Testo 350 Field Guide - Actoolsupply.com

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3.2 Combustion analysis for process control
3.2.1 Combustion plant for firing processes
A process firing plant, in contrast to the well known boiler plants, is characterized
by a direct contact between the flame and the hot firing gases and a material or
work pieces that shall be treated thermally. The heat as well as the specific atmosphere
to which the material is exposed causes certain steps in their production
process.
Production of cement clinker is a good example for such a firing process (see also
the application examples in chapter 5.3):
• The moist raw material is crushed and dried using hot off gases
The precipitated raw meal is heated up to 800 °C by hot gases in
counter-current
• CO 2 is driven off the raw meal at appr. 950 °C in the calcinator through
a multi-stage firing process (de-acidification)
• The raw meal together with additives is finally sintered in the kiln at appr.
1400 °C.
Combustion analysis at these locations provides critical information with regard to
excess air values, to detect and calculate false air flows and to perform balances
for each step separately. It is critical for the calcinator performance (measurement
of CO 2 and O 2 ) because a deficient level of calcination can cause considerable
malfunctions in kiln operation
During firing processes substances from the treated material may be released into
the "firing" gas and thus increase the emission rate of the flue gas. In some
cases, however, components including pollutants may be transferred from the gas
into either the production material or into substances (e.g. slag) especially provided
for this purpose. An example is the cement or lime industry where the sulfur
of the fuel is transferred as SO 2 to the product instead of being released to the
atmosphere. Inversely during glass or brick production SO 2 will escape from the
material and increase the level of emission considerably. Another example is an
increased CO content in processes where material and hot gases are in contact in
counter-current, e.g. in rotating kilns. Heavy metals may be either integrated into
the burnt material (cement, lime) or released from the material into the flue gas
(glass or metal industry).
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