Research on the Influence of Combustion Methods on NOx Emissions from Co-combustion of Various Tannery Wastes

To further increase combustion efficiency and reduce nitrogen oxide pollution caused by tannery wastes, three raw materials, including tannery sludge, chrome-tanned buffing dust, and chrome shavings, were burned together in a dual-bed model reactor under various conditions. In addition, a thermogravimetric analysis of co-combustion of three tannery wastes was studied in this study, which was conducive to understanding the combustion characteristics and positive effects. The comprehensive combustibility index S, the flammability index K-r, and the stable combustion characteristic index G(b) all increased when the tannery sludge was blended with chrome-tanned buffing dust and chrome shavings, indicating that the combustion behavior was improved by co-combustion. For normal combustion, decreasing the gas volume flow and temperature resulted in a decrease in the oxidation of nitrogen compounds, consequently lowering the NOx emission. During air staged combustion, at an appropriate secondary gas ratio of about 10-40%, the NOx reduction would be increased from 10.9 to 19.3%. By increasing the tertiary gas volume flow from 0.2 to 1.1 L/min in decoupling combustion, an average relative NOx reduction efficiency of 47% was attained compared with normal combustion. The results offered a viable technology that resulted in a lower NOx emission and realized the application of decoupling combustion.