Limits to Paris compatibility of CO2 capture and utilization

Time-dependent yield stress materials abound in nature and in industrial processes. Examples include clays, light metal alloys, paints and inks, adhesives, gelled waxy crude oils, drilling muds, fresh cement pastes, food products, biological fluids, ferrofluids, some lubricants, gypsum paste, and many other slurries, emulsions, suspensions, and foams. In this article, we describe the main features of time-dependent yield stress materials, present recent developments and applications, and discuss a number of important issues regarding the physics that govern the mechanical behavior of these complex materials. Finally, we discuss some recently developed experimental methods that are suitable to the rheological characterization of time-dependent yield stress materials.

Time-dependent yield stress materials

Process modeling, techno-economic assessment, and life cycle assessment of the electrochemical reduction of CO2: a review.

Meeting the sustainable development goals and carbon neutrality targets requires transitioning to cleaner products, which poses significant challenges to the future chemical industry. Identifying alternative pathways to cover the growing demand for chemicals and fuels in a more sustainable manner calls for close collaborative programs between experimental and computational groups as well as new tools to support these joint endeavours. In this broad context, we here review the role of process systems engineering tools in assessing and optimising alternative chemical production patterns based on renewable resources, including renewable carbon and energy. The focus is on the use of process modelling and optimisation combined with life cycle assessment methodologies and network analysis to underpin experiments and generate insight into how the chemical industry could optimally deliver chemicals and fuels with a lower environmental footprint. We identify the main gaps in the literature and provide directions for future work, highlighting the role of PSE concepts and tools in guiding the future transition and complementing experimental studies more effectively.

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Process modelling and life cycle assessment coupled with experimental work to shape the future sustainable production of chemicals and fuels

The physical problem under consideration is the boundary layer problem of an incompressible, laminar flow, taking place over a flat plate in the presence of a pressure gradient and radiation. For the mathematical formulation of the problem, the partial differential equations of continuity, energy, and momentum are taken into consideration with the boundary layer simplifications. Using the dimensionless Falkner–Skan transformation, a nonlinear, nonhomogeneous, coupled system of partial differential equations (PDEs) is obtained, which is solved via the homotopy analysis method. The obtained analytical solution describes radiation and pressure gradient effects on the boundary layer flow. These analytical results reveal that the adverse or favorable pressure gradient influences the dimensionless velocity and the dimensionless temperature of the boundary layer. An adverse pressure gradient causes significant changes on the dimensionless wall shear parameter and the dimensionless wall heat-transfer parameter. Thermal radiation influences the thermal boundary layer. The analytical results are in very good agreement with the corresponding numerical ones obtained using a modification of the Keller’s-box method.

https://www.mdpi.com/2073-8994/12/5/710/pdf

Solving the Nonlinear Boundary Layer Flow Equations with Pressure Gradient and Radiation

Carbon capture and utilization (CCU) has recently gained broad interest in the chemical industry. Direct electro- and thermocatalytic technologies are currently the focus of intense research, where the former employs electricity directly to reduce the CO2 molecule, while the latter comprises hydrogenation of CO2 in tandem with electrocatalytic water splitting. So far, it remains unclear which of the two is superior, yet this information is considered critical. Focusing on the platform chemical ethylene, the two CCU routes were compared using state-of-the-art performances with the fossil technology considering different power and CO2 sources. The thermo-route was found to be, at present, economically and environmentally better, yet under the same electrolyzer efficiencies, the electro-route would become superior. CCU routes could substantially improve the carbon footprint of the fossil ethylene (by 236 %) while decreasing at the same time impacts on human health, ecosystem quality, and resources (64, 140, and 80 %, respectively). However, they are economically unattractive even when considering externalities (indirect cost of environmental impacts), that is, 1.7- to 3.9-fold more expensive compared to the current fossil-based analogue. Acknowledging this limitation, the concept of hybridization was applied as a means to smooth the transition towards more sustainable chemicals. Accordingly, it was found that an optimal hybrid plant could produce carbon-neutral (cradle-to-gate) ethylene with a premium of only 30 % over the current market prices by judiciously combining CCU routes with fossil technologies.

Hybridization of Fossil- and CO2 -Based Routes for Ethylene Production using Renewable Energy.

We consider the steady axisymmetric Poiseuille flow of a Bingham plastic under the assumption that both the plastic viscosity and the yield stress vary linearly with pressure. An analytical solution is derived for the case where the growth coefficients of both rheological parameters are equal, which is indeed a reasonable assumption for certain oil-drilling fluids allowing the existence of a separable solution with a cylindrical unyielded core. The conditions for the occurrence of flow and the effects of the growth coefficient on the radius of the unyielded plug, the velocity profiles and the pressure distributions are discussed.

Axisymmetric Poiseuille flow of a Bingham plastic with rheological parameters varying linearly with pressure

The pressure and temperature dependence of the yield stress is well established in oil drilling. In the present work, the steady, annular pressure-driven flow of a Bingham plastic is considered under the assumption that both the plastic viscosity and the yield stress vary linearly with pressure. A semi-analytical solution is derived for the case where the growth coefficients of both rheological parameters are equal, which, for certain oil drilling fluids, is indeed a reasonable assumption allowing the existence of a separable solution with an annular unyielded core. The inner and outer radii of the unyielded core are determined by solving numerically an algebraic system of equations. The pressure, which is two-dimensional in the yielded parts of the domain, and the velocity, which varies only with the radius, are calculated by means of explicit analytical expressions. The conditions for the occurrence of flow and the effects of the growth coefficient and the radii ratio on the width of the unyielded annular plug, the velocity profiles, and the pressure distributions are discussed.

Annular pressure-driven flow of a Bingham plastic with pressure-dependent rheological parameters

The lubrication flow of a Bingham plastic in long tubes is modeled using the approach proposed by Fusi and Farina (Appl. Math. Comp. 320, 1–15 (2018)). Both the plastic viscosity and the yield stress are assumed to vary linearly with the total pressure. The resulting nonlinear system of an ordinary differential equation and an algebraic one with unknowns the total pressure and the radius of the unyielded core are solved by using two different techniques. A pseudospectral numerical method utilizing Chebyshev orthogonal polynomials and an analytical perturbation method with the small parameter being the difference of the two dimensionless parameters which are introduced due to the pressure-dependence of the yield stress and the plastic viscosity of the material. The effects of the pressure-dependence of the material parameters on the critical pressure difference required for flow to occur and on the shape of the unyielded core are investigated and discussed.

Iasonas Ioannou

Papers

Process modelling and life cycle assessment coupled with experimental work to shape the future sustainable production of chemicals and fuels

Hybridization of Fossil- and CO2 -Based Routes for Ethylene Production using Renewable Energy.

Axisymmetric Poiseuille flow of a Bingham plastic with rheological parameters varying linearly with pressure

Annular pressure-driven flow of a Bingham plastic with pressure-dependent rheological parameters

Lubrication solution of the axisymmetric Poiseuille flow of a Bingham fluid with pressure-dependent rheological parameters