A peak inside IBV – Europe’s largest pellet site

Located in Vielsalm, southeast Belgium, IBV is Belgium’s largest sawmill and is the largest unit within the Wood & Energy Group processing around 800,000 m³ of softwood sawlogs.

Comprising almost exclusively (90 percent) Norway spruce (Picea abies) with the balance being Douglas fir (Pseudotsuga menziesii), sawlogs are sourced from the region – Belgium, Germany, and Luxembourg and supplied both as tree-length as well as cut-to-standard lengths (4 m and 5.1 m), about 50/50.

Third capacity expansion

Using sawdust generated at the sawmill, the first pellet plant at IBV was commissioned in 2010 and subsequently expanded to its current 270,000 tonnes-per-annum (tpa) capacity. Complete with bagging lines and bulk delivery, this plant is kitted with a SwissCombi belt dryer and CPM presses.

In early 2023, the third phase of pellet capacity expansion was completed with a new plant located on a different part of the extensive IBV wood processing site. The new pellet plant adds another 180,000 tpa of capacity, bringing the total installed production capacity at IBV to 450,000 tpa.

Along with 50,000 tonnes of onsite pellet storage capacity, and 100 pallets per hour of bagging capacity, this makes IBV Europe’s largest pellet production site.

Compared to the existing pellet plant, the new facility has a significantly smaller physical and energy footprint, largely due to a novel compact dryer from compatriot company Dryer One.

Indeed, readers may recall an article in Pellets Special 2023 describing the installation of this “low-temperature continuous flow reverse counter-current” dryer at IBV that has been in operation for well over a year.

The small footprint, capacity, and process simplicity are very impressive. Compared to belt dryers, it is more energy efficient thus more economical, and it allows us to dry input materials with variable moisture content. Another important advantage is that less dust is emitted in the process, said Joseph Haas, Managing Director of the Wood & Energy Group when asked about Dryer One’s performance thus far.

Flexible heat sink

The DO400-HW, as the dryer model is called, has an evaporative power rating of 15 MW and an electrical power rating of 670 kW. It has an input capacity of 400 m³ per hour of material at 50 percent moisture content and an output capacity of 150 m³ per hour at 12 percent moisture content.

The heat source at IBV is hot water from a new biomass-fired combined heat and power (CHP) plant located next to the dryer.

HW stands for hot water indicating the heat source which is the case here at IBV. However, the dryer can be configured to use a hot air source directly which we have installed at other pellet plants. Furthermore, the heat exchangers can be designed to use multiple heat sources. We’ve installed other dryers fitted with heat exchangers that gather two or three separate hot water circuits, remarked Léon Crosset, Founder, Inventor, and Owner of Dryer One.

Supplied by Slovenian company GP sistemi, the 20 MWth, and 5MWe CHP plant is fired with paper sludge, post-consumer wood, and construction and demolition (C&D) wood and delivers hot water to new Mühlböck dry kilns at the sawmill as well as the Dryer One unit.

The latter is indirectly connected to the CHP plant circuit via a heat exchanger unit, housed in a container outside the dryer. The two heat exchangers are connected to the outgoing and return to the boiler and can draw heat from either or both to the dryer circuit.

The heat exchangers in the dryer are on an internal glycol circuit and use input temperatures in the 65 to 95^oC range with return temperatures in the 45 to 65^oC range. In normal operations, the dryer helps optimize boiler efficiency by drawing heat from the return lowering the overall temperature back to the boiler, which increases its overall efficiency. At the same time, it is possible to run the dryer even if the sawmill is not operating its kilns, Léon Crosset explained.

Low temperature and easy maintenance

Material from the underside of either of the two 2,300 m³ wet material storage silos passes a Rematec wet grinder and screw screen before entering a 12 m³ dryer buffer feed bin.

The feed bin ensures that there is always enough material for the dryer when it is operating. Once it drops to a certain level it automatically calls for more material. The dryer is fully synchronized with the pellet plant and automatically regulates the output of dried material, Léon Crosset said.

Sitting on a 20 cm thick concrete pad, the dryer unit measures 15 metres in height and 20 metres in diameter. It comprises four levels all fully accessible with 2 m headroom inside. Three levels are reached via an outside stairway, while the ground floor and internal fan room are reached from a door.

On the top floor is where the five heat exchanger batteries are located followed by the upper rotating disc, and lower rotating disc respectively, the latter is where the wet material enters the dryer.

Energy efficient

Ambient air is sucked in through mesh around the circumference of the dryer under the roof through the heat exchanger batteries, down through the two rotating discs, and the saturated air is then exhausted up into a central flue.

Each disc is equipped with a feed metering and material pick-up unit back-to-back, and the respective infeed and discharge points for the discs are aligned on the same side of the dryer.

The discs rotate in opposite directions to each other and are rotated using a gear motor of a few kW ensuring a constant speed and low energy consumption when in use.

This means that the material bed remains still, yet is moved as the gear motor moves the entire disc ensuring “first in, first out” of all the material.

It also means that the wettest material entering the dryer on the lower disc is directly under the driest material exiting the dryer on the upper disc.

The efficiency comes from the double air passage through the two levels. The air is heated and accelerated only once and then used twice, making the process very energy-efficient. In this way, the moisture is extracted gradually, and evenly from the biomass material without thermal shock, another advantage of our system, said Léon Crosset.

The hot air passing through the material on the upper- and lower discs will absorb different ratios of moisture from the material on each disc depending on where the discs are on their respective rotation.

The result is that hot air entering the dryer becomes saturated and the material dries to the required moisture content. The stainless-steel rotating discs comprise equal-sized segments of perforated grate sheeting that lead to a better regularity of the layer.

From the feed bin, the incoming wet material, typically with a 50 percent moisture content is loaded onto the lower disc that rotates counter-clockwise.

There is always an excess of material in the metering auger to ensure a continuous bed without gaps. Via a second auger the excess is taken back to the start of the material feed, highlighted Thomas Lambermont, Sales and Business Director at Dryer One.

A moisture sensor measures the incoming material as it enters the transversal metering auger thoroughly rotates and mixes the incoming material before dosing it along the radius of the moving disc.

The variations in moisture content of the incoming wet material automatically regulate the thickness of the material bed on the lower disc, Thomas Lambermont said.

Once the disc comes around 360 degrees, the pick-up unit takes up the material auguring it out to a vertical screw or bucket elevator to the infeed of the upper disc for a continuation of the drying process.

The combination of disc rotation, the transverse spring steel pick-up blade, and serrated tooth paddles pick up all the material keeping the disc clean. The smaller particles fall through the perforated floor to the bottom floor.

Here an automatic floor scraper keeps the bottom floor clean, and the removed material is returned to the upper disc infeed. Entering the upper disc that rotates clockwise, the incoming material has a moisture content of approximately 40 percent.

The auger metering unit mixes the partially dried material but this time applies an evenly thick material bed across the disc.

As the upper disc rotates the material passes under two sets of transverse harrows that passively furrow the surface of the material bed as it passes under to ensure airflow through the material bed and uniform drying.

Once the disc comes around 360 degrees, the pick-up unit takes up the material auguring it out past a moisture sensor to a conveyor for the dry material silo.

This time the variations in moisture content of the outgoing dried material automatically regulate the speed of the upper disc, explained Thomas Lambermont.

Reduced emissions and fire hazard

The seven suction fans are located in the wall of the inner cylinder structure at the bottom of the dryer under the lower disc.

Behind this wall is a fully insulated room that houses the electric motors that power the fans. Both the inner- and outer walls of the dryer are insulated. Being fully encapsulated, noise is kept to an absolute minimum making it almost inaudible.

Dust is kept to a minimum since particles from the driest material on the upper disc are drawn downward through the wetter material on the lower disc that acts as a natural filter.

Thanks to the low drying temperatures, the inherent risk of fire is significantly reduced since the temperatures are below the flashpoint of the sawdust. Consequently, emissions of volatile organic compounds (VOCs) are also low. Being steel, the material bed carrier cannot burn or melt.

Nonetheless, a water sprinkler system is installed on each floor as a precaution against other heat or ignition sources such as an over-heated drive or auger bearing.

All electrical motors are located outside the drying chamber to prevent ignition, and only the few auger bearings that are inside the dryer are fitted with temperature sensors.

Using water will not cause any structural damage to the dryer since it cannot accumulate anywhere or overload the bed carrier. It just percolates through the discs to the bottom floor and drains out, said Thomas Lambermont.

Utilizing frictional heat

A look at the comprehensive dryer control panel shows an outgoing target moisture content of 12 percent rather than 10 percent.

Twelve percent is the target as the frictional heat generated in the dry grinding after the dryer also removes moisture, explained Léon Crosset.

In the pelleting hall are four Salmatec six tph presses in a familiar of late Rematec-Salmatec setup – a Rematec dry grinder and feed bin supplies two Salmatec units, each sat on a Rematec cooler sieve.

A starch binder is used for the 6 mm ENplus A1 quality pellets production. From the pelleting hall, the cooled and sieved pellets are conveyed to one of the four bulk silos that also have a bulk truck loading bay.

Future plans

There is no bagging line at the new pellet plant. Instead, the two plants are connected both via an underground pellet conveying system to the existing bagging lines and via an overhead conveying system to the bulk loading silos.

In this way, shipping logistics for the entire pellet production at IBV are optimized.

What then is next for IBV?

We wish to diversify our production, feedstock, and client base. All our current production is geared toward the residential heat markets in Belgium, Germany, France, and the UK. We see regional growth opportunities in the industrial use of pellets, though not necessarily with ENplus A1 pellets but with larger pellets, 10-12 mm, made from post-consumer waste wood. We’re already doing trials in the old pellet plant as part of a feasibility study to retrofi t a part of production. We expect to make a final investment decision later this year, ended Joseph Haas with a cliff hanger.