More efficient and environmentally friendly combustion of low-rank coal in a down-fired boiler by a simple but effective optimization of staged-air windbox

Lun Ma, Qingyan Fang, Chungen Yin, Liu Zhong, Cheng Zhang, Gang Chen

Research output: Contribution to journalJournal articleResearchpeer-review

11 Citations (Scopus)

Abstract

Down-fired boilers are commonly used to burn low-rank coals for power generation. However, they often have operational problems such as low char burnout and high NOx emissions. This paper comprehensively investigates how to mitigate such problems in a 300 MWe down-fired utility boiler burning a low-volatile coal by optimizing the staged-air windbox structure. First, experiments and simulations are conducted on a 1:1-scaled model of the staged-air windbox to study the cold air flow in the original and two new windbox structures for understanding the effect of different staged-air windbox structures. Then, combustion simulations are performed for the utility boiler to further study the influence of the newly designed staged-air windboxes on the boiler performance, based on which the optimization scheme of the staged-air windbox in the boiler is more reliably concluded. Finally, the utility boiler is retrofitted by using a newly designed staged-air windbox. Performance tests are made for the boiler before and after the retrofit. The new staged-air windbox is confirmed to greatly improve the performance of the utility boiler, e.g., NOx reduction by 20.7% and thermal efficiency increase by nearly 2 percentage points (from 88.76% to 90.48%) at full load. The idea of the new staged-air windbox design can be readily implemented into down-fired boilers of this kind for more efficient and environmentally friendly firing of low-rank coal for heat and power generation.
Original languageEnglish
Article number106118
JournalFuel Processing Technology
Volume194
Number of pages9
ISSN0378-3820
DOIs
Publication statusPublished - Nov 2019

Keywords

  • Low-rank coal
  • Down-fired boiler
  • High efficiency
  • Low emissions
  • Staged-air windbox

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