Cascade relationship between flow field characteristics and smoke emissions in the industrial reheating furnace

Abstract

Abstract The temperature control process of reheating furnace is time delay and highly nonlinear to result in large temperature difference fluctuation and low temperature accuracy, because the complex flow field characteristics obviously affect the on-line temperature distribution of furnace and slab. Up to date, it is urgent to find out the heat balance cascade law between the key factors. Therefore, it is necessary to deeply study the coupling characteristics of key flow field parameters such as the nozzle injection angle, the air–gas ratio and the preheating temperature on the combustion mechanism and the smoke emission, so as to ensure that the temperature control accuracy and the environmental protection as well as the energy saving requirements are met. Firstly, the dynamic equivalent heat transfer coefficient could be obtained according to the flow field law of air and gas in the furnace. Secondly, according to coupling characteristics of the combustion model, the radiation model and the NOx generation model, the cascade relationship among the key combustion parameters, the temperature accuracy and the smoke emission was deeply analyzed. Finally, based on the actual engineering case, the combustion process optimization was implemented, and the practical problems such as the unstable furnace temperature and the excessive emission of pusher reheating furnace were successfully solved. On the basis of strictly controlling the temperature, the gas consumption and flue gas pollutant emission were significantly reduced via the new methods, which not only matched the downstream production but also satisfied the requirement of environmental protection.