ELECTROLYSIS INSTALLATION

The practice of disinfecting drinking water with chlorination, which began in Russia in St. Petersburg in the early 20s of the last century, practically solved the problem of effective sanitation of water supply to populated areas. However, the disinfection of water by gaseous chlorine delivered to water treatment plants in cylinders and tanks in a liquefied form has a number of disadvantages, among which the most significant is the ability of chlorine to damage not only maintenance personnel, but also the population of the territory adjacent to a water treatment plant. This is due to the volatility and toxic properties of chlorine and poses a real danger to cities and towns.
In recent decades, a solution of sodium hypochlorite NaClO containing active chlorine, which is equivalent to pure chlorine in its disinfecting and sterilizing qualities, has been increasingly used worldwide. Its use practically removes all dangerous and harmful production factors inherent in the use of liquid and gaseous chlorine of a potent toxic substance.
The advantages of using sodium hypochlorite include the possibility of obtaining it directly at the place of consumption by electrolysis of cheap and affordable raw materials - sodium chloride (sodium chloride). Moreover, the sodium hypochlorite solution obtained by the electrochemical method (grade E according to TU 6-01-29-93) is the purest and least toxic product (hazard class 4 according to GOST 12.1.007-76) and has the highest efficiency.
Designed and manufactured plants for the production of sodium hypochlorite have various capacities and various purposes. They can be used:
- for disinfecting natural and wastewater in drinking water supply;
- for the disinfection of equipment, facilities and structures in the food industry, in health facilities, catering, sanatoriums and rest homes, child care facilities, swimming pools and other facilities;
- for bleaching;
- to prevent biofouling in water heating and cooling systems.
Currently, the most promising method is the method of water disinfection using electrolytic sodium hypochlorite, obtained at the place of consumption by electrolysis of chloride solutions.
Technological schemes of electrolysis plants can be either flowing or periodic. When using flow-through electrolyzers, it becomes possible to reduce the cost of servicing plants, as it is much easier to control the process here.
Depending on the type of raw materials used, electrolysis plants can be divided into plants for the electrolysis of an artificially prepared solution and for the electrolysis of natural brines.
The consumption of table salt in direct-flow plants, as a rule, is slightly higher than that of a batch operation. However, their manufacture and operating conditions are much simpler. Therefore, such installations are often used at facilities of low throughput, when some salt overrun is justified by the simplicity of their design and maintenance.
The advantages of electrolytic sodium hypochlorite as an effective bactericidal agent, the simplicity and reliability of electrolysis plants, as well as the interest of consumers in the use of a safe electrochemical method of water disinfection, have led to the creation of a huge number of electrolyzers that are most diverse in design.
The most widely used electrolysis plants operating according to the following flow chart.
A saturated solution of sodium chloride is prepared in the tank, salt is loaded and filled with tap water. The supply of tap water to the tank is carried out through the float valve, with which a constant water level is maintained in the tank. Water passing through a layer of sodium chloride and dissolving it is saturated with sodium chloride. To obtain a saturated salt solution with a NaCl content of 30 g / l, the salt layer above the intake filter (dead volume) must be at least 15-20 cm. As the electrolysis work, the salt layer decreases and when it decreases to the dead volume level, it is necessary to replenish the tank.
The saturated solution of sodium chloride is taken by a metering pump through a pipeline located at the bottom of the tank. Pipe inlet with
In order to prevent the ingress of contaminants, it is equipped with a filter. A saturated solution of sodium chloride enters the pipeline for the preparation of a working solution of sodium chloride, which also contains tap water for dilution to a predetermined concentration of a solution of sodium chloride. The flow of tap water is controlled by a water meter or by a rotameter and is regulated by a valve or tap.
The prepared working solution enters a flowing electrolyzer consisting of several electrolytic cells in which electrolysis is carried out, as a result of which sodium hypochlorite of a given concentration of chlorine and hydrogen is formed. The cell is connected to a direct current source. The resulting sodium hypochlorite enters the buffer tank, where hydrogen is separated from hypochlorite. From the buffer tank, sodium hypochlorite is pumped by a metering pump for chlorination. Dosing of active chlorine is carried out by changing the speed of the pumps. Hydrogen released during electrolysis is removed by forced ventilation outside the room into the atmosphere.
In the process of electrolysis on the electrodes, the hardness salts contained in the sodium chloride solution increase. To remove salt deposits, acid washing of the electrolyzer is provided.
The buffer tank is equipped with an emergency overflow pipe. Overflow is carried out in the industrial sewer.
The electrolysis plant is equipped with automation elements that turn off the rectifier unit in violation of the technological mode of operation.