二氧化锰基吸波剂的微波成粒规律及反应机理

Microwave granulation law and reaction mechanism of the manganese dioxide-based absorbents

用微波辐照粉末状二氧化锰以制备颗粒状二氧化锰基吸波剂,探索其升温过程及成粒规律.发现存在决定二氧化锰是否升温成粒的"临界功率点",当二氧化锰质量为30.0g时,临界功率点为580W.在740W微波功率下,平均粒径主要分布在0.52mm与0.40mm,所占质量百分比分别为20.3%与43.9%.随微波功率升高,成粒粒径向增大的方向移动.提出了过程的反应机理,认为过程分为微波诱导、一次反应(少量)、一次反应(大量)、二次反应、成粒等5个步骤,一次反应、二次反应的临界点分别为535℃、1 870℃,且传热过程应尽量在二次反应临界点以内操作.发现中期升温速率高,前期与后期升温速率低,并对引起该现象的原因进行了分析.二氧化锰基吸波剂与煤以1∶3.0的质量比混合后在680 W微波场中气化的稳定温度达1 504℃,质量损耗率为1.11%,而相同条件下的颗粒活性炭的质量损耗率达43.78%.

Microwave was used for producing granular manganese dioxide-based absorbents from the powdered manganese dioxide, and the heating processes and granulation laws are ex- plored. The ＂critical power points＂ were found which decided whether manganese dioxide warming granulation. When the mass of the manganese dioxide was 30.0 g, the critical power point was 580 W. In the 740 W microwave power, the average particle sizes were mainly in 0.52 mm or 0.40 mm, accounted for 20. 3% or 43.9% of the mass percentage respectively. The particle sizes increase with the microwave powers increasing. Reaction mechanism processes that are divided into microwave-induced, first reaction （small）, first reaction （a lot）, secondary reaction and granulation are proposed. The critical point of the first reaction or the secondary reaction was 535℃ or 1870℃ respectively, and the heat transfer process should be within the critical point of the secondary reaction. The mid-heating rates were higher than the preheating or the post-heating, and a three-point analysis leading to the phenomenon is pro posed. When the manganese dioxide-based absorbent was mixed with coal according to the weight ratio of 1：3.0 in the 680 W, the gasification temperature can raise stability up to 1504℃. The mass loss rate was 1.11% under the above conditions, and it was 43.78% when the absorbent was instead of using granular activated carbon.