Patent NZ-577228-A (NZ)
Title: Improved method for chemistry control in cooling systems
Inventor: JOHNSON DONALD A
IPC: C02F1/00
Filed: 2007-10-26
Abstract: Disclosed is a method for controlling a cooling water tower comprising: a. providing a cooling tower system, which includes a recirculated evaporative cooling water stream, a source of make-up water, an evaporative cooling unit, a heat exchanger, a bleed-offline, 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 and a conductivity setpoint value and a deadband value above and below said setpoint value in said cooling tower system; d. 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; e. implementing the following response to said conductivity measurements and pH measurements: (i) if the conductivity is C1 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 stream 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 stream reaches a second predetermined level; or (ii) if the conductivity is C1 and the pH is P2, then said bleed-off valve is on and water is blowdown from said cooling tower until said evaporative cooling water stream 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 stream reaches a second predetermined level; or (iii) if the conductivity is C1 and the pH is P3, then said bleed-off valve is on and water is blowdown from said cooling tower until said evaporative cooling water stream 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 stream 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 stream 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 stream reaches a second predetermined level; or (v) if the conductivity is C2 and the pH is P2, 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 stream 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 stream reaches a second predetermined level; or (vi) if the conductivity is C2 and the pH is P3, then the bleed-off valve is on when the conductivity is falling from C11 and water is blowdown from said cooling tower until said evaporative cooling water stream 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 stream 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 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 stream reaches a second predetermined level; (viii) if the conductivity is C3 and the pH is P2, then the bleed-off valve is off; or (ix) if the conductivity is C3 and the pH is P3, then the bleed-off valve is off.