Efficient mixing of the process gas and air or oxygen is a critical parameter for secondary or autothermal reformer performance. Uneven mixing can result in large temperature variations above and into the catalyst bed. This causes variations in the degree of methane reforming achieved and results in a poor overall approach to reforming equilibrium, even when a highly active secondary reforming catalyst is used. An improved approach to reforming equilibrium results in improved yields and reduces plant energy consumption by reducing the requirement for inerts purging from the synthesis loop. The efficiency of gas mixing is primarily a function of the burner design. A poorly designed burner can, besides inefficient gas mixing, also damage the vessel walls, refractory or even the burner itself (Haldor Topsoe, 2011). Additinal benefits of improved burners can include the following:

• Good mixing between air/oxygen and process gas with an almost uniform field of temperature, velocities and composition at the catalyst bed interface.
• Better combustion efficiency without formation of carbon.
• Turndown as low as 20%
• Better CO+H₂ conversion.
• Combustion completed well before the process gas enters the catalyst bed. Almost homogeneous gas composition on the catalyst surface.
• Construction and operational simplicity.
• Short flame length avoids the risk of damage of the catalyst top layer due to flame impingement.
• Low pressure drop in both air and process gas streams.
• High flexibility in operation, allowing the burner to be run with good performance over a wide range of plant loads.
• Low temperature at burner surfaces exposed to flame.
• Low temperature of the refractory lining.
• Shielding of refractory lining from the flame hot core.
• Increased life time of catalyst (FAI, 2013).

Various suppliers offer improved designs for the secondary reformer burner (A2A Toolkit) and claim to achieve above-mentioned benefits. 

This measure is applicable both to new and existing plants.