Development and performance experiment of steam drying device of seedling-growing tray made of paddy-straw

Abstract: China is a large agricultural country with rich crop straw resources. The annual production of crop straw reached 840 million tons, of which rice straw production was over 211 million tons. A lot of rice straw is thrown away and burned, which not only causes great environmental pollution and affects farmers' life quality, but also causes a great waste of resources. Therefore, it has a positive meaning for agricultural efficiency and rural incomes, ecological agriculture promotion and sustainable agricultural development to develop a reasonably efficient and clean use of crop straw, and turn waste into treasure. A seedling-growing tray made of paddy-straw is a new type of rice seedling tray carrier, which is made of straw powder, water-soluble biological glue, fertilizer, and other soil nutrient medium. It is produced by mixing, pressing, and drying stereotypes. The drying stereotypes process is the key production. Its purpose is to mix well bonded straw powder, water-soluble biological glue, fertilizer, and other soil nutrient medium together to ensure the shaping rate wet strength and storage period of seedlings. The drying method and apparatus is a key factor for keeping these characteristics. The seedling tray drying method includes natural environmental ventilation drying, hot air drying, and steam drying. On an experimental basis, the three kinds of drying methods effects on the quality of seedling tray drying and the advantages of steam drying were considered in this paper. Then, the steam drying method was determined to be the major way of drying a seedling tray. To achieve the steam drying technology, the suitable drying apparatus is crucial. Therefore, the steam drying devices of a seedling tray fueled with rice straw rods was designed in this paper. The device consisted of a drying medium supply system, the steam dryer, and a control system. According to the steam drying theory, design requirements of drying apparatus, the maximum drying number of a seedling tray, the arrangement of a seedling tray in a drying vehicle and in the dryer, the steam boiler rated evaporation is of 0.5t/h, the rated operating temperature is of 144℃ in the drying medium supply system; the dryer size is Φ2400mm×5500mm, thickness 10mm, the thickness of insulation is 170 mm, and the maximum withstood pressure is 0.7MPa. The test results of the drying device performance showed that the dryer tightness and insulation is fine, the shaping rate of the seedling tray reaches 97%, the seedling tray drying is uniform, and the moisture content and drying wet strength of seedling tray meet the storage and production requirements well.