Abstract:

This paper aims to set up the theoretical model for co-absorption of SO₂ and CO₂ into sodium based solutions. Instantaneous reaction for SO₂ hydrolysis is assumed. For the hydrolysis of CO₂, there are two assumptions:finite kinetics and instantaneous reaction. Based on these two assumptions, the absorption rates of SO₂ were separately calculated and compared with dynamic experiments in the well stirred reactor. The trend for the absorption rate of SO₂ was well predicted by the instantaneous reaction for CO₂. The relative error for the absolute rates of SO₂ is high. The prediction based on the finite kinetics for CO₂ hydrolysis at pH>3 agrees well with experiments. The influences of CO₂ on the SO₂ absorption rate is primarily through gas phase mass transfer coefficient and total sulphur concentration at the same pH. Depending on the existence of CO₂ on SO₂ absorption rate, five pH regimes for interaction were observed. At pH>11.42, the absorption rate of SO₂/N₂ is higher than that of SO₂/CO₂ due to the influence of gas phase mass transfer coefficient. At 7.8 < pH < 11.42, the absorption rate of SO₂/N₂ is similar with that of SO₂/CO₂ due to the counteraction of gas phase mass transfer coefficient and total sulphur in liquid. At 5.41 < pH < 7.8, the absorption rate of SO₂/CO₂ is higher due to the influence of total sulphur in liquid. At 2.8 < pH < 5.41, the absorption rate of SO₂/CO₂ is relative lower primarily due to the influence of gas phase mass transfer coefficient. At pH < 2.8, the absorption rate of SO₂/N₂ is similar with that of SO₂/CO₂ due to liquid phase controlled region. Conversion of carbon and sulphur based ions at different pH and controlling regions for SO₂ absorption rate were obtained. The work provides guidance for the design and operation of flue gas cooler for oxy-fuel combustion flue gas.

Key words: oxy-fuel combustion, flue gas cooler, absorption

摘要：

建立SO₂与CO₂共吸收到钠基溶液中的吸收速率模型，假设该模型中SO₂的水解反应为瞬间反应；关于CO₂水解反应存在两种假设：有限动力学假设和瞬间反应假设。由这两种方法计算分别获得SO₂的吸收速率并与完全预混气液反应器中的的动态实验进行对比。采用瞬间反应假设可以预测反应速率的趋势，绝对反应速率误差仍然较大。而采用有限动力学假设的模拟值与实验值在pH>3吻合良好。CO₂对SO₂吸收速率的影响主要通过影响气相传质系数和相同pH下溶液总硫浓度产生。根据CO₂存在与否对SO₂吸收速率的影响，获得五个不同的相互作用pH的区间。pH>11.42时，SO₂/N₂吸收速率大于SO₂/CO₂，主要由于气相传质系数影响；7.8 < pH < 11.42时，SO₂/N₂的吸收速率和SO₂/CO₂吸收速率相似，主要由于气相传质系数和溶液总硫影响抵消；5.41 < pH < 7.8时，SO₂/CO₂的吸收速率相对较高，主要由于溶液总硫影响更大；2.8 < pH < 5.41时，SO₂/CO₂的吸收速率相对较低，主要由于气相传质系数影响；pH < 2.8时，SO₂/N₂和SO₂/CO₂吸收速率相似，主要受液相传质的控制。模拟同时获得不同pH下溶液中碳和硫相关离子的转化规律和SO₂吸收速率的控制步骤，为富氧燃烧冷却塔同时脱硫设备的设计和运行提供参考。

关键词: 富氧燃烧, 冷却塔, 吸收