A blast furnace stove control system, designed to improve performance and reduce operational costs, has been installed by ABB at the Kremikovtzi Corporation’s integrated steelworks in Bulgaria. The new control system has reduced operational costs by eliminating the potential for human errors. Additionally, the plant now only needs one operator per shift; due to the high degree of automation, the services of a shift gas technologist are no longer required. Costs are further lowered through reduced maintenance and through the automatic regulation of gas and air, which increases efficiency and decreases the consumption of raw materials and electricity. The new stove control system is based on ABB’s IndustrialIT platform. Kremikovtzi Corporation’s integrated steelworks is one of Bulgaria’s biggest industrial complexes. Its 40 year-old production facilities are currently being modernised with a EUR 56.2 million investment. This includes re-commissioning of the 11 year-old number one blast furnace, with a production capacity of 2300 tpd. The blast furnace control room features two operator stations based on the OperateIT SCADA Portal. Each stove is equipped with nine valves, one blower fan with a variable speed drive and one control valve for the gas. Two PID controllers in each AC800M control the air and gas flows. Each object has its own faceplate on the operator station screen. This presents, in real time, the technical and engineering settings, trend curves of important analogue signals, a list of alarms and a list of events. An overview display shows all the stoves, while each stove has a detailed display. The system has three normal operating modes: isolated, heating of the stoves and heating of the air blast, as well as a service mode. The controllers are responsible for executing the changeovers between the different operating modes. These can be executed in four different ways: manual changeover by the operator from a local control board; individual changeover from the operator station; cyclical changeover from the operator station; and automatic changeover. ABB supplied the low-voltage distribution and control equipment for the various stove auxiliaries. This includes incoming circuit breakers and bus ties of Isomax S6S type, with automatic changeover to ensure an uninterruptible power supply. Each object such as valves and fans is supplied and controlled via a relay-based feeder. This arrangement provides the necessary protection of the loads and cables, with coordinated discrimination between the upstream and the downstream circuit breakers. It also ensures the reliable transfer of data to the control system. Prior to the installation of the new ABB control system, the changeover of the stoves was done manually by actuating relevant valves and fans. With the new control system all the necessary activation of these objects is accomplished via commands from the control system. The contract for revamping the stoves was awarded to the Czech company Virkovice. It built one completely new stove and modernised the burning system of two others, replacing the old burners with ceramic.
