Reformer burner

Natural gas systems with endothermic steam reformers often make use of the residual fuel from the anode in a reformer burner. Alternatively, the residual fuel could be combusted prior to a gas expander to boost performance. In an MCFC system, the residual fuel often is combusted to maximize the supply of CO2 to the cathode while at the same time providing air preheating. In an SOFC system, the residual fuel often is combusted to provide high-temperature air preheating. 

Any hydrogen-rich fuel not used in the fuel cells is returned to the reformer burner. The pressurized exhaust gases from the reformer burner are expanded in a turbocompressor, which compresses the process air to about 17 psig (2.4 atm). Process air is distributed to the fuel cell power sedion. to the reformer burner, and to an auxiliary burner. 

Start-up was effected by feeding methanol directly to the burner. The integrated reformer/burner reactor and the integrated PrOx reactor/cooler fabricated at IMM are shown in Figure 2.74. Characterization of the single devices and their assembly is still pending. 

Figure 2.74 (Left) reformer/burner and (right) PrOx reactor/heat exchanger of the 100W fuel processor [ISMol 4] (source IMM).

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Compared to a fired reformer, catalyst tube damage is less likely. This is because direct flame impingement cannot occur, and flue gas distribution is not a concern. The maximum tube metal temperature is also limited to the temperature of the shell-side gases. Since die reformer burners have been eliminated, process control is less complicated. And the lack of a flue gas stream reduces emissions of NOx and C02 by as much as 60% to 75%203. 

What are the compositions (mole and mass fractions) and volumetric flow rates (m /kmol CH4 fed to burners) of (a) the effluent gas from the reformer burners and (b) the gas entering the stack What is the specific gravity, relative to ambient air (30X, 1 atm, 70% rh), of the stack gas as it enters the stack Why is this quantity of importance in designing the stack Why might there be a lower limit on the temperature to which the gas can be cooled prior to introducing it to the stack ... 

Figure 24.6 Integrated methanol reformer-burner for a lOOW fuel processor. Source IMM.

Table 5.5 Specifications of the conventional shell and tube methanol reformer/burner reactors of 100 Wei and 5 kWei power equivalent as assumed by Delsman etal. fortheircalculations[386].

Figure 7.1 Schematic diagram of the Haldor Topsoe methane steam reformer/burner reactor [476].

Ambient air (stream 200) is compressed in a two-stage compressor with intercooling to conditions of approximately 193 °C (380 °F) and 8.33 atmospheres (122.4 psia). The majority of the compressed air (stream 203) is utilized in the fuel cell cathode however, a small amount of air is split off (stream 210) for use in the reformer burner. The spent oxidant (stream 205) enters a recuperative heat exchange before entering a cathode exhaust contact cooler, which removes moisture to be reused in the cycle. The dehumidified stream (stream 207) is again heated, mixed with the small reformer air stream, and sent to the reformer burner (stream 211). The reformer burner exhaust (stream 300) preheats the incoming oxidant and is sent to the auxiliary burner, where a small amount of natural gas (stream 118) is introduced. The amount of natural gas required in the auxiliary burner is set so the turbine shaft work balances the work required at the compressor shaft. The cycle exhaust (stream 304) is at approximately 177 °C (350 F). 

FameU, P.W., Investigation and Resolution of a Secondary Reformer Burner Failure, Prepared for Presentation at the 45 Aimual Safely In Ammonia Plants and Related Facilities Symposium - Tuscon, Arizona - Paper no. ID, September 11-14,2000. 

Steam export, which is often undesirable in hydrogen plants, can be minimized by adiabatic pre-reforming which allows high preheat temperatures of the reformer feed, and by preheating of the combustion air to the reformer burners. 

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