| With technical development and deterioration of earth environment, "energy-saving & consumption-reducing" has become an important measure for enterprises to develop products of high quality and at the same time of low cost, which serves also a guarantee for them to get an edge in a highly competitive market. This necessity to save energy and reduce consumption, together with the call for development of cyclic economy, require the ferrous materials for modern iron-making, whether it is conventional blast furnace technique, or direct/melting reduction process, to be block-like furnace burden with certain profile. Travelling grate-rotary kiln process, due to its well-adaptability to different raw materials, large production scale, high pellet strength, even quality, low energy consumption and production cost, etc, has enjoyed a rapid development and is gradually becoming a major pellet production technology.Due to the complication and high level of the automatic control system of grate-kiln process, the performance of automatic equipment and efficiency of automatic control have direct effect to the physical and chemical properties to finished pellets. By introducing thorough research on development history, current situation and advantages and disadvantages of three indurations methods of pelletizing technique, as well as research on process flow, technical features, control requirements and existing problems etc. of grate-kiln process, this thesis introduces, in detail, the process flow, control requirements and interlocks among key equipment of the Brazilian grate-kiln pelletizing plant. With consideration of the practical production requirements, qualified two-level control system was designed, and real-time detection of process variables, real-time supervision and control of process flow parameters were achieved. The application of comprehensive automation technique, composed by fieldbus, PLC, industrial computer, industrial Ethernet in this plant is highlighted in this paper. With reference to the problems in similar plants, recommendations for improving the selection of key instruments, such as the engineering optimization of kiln body scanner, particle size analyzer, water content detector and dust content supervision system, ect, are raised. With its advanced control technique and methods, this automatic control system improves the control level and accuracy, as well as the pellet quality, at the same time reduces energy consumption, thus creating good economic benefits. So far it has been running in good conditions, and it is worthy of promotion and copied among pellet plants. |
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