Sources of SO2 in cement plant and its control measures
Date：2019-08-20 14:43 Source：cementepcViews:
The state council issued the opinions on key work of strengthening environmental protection, strengthened specific measures to reduce the total emission of major pollutants, and clearly put forward the implementation of economic policies conducive to environmental protection.The various environmental policies introduced in succession have undoubtedly made "environmental protection" a hot word.Reducing the total amount of major pollutants remains a priority for environmental protection.The guidelines specifically address sulfur dioxide and nitrogen oxides in cement, petrochemical, coal and chemical industries.China's cement production is all using raw coal as fuel, the combustion of coal produces a large number of SO2, and SO2 is the main air pollutant, is one of the two major culprits of causing acid rain, China's annual loss caused by acid rain is more than 10 billion yuan, therefore, the control of SO2 and NOx emissions are the same, it is urgent.
1 origin and form of SO2
1.1 sources of SO2
SO2 comes from two sources: raw material and fuel.It is mainly generated by the oxidation of inorganic sulfur and organic sulfur in raw materials and fuels.
1.2 main forms of sulfide
Inorganic sulfur and organic sulfur in raw materials and fuels include a variety of sulfur compounds, including sulfate and pyrite, etc., but low-priced sulfur compounds and elemental sulfur are mainly able to oxidize to form SO2.
2.Genesis and inhibition of SO2
2.1 causes of SO2
Sulfur compounds in raw materials and fuels, most of which combine with alkali to form sulfate in transition and firing zones of rotary kilns.The unbound part, which forms the SO2 gas, is taken into the decomposing furnace.There are a lot of active CaO in the decomposing furnace, and the temperature in the decomposing furnace is the optimal temperature for desulfurization reaction. Therefore, the SO2 gas generated by the firing band may be absorbed by CaO in the decomposing furnace.Normally, sulfur in fuel rarely affects sulfur emissions.However, when the following conditions occur, the emission concentration of SO2 will increase:
(1) fuel combustion is carried out in a reduced state;
(2) raw materials have poor flammability, and the temperature of firing band is raised very high;|
(3) the sulfur-alkali ratio was significantly higher.
2.2 strategies to curb emissions
The cause of formation of SO2 shows that if suitable conditions are available in the rotary kiln system, SO2 emission can be inhibited.From the perspective of production technology, controlling the CO, CO2 content and flame shape of the burned zone is conducive to inhibiting the generation of SO2.SO2 emission can be reduced by changing sulfur content and adjusting sulfur - base ratio.The removal efficiency of SO2 is closely related to the sulfur-alkali ratio of materials in the kiln and the existing form of sulfur in the raw combustion materials.Meanwhile, if preheater exhaust gas is used as drying heat source for raw material grinding, SO 2 emission will be further reduced.The removal efficiency can reach 50% ~ 70%.
Different process design of each enterprise leads to different operating conditions, SO2 gas emission concentration will be greatly different.Therefore, the desulfurization of cement plant should be targeted.According to the BAT best example technology recommendation issued by the European cement association, desulfurization scheme can be implemented step by step:
(1) optimize the collocation scheme of raw material and ore spots and adjust raw material ingredients.Improve the process operation and tap the desulfurization potential of the production process itself.
(2) if the SO2 discharge fails to meet the discharge standard through self-exploration, the desulfurization device shall be adopted for desulfurization.
There are many measures to curb SO2 emission in cement production line.It can be divided into three categories:
(1) remove SO2 with the clinker production line's own equipment;
(2) improve the technological operation of the clinker production system;
(3) adopt desulfurization device removal technology.
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