Flue gas deep dust removal and SCR (Selective Catalytic Reduction) integrated ultralow emission system and process

Abstract

The invention discloses a flue gas deep dust removal and SCR integrated ultra-low emission system and process, and the system comprises a wet electric dust remover which is connected to the downstream of a desulfurization system; the flue gas condenser is connected to the downstream of the wet electric dust collector; the flue demister is connected to the downstream of the flue gas condenser; the GGH heat exchanger-cold end is connected to the downstream of the flue demister; the flue gas heating system is connected to the downstream of the cold end of the GGH heat exchanger; the SCR denitration reactor is connected to the downstream of the flue gas heating system; and the hot end of the GGH heat exchanger is connected to the downstream of the SCR denitration reactor. By integrating multiple efficient technologies, comprehensive ultralow emission of particulate matter, SOs and NOx in industrial flue gas is achieved, meanwhile, energy consumption and maintenance are optimized, the long-term stability and operation convenience of the system are improved, and the system has the excellent pollutant removal effect and energy-saving and environment-friendly performance and is widely applied to various complex working conditions.

Description

Technical Field

[0001] The present invention relates to the field of industrial flue gas treatment and environmental protection technology, and specifically to a flue gas deep dust removal and SCR integrated ultra-low emission system and process. Background Art

[0002] With the continuous advancement of industrialization, production activities in industries such as iron and steel metallurgy and chemicals have generated a large amount of industrial flue gas, which contains various pollutants such as particulate matter, sulfur dioxide (SO2), and nitrogen oxides (NOx). In order to meet increasingly stringent environmental protection requirements and reduce the emission of these harmful substances, a variety of flue gas treatment systems and processes have been developed in the existing technology, including wet desulfurization, selective catalytic reduction (SCR) denitrification, wet electrostatic precipitator and other technologies. These technologies have been widely used in the field of industrial flue gas treatment and have achieved certain results in controlling pollutant emissions.

[0003] Among the existing flue gas treatment technologies, wet desulfurization technology removes SO2 from flue gas by chemical absorption, while SCR technology effectively reduces NOx emissions through catalytic reduction reactions. As the terminal equipment of the dust removal system, the wet electrostatic precipitator uses the electric field to remove tiny particles and acid mist from the flue gas. The full application of these technologies can control the concentration of major pollutants in the flue gas within the national emission standards. However, with the promotion and implementation of ultra-low emission standards, single or traditional combination flue gas treatment technologies often find it difficult to stably achieve comprehensive ultra-low emissions of particulate matter, SO2 and NOx when facing complex working conditions.

[0004] Although the existing technology has solved the pollution problem of industrial flue gas emissions to a certain extent, there are still some urgent problems to be solved and a series of challenges to be faced. First, the existing system often has reduced efficiency or instability when dealing with high-concentration particulate matter and complex flue gas components, resulting in occasional excessive particulate matter at the outlet of the desulfurization and denitrification system; secondly, the droplets and acid mist contained in the flue gas can easily cause equipment corrosion, increase the operating stability and cost pressure of environmental protection equipment, and make it difficult to meet more stringent environmental protection requirements. In addition, the existing SCR denitrification completely relies on the flue gas heating system to burn coal gas, natural gas and other fuels to heat the flue gas, which has high energy consumption and extremely low energy utilization. Therefore, there is an urgent need for a flue gas treatment system that is more efficient, stable and can adapt to different working conditions to solve the shortcomings of the existing technology.

[0005] At present, the desulfurization technologies represented by the limestone / lime-gypsum wet method, ammonia method, and circulating fluidized bed method can control the SO2 emission concentration at an ultra-low emission level. The current difficulty lies in the difficulty of achieving ultra-low emission levels for NOx and particulate matter. After the flue gas has been desulfurized, sulfur dioxide, hydrogen chloride, hydrogen fluoride and other acidic gas pollutants are basically removed, and the remaining NOx and particulate matter (including a small amount of acid mist formed by acidic substances such as sulfur trioxide) pollutants are reduced to 50mg / Nm 3 , can not reach the ultra-low emission 10mg / Nm 3 The present invention solves the problem of ultra-low emission of NOx and particulate matter. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention provides an ultra-low emission system and process integrating deep dust removal and SCR for flue gas, which solves the problems of unstable emissions, high energy consumption and difficult maintenance under complex working conditions.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions: A flue gas deep dust removal and SCR integrated ultra-low emission system and process, including: 1. It includes: a wet electrostatic precipitator, connected to the downstream of the desulfurization system, used to remove particulate matter and droplets in the flue gas; The flue gas condenser is connected downstream of the wet electrostatic precipitator to reduce the flue gas temperature and condense and condense the gaseous water in the flue gas, thereby reducing the water content in the flue gas; Flue demister: A demister is installed after the flue gas condenser to further remove fine droplets and particulate matter in the flue gas; GGH heat exchanger - cold end, connected downstream of the flue demister, is used to perform heat exchange on the flue gas and increase the flue gas temperature; The flue gas heating system is connected downstream of the GGH heat exchanger-cold end to further increase the flue gas temperature to the temperature required for the SCR reaction; The SCR denitration reactor is connected to the downstream of the flue gas heating system and is equipped with a medium-high temperature catalyst to reduce NOx in the flue gas to nitrogen and water vapor. A catalyst bed for CO oxidation is pre-installed at the front end of the SCR denitration reaction. When the CO content in the flue gas is high, the heat released by the catalytic oxidation of CO in the flue gas is fully utilized to reduce the gas required for the flue gas heating system. GGH heat exchanger-hot end, connected to the downstream of SCR denitration reactor, is used to exchange heat with flue gas, reduce the exhaust gas temperature, and recover heat energy; Induced draft fan, used to discharge treated flue gas into the chimney.

[0008] Preferably, a flushing spray system is provided inside the wet electrostatic precipitator for periodically flushing the inside of the wet electrostatic precipitator to prevent dust accumulation and scaling.

[0009] Preferably, the SCR denitration reactor is provided with a sonic soot blower for regularly removing dust from the catalyst surface to ensure the denitration efficiency of the catalyst.

[0010] Preferably, the flue gas heating system adopts an external heating furnace to increase the flue gas temperature from 245°C to 280°C by burning blast furnace gas.

[0011] Preferably, the anode tube of the wet electrostatic precipitator is made of conductive fiberglass, and the diameter of the inscribed circle of the anode tube is 360 mm.

[0012] Preferably, the catalyst in the SCR denitration reactor is a vanadium-titanium-based honeycomb catalyst, which is suitable for a reaction temperature range of 260°C to 320°C.

[0013] Preferably, a demister is provided between the flue gas condenser and the GGH heat exchanger-cold end to further remove fine droplets in the flue gas.

[0014] Preferably, a CO catalyst bed is pre-installed in the SCR denitration reactor, so as to make full use of the heat released by the catalytic oxidation of CO in the flue gas when the CO content in the flue gas is high, and reduce the gas required for the flue gas heating system; Preferably, the induced draft fan is an axial flow fan with adjustable moving blades and is started by a soft starter.

[0015] The flue gas deep dust removal and SCR integrated ultra-low emission process includes the following steps: S1. Deep dust removal: The flue gas after desulfurization is introduced into the wet electrostatic precipitator, and the particles and droplets are charged by corona discharge, and adsorbed to the surface of the anode tube under the action of the electric field force, and then the surface of the anode tube is cleaned by the flushing spray system; S2. Flue gas condensation: The flue gas temperature after desulfurization and deep dust removal is further reduced through process water heat exchange, so that the gaseous water in the flue gas is condensed and condensed, reducing the water content in the flue gas and thus reducing the energy required for subsequent flue gas heating; S3, Demisting treatment: a demisting device is set after the flue gas condenser to remove fine mist droplets in the flue gas; S4, flue gas heat exchange: The flue gas after desulfurization, deep dust removal and SCR denitrification is heat exchanged through the GGH heat exchanger, and the heat in the hot flue gas that meets the ultra-low emission requirements is recovered to heat the cold flue gas; S5. Secondary flue gas heating: Use an external heating furnace to further heat the preheated flue gas to raise its temperature to the temperature required for the SCR reaction; S6, SCR denitration reaction: The heated flue gas is introduced into the SCR denitration reactor, which is equipped with multiple layers of medium- and high-temperature vanadium-titanium-based honeycomb catalysts to perform selective catalytic reduction reaction within a specified temperature range; S7. Ammonia escape monitoring and control: An ammonia escape detection device is installed downstream of the SCR reactor to monitor the ammonia concentration; S8. Utilize the heat energy of CO in flue gas through catalytic oxidation: pre-install the catalyst bed for CO oxidation in the SCR denitration reaction. When the CO content in the flue gas is high, make full use of the heat released by the catalytic oxidation of CO in the flue gas to reduce the gas required for the flue gas heating system. S9. Flue gas emission: The treated purified flue gas is transported to the chimney through the induced draft fan for emission.

[0016] Preferably, in the deep dust removal step: The flushing spray system of the wet electrostatic precipitator automatically adjusts the flushing frequency and water film coverage according to the monitoring data of the particle concentration, flow rate and humidity in the flue gas.

[0017] The desulfurization system includes an ammonia absorption method-pre-washing tower and an ammonia absorption tower-absorption tower.

[0018] The present invention provides a flue gas deep dust removal and SCR integrated ultra-low emission system and process. It has the following beneficial effects: 1. The present invention integrates a variety of advanced technologies to achieve efficient removal of pollutants such as particulate matter and NOx in industrial flue gas after desulfurization. In particular, in the SCR denitrification system, the removal efficiency of NOx is significantly improved by adopting medium and high temperature catalysts and multi-layer catalyst design, and the final concentration of pollutants discharged is far lower than the national ultra-low emission standard. This advantage ensures that the system can stably meet strict environmental protection requirements under various complex working conditions.

[0019] 2. Through the application of GGH heat exchanger, the present invention effectively recovers waste heat and significantly reduces the energy consumption of flue gas heating. At the same time, the precise control of the external heating furnace and the reasonable process design enable the system to minimize energy consumption while meeting environmental protection requirements, thereby reducing operating costs and environmental burdens.

[0020] 3. The present invention reduces the frequency and complexity of manual maintenance by configuring advanced equipment such as automatic cleaning system and sonic soot blower; the optimized design of core equipment such as wet electrostatic precipitator and SCR catalyst prolongs the service life of the equipment and improves the long-term stability of the system; in addition, the modular design of the system makes installation, maintenance and expansion more convenient and more adaptable, effectively improving the operating efficiency and reliability in industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a process flow chart of the flue gas deep dust removal and SCR integrated ultra-low emission system of the present invention. DETAILED DESCRIPTION

[0022] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the specification of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] Please see attached Figure 1 The present invention relates to a comprehensive system and process for industrial flue gas treatment, which realizes ultra-low emissions of particulate matter, nitrogen oxides (NOx) and other pollutants in flue gas after desulfurization through the organic combination of multiple technologies. The system is particularly suitable for flue gas treatment in industries such as iron and steel metallurgy and chemical industry, and meets the strict requirements of current environmental protection laws and regulations on flue gas emissions. The design of the system and process comprehensively considers high efficiency, energy saving, adaptability and maintainability, can operate stably for a long time, and has strong adaptability, suitable for different industrial application scenarios.

[0024] 1. System Overview The whole system includes wet electrostatic precipitator, flue gas condenser, flue demister, GGH heat exchanger (including cold end and hot end), flue gas heating system, SCR denitration reactor, induced draft fan, reductant storage and supply system, chimney and related auxiliary equipment. These components are scientifically arranged and organically combined to form a complete flue gas treatment process. All equipment in the system is connected through the flue, and the power of flue gas flow comes from the fan arranged at the end of the system. The present invention mainly solves the problem of ultra-low emission of NOx and particulate matter after flue gas desulfurization. The selection and design of each part of the equipment are based on the characteristics and treatment requirements of industrial flue gas to ensure the stability and efficiency of the system under different working conditions.

[0025] 2. Process description Step 1: Deep dust removal In this embodiment, the wet electrostatic precipitator uses an anode tube made of conductive fiberglass material, and its design takes into account the corrosion and conductivity requirements in high temperature and high humidity environments. The inscribed circle diameter of the anode tube is 360mm, which ensures a large specific surface area and a high dust removal efficiency. The flue gas undergoes corona discharge in the wet electrostatic precipitator, and the charged particles and microdroplets are adsorbed to the surface of the anode tube under the action of the electric field force. Subsequently, the attached particles are effectively removed by water film flushing and discharged with the water flow, ensuring that the concentration of particles in the flue gas drops below 5mg / Nm³. The continuity and uniformity of the water film design are crucial to prevent secondary dust and accumulation of dust, thereby improving the overall dust removal effect.

[0026] Step 2: Flue gas condensation In this embodiment, the flue gas condenser is arranged at the rear end of the wet electrostatic precipitator. The flue gas temperature after desulfurization and deep dust removal is further reduced by process water heat exchange, so that the gaseous water in the flue gas is condensed and condensed. At the same time, the flue gas cooling helps some acidic gases (such as SO3) to condense into micro droplets, reducing the water content in the flue gas and thus reducing the energy required for subsequent flue gas heating, which is usually controlled at around 49°C. Through this process, not only can the corrosion risk of subsequent equipment (such as wet electrostatic precipitator) be reduced, but also the service life of the equipment can be extended. At the same time, the condensed liquid can be recovered or discharged through the pipeline system to reduce the concentration of acidic substances in the flue gas.

[0027] Step 3: Defogging A demister is installed after the flue gas condenser to further remove fine droplets in the flue gas to prevent them from causing corrosion and scaling in subsequent equipment and ensure the normal operation of the equipment.

[0028] Step 4: Flue gas preheating In this embodiment, the flue gas temperature after the wet electrostatic precipitator is about 49°C, which needs to be further increased to meet the working requirements of the SCR reactor. To this end, a GGH (gas-gas heat exchanger) is set up to use the treated hot flue gas to exchange heat with the cold flue gas. The GGH heat exchanger uses high temperature and corrosion resistant materials, and through reasonable airflow organization and heat exchange element design, the temperature of the cold flue gas is increased to about 245°C, providing the necessary temperature conditions for the subsequent SCR reaction.

[0029] Step 5: Secondary flue gas heating The flue gas heating system in this embodiment uses an external heating furnace, which further increases the flue gas temperature from 245°C to 280°C by burning blast furnace gas. The external heating furnace has an independent combustion control system that can flexibly adjust the heating amount of the flue gas and ensure the safety of the heating process. The combustion system is equipped with safety facilities such as flame detectors and combustion stabilization devices to prevent safety hazards caused by flame extinguishing or incomplete combustion. At the same time, blast furnace gas as the main fuel helps to reduce the overall environmental impact of the system.

[0030] Step 6: SCR denitrification reaction In this embodiment, the core of the SCR denitration reactor is a medium-high temperature vanadium-titanium-based honeycomb catalyst, which can work efficiently in the temperature range of 260°C to 320°C. The flue gas is fully mixed with the pre-injected ammonia in the SCR reactor, and NOx reacts with ammonia to generate nitrogen and water vapor under the action of the catalyst. In order to ensure the adequacy and uniformity of the reaction, a multi-layer catalyst module is set in the reactor. The design of each layer of the module is optimized by CFD numerical simulation and physical model cold test to ensure uniform flue gas flow field and avoid local overheating or insufficient reaction. In addition, the sonic soot blower equipped in the reactor regularly blows the catalyst surface to prevent dust accumulation and ensure the long-term effectiveness and reaction efficiency of the catalyst.

[0031] Step 7: Reductant Storage and Supply The reductant storage and supply system in this embodiment includes equipment such as an ammonia water storage tank, a delivery pump, an ammonia water evaporator, and a dilution fan. Ammonia water is delivered to the evaporator through a delivery pump, and evaporates into ammonia gas in the evaporator through hot air. The dilution fan mixes the ammonia gas with the hot flue gas to ensure that the concentration of ammonia meets the safety and reaction requirements. The entire ammonia water evaporation and delivery process is monitored and adjusted in real time by an automated control system to ensure that the ammonia supply in the SCR reactor is stable and the concentration is appropriate.

[0032] Step 8: Smoke Emission In this embodiment, the purified flue gas after denitration treatment is sent to the chimney for discharge through an axial flow fan with adjustable blades. The design of the fan with adjustable blades enables the fan to adjust the blade angle in real time according to the actual needs of flue gas flow and pressure, thereby ensuring the stable operation of the entire system. The soft starter design of the fan ensures the stability during the startup process and avoids damage to the equipment due to current shock. The final discharged flue gas enters the atmosphere through the chimney, and the pollutant concentration meets the national ultra-low emission standards, especially the NOx concentration is effectively controlled below 50mg / Nm³.

[0033] Embodiment 1: Flue gas desulfurization treatment: After the desulfurization process, the flue gas basically removes sulfur dioxide, hydrogen chloride, hydrogen fluoride and other acidic gas pollutants, and the remaining NOx and particulate matter (including a small amount of acid mist formed by acidic substances such as sulfur trioxide) pollutants. After desulfurization, the concentration of particulate matter is less than 50mg / Nm 3 . The subsequent work is to remove NOx and particulate matter.

[0034] Deep dust removal: The flue gas passes through the wet electrostatic precipitator, the diameter of the inscribed circle of the anode tube is 360mm, the flue gas flow rate is 1.5m / s, and the final particle concentration is reduced to 5mg / Nm³.

[0035] Flue gas condensation: The flue gas flow of 800,000 Nm³ / h is cooled to 49°C through the condenser.

[0036] Flue gas preheating: The cooled flue gas is heated from 49°C to 245°C by the GGH heat exchanger, and the standard flue gas flow rate remains unchanged.

[0037] Flue gas heating: In an external heating furnace, blast furnace gas is used to increase the flue gas temperature from 245°C to 280°C, and the initial NOx concentration is 350mg / Nm³.

[0038] SCR denitration reaction: Flue gas enters the SCR reactor, and the catalyst uses a medium-high temperature vanadium-titanium-based honeycomb catalyst, with a denitration efficiency of 92% and a final NOx concentration of 28mg / Nm³.

[0039] Flue gas emission: The treated flue gas is discharged through a fan with adjustable blades, and the fan is adjusted to 85% load.

[0040] Comparative Example 1: Deep dust removal: Electric bag composite dust removal is used to remove particulate matter in the flue gas. The dust collector is placed at the front end of the entire flue gas purification system, that is, at the front end of the desulfurization system.

[0041] Flue gas desulfurization treatment: same as in Example 1.

[0042] Flue gas condensation: There is no condensation system. The flue gas temperature is 52°C after passing through the deep dust removal system.

[0043] Flue gas preheating: GGH heat exchanger is not used, and the flue gas is directly heated to 230℃.

[0044] Flue gas heating: Due to insufficient temperature rise, the heating system heats the flue gas to 230°C, and the initial NOx concentration is 350mg / Nm³.

[0045] SCR denitration reaction: using medium and low temperature catalyst, the denitration efficiency is 80%, and the final NOx concentration is 70mg / Nm³.

[0046] Flue gas emission: The fan is set to 100% load.

[0047] Table 1: In Example 1, due to the use of wet electrostatic precipitator and flue gas condensation and heat exchange measures, the particle emission concentration is reduced from 25mg / Nm³ in the comparative example to within 5mg / Nm³. After the heat exchanger is used, the flue gas temperature rises by only 35°C and can stably reach the optimal reaction temperature of the catalyst; the measure of directly heating the flue gas in the comparative example requires the flue gas temperature to be increased by 178°C to barely reach the reaction temperature of the catalyst, which not only wastes energy but also has poor environmental benefits. The wet electrostatic precipitator and flue gas condensation and heat exchange measures used in the embodiment save about 80% of coal gas compared with the comparative example, and have better environmental benefits.

[0048] Embodiment 2: Flue gas desulfurization treatment: After the desulfurization process, the flue gas basically removes sulfur dioxide, hydrogen chloride, hydrogen fluoride and other acidic gas pollutants, and the remaining NOx and particulate matter (including a small amount of acid mist formed by acidic substances such as sulfur trioxide) pollutants. After desulfurization, the concentration of particulate matter is less than 50mg / Nm 3 . The subsequent work is to remove NOx and particulate matter.

[0049] Deep dust removal: The wet electrostatic precipitator is made of reinforced conductive fiberglass material, the diameter of the anode tube inscribed circle is 400mm, the flue gas flow rate is 1.2m / s, and the particle concentration is reduced to 4mg / Nm³.

[0050] Flue gas condensation: 400,000 Nm³ / h of flue gas flow is cooled to 50°C through the condenser.

[0051] Flue gas preheating: GGH heat exchanger heats the cooled flue gas from 50℃ to 250℃, and the standard flue gas flow rate remains unchanged.

[0052] Flue gas heating: The heating furnace increases the flue gas temperature from 250°C to 300°C, and the initial NOx concentration is 400mg / Nm³.

[0053] SCR denitration reaction: Using multi-layer medium-high temperature vanadium-titanium based catalysts, the denitration efficiency reaches 94%, and the final NOx concentration is 24mg / Nm³.

[0054] Smoke emission: The fan is adjusted to 80% load to emit smoke.

[0055] Comparative Example 2: Flue gas desulfurization treatment: same as Example 2.

[0056] Deep dust removal: The wet electrostatic precipitator does not use enhanced materials, the anode tube diameter is 350mm, the flue gas flow rate is 1.8m / s, and the particulate matter concentration is 8mg / Nm³.

[0057] Flue gas condensation: same as in Example 2.

[0058] Flue gas preheating: Without using GGH heat exchanger, the flue gas is directly heated from 50℃ to 240℃.

[0059] Flue gas heating: The heating furnace only raises the flue gas temperature to 240°C, and the initial NOx concentration is 400mg / Nm³.

[0060] SCR denitration reaction: Using a single-layer low-temperature catalyst, the denitration efficiency is 85%, and the final NOx concentration is 60mg / Nm³.

[0061] Flue gas emission: The fan is set to 100% load.

[0062] Table 2: Example 2 significantly improves the denitrification efficiency and has a better particulate matter removal effect by adopting multi-layer catalysts and a higher preheating temperature.

[0063] Embodiment 3: Flue gas desulfurization treatment: After the desulfurization process, the flue gas basically removes sulfur dioxide, hydrogen chloride, hydrogen fluoride and other acidic gas pollutants, and the remaining NOx and particulate matter (including a small amount of acid mist formed by acidic substances such as sulfur trioxide) pollutants. After desulfurization, the concentration of particulate matter is less than 50mg / Nm 3 . The subsequent work is to remove NOx and particulate matter.

[0064] Deep dust removal: using advanced wet electrostatic precipitator, the diameter of the anode tube inscribed circle is 380mm, the flue gas flow rate is 1.3m / s, and the particle concentration is reduced to 3mg / Nm³.

[0065] Flue gas condensation: 500,000 Nm³ / h of flue gas flow is cooled to 48°C.

[0066] Flue gas preheating: GGH heat exchanger heats the flue gas from 48℃ to 260℃.

[0067] Flue gas heating: The flue gas temperature is raised to 290°C by a heating furnace, and the initial NOx concentration is 360mg / Nm³.

[0068] SCR denitration reaction: The catalyst adopts a medium-high temperature multi-layer design, with a denitration efficiency of 93% and a final NOx concentration of 25mg / Nm³.

[0069] Flue gas emission: The fan is set to 85% load.

[0070] Comparative Example 3: Flue gas desulfurization treatment: same as Example 3.

[0071] Deep dust removal: The diameter of the anode tube of the wet electrostatic precipitator is 330mm, the flue gas flow rate is 2.0m / s, and the particle concentration is 9mg / Nm³.

[0072] Flue gas condensation: same as in Example 3.

[0073] Flue gas preheating: directly heat the flue gas from 48℃ to 240℃.

[0074] Flue gas heating: The heating furnace only raises the flue gas temperature to 240°C, and the initial NOx concentration is 360mg / Nm³.

[0075] SCR denitration reaction: Using a single-layer low-temperature catalyst, the denitration efficiency is 83% and the final NOx concentration is 61mg / Nm³.

[0076] Flue gas emission: The fan is set to 100% load.

[0077] Table 3: Since Example 3 adopts a multi-layer catalyst design and is heated to a higher temperature, the NOx removal effect is more significant.

[0078] Embodiment 4: Flue gas desulfurization treatment: After the desulfurization process, the flue gas basically removes sulfur dioxide, hydrogen chloride, hydrogen fluoride and other acidic gas pollutants, and the remaining NOx and particulate matter (including a small amount of acid mist formed by acidic substances such as sulfur trioxide) pollutants. After desulfurization, the concentration of particulate matter is less than 50mg / Nm 3 . The subsequent work is to remove NOx and particulate matter.

[0079] Deep dust removal: The diameter of the wet electrostatic precipitator anode tube is 400mm, the flue gas flow rate is 1.4m / s, and the particle concentration is reduced to 3mg / Nm³.

[0080] Flue gas condensation: 600,000 Nm³ / h of flue gas is cooled to 50°C.

[0081] Flue gas preheating: GGH heat exchanger heats the flue gas from 50℃ to 270℃.

[0082] Flue gas heating: The heating furnace raises the flue gas temperature to 310°C, and the initial NOx concentration is 380mg / Nm³.

[0083] SCR denitration reaction: Using multi-layer high-temperature catalysts, the denitration efficiency reaches 95%, and the final NOx concentration is 19mg / Nm³.

[0084] Flue gas emission: The fan is set to 80% load.

[0085] Comparative Example 4: Flue gas desulfurization treatment: same as Example 4.

[0086] Deep dust removal: The diameter of the anode tube of the wet electrostatic precipitator is 350mm, the flue gas flow rate is 1.9m / s, and the particle concentration is 7mg / Nm³.

[0087] Flue gas condensation: same as Example 4.

[0088] Flue gas preheating: Without using GGH heat exchanger, the flue gas is directly heated from 50℃ to 240℃.

[0089] Flue gas heating: The heating furnace raises the flue gas temperature to 240°C, and the initial NOx concentration is 380mg / Nm³.

[0090] SCR denitration reaction: Using a single-layer low-temperature catalyst, the denitration efficiency is 82% and the final NOx concentration is 68mg / Nm³.

[0091] Flue gas emission: The fan is set to 100% load.

[0092] Table 4: project Example 4 Comparative Example 4 Flue gas flow (Nm³ / h) 600,000 600,000 Flue gas temperature after cooling (℃) 50 50 Particle concentration (mg / Nm³) 3 7 Flue gas temperature after preheating (℃) 270 50 SCR denitration reaction temperature (℃) 310 240 Initial NOx concentration (mg / Nm³) 380 380 Final NOx concentration (mg / Nm³) 19 68 Denitrification efficiency (%) 95 82 Example 4 adopts a higher temperature and a multi-layer catalyst design, and the NOx removal efficiency is significantly higher than that of Comparative Example 4, and the particulate matter removal effect is also better.

[0093] Embodiment 5: Flue gas desulfurization treatment: After the desulfurization process, the flue gas basically removes sulfur dioxide, hydrogen chloride, hydrogen fluoride and other acidic gas pollutants, and the remaining NOx and particulate matter (including a small amount of acid mist formed by acidic substances such as sulfur trioxide) pollutants. After desulfurization, the concentration of particulate matter is less than 50mg / Nm 3 . The subsequent work is to remove NOx and particulate matter.

[0094] Deep dust removal: The diameter of the wet electrostatic precipitator anode tube is 420mm, the flue gas flow rate is 1.2m / s, and the particle concentration is reduced to 2mg / Nm³.

[0095] Flue gas condensation: 700,000 Nm³ / h of flue gas flow is cooled to 48°C.

[0096] Flue gas preheating: GGH heat exchanger heats the flue gas from 48℃ to 280℃.

[0097] Flue gas heating: The heating furnace raises the flue gas temperature to 320°C, and the initial NOx concentration is 390mg / Nm³.

[0098] SCR denitration reaction: Using high-temperature catalyst, the denitration efficiency reaches 96%, and the final NOx concentration is 16mg / Nm³.

[0099] Flue gas emission: The fan is set to 75% load.

[0100] Comparative Example 5: Flue gas desulfurization treatment: same as Example 5.

[0101] Deep dust removal: The diameter of the anode tube of the wet electrostatic precipitator is 350mm, the flue gas flow rate is 2.0m / s, and the particle concentration is 8mg / Nm³.

[0102] Flue gas condensation: same as Example 5.

[0103] Flue gas preheating: Without using GGH heat exchanger, the flue gas is directly heated from 48℃ to 250℃.

[0104] Flue gas heating: The heating furnace only raises the flue gas temperature to 250°C, and the initial NOx concentration is 390mg / Nm³.

[0105] SCR denitration reaction: Using a single-layer low-temperature catalyst, the denitration efficiency is 85%, and the final NOx concentration is 58mg / Nm³.

[0106] Flue gas emission: The fan is set to 100% load.

[0107] Table 5: project Example 5 Comparative Example 5 Flue gas flow (Nm³ / h) 700,000 700,000 Flue gas temperature after cooling (℃) 48 48 Particle concentration (mg / Nm³) 2 8 Flue gas temperature after preheating (℃) 280 48 SCR denitration reaction temperature (℃) 320 250 Initial NOx concentration (mg / Nm³) 390 390 Final NOx concentration (mg / Nm³) 16 58 Denitrification efficiency (%) 96 85 Example 5 demonstrates the excellent performance of the system under the action of a high-temperature catalyst. The NOx removal effect is much better than that of Comparative Example 5, and the particulate matter removal effect is also more significant.

[0108] Comparative experiment In order to further verify the superiority of the present invention, the following comparative experiment was designed to compare the performance of a conventional treatment system and the system of the present invention under the same working conditions.

[0109] Experimental setup: The experimental flue gas flow rate after desulfurization is 400,000Nm³ / h, and the sulfur dioxide concentration is 20mg / Nm³ (which has reached the ultra-low emission index requirements).

[0110] Flue gas initial temperature: 50℃ Initial NOx concentration: 400mg / Nm³ Initial particle concentration: 50mg / Nm³ Processing system comparison: System A (conventional system): GGH heat exchanger is not used, single-layer low-temperature catalyst, and the anode tube diameter is 350mm.

[0111] System B (system of the present invention): using GGH heat exchanger, multi-layer medium and high temperature catalyst, anode tube diameter of 400mm.

[0112] Experimental data table: project System A System B Flue gas flow (Nm³ / h) 400,000 400,000 Flue gas temperature after cooling (℃) 50 50 Final concentration of particles (mg / Nm³) 8 4 Flue gas temperature after preheating (℃) 50 250 SCR denitration reaction temperature (℃) 240 300 Flue gas heating temperature rise (℃) 190 50 Final NOx concentration (mg / Nm³) 65 24 Denitrification efficiency (%) 84 94 System energy consumption (kWh) 1500 1300 The experimental results show that system B (the system of the present invention) is superior to system A in terms of NOx removal efficiency, particulate matter removal effect and energy consumption. In particular, the denitrification efficiency of system B is significantly improved, and the final NOx concentration emitted is much lower than that of system A. At the same time, due to the use of GGH heat exchanger, the flue gas heating temperature rise of system B is much lower than that of system A, and the operating energy consumption is lower, showing a better energy-saving effect.

[0113] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. The flue gas deep dust removal and SCR integrated ultra-low emission system mainly solves the problem of ultra-low emission of NOx and particulate matter after flue gas desulfurization. It is characterized by: include: Wet electrostatic precipitator, connected downstream of the desulfurization system, is used to remove particulate matter and droplets from the flue gas; Flue gas condenser is used to lower the flue gas temperature so as to condense and condense the gaseous water in the flue gas and reduce the water content in the flue gas; A flue demister, connected downstream of the flue gas condenser, is used to further remove droplets and particulate matter from the flue gas; GGH heat exchanger - cold end, connected downstream of the flue demister, is used to perform heat exchange on the flue gas and increase the flue gas temperature; The flue gas heating system is connected downstream of the GGH heat exchanger-cold end to further increase the flue gas temperature to the temperature required for the SCR reaction; The SCR denitrification reactor is connected downstream of the flue gas heating system and is equipped with a medium- and high-temperature catalyst to reduce NOx in the flue gas to nitrogen and water vapor; GGH heat exchanger-hot end, connected to the downstream of SCR denitration reactor, is used to exchange heat with flue gas, reduce the exhaust gas temperature, and recover heat energy; Induced draft fan, used to discharge treated flue gas into the chimney.

2. The flue gas deep dust removal and SCR integrated ultra-low emission system according to claim 1 is characterized in that: The wet electrostatic precipitator is provided with a flushing spray system for regularly flushing the inside of the wet electrostatic precipitator to prevent dust accumulation and scaling.

3. The flue gas deep dust removal and SCR integrated ultra-low emission system according to claim 1 is characterized in that: The SCR denitration reactor is provided with a sonic soot blower for regularly removing dust from the catalyst surface to ensure the denitration efficiency of the catalyst.

4. The flue gas deep dust removal and SCR integrated ultra-low emission system according to claim 1 is characterized in that: The flue gas heating system adopts an external heating furnace to increase the flue gas temperature from 245°C to 280°C by burning blast furnace gas.

5. The flue gas deep dust removal and SCR integrated ultra-low emission system according to claim 1 is characterized in that: The anode tube of the wet electrostatic precipitator is made of conductive glass fiber reinforced plastic material, and the diameter of the inscribed circle of the anode tube is 360 mm.

6. The flue gas deep dust removal and SCR integrated ultra-low emission system according to claim 1 is characterized in that: The catalyst in the SCR denitration reactor is a vanadium-titanium-based honeycomb catalyst, which is suitable for a reaction temperature range of 260°C to 320°C.

7. The flue gas deep dust removal and SCR integrated ultra-low emission system according to claim 1 is characterized in that: A demister is provided between the flue gas condenser and the GGH heat exchanger-cold end to further remove fine droplets in the flue gas and reduce the water content of the flue gas.

8. The flue gas deep dust removal and SCR integrated ultra-low emission system according to claim 1 is characterized in that: The induced draft fan is an axial flow fan with adjustable moving blades and is started by a soft starter.

9. Flue gas deep dust removal and SCR integrated ultra-low emission process, according to the flue gas deep dust removal and SCR integrated ultra-low emission system described in claims 1-8, characterized in that: The following steps are involved: S1. Deep dust removal: The flue gas after desulfurization is introduced into the wet electrostatic precipitator, and the particles and droplets are charged by corona discharge, and adsorbed to the surface of the anode tube under the action of the electric field force, and then the surface of the anode tube is cleaned by the flushing spray system; S2. Flue gas condensation: The flue gas temperature after desulfurization and deep dust removal is further reduced through process water heat exchange, so that the gaseous water in the flue gas is condensed and condensed, reducing the water content in the flue gas and thus reducing the energy required for subsequent flue gas heating and reducing the corrosion of the flue gas to subsequent equipment; S3, Demisting treatment: a demisting device is set after the flue gas condenser to remove fine mist droplets in the flue gas; S4, flue gas heat exchange: The flue gas after desulfurization, deep dust removal and SCR denitrification is heat exchanged through the GGH heat exchanger, and the heat in the hot flue gas that meets the ultra-low emission requirements is recovered to heat the cold flue gas; S5. Secondary flue gas heating: Use an external heating furnace to further heat the preheated flue gas to raise its temperature to the temperature required for the SCR reaction; S6, SCR denitration reaction: The heated flue gas is introduced into the SCR denitration reactor, which is equipped with multiple layers of medium- and high-temperature vanadium-titanium-based honeycomb catalysts to perform selective catalytic reduction reaction within a specified temperature range; S7. Ammonia escape monitoring and control: An ammonia escape detection device is installed downstream of the SCR reactor to monitor the ammonia concentration; S8. Catalytic oxidation utilizes the heat energy released by the oxidation of CO in the flue gas: A catalyst bed for CO oxidation is pre-installed at the front end of the SCR denitration reaction. When the CO content in the flue gas is high, the heat released by the catalytic oxidation of CO in the flue gas is fully utilized to reduce the gas required for the flue gas heating system; S9. Flue gas emission: The treated purified flue gas is transported to the chimney through the induced draft fan for emission.

10. The flue gas deep dust removal and SCR integrated ultra-low emission process according to claim 9 is characterized in that: In the deep dust removal step: The flushing spray system of the wet electrostatic precipitator automatically adjusts the flushing frequency and water film coverage according to the monitoring data of the particle concentration, flow rate and humidity in the flue gas.

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