Centriskim - A continuous process for reducing DAF skimmings 0 pages

Centriskim
A continuous process for reducing DAF skimmings
Most meat and poultry processing companies have reduced
their potential pollution problems from process water by
installing DAF (dissolved air flotation) systems. More and more
of these companies, however, also face a secondary problem
– what to do with the recovered DAF skimmings.
These contain fat and suspended dry matter – mainly
proteins – all lost to the process water during the primary
processing of meat and poultry, and recovered using various
chemicals. Due to the nature of the DAF skimmings, with
their high moisture content and the presence of flotation
chemicals, this product waste is not very desirable. Traditional
recipients reject the product due to the chemical contents,
which downgrade the quality of the final product. The high fat
and moisture content makes agricultural application difficult
and very expensive.
The Centriskim process provides an inexpensive solution for
reducing DAF skimmings to recovered fat and an easily
disposable water phase, as well as a wet concentrated solid
phase. After this reduction process, the solid phase usually
comprises less than 15% of the original weight, and fat
recovery typically amounts to 10–15%.
All Centriskim processes use centrifugal separation in a
thermal process to extract fat and a highly concentrated
solids phase. The solids can be transported to a central
recycling plant, or further processing can be undertaken on
site. The fat is normally recovered in the process, either by
using a 3-phase decanter, or in a secondary separation
process using a high-speed separator.
Centriskim processes can be tailored to meet local
requirements, with or without the use of chemical conditioners.
Process description
DAF skimmings are collected in a buffer system and then
passed through a continuous steam injection heater to be
heated to a temperature suitable for the centrifugal separation
either by:
• single-stage separation using a 3-phase decanter to extract
solids, fat and water phase
or
• two-stage separation, which requires a 2-phase decanter
for the solids/liquid split and a high-speed separator to
extract the fat.
Single-stage separation is preferable in cases where the
composition and consistency of the DAF skimmings are fairly
constant. Two-stage separation is a more versatile method,
which provides the best separation performance on products
with more variations in composition, quality and chemicals,
etc. Two-stage separation thus normally produces a water
and fat phase of greater purity. The fat (grease) complies with
more demanding specifications as regards impurities, and the
water phase has a lower BOD loading.
The waste water separated from a single-stage system often
requires further processing (returned to DAF or concentrated
by evaporation), while the two-stage stickwater better
complies with discharge criteria.