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Powell Continuous Sodium Hypochlorite Wet Chlorine Process System

The sodium hypochlorite process is a unique process utilizing wet vapor chlorine and sodium hydroxide (caustic). It will safely produce high quality bleach at a minimum operating cost. The plant is equipped with numerous safety devices which are intended to shut down the system in the event of a process upset. The plant is completely automatic and requires only that someone be available if a process upset occurs. The systems are available in various production rates. Standard systems are rated for 50, 100, and 200 STPD of chlorine. Each system has an adjustable production rate and is able to produce strengths up to 200 grams per liter available chlorine. The bleach strength and residual caustic levels are controlled at very high tolerances and can be adjusted at any time during production. The systems are designed for a completely automatic operation and can be started or stopped at any moment. Systems are completely skid mounted on a structural steel frame approximately 30’ long x 12’ wide x 30’ high. The system can be designed (as shown in picture) with an integrated chlorine scrubber system. This would increase the width of the system to 24’.

Advantages

Bleach producers using the Powell Continuous System will considerably reduce the man-hours required to manufacture bleach in comparison to other bleach production processes. One operator can produce as much as 220,000 gallons of 200 grams per liter bleach in a 24 hour day.

The continuous system also offers major cost savings in raw materials due to its 99% plus efficiency when compared with a 93-96% efficiency experienced in batch operations. This increase in efficiency results in a decrease in the amount of sodium chlorate produced. The following example helps quantify these savings in efficiency.

Due to an extremely high repeatability of the continuous system, considerable savings are experienced from using fewer raw materials. Residual caustic levels can be lowered and final product strengths can be closer to the producer’s guaranteed strength, resulting in less product giveaway.

The type of cooling utilized by the continuous system also provides a major savings. Mechanical refrigeration is typically required with other processes. The Powell system utilizes cooling tower water for cooling resulting in considerable energy savings, lower equipment costs, and lower maintenance costs.

Utility and Raw Material Requirements

The basic utility and raw material requirements are as follows:

• Wet vapor chlorine at maximum temperature of 40 C.
• Sodium hydroxide at a minimum pressure of 45 PSIG.
• Process water (typically soft water) at a minimum pressure of 45 PSIG.
• Cooling water at a maximum temperature of 85° F.
• Instrument quality dry air at a minimum pressure of 80 PSIG.
• Three phase electricity for motors.
• Instrument quality power for control system.

Materials of Construction

Standard materials of construction are listed below. Other materials are available upon request.

• Process water and caustic: Schedule 40 stainless steel pipe and fittings.
• Chlorine: Schedule 80 CPVC pipe and fittings.
• Cooling water: Schedule 80 CPVC pipe and fittings.
• Sodium Hypochlorite: Schedule 80 CPVC pipe and fittings.
• Sodium Hypochlorite Pump: Titanium centrifugal pump with single mechanical seal.
• Sodium Hypochlorite Recycle Tank & Reaction Tower: Dual laminate FRP.
• Heat Exchangers: Plate and frame style with titanium plates and EPDM gaskets.

Construction Lead Time

Construction time for a continuous bleach system is typically 7 months. The systems are completely water tested and all control systems are thoroughly checked before the system is shipped. 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 completely tested at the factory.