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Elemental Analysis of Macro Samples of Biomass
Poster · June 2016
DOI: 10.13140/RG.2.2.10330.75205
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Elemental Analysis of
Macro Samples of Biomass
Aaron Johnson, Marc Ruppenthal, Sabine Kraus, Tony Szuppa, Christian Schmidt, Hans-Peter Sieper
Measurements of Biomass
Knowledge about the content of light elements is essential to make educated
statements about biomass, such as heating values. The vario MACRO cube in CHNS
mode reliably provides a fast and accurate elemental composition analysis of
solid biomass samples, even for samples containing low levels of nitrogen and
sulfur. With the vario MACRO cube, high sample weights can be analyzed, which
is especially important when inhomogeneous samples, such as waste and plant
material are analyzed
In this study, sixteen samples of pomace (samples 1-9 and 16) or wood chips
(samples 10-15) were treated by heating in inert atmosphere at various temperatures. These various samples were then all analyzed using the same method
in a vario MACRO cube running in CHNS mode. Each sample was analyzed three
times with 75-85 mg of analyte and an average measurement time of 13 minutes
per analysis. All samples were weighed into tin cups with WO3 added to aid the
conversion of sulfur to SO3. The tin cups containing samples were sealed using
a manual pressing tool. The results are shown below in Figure 2. The symbols
indicate the range one standard deviation above and below the average of the
measurements. Not that in some cases, the actual standard deviation is smaller
than the height of the symbols. These measurements are within the acceptable
reproducibility requirements of many international measuring standards.
Measuring Principle and Instrumentation
The vario MACRO cube elemental analyzer from Elementar functions via complete combustion of the sample and then detection of the resulting gases. The
samples are weighed in tin or silver vessels and loaded in the integrated 60 position carousel.
100
10
90
9
80
8
70
7
60
6
50
5
40
4
30
3
20
2
10
1
0
0
1
Advanced Purge and Trap System with Wide Dynamic
Range Detection
7
8
9 10 11 12 13 14 15 16
1,00
0,90
2,5
0,80
0,70
2,0
0,60
0,50
1,5
0,40
1,0
0,30
0,20
0,10
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0,00
Sample Number
TCD
Reduction Tube
FURNACE
6
3,0
0,0
Combustion Tube
5
0,5
Blank-Free Ball Valve
Figure 2: The results show that the CHNS content of biomass can be measured with a high precision. The homogeneity of the samples is an important factor in the measured precision.
GAS SEPARATION
Trapping Columns
DETECTION
COMBUSTION
Firgure 1: Functional principle of a high temperature combustion analyzer with APT technology.
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4
Sample Number
Nitrogen Content [%]
Sample Carousel
3
Sulfur Content [%]
Elementar’s Advanced Purge and Trap (APT) system achieves complete resolution
of all element signals, even samples with high C/N or C/S ratios. The gas mixture
is separated in its components via purge-and-trap chromatography, and the
components are afterwards detected by a thermal conductivity detector (TCD).
The Elementar solid state thermistor TCDs are stable for years and are not damaged even in the presence of oxygen. The TCD has a very large dynamic range
capable of measuring C/N ratios of several thousand without the need to change
any range or manual setting. An electronic gas flow controller is positioned just
before the detector and ensures absolutely stable pressure and flow conditions.
This results in a stable instrument calibration over months or even years.
2
Hydrogen Content [%]
In a fully automated process, the sample is transferred blank free to the combustion tube. Catalytic
combustion is carried out at a permanent temperature of up to 1200 °C. Oxygen is injected via a lance
directly at the hottest spot of the combustion furnace, which results in optimum combustion. This is
followed by reduction of the combustion gases on
hot copper in the reduction tube, which traps excess
oxygen while the formed analyte gases, N2, CO2, H2O
and SO2 continue on for processing. This multi-zone
technique guarantees complete conversion even for
very difficult to combust sample materials.
Carbon Content [%]
Introduction
Summary
Typically, elemental analysis of raw biomass requires the use of a high sample
mass in order to obtain valid results, due to the inhomogeneous nature of such
feedstocks. The high mass tolerance of the vario MACRO cube, however, allows
end-users to bypass this challenge with ease. The ability to measure both inhomogeneous samples and volatile liquids makes the vario MACRO cube very well
suited for research of bio-oil processes.