Thermodynamic hydrate inhibitors such as methanol, ethanol, (mono) ethylene glycol (MEG), and triethylene glycol (TEG) are widely used in the oil and gas industry. On modeling these compounds, we show here how the CPA equation of state was implemented in an in-house process simulator as an in-built model. To validate the implementation, we show calculations for binary systems containing hydrate inhibitors and water or hydrocarbons using the Cubic Plus Association (CPA) and Soave−Redlich−Kwong (SRK) equation of states, also comparing against experimental data. For streams containing natural gas and water, CPA was applied to calculate the loss of the inhibitor to the vapor phase as a function of temperature and pressure. Simulations of dehydration units using TEG were conducted, and the CPA results were compared with that of two commercial simulators which used their available thermodynamic packages for glycol applications, proving that the CPA calculations are in good agreement with these models and showing that this is an adequate way to simulate complex mixtures containing natural gas, water, and hydrate inhibitors.
Since
the discovery of the Pre-Salt layer in Brazilian waters, production
of high gas–oil ratio (GOR) has increased considerably. This
gas has a high content of water, CO2, and sometimes H2S. A study in different conditions was conducted using several
equations of state (EoS) such as Peng–Robinson, GERG-modified
Peng–Robinson (PR-ISO-04), Soave–Redlich–Kwong,
and Cubic Plus Association (CPA). Petrobras’ Process Simulator
has been used to perform the phase equilibrium calculations. All the
EoS except for CPA used parameters from the literature. A new parameter
estimation procedure for CPA has been proposed using a particle swarm
optimization algorithm followed by the SIMPLEX method presenting themselves
together as an optimal approach. The results show that PR-ISO-04 can
be considered to be an improvement compared to the original Peng–Robinson
but CPA appears to be the most promising approach to be used for predicting
dew points for water-containing mixtures, especially at high pressures.
-A method for analysis of the electric potential profile in saline solutions was developed for systems with one or two infinite flat plates. A modified Poisson-Boltzmann equation, taking into account nonelectrostatic interactions between ions and surfaces, was used. To solve the stated problem in the steady-state approach the finite-difference method was used. For the formulated pseudo-transient problem, we solved the set of ordinary differential equations generated from the algebraic equations of the stationary case. A case study was also carried out in relation to temperature, solution concentration, surface charge and salt-type. The results were validated by the stationary problem solution, which had also been used to verify the ionic specificity for different salts. The pseudo-transient approach allowed a better understanding of the dynamic behavior of the ion-concentration profile and other properties due to the surface charge variation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.