Replacement of straight through burners with single-ended, high-efficiency recuperative burners helped lower maintenance costs and increase efficiency of a rotary retort furnace.

Cutaway of AutoRecupe Ultra SER v3 burner

Chrysler Group sells over 2.5-million motor vehicles a year-one reason they operate one of the world's largest heat-treating facilities. One of the furnaces at the heat-treat plant was a rotary retort furnace with 28 premix burners. The burners were fired up from the bottom of the furnace and exited straight out the top. Burners were fired at the maximum rate constantly to provide furnace heat requirements, but they never maintained consistent heat and frequently failed. When burners failed, they were plugged off, creating cold spots in the furnace. Burner replacement costs for this furnace ran about $40,000 per year. Poor performance, high repair costs of rebuilding burners and loss of man-hours led the company to investigate replacing the burners with Eclipse AutoRecupe burners.

The AutoRecupe Ultra burner is a single-ended recuperative burner, which can be fitted to nearly any gas or electric furnace. It is available in a range of sizes and materials to accommodate a variety of retrofit installation requirements.

The burner is simple to operate and control. Burner operating selections are high/low, on/off and pulse firing. An integral air orifice meter simplifies burner adjustment and allows for pressure monitoring, a user-friendly feature that gives operators the ability to constantly monitor gas flow and to immediately pinpoint a heat fluctuation and correct the problem.

(Left) Bob McCully, Lead Heat Treat Supervisor at DaimlerChrysler on top of rotary retort furnace retrofitted with AutoRecupe Ultra burners

Lower emissions + fuel savings

The AutoRecupe Ultra uses a technique called flue gas recirculation, which lowers NOx formation by up to 50%. This is accomplished by increasing or adjusting combustion outlet velocity, flow rate (input), and the size of the gap between the combustor outlet and the inlet to the tube. Recirculated flue gases contain less oxygen than combustion air and are at a lower temperature than the flame envelope. Lowering the flame temperature and reducing oxygen in the combustion zone simultaneously achieves significantly lower NOx levels.

Reduction of CO2 and NOx emissions is a critical requirement for the corporation, and the Kokomo facility achieved that requirement by replacing its existing burners with the AutoRecupe Ultra. The company has now set an emission standard that must be met by all facilities by 2008. The Group team is proud to be a part of a CO2 reduction program.

In the AutoRecupe Ultra, exhaust and air are moved past the heat transfer tube in opposite directions, creating a highly efficient counter-flow pattern. The recuperative section of the burner is positioned in the furnace wall for minimum heat loss and maximum heat recovery.

The burner cuts fuel costs from 35 to 55% over sealed ambient air burners, and saves even more when replacing atmospheric burners. At the Chrysler Kokomo plant, the high-efficiency burners helped the company lower natural gas costs by 50% per month for this furnace.

AutoRecupe Ultra burner installation (top view of furnace) in a down-firing position with gas and air piping; Combustion air is supplied to the burners via Eclipse blower system (side view of furnace)

Gains in production, quality and performance

Chrysler reported an improvement in the efficiency of this furnace of 75% by replacing the 28 faulty burners with just 14 AutoRecupe Ultra burners. They now achieve higher efficiency and productivity with only half the number of burners. Due to the gains in furnace efficiency, the plant was able to increase its heat-treat production rate to 300 pounds of products per hour. The reliability and performance of the new burners allow the furnace to be operated at a constant speed without interruption.

Chrysler also reports a major improvement in the quality of its heat-treated products. The burner tube radiates uniformly creating a more even distribution of heat throughout the furnace. This increases the effective penetration of heat into the load to improve product quality.

Short payback

The new burners eliminated previous burner failure problems and lowered maintenance costs on this furnace. Chrysler predicts that it will realize a 67% savings in replacement costs in three years. The reductions in maintenance and natural gas costs and increased productivity will allow the plant to pay back the expense of the replacement project for this furnace in just eight months.