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Autoxidation of
Wood Distillation Wastes with Oxygen
BOYD T. RILEY, JR., Graduate Student
JOHN E. KIKER, JR.. Professor
CHARLES I. HARDING, Assistant Professor
Environmental Engineering Department
University of Florida
Gainesville, Florida
INTRODUCTION
The problem of developing technically and economically feasible industrial
waste treatment processes challenges the abilities of the environmental engineer.
One such process waste is that produced by the wood distillation industry. This
industry may be divided into two general classifications as follows: 1) plants
utilizing primarily deciduous woods as a raw material, and 2) plants utilizing
primarily coniferous woods as a raw material. The kind of plant depends mainly
upon the climate at the plant site, which determines the predominant type of tree
for the area. Both types of plants produce charcoal but differ somewhat in other
products. The research conducted in the preparation of this paper is confined to
wastes from the Cabot Carbon Corporation, a plant located in Gainesville, Florida,
which processes mainly coniferous woods.
The retort operation is a batch process (See Figure 1). The stump wood is
placed into rectangular slat-sided iron crates which are mounted on rail cars. A
train of several crates is assembled and moved into a retort by a small engine.
After it is sealed, the retort is heated by oil burners to about 800 F with the atmosphere inside the retort kept under reducing rather than oxidizing conditions.
Essentially all of the liquids present in the woodare driven out as the wood is carbonized. The wood remains in the retort for about eight hrs. The hot retort is
opened and the charcoal is moved to cooling chambers which are similar in construction. As soon as oxygen contacts the hot charcoal, it ignites. After the cooling chamber is sealed, the enclosed oxygen is used up and the flames disappear.
The charcoal cools for eight hrs after which it is removed from the cooling chambers and stored. After size classification, large pieces are sold as raw material
for the production of activated carbon and the small pieces are pulverized, mixed
with starch and pressed into briquets.
The liquid vapors pass out of the retort and through condensers. The liquids
are pumped to unlined settling lagoons where the heavy tars and oils are separated
from the aqueous portion of the liquid. The concentrated oils and tars are pumped
from the bottom of the settling lagoons to a steam distillation column where they
are further fractionated, barreled, and sold. The aqueous portion, known as acid
water or pyroligneous acid by the industry, seeps through the sandy walls of the
lagoons ana becomes surface drainage.
Acid water is either bacteriostatic or toxic. Veijolo and Mustakalio (1) sep-
erated wood tars into various gross fractions by solvent extraction, and tested the
effects of these fractions on biological systems. They concluded that the resin
acid fraction was primarily responsible for the bacteriostasis and that these resin
acids were effective in either the acid or salt form. A few of the characteristics
of acid water as sampled at Cabot Carbon Corporation are given in Table I,
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