| With the annual emissions of millions of phosphogypsum increasing, the rapid development of phosphate industry is a huge problem for dispose of phosphogypsum, utilization of phosphogypsum is not sufficient to eliminate the huge impact on the environment. This paper proposes that phosphogypsum is used for the production of sulphoaluminate cement, a part of the phosphogypsum is decomposed into Ca O,which replace the limestone of sulphoaluminate cement clinker. The unreacted phosphogypsum synthesis of sulphoaluminate cement clinker minerals, in order to absorb a great amount of phosphogypsum, which has practical value and theoretical significance of using utilization of phosphogypsum.The Free energy of chemical reaction in phosphogypsum and phosphorus coke system can be calculated by using HSC thermodynamic software, Combined with the thermal analysis of two system, We can know that improving the system of the initial heating temperature and reducing atmosphere are favorable to decomposition of phosphogypsum, And the oxygen concentration in later stage is conducive to the by-product of Ca S conversion to Ca O. It was discovered that constant temperature time, mass of phosphogypsum, ratio of C/S and duration of reducing atmosphere have certain influence on the decomposition ratio of phosphogypsum. Extending constant time is good for phosphogypsum decomposition rate, phosphogypsum decomposition rate decreased with the increase of phosphorusgypsum. In reducing atmosphere, decomposition rate of phosphogypsum in phosphogypsum-coke system with C/S=1 is higher than the rate of system with C/S=0.7, the crucible sealed can prolong the retention time of the reducing atmosphere which is conducive to improve the rate of decomposition of phosphogypsum. Experimental results show that the decomposition rate of phosphogypsum in the constant temperature of 1250 degrees celsius for 2h can reach 75%, the phosphogypsum-coke crucible sealing system decomposition rate reached 80% in the constant temperature of degrees Celsius for 30 min, The phosphogypsum in two kinds of state will melt at high temperatures, being glass state after cooling. Through the calculation of the theory concentrations of SO2 in these two systems, the former theoretical concentration is 9.7%, and the latter is 12.7%, which both can meet the requirements of SO2 concentration, so these two kinds of system after treatment in the follow-up test.Phosphogypsum decomposition rate reached 75% and 80%(residues of phosphogypsum and Ca O) used to produce sulphoaluminate cement clinker. Ca O from the decomposition of phosphogypsum can replace the limestone in raw material of traditional sulphoaluminate cement. The rest of the phosphogypsum completely replace natural gypsum in raw materials, then bauxite are mixed according to a certain proportion of clinker firing and made of cement, after that clinker and cement will be prepared with tradition alsulphoaluminate clinker and cement properties.The raw thermal analysis results show that exothermic peak with cement clinker produced by partial decomposition of phosphogypsum and traditional sulphoaluminate cement clinker is consistent. According to the analysis results of XRD clinker, the clinker mineral are SAC34 and C2S, The calculation results show that the different between clinker mineral composition content and design value is small, clinker has good quality. Comparative study of the properties of cement produced by partial decomposition of phosphogypsum and traditional sulphoaluminate cement, we can find that the sulphoaluminate cement produced by partial decomposition of phosphogypsum cement has similar hydration heat and traditional hardness, the hydration products are same and quite dense and rich.Thus, the preliminary verification shows that the ideas of partial decomposition of phosphogypsum instead of natural gypsum and limestone producing SAC is feasible, which can achieve a lot in the purpose of disposing phosphogypsum in this way... |
PDF Full Text Request