Gero Di Piazza Staff Writer
Perkins has teamed up with Belgium’s EVW to put the finishing touches to its tried and tested 4016 gas engines at one of Europe’s biggest landfill sites. The installation is using 13 of these engines to generate 9.5 MW at the site in Mont Saint Guibert, Belgium.
Six years ago, diesel engine manufacturer, Perkins, teamed up with E. Van Wingen (EVW), an expanding family-run Belgian engine supplier/manufacturer specialising in gas and diesel engines for the marine and power sectors. EVW was initially a Perkins customer before the two companies joined forces.
In becoming the OEM partner, the first major project the companies worked on was the installation of engines at what is claimed to be the biggest landfill site in Europe. The site has thirteen 4016 TESI gas engines producing a combined 9.5 MWe. In 2002, a single engine was added to the original six installed in 1996. A further six engines were added in December 2003. EVW took on its supporting role by being the local service centre responsible for repair and maintenance.
So far, the original implementation has accumulated some 50 000 hours of continuous use. At 80 000 hours these would have to be replaced with a similar Perkins batch, says EVW managing director Jean Pierre Van Wingen. The additional order came from the site operator, Cetem – part of the Shanks & McEwan group – who decided to maximize potential power generation from the Mont-Saint Guibert (MSG) site at Wallonia after the gas production level had risen.
To date, the power plant has supplied more than 60 million kWh of green power. In 2002, after 35 000 running hours, the engines received a major overhaul (including an engine swap with a spare service exchange engine). MSG has produced over 200 million kWh of electricity from the annual 300 000 t of waste dumped, which supplies some 20 000 homes. It can operate up to a limit of 72 GWh per year.
At the MSG site, all the engines are lined up in the easy-to-remove silver containers
The landfill gas produced from the waste is filtered and then compressed prior to cleaning, drying and screening so that the proportion of methane in the gas measures about 50 per cent. Each 16-cylinder engine has a gross output of 726 kWe and produces a net output of 700 kWe at 400 V. This voltage is then stepped up to 11 kV where it is distributed to the national grid.
A network of holes sunk into the mass of waste collects the biogas produced by the decomposition of household waste and similar products. These holes have connected tubes that converge towards extractors that pressurise the gas via high density polyethylene (PEHD) feeders.
The boosters press back the biogas into 45 cm PEHD collectors leading to the recovery station. The entire system is monitored directly by computer, enabling permanent control of the pressure in the catchment network and prevention of passive biogas emissions.
The PEHD pipes then transport the biogas to the flares and gas engines. Depending on its methane concentration, the biogas is either flared at 1200ºC or recovered as electricity via the 4016 engines.
After pre-filtration the biogas intended to be recovered is compressed to a delivery pressure of around 70 mbar by variable speed boosters. During pre-filtration the biogas undergoes cleaning, which consists of de-humidification, dust extraction and final filtration, in one of the the two pre-processing stations.
The 4016TESI engine inside the container at Cetem
The 13 engines are enclosed in an acoustic canopy on a large skid frame for easy maintenance. An engine, if needed, could be replaced within a day after removing the specially adapted roof. The 22 t genset measures 11.7 m in length and is 3.2 m wide and reaches 4.8 m in height. From a distance of 5 m the noise level is measured at 65 dBA. A single genset can consume more than 50 000 l of oil per year and more than 400 m3 per hour.
Engineers try to keep maintenance levels to a minimum, but they can expect the work to be carried out within a year to consist of 800 spark plug replacements and 700 oil filter changes. The oil change interval is made every 900 h (which amounts to nine per year). The engine is serviced every 12 000 hours. The 16-cylinder unit has a vee form arrangement. Each engine is equipped with a low voltage air-cooled alternator (400 V, three-phase, 50 Hz). The voltage is raised to the network level (11 kV) by 13 individual 1000 kVA transformers.
All the engines are equipped with protection and control equipment and mains paralleling facilities. All the data on operation, security and coordination of the different units are downloaded to a central control and monitoring unit thus ensuring control without continuous human operation.
After the internal consumption of the power plant auxiliaries and boosters have been deducted, the high voltage power produced is fed to the distribution station at Louvain-La-Neuve via an underground line over an approximate distance of 4 km.
Cetem’s recovery, development and biogas elimination process
The partnership worked well on many fronts as they teamed up to produce an engine that is “ahead of its time”, claims Van Wingen. He explains that at the time of the first installation preparations were made to lower the emission output.
This was the right move, which has paid dividends. If the partnership had gone down the route of higher emissions and thus higher generation capacity, then this may have set back the project, confesses Van Wingen.
The Kyoto agreement has laid down regulations that utilities have to abide by. So the emission level they had set themselves, un-known at the time was a blessing in disguise. If those targets had been surpassed with the 4016TESI engine then it could have broken the whole deal, as replacement engines would have created an “unbudgeted-for” expense. This in fact, said officials at EVW, was a worry during the early days.
Today paints a brighter picture, especially for the MSG team. Laurent Dauge, manager of Cetem, boasts that the g8 million invested for the engines thus far (which includes over g4 million for the engines, around g3 million for the transmission line that links the site and some g1 million for civil works) has seen a remarkable g7 million turnover. This yearly figure is estimated to be near g10 million in the coming year.
Shanks is seriously considering the idea of burning up the poor gases derived from the site to dry the sludge from wastewater treatment. This would then use the briquettes to fuel another engine installation which could be capable of generating another 4 MWe.
However, with or without the potential extra engine installation, the partnership remains tight. There is permission from the Belgian local authorities to carry on using the site until at least 2010. By this time, if the licence cannot be renewed, there will be a continuous gas supply for 15 to 20 years.
As the gas supply starts to dwindle the number of engines will be reduced from its current 13 to cope with the smaller volumes of gas. As this happens, the older engines from the initial installations will be decommissioned first. This process will continue until a single genset remains on site to squeeze out the remaining vapours of gas.
Legislation requirements in the European Union
The European Commission claims by 2050 one third of electric power generated will be derived from biogas. Europe committed itself to reduce by 2008-12 its emissions by eight per cent compared to 1990.
Belgium had fixed its reduction level at 7.5 per cent. But the country painted a similar picture with the rest of Europe as emission levels went up between 1990 and 1998. This cast some doubt as to whether Kyoto targets could realistically be met.
The Cetem biogas electricity recovery plant is designed for a biogas output of +/- 5.500 Nm3/h. of which methane content varies between 40 and 60 per cent. The engines were designed on the basis of CH4 content of 50 per cent. The remaining biogas (poor gas) is destroyed using flare bleeders.
Dauge said: “Wallonia is a major consumer of energy. In 1998, its gross internal consumption was nearly 50 per cent higher than the European average. This contributed substantially to the greenhouse effect. Its average production of CO2 is nearly 15 t per year per person compared to 12 t for Belgium as a whole and 9 t for the European average. With the same policy in place, energy consumption and therefore the production of emission will continue to increase around eight per cent by 2010.”
By 2010, Wallonia hopes to achieve an eight per cent green electricity production. This is based on a study estimating renewable energy potential in the Walloon Region. The annual 72 GWh of green power the Cetem site produces adds up to 40 per cent of the Wallonian biogas objective for 2010. Also, at this early stage, it has reached 9.6 per cent and four per cent of the total renewable energy sources.