The ECN unit Biomass, Coal and Environmental Research develops technology for the production of substitute ‘natural’ gas in a sustainable manner. It starts with the gasification of biomass. The gas cleaner OLGA plays a crucial role. This tar remover, developed by ECN, has been in the commercial hands of Dahlman since 2007 and seems to be conquering the world.
Dahlman announced in January that it had won an order to supply an OLGA for a gasification plant in Portugal intended to supply both heat and electricity. The gasifier, based on the circulating fluidized bed technology BIVKIN, will be supplied by HoSt and was also developed in collaboration with ECN. The fuel for the Portuguese gasifier is a combination of wood chips and chicken manure, and the residue of the gasifier will be used to make artificial fertilizer. The wood/chicken manure gasifier will process 1 tonne of fuel per hour. The system will generate electricity with an efficiency of almost 30 percent. It is to be in operation by the end of 2009 / start of 2010. The plant owner has signed a letter of intent with HoSt and Dahlman for the delivery of future systems. These will have a larger capacity, probably up to 3 tonnes of fuel per hour.
OLGA is usually referred to in combination with MILENA, ECN’s new and very promising biomass gasifier. This could create the impression that OLGA is only suitable for MILENA. “Not at all,” explained Robin Zwart of Biomass, Coal and Environmental Research (BKM). “OLGA’s great strength is that it can work with just about any gasifier, supplied by any manufacturer. This is what makes OLGA so interesting for Dahlman, as they can market the tar remover all over the world.” They are indeed doing this and report that they are active from Scandinavia to South Africa and from Japan to California. In this sense, OLGA is a complete success as an ECN concept: after innovation at the ECN site, it has been successfully distributed throughout the global market for sustainable gasifiers.
The philosophy of OLGA is dew point control
No gas produced by a gasifier is ever as pure as the methane-rich natural gas extracted from the earth’s crust. Every gasifier must have its product cleaned before it is suitable for a gas engine or gas turbine, or as a raw material for the chemical industry. Gas that has not been cleaned will very quickly cause excessive fouling of the machine that uses it.
OLGA is indispensable for gas cleaning. The tars that are removed from the gas, with a removal level of almost 100 percent, would otherwise seriously disrupt the rest of the gas cleaning process (see OLGA for information about the technology). One might clean gas with water, but this creates problems. “If the water becomes contaminated with tar, you need to clean it before you can dispose of it,” Zwart explains. “This is a very laborious and therefore expensive process. So it is desirable to prevent this contamination of the cleaning water, but it is then impossible to remove all the tar. ECN’s patented innovation is that OLGA uses oil rather than water to clean the gas, thus avoiding any mixing of tar and water.” In other words: OLGA removes tar at a temperature above the water dew point, thus preventing tars t mix with water. The smart design of OLGA enables the reduction of tars to very low levels, with tar dew points below 0 degrees Celsius.
OLGA is designed as a closed system. The captured tars are returned to the gasifier to heat the biomass. “This is very interesting from the point of view of energy, that you can use a waste product from your gasifier as fuel.”
Blue flames
It is important for gas producers that their process is stable. This ensures that small variations in the composition of the fuel do not lead to uncontrolled behaviour of the gasifier or the gas cleaning system. Here, too, OLGA has proven that it does not easily become unregulated, Zwart claims. “A demo system has been in operation for several years in Moissannes, France. This is a gasifier for wood chips and wine residues with an OLGA tar remover. The fuel is unconventional and the biomass gasifier is not of the MILENA or BIVKIN type, but the OLGA keeps track of all the variations closely and shows a stable temperature development.” Robin Zwart produces a night-time photo and points to the blue flames from the afterburner. “Compare that with the orange-yellow flames from an open fire or wood stove at home. Those pretty, characteristic orange tongues of fire are predominantly tar particles that are burning. Blue flames, like these ones, show that the gas is really free of tar.”
Contact
Robin Zwart
ECN Biomass, Coal and Environmental Research
Tel. +31 (0)22 456 4574
E-mail: Robin Zwart
Info
Dahlman Renewable Energy
www.renewableenergy.nl
HoSt
www.host.nl
