Oxygen-steam circulating fluidized bed gasification of biogenic waste enables biofuel production with low feedstock pretreatment, and its efficiency can be improved by an active bed material. This study presents the first oxygen carrier aided gasification (OCAG) tests with ilmenite at 1 MWth pilot scale. The non-optimized, autothermal plant achieves cold gas efficiencies including C2H4 up to 72 % and carbon conversion efficiencies of 86-97 % (gas-based) and 92 % (solids-based). A high oxidation degree in the bottom ash and a low one in the circulating material indicate oxygen transport to the upper reactor part. About 29 % of the measured carbon output (excluding CO2 and CO) and 42 % of the feedstock energy input (excluding H2 and CO) remain available for downstream conversion. Averaged over four balance points, ilmenite yields markedly lower heterocyclic and oxygenated aromatic hydrocarbons (0.3 g/kg feed ) and polycyclic aromatic hydrocarbons (3.3 g/kg feed ) than sand and olivine. Polycyclic aromatic hydrocarbon yields are similar to or lower than those from magnesite and dolomite, at higher monocyclic aro- matic hydrocarbon yields (22.1 g/kg feed ). Differences in reactor type, pressure, residence time, and measuring setup exclude attribution to the bed material alone.

Chemical looping gasification is an innovative process for chemical recycling of residues that enables the production of nitrogen-free syngas without requiring an air-separation unit. Recently, significant advancements of the technology were made such as the demonstration of autothermal gasification at megawatt scale. However, to optimize reactor design, there are still open issues. One such problem is the positioning of the feedstock feeding position, which can have a significant influence on the process efficiency and tar yields. In this work, the influence of the feeding position with respect to the reactor height was analyzed using coupled CFD-DEM simulation. The results indicate that feeding above the oxygen carrier (OC) return results in a higher carbon conversion and cold gas efficiency, while feeding below the OC inlet leads to lower tar yields and OC conversion. The main influences for this behavior are temperature during pyrolysis which increases with the height due to the addition of hot OC from the AR and residence time of the gases in contact with OC. Furthermore, feeding into the OC return line can be advantageous due to the higher temperatures in the air reactor. However, this effect can be diminished by the formation of cold spots during pyrolysis.

Biomass chemical looping gasification (BCLG) is emerging as a promising alternative to conventional gasification, addressing inherent limitations. This study systematically compares BCLG with conventional methods like air and air/steam gasification, using pine forest residue in an allothermal fluidized bed reactor. Key operational parameters such as reactor temperature (800-900 degrees C), equivalence ratio (0.18-0.36) and steam-to-biomass ratio (1.3) were examined. Performance indicators such as gas composition, yields, carbon conversion, and cold gas efficiency were evaluated and compared. BCLG without steam displayed similar performance to conventional methods. However, the performance of BCLG with steam surpassed conventional gasification methods and emerged as the most promising process. The results suggest enhanced catalytic performance of nickel smelter slag for reforming reactions under steam-rich conditions, with H2/CO ratio, product gas yield, cold gas and carbon conversion efficiency improved by approximately 111%, 30%, 14% and 2%, respectively, compared to air/steam gasification.

Combustion of biomass in existing coal-fired power plants is a promising near-term option for reducing green house gas emissions-particularly when combined with oxy-fuel combustion and subsequent Carbon Capture and Storage (CCS). However, the scale-up of biomass oxy-fuel technology is hampered by the lack of high-fidelity experimental data from combustion chambers of industrially relevant thermal loads. In large-scale facilities, the application of advanced diagnostics is often restricted by limited optical access and harsh conditions, which is why many previous studies rely on conventional probe-based measurements. This study demonstrates the successful transfer of planar Particle Tracking Velocimetry (PTV) and direct Tunable Diode Laser Absorption Spectroscopy (TDLAS) to a semi-industrial combustion chamber. Experiments were conducted for air-and oxy-fuel atmospheres with oxygen volume fractions ranging from 27% to 33 %, each under two swirl settings. PTV measurements delivered two-dimensional fields of the solid fuel particle velocities, while TDLAS provided information on gas-phase temperatures along several beam paths. The data presented in this work are the first of their kind for a semi-industrial biomass combustor, as comparable datasets were previously limited to laboratory-scale, optically accessible systems. The results indicate that the global particle velocity field and particle distribution are governed primarily by the swirl, with oxygen fraction causing secondary effects. For both swirl settings, the oxy-fuel case at 33 % O2 most closely matched the corresponding air-fired particle velocity field. TDLAS measurements captured swirl-dependent temperature patterns. The acquired data provide a valuable basis for the validation of numerical simulations and for the design and optimization of future combustors.

Gasification of biogenic residues utilizes energy and carbon from the feedstock, thereby providing sustainable chemicals at a price that is less susceptible to electricity price fluctuations than in Power-to-X applications. This paper carries out a comprehensive analysis of a bubbling fluidized bed gasifier with a post-gasification zone (PGZ) at pilot scale (2t/d), along with a mass balance of the gas treatment. The autothermal gasifier was operated for 100 hours, during which more than 8 tons of pelletized pine forest residues were converted with steam and oxygen to syngas consisting primarily of H , CO, CH4 , CO and H2O at ambient pressure. Located above the bubbling bed, the PGZ improves gas quality by reducing the hydrocarbon load to an extent dependent on lambda. Under optimal operating conditions, a cold gas efficiency of up to 78 % was achieved at pilot scale by increasing the oxygen supply. For industrial applications, efficiency levels exceeding 85 % are expected. To meet the sulfur and chlorine content criteria for a commercially available hydrogenation catalyst, the raw gas underwent successful purification in a gas treatment facility. This plant is equipped with a filter, a raw gas scrubber, a compression and a hydrolysis, a BTEX removal and a sour gas removal using an MDEA/MEA amine solvent. The separation efficiency of each process step was evaluated using samples of the syngas, waste streams and simulations. This study validates the presented concept of cost-effective biogenic waste gasification and gas cleaning, serving as a basis for scale-up and providing a framework for industrial applications.

High-temperature corrosion is a frequently observed phenomenon in waste incineration facilities. Municipal solid waste presents substantial corrosion potential attributed to elevated chlorine content and significant inhomogeneity in calorific value and chemical composition, rendering stable plant operation and corrosion control challenging. Conventional countermeasures, such as cladding or reduced steam parameters, lack temporal resolution and incur substantial costs or reduced efficiency. For this study, a waste incineration plant was equipped with an online corrosion monitoring system featuring ten sensors distributed across three vertical boiler passes. The system employs an electrochemical measurement principle to enable the detection of corrosion with temporal resolution. The recorded data reveals decreasing corrosion attack and increasingly stable deposits along the flue gas path. Combined with the temperature measurements, the sensor data proves the effectiveness of the shower cleaning in the third pass and confirms successful removal of the deposits. Statistical analysis shows a correlation between CO content and sensor data, while other parameters (e.g., steam flow, flue gas temperatures) exhibit no conclusive correlations, emphasizing the system’s added value. Chemical analysis of the electrodes and deposits reveal significant indications of chlorine and sulfur, suggesting chlorine-catalyzed active oxidation as the predominant corrosion mechanism.

Waste-to-energy (WtE) plants play a key role in waste management worldwide by providing a solution for the waste disposal, generating electric power, and supplying heat for district heating and industrial processes. Efficient CO2 capture solutions are required to abate the CO2 emissions from WtE facilities. Nevertheless, most capture processes entail high economic penalties. In this work, we introduce two highly integrated concepts for avoiding CO2 emissions. One concept uses carbon capture and storage (CCS), while the other consists of carbon capture, storage, and utilization (CCUS). CO2 capture is performed using a carbonate looping (CaL) process and utilization involves direct methanol synthesis. The CCUS concepts are analyzed for retrofitting a German WtE plant, which treats 200 kt of waste per year. We perform a techno-economic assessment that includes process modeling using the software Aspen Plus. The results show that the retrofitting concepts with polygeneration have the potential to reduce CO2 emissions in a cost-efficient manner. The solutions can be retrofitted with lower footprint than other capture technologies due to the combustion of pretreated waste in the capture unit. The cost of CO2 transport and storage is a main driver for the project costs. Producing methanol from captured CO2 and H2 is only feasible in scenarios with very low electricity costs (< 25 €/MWh). In other scenarios, it is more profitable to transport and store CO2 in geological sites (CCS). The avoidance costs of the CCS concept, including transport and storage, are approximately 65 €/tCO2,av, making it competitive with the current price of CO2 certificates in the European Union.

Oxy-fuel combustion is a promising way to avoid process-based CO2 emissions. In this paper, the operational range of a new semi-industrial oxy-fuel combustion chamber for pulverized biomass is analyzed. This approach is used to gain a deeper understanding of the combustion setup and to examine the differences between air and oxy-fuel combustion on an industrial scale. Both analyzed parameters—flame spread and temperature distribution—have a significant influence on heat transfer in commercial boilers. The stability of various operating conditions is assessed by monitoring the CO content in the flue gas via a gas analyzer unit. For stable operation using walnut shells as fuel in an air atmosphere, an overall air-to-fuel ratio of 1.57–1.75 and a local air-to-fuel ratio of 0.75–0.95 provide the most stable conditions. A high swirl number of 0.9 is found to be critical for stability, as the increased fuel momentum entering the combustion chamber promotes a fuel jet-dominated swirl flame. For the corresponding oxy-fuel combustion with the same volume flows and three different oxygen concentrations between 27% and 33%, stable combustion behavior is also observed. Using a camera setup to analyze flame shape and spread, it is observed that the flame formed with an oxygen content of 33% most closely resembles the flame shape achieved under air combustion conditions. However, the combustion temperatures most closely match those of the air operating condition when the oxygen content is 27%. Overall, it is shown that the approach for corresponding oxy-fuel conditions features similar flame shapes to oxy-fuel combustion with flue gas recirculation in a semi-industrial combustion chamber.

Carbonate looping (CaL) is a CO2 capture technology with the potential to efficiently decarbonize power plants and carbon-intensive industries, such as cement and lime production. Many pilot tests have demonstrated the feasibility of operating CaL in oxy-fuel and indirect-heating (IHCaL) modes. Still, there is no commercial facility in operation or planning. To support the scale-up of the technology, reliable reactor models are required. However, little progress has been made in calciner modeling in recent years. The available models are either too demanding in terms of computation complexity or lack support from empirical data. In this work, we develop a novel calciner model by combining a particle sub-model with a one-dimensional reactor sub-model. The model is validated with results from experiments in two different pilot plants in the 300-kWth and 1-MWth scales. The predictions of the model are interpreted using stochastic methods and dimensionless numbers. Furthermore, we introduce a three-step approach to designing calciners for CO2 capture. Calciners with oxy-fuel combustion should be operated at 930-965 degrees C to achieve sufficient sorbent regeneration. For indirectly heated calciners, an operating temperature of 950 degrees C is necessary for high performance, but lower temperatures (e.g., 900 degrees C) are also possible using steam for fluidization. Considerations regarding particle residence time are also discussed. Our guidelines are straightforward and enable the design of a calciner with simple calculations.

The study investigates biomass chemical looping gasification (BCLG) using nickel smelter slag as an oxygen carrier (OC). Key operating parameters, including reactor temperatures (800-900 °C), OC-to-biomass ratio (OCBR, 4:1-15:1), and steam as a gasification medium, were evaluated in a 5kWth fluidized bed reactor using pine forest residue. Performance metrics including gas composition and process efficiencies were assessed. OCs were characterized using XRD, BET and SEM-EDS analyses. Optimal performance was achieved at 850 °C, an OCBR (10:1) and a steam-to-biomass ratio (1.4). The gas composition was 38.87 vol% H2, 19.65 vol% CO, 34.48 vol% CO2, and 6.61 vol% CH4, with a product gas yield of 1.24Nm3/kg-biomass. Carbon conversion efficiency was 77.85 %, cold gas efficiency 58.70 %, and levelized cost of fuel was 0.15 €/Nm3 for product gas and 4.55 €/kg for H2.The results suggest that steam addition significantly enhanced char conversion, improving overall BCLG efficiency. Moreover, nickel smelter slag demonstrated stability, consistent reactivity, and limited sintering behavior.

The indirectly heated carbonate looping (IHCaL) process has been successfully demonstrated to be an innovative technology for CO2 capture in fossil-fueled power plants. Besides this, the IHCaL process is a promising technology for decarbonizing the cement and lime industry due to its synergy to the production process of cement and lime. The feasibility of the IHCaL process in industrially relevant conditions of the cement and lime industry has not yet been proven. In this study, experimental results of longterm pilot tests under conditions for cement and lime industries at a 300 kWth test facility are presented. The necessary heat for calcination was successfully generated by fueling lignite or waste derived fuels in the external combustor. The carbonator was fluidized with circulated flue gas from the combustor. The reactor system showed good hydrodynamic behavior and CO2 capture efficiencies of 90 % in the carbonator were achieved.