Reactivity of bio-coke with CO2

Incorporation of biomass-derived materials in coal blends for cokemaking is one of the strategies that could reduce the levels of greenhouse gas emissions produced by the steelmaking process. Bio-coke refers to the resultant coke prepared with the addition of charcoal to a coal blend. In this work, characteristics of bio-coke gasification by reacting with CO₂ were examined using Thermal Gravimetric Analysis. Bio-coke samples with different levels of charcoal addition to a coal blend were prepared in the CanmetENERGY pilot-scale coke oven. These samples were heated in CO₂ for identification of the minimum gasification temperature. Sample gasification rates at 1000 °C were also measured. It was observed that mineral content plays an important role in the gasification characteristics of the bio-cokes. Those with low mineral content behave very similarly to the reference coke. Higher mineral content bio-coke reacts with CO₂ at a lower temperature. It was found that the gasification characteristics of the bio-cokes are well described by the alkalinity index.     

The performances of higher alcohol synthesis over nickel modified K2CO3/MoS2 catalyst

Ni modified K₂CO₃/MoS₂ catalyst was prepared and the performance of higher alcohol synthesis catalyst was investigated under the conditions: T = 280–340 °C, H₂/CO (molar radio) = 2.0, GHSV = 3000 h^− 1, and P = 10.0 MPa. Compared with conventional K₂CO₃/MoS₂ catalyst, Ni/K₂CO₃/MoS₂ catalyst showed higher activity and higher selectivity to C₂⁺OH. The optimum temperature range was 320–340 °C and the maximum space-time yield (STY) of alcohol 0.30 g/ml h was obtained at 320 °C. The selectivity to hydrocarbons over Ni/K₂CO₃/MoS₂ was higher, however, it was close to that of K₂CO₃/MoS₂ catalyst as the temperature increased. The results indicated that nickel was an efficient promoter to improve the activity and selectivity of K₂CO₃/MoS₂ catalyst.     

Competitiveness of CO2 capture from an industrial solid oxide fuel cell combined heat and power system in the early stage of market introduction

In this article, it was investigated whether potentially low-cost CO₂ capture from SOFC systems could enhance the penetration of SOFC in the energy market in a highly carbon-constrained society in the mid-term future (up to year 2025). The application of 5 MWe SOFC systems for industrial combined heat and power (CHP) generation was considered. For CO₂ capture, oxyfuel combustion of anode off-gas using commercially available technologies was selected. Gas turbine (GT-) CHP plant was considered to be the reference case.Technical results showed that despite the energy penalties due to CO₂ capture and compression, net electrical and heat efficiencies were nearly identical with or without CO₂ capture. This was due to higher heat recovery efficiency by separating SOFC off-gas streams for CO₂ capture. However, CO₂ capture significantly increased the required SOFC and heat exchanger areas.Economic results showed that for above 40-50 $ t⁻¹ CO₂ price, SOFC-CHP systems were more economical when equipped with CO₂ capture. CO₂ capture also enabled SOFC-CHP to compete with GT-CHP at higher cell stack production costs. At zero CO₂ price, cell stack production cost had to be as low as 140 kW⁻¹ for SOFC-CHP to outperform GT-CHP. At 100 $ t⁻¹ CO₂ price, the cell stack production cost requirement raised to 350 $ kW⁻¹. With CO₂ capture, SOFC-CHP still outperformed GT-CHP at a significantly higher cell stack production cost above 900 $ kW⁻¹.     

Calcination and sintering characteristics of limestone under O2/CO2 combustion atmosphere

The O₂/CO₂ coal combustion technology is an innovative combustion technology that can control CO₂, SO₂ and NO_x emissions simultaneously. Calcination and sintering characteristics of limestone under O₂/CO₂ atmosphere were investigated in this paper. The pore size, the specific pore volume and the specific surface area of CaO calcined were measured by N₂ adsorption method. The grain size of CaO calcined was determined by XRD analysis. The specific pore volume and the specific surface area of CaO calcined in O₂/CO₂ atmosphere are less than that of CaO calcined in air at the same temperature. And the pore diameter of CaO calcined in O₂/CO₂ atmosphere is larger than that in air. The specific pore volume and the specific surface area of CaO calcined in O₂/CO₂ atmosphere increase initially with temperature, and then decline as temperature exceeds 1000 °C. The peaks of the specific pore volume and the specific surface area appear at 1000 °C. The specific surface area decreases with increase in the grain size of CaO calcined. The correlations of the grain size with the specific surface area and the specific pore volume can be expressed as L = 744.67 + 464.64 lg(1 / S) and L = − 608.5 + 1342.42 lg(1 / ε), respectively. Sintering has influence on the pore structure of CaO calcined by means of influencing the grain size of CaO.     

Comparison of solvent performance for CO2 capture from coal-derived flue gas: A pilot scale study

The performance of a proprietary solvent (CAER-B2), an amine-carbonate blend, for the absorption of CO₂ from coal-derived flue gas is evaluated and compared with state-of-the-art 30 wt% monoethanolamine (MEA) under similar experimental conditions in a 0.1 MWth pilot plant. The evaluation was done by comparing the carbon capture efficiency, the overall mass transfer rates, and the energy of regeneration of the solvents. For similar carbon loadings of the solvents in the scrubber, comparable mass transfer rates were obtained. The rich loading obtained for the blend was 0.50 mol CO₂/mol amine compared to 0.44 mol CO₂/mol amine for MEA. The energy of regeneration for the blend was about 10% lower than that of 30 wt% MEA. At optimum conditions, the blend shows promise in reducing the energy penalty associated with using industry standard, MEA, as a solvent for CO₂ capture.     

Comparative study of CO and CO2 hydrogenation over supported Rh–Fe catalysts

The hydrogenation of CO, CO + CO₂, and CO₂ over titania-supported Rh, Rh–Fe, and Fe catalysts was carried out in a fixed-bed micro-reactor system nominally operating at 543 K, 20 atm, 20 cm³ min^− 1 gas flow (corresponding to a weight hourly space velocity (WHSV) of 8000 cm³ g_cat^− 1 h^− 1), with a H₂:(CO + CO₂) ratio of 1:1. A comparative study of CO and CO₂ hydrogenation shows that while Rh and Rh–Fe/TiO₂ catalysts exhibited appreciable selectivity to ethanol during CO hydrogenation, they functioned primarily as methanation catalysts during CO₂ hydrogenation. The Fe/TiO₂ sample was primarily a reverse water gas shift catalyst. Higher reaction temperatures favored methane formation over alcohol synthesis and reverse water gas shift. The effect of pressure was not significant over the range of 10 to 20 atm.     

High stability of Ce-promoted Ni/Mg-Al catalysts derived from hydrotalcites in dry reforming of methane

Ce-promoted Ni/Mg-Al catalysts were synthesized by means of a methodology that involves the doping of Ni-Mg-Al mixed oxides derived from hydrotalcites with [Ce(EDTA)]⁻ and subsequent thermal decomposition. The effect of the nominal load of Ce in the catalytic performance of the materials was studied. The solids were characterized by means of XRD, BET area, TPR-H₂, TPD-CO₂, chemical analysis by ICPs, TGA, SEM and TEM and were evaluated in CO₂ reforming of methane at 700 °C. The results indicate the partial reconstruction of the periclase phase during the doping with [Ce(EDTA)]⁻ and the formation of a mixture of crystalline periclase and fluorite phases after the calcination. Catalysts with particle sizes of Ni⁰ between 5 and 9 nm were obtained. Ce presents a promote effect in the degree of reduction of Ni and the amount and strength of the basic sites. It was evident a beneficial effect of cerium in the catalytic activity and selectivity of the doped materials. The increase of the nominal Ce load between 1 and 10% causes no considerable effect in the catalytic activity and selectivity or in the size of crystallite in these materials but in the inhibition of the coke formation. The catalysts show excellent catalytic performance under drastic conditions of reaction and long operation times. The Ce-doped Ni/Mg-Al catalyst is stable up to 100 h of reaction using a feed mixture of CH₄/CO₂/He 10/10/80 at 24 L g⁻¹ h⁻¹, up to 20 h of reaction using CO₂/CH₄ 20/20 at 48 L g⁻¹ h⁻¹ and up to 15 h of reaction using CO₂/CH₄ 40/40 at 96 L g⁻¹ h⁻¹. The filamentous coke formation is demonstrated on the surface of the catalyst when gas of dilution in the reactants is not used. The developed method of synthesis becomes an interesting methodology for obtaining catalysts for CO₂ reforming of methane.     

Plastic wastes, lube oils and carbochemical products as secondary feedstocks for blast-furnace coke production

Two plastic wastes (polyolefin-enriched and multicomponent), two lube oils (paraffinic and synthetic) and one coal-tar were assessed as individual and combined additives to coal blends for the production of blast furnace coke. The effects of adding 2 wt.% of these additives or their mixtures (50:50 w/w) on the coking capacity of coal, coking pressure and coke quality parameters were investigated. It was found that the two plastic wastes reduce fluidity, whereas the addition of oils and tar helps to partially restore the fluidity of the coal-plastic blend. From the co-carbonization of the coking blend with the different wastes in a movable wall oven of over 15 kg capacity, it was deduced that polyolefins have a detrimental effect on coking pressure. The addition of oils and tar to the coal-plastic blend has different modifying effects. Whereas paraffinic oil eliminated the high coking pressure caused by the polyolefins, polyol-ester oil had a weak reducing effect unlike coal-tar which had a strong enhancing effect. The compatibility of the oils/tar with plastics and coal and the beneficial influence of these combinations on coking pressure is discussed in relation to the miscibility of the plastic and the oily and bituminous additives, and the amount and composition of the volatile matter evolved from each additive during pyrolysis as evaluated by thermal analysis. Furthermore, it was found that coke reactivity towards CO₂ (CRI) and coke strength after reaction with CO₂ (CSR) are heavily dependent on the composition of the plastic waste, with polystyrene (PS) and polyethylene terephthalate (PET) having a clear negative effect. The porosity of the cokes obtained from blends containing plastic wastes is always higher, but the pores are smaller in size.     

Characterization of pistachio shell-derived carbons activated by a combination of KOH and CO2 for electric double-layer capacitors

The micropores and surface oxygen functional groups of KOH-activated carbons were respectively extended and desorbed by the gasification of CO₂ during the activation process of chars derived from pistachio shells. These activated carbons (ACs) were found to exhibit ideal capacitive performances (i.e., a rectangular shape of CVs at a wide range of scan rates, high power property, and excellent reversibility) in aqueous electrolytes for electric double-layer capacitors. Although the specific capacitance of these ACs measured at a low scan rate (25 mV s⁻¹) is decreased with reducing the density of surface functional groups, the ideal capacitive characteristics can be maintained at a much higher scan rate (300 mV s⁻¹) when the CO₂ gasification time is equal to or longer than 30 min because of the relatively high proportion of mesopores.     

Kinetics of catalytic steam gasification of bitumen coke

The catalytic steam gasification of coke from Athabasca bitumen was investigated by thermogravimetric analysis using K₂CO₃ and Na₂CO₃ as catalysts, both of which reduced the activation energy of the reaction considerably to 1.2 × 10⁵ J mol⁻¹ and 1.3 × 10⁵ J mol⁻¹, respectively, down from 2.1 × 10⁵ J mol⁻¹ for the uncatalyzed reaction. The reaction rates varied with the partial pressure of steam between 60 kPa and 85 kPa consistent with a Langmuir-Hinshelwood model, but a first order equation was also sufficient given the low partial pressures. The initial rate of gasification of the coke particles correlated linearly with the estimated external surface area of the particles, as expected from a surface reaction involving a non-porous solid. The initial reaction rate increased with increasing the catalyst loading up to 2.4 (mol potassium)/kg. A portion of the catalyst penetrated into the coke, as confirmed by secondary ion mass spectroscopy analysis, where it could not promote the reaction with steam. This result was consistent with a small increase observed in the reaction rate at low catalyst loading. The shrinking core model was successful in predicting the rates at higher conversions from the initial rate data, despite increases in BET surface area with conversion.     

Preparation of a highly microporous carbon from a carpet material and its application as CO2 sorbent

In order to increase the use of carpet wastes (pre- and/or post-consumer wastes), this work studies for the first time the preparation and characterisation of a microporous material from a commercial carpet (pile fiber content: 80% wool/20% nylon; primary and secondary backings: woven polypropylene; binder: polyethylene) and its application for CO₂ capture. The porous material was prepared from an entire carpet material using a standard chemical activation with KOH and then, characterised in terms of their porous structure and surface functional groups. Adsorption of CO₂ was studied using a thermogravimetric analyser at several temperatures (25-100 °C) and under different CO₂ partial pressures (i.e. pure CO₂ flow and a ternary mixture of 15% CO₂, 5% O₂ and 80% N₂). In order to examine the adsorbent regenerability, multiple CO₂ adsorption/desorption cycles were also carried out. The surface area and micropore volume of the porous adsorbent were found to be 1910.17 m² g^− 1 and 0.85 cm³ g^− 1, respectively. The CO₂ adsorption profiles illustrate that the maximum CO₂ capture on the sample was reached in less than 10 min. CO₂ adsorption capacities up to 8.41 wt.% and 3.37 wt.% were achieved at 25 and 70 °C, respectively. Thermal swing regeneration studies showed that the prepared adsorbent has good cyclic regeneration capacities.     

High-pressure solution blending of poly(?-caprolactone) with poly(methyl methacrylate) in acetone + carbon dioxide

The miscibility of blends of poly(?-caprolactone) (PCL, M_w = 14,300) with poly(methyl methacrylate) (PMMA, M_w = 15K or 540K) in acetone + CO₂ mixed solvent has been explored. The liquid-liquid phase boundaries at different temperatures have been determined for mixtures containing 10 wt% total polymer blend, 50 wt% acetone and 40 wt% CO₂. The PCL and PMMA contents of the blends were varied while holding the total polymer concentration at 10 wt%. The polymer blend solutions all displayed LCST-type behavior and required higher pressures than individual polymer components for complete miscibility. Complete miscibilities were achieved at pressures within 40 MPa. The DSC scans show that the blends are microphase-separated. The blends display the melting transition of PCL and the glass transition temperature of the PMMA phases. The presence of PMMA is found to influence the crystallization and melting behavior of PCL in the blends. The DSC results on heat of melting and the FTIR spectra, specifically the changes at 1295 cm⁻¹ band show the changes (decrease) in overall crystallinity of the blend upon addition of PMMA.     

Calcium oxides for CO2 capture obtained from the thermal decomposition of CaCO3 particles coprecipitated with Al ions

Calcium-carbonate powders were coprecipitated with Al³⁺ and then decomposed in air and/or under a CO₂ flux between 590 °C and 1150 °C. The data were analysed using a consecutive-decomposition-dilatometer method and the kinetic results were discussed according to the microstructure analysis done by N₂ adsorption isotherms (78 K), SEM and FT-IR measurements. Below 1000 °C, CaCO₃ particle thermal-decomposition was pseudomorphic, resulting in the formation of a CaO grain porous network. When the CaO grains were formed, the Al³⁺ diffused among them, producing AlO₄ groups that promoted the CaO grain coarsening and reduced O²⁻ surface sites available to CO₂ adsorbed molecules to form CO₃²⁻. In pure CaO, CO₃²⁻ diffused through the grain boundary, enhancing Ca²⁺ and O²⁻ mobility; AlO₄ groups reduced CO₃²⁻ penetration and CaO sintering rate. Above 1000 °C, the sintering rate of the doped samples exceeded that of the undoped, likely because of Al³⁺ diffusion in CaO and viscous flow.     

Electrochemical reduction of high pressure CO2 at a Cu electrode in cold methanol

The electrochemical reduction of high pressure CO₂ with a Cu electrode in cold methanol was investigated. A high pressure stainless steel vessel, with a divided H-type glass cell, was employed. The main products from CO₂ by the electrochemical reduction were methane, ethylene, carbon monoxide and formic acid. In the electrolysis of high pressure CO₂ at low temperature, the reduction products were formed in the order of carbon monoxide, methane, formic acid and ethylene. The best current efficiency of methane was of 20% at −3.0 V. The maximum partial current density for CO₂ reduction was approximately 15 mA cm⁻². The partial current density ratio of CO₂ reduction and hydrogen evolution, i(CO₂)/i(H₂), was more than 2.6 at potentials more positive than −3.0 V. This work can contribute to the large-scale manufacturing of fuel gases from readily available and inexpensive raw materials, CO₂-saturated methanol from industrial absorbers (the Rectisol process).     

Design and operation of pilot plant for CO2 capture from IGCC flue gases by combined cryogenic and hydrate method

This project is a trial conducted under contract with CO₂CRC, Australia of a new CO₂ capture technology that can be applied to integrated gasification combined cycle power plants and other industrial gasification facilities. The technology is based on combination of two low temperature processes, namely cryogenic condensation and the formation of hydrates, to remove CO₂ from the gas stream. The first stage of this technology is condensation at −55 °C where CO₂ concentration is expected to be reduced by up to 75 mol%. Remaining CO₂ is captured in the form of solid hydrate at about 1 °C reducing CO₂ concentration down to 7 mol% using hydrate promoters. This integrated cryogenic condensation and CO₂ hydrate capture technology hold promise for greater reduction of CO₂ emissions at lower cost and energy demand. Overall, the process produced gas with a hydrogen content better than 90 mol%. The concentrated CO₂ stream was produced with 95-97 mol% purity in liquid form at high pressure and is available for re-use or sequestration. The enhancement of carbon dioxide hydrate formation and separation in the presence of new hydrate promoter is also discussed. A laboratory scale flow system for the continuous production of condensed CO₂ and carbon dioxide hydrates is also described and operational details are identified.     

Plasticized chitosan-PVA blend polymer electrolyte based proton battery

This paper focused on the transport studies of PVA-chitosan blended electrolyte system and application in proton batteries. The electrolytes were prepared by the solution cast technique. In this work, 36 wt.% PVA and 24 wt.% chitosan blend doped with 40 wt.% NH₄NO₃ exhibited the highest room temperature conductivity. The conductivity value obtained was 2.07 × 10⁻⁵ S cm⁻¹. EC was then added in various quantities to the 60 wt.% [60 wt.% PVA-40 wt.% chitosan]-40 wt.% NH₄NO₃ composition in order to enhance the conductivity of the sample. The highest conductivity obtained was 1.60 × 10⁻³ S cm⁻¹ for the sample containing 70 wt.% EC. The Rice and Roth model was applied to analyze the conductivity enhancement. The highest conducting sample in the plasticized system was used to fabricate several batteries with configuration Zn//MnO₂. The open circuit potential (OCP) of the fabricated batteries was between 1.6 and 1.7 V.     

Synthesis of spinel LiMn2O4 with manganese carbonate prepared by micro-emulsion method

Micro-spherical particle of MnCO₃ has been successfully synthesized in CTAB-C₈H₁₈-C₄H₉OH-H₂O micro-emulsion system. Mn₂O₃ decomposed from the MnCO₃ is mixed with Li₂CO₃ and sintered at 800 °C for 12 h, and the pure spinel LiMn₂O₄ in sub-micrometer size is obtained. The LiMn₂O₄ has initial discharge specific capacity of 124 mAh g⁻¹ at discharge current of 120 mA g⁻¹ between 3 and 4.2 V, and retains 118 mAh g⁻¹ after 110 cycles. High-rate capability test shows that even at a current density of 16 C, capacity about 103 mAh g⁻¹ is delivered, whose power is 57 times of that at 0.2 C. The capacity loss rate at 55 °C is 0.27% per cycle.     

Polyvinylidene fluoride and polyetherimide hollow fiber membranes for CO2 stripping in membrane contactor

Porous polyvinylidene fluoride (PVDF) and polyetherimide (PEI) hollow fiber membranes incorporating polyethylene glycol (PEG) were prepared via spinning process for CO₂ membrane stripping. CO₂ loaded diethanolamine solution was used as liquid absorbent while N₂ was used as a strip gas. The characterization study of the fibers was carried out in terms of permeation test, contact angle measurement and liquid entry pressure (wetting pressure). Performance study via membrane contactor stripping was carried out at specific operating condition. The experimental results showed that PVDF membrane have high gas permeation, effective surface porosity and contact angle despite having lower liquid entry pressure in comparison with PEI membrane. PVDF-PEG membrane showed the highest stripping flux of 4.0 × 10⁻² mol m⁻² s⁻¹ at 0.7 ms⁻¹ compared to that of PEI membrane. Although the stripping flux for PEI-PEG membranes was slightly lower than PVDF membrane (e.g. 3.5 × 10⁻² mol m⁻² s⁻¹ at liquid velocity of 0.85 ms⁻¹), the membrane wetting pressure of PEI membrane is higher than hydrophobic PVDF membrane. Long term performance of both membranes showed severe flux reduction but started to level-off after 30 h of operation.     

Direct synthesis of poly(l-lactic acid) in supercritical carbon dioxide with dicyclohexyldimethylcarbodiimide and 4-dimethylaminopyridine

The direct synthesis of poly(l-lactic acid) (PLLA) from an l-lactic acid oligomer has been performed in supercritical carbon dioxide (scCO₂) using an esterification promoting agent, dicyclohexyldimethylcarbodiimide (DCC), and 4-dimethylaminopyridine (DMAP) as a catalyst. PLLA within M_n of 13,500 g/mol was synthesised in 90% yield at 3500 psi and 80 °C after 24 h. The molecular weight distribution of the products was narrower than PLLA prepared with melt-solid phase polymerisation under conventional conditions. Both DCC and DMAP showed high solubility in scCO₂ (DCC: 7.6 wt% (1.63×10⁻² mol/mol CO₂) at 80 °C, 3385 psi, DMAP: 4.5 wt% (1.62×10⁻²mol/mol CO₂) at 80 °C, 3386 psi) and supercritical fluid extraction was found to be effective at removing excess DMAP and DCC after the polymerisation was complete. We show that DCC and DMAP are effective esterification promoting reagents with further applications for condensation polymerisations in scCO₂.     

Ca-based sorbent looping combustion for CO2 capture in pilot-scale dual fluidized beds

To demonstrate process feasibility of in situ CO₂ capture from combustion of fossil fuels using Ca-based sorbent looping technology, a flexible atmospheric dual fluidized bed combustion system has been constructed. Both reactors have an ID of 100 mm and can be operated at up to 1000 °C at atmospheric pressure. This paper presents preliminary results for a variety of operating conditions, including sorbent looping rate, flue gas stream volume, CaO/CO₂ ratio and combustion mode for supplying heat to the sorbent regenerator, including oxy-fuel combustion of biomass and coal with flue gas recirculation to achieve high-concentration CO₂ in the off-gas. It is the authors' belief that this study is the first demonstration of this technology using a pilot-scale dual fluidized bed system, with continuous sorbent looping for in situ CO₂ capture, albeit at atmospheric pressure. A multi-cycle test was conducted and a high CO₂ capture efficiency (> 90%) was achieved for the first several cycles, which decreased to a still acceptable level (> 75%) even after more than 25 cycles. The cyclic sorbent was sampled on-line and showed general agreement with the features observed using a lab-scale thermogravimetric analysis (TGA) apparatus. CO₂ capture efficiency decreased with increasing number of sorbent looping cycles as expected, and sorbent attrition was found to be another significant factor to be limiting sorbent performance.