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Efficient furnaces for hot dip galvanizing

Zink Körner cuts energy consumption in galvanizing by 15 percent

Controlled waste gas flow takes the heat in the furnace exactly where it is needed.

Hagen, Germany, May 9, 2017    The new RECU-CHANNEL recuperative heat exchanger system may achieve energy savings of more than 15 percent in batch-parts, wire and small-parts galvanizing. In typical batch-parts galvanizing plants, this may result in approx. 30,000 euros saved on natural gas costs every year.

For galvanizing at temperatures between 450 and 460 °C, Zink Körner has developed its new RECU-TEC hot dip galvanizing technology, which allows the input energy to be recovered directly in the furnace. These furnaces are equipped with a steel tank and natural-gas fired flat flame burners.

Innovative recuperation technology

The new RECU-CHANNEL recuperative heat exchanger system heats the kettle very uniformly and exactly to the required temperatures. Operation of the furnace requires more than 15 percent less energy than traditional systems. Thus, more than 30,000 euros per year can be saved on natural gas costs, for example, in case of a batch galvanizing plant with an average through-put rate of 6 tons per hour.

While in conventional systems without RECU-CHANNEL technology the waste gas collects at the top, RECU-CHANNEL systems suck the waste gas from below in a controlled way allowing the waste gas to flow downwards past the outside surface of the kettle wall. Thus the waste gas transfers to the lower part of the tank exactly that amount of energy that is required for the process.

The channels are arranged at both long sides of the furnace extending along their complete length. Thus the waste gas travels long distances, giving it more time for the heat transfer. Using the residual heat in the RECU-CHANNEL to preheat the combustion air leads to a further increase in furnace efficiency.

The result: While the waste gas temperature of furnaces without RECU-TEC usually reaches 550 °C or more, the waste gas temperatures of the new furnaces are always below 400 °C, even in case of full load operation. This is a clear indication that the input energy is extremely efficiently used.

Highly efficient burner technology

Zink Körner has developed the modulated KÖRNER FL 15/80 flat flame burners specifically for the heating of steel kettles. These burners feed just as much energy to the galvanizing furnace as necessary at any point in time.

Unlike intermittent burners, they operate with a combustion air ratio λ of only 1.10 – hence with much less surplus air than usual. Their efficiency is 10 to 20 percent higher and gas consumption correspondingly lower than that achievable by burners operating with a ratio of, let’s say, 1.20.

Additionally, the modulating operation avoids short-term consumption peaks. This saves on gas procurement costs as the gas suppliers calculate their provision fees based on the peak load of the furnace.

Each of the diffuser plates of the new burners is supported by three rods fix mounted to the burner port. This arrangement achieves constant pressure conditions which allow the flame to be adjusted with utmost precision. For the user this provides the benefits of ideal combustion ratios and minimal gas consumption.

The burners are installed along the long sides of the furnace at two thirds of the furnace height (from the bottom). At that position, the heat requirement is highest due to the heat loss at the bath level.

Low maintenance costs with low energy consumption

At WIRE 2018 this year, KÖRNER will be presenting a new type of wire galvanizing furnace in           

hall 9 Booth A78.

There will be a presentation of different design examples of this wire galvanizing furnace, which meets all requirements and is characterised by very low maintenance costs and very low energy consumption levels. These claims are supported by operating experience itself.

Thanks to new energy-saving burner technology, KÖRNER can heat up highly sturdy and durable wire galvanizing furnaces with ceramic baths, without using immersed burners, which are susceptible to breaking.

The latest plant designed and set up by KÖRNER is a wire galvanizing furnace with a throughput capacity of 6.3 to/h, for a major international steel group.

KÖRNER has been building galvanizing furnaces for more than 90 years and is one of the pioneers in ceramic galvanizing baths.

Furthermore, KÖRNER has many years of experience with immersed burners, induction heating and heating with heating cover. In this instance, the company combines the immersed burner’s low levels of energy consumption with the maintenance-free heating cover heating.

KÖRNER also builds galvanizing furnaces with steel kettles, with high velocity heating, with double-walled steel tanks and, for high requirements, flat flame burners. 

That way KÖRNER is always able to pick the right wire galvanizing furnace from all available versions to suit each customer, and can also back up its choice with operating experience.