Effects of Cofiring Coal and Biomass Fuel on the Pulverized Coal Injection Combustion Zone in Blast Furnaces

Gyeong-Min Kim,Jae Hyung Choi,Chung-Hwan Jeon,Dong-Ha Lim

doi:10.3390/en15020655

Gyeong-Min Kim, Jae Hyung Choi + Show 2 more

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https://doi.org/10.3390/en15020655

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Abstract

CO2 emissions are a major contributor to global warming. Biomass combustion is one approach to tackling this issue. Biomass is used with coal combustion in thermal power plants or with blast furnaces (BFs) because it is a carbon-neutral fuel; therefore, biomass provides the advantage of reduced CO2 emissions. To examine the effect of co-firing on pulverized coal injection (PCI) in BFs, two coals of different ranks were blended with the biomass in different proportions, and then their combustion behaviors were examined using a laminar flow reactor (LFR). The PCI combustion primarily functions as a source of heat and CO to supply the upper part of the BF. To create a similar PCI combustion environment, the LFR burner forms a diffusion flat flame with an oxygen concentration of 26% with a flame temperature of ~2000–2250 K at a heating rate of 105 K/s. The combustion characteristics, such as the flame structure, burning coal particle temperature, unburned carbon (UBC), and CO and CO2 emissions were measured to evaluate their effect on PCI combustion. With the increase in the biomass blending ratio, the brightness of the volatile cloud significantly increased, and the particle temperature tended to decrease. The fragmentation phenomenon, which was observed for certain coal samples, decreased with the increase in the biomass blending ratio. In particular, with an increase in the biomass blending ratio, the optimum combustion point occurred, caused by the fragmentation of coal and volatile gas combustion of biomass.

Highlights

At the 2015 Paris Conference of the Parties on Climate Change, the South Korean government joined most countries in agreeing to reduce greenhouse emissions (GHGs) [1]
CO2 emissions occur during the reduction of iron ore in blast furnaces (BFs), and the complete combustion of coal occurs in thermal power plant boilers
Two types of coal were chosen for this study, an Indonesian sub-bituminous coal (Coal A), an Australian bituminous coal (Coal B) and Malaysian wood pellet biomass was used

Summary

Introduction

At the 2015 Paris Conference of the Parties on Climate Change, the South Korean government joined most countries in agreeing to reduce greenhouse emissions (GHGs) [1]. The operators of one Korean thermal power plant are attempting to reduce CO2 emissions using various methods such as combusting biomass, reducing the fuel consumption ratio, and increasing the renewable energy ratio. Among these technologies, biomass is extensively used in thermal power plants. Five thermal power plants in South Korea use a 3–5% biomass mix with coal to reduce CO2 emissions; this technology is known as co-combustion. Because biomass fuel is carbon neutral, the co-combustion of biomass is an important technology for reducing CO2 emissions in thermal power plants and BFs [2,3].

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