Solutions for steel industryOptimise reheating furnaces and preheating processes with our innovative solutions.
Linde has developed leading technologies to optimise reheating furnaces. REBOX® is not a ”one size fits all” solution but a portfolio of approaches tailored to different furnace and application requirements. REBOX® solutions 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.
Linde also developed an effective way to optimize vessel preheating processes for the metal industry. Our OXYGON® preheating system is available in two versions for different vessel sizes and different levels of flexibility.
REBOX® HLL is designed for customers looking for a simple, cost-effective way of optimising 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 thus replaced with oxygen in zones targeted by 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, REBOX® HLL provides more uniform heating for improved billet quality. REBOX® HLL can be turned off at any time, enabling the furnace to revert back 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
• 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 you
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 vapour (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
REBOX® DFI (direct flame impingement) is for customers looking for rapid pre-heating, degreasing as well as pre-oxidation of steel strips in continuous galvanising and annealing lines.
One or several rows of REBOX® DFI burners are installed on each side of your strip; high intensity flames then impinge the surface of the strip, ensuring rapid heat transfer and degreasing.
Direct Flame Impingement oxyfuel is based on Linde’s vast experience in oxyfuel combustion and its application in steel heating processes. This expertise was adapted to continuous and large-scale use in reheating and annealing furnaces. With our DFI technology, where controlled oxyfuel flames are fired directly onto the moving metal, the heat transfer is drastically improved. Tests have verified the higher level with local heat flux for the DFI oxyfuel technology, reaching levels of 400 kW/m2 and even more.
Benefits of REBOX® DFI
• Up to 30% increase in productivity due to rapid pre-heating
• Surface pre-oxidation to promote wetting in subsequent process steps
• Effective degreasing of the strip surface