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NEXT GENERATION OF ELECTRICAL LADLE HEATERS: A CASE STORY

Marcus Andersson

Sandvik Heating Technology, Hallstahammar, Sweden

ABSTRACT

Sandvik is now introducing its next generation of Kanthal® electrical ladle heaters. By heating ladles with electricity instead of gas, aluminum producers and steel foundries can benefit from lower energy costs, increased process control, reduced CO2 emissions, and a cleaner working environment. The in situ testing of a Kanthal electrical ladle heater system compared to a conventional gas heated ladle heater shows that energy savings of 50% can be achieved in conjunction with better temperature uniformity in the ladle.

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Figure 1 Kanthal electrical ladle heater

1. INTRODUCTION

Sandvik is now introducing its next generation of Kanthal® electrical ladle heaters. By heating ladles with electricity instead of gas, aluminum producers and steel foundries can benefit from lower energy costs, increased process control, reduced CO2 emissions, and a cleaner working environment. The following report will introduce the reader to the benefits of electrical ladle heating through an in situ test at a customer site where the customer’s existing gas heated ladle heater’s performance is compared to a new electrical ladle heater supplied by Sandvik heating technology.

1.1 High net efficiency:

Kanthal electrical ladle heaters offer significantly higher net energy efficiencies compared with traditional gas heating. Their design enables the same heater tube to be used for both heating and holding. The heating elements are arranged in a reflector, allowing the radiation to be more accurately directed towards the target area. The uniform temperature profile achieved when using electrical elements to heat the ladle, and the fact that there is no flame or streaming hot exhausts, will prolong the lifetime of the refractory, typically by 10–15%.

1.2 Innovative monitoring and control:

An advanced heater monitoring and control system optimizes performance and prolongs the lifetime of the heater by eliminating overheating. The system ensures maximum and consistent power, which reduces process times.

Kanthal electrical ladle heaters are supplied as complete installations, comprising heating elements in a reflector casing, and control and regulation equipment. Commissioning and technical support are provided on site by Sandvik heating experts.

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1.3. Complete range:

Sandvik offers a broad portfolio of Kanthal electrical heating systems, for a range of applications in the primary aluminum industry, typically rodding shops, in secondary aluminum in foundries, and in steel foundries. We also provide systems for glass production and R&D purposes. See table 1 for a description of the full range of standard Kanthal electrical ladle heaters.

Product portfolio

Ladle heaters

Table 1 Standard range of Kanthal ladle heaters

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Electrical ladle heater system

Energy going in to the electrical heating system is the energy supplied by the power supply on the primary side of the control cabinet.

ENERGY IN (A): Power on the primary side (measured by amp meter): 131 kW (total energy consumption during heating cycle, measured)

ENERGY OUT: see Table 3

The different contributions to energy losses in the electrical heating system are described in Figure 12. Basis for estimations and calculations are described in figure 10.

Table 3: Energy losses of the electrical heating system

Figure 12: Energy losses in the electrical heating system

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4.4 Comparison energy efficiency between gas and electrically heated ladle:

Putting the two energy loss estimations next to each other the conclusion can easily be made that the electrical heating system is significantly more energy efficient than the gas heated system, the biggest difference being that with the electrical heating system there is no exhausts that transports heat energy away from the ladle and not contributing to the heating process. When comparing the energy need of heating the ladle to the desired temperature one can see that in the case of the gas heated system the customer previously needed to supply gas with an energy content of almost 278 kW to complete the heating cycle whereas the electrical heating system supplied from Sandvik will only require an electrical power of 134 kW to perform the same task.

From a pure energy perspective one can see from the data that an energy saving of 50% is achieved with the electrical heating system, see figure 14.

• In the same preheating conditions, the heat balance is as shown in the graph

• Pure efficiency improvement 50% (278 kWh / 134 kWh)

Figure 13: Energy balance comparison between the customer’s previous gas fired ladle heater compared to the electrical ladle heater supplied by Sandvik.

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5. Summary

Sandvik has launched their new generation of high efficient ladle heater systems to the market with a wide range of standard heaters. The high net efficiency of Kanthal electric ladle heater systems offers significant advantages, aluminum producers and steel foundries can benefit from lower energy costs, increased process control, reduced CO2 emissions, and a cleaner working environment.

This report describes a test at a customer site where their previous gas heated ladle heaters performance was compared to a new electrical system supplied by Sandvik Heating Technology.

Sandvik replaced the existing ladle heater which had a gas consumption of 6 Nm3/hr (278 kW per heating cycle) with an 54 kW electrical heating system comprising of , heating elements made of Kanthal® Super RA (12/24) with 3D configuration, an automatic hydraulic hoist configuration and a state of the art control system.

The tests confirmed that the electric ladle heater system reached the customer target temperature of 850ºC while at the same time offering better temperature uniformity both inside and outside of the ladle, this was confirmed by thermal imaging together with thermocouple readings, and a significant energy efficiency improvement.

A detailed energy balance for both systems was set up to take into account all losses for both system.

The test results show that an energy efficiency improvement of 50% was achieved.