Study On Key Techniques Of Threshing & Re-drying Quality Control

The key task of threshing and re-drying is to achieve the storage condition for cigarette factories by leaves blending, impurity rejecting, stems and laminas separation and moisture adjustment etc. During the course of threshing and re-drying, the targets to reach include uniform chemical compositions, reasonable lamina structures and suitable stem contents. In order to achieve uniform chemical compositions, leaves blending is a key factor. The experiments show that the nicotine variation coefficient can reduce about 60% by pure manpower blending on blending tables, about 10% by pure silo blending, about 80% by pure man blending on blending tables after tobacco leaves pre-sorting. Moistening is an important element to affect threshing qualities. The moisture contents and temperatures of laminas after moistening have certain influence on threshing qualities. With the increase of lamina moisture contents, big and middle size lamina contents of B-, C-and X-leaves all increase, but big influence on B-and X-leaves and unclear influence on C-leaves. The stem contents in lamina during threshing have some influences on big and middle size lamina contents and scrap contents, but different influences exist to different positions of tobacco leaves, and biggest influence on X-leaves, next is B-leaves, least is C-leaves. Different total stem contents have different influences on lamina output ratio, stem output ratio and scrap output ratio; to be exact, higher total stem contents are advantageous to increase of lamina output ratio, and less influence on stem output ratio; lower total stem contents will increase scrap contents during threshing. Considering physical targets and economical targets, total stem contents in lamina should be controlled within 1.0～1.5% for C-leaves,1.3～1.8% for B-leaves and 1.5～2.0% for X-leaves in the course of threshing. The increase of re-drying temperature will result in lamina shrinkage to an extent, especially it's very clear for B-and X-leaves whereas unclear for C-leaves when the re-drying temperature is over 75℃. The proper re-drying temperature is advantageous to conservation and increase of qualities of tobacco leaves, and the lower re-drying temperature favors the increase of quantity of aroma, especially for B-leaves, but the quality of aroma will reduce when the re-drying temperature is over 80℃. It's advantageous to uniformity of moisture after re-drying, meanwhile improvement of physical properties of lamina structure and conservation of aroma quantity of tobacco leaves when the re-drying temperature is controlled within 70～80℃.