Maize, or corn, is one of the most widely planted grains in the world. It is the main grain crop in Mexico, Brazil, Argentina, etc. While other countries like America, China, and most African counties also harvest large quantity of corn/maize every year.
The maize can be processed into flour, grits, or even starch. This article aims at discussing the process of maize flour milling (corn flour milling).
Maize kernels are fed from the material inlet and the flow rate is controlled by a baffle. When the maize kernels are transported by the bucket elevator into de-stoner, they first go through fine sieve, the sand or other impurities smaller than maize will be screened out and discharged from the taphole. After fine sieving, corn kernels enter coarse screen to screen out impurities that are bigger than corn, for example, corn cob particles; while these impurities are also discharged from taphole. At the same time, above the sieve, it is connected with a fan. The function of Fan 1 is to suck those light impurities still mixed in maize kernels; such impurities will be eliminated by the function of centrifugal sedimentation.
After cleaning, maize kernels go out the outlet and delivered into screw conveyor. Maize kernels flow in the screw conveyor and dust or similar small particle impurities are further screened out. Then, maize is delivered into dampener. In the dampener, maize kernels and water are fully stirred and mixed. Those maize kernels that meet dampening requirements will be delivered again by the elevator into storage barrel for temporary storage, whose purpose is to make sure the feeding flow in next step is even.
On the outlet of storage barrel, there is a baffle to adjust discharging flow. When maize kernels get out, they will enter slag mill for preliminary breaking, so that some maize skin is separated from embryo. After that, broken maize is delivered by the elevator into embryo selection machine. Inside it, maize skin and embryo are separated and expelled from different outlets. At the same time, on the top of embryo selection machine, there is connected Fan 2. Under the function of fan, some light impurities are sucked out, while the embryos discharged from the outlet of selection machine are delivered by Suction Fan 3 into Maize Flour Mill 1. Those maize skins discharged from the selection machine and some broken embryos will be delivered into Maize Flour Mill 2.
The maize flour milled by Flour Mill 1 and 2 are sucked by Suction Fan 3 and delivered into Double Bin Sieve 1 for sieving, and the maize flour that meet standards will be ejected by Suction Fan 4 for weighing and packaging. While the maize flour that does not meet crushing standard will be screened out from double bin sieve and then delivered by Suction Fan 3 into Flour Mill 3 for further grinding. The discharged material is delivered by Suction Fan 3 into Double Bin Sieve 2 for sieving: the corn flour that meets standard will be ejected by Fan 4; those substandard will be delivered by Fan 3 into Maize Flour Mill 4. After milling, maize flour is again delivered into Double Bin Sieve 2 for screening.
Over such cycling processing, maize flours can meet different classification standards. Depending on maize flour content and particle size maize flour is classified into 4 grades: Grade 1 and Grade 2 are mainly maize skin and small proportion of maize flour, so they are used for animal feed; while Grade 3 and Grade 4 are fine maize flour for edible.
100tpd maize flour milling plant