Research And Development Of Biomass Compression Molding Machine Based On Finite Element Simulation And Analysis

The development and utilization of new energy to replace conventional energy sources is a major issue bearing on economic sustainable development and social progress. And as a kind of safe, stable energy, biomass energy can be produced different kinds of energy through a series of conversion technology, there are broad development prospects, so the research of biomass brequetting technology and molding machine is very important. Based on the finite element simulation and experimental analysis of biomass straw extrusion molding process and temperature control, develop a new highly efficient biomass compression molding equipment, which has broad space for development and reasonably easy process, briefly analysis as follows:1. The Finite Element Analysis of Compression ProcessThe research of forming mechanism of biomass and compression molding process is the necessary preparation for finite element analysis. This section applies the finite element analysis software to simulate the biomass changes in the state of compression molding. Through the establishment of the finite element model, analysis the rule of the internal displacement in the extrusion process as well as the internal stress distribution.Simulation results show that biomass occur a relatively large deformation during extrusion, and deformation of the edge is more obvious, which is being squeezed by the friction between the surface of the mold and material as well as the change of mold shape. With the objects continue to be squeezed out of the mold, the deformation of the middle part gradually level off, the restoration on both sides are smaller, finally stabilized. The longitudinal coordinates near the beginning of the mold bend outward, this is because the core of the material flows faster, and materials on both sides of mold flow slower because of the friction resulting in exposure to material. As the squeeze continues, the vertical coordinates tends to bend to the village and to the largest deformation at the exit. And can see that the density of the edges higher than the core, which the degree of densification of the material's surface is higher than that in the core. For this study there is a larger size or larger fiber raw materials, through the simulation of changes in the process of material flow, we can see that the higher the degree of surface densification, the better of the compact nature of the internal material, the better of the quality of the molding products.At the same time, in the extrusion process, because the speed of the center is faster than the edge effects of the friction, therefore, the cross-sectional of the block has shear stress, and this stress can not be eliminated after the molding. Simulation results show that the larger shear stress exists in the head and the tail, the shear stress will result in the transverse crack of products, and because of the effects of shear stress and density difference, has elastic expansion and flexibility along the diameter direction, leading to vertical cracks. In addition, the friction at the conduct of the cone district gradually increases with the extrusion. It is very important for the right squeeze speed and pressure to reduce adverse consequences caused by stress in the molding process.2. The Finite Element Simulation and Analysis of Temperature FieldThrough the simulation of the temperature field, gets the changes of the raw material at different temperatures, shows that the corn stalks forms easiest when the heating at a temperature of about 250℃. Combined with the previous material densification laws and extrusion characteristics of analysis, we can see the strength and stiffness of the forming block is enhanced and for the material is not to be crushed, the long straw fibers are not damaged, the majority of fibers twisted and knot with each other, and the straw in contact with the mold surface forms carbide layer. In the actual molding process, the extrusion and heating effects at the same time, and produce a lot of friction heat in the extrusion process, the actual production may be appropriate to reduce the heating temperature. Based on the simulation of temperature field, provides reference data for controlling heating temperature the actual production and operation.3. Test Analysis1) Evaluation IndicatorsRelaxation density lower than the compression molding density, usually relaxation ratio is used to describe the extent of relaxation of the forming block; anti-permeability is mainly measured by the time that the molding block decomposes off in the water completely; anti-fragmentation uses the weight loss rate of the main trial process as a reflection of the standard.2) Test MethodRelaxation density test method: calculate the initial density when the block is forming just after the extrusion die, which is the largest compression density; then at room temperature conditions, exposed in the interior place one week, the measurement to be basically stable state one times is finally stable density- relaxation density.Durability Test Methods: take the stable molding block, weigh and record, and then vertical drop to the hard ground from 1m high place, repeat 5-10 times, and then weigh and record, then in accordance with the formula to calculate their weight loss rate, and so duplicate ways do several times seeking to the average, weight loss rate reflects the block's ability of anti-broken; at room temperature; and then take samples in water, record the time samples decomposes completely falling in the water, repeated several times for the average, this time reflect the forming block's anti-permeable.Through experiments to the conclusion that: other conditions being equal, the moisture content of biomass at 20% of the heating temperature at 200℃~250℃range, at large enough job under pressure to produce the best quality of the molding block At the same time, higher production efficiency.4. The Overall DesignThrough profound analysis of the function of molding machine, research the compression molding process, in accordance with the various features of the different molding machine's requirements and the principles of hot pressing forming, designed the structure of machine. The equipment system is made up of feeding system, extruding and cutting system, deformation heating systems, cooling and keeping systems, and is drove by the hydraulic system and electric control system.Device is activated, the natural air-dry straw is driven by the transmission system feed into the hopper, chain wheel, chain wheel passed to the feed roller, the feed roller drum feed Driven by extrusion roller mill After breaking into the extrusion cylinder compression continuous cavity at the same time, the hydraulic pump in the electric control device in conjunction with the hydraulic cylinder piston rod Driven to the side of mobile, solid-mounted on a piston rod end of the cutting knife to cut off the stalks , extrusion head will forward the compressed straw raw materials into the extrusion cylinder tapered cavity molding, extrusion head is installed at the back of the cylinder block into the entrance and exit will be sealed, at the same time, the heater at the outer surface of cone-shaped tube is sent electricity, far-infrared heating for brequetting cavity, under a certain pressure and temperature, biomass straw occurs plastic deformation and extrusion combination-type, after a certain time in the conformal tube , supplants and cuts block. Driven by the hydraulic, the piston rod moves to the other side at the role of the control system to complete the other side of the molding, and so forming a row of reciprocating.In short, on the basis of the finite element analysis, through the research of compression molding technology on biomass, this paper designs a new type of highly efficient biomass compression molding equipment, its development prospect is bright, and have a great significance in the path of sustainable development.