Online Measurements of Alkali and Heavy Tar Components in Biomass Gasification

• Tar and alkali metal compounds are released during biomass gasification and have a major impact on the operation and performance of gasification processes. Herein we describe a novel method for characterization of alkali and heavy tar compounds in the hot product gas formed during gasification. Gas is continuously extracted, cooled and diluted, which results in condensation of tar and alkali into aerosol particles. The thermal stability of these particles is subsequently evaluated using a volatility tandem differential mobility analyzer (VTDMA) method. The technique is adopted from aerosol science where it is frequently used to characterize the thermal properties of aerosol particles. Laboratory studies show that pure and mixed alkali salts and organic compounds evaporate in well-defined temperature ranges, which can be used to determine the chemical composition of particles. The performance of the VTDMA is demonstrated at a 4 MWth dual fluidized bed gasifier using two different types of online sampling systems. Alkali metal compounds and a wide distribution of heavy tar components with boiling points above 400°C are observed in the product gas. Implications and potential further improvements of the technique are discussed.

Ämnesord

NATURVETENSKAP  -- Kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences (hsv//eng)

Nyckelord

Aerosols

Alkali metals

Chemical compounds

Fluidized beds

Gasification

Heavy metal compounds

Online systems

Tar

Thermodynamic stability

Aerosol particles

Biomass Gasification

Chemical compositions

Dual fluidized beds

Gasification process

Laboratory studies

On-line measurement

Tandem differential mobility analyzers

Alkali metal compounds

differential mobility analyzer

fluidized-bed gasification

product gas

volatility

particles

evaporation

potassium

gasifier

aerosols

reactor

Energy & Fuels

Engineering

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)