A candidate technology
of the North Carolina Agreements Project:
Development of Environmentally Superior Technologies
per Agreements Between the Attorney General of North Carolina
and Smithfield Foods, Premium Standard Farms and Frontline Farmers
for Energy and Ash Recovery
Press Separator, Feed Tanks and Tangential Flow Separation System
Lift Stations and Tangential Flow Separation System
project includes two systems designed to separate the solid portion
of the waste stream coming from pig barns, while the separated solids
are then combusted to produce energy, and the ash that remains following
combustion was evaluated for use as fertilizer.
technology provider is Biomass Energy Sustainable Technology (BEST).
Dr. Garth Boyd, director of environmental technology for Smithfield
Foods, Inc., developed and manages the project in cooperation with Doug
Miller of QED Occtech. The
two solids separation systems are located at Corbett Farm, a Murphy-Brown
farm near Rose Hill in Duplin County, North Carolina.
Farm Unit 1, screw-press separator
This system is treating waste from five finishing barns, which contain
3,320 pigs when full. Manure flushed from the barns flows first to a
collection pit, then to an above-ground feed tank, then to a screw press
separator (FAN® Separator (USA), Inc.) on a raised platform. The separator
has a screen with .25 millimeter openings. The liquid that flows through
the screw press separator screen flows to a second feed tank, then to
two tangential flow gravity settling tanks sited parallel to each other.
Each tangential flow settling system consists of a 2.2-meter diameter
tank with a cone bottom followed by a 1.2-meter diameter sludge thickening
tank, also with a cone bottom. Tangential flow in the first tank causes
solids to concentrate in the center of the tank and settle to the bottom.
This settled slurry is then pumped to the second tank for sludge thickening.
The tangential flow settling system is manufactured by QED Occtech of
Australia. For about 10 minutes every hour the settled slurry from the
second tangential flow settling tank is pumped back to the tank that
feeds the screw press separator, where the settled slurry is combined
with the flushed manure that is being pumped to the screw press separator.
Farm Units 3 and 4, Filtramat separator
A second separation system is located at Corbett Farm Units 3 and 4,
which include a total of four finishing barns that house 4,048 pigs
when full. This system employs a Filtramat™ separator made by Denitral
of France and marketed in North America by Environgain of Quebec, Canada.
The separator consists of sloping concave screens and a hydraulic screw
press. The screen has .5 millimeter openings. Separated solids migrate
down the screen into a hopper. A wiper moves across the screen periodically
to clean it. The solids that drop to the hopper are fed to a chamber
to be dewatered by a hydraulic screw press. The liquid that leaves the
Filtramat flows to a tangential flow settling system identical to the
system used at Corbett Farm Unit 1. Settled solids from the sludge thickening
tank are periodically returned to the screw press.
Solids collected from both systems along with turkey litter were trucked
to Coeur d' Alene, Idaho, during the evaluation period. In Idaho, the
solids and turkey litter were combusted at a test facility/pilot combustion
plant operated by Energy Products of Idaho (EPI). The combustion and
emissions characteristics of turkey litter, swine manure solids and
various mixtures of the two were evaluated in an atmospheric bubbling
fluidized bed system maintaining minimum bed temperature above 1,300°
F. The ash that remains after combustion was sent to Alabama, where
it was evaluated by Applied Chemical Technology for its fertilizer value.
Dr. Phil Westerman
Department of Biological and Agricultural Engineering
North Carolina State University, Raleigh, NC
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