BIOS - Bioenergy

Analyses and characterisation of pellets

Analyses of pellets

BIOS offers a wide range of chemical analyses for biomass fuels (Analyses). For pellets, the following analyses are offered:

  • Based on the Austrian wood pellet standard ÖNORM M 7135 and the German wood pellet standard DIN 51731 the parameters dimensions, particle density, abrasion, gross calorific value, moisture content, ash content as well as the concentrations of the elements N, S, Cl, Cu, Zn, As, Cr, Pb, Cd and Hg are offered. In addition to the standards also the determination of the bulk density is offered.
  • For pellets from raw materials other than clean and untreated softwood fractions (e.g. agricultural residues) the parameters ash melting behaviour, K, Na, Ca und Mg (relevant for the evaluation of the ash melting behaviour and formation of fine particulates (K)), Si, Fe, Al, Mn und P (relevant for the evaluation of the combustion behaviour) as well as C and H (for the calculation of the gross and net calorific value) are offered.

Characterisation of pellets

In addition to the analyses results BIOS offers a detailed evaluation of the pellets analysed with regard to their combustion behaviour. This is especially of relevance for pellets from alternative raw materials, as this evaluation gives a good first indication about the combustion behaviour of the respective pellets and allows a statement, whether further investigations by lab-scale reactor and/or combustion tests (see below) are meaningful or the pellets are able to be used as a fuel or not.

Lab-scale reactor tests with pellets

BIOS offers, after preceded analyses and characterisation of pellets, lab-scale reactor tests and tests with a special drop-tube-furnace with pellets including a comprehensive evaluation (lab-scale reactor).
Lab-scale reactor tests aim at the determination of the burnout behaviour and the release of organic and inorganic compounds from the fuel during biomass combustion in a fixed-bed.

Straw pellets before ...
... and after a lab-scale reactor test

During lab-scale reactor tests the decomposition behaviour of pellets is investigated in detail and will then be compared to available reference data (usually from conventional softwood pellets). Important parameters in this context are mass loss over the residence time in the rector, development of the concentrations of the single flue gas components above the fuel bed (CO, H2O, CO2, O2, CxHy) as well as the fuel and flue gas temperatures.
Moreover, the release of NOx-precursors like HCN, NH3, NO, NO2 and N2O from the fuel bed is analysed in detail in order to gain basic data concerning NOx formation during the combustion process. This evaluation is especially for N rich fuels like herbaceous biomass fuels of great relevance, as it is well known that an increased release of NOx-precursors must be expected from such fuels.
The data from such lab-scale tests with pellets are evaluated in detail and compiled in a report by BIOS.

Combustion tests with pellets

The performance of combustion tests in a state-of-the-art Austrian pellet furnace and in a special drop-tube-furnace (Drop-Tube Furnace) is recommended as the last step for a detailed evaluation and characterisation of pellets. Such tests are also offered by BIOS.
During combustion tests all relevant operating conditions (start-up, nominal load, part load, load changes and shut-down) are tested, accompanied by flue gas analyses (CO, TOC, NOx, CO2, SO2), measurement of total and fine particulate matter (Measurements) as well as recording of all relevant operating parameters like combustion chamber temperature, power output and negative pressure. In addition, in the drop-tube furnace hot gas and deposit probe measurements can be performed in order to evaluate deposits on heat exchanger tubes and their corrosion potential.
The results are evaluated in detail by BIOS and are compared with data from reference fuels (usually conventional softwood pellets). Differences are highlighted and evaluated.