Prediction of Gas Consumption During Hydrate Formation With or Without the Presence of Inhibitors in a Batch System Using the Esmaeilzadeh-Roshanfekr Equation of State

In this work, the ability of different equations of state to predict the gas consumption during hydrate formation in a batch system has been evaluated using the model of Kashchiev and Firoozabadi. The first state equation used for this purpose was the one developed by Esmaeilzadeh and Roshanfekr. The predictions were then extended using PR, SRK and Patel Teja equations. The ability of the different equations of state were evaluated for single gases of methane and ethane and their mixtures adding to more than a thousand experimental data existing in the literature. The consumption of gas during hydrate formation was predicted both with and without the presence of kinetic inhibitors. In the case of double hydrate formation, the state equation based on the Kashchiev and Firoozabadi model for simple gas was modified by lumping the component of hydrate formation as a pseudocomponent. The results of this extension study show that the equation developed by Esmaeilzadeh and Roshanfekr is just as suitable for predicting gas consumption during hydrate formation as any of the other well known state equations such as PR and SRK

Evaluation of Performance of an Industrial Gas Sweetening Plant by Application of Sequential Modular and Simultaneous Modular Methods

In this study the simultaneous-modular and sequential modular methods are used to predict performance of desorption and absorption columns in the loop of an industrial sweetening plant. Mathematical model of absorption and desorption cycle for acid gases in methyldiethanolamine has been developed. This model is based on mass and energy balance and takes into account the chemical interactions between solvent and gases. Application of the simultaneous-modular method to model of the plant provides 31 equations with 31 unknowns. Simultaneous solution of these equations presents details of operating conditions on each section of the process. In the sequential modular method, the calculations have been carried out for each unit as a single module in the loop. This way, the output of each module supplies the input data to the next unit. Data of a commercial gas refinery has been used to validate the models and compare the two methods. After validating, the model effects of some parameters on the performance of the loop have been investigated

Comparison of Separation Performance of a Structured Packed Column with a Tray-Type Column for H

Absorption of acid gases, H2S and CO2, by methyl diethanol amine in a structured packed column equipped with Montz-Pak A3-500 was mathematically modeled. The dimensions of the channels as well as their number and liquid film flow model are similar to the Shilkin's work. Heat and mass transfer equations are derived for reacting liquid film and gas flowing counter currently into the column. Concentration distribution is calculated across the moving liquid film and no zone with equilibrium concentration conditions is considered in the reacting liquid. The results of the model for the structured column show a better performance for H2S absorption compared with a tray column operating in the same conditions. The results obtained by the model indicate appreciable distribution of concentration and temperature along the column

A grade transition strategy for the prevention of melting and agglomeration of particles in an ethylene polymerization reactor

To satisfy the diverse product quality specifications required by the broad range of polyethylene applications, polymerization plants are forced to operate under frequent grade transition policies. During the grade transition, the reactor temperature must be kept within the narrow range between the gas dew point and the polymer melting point, otherwise the particles melt or agglomerate inside the reactor. In the present study, a dynamic well-mixed reactor model is used to develop a grade transition strategy to prevent melting and agglomeration of particles in an ethylene polymerization reactor. The model predicts the conditions under which the temperature of the reactor is outside the allowable range in continuous grade transition. Manipulation of feed flow and cooling water flow rates has shown that the reactor temperature cannot be maintained within the allowable range. Hence, a semi-continuous grade transition strategy is used for this case so that the temperature is maintained within the allowable range. In addition, several continuous and semi-continuous grade transition strategies for the production of linear low-density polyethylene (LLDPE), medium density polyethylene (MDPE), and high-density polyethylene (HDPE) are compared