【作者】 张健；

【导师】 钱觉时；

【作者基本信息】 重庆大学 ， 材料科学与工程， 2015， 硕士

【摘要】 磷化工业的迅速发展给磷石膏的处理利用带来巨大难题,随着磷石膏的排放量每年以千万吨增加,但磷石膏资源化利用程度远不足以消除其对环境产生的巨大影响。本文提出利用磷石膏单独部分分解制硫铝酸盐水泥的思路,磷石膏未反应的磷石膏将全部替代天然石膏,分解的磷石膏生成Ca O将部分取代石灰石为硫铝酸盐水泥熟料提供Ca组分,以此达到大量消纳磷石膏的目的,对磷石膏的资源化利用具有实用价值和理论意义。通过采用HSC热力学软件对磷石膏和磷石膏-焦炭体系可能发生的化学反应自由能进行计算,并结合两种体系的综合热分析研究结果可知,提高体系初始升温温度及还原气氛有利于磷石膏的分解,后期存在一定的氧浓度有利于副产物Ca S向Ca O的转化。通过对磷石膏分解试验研究发现,恒温时间、磷石膏质量、磷石膏与焦炭体系中碳与硫物质的量之比(以C/S表示)及还原气氛持续时间对磷石膏分解率均存在一定的影响。恒温时间延长有利于磷石膏分解率的提高,磷石膏分解率随着磷石膏质量的增加而降低。在还原气氛下,C/S=1的磷石膏-焦炭体系中磷石膏分解率高于C/S=0.7磷石膏-焦炭体系中磷石膏的分解率,通过坩埚封存的方法可延长还原气氛存留时间有利于磷石膏分解率的提高。最终得出单独煅烧磷石膏在1250℃恒温2h分解率可达75%,磷石膏-焦炭坩埚封存体系在1300℃恒温30min分解率达到80%,同时两种状态下超过以上温度的磷石膏均会在高温时熔融,冷却后出现玻璃态。对两种制度下磷石膏释放的SO2进行理论浓度计算表明SO2理论浓度已达到收集制酸要求,因此选取这两种制度处理后的磷石膏进行后续试验。将分解率达到75%和80%的磷石膏(残余物以Ca SO4和Ca O为主)与矾土、石灰石按一定比例混合烧制熟料并制成水泥,将制得的熟料和水泥与传统的硫铝酸盐熟料及水泥性能进行对比研究。生料热分析研究结果表明,以部分分解的磷石膏配制的原料烧成过程与传统硫铝酸盐水泥熟料烧成过程矿物形成峰出现温度一致。熟料XRD分析结果表明,熟料矿物组成为SAC34和C2S相与所设计矿物组成一致。经计算熟料矿物组分含量与设计值相差不大,熟料烧成质量良好。部分分解的磷石膏制得的硫铝酸盐水泥与传统硫铝酸盐水泥性能相比,水化初期放热峰出现的时间及放热量大致相同,硬度与传统硫铝酸盐水泥相比略低,水化产物矿物组成相同且相当致密丰富。由此可见,磷石膏部分分解取代天然石膏和石灰石的思路经初步验证是可行的,分解率达到75%和80%的磷石膏烧制硫铝酸盐水泥熟料时,其磷石膏消纳量分别为未分解的磷石膏直接替代天然石膏烧制熟料所消纳磷石膏量的4倍和5倍,可以通过此方式达到大量消纳磷石膏的目的。更多还原

【Abstract】 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更多还原