The Blanket Creek Production Process: Firing the Kiln
Production Process » Firing the Kiln
This kiln was fired with propane from 2002 until the fall 2005 when I installed a pair of waste oil burners. I modified residential oil furnace burners by changing the nozzles and installing a heated filter that facilitates in the combustion process while also removing impurities. The stainless steel "siphon nozzles" work in conjunction with a small air compressor to atomize the oil. The filter has a "silicon blanket" heater wrapped around it which is thermostatically set to 200 F, and this setup can effeciently burn any kind of oil down to sub-zero temperatures.
So far (as of March 2008) about 125 firings have been done with this system, mostly with waste vegetable oil discarded by restaurants. I am also starting to incorporate automotive waste oils because I found a local mechanic with large quantities who was willing to sell it at a very reasonable price. Such oils burn hotter and are easier to filter than vegetable oils.
The Pump System
Oil is pumped from storage tanks outside through a filter and into the supply tanks that feed to the burners. The smaller tank mounted above the 55 gallon drum was initially part of a gravity feed system which is no longer used, but the tank was kept in place for extra fuel storage. The larger drum has a pipe fitting welded near the bottom that plumbs directly to a fuel pump. Both tanks have thermostatically-controlled heaters that are used in extreme cold weather when oil can solidify.
The furnace pump was a $10 ebay score - something I found by accident while searching for pumps under the wrong name, and this one just happened to be listed incorrectly. This kind is generally referred to as a "positive displacement" pump and, with the 1/3 hp enclosed motor it is far more powerful than this kiln needs - that is, until the temperature gets close to 0 degrees at night and I come out in the morning to start the kiln. Then it seems just right for getting the oil that has solidified in the pipes into circulation where it can be heated at the burners.
Fueling the Burners
Under normal operating conditions, there is a "looped return" system where the oil circulates continually from the outlet of the pump back into the inlet. Fuel from the pump outlet also Tees off to the two burners, with the fuel pressure controlled by the valve pictured above the pump. If that valve were closed completely, for example, then the loop would be blocked and the burners would receive the maximum pressure the pump is capable of, which would be far too much. Conversely, when the valve is totally open the fuel pressure at the burners is minimal because most of the fuel is circulating back to the inlet.
This dual-head air compressor, made by Thomas, supplies air to both burners. It actually provides more pressure than both siphon nozzles need so I use a small bleeder valve to reduce the air flow. I know someone who rebuilds these compressors and usually sells them for under $100. They are made primarily for the health care industry where they run continuously for over a year at a time before servicing.
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