Coal-fired thermal power plants are the major source of CO2 emission among fossil fuel power plants. In thermal power plants, coal combustion produces flue gas containing a number of gases including ...hazardous pollutants, such as CO2, mercury (Hg), sulfur dioxide (SO2), and oxides of nitrogen (NOx). Among all, CO2 is the largest contributor to global warming. CO2 capture and separation are therefore essential to keep the environment safe and secure. The present paper delineates the existing literature to examine the current status of various methods and technologies used for CO2 capture and separation from thermal power plant flue gas. Various emerging technologies like, chemical-looping combustion, integrated gasification combined cycle, enzyme based separation, dual-alkali absorption approach, facilitated transport membrane, hydrate based separations, mixed matrix membrane and, calcium looping are also thoroughly discussed.
► We critically examined existing literature on current status of various technologies of CO2 capture and separation. ► New emerging technologies were discussed in the paper. ► The major improvements to existing processes was needed for better overall removal efficiency of CO2.
Nanoporous activated garlic stem carbon (AGSC) was prepared from garlic stem waste and used to remove As(III)from synthetic water under complete batch experiments. Characterization studies of AGSC ...were performed by FTIR, SEM, EDX, BET, XPS and XRD techniques. Batch adsorption experiments were carried out to study the adsorption of As(III) onto AGSC. Maximum removal of 93.3% of As(III) was obtained at optimum condition of pH 6, the adsorbent dose 5 g/L, equilibrium time 150 min, initial As(III) concentration 400 µg/L and temperature 298 K. Both Langmuir and Temkin isotherm model fitted well to the experimental data as compared to Freundlich isotherm. Kinetics indicated that the adsorption of As(III) was more suitable for pseudo-second-order than pseudo-first-order and Elovich model. The mass transfer mechanism could be described by Weber-Morris and Boyd mass transfer model. The maximum adsorption capacity of AGSC for As(III) removal was found to be 192.30 µg/g. The negative enthalpy and free energy change indicated that the adsorption process of As(III) onto AGSC was exothermic and spontaneous. The negative value of entropy change suggested decreasing randomness at the AGSC-aqueous As(III) interface during As(III) adsorption.
The present study elaborates the use of sagwan sawdust biochar as an efficient adsorbent for Cr(VI) abatement. Effect of experimental variables like solution pH (2–10), initial Cr(VI) concentration ...(30–100 mg/L), temperature (30–40 °C), adsorbent dose/Cr(VI) concentration (16.67–200), and contact time (10–80 min) was studied through batch operations. The optimization and interaction study for process parameters was done by employing response surface methodology through Box-Behnken design. The optimized condition for the maximum adsorption was pH 2.07, temperature 30.72 °C, and dose/Cr(VI) concentration 160.93. The surface characteristics of the adsorbent were evaluated via pH
zpc
, FTIR, BET surface area, SEM-EDS, XRD, and XPS analysis. Functional groups like O-H, C-O, C-H, and C=O were responsible for the adsorption process, and change in the oxidation state of Cr was affirmed by XPS survey. The Cr(VI) adsorption was governed by second-order kinetics and the Langmuir isotherm with Q
0
of 9.62 mg/g. The thermodynamic study revealed the process to be exothermic and spontaneous. Mass transfer studies confirmed film diffusion to be favorable in the adsorption process. Adsorption occurred via electrostatic and physical attraction, reduction, and complexation. Therefore, the results suggest sagwan sawdust biochar is satisfactory and effective in removing Cr(VI) from aqueous solution.
•Equilibrium solubility of CO2 was measured in the aqueous blend of 2-(methylamino)ethanol (MAE) and aminoethylethanolamine (AEEA).•Modified Kent-Eisenberg thermodynamic model was developed using ...rigorous analysis.•Heat of absorption for MAE+AEEA+H2O+CO2 system was calculated using the modified Gibbs – Helmholtz equation.
In the present study, equilibrium solubility of CO2 was studied in the aqueous blend of 2-(methylamino)ethanol (MAE) and aminoethylethanolamine (AEEA). Total concentration of blend solution, weight fraction of AEEA in aqueous (MAE+AEEA) blend, temperature, and partial pressure of CO2 was varied from 10 to 30 wt %, 0.10 to 0.30, 298.15 to 323.15 K, and 8.11 to 20.67 kPa, respectively. Maximum loading 0.944 mol CO2/mol amine was occurred at 298.15 K, 20.27 kPa of CO2 partial pressure, 10 wt % total concentration with 0.30 wt fraction AEEA. The Kent-Eisenberg thermodynamic model was modified by incorporating newly introduced correction factor (Fk) to predict CO2 solubility in the aqueous blend of MAE+AEEA. Experimental data and model predicted data was in good agreement with each other. In addition, heat of CO2 absorption was also calculated for this amine blend and reported as -73.43 kJ/mol.
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► Mangifera indica sawdust as an efficient adsorbent for removal of Cr(VI) from aqueous solutions. ► The Langmuir and Freundlich model well described the adsorption equilibrium. ► Adsorption kinetics ...followed the pseudo-first-order kinetic model. ► Both boundary layer and intraparticle diffusion are found to affect the adsorption.
Present study was undertaken to evaluate the efficacy of Mangifera indica sawdust for the removal of Cr(VI) from aqueous solutions. Batch experiments were performed to evaluate the influence of various operating conditions viz., pH, contact time, initial concentration, adsorbent dose, etc. on Cr(VI) removal efficiency. Characterization of the adsorbent showed that OH, CO and NO groups might be responsible for Cr(VI) adsorption. Adsorption was found to be exothermic with first-order rate kinetics which followed both Langmuir and Freundlich isotherms. Thermodynamic parameters like standard free energy change (ΔG°), enthalpy change (ΔH°) and entropy change (ΔS°) were obtained as −1.0045kJmol−1, −24.8kJmol−1 and −0.0798kJmol−1K−1 respectively at 298K. The electrostatic attraction and film diffusion were found most favorable for Cr(VI) adsorption augmentation.
► Combined SO2 and NO removal using NaClO as low-cost alternative in magnetic stirrer reactor. ► Experimental data of SO2 and NO removal in light of coal-fired thermal power plant stack gases. ► The ...NaClO showed promising results on both SO2 and NO removal as compared to other absorbents available in literature.
The experiments were performed in a magnetic stirrer reactor to study the simultaneous absorption of NO and SO2 using NaClO solution from simulated gas stream. The effects of various operating parameters viz., absorbent concentration, reaction temperature, initial SO2 and NO concentration and initial pH of NaClO solution on simultaneous removal of SO2 and NO were investigated in regard to coal-fired thermal power plant stack gases. The maximum removal efficiencies of SO2 and NO were observed as 100% and 92%, respectively at 313K, initial NaClO solution pH 5.8 and 0.01M NaClO concentration. The important rate governing steps with appropriate reaction mechanisms for simultaneous removal of SO2 and NO using NaClO as absorbent were also discussed.
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•Torrefaction of Acacia nilotica was performed in a fixed-bed reactor.•Kinetic and thermodynamic parameters of torrefied Acacia nilotica were studied.•Severe torrefaction lowers the ...activation energy of Acacia nilotica.•Char yield increases during pyrolysis of torrefied Acacia nilotica.•Pyrolysis of torrefied Acacia nilotica followed the random nucleation model.
The objective of this work is to examine the suitability of torrefied biomass for bio-energy generation by investigating its physicochemical characteristics, kinetic and thermodynamic parameters as well as reaction mechanism during pyrolysis. Thus, torrefaction of Acacia nilotica was performed in a fixed bed reactor at 220, 250 and 280 °C, with constant residence time (40 min) and heating rate (15 °C/min). Pyrolysis of torrefied biomass obtained at 220 °C (T-220), 250 °C (T-250) and 280 °C (T-280) was performed using thermogravimetric analyzer at three different heating rate viz. 5, 10 and 15 K/min. Further, isoconversional models namely, Kissinger-Akahira-Sunose (KAS), Ozawa-Wall-Flynn (OWF), Friedman and Starink were employed to calculate the kinetic parameters (activation energy and pre-exponential factor) of raw and torrefied biomass. Using kinetic parameters obtained from KAS method, thermodynamic parameters (enthalpy, Gibbs free energy, and entropy) were calculated at a heating rate of 10 K/min. The activation energy for raw and T-220, T-250, and T-280 using KAS method were found to be 221.49, 241.58, 185.06, and 121.83 kJ/mol, respectively. The increase in activation energy of T-220 might be due to a higher percentage of cellulose content in it than raw biomass. Reaction mechanism during pyrolysis of raw and torrefied biomass was predicted using Criado method (Z-master plot). For raw biomass and T-220, diffusion models were followed; however, for T-250 and T-280, random nucleation models were dominant. Overall, results provide a deep understanding of kinetics and improved characteristics of torrefied biomass as good quality solid fuel.
The research work aims to estimate the bioenergy potential of pistachio shell and study its degradation kinetics which is necessary for the efficient design and optimization of thermochemical ...processes for bioenergy generation. Initial characterizations (proximate, ultimate, higher heating value, and compositional analysis), kinetic study, and thermodynamic analysis accompanied by reaction mechanism are investigated. Physicochemical characterization results confirmed high volatile matter (~ 79.8 wt%) and high heating value (16.85 MJ/kg) of pistachio shell. Thermogravimetric analysis (TGA) is performed at four different heating rates of 10, 20, 30, and 40 °C/min under nitrogen gas flow rate from ambient temperature to 900 °C. TGA results show the three-stage pyrolysis reaction which involves removal of moisture and light volatiles, degradation of cellulose and hemicellulose, and decomposition of lignin. The result also reveals that maximum degradation occurred in the temperature range of 200–400 °C. For calculating the kinetic (activation energy and pre-exponential factor) and thermodynamic parameters (enthalpy, entropy, and Gibbs free energy), different iso-conversional models, i.e. Flynn-wall-Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), Starink, and Friedman, are employed which gives the average value of activation energy as 168.86, 165.80, 166.29, and 190.10 kJ/mol, respectively and the pre-exponential factor values lie in the range of 10
7
-10
21
s
−1
. The average values of Gibbs free energy calculated for FWO, KAS, Starink, and Friedman methods are 182.09, 182.15, 182.13, and 181.42 kJ/mol, respectively. Criado method and
Z
plot are showing complex reaction mechanism. The results of kinetics and thermodynamic study reveal pistachio shell is an efficient biomass for bioenergy production.
•New experimental data of CO2 solubility into aqueous EAE and AEEA blend.•Kent-Eisenberg thermodynamic and empirical models proposed for prediction of CO2 solubility in the blend.•Heat of CO2 ...absorption and cyclic absorption capacity measurement for aqueous (EAE and AEEA) blend.•Lower heat of CO2 absorption for this blend as compared to MEA solution resulting less energy requirement for CO2 capture.
In the present study, carbon dioxide (CO2) solubility into aqueous blend of 2-(ethylamino) ethanol (EAE) and aminoehtylethanolamine (AEEA) was measured. The performance of CO2 capture by this amine blend was investigated in terms of CO2 solubility, heat of absorption, cyclic CO2 solubility, and initial rate of change of CO2 solubility. CO2 absorption study was carried out using bubble column reactor in the temperature range of 298.15 to 323.15 K, 8.11 to 20.27 kPa CO2 partial pressure, 0.10 to 0.30 wt fraction of AEEA in EAE and AEEA blend, and 10 to 30 wt% total concentration of blend solution. Desorption experiments were performed at 393.15 K. Maximum CO2 solubility was 1.033 mol CO2/mol amine at 298.15 K, 20.27 kPa, 0.30 wt fraction of AEEA in the blend, and 10 wt% of EAE and AEEA solution. A semi-empirical Kent-Eisenberg thermodynamic model and an empirical model were developed to calculate equilibrium CO2 solubility in the studied range of operating conditions with 2.56% and 0.45% average absolute deviation, respectively. At 313.15 K, 15.20 kPa CO2 partial pressure and total concentration of 30 wt% of EAE and AEEA blend, the equilibrium CO2 solubility was resulted as 0.748 mol CO2/mol amine and cyclic solubility of 0.503 mol CO2/mol amine was achieved. Heat of CO2 absorption was measured based on Gibbs Helmholtz equation and found as −72.25 kJ/mol for 30 wt% aqueous EAE and AEEA blend. Results of absorption capacity of EAE and AEEA solution and monoethylethanolamine (MEA) were compared at same operating conditions. This blend had higher CO2 solubility, lesser heat of absorption, more cyclic capacity and faster rate of change of initial CO2 solubility than MEA.
In this study, soybean stalk (SS) biomass was explored for its bioenergy generation prospective by thermal degradation. Proximate, ultimate, HHV (higher heating value), and thermogravimetric (TG) ...analyses were performed. For TG, three heating rates (10, 15, and 25 °C/min) in nitrogen atmosphere with temperature from room temperature to 800 °C were chosen. TG experiments affirmed that maximal devolatilization occurred between 205 and 510 °C. Four iso-conversional models (Friedman, Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), and Starink) were employed for kinetic and activation energy evaluation. Values of activation energy using these models came out to be 127.62, 124.15, 124.44, and 136.28 kJ/mol, respectively. Results of the FWO model were used for thermodynamic evaluation. Average values of change of enthalpy (∆
H
) and Gibbs free energy (∆
G
) were found to be 124.29 and 167.23 kJ/mol, respectively. The pre-exponential factor (
A
) values lie in the range of 10
5
–10
13
s
−1
. Master plots and Criado method indicated complex reaction mechanism during pyrolysis. Comprehensive pyrolysis index (CPI) affirmed that a higher heating rate is favorable for SS pyrolysis. The results of physicochemical, kinetics, thermodynamics, and pyrolysis performance index reflected high bioenergy potential of SS which emphasized that pyrolysis of SS is a pragmatic approach for affordable, sustainable, and green-clean energy production.
