Method for reducing carbon content of boiler fly ash

Abstract

The invention discloses a method for reducing the carbon content of boiler fly ash. The method comprises the following steps that S1, mixed coal is sequentially subjected to crushing, first-stage screening and second-stage screening, and then qualified pulverized coal is obtained; and S2, the qualified pulverized coal, hot air and exhaust gas from the second-stage screening are converged into an air-powder pipe and then mixed with reduced-pressure oxygen in the air-powder pipe, and then the mixture is conveyed into an oxygen-enriched boiler to be combusted. A local oxygen-increasing combustion technology is adopted, an oxygen pipeline is additionally arranged on a main pipe before air powder enters a hearth, and a front oxygen-enriched nozzle and a rear oxygen-enriched nozzle are mounted at air supply positions of air powder pipes at inlets of a front boiler wall and a rear boiler wall of the boiler, so that the oxygen concentration is increased, the burn-off rate of mixed coal is increased, the carbon content in fly ash is reduced, and the smoke exhaust amount of the boiler is reduced; the problems of economical and safe operation of the coal-fired power generation unit under the condition of large-proportion blending combustion are effectively solved.

Description

technical field [0001] The invention belongs to coal-fired power generation technology, and relates to a method for reducing the carbon content of boiler fly ash. The purpose of operating safety and improving thermal efficiency. Background technique [0002] The combustible material of the boiler fly ash of the coal-fired generator set is mainly unburned carbon particles, and its content directly reflects the combustion adjustment and the economic operation of the boiler; in addition, because the carbon in the fly ash has a wear effect on the heating surface of the boiler tail, it can be reduced. During the service life of the equipment, the increase in the carbon content of the fly ash will also reduce the efficiency of the electrostatic precipitator, cause environmental pollution, and threaten the safe operation of the entire boiler. Relevant studies have shown that when the carbon content of the fly ash decreases by 1%, the thermal efficiency of the boiler will be reduced...

AI Technical Summary

Problems solved by technology

[0002] The fly ash combustibles of coal-fired generator set boilers are mainly unburned carbon particles, and its content directly reflects the combustion adjustment and the economic operation of the boiler; The service life of the equipment, the increase of the carbon content of the fly ash will also reduce the efficiency of the electrostatic precipitator, cause environmental pollution, and pose a threat to the safe operation of the entire boiler; relevant studies have shown that for every 1% reduction in the carbon content of the fly ash, the thermal efficiency of the boiler will decrease. It can be increased by about 0.3%, and the standard coal consumption of power supply can be reduced by 0.9-1.2g / (kWh)

[0003] With the rapid development of the power industry, the supply of thermal coal market is becoming more and more tense. In addition to the unbalanced coal quality in our country, the limited transportation capacity, and the state's requirement that power stations use low-quality coal as much as possible, it is difficult for power plants to ensure long-term combustion. Single type of coal; in order to ensure the long-term supply of thermal coal and control the fuel cost of power plants, it has become an inevitable choice for power plants to burn multiple types of coal, such as the combination of bituminous coal and lean coal, but bituminous coal has more volatiles and higher water content than lean coal And the ash content is large. In the case of a large proportion of bituminous coal, it is easy to cause unstable and insufficient combustion, resulting in reduced boiler efficiency, aggravated ash accumulation, and increased pollutant emissions, which will seriously affect the safety and economy of the unit. run

[0004] In addition, because the volatile matter contained in coal is combustible gas, its ignition temperature is low, which makes coal easy to catch fire. When the volatile matter is precipitated from the inside of the coal powder particles, the coal powder particles will have porosity, and the combustion air will The contact area becomes larger, so it is easy to burn out; relevant practice shows that bituminous coal has a high volatile content, high combustion activity, and is easy to react with oxygen, thereby inhibiting the contact and reaction between refractory lean coal and oxygen; "Thermal Power Plant Boiler Operation According to the Guidance, the excess oxygen content of the boiler fluctuates between 4% and 6%, and the oxygen content is generally controlled at about 6% in actual operation; This kind of blending combustion, the "wind grabbing" phenomenon of flammable bituminous coal deteriorates the combustion and burnout process of the main reaction stage of the blended coal, resulting in the burnout time of the blended coal being determined by the refractory lean coal.

[0005] In the existing technology, for example, a 220MW coal-fired generating set is designed to burn poor coal in southeast Shanxi. In order to meet the need to reduce production costs during operation, a large proportion of bituminous coal is mixed. The ratio of lean coal to bituminous coal is 1:2, and an air preheater is used. The generated hot air dries the raw coal, which is sprayed into the furnace in the form of pulverized coal for combustion after passing through equipment such as a drum coal mill and a separator; however, there are still some problems in the operation of the coal-fired power unit: Because the bituminous coal in the mixed coal is easy to burn, there is a phenomenon of "grabbing wind", which causes the boiler to lack oxygen instantly, the center of the flame moves up, and the air powder cannot be mixed well, so that the lean coal cannot be burned out in time, and the carbon content of the boiler fly ash is increased. , which seriously affects the safe operation of the boiler; at the same time, as the flame center moves upward, the heat absorption of the convective heating surface of the boiler increases, the temperature of the exhaust gas at the tail also increases, the heat loss of the exhaust gas increases, and the thermal efficiency of the boiler decreases

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