PELLET power

Rodenhuize Power Station (RPS), a 240-megawatt biomass fuelled plant located in Ghent, Belgium, is one of the largest consumers of Canadian wood pellets. Formerly a coal power station, the plant was converted in 2011 to operate entirely on wood pellets. RPS is a joint venture between Electrabel (a subsidiary GDF SUEZ that owns 73 per cent) and Ackermans & van Haaren (owning 27 per cent). The project cost an estimated €125 million – about $170 million Canadian.

Canadian wood pellets are shipped to Rodenhuize Power Station through the Port of Ghent.

Dave Patterson of B.C.’s Forestry Innovations Investment and I attended the European Biomass Conference in Brussels in June 2013 as part of a mission to educate Europeans about Canada’s sustainable forest management practices and to promote Canadian wood pellet exports. As part of the conference, we joined a site visit to RPS where our tour guide was senior plant operator Cornelis Stevense.

According to Stevense, “This power station was originally developed as a coal-fired power plant with three boilers that used gas, heating oil and coal to generate electricity. Two boilers have since been decommissioned and the plant now operates with a single boiler and cooling tower. The plant was modified in 2005, at which time it began co-firing coal and wood pellets, and again in 2010-11 when the plant was converted to completely replace coal with wood pellets.”

RPS receives wood pellets by ship at the Port of Ghent. The Port is located 30 kilometres inland from the North Sea on the Ghent–Terneuzen Canal. This man-made canal was constructed between 1823 and 1827 on the initiative of the Dutch king when Belgium and the Netherlands were a united country. Over the years, the canal has been enlarged so that today it is 200 metres wide and 32 kilometres long, has a draft of 12.5 metres, and is capable of accommodating ships of up to 92,000 gross tonnage. The canal is more than sufficient for a Panamax-class vessel.

Wood pellets are unloaded at the dock with the use of a Vigan Engineering vacuum ship unloader, and stored in a 700-metre-long warehouse with a 100,000-ton capacity. The pellet storage and handling system includes a dedusting installation, sprinkler, spark and smoke detection and humidity measurement equipment.

Wood pellets are conveyed from the warehouse to three storage silos, each with 2,000 cubic metres of storage capacity. Pellets pass from the silos to the processing area where they are sifted, transported to hammer mills, and ground to a fine dust. The wood dust is then blown by air through pipes to the burners. There are four hammer mills per silo (12 total), each hammer mill feeding two burners. Additional air is added to the outer ring of each burner to aid combustion, and the wood dust is burned inside the boiler’s combustion chamber. The boiler is designed with three burner levels and each silo feeds a single level. Each level has eight burners for a total of 24 burners in the boiler.

Pellets pass from the silos to the processing area where they are sifted, transported to hammer mills, and ground to a fine dust.

The inside of the boiler contains tubes full of water. Heat from the 24 burners turns the water into steam. Pressure from the steam is used to turn a 300-megawatt capacity turbine, which then turns the generator to produce electricity. Spent steam passes though a cold-water condenser, is then turned back to water, which re-enters the boiler in a continuous cycle. Cold water from the condenser is heated by the steam, so is circulated through a single cooling tower. According to Stevense, “We lose almost no water in the process, just a little from evaporation in the cooling tower. So we replenish that from the river.”

The absence of people is noticeable. RPS operates 24 hours a day with three eight-hour shifts. Each shift requires just three people to operate the plant: a senior operator whose job is to manage the fuel supply; an operator who controls the power plant; and a production leader to oversee the operation. In addition there is a maintenance team that rotates between RPS and other power stations in Electrabel’s fleet.

The Belgian power mix includes wind, solar, nuclear, and thermal electricity. According to Stevense, electricity demand fluctuates with the weather, i.e., in response to demand for heat and air conditioning. When electricity demand drops off, wind, solar and nuclear energy are given priority. This means that there are times when RPS operates below capacity or even has to shut down. Stevense says, “Although the plant is rated for 240 megawatts, we usually operate at about 225 megawatts. We can go as low as 125 megawatts if we have to. And if we do shut down, it takes us about 10 hours to get back up to full capacity when we restart.”

“The plant consumes about 800,000 tons of wood pellets annually, producing at about 35 per cent efficiency. When operating at full capacity, the plant uses about 125 tons per hour, or 3,000 tons per day,” Stevense adds.

RPS sources wood pellets from Europe, the United States and Canada – including 225,000 tons annually from Pacific BioEnergy’s pellet plant in British Columbia, in which Electrabel is a joint venture partner.

Electrabel requires each wood pellet supplier to undergo a strict independent audit and certification process to ensure that wood pellets are produced from sustainably sourced fibre and that each supplier’s wood pellets reduce greenhouse gases compared to fossil fuels by at least 60 per cent. The switch to wood pellets from coal has enabled RPS to reduce CO2 emissions by about 1.6 million tons annually, while continuing to provide enough power for 420,000 homes in Belgium.

RPS is a great example of a successful coal to biomass thermal power plant conversion. Together, Electrabel and Ackermans & van Haaren have made a huge investment in helping Europe advance toward reaching its 20 per cent GHG reduction target by 2020. As Canadian pellet producers, RPS is a major consumer of our product. And we can expect more of the same from GDF SUEZ Group. The company aims to supply green energy to one million Belgian families by 2015. That’s a lot of wood pellets!