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

lower glass weight and combustion control together. The improved automation and control of glass forming
machines for the same time period has led to 3 percent energy savings in the container glass industry due to
weight reduction of bottles. The improved control of combustion has caused a reduction of 1.5 percent of the
energy input of glass furnaces in the same period. The improved control of the production has led to 2
percent increased energy efficiency due to improved production yields. An educated guess on the improved
furnace control (control of fuel input, boosting and batch composition) has a potential of 3 percent energy
savings compared to currently controlled glass furnace processes. These figures are restricted to the situation
in the Netherlands and depend greatly on the starting situation of the process. (Ruud Beerkens, the
Netherlands)
Temperature sensors
Furnace temperature sensors provide accurate and reliable measurements from key locations to quantify
operating parameters. They determine energy input rates and indicate any need to vary parameters. The
thermocouple is the most common and least expensive temperature sensor. In corrosive environments,
crown thermocouple blocks should be made of the same material as the crown, or replaced with breast wall
thermocouples in extreme environments.
Optical sensors for non-contact temperature measurements, such as thermopiles and infrared detectors, rely
on a focused lens and filtering system to measure emitting radiation of the molten glass material. A
detecting element converts the radiation into a calibrated electrical signal. These expensive sensors rely for
accuracy on a fixed line of sight between the sensor and the target material. The detectors may require
protection by purging or air-cooling. They are sensitive to ambient temperature and must be cooled with air
or water. Sensors with fiber optics convey the optical signal from the sighting lens to a remote detector.
Portable optical pyrometers are used to compare accuracy of in-situ temperature measuring devices and
measure intermittent targets throughout the furnace.
Furnace combustion process
Melter temperature is controlled primarily by the combustion process. With instrumentation, fuel flow and
combustion air are measured to compensate for temperature and pressure (mass flow corrections). Profiles of
specific temperatures are obtained by establishing fuel distribution between burner positions. These
combustion-process flow measurements typically include:
• Natural gas flow with orifice, turbine meter or integrated Pitot tube, correcting for temperature and pressure
mass flow;
• Propane/air with orifice, turbine meter, correction for specific gravity, temperature and pressure mass;
• Combustion air flow with orifice or venture meter, correcting for temperature and pressure mass flow;
• Oil flow with capacity-meter correction for temperature and differential pressure across filters;
• Oil atomization (air) with pressure at burner;
• Oil atomization (mechanical) with oil pressure at burner.
Parameter measurements
To determine energy input, a furnace operator can use a number of parameters. Hour to hour, the bridge wall
optical and crown thermocouple readings may indicate temperature trends that require gas input changes.
Shift to shift, changes in electric boost or superstructure temperature targets are determined by trends in the
batch line, glass quality, or melter bottom temperatures. Day to day, actual energy parameters can be
compared with expected values. Any deviations can require checks on actual pull rate calculations; incorrect
combustion ratios; optical pyrometer or thermocouple calibrations; batch/cullet redox control; or operator
performance. Furnace parameter set points are adjusted by the furnace operator.
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