Study On Crystallization Kinetics Of Potassium Nitrate

The crystallization kinetics of potassium nitrate was studied. It included the test about the stability of the crystallizer, the study on the crystal kinetic characters of potassium nitrate, and the simulation on the model of crystallization kinetics.In the study on the stability of MSMPR crystallizer whose volume was 5L, different factors were investigated according to different types of draft tubes and paddles. It showed that the particle size distribution had close relations with both the structure of draft tube and operating conditions. The structure of draft tube and the paddle were improved. And the operating conditions were elementarily studied. Good particle size distribution could be gotten in making use of the draft tube of Φ120mm, the matching paddle, the paddle of 150 and stirring downwards. In the aspect of operating conditions, the rate of agitation was a important factor, which should be adjusted over 350rpm in order to ensure the cycle in order.In the study on the kinetic characters of potassium nitrate, the results showed that: (l)Along with the residence time growing from 10min to 50min, the average particle size and the main particle size accreted, and the shape of potassium nitrate crystal was better and the phenomena of caking was less. When the residence time was over 30min, the growth of crystal particle size was slower. So the residence time should be controlled more than 30min to ensured the good quality of crystal. (2)When the supersaturation increased from 0.5℃ to 5℃, the average and main particle size both descended, tout the influence degree was small. So the supersaturation could be increased to some extend to. advance the production efficiency. (3)The crystal particle size decreased rapidly when the rate of agitation added from 350rpm to 550rpm, but when the rate of agitation dropped to 350rpm, the cycle was not very good. Therefore, The rate of agitation should be 400rpm around. (4)Along with the increasing of the concentration of ammonia as a additive, the crystal average particle size and the main particle size was minished. After the concentration of ammonia accreted to 3%, the effect that the concentration of ammonia worked on the crystal particle size was decreased. If only thought from the aspect of increase crystal particle size, adding ammonia was not a good idea. However, the influence to the particle size was less along with the concentration of ammonia and it was good at equality of particle size distribution. In production, in order to make use of the salting-out action and make the potassium nitrate separated out largely, the concentration of ammonia could be added properly on the base of assuring the product quality to increase the production efficiency.At last, in such conditions that the crystal temperature was 25℃, the supersaturation was 2℃, the rate of agitation was 400rpm and the residence time changed from lOmin to 50min the relational expression of crystal nucleation and growth rate of potassium nitrate was set up:B° = 6.19 × 1022 G2.02...