Steam Atmosphere Research Articles

Energy Recovery from Municipal Solid Waste through Co-Gasification Using Steam or Carbon Dioxide with Olive By-Products

The valorization of untreated municipal waste (MSW) biochar for energetic uses, through its co-gasification with olive stone (OST) biochar under a steam or carbon dioxide atmosphere, was investigated. The experiments were conducted in a fixed bed unit and a thermal analysis–mass spectrometer system. The thermal behavior, reactivity, conversion, product gas composition, syngas yield and energy potential were determined, while the influence of the fuel’s internal structure, chemical functional groups and operating conditions were examined. The concentrations of H2 and CO2 in the product gas mixture under a steam atmosphere were increased with steam/biochar ratio, while that of CO was reduced. At a steam/biochar = 3 H2 yield, the higher heating value and conversion for the OST were 52.8%, 10.8 MJ/m3 and 87.5%; for the MSW, they were 44.4%, 9.9 MJ/m3 and 51.5%, whereas for their blend, they were 50%, 10.6 MJ/m3 and 76.6%, respectively. Under a carbon dioxide atmosphere, the reactivity and conversion of the OST biochar (84%) were significantly higher as compared with the MSW biochar (50%). The higher heating value of the product gas was 12.4–12.9 MJ/m3. Co-gasification of the MSW with OST (in proportions 30:70) resulted in the enhanced reactivity, conversion, syngas yield and heating value of product gas compared with gasification of solely MSW material.

РАЗМОРАЖИВАНИЕ МЯСА ПТИЦЫ В УСЛОВИЯХ ВАКУУМА С ОДНОВРЕМЕННЫМ МАССИРОВАНИЕМ СЫРЬЯ

Poultry meat defrosting process has been studies in industry conditions with meat massaging in vacuum in water saturated steam atmosphere. Such approach gives the possibility to avoid losses and receive quality raw material for further processing.

SIMULATION OF BOILER FEED PUMP USING CONTROLLER PROGRAM: A CASE STUDY OF SAPELE POWER BOILER FEED PUMP

The goal of this work is to automate the Sapele Power Plant Boiler Feed Pumps (BFPs) using CODESYS software to simulate BFP controlled by a proposed PLC system that was manually controlled. The boiler pressure, level, feed stream flow, and primary heat transport (PHT) pressure BFP were restored to their optimal levels within a few seconds after trip. This was possible for the standby program used for automation within 14 seconds when compared to the manual process that was in place. During the simulation, the BFP goes into standby mode after 14 seconds. The results obtained under automated condition shows the boiler pressure rises to 40.3 kg/cm-1s-2 and remained stable for 147 seconds as against 55.9 kg/cm-1s-2 in 25 seconds under unautomated conditions. The flow rate of the feed water shows a decrease of -0.172 m at 50 seconds. The boiler pressure rose further to 44 kg/cm-1s-2 at 175 seconds, which corresponds to a specific gravity value of 59.5 kg/cm3 at the same time. At 146 seconds, the feed water hits the trip setting of -2.85m owed to low specific gravity (SG) level when compared to the unautomated condition. Thus, a further increase reached fluctuation level of -10m at 200 seconds. The PHT was 88.5 kg/cm-1s-2 at 146 seconds contrary to the expected pressure of 105.6 kg/cm-1s-2 for unautomated state. This change after 146 seconds results from generator trip. The pressure increases to 90.2 kg/cm3 at approximately 148 seconds and subsequently decreases to 48 kg/cm3 consequently opening of the condenser steam discharge valve (CSDVs) and atmospheric steam discharge valve (ASDVs) during the simulation state.

High Temperature Oxidation of Zircaloy-4 Under Conditions Simulating a Loss of Cooling Accident in Spent Fuel Pools Examined with Raman Imaging and 18o Tracer Techniques

Since the Fukushima accident, an increased attention is continuously paid to the vulnerability of the Spent Fuel Pools (SFPs). In SFPs, for different reasons, degradation of the fuel rods induced by oxidation in air-steam mixtures after dewatering is a major safety concern: (i) the cladding material is the only barrier left against fission product dissemination, (ii) the heat released by the oxidation reactions can overcome the residual decay heat of the fuel and may become the main driving force to the accident escalation, (iii) hydrogen production is a strong concern because of the presence of steam, (iv) presence of air in the atmosphere is known to be an aggravating factor because of the “catalytic” role of nitrogen on the oxidation mechanism.In this study, high temperature oxidation tests in oxygen, air and air - steam atmospheres were performed with Zircaloy-4 cladding tubes and plates specimens. Because spent fuels are concerned, the presence of the corrosion oxide scale formed in reactor during in-service operation was also considered. The tests described in this study were restricted to the 700 – 950°C range, and mostly performed at 850°C. Raman imaging was used to examine the specimens after the oxidation tests, either directly at the oxide surface, or on metallographic preparations for cross-section examinations.We first used new opportunities given by Raman imaging to analyze, at least qualitatively, the structural and mechanical phenomena involved in this particular corrosion phenomena. Indeed, this method can provide information on the nature of phases that are present in the scale and on the stress level with sub-micron spatial resolution. The different methods used to extract this information that is present in the Raman data will be described and discussed.Moreover, isotopic substitution was also considered. Actually, Raman spectroscopy has also the ability to quantitatively extract the 18O distribution in a zirconia oxide scale after a two stage experiment with a fair accuracy. Raman imaging gave clear evidence for different characteristic distributions of 18O in the scales. Some of them have been correlated with the development of cracks and porosity in the oxide which allows the corroding medium to penetrate locally in the scales. Nitrogen appears to have no or limited influence on the oxygen diffusion, but is observed to reach the metal/oxide interface much faster than oxygen. Thus, we also emphasize the potential of this method to investigate the 18O distribution in such complex corrosion scales.

Improvement of gelation properties of indica rice flour with stabilized rice bran from different thermal treatment

AbstractBackground and ObjectivesRice bran is enriched with bioactive compounds, which makes it more competitive as a functional food raw material. The stabilization of rice bran can inhibit the activity of endogenous enzymes, reduce its oxidation sensitivity, and change its physical and chemical properties, providing more possibilities for its application in the food industry. In this study, rice bran from five stabilization treatments (atmospheric pressure cooking, high‐pressure cooking, atmospheric steam, microwave heating, and extrusion cooking) were investigated for their effect on the gel properties of indica rice flour.FindingsStabilized rice bran could enhance the hydration properties and increase the enthalpy value of rice flour. The gelatinization properties indicated that the viscosity and fluidity of the rice paste were increased, and the aggregation and rearrangement of rice starch were promoted. From the rheological properties, stabilized rice bran enhanced the viscoelasticity of the rice flour gel. In addition, the stabilized rice bran could also reduce the yield of freeze‐thawing water of the rice flour gel. Rice bran with thermal treatments can significantly improve the gel properties of indica rice flour.ConclusionsIndica rice flour mixed with stabilized rice bran showed significant improvements in hydration, gelatinization, rheological properties, and freeze‐thaw stability.Significance and NoveltyIt is potential for the application of the gel from rice flour with stabilized rice bran in the starch‐based food industry.

Model development for oxidation and degradation behavior of accident tolerant Cr coating on Zr alloy cladding under high temperature steam atmosphere

The oxidation and degradation mechanisms of Cr coating on Zr alloy cladding under high temperature steam atmosphere are summarized. Six basic phenomena are considered for model development, including: oxidation of Cr, growth of ZrCr2, formation of Zr(Cr) solid solution, outward diffusion of Zr, reduction of Cr2O3, and volatilization of Cr2O3. The mathematical analysis model is established and validated, demonstrating its good capacity to predict the increase and subsequent decrease in the thickness of Cr2O3 scale, as well as the thickness changes in other individual layers. The developed model is applied in the analysis of the structure evolution of Cr coating under steady state, transient heating conditions and postulated accident scenarios.

Characterization and kinetics of iron oxide reduction by corn straw biochar prepared by pyrolysis using superheated steam atmosphere and hydrothermal processes

Current research on using biochar as foaming agents in electric arc furnace (EAF) steelmaking is limited to pyrolysis biochar treated with nitrogen. Therefore, this study used pyrolysis corn stalk biochar treated with nitrogen (PN) as a reference, the physical and chemical properties, the ability to reduce iron oxide, and the reaction mechanism of pyrolysis corn stalk biochar treated with superheated steam (PSS) and hydrothermal corn stalk biochar (HC) were investigated. HC contains a large number of hydrogen-containing functional groups, which can release large amounts of H2 during the reduction of iron oxide, while PSS has a higher fixed carbon content and produces higher amounts of CO and CO2 gas. Dividing the thermogravimetric results into three reduction stages, the results show that the large amount of volatile fraction contained in HC contributes to Stage 1 and that the gasification reaction ability of PSS is stronger than that of PN. The results of the kinetic analysis showed that the best reaction mechanism for the three reduction stages of the three biochars was the Jander diffusion equation. This work provides theoretical guidance for the use of PSS and HC as foaming agents in EAF steelmaking.

Water condensation zones around main sequence stars

Understanding the set of conditions that allow rocky planets to have liquid water on their surface, in the form of lakes, seas, or oceans, is a major scientific step in determining the fraction of planets potentially suitable for the emergence and development of life as we know it on Earth. This effort is also necessary to define and refine what is known as the habitable zone (HZ) in order to guide the search for exoplanets likely to harbor remotely detectable life forms. To date, most numerical climate studies on this topic have focused on the conditions necessary to maintain oceans, but not to form them in the first place. Here we use the three-dimensional Generic Planetary Climate Model, historically known as the LMD generic global climate model, to simulate water-dominated planetary atmospheres around different types of main sequence stars. The simulations are designed to reproduce the conditions of early ocean formation on rocky planets due to the condensation of the primordial water reservoir at the end of the magma ocean phase. We show that the incoming stellar radiation (ISR) required to form oceans by condensation is always drastically lower than that required to vaporize oceans. We introduce a water condensation limit, which lies at significantly lower ISR than the inner edge of the HZ calculated with three-dimensional numerical climate simulations. This difference is due to a behavior change of water clouds, from low-altitude dayside convective clouds to high-altitude nightside stratospheric clouds. Finally, we calculated the transit spectra, emission spectra, and thermal phase curves of TRAPPIST-1b, c, and d with H2O-rich atmospheres, and compared them to CO2 atmospheres and bare rock simulations. We show using these observables that JWST has the capability to probe steam atmospheres on low-mass planets, and could possibly test the existence of nightside water clouds.

Mechanical characteristics of reclaimed carbon fibre under superheated steam atmosphere and its feasibility for remanufacturing CFRP/CFRTP

This study is performed to investigate the effect of using superheated steam (SHS) in pyrolysis reclamation on the mechanical properties of reclaimed carbon fibres. The mechanical characteristics of the reclaimed fibres are evaluated by analysing their tensile strength and fracture toughness. The feasibility of the reclaimed fibres is assessed by using them to remanufacture composites with epoxy and polypropylene matrices. The performance of the remanufactured composites is evaluated via mechanical testing. The test results show that using SHS in pyrolysis effectively prevents the degradation of the reclaimed carbon fibres. Variations in the tensile strength and fracture toughness of the reclaimed fibres are lower when pyrolysis is performed under a SHS atmosphere. Moreover, the mechanical characteristics of the remanufactured composites show that using SHS during pyrolysis reduces the degradation of the bending strength and Izod impact strength.

Pyrolysis and steam gasification properties of mangroves

The rising atmospheric CO2 emissions from the burning of fossil fuels remains a global concern. Mangrove forests, which are important for global biodiversity, are known for their high carbon fixation capacity. However, the characteristics of the pyrolysis and gasification of mangroves remain unclear. Thus, this study focused on mangroves' basic pyrolysis and steam gasification properties for use as a gasification fuel. Three mangrove species: Rhizophora mucronata, Bruguiera cylindrica, and Avicennia marina, were used as experimental samples. In addition, three species of land wood were used for comparison: Eucalyptus, Japanese cedar, and Japanese cypress. In addition to the raw sample, a demineralized sample was used for each sample to account for the influence of the alkali and alkaline earth metals (AAEMs) on pyrolysis and steam gasification. Thermogravimetric analysis was performed to obtain thermogravimetric curves of mangroves and land wood. A laboratory-scale instrument for pyrolysis and gasification using a batch-type horizontal electric furnace was also used at 800 °C in an inert and steam atmosphere. The char yield of raw mangroves was high and independent of the Klason lignin content, suggesting that AAEMs influence char formation during the initial pyrolysis of the mangroves. The results of pyrolysis and gasification under steam atmosphere showed that the H2 production ratio (Steam/Inert) from mangroves was 2.52–5.33, compared to 1.76–2.35 for land woods, the addition of steam significantly enhanced the steam gasification of mangroves. Mangroves contain relatively large amounts of AAEMs, which indicates their potential as a gasification feedstock.

Elemental and isotopic fractionation as fossils of water escape from Venus

We develop a new model of diffusively modulated hydrodynamic escape to predict oxygen isotopic fractionations caused by the loss of water from a steam atmosphere of Venus. The chief technical advance over previous work is including CO2 as a major species. We find that ordinary (δ18O) and mass-independent (Δ17O) fractionations depend mostly on the extent of lithospheric buffering and the ferocity of EUV heating when escape took place, and relatively little on the size of the lost ocean(s). It is likely that Δ17O evolved significantly from its birth state, not only in the atmosphere but also in the silicates of the crust and upper mantle. If both δ18O and Δ17O of Venus are identical to Earth and Moon, we may conclude that Venus and Earth accreted from a common pool. But differences in δ18O and Δ17O can be attributed to escape rather than to genetics. If the differences are large enough, they can be used to constrain when escape took place and the extent of volatile exchange with the lithosphere. Neon and argon systematics are most consistent with minimal escape, especially if an Ar-rich source, possibly derived from comets, is added. However, we also find a novel class of solutions in which Ne and Ar of Venus, Earth, and Mars are evolved from a common source material subject to different vigors of hydrodynamic escape, least extreme for Earth and most extreme for Mars. These alternative models require that Venus was always rather dry (<10% of an Earth ocean) and its water lost very early (before <100 Myrs). The two styles of escape – minimal or extreme – should be readily distinguished by an unambiguous measurement of the Ar/Kr ratio. Finally, we find that predicted D/H enrichments are of order 100 for almost all model parameters. This result, a direct consequence of diffusion-limited escape of H and D, provides support for the overall scenario.

Carbon dioxide desorption behavior of potassium carbonate supported on gamma-alumina solid sorbent in wet fluidized bed under steam atmosphere

Since the carbon dioxide (CO2) capture using solid sorbent is a reversible reaction, the solid sorbent can be regenerated by the desorption process. Therefore, the desorption process is one of the key important processes for the CO2 capture system. Traditionally, most of the literature studies focus on the desorption of solid sorbent under an N2 atmosphere. However, the desorption process of the solid sorbent is inappropriate in the real system because the system will need another process to separate CO2 and nitrogen (N2) after the desorption process. This study focused on the CO2 desorption of potassium carbonate supported on gamma-alumina (K2CO3/γ-Al2O3) in a wet fluidized bed under a steam atmosphere by using the multiphase computational fluid dynamics (CFD) simulation. The effects of water thickness and dry restitution coefficient on CO2 desorption rate were investigated to provide a realistic particle collision behavior and to explore their effects on CO2 desorption phenomena. Moreover, the effect of steam velocity on the hydrodynamic behaviors of fluidization which on CO2 desorption rate was studied. The simulated results demonstrated that all the parameters, water thickness, dry restitution coefficient, and steam velocity had significantly affected system hydrodynamics and CO2 desorption rate in the wet fluidization desorption process. Furthermore, the effect of desorption temperature on CO2 desorption rate was evaluated for finding the appropriate temperature for CO2 desorption process of K2CO3/γ-Al2O3. The results showed that the appropriate desorption temperature for CO2 desorption under steam atmosphere was the temperature over 150 °C.

Agglomeration and transformation of different types of inorganic potassium in biomass during co-gasification with coal

Co-gasification of biomass and coal has many advantages, which also mitigates some of the ash-related problems induced by potassium (K) in biomass. However, this effect varies with the occurrence mode of inorganic K in biomass, which varies with the species of biomass. Therefore, the present work investigated the effect of a bituminous coal on the transformation of K and the ash chemistry of bed agglomeration (without considering the effect of fluidization) during co-gasification (steam and CO2 atmospheres) for different types of inorganic K (K2CO3, K2SO4 and KCl) in biomass. The results show that for both K2CO3 and K2SO4 in biomass, K is mainly retained as KAlSiO4 and K2SO4 in the gasification ash with KAlSiO4 being the dominant phase. In addition, for K2CO3 in biomass, more KAlSiO4 and less K2SO4 are formed under the steam atmosphere than under the CO2 atmosphere. However, the K retention of the ash or the agglomerate for both K2CO3 and K2SO4 in biomass is similar and is much higher than that for KCl in biomass, which tends to release and to induce other ash-related problems. In addition, both the organic compounds of coal and the gasification atmosphere significantly alter the reaction between coal with KCl in biomass: The majority of KCl reacts with coal to form KAlSiO4, the formation of which is quite limited for the coal ash; More K is retained in the ash and more KAlSiO4 is formed under the steam atmosphere than under the CO2 atmosphere. Lastly, although co-gasification with coal (silica sand as the bed material) cannot stop the formation of agglomerates for K2CO3, K2SO4 and KCl in biomass, these agglomerates are more easily to be broken than those produced from the gasification of biomass alone, thus mitigating bed agglomeration in fluidized-bed reactors.

Mechanisms of catalytic reforming of biomass pyrolysis volatiles by Ce promoted Fe–Ni/biochar under N2 and steam atmosphere

In this work, the promotion mechanism of Ce as Fe and Ni catalyst promoter for the catalytic reforming of biomass pyrolysis volatiles was investigated. Fe–Ni–Ce/biochar catalysts were prepared and evaluated for their catalytic performance under N2 and steam atmospheres. The yield of Fe–Ni–Ce/biochar catalyzed syngas (H2+CO) increased from 224.36 mL/g to 1299.14 mL/g (800 °C) with the change of N2 to steam atmosphere. The addition of Ce can introduce a large number of oxygen vacancies to the catalyst, and the increase of oxygen vacancies reduces the reaction barrier of the tar, thus promoting the catalytic activity of the catalyst. In the N2 atmosphere, the electron transfer of Ce3+ ⇄ Ce4+ during catalytic process promotes the production of Fe2+ to ensure the catalytic activity of the catalyst. In the steam atmosphere, Ni will activate the active sites in a steam atmosphere in water molecules. The activated active sites increase the catalyst activity by cyclic reaction with the oxygen vacancies introduced by Ce, resulting in a higher catalytic capacity of Fe–Ni/biochar than Fe–Ce/biochar. To provide the theoretical basis for the preparation of efficient catalysts based on Fe and Ni.

Tribological and Corrosion Behavior of Oxidized and Plasma Nitrided AISI 4140 Steel

Abstract Medium alloy steels are used in several components in the industry where wear and corrosion resistance are required. Different treatments can be used to enhance the surface properties. In this work, the tribological and corrosion behavior of the nitrided and post-oxidized AISI 4140 steel was studied. The samples were plasma nitrided in a 25 %/75 % (N2/H2) gas mixture at 500°C for 15 h. They were oxidized in the same chamber for 1 h in a water steam atmosphere at 400°C. The microstructure of the nitrided and oxidized layer was analyzed using X-ray diffraction (XRD) and scanning electron microscopy. The pin-on-disk tests were performed according to ASTM G99-17, Standard Test Method for Wear Testing with a Pin-on-Disk Apparatus, with a 6-mm diameter alumina ball as counterpart, a sliding distance of 500 m and 1,100 MPa of applied Hertzian pressure. Moreover, reciprocating sliding tests with a stroke length of 5 mm were performed using am AISI 52100 steel ball as a counterpart under a Hertzian pressure of 354 MPa in both dry and lubricated conditions. Salt spray tests following ASTM B117-19, Standard Practice for Operating Salt Spray (Fog) Apparatus, and electrochemical tests in sodium chloride were carried out to evaluate the corrosion behavior. The thickness was 0.5 μm and 3 μm for the oxide layer and the nitrided layer, respectively. Magnetite was detected by XRD. In the pin-on-disk tests conducted under high pressure, the nitrided + oxidized and only nitrided samples presented similar wear resistance. However, the oxide layer allowed a reduction in the friction coefficient in the first cycles with respect to the only nitrided sample in the sliding reciprocating test under low pressure. This behavior was observed in both the dry and lubricated conditions, but it was more noticeable in lubricated ones. Regarding the corrosion behavior, the nitrided + oxidized samples showed better corrosion resistance than the other samples in a chloride solution.

Potential Atmospheric Compositions of TRAPPIST-1 c Constrained by JWST/MIRI Observations at 15 μm

The first James Webb Space Telescope observations of TRAPPIST-1 c showed a secondary eclipse depth of 421 ± 94 ppm at 15 μm, which is consistent with a bare rock surface or a thin, O2-dominated, low-CO2 atmosphere. Here we further explore potential atmospheres for TRAPPIST-1 c by comparing the observed secondary eclipse depth to synthetic spectra of a broader range of plausible environments. To self-consistently incorporate the impact of photochemistry and atmospheric composition on atmospheric thermal structure and predicted eclipse depth, we use a two-column climate model coupled to a photochemical model and simulate O2-dominated, Venus-like, and steam atmospheres. We find that a broader suite of plausible atmospheric compositions are also consistent with the data. For lower-pressure atmospheres (0.1 bar), our O2–CO2 atmospheres produce eclipse depths within 1σ of the data, consistent with the modeling results of Zieba et al. However, for higher-pressure atmospheres, our models produce different temperature–pressure profiles and are less pessimistic, with 1–10 bar O2, 100 ppm CO2 models within 2.0σ–2.2σ of the measured secondary eclipse depth and up to 0.5% CO2 within 2.9σ. Venus-like atmospheres are still unlikely. For thin O2 atmospheres of 0.1 bar with a low abundance of CO2 (∼100 ppm), up to 10% water vapor can be present and still provide an eclipse depth within 1σ of the data. We compared the TRAPPIST-1 c data to modeled steam atmospheres of ≤3 bars, which are 1.7σ–1.8σ from the data and not conclusively ruled out. More data will be required to discriminate between possible atmospheres or more definitively support the bare rock hypothesis.

Origin-of-life Molecules in the Atmosphere after Big Impacts on the Early Earth

The origin of life on Earth would benefit from a prebiotic atmosphere that produced nitriles, like HCN, which enable ribonucleotide synthesis. However, geochemical evidence suggests that Hadean air was relatively oxidizing with negligible photochemical production of prebiotic molecules. These paradoxes are resolved by iron-rich asteroid impacts that transiently reduced the entire atmosphere, allowing nitriles to form in subsequent photochemistry. Here we investigate impact-generated reducing atmospheres using new time-dependent, coupled atmospheric chemistry and climate models that account for gas-phase reactions and surface catalysis. The resulting H2-, CH4-, and NH3-rich atmospheres persist for millions of years, until the hydrogen escapes to space. The HCN and HCCCN production and rainout to the surface can reach 109 molecules cm−2 s−1 in hazy atmospheres with a mole ratio of CH4/CO2 > 0.1. Smaller CH4/CO2 ratios produce HCN rainout rates of <105 molecules cm−2 s−1 and negligible HCCCN. The minimum impactor mass that creates atmospheric CH4/CO2 > 0.1 is 4 × 1020–5 × 1021 kg (570–1330 km diameter), depending on how efficiently iron reacts with a steam atmosphere, the extent of atmospheric equilibration with an impact-induced melt pond, and the surface area of nickel that catalyzes CH4 production. Alternatively, if steam permeates and deeply oxidizes the crust, impactors of ∼1020 kg could be effective. Atmospheres with copious nitriles have >360 K surface temperatures, perhaps posing a challenge for RNA longevity, although cloud albedo can produce cooler climates. Regardless, postimpact cyanide can be stockpiled and used in prebiotic schemes after hydrogen has escaped to space.

Bromine Migration and Product Analysis of Waste Printed Circuit Boards during Microwave Steam‐Gasification‐Assisted Pyrolysis

AbstractBromine in waste printed circuit boards has caused serious harm to the environment. How to deal with it safely is a problem. In this paper, the debromination of waste printed circuit boards by microwave gasification pyrolysis was studied, and the properties of pyrolysis products and the migration of bromine were analyzed. The optimum pyrolysis conditions of microwave steam atmosphere were 600 °C, 1000 W, 50 min, 2 mL/min. Compared with conventional pyrolysis and conventional steam pyrolysis, less solid products (60.39 wt %) were obtained, and more metal copper was enriched. The content increased from 27.46 % and 28.35 % to 30.63 %, respectively, and the diffraction peak intensity of copper was also enhanced. There is no obvious change in the type of functional groups of the solid product, and its microscopic morphology is smoother. Compared with conventional pyrolysis, the phenolic compounds in pyrolysis oil decreased, and increased compared with conventional steam pyrolysis. The content of H2 in the pyrolysis gas increased significantly, and the content of CO decreased significantly. Compared with conventional pyrolysis, the bromine content in pyrolysis gas and pyrolysis oil decreased from 94.5 % and 5.5 % to 1 %, respectively, and more bromine (98 %) in the raw material entered the aqueous solution.

Stability of Glass Ceramic Sealants in Atmospheres with Increased Water Contents

For Solid oxide fuel cells (SOFC), operating at temperatures above 800 °C, glass ceramic sealants are state of the art. The properties of the glass ceramics are adapted to the metallic and ceramic join partners, operation conditions, as also to the atmospheres: fuel gas and air. In SOFCs, glass ceramic sealants offer reliable, long term stable operation over several 10,000 hours of service. The demand to operate solid oxide cells (SOC) in fuel cell- as also in electrolysis cell mode increases the demands of the stability of the sealants against atmospheres. In the electrolysis mode, the SOC-stacks were impinged by gas with high water contents to produce H2. Water contents of up to 95 % and temperatures above 800 °C are hard conditions for all applied materials of SOC stacks. In addition, glass ceramic sealants have to electrical insulator under applied electric voltage. In the electrolysis mode, the applied voltage is even higher than in fuel cell mode. In conclusion, the electrolysis mode is much harsher as fuel cell mode and glass ceramic sealants have to be adapted to this. Glasses in the system BaO-CaO-Al2O3-B2O3-SiO2 with La2O3-additions have the potential to form glass ceramics with extraordinary high coefficient of thermal expansion (CTE)values, which are suitable for use as sealants compatible with Crofer 22 APU interconnect. Their characteristics have been generally described in various studies and are also in focus of our own work and have proven their suitability for use under SOFC operating conditions. However, achieving such high CTE values is especially challenging when these glasses must be designed for use in stacks operating with electrolyte supported cells because sealing and operating temperature are usually higher than in other stack designs. Their behavior under simulated electrolysis conditions together with a direct correlation of test by using these glasses as sealants in real stack designed to operate with electrolyte supported cells has not been investigated yet and presents the scope of this study.For this study, a series of glasses has been prepared as glass powders and characterized in terms of relevant thermophysical properties such as softening behavior, thermal expansion and formation of crystalline phases. La2O3-free sealing glasses established as standards for use in commercial stacks served as references and results of both groups of sealing glasses have been compared. The new La2O3-containing glasses showed CTE-values up 10.8 ppm K-1 at a glass transition temperature ranging between 640°C and 650°C for a partially crystallized microstructure. The softening and crystallization characteristics analyzed by hot stage microscopy and DSC/TGA allow sealing processes of stacks components in the temperature range between 900°C and 950°C. Helium-leakage rates of sealed sandwich type samples made of Crofer 22 APU showed values below 10-8 mbar l-1 s-1. From suitable glasses sandwich type sample sealings made of two Crofer 22 APU coupons have been prepared and exposed to a dual atmosphere in a special test rig under simulated electrolysis conditions at 850 °C with different electrical voltages applied across the sealants and a water content of 50 % in the steam atmosphere. In this out-of-stack environment, the resistance of the glass sealants can be recorded while being treated with high water atmosphere and electric voltage of up to 5 V at 850 °C. The development of resistance over 300 hours of aging show which glass composition fit to the conditions and which exhibit high degradation rates. Afterwards cross sections have been prepared and analyzed by SEM. Effects observed in the interfacial regions glass-Crofer 22 APU and glass-atmosphere have been correlated with the electrical measurements. A 30 layers stack was tested under typical SOEC conditions for approx. 3200 hours. Four different glass types were used and compared in terms of their degradation rate and the ASR value. The selection of the glasses was made according to their thermal expansion and softening behavior as well as their insulating properties.

CO2 Adsorption Behaviors of Biomass-Based Activated Carbons Prepared by a Microwave/Steam Activation Technique for Molecular Sieve.

In this study, the activated carbon was prepared with superior CO2 selective adsorption properties using walnut shells, a biomass waste, as a precursor. The activations were conducted at various times using the microwave heating technique in a steam atmosphere. The surface morphology and chemical composition of activated carbon were analyzed using a scanning electron microscope and energy-dispersive X-ray spectroscopy. The textural properties were investigated using the N2/77K isothermal method, and the structural characteristics were examined using X-ray diffraction analysis. The CO2 and H2 adsorption properties of activated carbon were analyzed using a thermogravimetric analyzer and a high-pressure isothermal adsorption apparatus, respectively, under atmospheric and high-pressure conditions. Depending on the activation time, the specific surface area and total pore volume of the activated carbon were 570-690 m2/g and 0.26-0.34 cm3/g, respectively. The adsorption behaviors of CO2 of the activated carbon were different under atmospheric and high-pressure conditions. At atmospheric pressure, a significant dependence on micropores with diameters less than 0.8 nm was observed, whereas, at high pressure, the micropores and mesopores in the range of 1.6-2.4 nm exhibited a significant dependence. However, H2 adsorption did not occur at relatively low pressures. Consequently, the prepared activated carbon exhibited superior selective adsorption properties for CO2.