Design and construction of a dampening unit of the maize milling system.

Abstract

Maize (zea mays L) accounts for almost a half of the calories and proteins consumed in East Africa (Dr. Harold Macauley, 2015). The maize milling operation is mainly aimed at separating the various components of the maize kernel through the process of dampening, de-hulling and milling. Dampening of maize is the controlled addition of moisture to the maize kernel to create a moisture gradient in the kernel so that the bran and the germ are at higher moisture content than the endosperm. The objective in maize dampening is to optimize the physical conditions of the grain so that a separation of the germ, the bran, and the endosperm can be achieved during milling (Larsen 1970, Scott 1936, Simon 1930). At local levels dampening of grains by maize millets is not a common practice, though' maize millers at kazimingi millers in Jinja district add 800 liters' of water to every 1000kgs of maize milled using jerry cans before de-hulling and the maize is spread on the ground for around 5 minutes to allow water penetration into the hull. This process leads to un even distribution of the sprinkled water hence making the de-hulling process hard, also the spreading of the maize on the ground leaves the kernels liable to contamination. Therefore, this project is carried-out to design and construct a dampening unit of the maize milling system. The maize dampening was constructed to resolve this problem for small scale millers. The dampener adds water to the maize, mixes the maize with the water using the auger and finally tempering of the wet maize in the tempering bin. The NPV value obtained is positive hence the project is highly viable. The efficiency obtained (27%) is low compared to the anticipated value, this is due to the high speeds of the conveying section. The maize dampening unit was constructed running at a capacity of 250 kg/hr. also a maize blower was joined to the dampening unit to deliver maize to the tempering bin. Water was added to the maize successfully and mixed increasing moisture by 0.8%. The maize dampening unit is suitable for small scale millers to improve the entire dampening process and also improve the maize hulling process.