Design And Experimental Study On New Straw Washing Device

With the exhaustion of fossil energy and degradation of environment, it becomes an inevitable trend to develop new energy. Biomass energy as a renewable new energy, has become the focus of world research. Crop straw in China with rich reserves is thought as an ideal biomass energy. But the present technology of making straw into cellulosic ethanol still remains many problems, especially the pretreatment of straw. The complex internal structure of crop straw hampered the accessibility of cellulose enzyme, and the materials are often mixed with sand, gravel and other impurities during the collection, transportation and human reasons. These impurities will affect the subsequent fermentation process, increase the wear and failure rate of subsequent equipment. Therefore, wet preparation is commonly used at home and abroad, in order to prevent the wear of subsequent equipment and improve the conversion of cellulose. The first step of the preparation process is washing and removing impurity of crop straw, then extrusion dehydration, and finally to the steam explosion pretreatment.Now, the washing device is mainly used water slurry machine, which is used in the paper industry, its structure is bulky, power consumption and washing effect is poor. The research on the straw washing device is rarely in china, so it is necessary to carry on deep research and discussion.A new straw washing device was designed in this paper, with wheat straw and corn straw as experimental materials, the stirring blade type, straw size and lower inlet flow are selected. Experiments were conducted to study the influences on the moisture content, impurity removing efficiency, power consumption per unit, by process parameters like agitator speed, water inflow and feed rate etc. The power consumption per unit as response value, three factors are selected to study response surface optimization experiments. And it provides references for the promotion and the use of straw washing device.A new straw washing device was designed, using integral blade, upper and lower water inlet, and weir type outlet. The integral blade can press the straw into the water to disperse agitation and washing. The upper water inlet can avoid straw sinking to impurities collector. The weir type outlet is easy to discharge and avoid waste of large amount of water.Through the comparative experimental research of different blade structures, the performance of grid strip type blade is good. Experimental study on lower flow, when the flow rate are 1000L/h and 1500L/h, the wheat straw and corn straw does not sink.Using wheat straw as raw material, the single factor experimental study was carried on washing device. We can get the moisture content of wheat straw, impurity removing efficiency and power consumption per unit changed with the change of agitator speed, water inflow and feed rate. The results show that power consumption per unit has a minimum value, its value is 9.25kJ/kg, when the agitator speed is 10r/min, water inflow 1.4 times saturated water inflow, feed rate 1500kg/h.Though the response surface optimization, it comes to a conclusion that the washing device can get the minimum power consumption per under the conditions, the agitator speed is 9.5r/min, water inflow 1.35 times saturated water inflow, feed rate 1400kg/h. the minimum value is 8.72kJ/kg. The error between the verification result and the prediction result is 1.61%. The model can be used in the experiment design and prediction.Using the optimized conditions of the washing device to washing corn straw, the power consumption per unit value is 8.97kJ/kg.Fluid-solid coupling analysis of the different blade structure based on ANSYS Workbench, the blade with the back bending radius 750 mm has the best performance. And a multi-stage washing device was designed, it can be directly carried out continuous multi-stage washing on straw.