New control system offers substantially
higher productivity in electric steelmaking

The Finnish high-tech company Real Time Systems has recently developed an advanced electrode control system that compared with conventional systems offers substantially higher productivity and reduced specific energy consumption in electric arc furnaces.

The first version of the system was tested in 2008 in a full scale trial during normal steel production on a Swedish arc furnace with an active power of 70 MW and currents of 60 kA.

"By examining the results we came to the conclusion that it would have been possible for the mill to produce about 45 000 tons more steel per year just by installing our system", says Dr. Lassi Toivonen at Real Time Systems (RTS). "At the same time the energy consumption per steel ton was reduced by over 3 %."

Since then RTS has developed the system further. For example the new computation unit is significantly more powerful and can track the process quantities in real time.

"As the system always has reliable and reasonably stable estimates of process quantities, the electrodes are moved more smoothly, which leads to reduced fluctuation of current and power, and also gives the actuators a longer life cycle", states Dr. Toivonen.

Pictured : Real Time Systems' novel control system incorporating advanced estimation of process quantities makes it possible to increase the production speed of electric arc furnaces without investments and to reduce the specific energy consumption. Reduced flicker and maintenance need are additional benefits.
Photo courtesy of Saironsteel (http://www.saironsteel.com/).
© Real Time Systems

Pictured (diagram): The new and existing control systems are installed in parallel and the operator can choose which control to use at any time. As Real Times Systems' new control system in addition is offered on a gain share basis, it's a very safe alternative.
© Real Time Systems

According to Dr. Toivonen, the new system was recently tested in a 120 MVA furnace of a Finnish steel mill with good results.

"We have developed the estimation methods for process quantities so that it's now possible to obtain reliable electrode resistances, which has not been possible before", he says. "It also allowed us to implement an electrode resistance control that is superior over the conventional impedance control. This makes it possible to predict the mutual interaction of electrode resistances when the electrodes are moved and compensate for the resistance changes."

Due to this there is no need for the endless and sometimes uncontrolled chain of subsequent adjustments that often take place in conventional electrode control.

"Normally, when you adjust one electrode, its effect on other electrodes must be compensated for. Then you have to re-adjust the first electrode again to compensate for the control actions made on the other electrodes and so on", Dr. Toivonen says. "As our system adjusts the electrodes as an entity, we are able to achieve more stable currents and power than it is possible with conventional electrode control systems."

No upfront investment necessary
The business concept that RTS offers is without any risk and need of investment for the customer. The new control units incorporating advanced process quantity estimation are primarily offered as a service on gain share basis without any upfront payments.

"The payments are entirely based on the improved cash flow from energy savings and increased production case by case", Dr. Toivonen says. "Savings can also come from reduced service costs and reduced costs for compensating flicker. We take care of maintenance and develop the production process together with the customer."

RTS' system is easy to install in parallel with the existing control system without need of production interruptions.

"The existing control can be instantly restored by turning a switch in the control room, which allows easy comparison of the existing traditional and the new system", Dr. Toivonen says. "The interface to the automation system is made via the furnace's existing interface and the operator uses the normal process display in the control room."

The process
Scrap iron is an important source of raw material for the steel industry. The scrap is melted in an electric arc furnace by means of powerful electric arcs that are formed between the graphite electrodes and the charged scrap metal. At the bottom of the furnace there is a measuring electrode.

"The conventional control systems are based on the assumption that the measuring electrode is located in the electrical symmetry point", says Dr. Toivonen. "But since all electrodes in reality interact and the charge is neither homogenous nor symmetrical, the assumption about the symmetry point is not valid. That's why direct measurements fail."

He points out that with conventional control system optimal results cannot be achieved since the arcs do not have equal, optimal lengths due to measurement problem mentioned.

"This leads to additional power losses subjected to furnace lining and exhaust gases", Dr. Toivonen says. "With our system it is possible to accurately position the electrodes so that the arcs are always of equal length and thus highest possible portion of the energy is used for melting the scrap."

According to Dr. Toivonen, the optimal position of electrodes and the stable process quantities employed in process control will lead to smaller thermal stress on the furnace lining, more stable currents and higher average power. "Since the power is more stable, the potential costs related to reactive power compensation are reduced as well", he points out.

Real Time Systems in profile
Real Time Systems was established about 20 years ago by the inventors of the system. Initially the focus was on improved diagnostics in medical equipment but, as computational power increased, the focus was shifted towards industrial processes.

The major breakthrough took place in year 2008 when the RTS system was proven in a full scale trial. Based on the results, the Finnish listed high tech company Outotec Oyj decided to join RTS Oy by obtaining a minority position in the company.

Together with Outotec Oyj, RTS has furthermore developed the technology, and is now ready for a global launch of the system.

The company is committed to continuously develop and improve the efficiency of the system together with the customers once the system is installed.

For further information, view website: www.realtsys.fi or e-mail: LaTo@realtsys.fi or mikael.abacka@realtsys.fi

MARECHAL Decontactors enhance electrical
safety in Eckes Granini fruit processing plant

MARECHAL Electric announces the installation of electrical safety Decontactors^™ to connect mobile processing equipment to the mains power supply in Eckes Granini's juice production plant. The water- and dust-tight Decontactors feature power ratings from 20A to 63A and provide enhanced electrical safety for operators in a production environment which has a high level of humidity and pressure-washing.

The combination of a quick-release button, integral load-break switch, and automatic watertight sealing means that MARECHAL Decontactors can be connected and disconnected safely and quickly, even under load, by any authorised employee. Eliminating the need for a qualified electrician, to connect and disconnect the electrical supply every time a piece of equipment is moved, significantly reduces maintenance times and costs as well as increasing productivity by making it faster to move mobile equipment between different locations.

"As a food production plant, power-cleaning of equipment is an almost constant operation and MARECHAL Decontactors have demonstrated their ability to provide a safe working environment for our employees whilst also increasing our operational flexibility and productivity," explains Mr Laurent Perrin, Head of Maintenance in the Preparation Department of Eckes Granini. "Following expansion in 2010, our use of MARECHAL DSN Decontactors has been extended to the pump supply and to the discharge machines, where the Decontactors are housed in MARECHAL stainless steel boxes."

MARECHAL's sales engineer, Mr Patrick Chevrot adds, "An in-house R&D service, backed by a global network of sales engineers or subsidiaries and the ability to customise connectors, means that MARECHAL can design and install electrical safety connectors which can meet the most challenging operating conditions."

In addition to automatic watertight sealing to IP66/67, when the plug is connected and disconnected, MARECHAL Decontactors feature a robust housing with a glass-fibre, polybutylene terephthalate (PBT) coating which provides long-term resistance to corrosion and shock. The nickel-silver butt contacts and metal jumpers also guarantee a reliable electrical performance regardless of the number of connection and disconnection cycles.

MARECHAL Electric's range covers standard and custom power connectors, boxes and accessories which are used throughout the food industry worldwide to increase electrical safety in applications where humidity and power-cleaning can present challenging safety issues. These applications include silos, production lines, packaging components and motors.

In addition to the food and drink processing sector, Decontactors are used in explosive environments and in the construction, marine, energy, mines and quarries sectors, as well as by emergency services.

Key Facts:
1) Ensure electrical safety despite high humidity and pressure-washing.
2) Automatic watertight sealing to IP66/67 on connection and disconnection.
3) Fast and easy connection and disconnection, even under load, by any authorized employee.
4) Eliminates the need for a qualified electrician to reduce maintenance time and costs and minimize transfer times for mobile equipment.

Eckes Granini in profile

Distributor of the Granini brand for more than 40 years, Eckes Granini International also produces the historic and market-leading Réa and Joker brands. The company has around a 13.7% market share, with a turnover of 190 million Euros in 2010.

MARECHAL Electric in profile
MARECHAL Electric pioneered the use of high performance, silver-nickel butt contacts in electrical socket systems, which are now available for applications from simple compact multipin to heavy duty 600A connections. This technology is used across a range of demanding environments such as the food and drink, nuclear power, heavy industry, infrastructure and ATEX sectors.  An effective alternative to both hard-wired equipment and pin/sleeve type contacts, the decontactor is a highly flexible method of connecting and disconnecting electrical equipment at the press of a latch - safely.  MARECHAL brought the decontactor, the high performance industrial connector with integral AC21 switch, to the electrical market.

For further information, e-mail: l.depiante@marechal.com or view website:  www.marechal-electric.com