Self optimising combustion control of an oil-fired power station boiler

Failure to achieve satisfactory control of combustion conditions in an oil-fired boiler leads to undesirable chimney emissions; insufficient combustion air results in the production of black smoke, whereas white acidic smoke is produced by excessive amounts of combustion air. A control strategy has been developed which automatically optimises the combustion conditions by adjusting the air/fuel ratio to minimise a performance index calculated from measurements of combustion products. This control strategy has been implemented on a 100 MW power station boiler using a standard commercially manufactured process control computer.As well as describing the development work necessary, the paper outlines the engineering of the system and discusses some of the contractual arrangements adopted. This system has been in operation for over three years and has proved capable of tight control of combustion conditions even during rapid load changes. Undesirable chimney emissions have now been virtually eradicated. The success of this system has led to the decision to install similar controls on the 500 MW boilers at Pembroke Power Station.