MODELLING OF A SLAB REHEATING FURNACE RETROFITTED WITH REGENERATIVE BURNERS

摘要

Several measures are currently under consideration, in the steel manufacturing industry, in order to reduce its CO_2 production. Namely, in the hot mills, introducing still-warm slabs in the reheating furnace and increasing heat recuperation on the furnace flue gas , appear rather obvious. However, to be economically attractive, they should be implemented through an increase of furnace capacity. This may be achieved by retrofitting regenerative burners in existing furnaces. The aim of this work, was to develop a tool allowing to quickly assess the furnace performance for different configurations of burners and different operating conditions, in order to select the most appropriate one(s). In particular, regarding the added regenerative burners, the following conditions are liable to an investigation ( location in the furnace, burner individual capacity, excess air,extracted" flue gas flow rate,regenerator efficiency). In the cases at hand, the reheating furnace is of the walking beam type. The furnace model is 1-D steady-state, taking into account the flow distribution as well as the heat generation, transfer and losses. As to the regenerators and the recuperators, they are modelled simply in terms of effectiveness. A problem arises in modelling as steady-state the operation of regenerative burners, since these devices are fundamentally cyclical. To take the measure of this problem, we have simulated ― separately ― the different phases of operation and compared the results. Such a study will be presented in the paper. Among the different industrial cases simulated with this model, we will present the following two ones : 1. Replacing all the existing (standard) burners by regenerative burners; 2. Replacing the burners of one heating zone only. It will be shown that for both schemes and for realistic burner performances, the efficiency of the whole installation is improved, and the furnace capacity is increased. If done properly, the latter configuration appears very attractive indeed.