Study On Continuous Explosion Mechanism And Technology Of Discarded Biomass Spiral Booster

The plant fiber of waste biomass should be pretreated regularly when it is processed withplastics to make composites. Among variety means of pretreatments, the steam explosion willnot damage anything to the environment, and the pretreatment productivity was high, whichare special advantages among all methods. The plant fiber modification usually adoptedintermittent steam explosion technology in domestic currently, however, the productivity ofwhich is low, and a steam equipment is needed for production. It makes the machine volumehuge, increases the production cost. Accordingly, the application is limited extremely, thus,the exploration on continuous steam explosion equipment and theory is of great significance.It was extremely similar that the solids conveying of single-screw extruder and thematerials conveying of single-screw continuous steam explosion equipment. However, thecompression ratio of the latter was much higher than that of the former. Thereby, for single-screw continuous steam explosion equipment, materials were no longer incompressible, andthe spiral grooves were not the traditional flat ones. Considering the basis that both thedensity and the velocity of materials were varying, a physical model of wedge-shaped spiralgrooves was established; on the other aspect, depending on the solids conveying theory oftraditional single-screw extruder, the movement and the force condition of solid biomassmaterials that processed in the continuous steam explosion equipment were analyzed. Then amathematical model was established, which made it possible to analyze the process ofpressure building and temperature increasing for the materials in the single-screw continuoussteam explosion equipment.It was a huge impact on the steam explosion effect with different designing diedimension. Thereby a physical model was built for the annular materials conveying of the die,and the movement and the force condition was analyzed for the annular materials, a pressuremathematical model was built. Moreover, the influence principle was analyzed for the diehorizontal section length to the steam explosion pressure. Furthermore, a temperaturemathematical model for the materials along the spiral groove direction was built according tothe principle of frictional force acting.Variety of experiments were carried out in the own designed equipment, since it wasrather difficult to measure the die pressure directly, then the steam explosion pressure wassubstituted by the screw backpressure, so that the variation principle for steam explosionpressure can be observed. The relationship between screw backpressure and main electriccurrent was studied, it was found that there was a consistency between them, which meant itcould be used to reflect the variety of the former. Furthermore, the relationship between the steam explosion temperature and the moisture content difference in materials that before andafter steam explosion. It was also found that there was a consistency between them, themoisture content difference could be used to represent the former. Through changing dieswith different diameters and horizontal lengths, different steam explosion pressures weremeasured, the principle was found that how the die sizes effected on steam explosionpressures. Some experiments were carried out to investigate how the parameters of materialvolume and main axis speed influenced the steam explosion pressure and temperature.Disadvantages for single-screw continuous steam explosion equipment performed as:low production, poor self-cleaning property, weak material conveying and mixing capacity. Itwas necessary to study triple-screw continuous steam explosion equipment which wouldovercome those disadvantages above. According to its powerful material conveying capacity,a positive displacement conveying model for the materials in the barrel was established. Itcontained calculating volumes of―C‖type chambers in mixing section, conveying section,pressurized section separately. After that, a mathematical model was built through volumecompression, which was used to analyze the pressure building process in the triple-screwcontinuous steam explosion equipment for the materials, furthermore, the theoreticalcalculating equation for the production of the equipment could be obtained. The triple-screwcontinuous steam explosion equipment was designed by our own. In addition, the online rapidreplenishment device, and the biomass materials metering feeding device, which could feedcontinuously, uniformly, controllable were designed specially.A series of experiments were carried out in the own designed triple-screw continuoussteam explosion equipment, Firstly, the relationship between steam explosion temperature andthe moisture content difference in materials that before and after steam explosion, it wasfound that there was a consistency between them; Moreover, the influence of technologicalparameters on steam explosion pressure and temperature, which contained feeding volume,original moisture content and particle size. Based on the theoretical analysis of equipmentproduction, a real production experiment was carried out, and the relationship that betweenthe production and the main axis speed was found. As the empirical equation related withpressure and density was applied in the theoretical analysis of pressure and temperature in thecontinuous steam explosion equipment, an important parameter was referred to, namely thematerial parameter, it was obtained when the temperature was at25oC and160oC separatelythrough experiments, which was laid a solid foundation for intensive research on theories andexperiments of triple-screw steam explosion equipment. Through the above theoretical analysis, the mathematical model for the pressure andtemperature in the continuous spiral pressurized steam explosion, the approximate analyticalsolution were obtained which contained the pressure, velocity, density and temperature of thematerials along the directions of spiral groove and die; The theoretical calculation formula ofthe production and the approximate analytical solution of the pressure along the direction,which revealed how the equipment do effect to the materials: The pressure and temperature ofthe materials were accumulated to a certain, which were then released through the die. It wascalled the mechanism of steam explosion effect, which provided theoretical guidance for thedesigning of continuous spiral pressurized equipment. It was found in the experiments thatthere was a coincidence in the steam explosion pressure and the main engine current; steamexplosion temperature and the moisture content difference in materials that before and aftersteam explosion. One varying patterns reflected the other; both the diameter decreasing of dieand the length increasing of horizontal section elevated the steam explosion pressure, theincreasing materials feeding volume also elevated the steam explosion pressure, however, itreduced steam explosion temperature, the speed increasing of main axis elevated the steamexplosion temperature, however, it decreased the steam explosion pressure; the lower of theoriginal moisture content, the higher of the steam explosion temperature.