“A GC-TCD Gazohrom 3101 gas analyzer and an FTIR Gasmet DX4000 gas analyzer with a continuous gas supply were used to measure the producer gas composition after it had been cleaned and cooled. For the GC-TCD analysis, a sample of the total producer gas was collected from the beginning until the end of the gasification process in a Tedlar bag. A total of 2 mL of the gas sample from the Tedlar bag was introduced into the GC-TCD with a gas syringe, and three replicates were made for each gas sample; the RSD between GC-TCD replicates was up to 7%. The GC-TCD measured H2, CO, CH4, and CO2. Two packed columns with a total length of 2.5 m long and 3.6 mm in diameter were used for the separation of gases at room temperature. Air at 70 mL/min was used as the gas carrier to detect H2, CO, and CH4, while Argon at 40 mL/min was used to detect CO2. The GC-TCD was calibrated beforehand through a linear relation between the area under the detected spectra peaks and the gas species concentration (vol%) (). The current changes (mA) provided by the GC were displayed using the Keysight Benchview software, and the area under the curve was calculated with the Clarity Chromatography Station software to determine the gas species concentration, based on the calibration.”
“Producer Gas Composition
The H2, CO, CH4, and CO2 concentrations in the producer gas obtained at 750, 850, and 950 °C with an average RSD of 11.8% are shown in a–c. H2, CO, CH4, and CO2 were the main gas species obtained from gasification; the rest of the producer was gas composed of H2O; O2; sulfur dioxide (SO2); hydrocarbons such as ethane (C2H6), ethylene (C2H4), propane (C3H8), hexane (C6H14), benzene (C6H6), and toluene (C7H8); and nitrogen-containing compounds NO, NO2, N2O, NH3, and other hydrocarbons.
Figure 3. Producer gas composition from the gasification of spruce (a), alder (b), and pine (c).
shows that the gas composition of each biomass species differed very slightly. The main component of the combustible gases was CO, with a concentration between 9.3–10.4 vol% at 750 °C, 14.7–15.9 vol% at 850 °C, and 19.9–21.4 vol% at 950 °C. For H2, there was a variation in concentration from 0.7–1.3 vol% at 750 °C, 2.4–2.5 vol% at 850 °C, and 4.0–4.3 vol% at 950 °C. CH4 concentration ranged from 2.5–3.1 vol% at 750 °C, 3.4–3.9 vol% at 850 °C, and 4.1–5.2 vol% at 950 °C. The CO2 concentration ranged from 1.9–5.9 vol% at all temperatures. In all the WB species, the producer gas composition was comparable because of their similarities in elemental composition and other properties such as moisture, fixed carbon, ash content, and heating values. This, together with the implementation of uniform operational parameters, led to a producer gas with a very similar composition.
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