Relevant Operating Conditions Research Articles

Analysis of Shunt Currents and Associated Corrosion of Bipolar Plates in PEM Fuel Cells

Proton exchange membrane (PEM) fuel cells are being developed for future NASA missions. These fuel cells use a bipolar construction, with internal manifolds to conduct product water and coolant water. The wetted surfaces of the manifolds present large voltage gradients across the product water and coolant water passages, which can induce water electrolysis in the manifolds of full-scale stacks. As such, shunt currents lead to parasitic power losses and corrosion of the fuel cell metal surfaces; therefore, it is important to understand and characterize the effects of shunt currents. The circuit analog models provide an approximation of the shunt currents, limited by the estimation of the charge transfer resistance. As such, the methods should be used cautiously. Shunt currents are influenced by cell voltage, cell number, manifold ohmic resistance, product water/coolant purity, and the charge transfer resistance of bipolar plate surfaces to electrolysis. In this work, electrochemical characterizations were performed to estimate these characteristics under relevant operating conditions. A numerical solution of the shunt currents is presented, and the distribution of corrosion and hydrogen evolution are described. The same calculations would apply to PEM electrolyzers used for hydrogen and oxygen production. With some adjustment, similar calculations may also be applied to other electrochemical system with common electrolyte channels, such as flow-batteries and other devices where an electrolyte manifold experiences voltage gradients.

The Power of in-Situ Studies: How X-ray Absorption Spectroscopy Can Help to Develop PEMFC Catalysts with Increased Activity and Stability

Low and high temperature polymer electrolyte membrane fuel cells (LT- and HT-PEMFC) are promising systems in a future sustainable energy scenario, where renewable energies can be implemented by a power-to-gas strategy. The supply of hydrogen or methanol produced by intermittently available wind and solar energy will then be converted into electricity on demand using a combination of water electrolysis and fuel cells. However, in order to make this dream a viable reality, costs need to be dramatically reduced and the material’s stability significantly improved. In our opinion, this is only possible after detailed insights into the reaction and degradation mechanisms in these systems have been obtained, so that a knowledge-based design of specifically tailored materials becomes possible. State-of-the-art catalysts in fuel cells are Pt(-M) with M=Ru, Co nanoparticles with particle sizes ranging between 2 nm and 5 nm and metal loadings between 20 and 80 wt.% supported on a high surface area carbon material. Recent research focuses also on functionalized carbons, ordered mesoporous and templated carbons, as well as carbon nanotubes (CNT) and even graphene. However, carbonaceous materials are very prone to corrosion, when subjected to the harsh operation conditions, in particular at the cathode side of the fuel cell. That is why current efforts in our group and others focus on the search for alternative support materials, such as electron-conducting oxides and polymers. Oxide-supported catalysts are well-known in heterogeneous catalysis, so that a closer collaboration between the two communities appears desirable in the future. X-ray absorption spectroscopy (XAS) is a technique optimally suited to studies under fuel cell operation conditions, as neither UHV conditions in the experiment, nor long-range order in the sample are required. It can be applied to monitor the geometric structure of the catalytically active nanoparticles directly following particle oxidation and growth during operation. With the delta µ XANES method and complementary theoretical FEFF8 calculations, it is furthermore possible to identify adsorbed species on small Pt nanoparticles and follow their change in coverage and their competition for free adsorption sites elucidating the reaction mechanism. Since diffuse reflectance infrared Fourier transformed spectroscopy (DRIFTS) has been applied manifold in heterogeneous catalysis for the study of oxidic support materials and – in contrast to XAS – is applicable in the lab, we decided to design a combined DRIFTS-XAS in-situ cell to investigate nanoparticle-support interactions in different gas atmospheres. This talk will highlight how sophisticated in-situ techniques, such as X-ray absorption spectroscopy, but also others, will help with rational materials design. When the reaction mechanisms can be unraveled, the catalyst can be tailored and hopefully lesser fractions of the costly noble metals will be required. Getting more insight into degradation phenomena should help to optimize the relevant operation conditions in order to avoid those stressing the catalyst unnecessarily. We will give examples of the anode and cathode side of a HT-PEM fuel cell and also show first results measured in our DRIFTS-XAS in-situ set-up.

Adiabatic modelling of CO2 capture by amine solvents using membrane contactors

The modelling of CO2 chemical absorption using hollow fiber membrane contactors is addressed. A one-dimensional, multicomponent adiabatic model for the CO2 absorption using an aqueous solution of monoethanolamine is established. The model is validated using both, laboratory and pilot-scale experiments. The simulation results are compared to those from an isothermal model in order to investigate the influence of heat release on contactor performance. When industrial relevant operating conditions are applied, the adiabatic simulations show significant axial temperatures peaks, up to 30°C. Correspondingly, local gas-phase vapor molar fractions values of up to 0.4 are attained. If compared to simulations from an isothermal model, deviations of about 60% were obtained, thus clearly demonstrating the necessity of adiabatic modelling under industrial conditions. Intensification factors comprised of between 2 and 10, for external fiber radiuses in the range of 300–100μm are attained. The mass transfer coefficient is varied from 10−4 to 10−3ms−1 which corresponds to experimentally observed values of microporous membranes that are presumably resistant to liquid breakthrough. However, wetting remains a major problem in microporous as well as composite membranes, as capillary condensation is likely to occur.

Liquid Jet Impingement Cooling of a Silicon Carbide Power Conversion Module for Vehicle Applications

Thermal management of power electronics is an extremely challenging problem in the harsh environment of military hybrid vehicles, where the local air and liquid coolant's temperature exceed 100 °C under regular operating conditions. This paper presents the development work of a high heat flux, jet impingement-cooled heat exchanger for a 600-V/50-A silicon carbide (SiC) power module (rated at 175 °C device junction temperature), used for bidirectional power conversion between a 28-V battery and a 300-V dc bus. A total of 50 volume% mixture of water–ethylene glycol (WEG) coolant at 100 °C inlet temperature is the only available coolant. An array of WEG coolant microjets impinges on the base plate of the SiC module. The jet impingement cooling system has been optimized by experimental studies on a surrogate module, along with a high-fidelity computational model, to accurately estimate the SiC device junction temperature in relevant operating conditions. Results indicate that at the design heat load of 151 W (worst-case scenario), the SiC device junction temperature is reduced from 290 °C with commercial-off-the-shelf (COTS) cold plate cooling and 215 °C with COTS microchannel heat exchanger cooling, to 169 °C with a jet impingement-cooled heat exchanger, using the same flow rate.

Need for In Operando Characterization of Electrochemical Interface Features

It has proven particularly difficult to determine the electrode reaction mechanisms in high temperature solid oxide cells (SOCs) that convert gases. The literature is full of contradictory statements and apparently contradictory findings. Often the same type of electrochemical kinetics that apply to low temperature aqueous systems are assumed valid for SOCs, but in our opinion this has not been fruitful as they do not describe the experimental findings properly. Classical room temperature wet electrochemistry has experienced a huge progress in understanding of the electrode reaction mechanisms during the recent 2 decades. This progress has to a large extent been based on combination of electrochemical characterization and in situ and in operando and in situ surface analysis techniques, which so far have been less developed for high temperature electrochemistry above 300 °C. In spite that such techniques have only recently started becoming available for SOC electrochemistry, they are strongly needed. The high temperature solid-solid and solid-gas interfaces tend to change a lot over time due to segregation of electrolyte and electrode constituents and unavoidable trace impurities on a level of few ppm. Furthermore, a porous electrode for solid-gas reactions has three phase boundaries (TPBs), where the electrolyte, the electrode and the gaseous reactants meet. The current density will be concentrated around the TPB. Also, the TPB seems particularly prone to collect trace impurities and minority components, probably because the TPB zone has many sites with higher free energy relative to the rest of the electrode and electrolyte surface. An example of the segregation is the enrichment of yttria to the yttria stabilized zirconia (YSZ – the common SOFC electrolyte) surface, which takes place during a few hours at operation temperature. Furthermore, most often a silica rich layer will form on top of the yttria enriched layer. These “interphase” (not interface) layers may grow and change over time and with changes in temperature and other test conditions. Such segregation seems to be equally pronounced for surfaces and interfaces of the popular perovskite structured metal oxide electrodes such as lanthanum strontium manganites or cobaltites on which a several nanometer thick skin of strontium rich oxide forms already during cell preparation and it is believed that this is changing significantly during electrode operation. However, our knowledge about the driving forces for and the kinetics of the formation of the interphases is very superficial. Thus, there is a strong need for in operando techniques that can characterize and monitor the development of the mentioned features as function of time and changing experimental conditions with respect to electrical, structural and chemical properties at the nano-scale. Going through the various known techniques, it becomes clear that there are not sufficient in operando techniques available to make a comprehensive electrode characterization, and therefore in situ techniques are usually employed, in which at least one of the operation conditions are fulfilled, e.g. temperature but not atmosphere is matching relevant operation conditions. Finally, our analysis of already published results points out the advantage of combining several different techniques such as electrochemical impedance spectroscopy with in operando scanning probe microscopy and surface sensitive chemical analysis methods. Examples of results will be presented.

Biogas to syngas conversion without carbonaceous deposits via the dry reforming reaction using transition metal catalysts

This study investigates how morphology, active metal content and oxygen storage capacity of various bimetallic NiCo/CeZrO2 materials influence their catalytic activity and stability in the methane dry reforming reaction. Catalyst preparation procedure and chemical composition were steered to finally obtain materials, which do not accumulate carbon during the CH4/CO2 reforming reaction. Oxygen storage capacity of the CeZrO2 catalyst support was identified to play a vital role in retarding carbon accumulation over the tested NiCo/CeZrO2 materials. This property can be fully developed when a nanocrystalline solid solution of CeO2 and ZrO2 is formed. Secondly, a high dispersion of nickel and cobalt is crucial for two reasons: (i) catalysts which contain larger NiCo bimetallic particles (for example with 12–18wt.% active metal loading) exhibit a low metal-support interphase that results in enhanced coke formation rates; (ii) additionally, only a marginal gain in methane reforming rates are achieved at higher loadings, compared to catalysts with a 3–6wt.% active metal content. We demonstrated that a NiCo/CeZrO2 catalyst under relevant operating conditions after 400h TOS maintains 79 and 84% conversion of CH4 and CO2, with negligible coke accumulation.

Electrochemical model for SOFC and SOEC mode predicting performance and efficiency

This article presents the combination of two established models: (i) a physically motivated zero-dimensional model that describes the static behavior of planar anode supported SOFCs with high precision in the whole range of technically relevant operating conditions and (ii) a performance model for large area SOFC which expands the behavior of a small cell to a large cell by a discretization of the gas channel. Their combination yields the possibility to make predictions of performance and efficiency of an SOFC or SOEC stack operated in technically relevant operating conditions. Examples will demonstrate the capability of this model as well as the obtained results show that very good electrochemical efficiencies are possible with the state-of-the-art SOCs.

Analysis of shunt currents and associated corrosion of bipolar plates in PEM fuel cells

Proton exchange membrane (PEM) fuel cells are being developed for future NASA missions. These fuel cells use a bipolar construction, with internal manifolds to conduct product water and coolant water. The wetted surfaces of the manifolds present large voltage gradients across the product water and coolant water passages, which can induce water electrolysis in the manifolds of full-scale stacks. If not controlled, shunt currents lead to parasitic power losses and corrosion of the fuel cell metal surfaces; therefore, it is important to understand and characterize the effects of shunt currents. This analysis also applies to electrolyzers, flow-batteries and other devices where an electrolyte manifold experiences voltage gradients. In this work, electrochemical characterizations were performed to estimate these characteristics under relevant operating conditions. A numerical solution of the shunt currents is presented, and the distribution of water electrolysis and corrosion is described.

Performance of diffusion distillation column for production of fuel grade ethanol

AbstractBACKGROUNDDiffusion distillation process was used for separation of ethanol–water mixtures of azeotropic composition. Experimental results were compared with a Stefan–Maxwell equations based mathematical model by assuming point behavior of the process.RESULTSThe performance of a diffusion distillation column for anhydrous ethanol production has been investigated by extending the point behavior to an integral column under process relevant operating conditions. New modeling results are in better agreement with the experimental data than old modeling results. The maximum variation in selectivity is obtained at lowest flow rate (0.05 mol m‐1 s‐1).CONCLUSIONSThe diffusion distillation column should be operated at the lowest possible feed rate and the highest possible vaporization temperature to minimize the column length requirement for anhydrous ethanol production. The effect of selectivity on enrichment of ethanol is negligible in long diffusion distillation columns and flux to flow ratio is more important for determination of enrichment. © 2014 Society of Chemical Industry

Bulk Hydraulic Disposal of Highly Concentrated Fly Ash and Bottom Ash–Water Slurries

Mine backfilling with power plant ash is gaining increasing attention from the power and mining industries for its bulk disposal. In the USA and other countries, mine backfilling with ash is considered as a viable option for stability improvement, subsidence control, and mine site rehabilitation. This paper presents the results of rheological studies conducted on fly ash and mixtures of fly ash and bottom ash samples collected from NTPC Talcher, Odisha. The complex hydro-mixture slurry indicated non-Newtonian pseudo-plastic behavior in the mass concentration range of 60–67.5%. A non-Newtonian power law head loss model was used to evaluate the head loss of ash slurry in pipelines having nominal bores in the range of 100–300 mm. The results indicated that the addition of bottom ash to fly ash slurry at a given solids concentration has a beneficial effect in reducing the pumping power requirement. A design chart for the fly ash mixture slurry has been formulated indicating the variation in backfilling rate with relative head requirements for a given length of pipeline for a range of pipe sizes and transport velocities. This is expected to provide relevant pipe flow and operational conditions for bulk disposal of fly ash for mine backfilling purpose.

Potentials for NOx and CO2 reduction of combined NSC + passive SCR system in Diesel passenger car application

The stringent pollutant and CO2 emission limitation in upcoming legislation norms for Diesel passenger car applications force the introduction of exhaust aftertreatment systems with maximum purification and energetic efficiency. The state-off-the-art technologies for NOx reduction, NOx storage and reduction catalyst (NSC) and selective catalytic reduction catalyst (SCR), show challenges for robust performance under strongly extended emission relevant operation conditions from cold start to high engine load and speed. One technical solution is the combination of NSC and passive SCR. This paper presents the experimental results obtained in the EU project “Powerful”. On engine test bench and demon-strator vehicle, an exhaust aftertreatment system combining NSC, passive SCR and fuel reformer technology was developed and experimentally investigated steady-state and on road. The engine independent NSC operation offers potentials for lowered fuel consumption penalty by avoiding engine rich operation. The intrinsic NH3 formation during the NSC regeneration is used for additional NOx conversion on the passive SCR and reduces NOx and CO2 emission.

Zonal rate model for axial and radial flow membrane chromatography, part II: Model‐based scale‐up

Membrane chromatography (MC) systems are finding increasing use in downstream processing trains for therapeutic proteins due to the unique mass-transfer characteristics they provide. As a result, there is increased need for model-based methods to scale-up MC units using data collected on a scaled-down unit. Here, a strategy is presented for MC unit scale-up using the zonal rate model (ZRM). The ZRM partitions an MC unit into virtual flow zones to account for deviations from ideal plug-flow behavior. To permit scale-up, it is first configured for the specific device geometry and flow profiles within the scaled-down unit so as to achieve decoupling of flow and binding related non-idealities. The ZRM is then configured for the preparative-scale unit, which typically utilizes markedly different flow manifolds and membrane architecture. Breakthrough is first analyzed in both units under non-binding conditions using an inexpensive tracer to independently determine unit geometry related parameters of the ZRM. Binding related parameters are then determined from breakthrough data on the scaled-down MC capsule to minimize sample requirements. Model-based scale-up may then be performed to predict band broadening and breakthrough curves on the preparative-scale unit. Here, the approach is shown to be valid when the Pall XT140 and XT5 capsules serve as the preparative and scaled-down units, respectively. In this case, scale-up is facilitated by our finding that the distribution of linear velocities through the membrane in the XT140 capsule is independent of the feed flow rate and the type of protein transmitted. Introduction of this finding into the ZRM permits quantitative predictions of breakthrough over a range of industrially relevant operating conditions.

EXPERIMENTAL AND CFD INVESTIGATION OF R410A DISTRIBUTORS FOR AIR CONDITIONER

In order to obtain a higher heat transfer coefficient of refrigerant flow, the diameter of tubes tends to be smaller and smaller, which leads to large pressure drop of the refrigerant flow. Therefore, multiple numbers of parallel refrigerant passages are employed by using distributors. It is very important to distribute the two-phase refrigerant evenly into each tube, otherwise the thermal performance is significantly deteriorated. The performance reduction by flow mal-distribution could be as large as 20–25%. The goal of this paper is to investigate the influence of different configurations to the performance of refrigerant distributors by experiments and computational fluid dynamic code. The effects of mass flow rate and quality of distributor inlet on the characteristics were also quantitatively considered. In this study, an experiment test rig was built to measure the mass flow rate and quality of four circuits after using distributors under different conditions respectively. Refrigerant R410A was used as working fluids. Three classic types (jet, cyclone and reservoir) of distributors with four paths were manufactured and tested under relevant operating conditions. The inlet temperature was 4°C, mass flow rate range was 50–100 kg/h and the quality range was 0.1–0.3. Experimental results show that the maximum deviation of mass flow rate for jet, cyclone and reservoir type is 13.0%, 21.6% and 10.9%, respectively; the maximum deviation of quality was 0.08, 0.10 and 0.05, respectively. In addition, the standard deviation of mass flow rate and quality over four paths were selected to evaluate the performance of different type distributors. The results show that the performance of jet and reservoir are better than cyclone. The flow behavior of two-phase refrigerant such as phase distribution and separation phenomena was studied by Computational Fluid Dynamics (CFD). The flow pattern of inlet for R410A was investigated and used in the present model. The results in the present model show good and reasonable approximation with experimental data which validate the CFD simulation. CFD simulation analysis elucidates the mechanics which shows how the configuration and operation conditions affect the refrigerant distribution.

Understanding Membrane Degradation Mechanisms Under Heavy Duty Fuel Cell Conditions: A Multi-Disciplinary Approach

The Automotive Partnership of Canada (APC) project on Next-Gen Heavy Duty Fuel Cell Buses is a government supported three-year project dedicated to research and product development of next generation heavy duty fuel cell buses in Canada (www.apc-hdfc.ca). The project represents a collaborative effort between Ballard Power Systems, Simon Fraser University and University of Victoria in British Columbia, Canada. The overarching objective is fundamental understanding of membrane degradation mechanisms, degradation rates, and failure modes under drive cycles and conditions that are typical for heavy duty vehicle operation. The aim is to help develop next generation fuel cell technology that is equivalent to or surpasses incumbent diesel engines in terms of durability and reliability, while reducing capital and warranty costs.In order to develop new durable membrane technologies and devise mitigation strategies to reach desired membrane lifetime, empirical and physical models need to be developed and employed. In this context, understanding the relationship between operation mode and membrane degradation under heavy duty fuel cell conditions is of vital importance. Apart from mechanical degradation such as thinning and pinhole formations, chemical and electrochemical degradation could also take place in perfluorosulfonated acid (PFSA) ionomer membranes. Due to complexity of the underlying processes, degradation mechanisms and their dependence on relevant operating conditions are not generally well established.We present results from an extensive effort that integrates multi-scale, multi-disciplinary modeling with large–scale accelerated degradation testing data. Results are analysed in view of the relative importance of various membrane degradation mechanisms via various chemical and mechanical processes. The versatile multi-scale modeling framework includes structure formation at molecular/meso-scales, water sorption characteristics, kinetics, as well as continuum modelling of chemical and mechanical degradation processes.

Poisoning of a Silica-Supported Cobalt Catalyst due to Presence of Sulfur Impurities in Syngas during Fischer–Tropsch Synthesis: Effects of Chelating Agent

The effects of sulfur impurities on the performance of cobalt-based Fischer–Tropsch catalysts are evaluated under industrially relevant operating conditions of temperature, pressure, and impurity levels. Chelating agents (CAs) were used to modify the SiO2 support, and the performances of the CA-modified catalysts are compared with conventional Co/SiO2 catalysts. For both the Co/SiO2 and CA-modified catalysts, the presence of sulfur in the inlet syngas results in a notable drop in the CO conversion, an undesired shift in the hydrocarbon selectivity toward short-chain hydrocarbons, more olefins in the products, and lower product yields. In the post-poisoning stage, i.e., after termination of sulfur introduction in the inlet syngas, the CA-modified catalysts recover activity and selectivity (to some extent at least), whereas such trends are not observed for the base-case, i.e., unmodified Co/SiO2 catalyst. The improved performance of the CA-modified catalysts in the presence of sulfur is attributed to higher...

Column dynamic studies and breakthrough curve analysis for Cd(II) and Cu(II) ions adsorption onto palm oil boiler mill fly ash (POFA)

This paper investigates the adsorption characteristics of palm oil boiler mill fly ash (POFA) derived from an agricultural waste material in removing Cd(II) and Cu(II) from aqueous solution via column studies. The performance of the study is described through the breakthrough curves concept under relevant operating conditions such as column bed depths (1, 1.5, and 2 cm) and influent metal concentrations (5, 10, and 20 mg/L). The Cd(II) and Cu(II) uptake mechanism is particularly bed depth- and concentration-dependant, favoring higher bed depth and lower influent metal concentration. The highest bed capacity of 34.91 mg Cd(II)/g and 21.93 mg Cu(II)/g of POFA was achieved at 20 mg/L of influent metal concentrations, column bed depth of 2 cm, and flow rate of 5 mL/min. The whole breakthrough curve simulation for both metal ions were best described using the Thomas and Yoon–Nelson models, but it is apparent that the initial region of the breakthrough for Cd(II) was better described using the BDST model. The results illustrate that POFA could be utilized effectively for the removal of Cd(II) and Cu(II) ions from aqueous solution in a fixed-bed column system.

A high-pressure and controlled-flow gas system for catalysis research

A high-pressure gas rig for in situ catalytic reactions at X-ray absorption spectroscopy beamline (BM26A) has been developed. The rig enables catalysts to be studied in a variety of cells under well controlled and industrially relevant operation conditions. A large variety of gas mixtures can be generated and pressures of up to 50 bar with dry gas and 20 bar with wet gas (steam) can be obtained. Analyses of reaction products can be performed using an on-line mass spectrometer.

High Temperature Polybenzimidazole Hollow Fiber Membranes for Hydrogen Separation and Carbon Dioxide Capture from Synthesis Gas

Sustainable reliance on hydrocarbon feedstocks for energy generation requires CO2 separation technology development for energy efficient carbon capture from industrial mixed gas streams. High temperature H2 selective glassy polymer membranes are an attractive option for energy efficient H2/CO2 separations in advanced power production schemes with integrated carbon capture. They enable high overall process efficiencies by providing energy efficient CO2 separations at process relevant operating conditions and correspondingly, minimized parasitic energy losses. Polybenzimidazole (PBI)-based materials have demonstrated commercially attractive H2/CO2 separation characteristics and exceptional tolerance to hydrocarbon fuel derived synthesis (syngas) gas operating conditions and chemical environments. To realize a commercially attractive carbon capture technology based on these PBI materials, development of high performance, robust PBI hollow fiber membranes (HFMs) is required. In this work, we discuss outcomes of our recent efforts to demonstrate and optimize the fabrication and performance of PBI HFMs for use in pre-combustion carbon capture schemes. These efforts have resulted in PBI HFMs with commercially attractive fabrication protocols, defect minimized structures, and commercially attractive permselectivity characteristics at IGCC syngas process relevant conditions. The H2/CO2 separation performance of these PBI HFMs presented here in realistic process conditions is greater than that of any other polymeric system reported to-date.

Modeling of CO2 post-combustion capture using membrane contactors, comparison between one- and two-dimensional approaches

This work presents a numerical comparison between a one-dimensional and a two-dimensional model for CO2 capture through solvent absorption with chemical reaction in a hollow fiber membrane contactor. The relevance of the two approaches is discussed. Industrially relevant operational conditions of post-combustion capture using MEA as reactive solvent were applied for both models. Variable gas and liquid mass transfer resistances, depending on the concentrations and the fluids velocity, were employed for the one-dimensional approach, while differential mass-balances considering convection, diffusion and reaction contributions were employed for the two-dimensional approach. The space-averaged specific molar CO2 absorbed flux estimated by both models was almost identical, with a maximum relative difference of 5.73% for membrane permeabilities (ε/τ) comprised between 0.001 and 0.2 and external fiber radiuses comprised between 0.2 and 0.9mm. Thus it turns out that the one-dimensional approach provides results similar to a two-dimensional approach in the investigated domain with significant lower calculation times.

Transformation and Release of Potassium, Chlorine, and Sulfur from Wheat Straw under Conditions Relevant to Dual Fluidized Bed Gasification

The release and transformation of potassium (K), chlorine (Cl), and sulfur (S) from biomass during thermochemical conversion processes may lead to problems, such as the corrosion and fouling of heat transfer surfaces, agglomeration of bed material, and the poisoning of catalysts used in the downstream processes of gasifiers. To predict and to mitigate effectively these problems, information regarding the quantity and mechanism of the release of these elements under relevant operating conditions is required. In the present work, the release of K, Cl, and S from wheat straw under conditions relevant to dual fluidized bed gasification were quantified in a laboratory-scale bubbling fluidized bed reactor. During the pyrolysis step, the bed temperature ranged from 550 to 900 °C, while the residence time for the fuel in the reactor was fixed at 3 min. The char samples obtained from the pyrolysis step were partially combusted at the same temperature at which they were produced for an additional 3 min. The fractio...