Desulfurization of castings.

- Sep 09, 2018-

The fly-off desulfurization process of the first-stage dust removal adopts the double-alkali flue gas desulfurization process, and the desulfurization reaction speed is fast, and the desulfurization efficiency is high. The double-alkali flue gas desulfurization process is a deformation of the limestone (lime)/gypsum washing method, overcomes the disadvantage of overcoming the easy scaling of the limestone/lime method, and improves the SO2 removal rate. Therefore, this program uses the "double alkali method" process. The double alkali method is a relatively important process in the wet process. It has the characteristics of high desulfurization and dust removal efficiency, low investment, small land occupation and low operating cost, which is very suitable for China's national conditions. Desulfurization utilizes the characteristics of sulfur dioxide, namely, acidity, solubility, oxidizability, and reducibility. However, the speed at which sulfur dioxide is dissolved in water and reacts with alkali quickly does not need to be considered. Under normal circumstances, when the flue gas generated by the cupola is discharged into the desulfurizer and a certain amount of alkali liquid is sprayed, the better the atomization quality of the alkali liquid and the higher the desulfurization efficiency. The unique design of the desulfurization dust collector enables the high-speed moving airflow to stir vigorously on the lye, generate eddy current circulation, repeat atomization, completely atomize the lye, and the droplet size is basically below 0.2mm, which is the best. The atomization quality, the liquid mist and SO2 are fully stirred together to achieve the best contact mode and contact area, so as to achieve the desired desulfurization effect. When the SO 2 -containing gas is washed with an alkaline liquid, first, SO 2 and water react with each other to form sulfurous acid, and some sulfurous acid is hydrolyzed to form H-, HSO 3 and a small amount of SO 32 - ions. At the same time

The base is dissociated into Na+ and OH- ions. When the OH-ion is formed, the H+ ion is reduced by the following reaction: SO2

H2SO3 H ++ HSO3- OH- + H + H2O H + HSO3- result that the reduction and increase the amount of ions SO32-, so that the SO2 content of the solution undissociated sulfurous acid dissolved and reduced physical, so continue to absorb SO2 from the gas. When the base is excessive, SO2 reacts with the base to form sodium orthosulfite (Na2SO3). 2NaOH + SO2 → Na2SO3 + H2O continue to be depleted when a base to absorb SO2 from the flue gas, the acid salts of sodium bisulfite (of NaHSO3) generation. Na2SO3 + SO2 + H2O → the reaction of sodium bisulfite with a base to give birth again positive 2NaHSO3 alkylene sulfite salt. NaHSO3 + NaOH → Na2SO3 + H2O during operation, inevitably occurs a side reaction, i.e., a small amount of sodium sulfite is oxidized to sulfate (Na2SO4). 2Na2SO3 + O2 → 2Na2SO4 added Ca (OH) flows into the sedimentation tank after spraying 2, NaOH and regenerated gypsum precipitate Na2SO3 + Ca (OH) 2 → CaSO3 ↓ + 2NaOH Na2SO4 + Ca (OH) 2 → CaSO4 ↓ + The oxidation rate of 2 NaOH sodium sulfite is related to the oxygen content in the flue gas, the type of dust impurities and the concentration of circulating fluid, and the pH value. When the system is in normal operation, the desulfurization operation is carried out in the absorption-regeneration process. It can be seen that the circulating fluid is a solution system composed of Na2SO4---Na2SO3---NaHSO3, and the concentration and ratio of Na2SO3 and NaHSO3 in the solution are A key factor affecting absorptivity.