General methodology for exergy balance in ProSimPlus® process simulator

This paper presents a general methodology for exergy balance in chemical and thermal processes integrated in ProSimPlus® as a well-adopted process simulator for energy efficiency analysis. In this work, as well as using the general expressions for heat and work streams, all of exergy balance is presented within only one software in order to fully automate exergy analysis. In addition, after exergy balance, the essential elements such as source of irreversibility for exergy analysis are presented to help the user for modifications on either process or utility system. The applicability of the proposed methodology in ProSimPlus® is shown through a simple scheme of Natural Gas Liquids (NGL) recovery process and its steam utility system. The methodology does not only provide the user with necessary exergetic criteria to pinpoint the source of exergy losses, it also helps the user to find the way to reduce the exergy losses. These features of the proposed exergy calculator make it preferable for its implementation in ProSimPlus® to define the most realistic and profitable retrofit projects on the existing chemical and thermal plants

HIx system thermodynamic model for hydrogen production by the sulfur-iodine cycle

The HIx ternary system (H2O – HI – I2) is the latent source of hydrogen for the Sulfur – Iodine thermo-chemical cycle. After analysis of the literature data and models, a homogeneous approach with the Peng-Robinson equation of state used for both the vapor and liquid phase fugacity calculations is proposed for the first time to describe the phase equilibrium of this system. The MHV2 mixing rule is used, with UNIQUAC activity coefficient model combined with of hydrogen iodide solvation by water. This approach is theoretically consistent for HIx separation processes operating above HI critical temperature. Model estimation is done on selected literature vapor – liquid, liquid – liquid, vapor – liquid – liquid and solid – liquid equilibrium data for the ternary system and the three binaries subsystems. Validation is done on the remaining literature data. Results agree well with the published data, but more experimental effort is needed to improve modeling of the HIx system

Bunsen section thermodynamic model for hydrogen production by the sulfur-Iodine cycle

A model for the Bunsen section of the Sulfur – Iodine thermo-chemical cycle is proposed, where sulfur dioxide reacts with excess water and iodine to produce two demixing liquid aqueous phases (H2SO4 rich and HI rich) in equilibrium. Considering the mild temperature and pressure conditions, the UNIQUAC activity coefficient model combined with Engels’ solvation model is used. The complete model is discussed, with HI solvation by water and by iodine as well as H2SO4 solvation by water, leading to a very high complexity with almost hundred parameters to be estimated from experimental data. Taking into account the water excess, a successful reduced model with only 15 parameters is proposed after defining new apparent species. Acids total dissociation and total H+ solvation by water are the main assumptions. Results show a good agreement with published experimental data between 25 °C and 120 °C

CMAS interaction with yttrium based systems: Towards a promising solution?

Anti-CMAS coatings are designed to protect thermal barrier coatings against degradations due to CMAS infiltration. They are dedicated to react as fast as possible with CMAS compounds in order to generate a new phase that will not let the CMAS infiltration going on. In addition to the fast kinetics, the preparation of large quantities of phases with as less as anti-CMAS material as possible is sought as well as the obtaining of a dense and impermeable phase. Reference anti-CMAS material is gadolinium zirconate, it has been demonstrated as efficient to block CMAS infiltration. The efficiency of yttria for the same application has been studied by previous works at the CIRIMAT laboratory [1]. The starting point of this work was first, to make a comparative study of the anti-CMAS properties of gadolinium zirconate and yttria based anti-CMAS compositions and secondly, to discuss on the behaviour of a mixed composition i.e. yttrium zirconate. This insight on the mechanism of interactions of CMAS with the yttrium based systems and gadolinium reference is obtained at the light of a large number of interactions experiments and characterizations. Interaction durations between 1h and 100h were investigated, with either 50/50 or 80/20 mass ratio of CMAS/anti-CMAS. Different temperatures of interaction between 1200°C to 1300°C were also scanned. The phases in presence were systematically characterized by XRD, SEM, EDX and Castaing microprobe local analyses and cartographies (Figure 1a)). In particular, the proportion and composition of phases are detailed as a function of the interaction time (Figure 1b)) for each anti-CMAS-CMAS interaction system. From these experiments, the mechanisms of interaction between CMAS and Y2O3, Y2Zr2O7 and Gd2Zr2O7 are evidenced. Whereas Y2O3 interaction leads to the higher proportion of reaction products, the products impermeability is also superior for this composition. The depth of infiltration of CMAS into a dense pellet anti-CMAS material for a given time is longer for Y2Zr2O7 as compared to the two others. However Y2Zr2O7 benefit is due to a higher Ca2+ trapping capability with the formation of Ca4Y6 like phase instead of Ca2Y8 for Y2O3 (Figure 1c)). In this respect, yttrium zirconate demonstrates a synergetic effect as compared to Y2O3 and Gd2Zr2O7. The origin of this synergy is interpreted as coming from the presence of both zirconium and yttrium. A large part of the discussion is based on the study of powders interactions, an insight into the interactions of CMAS with anti-CMAS pellets of the different compositions will also be presented and discussed. Fundamental and applicative aspects will be covered. Please click Additional Files below to see the full abstract

Synthesis of yttria by aqueous sol-gel route to develop anti-CMAS coatings for the protection of EBPVD thermal barriers

Anti-CMAS yttria coatings have been prepared by sol-gel routes. Yttria powders with controlled morphology are prepared via auto-combustion of yttrium precursors in a polymerized matrix. The influence of key parameters of the water-based sols is assessed. Indeed, the pH of the initial sol and the temperature of thermal treatment play a major role in the morphology and grain size of yttria powders. To prevent infiltration of CMAS, yttria powders are proposed to be synthesized at pH=1 of the aqueous sol, with drying of the sol and heating at 900 °C. After optimization of the synthesis and deposition conditions via sol-gel route, yttria-based coatings with high specific surface area are obtained. They promote the interaction with melt CMAS and consequently limit the degradation of the thermal barrier coatings situated underneath. It was proved that anti-CMAS yttria coating is effective against the infiltration of CMAS at 1250 °C for 15 min and even 1 h

Synthesis of yttria by aqueous sol-gel route to develop anti-CMAS coatings for the protection of EBPVD thermal barriers

Anti-CMAS yttria coatings have been prepared by sol-gel routes. Yttria powders with controlled morphology are prepared via auto-combustion of yttrium precursors in a polymerized matrix. The influence of key parameters of the water-based sols is assessed. Indeed, the pH of the initial sol and the temperature of thermal treatment play a major role in the morphology and grain size of yttria powders. To prevent infiltration of CMAS, yttria powders are proposed to be synthesized at pH=1 of the aqueous sol, with drying of the sol and heating at 900 °C. After optimization of the synthesis and deposition conditions via sol-gel route, yttria-based coatings with high specific surface area are obtained. They promote the interaction with melt CMAS and consequently limit the degradation of the thermal barrier coatings situated underneath. It was proved that anti-CMAS yttria coating is effective against the infiltration of CMAS at 1250 °C for 15 min and even 1 h

Fibers and sol-gel matrix based thermal barrier coating systems for outstanding durability

Thermal barrier coatings (TBC) are critical elements of the turbomachines. On turbine blades for aircraft engines, their preparation is based on EB-PVD industrial process. Such TBCs on first generation AM1 superalloy with a beta-NiPtAl bond coating exhibit 20% of surface spallation after about 600 1h oxidation cycles at 1100°C. In this work, a new method of TBC preparation was proposed and high durability of such structures was obtained with more than 1000 1h cycles at 1100°C before 20% of spallation. More than 1400 1h cycles was even obtained with the most performing formulations. A key point was that the surface spallation was lower than 10 % after 1000 cycles for TBCs made with the 70% and 80% fiber mix (Figure 1a). In the same conditions, EB-PVD TBCs exhibit 50-80% of spallation. The preparation process relied on the addition of a high temperature binder, namely a zirconia sol, to a mix of zirconia powder and fibers. TBCs with equiaxed porosity were obtained (Figure 1b). After thermal treatments, ceramic sintering bridges between the powder, the fibers and the ceramic derived from the sol transformation formed (Figure 1c). Another benefit was obtained from the anchoring of the fibers in the thermally grown oxide (TGO), inducing a tougher TGO layer. The outstanding durability of these fibers and sol-gel matrix based thermal barrier coatings is believed to be the consequence of higher toughness of both the TBC coating and modified TGO. Indeed, crack deviations were observed in these two elements. Moreover, contrary to EB-PVD TBCs, the porosity is isotropically distributed, limiting heat diffusion towards the superalloys. Please click Additional Files below to see the full abstract

Thermodynamic modeling of HIx part of the Iodine – Sulfur thermocycle

The thermochemical water splitting cycle is an environmentally attractive way to produce hydrogen without using fossil fuels. Among a hundreds possible cycles, the sulfur – iodine (IS) is a promising one, expected to become a major source of hydrogen production from nuclear or solar energy. The IS process cycle is divided into three sections; namely: (1) the Bunsen section whose purpose is to produce the two immiscible liquid acid phases: one containing mainly sulfuric acid and the other hydrogen iodide and iodine (2) sulfuric acid concentration and decomposition section and (3) Hydrogen iodide concentration and decomposition section, known by HIx section. The thermodynamics of aqueous sulfuric acid system has already been described by chemical engineers and the challenge actually remains in describing the thermodynamics of the HIx system (H2O – HI – I2) which is a strong electrolyte system, extremely complex because of various phase behavior that occurs (vapor – liquid – liquid – solid) over the large range of pressure and temperature spanned in the process. A review of existing models shows that two approaches can be adopted to deal with phases equilibrium ; (1) homogeneous one in which the same equation of state is applied to different phases in equilibrium and (2) combined approach where the vapor phase is described by an equation of state and the liquid one by a coefficient activity model. The homogeneous approach would be effective for the high pressure HIx system but cannot capture alone the strong non ideality of the liquid phase. That may explain why the current HIx model written by Neumann has been done based on an activity coefficient model coupled with a solvatation formalism proposed by Engels . Unfortunately, activity coefficient models fail for critical compounds in mixtures as is the case for HI under temperature conditions expected in the process. Based on this analysis, we propose a novel modeling of the HIx system that matches all the constraints enounced

A Myrtus communis extract enriched in myrtucummulones and ursolic acid reduces resistance of Propionibacterium acnes biofilms to antibiotics used in acne vulgaris

Recent works present evidence of Propionibacterium acnes growing as a biofilm in cutaneous follicles. This formation of clusters is now considered as an explanation for the in vivo resistance of P. acnes to the main antimicrobials prescribed in acne vulgaris. Purpose : Our objective was to explore this hypothesis and propose a new therapeutic approach focusing on anti-biofilm activity of Myrtacine® New Generation (Mediterranean Myrtle extract–Botanical Expertise P. Fabre) alone or combined with antibiotics. Methods/Results : Using in vitro models able to promote the growth of adhered bacteria, the loss of sensitivity of P. acnes biofilms (48 h) towards erythromycin and clindamycin was checked considering either sensitive or resistant strains. In the same time, the activity of Myrtacine® New Generation against biofilm formation and mature biofilm (48 h) was evaluated. Using a dynamic model of biofilm formation, we noted an inhibition of biofilm formation (addition of Myrtacine® New Generation at T 0) and a significant effect on mature biofilm (48 h) for 5 min of contact. This effect was also checked using the static model of biofilm formation for Myrtacine® New Generation concentrations ranging from 0.03% to 0.0001%. A significant, dose-dependent anti-biofilm effect was observed and notable even at a concentration lower than the active concentration on planktonic cells, i.e. 0.001%. Finally, the interest of the combination of Myrtacine® New Generation with antibiotics was explored. An enhanced efficacy was noted when erythromycin (1000 mg/l) or clindamycin (500 mg/l) was added to 0.001% Myrtacine®, leading to significant differences in comparison to each compound used alone

Transient and steady states of Gd2Zr2O7 and 2ZrO2∙Y2O3 (ss) interactions with calcium magnesium aluminium silicates

Reactions between calcium magnesium aluminium silicates (CMAS) and Gd2Zr2O7 or 2ZrO2∙Y2O3 (ss) are investigated within a temperature range of 1200–1300 °C and for durations of 1 h–100 h. The evolution of CMAS penetration depth in Gd2Zr2O7 and 2ZrO2∙Y2O3 (ss) pellets varies considerably depending on the interaction time. A quantitative analysis of the nature and composition of phases observed in stationary conditions (powder/powder interaction) is performed by SEM-FEG coupled with WDS analyses using micro-agglomerated nanoparticles of Gd2Zr2O7 and 2ZrO2∙Y2O3. Faster kinetics of the gadolinium-based system are illustrated through an analysis of the morphology of the reaction area and of the resulting CMAS tightness of reaction products. The compositions and quantities of reaction products observed at equilibrium are very similar for the two systems, but transient states are significantly different