Simulation And Research Of A New Straw Forming Equipment With Multiple Extrusion Heads

Biomass energy is an important renewable energy and the straw is an important part of it.Through the compression molding technology of biomass,the loose straw can be formed to a kind of biomass fuel. This technology can make better use of rich straw resources in rural area of our country.The purpose of this study is to develop a straw molding equipment which can be widely used in rural areas with lower energy consumption and higher productivity. The main content of this paper is described as follows:1.The finite element theory of biomass compression moldingReaserch the finite element theory of biomass compression molding and prepare for the finite element analysis. The straw moilding is a nonlinear process and choose the theory of finite strain elastic-plastic to describe this problem after comparing the advantages and disadvantages of oher finite element methods.In order to study the elastic-plastic theory of the straw molding, yield criterion, flow rule and hardening law are given.Moreover, the constitutive equations and basic Equations are derived after that.2. The finite element analysis of the straw molding processThrough the analysis the stress and strain field and temperature field in the straw molding process,we use the results to guide the design of a new straw forming equipment.Through the analysis of stress and strain fields,the equivalent friction distribution, equivalent strain distribution and equivalent strain of X direction are obtained.we can see the trend of the equivalent stress,equivalent friction and the equivalent strain.Also,these dates obtain maximum in the corner of the molding cavity and it's where the wear is the most serious.We should make a rational design of the molding cavity size and aspect ratio of cone angel.Through the analysis of of the temperature field,the different temperature distributions are obtained under different temperature loads and time nodes.The overall temperature of straw will increase with the exaltation of the temperature loads.when the temperature load is 250℃,the lignin is softening and it is the best time to forming the straw with lower energy consumption.3. The overall design of the molding equipmentBy analyzing the molding equipment applications, requirements,functional requirements and the main technical parameters,the machine includes the main parts as follows:pre-feed extrusion system, heating system, security-type molding system and cooling system.Using the two squeeze rollers'relative rotation to precompression the straw.In the heating system,we use the far infrared heating.We also analyze the stress of the Molding cavity and design the hydraulic system. By comparing the current molding equipments, we design a molding machine with multiple extrusion heads which improves production efficiency and reduce energy consumption. In the above basis, the overall structure of the machine was designed and the workflow of the entire machine was established.4. The physical quality evaluation of the forming fuelEvaluating the physical quality of the forming fuel is one of the key research.,because it will directly affect the storage, transportation and use of them.The main content of the evaluation include the density and durability. In this paper,we obtained some daters about forming temperature,water content, density and durability of the straw through experiment and drawn some curves.The density of the forming fuel have great differences under different water contents and molding temperatures.We get the relation curves between water contents, molding temperatures and density.We can see that the forming fuel have better density under the conditions that the temperature is 190℃and water content is 12%.It provide the experiment data for the actual production to improve the density.The durability of the forming fuel also have great differences under different water contents and molding temperatures. We get the relation curves between water contents, molding temperatures and durability. The anti-broken ability and anti-water permeability are worse while the forming temperature are higher. The molding fuel has good defensive performance and water permeability properties if the moisture content is about 10%. It provide the experiment data for the actual production to improve the durability.