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“Maxima” pellet production with Mühlböck belt-dryer

“Maxima” pellet production with Mühlböck belt-dryer
Due to the confined space available on site, the belt dryer had to be positioned at a height of 15 metres, on the rooftop of one of the production buildings (photo courtesy Mülböck).

German sawmiller and pellet producer van Roje’s less than conventional approach to things was once described as a “way of striking a balance between technical, logistical, environmental, and economical efficiency.” Its latest out-of-the-box thinking has, quite literally, resulted in an “on top-of-the-box” installation of a new Mühlböck belt dryer.

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A family owned business founded in 1929, I. van Roje & Sohn Sägewerk und Holzhandlung GmbH & Co. KG (van Roje) operates a softwood sawmill and pellets plant on a 24 ha site in Oberhonnefeld-Gierend, about 30 km northeast from the German city of Koblenz.

The company processes around 500 000 m3 of spruce (Picea abies) and Douglas fir (Pseudotsuga menziesii) sourced from the region and pellets under the ‘Energiepellets Oberhonnefeld’ (EPO) brand.

Outside the box hallmark

Longstanding readers may recall an article about van Roje in Bioenergy International no. 69 (2013). Back then, the unconventional approach was related to the deliberate use of cheap off-spec biomass fuel (green waste) paired with a novel flue gas condenser that doubled as a particulate scrubber from IS SaveEnergy.

Despite higher operations and maintenance (O&M) costs for the boiler, the overall annual costs for heat were significantly reduced while more sawdust and woodchips from the sawmill could be used to produce higher-value pellets instead.

In 2013 van Roje had an annual pellet production capacity of 45 000 tonnes on two Salmatec pellet lines producing for bulk delivery.

In 2014 new Rematec hammer mills were installed to grind woodchips to enable full pellet production when there wasn’t enough sawdust and in 2015 a bagging and palletizing line with a then-new Lachenmeier Power Flex T1 stretch-hood wrapping system was installed.

Increasing pellet capacity with Maxima

In 2018 van Roje installed a new 5 000 tonne pellet storage silo and in 2019, it was time to double production capacity.

Van Roje started with biomass pelleting in 2007/2008 and, therefore, was somewhat of an “early bird” in this field. We replaced our older machines with two of our new MAXIMA 840- 125. These are equipped with our latest features and each produces about 6 tonnes per hour of premium pellets, said Timo Müller, Head of Marketing and Sales at Salmatec GmbH.

Features highlighted by Timo Müller include a forced feeder on the front that uniformly conveys the raw material into the press chamber. A dual motor direct drive allows the power to be transmitted directly to the main pulley.

This he says, guarantees a highly energy-efficient and low-wear machine operation. The Maxima’s run with a three-roller system on the inside of the ring die which enables a well-balanced pressure distribution on the die, while a central lubrication system that can automatically lubricate the rollers and main bearings.

Together this translates into keeping maintenance downtime to a minimum. There is a so-called maintenance drive at the rear that allows a slow and safe rotation of the die which brings about greater safety and efficiency when carrying out maintenance operations on the press tools, said Timo Müller.

The new Salmatec Maxima (image courtesy Salmatec).


A roof-top Mülböck belt dryer

With the new Maxima 840s in place, the next production bottleneck for van Roje to address was the dryer. Therefore, a decision was made in 2020 to replace the existing belt dryer with a highly efficient drying system with heat recuperation from Austrian drying specialists Mühlböck Trocknungsanlagen GmbH (Mühlböck).

The scope for expanding capacity with a limited supply of heat could be achieved through the two-fold use of the heat energy we have, explained Richard Mühlböck, CEO of Mühlböck.

Through the installation of the 1003 Premium belt dryer from Mühlböck, production capacity has increased.

This drying system is the optimum solution for us, even when it comes to avoiding drying bottlenecks in the winter months, or to the reduction of emissions, said Oliver Mühmel, CEO of van Roje.

Due to the confined space available on site, the belt dryer had to be positioned at a height of 15 metres, on the rooftop of one of the production buildings. As an additional challenge, the installation of this new system was required to have as little disruption as possible to the ongoing pellet production.

To satisfy this particular requirement, the dryer was prefabricated on a steel frame at ground level, then hoisted up onto the roof using a crane.

The perfect interaction between the people in charge of this project, the employees at EPO and the installation and commissioning staff from Mühlböck reduced downtime for pellet production to a minimum, commented Gerhard Hauschulte, Director of EPO.

Fulfills all requirements

To avoid any restrictions on the service and maintenance of this dryer from arising at this exposed installation location, staircases and platforms were erected on the roof of the building and also right around the dryer.

View of the Mülböck belt dryer
Due to the confined space available on site, the belt dryer had to be positioned at a height of 15 metres, on the rooftop of one of the production buildings (photo courtesy Mülböck).

Also, many noise abatement measures were implemented to comply with the noise emission stipulations of government bodies. These measures included silencers on the intake air system and the flue stacks, as well as enclosures around the housing and the air pipework made of a specialist insulation material.

Other customer requirements that we were able to satisfy included the integration of a fully automatic fire protection system, as well as clarification and adaptation of the drying conveyor technology to suit the conveying equipment available on site, ended Richard Mühlböck.

For van Roje, the pellet plant is fully primed for 90 000 tonnes per annum allowing the company to focus on planning its next investment project in Oberhonnefeld, a cross-laminated timber (CLT) production plant.

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