As the new breed of power generation and industrial plants turn to a combination of coal and biomass, Siwertell screw-type unloaders provide the flexibility and efficiency necessary to safely handle the mix of fuels.

Biomass, generally used in some form of combination with coal, is moving out of small scale processes into major power generation and industrial applications, says Lars-Eric Lundgren, Siwertell regional sales manager. “Biomass comes in a wide range of shapes sizes with varying properties. If you are faced with the need to deliver a mix of fuels it makes good commercial sense to install an unloader that can handle all types of biomass, as well as coal, economically and efficiently, without the need to make any adjustments for the various types and grades of material to be handled.

“Siwertell’s multi-purpose unloaders can handle almost any type of bulk material; this makes them ideal for the coal and biomass intakes at the new generation of plants employing this combination of fuels to reduce the environmental impact of their operations,” he notes. “In the longer term, the use of biomass as fuel should be a significant factor in delivering a more sustainable, carbon-neutral industrial environment. Alongside the increase in large-scale plants burning biomass, small-scale biomass operations still have their place. Siwertell road-mobile unloaders are ideal in these circumstances, especially where barges are used with lower capacity requirements.” Although biomass has excellent environmental credentials, handling it in bulk presents some serious issues, in particular the possibility of heating, fire and dust explosions.

Lundgren says that a number of features of Siwertell unloaders, along with the brand’s lengthy experience of handling hazardous cargoes, especially sulphur, minimizes or even eliminate the risks associated with the bulk handling of biomass.

“For sulphur handling we have developed our 4S system, which incorporates a number of features to detect, contain and extinguish any fire in the unloader’s conveyors. In fact, Siwertell unloaders are the only mechanical, continuous unloaders used for the large-scale handling of hazardous cargoes such as sulphur. The safety elements include fire sensors and an extinguishing system. In the event of a fire the unloader automatically stops the conveyors; this ensures that no burning material is transferred into the bulk storage facility ashore. Dust collectors minimize the risk of dust explosions; however the enclosed system is designed to be strong enough to withstand an explosion and is fitted devices that will release the pressure resulting from an explosion within the system.

“We have adapted the elements of the 4S system and incorporated them, as appropriate, in projects involving other hazardous materials such as wood dust and wood pellets.

Furthermore, our screw technology is very kind to the materials it handles; that is to say there is little cargo degradation and therefore very little dust creation. Dust creation is also minimized at the point of cargo take up. The inlet feed is below the material’s surface and cargo is removed in layers, so there is little likelihood of cargo avalanches. Both of these dust- reducing factors are important in reducing the explosion risk,” says Lundgren.

“You can see that when it comes to large scale projects, for power generation or for industrial processes including steel and cement production, Siwertell’s high-capacity screw type unloaders have all the right characteristics for safe and efficient multi-fuel handling.”

This view is supported by an important contract from Denmark’s leading power company, Dong Energy, one of Northern Europe’s largest energy groups. In 2012 it ordered a Siwertell type ST 790-M ship unloader from Cargotec to be used for unloading wood pellets and coal for the company’s combined heat and power station at Avedøre, discharging ships of up to 12,000dwt at a rated capacity of 800tph (tonnes per hour).

Dong Energy, which is majority owned by the Danish Government, says that the Avedøre multi-fuel power station, situated just south of Copenhagen, is one of the most efficient of its kind in the world, achieving fuel efficiencies of up to 94%.

Lundgren says the Siwertell unloader, which will be delivered in June this year, will be a vital part of this high-efficiency operation. “It was chosen, amongst other considerations, for its environmental credentials, which include totally-enclosed bulk transfer, resulting in a clean, dust-free environment. Our long experience with bulk handling systems was also an important factor in winning this contract,” he adds.

Siwertell has already accumulated considerable experience of handling all kinds of biomass, and has market leading knowledge of handling all types of coal. Siwertell’s totally enclosed, continuous conveyor system extends from the cargo pick up in the ship’s hold all the way to the receiving facility ashore. Cargo pick up is optimized by virtue of the high degree of manoeuvrability enjoyed by the vertical arm system. Cargo is picked up, layer-by-layer, right out to the corners of the hold as well as underneath the hatch coamings. This provides not only the most efficient but also the best environmental unloading solution available, says Lundgren.

“We can discharge the most common varieties of wood pellets at between 800 to 2,000tph, depending on the density. Coal is denser than biomass, so any specific Siwertell machine will achieve a higher discharge rate for coal.”

Naturally there are major economic benefits associated with handling coal and biomass with the same unloader. Jetty occupancy is minimized, while the annual intake over the jetty is optimized. The capital investment required is considerably reduced when one unloader can handle all the materials delivered to the jetty; this is also true of the associated shore -based conveying system.

“Our customers operate in all dry bulk trades and we have extensive references from those who appreciate the reliability, efficiency, safety and economic advantages that come as standard with our products. In addition, our totally enclosed systems have unrivalled environmental credentials and this is very important in a world where providing clean operations is rapidly becoming much less a matter of choice.

“At Siwertell we offer the best solutions for handling almost all dry bulk commodities with our range of fully multi-purpose machines, tailor made to meet your exact requirements.”