THERMAL SCIENCE

International Scientific Journal

Huanbao Fan

,

Junxiao Feng

,

Wei Bai

,

Yujie Zhao

,

Weidong Li

,

Jun Gao

,

Changpeng Liu

,

Lidi Jia

NUMERICAL SIMULATION ON HEATING PERFORMANCE AND EMISSION CHARACTERISTICS OF A NEW MULTI-STAGE DISPERSED BURNER FOR GAS-FIRED RADIANT TUBES

ABSTRACT
To enhance the temperature uniformity and NOx reduction performance of the gas-fired radiant tubes, we proposed a new multi-stage dispersed burner based on fuel-staging combustion technology in this study. The effect of fuel nozzle structural parameters, including secondary fuel nozzle distance, D, (30 mm, 50 mm, 70 mm), secondary fuel nozzle diameter, ds, (2-6 mm), and tertiary fuel nozzle diameter, dt, (2.5 mm, 5 mm, 7.5 mm, 10 mm) on the flow field, temperature distribution, NOx generation and thermal efficiency were analyzed by numerical simulations. The results show that the multi-stage dispersed fuel nozzle could slow down the combustion rate and form a low oxygen dilution zone in the reaction process, reducing the maximum combustion temperature and NOx emission. With the increase of the secondary fuel nozzle distance, the NOx concentration at the outlet decreased from 69.0 ppm to 54.6 ppm, and a decrease of 20.9%. When the secondary fuel nozzle diameter increased from 2-6 mm, the maximum wall temperature difference gradually increased 72.8-76.3 K. The NOx emission at the outlet first decreased, then increased, and was as low as 45.6 ppm at a 5 mm diameter. Furthermore, increasing the tertiary fuel nozzle diameter could reduce the maximum wall temperature difference and NOx emission, and improve thermal efficiency. When dt = 7.5 mm, the overall performance of the radiant tube was the best, and the outlet NOx concentration, wall temperature difference and thermal efficiency were 46.1 ppm, 73.0 K, 63.7%, respectively.
KEYWORDS
Radiant tube, Fuel-staging, NOx emission, Dilution combustion, temperature uniformity
PAPER SUBMITTED: 2021-07-23
PAPER REVISED: 2021-09-30
PAPER ACCEPTED: 2021-10-04
PUBLISHED ONLINE: 2021-11-06
DOI REFERENCE: https://doi.org/10.2298/TSCI210723323F
CITATION EXPORT: view in browser or download as text file
THERMAL SCIENCE YEAR 2022, VOLUME 26, ISSUE Issue 5, PAGES [3787 - 3801]
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Numerical simulation on heating performance and emission characteristics of a new multi-stage dispersed burner for gas-fired radiant tubes

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