Presence Of CaO Research Articles

Physical chemistry and technology of mullite-corundum refractories for casting special steels

ABSTRACT The article summarises the research on the theoretical foundations of the mullite-corundum refractories technology used in casting special steels by the siphon method. The resistance of these refractories to metal jet casting is achieved with a minimum content of residual silica glass in the bond after firing. To search for the factors providing this condition of work, we focused on the following areas: synthesis and sintering of mullite in the presence of CaO and TiO2 mineralisers; structural properties of invariant compositions of melts of the CaO–Al2O3–SiO2–TiO2 system; physicochemical model of mullite synthesis in the presence of high-silica melt and the kinetics of this transformation; improvement of refractory production technology.

Crystallization and microstructure in K2O substituted SiO2–MgO–Al2O3–Li2O–AlPO4 glass-ceramics

The substitution of K+ ion by Ca2+ or Sr2+ in K2O–SiO2–MgO–Al2O3–B2O3–MgF2–Li2O–AlPO4 glass is executed and the relevant effects on crystallization and microstructure are explored. The glass monoliths obtained by single-step melt-quenching at 1500 ± 10 °C were transparent in nature. Density of base glass was evaluated as 2.66 ± 0.03 g cm−3 and found to be decreased by in presence of CaO or SrO. Opaque glass-ceramics were derived from the transparent glasses by controlled heat-treatment at 1000 ± 10 °C and the predominant crystalline phase was identified as fluorophlogopite mica, KMg3AlSi3O10F2 by X-ray diffraction. Field emission scanning electron microscopy revel that the plate like fluorophlogopite mica crystals predominated in base glass-ceramic (without CaO or SrO doped) but changed to nanocrystalline morphology containing droplet like spherical shaped mica crystallites (average size 200–400 nm) on addition of CaO and SrO. Highest density (=2.74 ± 0.03 g.cm-3) observed for SrO containing glass-ceramic is attributed to the nanocrystalline morphology.

Mechanism insights into sorption enhanced methane steam reforming using Ni-doped CaO for H2 production by DFT study

Sorption Enhanced Steam Methane Reforming (SESMR) provides a promising method to produce high purity hydrogen by in-situ CO2 capture. Ni-doped CaO (Ni-CaO) with catalytic and adsorption active sites can effectively improve the hydrogen production in the SESMR process. It is difficult to determine the enhancement mechanism of Ni-CaO in the SESMR simply by the research experiment. In this study, the reaction mechanisms of SESMR promoted by Ni in the presence of CaO were investigated by the density functional theory (DFT) calculations. The reaction pathway was determined by analyzing the activation barriers along the possible reaction pathways in the SESMR reaction. The SESMR reaction promoted by CaO was also studied as a comparison to clarify the catalysis of Ni. The reaction mechanism of SESMR on Ni and Ni-CaO surfaces was also compared. The results show that the SESMR reaction is more prone to follow path CH4 → CH3 → CH2 → CH → CHO → HCOO → CO2. The OH-assisted dissociation assists in the breaking of first C–H bond in CH4. Process CH3 → CH2 → CH is accomplished by direct dissociation in two steps. Next, CHO is spontaneously formed from CH and O. CHO is oxidized to generate HCOO. Finally, the CO2 is formed by the HCOO dehydrogenation path. The presence of Ni atoms causes a change in the reaction rate limiting step of the SESMR reaction from CH dissociation (on CaO surface) to CH3 dissociation (on Ni-CaO surface). Compared with the reaction energy barrier of CH dissociation (3.215 eV), the SESMR reaction of the Ni-CaO surface is easier to occur with lower reaction energy barrier of 2.030 eV. Besides, Ni reduces the adsorption energy of CH4 (-0.106 eV) and H2O (-1.32 eV) as well as increases the adsorption energy of H2 (-0.047 eV). The SMR reaction is easier to occur on the Ni surface than Ni-CaO surface. The DFT calculations determine the possible mechanism of Ni-CaO in SESMR for H2 production.

Dechlorination of persistent organic pollutants in petrochemical wastewater sludge through a planetary ball mill using synthesized nanocomposite

ABSTRACT Numerous tons of hazardous wastes containing persistent organic pollutants (POPs) are stored in an unsafe manner in the petrochemical industries. The planetary ball mill causes the formation of mineral Cl compounds during the degradation of polychlorinated compounds in the presence of various reagents. In addition, the planetary ball mill has been applied for the synthesis of diverse organic-inorganic hybrid nanomaterials. In the present study, Fe-metal organic framework was prepared using a planetary ball mill, and then Fe@C nanocomposite with core/shell structure was synthesised by carbonisation. X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM) were utilised to study the synthesised materials. The nanocomposite was used as a reagent to degrade persistent organic pollutants in the sludge of a petrochemical wastewater treatment plant by a planetary ball mill. CaO was also used to compare the effect of nanocomposites on system performance. Ion chromatography (IC) analysis was carried out to determine chlorine mineralisation. Furthermore, Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy were applied to determine chemical bonds. The results illustrated a zero-valent iron nanoparticle in the core protected by carbon shell in a synthesised nanocomposite with a core/shell structure. Hence, nanocomposite was the most efficient additive, with 97% dechlorination efficiency in the first hour while the efficiency of the planetary ball mill in the presence of CaO was only 76% after 12 hours of milling. Furthermore, major changes occurred in the organic phases, carbon and chlorine bonds. Simultaneously, graphite and amorphous carbon were produced in the final products after milling. This indicates that aromatic structures and C-Cl bonds were broken down into inorganic compounds. Thus, this study presented a practical method of producing materials while degrading hazardous pollutants in petrochemical wastewater sludge through a planetary ball mill.

Effect of adding Ce on the optostructural and electrical properties of cubic CaSnO3

CaSnO3 and Ce doped CaSnO3 particles were synthesized by co-precipitation method. An X-ray diffraction study shows that the synthesized CaSnO3 particles belongs to orthorhombic structure and the crystalline peaks shift toward higher angle with increasing Ce concentration. The Fourier Transform Infrared Spectra witnessed the presence of Ca-O, Sn-O and Ce-O vibrations in the synthesized particles. The optical absorption is higher in the UV-region and the band gap energy is decreased from 4.3 eV to 3.2 eV. The photoluminescence spectra affirmed that the emission peak shifts toward the visible region during the incorporation of Ce. Scanning electron microscope images depicted the cubic block-like morphology with sharp edges. From the electrochemical measurements, 0.02 M Ce doped CaSnO3 electrode exhibited higher specific capacitance value of 916 F/g due to its lower charge transfer resistance value than that of 0.01 M and 0.03 M Ce doped CaSnO3.

Revealing the effects of Ni on sorption-enhanced water-gas shift reaction of CaO for H2 production by density functional theory

The sorption-enhanced water-gas shift (SE-WGS) reaction promoted by Ni-doped CaO (Ni-CaO) was sufficiently investigated by experiments that only displayed macroscopic results instead of microscopic reaction mechanisms. In this work, density functional theory (DFT) was employed to clarify the mechanisms of SE-WGS reaction which was catalyzed by Ni in the presence of CaO. The SE-WGS reaction only promoted by CaO was used as a comparison to clarify the catalysis of Ni. The analysis of electron differential densities, the partial density of states, and formation energy indicate that Ni causes the higher stability and reactivity of the Ni-CaO model than the CaO model. The Ni promotes the release of H2* by rising the adsorption energy of H2*(−0.05 eV) and retains the efficient CO2 capture with the adsorption energy of −1.56 eV. The transient state calculations indicate the SE-WGS reaction prefers to proceed along with the redox mechanism compared with the carboxyl and formate mechanisms on the Ni-CaO surface. The energy barriers for the CO2* generation, H2* generation and desorption are respectively 0.74, 1.77 and 0.10 eV on the Ni-CaO surface, which are lower than those on the CaO surface. Therefore, Ni helps to improve CO conversion and H2 productivity which is consistent with the previous experimental results.

NO removal performance of CO in carbonation stage of calcium looping for CO2 capture

Calcium looping realizes CO 2 capture via the cyclic calcination/carbonation of CaO. The combustion of fuel supplies energy for the calciner. It is unavoidable that some unburned char in the calciner flows into the carbonator, generating CO due to the hypoxic atmosphere in the carbonator. CO can reduce NO in the flue gases from coal-fired power plants. In this work, NO removal performance of CO in the carbonation stage of calcium looping for CO 2 capture was investigated in a bubbling fluidized bed reactor. The effects of carbonation temperature, CO concentration, CO 2 capture, type of CaO, number of CO 2 capture cycles and presence of char on NO removal by CO in carbonation stage of calcium looping were discussed. CaO possesses an efficient catalytic effect on NO removal by CO. High temperature and high CO concentration lead to high NO removal efficiency of CO in the presence of CaO. Taking account of better NO removal and CO 2 capture, the optimal carbonation temperature is 650 °C. The carbonation of CaO reduces the catalytic activity of CaO for NO removal by CO due to the formation of CaCO 3 . Besides, the catalytic performance of CaO on NO removal by CO gradually decreases with the number of CO 2 capture cycles. This is because the sintering of CaO leads to the fusion of CaO grains and blockage of pores in CaO, hindering the diffusion of NO and CO. The high CaO content and porous structure of calcium-based sorbents are beneficial for NO removal by CO. The presence of char promotes NO removal by CO in the carbonator. CO 2 /NO removal efficiencies can reach above 90%. The efficient simultaneous NO and CO 2 removal by CO and CaO in the carbonation step of the calcium looping seems promising.

Sulfate-bearing clay and Pietra Serena sludge: Raw materials for the development of alkali activated binders

The feasibility of transforming the residues of cultivation of two rocks into secondary raw materials through the alkali activation process has been assessed. Mixtures of a sulfate-bearing kaolinitic clay (L02-K) and a sludge derived by the sewing of Pietra Serena stone (sPS) have been investigated. These materials were preliminarily treated at high temperature to improve their reactivity (heat-treated samples are hereafter labelled as L02-MK and sPS-800). Pastes were prepared with mixtures of L02-MK and sPS-800 in different weight proportions by using 8 M NaOH solutions as alkaline activator and cured at 85 °C for 24 h. Mechanical strength was determined after 1, 7 and 28 days and the reaction products were characterized by XPRD, SEM/EDX and MAS-NMR. Sulfate solubility was quantified by leaching tests.The alkali activation of the sole sulfate-bearing clay gives a material with developed mechanical strength of 4(1) MPa. Some N-A-S-H gel forms together with gibbsite and thenardite, which can be easily leached. Better results are obtained by the activation of mixtures of the two precursors, and mixed alkali cements or hybrid cements are obtained. The presence of CaO from heat-treated Pietra Serena sludge improves the mechanical strength of the resulting pastes up to 11.8(9) MPa. In this case, a mixture of gels forms, specifically, a calcium-rich gel (C-A-S-H-type) co-exists with (N,C)-A-S-H-type gel. U-phase and CAN-type zeolites also form. They trap sulfate from the clay and considerably reduce sulfate solubility. In conclusion, L02-MK and sPS-800 are promising raw materials for alkaline cements, whose properties may suggest application in soil stabilization or in waste confinement.

Understanding the enhancement of CaO on water gas shift reaction for H2 production by density functional theory

The water gas shift reaction is an important reaction for H2 production in various industrial applications. The presence of CaO can promote the reactivity of the water gas shift reaction without any catalysts, but the enhancement mechanism of CaO in this reaction is difficult to determine just by the experiment. In this work, the water gas shift reaction along four possible pathways on the CaO surface were studied by density functional theory (DFT) analysis. The energy barriers along the pathways were analyzed to determine the most possible reaction pathway and role of the CaO surface. The DFT calculation results show that the WGS reaction is more prone to proceed along the redox-a pathway probably: H2O dissociates into hydroxyl and atomic H spontaneously when H2O and CO co-adsorb on the CaO surface, then the hydroxyl continues to dissociate and CO is oxidized by the generated atomic O. Afterwards, H2 molecule generates from two atomic H, and then CO2 adsorbs and H2 desorbs simultaneously on the CaO surface. The CaO surface enables the spontaneous dissociation of H2O, which is the rate-limiting step of WGS reaction. The generation of CO2 is facilitated, and the energy barrier is reduced from 2.304 to 0.757 eV on the CaO surface. Besides, the formation of CO32− on the surface avoids the energy barrier for CO2 desorption, while the CO2 also occupies the active site and reduces the enhancement of CaO on WGS reaction. The calculation result reinforces the comprehension on the mechanism of CaO on WGS reaction.

Design and fabrication of photocatalytic coatings with α/β-Bi2O3 and recycled-fly ash for environmental remediation and solar fuel generation

To promote a circular economy, alkali-activated recycled fly ash (AAFA) can be used as an alternative binder for fabricating mortar coatings. The AAFA binder can also be functionalized with photocatalysts for application in environmental remediation. Here, α/β-Bi2O3 homojunction photocatalysts were incorporated into AAFA mortar coatings to confer photocatalytic properties for two applications, namely, self-cleaning and solar fuel generation from CO2 photoconversion. The α/β-Bi2O3 homojunctions were prepared using three methods. The homojunctions had a higher proportion of the β-Bi2O3 phase compared to α-Bi2O3; additionally, they exhibited with a 2D morphology and a bandgap suitable for visible-light activation. X-ray diffraction and energy dispersive spectroscopy analysis of the mortar coatings showed that the inorganic matrix comprised two frameworks based on calcium silicate hydrate and aluminosilicate hydrate, with high porosity. The photocatalytic mortar coatings exhibited self-cleaning activity, with the highest efficiency of 31%. This result was corroborated by total organic carbon analysis, which showed ~15% mineralization. The specimens also showed high activity for CO2 photoconversion to solar fuels such as formic acid (1932 μmol/g) and methanol (6 μmol/g) under visible light. These results were related to the synergistic effect of the mesoporous framework developed after alkaline activation, more efficient charge transfer in the homojunctions, enhanced CO2 affinity, and the presence of CaO, MgO, Na2O, and SiO2 in the binder. The efficiencies for both applications are comparable to those reported previously. The present approach is potentially applicable not only for minimizing the environmental impact of waste materials by reducing the disposal of fly ash in landfills, but also for producing value-added compounds and reducing the maintenance cost of buildings.

Modeling on the pyrolysis of particles of low-rank coal and CaO mixture

Pyrolysis of low-rank coal at the presence of CaO can result in uniform mixture of residual char and CaO, which can further produce calcium carbide for providing alternative way of ethyne production. Large mixture (i.e. with the addition of CaO) coal particle at centimeter-scale is usually used in such industrial pyrolysis process, for which intraparticle phenomena and pyrolysis behaviors remain largely unknown. The pyrolysis process of a centimeter-scaled mixture coal particle in ellipsoidal shape was studied with a model coupling pyrolysis kinetics and intraparticle transport phenomena. The model was validated against experimental data from both the literature and the present experiments. It was demonstrated that the addition of CaO into the coal particle can promote coal pyrolysis. Quantitative results regarding the effect of particle properties show that smaller particle size can promote the whole pyrolysis process while larger porosity is favorable for the timely removal of volatile from the particle. As for the effect of operating conditions, higher operating temperature and higher purge rate of nitrogen can promote particle heating, and therefore beneficial for the pyrolysis process. Considering pyrolysis efficiency, energy consumption and process complexity, the mixture coal particle with the size of a = 40 mm, b = 29 mm and c = 20 mm in ellipsoidal shape and the porosity of 0.07 at the operating temperature of 923 K and nitrogen purge rate of 0.1 m/s was appropriate for the potential industrial pyrolysis process. The present simulation results on the effect of particle properties and operating conditions could help to provide a simple, quick method of selecting proper particle properties and operating conditions for the industrial application of low-rank coal through pyrolysis with the addition of CaO.

Techno-economic Assessment of Co-gasification of Rice Husk and Plastic Waste as an Off-grid Power Source for Small Scale Rice Milling - an Aspen Plus Model

Inadequate access to electricity has necessitated other alternative energy sources in Nigeria. As a result, small modern rice milling uses mainly energy from diesel-fired generator, while traditional milling still uses energy from the combustion of wood. Consequently, the cost of diesel as fuel has contributed to the high operating cost of the rice mills. Moreover, these sources of energy contribute hugely to CO2 emission. Also, rice husk (RH) generated as waste from the mill is not utilized properly in the country, thereby adding to the environmental issue due to open burning disposal. In addition, a large amount of sachet water plastic waste (SWPW) is also generated in Nigeria. This research therefore presents co-gasification of RH and SWPW in the presence of CaO with integrated combined heat and power (CHP) generation for small scale rice mills in Nigeria using Aspen plus model. Optimum operating conditions in the gasification section were determined as inputs to the CHP section. At 800 °C gasification temperature with feed capacity of 30 kg SWPW/hr and 70 kg RH/hr, the system showed a CHP efficiency of 70%, which is sufficient for the rice mill energy requirement. The economic assessment of the system showed promising economic feasibility with a net present value (NPV) value of $1.47 million over 15 years. While the levelized cost of electricity (LCOE) value of $0.07-0.11/kWh indicates the cost attractiveness of the system as compared to other sources of energy in Nigeria. The system demonstrated an alternative cost and GHG emission savings source of energy. The project will promote the UN’s sustainable development goals of affordable and clean energy.

Effect of calcite on desulfurization and denitration performance of activated coke and its mechanism

Different contents of calcite (CaCO3) were loaded ondeminerized Ningxia anthracite during the activated coke (AC) preparation, the influence of which on the preparation, desulfurization and/or denitrification of AC was investigated. The results show thatcalcite could regulate the pore structure and surface chemistry of AC. The total specific surface area and the micropore specific surface area decrease from 746 m2/g and 645 m2/g to 408 m2/g and 244 m2/g, respectively, when the calciteaddition was up to 8%. The total volume and the micropore volume alsodecrease with calcite addition, while the volume of mesopores and macropores increases. As the calcite addition rises, the oxygen-containing functional group and π–π* are increased linearly, and the sulfur capacity of AC first increases and then decreases during single desulfurization, the NX-2%CaCO3-AC having the best desulfurization capacity (84.0 mg /g). The increase in the content of π–π* by the addition of calcite promotes the SO2 oxidation process, and also promotes the denitrification process, the NO conversion (16.9%) with the addition of 2%CaCO3 is 1.14 times higher than that of AC (7.9%), mainly owing to the increase in the number of basic groups. However, during simultaneous desulfurization and denitrification, the presence of CaO in the AC promotes the sulfur capacity but decreases the NO removal efficiency due to the competitive adsorption and ammonium salt generation.

Investigation on the Kinetics and Mechanism of Aluminothermic Reduction of Molybdenum Trioxide: Non-isothermal Kinetics

In this work, effect of milling process and CaO addition on the reaction mechanism and kinetics of aluminothermic reduction of molybdenum trioxide were studied by simultaneous thermal analysis, differential scanning calorimetry, X-ray diffraction analysis and Coats–Redfern method, respectively. For this purpose, molybdenum trioxide was reduced by Al powder under two different conditions of mechanical activation by milling process and as received form mixed by stoichiometric amount of CaO that was required for creation of CaMoO4 intermediate phase. In the case of using milled molybdenum trioxide, 20 wt% of aluminum oxide was used as heat absorber. The results showed that by using mechanically activated MoO3, the reduction reactions proceeded through the formation of intermediate phases of Al2(MoO4)3 and MoO2. In the presence of CaO, the intermediate phase was changed to CaMoO4. In both cases, the reaction temperatures and their activation energies decreased. The kinetic model for the aluminothermic reduction of un-milled and milled molybdenum trioxide was determined as chemical control, where by addition of CaO, mechanism of the reduction reaction was changed to diffusion control.

Electrochemical Methods for Analysis of Hydroxide and Oxide Impurities in Li, Mg/Na, and Ca Based Molten Chloride Salts

Due to their highly hygroscopic nature, molten chloride salts are known to resist complete thermal dehydration, resulting in incomplete water removal prior to use in high temperature applications. At temperatures required to melt these salts, this can result in hydrolysis, leading to formation of oxides or hydroxides. Depending on application, these hydrolytic impurities can cause further adverse effects through the formation of insoluble oxides and oxychlorides. In this paper, previously published work is reviewed to discuss electrochemical methods used for identification and measurement of hydrolytic impurities in LiCl and CaCl2 as well as their effect on electrolytic processes. Cyclic voltammetry shows that thermal dehydration of LiCl and CaCl2 promotes LiOH and CaO formation, respectively. The presence of CaO in a CaCl2-CeCl3 salt meant to emulate a typical actinide-chloride electrorefining salt causes insoluble Ce2O3 and CeClO to form, reducing electrochemical signals as the active species is precipitated as an insoluble phase.

The potential oxidation characteristics of CaCr2O4 during coal combustion with solid waste in a fluidized bed boiler: A thermogravimetric analysis

CaCr2O4 (Cr (III)), mainly generated through the decomposition of CaCrO4 (Cr (VI)), is a significant intermediate for toxic Cr (VI) formation during solid fuel combustion. In this study, the formation, oxidation and sulfation kinetics of CaCr2O4 were analyzed to forecast the potential of CaCr2O4 oxidation during co-firing of coal and solid waste in a circulating fluidized bed boiler. The results indicated that the formation and oxidation of CaCr2O4 were fitted to a single step nucleation and growth model while CaCr2O4 sulfation was fitted to a shrinking core model. CaCr2O4 formation through CaCrO4 decomposition was favored in oxygen-lean atmosphere and considerably suppressed in the presence of oxygen. In contrast, CaCr2O4 oxidation was mainly determined by the contacts between CaCr2O4 and CaSO4/CaO, which influenced not only oxidation rates but also the product species. Moreover, the oxidation reactivity of CaCr2O4 was higher in the presence of CaO than that of CaSO4. On the other hand, CaCr2O4 sulfation can occur more easily than CaCr2O4 oxidation, the reaction rate of which was deeply affected by sulfate product layer. Findings in this study suggested that spraying calcium in furnace for desulphurization may increase the risk of CaCr2O4 oxidation. Measures including the adjustment of Ca/S ratio in blended fuel (with added limestone) and operating conditions (such as temperature and local atmosphere) in co-firing system could be taken to control CaCr2O4 formation and oxidation.

Temperature dependent reduction of Cr(VI) to Cr(V) aroused by CaO during thermal treatment of solid waste containing Cr(VI)

Cr(VI) compounds at high temperature usually tend to decompose and reduce into Cr(III) due to thermodynamically instability for Cr(VI). This study found Cr(VI) could be reduced into Cr(V) instead of Cr(III) in the presence of CaO during heating solid waste containing Cr(VI). CaCrO4 is prepared and mixed with CaO as simulated solid waste containing Cr(VI). It was found that CaCrO4 reacted with CaO and formed a new product Ca5(CrO4)3O0.5 at temperature range of 800 and 1000 °C. The valence state of Cr in Ca5(CrO4)3O0.5 is determined to be +5 b y XPS analysis, and the color for new formed Cr(V) is observed in green, similar to Cr(III) compounds. The temperature and CaO are two keys to arouse the reduction reaction of Cr(VI) into Cr(V). In particular, the reduction of Cr(VI) into Cr(V) is strongly depended on temperature (800–1000 °C), this reaction can be balanced within 10 min, while prolonging sintering time has little help for promoting the reduction of Cr(VI) to Cr(V). Additionally, it was found Cr(V) can keep stable and not be re-oxidized into Cr(VI) at 800–1000 °C. Above results offers some new understanding and knowledge about the formation of Cr(V) in presence of much CaO or CaCO3 during heating solid waste containing Cr(VI).

Two Routes for the Synthesis of Phosphorothioates via P‐S Coupling Reaction of Dialkyl Phosphites with Thiols or a Mixture of Alkyl Halides and Thiourea in the Presence of CaO

AbstractIn this report, two routes for the synthesis of phosphorothioates via a P−S cross coupling reaction of thiols with dialkyl phosphites or a three component reaction of alkyl halides, thiourea and dialkyl phosphite in the presence of CaO has been studied. By presented methods, various phosphorothioates are obtained under transition metal‐free condition. The reactions are proceeded with formation of a known intermediate of disulfide via the oxidation of thiols and followed by nucleophilic substitution of dialkyl phosphite with the disulfide intermediate gave phosphorothioate.

Porous carbon supported calcium oxide for CO2 adsorption and separation of CO2/CH4

ABSTRACT Calcium oxide incorporated porous carbon materials were synthesized by the impregnation method to study CO2 adsorption and separation of CO2/CH4. The X-ray diffraction, Raman analysis, N2 isotherms at 77 K, and SEM with EDX analysis were used to characterize synthesized materials. XRD and N2 isotherm results have confirmed that synthesized carbon has porosity, and EDX analysis has reported that the presence of CaO on porous carbon. 10CaO/porous carbon has shown 31 cm3 g−1 of CO2 adsorption which was higher than bare porous carbon CO2 adsorption 17.5 cm3 g−1 at 298 K, 1 bar. It was attributed to electrostatic interaction between CaO and CO2. However, CH4 adsorption was decreased by a decrease in surface area. The selectivity of CO2/CH4 was higher for 10CaO/porous carbon and the heat of CO2 adsorption was 36 KJ/mol at high adsorption of CO2. Moreover, CO2 adsorption was the same in each adsorption cycle.

Surface characterization of ash-layered olivine from fluidized bed biomass gasification

The present study aims to present a comprehensive characterization of the surface of ash-layered olivine bed particles from dual fluidized bed gasification. It is well known from operation experience at industrial gasification plants that the bed material is activated during operation concerning its positive influence on gasification reactions. This is due to the built up of ash layers on the bed material particles; however, the chemical mechanisms are not well understood yet. Olivine samples from long-term operation in an industrial-scale gasification plant were investigated in comparison to fresh unused olivine. Changes of the surface morphology due to Ca-enrichment showed a significant increase of their surface area. Furthermore, the Ca-enrichment on the ash layer surface was distinctively associated to CaO being present. The presence of CaO on the surface was proven by adsorption tests of carbon monoxide as model compound. The detailed characterization contributes to a deeper understanding of the surface properties of ash layers and forms the basis for further investigations into their influence on gasification reactions.