Modeling of the Coldfinger Water Exhauster for Advanced TEG Regeneration in Natural Gas Dehydration
Author
Romero Logrono, Iveth Alexandra
Term
4. term
Education
Publication year
2019
Submitted on
2019-06-07
Pages
48
Abstract
Naturgas indeholder vand, som skal fjernes for at undgå korrosion og driftsproblemer. Triethylenglycol (TEG) er en væske, der bruges til at tørre naturgas, men den virker bedst, når den selv er meget ren. Regenerering er processen, hvor vand fjernes fra brugt TEG, så den kan bruges igen. Coldfinger er en regenereringsteknologi, der er rapporteret til at kunne øge TEG-renheden til over 99,8 vægtprocent, men der mangler en klar, begrebsmæssig beskrivelse af, hvordan udstyret virker. Denne afhandling præsenterer en enkel metode til at modellere Coldfinger. I modellen repræsenteres Coldfinger som to teoretiske ligevægts-trin, der opererer ved forskellige temperaturer og med intern recirkulation af damp. Vi gennemfører simuleringer, hvor vi varierer top-temperaturen, forholdet for intern recirkulation og mængden af tør gas, der injiceres som strippende gas (en tør gas, der hjælper med at fjerne vanddamp). Vi undersøger også køleeffekten af Coldfinger ved at beregne den varme, systemet udveksler, og hvordan det påvirker den opnåede TEG-renhed. Først analyseres en forenklet tre-komponent blanding for at forstå principperne. Derefter implementeres den foreslåede Coldfinger-model i regenereringstrinnet i en egentlig gasdehydrering med et multikomponent-system. Som reference sammenlignes resultaterne med en konventionel enkelt-trins stripping-proces. Resultaterne viser, at TEG kan regenereres til omkring 99,9 vægtprocent ved at injicere små mængder tør gas, betydeligt mindre end i almindelig forbedret TEG-regenerering med gasstripping. Dele af arbejdet blev præsenteret på den 14. International Congress on Chemical and Process Engineering i Bologna, Italien, 26.–29. maj 2019, og publiceret i tidsskriftet Chemical Engineering Transactions.
Natural gas contains water that must be removed to prevent corrosion and operating issues. Triethylene glycol (TEG) is a liquid used to dry natural gas, and it works best when it is very pure. Regeneration is the step that removes water from used TEG so it can be reused. Coldfinger is a TEG regeneration technology reported to raise TEG purity above 99.8 wt.%, but clear conceptual models of how the unit operates have been lacking. This thesis presents a straightforward way to model the Coldfinger. In the model, the Coldfinger is represented as two theoretical equilibrium stages operating at different temperatures with internal vapor recirculation. We run simulations that vary the top temperature, the internal recirculation ratio, and the amount of dry gas injected for stripping (dry gas used to sweep out water vapor). We also assess the cooling effect of the Coldfinger by quantifying the heat exchanged in the system and linking it to the purity levels achieved. We first test the concept using a simplified three-component mixture, then implement the proposed Coldfinger model in the TEG regeneration step of a full gas dehydration unit with a multicomponent system. As a benchmark, we compare performance to a conventional single-stage stripping process. The results show that TEG can be regenerated to about 99.9 wt.% by injecting small amounts of dry gas, much less than in typical enhanced TEG regeneration by gas stripping. Parts of this work were presented at the 14th International Congress on Chemical and Process Engineering in Bologna, Italy (May 26–29, 2019) and published in Chemical Engineering Transactions.
[This abstract was generated with the help of AI]
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