中温条件下氧化铁对氧化钙脱硫的活化作用

运用热重分析仪对石灰与氧化铁混合物的固硫效果进行了分析.发现氧化铁在200～700 ℃和二氧化硫不发生反应.石灰的固硫效果随温度的提高而有所改善：500 ℃以下基本不能固硫，600 ℃、700 ℃有一定的硫化效果.加入氧化铁后，石灰固硫特性随温度变化的趋势没有改变，但石灰的钙利用率不仅大大提高，而且随氧化铁的混合配比单调递增.氧化铁对石灰中温烟气脱硫反应并没有传统意义上的催化作用.氧化铁所起的是改变石灰颗粒表层产物生成方式的活化作用，使反应生成物不会形成一个致密的外壳，而以氧化铁为活性中心进行硫化反应，形成了分散的硫酸钙产物堆积,改善了硫化过程中的表面孔隙结构，减少了石灰颗粒表面硫化产物层对反应气体向石灰颗粒内部扩散的阻力.

ACTIVATION OF Fe2O3 TO DESULFURIZATION WITH CaO AT MEDIUM TEMPERATURE

The FGD process of mixture of lime and Fe₂O₃ is analyzed by using TGA in this paper.It is shown that Fe₂O₃ can’t react with SO₂ from 200℃ to 700℃.The desulfurization efficiency of lime is improved with temperature rising.SO₂ can be captured by lime at 600℃ or 700℃. But there is almost no desulfurization reaction taking place with lime when temperature is below 500 ℃. The behavior of lime in desulfurization reaction does not change with added Fe₂O₃. But the conversion rate of CaO is greatly improved:the more Fe₂O₃, the higher the conversion rate.Fe₂O₃ acts as an activator more than a catalyst in the desulfurization reaction with lime.Fe₂O₃ acts as the “activation center”around which CaO particles are sulfurized.The new dispersal formation mode of product differs from the compact layer that used to be. And the pore structure of product layer on the surface of lime particles is optimized, which makes SO₂ penetrate into core parts of lime more easily. As a result, the desulfurization reaction is developed deeper into the core parts of absorbent.