The vast majority of VIGAN equipment installed worldwide is used for the bulk handling of seeds and cereals (with densities of up to 0.75kg/m³).
The company’s machines have gained wide acceptance thanks to their ability to convey this type of cargo efficiently, as far as performance, energy consumption, hold cleaning, safety and environment are concerned.
However, VIGAN’s pneumatic unloading machines are not limited to grain handling. They are also suitable for conveying all types of cereals, beans, seeds and most of the raw materials used for animal feeding, as well as delicate cargoes (including malt, rice and cocoa bean). They are also ideal for many other products including chemicals, slightly compacting products such as soy bean meal (SBM) and DDGS. For over ten years, VIGAN has proven to be a reliable partner of choice for the unloading of wood pellets.
Cargo to be unloaded pneumatically is generally free flowing. The natural angle of repose is usually around 30°: the particle size and physical form must allow this free-flowing nature, for an easy separation of the transporting air and the product in the receiving hopper.
Two VIGAN NIV 600 installed in Tilbury in 2011.
Wood pellet handling
Wood pellet is a solid fuel produced by crushing and densifying waste timber like sawdust, forestry residues and wastes, but also industrial byproducts like old paper.
The transport of any kind of wood residue is problematic, due to the low density of this kind of material. Therefore, the most common process is pelletizing in order to compact the material into granules (usually about 10–15mm in length and with a 5–6mm diameter).
Thanks to this process, and with a minimal humidity content, the wood pellets have good free-flowing properties and therefore allow smooth transport from the production facility up to the customer’s site.
VIGAN’s NIV-type pneumatic ship unloader is ideal for the handling of wood pellets and enjoys numerous advantages, such as:
* high unloading rates;
* a high level of safety in accordance with the required standards;
* dust-free unloading (less than 10mg/m³);
* no spillage;
* minimal breakage; and
* low weight.
VIGAN NIV 600 installed in Amer/Geertruidenberg in 2019.
VIGAN case studies
Europe is a massive pellet consumer and its local large production sources are still not sufficient. Therefore, Europe is also the largest pellet importer in the world. The imported pellets are mainly sourced from North America and European countries outside the EU27.
A co-firing power plant produces more ecological energy with wood pellets.
New power plants, as well as existing energy producers, are upgrading their existing facilities with the latest innovations in order to fulfill their legal requirements of protecting the environment while containing costs.
In 2009, VIGAN supplied a NIV-type pneumatic ship-unloader for wood pellet unloading with a capacity of 600m³/h to ELECTRABEL (GDF SUEZ group) in Nijmegen, The Netherlands.
The 585MW co-firing power plant (coal + biomass) was therefore able to increase by around tenfold its incorporation of wood pellets, resulting in 20 % of the total energy produced by this renewable energy source.
Wood pellets were transported to GDF SUEZ plant by vessels from various origins (namely from Canada), thanks to the excellent hinterland river and canal network in the Netherlands for bulk transport.
In 2011, VIGAN supplied two NIV-type pneumatic unloaders for wood pellet unloading at a capacity of 600tph (tonnes per hour) to RWE in Tilbury (United Kingdom).
The 100% biomass power plant (wood pellets: 750MW), was the biggest biomass generating site in the world at that time: 2.5 million tonnes of wood pellets were unloaded per year from Panamax vessels (60% import from Canada).
In 2015, RWE built an ultramodern coal-fired power plant in Eemshaven (the Netherlands). The plant plays an important role in supplying the Netherlands with affordable and reliable electricity.
In order to modify the existing coal-fired power plant to allow for the use of biomass (wood pellets), in 2018 VIGAN supplied a NIV-type pneumatic unloading equipment with a capacity of 600m³/h for the unloading of wood pellet from coasters.
The co-firing plant of 1,560MW, now 50/50 coal – wood pellets, currently accounts for ±20% of renewable energy production for the Netherlands, and is to be upgraded to 100% biomass plant.
In 2019, VIGAN supplied a NIV pneumatic ship-unloader, with a capacity of 600 m³/h, to RWE in Amer/Geertruidenberg (the Netherlands) for the unloading of wood pellet from barges.
Different fuels are being used in the Amer power plant, the main types being hard coal and biomass. To enable processing of the wood pellets, the power plant has a special biomass unloading quay, with facilities for storing biomass in different silos. The 1,245MW power plant has chosen VIGAN for its capacity increase and for the upgrade of the existing installation, in order to switch from 40% to 80% biomass (coal/wood pellets).
Adapted technical solutions
During transportation to the plant, wood pellets can easily break thereby causing dust and dust emissions.
Power plants are usually very cautious and strict when it comes to safety and quality.
VIGAN therefore adapts its machine design to the specific site and customer requirements, as far as dust and explosion protection, noise insulation and product breakage are concerned.
Dust and explosion protection
Proper procedures are taken into consideration on-site by the power plant in order to obey to specific rules when working with potential explosive atmosphere: ATEX tools/equipment, cleaning procedures, monitoring of product temperature and moisture inside the ship prior to unloading operation, smoking restriction, etc.
In addition to this, VIGAN manages the explosion risk on its machines depending on risk analysis and site rules, and adequate preventative measures are in accordance with the potential explosive atmosphere identified, like the following ones taken at Eemshaven:
* Equipment selection: electrical equipment is selected depending on the explosive atmosphere zone and the product explosive properties. In-house equipment is subject to an Ignition Hazard Assessment.
* Earth bounding: to avoid static discharge build-up, the complete machine is earthed and all main structural components are earthed together to ensure a safe equipotential of the machine.
* Dust filter: due to involved process speeds and volumes, the potential explosion area in operation is the VIGAN dust filter. In order to remove the possibility of blowing away objects due to an explosion, the filter is protected by explosion panels to protect its structural integrity. The explosion panels are directed in a safe area to avoid additional hazards and equipped with opening detection to act as an emergency stop on the machine. Antistatic filter sleeves are used for both the main filter and the secondary loading filter.
* Explosion propagation: to prevent dust explosion propagation, the explosion is detected before the explosion panel opening with a pressure sensor in the filter. When an explosion is detected, fast insulation bottles are set to isolate the explosion in the filter and avoid propagation of a flame through the unloading pipes (inlet) or the loading chute (outlet).
* Emergency stop: the complete system is controlled by a STUVEX control unit triggering an emergency stop of the machine. The emergency stop will also remove power supply on the equipment thereby immediately stopping the airlock. The airlock, with its pressure-resistant design and tight air gap, will also act as a fire propagation stop.
Another specificity of VIGAN pneumatic equipment is the bearings of the rotary lock (the rotation speed of the rotary lock is low, less risk of heating,…): they are located outside the areas at risk of explosion, contrary to mechanical screw-type unloaders where the bearings are buried in the material, causing hot spots that are more likely to cause explosions.
Power plants generally have specific noise level requirements. VIGAN noise insulation namely consists of:
* complete machine room insulation with perforated plates and roof insulation;
* turbo blower with silencer at both inlet and outlet;
* acoustic baffle at the ventilation inlet and outlet of the machine room; and
* horizontal pipe, elbow and vertical fixed part of the vertical pipe are acoustically insulated with high-density rockwool.
Minimal product breakage
By optimizing the air and product speed in the pipes, VIGAN pneumatic continuous ship-unloaders cause very low — to no — product breakage.
Recently, tests have been performed at NORD CEREALES in Dunkirk (France). The company namely uses VIGAN machines for the unloading of around 100,000 tonnes of wood pellets per year.
Measurements made by an independent body confirmed an insignificant increase in the fine dust rate after the handling of wood pellets by VIGAN type NIV 600 pneumatic ship-unloader (before NIV: 0.9% — after NIV: 1%).
Like NORD CEREALES, other VIGAN customers are using their pneumatic unloading machines for the handling of wood pellets, even if they were originally designed for grain.
The use of VIGAN unloaders for wood pellets is in no way a coincidence. It should be noted that the characteristics of wood pellets are similar to animal feed pellets. VIGAN already has long-lasting expertise with this kind of product, e.g. through a pneumatic ship-unloader installed at GRANOVIT (former Provimi – part of CARGILL group) in Kaiseraugst (Switzerland).