The energy research kiln in operation
This project is sponsored by the California Department of Conservation and managed by the Center for Environmental Economic Development.
As part of this project we are testing the energy implications of using recycled glass as a raw material in brick manufacturing. Over the years there have been a number of studies of the use of glass as a raw material to save energy in ceramics kiln processes. One of the most recent can be downloaded at
http://www.wrap.org.uk/applications/glass/documents/details.rm?doc_id=489
One of the reasons these studies have not resulted in widespread use is that all of the previous work focused on using very finely graded glass as an additive to other ceramic raw materials. The disadvantages of using very finely graded glass include:
Uniformly crushing glass to fines is relatively expensive,
Large quantities of uniformly crushed fine glass are not currently available, and
Very fine glass hurts the workability of clay mixes.
In contrast, this study will test coarser glass, crushed to 12 mesh and finer, as a substitute for grog in brick manufacturing. 12 mesh recycled container glass is readily available as a raw material in fiberglass manufacturing. For forming bricks, the coarse glass reduces the amount of water needed and accelerates drying. This work will especially investigate the firing implications for energy use.
A special kiln was built for this study. The kiln needs to be very fast and accurate. It is always a challenge to separate the energy issues associated with the kiln itself from the firing issues associated with the material in the kiln.
For good control and monitoring, an electric kiln with quartz halogen heating elements was designed and built. Quartz halogen elements have virtually zero thermal mass and radiate instantaneously at an equivalent black body temperature approaching 3000 degrees F, peaking in the near infra-red range. They therefore do not present the complicating factors of slow heat-up and transition periods between conductive and radiation heat transfer that are associated with resistance elements.