The presence of tars in the product gas is a big problem in the commercial utilisation of biomass / waste product gas as a source of sustainable energy. Tar is formed in thermal or partial-oxidation regimes such as gasification and comprises a wide spectrum of organic compounds, generally consisting of several aromatic rings. Tar components can be classified into primary, secondary and tertiary tars, referring to the process conditions in which the compounds are formed.
Updraft gasifiers largely produce primary tar; down draft gasifiers produce tertiary tar; and fluidized-bed gasifiers produce a mixture of secondary and tertiary tar components. Tar concentration in biomass producer gas are in order of >100 g/Nm3 for updraft gasifiers, 10-50 g/Nm3 for fluidized-bed gasifiers, and < 1 g/Nm3 for downdraft gasifiers.
Tars can be removed by a number of technologies, all have their pros and cons:
- Aqueous scrubbing
- Thermal cracking
- Catalytic cracking
- Oil scrubbing RME
- Oil scrubbing advanced OLGA
Royal Dahlman can offer the patented OLGA technology which is worldwide and independently recognized as the most efficient tar removal technology and TARA which makes use of a catalytic process to removes heavy tars and will also remove dust. Retrofitting existing scrubbers to OLGA can also be discussed.
Read more about the tar problem in gasification and the pros and cons of the above described technologies.