Valmet's advanced process control (APC) application improved combustion for the biomass boiler at WestRock's Covington mill in Virginia. Valmet DNA FBB Combustion Manager estimates the heat output (BTUs) of the biomass fuel in real time and helps ensure a consistent, optimum fuel power-to-air ratio.

By optimizing combustion, the mill has been able to maximize and increase the main steam output of the biomass boiler beyond the maximum continuous rating (MCR). Other benefits include more stable and controlled boiler steam output as well as improved operational uniformity across shifts, furnace symmetry and spray valve control.

The application lowered the average O2 by about 0.3 percentage points, which improves boiler efficiency, reduces NOX emissions and minimizes NH3 consumption. In addition, Valmet's load controller properly allocates the fuel demand between the feeders.

According to WestRock, the improvements have enabled the company to run a higher, more stable load, resulting in a record-setting steaming average the following month.