High-quality kraft paper from the heart of Europe

Mondi* has made investments at its Štetí paper mill in the Czech Republic to provide top-quality packaging paper from the heart of the European market. The new machine-glazed paper machine supplied by Voith Paper is run by Vacon common DC bus modules and AC drives.

Mondi is a leading international paper and packaging group with operations across 31 countries. Mondi Štetí’s start-up of the PM6 in autumn 2009 was very successful. The new MG (machine-glazed) paper machine is designed to produce annually 55,000 tonnes of white kraft paper in the basis weight of 30-90 g/m2.

This investment was a logical step forward after the PM3 rebuild for white MG grades during 2002. With the new PM6, Mondi Štetí, Czech Republic, now owns two world-class MG machines side by side, strategically located in Central Europe to ensure outstanding delivery service and optimized supply-chain management. The PM6 further reinforces Mondi's position as a leading supplier of bleached, machine-glazed paper for the high-end packaging paper segment.


Vacon products - important tools for improving process and machine control

The new MG paper machine from Voith Paper was started up successfully in August 2009. Voith Paper’s scope of supply included a state-of-the-art head box, wire section, NipcoFlex press, MG cylinder, EcoSoft Calender, MasterReel and leading automation technology. The drive system application and drive control system were supplied by Voith Paper Automation.

Vacon supplied Voith Paper Automation with common DC bus modules and AC drives with a total power of 3.6 MW, providing seamless integration to Voith Paper’s ODC DriveSystem. The common DC bus modules, including non-generative front-end units, active front-end units and inverter units, control the motors of the PM6 and improve process control in terms of runnability, efficiency and quality. The auxiliary drives around the PM6 have also been integrated into machine control, and are controlled by the Vacon AC drives, thus enabling accurate motor controls.

Voith Paper provides solutions that improve the productivity and efficiency of the papermaking process. In a global cooperation agreement signed in May 2008, Voith Paper Automation chose Vacon as their preferred AC drives supplier for paper machine deliveries worldwide. “Reliable and versatile AC drives are an integral part of our solutions, and that is why we chose a supplier with an independent position and a large number of references in the pulp and paper industry,” says Antti Kaunonen, President, Voith Paper Automation. “The Mondi Štetí project demonstrated clearly that the integration of paper machine, automation and drives knowhow provides clear benefits for paper machine performance. This successful project shows that our chosen strategy is the correct one, and we shall continue with this strategy in the future,” Mr Kaunonen concludes.

Positive impact on the environment

Since cleaner production plays a key role in Mondi's sustainability commitments, the new investment was planned with the environment in mind. Despite increasing the volume of paper production in Štetí, the new PM6 machine will actually improve the environmental performance of the mill, with significant reductions in both water consumption and noise emissions.

The PM6 investment also has a positive influence on the surrounding communities by creating new jobs at the mill for highly qualified engineers, lab technicians and machine operators.

Vacon’s scope of supply to PM6

* Common DC bus modules in the power range 6 to 500 kW and with a total power of 3.6 MW
o 4 x Vacon non-regenerative front-end (NFE) power supply
o 1 x Vacon active front-end (AFE) power supply
o 22 x inverter units
* 40 auxiliary drives with a total power of 1750 kW and in the power range 0.3 to 630 kW

The NFE units are connected to a transformer with a 12-pulse supply system to achieve a low THD level.

Vacon’s common DC bus product portfolio meets all the requirements with a flexible architecture, comprising a selection of active front-ends, non-regenerative front-ends, fundamental front-ends, inverters and brake choppers in the entire power range up to 5300 kW at 380 VAC to 690 VAC. The drive components are based on Vacon NX technology. Common DC bus components are used in a wide range of combinations. In a typical DC bus configuration, drives that are braking can transfer the energy directly to drives in motoring mode.

The NFE (non-regenerative front-end) unit is a unidirectional (motoring) power converter for the front-end of a common DC bus drive line-up. The NFE is a device that operates as a diode bridge using diode/thyristor components. A dedicated choke is used at the input.

The AFE (active front-end) unit is a bidirectional (regenerative) power converter for the front-end of a common DC bus drive line-up. An LCL filter is used at the input. This unit is suitable for applications where low mains harmonics are required. AFE is able to boost DC link voltage (default +10%) higher than nominal DC link voltage (1.35x UN).

The INU (Inverter unit) is a bidirectional DC-fed power inverter for the supply and control of AC motors. The INU is supplied from a common DC bus drive line-up. A charging circuit is needed if the possibility of connecting to a live DC bus is required. The DC charging circuit is integrated up to 75 kW (FR4-FR8) and external for higher power ratings (FI9-FI14).

* Mondi is a leading international paper and packaging group with operations across 31 countries and an average of 33,400 employees.

Located in Štetí, on the banks of the Elbe River, 40 kilometres north of Prague in the Czech Republic, Mondi Štetí a.s. is a leading manufacturer of high grade sack kraft and kraft papers, as well as a major European supplier of corrugated case materials and market pulp.

The production of pulp at the site began in 1949, when the mill was called “Sepap”. Over the following decades the name and ownership of the mill changed several times. Today, Mondi Štetí a.s. annually produces 500,000 metric tonnes of pulp, paper and board of world-class quality that is sold on all continents.