PYROLYSIS OF INDUSTRIAL WASTES
R. Srinivasaraghavan, Process Engineer
T. E. Wilson, Associate
M. J. Stark, Engineer
Greeley and Hansen, Engineers
Chicago, Illinois 60606
INTRODUCTION
Solid wastes generated from the industries, in the form of waste products, by-products
and discarded material, as well as sludge solids from wastewater treatment, are reaching
enormous proportions, amounting to billions of tons. These wastes are generated in small
areas and their disposal has become a problem. The conventional methods of solid waste
disposal in landfill sites and by incineration are being restricted due to air pollution and
other considerations. The potential energy value of these waste products is in trillions of
Btu's. One of the methods of tapping some of this energy is by pyrolysis.
In order to include most of the systems referred to as pyrolysis systems, the following
definition for the term has been adopted for this paper:
"Pyrolysis is the gasification and/or liquefaction of the combustUes of a solid waste by
heat, either in the total absence, or in the presence of a controUed amount of oxygen."
The pyrolysis concept has been employed in various industries.   However, the extension of this concept to waste disposal industry is relatively new.   Pyrolysis of domestic
refuse has been tested at several locations to varying degrees of success.   As for industrial
solid waste by-product pyrolysis, the experience is minimal.   Some large-scale pUot studies
on forestry wastes, employing saw dust, timber and some agricultural by-products, have
been reported [ 1 ].   Some conceptual information, based on small laboratory and pUot-
scale studies, has been developed on plastic, rubber, food, animal and wood wastes.   Some
basic data are being developed on sewage sludge pyrolysis, but little information is avaU-
able on industrial waste sludge pyrolysis.
The purpose of this paper is to present pertinent available information on the potential
of some industrial solid wastes and sludge pyrolysis.   Included in this paper are also discussions and analyses of potential by-product uses, as weU as the operational features of
the process.
PYROLYSIS
The pyrolysis process can be carried out in a furnace similar to an incinerator.   It may
be performed in a vertical shaft, horizontal shaft, rotary kUn, fluidized bed, multiple hearth
or one of many other types of furnaces.   The specific type of furnace to be employed
wUl depend upon the specific feed material and other factors.
The three main process reactions that take place in a pyrolysis furnace may be briefly
described as follows [2]:
1. Drying-Where the moisture in the feed material is driven off.
2. Pyrolysis-Where the volatile matter in the feed is converted to combustible gases
and/or liquid: part of this gas/liquid is combusted within the furnace to provide the
required heat; automatic controls regulate the air supply to maintain the temperature in the furnace and provide an oxygen-starved atmosphere.
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