Improving the Energy Efficiency of Industrial Power Plants at Metallurgical Enterprises
The development of on-site electrical energy generation is a distinctive feature at metallurgical enterprises. Thanks to the using of secondary energy resources - blast furnace and coke oven gases, electricity produced at industrial power plants is significantly cheaper than the electricity received from the power system. On-site power plants of the largest Russian metallurgical plants, such as PJSC MMK, PJSC NLMK, PJSC Severstal, currently cover 60-70% of the total electricity consumption at these enterprises. The article is devoted to the electric energy saving reserves study in the in-house needs system at one of the oldest power plants, at PJSC MMK. This power plant includes 8 power boilers and 9 turbogenerators with a capacity of more than 200 MW; it provides electricity and heat to the main workshops of the enterprise, as well as to one city district. Transportation and supply of the main components for the technological process, such as water, air and fuel, is carried out by unregulated asynchronous electric drives. The most powerful and critical ones are the electric drives of the feed pumps, which supply water to the boilers with the specified flow rate and pressure. To date, the pressure in the system is regulated by manual throttling by turning on or off one of the pumps. An urgent and practically significant problem is to ensure the main parameters of feed pumps by controlling the electric drives speed, which will significantly increase the station energy efficiency. Using a mathematical model, a study was carried out to investigate the operating modes of a pump group with a common manifold, where special attention is paid to modeling the hydraulic part of the system. The article considers the most effective ways to maintain the required pressure level. According to the results of comprehensive studies carried out on the developed model, the authors proposed a cascade-frequency control of adjustable electric drives of feed pumps. The implementation of such a solution will reduce the pump electricity consumption by more than 20%.