Patent ID: 7632412
Filing Date: 2009-12-15
Classification: C02F

Abstract:
1. A method for controlling a cooling water tower comprising: a. providing a cooling tower system, which includes a recirculated evaporative cooling water stream defined by an evaporative cooling water volume, a source of make-up water, an evaporative cooling unit, a heat exchanger, a bleed off line, and a bleed-off valve which is in communication with said bleed-off line; b. providing a plurality of conduits through which said makeup water flows into said evaporative cooling water stream, wherein there is at least a first conduit that contains a weak acid cation ion exchange column and a second conduit that does not contain a weak acid ion exchange column, and wherein each conduit has at least one conduit valve; c. choosing a pH setpoint value, a conductivity setpoint value and a deadband value above and below said pH setpoint value, a deadband value above and below said conductivity setpoint value, in said cooling tower system; d. defining conductivity values C1-C3 and pH values P1-P3, wherein C1 is the conductivity value when conductivity is greater than sum of the setpoint value and deadband value, C2 is the conductivity value when conductivity is less than the sum of the setpoint value and deadband value and higher than the setpoint value less the deadband value, C3 is the conductivity value when conductivity is less than the setpoint value lowered by the deadband value, P1 is the pH value when the pH is greater than sum of the setpoint value and deadband value, P2 is the pH value when pH is less than the sum of the setpoint value and deadband value and higher than the setpoint value less the deadband value, P3 is the pH value when pH is less than the setpoint value lowered by the deadband value; e. measuring both the pH of said evaporative cooling water stream with one or more pH meters and conductivity of said evaporative cooling water stream with one or more conductivity meters; f. implementing the following response to said conductivity measurements and pH measurements: (i) if the conductivity is C1 and the pH is PI, then said bleed-offvalve is on and water is blowdown from said cooling tower until said evaporative cooling water volume reaches a first predetermined level, and makeup water is added to said evaporative cooling water stream through said first conduit until said evaporative cooling water volume reaches a second predetermined level; or (ii) if the conductivity is C1 and the pH is P2, then said bleed-offvalve is on and water is blowdown from said cooling tower until said evaporative cooling water volume reaches a first predetermined level, and makeup water is added to said evaporative cooling water stream through said second conduit until said evaporative cooling water volume reaches a second predetermined level; or (iii) if the conductivity is C1 and the pH is P3, then said bleed-offvalve is on and water is blowdown from said cooling tower until said evaporative cooling water volume reaches a first predetermined level, and makeup water is added to said evaporative cooling water stream through said second conduit until said evaporative cooling water volume reaches a second predetermined level; or (iv) if the conductivity is C2 and the pH is P1, then the bleed-off valve is on when the conductivity is falling from C1 and water is blowdown from said cooling tower until said evaporative cooling water volume reaches a first predetermined level, and makeup water is added to said evaporative cooling water stream through said first conduit until said evaporative cooling water volume reaches a second predetermined level; or (v) if the conductivity is C2 and the pH is P2, then the bleed-offvalve is on when the conductivity is falling from CI and water is blowdown from said cooling tower until said evaporative cooling water volume reaches a first predetermined level, and makeup water is added to said evaporative cooling water stream through said second conduit until said evaporative cooling water volume reaches a second predetermined level; or (vi) if the conductivity is C2 and the pH is P3, then the bleed-offvalve is on when the conductivity is falling from C1 and water is blowdown from said cooling tower until said evaporative cooling water volume reaches a first predetermined level, and makeup water is added to said evaporative cooling water stream through said second conduit until said evaporative cooling water volume reaches a second predetermined level; or (vii) if the conductivity is C3 and the pH is P1, then said bleed-off valve is on and water is blowdown from said cooling tower until said evaporative cooling water volume reaches a first predetermined level, and makeup water is added to said evaporative cooling water stream through said first conduit until said evaporative cooling water volume reaches a second predetermined level; (viii) if the conductivity is C3 and the pH is P2, then the bleed-offvalve is off; or (ix) if the conductivity is C3 and the pH is P3, then the bleed-offvalve is off.