YNHJ Type Sodium Hypochlorite Generator

Source: B&R Working Committee

Applicating Company

Liaoning Innovation Environment Group Corp.，Ltd

Technology Name

Technical principle

The following is the electrolytic main reaction process of sodium hypochlorite generators.

NaCl+ H2O = NaClO + H2↑

First, YNHJ type sodium hypochlorite generator make use of pretreatment system to conduct hardness reduction of tap water;

Raw salt is carried to a salt dissolving tank for storage through an efficient salt loader. And the raw salt is dissolved to concentrated brine by an automatic water inlet system and hydraulic circulating unit of the salt dissolving tank;

Next, diluent brine with specified concentration is prepared by a diluent brine configuration system and then carried to the electrolysis system of a sodium hypochlorite generator;

The electrolysis system of the sodium hypochlorite generator conducts DC electrolysis of low concentration brine with diaphragm free DC electrolysis process, sodium hypochlorite solution of 6000~8000ppm concentration produced is stored in the sodium hypochlorite storage system;

Water disinfecting treatment process can be realized through quantified delivery to the disinfection point by sodium hypochlorite dosing system.

Meanwhile, hydrogen exhaust system processes the only by-product, improving the operation safety of the system;

The automatic pickling system realize the online maintenance of automatic pickling without disassembly. All the above functions can be automatically controlled by Innovation Environment Control System. In addition, the communication monitor of upper computer (Communication Interface of Ethernet as standard) and mobile phone APP monitoring function (selected) can be achieved to make the whole set of the system automated and intelligent.

Scope of application

Sodium hypochlorite widely applies to disinfection of various waters such as tap water, recycled water, industrial circulating water, swimming pool water, and hospital sewage.

Process flow and description

(1) Water Softening System: Water Softening Device　is supposed to be applied when the water hardness is higher than 8 degrees. Tap water passes through the water softener and ion exchange reaction occurs to remove the calcium and magnesium hardness in the water. A part of the softened water provides dilute water for the sodium hypochlorite generator, and another part enters the salt dissolving tank.

(2) Automatic Salt Dissolution and Preparation System: A set of automatic salt dissolving and saturated brine forming device is make up of salt dissolving tank, liquid level control, distributor, electric valve, transfer pump, pipeline and other components; Then the device automatically mixes saturated brine and production water and dilutes them into 3.0% diluent brine for electrolysis use; The system is equipped with automatic salt loader. When the device needs adding salt, just turn on the automatic salt loader to operate the equipment without manual salt addition, so that the work efficiency of the water plant staff can be improved. Stainless steel anti-corrosion material is adopted, so there is no need to worry about the damage on the device caused by corrosion.

(3) Electrolysis System:High frequency regulated constant current rectifier power supply of air-cooled type with power conversion efficiency reaches 95%. The electrolysis tube adopts modular design, which can increase or decrease the module based on the different amount of sodium hypochlorite required. It can meet the needs of users and ensure the maturity and perfection of the stereotyped module production process and guarantee the product quality. The host machine is a closed housing with a highly translucent Plexiglas panel window, which is convenient to observe the operation status of the electrolysis tank. As for the composite electrode connection mode, there are very few connecting parts in the whole structure, which reduces the heat production on the connecting parts and greatly reduces the salt and electricity consumption during sodium hypochlorite production, and has a positive effect on reducing by-products. The housing of electrolysis tank is made of transparent UPVC, so as to observe the electrolysis process and electrode surface in real time, which is easy to learn about the status of electrode, determine the pickling cycle and ensure the safety of electrode.

(4) Control System: The control system collects the detection signals of each working area, drive the corresponding controller and ensure the normal operation of the system;It displays and sets the working parameters of each area and alarm the abnormal parameters;It can automatically control intelligent industrial man-machine interface, support various communication protocols, and realize comprehensive data remote transmission and monitoring with the host computer.

（5）Storage system: It mainly consists of NaClO storage tank, ultrasonic level meter and fan. HDPE material storage tank is set to meet the reserve quantity of the system at least 4h continuous dosing. The storage tank is equipped with water inlet and outlet, overflow port, air inlet and outlet and level meter installation hole. Ultrasonic level meter is set to monitor the tank level and 4-20mA signal is conveyed to PLC to link up with PLC control system to start and stop.Hydrogen exhaust fan is set up to dilute the H2 produced by electrolysis below 0.1% and safely exhaust it to the outdoor air according to the requirement. When one fan brakes down, it can automatically switch to another backup fan.

（6）Hydrogen Exhaust System: Hydrogen separator between poles is equipped above the electrolysis tank to exhaust the hydrogen produced during the electrolysis of each electrolytic tank in time; hydrogen Exhaust fan is equipped in the storage tank to dilute the hydrogen concentration to less than 0.1% and discharge it to the outdoor, and the hydrogen exhaust pipe is equipped with wind pressure switch for Level 3 protection.

（7）Dosing System: Automatic dosing is realized according to the actual water requirement; Quantitative dosing, flow control, residual chlorine control, flow + residual chlorine control dosing can be realized. An imported corrosion-resistant diaphragm metering pump is used in dosing pump for automatic dosing.

(8) Safety Monitoring System: The whole set of the device is equipped with residual chlorine monitor, chlorine leakage alarm meter and hydrogen alarm meter to safely monitor the residual chlorine value in water, indoor chlorine concentration and hydrogen concentration, and to link with PLC control system.

(9)Electrode Pickling System: In order to keep the electrodes in good electrolytic condition, automatic pickling device can be used to clean the electrode regularly. The system is equipped with pickling device without storing large amount of hydrochloric acid or citric acid. It is only available when pickling is required.

Promotion prospects

Hypochlorite has been used to disinfect drinking water in the water industry for over 100 years, and in 1904 JERSEYCITY, New Jersey became the first municipality in the United States to use hypochlorite for public water disinfection.

Due to the high risk associated with the use of chlorine for disinfection， if the chemical materials used to produce hypochlorite are not handled properly, fire, explosions and even injuries will be caused during storage and transport. Chlorine itself is also highly toxic, so its storage and use can be quite dangerous. To avoid these dangers, chlorine disinfection has been decreasing.

In 1998 a survey of on the disinfection status of large and medium-sized tap water in the US conducted by the Disinfection Systems Committee of the Water Quality Section of the American Water Works Association showed that the use of chlorine for disinfection had decreased from 91% in 1978 to 83.8% in 1998, and a survey of the disinfection status of small waterworks also showed that the use of chlorine in small groundwater-based waterworks accounted for only 61% of the waterworks surveyed. In contrast, on-site disinfectant preparation techniques are gradually being developed and utilized, with electrolysis being one of the main methods of on-site disinfectant preparation. As a result, sodium hypochlorite generators, which use the chemical electrolysis principle to produce sodium hypochlorite disinfectant on site, are becoming more and more widely used.

Sodium hypochlorite generators were introduced for drinking water disinfection in the early 1970s, but because of the low price of chlorine and lax drinking water regulations in the USA, the generators were not widely used. Nowadays, with the increasing stringency of drinking water regulations and the rising price of chlorine, the fact that sodium hypochlorite generators have been proven to be an effective disinfection method, so they are being used more and more widely in the United States. By 2002, more than 1,500 waterworks in the USA had switched from using chlorine gas to using sodium hypochlorite field generators for waterworks disinfection. Hubert Fleming and Mayne Huebner also pointed out that sodium hypochlorite generators would be more commonly used in the southern states of the USA due to the climate.

Actually, sodium hypochlorite widely applies to disinfection of various waters such as tap water, recycled water, industrial circulating water, swimming pool water, and hospital sewage.

Sodium hypochlorite is also capable of destroying cyanide ions and benzene rings, etc., and is used for advanced oxidation of cyanide-containing wastewater and some heavily polluted industrial wastewaters, as well as for bleaching of paper pulp, etc. Highly concentrated sodium hypochlorite liquids can also be used to strip mud from equipment and pipes.

Sodium hypochlorite sterilization is based on the hydrolysis of hypochlorite to form hypochlorous acid, which further decomposes to form neo-oxygen [O]. The strong oxidizing properties of which denature the proteins of bacteria and viruses, thereby killing the pathogenic microorganisms. The principle of chlorine disinfection is also based on the production of hypochlorous acid.