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Show 17 the bottom. Due to this concern, a design constraint for the field test was to devise a means of installation from the bottom of the heater. The segmented burner design is beneficial in this regard, as typical vertical access under a reformer would be at least 6 feet, and the maximum burner segment length is 3 feet. A lifting mechanism was designed that allows for burner installation. This hardware was demonstrated first at Alzeta and has now been demonstrated in the field with the full 6 segment burner. This, or a similar, installation method will be used in future upfired installations. In downfired reformer installations it is expected that burners will be lowered into place by a crane. System Turndown - In typical operation, steam-methane reformer heater turndown will not exceed 3: 1, and this level of turndown is easily be achieved using a single radiant burner element. During plant startup greater turndown is desired, with 8: 1 turndown being the value targeted for the ARCS. This turndown requirement presents a significant challenge in single burner systems, in that burners are typically limited to maximum turndown of 3 or 4 to 1. In multiple-burner Pyrocore systems, such as the 48 MMBtu/hr RCB at the UC Irvine Medical Center, greater turndown was achieved by removing individual burners from service. In a single burner system, this is not an option. Burner turndown of 8: 1 was achieved by inserting an internal baffle into the premixed portion of the burner, with the baffle separating the bottom 2 segments of the burner (approximately 35 percent of burner surface area) from the top 4 segments. The baffle was sized to provide uniform flow of premixed fuel and air to the top and bottom sections of the burner during normal operation. During normal operation, gas injection and mixing occur far upstream of the flow split, so if properly sized the baffle has no effect on flow distribution or stoichiometry. During startup, the main gas supply line is shut, and a secondary "startup" gas supply line is opened. This startup line injects gas into the flowstream downstream of the baffle inlet, and therefore feeds gas only to the bottom 2 burner segments. Using |
