Page 203 - Environmental Control in Petroleum Engineering

Waste Treatment Methods 189

A suspension of contaminated soil and the carbon can be tumbled in
water at elevated temperatures to allow the oil to be absorbed by the
carbon. The oily carbon is then separated from the water and clean
sand by flotation. The oily carbon can then be burned in conventional
coal-fired power plants or buried in an approved facility.

Heating

Heating cuttings contaminated with hydrocarbons can help separate
the hydrocarbons from the solids, particularly when being washed in
water (Henriquez, 1990). This procedure is similar to using heat to
break emulsions and separate hydrocarbons and water.
Heating can also be used for hydrocarbon sludges (Hahn, 1993).
In this process, the sludges are heated above the boiling point of water
and allowed to flash to vapor. This separates the water and light
hydrocarbons from the heavier hydrocarbons. The high temperature
also lowers the viscosity of the heavy hydrocarbons, facilitating their
separation as a slurry.

Distiliation/Pyrolysis

A more expensive method for removing light- and intermediate-
weight hydrocarbon compounds is to distill them from the solids in a
retort furnace. The solid/hydrocarbon mixture is heated to vaporize the
light and medium molecular weight hydrocarbons and water. The gases
are removed from the high-temperature chamber by either a nitrogen
or steam sweep. After the vapors are subsequently cooled and con–
densed, the oil is separated from the water. The oil can be reused and
the solids and water sent to an appropriate disposal facility. To maxi-
mize the separation of liquids and solids, the heating can be done in
a rotating drum with hammers to crush the solids while rotating.
Several commercial thermal distillation processes are available (Ruddy
et al, 1990).
Distillation systems, however, have several significant operations
limitations. Hydrocarbon vapors at high temperatures are a fire hazard,
corrosion problems increase significantly at high temperatures, and air
pollutants are emitted. The chemical structure of some hydrocarbons
is altered at high temperatures, making their reuse in some applica-
tions, like drilling muds, impossible. If heavy hydrocarbon components