Combining with engineering examples, the article compares and analyzes the configuration of the three types of furnaces and the dust removal and desulphurization equipment from a technical and economical point of view. Finally, it is proposed to use a circulating fluidized bed combustion technology to add a configuration scheme for the corresponding dust removal and desulfurization equipment.
1 Two basic types of coal-fired boilers
1.1 Chain furnace
The chain furnace realizes the coal supply through the coal hopper in front of the furnace, and can adjust the thickness of the coal seam, the operating speed of the grate, and the air intake in real time so as to realize the control of the thermal power. In addition, the choice of coal types requires reference to the structure of the furnace. The grate is the main “place†for the combustion of the coal seam, so the coal seam on the grate must not only ensure uniform particle size, but also satisfy conditions such as flammability and non-coking. The advantages of the chain furnace are as follows: low cost, not only in the low cost, but also in the low operating cost; the dust removal device is not high; the technology has matured, safe and reliable operation, operation is relatively simple. The disadvantages of the chain furnace are as follows: the desulfurization cannot be performed in the furnace; the adaptability of the coal is not satisfactory and poor; the NOx is easily generated during the high temperature combustion process; the thermal efficiency is low, and the adaptability to the load variation is poor.
1.2 Circulating fluidized bed boiler
In recent years, circulating fluidized bed boilers have begun to enter the field of vision. The advantages of this equipment are as follows: high efficiency; low pollution; better adaptability of coal types; lower NOx formation rate, which can be desulfurized in the furnace; The load status enables effective adjustment of performance. The disadvantages of this equipment are as follows: high cost; high requirements for dust removal devices; large power consumption; unfavorable for long-term uninterrupted operation; large maintenance costs and complicated operation operations.
2 Dust removal and desulfurization equipment and integrated technology
According to the original emission concentration of dust in the boiler flue gas, commonly used dust removal devices can be classified into cyclone dust collectors, multi-tube dust collectors, water film dust collectors, bag dust collectors, and electrostatic dust collectors, of which the first three are suitable for chain furnaces. The latter two are suitable for circulating fluidized bed boilers. There are mainly three kinds of commonly used desulfurization devices, namely, a desulfurization device before combustion, a desulfurization device during combustion, and a desulfurization device after combustion. The pre-combustion desulfurization device adopts the washing method and the magnetic separation method. The desulfurization device in the combustion adopts the calcium injection in the furnace and the circulating fluidized bed combustion technology, and the desulfurization device after combustion uses the limestone-gypsum wet desulfurization method.
Dust removal and desulfurization integration technology can be divided into dry and wet two, dry controllable super turbulent mass transfer dust removal desulfurization technology, its effect is obvious, but the cost and operating costs are extremely high, it is not easy to promote. The wet type is spray swirl flue gas dust removal desulfurization and granite water film dust removal efficiency desulfurization, and its cost and running cost are low.
The water bath high-efficiency dust collector and desulfurizer has high dust removal efficiency and desulfurization efficiency, which are as high as 93% to 99% and 80% to 85%, respectively. It is a dust removal and desulfurization equipment that can better meet actual needs. It is not only mature in technology but also stable in operation. .
Steel (Ma Shishi) high-efficiency dust collector and desulfurizer has the same working principle. Both use some kind of reinforced gas to react with alkaline water to produce dust and desulfurization. The difference is that the materials used are different. of. The dust removal and desulphurization equipment is not only mature in technology, but also stable in operation. Compared with electrostatic precipitators, it has the advantage of small investment. In addition, whether the dust content or the sulphur content in the exhaust gas is in the national current “boiler air pollutionâ€. Within the requirements of the "Emission Standards", the user's unanimous approval and praise.
High-temperature (about 250°C) dust-containing sulfur-containing flue gas enters the interior of the precipitator at a prescribed smoke velocity, forms an impact on the surface of the water, and stirs up water droplets to form a certain amount of water mist. The water droplets will interact with the dust particles. After effective contact, the dust particles contained in the final flue gas will be flushed into the water under the action of the inertial force. At this time, the dust particles are affected by the surface tension of the water and the mass becomes larger, which is integrated with the water droplets. Eventually it settles on the bottom of the dust collector, forming a slurry and discharging it regularly. A small amount of dust particles with a particle size of about 1 μm have a certain probability of rising with the smoke after the washing process, and are eventually intercepted by the baffle and fall down with the water droplets. In order to achieve a more thorough purification of the flue gas, a specific flow rate can be applied to the flue gas to allow it to enter the cyclone type drift eliminator. Under the high-speed rotation of the cylinder wall, the dust particles in the flue gas will be Will be thrown to the wall, with the water droplets into the overflow tank in the cyclone, after a certain period of time after precipitation by the drain valve. Finally, the purified flue gas will be treated and discharged from the chimney.
Dust-laden high-temperature flue gas (about 250°C) is poured into prefabricated alkaline water and then mixed with provocative spray or water mist. At this time, harmful gases such as CO and SO2 are contained in the flue gas. It will react with alkaline water and produce H2CO3 and H2SO3 dissolved in water, which is separated from the flue gas. The harmful gases in the flue gas will be better purified, and the purpose of desulfurization is finally achieved.
Compared with high-efficiency dust-removing desulfurizers made by steel, high-efficiency dust-removing desulfurizers made of steel have lower overall investment, but the maintenance cost is relatively large, and it is generally not recommended to arrange them outdoors. 29 ~ 58MW medium-sized coal-fired boilers, because the boiler exhaust smoke has increased, resulting in a large volume of equipment, which requires a larger plant area, it is also not applicable.
High efficient desulfurization water bath dust collector, commonly used in medium-sized coal-fired boilers, can be placed outdoors, thereby reducing the costs associated with civil works of industrial plants, but a gray water settlement pool construction. In a comprehensive comparison, the cost of the high-efficiency desulfurization water bath dust remover is slightly higher than that of the steel high-efficiency desulfurization water bath dust remover, but the cost is lower in operation and maintenance, and the service life is longer.
3 Configuration Scheme Determination and Selection
In determining the configuration of the furnace type and desulphurization and desulfurization equipment, technical considerations must be considered on the one hand, and economically acceptable on the other hand. In addition, relevant requirements for energy conservation and environmental protection must also be considered. Chain furnace is no way to achieve desulfurization in the furnace, therefore, must have the configuration of flue gas desulfurization and dust removal device. In the process of circulating fluidized bed boilers, limestone is usually used for furnace desulfurization, and there is no need for a flue gas desulfurization device specially configured for it. It is worth noting that the flue gas contains a relatively high concentration of soot. Therefore, it is necessary to use Configure a bag filter or use an electrostatic precipitator to handle it.
From the technical point of view and economical analysis, three schemes are tentatively identified: (1) Integrated equipment for chain furnace + wet flue gas dust removal and desulfurization (Ganshi water film dust removal and efficiency desulfurization equipment); (2) Circulating fluidized bed boiler + bag dust removal + desulfurization device in the furnace; (3) circulating fluidized bed boiler + electrostatic precipitator + desulfurization device in the furnace.
Take a single 58MW hot water boiler in a non-coal-producing area in North China as an example. The heating period is set at 4 months and the coal price is set at 408 yuan/t.
From an economic perspective, Option 1 "Chain Furnace + Wet Flue Gas Dust Desulfurization Integrated Equipment" is optimal, Option 2 "Circulating Fluidized Bed Boiler + Bag Dust Collector + Furnace Desulphurization Device" Second, Option 3 "Circulation Fluidization "Bed boiler + electrostatic precipitator + furnace desulfurization device" the most time.
4 Conclusion
Option 1, the "chain furnace + wet flue gas dust removal and desulfurization integrated equipment" is economically better than the other two schemes, but its SO2 and NOx emissions are inferior to the other two programs. From a long-term point of view, the configuration scheme for the addition of a dedusting device for circulating fluidized bed combustion technology has a certain application prospect.
1 Two basic types of coal-fired boilers
1.1 Chain furnace
The chain furnace realizes the coal supply through the coal hopper in front of the furnace, and can adjust the thickness of the coal seam, the operating speed of the grate, and the air intake in real time so as to realize the control of the thermal power. In addition, the choice of coal types requires reference to the structure of the furnace. The grate is the main “place†for the combustion of the coal seam, so the coal seam on the grate must not only ensure uniform particle size, but also satisfy conditions such as flammability and non-coking. The advantages of the chain furnace are as follows: low cost, not only in the low cost, but also in the low operating cost; the dust removal device is not high; the technology has matured, safe and reliable operation, operation is relatively simple. The disadvantages of the chain furnace are as follows: the desulfurization cannot be performed in the furnace; the adaptability of the coal is not satisfactory and poor; the NOx is easily generated during the high temperature combustion process; the thermal efficiency is low, and the adaptability to the load variation is poor.
1.2 Circulating fluidized bed boiler
In recent years, circulating fluidized bed boilers have begun to enter the field of vision. The advantages of this equipment are as follows: high efficiency; low pollution; better adaptability of coal types; lower NOx formation rate, which can be desulfurized in the furnace; The load status enables effective adjustment of performance. The disadvantages of this equipment are as follows: high cost; high requirements for dust removal devices; large power consumption; unfavorable for long-term uninterrupted operation; large maintenance costs and complicated operation operations.
2 Dust removal and desulfurization equipment and integrated technology
According to the original emission concentration of dust in the boiler flue gas, commonly used dust removal devices can be classified into cyclone dust collectors, multi-tube dust collectors, water film dust collectors, bag dust collectors, and electrostatic dust collectors, of which the first three are suitable for chain furnaces. The latter two are suitable for circulating fluidized bed boilers. There are mainly three kinds of commonly used desulfurization devices, namely, a desulfurization device before combustion, a desulfurization device during combustion, and a desulfurization device after combustion. The pre-combustion desulfurization device adopts the washing method and the magnetic separation method. The desulfurization device in the combustion adopts the calcium injection in the furnace and the circulating fluidized bed combustion technology, and the desulfurization device after combustion uses the limestone-gypsum wet desulfurization method.
Dust removal and desulfurization integration technology can be divided into dry and wet two, dry controllable super turbulent mass transfer dust removal desulfurization technology, its effect is obvious, but the cost and operating costs are extremely high, it is not easy to promote. The wet type is spray swirl flue gas dust removal desulfurization and granite water film dust removal efficiency desulfurization, and its cost and running cost are low.
The water bath high-efficiency dust collector and desulfurizer has high dust removal efficiency and desulfurization efficiency, which are as high as 93% to 99% and 80% to 85%, respectively. It is a dust removal and desulfurization equipment that can better meet actual needs. It is not only mature in technology but also stable in operation. .
Steel (Ma Shishi) high-efficiency dust collector and desulfurizer has the same working principle. Both use some kind of reinforced gas to react with alkaline water to produce dust and desulfurization. The difference is that the materials used are different. of. The dust removal and desulphurization equipment is not only mature in technology, but also stable in operation. Compared with electrostatic precipitators, it has the advantage of small investment. In addition, whether the dust content or the sulphur content in the exhaust gas is in the national current “boiler air pollutionâ€. Within the requirements of the "Emission Standards", the user's unanimous approval and praise.
High-temperature (about 250°C) dust-containing sulfur-containing flue gas enters the interior of the precipitator at a prescribed smoke velocity, forms an impact on the surface of the water, and stirs up water droplets to form a certain amount of water mist. The water droplets will interact with the dust particles. After effective contact, the dust particles contained in the final flue gas will be flushed into the water under the action of the inertial force. At this time, the dust particles are affected by the surface tension of the water and the mass becomes larger, which is integrated with the water droplets. Eventually it settles on the bottom of the dust collector, forming a slurry and discharging it regularly. A small amount of dust particles with a particle size of about 1 μm have a certain probability of rising with the smoke after the washing process, and are eventually intercepted by the baffle and fall down with the water droplets. In order to achieve a more thorough purification of the flue gas, a specific flow rate can be applied to the flue gas to allow it to enter the cyclone type drift eliminator. Under the high-speed rotation of the cylinder wall, the dust particles in the flue gas will be Will be thrown to the wall, with the water droplets into the overflow tank in the cyclone, after a certain period of time after precipitation by the drain valve. Finally, the purified flue gas will be treated and discharged from the chimney.
Dust-laden high-temperature flue gas (about 250°C) is poured into prefabricated alkaline water and then mixed with provocative spray or water mist. At this time, harmful gases such as CO and SO2 are contained in the flue gas. It will react with alkaline water and produce H2CO3 and H2SO3 dissolved in water, which is separated from the flue gas. The harmful gases in the flue gas will be better purified, and the purpose of desulfurization is finally achieved.
Compared with high-efficiency dust-removing desulfurizers made by steel, high-efficiency dust-removing desulfurizers made of steel have lower overall investment, but the maintenance cost is relatively large, and it is generally not recommended to arrange them outdoors. 29 ~ 58MW medium-sized coal-fired boilers, because the boiler exhaust smoke has increased, resulting in a large volume of equipment, which requires a larger plant area, it is also not applicable.
High efficient desulfurization water bath dust collector, commonly used in medium-sized coal-fired boilers, can be placed outdoors, thereby reducing the costs associated with civil works of industrial plants, but a gray water settlement pool construction. In a comprehensive comparison, the cost of the high-efficiency desulfurization water bath dust remover is slightly higher than that of the steel high-efficiency desulfurization water bath dust remover, but the cost is lower in operation and maintenance, and the service life is longer.
3 Configuration Scheme Determination and Selection
In determining the configuration of the furnace type and desulphurization and desulfurization equipment, technical considerations must be considered on the one hand, and economically acceptable on the other hand. In addition, relevant requirements for energy conservation and environmental protection must also be considered. Chain furnace is no way to achieve desulfurization in the furnace, therefore, must have the configuration of flue gas desulfurization and dust removal device. In the process of circulating fluidized bed boilers, limestone is usually used for furnace desulfurization, and there is no need for a flue gas desulfurization device specially configured for it. It is worth noting that the flue gas contains a relatively high concentration of soot. Therefore, it is necessary to use Configure a bag filter or use an electrostatic precipitator to handle it.
From the technical point of view and economical analysis, three schemes are tentatively identified: (1) Integrated equipment for chain furnace + wet flue gas dust removal and desulfurization (Ganshi water film dust removal and efficiency desulfurization equipment); (2) Circulating fluidized bed boiler + bag dust removal + desulfurization device in the furnace; (3) circulating fluidized bed boiler + electrostatic precipitator + desulfurization device in the furnace.
Take a single 58MW hot water boiler in a non-coal-producing area in North China as an example. The heating period is set at 4 months and the coal price is set at 408 yuan/t.
From an economic perspective, Option 1 "Chain Furnace + Wet Flue Gas Dust Desulfurization Integrated Equipment" is optimal, Option 2 "Circulating Fluidized Bed Boiler + Bag Dust Collector + Furnace Desulphurization Device" Second, Option 3 "Circulation Fluidization "Bed boiler + electrostatic precipitator + furnace desulfurization device" the most time.
4 Conclusion
Option 1, the "chain furnace + wet flue gas dust removal and desulfurization integrated equipment" is economically better than the other two schemes, but its SO2 and NOx emissions are inferior to the other two programs. From a long-term point of view, the configuration scheme for the addition of a dedusting device for circulating fluidized bed combustion technology has a certain application prospect.
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