CN204005957U - A kind of cooperation-removal system that realizes the minimum discharge of coal steam-electric plant smoke multi-pollutant - Google Patents

Abstract

A collaborative dedusting system that realizes ultra-low emission of multi-pollutants in the flue gas of a thermal power plant. Emissions are controlled within 5mg/m ³ . The coordinated mercury removal system composed of selective catalytic reduction denitration system, high-efficiency dust collector, high-efficiency wet desulfurization system, and wet electrostatic precipitator can achieve a mercury emission concentration of less than 6 μg/m ³ in the flue gas at the chimney. The high-efficiency denitrification system composed of low nitrogen burner, selective non-catalytic reduction denitrification system and selective catalytic reduction denitrification system can control the NOx concentration to within 50mg/ ^m3 . The dual-stage circulation and twin-tower limestone-gypsum wet desulfurization system is adopted, and the rotary gas-gas heat exchanger is eliminated to avoid the leakage of the original flue gas to the clean flue gas, and the SO ₂ concentration in the flue gas can be controlled within 35mg/m ³ . In addition, the overall investment level of the utility model is low, and waste heat in the flue gas can be recovered to reduce energy consumption.

Description

A collaborative removal system for realizing ultra-low emission of multi-pollutants in flue gas of thermal power plants

technical field

The utility model belongs to the field of removal of atmospheric pollutants, in particular to a coordinated removal system for realizing ultra-low emission of multi-pollutants in flue gas of a thermal power plant.

Background technique

Following the announcement of the State Council on Air Pollution Prevention and Control Action Plan Guofa [2013] No. 37 "Air Pollution Prevention and Control Action Plan", the state has recently introduced a series of environmental protection policies: the National Energy Administration issued "Strengthening the Energy Industry" on January 23. The Air Pollution Prevention and Control Work Plan, the Measures for the Supervision of Environmental Protection Electricity Prices for Coal-fired Generating Sets and the Operation of Environmental Protection Facilities have been implemented since May 1, 2014, and the new version of the "Emission Standards of Air Pollutants for Thermal Power Plants" will be implemented on July 1. Announcement No. 14 of 2013 by the Ministry of Environmental Protection requires coal-fired units in the thermal power industry in key control areas to implement special smoke and dust emission limits on July 1, 2014, and the "Environmental Protection Law of the People's Republic of China" will be implemented on January 1, 2015.

Some local governments have also introduced more stringent environmental protection requirements: Guangzhou, Shandong (Zibo), Shaanxi (Guanzhong), Hebei (Handan), Xinjiang (Fukang) and other places require coal-fired units in the region to implement special emission limits; Coal-fired units of 600MW and above must meet gas turbine emission standards (sulfur dioxide 35mg/m ³ , nitrogen oxides 50mg/m ³ , smoke and dust 5mg/m ³ ) before 2017.

Domestic environmental protection requirements are becoming increasingly stringent. Clean production of coal-fired units is the general trend. Special emission limits and even gas turbine standards may become the emission requirements for coal-fired units in the next stage. It is a development trend for coal-fired power plants to meet the emission requirements of natural gas power plants.

At present, denitrification technologies mainly include low nitrogen burners, selective non-catalytic reduction denitrification (SNCR) and selective catalytic reduction denitrification (SCR) methods; new boilers adopt low nitrogen burners or existing boilers are retrofitted with low nitrogen burners, The NO _x emission at the furnace outlet has been reduced to varying degrees. However, the adoption of low-nitrogen combustion technology may have some impact on boiler performance: boiler combustion efficiency may be reduced, causing problems such as slagging and corrosion on the heating surface of the water wall in the burner area. The main problem of the SNCR denitrification system in practical application is that the denitrification efficiency is not high (about 15% to 50%), and the larger the boiler capacity, the lower the SNCR denitrification efficiency. In addition, the utilization rate of urea is low (about 15%-30%), and the large consumption of urea leads to high ammonia slip (about 5-10ppm). When SNCR denitrification is used alone, ammonium bisulfate generated by the reaction of ammonia escape and SO ₃ in the flue gas will cause contamination, ash, and blockage of the heating surface of the air preheater. Almost all thermal power plants in China have installed dust removal devices, and WFGD has also become the main technology for desulfurization in thermal power plants in China. Wet desulfurization also consumes a large amount of water resources. It is necessary to balance the desulfurization system of coal-fired power plants with the supply of water resources and desulfurization agent resources (such as limestone resources), and at the same time solve the problem of sulfur resource utilization and wet chimneys. In terms of dust removal, it is necessary to balance the overall optimal combination of dust collectors and desulfurization to achieve technical and economical dust removal effects and save investment and operating costs.

Internationally, it is a new technological trend to study the coordinated control of multi-pollutants in coal-fired flue gas, and the integrated control of flue gas multi-pollutant treatment systems is the main direction. For the four main pollutants in the national thermal power plant environmental protection emission standards: NOx, soot, SO ₂ and the highly toxic pollutant mercury that will be strictly controlled in the future, thermal power units need to take a series of in-depth environmental protection measures to ensure that each pollutant ultra-low emissions.

Utility model content

The purpose of the utility model is to provide a cooperative removal system that can realize ultra-low emission of multi-pollutants in the flue gas of a thermal power plant.

In order to achieve the above-mentioned purpose, the technical solution adopted by the utility model is: including low-nitrogen burners connected in series, selective non-catalytic reduction denitrification system, selective catalytic reduction denitrification system, high-efficiency dust collector, high-efficiency wet desulfurization system and wet electric dust collector.

An induced draft fan is arranged between the high-efficiency dust collector and the high-efficiency wet desulfurization system.

The induced draft fan is a two-stage axial flow fan with adjustable blades.

The outlet denitrification flue of the selective non-catalytic reduction denitrification system is provided with a plurality of characteristic nozzles.

The outlet of the selective catalytic reduction denitrification system is provided with an air preheater, a flue gas cooler is provided between the air preheater and the high-efficiency dust collector, and a flue gas reheater is provided at the outlet of the wet electrostatic precipitator, and The heat absorbing end of the flue gas cooler forms a loop with the heat releasing end of the flue gas reheater.

The outlet of the flue gas reheater is connected with the chimney.

The high-efficiency wet desulfurization system consists of a primary limestone-gypsum wet desulfurization system and a secondary limestone-gypsum wet desulfurization system connected in series, and the primary limestone-gypsum wet desulfurization system and the secondary limestone-gypsum wet desulfurization system The absorption tower of the wet desulfurization system is equipped with a liquid accumulation plate and a tube type demister. The entrance of the absorption tower of the first-grade limestone-gypsum wet desulfurization system is equipped with a flue gas cooler, and the outlet of the electrostatic precipitator It is connected with the inlet of the absorption tower of the primary limestone-gypsum wet desulfurization system, and the outlet of the absorption tower of the secondary limestone-gypsum wet desulfurization system is connected with the wet electrostatic precipitator.

Compared with the prior art, the utility model has the beneficial effects of:

1. The utility model combines the SNCR denitrification technology of the selective non-catalytic reduction denitrification system and the SCR denitrification technology of the selective catalytic reduction denitrification system with the low-nitrogen combustion technology of the low-nitrogen burner to realize the deep denitrification of the flue gas in the power plant At the same time, high-efficiency dust collectors, high-efficiency wet desulfurization systems, and wet electrostatic precipitators form a collaborative dust removal system. Among them, the high-efficiency dust collector can effectively reduce the dust specific resistance, improve dust removal efficiency, and control the smoke concentration at the outlet of the high-efficiency dust collector at 30mg/m within ³ . The wet electrostatic precipitator is arranged after the wet desulfurization device as the last stage of dust removal equipment. In the wet electrostatic precipitator, the liquid flows through the dust collecting plate and removes the adsorbed substances from its surface, which can effectively remove the dust in the flue gas. Fine particles such as SO ₃ acid mist, gypsum rain carried by the flue gas, and pollutants such as PM _2.5 and mercury oxide, the total particle emission in the flue gas emitted from the chimney can be controlled within 5mg/m ³ . In addition, the selective catalytic reduction denitrification system, high-efficiency dust collector, high-efficiency wet desulfurization system, and wet electrostatic precipitator constitute a collaborative mercury removal system, which can stably oxidize more than 90% of elemental mercury into divalent mercury, This part of divalent mercury can be removed by high-efficiency dust collector, high-efficiency wet desulfurization system, and wet electrostatic precipitator, and the removal rate is above 90%. The collaborative mercury removal system proposed by the utility model has a removal rate of more than 80% of total mercury, and realizes the goal that the emission concentration of mercury in the flue gas at the chimney is lower than 6 μg/m ³ . Therefore, the utility model can realize ultra-low emission of multiple pollutants in the flue gas.

2. The utility model organically connects the existing systems in series, integrates the environmental protection facilities of the power plant, and is beneficial to realize the overall control optimization.

3. The utility model adopts an air preheater and an MGGH system composed of a flue gas cooler and a flue gas reheater, so that the waste heat in the flue gas can be recovered, reducing energy consumption and corrosion.

Description of drawings

Fig. 1 is the schematic diagram of the utility model system;

1. Low nitrogen burner, 2. Selective non-catalytic reduction denitrification system, 3. Selective catalytic reduction denitrification system, 4. Air preheater, 5. Low and low temperature electrostatic precipitator, 6. Induced fan, 7. High efficiency humidifier 8. Wet electrostatic precipitator, 9. Chimney, 10. Flue gas cooler, 11. Flue gas reheater.

Detailed ways

Below in conjunction with accompanying drawing, the utility model is described in further detail.

Under the premise of meeting ultra-low emission requirements, the utility model needs to optimize the overall optimization of various environmental protection facilities in order to minimize the impact of the operation of environmental protection facilities on boiler thermal efficiency, plant power consumption rate and unit efficiency. At the same time, the utility model is suitable for new coal-fired units and old coal-fired units, and can regard the environmental protection facilities of the power plant as an organic whole. It has the advantages of reliable technical route, advanced environmental protection indicators, low overall investment level, and significant energy saving and consumption reduction. . For old coal-fired units, it is necessary to transform them based on existing environmental protection facilities to save costs. For new coal-fired units, combined with the characteristics of coal-fired power plants, a thermal power plant flue gas multi-pollutant ultra-low emission system can be built at one time.

Referring to Fig. 1, the utility model includes a low-nitrogen burner 1, a selective non-catalytic reduction denitration system 2, a selective catalytic reduction denitrification system 3, an air preheater 4, a flue gas cooler 10, and a high-efficiency dust collector 5 connected in series. , high-efficiency wet desulfurization system 7, wet electrostatic precipitator 8, flue gas reheater 11, and chimney 9; wherein, the electric precipitator is connected to the high-efficiency wet desulfurization system 7, and the induced draft fan 6 is a two-stage movable blade adjustable axial flow The fan, the heat absorbing end of the flue gas cooler 10 and the heat releasing end of the flue gas reheater 11 form a loop.

Low-nitrogen burner in the utility model 1, selective non-catalytic reduction denitrification system 2, selective catalytic reduction denitrification system 3, air preheater 4, high-efficiency dust collector 5, high-efficiency wet desulfurization system 7, wet electrostatic precipitator 8. The chimney 9, flue gas cooler 10, and flue gas reheater 11 cooperate to form the following systems:

(1) Efficient denitrification system

The high-efficiency denitrification system of the utility model is composed of a low-nitrogen burner 1, a selective non-catalytic reduction denitrification system 2 and a selective catalytic reduction denitrification system 3. Overall optimization of the combination scheme to achieve deep denitrification. And the outlet denitrification flue of the selective non-catalytic reduction denitrification system 2 is provided with multiple nozzles, so that the selective catalytic reduction denitrification system 3 can achieve better denitrification effect; and during operation, by optimizing the operation mode of the low nitrogen burner (such as OFA wind rate), strictly monitor the fly ash combustible content and CO content in the boiler exhaust smoke, to ensure the safety and economy of boiler operation.

(2) Efficient wet desulfurization system

The high-efficiency wet desulfurization system of the utility model adopts a double-stage circulation double-tower limestone-gypsum wet desulfurization system, cancels the rotary gas-gas heat exchanger, and avoids the leakage of the original flue gas to the clean flue gas. In order to effectively alleviate the problem of "chimney rain", the utility model high-efficiency wet desulfurization system 7 is composed of a first-level limestone-gypsum wet desulfurization system and a second-level limestone-gypsum wet desulfurization system connected in series, and the first-level limestone-gypsum wet desulfurization system The absorption towers of the wet desulfurization system and the secondary limestone-gypsum wet desulfurization system are equipped with a liquid accumulation plate and a tube type demister, and the entrance of the absorption tower of the primary limestone-gypsum wet desulfurization system has The flue gas cooler and the outlet of the electrostatic precipitator are connected to the inlet of the absorption tower of the primary limestone-gypsum wet desulfurization system, and the outlet of the absorption tower of the secondary limestone-gypsum wet desulfurization system is connected to the wet electrostatic precipitator 8 . In addition, in order to further reduce the _SO2 concentration at the outlet of the high-efficiency wet desulfurization system, the utility model adopts a desulfurization system for thermal power units that have been equipped with desulfurization devices to carry out capacity-increasing transformation, that is, to expand the original limestone-gypsum wet desulfurization system to be connected in series A combined primary limestone-gypsum wet desulfurization system and a secondary limestone-gypsum wet desulfurization system.

(3) Cooperative dust removal system

The utility model adopts a high-efficiency dust collector 5, a high-efficiency wet desulfurization system 7, and a wet electric dust collector 8 to form a cooperative dust removal system.

The flue gas cooler 10 arranged in front of the high-efficiency dust collector 5 of the utility model can reduce the temperature of the flue gas to below the acid dew point temperature, the amount of flue gas decreases correspondingly with the reduction of the flue gas temperature, and the reduction of the speed of the flue gas in the electric field is beneficial to fine Dust capture; at the same time, it can realize the recovery and utilization of waste heat of flue gas; it has the advantages of efficient dust removal, energy saving and water saving. Adopting the high-efficiency dust collector of the utility model can effectively reduce the dust specific resistance, improve the dust removal efficiency, and control the smoke concentration at the outlet of the high-efficiency dust collector within 30mg/ ^m3 .

The wet electrostatic precipitator 8 is arranged after the high-efficiency wet desulfurization system 7, as the last stage of dust removal equipment. In the wet electrostatic precipitator 8, the liquid flows through the dust collecting plate and removes the adsorbed substances from its surface, which can effectively remove SO ₃ acid mist in the flue gas, fine particles such as gypsum rain carried by the flue gas, and pollutants such as PM _2.5 and mercury oxide, the total particle emission of the chimney can be controlled within 5mg/m ³ .

(4) Collaborative mercury removal system

The collaborative mercury removal system in the utility model is composed of a selective catalytic reduction denitrification system 3, a high-efficiency dust collector 5, a high-efficiency wet desulfurization system 7, and a wet electrostatic precipitator 8, which can effectively control the emission concentration of mercury.

First, a part of the gaseous elemental mercury is oxidized to divalent mercury by means of the SCR vanadium-based catalyst in the selective catalytic reduction denitrification system 3. Due to the difference in coal type and other conditions, the oxidation rate varies from 40% to 60%. In order to further improve the mercury oxidation rate of the SCR vanadium-based catalyst, the utility model adds MnOx-CeO ₂ to the SCR vanadium-based catalyst arranged in the selective catalytic reduction denitrification system 3, and MnOx-CeO ₂ accounts for the mass of the SCR vanadium-based catalyst 1% to 3%; thus ensuring that the oxidation rate of elemental mercury can reach more than 90% stably.

With the help of the high-efficiency dust collector 5, the high-efficiency wet desulfurization device 7 and the wet electrostatic precipitator 8, the granular mercury in the form of particles in the flue gas and the divalent mercury that is easily soluble in water can be removed, and the removal of granular mercury and divalent mercury The removal rate is above 90%. At the same time, in order to suppress the reduction of divalent mercury in the slurry and improve the mercury removal efficiency of the WFGD system, the utility model uses a sodium hydrosulfide additive to solidify divalent mercury. Finally, the utility model has a removal rate of more than 80% of total mercury, and realizes the goal that the emission concentration of total mercury in the flue gas at the chimney is lower than 6 μg/m ³ .

(5) MGGH

The flue gas cooler 10 and the flue gas reheater 11 of the utility model form the MGGH system. The flue gas after denitrification enters the flue gas cooler 10 after heat exchange by the air preheater 4, and the flue gas cooler 10 circulates The substance (water) absorbs the heat in the flue gas, reduces the temperature of the flue gas to about 90°C, and transfers the heat to the exothermic end of the flue gas reheater 11, SO ₃ combines with water vapor to generate sulfuric acid mist, and Adsorbed by fly ash particles, it can effectively reduce the specific resistance of dust, improve the efficiency of dust removal, and then remove dust through high-efficiency dust collectors. Through the closed circulation of heat medium water, the heat obtained from the cooling heat exchanger is used to heat the clean flue gas after desulfurization, so that its temperature rises from about 50°C to above 80°C.

In order to achieve the ultra-low emission target of controlling NOx emission below 50mg/m ³ (standard state, dry basis, 6% O ₂ ), first, the NOx concentration is initially controlled by the low nitrogen burner 1, and then enters the selective non- The catalytic reduction denitrification system 2 reduces the NOx concentration at one time, and finally the selective catalytic reduction denitrification system 3 controls the NOx concentration to within 50 mg/ ^m3 to obtain denitrified flue gas;

Secondly, the flue gas after denitrification enters the flue gas cooler 10 after being heat-exchanged by the air preheater 4, and the flue gas cooler 10 lowers the temperature of the flue gas to below the acid dew point temperature, and then passes through the high-efficiency dust collector 5, and then passes through the high-efficiency dust collector. 5 Effectively reduce the dust specific resistance and recover waste heat, and control the soot concentration in the flue gas after dust removal at the outlet of the high-efficiency dust collector 5 within 30 mg/ ^m3 ; the flue gas after dust removal enters the high-efficiency wet desulfurization system 7 for desulfurization, The concentration of SO ₂ in the flue gas is lower than 35mg/m ³ ;

The wet electrostatic precipitator 8 is arranged after the high-efficiency wet desulfurization system as the last stage of dust removal equipment. Finally, the desulfurized flue gas enters the wet electrostatic precipitator 8, and the liquid flows through the dust collecting plate of the wet electrostatic precipitator and flows from it. The surface removes the adsorbed substances, which can effectively remove SO ₃ acid mist in the flue gas, fine particles such as gypsum rain carried by the flue gas, and pollutants such as PM _2.5 and mercury oxide. The total particle emission in the flue gas can be controlled within Within 5 mg/m ³ , the flue gas enters the flue gas reheater 11 under the gravitational force of the induced draft fan 6 to absorb the heat from the circulating working fluid at the cooling end of the flue gas cooler 10, and finally discharges into the atmosphere through the chimney 9. The concentration mentioned in the utility model is all standard state, dry basis, 6% O ₂ when measured.

The effect of the utility model is that: this patent combines denitrification, desulfurization, dust removal, waste heat utilization, fan, chimney, etc., and combines the fan system with the pollutant removal system; the relatively independent flue gas flow becomes a organic whole. The heat medium water heat recovery system (MGGH) and the high-efficiency dust collector organically combine the dust removal technology and waste heat utilization technology to realize the unity of energy saving and environmental protection. The utility model combines low-nitrogen burner 1, selective non-catalytic reduction denitrification system 2, selective catalytic reduction denitrification system 3, air preheater 4, high-efficiency dust collector 5, high-efficiency wet desulfurization system 7, and wet electrostatic precipitator 8 and the chimney 9 are reasonably combined to finally achieve the ultra-low emission requirements of NOx emissions below 50mg/m ³ , smoke concentration below 5mg/m ³ , and SO ₂ emissions below 35mg/m ³ , and at the same time ensure that the chimney The emission concentration of mercury in flue gas is lower than 6μg/m ³ .

Claims (7)

1. A collaborative removal system for realizing ultra-low emission of multi-pollutants in thermal power plant flue gas, characterized in that it includes sequentially connected low-nitrogen burners (1), selective non-catalytic reduction denitrification system (2), selective Catalytic reduction denitrification system (3), high-efficiency dust collector (5), high-efficiency wet desulfurization system (7) and wet electric dust collector (8). 2. The coordinated removal system for realizing ultra-low emission of multi-pollutants in thermal power plant flue gas according to claim 1, characterized in that: between the high-efficiency dust collector (5) and the high-efficiency wet desulfurization system (7) An induced draft fan (6) is provided. 3. The coordinated removal system for achieving ultra-low emission of multi-pollutants in thermal power plant flue gas according to claim 2, characterized in that: the induced draft fan (6) is a two-stage axial flow fan with adjustable blades. 4. The coordinated removal system for realizing ultra-low emission of multi-pollutants in thermal power plant flue gas according to claim 1, characterized in that: the outlet denitrification flue of the selective non-catalytic reduction denitrification system (2) is provided with Multiple characteristic nozzles. 5. The synergistic removal system for realizing ultra-low emission of multi-pollutants in thermal power plant flue gas according to claim 1, characterized in that: the outlet of the selective catalytic reduction denitrification system (3) is provided with an air preheater (4), a flue gas cooler (10) is provided between the air preheater (4) and the high-efficiency dust collector (5), and a flue gas reheater (11) is provided at the outlet of the wet electrostatic precipitator (8), In addition, the heat absorbing end of the flue gas cooler (10) and the heat releasing end of the flue gas reheater (11) form a loop. 6. The coordinated removal system for achieving ultra-low emission of multi-pollutants in thermal power plant flue gas according to claim 5, characterized in that: the outlet of the flue gas reheater (11) is connected to the chimney (9). 7. The coordinated removal system for realizing ultra-low discharge of multiple pollutants in thermal power plant flue gas according to claim 1, characterized in that: the high-efficiency wet desulfurization system (7) consists of a series of first-stage limestone- The gypsum wet desulfurization system and the secondary limestone-gypsum wet desulfurization system are composed, and the absorption towers of the primary limestone-gypsum wet desulfurization system and the secondary limestone-gypsum wet desulfurization system are installed with liquid accumulation plates in the tower and Tube type mist eliminator, a flue gas cooler is installed at the entrance of the absorption tower of the primary limestone-gypsum wet desulfurization system, and the outlet of the electrostatic precipitator is connected with the inlet of the absorption tower of the primary limestone-gypsum wet desulfurization system. The outlet of the absorption tower of the secondary limestone-gypsum wet desulfurization system is connected with the wet electrostatic precipitator (8).