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.     

Simulation Analysis of a GTL Process Using Aspen Plus

Gas‐to‐liquid (GTL) processes are becoming attractive due to the increasing price of crude oil. Process simulation analysis on the integrated GTL process is essential as part of an extended process integration analysis of the research subjects. The two sub‐process models for the GTL process, i.e., the syngas generation process and the Fischer Tropsch synthesis (FTS) process, are analyzed in detail with ASPEN Plus. The autothermal reforming process (ATR) is analyzed using Aspen Plus based on the Gibbs reactor model, while FTS is simulated with ASPEN Plus based on detailed kinetic models for industrial iron and cobalt catalysts. Integrated GTL processes with iron and cobalt‐based catalysts were simulated using ASPEN Plus. The optimal flowsheet structures were selected for each catalyst based on the overall performance in terms of thermal and carbon efficiency and product distributions. For the cobalt‐based catalyst, the full conversion concept without CO₂ removal from the FT tail gas is optimal. On the other hand, the once‐through concept with two series reactors and CO₂ removal from raw syngas is considered optimal for the iron‐based catalyst. The thermal efficiency to crude products is likely to be ca. 60 % for the cobalt‐based catalyst, whereas it is in the range of 49–55 % for the iron‐based catalyst. The carbon efficiency using the water‐gas shift reaction is lower using the iron‐based catalyst (61–68 %) than the cobalt‐based catalyst (73–75 %). As expected, the cobalt‐based catalyst is more active and selective, which offers better selectivity towards C₅+ (75–79 %). The selectivity towards C₅+ for the iron‐based catalyst lies in the range 63–75 %.     

Electrochemical synthesis of dimethyl carbonate from methanol,CO2 and propylene oxide in an ionic liquid

BACKGROUND: Dimethyl carbonate (DMC) can be used effectively as an environmentally benign substitute for highly toxic phosgene and dimethyl sulfate in carbonylation and methylation, as well as a promising octane booster owing to its high oxygen content. Two‐step transesterification from epoxide, methanol, and CO₂ is widely used in the bulk production of DMC. However, major disadvantages of this process are high energy consumption, and high investment and production costs. A one pot synthesis of DMC from carbon dioxide, methanol, and epoxide was, therefore, developed. But the yields of DMC are below 70% due to the thermodynamic limitation. RESULTS: Electrochemical synthesis of DMC was conducted with platinum electrodes from methanol, CO₂ and propylene oxide in an ionic liquid was conducted. The bmimBr (1‐butyl‐3‐methylimidazolium bromide)‐methanol‐propylene oxide system with CO₂ bubbling allows DMC to be effectively synthesized and a high yield (75.5%) was achieved. CONCLUSION: In this electrolysis, redox reactions of substrates, CO₂, methanol, and propylene oxide, on Pt electrodes were carried out, producing the activated particles, CH₃O^?, CH₃OH⁺, CO₂^? and PO^?, resulting in the effective synthesis of DMC with a 75.5% yield in an ionic liquid (bmimBr). Finally, a mechanism for this synthesis reaction was proposed, which is very different from those reported in the literature. Copyright © 2011 Society of Chemical Industry     

Techno-economic evaluation of advanced IGCC lignite coal fuelled power plants with CO2 capture

The techno-economic evaluation of four novel integrated gasification combined cycle (IGCC) power plants fuelled with low rank lignite coal with CO₂ capture facility has been investigated using ECLIPSE process simulator. The performance of the proposed plants was compared with two conventional IGCC plants with and without CO₂ capture. The proposed plants include an advanced CO₂ capturing process based on the Absorption Enhanced Reforming (AER) reaction and the regeneration of sorbent materials avoiding the need for sulphur removal component, shift reactor and/or a high temperature gas cleaning process. The results show that the proposed CO₂ capture plants efficiencies were 18.5–21% higher than the conventional IGCC CO₂ capture plant. For the proposed plants, the CO₂ capture efficiencies were found to be within 95.8–97%. The CO₂ capture efficiency for the conventional IGCC plant was 87.7%. The specific investment costs for the proposed plants were between 1207 and 1479 €/kW_e and 1620 €/kW_e and 1134 €/kW_e for the conventional plants with and without CO₂ capture respectively. Overall the proposed IGCC plants are cleaner, more efficient and produce electricity at cheaper price than the conventional IGCC process.     

Thermodynamics of Hydrogen Production Based on Coal Gasification Integrated with a Dual Chemical Looping Process

The performance of an innovative hydrogen production technology, which is based on a coal gasification system integrated with a dual chemical looping process, namely, chemical looping air separation (CLAS) and calcium looping CO₂ absorption (CaL), is evaluated. CLAS offers an advantage over other mature technologies in that it can reduce capital costs considerably. CaL is an efficient method for hydrogen production and CO₂ capturing. The proposed technologies are studied by Aspen Plus based on the Gibbs free energy minimization principle. The key factors in terms of reduction temperature, gasification pressure, temperature of water‐gas shift reaction, and water consumption, which proved to have a significant impact on the performance of the whole hydrogen generation process, are discussed.     

CO2 utilization for methanol production; Optimal pathways with minimum GHG reduction cost

Mitigating CO₂ emissions from industries and other sectors of our economy is a critical component of building a sustainable economy. This paper investigates two different methanol synthesis routes based on CO₂ utilization (CO₂ capture and utilization [CCU], and tri-reforming of methane [TRM]), and compares the results with the conventional methanol production using natural gas as the feedstock (NG-MeOH). A comprehensive techno-economic analysis (TEA) model that includes the findings of the life cycle assessment (LCA) models of methanol production using various CO₂ utilization pathways is conducted. Economic analysis is conducted by developing a cost model that is connected to the simulation models for each production route. Compared to the conventional process (with a GHG emission of 0.6 kg CO₂/kg MeOH), the lifecycle GHG reduction of 1.75 and 0.41 kg CO₂/kg MeOH are achievable in the CCU and TRM pathways, respectively. Furthermore, the results indicate that, under current market conditions and hydrogen production costs, methanol production via CO₂ hydrogenation will result in a cost approximately three times higher than that of the conventional process. The integrated TEA–LCA model shows that this increased cost of production equates to a required life cycle GHG reduction credit of $279 to $422 per tonne of CO₂ utilized, depending on construction material and selected pathway. Additionally, when compared to the CO₂ hydrogenation route, the tri-reforming process (TRM-MeOH) can result in a 42% cost savings. Furthermore, a minimum financial support of $56 per tonne utilized CO₂ will be required to make the TRM-MeOH process economically viable.     

Extraction,purification and characterization of wax from flax (Linum usitatissimum) straw

The chemical composition and selected physical parameters of wax extracted from flax straw with supercritical CO₂ (SC‐CO₂) and hexane have been determined. From the GC/MS results, clear variations in composition and component distributions were observed between SC‐CO₂‐ and hexane‐extracted samples. The major components of the SC‐CO₂ and hexane extracts from three flax cultivars were: fatty acids (36–49%), fatty alcohols (20–26%), aldehydes (10–14%), wax esters (5–12%), sterols (7–9%) and alkanes (4–5%). Purification of SC‐CO₂‐extracted wax with silica gel chromatography yielded 0.4–0.5% (dry matter) and was composed primarily of wax esters (C₄₄, C₄₆ and C₄₈) and alkanes (C₂₇, C₂₉ and C₃₁). UV‐Vis scans of the purified wax samples exhibited two main peaks indicating the presence of conjugated dienes and carotenoids or related compounds. Fourier transform infrared results showed prominent peaks at 2918 (‐C‐H), 2849 (‐C‐H), 1745 (‐C=O), 1462 (‐C‐H), 1169 (‐C‐O) and 719 cm^–1 (‐(CH₂)_n‐), with NorLin wax showing a slightly deviating pattern compared to the other samples. Thermal analysis by differential scanning calorimetry revealed a mean melting point of 55–56 °C and oxidation temperatures of 146–153 °C for purified wax from flax straw processed using different procedures.     

A new model for correlation and prediction of equilibrium CO2 solubility in N‐methyl‐4‐piperidinol solvent

In this work, the equilibrium CO₂ solubility in the aqueous tertiary amine, N‐methyl‐4‐piperidinol (MPDL) was measured over a range of temperatures, CO₂ partial pressures and amine concentrations. The dissociation constant of the MPDL solution was determined as well. A new thermodynamic model was developed to predict the equilibrium CO₂ solubility in the MPDL‐H₂O‐CO₂ system. This model, equipped with the correction factor (C_f), can give reasonable prediction with an average absolute deviation of 2.0%, and performs better than other models (i.e., KE model, Li‐Shen model, and Hu‐Chakma). The second‐order reaction rate constant (k₂) of MPDL and the heat of CO₂ absorption (–ΔH_abs) into aqueous MPDL solutions were evaluated as well. Based on the comparison with some conventional amines, MPDL revealed a high‐equilibrium CO₂ loading, reasonably fast absorption rate when compared with other tertiary amines, and a low energy requirement for regeneration. It may, therefore, be considered to be an alternative solvent for CO₂ capture. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3395–3403, 2017     

Optimization of process parameters and catalyst compositions in carbon dioxide oxidative coupling of methane over CaO–MnO/CeO2 catalyst using response surface methodology

The optimization of process parameters and catalyst compositions for the CO₂ oxidative coupling of methane (CO₂-OCM) reaction over CaO–MnO/CeO₂ catalyst was developed using Response Surface Methodology (RSM). The relationship between the responses, i.e. CH₄ conversion, C₂ hydrocarbons selectivity or yield, with four independent variables, i.e. CO₂/CH₄ ratio, reactor temperature, wt.% CaO and wt.% MnO in the catalyst, were presented as empirical mathematical models. The maximum C₂ hydrocarbons selectivity and yields of 82.62% and 3.93%, respectively, were achieved by the individual-response optimization at the corresponding optimal process parameters and catalyst compositions. However, the CH₄ conversion was a saddle function and did not show a unique optimum as revealed by the canonical analysis. Moreover pertaining to simultaneous multi-responses optimization, the maximum C₂ selectivity and yield of 76.56% and 3.74%, respectively, were obtained at a unique optimal process parameters and catalyst compositions. It may be deduced that both individual- and multi-responses optimizations are useful for the recommendation of optimal process parameters and catalyst compositions for the CO₂-OCM process.     

Wind und Kohle: Die technische Photosynthese

The increasing energy demand, the associated CO₂ emissions, and the concurrently decreasing reserves of fossil fuels require new concepts for sustainable energy production. The so‐called Adam‐and‐Eve principle for CO₂‐free production of methanol from coal and nuclear energy is revisited and adapted to today's circumstances. Electrolysis of water using renewable electricity is applied for H₂ production. Simultaneously, coal and the oxygen formed during electrolysis are burned in an oxyfuel process, generating electricity and relatively pure CO₂. Hydrogen from electrolysis and CO₂ are converted to methanol, which can then be used as chemical‐ and energy feedstock.     

Widening the Product Profile of Carbon Dioxide Reduction by Vanadium Nitrogenase

Two reaction systems based on vanadium nitrogenase were previously shown to reduce CO₂ to hydrocarbons: 1) an enzyme‐based system that used both components of V nitrogenase for ATP‐dependent reduction of CO₂ to ≤C₂ hydrocarbons; and 2) a cofactor‐based system that employed SmI₂ to supply electrons to the isolated V cluster for an ATP‐independent reduction of CO₂ to ≤C₃ hydrocarbons. Here, we report ATP‐independent reduction of CO₂ to hydrocarbons by a reaction system comprising Eu^II DTPA and the VFe protein of V nitrogenase. Combining features of both enzyme‐ and cofactor‐based systems, this system exhibits improved C?C coupling and a broader product profile of ≤C₄ hydrocarbons. The C?C coupling does not employ CO₂‐derived CO, and it is significantly enhanced in D₂O. These observations afford initial insights into the characteristics of this unique reaction and provide a potential template for future design of catalysts to recycle the greenhouse gas CO₂ into useful products.     

Ionic Liquid with Silyl Substituted Cation: Thermophysical and CO2/N2 Permeation Properties

Novel functionalized ionic liquid (IL) combining an imidazolium‐based cation with branched alkyl chain bearing silyl group, 1‐methyl‐3‐(2‐methyl‐3‐(trimethylsilyl)propyl)imidazolium ([Si?C₁?C₃‐mim]⁺), and bis(trifluoromethylsulfonyl)imide ([NTf₂]^?) anion was synthesized and its thermophysical properties (density, viscosity, surface tension, surface entropy and enthalpy, thermal stability) were studied in a wide temperature range and compared with those of ILs having linear alkyl ([C_n‐mim][NTf₂]) and siloxane ([(SiOSi)C₁mim][NTf₂]) side chains. It was found that at 25 °C [Si?C₁?C₃‐mim][NTf₂] is a liquid with dynamic viscosity of 224 cP (224 mPa s) and density of 1.32 g cm^?3. The presence of side branched alkyl chain with trimethylsilyl end‐group prevents crystallization of IL and leads to higher viscosities and lower densities in comparison with commonly known [C_n‐mim][NTf₂] (n=2–4). As surface excess enthalpy was found to be in the lower end of the usual range of values for ILs, the interactions between silyl‐functionalized cation and [NTf₂] anion can be considered as relatively weak. Finally, [Si?C₁?C₃‐mim][NTf₂] was used for the preparation of polymer supported ionic liquid membranes (SILMs) and their CO₂ and N₂ permeation properties at 20 °C and 100 kPa were determined: permeability PCO₂=311, PN₂=12 Barrer, diffusivity DCO₂=115×10¹², DN₂=227×10¹² m² s^?1 and CO₂/N₂ permselectivity αCO₂/N₂=25.3.     

Impact of liquid absorption process development on the costs of post-combustion capture in Australian coal-fired power stations

Australian power generators produce approximately 170 TWh per annum of electricity using black and brown coals that accounts for 170 Mtonne of CO₂ emissions per annum or over 40% of anthropogenic CO₂ emissions in Australia. This paper describes the results of a techno-economic evaluation of liquid absorption based post-combustion capture (PCC) processes for both existing and new pulverised coal-fired power stations in Australia. The overall process designs incorporate both the case with continuous capture and the case with the flexibility to switch a CO₂ capture plant on or off depending upon the demand and market price for electricity, and addresses the impact of the presently limited emission controls on the process cost. The techno-economic evaluation includes both air and water cooled power and CO₂ capture plants, resulting in cost of power generation for the situations without and with PCC. Whilst existing power plants in Australia are all water cooled sub-critical designs, the new power plants are deemed to range from supercritical single reheat to ultra-supercritical double reheat designs, with a preference for air-cooling. The process evaluation also includes a detailed sensitivity analysis of the thermodynamic properties of liquid absorbent for CO₂ on the overall costs. The results show that for a meaningful decrease in the efficiency and cost penalties associated with the post combustion CO₂ capture, a novel liquid sorbent will need to have heat of absorption/desorption, sensible heat and heat of vaporisation around 50% less in comparison with 30% (w/w) aqueous MEA solvent. It also shows that the impact of the capital costs of PCC processes is quite large on the added cost of generation. The results can be used to prioritise PCC research in an Australian context.     

Hydrogen Production by Sorption‐Enhanced Steam Glycerol Reforming: Sorption Kinetics and Reactor Simulation

Sorption‐enhanced glycerol reforming, an integrated process involving glycerol catalytic steam reforming and in situ CO₂ removal, offers a promising alternative for single‐stage hydrogen production with high purity, reducing the abundant glycerol by‐product streams. This work investigates this process in a fixed‐bed reactor, via a two‐scale, nonisothermal, unsteady‐state model, highlighting the effect of key operating parameters on the process performance. CO₂ adsorption kinetics was investigated experimentally and described by a mathematical reaction‐rate model. The integrated process presents an opportunity to improve the economics of green hydrogen production via an enhanced thermal efficiency process, the exothermic CO₂ adsorption providing the heat to endothermic steam glycerol reforming, while reducing the capital cost by removing the processing steps required for subsequently CO₂ separation. The operational time of producing high‐purity hydrogen can be enhanced by increasing the adsorbent/catalyst volume ratio, by adding steam to the reaction system and by increasing the inlet reactor temperature. © 2012 American Institute of Chemical Engineers AIChE J, 59: 2105–2118, 2013     

Climate‐friendly polyurethane blowing agent based on a carbon dioxide adduct from palmitic acid grafted polyethyleneimine

To explore a new blowing agent for polyurethanes (PUs), palmitic acid was grafted onto a branched polyethyleneimine (bPEI; weight‐average molecular weight = 25,000 Da) via N,N′‐carbonyldiimidazole condensation to form a hydrophobically modified bPEI [palmitic acid grafted branched polyethyleneimine (C₁₆–bPEI)] with a grafting rate of 12%. A CO₂ adduct of C₁₆–bPEI, which trapped 16.8% CO₂ in it, was synthesized from C₁₆–bPEI. The long alkyl chain grafting improved the dispersibility of the CO₂ adduct in the PU raw materials and favored a homogeneous release of CO₂ to blow PUs during the exothermic foaming process. The preliminary results show that the foams possessed a density of 72.0 kg/m³ and a compressive strength of 246 kPa; this matched the required values of foams for the thermal insulation of underground steel pipes. This new blowing agent emitted nothing but CO₂ to the atmosphere, so it will not promote ozone depletion and will avoid global warming problems that are associated with traditional blowing agents such as chlorofluorocarbons and hydrochloroflourocarbons. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43874.     

The role of carbon dioxide in the oxidative dimerization of methane over Li/MgO

CO₂ is strongly adsorbed on Li/MgO as a surface carbonate and desorbs concomitantly with Li with an activation energy of desorption of 210 kJ/mol. The C₂ product is strongly influenced by the presence of CO₂,0.5 Torr being sufficient to substantially lower the rate of C₂ production and to establish an activation energy for reaction of 210 kJ/mol. In the absence of CO₂, the activation energy of C₂ production falls to 105 kJ/mol.     

Oxidative Coupling of Methane in a Negative DC Corona Reactor at Low Temperature

Oxidative coupling of methane (OCM) in the presence of DC corona is reported in a narrow glass tube reactor at atmospheric pressure and at temperatures below 200°C. The corona is created by applying 2200V between a tip and a plate electrode 1.5 mm apart. The C₂ selectivity as well as the methane conversion are functions of methane‐to‐oxygen ratio, gas residence time, and electric current. At CH₄/O₂ ratio of 5 and the residence time of about 30 ms, a C₂ yield of 23.1% has been achieved. The main products of this process are ethane, ethylene, acetylene as well as CO and CO₂ with CO/CO₂ ratios as high as 25. It is proposed that methane is activated by electrophilic oxygen species to form methyl radicals and C₂ products are produced by a consecutive mechanism, whereas CO_x is formed during parallel reactions.     

Fullerene polymer film as a highly efficient photocatalyst for selective solar fuel production from CO2

C₆₀-based polymeric systems have been constantly anticipated for sustainable solar energy conversion. Reported, herein is a C₆₀ polymer film as visible light active photocatalyst for efficient and selective reduction of CO₂ for the first time. The C₆₀ polymer photocatalyst is synthesized via covalent coupling of C₆₀ monomer units consisting of tetra substituted C₆₀-pyrene conjugates through spacer groups. The synthesized C₆₀ polymer photocatalyst possesses an extended network of well-defined repeating monomer units with good stability and visible light-induced photocatalytic activity. The enhanced visible light harvesting ability of C₆₀ polymer photocatalyst reasonably yields it with higher catalytic ability than its monomer unit. The C₆₀ polymer film photocatalyst upon coupling with the biocatalyst carries out highly selective visible light driven reduction of CO₂ to HCOOH (239.46 μmol). The tandem way of incorporating C₆₀ into visible light active polymeric films for continuous use may be highly rewarding for their extended photocatalytic activity for solar fuel production from CO₂. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48536.     

Tuning millisecond chemical reactors for the catalytic partial oxidation of cyclohexane

It is demonstrated that millisecond partial oxidation of cyclohexane can be tuned by varying the catalyst and operating conditions to generate product distributions that favor (1) oxygenates, (2) olefins, or (3) syngas (H₂ and CO). High selectivities to parent oxygenates require low conversions using low-temperature catalysts, such as Ag or Co. Olefins are favored by Pt or Pt-Sn and H₂ addition eliminates the production of CO and CO₂, thereby increasing olefin selectivities. For syngas, Rh is the catalyst of choice. Finally, a Pt-10% Rh single gauze gives high selectivities to both oxygenates and olefins.Conventional methods for the partial oxidation of cyclohexane are liquid-phase processes that are plagued by poor conversions, high recycle costs, long residence times (minutes to hours), and expensive catalysts. In contrast, with a cyclohexane–oxygen feed at C₆H₁₂/O₂=2, a Pt-10% Rh single gauze catalyst can give total selectivities exceeding 80% to oxygenates and olefins at 25% cyclohexane conversion and complete oxygen conversion. The products consist of nearly 60% selectivity to the C₆ products, cyclohexene and 5-hexenal. The temperature profile attained in the single-gauze reactor allows the preservation of these highly non-equilibrium products.Alternative catalysts for cyclohexane oxidation to oxygenates and olefins include α-alumina monoliths coated with Pt, Rh, Pt-Rh, Pt-Sn, Co, Mo or Ag. The Co, Mo and Ag catalysts give very high selectivities to C₆ oxygenates but are hindered by poor conversions (<5%) of both cyclohexane and oxygen at these millisecond contact times. H₂ addition to cyclohexane oxidation feed mixtures over Pt and Pt-Sn is shown to significantly increase the selectivities to C₆ olefins while reducing the formation of CO and CO₂.Cyclohexane oxidation in air over Rh monoliths enables the production of high yields (>95%) of syngas. This process could find applications in the automotive industry as the production of hydrogen from liquid fuels becomes important.     

Effect of the molecular weight between crosslinks of thermally cured epoxy resins on the CO2‐bubble nucleation in a batch physical foaming process

Epoxy resins (bisphenol A type epoxy resins/2‐ethyl‐4‐methylimidazole) consisting of oligomers with different molecular weights were foamed using a temperature‐quench physical foaming method with CO₂. The resulting cell morphologies could be classified into four types: non‐foamed structure, cracked structure, star‐shaped structure, and sphere‐shaped structure. The effects of the gel fraction and molecular weight between crosslinks (M_C) on the cell morphology were investigated for the preparation of microcellular epoxy foams. M_C was calculated by measuring the plateau rubber modulus of the rheological properties and the weight uptake of acetone. By varying the molecular weight of the epoxy oligomers and the cure time, the M_C of the epoxy was controlled to modulate the cell morphology. The experiments elucidated the threshold M_C value that permits CO₂‐bubble nucleation: CO₂‐bubble nucleation in the epoxy resin could be induced when the distance between the crosslinking points exceeded the critical size of bubble nucleus. Based on this information, the microcellular epoxy foam was prepared by maintaining M_C above 10⁴g mol⁻¹ and the complex modulus above 6 × 10⁸ Pa. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40407.