Combustion, gaseous fuels staged

New units can be ordered having dry, low NO burners that can reduce NO emissions below 25 ppm on gaseous fuels in many cases, without back-end flue-gas cleanup or front-end controls, such as steam or water injection which can reduce efficiency. Similar in concept to low NO burners used in boilers, dry low NO gas turbine burners aim to reduce peak combustion temperatures through staged combustion and/or improved fuel—air mixing. 

Fuel-Staged Burners Use of fuel-staged burners is the preferred combustion approach for NO control because gaseous fuels typically contain little or no fixed nitrogen. Figure 27-36 illustrates a fuel-staged natural draft refineiy process heater burner. The fuel is spht into primaiy (30 to 40 percent) and secondary (60 to 70 percent) streams. Furnace gas may be internally recirciJated by the primaiy... 

When considering the possibility of using internal combustion drivers, evaluate process requirements and costs. If a low-cost, gaseous fuel is available, gas engines and gas turbines may surpass other drivers in economical installation and operation. In the initial process design stage, a method of establishing the cost of purchase, installation, and operation for drivers is needed. 

Among the additives which may be used as substitutes for these systems, intumescent additives seems to be particularly attractive. Fire protection of flammable materials (in particular, paints, varnishes and cellulose-based materials) by an intumescence process has been known for several years [1]. Intumescent technology has more recently found a place in polymer science as a method of providing flame retardancy to polymer formulations, especially polypropylene (PP) formulations [2]. These systems interrupt the self-sustained combustion of the polymer at its earliest stage, i.e. the thermal degradation with evolution of the gaseous fuels. 

Ionization is one of the later steps of combustion and is not the essential first step. The presence of ions formed by / rays from radium bromide makes no difference in the ignition temperatures of fuels.17 18 The primary step in combustion is the combination of oxygen molecules with fuel molecules, but as the temperature at which this combination occurs increases and the energy level of the molecules becomes greater, ionization occurs as a late stage of the process.111 The conclusion has been that ionization in gaseous explosions is mainly a thermal process and that the action of knock inducers and suppressors on combustion phenomena cannot be adequately explained on the basis of ionization effects. 

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