MIL-HDBK-1005/9A
The selection of demulsifiers requires practical
experience. There follows, then, a trial and error narrowing of
the choice according to activity and tolerance toward existing
system variables. The identification of the best demulsifier and
the optimum concentration range is best realized by the jar/bottle
test. This is a standard technique (API Code 2500) accepted in
the oil industry that has, for many decades, aided the operator in
demulsifier selection. A list of suggested vendors and further
information on the demulsification of oily wastes can be found in
NCEL TM 71-85-35, Treatment, Handling, and Disposal Methods for
Chemical Demulsification Sludges.
3.10.10
Pumps, Valves, and Piping
3.10.10.1 Pumps. Primary emphasis should be placed on arranging
treatment units for gravity flow operation. Where gravity flow is
not feasible or there is a need to control feed rates into
treatment units, pumping should be used. Pumps specified for
transfer of oily waste should not shear emulsions or mechanically
emulsify free oil.
a) Use progressive cavity pump or recessed impeller
vortex pump. Progressive cavity pumps require that influent be
fine screened to remove any solids large enough to jam the cavity
between the stator and rotor components. Pump selection should be
based on low speed operation of 700 to 1,100 rpm. Provide a
pressure relief system to protect the pumps and discharge piping
from being overpressurized if the pump discharge line becomes
blocked.
b) A conventional centrifugal pump with high
efficiency, fully enclosed impeller and operating speed < 1,750
rpm is recommended to pump treated effluent to a discharge point.
c) Facility designs should provide 100 percent
redundancy in pump installations to preclude total plant shutdown
on loss of a single pump.
174
Previous Page
