Feed Delivery . In addition to the technical considerations of pumping the
material, there are operational considerations in regard to coordination of the
transfer of feed material. The melter feed process necessitates a " atch feed"
type system, which allows the melter to operate in a continuous feed manner
with parallel processing of a new feed batch. Multiple tanks are required for a
batch feed system with a minimum requirement for two tanks. One tank is
required to contain the waste material for at least one feed batch. The second
tank is required to mix the glass formers, other chemicals required for the
waste form, and the waste material being processed. Usually the feed tank
will be significantly larger than the tank in the vitrification plant receiving the
waste. Adequate operational communication and interlocks to prevent tank
overfill are important considerations.
Feed Sampling . One of the first steps in the actual vitrification process is to
maintain melter feed material within an appropriate process range. This may
be for glass quality reasons but is also very important to prevent unusual
reactions in the melter.
The sampling process should adequately address the number and volume of
samples to be collected. Often several samples may be needed to support a
given laboratory analysis and the statistical evaluation of the results.
The sampling process often has many manual steps and is, therefore, error
prone, particularly when slurry feeds are involved. Design should minimize
the potential for error, providing reliable indications to operators and
minimizing the number of manual steps. To ensure that the sample system
does not introduce additional process errors, consideration should also be
given to ensuring the pumping system for taking samples has the same
operational characteristics as the pumping system feeding the melter.
Slurry Handling is of concern throughout the feed preparation of most
facilities. Slurries present particular issues in line sizing, flow rates, valve
operations, flushing allowances, and designs that accommodate plug clearing
operations. These should be considered when developing slurry sampling