Patent ID: 7055395

Claim:
A method for controlling the amount of sulfur deposition in a gas fuel control valve for unchoked flow valve operation, comprising the steps of: measuring (a) the gas flow rate through the control valve, (b) the gas temperature, (c) the gas pressure upstream of the control valve and (d) the static gas pressure downstream of the control valve; calculating the effective valve area of the gas fuel control valve as determined by the equation: A eff = W × T P 0 × ( P 0 P s ) ( k + 1 ) ( 2 × k ) ( ( P 0 P s ) k - 1 k - 1 ) × 2 × k × g ( ( k - 1 ) × R ) wherein: A eff is the valve effective area in square inches; W is the gas mass flow rate in pounds per second; T is the gas absolute temperature in degrees Rankine; P 0 is the gas upstream total pressure in psia; P s is the gas valve throat static pressure in psia; k is the gas specific heat ratio; g is the acceleration due to gravity, 32.175 feet per second per second; and R is the universal gas constant, 1545.34 foot-pounds force per pound-mole degrees Rankine. determining a sulfur deposition feedback control parameter for the control valve based on a comparison of the effective valve area to a known valve position; and adjusting the gas temperature upstream of the control valve using the thus determined feedback control parameter.