PZ Concentration Research Articles

Precipitation behavior, density, viscosity, and CO2 absorption capacity of highly concentrated ternary AMP-PZ-MEA solvents

This study explored potential of highly concentrated AMP-PZ-MEA solvent for capturing CO2 in terms of solvent precipitation, density, viscosity, and CO2 absorption capacity. It was found that most of the studied AMP-PZ-MEA solvents precipitated at high AMP and PZ concentrations and at high CO2 loading. The minimum possible MEA concentration (which can maintain a clear solvent) was 1.5 M for 6 M total amine concentration. It was also observed that an increase of AMP and/or PZ concentration in the 6 M blends induced the solvent precipitation. MEA was the only amine component that can be added to the blends to elevate the total amine concentration from 6 M to 7 M. As a result, the six AMP-PZ-MEA blends were suggested: 2:2.5:1.5, 1.3:3.2:1.5, 0.95:3.55:1.5 (for 6 M) and 2:2.5:2.5, 1.3:3.2:2.5, and 0.95:3.55:2.5 (for 7 M). The proposed blends are corresponding to PZ:AMP molar ratio of 1.25, 2.5, and 3.75, which are much higher than that of the first-generation AMP-PZ-MEA solvents. Regarding the visualized observation, there was no solid sediments observed throughout precipitation and CO2 absorption studies of the six blends. Interestingly, densities of the proposed blends were close to that of 5 M MEA, while their viscosities were much higher than that of 5 M MEA but were close to that of MDEA-PZ and AMP-PZ. Additionally, CO2 absorption capacities of the proposed 6 M and 7 M blends were 56-58% and 64-71% higher than that of 5 M MEA. These numbers are much higher than those of the first-generation AMP-PZ-MEA solvents.

CO2 Absorption from Biogas Using Piperazine-Promoted 2-Amino-2-methyl-1-propanol: Process Performance in a Packed Column

In this work, CO2 absorption from simulated biogas is investigated using different blends of a PZ + AMP solution in an absorption system at CO2 partial pressures ranging between 20 and 110 kPa. The collected data were presented as CO2 removal profiles along the packed column and were evaluated in terms of CO2 removal efficiency (%) and average overall volumetric mass transfer coefficient in the gas phase (KGav¯). An increased PZ concentration in the AMP solution was found to significantly increase the CO2 removal efficiency and KGav¯ values. It was observed that, when conducted at different CO2 partial pressures, gas and liquid flow rates, and chemical concentrations, the Lamine/GCO2 ratio strongly influenced the process behaviour in the packed column. Additionally, the optimal inlet liquid temperature was observed to be 35 ± 2 °C in this study.

Pre-combustion CO2 capture using amine-based absorption process for blue H2 production from steam methane reformer

A novel pre-combustion CO2 capture process using methyl diethanolamine with piperazine (MDEA/PZ) was investigated for the production of blue H2 from a steam methane reformer (SMR). A sensitivity analysis was performed at various operating parameters (such as MDEA or PZ concentration, flash drum pressure, CO2 loading in a lean-amine solvent, and CO2 removal efficiency) using a validated rate-based model. The energy consumption to capture CO2 from SMR gas at 21 bar was evaluated, including the compression energy (up to 30 bar) for the dehydration of captured CO2. For 90% and 95% CO2 removal efficiency, reboiler duties were 1.318 GJ/tonCO2 and 1.364 GJ/tonCO2, and CO2 compression works were 11.673 kW/molCO2 and 11.615 kW/molCO2. The results indicated more than 40% lower reboiler duty than the energy consumption of conventional CO2 capture processes in post-combustion. Subsequently, artificial neural network model (ANN)-based optimization using the differential evolution method was performed. The developed ANN-based optimization suggested the possibility of additional 0.3 % reduction in the equivalent work at a low computational cost. The results indicated that the developed pre-combustion CO2 capture for a SMR was highly competitive in industrial applications. Moreover, the H2 mixture produced at 21 bar is beneficial for a H2 recovery unit because of no need for additional compression energy. Therefore, the MDEA/PZ-based absorption process can effectively contribute to centralized or semi-central blue H2 production from a SMR. This study provides a guideline for the feasible optimization and control of the CO2 absorption process at high feed pressures.

Experimental and thermodynamic modeling of CO2 absorption into aqueous DEA and DEA+Pz blended solutions

The important environmental concern of the carbon dioxide (CO2) capture by the absorption process with amine solutions is studied in the current study. The experiments are performed at operating conditions of a temperature range of 25 65 °C, a pressure range of 1.5 6.5 bar, diethanolamine (DEA) concentration of 0 1.5 M, PZ concentration of 0 0.5 M, and stirrer speed of 0 300 rpm. The effects of operating conditions on CO2 loading, absorption rate, and mass transfer flux are investigated into two solutions of DEA and DEA+piperazine (Pz) blend in a stirred reactor. In the DEA+CO2+H2O system, by increasing stirrer speed from 0 to 300 rpm, the maximum values of CO2 loading and mass transfer flux at the same DEA concentration are increased 65% and 137%, respectively. The CO2 loading and mass transfer flux have higher values at higher initial pressures. The predicted values for species concentrations into the DEA+CO2+H2O system are also evaluated based on the Pitzer model, mass, and charge balance equations. The results showed that by increasing stirrer speed, the concentration of DEA molecule is decreased 40% but the concentrations of other ions and molecules are increased. In the DEA+Pz+CO2+H2O system, the results indicated that adding Pz to the absorbent solution was more efficient in CO2 capture relative to only the DEA solution. The equilibrium CO2 loading is increased by 20% and 16% for blend solutions with 4:6 and 6:4 molar ratios of DEA and Pz, respectively, but using only Pz solution is increased it up to 29%.

Hydrodynamic and mass transfer parameters for CO2 absorption into amine solutions and its blend with nano heavy metal oxides using a bubble column

ABSTRACT In this work, hydrodynamic and mass transfer of CO2 absorption into metal oxide nanofluid includes TiO2, ZnO, and ZrO2 nanoparticles at Piperazine (Pz) solution in the bubble column was studied. The novel rigorous correlations were extended based on the variable parameters for the calculation of gas holdup, enhancement factor, and mass transfer coefficients in the reactive absorption processes using the π-Buckingham method. The correlations were constructed based on dimensionless numbers, including nanoparticle loading, film parameter, CO2 partial pressure ratio to the total pressure, the film thickness of phases, CO2 loading, and ratio of diffusion coefficients of CO2 in the gas and liquid phases. Experimental data were used to calculate the correlations, consisting of Pz concentration, CO2 partial pressure, nanoparticle loading, and stirrer speed in the range of 0.1–0.5 mol/l, 16.0–35.2 kPa, 0.0–0.1 wt%, and 0–300 rpm, respectively. The film parameter was applied to exert the influence of chemical reactions on the performance of absorption. The mean squared error (RMSEP), the average absolute error (%AARD), and the coefficient of correlation of the results (R2 ) for the correlations were in the range 0.021–2.604, 3.78–18.14, and 0.861–0.980, respectively, which represents the excellent accuracy of the proposed correlation.

Electrolyte solution of MDEA–PZ–TMS for CO2 absorption; response surface methodology and equilibrium modeling

This research aims to study the performance of MDEA–PZ–TMS​ blends solution in CO 2 reactive absorption via a stirrer reactor. Two modeling approaches of the response surface methodology (RSM) and equilibrium modeling using the modified Pitzer model were employed to predict process behavior at the equilibrium state. Five independent variables of temperature, pressure, MDEA, PZ, and TMS concentrations were considered in the ranges of 20–75 °C, 2–8 bar, and 1–5wt%, respectively. Based on the RSM modeling, both CO 2 loading and absorption percentage were simultaneously maximized with the degree of importance of 1 and 5, respectively, at operating conditions of 3.5 bar, 32.5 °C, 2wt% TMS, 4wt% MDEA, and 4wt% PZ concentrations. In the equilibrium modeling, the equilibrium CO 2 loading was predicted with an average relative error of 4.85% for all empirical data. The present modeling can be applied to various CO 2 absorption processes using different electrolyte solutions. • The CO 2 reactive absorption process is examined by MDEA-PZ-TMS blends solution. • The process is modeled by response surface methodology and equilibrium modeling. • Pressure, temperature, MDEA, PZ, and TMS concentrations are optimized by RSM. • Equilibrium modeling error is less than 5% makes suitable for different solvents. • The concentrations of all existing species in the electrolyte system are predicted.

Experimental Modeling and Optimization of CO2 Absorption into Piperazine Solutions Using RSM-CCD Methodology.

The present work evaluates and optimizes CO2 absorption in a bubble column for the Pz-H2O–CO2 system. We analyzed the impact of the different operating conditions on the hydrodynamic and mass-transfer performance. For the optimization of the process, variable conditions were used in the multivariate statistical method of response surface methodology. The central composite design is used to characterize the operating condition to fit the models by the least-squares method. The experimental data were fitted to quadratic equations using multiple regressions and analyzed using analysis of variance (ANOVA). An approved experiment was carried out to analyze the correctness of the optimization method, and a maximum CO2 removal efficiency of 97.9%, an absorption rate of 3.12 g/min, an NCO2 of 0.0164 mol/m2·s, and a CO2 loading of 0.258 mol/mol were obtained under the optimized conditions. Our results suggest that Pz concentration, solution flow rate, CO2 flow rate, and speed of stirrer were obtained to be 0.162 M, 0.502 l/h, 2.199 l/min, and 68.89 rpm, respectively, based on the optimal conditions. The p-value for all dependent variables was less than 0.05, and that points that all three models were remarkable. In addition, the experiment values acquired for the CO2 capture were found to agree satisfactorily with the model values (R2 = 0.944–0.999).

Assessment of mass transfer correlations used in post-combustion CO2 capture by piperazine activated 2-amino-2-methyl-1-propanol (a-AMP)

The prevalent solvents used in CO2 capture processes have such drawbacks as degradability, high energy consumption for solvent regeneration, low absorption capacity, and corrosive nature which have convinced the researchers to suggest a new combination of alkanolamines in place of the commonly-used solvents like MEA. Since Rate-Based model, compared to Equilibrium model, gives more accurate simulations of CO2 capture processes by amine solvent, it is used in this study. Mass transfer correlations are significant parameters in Rate-Based model, and using them improperly will lead to considerable disagreement between real and simulated results.In the present work, mass transfer coefficients in CO2 capture processes are evaluated using an aqueous blend of piperazine activated 2-amino-2-methyl-1-propanol (a-AMP) solution for the first time. It is done according to Khan et al. (2016) experimental results in 36 points and for different operational conditions. In the first evaluation, 12 sets of data are achieved following the changes of the operational parameters, gas flow rate and CO2 partial pressure, while other parameters such as operational absorption temperature, solvent flow rate and solvent blends of AMP + PZ remain constant. The studies indicate that considering the amount of CO2 absorbed, the Mean Absolute Errors (MAE) of Onda et al., Bravo-Fair, and Billet-Schultes mass transfer coefficients are 12%, 7.63%, and 3.2% respectively in comparison with Khan et al. results. The second evaluation is also done in 12 operational points regarding the variations of PZ concentration and operational absorption temperature. Other parameters remain unchanged in this evaluation, too.This study demonstrates that Billet-Schultes correlations own higher accuracy compared to the Onda et al. and Bravo-Fair. Mean Absolute Errors (MAE) of Onda et al., Bravo-Fair, and Billet-Schultes are 12.74%, 8.26%, and 2.04% respectively. The third evaluation of this work is of rich solvent loading (absorber loading). Similarly, this evaluation is performed in 12 operational points in regard to the changes of CO2 partial pressure and the ratio of AMP to PZ, while other operational parameters are kept constant. This evaluation likewise shows that, compared to two other ones, Billet-Schultes correlations have more precision when utilized in CO2 capture processes by the a-AMP solvent. Mean Absolute Error (MAE) of Onda et al., Bravo-Fair, and Billet-Schultes in predicting absorber loading and in accordance with experimental data are 24.21%, 16.44%, and 6.23% respectively.

Reactive absorption of CO2 into Piperazine aqueous solution in a stirrer bubble column: Modeling and experimental

The present work focuses on CO2 reactive absorption using Piperazine aqueous solutions in a stirrer bubble column. A stirrer bubble column has been applied for operating conditions, including CO2 partial pressures in the range of 16.0–35.2 kPa, stirrer speed in the range of 0–300 rpm and CO2 loading in the range of 0.01–0.3 mol CO2.mol Pz−1. The results reveal that the absorption reaction rate increases with increasing the CO2 partial pressure and Pz concentration. The film parameter increases with increasing the Pz concentration and decreasing the CO2 partial pressure. Experimental results show that mass transfer flux, overall mass transfer coefficient and removal efficiency of CO2 are varied in the range of (0.35–4.32)×10−6 kmol.m−2.s−1, (2.39–2.58)×10−6 kmol. m−2.s−1.kPa−1 and 65.5–82.1%, respectively. Hydrodynamic studies illustrate that gas holdup, gas-liquid interfacial area, and Sauter mean diameter increases with increasing CO2 partial pressure and decreasing Pz concentration. Also, it was found that gas holdup, Sauter mean diameter and interfacial area values obtained in this work are within the range of 0.06–0.076, 10–13 mm and 44.0–46.1 m2 m−3, respectively.

Process simulation, parametric sensitivity analysis and ANFIS modeling of CO2 capture from natural gas using aqueous MDEA–PZ blend solution

Carbon dioxide (CO2) capture from natural gas is integral towards meeting pipeline sales gas specifications and avoiding operational problems during natural gas liquefaction. Therefore, it is important to understand how different process parameters would affect the performance of the CO2 capture process plant. In this research, CO2 capture from a typical Nigerian natural gas composition was simulated using ProMax® 4.0. The validated simulation was used to generate 3125 datasets while varying a number of process parameters. A parametric sensitivity analysis was conducted by varying lean amine flow rate (LAF, 3500–4300t/day), lean amine temperature (LAT, 40–60°C), lean amine pressure (LAP, 60–75bar), MDEA–PZ concentration difference (CMDEA–PZ, 36–44wt.%) and heat duty (HD, 50.4–56.52 GJ/h) to determine their effects on CO2 capture efficiency alongside foaming and amine vaporization. The parametric analysis showed that the LAF and MDEA–PZ concentration have the highest effect on the CO2 capture plant. In addition, 70% of the generated datasets was used to train the intelligent model named adaptive neuro–fuzzy inference system (ANFIS) while 30% was used for validation. Results revealed that the ANFIS model accurately predicted the simulation results with 2.4%AAD and RMSE of 4.0E-03, respectively.

Kinetics of CO2 Absorption in Concentrated K2CO3/PZ Mixture Using a Wetted-Wall Column

Using a K2CO3/piperazine (PZ) mixture as a typical phase-change absorbent has promising applicability for carbon dioxide (CO2) capture in coal-fired power plants that would contribute to low energy consumption for solvent regeneration. In this study, the reaction rate of CO2 with a concentrated K2CO3/PZ mixture was measured in a wetted-wall column. At a CO2 loading close to saturation absorption, correlative physical parameters were calculated. The effects of operating conditions, including gas flow rate, slurry flow rate, PZ concentration, CO2 loading, K2CO3 mass fraction, and temperature, on the absorption rate of CO2 were investigated. The results showed that the absorption rate was sensitive to the effects of the gas flow rate and CO2 loading. The PZ concentration and K2CO3 mass fraction also substantially influenced the CO2 absorption rate. However, minor changes in the CO2 absorption rate were observed when the slurry flow rate and temperature were increased. On the basis of a pseudo-first-order mod...

CO2 chemical absorption into aqueous solutions of piperazine: modeling of kinetics and mass transfer rate

Modeling of carbon dioxide (CO2) chemical absorption kinetics and mass transfer rate, is essential to reliably model and simulate regenerative amine based absorption/desorption units. In this paper, a new rigorous semi-empirical correlation, was developed to accurately model CO2 mass transfer rate into aqueous solutions of piperazine (PZ: C4H10N2), a high reactive secondary diamine, as a function of liquid physical mass transfer coefficient (kl0), and distinctive dimensionless numbers including Hatta number (Ha) and interface CO2 loading (αCO2,i). Moreover, two new correlations for kinetic rate constants were developed. To achieve these goals, a series of CO2 chemical absorption experiments were carried out over PZ concentration and temperature ranges of (0.3–1.1) kmol/m3 and (300–310) K, respectively and CO2 partial pressures up to 9.2 kPa. Compared to previously developed correlations, the proposed one in this work, accounts for all important CO2 involving reactions, where species concentrations at the gas–liquid interface, were precisely calculated via a proper (γ−φ) approach, avoiding pseudo-first-order (P.F.O) simplifying assumption. Comparison of the developed correlation predicted values with the experimental data (%AARD = 2.93%), has revealed its high prediction ability.

Modeling of CO2 loading in aqueous solutions of piperazine: Application of an enhanced artificial neural network algorithm

Carbon dioxide (CO2) separation by chemical absorption is widely regarded as the most effective method for its mitigation in natural gas streams or flue gas of the fossil fuel power plants. In this paper, CO2 loading (αCO2) in aqueous solution of piperazine (PZ: C4H10N2), a high reactive cyclic secondary diamine, is modeled over extensive ranges of operational conditions: temperature (287–395 K), PZ concentration (0.1–8 mol kg H2O−1) and CO2 partial pressure (0.0215–9510.3 kPa). To achieve this goal, a feed-forward back-propagation multilayer perceptron artificial neural network (FFANN) was developed and tested via employing the Levenberg–Marquardt training algorithm, enhanced through combination with Bayesian regularization technique. Regression analysis results (R2 = 0.9977) and comparison of the ANN predicted αCO2 values with corresponding experimental data (%AARD = 2.3927) as well as with some correlations in the literature, have revealed high prediction ability and robustness of the developed neural network.

Pilot Plant Activities with Concentrated Piperazine

Amine aerosol testing was conducted at the University of Texas at Austin CO 2 capture pilot plant using concentrated piperazine (3.7 molal) and high temperature flash with cold rich bypass (140 °C). Two methods of piperazine aerosols generation were tested: H2SO4 injection with a liquid vaporizer injector, and direct injection 20 ppm of SO2 into the synthetic flue gas. A Phase Doppler Interferometer (PDI) analyzer from Artium Technologies was used to measure piperazine aerosol droplet sizes and distributions at the absorber gas outlet. A FTIR system with new upgraded heated probes was used to make measurements of total PZ concentrations at the absorber gas inlet and outlet. A manual sampling train method was used to provide secondary validation of FTIR and PDI measurements.

Modeling of the CO2Absorption in a Wetted Wall Column by Piperazine Solutions

Theoretical and experimental investigations on the reactive absorption of CO2 in aqueous solutions of PZ using a wetted wall column are presented. A rigorous two dimensional absorption model, accounting for kinetics, hydrodynamics and thermodynamics, has been developed for a wetted wall column. Major innovative features of the model, compared to previous work, are the account on the variation of the gas-side CO2 concentration over the reactor height as well as the computation of the gas-liquid equilibrium by a thermodynamically consistent approach.A laboratory-scale wetted wall column was conceived and constructed and the gas-side mass-transfer coefficient was estimated. CO2 absorption experiments were carried out on unloaded and loaded aqueous solutions of PZ over the range of 298-331 K, and for total PZ concentrations varying from 0.2 to 1 M. The reactor model permitted to predict the absorption fluxes in loaded as well as in unloaded solutions with an excellent accuracy, i.e. 3.2% AAD. In loaded solutions, the gas-side CO2 concentration gradient, as well as the dicarbamate formation reaction has to be taken into account.

Managing n-nitrosopiperazine and dinitrosopiperazine

Formation and decomposition of nitroso-piperazine (NNO) compounds were studied under conditions pertinent to amine scrubbing. Nitrogen dioxide (NO2) has an overall liquid-side mass transfer coefficient of approximately 10−6mol/Pa·m2·s at 40°C in 8m PZ. In an amine scrubber designed to remove 90% will travel to the absorber where it will react with PZ to form MNPZ and trace amounts of dinitrosopiperazine (DNPZ). NNO formation is first order in NO2−, carbamated amine, and hydronium ions. The NNO will thermally decompose in the stripper. Thermal decomposition is first order in NNO and dependent on PZ concentration and loading. NNO formation from the flue gas NO2 will balance out with NNO thermal decomposition to give steady state NNO concentrations. The NNO steady state concentration is proportional to the inlet NO2. It is inversely proportional to the decomposition rate constant and the volume of the stripper sump. An amine scrubber using a flue gas without NOx removal will have a steady state MNPZ concentration on the order of 1mM. Reaching the steady state concentration takes on the order of 10 days. DNPZ concentration will be on the order of 10−5 mM, which is undetectable using the methods in this work.

Study on mass transfer and kinetics of CO2 absorption into aqueous ammonia and piperazine blended solutions

A small wetted wall column (WWC) was used to study the kinetics of CO2 absorbed in PZ and NH3/PZ blended solution. The experiments of CO2 absorption into 0.1–0.4M PZ and 0.53–4M NH3/0.1–0.4M PZ mixed solution at 10–40°C have been done in wetted wall column under the driving force of 8–25kPa in this paper. The ‘interface concentration corrected-pseudo first order’ mass transfer model and ‘Ternary-termolecular’ reaction mechanism were proposed to describe the CO2 absorption into NH3/PZ system for the high driving force and low PZ concentration condition. Both of the models in this study used for CO2 with NH3/PZ blended solution were in a good agreement with the experimental results.

Critical slowing down in lead magnesium niobate–zirconate ceramic

Dielectric relaxation behaviour of (1 − x)PMN − xPZ, for x = 0.10, 0.30 and 0.40 have been studied. The nature of relaxational behaviour was found to change with PZ concentration. A crossover from a static freezing to critical slowing down like behaviour is observed with increase in Zr4+ concentration. We have used Glazounov and Tangastev criterion to distinguish freezing and critical slowing down like behaviour.

Dielectric Properties of Solid Solutions (1-x)Pb(Sc1/2Ta1/2)O3–xPbZrO3 (0 < x < 1)

Dielectric properties of (1-x)Pb(Sc1/2Ta1/2)O3(PST)–xPbZrO3 (PZ) (0<x<1) were investigated. For PZ concentrations x<0.7, a diffuse phase transition was observed. With increasing x, the maximum permittivity εrm′ increased, and the temperature Tm at which εrm′ appeared shifted towards the higher temperature region. For x>0.7, the permittivity εr′ exhibits a peak at the phase transition temperature Tc. With increasing x, the peak value decreased and Tt shifted towards the higher temperature region. The phase below Tc was confirmed to be ferroelectric by observation of P-E hysteresis loops. Phase transformation from the relaxor to the ferroelectric state occurred at x=0.7. For x>0.8, a steplike anomaly appeared at Tt below Tc. With increasing x, Tt shifted towards the higher temperature region. There was a structural change characterized by the splitting of the structure-sensitive maximum of the (200) reflection of XRD patterns, similar to orthorhombic PZ, around x=0.8. Two morphotropic phase boundaries were found: one between the pseudocubic and rhombohedral phases with εrm′ of 15000 at 100 kHz was at x=0.7, and the other between the rhombohedral and orthorhombic phases was at x=0.8.

The adsorption and orientation of pyrazine on silver electrodes: a surface enhanced Raman scattering study

Surface enhanced Raman scattering (SERS) spectra of pyrazine (pz) adsorbed on a silver electrode from aqueous solutions containing either 1.0 M KCl or 1.0 M KBr are presented. The SER spectra display bands which are usually forbidden in the normal Raman spectrum of pz. The presence of these forbidden bands and the orientation of the molecules on the electrode surface are discussed under the two most accepted surface enhancement theories: the charge transfer and the electromagnetic model. The dependence of SERS intensity of several pz vibrational modes on the applied potential (potential profile) is also presented for different pz concentrations and excitation wavelengths. SER spectra, obtained at potentials more negative than −900 mV (vs. SCE), contain new bands due to reduction of the pz molecule. It is clear that some of these products of decomposed pz remain trapped on the electrode surface, and this can lead to misunderstandings of the interpretation of the adsorbed pz spectrum. Several controversial aspects presented in the literature about the surface Raman spectrum of pz are clarified and discussed.