Avaliação técnica do sistema operacional de uma unidade armazenadora composta por silos-secadores e a qualidade de grãos de arroz

Abstract

Rice is a crop of prominence for cultivation worldwide, in addition to being essential in the basic diet of human beings. The guarantee of standardization and quality of grains is due to good cultivation and post-harvest practices, especially drying and storage of grains. Therefore, the general objective of this work was to evaluate the technical operational performance and the quality of dry rice grains stored in silos-dryers, with complementary heating of the gas drying air. The work was carried out in a rice drying and storage unit, composed of five metallic perforated silos, used as natural aeration silos-dryers and with complementary heating of gas air. In this first stage, rice paddy grains were stored in five dryers, for different masses and column height. Thus, the movement of air in the silos was analyzed using a paddle thermometer, as well as the temperature of the mass of grains stored from thermocouple temperature sensors. In the second stage, the movement of the air inside the grain mass in the silos-dryers was evaluated for the following grain processes: without process, re-sieved, in a sieving process, not sieved, and partially re-sieved. In this stage, air velocities, flow rates and flows, drying air temperature and relative humidity were evaluated. Then, samples were collected, using thermometry cables, in upper and lower points of the silos, to evaluate water content, apparent specific mass, yield of whole and broken grains. From the simulations and experiments, it can be concluded that the variations in the heights and the quality of the grain mass processing form influenced the static pressure and the performance of the silos-dryers and exhaust fans, reducing the work capacity, and consequently interfering with the quality of the stored grains over time. The technical operational performances of the silos-dryers set were not satisfactory, with low drying efficiency and maintaining the quality of the stored grains. The drying efficiency of rice grains was inversely proportional to the increase in static pressure, with an increase in the height of the mass of rice grains, with incomplete drying levels in the upper layers. The sieving operations of the rice grain mass contributed to the reduction of impurities and a better distribution of the static pressure of the grain layers, favoring a more homogeneous movement of the intergranular drying air and the quality of the grains. The batches of rice grains not re-sieved and stored in the silos-dryers had the formation of air passage corridors at specific points of the grain mass, impairing the drying and the quality of the grains. It was concluded that the complete sieving of the grain mass and the homogenization of the grain lots is essential to perform an adequate drying and storage of paddy rice in silos-dryers.