An Energy Analysis of a Slab Preheating Chamber for a Reheating Furnace

Abstract

Abstract. The iron and steel industry is one of the major industries for developing countries, and it is ranked as one of the industrial sectors that have the highest energy consumption. It is also served as a primary industry that provides materials to secondary industries as well. This present study focuses on a slab, a product from a steelmaking process, which will be sent to a hot-rolling mill to form a final product. Before the rolling process, slab is heated to a proper temperature by charging into a reheating furnace. Heat is generated by a combustion process from direct-fired burners. In general, heat loss from the reheating furnace occurs by several mechanisms including the flue gas loss. Although a recuperator is used to reduce heat loss by recovering some of that to preheat the combustion air, the exit flue gas temperature is still as high as 350-450C. This research paper aims for the investigation of the energy efficiency resulted from the implementation of a slab preheating chamber before charging into a reheating furnace. Four different sizes of the preheating chamber are selected as the case studies for the energy analysis. Another consideration includes the acid dew point of the flue gas as the lowest criteria for the flue gas temperature. The result indicates that the flue gas temperatures are above the acid dew point for all four cases under consideration. The slab temperatures increase from the ambient temperature of 30 o C to 59.52 o C, 75.98 o C, 84.98 o C and 89.46 o C, respectively, before begin charged into the reheating furnace. As a result, the fuel energy consumption after the implementation of the reheating chamber is reduced by 0.94%, 1.46%, 1.75% and 1.89%, respectively comparing to the furnace without the reheating chamber. The reheating furnace efficiency also increases from 69.88% to 70.54%, 70.92%, 71.13% and 71.22%, respectively.

Performance evaluation of a walking beam type reheating furnace based on energy and exergy analysis

“…The energy efficiency of the furnace is found to be 71.01%, which is higher than the results in cited studies. The benefit of preheated slabs has also been confirmed by Kangvanskol et al [16]. Therefore, the comparison helps to validate the calculation results and proves the advantage of preheated slabs in the current reheating furnace.…”

“…On the other hand, the scale formation as a separate input energy flow occurs in the present paper and Ref. [16]. Compared with their results, the energy flow due to scale formation in the present reheating furnace is slightly higher.…”

“…2.18%) is lower compared with those in the Refs. [3,7,16,32] which shows a good insulation situation of the present walking beam type reheating furnace. Moreover, the energy flow of skid loss accounts for 12.82% which is closer to that in Ref.…”

“…Recently, numerous studies have been done on heating furnace [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Relatively thorough studies were carried out on the reheating furnace by Han et al from 2007 to 2012 [3][4][5][6][7][8].…”

“…Nevertheless, the temperature of the flue gas exited from the heat exchanger was still high. Kangvanskol et al [16] proposed a slab preheating chamber to further recover the energy of flue gas to preheat slabs before charged into the furnace. They reported that the fuel consumption reduced, and the energy efficiency increased due to the implementation of the slab preheating chamber.…”