Process and Product Quality Control
There are a few
process parameters that must be control properly to minimize oil loss while
maintain the desired quality. They are caustic dosage in neutralization and
sulfuric acid dosage in acidulation.
The
selection of proper amount and strength of caustic is very important in
neutralization process. It is customary to measure the strength of caustic for
refining in terms of their specific gravity expressed in degree Baume.
First,
the strength or concentration of caustic is determined by type of oil to be
neutralized. Lower FFA feed will require lower concentration of caustic. After
this, the amount or usually term as treat is determined as shown in equation
below:
Where treat is the amount
caustic added, 0.142 is ratio of molecular weight of sodium hydroxide and oleic
acid, FFA is the percent of free fatty acid in crude oil, % NaOH is the
strength of caustic and Excess is the excess sodium hydroxide selected. The oil
loss due to neutralization process can be determined as follow.
If the caustic is overdose, more soap will be produced.
Hence, more sulfuric acid is required to convert the soap into fatty acid and
salt. As a result, more acid oil which is a lower grade product will be
produced. Sulfuric acid dosage plays another important role in the quality of
the process. Excess sulfuric acid will cause problems in effluent plant where
more caustic is required to neutralize the sulfuric acid. Low sulfuric acid
will lead to incomplete conversion of soap to fatty acid.
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