New Features and Changes in Version 3.5

Introduction

There are several improvements and extensions in Multiflash 3.5. The major development for this version is the extension of the salt analysis for hydrate calculations to include potassium and calcium ions as well as sodium and chloride ions. For those using the Excel interface an important change is the ability to launch the Multiflash GUI from Excel.

As always changes have been made to improve the robustness of calculations, including extended search procedures for solving tolerance calculations. In some cases you may find that calculated results vary slightly from previous versions. Where we are aware of significant differences we will point these out. All our hardware dongles are valid for previous licensed versions of Multiflash so you can reproduce earlier calculations if required.

Models

Descriptions and references detailing the models are provided in our "Models and Physical Property Guide"

Hydrates

The Electrolyte model for salts has been extended to represent aqueous salt solutions in terms of four ions, Na⁺, Ca⁺⁺, K⁺ and Cl^-. This provides an overall improvement to the representation of salt solutions for hydrate inhibition but particularly for high concentration calcium chloride solutions. Br^- has been added to the list of ions in the ion analysis table.

The CPA model has been extended and upgraded. New parameters allow ethanol to be included in the list of hydrate inhibitors handled by the CPA model although it has not yet been included in the list of inhibitors in the inhibitor calculator. Compositions must be entered directly in the Composition drop down box.

The parameters for water/methanol, water/hydrocarbons and methanol/hydrocarbons were modified in Multiflash 3.4 in the light of our work on hydrate kinetics. However, these parameters favoured high pressure data and produced less conservative results for the amount of methanol to be added to inhibit hydrates at given conditions. A further re-fit has concentrating on the lower pressure data has resulted in new parameters which give a more conservative estimate of how much methanol is required for inhibition.

Tetrahydrofuran (THF) has been added to the list of potential hydrate formers.

Pedersen viscosity model

The Pedersen viscosity model has been modified to include the effect of the additional ions introduced for the Salt analysis.

BIPs

Modification of BIPs

In earlier versions of Multiflash any BIPs modified during a calculation were cleared if the model definition was redefined, even if the change was as simple s removing one of the phases. In MF3.5 modified BIPs are retained during calculation unless re-defining the model requires a new bipset.

BIPSET Names

The names of some bipsets has been modified. The names of the LLE variants of NRTL and Uniquac are now different to those used for the VLE variants; NRTLLLEBIP3 and UNIQUACLLEBIP2. The bipset for Flory-Huggins is called FHBIP to distinguish it from the name used for Regular Solution.

Revisions and additions

INFOBIPS has been extended with the addition of BIPs for mixtures including ketones and ethers.

Fluid characterisation

n-Paraffin distribution

The fitting and splitting procedures for the n-paraffin distribution has again been improved. This may result is different values for the WAT when using the Coutinho model.

Matching

The matching facilities in Multiflash have been improved and extended in version 3.5.

Simultaneous matching of GOR/Bubble point

The bubble point matching facility has now been extended to include the ability to simultaneously fit bubble points, GOR at given conditions and liquid density at the same conditions if data is available. The GOR matching modifies the component compositions, see “Matching dew and bubble points” on page 110.

Density/Volume

In MF3.4 we introduced the facility to match to known data for the density/volume of the multiphase fluid at the conditions supplied. However care had to be taken when matching to liquid density that the overall fluid was in the single phase region. In MF3.5 you can now specify the phase for which the density matching is required, see “Matching Density/Volume” on page 115.

This is done by amending the Peneloux volume shift. The matching option is only available with RKSA, PRA and CPA model options. The Peneloux volume shift is described as a function of temperature, see “The Peneloux density correction” on page 31. The three coefficients in the correlation are stored as pure component properties. Multiflash matches density/volume by adjusting the first two coefficients. However, all three may also be provided directly by the user if they are known or available from other simulation packages.

Plots

The graphic display in the matching now displays a plot of the property before and after matching.

Databanks

DIPPR

The latest version of DIPPR linked to Multiflash is now 2005. This has increased the number of components by 52. A list of the additional components is available on request.

Infodata

The number of components in Infodata has increased to 223. Those added for Multiflash 3.5 are:

2,2-dimethylhexane,

2,3-dimethylhexane,

2,4-dimethylhexane,

2,5-dimethylhexane,

3,3-dimethylhexane,

3,4-dimethylhexane,

2-methylheptane,

3-methylheptane,

4-methylheptane,

3-ethyl hexane,

2-methyloctane,

3-methyloctane,

4-methyloctane,

2,3-dimethyloctane,

2,4-dimethyloctane,

2-methylynonane,

Tetrahydrofuran

K+,

Cl-.

Physical Properties

Datum Point

The datum point for enthalpy and entropy can now be set to different bases, see “Specifying enthalpy, entropy and internal energy” on page 125. This results in an additional command line in the problem definition and makes the “Thermal properties re elements” option in the Physical Property Output menu redundant.

Molecular weight

For discrete components stored in the databanks the MW is a fixed value that normally remains unchanged, However, for petroleum fractions and polymers it is possible that the user may wish to change the value of MW. If this is amended then molar compositions will be changed to reflect this but mass compositions will not be altered.

Front-end

Toolbar Buttons

New icons have been added for calculation of the Wax Appearance Temperature and Amounts of Wax Precipitated over a temperature range. The WAT button, , allows you to calculate the wax appearance temperature for zero amount of wax, without using the fixed phase fraction option. The latter should still be used if you wish to search for the temperature at which a non-zero amount of wax forms. The button produces a table of amount of wax precipitated at a given pressure as a function of temperature, see “Wax calculations” on page 135.

Similarly icons have been added to calculate the hydrate dissociation temperature, for a given pressure,, or the hydrate dissociation pressure for a given temperature,. The calculation determines which is the most stable hydrate structure from those set in the model definition rather than the user having to define which hydrate structure they are searching for.

Graphics

The graphics package used for the phase envelope display has been upgraded to a more recent version. A consequence of this is that line colour choices will have changed.

HELP

The About Multiflash display ahs been modified to show the expiry date of your Multiflash lease if you do not have a perpetual licence.

Interfaces

The Matlab/Simulink interface is upgraded with each new Multiflash release.

GUI launched from Excel

In order to help users set up calculations in Excel there is now an option to launch the Multiflash GUI from an Excel spreadsheet. This allows the user to define a problem, including the PVT Analysis, with the GUI and the problem definition is automatically written to the spreadsheet. The User Guide to the Multiflash Excel Interface provides more details.

Installation

Users are recommended to look at the most recent Installation Guide for information on the latest drivers. MF3.5 also includes an upgraded graphics package which will be installed to replace that used with earlier versions.