Chemical equilibrium model simulation

Several workers have intended to estimate the chemical compositions of Kuroko ore fluids based on the chemical equilibrium model (Sato, 1973 Kajiwara, 1973 Ichikuni, 1975 Shikazono, 1976 Ohmoto et al., 1983) and computer simulation of the changes in mineralogy and chemical composition of hydrothermal solution during seawater-rock interaction. Although the calculated results (Tables 1.5 and 1.6) are different, they all show that the Kuroko ore fluids have the chemical features (1 )-(4) mentioned above. 

The functions of transfer can be simulated with the chemical equilibrium model of Roux et al. ( )... 

Figure 3 Volumes of transfer of sodium decanoate from water to 2-butoxyethanol solutions at 25 C. Simulations (curves A and 6) with a chemical equilibrium model ...

Bertero, L., Chierici, G.L., Gottardi, G., Mesini, E. Mormino, G. 1988. Chemical equilibrium models their use in simulating the injection of incompatible waters. In Society Petroleum Engineers. Reservoir Eng., pp. 288-294. 

The difficulties of experimentally determining the speciation of actinides present at very low concentrations in natural waters have encouraged the use of computer simulations, based on thermodynamic data, as a means of predicting their speciation and hence their environmental behaviour. The use of modelling techniques to describe the speciation, sorption, solubility and kinetics of inorganic systems in aqueous media has been reviewed in the papers given at an international conference in 1978. Both chemical equilibrium models, exemplified by computer programs such as MINEQL and SOLMNQ, and dynamic reaction path models, exemplified by EQ6, have been developed. Application of the equilibrium models to radioactive waste disposal... 

When the simulation of deep-well temperatures, pressures, and salinities is imposed as a condition, the number of codes that may be of value is reduced to a much smaller number. Nordstrom and Ball121 recommend six references as covering virtually all the mathematical, thermodynamic, and computational aspects of chemical-equilibrium formulations (see references 123-128). Recent references on modeling include references 45, 63, 70, 129, and 130. 

The earliest or Level I fugacity models simulate the simple situation in which a chemical achieves equilibrium between a number of phases of different composition and volume. The prevailing fugacity is simply/ = M/Y.V, x Z where M is the total quantity of chemical (mol), V, is volume (m3), and Z, is the corresponding phase Z value (mol Pa-1 m-3). Although very elementary and naive, this simulation is useful as a first indication of where a chemical is likely to partition. It is widely used as a first step in chemical fate assessments. 

Chemical equilibrium methods provide useful predictions of the EOS of detonation processes and the product molecules formed, but no details of the atomistic mechanisms in the detonation are revealed. We now discuss condensed-phase detonation simulations using atomistic modeling techniques to evaluate reaction mechanisms on the microscopic level. 

As a further model simplification, a linearization of the film concentration profiles has been studied. This causes no significant changes in the simulation results and at the same time reduces the total number of equations by half and stabilizes the numerical solution (142). The assumption of chemical equilibrium in... 

The steps in setting up the Aspen Plus simulation are outlined below. The rigorous RCSTR model is used, which requires specifying reactions and kinetic parameters. An alternative, which is useful in some systems with reversible reactions, is the RGIBBS reactor module. Kinetic parameters are not required. Chemical equilibrium compositions are calculated for given feed and reactor temperature and pressure. If the forward and reverse reactions are known to be fast, so that the reactor effluent is at equilibrium conditions, the RGIBBS reactor provides a simple way to model a reactor. In Chapter 3 we will illustrate how this type of reactor can incorporate some approximate dynamics for developing control systems. 

The persistent organochlorine compounds, once released, will partition between environmental media according to their physical and chemical properties. Steady state equilibrium partitioning between these media has been considered as the simplest model simulating their behaviour. Over recent years, modelling the environmental partitioning and fate of these compounds has led to a broad... 

The cloud chemistry simulation chamber (5,6) provides a controlled environment to simulate the ascent of a humid parcel of polluted air in the atmosphere. The cloud forms as the pressure and temperature of the moist air decreases. By controlling the physical conditions influencing cloud growth (i.e. initial temperature, relative humidity, cooling rate), and the size, composition, and concentration of suspended particles, chemical transformation rates of gases and particles to dissolved ions in the cloud water can be measured. These rates can be compared with those derived from physical/chemical models (7,9) which involve variables such as liquid water content, solute concentration, the gas/liquid interface, mass transfer, chemical equilibrium, temperature, and pressure. 

Equilibrium compositions of the simulated exhaust were calculated as a function of temperature for several assumed reaction models. The calculations consisted of solving simultaneously, by the Newton iteration procedure, a set of material balance equations and chemical equilibrium... 

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