Contributions of CH4-amine interactions by primary, secondary, and tertiary amines on CO2/CH4 separation efficiency

In designing amine-incorporated adsorbents for CO2/CH4 separation, it is essential to understand the individual effects amine moieties have on the separation of CO2/CH4 mixtures. In this work, primary, secondary, and tertiary amines are moderately grafted on SBA-15 to examine factors affecting adsorption of CO2 and CH4. Materials were characterised by thermogravimetric and elemental analysis, and their performance was measured by volumetric and gravimetric gas adsorption. An amine density of 1.6–1.7 mmol/g in secondary and tertiary amines showed an equivalent CH4 uptake of <0.04 mmol/g at 25 °C, while primary amines adsorbed 0.05 mmol/g, indicating stronger interaction forces with CH4. In terms of selectivity, primary and secondary amines grafted at 1.3–1.4 mmol/g had similar values, unaffected by amine type. Adsorption results cross analysed with DFT simulations indicate similar binding energies for CH4 by both amine moieties, concluding the facilitated access of gas molecules to primary amine moieties is the primary factor dictating degree of adsorption. At an amine density of ∼ 1.7 mmol/g for both primary and secondary amines, an increase in temperature from 25 to 40 °C at a CO2 partial pressure of 40 kPa showed a decrease in CO2/CH4 selectivity of only primary amines. Secondary amines are thus more selective amine moieties at these conditions. Furthermore, in isothermal adsorption–desorption conditions, moderately grafted secondary amines have an equal working capacity to primary amines. Both these qualities support secondary amines at moderate densities as candidates for adsorbent development in CO2/CH4 separations

Direct Numerical Simulation (DNS) of packed and monolith Syngas Catalytic Combustors for Micro Electrical Mechanical Systems (MEMS)

Data availability; Data will be made available on request.Copyright © The Author(s) 2023. In this work, a catalytic combustor for micro electrical mechanical system for syngas was designed and analysed using Direct Numerical Simulation (DNS) in conjunction with finite rate chemistry. The effect of catalyst (platinum (Pt), palladium (Pd), palladium oxide (PdO), and rhodium (Rh)), bed type (packed with twelve catalyst shapes and four catalyst monolith), shapes (packed: cylinder, hollow cylinder, four cylinder, single cylinder, single cylinder, cross-webb, grooved, pall-ring, hexagonal, berl-saddle, cube, intalox-saddle, and sphere, monolith: triangular, rectangular, hexagonal, and circular), and operating conditions (inlet temperature and velocity, fuel/air ratio, different concentrations CH4-H2-CO) on combustion efficiency and pressure drop were studied using different parameters (combustion efficiency (η), pressure drop, effectiveness factor (ψ), and fuel conversions (H2 and CH4 conversions)). Analysis under different operating conditions reveals that the designed combustor can operate effectively with syngas of varying compositions with a high combustion efficiency of over 85%. Combustion mainly takes place on the surface of the catalyst without gas phase reaction with pressure drops between 18 Pa to 155 Pa. The intalox saddle shape catalysts resulted in the bed effectiveness factor 0.931. The Damköhler for hydroxyl radicals (OH) over the entire length of the reactor is uniformly distributed and well below 3, suggesting uniform combustion

Towards decarbonisation of sugar refineries by calcium looping: Process integration, energy optimisation and technoeconomic assessment

Data availability: https://doi.org/10.17633/rd.brunel.25864513.v1.Supplementary material is available online at: https://www.sciencedirect.com/science/article/pii/S0196890424005387?via%3Dihub#s0075:~:text=Appendix%20A.-,Supplementary%20material,-Data%20availability .The sugar refinery process as a food industry is at the pinnacle of the energy hierarchy. Depending on the source of carbon in this industry that could be either from biomass or fossil fuel hydrocarbons, this sector has the potential to become a carbon–neutral or negative industry depending on the type of fuel for power generation. This work will deliver a new proof of concept model for simultaneous sugar refining and carbon capture, thereby transforming sugar into the carbon negative commodity which relies on the utilisation of CO2 and fresh lime in the sugar refineries carbonisation tanks and in return byproduction of calcium carbonate that can be converted in the calciner of a calcium looping process. This study begins with the design and development of the calcium looping (CaL) process for the integration to the sugar refineries using various coupled and decoupled scenarios for the boiler units based on the type of the fuel, continues with an energy optimisation and techno-economic assessment of the proposed process, and finally culminates with the parametric study on the thermodynamic and economic performance of the sugar refinery retrofitted with the calcium looping. The process simulations revealed that the integrated CaL-sugar refinery can support the electricity exporter by installation of an onsite steam cycle which is able to generate electricity from surplus carbonation heat. The cost of CO2 avoided for integration of CaL to the reference sugar refinery for natural gas boilers and calciner will be 62 £/tCO2 which drops to 25 £/tCO2 if the carbon tax is considered in the analysis and negative carbon emissions are credited. This is equivalent to 61% costs reductions associated refining sugar combined together with carbon capture and storage (CCS)

A systematic review of key challenges of CO2 transport via pipelines

Transport of carbon dioxide (CO2) via pipeline from the point of capture to a geologically suitable location for either sequestration or enhanced hydrocarbon recovery is a vital aspect of the carbon capture and storage (CCS) chain. This means of CO2 transport has a number of advantages over other means of CO2 transport, such as truck, rail, and ship. Pipelines ensure continuous transport of CO2 from the capture point to the storage site, which is essential to transport the amount of CO2 captured from the source facilities, such as fossil fuel power plants, operating in a continuous manner. Furthermore, using pipelines is regarded as more economical than other means of CO2 transport The greatest challenges of CO2 transport via pipelines are related to integrity, flow assurance, capital and operating costs, and health, safety and environmental factors. Deployment of CCS pipeline projects is based either on point-to-point transport, in which case a specific source matches a specific storage point, or through the development of pipeline networks with a backbone CO2 pipeline. In the latter case, the CO2 streams, which are characterised by a varying impurity level and handled by the individual operators, are linked to the backbone CO2 pipeline for further compression and transport. This may pose some additional challenges. This review involves a systematic evaluation of various challenges that delay the deployment of CO2 pipeline transport and is based on an extensive survey of the literature. It is aimed at confidence-building in the technology and improving economics in the long run. Moreover, the knowledge gaps were identified, including lack of analyses on a holistic assessment of component impurities, corrosion consideration at the conceptual stage, the effect of elevation on CO2 dense phase characteristics, permissible water levels in liquefied CO2, and commercial risks associated with project abandonment or cancellation resulting from high project capital and operating costs

Characteristics of Copper-based Oxygen Carriers Supported on Calcium Aluminates for Chemical-Looping Combustion with Oxygen Uncoupling (CLOU)

Eight different oxygen carriers (OC) containing CuO (60 wt %) and different mass ratios of CaO to Al2O3 as the support were synthesized by wet-mixing followed by calcination at 1000 °C. The method of synthesis used involved the formation of calcium aluminum hydrate phases and ensured homogeneous mixing of the Ca2+ and Al3+ ions in the support at the molecular level. The performance of the OCs for up to 100 cycles of reduction and oxidation was evaluated in both a thermogravimetric analyzer (TGA) and a fluidized bed reactor, covering a temperature range of 800 to 950 °C. In these cycling experiments, complete conversion of the OC, from CuO to Cu and vice versa, was always achieved for all OCs. The reactivity of the materials was so high that no deactivation could be observed in the TGA, owing to mass transfer limitations. It was found that OCs prepared with a mass ratio of CaO to Al2O3 in the support >0.55 agglomerated in the fluidized bed, resulting in an apparent deactivation over 25 cycles for all temperatures investigated. High ratios of mass of CaO to Al2O3 in the support resulted in CuO interacting with CaO, forming mixed oxides that have low melting temperatures, and this explains the tendency of these materials to agglomerate. This behavior was not observed when the mass ratio of CaO to Al2O3 in the support was ≤0.55 and such materials showed excellent cyclic stability operating under redox conditions at temperatures as high as 950 °C.The authors thank Mohammad Ismail and Matthew Dunstan for helping with the XRD analysis and Alex Casabuena-Rodriguez and for helping with the SEM. This work was supported by the Engineering and Physical Sciences Research Council (EPSRC grant EP/I010912/1).This is the final version of the article. It first appeared from ACS via http://dx.doi.org/10.1021/acs.iecr.5b0117

Thermodynamic analysis of methanation of palm empty fruit bunch (PEFB) pyrolysis oil with and without in situ CO2 sorption

Thermodynamic equilibrium analysis for conversion of palm empty fruit bunch (PEFB) bio-oil to methane using low-temperature steam reforming (LTSR) process was conducted by assuming either isothermal or adiabatic condition, with and without sorption enhancement (SE-LTSR), with CaO(S) or Ca(OH)2(S) as CO2 sorbent. Temperatures of 300-800 K, molar steam to carbon (S/C) ratios of 0.3-7.0, pressures of 1-30 atm and molar calcium to carbon ratios (Ca:C) of 0.3-1.0 were simulated. For reasons of process simplicity, the best conditions for CH4 production were observed for the adiabatic LTSR process without sorption at S/C between 2.5 and 3 (compared to the stoichiometric S/C of 0.375), inlet temperature above 450 K, resulting in reformer temperature of 582 K, where close to the theoretical maximum CH4 yield of 38 wt % of the simulated dry PEFB oil was obtained, resulting in a reformate consisting of 44.5 vol % CH4, 42.7 vol % CO2 and 12.7 vol % H2 and requiring only moderate heating mainly to partially preheat the reactants. Temperatures and S/C below these resulted in high risk of carbon by-product

Influence of non-uniformity of coal and distribution of active calcium on sulfur self-retention by ash - A case study of lignite Kolubara

Self-retention Of SO2 by ash of different grades of Kolubara lignite was experimentally investigated in a laboratory furnace. The peculiarity of this type of coal is that in the open pit there are distinct layers of coal and ballast matter, which complicates the formation of representative samples. Two grades of this coal (differing in ballast matter content) were investigated using 3 sieved fractions: 1-1.6 mm, 2.5-3.15 mm, and 4.76-7 mm. It was found that particle size had no significant effect on the sulfur self-retention efficiency (etaSO(2)). The effect of ballast matter content on etaSO(2) was investigated by classifying two sieved fractions into classes with different density ranging from LT 1000 kg/m(3) to GT 1600 kg/m(3). It was found that most of sulfur self-retention occurs in less dense particles., For this coal only 60% of the total calcium was found to be active in relation to sulfur self-retention capability. Most of the active calcium and sulfur were found to be present in particles of lower density, which explains their dominant contribution to overall sulfur self-retention