Study On The Influence Of The Inorganic Impurities On The Crystal Of Ammonium Sulfate In Ammonia Desulphurization

The effective regulation of（NH₄）₂SO₄ crystallization process in ammonia desulfurization is of great significance to the application of ammonia desulfurization technology in typical industries.At present,the research on the effect of operating conditions on the crystallization of（NH₄）₂SO₄ has been relatively perfect,but the mechanism of the influence of inorganic impurities on the crystallization of（NH₄）₂SO₄ is still unclear,and there is a lack of comprehensive analysis for the whole process of ammonia desulphurization process,which is very important for the effective regulation and control of（NH₄）₂SO₄ crystallization in ammonia desulfurization.In this paper,based on the experimental study and molecular dynamics simulation,the influence mechanism of inorganic impurities on the crystallization of（NH₄）₂SO₄ was revealed from the microscopic scale.At the same time,from the macro scale,the ammonia desulphurization process of typical coal chemical enterprises was taken as the research object,combined with the field sampling and the comprehensive analysis of the whole process,the source of inorganic impurities affecting the crystallization of（NH₄）₂SO₄ was traced back,and the crystallization control scheme was formed.On the basis of the experimental results,the whole process was optimized and controlled.Based on the field sampling analysis and laboratory crystallization research,it was preliminarily analyzed that the inorganic impurities affecting the crystallization of（NH₄）₂SO₄ mainly include liquid phase impurities and solid phase impurities.In the liquid phase impurities,the main ions affecting the crystallization quality of（NH₄）₂SO₄ are Fe³⁺and Al³⁺.In the solid phase impurities,the main ions affecting the crystallization quality of（NH₄）₂SO₄ are fly ash and CaSO₄.Through the systematic study of the effect of liquid phase impurities such as Fe³⁺and Al³⁺on the crystallization of（NH₄）₂SO₄,it was concluded that when the concentration of Fe³⁺or Al³⁺in（NH₄）₂SO₄ solution is lower than 200 or 400 mg/L,the crystallization of（NH₄）₂SO₄ will not be affected.With the increase of Fe³⁺or Al³⁺concentration,the crystal shape of the crystal changes from prism to flake,and the average particle size and uniformity of the crystal show a significant downward trend,which is related to the binding energy of the two molecules to the（NH₄）₂SO₄ crystal（020）plane is greater than that of the（NH₄）₂SO₄molecule to the（NH₄）₂SO₄ crystal and the decrease of the solution p H.Through the systematic study of the effect of fly ash,calcium sulfate and other solid phase impurities on the crystallization of（NH₄）₂SO₄,it was concluded that the existence of proper amount of fly ash（1200 mg/L）promotes the growth of the crystal plane of（NH₄）₂SO₄ crystal.When the content of CaSO₄ in（NH₄）₂SO₄ solution is less than 2000mg/L（calcium is not saturated）,the increase of Ca²⁺concentration will affect the crystal shape,decrease the average particle size and uniformity,which is related to the large binding energy of CaSO₄ molecule to crystal plane and the decrease of p H in solution.When the content of CaSO₄ in（NH₄）₂SO₄ solution is too high（calcium supersaturation）,the regularity of the crystal is higher,which is related to the occurrence of heterogeneous nucleation.Based on the field sampling and the comprehensive analysis of the whole process,it was concluded that the liquid phase impurities such as Fe³⁺and Al³⁺come from equipment corrosion and fly ash introduction,and the solid phase impurities such as fly ash and calcium sulfate come from coal combustion and desulphurization in calcium carbide slag furnace.Finally,the optimum conditions of inorganic impurities for crystallization of（NH₄）₂SO₄ are as follows:liquid phase impurities Fe³⁺and Al³⁺are about 100 mg/L,solid phase impurity fly ash is about 1200 mg/L,calcium sulfate is about 3000 mg/L.On this basis,the control scheme of real-time monitoring and timely regulation was put forward for the operation of ammonia desulphurization process in typical industries.Through the field operation test,the（NH₄）₂SO₄ product with greatly improved appearance and particle size is obtained.