Miller Magazine Issue: 125 May 2020

54 COVER STORY MILLER / MAY 2020 Moisture and Temperature changes in stored grains air movement inside the storage The migration of moisture in stored grain takes place due to change in temperature as per season i.e. winter and sum- mer. One of the most important factors influencing storage life of the grain is moisture content. High moisture content and a warm climate promote mold growth, insect growth and increase rate of respiration of grains and due to this deterioration and losses of the stored grains takes place. Moisture migration takes place in stored bin even though the grains are stored at a desired moisture level i.e. safe for storage. Angle of Repose The angle of repose is the greatest angle from the hor- izontal to which a grain can be raised without it sliding or rolling on itself in an unconsolidated form. This determines whether a grain mass will flow by gravity, or need outside forces to move. It will determines the minimum spouting angles for gravity flow. The angle of repose of grains var- ies with type, variety, moisture content, quality and level of contamination. Angle of Repose for common grains is shown below. These angles will increase for wet grain and may also vary slightly GRAIN ANGLE (degrees) BARLEY 28 WHEAT 25 SORGHUM 30 SUNFLOWER 30 MAIZE 23 OATS 28 SOYBEANS 25 Abrasion All grains will wear the surfaces that are in con- tact with flow. The amount of wear will vary ac- cording to the type of grain, the volume of grain, speed of grain, the impact of grain streams on sur- faces and the slope of the contact surface. All aspects of the distribution system are affected by these characteristics. When analyzing systems, components such as spouting, transitions, gates, valves, conveyors and future access to these components must be designed into the system for maintenance requirements. Corrosion Wet grains, ground processed grains and chemically treated grains can corrode standard carbon steel fabrica- tions. Each grain type to be handled must be checked to determine if stainless steel is needed, or will reduce pos- sible life cycle costs. If water wash down, or cleaning place systems are required, materi- als used for fabrication in the distribution system should be considered. Respiration of Grains Grains get oxygen from the air and burn food from its endosperm. This process liberates heat, water vapors and carbon dioxide. This pro- cess in grains is called respira- tion. The respiration in grains, during the storage period, causes a dry matter loss of 1% or more. Respiration is a process of slow combustion of carbohy- drates in presence of oxygen in living system to produce the energy. C6H12O6 + 6O2 —> 6CO2 + 6H2O + Energy This process is affected by temperature and concentra- tion of O2 and CO2. Decreasing the concentration of O2 and increasing concentration of CO2 reduces the rate of