Injection of Pulverized Coal and Natural Gas into Blast Furnaces for Iron-making: Lance Positioning and Design

Abstract

Injecting pulverized coal and natural gas into blast furnaces for ironmaking decreases metallurgical coke requirements, providing a net decrease in the CO₂ emissions and in many cases, operating costs associated with iron production. Ideally, the fuel would enter the raceway partially reacted and the injection would not have negative impacts on the equipment or process. Success in achieving this outcome is sensitive to the details of how the injection is implemented. Given this sensitivity and that it is difficult to make accurate, detailed observations in blast furnaces or devise representative pilot-scale experiments, computational fluid dynamics (CFD) has become a useful and complementary tool for the analysis and design of fuel injection methodologies. This study uses CFD to examine the interaction of the blast air and fuel flows in the blowpipe and tuyere nozzle for different fuel injection strategies. Important operating issues such as initiation of partial combustion and heat loads on the tuyere nozzle are examined. It was found that two key fuel injection strategies developed separately for coal and natural gas can be combined effectively in a single combined fuel lance that leverages a bluff body effect to help coal dispersion and has radial nozzles to improve natural gas combustion. The bluff body effect is a simple process whereby the interaction between the blast air flow and a thick-walled lance creates a wake that can impart coal dispersion without the complexity or costs of adding an auxiliary dispersive fluid, such as an annular swirling flow of air. The performance of this combined fuel lance is compared against two configurations for separate fuel lances.