VITA
TECHNICAL BULLETIN
WASTE OIL-FIRED KILN
by Ali Sheriff and Bashir Lalji
This technical bulletin briefly describes a new technique
for using the spent lubricating
oil removed from automobiles.
This oil normally has no immediate use.
It is often discarded
in ways that can foul local groundwater or upset wastewater
treatment systems.
The "waste oil" can be burned as fuel by using a
special "oil-drip" technique.
A ready
supply of waste oil can usually be found at nearby gas
stations.
The oil-drip method is based on an original application
designed by Ali H. Sheriff with
the aid of Bashir M. Lalji. Sheriff is the owner and
operator of a number of small-scale
industries in Arusha, Tanzania.
The oil-drip technique was developed at his pottery
works. It is
currently in use there and at a number of schools and institutions in the
Arusha area. Sheriff
is a long time VITA Volunteer.
This bulletin is not intended to serve as a construction
guide for building a waste-oil
burner. It does
provide a description of a new technique for using a resource that otherwise
would be wasted.
VITA makes this material available to generate ideas among
as wide an audience as possible.
Readers are asked to write VITA about their experience with
the design. Please
send test results, suggestions, and requests for further
information to:
Technical Bulletins
VITA
1600
Wilson Boulevard, Suite 500
Arlington, Virgnia 22209 USA
Tel:
703/276-1800 . Fax: 703/243-1865
Internet:
pr-info @ vita.org
12:81
ISBN 0-86619-160-7
VOLUNTEERS IN TECHNICAL
ASSISTANCE
VITA TECHNICAL
BULLETINS
This Technical Bulletin is one of a series of
publications that offer do-it-yourself technology
information on a wide variety of subjects.
Technical Bulletins are idea generators, intended
not so much to provide a definitive answer as to
guide the user's thinking and planning.
Premises
are sound and testing results are provided, if
available.
Users of the information are asked to send us their
evaluations and comments based on their experiences.
Results are incorporated into subsequent
editions, thus providing additional guidelines for
adaptation and use in a greater variety of conditions.
WASTE OIL-FIRED KILN
by Ali Sheriff and Bashir Lalji
INTRODUCTION
HOW IT WORKS
The Pottery Works
Clay Preparation
Collecting The Waste Oil
Cleaning The Oil
The Modified Kiln
Firing The Kiln With Waste Oil
A Cook Stove
2
INTRODUCTION
The increasing price and decreasing availability of
petroleum products continue to
be serious problems, particularly in developing
countries. It is thus especially
important to make maximum use of current petroleum
supplies. The lubricating oil
removed from automobiles is an example of a valuable
reusable petroleum product.
It cannot be used for the same lubricating purposes without
expensive re-refining
techniques. But it
can be used for other purposes.
In the past, waste oil has been used in a variety of
ways: as a coating to protect
wood against insects, to control the dust on unpaved roads,
and to fire simple
stoves. Most stoves
that burn waste oil use a drip technique.
However, few of them
mix the oil with water and none uses the system of splash
plates described here.
WARNING!
Waste oil
from engine crankcases or gear boxes can
be a
useful, low-cost fuel in certain applications.
However,
users of waste engine oil are
warned
that the oil might contain lead from leaded
gasoline. The lead would be
released into the air
as the
oil burned. It could possibly
contaminate
pottery fired in the kiln, and be a
hazard to kiln
operators.
Users of
waste engine oil should have the oil
tested to
find out if it contains lead. The
combustion
chamber
of the kiln should be sealed, and
the
chimney should be high enough to carry combustion
products
well away from the work area. The
kiln
should be operated in a well-ventilated
place.
Do not
use engine oil to fire space heaters or
food
dryers. Waste oil from electric
transformers
should
not--repeat, not--be used as fuel in any
circumstances. Transformer oil
contains poly
chlorinated biphenol (PCB) compounds.
PCB is highly
toxic and
should not be burned at all. It
should
not even be handled at all. If you
think
your
waste oil supply might come from electric
transformers, do not take chances.
Do not burn the
oil.
HOW IT WORKS
Waste oil by itself will not burn.
However, it can be made to burn under certain
conditions. The
waste oil is mixed with a small amount of water and dripped onto
a hot surface in a fire box chamber.
The water vaporizes instantly and the oil
becomes a flammable mist.
If the chamber has been sufficiently preheated, the oil
mist will burst into flame.
The heat of the burning oil will then maintain a high
enough temperature in the firebox to continue the burning process.
The operation of the waste oil burner is very simple.
It does require frequent
attention and a specially designed firebox.
The firebox is fitted with two metal
doors. A large upper
door allows the loading of the wood or charcoal fuel used to
preheat the firebox.
A smaller door, positoned below the large door, permits
control (see Figure 1).
Inside the firebox, three cast-iron plates are slant-mounted
wokfig1.gif (486x486)
in a stair-step fashion (see Figure 2).
These plates are called
"splash-plates."
wokfig2.gif (600x600)
Separate oil and water containers are positioned above and
to the side of the firebox.
Tubes lead from the containers to a short metal trough
located on top of the firebox.
The oil and water are gravity fed into the trough where the
two liquids mix. The
mixture then flows through a hole in the top of the firebox
and drips onto the
splash-plates.
The splash-plates are first heated by a charcoal or wood
fire beneath them. Gate
valves on the oil and water containers are adjusted to
permit a flow of four drops
of oil to one drop of water.
The oil and water mix in the metal trough on the firebox.
The mixture then drips onto the hot splash plates in the
firebox. The waste oil
ignites after splashing off the iron plates.
The heat generated by the burning oil
keeps the splash-plates hot and the charcoal or wood fire is
allowed to die out.
It is important to control closely both the amount of oil
and water dripping into
the firebox and the draft through the lower firebox door.
The height of the chimney for the firebox will depend on the
intensity of the heat
required. The higher
the chimney, the hotter the fire.
The Pottery Works
A kiln using waste oil as a fuel operates at a pottery works
in Arusha, Tanzania.
VITA Volunteer Ali Sheriff, one of the principal developers
of the oil-drip technique,
owns and operates the pottery works.
The small factory is set up in a warehouse
in an industrial area of Arusha.
Clay and the waste oil are obtained locally
and brought to the pottery works by truck.
Clay Preparation
The pottery factory produces cups, bowls, and other
household containers. Typically,
the clay is mixed with water to form a slurry.
It is then dried to obtain a consistent
lump free quality.
After each of the items has been formed, it is dried, heat
treated to improve the clay's strength, and dipped in a
glaze mixture. The "green
ware," as it is called, is placed in rounded clay
containers to protect the glazed
pieces from direct flames and the containers are stacked
inside the kiln.
Collecting The Waste Oil
The waste oil for the kiln is collected from gas stations
located within Arusha.
At each of the stations the oil is either extracted from the
gas stations's containers
or a full barrel is exchanged for an empty 55-gallon
drum. Occasionally, the waste
oil collector offers to leave a 55-gallon drum at a gas
station which is discarding
its oil by pouring the oil over the land in back of the
garage or dumping it down
drains. The oil is
then cleaned as described below.
Cleaning The Oil
Waste oil requires simple treatment before it can be used as
fuel. Drums left at
gas stations will often contain metal filings, rocks, sand,
water, and other debris.
All of these foreign solids and the water must be removed as
illustrated in Figure 3.
wokfig3.gif (540x540)
The oil is first poured through a screen (60 mesh or finer)
into a clean drum that
is equipped with a tap located as near the bottom as
possible. The oil is left to
stand for a few minutes and the water settles to the bottom
of the barrel. The
water is removed by opening the tap.
The tap remains open until only oil flows
from
the drum. The waste
oil is now ready for use.
The Modified Kiln
The kiln is a down draft type that normally would be fired
by the more expensive
process of injecting fuel oil under pressure to vaporize it
in the firebox. The
kiln has been modified to use waste oil (Figure 4).
The modified kiln has three
wokfig4.gif (486x486)
fireboxes on each side.
Each firebox contains three cast iron plates measuring
18 by 13 centimeters and slant mounted in stair-step fashion
(Figure 2).
Each firebox has two doors.
The larger top door is used for loading the wood or
charcoal that is burned to preheat the metal plates.
The smaller lower door acts
as a damper to control the flow of air into the kiln.
Careful operation of the lower
door is very important.
The kiln does not require a blower, as the draft through
the lower door and out the chimney is sufficient.
A tank of water and a tank of waste oil are located on each
side of the kiln.
Tubes leading from the tanks have gate valves located above
each of the fireboxes.
The gate valves are adjusted during operation to allow a
mixture of about 4/5 oil
and 1/5 water to drip through a hole into the firebox.
The oil-water mixture
splashes off the hot iron plates, vaporizes, and ignites.
Firing The Kiln With Waste Oil
The firing of the kiln requires two men, one for the three
burners on each side.
The fireboxes are loaded with wood kindling through the
large, upper doors and fires
are started in all of the chambers.
This heats up the iron splash-plates and
starts
a good draft.
Openings at the top of the kiln let out the smoke and hot air until
a draft is moving wall in the large chimney.
Both the upper and lower doors on all
the fireboxes are left open during this preheating of the
kiln. After about half
an hour the iron splash-plates are hot enough to vaporize
the oil-water mixture.
The vents on top of the kiln are closed with brick and clay,
and the oil and water
are turned on. The
gate valves above each of the fireboxes are adjusted so that
four drops of oil enter for each drop of water.
The oil and water mix in a short
metal trough, fall through a hole on the firebox top, and
onto the splash-plates.
There is a sharp sizzling noise as the water is vaporized,
and the oil bursts into
a bright, wild flame that shoots toward the kiln with the
increasingly strong draft.
Proper adjustment of the oil and water flow requires
frequent attention. The draft
control doors on the fireboxes may also need to be checked
frequently. The operators
remain with the kiln all night, to be replaced by two more
men in the morning.
The burning rate is controlled so that the temperature
inside rises at approximately
100[degrees]C per hour (so as not to crack the worked clay
containers). The peak temperature
is reached approximately 18 hours after the start of the
firing. At this point all
entrances, including a damper for the large chimney, are
closed, the oil and water
are turned off, and the kiln is allowed to cool slowly.
Two firings a week is normal
and each firing consumes approximately 300 liters of waste
oil.
A Cook Stove
The waste oil-drip method has also been used for a domestic
stove as shown in Figure 5.
wokfig5.gif (534x534)
An oversized brick box serves as the burner housing through
which oil and water
drip together onto the splash-plate inside.
The flames then shoot through a narrow
space underneath a 3/4-inch steel plate, which serves as the
cooking surface.
This plate measures approximately 0.75 x 1.0 meters.
It supports large flat-bottomed
cooking pots.
Exhaust from the stove passes through a 13 centimeter diameter duct,
welded through the inside of a 55-gallon metal drum.
Water in the drum is heated
to near-boiling by the exhaust gases.
The hot water is used for washing in the
dormitory next door to the kitchen.
VITA Technical Bulletin #51060 Waste Oil-Fired Oven,
describes a different technique
of burning waste oil to heat an oven for baking bread and
other foods.
VITA
VOLUNTEERS
IN TECHNICAL
ASSISTANCE
ABOUT VITA
Volunteers in Technical Assistance (VITA) is
a
private, nonprofit, international development
organization. Started in 1959 by
a
group of concerned scientists and engineers,
VITA
maintains an extensive documentation
center and worldwide roster of volunteer
technical experts. VITA makes available to
individuals and groups in developing countries
a
variety of information and technical
resources aimed at fostering self-sufficiency
--needs assessment and program development
support; by-mail and on-site consulting
services; information systems training. It
also
publishes a quarterly newsletter and a
variety of technical manuals and
bulletins.
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