Although manufacturers have made significant improvements in process heating efficiency, the total energy use for process heating in the U.S. is expected to increase. With overall thermal efficiency of process equipment varying from 15% to 80%, compared to the thermal efficiency of steam generation (65% to 85%), there is clearly an opportunity to achieve significant energy savings, improve productivity and enhance competitiveness.
The U.S. Department of Energy's Industrial Technologies Program (www.eere.energy.gov) has identified improved burner control systems as a significant opportunity for reducing energy operating costs, waste and environmental emissions. Tuning burners to reduce excess air is a cost-effective technique for reducing heat lost in exhaust. Monitoring and adjusting air-to-fuel ratios to maintain optimum combustion not only conserves fuel but also helps reduce emissions. This is also important in the wake of EPA regulations (40 CFR Part 98 Subpart C and 40 CFR Part 63) requiring monitoring and reporting of emissions.
One of the most effective techniques for improving efficiency and reducing emissions in these applications is a precise control strategy, based on mass flow measurement of fuel and airflow rates. Sophisticated burner control systems optimize air/fuel ratio control to obtain peak thermal efficiency over the entire range of the burner, and to facilitate proactive emissions control. Mass flow control of air and fuel is used to automatically correct for changes in temperature or pressure that affect combustion performance. Many systems also integrate fuel totalizing, air/fuel flow and valve position analog outputs for DCS interfacing and remote system monitoring.
Conventional flow meters (orifice plates, venturis, vortex, turbine meters, etc) are volumetric measuring devices, and they require pressure and temperature transmitters to compensate for density changes. The thermal mass flow meter, however, measures gas mass flow directly, with no need for additional hardware.
Fox Thermal Flow Meters are designed for use in fuel gas and air feed lines found in process heating and utility operations. In addition to the primary benefits of direct measurement of mass flow rate, low-flow sensitivity, and fast response, the meter's no-moving parts design also helps reduce maintenance costs.
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