Kenneth L. Maloney, Ph.D., Inc.


A Low Cost Gas Conversion for Stoker Boilers

Kenneth L. Maloney PhD., Inc. is pleased to offer the new Stoker Gas Matrix Burner (SGMB) for Stoker Boiler conversions to natural gas firing. This is a low cost conversion for stokers that requires no modifications to the existing boiler and maintains the boilers coal firing capabilities.

Low NOx Burner System

The SGMB system is a low NOx burner system that uses:

  1. Low individual burner heat release rates.
  2. Staged combustion (air and fuel)
  3. Flue Gas Recirculation (if installed on stoker)
  4. Staged fuel configurations

to achieve very low NOx emission levels on converted stoker boilers.

Click here to view statistical data on combustion.

The Concept

SGMB is a way to convert stoker boilers to burn natural gas without having to install burners in the side walls of the boilers. This method allows the stokers to remain intact and have the capability to be back on coal with minimum boiler downtime.

The SGMB is mounted on the existing grate of the stoker boiler. It uses the existing fans and requires no water wall tube bends. The conversion can be accomplished without dismantling the original stoker equipment. The boiler can be back on coal in only a few hours. Only the feeders are bricked over to prevent overheating.

The SGMB system is based on the principle of controlled mixing by the gas fuel rather than the forced mixing of high velocity swirling air. The SGMB system is designed such that the fuel/air mixing is provided by the large Reynolds number gas jets issuing into low Reynolds number combustion air in cross flow. This design offers a "naturally staged combustion" of the fuel and hence its low NOx emission characteristic.

The Matrix Design

The SGMB system uses a matrix of vertically fired gas burners. This feature eliminates the problems of long flame length and wall impingement. The SGMB does not require any pressure part modification since the SGMB system rests on the grate.

The SGMB modular firing system provides flexible heat release zones to tailor the balance of heat input to the radiant and convective section requirements of the boiler. This system provides the heat release low in the furnace so that the entire heat absorption surface of the boiler is used. There are no cold corners or hot spots in superheaters or on waterwall tubes. This uniform distribution of heat release low in the furnace with short flame length avoids the problems that wall fired burner encounter with stoker retrofits.

The Benefits

Comparison of Coal vs. Gas Firing

Click here to view the benefits of converting from coal to natural gas.

The Hardware

The SGMB system has the same Natural Gas Piping Train and Burner Management System that the standard register burners have. The burner management system can have as many safety features as required by the insurer of the boiler. The piping train supplied can be either NFPA or IRI approved depending on the customers requirements. These items are identical to the ones supplied with standard register burners. The big difference is in the burner designs and the cost of installation.

SGMB Testing Results

All burner management systems worked as planned on the SGMB systems and the turndown on the burner was only limited by the ability of the boiler to maintain drum pressure. ASME boiler efficiencies ranged from 80% to 83%, depending on excess air and stack temperature, for all of the SGMB installations.

Fairmont Utilities has 2 SGMB systems operating on 100,000 pph Spreader Stokers with traveling grates.

Kutztown University in Kutztown, Pa. has an SGMB system on a 35,000 pph traveling chain grate stoker.

Selinsgrove Center in Selinsgrove, Pa. has an SGMB system on a 35,000 pph traveling chain grate stoker.

SGMB installed and firing

SGMB Information

Click here to download detailed information about the SGMB system for stoker boilers.

Stoker Gas Matrix Burner Image Gallery

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Copyright 2011
Kenneth L. Maloney, Ph.D., Inc.