沉积MgO涂层提高镁钙砂抗水化性能

Improvement of hydration resistance of MgO-CaO clinkers by depositing MgO coating

为了提高MgO—CaO材料的抗水化性能，采用MgO碳热还原和扩散氧化法在镁钙砂上沉积MgO涂层，研究了碳还原剂类型（炭黑、石墨和焦炭）、沉积温度（1450～1600℃）、保温时间（2～8h）和氧气流量（分别为250和500L·h^-1）对叫（CaO）约为22％和55％的两种镁钙砂沉积MgO涂层后的抗水化性能的影响。结果表明：（1）炭黑与石墨和焦炭相比，由于粒度细、反应活性高，用其作为还原剂的效果优于其他两者。（2）在1450～1600℃范围内，随着沉积温度升高，处理后镁钙砂的抗水化性能提高。（3）随MgO涂层沉积时间的延长，处理后镁钙砂的抗水化性提高，但超过4h后，沉积生成的MgO达到了一定厚度，抗水化性不再变化。（4）在本试验条件下，氧气流量对涂覆后镁钙砂的抗水化性能影响不大。（5）用炭黑作还原剂，氧气流量为250L·h^-1，在1600℃下沉积MgO涂层4h后，镁钙砂的抗水化性大大提高：加（CaO）≈22％的镁钙砂水化质量增加率从处理前的3．0％降至0．09％，粉化率从42．27％降至0．12％；W（CaO）≈55％的镁钙砂水化质量增加率从处理前的2．8％降至0．10％，粉化率从26．47％降至1．16％。

MgO coating was prepared and deposited on MgO-CaO clinkers by carbothermal reduction of MgO with carbon as reduction agent,transportation of Mg steam and then the oxidation of Mg steam in order to im- prove hydration resistance of MgO-CaO clinker. Effects of carbon reduction agent type （carbon black, graphite,and coke） ,deposition temperature （1 450-1 600℃） ,holding time （2-8 h） and 02 flow rate （250 and 500 L ·h^-1） on the hydration resistance of two treated MgO-CaO clinkers （CaO contents were about 22% and 55% ,respectively） were investigated. The results indicate that： （1）carbon black has better reduction effect than graphite and coke due to its finer particle size and higher reaction activity; （2）with the deposition temperature rising from 1 450 to 1 600 ℃,the hydration resistance of treated MgO-CaO clinker improves; （3）the hydration resistance of treated MgQ-CaO clinker improves as holding time prolonging; but when the holding time is over 4 h,the deposited MgO reaches to a certain thickness and the hydration resistance doesn＇t change; （4）O2 flow rate has little influence on hydration resistance; （5）when carbon black is used as reduction agent,O2 flow rate is 250 L· h^-1 ,MgO-CaO clinkers are coated at 1 600 ℃ for 4 h,the hydration resistance is improved obviously：the mass gain percent of treated MgO-CaO clinker （w（CaO） about 22%） decreasing from 3. 0% to 0. 09% and pulverization percent decreasing from 42.27% to 0.12% ;the mass gain percent of treated MgO-CaO clinker （w（CaO） about 55% ） decreasing from 2.8% to 0.10% and pulverization percent decreasing from 26.4% to 1.16%.