Furnaces burners

Velocity flame stoppers have been used for feeding waste fuel gas to furnace burners when the gas can become flammable due to contamination with air. They have also been used for feeding waste or depleted air streams to furnaces when the air streams can become contaminated with flammable gases (Howard 1982). It should be noted that a furnace pressure transient may render this device ineffective and consideration should be given to providing an upstream detonation flame arrester. In this arrangement a demand will only be placed on the detonation flame arrester when the velocity flame stopper fails. Therefore, detonation flame arrester maintenance should be minimal. 

For walls B-l and B-2, which had plywood as the interior finish, the heat release rate from the furnace (burners plus wall), heat release rate from the wall, and potential heat release rate are shown in Figures 5 and 6. The difference between the potential heat release rate and the wall contribution is the possible contribution by CO. 

An afterburner can be expected to achieve between 80 % and 98 % efficiency for burning the combustible particulates emitted from the rotary furnace. Hot gases from the afterburner can be ducted through a recuperator and can assist in preheating the combustion air to the main furnace burner. Recuperators offer an energy saving of up to 15 %. 

Finally, the fuel gas was distributed throughout the refinery to a number of furnaces. At each furnace, there was a fuel-gas KO drum. These drums also filled up. Only when naphtha was observed raining down from the furnace burners and a number of fires had started did operating personnel notice that the fuel-gas system was full of naphtha. 

The recent development of Claus plant sulfur furnace burners that can handle acid gas streams containing significant percentages of ammonia can improve the economics of simple sour water stripper-sulfur recovery unit systems. Such burners are available from LD Duiker, B. V. of Holland (1990) and Lurgi Corporation (Fischer and Kriebel, 1988). See Chapter 8 for additional information on sulfiir plant burners. 

Reaction furnace burner design varies considerably, from the simple coaxial type with the acid gas injected through a central tube and the combustion air through an outer annular. space, to the complex, high-intensity type designed for efficient combustion, and used especially when ammonia and hydrocarbons are present in the feed gas (Stevens et al., 1996 Fischer and Kriebel, 1988 Babcock Duiker, 1983 Schalke et al., 1989). 

Special techniques have to be used for processing gas streams containing appreciable amounts of ammonia such as effluents from refinery sour water strippers. The ammonia must be destroyed in the reaction furnace to avoid deposition of ammonium salts on the cataly.st beds. Two methods are available to successfully accomplish this. The first method involves a split-flow reaction furnace design the second requires a high-intensity reaction furnace burner. It is essential that the ammonia be almost completely destroyed because ammonia concentrations as low as SOO to 1,000 ppmv can cause plugging problems (Anon., 1973). 

The COPE process is illustrated in Figure 8-13. This Claus process modification includes the addition of a specialized reaction furnace burner and a recycle blower, which are the keys to the effectiveness of the process. Enriching the combustion air with oxygen increases the reaction furnace tempterature. For a rich gas feed, the typical maximum temperature of 2,700° to 2,900°F is reached when the oxygen content of the air reaches approximately 45 vol%. To avoid exceeding this temperature limitation, the COPE process recycles cool gas from downstream of the first condenser back to the reaction furnace. As the level of oxygen... 

Figure 8-15. Lurgi OxyClaus reaction furnace burner. Stevens et el., 1996 ...

Figure 8-16 depicts a SURE reaction furnace burner being installed in a North American refinery Claus plant. The SURE burner, like the Lurgi OxyClaus burner, can operate at oxygen concentration levels of 45 vol%, achieving Claus plant capacity increases of about 80%. See Figure 8-12. Further details regarding the SURE process are provided by Chen et al. (1995), Hull et al. (1995), and Watson et al. (1995,1996).

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