Computational fluid dynamics investigation on the effect of co-firing semi-coke and bituminous coal in a 300 MW tangentially fired boiler

Abstract

In this paper, the effect of co-firing semi-coke in a 300 MW tangentially fired boiler was numerically investigated. The results indicate that the incomplete combustion heat loss and NO _x emission both increase with semi-coke co-fired ratio. Semi-coke may be injected into the furnace at a different height, which can lead to different thermal efficiency and NO _x emission. It is suggested that semi-coke should not be fed from the top or bottom layer burners, since this could give rise to high carbon content respectively in fly ash and bottom slag. In addition, injecting semi-coke from the top burners could significantly increase the NO _x emission. Under 1/2 co-firing ratio, the optimal fuel allocation is that feeding semi-coke from the B, D, and E layer burners. The growth in semi-coke particle size could increase the unburned carbon loss and NO _x emission. It is highly recommended to reduce the unburned carbon loss under semi-coke co-fired condition by increasing the stoichiometric ratio of primary air for semi-coke. As it is increased from 0.25 to 0.3, the combustion efficiency of the co-fired condition is 99.47%, the same as when only firing bituminous coal, and the NO _x emission is about 30% higher.

Keywords

Pulverized boiler semi-coke co-firing computational fluid dynamics

Get full access to this article

View all access options for this article.

References

Zhang

et al.

Study on the structural evolution of semi-chars and their solvent extracted materials during pyrolysis process of a Chinese low-rank coal. Fuel 2018; 214: 363–368.

Dharmalingam

Sivakumar

Anandhi

et al.

Improved method to mitigate the effect of coal fuel switching on critical process parameters of a steam generator in a thermal power plant. Proc IMechE, Part A: J Power Energy 2011; 225: 1026–1040.

Chen

Lin

et al.

Pollutant emission characteristics and interaction during low-temperature oxidation of blended coal. J Energy Inst 2016; 89: 40–47.

Hassan

Imran

Akbar

et al.

Impacts of proposed utilization of various indigenous coal reserves for power generation on production cost and environment. Proc IMechE, Part A: J Power Energy 2011; 225: 233–241.

Yao

Zhu

. Experimental study on nitrogen transformation in combustion of pulverized semi-coke preheated in a circulating fluidized bed. Energy Fuels 2015; 29: 3985–3991.

Ouyang

Zhu

et al.

The effect of limestone on SO₂ and NO _x emissions of pulverized coal combustion preheated by circulating fluidized bed. Fuel 2014; 120: 116–121.

Wang

Song

Zhi

et al.

Combustion kinetics of Chinese Shenhua raw coal and its pyrolysis carbocoal. J Energy Inst 2017; 90: 624–633.

Yao

Zhu

et al.

Experimental study on preheated combustion of pulverized semi-coke. J Therm Sci 2015; 24: 370–377.

Valdés

Chejne

Marrugo

et al.

Energy evaluation of pelletized mixtures of IWTP sludge and coal-fired boiler ashes by co-combustion: Identification of synergistic effects. Appl Therm Eng 2017; 124: 191–201.

10.

Wang

Liu

Zhang

et al.

A study on coal properties and combustion characteristics of blended coals in Northwestern China. Energy Fuels 2011; 25: 3634–3645.

11.

Bhuiyan

Blicblau

Naser

. Co-firing of biomass and slagging in industrial furnace: A review on modelling approach. J Energy Inst 2017; 90: 838–854.

12.

Feng

et al.

Numerical study of co-firing biomass with lean coal under air–fuel and oxy-fuel conditions in a wall-fired utility boiler. Energy Fuels 2017; 31: 5344–5354.

13.

Zhang

Wang

Wei

et al.

Numerical modeling and experimental investigation on the use of brown coal and its beneficiated semicoke for coal blending combustion in a 600 MWe utility furnace. Energy Fuels 2015; 29: 1196–1209.

14.

Yin

. Effects of moisture release and radiation properties in pulverized fuel combustion: A CFD modelling study. Fuel 2016; 165: 252–259.

15.

Wang

et al.

CFD investigation on combustion and NO _x emission characteristics in a 600 MW wall-fired boiler under high temperature and strong reducing atmosphere. Appl Therm Eng 2017; 126: 407–418.

16.

Drosatos

Nikolopoulos

Agraniotis

et al.

Numerical investigation of firing concepts for a flexible Greek lignite-fired power plant. Fuel Process Technol 2016; 142: 370–395.

17.

Jayanti

Saravanan

Sivaji

. Assessment of retrofitting possibility of an Indian pulverized coal boiler for operation with Indian coals in oxy-coal combustion mode with CO₂ sequestration. Proc IMechE, Part A: J Power Energy 2012; 226: 1003–1013.

18.

Álvarez

Yin

Riaza

et al.

Oxy-coal combustion in an entrained flow reactor: Application of specific char and volatile combustion and radiation models for oxy-firing conditions. Energy 2013; 62: 255–268.

19.

Panagiotis

Athanasios

Nikolaos

et al.

Numerical investigation of NO _x emissions for a flexible Greek lignite fired power plant. J Energy Eng 2016; 142: 1–21.

20.

Hanson

Salimian

Survey of rate constants in the N/H/O system. In: Gardiner

(ed). Combust chemistry, New York: Springer US, 1984, pp. 361–421.

21.

De Soete

. Overall reaction rates of NO and N₂ formation from fuel nitrogen. Symp Int Combust 1975; 15: 1093–1102.

22.

Kambara

Takarada

Yamamoto

et al.

Relation between functional forms of coal nitrogen and formation of nitrogen oxide (NO _x ) precursors during rapid pyrolysis. Energy Fuels 1993; 7: 1013–1020.

23.

Visona

Stanmore

. Modeling NOx release from a single coal particle II. Formation of NO from char-nitrogen. Combust Flame 1996; 106: 207–218.

24.

Chen

et al.

Effect of outer secondary-air vane angle on the flow and combustion characteristics and NO _x formation of the swirl burner in a 300-MW low-volatile coal-fired boiler with deep air staging. J Energy Inst 2017; 90: 239–256.

25.

Wang

Che

. Investigation on the NO reduction with coal char and high concentration CO during oxy-fuel combustion. Energy Fuels 2012; 26: 7367–7377.

26.

Chen

et al.

Effect of outer secondary air vane angles on combustion characteristics and NOx emissions for centrally fuel rich swirl burner in a 600-MWe wall-fired pulverized-coal utility boiler. Appl Therm Eng 2017; 125: 951–962.

27.

Liu

et al.

Effects of air staging conditions on the combustion and NO _x emission characteristics in a 600 MW wall fired utility boiler using lean coal. Energy Fuels 2013; 27: 5831–5840.

28.

Ren

Zeng

et al.

Numerical simulation of flow, combustion, and NO _x emission characteristic in a 300 MW down-fired boiler with different of a ratios. Numer Heat Transfer Part A: Appl 2012; 62: 231–249.

Supplementary Material

Please find the following supplemental material available below.

For Open Access articles published under a Creative Commons License, all supplemental material carries the same license as the article it is associated with.

For non-Open Access articles published, all supplemental material carries a non-exclusive license, and permission requests for re-use of supplemental material or any part of supplemental material shall be sent directly to the copyright owner as specified in the copyright notice associated with the article.

0.00 MB

0.42 MB