Fate of coal nitrogen during combustion

✍ Scribed by S.L. Chen; M.P. Heap; D.W. Pershing; G.B. Martin

• Publisher: Elsevier Science
• Year: 1982
• Tongue: English
• Weight: 679 KB
• Volume: 61
• Category: Article
• ISSN: 0016-2361
• DOI: 10.1016/0016-2361(82)90023-0

✦ Synopsis

A total of 21 coals covering all ranks have been burned under a wide variety of conditions to ascertain the impact of coal properties on thefate of fuel nitrogen. Fuel NO was identified with a nitrogen-free oxidant consisting of Ar-02C02. In general, under fuel-lean conditions fuel NO formation increases with increasing fuel nitrogen content; however, other fuel properties also significantly affect the fate of fuelbound nitrogen during combustion. In particular, fuel nitrogen conversion appears to be greater with coals containing a high fraction of volatile reactive nitrogen. Under fuel-rich conditions measurements of first-stage and exhaust-species concentrations suggest that the optimum stoichiometryfor minimum emissions is a function of fuel composition. As first-stage stoichiometry is decreased, the NO formed in the first stage decreases, but other oxidizable gas nitrogen species increase as does nitrogen retention in the char. Total fixed nitrogen generally increases with increasing fuel nitrogen and correlates well with excess air exhaust emissions. The distribution of the total fixed nitrogen species leaving the first stage is strongly dependent upon the coal composition. Of the 12 coals tested in detail, only 1 (the high-volatile B bituminousfrom Utah) produced high HCN concentrations. The low-volatile Pennsylvania anthracite formed almost no HCN or NH, even under extremely fuel-rich conditions. In general, the first stage NO percentage decreased significantly with decreasing coal rank from anthracite to lignite. Conversely, the relative importance of NH, grew with decreasing rank. HCN was greater than NH, in all bituminous tests, but less than NH, with all subbituminous and lignite coals.