Method and system for collectively removing NOx and mercury (Hg) in coal-fired flue gas by utilizing secondary combustion of biomass charcoal

Abstract

The invention discloses a method for collectively removing NOx and mercury (Hg) in coal-fired flue gas by utilizing the secondary combustion of biomass charcoal, which is characterized in that: on the basis of the secondary combustion denitrification and the recycling of flue gas, the biomass charcoal is used as secondary-combustion fuel, the characteristics of the biomass charcoal such as low sulfur, low nitrogen, chloride containing, high ash-coke activity, high energy density, zero carbon dioxide (CO2) net emission and the like are utilized, and the biomass charcoal is sent into a secondary-combustion area of a hearth, the combined removal of multiple pollutants such as NOx, Hg and the like in the coal-fired flue gas can be realized through the catalyst reduction effect of anoxic combustion and biomass charcoal as well as the catalyst oxidation effect of chloride contained flue gas and high-activity ash and coke. The invention also discloses a system for realizing the method, which comprises a biomass charcoal preparing system, a coal pulverizing system, a hearth, a combustion system of the hearth, a flue gas recycling system and a boiler tail-gas processing system. The biomass charcoal is used as the secondary-combustion fuel, so the technical advantages of the secondary combustion of the fuel and the recycling of the flue gas can be integrated, and the method and the system have the advantages that: the investment cost and the running cost are low, the denitrification efficiency and the mercury removal efficiency are high, the CO2 net emission can be reduced, and the like.

Description

technical field [0001] The invention relates to a method for combined removal of NO in coal-fired flue gas by reburning biomass charcoal x The method and system of Hg and Hg belong to the technical field of combustion. Background technique [0002] According to the forecast of the International Energy Agency, by 2030, coal will still be one of the main energy sources in the world today, accounting for 27% of the world's total energy consumption. A large amount of coal utilization leads to NO x And the discharge of pollutants such as heavy metal Hg is increasing continuously, causing serious environmental pollution. Worldwide, mercury emissions due to human activities are 2,000-3,400 tons, accounting for 30-55% of the total mercury emissions (natural and man-made), and mercury emissions from coal-fired power stations have become the largest anthropogenic mercury emissions. source of pollution. Coal is the main energy source in our country. At present, the SO produced by ...

AI Technical Summary

Problems solved by technology

Natural gas is the best fuel for reburning, but due to its high price and limited reserves, it is not suitable for large-scale promotion

Studies have shown that fine pulverized coal with high volatile content (such as lignite and bituminous coal) is also a good reburning fuel, but purely using pulverized coal reburning technology requires high coal fineness (usually x The reduction efficiency is difficult to break through the bottleneck of 60%

Because biochar has low sulfur, low nitrogen, high chlorine, high gray coke activity, zero CO 2 Net emissions and other characteristics, Chinese patents ZL200610098040.X and ZL200710021748.X respectively provide the use of biomass and pulverized coal reburning to control NO in coal-fired flue gas x However, due to the disadvantages of conventional biomass fuels such as low energy density, high transportation costs, perishability, difficulty in grinding, and inconvenient storage, the industrial application of this technology is limited.

Under normal conditions, elemental mercury (Hg 0 ) is relatively high, it is difficult to remove it by fly ash adsorption and flue gas washing in conventional flue gas treatment devices

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