Energy and furnace technology
The laboratory facilities at the Unit of Process Engineering that support high-temperature kinetic studies include numerous custom-built and specially adapted furnaces, including dedicated pyrolysis systems, as well as chemical preparation laboratories and advanced measurement devices. Research activities primarily focus on pyrolysis and the conversion of organic materials into fuel-grade liquids and gases. All experimental setups are supported by comprehensive diagnostic and analytical instrumentation.
Furnaces and reactors
Vertical pyrolysis furnace (BTF)
Pyrolysis experiments are conducted in a batch-scale, electrically heated, tubular, fixed-bed reactor designed for the controlled thermal conversion of organic materials. The reactor consists of a quartz tube with a total length of 60 cm and an inner diameter of 5 cm, capable of operating at temperatures up to 1200 °C under an inert nitrogen atmosphere. The system enables batch-wise pyrolysis at defined temperatures, heating rates, and residence times. Biomass or other feedstocks (e.g., lignocellulosic biomass, hydrochar, coal, or plastics) are loaded into a stainless-steel mesh basket. During furnace heating, the sample is initially positioned in a water-cooled zone (Position 1) to prevent premature thermal degradation. Once the furnace reaches the target temperature, the basket is rapidly introduced into the central hot zone (Position 2), where the material forms a fixed bed and undergoes pyrolysis.
A continuous nitrogen flow (typically 200–400 mL min-1) maintains inert conditions and transports volatile products through the system. Heating rates generally range from 1 to 20 K min-1, depending on experimental design. Typical experiments involve sample masses of 5–30 g, with smaller amounts used for highly volatile materials to ensure efficient condensation and tar recovery. Total experimental duration, including heating, holding, and cooling phases, is approximately 5–9 hours.
Volatile compounds released during pyrolysis pass through a cold trap and a condenser maintained at approximately −15 °C, where condensable fractions (bio-oil and tar) are collected. The remaining non-condensable gases (syngas) are directed to a micro gas chromatograph (micro-GC) for real-time compositional analysis and subsequently through a gas flow meter for volume measurement. The analyzed gas stream may then be collected in gas sampling bags for offline analysis or safely vented through an exhaust system.
The produced syngas typically contains hydrogen (H2), carbon monoxide (CO), carbon dioxide (CO2), methane (CH4), and light hydrocarbons, with composition strongly influenced by feedstock properties and heating conditions. Depending on operating conditions, the system generates between 60 and 200 L of exhaust gas per experiment, containing approximately 30 vol.% combustible syngas (balance nitrogen).
Twin-bed (Pi) reactor
Pyrolysis experiments are conducted in a batch-scale twin-bed reactor system designed for the thermal treatment of organic waste, including biomass, plastics, and e-waste, under an inert nitrogen atmosphere at temperatures up to 600 °C. The system enables both primary pyrolysis and secondary catalytic upgrading of volatile products within a single integrated setup. Typical sample masses range from 4 to 20 g per experiment. The material is initially loaded into a top feeding funnel and rapidly introduced into the hot zone of the primary reactor. Heating rates between 5 and 20 K min-1 are applied, depending on experimental requirements. Nitrogen is used as a carrier gas to ensure inert conditions and to transport volatile products through the system. The typical nitrogen flow rate is maintained at approximately 200 mL min-1.
During operation, volatile products released from the primary pyrolysis reactor subsequently pass through a secondary catalytic reactor operated up to 800 °C. This second reactor contains a catalytic bed that promotes vapor-upgrading reactions, enhancing the formation of aromatic hydrocarbons and improving the quality of the gaseous products.
After catalytic treatment, volatile compounds pass through a cold trap and a condenser maintained at approximately −15 °C, where condensable fractions (bio-oil and tar) are collected. The remaining non-condensable gases (syngas) are directed to a micro gas chromatograph (micro-GC) for compositional analysis and then through a gas flow meter (gas clock) for volumetric measurement. The analyzed gas stream is either collected in gas sampling bags or safely vented outside the laboratory through a designated exhaust outlet. The produced syngas typically consists of hydrogen (H2), carbon monoxide (CO), carbon dioxide (CO2), methane (CH4), and other light hydrocarbons. Gas composition depends on feedstock characteristics, heating rate, and catalytic performance. Each experiment has a total duration of approximately 5–6 hours, including heating, reaction, holding, and cooling phases.
Horizontal furnace
Thermal treatment of carbon materials is performed in a laboratory-scale horizontal batch furnace capable of operating between 500 and 1300 °C. The system consists of a two-zone electrically heated horizontal tube furnace manufactured by Kejia Furnace, enabling controlled, uniform high-temperature operation.
The feedstock biochar is produced by pyrolyzing sawdust at temperatures above 500 °C. At such temperatures, the primary biomass components hemicellulose, cellulose, and lignin are fully decomposed. As a result, the biochar consists predominantly of fixed carbon (up to 96%), with approximately 2% volatile matter and 2% ash content.
During experiments, nitrogen is used as a carrier gas at a flow rate of approximately 100 mL min-1 to maintain an inert atmosphere and prevent oxidation. The biochar loading ranges from 10 to 50 g per batch. The main product remains solid biochar (>98%), while only a small fraction (~2%) of volatile gases is released, corresponding to less than 100 mL of gaseous products, primarily carbon monoxide (CO).
The average experimental duration is approximately 6 hours. During operation, about 36 L of exhaust gas is generated, consisting of more than 99% nitrogen. The gaseous products are first cooled and then discharged together with the carrier gas into the laboratory exhaust system and vented outside the building. After cooling, the exhaust gas temperature remains below the melting point of the polymer exhaust tubing, ensuring safe discharge.
Auger reactor
This experimental system is a pilot-scale continuous pyrolysis unit consisting of an auger reactor coupled with a vertical fixed-bed catalytic reactor, a condensation system, and an online gas analysis module. The setup is designed for controlled thermal conversion and catalytic upgrading of solid feedstocks under inert conditions.
The auger reactor is equipped with two screw feeders to ensure stable and continuous material transport. The primary screw feeder regulates the feedstock supply, while the secondary internal screw (54 mm outer diameter, 1200 mm length) conveys the material through the heated reactor zone. Two pneumatic valves positioned between the feeders maintain continuous solid flow and system sealing. Nitrogen is introduced between the valves to purge air and maintain an oxygen-free environment. An additional nitrogen stream (1 L min-1) is supplied directly into the reactor to control vapor transport and residence time.
The reactor contains three independently controlled heating zones to provide a uniform and adjustable temperature profile. The inlet zone is typically maintained at 300 °C to prevent premature melting and potential blockage. The downstream zones operate up to 600 °C for pyrolysis. The generated vapors are subsequently directed to a vertical fixed-bed catalytic reactor operated up to 800 °C. Downstream of the catalytic reactor, volatile products pass through a condensation system for liquid recovery. The non-condensable gases are analyzed online using a micro gas chromatograph (Micro-GC) and quantified via flow measurement. Gas products may be collected or vented through the exhaust system.
The setup enables continuous operation with controlled feeding, temperature regulation, catalytic upgrading, and real-time gas analysis, making it suitable for studies on feedstock conversion efficiency, product distribution, and catalyst performance.
Analysis instruments
Micro gas chromatography (µ-GC)
Gas composition is analyzed using an Agilent 490 Micro Gas Chromatograph, designed for rapid and online quantification of permanent and light hydrocarbon gases. The instrument is equipped with multiple parallel microcolumns and thermal conductivity detectors (TCDs), enabling simultaneous separation and detection of gas components in short analysis times (typically 1–5 minutes per run).
The Micro-GC operates with an automated gas sampling valve and controlled carrier gas flow (commonly helium or argon, depending on column configuration). The system typically includes dedicated columns for permanent gases (H2, CO, CO2, O2, N2) and light hydrocarbons (e.g., CH4, C2–C3 species). Column temperatures and injection parameters are electronically regulated to ensure reproducible retention times and peak resolution.
Gas samples from the reactor outlet are continuously or periodically directed to the Micro-GC for real-time composition analysis. Quantification is performed using pre-established calibration curves obtained from certified standard gas mixtures. The measured gas composition, together with volumetric flow data, is used to calculate gas yield, carbon balance, and reaction performance metrics. The compact design, short analysis time, and high repeatability make the Micro-GC suitable for batch and continuous laboratory-scale pyrolysis, gasification, and catalytic reaction studies.
Gas chromatography-mass spectrometry (GC-MS)
Agilent 7890A Gas chromatography-mass spectrometry (GC-MS) is used for qualitative and quantitative analysis of volatile and semi-volatile organic compounds. The system consists of a gas chromatograph coupled to a mass spectrometer operating under electron ionization (EI) mode. The gas chromatograph is equipped with a capillary column suitable for separating complex organic mixtures. Sample introduction is performed using an autosampler with split or splitless injection, depending on sample concentration. Helium is typically used as the carrier gas at constant flow conditions to ensure reproducible separation. The oven temperature program is adjustable and optimized for effective compound resolution based on volatility and boiling-point distributions.
After chromatographic separation, analytes enter the mass spectrometer, where they are ionized using electron ionization (70 eV). The generated ions are separated according to their mass-to-charge ratio (m/z) using a quadrupole mass analyzer (or equivalent mass filter, depending on configuration). The detector records the ion signal, producing mass spectra characteristic of each compound.
Compound identification is achieved by comparing experimental mass spectra with reference libraries (e.g., the NIST database) and by retention time matching when standards are available. Qualification can be performed using calibration curves derived from external or internal standards. The GC-MS system enables detailed molecular characterization of condensable pyrolysis products, bio-oils, aromatic hydrocarbons, and other organic compounds present in complex mixtures.
Elemental analyzer
Elemental analysis of carbon, hydrogen, nitrogen, and sulfur in solid samples is performed using a Vario EL Cube elemental analyzer (Elementar Analysensysteme GmbH, Germany). The instrument operates on the principle of high-temperature combustion followed by gas detection, enabling precise, simultaneous quantification of multiple elements in a single sample.
During analysis, solid and liquid samples are weighed into tin or silver capsules and introduced into the combustion furnace, where temperatures reach up to 1,000–1,200 °C. Oxygen is supplied to ensure complete oxidation of the sample, converting carbon to CO2, hydrogen to H2O, nitrogen to N2/NOx, and sulfur to SO2. The resulting gases are separated via a chromatographic column and quantitatively detected using thermal conductivity detectors (TCDs).
The Vario EL Cube offers high sensitivity, reproducibility, and rapid analysis times, typically providing results within a few minutes per sample. The instrument includes automated sample introduction, carrier gas control, and software-assisted calibration and data acquisition. This analyzer is suitable for a wide range of organic and inorganic materials, including biomass, biochar, coal, and polymeric materials.