EMP Makes Improvements for Dry Hearth Furnaces
Pyrotek’s EMP Division is the world leader in electromagnetic pumping, stirring and metal transfer systems. In this article Jim Grayson, General Manager EMP North America, outlines some recent improvements, particularly for use with dry hearth furnaces.
Electromagnetic Pumps (EMP) are powerful and can be reversed instantly, providing metal circulation and scrap melting systems with no moving parts. EMP uses the principle of electromagnetics to circulate molten metal. The proper bath circulation ensures effective heat transfer from the combustion space to the bath, minimising dross formation and improving the thermal efficiency of the furnace. Melt cycle times can also be reduced by using the EMP charge well which will improve the melt rate. The furnace can be sampled and some types of scrap and alloying elements can be added without opening the furnace door.
The design of the original EMP charge well provided for excellent bath circulation in the furnace, but the metal action in the charge well was more of a churning action. This allowed for some heavy type scrap and alloying elements to be added in the charge well, however problems arose when very light gauge scrap was charged. The original design did not have a strong submergence action, limiting customers from charging light guage scrap. This design reduced opportunities of financial savings to the customers.
When EMP was purchased by Metaullics, the Lotuss system was adapted into the EMP system. The Lotuss has a unique shape that provides a very strong vortex with no moving parts. It was specifically designed for efficient melting of light gauge scrap, chips and alloying elements. The Lotuss provides a very powerful submergence action, the light gauge scrap is instantly wetted and submerged, while the powerful vortex provides shear forces to break the surface tension of the oxide layer. This results in very high charge rates, world-class metal recovery and significant savings to the customer.
EMP has been very successful in implementing the Lotuss into the EMP system providing the customers with enhanced return on investments and also the ability to transfer metal using the EMP system. Most of these successes involved processes where the furnace maintained a bath heel, which allowed for continuous operation of the EMP system. A good example is the single or two chamber furnace where a customer could not use the lower cost light gauge scrap. By implementing the EMP with Lotuss charge well they could now take advantage of the lower cost scrap and achieve excellent metal recoveries.
EMP has experienced past success with dry hearth furnaces using the standard EMP charge well. Due to customer desire to improve yield from light gauge scrap, EMP began installing the Lotuss system on dry hearth furnaces.
Original design, Lotuss charge well
With the original Lotuss Chargewill design, it was necessary to hold metal in the EMP system for up to one hour or longer to start the system. This type of repeated start up from a dry hearth situation sometimes resulted in lengthy pump start ups, which diminished the positive results of powerful furnace circulation experienced with the EMP pump.
The EMP engineers and product development team formulated an idea to produce a charge well design to enhance quick start ups from dry hearth like the original charge well, but provide a powerful submergence vortex like the Lotuss (best of both worlds). After many hours of design and water modelling at both EMP in the UK and Metaullics in Solon, Ohio, the EMP team has developed the new hybrid vortex for dry hearth furnaces.
A European company, have had an EMP / Lotuss on their dry hearth furnace for some time. They had experienced repeated plugging issues, and were frustrated with the system. EMP installed the first hybrid vortex on this furnace in September of 2007, since that time they have not experienced one issue. They also hosted a customer visit by an American company who provided EMP / Pyrotek with an excellent reference.
The second system with the Hybrid Vortex was installed in December 2007 on a customers new tilting dry hearth furnace in the USA, they have experienced no issues in regard to reliability, in addition they have seen financial advantages in regard to improved furnace cycle time, recovery for light gauge scrap and alloying elements.
Improvement modifications
Using the modified design, the system is started in the reverse position, something which can only be achieved by using the electromagnetic technology employed by the EMP system. When metal enters the return leg it flows directly to the pump leg. When the pump leg is around 50% full the pump begins moving metal through the system. Advantages resulting from the modifications include the following items.
• When the pump is switched to forward a powerful vortex is formed
• Metal is not dormant in the pump during the start up phase and freezing is eliminated
• The system is much more operator friendly and provides a much wider margin for operator error.
Major system improvements
Changes were made to the furnace connection tubes which increased the temperature in this area and reduced the potential for plugging of the tube. The EMP pump design improvement resulted in increased pump power at the same power setting.
Larger inspection ports allow for easy tube inspection and cleaning access if dross is pushed into the system when charging and cleaning the furnace.
Removable thermocouples are included in the flange area to give an indication of leg temperature and thereby reduce the risk of overcharging by operations.
An improved operator-training program was devised, to include both class room and hands-on skills training, with 24 hour coverage during commissioning and start up.
Detailed site-specific operator training manuals are developed which clearly define how to properly operate not only the EMP pump, but also the furnace in conjunction with the pump to achieve pump reliability and maximum customer return on investment.
HMI help screens are available from the operator control panel. In the event of an alarm, the operator can push the appropriate help screen and get detailed instructions on how to resolve the alarm.
Customers using EMPs with these improvements on dry hearth furnaces are now experienceing excellent reliability from the system. In addition to the benefits of proper furnace circulation they can now take advantage of:
• Improved yield from alloying elements
• Very fast alloy dissolution
• The ability to charge light gauge scrap with excellent yield.
Due to the EMP system improvements, which have led to greater flexibility and system up-time, EMP customers are experienceing even larger returns on their investment in Pyrotek’s EMP technology.
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