pH Reduction of Sodium Hypochlorite Solutions using CO2 Addition

 pH Reduction of Sodium Hypochlorite Solutions using CO2 Addition)

Household sodium hypochlorite (bleach) normally maintains a pH from 12.0-13.5. Grocery store chains, discount stores, pool suppliers, and other points of distribution often require environmental hazardous cleanup with spillage of bleach having a pH greater than 12. Bleach with a pH of less than 12 allows for less rigorous clean up procedures. Powell now offers new technology for low pH sodium hypochlorite as a skid mounted system. The Powell process is an independent design that can be added onto any bleach production process.

The Powell process uses carbon dioxide (CO2) to convert excess sodium hydroxide (NaOH) to sodium carbonate (Na2CO3). This reduction process lowers the pH of the bleach and creates a superior stable product. The creation of the carbonate ion stabilizes the solution after 60 days when compared to normal bleach and produces a buffering effect that decreases the likelihood of acid catalyzed decomposition when the hydroxide ion concentration is very small.

In order to maintain an efficient bleach production process, low pH bleach should not be produced less than 12.5-13.5 pH since operating in these low regions will increase chlorates and waste chlorine and caustic at a significant raw material loss.

Utility and Raw Material Requirements

The basic utility and raw material requirements are as follows:

  • Carbon Dioxide vapor with a minimum pressure of 40 PSIG.
  • Three phase electricity for motor.
  • Instrument quality power for control system.

Materials of Construction

All units are constructed from the best materials available to maximize the service life of the system. Standard materials of construction are listed below. Other materials are available upon request.

  • Carbon Dioxide: Steel schedule 80 with PFA lined block & control valves.
  • Sodium Hypochlorite: Teflon lined steel pipe and fittings or optional CPVC or PVC schedule 80 pipe and fittings.
  • Sodium Hypochlorite Pump: Titanium centrifugal pump with single mechanical seal or sealless ETFE lined magnetic drive pump.

Construction Lead Time

Construction time for a continuous Low pH Sodium Hypochlorite System is typically four months. As a standard practice, Powell performs non-destructive testing on all assembled equipment before it is shipped. This includes mechanical inspections, process testing, process control testing, control panel and electrical testing, PLC program debugging, hydrostatic testing, and pressure testing. After delivery, the purchaser must make all raw material and electrical connections. After these connections are made, Powell technician(s) will perform additional water testing, startup, and training. Startup is typically performed in a relatively short time since the unit is competely tested at the factory.

Contact us for more information.