linde flameless Oxyfuel Technology for reheating furnaces 

Maximizing efficiency and flexibility in reheating furnaces

Linde can help you optimize your reheating furnaces with REBOX technologies. The REBOX portfolio of products is tailored to different furnace and customer requirements. They can be incorporated into new and existing furnaces without increasing the existing footprint. They are compatible with all conventional fuels and most types of furnaces, from large pushers and walking beams through rotary hearths, roller hearths to various batch furnaces.

Both leading REBOX technologies are designed to optimize reheating furnaces. If you would like maximum benefits with minimum changes to your existing operation, we recommend increasing the oxygen content using high velocity lances. Alternatively, for customers who want to maximize the benefits of oxygen and are willing to replace the combustion system, we have developed flameless oxyfuel.

When you want to maximize the benefits of oxygen and are willing to replace the combustion system, we have developed flameless oxyfuel. REBOX® flameless oxyfuel solutions are targeted at operators of continuous and batch-type reheating furnaces looking to maximize production capacity.

Building on its long-standing and close ties with customers in the steel industry, Linde developed REBOX flameless oxyfuel technology to significantly boost furnace efficiency. It is designed to give operators of reheating furnaces maximum production capacity while optimizing energy consumption. REBOX flameless oxyfuel replaces the nitrogen ballast in air (around 78%) with pure oxygen. As nitrogen is not combustible and is also poor at radiating heat, it only makes a marginal contribution to the heating process at high temperatures. By comparison, combustion gases such as carbon dioxide (CO₂) and water vapor (H₂O) are good at radiating heat. Consequently, nitrogen results in low thermal efficiency and high volumes of exhaust gases and emissions. The REBOX flameless oxyfuel combustion system replaces the existing air/fuel burners with burners that run on 100% oxygen. This improves heat transfer by increasing the concentration of radiating compounds such as CO₂ and H₂O. By improving heat transfer, REBOX flameless oxyfuel can reduce CO₂ emissions and cut fuel bills by up to 50%.
In addition, the flameless combustion creates a more uniform temperature inside the furnace by distributing radiating gases more evenly. Lower peak flame temperatures reduce the formation of NOx and lower the risk of refractory damage caused by hotspots.

Benefits of REBOX flameless oxyfuel:

• Up to 50% throughput gains due to improved radiation and low flue gas volumes
• Lower flue gas temperatures and volumes allowing a shorter dark/recuperative zone
• Significant reduction in fuel consumption (up to 50%) by eliminating nitrogen ballast
• Lower NOx emissions, CO₂ emissions and fuel-based SOx emissions

Fuels with low calorific values can be burnt more efficiently using pure oxygen, enabling it to be used even in high temperature processes.

When you want to improve the performance with minimum changes to your existing operation, we recommend increasing the oxygen content using high velocity lances. REBOX HLL oxygen technology is designed for customers looking for a simple, cost-effective way of optimizing reheating furnaces that can be deployed on demand without any changes to the existing furnace infrastructure.
With REBOX HLL, oxygen lances are mounted in the furnace walls next to conventional burners. These are then used to inject oxygen at high velocity into the furnace and replace most of the air used for combustion. Up to about 75% of the combustion air is replaced with oxygen in zones targeted by REBOX HLL. The elimination of nitrogen increases thermal efficiency, also decreasing exhaust gas volumes and reducing NOx emissions. In fact, it cuts exhaust gas volume per MW by more than 50%. Improved heat transfer also helps to reduce energy consumption. In addition, the REBOX HLL version provides more uniform heating for improved billet quality. This technology can be turned off at any time, enabling the furnace to revert to its normal air/fuel operating mode. Hence it is an ideal way to ramp up performance temporarily, for instance to accommodate fluctuations in demand.

Benefits of REBOX HLL Steel Reheating Technology:
• Up to 25% reduction in fuel consumption
• More homogenous heating due to flameless high impulse HLL combustion
• Higher thermal efficiency and heat transfer in the installed zone
• Up to 30% less NOx emissions per installed zone due to reduced nitrogen ballast and recirculated flue gas which effectively lowers flame temperature
• Can be switched on and off only when beneficial for your operations

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