Українська   Русский
DonNTU   Masters' portal

Abstract

Contents

Introduction

The development of industry and modern technology makes high demands on the quality of metals and alloys. Today, electric arc furnaces are considered the most common and environmentally friendly units for steelmaking. The possibility of a concentrated input of a significant amount of thermal energy, combined with the simplicity of controlling the input of electrical power, is an indisputable advantage of electric arc furnaces over other units for steel production.

1. Relevance of the topic

Reducing maintenance costs and extending the turnaround time, as well as simplifying the diagnosis of malfunctions, together with increasing reliability and efficiency, allows us to speak of a significant economic effect, which is associated with the use of the proposed methods and automation tools in comparison with those traditionally used at the technological facility under consideration - oxygen lance of an arc steel-making furnace.

The existing systems for automatic control of the parameters of EAF oxygen tuyeres do not fulfill all the necessary functions to control and monitor the parameters of this control object, taking into account the relationship with the ACS of other processes of the arc steelmaking furnace. Therefore, the development and study of an automatic control system for the parameters of the EAF oxygen lance is urgent.

2. The purpose and objectives of the study

The purpose of the study is to increase the efficiency of the oxygen lance of an arc steel-making furnace by developing an automatic control system, which will reduce operating costs, extend the service life of technological equipment and improve the quality of the steel obtained.

To achieve this goal, it is necessary to solve the following research tasks:

  1. To develop mathematical models of an oxygen lance of an arc steelmaking furnace as an object of temperature control and as an object of oxygen pressure control.
  2. Carry out studies of dynamic processes in the control object and, on the basis of this, formulate requirements for algorithms and control laws.
  3. To synthesize the necessary algorithms for controlling the technological parameters of the oxygen lance of an arc steelmaking furnace.
  4. Simulate the ACS an EAF oxygen lance and evaluate the proposed control algorithms.
  5. Perform technical design of an automatic control system, taking into account the features of the object under study and synthesized control algorithms.
  6. Develop algorithmic and software for ACS.
  7. Assess the economic efficiency of the proposed solutions.
  8. To develop measures for labor protection and life safety.

Object of study: automatic control system for the oxygen lance parameters of the arc steel-making furnace.

Subject of study: methods of analysis, synthesis and modeling of multi-loop control systems.

3. Formalization of the EAF oxygen lance as a control object

The normal functioning of the oxygen lance is determined by maintaining the required parameters of the oxygen supply process and the process of its cooling. The process of oxygen supply to the EAF working space is characterized by the required oxygen consumption at this stage of melting while maintaining the required oxygen pressure. The deviation of the oxygen flow rate and pressure from the required values ??leads to an increase in operating costs for the steel production process in EAF or to a deterioration in the quality of the resulting steel. When cooling the lance, it is necessary to change the flow rate of the cooling water to maintain the required temperature difference at the outlet and inlet of the oxygen lance, which, at a relatively constant temperature of the cooling water at the inlet to the lance, is reduced to maintaining the specified temperature of the cooling water at the outlet of the oxygen lance.

The above analysis of the features of the oxygen lance of an arc steelmaking furnace made it possible to carry out the process of its formalization as a control object, as a result of which a diagram of material flows (Fig. 1) and information variables (Fig. 2) for this control object was obtained.

Scheme of material flows of an oxygen lance

Figure 1 - Scheme of material flows of an oxygen lance

Scheme of oxygen lance information variables

Figure 2 - Scheme of oxygen lance information variables

The main controllable variables that determine the efficiency of the functioning of the oxygen lance of an arc steelmaking furnace, and, accordingly, the entire electric arc furnace process, are (Fig. 2):

The necessary change in the controlled variables - Рк and tгв in the developed system of automatic control of the oxygen lance of an arc steel-making furnace is carried out through the use of the following control actions (Fig. 2):

The control object under consideration, the oxygen lance of an arc steel-making furnace, is influenced by the following disturbing influences:

4. Analysis of existing ACS oxygen lance parameters

The functional scheme of a typical solution for the automation of an oxygen lance is shown in Figure 3.

Typical automation scheme for EAF oxygen lance

Figure 3 - Typical automation scheme for EAF oxygen lance

The required temperature of the oxygen lance during its cooling can be achieved by changing the flow rate of water at the entrance to the jacket of the oxygen lance according to the value of an indirect controlled parameter - the temperature of hot water at the outlet of the jacket of the oxygen lance, which is implemented by the TC controller (Fig. 3).

The required value of the pressure of the oxygen supplied to the lance can be achieved by changing the oxygen consumption at the inlet of the oxygen lance, which is implemented by the PC regulator (Fig. 3).

The functional scheme of the system for automatic monitoring and control of the purge of the bath of an arc steelmaking furnace with oxygen is shown in Figure 4.

Functional scheme of the automatic control and regulation system by blowing the EAF bath with oxygen

Figure 4 - Functional scheme of the automatic control and regulation system by blowing the EAF bath with oxygen

The functional diagram of the automatic control and regulation system of the EAF bath with oxygen (Fig. 4) shows the following elements: 1–1 - a constriction device for measuring oxygen consumption; 1–2 - measurement of oxygen consumption; 1–3 - secondary device for recording oxygen consumption; 1–4 - oxygen consumption regulator; 1–5 - oxygen flow rate regulator; 1–6 - contactless starter; 1–7, 6–3, 7–1 - actuator; 1–8, 7–2 - control valve; 1–9 - indicator of the position of the actuator shaft; 2–1 - measurement of oxygen temperature; 3–1 - measurement of oxygen pressure with remote transmission of readings; 3–2 - measurement of oxygen pressure at the site; 4–1 - constriction device for measuring the flow rate of cooling water; 4–2 - measuring the flow rate of cooling water; 4–3 - secondary device for recording the flow rate of cooling water; 5–1 - measurement of cooling water pressure with remote transmission of readings; 5–2 - measurement of the pressure of the cooling water on site; SA1, SB1, SA2, SB2, SB3 - universal cam switch.

Source List

  1. Сведчанский, А.Д. Электрические промышленные печи: Дуговые печи и установки специального нагрева: учебник для вузов. / А.Д. Сведчанский, И.Т. Жердев, А.М. Кручинин – 2-е изд., перераб. и доп. – М.: Энергоиздат, 1981. – 296 с.: ил., табл.
  2. Поволоцкий, Д.Я. Электрометаллургия стали и ферросплавов. / Д.Я. Поволоцкий – М.: «Металлургия», 1978. – 550с.
  3. Окороков, Н. В. Электроплавильные печи черной металлургии. / Н.В.Окороков – М.: Металлургия, 2005. – 220 с.
  4. Марков, Н.А. Электрические печи и режимы дуговых электропечных установок. / Н.А. Марков. – М.: Энергия, 2003. – 204 с.
  5. Пирожников, В.Е. Автоматизация контроля и управления электросталеплавильными установками. / В.Е. Пирожников, А.Ф. Каблуковский – М.: «Металлургия», 1974. – 208 с.: ил., табл.
  6. Лапшин, И.В. Автоматизация дуговых печей. / И.В. Лапшин – Москва, 2004. – 166 с.
  7. Глинков, Г.М. АСУ ТП в черной металлургии: учебник для вузов. / Г.М. Глинков, В.А. Маковский – 2-е изд., перераб. и доп. – М.: «Металлургия», 1999. – 310с .: ил., табл.
  8. Глинков, Г.М. АСУ технологическими процессами в агломерационных и сталеплавильных цехах: учебник для вузов. / Г.М. Глинков, В.А. Маковский – М.: «Металлургия», 1981. –360 с.: ил., табл.
  9. Бигеев, А.М. Математическое описание и расчеты сталеплавильных процессов. / А.М. Бигеев. – М.: Металлургия, 1982. – 160 с.
  10. Грачев, В. В. Динамика трубопроводных систем. / В. В. Грачев, С.Г. Щербаков, Е. И. Яковлев. - М: Наука, 1987. – 438 с.
  11. Чермак, И. Динамика регулируемых систем в теплоэнергетике и химии. / И. Чермак, В. Петерка, И. М. Заворка. - М.: Мир, 1972. ? 624 с.
  12. Клюев, А.С. Наладка средств автоматизации и автоматических систем регулирования: Справочное пособие. / А.С. Клюев, А.Т. Лебедев, С.А. Клюев, А.Г. Товарнов; — 2-е изд., перераб. и доп. - М.: Энергоатомиздат, 1989. - 368 с.
  13. Лукас, В. А. Теория управления техническими системами. Компактный учебный курс для вузов / В.А. Лукас. - 3-е изд., перераб. и доп. - Екатеринбург: Изд-во УГГГА, 2002. - 675с.: ил.
  14. Филлипс, Ч. Л. Системы управления с обратной связью / Ч. Л. Филлипс, Р. Д. Харбор; пер. с англ. Б. И. Копылова. - М.: Лаборатория Базовых Знаний, 2001. - 616с.: ил. - (Техн. ун-т. Автоматика). - Перевод изд.: Feedback Control Systems/Phillips C.L., Harbor R.D.