Surface® Combustion leads the way with a versatile exothermic design that is used in many annealing, normalizing and bluing applications used widely in the pipe, tube, wire and motor industries. Many customers want the flexibility of higher combustibles in the range of 10% CO (Carbon Monoxide) and Hydrogen (rich exothermic) AND lower combustibles in the range of 4% CO and Hydrogen (lean exothermic). Surface Combustion can offer both capabilities in the same generator with a simple change of the burner air/gas ratio. To complete the exogas production process, this gas is further chilled to lower dewpoints before it is suitable to be introduced into various styles of batch and continuous furnaces.

Surface named this miracle exothermic gas with a tradename of DX® gas.

Today’s exogas generator involves an insulated firing chamber with a top mounted burner firing downward into a water sump of sorts located at the bottom of the generator to quench the flame. This quenched gas is at approximately 100 degree dewpoint at this initial step which is too damp for most applications. First stage drying happens when the DX gas is passed through an integral refrigerant based direct expansion chiller which drives the gas dewpoint down further into the range of 35 to 40 degrees. The majority of annealing and normalizing processes can use the DX gas at after this first chilling stage. Several applications in electric motor application require a third stage of drying using desiccant technology to drive the moisture down further to approximately 20 degrees. All of this is necessary for properly balancing the CO/CO2 and H2/H20 ratios in the presence of steels of different carbon potentials.

Depending on the physical size of the units, various sizes can produce a minimum of 2000 cfh (cubic feet per hour) up to a maximum of 30,000 cfh. Typical DX generators have 2 to 1 turn down capabilities to allow for reducing flow when furnaces are taken off line or when furnace vestibules need to be purged with higher flows before returning to lower flows. For many continuous applications where possible large swings in gas flow requirements might be possible, we offer the capabilities of multiple units to operate in tandem to allow for 4 to 1 capability as well without sacrificing any quality of gas composition whatsoever.

DX generators are designed and intended to run and run with minimal downtime. Controls technology at the generator are dewpoint sensor or oxygen probe based. It is possible that the gas can be leaned out even further or enriched. Indeed some wire and tube applications of medium carbon steels require an RX^® Generator and a DX^® Generator precisely balanced in various zones of a continuous furnace.