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The Study on the Decomposition Mechanism of Potash Feldspar and Its Influencing Factor with Addition of Phosphogypsum Additives

Author: ChaiNi
Tutor: ShiLin
School: South China University of Technology
Course: Environmental Engineering
Keywords: potassium fertilizer K-feldspar phosphogypsum reaction mechanism
CLC: TQ443
Type: Master's thesis
Year: 2011
Downloads: 139
Quote: 0
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Abstract


Potassium is the essential nutrition to the growth of plants, and it has very important effect on the yield and quality of plants. However, the application amount of potassium fertilizer is too low to meet the demanded quantum. Lack of potassium has become the main restriction to the yield of plants in lots of area around China. So far, the hoevellite resource is extremely bare in China. Meanwhile, the insoluble potassium resource, the principal mineral of which is K-feldspar （KAlSi3O8）, is very abundant, with large content of potassium, wide distribution, and abundant reservation. Therefore, extraction of various potassium compounds from insoluble potassium ores has become a strategy need.What’s more, the utilization of phosphogypsum is not satisfactory, because of the radioactivity of phosphogypsum and the impurities contained in phosphogypsum, such as quartz, calcium carbonate, bauxite, Fluorine compound, and chlorine compound. In case of utilization of phosphogypsum, the impurities should be removed, which would increase cost.The main purpose of this paper is to study the decomposition mechanism of potash feldspar and its influencing factor with addition of phosphogypsum additives, to discuss the effect of heavy metal and radioactivity on environment. This study would ameliorate the potassium shortage of plants, enlarge the phosphogypsum utilization area, and decrease the cost of phosphogypsum utilization.The K-feldspar-CaSO4-CaCO3 system was discussed in this paper. Firstly, the calcined product was discussed with the aid of XRD, TGA-DSC and phase diagram systems. Secondly, the seven reaction equations in K-feldspar-CaSO4-CaCO3 system suggested by formers were reassessed and revised. The highest extraction ratio of soluble K2O from K-feldspar occurred in the reaction KAS6+CaSO4+14CaO→K2SO4+ C3A +6C2S. Its free enthalpyΔG01100-1400K was -678.190 -818.454 kJ·mol-1 according to thermodynamic data, which was obviously lower than that of other six reactions. Thirdly, the influencing factor of K-feldspar resolution rate was discussed, and we found that K-feldspar resolution rate was in direct proportion with calcined time and temperature, and in inverse proportion with quartz.The K-feldspar-phosphogypsum-carbonate system was discussed on the basis of K-feldspar-CaSO4-CaCO3 system, we studied the effect of impurities contained in phosphogypsum（ in present of CaHPO4 and CaF2） on the K-feldspar decomposition rate, and found that both could promote the decomposition rate. The heavy metal and radioactivity were measured, which would not do any harm to environment.Finally, The reaction mechanism of K-feldspar-CaSO4-CaCO3 system and K-feldspar-phosphogypsum-CaCO3 system were discussed.

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CLC: > Industrial Technology > Chemical Industry > The chemical fertilizer industry > Potash
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