Pilot Study On Technology Of Extracting Potash From The K-feldspar And Comprehensive Utilization By Fluorine Chemical Method

Potash fertilizer is essential fertilizer for crops growth.However,the soluble potash that can provide for exploitation and utilization in China are serious shortage,which cause as much as 60%of potash need to import each year.But taking potassium feldspar as the representative of the insoluble potassium ore resources'reserves are very rich in the world and distributed widely in china.The study on technology of extracting potash from insoluble potassium ore resources has reached hundreds of years,however,the economic problem of large-scale industrial developmenet has always been the world difficult problem.Therefore,in this study,we proposed the new technology of extracting potash from the K-feldspar and comprehensive utilization on the basis of fluorine chemistry and tried to study in pilot-scale.The study on technology of extracting potash from the K-feldspar and comprehensive utilization by fluorine chemical method has the following characteristics:firstly,the potassium feldspar fluoride chemical reaction is exothermic reaction,it's a low energy consumption technology in theory.Secondly,the use of potassium alum crystal cleverly separated acid system,and achieved conversion from acid method to alkali method,theoretically this can be realized on the sulfuric acid consumption when engineering,low material consumption.Finally,characterized by the use of acidic reaction,the aluminum element in potassium feldspar achieve the separation of mineral silica in the course of reaction of slag leach,this make the ratio of Al-Si to reach more than 20 and even very low alkali consumption in theory in the process of production of alumina according to the principle Bayer.In addition,in the process of producing potassium sulfate and the alumina,there will be a by-product gypsum and quartz powder that the iron content is very low.In the whole process of silicate mineral extraction,the elements can be utilizated comprehensively.In the lab,we study the effects of the material ratio,reaction temperature,reaction time,the concentration of sulfuric acid and the concentration of fluosilicic acid on potassium conversion rate.The optimum reaction conditions are obtained which are mass ratio of msulfuric acid:mfluosilicicacid:MK-feldspar=1.2:1.4:1,the concentration of fluosilicic acid 30%,reaction time 2h,reaction temperature 90?,the concentration of fluosilicic acid 70%,in this condition,the maximum conversion rate of K is 99%.Designed and constructed the pilot line with daily processing capacity of 5 tons of potash feldspar scale and focused on the reactor and the separation method of solid and liquid,which indicated that the design of reactor and separation method is reasonable,but also can be used for continuous production in industrial scale.The experimental conditions are verified in the pilot scale production line that is continuous production process,which showed that the process conditions which are the mass ratio of mK-feldspar:msulfuric acid:mfluosilicic acid=1:0.84:0.42,reaction temperature 90?,reaction time 2h,in this condition,conversion rate of K is 96%.The pilot case,the consumption of sulfate and fluoride less than laboratory's consumption greatly.In the pilot scale,the study on dissolution and washing experimental of the reaction residue showed that the optimal process conditions which are dissolution time more than 50minutes,dissolution temperature 80?,the ratio of liquid to solid 2.5-3.0,material particle size less then or equal to 40 meshes.The appropriate conditions of washing:liquid to solid of washing should be controlled at around 1.5:1,washing temperature is more than 80 ?,agitator washing time is 15-20 minute.The study on size mixing experiment indicated that the optimal conditions which are pH6-8,mixing time 15 min,mixing temperature 80?,the ratio of liquid to solid 4:1.The study on comprehensive utilization of gypsum slag that produced in the process of extracting potassium by fluorine chemical method showed that the optimal conditions of gypsum dissolution process which are the ratio of caustic 1.6:1,leaching temperature 136?,stripping pressure 0.45 MPa,dissolution time 60 min,in this condition,aluminum included in gypsum slag can be fully dissolved.The research on material balance about reaction residue to the final product showed material is balance.Based on pilot study,preliminary technical economy analysis of extracting potash from the K-feldspar and comprehensive utilization by fluorine chemical method shows the gross profit is about 40.1%,which indicates this technical route has the very good development prospect.