Stein horizontal furnaces
The furnace configuration for continuous galvanizing lines (CGL) depends on several criteria, such as heat treatment, strip quality requirements and the available space. The combination of a long thermal cycle and high processing speed directly influences the strip length in the furnace.
Fives has developed a range of Stein horizontal furnaces for CGLs up to 150m (different carbon steel applications); for hot and cold annealing and pickling lines (HAPL/CAPL) for stainless steel applications, as well as for silicon steel strip processing lines (up to 300m).
In continuous galvanizing lines, the Stein horizontal furnace typically includes several sections: a non-oxidizing furnace (NOF), a radiant tube furnace (RTF), soaking / over-aging sections and rapid cooling. Modern galvanizing and coating lines are tasked with producing any metal coated carbon steel products for construction, home appliances, white goods and automotive grades. The Stein horizontal furnace is up to the challenge.
Offering efficient strip heating and cleaning, as well as safe operation, the NOF gives good surface preparation for the galvanizing process, to the extent that no additional pre-cleaning is required up to 1000 mg rolling oil and iron fines per m2.
The NOF features one entry seal where the strip is introduced to the furnace. The gap opening is adjustable, allowing for strip introduction as well as easy inspection of the furnace chamber, while avoiding furnace waste gas leakage into the workshop. Other key features include the exhaust system for safe operation and the bottom cooling roll, which supports the strip and avoids scratches. The NOF incorporates one recuperative zone where the strip is preheated with waste gases and one heating zone where it is heated with direct fire burners.
AdvanTek® DFR (Direct Fired Reducing) burners offer quick combustion and excellent air/gas ratio control. The lateral location of the strip ensures the strip temperature remains homogenous crosswise including processing full hard or hot rolled strips with low thermal cycle.
The anti-oxidation system has been implemented to avoid strip oxidation in the preheater during line shutdowns and hence a strip breakage at the restart, which is critical - particularly for thin strips.
Best of all, the non-oxidizing furnace is environmentally friendly, ensuring low NOx emissions complying with the European environment rules.
Radiant tube furnace
The RTF has been designed by Fives with on-off technology to ensure that the burner operates only at optimal efficiency. This provides the following process benefits:
- Improved combustion efficiency
- Enhanced temperature homogeneity
- Constant air/gas ratio with low oxygen excess to reduce emissions
In addition, the energy-saving RTF features gas-tight steel casing, strip support rolls, ceramic fiber-based insulation and a flue gas exhaust circuit and fan. Steelmakers can opt for the ‘U’ radiant tube fitted with air/fuel burners or a ‘W’ radiant tube.
Electrical soaking section is equipped with I type electrical heaters. It offers low installed heating capacity, better thermal efficiency, high life time, low investment cost and easy maintenance.
Stein horizontal furnace layout
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