Multicomponent Vapor–Liquid Equilibrium Measurement and Modeling of Ethylene Glycol, Water, and Natural Gas Mixtures at 6 and 12.5 MPa

High pressure subsea natural gas dehydration (NGD) units using ethylene glycol (MEG) absorption have been proposed. To expand the experimental database and assist design qualification, new vapor–liquid equilibrium (VLE) experimental data have been measured for a 20-component glycol–water–natural gas mixture at T = (288–323) K, p = (6.0, 12.5) MPa, and wMEG,feed = (90, >99.8) %. MEG, H2O, CO2, N2, and alkane (methane to n- and i-pentane) phase distributions have been quantified. Experimental uncertainty ranges from ±2–42%, with the greatest uncertainty for the quantification of trace components. Experimental results are modeled using the Cubic-Plus-Association (CPA) equation of state. Overpredictions (∼9%) are observed for the water content of the vapor phase. CO2 is shown to have a large effect on yMEG, leading to modeling deviations in the order of 65%. A relatively accurate prediction of the natural gas partition coefficients was observed for major components C1–C3 and CO2, with modeling errors ranging from 5% for methane to 10% for CO2. More significant deviations were observed for trace components, with the largest deviation of 73% N2. The CPA model provides both satisfactory and conservative results suitable for use in NGD process designs. On the basis of this work, operation at subsea conditions would significantly improve dehydration capability

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing

The objective of this work has been to study equilibrium and non equilibrium situations during high pressure gas processing operations with emphasis on utilization of the high reservoir pressure. The well stream pressures of some of the condensate and gas fields in the North Sea are well above 200 bar. Currently the gas is expanded to a specified processing condition, typically 40-70 bar, before it is recompressed to the transportation conditions. It would be a considerable environmental and economic advantage to be able to process the natural gas at the well stream pressure. Knowledge of thermodynamic- and kinetic properties of natural gas systems at high pressures is needed to be able to design new high pressure process equipment. Nowadays, reactive absorption into a methyldiethanolamine (MDEA)solution in a packed bed is a frequently used method to perform acid gas treating. The carbon dioxide removal process on the Sleipner field in the North Sea uses an aqueous MDEA solution and the operation pressure is about 100 bar. The planed carbon dioxide removal process for the Snøhvit field in the Barents Sea is the use of an activated MDEA solution. The aim of this work has been to study high-pressure effects related to the removal of carbon dioxide from natural gas. Both modelling and experimental work on high-pressure non-equilibrium situations in gas processing operations have been done. Few experimental measurements of mass transfer in high pressure fluid systems have been published. In this work a wetted wall column that can operate at pressures up to 200 bar was designed and constructed. The wetted wall column is a pipe made of stainless steel where the liquid is distributed as a thin liquid film on the inner pipewall while the gas flows co- or concurrent in the centre of the pipe. The experiments can be carried out with a well-defined interphase area and with relatively simple fluid mechanics. In this way we are able to isolate the effects we want to study in a simple and effective way. Experiments where carbon dioxide was absorbed into water and MDEA solutions were performed at pressures up to 150 bar and at temperatures 25 and 40°C. Nitrogen was used as an inert gas in all experiments. A general non-equilibrium simulation program (NeqSim) has been developed. The simulation program was implemented in the object-oriented programming language Java. Effort was taken to find an optimal object-oriented design. Despite the increasing popularity of object-oriented programming languages such as Java and C++, few publications have discussed how to implement thermodynamic and fluid mechanic models. A design for implementation of thermodynamic, mass transfer and fluid mechanic calculations in an object-oriented framework is presented in this work. NeqSim is based on rigorous thermodynamic and fluid mechanic models. Parameter fitting routines are implemented in the simulation tool and thermodynamic-, mass transfer- and fluid mechanic models were fitted to public available experimental data. Two electrolyte equations of state were developed and implemented in the computer code. The electrolyte equations of state were used to model the thermodynamic properties of the fluid systems considered in this work (non-electrolyte, electrolyte and weak-electrolyte systems). The first electrolyte equation of state (electrolyte ScRK-EOS) was based on a model previously developed by Furst and Renon (1993). The molecular part of the equation was based on a cubic equation of state (Scwarzentruber et.al. (1989)’s modification of the Redlich-Kwong EOS) with the Huron-Vidal mixing rule. Three ionic terms were added to this equation – a short-range ionic term, a long-range ionic term (MSA) and a Born term. The thermodynamic model has the advantage that it reduces to a standard cubic equation of state if no ions are present in the solution, and that public available interaction parameters used in the Huron-Vidal mixing rule could be utilized. The originality of this electrolyte equation of state is the use of the Huron-Vidal mixing rule and the addition of a Born term. Compared to electrolyte models based on equations for the gibbs excess energy, the electrolyte equation of state has the advantage that the extrapolation to higher pressures and solubility calculations of supercritical components is less cumbersome. The electrolyte equation of state was able to correlate and predict equilibrium properties of CO2-MDEA-water solutions with a good precision. It was also able to correlate high pressure data of systems of methane-CO2-MDEA and water. The second thermodynamic model (electrolyte CPA-EOS) evaluated in this work is a model where the molecular interactions are modelled with the CPA (cubic plus association) equation of state (Kontogeorgios et.al., 1999) with a classical one-parameter Van der Walls mixing rule. This model has the advantage that few binary interaction parameters have to be used (even for non-ideal solutions), and that its extrapolation capability to higher pressures is expected to be good. In the CPA model the same ionic terms are used as in the electrolyte ScRK-EOS. A general non-equilibrium two-fluid model was implemented in the simulation program developed in this work. The heat- and mass-transfer calculations were done using an advanced multicomponent mass transfer model based on non-equilibrium thermodynamics. The mass transfer model is flexible and able to simulate many types of non-equilibrium processes we find in the petroleum industry. A model for reactive mass transfer using enhancement factors was implemented for the calculation of mass transfer of CO2 into amine solutions. The mass transfer model was fitted to the available mass transfer data found in the open literature. The simulation program was used to analyse and perform parameter fitting to the high pressure experimental data obtained during this work. The mathematical models used in NeqSim were capable of representing the experimental data of this work with a good precision. From the experimental and modelling work done, we could conclude that the mass transfer model regressed to pure low-pressure data also was able to represent the high-pressure mass transfer data with an acceptable precision. Thus the extrapolation capability of the model to high pressures was good. For a given partial pressure of CO2 in the natural gas, calculations show a decreased CO2 capturing capacity of aqueous MDEA solutions at increased natural gas system pressure. A reduction up to 40% (at 200 bar) compared to low pressure capacity is estimated. The pressure effects can be modelled correctly by using suitable thermodynamic models for the liquid and gas. In a practical situation, the partial pressure of CO2 in the natural gas will be proportional to the total pressure. In these situations, it is shown that the CO2 capturing capacity of the MDEA solution will be increased at rising total pressures up to 200 bar. However, the increased capacity is not as large as we would expect from the higher CO2 partial pressure in the gas. The reaction kinetics of CO2 with MDEA is shown to be relatively unaffected by the total pressure when nitrogen is used as inert gas. It is however important that the effects of thermodynamic and kinetic non- ideality in the gas and liquid phase are modelled in a consistent way. Using the simulation program NeqSim – some selected high-pressure non-equilibrium processes (e.g. absorption, pipe flow) have been studied. It is demonstrated that the model is capable of simulating equilibrium- and non-equilibrium processes important to the process- and petroleum industry

Experimental study of accelerators in floor concrete mixture under cold climatic conditions

Denne masteroppgaven omhandler eksperimentelle undersøkelser av akselererende tilsetningsstoffer i en typisk gulvbetongresept. Undersøkelsene ble gjennomført vinteren 2017/2018, i reelle norske vintertemperaturer. Formålet har vært å finne ut hvilke akselererende tilsetningsstoffer som ga best effekt på områdene avbindingstid, glattetidspunkt, bearbeidbarhet og tidligfasthet. I tillegg er det økonomiske aspektet ved bruk av akselererende tilsetningsstoffer blitt belyst. For å skape et godt grunnlag for undersøkelsene, ble det gjennomført et grundig litteratursøk. Dette ga dybdekunnskap om temaet. Undersøkelsesmetodene har gått ut på laboratorie- og feltundersøkelser, både med metoder gitt av Norsk Standard, og empiriske metoder gitt av veiledere og utgitte publikasjoner om gulvbetong. Tre tester med totalt 15 betongresepter ble utført. Hver test har hatt en referanseresept uten akselererende tilsetningsstoffer, som sammenligningsgrunnlag for de andre reseptene. De andre reseptene har bestått av den samme referanseresepten, men med forskjellige kombinasjoner av tilsetningsstoffer. Tilsetningsstoffene som er brukt er Mapefast HA, Mapefast SA, Mapefast R, Mapefast Ultra N og Master X-Seed 100. I litteraturen fremkommer det at herdnings- og størkningsakselererende tilsetningsstoffer gir positiv effekt på flere områder, men dette baseres på undersøkelser gjennomført i laboratoriekontrollerte forhold. Resultatene i denne oppgaven, viser at de akselererende tilsetningsstoffene gir gode resultater på alle områder, men ikke alle er like effektive i kaldt klima. Master X-Seed 100 tilsetningsstoffet viste seg samlet sett å gi de beste resultatene. Konklusjonen er at glattetidspunktet og avbindingstiden kan framskyndes. Metoden benyttet for å bestemme glattetidspunktene, førte til glattetidspunkter lenge før avbindingstidene var ferdig. Utviklingen av trykkfasthet øker ved bruk av akselererende tilsetningsstoffer, og betongens konsistens kan styres rimelig nøyaktig med bruk av retarderende tilsetningsstoff. Økonomisk gir de akselererende tilsetningsstoffene kostnadsbesparelser, og de gir større besparelser på mindre prosjekter kontra større prosjekter.This master thesis investigates the effect of accelerating additives, used in a typical concrete floor mixture. The investigations were conducted in the winter 2017/2018, in average Norwegian winter conditions. The purpose of the thesis was to determine which accelerating additives are most effective regarding the setting time, the brushing time, workability and early-strength accumulation for the concrete. In addition, the economic profitability of using accelerating additives in concrete has been considered. In order to provide a good basis for the investigations, a thorough literature research was conducted. This resulted in gaining theoretical knowledge about the topic. The investigation methods have consisted of laboratory and field studies, both using methods provided by Norwegian Standard, and empirical methods provided by supervisors and publications on floor concrete. Three tests with a total of 15 concrete mixtures were executed. Each test had a reference mixture without accelerating additives, as a basis for comparison to the other mixtures. The other mixtures have consisted of the same reference mixture, with different combinations of additives. The additives used are Mapefast HA, Mapefast SA, Mapefast R, Mapefast Ultra N and Master X-Seed 100. The literature study has provided information about hardening and setting accelerators and their positive effect in several areas, but these studies are based on tests carried out in laboratory-controlled conditions. The results in this thesis, show that the accelerating additives enhance the behaviour of the concrete mixture, but not all are as effective in cold climate conditions. Master X-Seed 100 additive was proven to be the most efficient. The conclusion is that both the brushing time and the setting time have been accelerated when using additives. The method used to determine the brushing time, lead to brushing time long before the setting time. The compressive strength increases, and the consistency can be controlled quite accurately with the use of retardant additives. Regarding cost factor, the accelerating additives provide cost savings, but greater savings are found on smaller then in larger projects.M-B