MINIMIZING TOTAL OPERATIONAL COSTS FOR AN INDUSTRIAL STEAM BOILER FIRING FUEL OIL/GAS

Abstract

A cost-based method for determinicig optimum combustion air supplied to a 90 t/h industrial steam boiler is proposed to attain the highest thermal boiler efficiency with the minimum environmental impact. The total sum of “internal” costs (associated with the boiler fuel consumption) and “external” costs (or costs of damage done to the environment and humans by the gaseous pollutants from the boiler) representing the objective function for the optimization, is required to be minimized. The measurement of gaseous emissions (NO_x, SO₂, and CO) was carried out for 3 reduced boiler loads of 84 t/h, 70 t/h and 64 t/h. The optimum values of excess oxygen were found to be 1.2%, 1.8% and 2.7% for the above boiler loads, respectively. However, for higher boiler loads, the specified excess air should be selected taking into account fluctuations of the (excess) oxygen concentration in the boiler furnace. Fuel firing at the optimum excess air ratio ensures a noticeable benefit (energy saving) per unit boiler.