Известия Томского политехнического университета: Инжиниринг георесурсов (May 2019)
Study of leonite crystallization from sulphate potassium-magnesium liquor
Abstract
The relevance of the research consists in possibility of using leonite, obtained at crystallization from sulphate liquor, as a complex sulphate potassium-magnesium fertilizer. Production of such fertilizer is a promising direction in development of potassium industry. The main advantage of sulphate fertilizers is the possibility of using them for plants, which cannot endure the chlorine excess. In addition they can be used for different soils and large number of culture of plants. The main aim of the research is to investigate the crystallization stage in leonite production from polyhalite ore, to select the required mode of crystallization. The methods used in the study: modeling of technological process in laboratory conditions, determination of size, quantity and form of crystals, formed at different time intervals, by system of continuous video registration of suspension particles «PVM Lasentec V819», X-ray analysis of product, obtained at different conditions. The results. The authors have carried out the investigations of isothermal and polythermal crystallization of leonite and syngenite from sulphate potassium-magnesium liquors. It is shown that the mixture of leonite and syngenite is crystallized in isothermal mode, and pure leonite is formed in polythermal mode. The leonite crystal form transforms from globular in tabulated, and then in acicular, at polythermal crystallization. The mechanical abrasion of crystal occurs at achievement of size of 50 microns, the crystal size decreases, it is also related with recrystallization of globular crystals into tabulated ones. The leonite crystal acquires acicular form at process duration of 90 minutes or longer, the intensive growth of crystal size occurs. The findings. It was determined that it is advisable to carry out polythermal crystallization in complicated system K2SO4-MgSO4-CaSO4, it allows obtaining pure product - leonite, which is suitable for further use. There is a possibility to obtain crystal of the given size and form when controlling the parameters of polythermal crystallization. The process duration should not exceed 45 minutes (liquor temperature is 68 °С) if it is necessary to obtain globular crystal. The tabulated crystal can be prepared by liquor cooling to 45 °С. If process duration is more than 90 minutes (at liquor temperature below 45 °С), the acicular crystals are formed.
