An adaptive grain-bulk aeration system for squat silos in winter: Effects on intergranular air properties and grain quality

Abstract

Grain can be stored for long periods under suitable storage conditions. The present study investigated the effects of cooling aeration on the intergranular air properties and grain quality of wheat stored in two squat silos during winter. In the first silo, 4759 tonnes of bulk wheat were downward-aerated in a suction-type way by four 11 kW centrifugal ventilation fans at an airflow rate of 10.1 m3/(h·t). The fans were firstly controlled by software based on a smart de-moisturization aeration model, and the grain bulk lost 0.8% moisture content (MC) and its average temperature was decreased by 5.8 °C. When the fans were then controlled using smart cooldown aeration model, the average bulk temperature decreased from 17.0 to 5.2 °C, and the average bulk MC was reduced by 0.6%. The cooling fronts moved predictably through the bulk layers during cooldown aeration, which consumed energy at a rate of 0.067 . In a second silo, 4,675 tonnes of wheat were also downward-aerated at 9.8 m3/(h·t) using smart cooldown aeration model and four 5.5 kW mixed-flow fans. There was a 0.7% MC loss and the average bulk temperature decreased by 6.7 °C. Except for the middle part (fourth and seventh) bulk layers, the other bulk layers in this silo had cooling fronts that moved at similar speeds. The energy consumed by cooldown aeration was 0.040kWh(t·∘C)−1 and 58% unit energy consumption was lowered when compared to a local grain squat silo with geosynclinal ventilation ducts under artificially controlled cooling-ventilation operations. The running conditions for the ventilation fans during cooldown aeration in the squat silos were verified. (i) The temperature difference between the grain bulk and ambient air was ≥ 4 °C. (ii) The humidity ratio of the grain bulk was higher than that of the ambient air. The equilibrium relative humidity of the intergranular air tended to decrease in both silos. After cooldown aeration, the wheat kernels had a higher water absorption rate and fatty acid value, retentive peak temperature of gelatinization, and a higher dough development time, protein network strength, and starch gelatinization rate. The proposed aeration control system has good application potential in squat silos used for grain storage.