Flow Charts

Flow chart of sodium hypochlorite (NaCLO) dosing and control of residual chlorine dose

Automatic test set of chlorine dose

Flow rate adjustment of dosing pumps is performed with the help of ETATRON chlorine controller proportionally to the chlorine dose at the outlet of clean water reservoirs.

The chlorine dose is determined by ETATRON chlorine sensor. Depending on the chlorine dose set on the controller, there is 4-20 mA proportional output activated, which leads to dosing pump start-up.

For example: set chlorine dose is 1.5 mg/l; chlorine dose changed by chlorine sensor is 0.3 mg/l.

In this case the maximal value of analog signal is 20mA, and the dosing pump works with maximal flow rate. When the chlorine dose is closer to that set on the controller, the value of the analog signal decreases proportionally. When the value of the set dose is reached, the value of the analog signal is 4 mA. As the result, the controller’s relay is switched off, and the dosing pump is in standby.

Система автоматизированного контроля дозы хлора

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Flow chart of sodium hypochlorite (NaCLO) dosing proportionally to water consumption

Sodium hypochlorite (NaCLO) dosing proportionally to water consumption

Sodium hypochlorite (NaCLO) dosing is performed according to pulse or analog signals of ultrasonic flow meter proportionally to water consumption.

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Flow chart of sodium hypochlorite (NaCLO) dosing proportionally to water consumption and residual chlorine dose

Computerization of dosing system
Dosing of NaCLO is performed in two stages:

Primary chloration at the entry to the wastewater treatment facilities with NaCLO inlet into hydraulic mixer;
Secondary chloration with NaCLO inlet before the clean water reservoir.

During primary chloration, the dosing of NaCLO is performed proportionally to water flow rate. 4-20 mA signal incomes to the dosing unit from two ultrasonic flow meters.

During secondary chloration, the dosing of NaCLO is determined by chlorine controller proportionally to the dose of residual chlorine at the outlet of the clear-water reservoir due to the chlorine sensor installed in the place of sample collection.

There is a chloration room used for storage of NaCLO and preparing process solution There should be a ventilation system with 6 rate air change installed in the room for storage of sodium sulphite (NaCLO) according to SNiP (Construction Norms & Regulations) 2.04.02-84 «Water supply» and «Safety rules in the production, storage, transportation and use of chlorine».

Tanks for storage and preparing of NaCLO, fittings and conduits connections are to be made of constructing materials resistant to sodium hypochlorite (polyethylene).There is a chemical pump installed for pumping sodium hypochlorite out of vehicles into the storage tank.

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Flow chart of water chemical deaeration and pH control

There are chemical agents dosed for direct chemical bonding of oxygen during chemical deaeration of water into feed water. Normally it is sodium sulphite Na2SO3, the amount of which is as follows: 8 mg per 1mg of dissolved oxygen per 1 dm³ of water or 8 mg per 1 m³ of water when the volume of dissolved oxygen is 1 mg/dm³.

If the volume of dissolved oxygen is bigger, the dosing of sodium sulphite will proportionally increase. Oxygen bonding is carried out according to the following reaction:

2Na2SO3+О2=2Na2SO4

The reaction goes intensively when the water is heated to the temperature 70^оС and pH value range is рН=8.3 … 8.5. At the same time sodium sulfite is connected to the oxygen atom and is converted into sodium sulphate which is easily soluble and harmless in terms of corrosion. For more complete bonding of oxygen, sodium sulfite is dosed in plenty ranging from 10 to 15%.

Changing of pH value is performed by water alkalizing. The live carbon dioxide sweetens during water alkalizing, which excludes carbon dioxide corrosion of the equipment and the elements of cogeneration system. Usually caustic soda (NaОН) is used for this purpose; it takes up free aggressive carbon dioxide in accordance with the following equation:

2NaОН+СО2=Na2СО3+Н2О

When the quality of feed water is stable, the chemical deaeration can be performed by dosing chemical agents proportionally to the flow rate of feed water measured by impulse meter. The flow chart can be realized by means of dosing pumps of DLX–VFT/M series.

Water alkalizing is performed by the dosing pump controlled by pH controller depending on the set value of pH. DLX–СС/M series is recommended.

Технологическая схема химической деаэрации воды и контроля рН

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