Since the introduction of direct firing pulverizers to power generation in the 1920’s, the inability to balance the coal flows among the multiple burner lines has eluded the industry. Many believed that the problem lay in unequal burner line equivalent lengths and sought to remedy the situation by inserting additional bends, orifices etc. to the shorter lines. Current practice by the supplier is to achieve a maximum deviation of +/− 5% air flow in a clean air test but coal flow deviations are typically +/− 35%, or higher, when tested. The impact of uneven coal flows on the side to side imbalance within the furnace and boiler is detrimental to the unit operation from emissions to thermodynamic performance and maintenance costs.
This paper will derive the governing equation for the two phase flow in the burner lines. From this equation a simple method for on-line measurement will be developed and a robust control solution for coal flow balancing described.
On-line measurement of pneumatic conveying of pulverized coal in pipes