• Journal of Institute of Convergence Technology
• /
• v.2 no.2
• /
• pp.30-34
• /
• 2012

The SI thermochemical cycle process accomplishes water splitting through distinctive three chemical reactions. We focused on thermodynamic models applicable to the process. Recently, remarkable models based on the assumed ionic species have been developed to describe highly nonideal behavior on the liquid phase reactions. ElecNRTL models with ionic reactions were proposed in order to provide reliable process simulation results for phase equilibrium calculations in Section II and III. In this study, the current thermodynamic models of SI thermochemical cycle process were briefly described and the calculation results of the applied ElecNRTL models for phase equilibrium calculations were illustrated for binary systems.

• Carbon letters
• /
• v.20
• /
• pp.10-18
• /
• 2016

Nanoporous carbon structures were synthesized by pyrolysis of grass as carbon precursor. The synthesized carbon has high surface area and pore volume. The carbon products were acid functionalized and characterized by Fourier transform infrared spectroscopy, X-ray diffraction, Brunauer–Emmett–Teller, transmission electron microscopy, and Energy Dispersive X-ray microanalysis. Acid functionalized nanoporous carbon was explored for use in removal of toxic Cr(VI) ions from aqueous media. An adsorption study was done as a function of initial concentration, pH, contact time, temperature, and interfering ions. The experimental equilibrium data fits well to Langmuir isotherm model with maximum monolayer adsorption capacity of 35.335 mg/g. The results indicated that removal obeys a pseudo-second-order kinetic model, and that equilibrium was reached in 10 min. A desorption study was done using NaOH. The results of the present study imply that acid functionalized nanoporous carbon synthesized from grass is an efficient, renewable, cost-effective adsorbent material for removal of hexavalent chromium due to its faster removal rate and reusability.

• Bulletin of the Korean Chemical Society
• /
• v.29 no.3
• /
• pp.555-561
• /
• 2008

In air stripping of ammonia from the aqueous solution, a new removal model was presented considering the equilibrium principles for the ammonia in aqueous solution and between the aqueous and air phase. The effects of pH, temperature and airflow rate on the ammonia removal were evaluated with the model. In addition, the saturation degree of ammonia in air was defined and used to evaluate the effect of each experimental factor on the removal rate. As pH (8.9 to 11.9) or temperature (20 to 50 oC) was increased, the overall removal rate constants in all cases were appeared to be increased. Our presented model shows that the degrees of saturation were about the same (0.45) in all cases when the airflow condition remains the same. This result indicates that the effect of pH and temperature were directly taken into consideration in the model equation. As the airflow increases, the overall removal rate constants were increased in all cases as expected. However, the saturation degree was exponentially decreased with increasing the airflow rate in the air phase (or above-surface) aeration. In the subsurface aeration the saturation degree remains a constant value of 0.65 even though the airflow rate was increased. These results indicate that the degree of saturation is affected mainly by the turbulence of the aqueous solution and remains the same above a certain airflow rate.

• Journal of Institute of Convergence Technology
• /
• v.5 no.1
• /
• pp.1-5
• /
• 2015

SI thermochemical hydrogen production process achieves water splitting into hydrogen and oxygen through three chemical reactions. The process is comprised of three sections and one of them is HI decomposition into $H_2$ and $I_2$ called as Section III. The production of $H_2$ included processes involving EED for concentrating a product stream from Section I. Additionally an $I_2$ crystallization would be considered to reduce burden on EED by removing certain amount of $I_2$ out of a process stream prior to EED. In this study, the current thermodynamic model of SI process was briefly described and the calculation results of the applied Electrolytes NRTL model for phase equilibrium calculations was illustrated for ternary systems of Section III. We calculated temperature and heat duty of an $I_2$ crystallizer and heat duty of heaters using UVa model and heat balance equation of simulation tool. The results were expected to be used as operation information in optimizing HI decomposition process and setting up material balance throughout SI process.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2007.04a
• /
• pp.143-147
• /
• 2007

Kerosene and diesel are compounded fuels with various types of hydrocarbon elements and difficult to model the chemical kinetics. This study focuses on the prediction of the non-equilibrium reaction of fuel-rich combustion with detailed kinetics developed by Dagaut using PSR(perfectly stirred reactor) assumption. In Dagaut's surrogate model for kerosene and diesel, chemical kinetics consists of 2352 reaction steps with 298 chemical species. Also, Frenklach's soot model was implemented along with detailed kinetics to calculate the gas properties of fuel rich combustion efflux.

• Bulletin of the Korean Chemical Society
• /
• v.24 no.7
• /
• pp.931-936
• /
• 2003

By the use of multi-loop thermodynamic boxes developed here by us, we show that models of enzyme catalysis (e.g., split-site model) developed in an attempt to emphasize the importance of the reactant-state destabilization and, thus, demonstrate misleading nature of the fundamentalist position which defines Pauling's transition-state stabilization as the entire and sole source of enzyme catalytic power, should be reduced to the fundamentalist formulation which completely neglects dynamical aspects of mechanism between the reactant and the transition states and dwells only on events restricted to the reactant and transition states alone, because the splitsite (and other canonical) formulations as well as fundamentalist formulations are based, in common, on equilibrium assumptions stipulated by the thermodynamic box logics. We propose to define the equilibrium assumptions as the requisite and sufficient conditions for the fundamentalist position to enjoy its primacy as central dogma, but not as sufficient conditions for its validity, because it is subjected to contradictions presented by existing data.

• Nuclear Engineering and Technology
• /
• v.52 no.11
• /
• pp.2543-2551
• /
• 2020

Calculations of chemical equilibrium for multicomponent aqueous systems of the HyBRID dissolution of magnetite were performed by using the HSC Chemistry. They were done by using a Pitzer-based aqueous solution model with the recipe of raw materials in experiments conducted at KAERI. The change in the amounts of species and ions and the pH values of the solution at equilibrium was observed as functions of temperature and raw amount of CuSO₄. Precipitation of Cu₂O occurred at a large amount of CuSO₄ added to the solution, while no precipitation of Cu(OH)₂ was found at any amounts of CuSO₄. The E-pH diagrams for Cu were constructed at various Cu concentrations to provide the effect of the Cu concentration on the pH values at boundaries where the coexistence of Cu⁺ ion and Cu₂O solid occurred. To prevent Cu⁺ ions from being precipitated to Cu₂O, the raw amount of CuSO₄ should be adjusted so that the pH value of the solution from the equilibrium calculation is less than that from the E-pH diagram. We provided guidelines for the raw amount of CuSO₄ and the pH value of the solution, which prevent the formation of Cu₂O precipitates in the HyBRID dissolution experiments for magnetite.

• Biotechnology and Bioprocess Engineering:BBE
• /
• v.6 no.5
• /
• pp.347-351
• /
• 2001

A study was made on the extraction equilibria of succinic and formic acids from aqueous solutions using tri-n-octylamine (TOA) in 1-octanol. It was shown that the loading values of TOA decreased with increasing pH values. The apparent equilibrium constants for each acidamine complex were determined by an equilibrium model. In the case succinic acid, the formation of a bisuccinate anion played an important role in the stoichiometry of the acid-amine complex.

• Macromolecular Research
• /
• v.11 no.1
• /
• pp.53-61
• /
• 2003

A molecular-thermodynamic model is developed for the salt-induced protein precipitation. The protein molecules interact through four intermolecular potentials. An equation of state is derived based on the statistical mechanical perturbation theory with the modified Chiew's equation for the fluid phase, Young's equation for the solid phase as the reference system and a perturbation based on the protein-protein effective two body potential. The equation of state provides an expression for the chemical potential of the protein. In a single protein system, the phase separation is represented by fluid-fluid equilibria. The precipitation behaviors are simulated with the partition coefficient at various salt concentrations and degree of pre-aggregation effect for the protein particles. In a binary protein system, we regard the system as a fluid-solid phase equilibrium. At equilibrium, we compute the reduced osmotic pressure-composition diagram in the diverse protein size difference and salt concentrations.

• Bulletin of the Korean Chemical Society
• /
• v.23 no.1
• /
• pp.107-111
• /
• 2002

The OSS2 (Oj？me-Shavitt-Singer 2)[L. Oj？me et al., J. Chem. Phys. 109, 5547 (1998)] model for the solvated proton in water is examined for $H_2O,\;H_3O^+,\;H_5O_2^+,\;H_7O_3^+,\;and\;H_9O_4^-$ by molecular dynamics (MD) simulations. The equilibrium molecular geometries and energies obtained from MD simulations at 5.0 and 298.15 K agree very well with the optimized calculations.