MIC-USA Offers Real-time Continuous Coal Flow Measurement System

A new real-time continuous coal flow measurement system now affords an alternative to extractive pulverized coal sampling. It is being offered by a German company, Measuring Ideas Consulting, and its affiliate MIC-USA. The system is based on current high frequency microwave technology. The system can be mobile or permanent and is capable of measuring eight coal pipes at a time, a total of 24 sensor inputs. High frequency microwave energy is transmitted perpendicular to the flow of pulverized coal in the pipe. Measurement is not influenced by the temperature of the coal or the moisture in the coal. Simply stated, the system counts the number of particles passing through the microwave beam and, based on analysis of the number and the intensity of the signal returns (larger particles return more energy than smaller particles), the system determines the relative flow in each of the coal pipes. The sensors are pre-calibrated to transmit identical microwave frequency and do not require any field calibration.

“We are learning that there is much more happening in pulverized coal lines than we originally would have thought, but based upon field testing and permanent system installations, we are seeing that the data is repeatable and reliable,” says Alan Jensen, general manager of MIC-USA. “One thing that we have noted is that pulverized coal flow becomes more chaotic as the mill grinding elements wear.”

MIC demonstrated its portable coal flow measurement system on 660-MW opposed wall-fired Unit 1 at JEA’s St. John’s River. Units 1 and 2 each have seven coal pulverizers and 28 burners. Based on the demonstration, JEA placed an order for a permanent MIC 1 system on 660-MW Unit 2. During its scheduled spring outage in 2004, JEA installed new low NO_x burners on Unit 2 and during the same outage, installed adjustable orifice valves on each coal pipe and a permanent MIC 1 measurement system. JEA operators have a control room screen showing individual burner secondary air shroud positions and the coal flow distribution to each of the burners associated with a given pulverizer. As JEA continues to optimize combustion on Unit 2, coal flow distributions will be balanced using the orifice valves.

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