Lionel Limousy

Concentration polarization phenomenon during the nanofiltration of multi-ionic solutions: influence of the filtrated solution and operating conditions.

One of the major difficulties for the prediction of separation performances in the case of multi-ionic mixtures nanofiltration lies in the description of the concentration polarization phenomenon. Usual models available in literature do not take account of the polarization phenomenon or only describe it cursorily. Very few studies dedicated to the understanding and the specific description of the concentration polarization phenomenon are available in literature and a 2-D multi-ionic model describing the layer heterogeneity along the membrane length has never been proposed yet. The model used in the present work, called Pore and Polarization Transport Model (PPTM), allows an accurate description of the concentration polarization layer occurring during the filtration of multi-ionic solutions by taking account of the radial electromigrative transport in the layer, the turbulence, as well as the axial heterogeneity. In this context, the present paper aims at proposing a numerical investigation of the influence of operating conditions on the behavior of the polarization layer occurring at the membrane vicinity. The input parameters governing the transport through the membrane have been assessed in a previous study in the same experimental conditions so that only the polarization layer is investigated here. The proposed model which was previously validated on experimental observed rejection curves is then used to understand how operating conditions, such as applied pressure, feed flow-rate, or divalent ion proportion, govern the polarization phenomenon. For this purpose, concentration and thickness axial profiles along the membrane length and radial profiles within the polarization layer are investigated for various conditions. Finally, the impact of the type of divalent ion and the number of ions is also studied on various mixtures.

Characterization of coffee residues pellets and their performance in a residential combustor

ABSTRACT Spent coffee grounds (SCG) and coffee husks (CH) were evaluated as biofuels, after densification, for energy production. CH represent a specific problem for the coffee industry due to a low calorific value, high ash content, and a very low bulk density. Hence, the energetic potential of SCG (95 wt%)/CH (5 wt%) blend and pure SCG (100%) were examined. The blend of SCG and CH was limited to 5 wt% of CH because of the low bulk density of CH. Therefore, physicochemical and energetic characterizations of the produced pellets were performed. Thermogravimetric analyses were performed under nitrogen and air atmospheres to evaluate the CH behavior in the blend. Characterization study shows that both produced pellets could reach the French Agropellets standard (AQI). Thermal degradation showed that the mean reactivity of the SCG/HC pellets was higher than pure SCG. Then, combustion experiments were performed in a domestic combustor, after modification of the boiler power in order to improve its energetic performances. The presence of CH led to a rise of CO, NOx, VOC’s, and particle emissions. Nevertheless, the performances of the biofuels are almost in agreement the NF EN 12809 standard.

Hydraulic Performance Modifications of a Zeolite Membrane after an Alkaline Treatment: Contribution of Polar and Apolar Surface Tension Components

Hydraulic permeability measurements are performed on low cut-off Na-mordenite (MOR-type zeolites) membranes after a mild alkaline treatment. A decrease of the hydraulic permeability is systematically observed. Contact angle measurements are carried out (with three polar liquids) on Na-mordenite films seeded onto alumina plates (flat membranes). A decrease of the contact angles is observed after the alkaline treatment for the three liquids. According to the theory of Lifshitz-van der Waals interactions in condensated state, surface modifications are investigated and a variation of the polar component of the material surface tension is observed. After the alkaline treatment, the electron-donor contribution (mainly due to the two remaining lone electron pairs of the oxygen atoms present in the zeolite extra frameworks) decreases and an increase of the electron-receptor contribution is observed and quantified. The contribution of the polar component to the surface tension is attributed to the presence of surface defaults, which increase the surface hydrophilicity. The estimated modifications of the surface interaction energy between the solvent (water) and the Na-mordenite active layer are in good agreement with the decrease of the hydraulic permeability observed after a mild alkaline treatment.

Energy applications of coffee processing by-products

Abstract This chapter explores the possibilities of using coffee processing by-products (e.g., coffee husks and spent coffee grounds [SCG]) for energy applications (e.g., biofuels, biodiesel, bioethanol). In particular, the recovery of energy from biomass through thermochemical processes (pyrolysis, gasification, combustion, hydrothermal treatment, etc.) and biochemical processes is presented. The energy recovery from biomass is an ecological route to produce energy from renewable sources, reduce waste, produce cleaner-burning fuels, protect the environment, reduce fossil fuels consumption and dependence, decrease fuel costs, lower greenhouse gas (GHG) emissions, and find a solution for the limited availability of fossil fuels. Moreover, it has a good impact on economic, social, and agricultural development and ensures a regular supply of energy.

The relationship between mineral contents, particle matter and bottom ash distribution during pellet combustion: molar balance and chemometric analysis

This paper aims to identify the correlation between the mineral contents in agropellets and particle matter and bottom ash characteristics during combustion in domestic boilers. Four agrifood residues with higher mineral contents, namely grape marc (GM), tomato waste (TW), exhausted olive mill solid waste (EOMSW) and olive mill wastewater (OMWW), were selected. Then, seven different pellets were produced from pure residues or their mixture and blending with sawdust. The physico-chemical properties of the produced pellets were analysed using different analytical techniques, and a particular attention was paid to their mineral contents. Combustion tests were performed in 12-kW domestic boiler. The particle matter (PM) emission was characterised through the particle number and mass quantification for different particle size. The bottom ash composition and size distribution were also characterised. Molar balance and chemometric analyses were performed to identify the correlation between the mineral contents and PM and bottom ash characteristics. The performed analyses indicate that K, Na, S and Cl are released partially or completely during combustion tests. In contrast, Ca, Mg, Si, P, Al, Fe and Mn are retained in the bottom ash. The chemometric analyses indicate that, in addition to the operating conditions and the pellet ash contents, K and Si concentrations have a significant effect on the PM emissions as well as on the agglomeration of bottom ash.

Process engineering for pollution control and waste minimization

The Biomass Energy, Environment and Sustainable Development workshop has been successfully organized in the frame of the International Renewable Energy Congress (IREC) conference which was organized in Hammamet (Tunisia) from March 22 to 24 2016. Approximately, 50 scientists joined the workshop to discuss the challenges of waste minimization and recovery, pollution analysis and treatment. IREC covers a wide range of topics concerning renewable energies from solar thermal energy to biomass energy and others. During this congress different scopes are approached such as materials and technologies, modelling and simulation, optimization, energy efficiency, sustainability... The seventh edition of IREC offered the possibility to organize a workshop dedicated to the chemical engineering community, which works specifically on applications for biomass treatment, transformation and valorisation. This event offers the possibility to build new collaborations between foreign research teams but also benefit from a convenient environment to welcome researchers. The workshop mostly focused on two research fields: water treatment and energy production from biomass. Protection of environment as well as the energetic valorisation of biomass resources has become crucial since more than 20 years. The world faces to a complex situation with the emergence of developing countries, which lead to an increase of fossil fuel demand, to an acceleration of feedstock consumption and to the generation of large amount of wastes and pollutions. The latter has led to a lot of researches, in order to minimize the impact of wastes and pollutants on the environment. Among the different processes which are used to remove pollutant from wastewater, adsorption is one of the more studied. To reach high pollutant abatement without a prohibitive cost, new cheap materials were developed these last years mainly from biomass and waste solids. Biomass may origin from different sources: sawmill industry, agriculture, agro-industry... Depending on its origin, biomass compositionmay be different in composition and in structure. Raw biomass can be used as biosorbent, but generally, a thermal treatment is applied (torrefaction, pyrolysis) in order to increase the surface area and the porosity of the biomass, offering higher adsorption capacities for organic and mineral compounds. At this stage, the adsorbent is called biochar. To obtain higher adsorption properties and to obtain sorbents with high selectivity, biochars can be activated by chemical or physical routes. The activated carbons present important surface areas (sometimes more than 2000 m/g) and their porosities can be designed depending on the final application (micro and/or mesoporosity). These materials are often used for the removal of organic pollutants present in wastewater at low concentration, as it is described in several papers of the special issue. Water treatment can be also investigated by filtration process. Depending on the nature of the compounds present in the feed solution (organics, salts, bacteria, particles), the process has to be adapted in order to reach the best performance with high durability. The main problem which is encountered when using filtration membranes corresponds to fouling due to the adsorption of molecules and bacteria at the surface of the filtration layer. Different treatments have to be applied to recover good performances of the membranes, they are at the origin of additional costs (chemical reagents, process stop, etc.) and environmental impacts. These aspects Responsible editor: Philippe Garrigues

Thermal degradation kinetics and mechanisms of Posidonia Oceanica under inert and oxidative atmospheres

ABSTRACT The thermal degradation characteristics of Posidonia Oceanica (PO), a marine biomass abundantly available on the coastal zone of the Mediterranean Basin, were investigated using thermogravimetric analysis under inert and oxidative atmospheres. The kinetic parameters of the both thermal degradations conditions were determined using n-reaction order model. Coats–Redfern and Phadnis–Deshpande methods were used to discuss the probable degradation mechanisms. Results showed that PO is an attractive alternative for energy production owing to its elevated heating value. Moreover, PO thermal degradation follows the usual shape of biomass decomposition. Hence, under inert atmosphere, its thermal degradation had two different stages after moisture release. The first stage corresponded to the volatiles release while the second stage corresponded to the char formation. The solid-state decomposition mechanisms followed by the devolatilization step of PO were two or three dimensional diffusion controlled reaction. However, the decomposition mechanism during PO char formation corresponded to a nucleation and growth mechanism. Under oxidative atmosphere, two stages were also observed corresponding to volatiles release and char combustion, respectively. The solid-state mechanism of volatiles release followed three dimensional diffusion controlled reaction while the char combustion mechanism corresponded to a contracting area phase boundary controlled reaction.

Numerical Ways to Characterize the Deterioration of Nanofiltration Membranes

In this study, a transport model is used to characterize structural and physico-chemical changes in a nanofiltration membrane during the filtration of ionic mixtures. The membrane state is analyzed by a set of four model parameters identified from glucose and salts filtration: the membrane water permeability (Lp), the mean pore radius (rp), the membrane charge density (Xd), and the dielectric constant of the solution inside pores ( p). The study of these structural and physico-chemical properties allows us to determine if deterioration or fouling occurred during filtration. Two distinct identification procedures from filtration of synthetic solutions are investigated in this paper. One is based on the filtration of single salt solutions, whereas the other lies in parameters identification from mixtures containing at least three ions. These methods are applied here to characterize influence of fouling deposit formation and membrane cleaning.

Simulation of the Denitrification Process of Waste Water with a Biochemical Systems Model: A Non-Conventional Approach

Abstract Matching experimental and theoretical approaches have often been fruitful in the investigation of complex biological processes. Here we develop a novel non-conventional model for the denitrification of waste water. Earlier models of the denitrification process were compiled by the International Association on Water Quality group. The Activated Sludge Models 1–3, which are the most frequently used all over the world, are presently not adapted towards the integration of both nitrous and nitric oxide emissions during the denitrification process. In the present work, a Generalized Mass Action model, based on Biochemical Systems Theory, was designed to simulate the nitrate reduction observed in specific experimental conditions. The model was implemented and analysed with the software package PLAS. Data from a representative experiment were chosen (T=10°C, pH=7, C/N=3, with acetate as carbon source) to simulate greenhouse NO and N2O gas emissions, in order to test hypotheses about the corresponding bacterial metabolic pathways. The results show that the reduction of nitrate and nitrite is kinetically limiting and that nitrate reduction is limited by diffusion and support that distinct microbial subpopulations are involved in the denitrification pathway, which has consequences for NO emissions.

Factors Influencing NO2 Adsorption/Reduction on Microporous Activated Carbon: Porosity vs. Surface Chemistry

The textural properties and surface chemistry of different activated carbons, prepared by the chemical activation of olive stones, have been investigated in order to gain insight on the NO2 adsorption mechanism. The parent chemical activated carbon was prepared by the impregnation of olive stones in phosphoric acid followed by thermal carbonization. Then, the textural properties and surface chemistry were modified by chemical treatments including nitric acid, sodium hydroxide and/or a thermal treatment at 900 °C. The main properties of the parent and modified activated carbons were analyzed by N2-adsorption, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) techniques, in order to enlighten the modifications issued from the chemical and thermal treatments. The NO2 adsorption capacities of the different activated carbons were measured in fixed bed experiments under 500 ppmv NO2 concentrations at room temperature. Temperature programmed desorption (TPD) was applied after adsorption tests in order to quantify the amount of the physisorbed and chemisorbed NO2. The obtained results showed that the development of microporosity, the presence of oxygen-free sites, and the presence of basic surface groups are key factors for the efficient adsorption of NO2.