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This work presents a techno-economic and greenhouse gas emissions assessment of a proposed low-carbon methanol production process. The process takes a novel low-carbon methanol production method and reduces its emissions further by integrating a solar thermal energy (STE) system to provide for its electricity requirements. The authors investigate three different scenarios for the STE system, analysing the effects of solar irradiance design point, and the impact of thermal energy storage on system performance. Case-1 (15.57 MW) was designed for daytime operation and sized for the maximum annual solar irradiance, with Case-2 (24.91 MW) incorporating thermal energy storage to enable 24-hour operation. Case-3 (48.66 MW) also utilised thermal energy storage to enable 24-hour operation, but was sized for the minimum annual solar irradiance. The methanol process and the STE system were modelled in Aspen Plus and Aspen HYSYS, with the simulation data being used with mass and energy balances to conduct a techno-economic and greenhouse gas emissions assessment. The standalone methanol plant was estimated to emit 0.37 t CO2/t CH3OH, with the integration of the STE system reducing this to 0.29 (Case-1), 0.23 (Case-2), and 0.10 (Case-3), resulting in one of the lowest emitting traditional methanol production methods available. The cost of abatement of these remaining emissions through carbon capture and storage was also considered. The economic analysis found that the integrated processes in Case-1 and 2 were financially viable, resulting in a net present value of $247 million and $72 million respectively. The net present value was reduced to $185 and $21 million when considering the cost of carbon capture and storage. Conversely, the net present value for Case-3 was negative, requiring an increase in the price of methanol to ∼" role="presentation" style="font-size: 90%; display: inline-block; position: relative;">∼∼$600/t, and a reduction in the cost of capital to ∼" role="presentation" style="font-size: 90%; display: inline-block; position: relative;">∼∼8%, to become financially viable. [ABSTRACT FROM AUTHOR]

• Packing hydrodynamic performances as pressure drop and liquid holdup are investigated both experimentally and numerically. • 3D-printed packing replicas can be used as substitutes for CFD model validation, products defeaturing and lab experiments. • The research method in this manuscript can help optimise packing parameters and develop new products. Structured packings are widely used in oil & gas industries, as they can provide substantial surface area and high void fraction, thus enabling high mass transfer efficiency at a low pressure drop. This study investigates the hydrodynamic performance of two structured packings, namely, Mellapak 250Y and Montzpak B1−500. The pressure drop and liquid distribution are reported for a column of 200 mm diameter and 400 mm packing height. Wire-mesh sensor (WMS) is used to monitor the liquid distribution at the location of packing transitions. Packing replicas manufactured using a Fused Deposition Modelling (FDM) 3D printer is compared with commercial packings in terms of pressure drop and liquid distribution. A Computational Fluid Dynamics (CFD) model is initially validated using experimental data and then is used to investigate the effects of packing features, such as plate thickness, packing corrugation angles, holes, and packing transitions. The 3D-printed replicas show consistent performance compared to the commercial packings but can provide more information when measuring liquid distribution. The methodology and results discussed in this study can provide in-depth insights into the performance of structured packings, which is of critical importance when optimising packing parameters and testing new designs. [ABSTRACT FROM AUTHOR]

• Gas-liquid hydrodynamics characterization of a multi-channel fractal flow mixer. • the effect of liquid-to-gas superficial velocity ratio was studied. • High-speed imaging was used to identify different flow regimes in microchannels. • Optical probe was used to measure bubble mean size and velocity at each outlet. Gas-liquid hydrodynamics of a micro-structured device (fractal flow mixer) was experimentally investigated. Experiments were conducted for a range of liquid-to-gas superficial velocity ratios (V SL /V SG). High-speed imaging was used to identify the flow regimes inside the microchannels of the device at different V SL /V SG. At different V SL /V SG , two or more flow regimes were observed simultaneously in different micro-channels. Consequently, a new flow regime map was developed. An optical probe was used to measure the bubble mean size and velocity. The effect of the V SL /V SG towards the bubble mean size, mean velocity, and frequency were analyzed. The bubble mean size decreases with the increase of the V SL /V SG , which can be attributed to the uniform shearing of gas slugs across all channels. To check the consistency of the fractal flow mixer in producing gas bubbles over a single experiment run, the global relative standard deviation (RSD) was used. The fractal flow mixer was able to generate equal flow distribution across the 16 outlets and maintain a Taylor flow over a range of V SL /V SG.. However, depending on the V SL /V SG , the G B and G S vary to a certain extent, governed by the capillary effect and the back-pressure. [Display omitted] [ABSTRACT FROM AUTHOR]

• Novel multistage packed bed reactor with flow diverters is proposed. • Performance of the reactor was investigated for methanol synthesis. • Multi-objective optimisation was performed. • Proposed reactor configuration can produce higher methanol yield per kg catalyst. • Reactor was also simulated to obtain an isothermal operation. This study proposes a novel forward mixed multistage packed bed reactor (FMMPBR) for methanol synthesis. The reactor and reactants are divided into multiple stages with the provision of flow diverters to optimise the concentration of reactants and amount of catalyst along the length of the reactor. A steady state 1-D reactor model of the FMMPBR for methanol synthesis was developed and validated against previously published experimental data. Multi-objective optimisation was carried out to optimise inlet flowrate, space velocity and the concentration of reactants in each stage of the reactor. Simulations were carried out with an objective to achieve either maximum carbon conversion or minimum temperature deviation (isothermicity). The performance of FMMPBR was compared with that of the standard tubular reactor. When optimised for maximum carbon conversion, the FMMPBR resulted in ∼5% higher carbon conversion, ∼15% lower catalyst requirement and lower operating flowrate compared to the standard single tube reactor; and when optimised for minimum temperature deviation along the reactor length, the FMMPBR resulted in slightly lower carbon conversion, ∼34% lower catalyst requirement, reduced temperature standard deviation by 25%, and higher production rate. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Many models for describing the Fischer–Tropsch synthesis (FTS) over supported cobalt catalysts have been postulated but there is still much debate over its mechanisms and governing physio-chemical phenomena, particularly those relating to secondary reactions of olefins. In this work, a comprehensive kinetic model for the FTS over Co/Al2O3 catalyst, was developed to provide mechanistic explanations for deviations from Anderson–Schulz Flory (ASF) distributions. Experiments were conducted in a fixed bed reactor over a wide range of operating conditions (T=483–493 K, P=1.5–2MPa, feed ratio H2/CO=1.4–2.1 and CO conversion XCO =15–75%). Models were developed using, carbide, enolic and CO insertion mechanisms. The concept of 1-olefin re-adsorption and its chain length dependency was introduced. Chain length dependency was assumed to be due to an increased probability of 1-olefin interaction with the active site, with an increasing carbon number. Model results were analysed for statistical and physio-chemical robustness. The calculated apparent activation energies for the selected model were in good agreement with the values reported in the literature. It was found that FTS proceeded via the CO insertion mechanism and chain length dependent 1-olefin re-adsorption phenomena primarily governed the deviations from ASF distributions. [Copyright &y& Elsevier]

A kinetic model for Fischer–Tropsch synthesisis derived using a Langmuir–Hinshelwood–Hougen–Watsonapproach. Experiments were conducted over 25% Co/0.48% Re/Al2O3catalyst in a 1 L slurry reactor over a range of operatingconditions (T= 478, 493, 503 K; P= 1.5, 2.5 MPa; H2/CO = 1.4, 2.1; WHSV = 1.0–22.5NL/(gcat·h)). Rate equations were based on the elementaryreactions corresponding to a form of well-known carbide mechanism.The 1-olefin desorption rate constant was assumed to be a functionof carbon number due to the effect of weak interaction of the hydrocarbonchain with the catalyst surface. Values of estimated activation energiesare in good agreement with those reported previously in the literature.The kinetic model was able to correctly predict all of the major productdistribution characteristics, including the increase in chain growthprobability and decrease in olefin-to-paraffin ratio with carbon number,as well as formation rates of methane and ethylene. [ABSTRACT FROM AUTHOR]

• A novel packing, namely SpiroPak, is proposed as it demonstrates superior hydrodynamic performance. • SpiroPak is compared experimentally with different commercial packings in terms of pressure drop and liquid holdups. • The method of integrating 3D printing, modelling and lab experiments can help optimise packing parameters and develop new products. Hydrodynamic performance of an ultra low-pressure drop and high surface area, 3D printed structured packing (SpiroPak) was investigated in this study. Computational fluid dynamics (CFD) modelling combined with single-phase (dry) and irrigated (multiphase) experiments were carried out to validate the CFD modelling results. Experiments were conducted to measure the dry and wet pressure drop at a range of liquid load (0–38.2 m3/m2∙h) and F-factor (0–1.2 Pa0.5). Liquid distribution was measured using Wire Mesh Sensor (WMS) for SpiroPak and compared with a commercial and 3D printed replica of Mellpak 250X and Montzpak B1–500. The topology of the packing was analysed to calculate the specific surface area that could be available for mass transfer. It was found that the SpiroPak can have up to 50~200% more surface area per unit volume when compared with commercial packing. Experimental and modelling results showed that SpiroPak could reduce the dry pressure drop by approximately 50%. Parametric study found that reducing corrugation size to increase surface area and increasing the gap size to reduce the pressure drop were key design parameters of SpiroPak. Finally, scale-up and scale-out (tessellation) techniques were compared to determine the optimum element size for the application of SpiroPak on a large scale. [Display omitted] [ABSTRACT FROM AUTHOR]

• A highly uniform flow distributor has been developed for process intensification applications. • The distributor design was modelled using CFD and tested experimentally with additively manufactured prototypes. • The design is highly-scalable in the number of possible outlets and flow conditions. • Additive manufacture is efficiently achieved without the need for support structures. The ability of flow distributors to achieve high flow uniformity over multiple outlet channels is fundamental to the scalability of the synthesis of pharmaceuticals, polymers, fine chemicals, nanoparticles, and medical devices for drug delivery. Recent developments in the field of additive manufacturing (AM) have significantly increased the range of manufacturable geometries and materials, enabling the construction of high-performance flow distribution devices. Such devices can be manufactured at a wide range of scales (from microns to meters) and from a variety of metal and polymer materials. In this work, we describe a flow distribution system based on a fractal bifurcation scheme which achieves high outlet flow uniformity and packing density, while satisfying additive manufacturing constraints. Performance is predicted using an extensive numerical study and subsequently validated using experimental testing of additively manufactured prototypes. The experimental results confirm the predicted high flow uniformity. The resulting flow distribution system has the potential for use in a wide range of applications. [ABSTRACT FROM AUTHOR]

The heterogenous mineralogy of ultramafic deposits hosting mining operations makes it challenging to accurately determine the waste rock's mineral carbonation potential (MCP). Additionally, the significantly higher carbonation capabilities of olivine than serpentine add to the difficulty. To address this issue, in this work, a new and unique tool called the MCP calculator was developed as a Microsoft ExcelTM spreadsheet to accurately determine the amount of anthropogenic CO2 that a given rock mass can sequester through mineral carbonation. The program estimates the modal mineral abundance of ultramafic rocks to aid in MCP estimation. This tool is designed to be cost-effective and tailored for use by the mining industry, utilising abundant lithogeochemical data to evaluate their deposit as a potential substrate for industrial mineral carbonation operations. The paper introduces the MCP calculator, outlines a framework for developing the MCP parameter, and presents an example of its application. The calculator is specific to the mineral assemblage investigated at the Turnagain ultramafic complex in northern British Columbia but can be adjusted to study comparable deposits. The paper acknowledges that using waste rock in a mineral carbonation operation requires economic and practical decisions beyond the scope of the research. [ABSTRACT FROM AUTHOR]

• Annulus reactor minimising the influence of heat produced on the catalytic activity. • Zr addition to the commercial Cu/ZnO/Al 2 O 3 catalyst enhanced the methanol yield. • CO 2 conversion reduced for Zr modified Cu/ZnO/Al 2 O 3 catalyst. • The addition of Ga and Mg reduced the performance of the Cu catalyst. • Reducibility and copper crystallite size strongly influenced catalyst activity. The effect of metal additives, including Zr, Mg, and Ga, on the conventional Cu/ZnO/Al 2 O 3 (CZA) catalyst, was investigated for methanol synthesis using an oil-cooled annulus reactor. The annulus reactor was found to reduce the temperature gradient within the diluted catalyst bed by effective cooling and thus provide experimental data at steady-state and in kinetic regime allowing for the comparison of intrinsic activity between different catalysts. The addition of Zr enhanced the overall performance of methanol synthesis. However, the CZA-Zr catalyst displayed significantly reduced CO 2 conversion, possibly due to intensified water-gas shift reaction activity. The addition of Ga and Mg to CZA was found to be detrimental to the catalytic performance and is attributed to difficulties in reducibility and the increased crystalline size of copper particles. A relatively long induction period was observed for CZA-Zr sample in this study, which is attributed to the effective cooling imparted by the annulus reactor suppressing the r-WGS reaction. [ABSTRACT FROM AUTHOR]

Fischer-Tropsch Synthesis (FTS) yields a spectrum of products with carbon lengths of 1 to upwards of 100 units. In order to make use of the full spectrum of hydrocarbon fractions, particularly the heavier units, secondary processing is required. Modifying the FTS product distribution and catalyst activity in order to decrease the amount of long chain hydrocarbons (C 25 + ) may allow significant simplification of FTS based processes. To this end we report the results of in-situ pre-treatment of alumina supported cobalt catalysts (Co/Ru/La – Al 2 O 3 ) with acetylene in a fixed-bed reactor. It is postulated that acetylene dissociation and dehydrogenation resulted in the generation of carbidic and C x H y species on the catalyst surface. The formation of these carbonaceous species on different active sites of the catalyst surface following pre-treatment also significantly altered the FTS product distribution by affecting the extent and pathway of 1-olefin secondary reactions. It is thought that these changes resulted from decreased incorporation of 1-olefins in further chain growth and a decrease in secondary hydrogenation rate. The amount of heavy hydrocarbons (waxes) produced was reduced by more than two-fold. [ABSTRACT FROM AUTHOR]

• A newly designed fractal flow mixer was proposed. • Mixer was successfully manufactured using two additive manufacturing techniques. • Simulations were conducted to characterise the hydrodynamics and mixing. • Majority of the flow was uniformly mixed with a distribution index close to unity. The uniform distribution and mixing of fluids is a common functional requirement in a range of process intensified fluid handling applications. Traditional manufacturing processes have limited the design and performance of flow distributors and mixers. However, the maturing of additive manufacturing (AM) has increased the range of manufacturable geometries, enabling the construction of novel high-performance flow distribution devices. An additively manufactured fractal flow mixer was designed using the concept of self-similar bifurcating channels that symmetrically bifurcates a flow into multiple channels, achieving flow uniformity through a series of sequential stages. After four stages of bifurcation, a y-junction on each channel was introduced before the outlet, mixing the flow from two modules. Computational fluid dynamics (CFD) simulations were carried out to characterise the hydrodynamics and mixing performance of the newly designed mixer over a range of operating conditions and for mixing two gases. Effect of inlet Reynolds numbers (Re) and flow ratio was studied, the maximum relative standard deviation (RSD) was found to be ∼8%, and majority of the flow was uniformly mixed with a distribution index close to unity. The fractal flow mixer was successfully manufactured using vat photopolymerisation (VP) and laser powder bed fusion (L-PBF) techniques without any supports. [Display omitted] [ABSTRACT FROM AUTHOR]

Highlights: [•] TPR-EXAFS/XANES provides a transparent picture of reduction steps during activation. [•] The impact of promoters on H2-reduction/CO-carburization rates can be assessed. [•] Pt, Re, and Ru promoters are typically atomically coordinated to Co after activation. [•] Links between promoter local atomic structure and selectivity can be obtained. [•] Catalyst deactivation and sensitivity to H2O can be examined by synchrotron methods. [Copyright &y& Elsevier]

Pd was examined as a promoter for Fischer-Tropsch synthesis, and its effects on cobalt oxide reduction and product selectivities relative to commonly used promoters (i.e., Pt, Re, and Ru) at atomically equivalent levels were compared. Pd was identified to promote cobalt oxide reduction to even lower temperatures than Pt and Ru. However, Pd addition deleteriously affected product selectivity, and a clear shift to favor light products was observed. XANES analysis of an activated model catalyst revealed that Pd was in the reduced state. Local atomic structure was examined by EXAFS. Unlike Pt, Re, and Ru promoters, where previous investigations by groups such as Dr. Guczi's and ours have only observed coordination of the promoter with cobalt, Pd displayed both direct coordination to Co as well as other Pd atoms. The results suggest that this feature may be responsible for the measurably higher light gas selectivities observed. [ABSTRACT FROM AUTHOR]

The effect of CO conversion on hydrocarbon selectivities (i.e., CH, C, olefin and paraffin), H/CO usage ratios, CO selectivity, and catalyst stability over a wide range of CO conversion (12-94%) on 0.27%Ru-25%Co/AlO catalyst was studied under the conditions of 220 °C, 1.5 MPa, H/CO feed ratio of 2.1 and gas space velocities of 0.3-15 NL/g-cat/h in a 1-L continuously stirred tank reactor (CSTR). Catalyst samples were withdrawn from the CSTR at different CO conversion levels, and Co phases (Co, CoO) in the slurry samples were characterized by XANES, and in the case of the fresh catalysts, EXAFS as well. Ru was responsible for increasing the extent of Co reduction, thus boosting the active site density. At 1%Ru loading, EXAFS indicates that coordination of Ru at the atomic level was virtually solely with Co. It was found that the selectivities to CH, C, and CO on the Co catalyst are functions of CO conversion. At high CO conversions, i.e. above 80%, CH selectivity experienced a change in the trend, and began to increase, and CO selectivity experienced a rapid increase. H/CO usage ratio and olefin content were found to decrease with increasing CO conversion in the range of 12-94%. The observed results are consistent with water reoxidation of Co during FTS at high conversion. XANES spectroscopy of used catalyst samples displayed spectra consistent with the presence of more CoO at higher CO conversion levels. [ABSTRACT FROM AUTHOR]

• The dynamic process of frost formation on cryogenic surface is investigated. • The multiphase CFD model is developed to study the frosting behaviour at different conditions. • The temperature effect is evaluated with a range from refrigeration to cryogenic conditions. • Conditions of natural and forced convections are compared under cryogenic temperature. In this study, a multiphase computational fluid dynamics (CFD) model is developed to investigate the heat and mass transfer phenomenon of frost formation under cryogenic conditions. It is observed from experimental studies that frost formation on a vertical cryogenic surface showed different behaviours compared to refrigeration conditions. Through comparing different empirical correlations of mass transfer, it is found that the Rans–Marshall correlation is suitable to be used to account for frost formation under cryogenic conditions. The simulation results show a good agreement with the experimental study in terms of temperature profile. The mass transfer rate is taken as the parameter to characterise the differences of frost formation under different conditions. Surface temperatures ranging from refrigeration to cryogenic are investigated in order to understand the systematic change of frosting behaviour. Conditions of forced convection at different air velocities are studied to evaluate the mass transfer process. The methodology and results discussed in this study can provide in-depth understandings of mass transfer phenomenon at cryogenic conditions. [ABSTRACT FROM AUTHOR]

• Different designs of tubular reactor for methanol synthesis were investigated. • A novel reactor with metal inserts was proposed. • The reactor with the metal inserts resulted in significantly higher yields. • Conventional reactors performance can be improved by retrofitting with metal inserts. The performance of different tubular reactor designs for methanol synthesis was investigated by using computational fluid dynamics (CFD) simulations and experiments. The validated model was used to investigate the effect of various reactor geometries, coolant temperature, feed temperature, inlet composition, and flow rate on the methanol yield and heat transfer performance. New designs using metal inserts were proposed with an aim to improve the methanol yield by simple retrofitting. It was observed that the metal inserts can be utilized to relocate the catalyst close to the cooling surface, and as a result, near isothermal operating condition was achieved in both tube-cooled and tubular reactors. The methanol yield in tube-cooled and tubular reactors with the proposed metal inserts was improved by an average of 36% and 27% respectively over the range of space velocity. [ABSTRACT FROM AUTHOR]