World Grain - May 2018 - 64
Feed mill design must account for the
amount of raw materials received
by Fred Fairchild
In the previous article (April 2018 issue) we discussed and explored the types and amounts of feed to be made in the facility.
At 2,000 tons per week (tpw) operating 40 hours per week, the
needed capacity would be 50 tons per hour (tph). If the needed
capacity increased to 3,000 tpw in two years, the mill would
work 50 hours per week making the needed capacity 60 tph.
The ultimate capacity required would be 5,500 tpw. The mill
ultimately would work 96 hours a week to make the hourly
capacity needed 57 tph.
Based on these capacities, the mill should be able to ultimately produce 60 tph. Since factors occur that won't let the
factor. This would make the design capacity required 75 tph.
We now need to list the ingredients needed to produce the
feed. Following in Tables 1 and 2 (pages 66 and 68) are two
typical formulas we will use for this mill design. Each formula shows the ingredients required, amount required, and the
source used to add each ingredient to the mix. Overhead bins
store those ingredients above a batching scale(s).
GRAIN STORAGE REQUIREMENTS
The amount of ground corn needed is approximately 45% of
the formula. This means that at 2,000 tpw, 900 tons of corn
would be needed. That converts to 32,143 bushels of corn
used per week. At a maximum capacity of 5,500 tpw, nearly
88,500 bushels of corn would be used per week. Let's assume
the mill can get corn on a regular basis, but always wanted to
have a two-week supply of corn on hand at all times. Initially
60,000 bushels of corn storage would be needed. At maximum capacity, about 177,000 bushels of corn storage would
be needed. The corn storage could initially have 1 to 2 bins but
would need added bins to store corn when maximum production capacity is needed. If corn deliveries are not available
on a daily basis, then the amount of corn storage needs to be
greater so that you don't run out of corn and still have a minimum of 1 to 2 weeks of corn use in storage.
OVERHEAD INGREDIENT STORAGE REQUIREMENTS
Now let's look at the ingredients to be stored in overhead bins
that would be installed in the scaling and mixing tower. Using the two formulas from Tables 1 and 2, Table 3 (page 70)
shows the amount of each ingredient needed in the overhead
bins to be able to produce either formula at the amount needed
One or more overhead bins will be needed to store each of
the ingredients listed in Table 3. Let's explore the type and
size of bins that might be available. Bin capacities are nominally sized by the cross section of the bin times its straight
wall height. The hopper volume isn't normally included as
the hopper section is considered to offset the cone or pyramid
volume of the product at the top of a full bin.
Square bins are normally used for overhead bins and are
built into clusters. These can be metal or slip-formed concrete.
Square bins are nominally available in 7-foot x 7-foot, 8-foot
x 8-foot and 10-foot x 10-foot cross sections. Metal bins are
limited in wall height to about 50 feet, but concrete can be
made much taller. Bin capacities are determined by calculating their cubic volume times the density of the ingredient
stored in them. Soybean meal has a density of 36 to 40 pounds
per cubic foot. If we choose a to use a 10-foot by 10-foot horizontal wall dimensions by a sidewall height of 50 feet, the
nominal cubic capacity for the bin would be 10 x 10 x 50 =
5,000 cubic feet. The bin will hold 5,000 feet3 x 40 pounds/
feet3 = 200,000 pounds divided by 2,000 pounds per ton =
100 tons of soybean meal. This bin would hold enough for
initial production, but a second bin would be needed to hold
May 2018 / World Grain / www.World-Grain.com