Chemical Modeling Software Research Articles

Reaction Characteristics of NOx and N2O in Selective Non-Catalytic Reduction Using Various Reducing Agents and Additives

Artificial nitrogen oxide (NOx) emissions due to the combustion of fossil fuels constitute more than 75% of the total NOx emissions. Given the continuous reinforcement of NOx emission standards worldwide, the development of environmentally and economically friendly NOx reduction techniques has attracted much attention. This study investigates the selective non-catalytic reduction (SNCR) of NOx by methane, ammonia, and urea in the presence of sodium carbonate and methanol and the concomitant generation of N2O. In addition, the SNCR mechanism is explored using a chemical modeling software (CHEMKIN III). Under optimal conditions, NOx reduction efficiencies of 80–85%, 66–68%, and 32–34% are achieved for ammonia, urea, and methane, respectively. The N2O levels generated using methane (18–21 ppm) were significantly lower than those generated using urea and ammonia. Addition of sodium carbonate and methanol increased the NOx reduction efficiency by methane to ≥40% and 60%, respectively. For the former, the N2O level and reaction temperature further decreased to 2–3 ppm and 850–900 °C, respectively. The experimental results were well consistent with simulations, and the minor discrepancies were attributed to microscopic variables. Thus, our work provides essential guidelines for selecting the best available NOx control technology.

Carbon Dioxide Contamination of Aqueous Morpholine Solutions and Effects on Secondary Coolant Chemistry Under CANDU Conditions

Exposure to air can cause amine solutions in CANada Deuterium Uranium (CANDU) reactor secondary coolant circuit feed tanks to absorb carbon dioxide (CO2). Likewise, carbon dioxide can be absorbed directly into the amine-containing secondary coolant by air ingress during shutdown, lay-up, and startup. Sampling operations, including transferring the sample to the laboratory and subsequent analyses, can also provide opportunities for CO2 contamination. This paper reports the results of laboratory and chemical modeling studies to examine the effects of CO2 contamination on aqueous morpholine solutions. The chemistry of CO2 uptake by feed tanks containing up to 50 wt% (11.5 mol·kg−1) morpholine at 25°C was modeled using the OLI Studio 9.5.2 chemical equilibrium model, and the speciation was confirmed by 13C nuclear magnetic resonance spectroscopy (NMR) measurements. The effects of CO2 contamination on the pH of the secondary coolant containing 60 ppm (0.006 wt%, 7.00 × 10−4 mol·kg−1) morpholine and the resulting effects on the solubility of magnetite and nickel oxide from 25°C and 250°C at steam saturation were modeled as a function of CO2 loading using the Electrical Power Research Institute chemical modeling software MULTEQ v.8. The chemical modeling calculations show that concentrated alkaline morpholine solutions at room temperature and pressure would be expected to have a strong tendency to absorb CO2 and have additional uptake abilities due to the formation of morpholine carbamates. For dilute morpholine solutions at room temperature and pressure, the solutions are still sufficiently alkaline to absorb enough CO2 to cause a measurable change in the pH of the secondary coolant. This effect was shown to be negligible under reactor operating conditions. The absorption of CO2 would potentially have the most effect on either unprotected feed tanks or during lay-up conditions in the steam generators, as it could depress the pH of the lay-up solution and adversely affect the rate of corrosion in the internal components of the steam generators (e.g., carbon steel materials). The 13C NMR measurements on samples of 50 wt% aqueous morpholine solutions from feed tanks at the Ontario Power Generation’s Pickering Nuclear Generating Station found that CO2 was below the 0.02 wt% detection limit, and suggest that the procedures used to avoid CO2 contamination in feed tanks are effective. The 13C NMR was shown to be an effective tool for monitoring CO2 uptake by morpholine solution in the feed tanks under conditions in which they may have undergone abnormal exposure to air.

Prediction of gaseous products from refuse derived fuel pyrolysis using chemical modelling software - Ansys Chemkin-Pro

There can be observed global interest in waste pyrolysis technology due to low costs and availability of raw materials. At the same time, there is a literature gap in forecasting environmental effects of thermal waste treatment installations. In the article was modelled the chemical composition of pyrolysis gas with main focus on the problem in terms of environmental hazards. Not only RDF fuel was analysed, but also selected waste fractions included in its composition. This approach provided comprehensive knowledge about the chemical composition of gaseous pyrolysis products, which is important from the point of view of the heterogeneity of RDF fuel. The main goal of this article was to focus on the utilitarian aspect of the obtained calculation results. Final results can be the basis for estimating ecological effects, both for existing and newly designed installations.Pyrolysis process was modelled using Ansys Chemkin-Pro software. The investigation of the process were carried out for five different temperatures (700, 750, 800, 850 and 900 °C). As an output the mole fraction of H2, H2O, CH4, C2H2,C2H4, C3H6, C3H8, CO, CO2, HCl and H2S were presented. Additionally the reaction pathways for selected material were presented.Based on obtained results, it was established that the residence time did not influenced on the concentration of products, contrary to temperature. The chemical composition of pyrolytic gas is closely related to wastes origin. The application of Chemkin-Pro allowed the calculation of formation for each products at different temperatures and formulation of hypotheses on the reaction pathways involved during pyrolysis process. Further, based on the obtained results confirmed the possibilities of using pyrolysis gas from RDF as a substitute for natural gas in energy consumption sectors. Optimization of the process can be conducted with low financial outlays and reliable results by using calculation tools. Moreover it can be predicted negative impact of obtained products on the future installation.

Potassium sarcosinate promoted aqueous ammonia solution for post‐combustion capture of CO2

AbstractAqueous ammonia (NH3) is regarded as one of the most cost‐effective solvents for carbon dioxide (CO2) separation processes but suffers from low CO2 absorption rates and high NH3 vapor losses which hinder industrial application of this solvent in CO2 capture from the flue gas of the coal‐fired power sectors. In an attempt to address these issues, the effect of adding of potassium sarcosinate (K‐SAR) to NH3 solutions as a rate promoter on CO2 mass transfer and NH3 vapor loss in the aqueous NH3‐based post‐combustion capture process was investigated in this work. Overall mass transfer coefficients (KG) describing CO2 absorption and NH3 vapor loss in 3.0M NH3 and blended 3.0M NH3 solutions containing a wide range of K‐SAR concentrations from 0.0 to 3.0M were determined using a wetted‐wall column contactor at 15–25 °C and CO2 loadings from 0.0 to 0.5(molCO2/mol total amine). Additionally, prediction of equilibrium species distribution using fundamental chemical modelling software (ReactLab) in CO2‐loaded NH3 containing blended solutions were used to explain our experimental results. Addition of K‐SAR resulted in significant improvement of KG of CO2 absorption in NH3 solutions, but also increased NH3 vapor losses. The effect of temperature on KG of CO2 absorption in K‐SAR solution was greater than in the NH3/K‐SAR blended solution. The improvement in mass transfer upon addition of K‐SAR is due to the faster reaction of CO2 with K‐SAR than with NH3. The greater loss of NH3 upon addition of K‐SAR can be ascribed to the availability of more free NH3 and the decrease of solubility of CO2 and NH3 in the NH3/K‐SAR blended solution. The investigation of KG of CO2 and NH3 vapor losses in NH3 and other amines (PZ, 1‐MPZ, DEA and MEA) blended solutions also proved the competition for CO2 is one of the reasons for the increasing of NH3 vapor losses.

Transport and Precipitation of Gold in Phanerozoic Metamorphic Terranes from Chemical Modeling of Fluid-Rock Interaction

This study reports results of mass transfer calculations using chemical modeling software (HCh) to determine chemical parameters that may have had a significant effect on gold deposition in turbidite-hosted Phanerozoic metamorphic terranes. The chemical system modeled was Al-As-Au-C-Ca-Cl-Cu-Fe-H-K-Mg-N-Na-O-S-Sb-Si to simulate fluid-rock interaction, gas partitioning, and mineral precipitation in veins. Each modeling run takes into consideration both (1) the composition of the vein fluid and the minerals predicted to precipitate in the vein and (2) the composition of the fluids during fluid-rock interaction and the predicted alteration assemblage of the host rocks. Results of the modeling are in good agreement with observed mineral assemblages in variably endowed Paleozoic orogenic gold provinces (central Victoria and northeast Tasmania, Australia; Buller terrane, New Zealand; Meguma terrane, Canada; Sierra de Rinconada, Argentina), and illustrate that gold is precipitated efficiently and over a wide temperature range (400°–200°C) from low-salinity, mixed aqueous-carbonic fluids. The modeling also allowed us to vary the critical components of the fluid (e.g., confining pressure that affects phase separation, ∑CO2, ∑S, f O2, and pH) to investigate how each of these parameters influences the amount of gold predicted to precipitate in the vein and the associated mineral assemblage. With the exception of the low ∑S fluid, the modeling scenarios predict the precipitation of gold mainly in the vein due to desulfidation processes. Carbon dioxide and other gases in the fluid play an important role: they limit the f O2 to a range where elevated gold concentrations can be maintained and transported in the fluid and also have an important effect on fluid immiscibility. We also investigated what effect a range of possible source rock compositions (i.e., granite, turbidites, greenstones, auriferous exhalative interflow sediments) have on gold solubility in fluids equilibrated with these rocks and hence, how rock compositions may influence ore transport and deposition. The results indicate that, at high temperatures, fluids in equilibrium with auriferous exhalative interflow sediments or greenstones will contain the highest gold concentrations. This outcome suggests that tectonic settings that enable preconcentration of gold in sulfide-rich siliciclastic or exhalative interflow sediments might provide more favorable conditions for the formation of well-endowed gold provinces.

Conformational and microwave dielectric relaxation studies of hydrogen bonded polar binary mixtures of propionaldehyde with isopropyl amine

The dielectric behaviour of the polar liquids like propionaldehyde, isopropyl amine and their equimolar binary mixture in nonpolar solvent benzene is studied in the microwave frequency range using the cavity perturbation technique at 6.218 GHz (J band), 9.880 GHz (X band), 16.331 GHz (P band) and 24.951 GHz (K band). Hamiltonian quantum mechanical calculations such as AM1, PM3, and MNDO optimized converged geometry operation is performed by using Argus lab chemical modelling software 2004 for both pure and binary systems of propionaldehyde and isopropyl amine. Dipole moments of the binary mixtures are calculated from the dielectric data using Higasi's method and compared with the theoretical results. Conformational analysis of the formation of a hydrogen bond between the propionaldehyde and isopropyl amine is supported by FT-IR, proton NMR spectra and molecular polarizability calculations. The average relaxation times are calculated from their respective Cole–Cole plots.

Microwave dielectric absorption studies of hydrogen bonded polar binary mixtures of isobutanol with tertiary butyl amine

The dielectric behaviour of polar liquids like isobutanol, tertiary butyl amine and their equimolar binary mixture in nonpolar solvent benzene is studied in the microwave frequency range using the cavity perturbation technique at 6.218 GHz (J band), 9.880 GHz (X band), 16.331 GHz (P band) and 24.951 GHz (K band). Hamiltonian quantum mechanical calculations such as AM1, PM3 and MNDO optimized converged geometry operation is performed on isobutanol, tertiary butyl amine and their equimolar binary mixtures using Argus lab chemical modelling software, 2004. Dipole moments of the binary mixtures are calculated from the dielectric data using Higasi's method, and compared with the theoretical Hamiltonian quantum mechanical results. Conformational analysis of the formation of hydrogen bond between the isobutanol and tertiary butyl amine is supported by FT-IR and proton NMR spectra. The average relaxation times are calculated from their respective Cole–Cole plots.

Conformational and dielectric analysis of hydrogen bonded polar binary mixtures of propan-1-ol with isopropyl amine

The dielectric behavior of the polar liquids like propan-1-ol, isopropyl amine and their equimolar binary mixture in nonpolar solvent benzene is studied in the microwave frequency range using the cavity perturbation technique at 6.218 GHz (J band), 9.880 GHz (X band), 16.331 GHz (P band) and 24.951 GHz (K band). Hamiltonian quantum mechanical calculations such as AM1, PM3, and MNDO optimized converged geometry operation is performed by using Argus lab chemical modeling software 2004 for both pure and binary system of propan-1-ol and isopropyl amine. Dipole moments of the binary mixtures are calculated from the dielectric data using Higasi’s method and compared with the theoretical results. Conformational analysis of the formation of hydrogen bond between the propan-1-ol and isopropyl amine is supported by the FT-IR and proton NMR spectra. The average relaxation times are calculated from their respective Cole–Cole plots.