煤灰中高岭石熔融性的密度泛函理论研究

Density Functional Theory Regarding the Meltbility of Kaolinite in Coal Ash

选出两种复盐,熔融温度高的高岭石和熔融温度低的含钾高的微斜长石.以第一性原理的密度泛函理论(DFT)和量子化学从头算法为理论基础,结合PW 91算法和广义梯度近似(GGA),对煤灰中高岭石和微斜长石的反应活性进行计算,然后分析它们的最高能量占据轨道(HOMO)、最低空轨道(LUMO)、态密度和Milliken布局数.计算结果表明:高岭石轨道的能级差ΔE较大、化学活性低,高温脱水后生成莫来石,莫来石的结构比较稳定;高岭石脱水后易和电子接受体反应,不易和电子给予体反应,K^+作为电子接受体进入高岭石晶格变成微斜长石,煤灰熔融温度降低.

Two kinds of double salts were selected：kaolinite with high melting temperature and microcline rich in potassium with lower melting temperature.The reaction activity of kaolinite and microcline was calculated based on the density functional theory（DFT）of First Principle and the quantum chemistry ab initio calculation by using the generalized gradient approximation（GGA）and the PW91 algorithm.Then the hinghest occupied molecular orbital,lowest unoccupied molecular orbital,density of states and Milliken population of kaolinite and microcline were analyzed.The results show that the value of energy level differenceΔE of kaolinite is quite large which reduces the chemical reaction activity and mullite forms after kaolinite loses H2 O molecular in high temperature.It is easy for kaolinite to react with the electron acceptor when it loses H2 O molecular,while it is difficult for kaolinite to react with the electron donor.Kaolinite becomes microcline when K＋as an electron accepter enters into the crystal lattice of kaolinite losing H2 O molecular which lowers the melting temperature of coal ash.