【作者】 应国量；

【导师】 周明凯；

【作者基本信息】 武汉理工大学 ， 材料学， 2011， 博士

【摘要】 磷化工的迅速发展,一方面对硫酸的需求量增大,而我国硫资源缺乏,大部分依赖进口硫磺制硫酸；另一方面,磷石膏排放量增加迅速而利用率低,大量磷石膏堆积造成严重的环境污染。为此,本文提出了磷石膏流态化分解制硫酸联产石灰的新工艺,并开展了磷石膏分解特性及其流态化分解工艺的研究。采用)(RD、XRF、激光粒度分析、高温显微镜等方法研究了磷石膏的基本特性。磷石膏主要矿物成分为CaSO4.2H2O,纯度高达90%以上,干基CaO含量一般在30%左右,SO3含量35～45%,是一种优质的制硫酸联产石灰原料；颗粒粒径≤0.075mm的颗粒含量高达91.25%,因此可不用粉磨,烘干破碎后直接分解制酸；磷石膏中的杂质降低了CaSO4的熔点,1200℃左右开始产生液相,磷石膏熔点在1280℃左右,随杂质含量的变化而略有不同。采用HSC热力学计算软件,研究了CaSO4在还原分解的过程中可能发生的反应,并计算了理论热耗。CO和焦炭均能降低CaSO4的起始分解温度和理论热耗,但是低温条件下易发生副反应生成CaS,应避免低温预热过程中形成CaS。采用热分析法,研究了分析纯石膏和磷石膏在不同条件下的分解过程及相演变规律。磷石膏中所含杂质降低了CaSO4的起始分解温度,对分解有促进作用；在N2气氛下焦炭掺量对还原分解CaSO4的最终产物有重要影响,掺量为C/S=0.5时主要产物为CaO,当C/S=2时主要产物为CaS。磷石膏在低温易与焦炭反应生产CaS,CaS在高于1100℃、3%O2浓度的高温低氧条件下能被缓慢氧化为CaO并释放出SO2。采用高温气氛炉模拟分散态研究了磷石膏在还原气氛的分解动力学。磷石膏在1000℃～1100℃,CO:3%～5%,CO2:25%～30%,PCO/PCO2=0.1～0.2,反应时间20min,分解率达到95%左右,脱硫率85%左右。设计了红外定硫仪法研究磷石膏的分解动力学,使用红外定硫仪可以快速、方便、连续、精确得测定磷石膏的脱硫率。磷石膏热分解的脱硫率方程为：α=Vmaxt/(kn+tn),式中k值为磷石膏脱硫率达到50%的时间,可利用k值判断磷石膏热分解的难易程度。在1000℃,3%CO,反应15min脱硫率可达75%,升高温度至1150～1200℃再通入适量氧气可将副产物CaS进一步快速氧化脱硫,达到90%以上的脱硫率。最后,探讨了磷石膏的分解特性,在此基础上提出了磷石膏流态化分解制硫酸联产石灰的工艺要求,并对磷石膏分解制硫酸联产石灰工艺的可行性进行了分析。更多还原

【Abstract】 The rapid development of phosphorous chemical industry brings about two problems, which are the comprehensive utilization of phosphogypsum(PG) and the quick increase of sulphuric acid demand. Thus, PG fluidization decomposition process for producing sulphuric acid and lime is proposed, which is a good way to solve the two ploblems mentioned above. The research of decomposition characteristics of PG and its fluidization decomposition process is carried out.Firstly, XRD, XRF, laser particle size analyzing and high temperature microscope tests were used to study the basic characteristics of PG. The results showed that the main mineral composition of PG is CaSO4·2H2O, which is more than 90%, and the content (dry basis) of CaO and SO3 is about 30% and 35～45% respectively, which shows it is a high-quality raw materials for sulfuric acid and lime generation. Besides, particles with the size≤0.075mm are more than 91.25%, so the raw material may be directly used to produce acid after being crushed and dried. Also, the results showed that the impurity in PG causes the lowering of melting point to approximately 1280℃, and liquid phase may occur after 1200℃, which differs with the variation of impurity content.Secondly, HSC Chemistry was used to study the reactions in the reductive decomposition of PG. The results of thermodynamic calculation showed that CO and carbon both lower initial decomposition temperature and theoretical heat consumption. However, CaS is easily generated under low temperature conditions. Therefore, the formation of CaS should be avoided in the course of low-temperature pre-heating of PG.Thirdly, thermal analysis was used to study PG decomposition course and phase change law. The results showed that the impurity in PG lowers its initial decomposition temperature and promotes the decomposition. In the nitrogen atmosphere, coke dose has a great influence on the decomposition result of CaSO4. The main product is CaO in the case of C/S=0.5, while CaS becomes the main product in the case of C/S=2. Under the condition of high than1100℃, O2=3%, CaS can be slowly oxidized to CaO, releasing SO2. Fourthly, high-temperature atmosphere furnace tests were used to study the decomposition characteristics of PG in decentralized state. Under the condition of 1000℃～1100℃,3%～5% CO,25%～30% CO2, and 20min of decomposition time, decomposition degree can reach 95% while desulfurization degree can exceed 85%. An Infrared Sulfur Analyzer is set to study PG decomposition. The desulphurization degree of PG can be obtained quickly, conveniently, continuously and accurately with Infrared Sulfur Analyzer. The desulphurization degree equation of PG thermal decomposition isα=Vmax(?), in which, theκvalue is a useful parameter to predict the reaction time of complete decomposition. Under a condition of 1000℃, 3%CO and 15min of decomposition time, desulfurization degree can reach 75%. At 1150～1200℃, the desulfurization degree can quickly exceed 90% if proper amount of O2 is added because of the oxidizing reaction of CaS.The technological requirements of PG fluidization decomposition process for producing sulphuric acid and lime is obtained on basis of decomposition characteristics of PG. Then, the critical process is designed according to the technological requirements. Lastly, the feasibility of this process is analysed.更多还原