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Dioxide Pacific was engaged by a large mining company in north Western Australia to provide a shipping container mounted sodium hypochlorite dosing system. Water is stored in 2 x 1ML reservoirs which are used for potable water and fire service. Water is recirculated by a 250 m3/hr centrifugal pump between the two reservoirs. Sodium hypochlorite is provided in 1,000L IBC’s and placed into a fiberglass IBC bund. One Delta dosing pump with degassing solenoid injects sodium hypochlorite at a controlled rate based on the chlorine setpoint of 2ppm. A chlorine residual analyser (D1Cb) is provided with CTE sensor. The complete system is mechanically and electrically installed in a 20ft shipping container, painted to the customer specifications. Dioxide Pacific provided 2D and 3D GA drawings so the customer knew exactly what would be provided before arrival on site. View the 3D presentation.

Logan Pollution Control Centre originally had an electrolytic chlorination system operating to produce chlorine in recirculating scrubber liquor. This was done by adding salt to the liquor and by-passing some of the recirculation flow through the electrolytic cells. This system was fraught with many problems including fouling of the cells and subsequent manual cleaning of the cells with acid. OH&S risk assessment determined that sodium hypochlorite was a better alternative.

The old system was removed and replaced with a sodium hypochlorite dosing plant. Dual IBC chemical tanks (duty and standby) were installed in fibreglass IBC bunds. Chemical is delivered and placed by forklift into the IBC bund. Chemical dosing equipment is mounted on an HDPE backboard which is also mounted to the scrubber outside wall. Chemical dosing lines are run through the wall to the scrubber recirculation line. Chlorine residual is controlled via redox measurement and an auto-tune PID controller. pH control is also included with caustic dosing to maintain pH at around 8.0 and ORP at 750 mV. Conductivity of the scrubber liquor is monitored and controlled via an automatic bleed valve. The complete system was designed, supplied and installed by Dioxide Pacific. It has achieved its aim of reducing operator involvement with chemical handling and increased reliability and therefore odour complaints.

Sodium hypochlorite is pumped from 20L drums into a 60L tank using a drum pump. At the same time, automatic dilution of the hypochlorite from 12.5% to 6% occurs (to extend the life of the hypochlorite). Water is recirculated from the filtered water storage tank through the dosing skid and back to the tank again.

Sodium hypochlorite is dosed with duty and standby dosing pumps using an auto-changeover timed sequence. Chlorine residual in the water is monitored using a residual analyser and controlled to a set point of 1 ppm.

The skid is made from HDPE and FiberStrut for chemical resistance and is assembled complete mechanically and electrically prior to delivery.

View a 3D presentation of this plant.