Faïçal Larachi

Ionic liquids (EMIM)(BF4), (EMIM)(Otf) and (BMIM)(Otf) as corrosion inhibitors for CO2 capture applications

We present the viability of using thermally stable, practically non-volatile ionic liquids as corrosion inhibitors in aqueous monoethanolamine systems. Carbon steel 1020, which is widely used as a construction material in CO2 capture plants, has been taken as a test material. Corrosion inhibition capabilities of typical room-temperature ionic liquids constituting imidazolium cation in concentration range ≤3% in CO2 capture applications were investigated. Electrochemical corrosion experiments using the potentiodynamic polarization technique for measuring corrosion current were carried out. Subsequent calculation of corrosion rate via Tafel fit was performed. The experimental findings suggest that the corrosion rate is significantly dependent on the process parameters, such as the CO2 loading and the presence of oxygen. In addition, the value of the corrosion rate is sensitive to the type of ionic liquid added. Moreover, the results show that ionic liquids possess the ability of suppressing severe operational problems of corrosion in typical CO2 capture plants to a reasonable extent (≥50%).

Allothermal Fluidized Bed Reactor for Steam Gasification of Biomass

This article evaluates a hybrid multi-compartment cyclic fluidized-bed reactor for the allothermal steam gasification of biomass. The concept combines space and time delocalization to approach an ideal allothermal gasifier. Thermochemical conversion of biomass in time and space sequences of steam biomass gasification and char/biomass combustion is envisioned in which the exothermic combustion compartments provide heat into an array of interspersed endothermic steam gasification compartments. This concept may enhance unit heat integration and thermal efficiency while procuring nitrogen-free synthesis gas without requiring addition of oxygen (or air) to the steam gasification compartment nor contact between the flue gas and the synthesis gas. The strengths and weaknesses of existing autothermal and allothermal gasification technologies are analyzed and a new allothermal reactor concept is introduced. Elements of gasification chemistry, fluidization hydrodynamics, and heat transfer requirements are described that are relevant for the design of the multi-compartment fluidized-bed gasifier/combustor. A preliminary design of the experimental hot mock-up is presented, including a discussion of process diagrams and mass balance.

Dynamics of fines/bacterial cells accumulation in trickle-bed reactors/bioreactors—Multiscale modeling framework

Abstract Modeling the dynamics of fines/bacterial cells accumulation in gas–liquid–solid reactors/bioreactors is a difficult task which demands an improved understanding and quantification of the complex fluid dynamics, surface physical and microbiological phenomena coupled with (bio)chemistry and thermodynamic backgrounds. This contribution is offered as a step in that direction and presents two case studies with reference to modeling the complex physical and biological plugging/clogging phenomena in trickle-bed reactors/bioreactors, induced, respectively, by the retention of fine particles and by the formation of an excessive amount of biomass. The complex gas–liquid flow and space–time evolution of fines/bacterial cells capture, aggregation, detachment and migration in trickle-bed reactors/bioreactors were analyzed after a mathematical description was cast in terms of Euler–Euler two-fluid dynamic models based on the volume-average mass and momentum equations developed for multiphase systems coupled with species balance equations, solid deposit/biomass dynamics equations, filtration equations for the fines/bacterial cells and the aggregates, population balance equations for the fines/bacterial cells agglomeration.

Hydrodynamics and Reaction Performances of Multiphase Reactors for Marine Applications – A Review

Abstract Hydrodynamics and (catalytic & non-catalytic) reaction [high-pressure hydrodesulfurization; Fischer-Tropsch synthesis; CO2-monoethanolamine (MEA) absorption; simultaneous CO2 and H2S absorption in MEA; CO2 thermal desorption, enzymatic CO2 hydration] performances of trickle-bed and packed-bed column reactors subjected to static inclination, rolling (symmetrical/asymmetrical externally-generated reactor oscillations) and heaving motions were analyzed via detailed dynamic 3-D models which couple the macroscopic volume-averaged momentum, mass, energy and species balance equations in the liquid/gas phases with diffusion/chemical reaction inside the catalyst particles, enzyme washcoat or liquid film near the gas-liquid interface. Axial symmetry breakdown once the packed bed systems become inclined inflicts noticeable reductions of the reactor (or scrubber) performances. Only the performance of Fischer-Tropsch synthesis in the presence of water-gas shift reaction increases slightly with the increase of trickle-bed reactor inclination because of facile uptake of reactants in the key reactions from the gas phase while a fraction of valuable CO can be forwarded in water gas-shift reaction. For most of the reactions examined, the reactor performance is negatively impacted in asymmetric oscillating multiphase reactors with Fischer-Tropsch synthesis as an exception owing to the presence of water-gas shift reaction the performance of which is slightly improved. This performance deterioration/enhancement is maximal for the reactor moving between vertical and an inclined position when the time-dependent performance waves develop around the steady-state solution of the mid-inclination angle. The oscillatory reactor performance moves towards the steady-state solution of the vertical state when the asymmetry between the two inclined positions dwindles. Symmetric oscillating and heaving trickle-bed and packed-bed column reactors generate an oscillatory performance around the steady-state solution of vertical state which is affected by the amplitude and period of the angular and heaving motions of the vessel.