Study On Stem-Leaf Separation Properities Of Corn Straw And Development Of Separator

Corn straw accounts for 27.39% of crop straw resources and accounts for 46% of collectable crop straw resources in our country, but its utilization is still inefficient and most corn straws are only treated with simple methods. The leaves and stem piths of corn straw, containing abundant nutritional ingredients, are suitable for fertilizer or fodder. However, the stem barks, containing abundant cellulose, hemicelluloses and lignin, are suitable for biofuel or substitute of wood. How to separate leaves, stem piths and stem barks from corm straw is prerequisite for efficient utilization of corn straw. So, stem-leaf separation is one of key technologies to employ corn straw more efficiently.Three varieties of fresh corn straw, Zhendan958, Shandanl36 and Shendanl6, were used as experiment materials in the study. The influences of variety, node and water content of samples on stem-leaf bond intensity were studied. The change regularity of stem-leaf bond intensity of corn straw with flattened thickness and the structure breakdown caused by flattening were researched. On the basis of above experiments, a kind of new method for stem-leaf separation, named as "flatten-robbed method", was put forward. According to the method, a machine for stem-leaf separation test was designed and produced. By Orthogonal experiment of stem-leaf separation with the test machine, the parameters of separation machine were optimized and separation effect was evaluated. The conclusions are as follows:(1) The differences of stem-leaf bond intensity among three straw varieties were small, within 10.1N/mm-10.3 N/mm. Though the node position in which the stem-leaf bond intensity is maximal was different, the maximum stem-leaf bond intensity of the three straw varieties all were founded in about ear position of corn. Node position had a prominent influence on the stem-leaf bond intensity. Generally, the stem-leaf bond intensitys increased in order with the node positions from root to ear position, where the bond intensity reached maximum, and then decreased in order.(2) Reducing of water content cut down the maximum of bond intensitys evidently. The maximal bond intensity of Shendan 16 corn straw, with a water content of 82.56%, was 10.15 N/mm before drying, then dropped to 2.67 N/mm when the water content reduced to 55.26% when dried 12 hours at 80℃. So the maximum of bond intensity reduced to 26.3% of sample that not be dried. Meanwhile, by comparing the influences of water content of stem with leaf sheath, it could be founded that stem-leaf bond intensitys and water contents of leaf sheath had same change trend with node position.(3) Flattening decreased stem-leaf bond intensity of corn straw obviously. The smaller the thickness flattened, the bigger the decreased stem-leaf bond intensity. The stem-leaf bond intensity had maximum when corn straw wasn't flattened. When corn straws with a water content of about 17% were pressed to 4mm,6mm and 8mm separately, the average stem-leaf bond intensity decreased to 9.2%,24.9% and 35.9% of original value correspondingly. Considering energy consumption during flattening,8mm of the optimal flattening thickness for corn straw should be used for Shendan 16.(4) Transverse cracks with different degrees were found at the node position where leaf sheath joins stem after the samples were flattened. Moreover, the smaller the flattened thickness of corn straw, the bigger the transverse crack in the leaf sheath. That indicates flattening of corn straw can reduce stem-leaf bond intensity evidently.(5) The designed stem-leaf separation test machine has adjustable parameters and can completely meet the demands of stem-leaf separation test. Orthogonal experiment of stem-leaf separation was conducted by selecting corn straw of Zhongke 11 variety with a water content of 21.68%. The results show that the sequence of factors effectiveness was: gap between press rollers, linear speed ratio between separation rollers and rotate speed of press rollers. The optimal scheme for stem-leaf separation of corn straw was:rotate speed of press rollers,200r/min; gap between press rollers,8mm; linear speed ratio between separation rollers,1.6. Under this condition, the separation rate was 92.9%.(6) "Flattening-robbed method" achieved good results for stem-leaf separation of corn straw. The test machine for stem-leaf separation of corn straw had good performance. This research offers a new way for stem-leaf separation of corn straw and laid a good foundation for efficient utilization of corn straw.