COOLINGOFSINTERONLINEARCOOLERSOFTHENLMKSINTERPLANT

Abstract

Requirements for sinter cooling in linear coolers are presented. A brief literature review of laboratory, industrial and theoretical studies in the field of cooling in these type of coolers is performed. Peculiarities of heat transfer in the sinterbed, caused by its different size and distribution of particle size distribution along the bed height on the cooler, are noted. A significant difference in the distribution of the blown air velocity across the bed width is revealed with the same and different widths of sintering cars and linear cooler cars. It is noted that the presence of hot return separation and cooling units is associated with significant operating costs for the maintenance and repair of mechanical screens, drum coolers and conveyor systems, while the return heat may not be utilized. Data of the implementation results of the reverse loading system at KarMK and ZSMK are presented. The cooling conditions for sinter using ОП-315 linear coolers in department No. 2 of NLMK's sinter plant are examined. Return heat is not used to preheat the mix: it is primarily screened before the cooler on a “hot” screen and “quenched” with water in a drum. Due to the high productivity of the sintering machines, the speed of the cooler carriages is 2.75–2.90 m/min, compared to 1.60–1.75 m at other plants with similar sinter bed heights. Before analyzing the sinter cooling process using a mathematical model, measurements were taken to adapt the model to the bed's surface temperature distribution and the air velocity at the bed's outlet before sinter unloading. The model was used to study 11 variants of cooler operation with different sinter bed heights, its initial current and elevated temperatures, the presence of large pieces, wear of longitudinal seals, operation in summer and winter, with a high (1050 mm) bed and with high-power blower fans. In the warm season, the average final temperature in different variants varies from 155 to 180 °C, and the maximum – from 365 to 420 °C, in the cold season it decreases to 118 and 230 °C, respectively. The efficiency of increasing the sinter bed height and the use of a reverse sinter loading system were confirmed. At the same time, due to the transportation of sinter to the blast furnace shop by sinter cars and the absence of problems due to its high final temperature, the implementation of a reverse loading system will require lengthening the sinter machine collecting manifold, adding two vacuum chambers, will be accompanied by an increase in the flow rate and velocity of exhaust gases in the manifold and battery cyclones will require reconstruction of building structures. Therefore, under current conditions, there is no need for such difficult reconstruction. The research conducted may be of both theoretical and practical interest in the modernization of existing and the design of new sinter plants.