The Research Of The Dewatering Of Rice Straw By Mechanical Thermal Expression

Rice straw, which is common agriculture byproduct, has become much more important in agriculture development and environmental protection. The energy utilization of straw can greatly reduce the shortage of energy in China. How to utilize this kind of biomass effectively is of great important. While a high content of alkali metals and high moisture brings kinds of matters during thermalchemical. With high moisture, the burns of straw will be influenced, and most of ways of biomass thermalchemical need the moisture under 15%.In order to better understanding the character of some biomass, such as rice straw, wheat straw, peanut straw, corn straw, soybean straw, mulberry and so on, some tests were carried out, such as: (1) ultimate analysis of biomass, (2) proximate analysis of biomass, (3) determination of calorific value of biomass, (4) microelement analysis of biomass, (5) microelement analysis of biomass ash.The results show that the average Q_ar,net of straw is about 16000kJ/kg. The existence and latent harmful element to the environment in the straw or dust is few. And the content of K is high, and which is easily to volatilize during thermalchemical.To better understand the MTE (mechanical/thermal expression) of rice straw We designed and manufactured the mechanical/thermal dewatering laboratory equipment. Test is shown that MTE can be used to effectively dewatering a range of biomaterials. The underlying dewatering mechanisms relevant to MTE, include (1) filtration of water expelled due to thermal dewatering, (2) compression forming, (3) separating out of alkali meters are discussed. At lower temperatures, the dominating dewatering mechanism is pressure, but with the increasing of temperature, thermal dewatering becomes more important. A major focus is the investigation of the effects of processing parameters in rice straw MTE, including temperature (10 and 140℃), pressure (0.1～0.9 MPa) and time (1～10min).Compression forming divides into three stages, relax compitession forming, transition compression forming and impaction compression forming, The density of rice straw is about 1g/cm³, and well-set after MTE.Thermal dewatering divides into three stages too, compression-fast dewatering, slow dewatering and the separating out of inherent moisture. MTE shows a same compression forming and dewatering efficiency of rice straw with different moisture.And, MTE shows a good effect of alkali metals decreasing; about 65% of Na and 40% of K is decreasing. The effect of alkali meters decreasing of MTE is not better than ME(mechanical expression), because most of the water is decreasing at the first stage of dewatering, at the same time, some alkali meters separate out with the water.According to the test datum, we summarize the rice straw MTE equipment ideal operating mode is: Temperature (140℃), pressure (0.6～0.8MPa), and time (10min).With the experimentation, this paper appraises theeffect of the rice straw mechanical/thermal dewatering laboratory equipment, gives some opinions to further improve this experiment system, and provides certain instruction for later research.