Derawi, Samer

Der har i den senere tid været en stigende interesse i den petrokemiske industri for at modellere fordelingen af produktionskemikalier, som f.eks. gashydratinhibitorer, korrosionsinhibitorer, opløsningsmidler osv. mellem råolie og vand. Grundlæggende kræver dette en termodynamisk model enten i form af en aktivitetskoefficientmodel eller en tilstandsligning. Vort mål i denne afhandling er at gennemgå og udvikle sådanne modeller som gør det muligt at beskrive kvalitativt såvel som kvantitativt faseligevægte for multikomponent, multifase systemer indeholdende ikke-polære, polære, og associerende komponenter. I kapitel 1 præsenteres baggrunden og hovedformålet med denne afhandling. I kapitel 2 udføres en omfattende gennemgang af anvendelsen af gruppebidragsmodeller såsom adskillige UNIFAC versioner samt den såkaldte AFC (forkortelse af: Atom og Fragment Bidrag) korrelationsmodel til owP (oktanol-vand fordelingskoefficient) beregninger. UNIFAC er en aktivitetskoefficientmodel, medens AFC er en model der specifikt er udviklet til owP beregning. Fem forskellige udgaver af UNIFAC samt AFC korrelationsmodellen sammenlignes med hinanden og med eksperimentelle data. Omfanget af gruppebidragsmodellernes anvendelighed til owP forudsigelse diskuteres og der drages generelle konklusioner. Der udføres en grundig analyse af modellerne som indbefatter residual plot samt numeriske og grafiske sammenligninger. Det konkluderes, at gruppebidragsbegrebet muligvis ikke er helt egnet til at beskrive stærkt asymmetriske blandinger og specielt vandige opløsninger indeholdende komplekse multifunktionelle kemikalier. I kapitel 3 diskuteres eksperimentelle målinger af væske-væske ligevægtsdata for 7 binære glykol-kulbrinte blandinger i temperaturområdet 32 °C til 80 °C og med et tryk svarende til 1 bar. De målte systemer er monoethylenglykol + heptan, methylcyclohexan + hexan, propylenglykol + heptan, diethylenglykol + heptan, triethylenglykol + heptan samt tetraethylenglykol + heptan. De opnåede eksperimentelle data blev korreleret med NRTL modellen samt to forskellige udgaver af UNIQUAC ligningen. NRTL modellen samt en af UNIQUAC ligningen (UQ 4) har et lineært temperaturafhængigt interaktionsparameterled, medens den anden UNIQUAC ligning (UQ 2) har et interaktionsparameterled der er temperaturuafhængigt. Der var en ganske god overensstemmelse mellem de eksperimentelle data og de 2 temperaturafhængige modeller med en afvigelse i sammensætningen i begge faser på 3 % for både NRTL og UQ 4, hvorimod afvigelsen er på 15 % for UQ 2. Disse resultater viser nødvendigheden af temperaturafhængigheden i modellerne. CPA tilstandsligningen er en termodynamisk model som kombinerer den velkendte kubiske SRK tilstandsligning med et associationsled foreslået af Wertheim. Dette associationsled er typisk anvendt i de forskellige versioner af SAFT. CPA har vist sig at være en vellykket model for faseligevægtsberegninger for blandinger indeholdende vand, kulbrinter og alkoholer. I kapitel 4 anvendes CPA for første gang til væske-væske ligevægtsberegninger for binære blandinger indeholdende glykoler og kulbrinter. Det vises, at man kan opnå en udmærket korrelation med kun en enkel interaktionsparameter for hvert binært system. Det vises, at korrelationsproceduren såvel som kvaliteten af de eksperimentelle data spiller en afgørende rolle i parameterestimeringsmetoden og er derfor grundigt diskuteret. I kapitel 5 er anvendelsen af CPA tilstandsligningen blevet udvidet til blandinger som indeholder krydsassocierende komponenter såsom glykoler og vand. I dette tilfælde har man brug for kombinationsregler i associationsleddet af CPA tilstandsligningen for krydsassociations- energi og volumen parametrene. Forskellige typer af kombinationsregler har været foreslået igennem de sidste år for associationsmodeller såsom SAFT. Disse er afprøvet i dette arbejde for CPA modellen i form af deres korrelations- og forudsigelsesevne for damp-væske ligevægtsberegninger for glykoler-vand blandinger. Sammenligninger med SRK er også inkluderet. Det vises, at den aritmetiske kombinationsregel for krydsassociationsenergi parameteren samt den geometriske for krydsassociationsvolumen parameteren overordnet giver de bedste resultater for krydsassocierende blandinger indeholdende glykoler og vand. Ydermere viser indledende resultater at CPA modellen kan anvendes til at forudsige multikomponent, multifaseligevægte for glykol/vand/kulbrinter systemer udelukkende baseret på binære interaktionsparametre. I kapitel 6 er konklusioner og forslag for fremtidigt arbejde præsenteret.In recent years, there has been an increasing interest of the petrochemical industry in modeling of the partitioning of production chemicals e.g. gas hydrate inhibitors, corrosion inhibitors, solvents etc. between the crude oil and water. This requires basically a thermodynamic model either in terms of an activity coefficient model or an equation of state. Our target in this thesis is to review and develop such models capable of describing qualitatively as well as quantitatively phase equilibria in multicomponent multiphase systems containing non-polar, polar, and associating compounds. The background and main targets for this thesis are presented in Chapter 1. In Chapter 2, a comprehensive review of the application of group contribution (GC) models such as various forms of UNIFAC and the so-called AFC (Atom and Fragment Contributions) correlation model for Pow (octanol-water partition coefficient) calculations has been carried out. UNIFAC is an activity coefficient model while AFC is a model specifically developed for Pow calculations. Five different versions of UNIFAC and the AFC correlation model have been compared with each other and with experimental data. The range of applicability of the GC models to Pow is discussed, and general conclusions are obtained. A thorough analysis of the models was conducted including residual plots and numerical and graphical comparisons. We conclude that the group-contribution concept has possibly exhausted its applicability to account for highly asymmetric systems, especially for aqueous solutions with complex poly-functional chemicals. In Chapter 3, liquid-liquid equilibrium data for 7 binary glycol-hydrocarbon systems have been measured in the temperature range 32 °C to 80 °C and pressure equal to 1 bar. The measured systems are monoethylene glycol + heptane, methylcyclohexane, hexane, propylene glycol + heptane, diethylene glycol + heptane, triethylene glycol + heptane, and tetraethylene glycol + heptane. The data obtained were correlated with the NRTL model and two different versions of the UNIQUAC equation. The NRTL model and one of the UNIQUAC equations (UQ 4) have a linear temperature-dependent interaction parameter term, while the other UNIQUAC equation (UQ 2) has an interaction parameter that is independent of the temperature. There was a fairly good agreement between the experimental data and the two temperature dependent models with an average deviation in the composition for both phases of 3 % for both NRTL and UQ 4 while deviation is 15 % for UQ 2. These results indicate the necessity of using the linearly dependent interaction parameters. The CPA equation of state is a thermodynamic model, which combines the well–known cubic SRK equation of state and the association term proposed by Wertheim, typically employed in models like the various variations of SAFT. CPA has been shown in the past to be a successful model for phase equilibria calculations for systems containing water, hydrocarbons and alcohols. In Chapter 4, CPA is applied for the first time to liquid-liquid equilibria for systems containing glycols and hydrocarbons. It is shown that excellent correlation is achieved with solely a single interaction parameter per binary system. The correlation procedure as well as the nature of the experimental data play a crucial role in the parameter estimation and they are thus extensively discussed. In Chapter 5, the application of the CPA equation of state is extended to mixtures containing cross-associating compounds such as glycols and water. In this case, combining rules are required in the association term of CPA for the cross-association energy and volume parameters. Different types of such combining rules have been suggested over the past years for association models such as SAFT. These are tested in this work for CPA in terms of their correlation and prediction capabilities for vapor-liquid equilibria of glycol-water systems. Comparisons with SRK are also provided. It was found, that the arithmetic mean combining rule for the cross-association energy parameter and the geometric mean for the cross-association volume parameter provide overall the best results for cross-associating systems containing glycols and water. Moreover, preliminary results show that the CPA model can be used to predict multi-component, multiphase equilibria for glycol/water/hydrocarbon mixtures based solely on binary interaction parameters. In Chapter 6, conclusions and suggestions for future work are presented

Online Research Database In Technology

Modeling of Phase Equilibria Containing Associating Fluids

http://orbit.dtu.dk/ws/files/5653725/PhD_Derawi.pdf

Modeling of Phase Equilibria Containing Associating Fluids

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Online Research Database In Technology