Numerical analysis on effect of blend ratio on co-combustion characteristics of semi-coke and bituminous coal in swirl burner

ABSTRACT

Semi-coke is the coproduct of low-rank coal in the preparation of oil and gas, but the current utilization rate of fine-powder semi-coke is low, which limits the development of the low-rank coal pyrolysis industry. This paper uses the numerical simulation method to study the co-combustion characteristics of a large proportion of bituminous coal mixed with semi-coke in a swirl burner. The results show that, in the primary combustion region, with the increase of the blend ratio of semi-coke, the flue gas temperature and NO concentration are lower, and the O₂ concentration increase is higher. In the over-fired air (OFA) nozzle area, with the increase of the blend ratio of semi-coke, the flue gas temperature and NO concentration are higher, and O₂ concentration is lower. In addition, with the increase of the blend ratio of semi-coke, the main combustion position of the fuel is transferred to the vicinity of the OFA nozzle area, which weakens the degree of air-staging combustion of the furnace. The synergistic effect of co-combustion of semi-coke and bituminous coal helps to reduce the NO concentration at the furnace outlet and improve the combustion efficiency. By comprehensive considering the stable operation of the boiler, burnout rate, and NO emission concentration, the recommended blend ratio of semi-coke should not exceed 60%.

KEYWORDS:

• Large-scale semicoke co-combustion
• Swirl burner
• Synergistic effect
• Burnout
• NOx reduction

Acknowledgments

This work is supported by the Open topic of State Key Laboratory of clean and efficient coal-fired power generation and pollution control (Grant No. D2021Y001).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Open topic of State Key Laboratory of clean and efficient coal-fired power generation and pollution control [D2021Y001].