TURPENTINE RECOVERY SYSTEM


Sulfate turpentine is an economically important by-product which can be recovered from
the kraft pulping of resinous woods. About 80% to 85% of the turpentine in wood
charged to the digester comes off during the relief cycle. Efficient recovery of this
turpentine can be accomplished in an A. H. Lundberg, Inc., Turpentine Recovery System.

Relief gases from the digester pass through a fiber separator into the turpentine
condenser. Condensate from the condenser is then decanted to separate the turpentine.
Turpentine then overflows to turpentine storage while the water underflow is removed for
treatment as effluent.

The Fiber Separator is provided to remove fiber that may not have been separated in the
digester relief strainer. More important, however, is the removal of liquor droplets ahead
of turpentine condensation. Liquor mixed with the condensate can cause emulsification
of the turpentine and prevent or delay separation during decanting.

The Turpentine Condenser is a vertical shell and tube unit designed for condensation
inside the tubes. As the relief gases are condensed, the condensate flows down the
tubes and is cooled to the desired temperature for efficient separation in the decanter.
Condensate temperature is controlled by recycling some heated cooling water with a
tempering pump. The optimum temperature for decanting varies from mill to mill, but is
usually in the range of 110 degrees F. to 120 degrees F.

In Turpentine Decanter design, special consideration is required for providing adequate
retention time and suitable cross-sectional area to insure proper separation. The
decanter operates on the specific gravity differential between turpentine (0.82 to 0.88) and
water (1.0). The condensed turpentine is immiscible and will float on the condensed
water permitting separation and transfer to storage. Accumulated condensate, or
underflow, flows from the bottom of the decanter through an adjustable overflow, weir
box. Adjustment of the overflow permits all the turpentine in the decanter to be
transferred to storage in the event that the decanter needs to be subsequently emptied.
The underflow from the decanter is normally treated in the mill condensate or effluent
systems.

When the elevation of the decanter permits, the turpentine can flow directly to storage.
When overflow to storage is not possible, a Turpentine Transfer Tank can be provided.
The transfer tank operates as an accumulator for turpentine. When the tank is full of
turpentine, the turpentine is displaced with water for transfer to storage.

Turpentine storage capacity should be provided in a quantity that permits convenient
accumulation for shipment. A storage tank with a capacity of 1.5 to 2 times the capacity
of the shipping tanker is recommended. The A. H. Lundberg, Inc., Turpentine Storage
Tank design provides for a full tank at all times. The turpentine is stored over water
which is displaced as turpentine is added. To unload the storage for shipment, water is
added to the storage and turpentine is displaced through the transport tank fill line.

Turpentine Recovery System Flowchart

Lundberg Turpentine Recovery System
SH-1041-B