ThermalNet, WP 2A: Characterisation and Analysis.
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Table 1. Analytical methods for wood-based pyrolysis liquids
| Water, wt %
|| ASTM E 203
|| 7-day standing test
| Solids, wt %
| Si, wt %
|| XRF, ICP
| Flash point, °C
|| ASTM D 93
| Stability test
|| 80 °C, 24 hours
| Viscosity (20 and 40 °C), cSt
|| ASTM D 445
| Viscosity, mPas
|| Rotational viscometry
| Density (15 °C), kg/dm3
|| ASTM D 4052
| HHV, MJ/kg
|| DIN 51900
| LHV, MJ/kg
|| HHV [J/g] - 218.13 x H% [wt %].
| Particle size distribution
|| Microscopy and particle counter
| Ash, wt %
|| EN 7
| CHN, wt %
|| ASTM D 5291
| Sulfur and chlorine, wt %
|| Capillary electrophoresis
| Metals, wt %
|| AAS, ICP
| Pour point, °C
|| ASTM D 97
|| pH meter
- Karl-Fischer titration. 50 ml solvent for two determinations.
Sample size about 0.25 g (water content >20 wt %). Stabilization
time 30 s. Sample solvent chloroform:methanol (1:3), K reagents
(Composite 5K and Working Medium K) in case of a fading titration
end-point. Titration reagent e.g. 2-methoxyethanol. The system is
calibrated with pure water (25 µm distilled water), water
standards (e.g. 5mg water/ml MERCK 1.09259 250), and using the water
addition method . Accuracy of the titre is re-checked on daily
basis. Titration is done in triplicates.
- In the method  a homogenous sample is let to stand for a week
in room temperature and the water content from different depths
are determined by Karl Fischer titration. Criterias for poor-quality
liquid product are: water content above 30 wt % and/or duplicates
differ more than 1 wt %.
- Solids content of pyrolysis liquids is recommended to be measured
as insoluble material in MeOH (methanol)-DCM (dichloromethane)-solution
(1:1). In the method the sample size (1, 5, 10 g) is determined
in order to obtain 10 - 20 mg of dry solid residue. A representative
sample of pyrolysis liquid is dissolved in excess (10 folds) of
solvent. The solution is filtered through a 1 µm pore size
filter (i.e. Schleicher & Schüll, GF50, ? 47 mm, glass
fibre papers) using e.g. Millipore or multi-place filtration system,.
The solids content is calculated based on the original pyrolysis
liquid sample. Maximum 10 wt % difference between duplicates can
be accepted. Ethanol can also be used for white wood liquids if
similar solid content is obtained. This solvent does not dissolve
properly all extractives in bark-containing liquids.
- Si and metals can be analysed from ash either by XRF (X-Ray Fluorescence
spectrometry) or by ICP (Inductively Coupled Plasma Emission spectrometry).
- Elimination of air bubbles before sampling. The flash point cannot
be measured for pyrolysis liquids at 70–100°C, where the
evaporation of water suppresses the ignition [5, 6].
- The use of accelerated ageing test (24 h @80°C, viscosity
@40°C) is recommended as a rapid test for measuring the stability
. In the method pyrolysis liquid is mixed properly and let to
stand, until the air bubbles are removed. 90 ml of the sample is
poured in 100 ml tight glass bottles (or 45 ml in 50 ml bottles).
The bottles are firmly closed and pre-weighed before placing to
80 °C in a heating oven. The bottles are re-tightened a few
times during the heating-up period. After 24 hours the closed sample
bottles are cooled under tempered water, weighed, and analyses are
performed. The samples are mixed and measured for viscosity and
water. The viscosity of the liquid at 40 °C is measured as kinematic
viscosity by the standard method ASTM D 445. The water content is
analysed by Karl Fischer titration according to ASTM E 203. For
obtaining representative results the test should each time be carried
out exactly by the same way.
- Cannon-Fenske viscometer tubes at room temperature and for non-transparent
liquids, Ubbelohde tubes may be used for transparent liquids. No
prefiltration of the sample. Elimination of air bubbles before sampling.
Equilibration time 15 minutes. Dynamic viscosity by rotating viscotesters
can also be used for measuring the viscosity of pyrolysis liquid,
eventhough it is not as accurate as kinematic viscosity. The evaporation
of the sample can cause too high viscosity values, especially above
60°C, and hence a cover should be used on the sample cup.
- Careful mixing of foam-prone forestry residue liquids in order
to avoid air bubbles. The method covers the materials which can
be handled as liquids between 15 oC and 35 oC. Vapor pressure of
the samples should be lower than 80 kPa and viscosity below 15 000
- Use of a fine cotton thread for ignition. The heat content of
the thread is subtracted from the result. No subtraction of free
water has to be done  because the water in the pyrolysis liquid
cannot be removed by centrifugation as for heavy petroleum fuel
- Light microscopy with photoanalysis program (Leica Qwin).
- Controlled evaporation of water to avoid foaming.
- Because of the small sample size, the reproducibility of the
elemental analysis is dependent on the homogeneity of pyrolysis
liquids. At least triplicates are recommended, if the sample is
inhomogeneous. As large a sample size as possible.
- Sample pretreatment by combustion according to ASTM D 4208.
- Wet combustion as a pretreatment method. In samples with a large
amount of silicates, Si can precipitate as SiO2 during the sample
pretreatment. For accurate determination of Si, the sample should
be ashed by dry combustion and a fusion cake prepared from the ash.
- No preheating of the sample.
- The fouling of electrodes causes error to the result. Hence pH
is recommended to be used mainly for determination of pH level .Cleaning
and calibration of the pH meter after each measurement.