Numerical study on characteristics of combustion and pollutant formation in a reheating furnace

Energy consumption of fuel-fired industrial furnace accounts for about 23% of the national total energy consumption every year in China. Meanwhile, the reduction of combustion-generated pollutants in furnace has become very important due to the stringent environment laws and policy introduced in the recent years. It is therefore a great challenge for the researchers to simultaneously enhance the fuel efficiency of the furnace while controlling the pollution emission. In this study, a transient three- dimensional mathematical combustion model coupled with heat transfer and pollution formation model of a walking-beam-type reheating furnace has been developed to simulate the essential combustion, and pollution distribution in the furnace. Based on this model, considering nitrogen oxides formation mechanism, sensitivity study has been carried out to investigate the influence of fuel flow rate, air-fuel ratio on the resultant concentration of nitrogen oxides in the flue gas. The results of present study provide valuable information for improving the thermal efficiency and pollutant control of reheating furnace

Numerical Simulation Study of Gas-Solid Heat Transfer and Decomposition Processes of Limestone Calcined with Blast Furnace Gas in a Parallel Flow Regenerative Lime Kiln

Quicklime is an essential reducing agent in the steel smelting process and its calcination from limestone is accompanied by considerable energy consumption. As a relatively economical lime kiln, the Parallel Flow Regenerative (PFR) lime kiln is used as the main equipment for the production of quicklime by various steel industries. PFR lime kilns generally use natural gas as the fuel gas. Although natural gas has a high calorific value and is effective in calcination, with the increasing price of natural gas and the pressure saves energy and protect the environment, it makes sense of exploring the use of cleaner energy sources or other sub-products as fuel gas. The use of blast furnace gas (BFG) as a low calorific value fuel gas produced in the steel smelting process has been of interest. This paper therefore develops a set of mathematical models for gas-solid heat transfer and limestone decomposition based on a Porous Medium Model (PMM) and a Shrinking Core Model (SCM) to numerically simulate a PFR lime kiln using BFG in order to investigate the feasibility of calcining limestone with low calorific fuel gas and to provide a valuable reference for future development of such processes and the kiln structure improvement