China has a large number of living and industrial coal-fired hot blast furnace, the use of coal-fired hot air furnace SO2, smoke and other pollutants, causing great pollution to the atmosphere. In order to strengthen the comprehensive improvement of the atmospheric environment, many cities have gradually eliminated or reformed small coal-fired hot blast stoves (converted to clean fuel). On the one hand, it can effectively reduce the emission of SO2 and smoke, and on the other hand, it can avoid the economic burden of using the fuel (gas) hot blast stove on the one hand, and promote the development of renewable energy and the comprehensive utilization of organic waste in agriculture and forestry. The structure of the chemical energy has an important role. 二、热风炉改造大气污染物排放量分析
Two. Analysis of air pollutants emission from hot blast stove retrofit
(1) characteristics of biomass briquette fuel
Biomass briquette is the use of crop residues (straw, rice husk, etc.), forestry remainder (cutting remainder, withered branch, etc.) as raw materials, and compressed into rod like, lumpy or granular fuel through special equipment.
The comparison of the main characteristics of the biomass briquette and the general industrial coal can be seen that the calorific value of the biomass plow fuel is slightly lower than that of the coal, and the 1 ton biomass briquette is equivalent to the calorific value of 0.73 to 0.97 tons of coal; the sulfur content of the biomass briquette is much lower than that of the coal, and the sulfur content of the nitrogen and ash is slightly lower than that of the coal, and the SO2 produced during the combustion is large. Large reduction, NOx and smoke less.
(2) transformation of air pollutants by hot air furnace
Taking 1 1t/h coal-fired hot blast furnaces to transform into a biomass briquette hot blast stove as an example, using the theoretical calculation formula of air pollutant emission from the flue gas of the hot blast stove in the "Environmental Statistics Manual", the emission of air pollutants in the flue gas before and after the hot blast furnace is predicted respectively. The mean value was calculated, and the results of air pollutant concentration monitoring after a 0.8t/h coal fired hot blast stove was transformed into a biomass briquette hot blast stove in Henan Province, and the air pollutant concentration was monitored after the wet spray dust removal.
The comparison of the prediction results before and after the remolding of the hot blast stove shows that when the hot blast stove reaches the same working force, the SO2 and dust produced by the biomass briquette fuel are reduced to a certain extent, the production and concentration of SO2 are reduced by 93% and 94% respectively, and the production and concentration of smoke and dust are reduced by 29, respectively. % and 42%, and NOx pollution is not quite different from that before the transformation. The prediction results and monitoring results after the remolding of the hot blast stove show that the SO2 concentration is much lower than the maximum permissible concentration in the period of the air pollutant discharge standard (GB13271 - 2001) II of the hot blast stove after the remolding of the hot blast stove.
The concentration of smoke and dust exceeded 4.86 times, and the dust removal rate reached more than 83% after wet spraying. The discharge standard can be reached.
Three. Technical analysis of hot blast furnace transformation
The biomass briquette is compressed. High density, slow volatilization spillover speed, water content people, if the current operation of coal-fired hot blast furnace without modification directly use biomass briquette fuel, hot blast stove is easy to appear power and small stability, easy to take black smoke, powder, superimposed pollution and so on.
By reforming the combustion chamber and auxiliary air supply system of the coal-fired hot stove, it is mainly to adopt the forced mechanical ventilation, increase the air distribution room in the lower part of the hot blast stove, increase the two air supply of the furnace, and adjust the thickness of the fuel layer of the hopper, so as to solve the bad phenomenon and satisfy the full combustion of the material of the material of the cow. The test results show that the same output can be achieved after the coal-fired hot blast stove is transformed into a biomass briquette hot blast stove, and the thermal efficiency of the hot blast stove is over 58%.
Four. Economic analysis of hot blast furnace transformation
The economy of the hot air furnace running with the same force depends mainly on the calorific value of the fuel, the price and the heat efficiency of the hot air furnace. The comparison of the running cost of the hot blast stove with the fuel of biomass briquette, coal, diesel and natural gas can be compared with the natural gas > diesel > biomass fuel > coal. Although the cost of burning biomass fuel is slightly higher than that of coal, it is necessary to reduce the cost of FGD by taking into account that the SO2 produced by biomass fuel can be reduced greatly. On the other hand, fossil fuels such as coal, diesel and natural gas will continue to grow with the demand and gradually decline with a large amount of exploitation. The economic burden will be brought about by the rising prices. Comprehensive comparison of coal fired hot stove into biomass briquette stove has a certain economic competitive advantage.
Five, development prospects and existing problems of biomass briquette fuel
The collection of crop straw in China is 6.87 billion tons, about 3.43 million tons can be used as fuel, and the availability of forestry residues is 8 to 10 million tons, and about 3 billion tons can be used as energy. Compressing the two into biomass briquette fuels yields about 372 million tons of standard coal, thus realizing the comprehensive utilization of agricultural and forestry organic wastes. It has certain social and economic benefits. At the same time, promoting the development of renewable energy plays an important role in alleviating the energy shortage and optimizing the energy structure, with great potential resources and good prospects for development.
But because of our country's biomass fuel industry is in the early stage of development, the market is not mature, the difference of quality and price is relatively human, the supply and demand is not stable, and the industry standard is still small and sound. Relevant state departments are required to formulate corresponding supporting policies to support and promote industrial development.
It is economically and technically feasible to transform the small and medium coal-fired hot blast furnace into a burning biomass briquette hot blast stove, which can effectively reduce the emission of SO2, and the flue gas can reach the national emission standard by dust removal. Bright