Calcium looping is a promising process for carbon dioxide removal. The flow and heat transfer processes of the granular sorbent in a calcium looping CO₂ capture system and the effects of the operating parameters on calcination efficiency and transport properties were studied. Both the rotation speed and the inclination angle significantly influence the dynamic properties of the granular matter.

Abstract

The calcium looping process has become a promising technology for reducing carbon dioxide emissions because of its lower energy consumption compared with other methods. A three-dimensional multifluid model based on the kinetic theory was employed to study the movement of granules in the calciner. The results demonstrated that an increase in the rotation speed and inclination angle of the calciner led to a decrease in the residence time of the particles. Simultaneously, the probability of the particles being heated was reduced. Insufficiently calcined particles reduce the carbon capture capacity in the next cycle; therefore, suitable operating conditions and mechanism designs are very important.

The controllability and energy-saving ability of the dividing wall column for batch distillation (batch DWC) was proved. The performances of temperature control were slightly better than those of composition control. The batch DWC outperforms the other batch configurations in terms of distillation time and energy loss.

Abstract

The batch distillation is significant and flexible to separate liquid mixtures. However, it is usually energy intensive. The dividing-wall column (DWC) is a promising and practical energy-saving process intensification technology. The DWC for batch distillation (batch DWC) to separate benzene, toluene, and xylene mixtures was examined with composition and temperature control structures to verify its controllability. Besides, the batch DWC outperforms the conventional single-column batch distillation and middle-vessel batch distillation in terms of distillation time and energy consumption under the same conditions. In terms of more practical temperature control results, the batch DWC saves 63 % of energy compared with the conventional single-column batch distillation and 47 % of energy compared with the middle-vessel batch distillation.

Post-combustion technologies are essential to reduce CO₂ emissions. CO₂ separation from flue gases by membranes has advantages over other methods. Membranes must be robust, with a high CO₂ permeation flux and reduced environmental impact manufacture. Life cycle assessment is applied to compare environmental impacts of the membrane manufacture based on chitosan and fossil fuels with the same CO₂ permeation flux.

Abstract

The environmental impacts of the manufacture of chitosan (CS) and polymeric poly(1-trimethylsilyl-1-propyne) (PTMSP) mixed-matrix membranes (MMMs) for CO₂ separation by life cycle assessment (LCA) are compared. An ionic liquid of non-reported toxicity is used in CS membranes to enhance the mechanical strength, and different fillers are used to increase mechanical and functional properties: ETS-10, ZIF-8, HKUST-1, and Zeolite A. Results with the same CO₂ permeation flux indicate that ETS-10/IL-CS is the membrane manufacture with highest impacts due to its lower permeability. When comparing impacts with same permeation areas, the polymeric one is the membrane with highest impacts. Biopolymer and polymer manufacture are the components with highest contribution to the total environmental impacts of each membrane. To decrease all their impacts below fossil polymer membrane for the same CO₂ permeation flux, CS membranes permeabilities should be improved by a numerical factor of 1000, 100, and 2 for the ETS-10, ZIF-8, and HKUST-1/IL-CS MMMs, respectively.

Aqueous two-phase systems (ATPSs) have potential applications in the recovery of residual dyes in wastewater, which pose a threat to human health and the environment. This work determined the partition coefficients and thermodynamic transfer parameters of Remazol textile dyes in alcohol-salt-water ATPSs. It highlighted that ATPS is a promising route for removing dyes from contaminated wastewaters.

Abstract

The aim of this work was a complete thermodynamic study on the partitioning of Remazol Yellow l, Remazol Brilliant Blue, and Remazol Red dyes in isopropyl alcohol + sodium phosphate + water aqueous two-phase systems at different temperatures. The free energy change of transfer, enthalpy change of transfer, and entropy change of transfer were evaluated. The effects of the structure of the dye, tie line length, and temperature on the partitioning were studied. The results indicate that these aqueous two-phase systems have high capacity to extract the dyes from aqueous matrices to the organic phase of these systems and are an interesting alternative to effluent treatment process.

The slug flow tubular reactor is a promising continuous manufacturing or next-generation approach that can address problems in the traditional tank-based batch reactor, such as batch-to-batch variation and scale-up difficulties. The study shows how to control the parameters of a slug flow reactor and how to scale up a process without changing the reactor itself.

Abstract

Slug flow has received increased interest due to the slugs serving as individual microreactors for enhanced process efficiency and product quality. In this study, slugs were continuously generated in various scales and sizes, with slug size uniformity studied by in-line imaging. Different strategies of gas flow control and slug scale-up were evaluated regarding the slug size distribution. With modified gas flow control, the slug uniformity was improved significantly. Slug flow can also be scaled up without sacrificing slug size uniformity, either by increasing the reservoir feeding volume or the flow rate. The type of gas used (air and nitrogen) to generate slugs does not affect the slug size uniformity. A narrow slug size distribution can improve the particle size distribution and, hence, lead to better product quality.

Mn-based catalysts for ammonia selective catalytic reduction of NO_x exhibit good low-temperature activity but poor sulfur resistance. Doping with Sb resulted in a perforated porousness layered foam micromorphology, which promoted molecular mass transfer of the reaction gas and diffusion of the reactants/products, enhanced the catalytic activity, and increased the resistance to sulfur poisoning.

Abstract

Manganese-antimony composite oxide catalysts were prepared for use in low-temperature selective catalytic reduction of flue gas, by adopting the strategy of passivation to regulate the valence state of the active component and control catalytic activity. Activity evaluation results found that MnSb_0.36O_y delivered 80 % NO conversion in the presence of SO₂ at 200 °C, and nearly 90 % conversion at 250 °C. Doping with Sb changed the surface micromorphology, resulting in a perforated porousness layered foam with a porous structure of tens of nanometers, which was conducive to molecular mass transfer of the reaction gas. Doping with Sb regulated the valence state of the active MnO_x component, which diminished catalytic oxidation of SO₂, thus promoting catalyst stability and limiting the toxic effect of SO₂.

The conversion of synthesis gas to a broad spectrum of products via Fischer-Tropsch reaction is one of the most important processes to solve the problem of decreasing fossil fuel resources. The effects of some operating conditions on the performance of a new kind of perovskite nanocatalyst (LaFe_0.5Mn_0.5O_{3 ±  δ} ) in a fixed-bed catalyst microreactor were investigated.

Abstract

Operating conditions and selectivity of a new perovskite nanocatalyst were studied in Fischer-Tropsch synthesis using a fixed-bed microreactor. Selectivity equations were obtained using the experimental data collected from a hydrogenation process in a fixed-bed microreactor. The operating conditions were obtained by defining the design-of-experiment scope based on response surface methodology, on 3 levels and in 15 tests. The optimum selectivity for alkenes relative to alkanes was obtained at 349.7 °C, 3.2 bar, and a H₂/CO volumetric ratio of 1. Also, the optimum selectivity for alkenes relative to the overall selectivity for other products was attained at 250 °C, 2.3 bar, and a feed volumetric ratio of 2.

Shiny water drops puprle leaf. Copyright: Getty Images

The prospects of algae as an alternative raw source for biofuel production, various cultivation, harvesting, and conversion methodologies with merits and demerits, and the formation of bioproducts by thermochemical processes are reviewed. Technological breakthroughs like genetic engineering, synthetic biology, and nanotechnology can enhance biofuel manufacturing techniques by altering or introducing specific genes.

Abstract

The objective of this review is to interpret the usage of alternative renewable systems that is imperative for future developments on a global industrial scale. Microalgae have appeared as the most realistic source for biofuel generation due to the accumulation of lipids in most of the strains with rapid biomass expansion and greater photosynthetic efficiency than land plants. Microalgal-derived feedstocks have a broad range of commercial advantages and can be used as promising renewable fuel substitutes with zero net CO₂ emission. Important facets of algal-based biofuel production, growing and harvesting techniques, approaches to thermochemical conversion, synthesis of commodities with added value, and recent breakthroughs in the field of synthetic biology for fuel production are covered.