Experimental Study On Crystal Orientation Growth Behavior Of Desulfurized Gypsum In Hydrothermal System

Although China has ranked first in steel production in the world for many years,the problem of energy conservation and emission reduction has been the bottleneck restricting the development of steel industry.As one of the main emission reduction targets of enterprises,the utilization of desulfurization products is not only related to the iron and steel industry,but also related to thermal power,nonferrous metals and chemical industry Therefore,the resource utilization and large-scale utilization of calcium based desulfurization products are of great significance.In this paper,the growth behavior of FGD gypsum crystals in a controlled solution system was studied by hydrothermal process,and the growth mechanism of calcium sulfate crystals was explored with the help of Materials Studio software.Under the experimental conditions,the following conclusions are obtained:(1)In the controlled solution system,the hydrothermal process can effectively control the crystal growth behavior of FGD gypsum,make the crystal growth of gypsum oriented,and contribute to the resource utilization of FGD gypsum.(2)With the increase of hydrothermal temperature,calcium sulfate dihydrate in FGD gypsum gradually transforms into calcium sulfate hemihydrate;With the prolongation of holding time,the increase of liquid-solid ratio and the increase of citric acid content,it can promote the growth of(200)and(002)crystal planes and inhibit the growth of(110)crystal planes in gypsum crystal,effectively reduce the aspect ratio of gypsum crystal and form short columnar or thin-walled crystal materials.(3)When the reaction temperature is 140℃,the holding time is 30min,the pH value is 5.5～6,the concentration of magnesium chloride is 2%,the concentration of sodium dodecylbenzene sulfonate is 0.2%,the adding amount of citric acid is 0.4%and stirring Under the condition of rotation speed 450r/min,even if the raw materials are not pre-grinded,the hydrothermal process can be used to prepare short columnar calcium sulfate hemihydrate crystals material with a relatively uniform particle size distribution and a relatively smooth crystal surface.(4)The simulation results show that MgCl2 can promote the(021)crystal plane and inhibit the(020)crystal plane;However,citric acid only promotes the crystal face of calcium sulfate dihydrate(021);The synergistic effect of citric acid and magnesium chloride can promote the(021)and(110)crystal faces of calcium sulfate dihydrate.(5)The simulation results show that magnesium chloride can promote the growth of crystal surface of calcium bisulfite(200)and(002),and inhibit the growth of(110)and(1-10)crystal surface;Although citric acid has no obvious effect on the growth of calcium bisulfite crystal surface,the growth rate of calcium sulfate crystal can be changed by affecting the binding capacity of solution to Ca2+.