206
Views
1
CrossRef citations to date
0
Altmetric
Research Article

Modeling of Fluidized Bed Combustion of Lignite with High Nitrogen Content Cotton Residue

, &
Pages 435-448 | Received 18 Jan 2019, Accepted 31 Oct 2019, Published online: 08 Nov 2019
 

ABSTRACT

A comprehensive system model, previously developed for prediction of combustion behaviors of Turkish lignites, lignite/hazelnut shell, and lignite/olive residue blends in a 0.3-MWt atmospheric bubbling fluidized bed combustor (ABFBC), is extended for modeling of co-combustion of Turkish lignite and cotton residue. Cotton residue has high nitrogen content (~4.1 wt% ar) unlike lignite (~0.9 wt% ar), olive residue (~1.6 wt% ar), and hazelnut shell (~0.5 wt% ar), which leads to relatively high emissions of nitric oxides (NOx) and nitrous oxide (N2O). For accurate prediction of emissions of NO and N2O, a sufficiently detailed NO and N2O formation and reduction reaction scheme is incorporated into the existing model. The assessment of the accuracy of the model is tested by comparing its predictions with the experimental data obtained in a 0.3-MWt ABFBC where a typical Turkish lignite is co-fired with limestone and cotton residue. Reasonable agreement is obtained between the predicted and measured O2, CO, CO2, SO2, NO, and N2O concentrations and temperature profiles. The results obtained in this study show that the addition of cotton residue increases emission of total nitrogenous species due to its high nitrogen content, but the main effect is observed in the increase of N2O formation. Furthermore, determination of the fuel nitrogen partitioning into char and volatiles and distribution of volatile nitrogen species are found to be the most important parameters for modeling of NO and N2O emissions in bubbling fluidized bed combustors.

Nomenclature

A0=

Adjustable parameter

Ci=

Concentration of the species i (mol/cm3)

dp=

Particle diameter (m)

M=

Molecular or atomic weight (g/mol)

rHCN=

Rate of HCN oxidation (mol/cm3.s1)

rC=

Rate of char combustion (mol/cm3.s1)

T=

Temperature (K)

xN=

Weight fraction of nitrogen in the fuel

xfc=

Weight fraction of fixed carbon in the fuel

xN,vol=

Weight fraction of volatile nitrogen in the fuel nitrogen

Subscripts

d=

Char

g=

Gas

Abbreviations

ar = As received=

Reprints and Corporate Permissions

Please note: Selecting permissions does not provide access to the full text of the article, please see our help page How do I view content?

To request a reprint or corporate permissions for this article, please click on the relevant link below:

Academic Permissions

Please note: Selecting permissions does not provide access to the full text of the article, please see our help page How do I view content?

Obtain permissions instantly via Rightslink by clicking on the button below:

If you are unable to obtain permissions via Rightslink, please complete and submit this Permissions form. For more information, please visit our Permissions help page.