Intellectual control of the electrolysis process in the production of caustic soda

Intellectual control of the electrolysis process in the production of caustic soda

Olim Sattorov¹, Mokhinur Kosimboeva^2
1Navoi State University of Mining and Technologies, Department of Automation and Control, Energy-mechanics faculty, 210100 Navoi, Uzbekistan [e-mail]
¹Navoi State University of Mining and Technologies, Department of Automation and Control, Energy-mechanics faculty, 210100 Navoi, Uzbekistan [e-mail]

Abstract: This article is based on the modeling of the operating mode of the membrane electrolyzer in the production of caustic soda through a neural network. In the course of work, a neural network model of the operation of the electrolyzer element was developed. Neural network software was used to create and train neural networks. The purpose of this work is to create an accurate model of the electrolyzer element using the following tasks was to create: the process of designing optimal structures of neural networks and their training, creating an electrolyzer model by training neural networks, as well as processing the modeling results. As a result of this work, a neural network model was developed, which allows to quickly and accurately calculate the result of the operation of the electrolyzer under any initial conditions.
Key words: caustic soda, membrane electrolysis method, electrolyzer, neural network, modeling, process neuroregulator program.


1Introduction
In industry, chlorine, chlorine products and caustic soda are obtained by electrolysis of an aqueous solution of table salt. In this case, the table salt solution breaks down as a result of passing an electric current. As a result, together with chlorine, a solution of caustic soda and hydrogen is formed.
The process can be represented by the following chemical reaction:

2NaCl + 2H₂O Cl₂↑ + 2NaOH + H₂↑ (1)
The sodium hydroxide formed in the reaction is sent to the production units of 32%, 50% caustic soda and granulated soda. And hydrogen and chlorine are processed to produce chlorine compounds. Nowadays, caustic soda is widely used in the chemical and oil industry, non-ferrous metallurgy, paper production, and the production of artificial fibers.
There are several methods of producing chlorine and caustic soda:
1. Mercury electrolysis method
2. Diaphragm electrolysis method
3. Membrane electrolysis method.
Among these 3 methods, the most important and developing method is the membrane electrolysis method. The membrane electrolysis method is based on the phenomenon of ion exchange through ion-exchange membranes under the influence of electric current. Ion exchange varies with membrane functionality, polymer film composition and design. Depending on the functional purpose, the membranes can be cation exchange, ion exchange and bipolar. The main advantages of the membrane electrolysis method are environmentally friendly, high energy efficiency, the possibility of obtaining a high-quality product, considerable ease of use, and a small production area. Comparing the membrane method with the mercury method, the membrane method saves energy by reducing the voltage on the electrolyzers. The advantage of the membrane method over the diaphragm method is that evaporation costs are significantly lower. The quality of caustic soda obtained during membrane electrolysis is very high. Chlorine produced by the membrane method does not contain hydrogen compounds, which allows to increase its level of liquefaction.
In addition to these advantages, there are also a number of disadvantages of the production of caustic soda by membrane electrolysis:

• 
  As a result of the deviation of parameters such as current and voltage from the given value, it causes a number of serious problems. In particular, as a result of the increase in current, it causes an increase in the pressure in the chlorine collector, which in itself leads to the rupture of the pipeline and damage to the chlorine compressors. If the problem is not solved in time, the situation can lead to the explosion of the electrolyzer.
  
• 
  Outcome of the increase in current and voltage, the temperature of the electrolyzer itself increases, which causes the electrolyte to boil, and as a result, an emergency situation is observed in the process.
  
• 
  As a result of the decrease in voltage, the process of formation of sodium and chlorine slows down, as a result, it causes the production of low-quality products. A significant decrease in voltage beyond the norm leads to a complete stop of the electrolysis process.
  

Fig.1.
Modeling the operating mode of the membrane electrolyzer using a neural network ensures the elimination of such shortcomings and the safety of the technological process. Keeping the parameters of the electrolyzer at the specified value is somewhat complicated, as a result, the use of other modeling methods, including modeling through PID regulators, is ineffective. Because, as mentioned above, the deviation of electrolyzer parameters from the specified value can lead to serious consequences.