A New Process Of Magnesium Desulfurization And Denitrification

To reallize the ecological environment of sustainable development, the control targets of main pollutants(sulfur dioxide, nitrogen oxides, solid particles) become more stringent.Currently,there are a deal of flue gas desulfurization and denitrification techniques. However, the wastes produced have been not properly treated, lots of the products are not to be recycled, resulting in waste of resources and secondary pollution. To solve these problems above, this study proposes a new desulfurization and denitrification technology of a fusion of calcium and magnesium with byproduct of high-quality gypsum whiskers. This process is a kind of new clean production process which controls pollution from start and achieves an efficient recycling of materials.We use magnesium desulfurization waste as raw material to product gypsum whiskers with calcium nitrate solution on the basis of the existing magnesium wet desulfurization process. Optimal conditions are as follows: when the reaction temperature was 100℃, reaction time was 30 minutes, stirring speed was 300r/min, the calcium nitrate solution concentration was 20%, put calcium nitrate into magnesium sulfate solution, the appearance of the generated gypsum whisker was thin rod, diameter was between 2 to 3μm, length to diameter ratio could reach more than 50, white degree was 96%. Magnesium nitrate solution as the filtrate could be sent to magnesium hydroxide regeneration step after evaporation concentrates.In this paper, we use lime liquor reacted with magnesium nitrate solution, magnesium hydroxide filter cake and calcium nitrate solution were generated. Magnesium hydroxide filter cake could be sent to desulfurization process, calcium nitrate solution could be used to product gypsum whiskers. Optimal conditions of magnesium hydroxide regeneration are as follows: when the reaction temperature was 65 ℃, reaction time was 3h, the magnesium nitrate solution concentration was 1.5mol/L, lime liquo concentration was 0.8mol/L,the amount of seed was 1.5%, calcium / magnesium molar ratio was 0.9, calcium content(CaO%) in the magnesium hydroxide regenerated was less than 2.7% and Mg(OH)2 content was more than 93%. The product can meet the needs of desulfurization, and its sedimentation and filtration properties was excellent.In this papert, the absorption experiment of NOx in magnesium hydroxide slurry was conducted in self-made packed tower.The effect of magnesium hydroxide concentration, O2 concentration, NOx composition, NOx concentration, the amount of oxidant was investigated. The impact on the denitrification efficiency of the liquid product was also investigated. Highest denitration rate is more than 88%, when H2O2 was added to magnesium hydroxide slurry. We found that NO2- inhibits further absorption in magnesium hydroxide slurry, while NO3- has no obvious effect on NOx absorption. This conclusion has laid a good theoretical basis of magnesium nitrate accumulation and use in the subsequent processes.Gypsum whiskers and calcium nitrate could be produced with using calcium oxide and H2O2 only throughout the process. Magnesium, nitrate and water could be recycled without waste emissions. The maximum utilization of various substances was achieved.