Zink Körner Supplies Efficient and Eco-Friendly Galvanizing Furnace to Wiegel
By introducing design features such as infinitely adjustable, modulating flat flame burners, a wall construction with a markedly reduced heat transfer and a novel reflecting refractory coating, Zink Körner has significantly increased the energy efficiency of batch galvanizing. The new furnace has been in “liquid” operation since 5 May 2013. In early June, Wiegel commissioned the complete galvanizing line in its new works in Neuwied.
In response to the growing demand for hot dip galvanized components, Wiegel has built a new hot dip galvanizing plant in Neuwied — the most modern and environmentally friendly of all plants operated by the Wiegel Group. The galvanizing furnace was supplied by Zink Körner. The new furnace is mainly used to galvanize structural components made of steel or other metals.
The galvanizing tank is 15.5 m long, 3.2 m deep and 1.8 m wide. These dimensions enable it to handle parts of up to 15.3 m length. The plant is designed for throughput rates of up to 16.5 t/h.
Pictured below: Arrival of the hot dip galvanizing furnace at the Wiegel plant in Neuwied.
The furnace features 14 flat flame burners of the FL 20/50 type, which Körner developed specifically for batch galvanizing. These burners use natural gas as fuel, which is available at relatively moderate cost. Their design allows them to provide the same smooth and mild heating as previously only achievable by electrically heated furnaces.
The burners achieve an efficiency of >72 percent. This makes Zink Körner a market leader also in terms of energy efficiency. Unlike burners commonly used in the past, they operate in a modulating mode which makes them infinitely adjustable within a range of 1:10.
Diffusor plates mounted on the burners direct the gas flow along the inner furnace wall. This produces a combination of radiant and convective heat, which has the positive effect that a high input of heat into the liquid zinc is achieved at relatively low furnace temperatures.
Peter Kordt, managing partner of Zink Körner, explains why the furnaces operate at such an excellent efficiency level: “We exploit every possibility that may help reduce the consumption of energy. Let’s take, for example, the flat flame burners, which we developed specifically for use in batch galvanizing. Compared with plants using non-continuous burners, furnaces using our flat flame burners achieve impressive energy savings of, for example, some 500,000 kWh in a facility with a throughput rate between 10 and 15 t/h operated in two shifts for 4,000 hours per year. At a price of 5 cents per kWh, this results in cost savings of € 25,000 per year.”
Pictured below: The installed hot dip galvanizing furnace with flat flame burners arranged at its side walls.
The output of the burners is constantly infinitely adjusted to the throughput of the furnace. Thus the temperature drop in the zinc bath caused by the dipping of a new batch is minimized. Another positive feature is that the furnace always consumes just the amount of energy needed in a certain situation. This regulating mode also avoids abrupt temperature changes, which otherwise would cause strain in the galvanizing tank structure. Thanks to these features, furnaces from Körner achieve long service lives.
Controlling the overpressure in the furnace chamber guarantees that the heat is evenly distributed in all areas of the furnace and that the energy is optimally exploited.
The multi-layer, 300-mm-thick insulation material reduces heat losses. As an additional measure, the internal surfaces of the furnace are covered with a reflecting refractory coating. This coating protects the furnace insulation against erosion and cuts thermal losses. This results in lower furnace wall temperatures, a lower waste-gas temperature and, consequently, higher efficiency.
As the waste-gas ducts are installed inside the furnace, they also contribute to a uniform, extensive and smooth heating of the tank. Körner also uses the waste heat from the furnace to heat the inlet air.
The entire firing system achieves efficiencies better than 72 percent. In hot-dip galvanizing applications, such high efficiencies used to be achieved only by electric heating systems, which are much more expensive.
Dr.-Ing.Thomas Happle, managing director technology of the Wiegel group, explains his decision: “Our company is renowned for its awareness of resource utilization, which we have repeatedly demonstrated in numerous projects. With its highly efficient burners, elaborate control system, consistent insulation concept and its heat recovery system, the new furnace for the Neuwied plant represents the optimum of what is currently available on the market.“