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VCEM5100 Gas Velocity Case Study
The Customer and The Requirements:
Electric Arc Furnace (EAF) Steel Mills present many challenges when it comes to monitoring exhaust gases from the furnace outlet. The process is extremely dusty and hot and in no way suitable for most in-situ type measurement instruments. Measuring exhaust gas flow can be invaluable for process control and sometimes a necessary requirement for emissions monitoring system compliance.
Two EAF mill sites have solved their flow monitoring requirements with the CODEL VCEM5100 Infrared Continuous Flow Monitoring System.
In the Midwest United States, a plant was challenged with measuring flow on their mini-mill electric arc furnace ducts (two of them). The temperatures range from 300° to 700° degrees Fahrenheit and the particulate loading is heavy. Because the two furnaces blend into a common stack, measuring back in the ducts was required, and the flow monitor needed to be used as part of their CEMS. This was possible with the VCEM5100 being certifiable to US EPA 40CFR part 75 regulations.
In another plant in the Southwest United States a steel mill wanted to measure flow and oxygen to optimize their electric arc furnace. This measurement is made in the direct exhaust (in the hot gas offtake) which runs in excess of 1000° Fahrenheit. While the exhaust gas is dry, it’s extremely dusty. The VCEM5100 is not only able to accommodate this environment, but the very high heat and turbulent dust actually help it’s ability to accurately measure flow.
While there are other flow monitor measurement technologies available on the market, only the VCEM5100 could meet these two demanding applications. Both S-type Pitot and Ultrasonic flow monitors would not work in the high dust conditions found in these exhaust streams. The pitot tube would get plugged too quickly and the ultrasonic could not attain a signal reading through the dust.
The Solution:
So why does the VCEM5100 do what other flow monitoring systems cannot do? The answer is in the measurement technology. The VCEM 5100 measures the velocity of stack gases using a highly accurate time of flight measurement that is derived from a cross-correlation analysis of the infra-red emissions of the turbulent gas. Two robust infrared detectors are used for the prime sensing, mounted on the stack or duct typically one meter apart in the direction of flow. High-efficiency air curtains are fitted to considerably extend the time between maintenance periods and window cleaning (typically 1 year).
The total release is then calculated as follows:
Mass flow = Mass concentration x Gas velocity x Area of Duct
The method used is similar in principle to the technique of flow measurement by the injection of chemical dye or radioactive tracers, where the velocity is derived from the transport time of the tracer between two measuring points a known distance apart. Instead of an artificial tracer being added, the naturally occurring turbulence of the gas stream is used as the tracer.
The VCEM5100 works in a lot more applications besides EAF steel mills. Anywhere where flow measurement is a challenge due to temperature or dust loading is likely a great candidate for the VCEM5100.
Summary of Benefits:
Stands up to high heat: with the transmitter and receiver mounted on the outside of a stack or duct, the high exhaust gas temperature limit of the VCEM5100 is in excess of 1832°F. A minimum exhaust gas temperature of 158°F is required to create enough IR signal to generate a signal.
Stands up to high dust: Because it uses the IR temperature of moving particles, and measures on a straight plane (versus cross stack or duct), the VCEM5100 has no problem working in high dust applications where other instruments could clog or have signals blocked.
QAL1 Certified & EPA certification Ready: The VCEM5100 is a certifiable flow monitor that can be used as a stand-alone instrument or in conjunction with a CEMS (Continuous Emissions Monitoring System) where mass emissions are required to be measured and reported. To meet the requirements, the VCEM5100 is equipped with full high and low span automated calibration checks.
Extremely low Maintenance Requirements: with the VCEM5100 not in direct contact with the exhaust gas, maintenance is minimized to simple window cleaning once a year. Purge air connections allow the lenses to be kept clean between maintenance intervals. No moving components increases reliability even more.
For more information on VCEM5100 Gas Velocity Case Study talk to Codel International Ltd