Boilers loading optimization

The reason for using boiler 1 as the basis is that boiler 2 has reached the limit after boiler loading optimization in Figure 19.2. 

Optimizing boiler loading leads to cost savings of 360,000 per year. 

A 1% loss in efficiency on a 45,360 kg/h (100,000 lb/h) boiler will increase its yearly operating cost by about 25,000. A 1% efficiency loss can result from a 2% increase in excess 02, or from about a 28°C (50°F) increase in flue gas temperature. The purpose of optimization is to continuously maximize the boiler efficiency, as variations occur in the load, fuel, ambient, and boiler conditions. The various goals of optimization include the following ... 

Boiler trimming methodology varies by boiler manufacturer, fuel type, and control scheme regulating injected air, fuel, or both. However, in any scheme, it is critical, for safety and efficiency, to know the amount of oxygen in the process. This optimization is normally based on overall excess oxygen estimation maintaining an adequate local stoichiometry for each burner, adjustment of the flame type (based on an appropriate control of the air inputs and the operation of the mills), and identification of the optimum number of active burners for each operating load. 

Mortensen, J.H., Moelbak, T., Andersen, R, Pedersen, T.S., December 1998. Optimization of boiler control to improve the load-following capability of power-plant units. Control Engineering Practice. ISSN 0967-0661 6 (12), 1531-1539. 

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