Glass Melting Technology: A Technical and Economic ... - OSTI

Data control
Data logging is required for a permanent record of operating parameters and trends. Some instrumentation
provides analog or digital readouts, but no hard copy. To integrate the readings from furnace operation with
other aspects of operation, data are recorded manually on a log sheet on an hourly basis. Portable optical
temperatures, excess oxygen readings, routine inspections and process changes are manually recorded on
another log. Measured data for most key functions of the furnace are recorded on circular or strip charts,
which are easier to read daily and require less operator attention to change paper for strip charts, so the
operator checks the measurements less frequently. If a system is computerized, shift and daily summary
reports are printed out for periodic review of key parameters. Statistical trending calculations for process
control functions are obtained from newer graphic systems.
Manual checklists and alarm systems indicate status of the furnace-supporting utility for various items:
blowers and fans (combustion air stack draft, sidewall and throat cooling; compressed air pressure; cooling
water temperature and pressure; cooling air temperature and pressure.
To control refiner-distributor temperature, a reliable reference temperature of the glass is needed. The glass
temperature is lowered to a target temperature for exiting into forehearths or other processing devices by
controlling heating and cooling equipment devices. Best results are usually obtained by monitoring the
actual exit glass temperature with an immersion thermocouple and cascading back to the distributor’s set
point. This measurement can vary from tonnage changes or impact of melter variables on throat temperature.
Manual readings
Manual readings are obtained with portable analyzers that pump a collected sample through probes inserted
into the atmosphere. These devices rely on measuring paramagnetic principles or oxygen cell references.
Accuracy is checked by measuring known mixtures of calibration gases. Some devices can detect carbon
monoxide to indicate combustibles.
Regenerative furnace operation is controlled by the reversal system, which mechanically closes and opens
fuel valves and moves dampers to reverse flow of combustion air and exhaust gases. Purge timers delay
valve movements. A manual furnace operator must be aware of reversal schedules when obtaining portable
optical pyrometer readings while firing is off. Reversals should be analyzed and adjusted to arrive at
minimum time of fire offs. Spent fuel should be purged from the exhaust chamber before fresh air becomes
available for fuel ignition.
Stack and flue conditions
Stack and flue conditions that indicate combustion and firing changes can be monitored by the graphic
pattern of the temperature cycles of thermocouples. Effects from reversal failures can be compensated for,
and stack valve opening can be controlled for furnace pressure when these data are available.
Advanced Process Control technology
Advanced Process Control has proven to be an excellent methodology to assist plants in achieving goals as
defined in the Glass Industry Vision Statement. To make these applications more cost effective, more
availability and increased industry usage are needed.
Advanced Process Control (APC) is available for installation in a number of forms to reduce energy
consumption, increase production, optimize furnace operation, reduce product change over time and
maintenance costs, as well as other aspects of the glassmaking process. Total automated systems for
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