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Carbon Capture Utilization or Storage (CCUS) has gained widespread attention as an option for reducing CO2 emissions from power plants but specific developments are still needed for the application to cement plants. More precisely, the post-combustion CO2 capture process by absorption-regeneration is the more mature technology but its cost reduction is still necessary. The present study is focusing on Aspen Hysys™ simulations of different CO2 capture process configurations (namely “Rich Solvent Recycle” (RSR), “Solvent Split Flow” (SSF), “Lean/Rich Vapor Compression” (L/RVC)) applied to the flue gas coming from the Norcem Brevik cement plant (taken as case study) and using three different solvents, namely: monoethanolamine (MEA), piperazine (PZ) and piperazine-methyldiethanolamine (MDEA) blend. For each configuration and solvent, different parametric studies were carried out in order to identify the operating conditions ((L/G)vol., split fraction, flash pressure variation, etc.) minimizing the solvent regeneration energy. Total equivalent thermodynamic works and utilities costs were also analyzed. It was shown that the configurations studied allow regeneration energy savings in the range 4–18%, LVC and RVC leading to the higher ones. As perspectives, other configurations and combination of configurations will be considered in order to further reduce the energy consumption of the process.

The present study is focusing on the investigation, for the cement industry, of the post-combustion CO2 capture process using amine(s)-based solvents. The novel aspect of the work is the flue gas considered, namely the high CO2 contents (between 20 and 60 vol.%), representative of flue gases coming from oxygen-enriched air combustion process (also called partial oxy-fuel combustion). Using the results of preliminary solvents screening tests at laboratory scale, absorption-regeneration micro-pilot experiments were carried out for the best solvents in order to characterize their respective absorption and regeneration performances. The use of the activated solution of DEA (diethanolamine) 30 wt.% with PZ (piperazine) 5 wt.% led to particularly high absorption performances in all CO2 concentration range. Besides the experimental measurements, Aspen Hysys™ simulations of the micro-pilot tests were performed for three solvents (monoethanolamine (MEA) as the reference case, then PZ and DEA + PZ) to validate the models implemented. Finally, the validated models were used to perform industrial scale simulations. These simulations confirmed that both the regeneration energy, the equivalent work and the operating costs are reduced when the absorption-regeneration process is implemented to flue gases with high CO2 contents.

In the context of sustainable development, one of the major challenges of Chemical Engineering is the design of clean and efficient new processes for greenhouse gases emission reduction, the valorization of bio-based raw materials, renewable energy production, water/gas/soil treatment, advanced materials production…

In relation with CO2 capture by chemical absorption into aqueous amine-based solvents, absorption and regeneration parameters by separate absorption and regeneration tests are determined. An absorption parameter for different types of amine-based solvents is evaluated by performing absorption tests at 298 K and atmospheric pressure with a gas-liquid contactor and deducing apparent kinetic constants. The regeneration parameter is obtained from a CO2 concentration temporal profile measured in a regeneration cell at the boiling temperature of each solvent. By combining both parameters it is possible to compare the absorption-regeneration performances of all the solvents studied. Good absorption-regeneration performances of cyclical amines, especially of piperidine (PIP) and piperazine (PZ), are highlighted. The interesting potential of 2-amino-2-methyl-1-propanol (AMP) and methyldiethanolamine (MDEA) activated with PZ and PIP is also considered.

Biogas is a common renewable energy resource. A very important stage of biogas upgrading, studied in the present work, is its purification from H 2 S traces. The selective absorption of H 2 S and CO 2 into oxido-alkaline solutions containing hydrogen peroxide and into amine solutions was compared by performing absorption test runs in a cables-bundle scrubber at 293.15 K and atmospheric pressure. The absorption rate and selectivity for H 2 S over CO 2 were determined for various solute partial pressures, different alkaline absorbents and hydrogen peroxide concentrations in the scrubbing liquid, and different pH values. Higher H 2 S-selective absorption performances with oxido-alkaline solutions than with amine solutions could be observed provided that the solution is at a low pH value (9.5) and contains a sufficient hydrogen peroxide concentration.

Among numerous techniques existing for reducing CO 2 emissions, CO 2 capture by absorption in aqueous alkanolamine solutions was specifically studied in this work. For the choice of the adequate amine solution, two major criteria must be taken into account: absorption performances (higher with primary and secondary amines) and energy costs for solvent regeneration (more interesting with tertiary and sterically hindered amines). The different types of amines can also be mixed in order to combine the specific advantages of each type of amines, an activation phenomenon being observed. Aqueous solutions of (piperazinyl-1)-2-ethylamine (PZEA, a polyamine known as absorption activator) and 1-amino-2-propanol (AMP, a sterically hindered amine), pure or mixed with other amines, are experimentally compared with respect to CO 2 removal performances by means of absorption test runs achieved in a special gas-liquid contactor at 25 °C. The positive impact of addition of PZEA to monoethanolamine (MEA), N-methyldiethanolamine (MDEA), and AMP solutions was clearly highlighted. The absorption performances have also been satisfactorily simulated with coherent physicochemical data.

The removal of carbon dioxide from industrial gases, e.g. in thermal power stations to meet the discharge limits for CO 2 in flue gases, is usually achieved with a reactive absorption technique using aqueous solutions of alkanolamines. From the absorption performance point of view, primary and secondary amines are preferred. However, in case the costs of the solvent regeneration are also taken into account, tertiary amines are much more attractive. In order to combine the specific advantages of tertiary and primary/secondary alkanolamines, both types of solvents are mixed. In this paper, mixtures of monoethanolamine and methyldiethanolamine with piperazine as absorption activator are experimentally compared with respect to CO 2 removal performances at 25 °C. The absorption process in a special packed column has also been simulated with the use of published data on reaction kinetics, physicochemical properties (densities, viscosities, diffusivities, Henry coefficients) of the CO 2 -amines systems, including experimentally determined hydrodynamic and mass transfer characteristics of the CO 2 scrubber.

A widely operated way to treat industrial air loaded with VOCs is the absorption technique. For this, the choice of a well-adapted solvent is obviously of prime importance. In the present work an absorption process using viscous organic absorbents, namely, phthalates was studied to scrub flue gases. A suitable thin film device, the cables-bundle contactor, was applied both to favor mass transfer and to limit the pressure drops, and various experiments were achieved at the pilot-scale. Correlations predicting hydrodynamic and mass transfer parameters (interfacial area, liquid hold-up, liquid phase mass transfer coefficients) essential for the design of industrial absorption units, were deduced from experimental results. A comparison of performances of the cables contactor and a packed bed scrubber of same void fraction was made for absorption of toluene into DEHP.

A mathematical model previously developed for the absorption at 20 °C of sulphur dioxide into sulphuric acid solutions containing hydrogen peroxide was adapted to take the effect of the temperature into account. This model was exploited to determine at 35 and 50 °C the overall kinetic parameter relative to the absorption–oxidation of SO 2 , for increasing H 2 SO 4 molarities (from 1 to 6.4 M) and in the presence of a variable concentration of H 2 O 2 (1.2–4.4 M) from absorption test runs performed in a cables-bundle laboratory scrubber. It was clearly observed that an increase in temperature enhances the global process of SO 2 absorption (solubility + diffusion + reaction), whereas at a given temperature, an increase in the sulphuric acid content slows down the process.

An investigation relative to a regenerative absorption-based process for removal of volatile organic compounds (VOC) in high-boiling solvents, namely phthalates, is presented here, discussing largely the influences of the type of VOC (linear paraffins, iso and/or cyclic paraffins or aromatic hydrocarbons), of the phthalate and of the temperature parameter. In a previous paper was published the solubility study of VOC in phthalates. The aim of this work is the determination of the liquid diffusion coefficients of VOC into phthalates. Absorption experiments were achieved in a wetted-wall column characterized by a co-current contact mode between gas and liquid phases. The temperature range (10–40 °C) was investigated. Liquid diffusivities were determined by an indirect method requiring the adequate simulation of the absorption test runs which has to fit the experimentally measured VOC concentrations of the exit gas. Orders of magnitude of estimated parameters are here discussed and attempts at correlations are presented.

Absorption of sulfur dioxide into aqueous solutions containing hydrogen peroxide results in the irreversible oxidation to sulfuric acid. As shown in previous works, the absorption rate increases with the concentration of oxidizing agent but decreases with the rise of acidity. This paper presents a thorough kinetic investigation of the liquid-phase reaction of SO 2 for a wide range of H 2 O 2 and H 2 SO 4 concentrations. Absorption of sulfur dioxide was carried out at 20 °C in a pilot-scale packed column. The experimental data were modelled thanks to the theory of absorption in the fast or moderately fast chemical reaction regimes defined by classical Hatta numbers and depending on the H 2 O 2 concentration at a given acidity. For both regimes, a satisfactory agreement was obtained between experimental results and predictions of models including original values of kinetic parameters.

Sulphur dioxide removal efficiencies were measured in a pilot-scale column packed with Pall plastic rings, at 20 °C and atmospheric pressure, with sulphuric acid solutions (1.2–6.6 M) containing hydrogen peroxide (0.13–0.83 M) as the scrubbing liquid, for different sulphur dioxide partial pressures in the range of 100–500 Pa in the inlet air. A mathematical model previously developed to interpret laboratory experiments was adapted and used to treat the results of the pilot-scale runs for a wide range of operating conditions of gas and liquid flow rates, SO2 partial pressures in the gas phase, H2O2 and H2SO4 concentrations of the solution. A quite satisfactory agreement was found between kinetic parameters deduced from the tests achieved in laboratory and pilot-scale contactors up to 5 M in H2SO4. It appears, therefore, that this model can provide good predictions of the absorption performances of industrial columns and be really helpful to design scrubbers for SO2 abatement with hydrogen peroxide.

Absorption of SO2, diluted with nitrogen up to partial pressures of 500 Pa, was performed at 20 °C and 1 atm with water and sulphuric acid solutions containing hydrogen peroxide in a cable contactor. The absorption rate was determined for various SO2 partial pressures and different concentrations of sulphuric acid (within the range 0–40 wt.%) and hydrogen peroxide in the scrubbing liquid. It was found that the SO2 absorption rate increases with the hydrogen peroxide concentration and decreases as the acidity of the scrubbing liquid increases. Experimental results were interpreted according to the two-film theory of absorption with chemical reaction, considering fast irreversible reaction of SO2 with H2O2. This led to the determination of an overall kinetic parameter, depending on the sulphuric acid concentration, which can be used to design absorption towers. A kinetic constant, which decreases strongly with the rise of cH2SO4, was deduced thanks to the estimation of diffusivities and Henry's coefficients of SO2 for sulphuric solutions.

Absorption of SO 2 , diluted with nitrogen up to concentrations of 500 Pa, was performed at 20°C and 1 atm, with water and sulfuric acid solutions containing hydrogen peroxide in two different contactors: a packed column and a cable scrubber. The absorption rate was determined for various SO 2 partial pressures, as well as different concentrations of sulfuric acid (up to 40 wt%) and of hydrogen peroxide in the scrubbing liquid. It was found that the SO 2 absorption rate increases with the hydrogen peroxide concentration, and decreases as the acidity of the scrubbing liquid increases. Taking into account hydrodynamic and mass transfer characteristics of the packing for both scrubbers, a practical enhancement factor depending on the liquid phase H 2 SO 4 and H 2 O 2 contents, was deduced from semi-continuous tests. As a good concordance was observed between results determined for both contactors, a single correlation is proposed, allowing the computation of this kinetic factor for quite simple simulation or design of SO 2 scrubbers, provided the gas and liquid phase mass transfer coefficients k G a and k L a are known.

The absorption of NOx into sodium hydroxide solutions was studied in a small packed column. A simple mathematical model developed for this absorption was used for the determination of rate parameters relative to NOx species in such solutions. While hydrolysis is the main controlling step for NO2, N2O4 and N2O3 species, nitrous acid HNO2 plays an essential role for the NOx absorption in NaOH solutions. Our mechanistic and kinetic findings were validated as the model has worked with fair success in predicting both NOx removal efficiencies and liquid phase compositions.

The absorption of NO x (IV) into nitric acid solutions containing a low concentration of hydrogen peroxide was studied in a small packed column. A simple mathematical model developed for this absorption was used for the determination of kinetic parameters relative to NO 2 and N 2 O 4 in such solutions. Results obtained at 10, 20, 30°C lead to the same interpretation: hydrolysis is the main controlling step for tetravalent nitrogen oxides absorption and there is no sensible effect of the acidity on the absorption efficicency. Hydrogen peroxide, however, plays an essential role in solution by preventing the HNO 2 decomposition. The mechanistic and kinetic findings were validated as the model has worked with fair success in predicting NO x removal efficiencies in a pilot-scale packed column.

A mathematical model previously developed by us for the absorption of NOx into nitric acid solutions containing hydrogen peroxide at 20 °C was adapted to take the effect of temperature into account. It was used to determine at 10 and 30 °C the overall kinetic parameters relative to the absorption of the different NOx species, for increasing HNO3 molarities (up to 2 M) and a low concentration of H2O2 (0.02 M), from test runs performed in a small packed column. The interpretation of the experimental results obtained at 10 and 30 °C according to the model confirmed the previous findings: hydrolysis is the main controlling step for tetravalent nitrogen oxides, and nitrous acid is likely to contribute for the most part to the absorption of trivalent species.

A mathematical model was developed for the isothermal absorption of nitrogen oxides into nitric acid solutions containing hydrogen peroxide. This model, based on the two-film theory of absorption with chemical reactions, includes diffusive transport and equilibrium between species in the gas phase and simultaneous absorption of the NOx components with fast irreversible reactions in the liquid phase. Kinetic parameters relative to the absorption of the different NOx species were determined at increasing acidities and for a low concentration of H2O2 from test runs performed in a small packed column at 20 °C and atmospheric pressure for various NOx partial pressures up to 500 Pa and the whole range of NOx oxidation ratios. Only the parameter relative to trivalent NOx was found to increase with the HNO3 molarity, the other ones remaining constant. Interpretation of the experimental results according to the model showed that the hydrolysis is the main controlling step for tetravalent nitrogen oxides and that a...

The physical absorption of three Volatile Organic Compounds (dimethyldisulphide (DMDS), dimethylsulphide (DMS) and toluene) in “water/silicone oil” systems at a constant flow rate for mixtures of different compositions (ϕ = 0%, 5%, 10%, 15%, 20%, and 100%) was investigated using a dynamic absorption method. The results indicate that silicone oil addition leads to a dramatic decrease in KLa which can be related to the change in the partition coefficient (Hmix). They confirm the results obtained for styrene absorption using another measurement technique [15] . The interpretation of the results using dimensionless ratios KLa(ϕ)/KLa(ϕ=0%) and KLa(ϕ)/KLa(ϕ=100%) versus ϕ also confirms the importance of the partition coefficient ratio mR = Hwater/Hoil in the KLa change. Moreover, the results obtained for toluene absorption in “air/water/silicone oil” systems (ϕ = 10%, 15%, and 20%) suggest that the mass transfer pathway is in the order gas → water → oil for these operating conditions.

Absorption of NOx up to partial pressures of 500 Pa was experimented at 20°C and atmospheric pressure with aqueous and nitric acid solutions containing hydrogen peroxide. Various NOx oxidation ratios in the gas phase, and different concentrations of nitric acid and hydrogen peroxide in the scrubbing liquid were investigated. It was shown that the absorption rate was enhanced by H 2 O 2 but remains constant if increasing excess quantities of H 2 O 2 are used. Absorption of NOx into H 2 O 2 is considerably catalyzed by nitric acid. A mathematical model was developed in which all these experimental observations were included, and overall kinetic parameters for different NOx species were determined. Favorable agreement was shown between the model predictions and the experimental results obtained both in a laboratory-scale and a pilot-scale absorption column.

International audience; A methodology to determine the diameter of an absorber contacting a gas phase and two immiscible liquid phases (water/silicone oil mixture) is presented. The methodology is applied to a countercurrent gas/liquid randomly packed column for the absorption of three VOCs (toluene, dimethyl sulfide, or dimethyl disulfide). Whatever the silicone oil volume fraction, Eckert's generalized pressure drop correlation was used. The results present the change in the column diameter through the change in the dimensionless ratio D(ϕ)/D(ϕ=1) versus the silicone oil volume fraction for the same operating conditions. For toluene and dimethyl disulfide, characterized by Hvoc,silicone oil values equal to 2.3 and 3.4 Pa m3 mol−1, respectively, it is highlighted that it is unwise to use water/silicone oil mixtures for mass transfer. In these cases, the contact between the polluted air and pure silicone oil requires roughly the same amount of silicone oil as for a (90/10 v/v) water/silicone oil mixture, but enables a 2-fold decrease in the column diameter. For dimethyl sulfide, which is characterized by a larger partition coefficient value (Hvoc,silicone oil=17.7 Pa m3 mol−1), the mass transfer operation should not be considered because large amounts of silicone oil are required (whatever the silicone oil volume fraction), which is not acceptable from an economic point of view. The feasibility of using a bioscrubber for the treatment of hydrophobic pollutants depends mainly on the partition coefficient Hvoc,silicone oil. VOC absorption in TPPB should therefore be restricted to pollutants characterized by a Hvoc,silicone oil value of around 3 to 4 Pa m3 mol−1 or less. In this case, absorption can be efficiently carried out in a biphasic air/silicone oil system.

International audience; A calculation procedure to determine the influence of the silicone volume fraction on the physical absorption of VOCs in water/silicone oil mixtures is presented (eta(silicone) oil = 5 mPa s). It is based on the ''equivalent absorption capacity'' concept previously developed by Dumont et al. (2010)111 and applied to a countercurrent gas-liquid absorber. The calculation procedure is first applied to three VOCs: dimethylsulphide (DMS), dimethyldisulphide (DMDS) and toluene, and then generalised to other VOCs. The influence of VOC partition coefficients (H(voc,water) and H(voc,solvent)) and the ratio MR = H(voc,water)/H(voc,solvent) is shown. For VOCs having a much higher affinity for silicone oil than for water (m(R) > 20 as for DMDS and toluene). it is preferable to use pure silicone oil rather than water/silicone oil mixtures for absorption. (C) 2011 Elsevier B.V. All rights reserved.

International audience; The main objective of this work was to propose a model able to predict the partition coefficient of odorous or toxic gaseous pollutants (dimethylsulphide, dimethyldisulphide and toluene) in water/silicone oil mixtures. Experimental measurements using a static headspace method were carried out for pure water (H(voc,water)), for pure silicone oil (H(voc,solvent)) and for mixtures of varying composition (H(voc,mixture)). The dramatic decrease in the partition coefficient (H(voc,mixture)) with oil addition clearly showed a deviation from linearity, which was more pronounced for increasing H(voc,water)/H(voc,solvent) ratios. Moreover, experiments using a dynamic absorption method underlined that the absorption capacity of a biphasic water/silicone oil mixture can be classed as the absorption capacity of a pseudo-homogeneous phase whose physical properties (molecular weight and density) can be calculated from the physical properties of water and solvent, and balanced using the ''equivalent absorption coefficients'' H(voc,mixture)/H(voc,water) and H(voc,mixture)/H(voc,solvent). An ''equivalent absorption capacity'' concept is then proposed, which should be useful to design absorption units using two-phase liquid mixtures for the treatment of industrial air loaded with volatile organic compounds. (C) 2010 Elsevier B.V. All rights reserved.