OCR Text |
Show This study is based on data collected from trials during which simulated PSA gas and flexicoker gases were flred in varying amounts with a higher heat release fuel gas. The third gas blend considered consisted of varying H2/C02 combinations. The burners tested were of two designs. Data from PSA and H2/C02 blends result from raw gas burner trials, the flexicoker gas trials were conducted using an internal recirculation staged fuel burner design. However, in the latter case the low heating value flexicoker gas was introduced through a central gas nozzle similar to the raw gas burners, the higher heating value refmery gas was introduced through staged and secondary gas lances; this had the additional effect of inspirating furnace gases into the flame envelope causing further NOx reduction, the furnace gas eduction rates have been quantified and allowed for in the analysis presented here. V. Low Heating Value Test Gases PSA off gas is primarily a mixture of hydrogen, methane and carbon dioxide that has a lower heating value in the range of 225 - 240 Btu/fe. The typical PSA off gas composition, while some variation will occur, can be simulated with a mixture of 31 % hydrogen, 14% methane, and 55 % carbon dioxide. The calculated adiabatic flame temperature for this fuel composition is 2814 OF with 2 % oxygen in the combustion products, which is relatively low when compared to the adiabatic flame temperature for natural gas which is 3300 to 3400°F depending on the excess air. Typically PSA off gas is fired in combination with other fuel gases. The range of PSA gas fired normally ranges from 40 % to 75% of the heat duty . Flexicoker off gas is primarily a mixture of hydrogen, carbon monoxide, methane, and nitrogen that has a lower heating value in the range of 125 - 140 Btu/fe. The typical flexicoker off gas composition can be simulated with a mixture of 40 % hydrogen, 1 % methane, and 59% nitrogen. The calculated adiabatic flame temperature for this fuel 5 |