Study of pulse drying of grain in the S-30 dryer

Innovative technologies and technical means of drying which allow to dry the grain efficiently and with minimal costs are very important for development and improvement of grain industry. These technologies include the oscillating modes, the essence of which is that the material is periodically affected by heated and unheated drying agent. These modes provide periodical grain cooling, that allows to increase drying agent temperature and decrease heat losses. However, periodical grain cooling with unheated air often lowers the effect of oscillating mode. Pulse mode, unlike the oscillating one, is characterized only by decreased liquid fuel supply in the dryer, and grain cooling on a value close to theoretical one, which allows to decrease heat losses and increase dryer efficiency. The mathematical methods of calculation of temperature and duration of impact of low-heated drying agent on the grain are suggested. To determine the temperature of low-heated drying agent and its impact duration, the heat and mass transfer equations in layer and caryopsis were composed and solved; the calculated expressions were obtained from them. During acceptance testing of the S-30 dryer, the calculated dependences for determining these parameters were checked. The wet grain was continuously sent into grain dryer, the dried and cooled grain was withdrawn at the same time. The «big fire» nozzle in firebox was periodically enabled and disabled, and the «low fire» nozzle remained in working mode, thus a pulse mode of drying was created. The maximum temperature of heated drying agent was 105 degrees С, while the temperature of low-heated drying agent was 46 degrees С. It was established that curves of changing in temperature and moisture of grain did not differ from the classic curves under oscillating drying mode. The use of pulse drying mode allows to shorten by two times the amplitude of temperature oscillations of drying agent and to reduce heat losses by 10-12%. The temperature of low-heated drying agent should not be below the maximum permissible heating temperature of grain by more than 8-10 degrees C.

drying, grain, pulse mode, parameters