Keywords: thermal power plants, energy efficiency, maximum continuous rating, MCR, unit loadability, design margins, heat rate, coal, fuel quality, higher heating value, HHV
Optimal maximum continuous operating load of fuel fired steam–based generating units
This paper establishes the optimal maximum continuous operating load of fuel fired steam based thermal units without endangering the operation, asset life or carbon footprint. The interconnectivity between unit loadability and energy efficiency (represented by heat rate) enables the unit to be loaded to as high as 10% over and above the 100% maximum continuous rating (MCR) provided the energy efficiency is sufficiently high and the fuel quality (coal in this case) is maintained at around 400–600 kcal/kg above the design higher heating value (HHV) of around 3,400 kcal/kg. Loadability is basically limited by quantity parameters (flow and current) and not by plant load (active power) while quality parameters are designed to be load independent. It is concluded that the optimal maximum operating point is 110% of the MCR with optimal cost and is not detrimental to the life and safety of the unit.