Study And Analysis On Ring Rolling Process And Structural Optimization Of Ring Die Used In Biomass Pellet Mill

Compared with traditional fossil fuels such as oil, coal and natural gas, agriculture and forestry waste, as an important part of rural energy, has many advantages, such as possessing renewable, periodicly short, biodegradable and environmentally friendly, etc. The most effective way of using biomass resources is biomass fuel which made by pellet mill. The quality of ring die, as the core part of pellet mill, directly affects the efficiency and the service life. The highly fibrous character of biomass resources easily cause ring die to wear and crack, resulting in poor quality and low life, which has become a serious constraint to promote biomass fuels. Improving the mechanical properties and service life of ring die from the manufacturing process and structural design has become the hot topic in industry. Therefore, this paper studies how to improve mechanical properties and service life of ring die in terms of the biomass forming mechanism, the new ring rolling process of ring die and the structure of the ring die. The main research contents and results are as follows:Firstly, design of new ring rolling process of ring die: Traditional ring die processing technology which was defective was researched, and then the ring rolling process was proposed which firstly used in the machining process of the ring die. Ring die which belongs to the typical outer groove special-shaped ring has difficulty in rolling. This paper systematically analyzed the rolling process of outer groove special-shaped ring, established mathematical model of rolling process, determined the reasonable range of rolling conditions, and then designed ring rolling scheme and process parameters.Secondly, numerical simulation and experiment of new ring rolling process of ring die: the virtual process of ring was designed based on simufact software, the initial case was optimized and the case of " semi-closed and lengthened barrels pass" was determined. Then, the influence of Mandrel radial speed and driving roll rotational speed on rolling force and equivalent plastic strain were analyzed, and reasonable ring rolling process parameters were established. The results of rolling experiments and tensile test showed that the new rolling process proposed by this paper could successfully improve its quality and mechanical properties.Thirdly, Study on the forming mechanism of biomass fuel particles: this paper systematically analyzed granulating mechanism of ring die biomass forming machine, and the granulation areas were divided into stock area, deformed area and extrusion forming area., The working state of each area was discussed to derive the uptake conditions of the biomass raw materials in the die-roller mechanism, and then the influence of the die hole structural parameters on the ring die strength and granulation process was analyzed.Finally, structural optimization of ring die: this paper calculated of the force on the ring die structure and analyzed the structural parameters. The release type of die hole could ensure strength of ring die and reasonable compression ratio. Through the stress analysis of die hole, we found that the cone angle area which bear greater force and easier to wear, the reasonable angle was obtained after analysis. By studying the relationship between maximum stress and thickness of ring die, this study obtained the influence pattern and determined the thickness requirements to ensure the strength of the ring die was. In the last, the production experiment showed that the performance, life span, benefit of ring die which used the new ring rolling process and optimized structural parameters were effectively improved.