Study On Absorption Of So₂ By Naclo₂ In Falling Film Flow

Because of many reasons such as large investment, much equipment, complex operation, scaling, plugging and corrosion, calcium-based wet flue gas desulfurization, which has been widely used in large power generation boilers, are not fully applicable to small and medium coal-fired boilers. But no desulfurization method is particularly suitable for small and medium sized boiler. Therefore major cities, which belong to sulfur dioxide control area and acid rain control area are limited to using coal-fired boiler. To share the harmonious relation between environmental protection and economic development, it is a critical need to develop a desulfurization process with little investment, simple equipment, low cost, and no waste water.This paper put forward a new desulfurization technique using NaClO₂ solution as oxidative absorbent and multitubular cocurrent film-falling tower as contact reactor. It studies the desulfurization efficiency of sodium chlorite under different experimental conditions.The results show that the desulfurization efficiency is about 92% in the following experiment condition: pH of the absorption solution is 7⁸, concentration of NaClO₂ is 0.01 mol/L, inlet SO₂ concentration is 1500 mg/m³, liquid-gas ratio is 15 L/m³, liquid flow rate is 150 L/h, smoke gas flow rate is 10 m³/h.According to gas-liquid mass transfer mechanism, this paper builds mass transfer coefficient model, and get the regression correlation by dimensional analysis. Experimental data is identical with theoral result. It is proved that the reaction in the liquid film of mass transfer between SO₂ and NaClO₂ is fast reaction. It also studies the thermodynamics of desulfurization by NaClO₂. Then according to laws of thermodynamics,ΔG°,K°,ΔH°in the neutral or weak acid and alkaline conditions are calculated respectively. The results show that the reaction of sodium chlorite and sulfur dioxide can be carried forward, and the response limit is deep. It verifies the feasibility of NaClO₂ as SO₂ absorption.Compared with the traditional desulfurization, the desulfurization method uses NaClO₂ solution as oxidative absorbent and multitubular cocurrent film-falling tower as contact reactor. This method is suitable for flue gas desulfurization of medium and small coal-fired boiler because of low investment, simple equipment, easy operation, by-product sulfuric acid can be recycled, and no secondary pollution. Therefore, it has important practical significance to control emission of SO₂ from medium and small coal-fired boiler with wide range and heavily pollution.