Experimental Study Of Straw Dehydration Using Screw Extruder

With the exhaustion of fossil energy and degradation of environment, it becomes an inevitable trend to develop and utilize biomass energy. In China, crop straw with rich reserves and low price is thought as an ideal biomass resources. But the present technology of making straw into cellulosic ethanol and other combustible energy remains many problems, especially the pretreatment of straw.The materials in China are often mixed with sand, soil, iron and other debris during the acquisition and transportion. In order to prevent the abrasion of follow-up device and improve the conversion of cellulose, wet preparation and the dehydration process are commonly used before the steam explosion pretreatment at home and abroad. Screw extruder is a kind of continuous straw dewatering equipment. the experimental study on its structural parameters, material parameters and operational parameters is still rarely reported, so it is necessary to carry on deep research and discussion.This paper uses the prepreg straw as the test materials, the piston dewatering device and strew extruder were used to study the influence of the compression ratio, the type and the size of plug pipe, the initial moisture content and pre-leaching time of materials, the screw speed and the extrusion times on extrusion process. In addition, three main factors are selected to study the response surface optimization experiments. And it provides references for the promotion and the use of strew extruder.Firstly, A new kind of non slip device, setting up anti-skid screw in the barrel, is deviced. Only screwing the screws into or out the barrel wall a little can adjust the friction of the inner wall of the cylinder according to the working hours and the treatment effects.Secondly, we found that increasing the compression ratio of device in a certain extent can decrease the export moisture content of materials, increase removal rate of water and density of the materials. But increasing the compression ratio comes with more power consumption of equipment.Meanwhile, altering the type and the size of plug pipe, the initial moisture content of materials, the screw speed and extrusion times can change the dewatering rate, the productivity and output per k W·h of device and obtain a different material form through the dewatering test of screw extruder. Therefore, it needs to select the reasonable structural parameters, the appropriate material parameters and the suitable process parameters to get the maximum device efficiency.Finally, we can conclude that the extruder can get the best comprehensive efficiency under the conditions: the length of the straw plug pipe of 27 mm, the moisture content of materials of 85%, the screw speed of 50.8 r·min-1. And the error between the validation results and prediction results is 1.63%. So, the response surface model can be used for the design and the prediction of the experiments.