Use of Centrifuges in De-Oiling Silt
WILLIAM L. LEWIS, Engineer
Petroleum Technical Department
Manufacturing Division
Humble Oil and Refining Company
Baton Rouge, Louisiana
A silt disposal process, utilizing centrifuges to de-oil silt, can now be considered a successful operation at the Baton Rouge Refinery of Humble Oil & Refining
Company. This paper discussed the sUt disposal problem that led to the installation of a Silt Disposal Unit and presents a description of the faciUties being utilized in the silt de-oUing operation.
RIVER WATER AND SILT FLOW RATES
Mississippi River water has been used for cooling purposes in the Baton Rouge
Refinery since it was constructed in 1909. CooUng water needs increased through
the years as the refinery expanded. Current requirements now range from 100, 000
gpm in the winter and 150, 000 gpm in the summer. This water is used in a once-
through system primarily for process coofing with a smaU amount being used for
fire water and equipment cleaning.
After use the water flows through the refinery sewer system, primary oil separators, a large master separator for final cleanup of aU waste water streams, and
thence to the river. Approximately 240 cu yd/day of river silt enters the refinery
with the river water. This river sUt is made up of three types of solids: 1) course
(fine gravel and sand); 2) medium (silt and clay); and 3) fine (microscopic particles). The silt and clay particles wUl form an agglomerate with oil probably due
to an electrical attraction. The other two types of soUds(course and fine particles) are not affected by oil. Whenever the velocity of flow is reduced, such as
in a primary separator, the fine gravel, sand, and silt particles wiU settle. The
microscopic particles flow through the waste water system into the river unaffected.
SILT PROBLEM
Prior to 1945, settled sludge was removed from the primary separators by periodic washing into a bayou. During periods of high rainfaU, silt that had settled
in the bayou was scoured into the river releasing some oU particles that had combined with the sUt on its way through the refinery. Two corrective steps were
taken. The first step was an air agitation type silt treating unit to remove oU particles from the sUt. The second step was to convert Callahan'sBayou into a master separator to provide a final cleanup stage for aU effluent streams prior to discharge into the river. Figure 1 is an aerial view looking east over our dock and
encompasses most of the Baton Rouge waste water facilities. The air agitation silt
unit was designed to produce a slurry that could be returned to the river. However, the silt, after this treatment, still had enough oU retained so that it could
not be discharged to the river. AU air agitated sUt was retained in silt ponds that
were constructed on ba'tture land adjacent to the master separator. Since the master separator increased the amount of sUt requiring processing and river water requirements increased as the refinery expanded, all the available batture land
would eventuaUy be fUled with sUt.    Anticipating the fiUing of the silt ponds,
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