Automatic control system of pyrogas parameters in pyrolysis process in acetylene production

Nowadays existing technological process management systems increasingly require the development of criteria related to ensuring the quantity, quality and technological safety requirements of chemical technological processes. Due to the specific characteristics of these criteria and their subjectivity, the task of repeatedly checking and evaluating remains relevant. In this article, the parameters important in the production of pyrogas, which is the main product in the production of acetylene, and a method of complete control of the safety of the technological process have been developed. In the specified installation, an optimal automatic control system is installed so that we can control the parameters of the pyrolysis process: flow, temperature and pressure. In the article, the parameter control system in the technological process in the TIA Portal V15.1 software is built on the basis of the PID controller. In addition, system functionality, specifications, hardware and device models were also reviewed. It is aimed at reducing the impact of the human factor and increasing safety in production. Also, the basic principles of hardware management at different levels are presented to ensure high reliability of the entire system.


Introduction
In the article, the process of obtaining acetylene by oxidative pyrolysis of natural gas is proposed, its technological safety and optimal automatic control system.Also, during the development of the article, G. N. Sanayeva article "Development of the technological safety management system of the acetylene production process with oxidative pyrolysis of natural gas" was introduced.Sanayeva's dissertation covered technological process safety.In addition, the thesis of S. N. Rodin "Development of acetylene production control system based on fuzzy logic apparatus taking into account environmental factors" was analyzed.In the dissertation, an automatic control system for preventing harmful effects on the environment was developed.Summarizing the analyzed articles and dissertations, in this article we use the PID-regulator.If we use only a P-regulator, the steady-state will quickly exceed our set value and then decrease again, causing the output signal to fluctuate by a large margin.This can cause our managed devices to change their set measurement limits or fail completely.If we use a PI-adjuster, the settling time will be increased and it will be inefficient as it slowly reaches our set point.We can see from this article that if we use the PID controller, it will gradually approach the value we have set by entering a standard value for the process into its parameters and reach stability in a short time.So, it is known from the article that the use of a PID controller is considered to be the optimal choice for controlling parameters in this process [1][2][3][4].

Materials and methods
The empirical (chemical) formula is C2H2.Gaseous acetylene is a colorless, flammable and explosive gas with a density of 1173 kg/m 3 at 0 °C and 101.3 kPa (1.3 kgf/sm 2 ), (760 mm H2O).The relative molecular weight of acetylene is -26,038.Acetylene is highly soluble in many organic and inorganic liquids, which makes it possible to extract concentrated acetylene from the reforming gases.Acetylene is one of the most important products of organic chemistry, based on which the synthesis of substances used to obtain fibers, plastics, rubber, production of polyvinyl chloride, ethyl alcohol, aromatic hydrocarbons, acetic acid, various solvents, technical carbon, etc.The finished product is gaseous acetylene, after its volume fraction is purified, in an amount not less than 99.56%, it is supplied to the unit of the VXM (vinyl chloride monomer) workshop as a raw material for the synthesis of PVC (polyvinyl chloride).The main product required for the production of acetylene is the formation of pyrogas through the oxidative pyrolysis method.It uses natural gas as the main raw material, and oxygen as the auxiliary raw material.The reaction is carried out without a catalyst and a heat carrier (teplonocitel).Oxidation pyrolysis means burning oxygen in one place at the same time as gas.In addition, the heat released by combustion is used to decompose the gas.In the preheating tank, natural gas is heated from 30°C to 650°C, the heating temperature cannot rise above 650°C, because the boiling point of natural gas with oxygen is about 650°C, natural gas and oxygen are mixed, it is its own can spontaneously combust and burn.Oxygen is also heated to 650 °C in a preheated tank.This preheating tank uses a high velocity air velocity design (construction) to provide gradual heating of the oxygen.The temperature in the line of combustible gases in oxygen and natural gas heating furnaces is controlled by the regulating valve 150XV-20012, 150XV-20012, respectively.In the heating tanks, oxygen and natural gas, heated to a maximum temperature of 650 ° C, enter the mixing area at the top of the acetylene tank (reactor), and in this process combustion occurs.Early combustion occurs due to high oxygen content.However, to avoid this, the 150XV-20016 valve is opened, automatically vented and purged with nitrogen.From the following technological process, we know that the temperature of the internal environment during the reaction of the substances in the oxygen and natural gas heating column and the reactor and the amount of natural gas and oxygen entering these devices are the main factors.parameters and these parameters change depending on each other.For this reason, controlling the amount, temperature, and pressure of substances in the pyrolysis process at the same installation interval is a somewhat complicated issue due to external and unaccounted for effects in the technological process [5][6][7][8].

Figure 1. Amount of products needed to produce 1 ton of acetylene
In the recent years, SIMATIC S7 400, S7 1200, S7 1500 controllers are used in the implementation of software for automatic control systems of acetylene production technology.HMI (human machine interface) Comfort TP 700, 900, 1200 control panels are also widely used.In this article, we created a temperature, consumption and pressure control system using a PID controller using S7 1500 and Comfort TP 900 devices in the TIA Portal V15.1 software environment.In addition, this system was used in the article because it is the most efficient and easy way to control remote manufacturing processes directly using ACS.Using this system to control the amount of substance at the time of reacting substances, it is advisable to change the consumption of products to control the consumption of the consumption measuring device and the control device(valve) directly related to it and the reaction temperature, or to give water to the reactor side walls and steam so that no explosion occurs.

Results and discussion
In figure 2, with the help of valves 150XV-20011 and 150XV-20012, the main raw material for the preparation of pies is directed to the mixing cylinder of natural gas and secondary raw material, oxygen.In this case, the function of the steam provided by valves 150XV-20013 is to ensure that the temperature in the reactor increases during the mixing of oxygen and natural gas and does not lead to a spark explosion.The function of the water supplied by valves 150XV-20014 and 150XV-20015 is to adjust the temperature in both heaters.With the help of an internal mixing device, the substances in the reactor are rotated and ensure that the substances are mixed with each other.In this case, the purpose of the nitrogen supplied by the valves 150XV-20016 is to prevent the overtemperature of the reaction occurring in the reactor.With the help of temperature measuring instruments located at positions 150TT-10100, 150TT-10101, 150TT-10102 shown in Figure 2, we will be able to control the temperature A simulation model of the pyrolysis process device is presented in Fig. 2. In the scheme, 1-natural gas consumption control device (valve); 2-natural gas consumption measuring device; 3-natural gas pressure measuring device; 4-water valve entering to oxygen heating tank; 5-oxygen consumption measuring device; 6. oxygen consumption control device (valve); 7. temperature measuring device of oxygen heating tank; 8. temperature measuring device of natural gas heating tank; 9. water valve entering natural gas heating tank; 10. nitrogen valve; 11. reactor temperature measuring device; 12steam valve.   in the graph that the specified values can be achieved in a short time with high accuracy.Including time and stability can be maintained.

Conclusion
In this article, we used TIA Portal V15.1 software to create a control part of the pressure, temperature and amount of substance at the set value in adjusting the value of the main parameters for the production of pyrogas, which is the main product required for the production of acetylene.From the graph of the constructed model, we can see that when we adjust the basic parameters in this method, the process values can be returned to the working state in a short time even when the dangerous situation occurs.The automation control system used by us are considered to have a high level of accuracy, which allows to increase product quality and productivity several times.If we use these automation control system, it is also appropriate for security reasons.

Figure 2 .
Figure 2. a) a structure and b) imitation model of a pyrogas reaction device is presented.

Figure 3 .
Figure 3.The logic part of the model is put into operation and the verification (simulation) of the program created using PLC (programmable logic controller) software is shown.

Figure 4 .
Figure 4. Temperature control graph result and working condition.

Figure 4
Figure4shows the value of each parameter in a different color: red -the temperature of the heating tank, blue -the value of the valve, which changes depending on the temperature.We can see the result