刨花微波干燥特性研究

研究了常规微波干燥、热空气干燥、微波-热空气联合干燥下刨花含水率和干燥速率的变化特征,微波功率和刨花形态对含水率变化和干燥速率等特性的影响,计算了刨花在微波干燥下的单位能耗.结果表明:微波干燥比热空气干燥省时约80%;微波功率对干燥特性有显著影响,功率越大,干燥速率越快,干燥时间也越短;微波干燥过程中,刨花形态对干燥速率有影响,表面积越大的刨花,含水率变化越明显,干燥速率越快;微波输出功率与试样量比为4~7W/g时,微波能耗最省;微波干燥过程中易发生能量集中而导致刨花焦化,微波-热空气联合干燥可以防止焦化现象,同时能实现更低的目标含水率,微波-热空气联合干燥比热空气干燥省时约70%.

Study on Microwave Drying Characteristics of Wood Flakes

Change of moisture content(MC) and drying velocity characteristics of wood flakes,the influence of microwave power and flake form on the change properties of MC and drying velocity were studied by experiments with regular microwave drying,air oven drying and combined drying of microwave pretreatment and air oven drying.Per unit energy consumption(UEC)during microwave drying was calculated.The following results were obtained:The microwave drying saved about 80% of the time taken by air oven drying.The drying characteristics were significantly influenced by the microwave power,i.e.,the greater the microwave power,the faster the drying velocity,the shorter the time consumed.The form of wood flakes influenced upon the microwave drying velocity,the bigger the surface area was,the more obviously the MC changed and the faster the drying velocity was.For energy efficiency,the optimal ratio of microwave power output and the sample mass was between 4~7 W/g.Microwave drying would cause charring damage to wood flakes by generating concentrative energy in the microwave field.Combination of microwave pretreatment with air oven drying could avoid charring damage in the microwave drying process,and realize the minimum target MC.Compared to traditional air oven drying,combination of microwave pretreatment with air oven drying could save about 70% of the drying time.