Continuous Production Electrochlorinator- Brine based
Continuous Production Electrochlorinators – Sea water based systems are designed for high capacity production of sodium hypochlorite solution from brine water. The system contains all the equipment required for continuous production of 0.6 to 0.8% Sodium Hypochlorite. This system can be offered as a pre-assembled skid mounted system which makes the commissioning process very quick with predictable.
Water & Wastewater treatment, Cooling water treatment and other disinfection process require Chlorine. But procuring and storing Chlorine is cumbersome and hazardous. The pollution control boards of various countries is actively discouraging the use of gas chlorine for this very reason.
The best and most convenient alternative is Sodium Hypochlorite. Continuous Production Electrochlorinators using salt, water and electricity are designed for high capacity production of Sodium Hypochlorite. The system can be easily automated by including instruments that are necessary for automatic operation. The system can be offered with PLC controls or with Relay logic control panel.
The purpose of Brine based Hypo Chlorination System is to generate and Inject Hypochlorite solution into feed water to inhibit the growth of biological organism and to prevent slime deposits on the wall of circulating cooling water pipes.
The raw water is delivered to the salt water dilution tank. Here the salt is dumped manually or with the help of salt feeders. The dissolved highly saturated salt solution is pumped in to the system, here the solution is further diluted by controlled flow of fresh water.
The diluted salt water will then be passed through Hypochlorite Generators where sodium hypochlorite solution will be generated from salt water by the electrolysis process. The generated sodium hypochlorite solution will be stored in the downstream Hypochlorite Solution Storage Tanks.
Hypochlorite solution from storage tanks will then be dosed continuously as well as intermittently (shock dosing) to the intake structure. The continuous Hypochlorite dosing rate shall be controlled manually in order to maintain a level of 0.2 mg/l free of residual chlorine in cooling water discharge at seal pit. Shock chlorination has been envisaged at 5 mg/l with frequency of once every 8 hours for duration of 20-30 minutes.
Main equipments in the Brine based Hypochlorination System
Brine Preparation Tank
The Brine preparation Tank is either made of HDPE of FRP in small capacity systems and RCC or FRP in large capacity systems. These tanks are provide with Agitators, multi-grade filter media, float valve, drain valve etc. These pumps are required if inlet seawater is not provided at a pressure of at least 2 kg/cm3. These pumps are normally made up of Duplex Stainless Steel. Working and stand by pumps are provided with Inlet and Outlet valves, Check valves and required instruments.
The Salt Feeders are provided to carry salt to the Brine Tank. The design and type of the feeder will be customised to the type of salt used. Salt comes in small 50 kg bags, or in 1-ton jumbo bags or loosely supplied in a dumper truck. The Feeder can be Electric Screw conveyer, Pneumatic Conveyer or EOT Crane.
The main equipment of the system is the Sodium Hypochlorite Generator, otherwise known as the Electrolyzer. The generators will be used to produce the hypochlorite solution and will be installed indoors. These can be of Horizontal type or Vertical type depending on the space available, capacity and configuration. Most of the time two or three Electrolyzer cells are connected together to achieve the desired capacity. The hydraulic connections are either parallel or in series.
The transformer rectifier controlled power supply will be self-cooling. These can either be Air cooled or Seawater cooled or Oil cooled and fitted with rectifiers of either Thyristors or Diodes. The output of hypochlorite from each generator is directly proportional to the D. C. output of the power supply. The Transformer/Rectifiers are provided with control panels for local and/or remote control and monitoring.
Acid Cleaning Unit
Acid Cleaning system is provided with Acid tank that will hold diluted Hydrochloric Acid. HCl dosing pump will pump the diluted acid through the Electrolyzer to remove the deposit of Calcium and Magnesium salts. The tank is designed to hold enough acid for one complete operation.
Hypochlorite Degassing cum Storage Tanks
The hypochlorite solution flows to the sodium hypochlorite degassing cum storage tank. The tanks are made of fiberglass. The storage capacity shall be sufficient to cover the shock dosing requirements. The necessary level switches are provided, for high level alarm, level switch for switching on/off the hypochlorite generator, low level switch which will, in case of being triggered, interrupt the continuous hypochlorite injection and will stop the shock dosing pumps.
Two sets of (100%) fresh air blower are installed next to the tank to blow air into the tank to blow out the entrapped Hydrogen. Auto switchover of the Blower occurs in the event of the operating blower tripping. Open Top Tanks do not need Blowers.
Dosing System for Continuous Chlorination and Shock Chlorination
Normally two continuous dosing pumps are provided, for continuous flow of hypochlorite solution to the dosing point. Most of the time a set of Shock Dosing pumps are provided to meet the demand of biofouling control. While the continuous pumps dose hypo solution at a lower rate, the shock dosing pumps dose a higher rate of the solution but for a shorter time.
Instrumentation and Control
Pressure Gauges, Pressure Switches, Flow Meter, Temperature Controller, Level Switches, Level Controllers, Hydrogen Detectors etc., are provided in the system to monitor the operation of the chlorine production. Output from all the instruments are connected to a Control Panel to properly control and monitor the operation. These Control Panels are either Relay based or PLC based. PLC based system have an interface with the plant DCS through SCADA.
Piping and Valves
Normally PVC or CPVC pipes are used in Sodium Hypochlorite Generation Systems, with PVC or CPVC Valves and fittings. These items are not only resistant to corrosion but easy to fabricate and erect.
- The Electrolyzer cell is housed in a chamber made of FRP/Acrylic/PVC.
- Large Brine tank to hold salt stock for days.
- Brine agitator creates a saturated salt solution.
- Actuate Brine Dosing pump ensures a proper concentration.
- Advanced cell design ensures proper production of chlorine.
- Compact cell cleaning system for periodic cleaning
- Hypo tank level controller controls the production
- Hydrogen blower ensures safe operation and proper venting of hydrogen
- PLC/ Relay based panel controls the automatic operation of the system.
- Heavy duty power supply is built for long hours of operation.
- Fill salt in the Brine Tank.
- Switch on the system in the control panel.
- Solenoid/Motorized valve will open and allow the water to flow into the system.
- Part of the water shall flow to the Brine tank to dissolve the salt.
- Adjust the water flow into the Electrolyzer with the Flow control Valve and Rotameter, as per instruction.
- The Brine dosing pump starts and injects the saturated brine solution in the water line.
- In the Electrolyzer chamber the salt solution gets converted to sodium hypochlorite
- The outlet of the Electrolyzer is connected to the Hypo storage tank.
- A blower connected to the storage tank blows away the Hydrogen, through a vent pipe.
- A temperature sensor is also provided in the Electrolyzer, if the temperature of Sodium Hypochlorite produced, exceeds the preset temperature limit, sodium hypochlorite generator switches itself off giving a cooling off period for the Electrolyzer.
- A level switch provided in the Hypochlorite storage tank does not allow the production of Hypochlorite once the storage tank is full.
- It automatically switches sodium hypochlorite generator on when the level in storage tank is reduced.
|PCP 1000||PCP 1500||PCP 2000||PCP
|500 Grams/hr||1000 Grams/hr||1500 Grams/hr||2000 Grams/hr||5000 Grams/hr|
|2 kgs/per hour||4.5 kgs/per hour||7 kgs/per hour||9 kgs/per hour||22.5 kgs/per hour|
|7 ~ 8.0 Gpl||7 ~ 8.0 Gpl||7 ~ 8.0 Gpl||7 ~ 8.0 Gpl||7 ~ 8.0 Gpl|
|70 liters||140 liters||210 liters||280 liters||700 liters|
|Water that can be treated with 1 ppm of chlorine(approx.)||500,000 liters per hour||1000,000 liters per hour||1500,000 liters per hour||2000,000 liters per hour||5000,000 liters per hour|
|AC Power Consumed||2.5kw/per hour||4.5kw/per hour||7kw/per hour||9 kw/per hour||22.5kw/per hour|