Experimental Study On Desulfurization And Denitrification Of Flue Gas From Industrial Boiler By Magnesium Method

At present,there are more than 470,000 small and medium sized coal-fired industrial boilers in use in China,which are large in number and widely distributed.Its coal-fired efficiency,emission control and environmental protection facilities are much lower than those of large-scale utility boilers and have become the major source of SO₂ and NO_x emissions.In the face of severe air pollution situation,China's pollutant discharge standards are also more stringent,therefore,for the characteristics of coal-fired industrial boiler flue gas,the development of economic,safe and efficient desulfurization and denitrification technology has important practical significance and broad application prospects.In this paper,based on the characteristics of flue gas in small and medium-sized coal-fired industrial boilers,a desulfurization and denitrification process by wet-process magnesium desulfurization combined with sodium chlorite solution liquid-phase oxidation and absorption denitrification was proposed and carried out experimentally,with a view to being a large number of medium and small Industrial boiler desulfurization and denitrification to provide some experimental parameters and theoretical data.Experiments were first conducted in a bubbling reactor were studied MgO absorbent on SO₂ and NO_x removal performance experiments and NaClO₂ absorbent on SO₂ and NO_x removal performance experiments to initially explore the reaction process and mechanism.On the basis of this,MgO and NaClO₂ were used as absorbents to conduct flue gas desulphurization and denitrification experiments in two series of laboratory-scale bubbling reactors.In the first bubbling reactor,MgO absorbent was used and in the second bubbling reactor,NaClO₂ absorbent was used.During the experiment,the operating parameters of No.1 MgO desulfurization bubbling reactor were fixed,and the desulfurization efficiency was stabilized at about96%.The experimental parameters of No.2 bubbling reactor were changed.The influence of NaClO₂ solution concentration,NaClO₂ solution pH,NaClO₂ solution temperature,flue gas flow rate,initial NO and SO₂ concentration on the desulfurization and denitrification efficiency of the experimental system was mainly investigated.The optimum experimental conditions were determined according to the practical application.Under the optimal experimental conditions,the experimental system can keep SO₂ removal efficiency 100%,NO oxidation rate 100%and NO_x removal efficiency 65%for a long time.Using the principle of chemical thermodynamics,the standard Gibbs function?35?G^?,standard equilibrium constantsK^?and partial pressure of gas for the desulfurization and denitrification of MgO and NaClO₂ absorbing solution in the experimental system were calculated and analyzed.The results show that all the reactions can proceed in the forward direction,and the reaction very deep.Finally,the chemical analysis method was used to test and analyze the experimental system products.The possible chemical reaction equations in the reaction process were summarized,and the reaction mechanism was explored.