Patent ID: 7931041

Claim:
A method for controlling a liquid level in a vessel having a two-phase medium; the system comprising: measuring parameters related to the vessel using sensors; wherein the parameters comprise liquid level in the vessel; gas flow rate from the vessel; pressure in the vessel, temperature of the vessel; and feed-liquid flow rate into the vessel; generating a first filtered output signal representative of liquid level in the vessel, a second filtered output signal representative of gas flow rate from the vessel, a third filtered output signal representative of feed-liquid flow rate into the vessel, a fourth filtered output signal representative of pressure in the boiler drum, and a fifth filtered output signal representative of temperature of the boiler drum based on the measured parameters; generating an output signal representative of feed-liquid flow demand from the first filtered output signal; generating an output signal representative of shaped gas flow rate as a function of pressure, temperature, or combination thereof in the vessel from the second, fourth, and fifth filtered output signals; and controlling the liquid level in the vessel within predetermined limits by controlling one or more components coupled to the vessel based on the output signal representative of feed-liquid flow demand, the output signal representative of shaped gas flow rate, and the third filtered output signal.