EQ-COMP PRESENTATION

EQ-COMP: THE VLE APPLICATION

Vapor-Liquid Equilibrium properties of hydrocarbon mixtures play an important role in designing of flash chambers and distillation equipments like distillation colums in oil refineries and gas processing plants like LPG plants and LNG liquefaction and gasification plants. Also VLE properties like dew points and retrograde compositions are required for well simulation of oil and gas wells. Prediction of these properties can be useful in simulating planetary atmosphere of other heavenly bodies which is composed of varying proportions of various hydrocarbons like Methane, Ethane and Propane and some inorganic gases like H2S, CO2 and N2. Acuurate calculation of binary and multicomponent Vapor-Liquid equilibrium properties require complex calculations involving complex equations. These calculations can only be executed using latest computers. These calculations further require very complex computer programs for automating them so that correct values are calculated at just the click of a button.

EQ-COMP is a very complex combination of various macros written in MS Excel using Visual Basic for Application programming language for calculating multicomponent vapor-liquid equilibrium properties and automating the procedure involved so that the calculations can be executed at the click of a button. It is useful in finding out vapor-liquid equilibrium properties for a hydrocarbon mixture for almost any composition with upto a maximum of 112 components. The possible components can include non-polar hydrocarbons, mildly polar hydrocarbons, non-polar inorganic gases or mildly polar inorganic gases. LIST OF HYDROCARBONS – EQ-COMP. Its various modules can be used to find out bubble point temperature, bubble point pressure, hydrocarbon dew point temperature, hydrocarbon dew point pressure, phase envelop and two phase composition even in retrograde region and for compositions involving high proportions of non-condensables. A separate module is designed to find out water dew point temperature for mixtures containing water between 1 weight % and 50 weight %. The phase envelope generated using EQ-COMP consists of equilibrium temperature values at a specified interval of 0.4 bars. It clearly marks the critical point of mixture and cricondenbar and cricondentherm for the mixture can also be located on the phase envelope.

VLE properties for binary mixtures calculated using various modules of EQ-COMP can be further post-processed using a post-processing module of EQ-COMP to extensively analyze the distillation characteristics of the binary mixture. EQ-COMP can be used to plot x-y, T-x-y and critical point profile for binary mixtures. These can be used directly for design calculations of distillation column for separation of binary mixtures. EQ-COMP can plot x-y and T-x-y curves for binary mixtures even at extended pressures much above atmospheric pressure.

The preferred method for calculating multicomponent VLE properties for non-polar hydrocarbon mixtures involves use of Peng-Robinson cubic equation of state. EQ-COMP uses the same method for calculating VLE properties of multicomponent hydrocarbon mixtures. In designing of EQ-COMP, trends of various phase envelop curves for different compositions developed using first principles have been carefully studied and generalized to fit other compositions. As EQ-COMP uses first principles and standard calculation tools like MS excel for carrying out the calculations so generating results may take as long as an hour but the chances of the results being incorrect under the preview of Peng-Robinson cubic equation of state is almost nil. Binary interaction parameters values can be included in the calculations in EQ-COMP to increase the accuracy of the VLE results. EQ-COMP is among the very few similar software in the world which have included temperature dependent binary interaction parameters as per Predictive Peng Robinson 78 (PPR 78) equation in its calculations. PPR 78 equation is given by Jaubert and his colleagues and is applicable to alkanes, alkenes, cyclic hydrocarbons, aromatics, water, N2, H2S, H2 and CO2. It is becoming an industrial benchmark as far as binary interaction parameters for Peng Robinson equation are concerned as the results derived after using PPR 78 are considerably more accurate then that derived from using no binary interaction parameters or constant binary interaction parameters. EQ-COMP can provide results for most of the compositions using PPR 78 equation subject to its applicability for the compounds involved.

EQ-COMP can give almost any result involving hydrocarbon VLE most accurately using the preferred Peng-Robinson equation of state. Some of the results possible with EQ-COMP are given below:

  1. Phase equilibrium curve with temperature-pressure data for any pure non-polar or mildly polar compound with known critical temperature, critical pressure accentricity factor.

  2. VLE properties like bubble point temperature, bubble point pressure, dew point temperature, dew point pressure, two phase composition, bubble point composition, dew point composition etc. for almost any hydrocarbon mixture including upto a maximum of 112 components. The possible components can include non-polar hydrocarbons, mildly polar hydrocarbons, non-polar inorganic gases or mildly polar inorganic gases.LIST OF HYDROCARBONS – EQ-COMP.

  3. Complete phase envelope for almost any hydrocarbon mixture with critical point, cricondenbar, cricondentherm and multiple critical points.

  4. VLE properties in the retrograde region.

  5. VLE properties and Phase envelope for hydrocarbon mixtures involving high concentration of non-condensables.

  6. Prediction of state of hydrocarbon mixture (liquid, vapour, two phase or super critical) at a particular temperature and pressure.

  7. Customisation of software to include any other non-polar or mildly polar hydrocarbon in the calculations as per client’s requirement.

  8. Inclusion of values of binary interaction parameters provided by the client to generate results.

  9. Inclusion of temperature dependent binary interaction parameters in case desired by the client.

  10. Generation of liquid and vapour compressibility factors for any hydrocarbon mixture over a range of temperatures and pressures.

  11. Generation of x-y, T-x-y and critical point profile for any binary mixture comprising of non-polar or mildly polar hydrocarbons.

The phase envelop result for a standard natural gas composition calculated using EQ-COMP is given below:

Methane         :           70 %,   Ethane                        :           15 %,   Propane           :           8 %
i-Butane          :           2 %,     n-Butane         :           2 %,     n-Pentane       :           1 %
2 Methyl Butane         :           1 %,     n-Hexane        :           1 %
           
 
The phase envelop result for a non-standard composition with high proportion of inorganic gases using EQ-COMP is given below:

Methane         :           10%,n-Hexane                        :           10%, n-Heptane          :        10%
n-Octane         :           20 %,   Nitrogen          :           50 %

                                                                                                                                               

 

 

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