the fuel products pass through this zone, the NO generated is x Will be partially reduced to N2; B) Flue gas pretreatment: Pre-treat low NOx combustion flue gas to remove large particles and impurities; C) Desulfurization treatment: The pretreated flue gas is introduced into the desulfurization reactor, and seawater is sprayed to react with SOx in the flue gas to generate sulfate; D) Decarbonization treatment: The flue gas treated with desulfurization is brought into contact with an alcohol amine solution, and the CO2 in the flue gas is dissolved in the solution to form an alcohol amine solution containing CO2. Then, the CO2 is desorbed from the alcohol amine solution by reducing the pressure or heating to obtain pure CO2 gas. The CO2 in the alcohol amine solution is released by heating or distillation to turn the solution into pure alcohol amine again. Finally, the obtained pure CO2 gas is compressed for easy storage and transportation; E) Purification of dry tail gas by adsorption: The decarbonized flue gas is treated to further remove residual pollutants.

[0021] In the B) flue gas pretreatment step, a cyclone separator, filter or dust collector is used to remove large particles and impurities, and large particles and heavy metal impurities in the exhaust gas are removed by physical separation to ensure the purity of the exhaust gas entering the desulfurization reactor and improve the subsequent treatment efficiency to prevent affecting the subsequent desulfurization, denitrification and decarbonization processes.

[0022] In the desulfurization treatment C), fresh seawater is filtered through a filter to remove impurities and then introduced into an absorption tower via a centrifugal pump.

[0023] In the desulfurization treatment described above, the Flakt-Hydro process is used to desulfurize the natural alkalinity of seawater. Rainwater brings alkaline substances from the rock formations on the road to the sea. Natural seawater also contains a large amount of soluble salts, the main components of which are sodium chloride and sulfate, and a certain amount of soluble carbonate. Seawater is usually alkaline, with a natural alkalinity of about 1.2 to 2.5. mmol / L, which makes seawater have natural acid-base buffering capacity. The process mainly includes flue gas system, seawater supply and exhaust system and seawater recovery system. After dust removal and cooling, the flue gas is sent to the absorption tower from the bottom of the tower through the flue, and is fully contacted and mixed with the pure seawater evenly sprayed from the top of the tower in reverse. The seawater absorbs SO2 in the flue gas to generate sulfite ions. The purified flue gas is heated by the heat exchanger and sent to the decarbonization device through the flue. The main structure of the seawater recovery system is the aeration tank. The acidic seawater from the absorption tower and the alkaline seawater discharged from the condenser are fully mixed in the aeration tank. At the same time, an appropriate amount of compressed air is blown into the tank through the aeration system to convert the sulfite in the seawater into stable and harmless sulfate. At the same time, CO2 is released to raise the pH of the seawater to above 6.5, and it is discharged into the sea after meeting the standard. By using seawater as a desulfurization agent, the removal efficiency of SOx is improved, and the sulfite in the seawater is converted into stable and harmless sulfate.

[0024] In the A) low NOx combustion step, a primary flame zone is first formed, and combustion close to the theoretical air amount can ensure flame stability; the reducing agent is mixed at a certain distance downstream of the primary flame to form a secondary flame. In this area, the generated NO x The reducing agent is reduced to N2; the graded air is sent into the third stage to complete the burnout stage. The reducing agent is one or more of ammonia, urea, CH, and HCN, while maintaining the stability of combustion and a high burnout rate. Compared with traditional technologies, this technology not only significantly improves the denitrification efficiency, but also reduces environmental pollution; selecting ammonia or urea as a denitrification reducing agent can efficiently reduce NOx in the exhaust gas, generate harmless nitrogen and water, and ensure that the exhaust gas emissions meet environmental protection standards.

[0025] In the step of purifying and drying the tail gas by adsorption method E), activated carbon adsorption or zeolite and other adsorption materials are used to remove residual pollutants, and drying is performed to obtain the final purified gas. Activated carbon and zeolite have high specific surface area and good adsorption performance, and can effectively remove trace organic pollutants, heavy metals and residual acidic gases in the tail gas, thereby ensuring the cleanliness of the final exhaust gas.

[0026] Zeolite uses 5A and 13X zeolites, whose surfaces have porous structures and larger pores, and the surface ions can also be modified by other metals, thereby having better catalytic performance.

[0027] It also includes monitoring and control steps. During the whole process, online monitoring equipment is used to monitor the exhaust gas composition in real time, and the treatment parameters of each link are adjusted through the control system to ensure the desulfurization, denitrification and decarbonization effects, and ensure the efficient operation and stability of the system. The online monitoring equipment includes gas analyzers, particulate matter monitors and flow meters, etc., which monitor the concentrations of SOx, NOx, particulate matter and other pollutants in the exhaust gas in real time; the control system collects and analyzes monitoring data, automatically adjusts the spray volume of the spray device, the amount of reducing agent added, and the temperature, pressure and other parameters in the reactor to ensure the efficient desulfurization and denitrification reactions, and performs early warning and fault processing as needed. Through the application of intelligent control systems, the automated management of the treatment process is realized, human intervention is reduced, and the reliability and operation efficiency of the system are improved.

[0028] By innovatively combining the low NOx burner with the seawater desulfurization process, not only the generation of NOx is reduced, but also the removal efficiency of SOx is enhanced. By improving the amine capture system, the problems of high energy consumption and large equipment footprint of the traditional method are overcome, and the efficient capture and separation of CO2 is achieved.

[0029] The above embodiments are intended to illustrate the present invention, not to limit the present invention. Any solution that is a simple transformation of the present invention belongs to the protection scope of the present invention.

Claims

1. A treatment method for integrated ship exhaust gas desulfurization, denitrification and decarbonization, characterized in that: The following steps are involved: A) Low NOx combustion: using air / fuel staged low NO x The burner forms a low oxygen reduction zone downstream of the primary flame zone by precisely controlling the ratio and position of air and fuel. When the fuel products pass through this zone, the NO generated is x Will be partially reduced to N2; B) Flue gas pretreatment: Pre-treat low NOx combustion flue gas to remove large particles and impurities; C) Desulfurization treatment: The pretreated flue gas is introduced into the desulfurization reactor, and seawater is sprayed to react with SOx in the flue gas to generate sulfate; D) Decarbonization treatment: The flue gas treated with desulfurization is brought into contact with an alcohol amine solution, and the CO2 in the flue gas is dissolved in the solution to form an alcohol amine solution containing CO2. Then, the CO2 is desorbed from the alcohol amine solution by reducing the pressure or heating to obtain pure CO2 gas. The CO2 in the alcohol amine solution is released by heating or distillation to turn the solution into pure alcohol amine again. Finally, the obtained pure CO2 gas is compressed for easy storage and transportation; E) Purification of dry tail gas by adsorption: The decarbonized flue gas is treated to further remove residual pollutants.

2. The integrated ship exhaust gas desulfurization, denitrification and decarbonization treatment method according to claim 1, characterized in that: In the B) flue gas pretreatment step, a filter or dust collector is used to remove large particles and impurities, and large particles and heavy metal impurities in the exhaust gas are removed by physical separation.

3. The integrated ship exhaust gas desulfurization, denitrification and decarbonization treatment method according to claim 1, characterized in that: In the desulfurization treatment C), fresh seawater is filtered through a filter to remove impurities and then introduced into an absorption tower via a centrifugal pump.

4. The integrated ship exhaust gas desulfurization, denitrification and decarbonization treatment method according to claim 1, characterized in that: In the desulfurization treatment described in C), the Flakt-Hydro process is used to utilize the natural alkalinity of seawater for desulfurization. The process mainly includes a flue gas system, a seawater supply and exhaust system, and a seawater recovery system. After dust removal and cooling, the flue gas is sent to the absorption tower from the bottom of the tower through the flue, and is reversely contacted and mixed with pure seawater evenly sprayed from the top of the tower. The seawater absorbs SO2 in the flue gas to generate sulfite ions. The purified flue gas is heated by a heat exchanger and sent to the decarbonization device through the flue. The main structure of the seawater recovery system is an aeration tank. The acidic seawater from the absorption tower and the alkaline seawater discharged from the condenser are fully mixed in the aeration tank. At the same time, an appropriate amount of compressed air is blown into the tank through the aeration system to convert the sulfite in the seawater into stable and harmless sulfate, and at the same time, CO2 is released to raise the pH of the seawater to above 6.5, and it is discharged into the sea after reaching the standard.

5. The integrated ship exhaust gas desulfurization, denitrification and decarbonization treatment method according to claim 1, characterized in that: In the A) low NOx combustion step, a primary flame zone is first formed, and combustion close to the theoretical air amount can ensure flame stability; the reducing agent is mixed at a certain distance downstream of the primary flame to form a secondary flame. In this area, the generated NO x The reducing agent is reduced to N2; the graded air is sent into the third stage to complete the burnout stage, and the reducing agent is one or more of ammonia, urea, CH, and HCN.

6. The integrated ship exhaust gas desulfurization, denitrification and decarbonization treatment method according to claim 1, characterized in that: In the step of purifying and drying the tail gas by adsorption method E), activated carbon adsorption or zeolite is used to remove residual pollutants, and drying is performed to obtain the final purified gas.

7. The integrated ship exhaust gas desulfurization, denitrification and decarbonization treatment method according to claim 6, characterized in that: The zeolite used is 5A and 13X zeolite.

8. The integrated ship exhaust gas desulfurization, denitrification and decarbonization treatment method according to claim 1, characterized in that: It also includes monitoring and control steps. During the entire process, online monitoring equipment is used to monitor the exhaust gas composition in real time, and the treatment parameters of each link are adjusted through the control system.

9. The integrated ship exhaust gas desulfurization, denitrification and decarbonization treatment method according to claim 8, characterized in that: The online monitoring equipment includes a gas analyzer, a particulate matter monitor and a flow meter to monitor the concentrations of SOx, NOx, particulate matter and other pollutants in the exhaust gas in real time; the control system automatically adjusts the spray volume of the spray device, the amount of reducing agent added and the temperature and pressure parameters in the reactor by collecting and analyzing monitoring data to ensure the efficient desulfurization and denitrification reactions, and performs early warning and fault processing as needed.

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