A method for controlling a steam boiler or oil heater for maximum fuel efficiency
by systematically finding the most fuel-efficient combination of input control
values. A characteristic multi-dimensional look-up table is created by temporarily
operating the process at all the possible functional combined settings of a plurality
of input operators and recording for each combination of settings the resulting
output values of a plurality of process parameters, for example, steam flow, steam
pressure, and exhaust composition. Input combinations resulting in either non-functional
process or unacceptable output values are eliminated. Steam flow rate is the primary
output control parameter. A selected value of steam flow rate is the primary control
setpoint for the process. If several combinations of input values can cause the
process to meet the primary control setpoint, the combination using the minimum
fuel flow is selected as optimal. If the desired setpoint does not correspond exactly
to discrete input values in the table, the correct input settings may be inferred
by interpolation. Valves and dampers are dynamically controlled by output drive
signals in an improved closed-loop control, using a function of the process output
value and time to recalculate and adjust the drive signals.
