مدل شبیه سازی آنلاین از فرایند گرم کردن مجدد تحت فشار تخته سنگ در یک کوره

This paper presents an online simulation model of the slab-reheating process in a pusher-type furnace in Acroni d.o.o. in Slovenia. The simulation model is connected to the information system of a hot-processing plant that provides online measuring and charging data of the furnace. The simulation model considers the exact geometry of the furnace enclosure, including the geometry of the slabs inside the furnace. A view-factor matrix of the furnace enclosure was determined using the Monte Carlo method. The heat exchange between the furnace gas, the furnace wall and the slab’s surface is calculated using a three-temperature model. The heat conduction in the slabs is calculated using the 3D finite-difference method. The model was validated using measurements from trailing thermocouples positioned in the test slabs during the reheating process in the furnace. A graphical user interface (GUI) was developed to ensure a user-friendly presentation of the simulation-model results.

A computer-controlled hot-rolling process for steel slabs requires high-quality reheated slabs in terms of time, temperature, thermal profile and furnace atmosphere. Each steel slab has to be reheated at a suitable temperature for hot-rolling with the prescribed temperature difference inside the slab. Temperature differences during the whole reheating process should not cause the maximum-allowed thermal stress inside the slab to be exceeded. The slabs are reheated in the gas-fired pusher-type furnace (Fig. 1). The furnace has six control zones: the upper and lower preheating zones, the upper and lower heating zones, and the left and right soaking zones. The material flow through the furnace is discontinuous, with the movement happening in push steps. At each push step the pushing machine pushes all the slabs until the slab at the exit drops out from the furnace. The length of the pushing step depends on the width of the discharged slab. The number of slabs inside the furnace can vary and depends on the width of the individual slabs.

The presented online simulation model of the steel-slab reheating process in a pusher-type furnace allows the monitoring of non-measurable values (temperature fields of slabs in the furnace). It considers the exact geometry in thermal radiation calculations of the furnace enclosure, including the geometry of the slabs inside the furnace. The algorithms are optimized to allow online simulation. The thermal radiation of the surfaces is calculated online for the whole furnace enclosure. The geometric relations between the individual surfaces in the furnace enclosure are written in the form of a view-factor matrix. The matrix for the whole furnace enclosure, including slabs, is determined by the Monte Carlo method. The matrix is determined once before the simulation. At the beginning of the simulation the model reads the view-factor matrix data. The temperatures of the furnace-floor segments are calculated on the basis of heat balance. Good agreement between the measured and the calculated heating curves shows that the model includes the main physical phenomena occurring during the reheating process in the pusher-type furnace. The model is implemented online in Acroni d.o.o. Jesenice, where it has been used to monitor slab reheating during the regular production process since September 2004.