Title:
Experimental Study on the Biomass-biomass Co-combustion for Reducing NOx in a Fluidized-bed Combustor: A Comparison between the Co-firing Techniques
Author(s):
Kuprianov, V.I., Ninduangdee, P.
Document(s):
Paper
Abstract:
This work was performed to explore the potential of three co-firing methods for the reduction of NOx in a fluidized-bed combustor. Pelletized rice husk (as a base fuel) was co-fired with moisturized rice husk (secondary fuel) in this reactor using silica sand as the bed material. Four groups of experiments, for (1) conventional combustion of rice husk pellets (a base case), (2) co-firing pre-mixed fuels (using bottom air injection), (3) co-firing using fuel staging (with bottom air injection), and (4) co-firing using a reburning method (combining fuel staging and air staging), were performed at a 200 kWth heat input to the reactor. In each test series, the energy fraction of the secondary fuel in the total fuel supply (EF2) ranged from 0 to 0.25, with excess air (EA) varying from 20% to 80%. In the tests for reburning, the secondary-to-total air ratio (SA/TA) ranged from 0.1 to 0.4 at each EA. In a test run under fixed operating conditions, temperature and gas concentrations (O2, CO, CxHy as CH4, and NOx as NO) were recorded along the combustor height, as well as at stack. The findings revealed that the effects of EF2, EA, and SA/TA on combustion and emission characteristics of the reactor were substantial. An optimization analysis was performed to determine the optimal EF2, EA, and SA/TA leading to minimal emission costs of the applied co-firing methods. Under optimum operating conditions, the combustor ensures high (.99%) combustion efficiency with minimum emission costs and reduced NOx emissions: by 15% when co-firing pre-mixed fuels, by 40% for the fuel-staged co-combustion with bottom air injection, and by about 50% when using the reburning technique.
Keywords:
biomass, co-firing, NOx emissions, fluidized bed
Topic:
Biomass Conversion Technologies for Heating, Cooling and Electricity
Subtopic:
Biomass and Bioliquids Combustion for Small and Medium Scale Applications
Event:
25th European Biomass Conference and Exhibition
Session:
2AO.5.5
Pages:
384 - 392
ISBN:
978-88-89407-17-2
Paper DOI:
10.5071/25thEUBCE2017-2AO.5.5
Price:
FREE
