====== Tar sampling and -analysis ======

===== Methods and tools for the sampling and analysis of gas phase 'tar' =====

The term 'tar' represents semi-liquid mixtures of organic compounds that originated in thermal conversion processes and then condensed while cooling down the gas phase. Tars have a yellowish or brownish to black appearance and a pungent smell. A number of tar constituents is harmful to health or environment. 
Tar is seen problematic in a number of processes. 
In gasification, pyrolysis and even combustion processes tar occurs, is unwanted and shall be removed with the lowest possible effort. A scientific aim is to identify parameters for characterizing 'tar' in order to run the conversion process still efficiently, meaning at desirable gas compositions as output and low on tar. This section gives some information and relevant sources of information on common techniques applied to tar sampling and analysis. Furthermore approaches to analyze 'tar' on-line or to monitor a 'tar-content' are presented and described.

==== The 'standard'-methods for sampling organic and anorganic species of interest from the gas phase and their off-line analysis ====

Species from the gas phase which are not to be analyzed within the gas matrix or which are possible condensible, or which dissolve in condensing substances are by standard trapped in liquids (solvents) ar brought onto solid adsorbents. Further the liquid solvents can be prepared for subsequent analysis with e.g. gas chromatography and different detector systems. The species adsorbed onto solid phases are either extracted with liquid solvents (solid phase (micro) extraction - SP(M)E) or reevaporated by thermal desorption (TD). 
Some information about methods applied to tar species analysis in process gases is given below. 


==== Analysis of sampled tar species off-line by gas chromatography ====

  * [[SPA-method|Solid Phase Adsorption - SPA-method]]\\
  * [[tar protocol|Liquid sampling and the tar-protocol]]


==== Approaches for on-line tar-analysis or tar-monitoring directly in the hot process gases ====

  * [[On-line Tar Analyzer - University Stuttgart and Ratfisch Analysensysteme GmbH ]]
  * [[UV-Fluorescence tar detection at TU Berlin|Laser/LED induced fluorescence (CON-TAR) - TU Berlin, Germany ]]
  * [[Photo ionization detection (PID) - KTH, Sweden and BTG, Netherlands ]]
  * [[Liquid quenche system coupled with UV/VIS or UV/VIS in the gas phase - Paul-Scherrer-Institute Villigen, Switzerland ]]
  * [[UV/VIS in the gas phase - Danish Technical University (DTU), Roskilde, Denmark ]]
  * [[GC/MS with laser ionization - TU Berlin, Germany]] 
  * [[Molecular beam mass spectrometer - National Renewable Energy Laboratories (NREL) - Golden, Colorado, USA ]]

==== Video-Blogs on how to use the 'standard' methods ====

[[https://www.youtube.com/channel/UCjZQMdEdmaDzNCScS6ckINw/featured|Video-Blogs on tar sampling and -analysis]]