石灰石－石膏法脱硫工艺 / Process Introduction of Limestone – Gypsum Desulfurization System
一、石灰石-石膏法（简称FGD）脱硫系统的工艺简述
石灰石-石膏法脱硫工艺有着悠久的发展历程，随着近些年不断的深入研究和改进，其技术成熟，脱硫效率高，运行稳定，对煤种变化适应性强，脱硫剂来源丰富且价格便宜，脱硫副产物便于综合利用等特点已成为国内外脱硫行业的主流。 脱硫工艺过程：锅（窑）炉烟气经过引风机后，进入脱硫吸收塔反应区，与吸收塔内喷淋管组向下喷出的悬浮液滴逆流接触，发生传质与吸收反应，脱除烟气中的S02、S03及HC1、HF。 脱硫后的烟气经除雾器去除烟气中夹带的液滴后，从顶部离开吸收塔，由烟囱排出。
S02和S03与浆液中石灰石反应，生成亚硫酸钙和硫酸钙。在吸收塔浆池中鼓入空气将生成的亚硫酸钙氧化成硫酸钙，硫酸钙结晶生成半水石膏(CaS04．2H20)。经过滤机脱水得副产品石膏。
I. Process Introduction of Limestone – Gypsum Desulfurization System (referred to as FGD)
Limestone – gypsum desulfurization process has a long development history. With the recent in-depth research and constant improvement, it has mature technology, high desulfurization efficiency, stable operation, good adaptability to the changes in coals. The desulfurization chemicals have rich source and low price, and by-product of desulfurization is easy for comprehensive utilization. These features have become the mainstream of desulfurization home and abroad. Desulfurization Process: Flue gas in boiler (furnace) passes induced draught fan and enters reaction zone of desulfurization absorption tower, in which it contacts counter current of droplet run downward out of sprinkler pipe. S02, S03 and HC1, HF are removed from flue gas in mass transfer and absorption reaction. Then liquid droplets in the flue gas after desulfurization are removed by mist eliminator, and the flue gas leaves absorption tower from the top and is discharged from the chimneys.
SO2 and SO3 react with limestone in slurry to form calcium sulfite and CaSO4. Blow air into slurry tank of absorption tower to oxidize calcium sulfite to form CaSO4; CaSO4 crystallizes to form semi-hydrated gypsum (CaS04. 2H20); it is dehydrated by filter and we get by-product gypsum.
二、工艺流程图 Process chart
三、反应机理 Reaction mechanism
SO2 + H2O → H2SO3 吸收(Absorption)
CaCO3 + H2SO3 → CaSO3 + CO2 + H2O 中和(neutralization)
CaSO3 + 1/2 O2 → CaSO4 氧化(oxidization)
CaSO3 + 1/2 H2O → CaSO3．1/2H2O 结晶(crystallization)
CaSO4 + 2H2O → CaSO4．2H2O 结晶(crystallization)
CaSO3 + H2SO3 → Ca(HSO3)2 pH 控制(control)
四、性能保证：
FGD的脱硫效率≥95％
钙硫比Ca／S(摩尔比)不大于1.05
烟气脱硫系统可利用率不低于98％
压降：800–1200Pa
除雾器后烟气含湿量：小于75mg／Nm3
负荷变化范围：30-130％
电力消耗量：约机组容量的l.0％一l.2％
IV. Performance guarantee
FGD desulfurization efficiency ≥95％
calcium sulfur ratio Ca／S (mole ratio ) ≤1.05
FGD availability is no less than 98%
Pressure drop: 800–1200Pa
Moisture content of flue gas after demister: less than 75mg／Nm3
Load change range: 30-130％
Power consumption: about l.0％一l.2％ of unit capacity
