At AISTech 2013, MST will report a 63% reduction in specific fuel consumption in its rotary hearth billet-reheating furnace operation after retrofitting the furnace with “flameless” REBOX® oxyfuel technology from Linde North America.

The REBOX technical solution also greatly improved reheating capacity and eliminated the need for a walking beam furnace previously needed to preheat larger diameter billets.

Results will be co-presented with Linde at 3pm May 8th in the Pipe and Tube Committee session titled “Seamless Pipe.” Full results will be published in the AISTech Conference Proceedings.  In the presentation, MST Hot Mill Manager Tom Sleder describes project objectives, details of the implementation, as well as results and performance goals.

“Even though the burners for our furnace were relatively new, we saw the opportunity to improve our process with REBOX oxyfuel technology,” Sleder said.

The MST mill produces approximately 39,000 tonnes of cold-drawn seamless carbon and alloy tubing and pipe per year. First, solid steel round billets are reheated in a rotary hearth furnace, then the billets are rotary pierced in a Mannesmann style piercing mill. The rotary furnace, originally built in the late 1940s, was equipped with a traditional air-fuel heating system, and most recently updated in 2007. As MST increased the size of billets over the years, currently ranging from 2 7/8” to 4 ¾” in diameter, it installed a walking beam furnace for pre-heating large diameter material prior to charging in the rotary hearth furnace.

The REBOX® oxyfuel solution proposed by Linde included a revised heating profile. The faster and optimised heating rate of the actual solution reduced heating time of the 4 ¾” billets by 50% compared to the previous air-fuel heating system including a walking beam furnace. It also reduced power consumption by 63%. The MST conversion included replacement of the air-fuel burners in the rotary hearth furnace with REBOX® flameless oxyfuel burners, modification of the flue gas system and a new stack as well as installation of new baffles at the charge and discharge doors.

“With the implementation of REBOX technology, we maintained our quality standards while increasing overall throughput, all while reducing our natural gas usage by 63%. Process control also took a major step forward with the Linde technology. The Linde REBOX technical solution enables us to monitor and control the entire heating process to ensure billet quality – and that quality is critical to our success at MST. The process improvement also eliminates the need to use the walking beam furnace for preheating, which made our operation more efficient and improved the working environment,” Sleder said.

Linde has been a pioneer in oxyfuel solutions since the 1990’s and has performed more than 130 installations around the globe. Over the past few years, the Linde REBOX® technology has become the premiere method for reducing specific fuel consumption in steel reheat furnaces. In addition to more efficient energy input and increased heating rate, the precision oxyfuel technology offers significant environmental and maintenance advantages, including reduced scaling, and minimising NOx formation and total flue gas emissions.

The REBOX® portfolio includes equipment and control systems for oxygen-enrichment, oxygen-lancing, oxyfuel-boosting and 100 percent oxyfuel operation in reheat furnaces and annealing lines. Linde develops and produces powerful, compact and rugged oxyfuel burners needed to retrofit existing furnaces.