10    RECLAIMING PETROLEUM CONTAMINATED SOIL IN HOT
MIX ASPHALT FACILITIES
Kathryn O'C. Gunkel, Director of Environmental and Safety Operations
National Asphalt Pavement Association
Riverdale, Maryland 20737
INTRODUCTION
The National Asphalt Pavement Association (NAPA) has received many, many calls over the last
year or so regarding the feasibility of processing petroleum contaminated soils through Hot Mix
Asphalt (HMA) facilities primarily for the purposes of removing hydrocarbons (THC) from the soil.
These callers believe that, with the direct-fired system used for heating and drying aggregates in a
HMA facility, the THC would be destroyed. Unfortunately, this not necessarily the case. Limited
testing has indicated that some of those THC will be destroyed, however a substantial portion may be
exhausted to the environment.
EQUIPMENT PROCESS TECHNOLOGY
A Hot Mix Asphalt (HMA) facility is used to manufacture HMA pavement. There are two basic
types of manufacturing processes, both of which dry aggregates in a rotating kiln, using direct-fired
heat, and coat the aggregates with asphalt cement (AC). It is the ability of the HMA facility to dry
aggregates that has gained it attention from the environmental arena for the purpose of decontaminating petroleum contaminated soils. That is, removal of the petroleum product from the soil.
One manufacturing process mixes aggregate with AC on a batch basis (Figure 1), while the other
process is basically a continuous process. The latter process employs parallel-flow heat exchange (the
batch process employs counter-flow), but in the last two years the equipment manufacturers have
made substantial design modifications to the continuous process. In the HMA Industry the term
applied to the continuous process is "drum mixer," because the process employs mixing of the
aggregates and AC in the drum, out of the combustion zone (Figure 2). New designs generally
maintain the in-the-drum mixing concept, but have gone back to the counter-flow heat exchange
design.
|DU8T
LADEN
1  GAR i '
TO  TRUCK
ASPHALT or  STORAGE
Figure    1.    Aggregate/ AC
mix on a batch basis.
44th Purdue Industrial Waste Conference Proceedings, © 1990 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
91