Fuel nitrogen content

The objective of one of the papers, which was a part of Orlanders thesis [9], was to study the effects of the bed stoichiometric ratio (SRb) (air factor of conversion system) and fuel nitrogen content on the formation of various gaseous species (O2, CO, CO2, H2 and NO) in the interstitial gas, off-gas and flue gas. 

Figure 5. Fuel nitrogen content as it influences subscale combustor NOx emissions...

Effect of fuel nitrogen content on total and From Grumer (1979). 

Figure 7. Importance of fuel nitrogen content. All data taken in AR/O2/CCL, tunnel furnace, ultrasonic nozzle, 5% excess 02 (Reproduced with permission from Ref. 16. Copyright 1979, The Combustion Institute.)...

Turner, D. W., R. L. Andrews, and C. W. Siegmund, "Influence of combustion modification and fuel nitrogen content on nitrogen oxides emissions from fuel oil combustion," presented at 64th Annual AIChE Meeting, San Francisco, Calif., American Institute of Chemical Engineers, New York, November 1971. 

Tests were performed with middle distillate fuels produced by the SCR-II, H-Coal, and EDS processes. The composition of these fuels represented significant variations in the fuel-hydrogen content, the fuel-nitrogen content, and the mix of characteristic hydrocarbon compounds. 

Combustion tests of fuel oil blends derived from the Exxon Donor Solvent (EDS) process were carried out in a laboratory 50 hp test boiler and a commercial 1425 hp boiler. All tests showed that coal derived fuel oils burn cleanly compared to petroleum fuels with low levels of smoke and particulates. Emissions of N0X were related to fuel nitrogen content for both the petroleum and coal-derived fuels. 

The emission results from the combustion tests, along with the PNA analyses of the fuels, are shown in Table II. In agreement with previous work 02,3), particulates and smoke from EDS fuel oil combustion were generally low relative to petroleum fuel oils. N0X emissions tended to be higher due to the higher fuel nitrogen content of EDS fuel oils. 

The SRC, due to their relatively high fuel nitrogen contents, have a high N0X formation potential under conventional firing conditions. However, staging the combustion air can result in acceptably low N0X emissions without jeopardizing their combustion efficiencies. 

TABLE III. NOy Emissions as a Function of Fuel Nitrogen Content... 

The conversion from fuel nitrogen to ammonia in the gasifier was found to be around of 60-65% for all fiiels. The conversion ratio was independent of fuel type and fuel nitrogen content. No dependency on operational parameters of the gasifier was found. 

Based on the volatiles composition shown above calculations were performed at 10 v-% O2, air-to-fuel ratio A of 1.2, a bed temperature of 850°C, a residence time of 3 s, and a fuel-nitrogen content of 1 w-%. In accordance to the results of Wartha et al [18] HCN was considered in the volatiles of the biomass fuel. The ratio of HCN to the total volatile N was assumed 0.2. Singe the composition of the volatiles and the ratio of HCN and NH3 are uncertain, this parameter was varied in a wide range. To reduce the amount of calculations standard conditions were defined. Coming from these each parameter was varied one by one as indicated in Table 2. 

Modification and Fuel Nitrogen Content on Nitrogen Oxides Emissions from Fuel Oil Combustion, Esso Research and Engineering Co. Report, Linden, N.J. 1971. 

Proximate and ultimate analysis data are also available for other agricultural biomass fuels such as rice hulls, vineyard prunings, and other related potential opportunity fuels. These are shown in Table 5.3. Note the variability in these fuels with respect to moisture and ash contents. Note, also, the variability in fuel nitrogen contents. The cotton gin trash, vineyard prunings, and rice hulls are particularly high in nitrogen content. 

---