The ever-increasing world demand of energy predicted by the main international outlooks leads to several new challenges in the energy market. In this scenario, the natural gas is the most promising source of energy to meet the world energy request. Moreover, the increasing demand of natural gas has driven the market to the development of sub-quality, unconventional and remote gas reserves not exploited in the past. The existing technologies for gas processing are not ideal to treat these new natural gas sources because, as the acid gas content increases, the purification of natural gas becomes more and more difficult and expensive. In recent years a lot of studies have been developed to make economically feasible the production of natural gas from these reservoirs and the most promising technologies are the low-temperature ones and the transportation of natural gas in liquid phase. This work aims at studying the energy demand for the purification and liquefaction of several acid natural gas streams composed of CH4 and CO2. These streams differ from each other because of the CO2 concentration, which varies in the range 10-70 % (mol/mol). The conventional amine chemical absorption process, where Methyl-DiEthanolAmine (MDEA) is utilized as solvent, is compared with the recently patented dual pressure low-temperature purification (DPLT) technology for the CO2 removal from natural gas. Two commercial liquefaction technologies are considered in this work for the liquefaction of natural gas: the Mixed Fluid Cascade (MFC) and the Propane Precooled Mixed Refrigerant (C3MR). Both the technologies are analyzed to study if there is an advantage related to the coupling of the DPLT purification and the liquefaction of the sweet natural gas in terms of energy consumptions of the overall process. The results of the simulations developed in Aspen HYSYS® V9 (AspenTech, 2016) are utilized to carry out the energy analysis, based on the net equivalent methane method, and the exergy analysis, based on the second-law efficiency. The handouts allow assessing which is the most convenient acid gas removal technology for LNG production depending on the CO2 content in the raw natural gas.
La sempre crescente domanda energetica mondiale, predetta dai maggiori studi del settore, richiede molte nuove sfide per il mercato energetico. In questo scenario il gas naturale risulta essere la più promettente risorsa energetica. La crescente domanda di gas naturale richiede lo sfruttamento di riserve di gas naturale di bassa qualità, non convenzionali e localizzate in luoghi remoti, non considerate in passato in quanto le tecnologie di purificazione disponibili risultavano economicamente non convenienti all’aumentare del contenuto di gas acidi. Negli ultimi anni sono stati condotti diversi studi per rendere economicamente sostenibile la produzione di gas naturale da queste riserve e le tecnologie più promettenti sono le purificazioni a bassa temperatura ed il trasporto in fase liquida. L’obiettivo di questa tesi è studiare i consumi energetici per la purificazione e liquefazione di diverse correnti acide di gas naturale composte da CH4 e CO2 che differiscono l’una dall’altra per la concentrazione di CO2 che varia nell’intervallo 10-70% (mol/mol). Il processo convenzionale di assorbimento chimico ad ammine, dove la Metil-DiEtanolAmmina (MDEA) è utilizzata come solvente, è confrontato con la recentemente brevettata tecnologia “dual pressure low-temperature (DPLT) distillation” per la rimozione della CO2 dal gas naturale. Due tecnologie commerciali di liquefazione sono considerate in questo lavoro per la liquefazione del gas naturale: il processo “Mixed Fluid Cascade (MFC)” ed il processo “Propane Precooled Mixed Refrigerant (C3MR)”. Entrambe le tecnologie sono analizzate per verificare l’esistenza di un vantaggio legato alla combinazione del nuovo processo DPLT con la liquefazione del gas purificato in termini di consumi energetici dell’intero processo. I risultati delle simulazioni condotte in Aspen HYSYS® V9 (AspenTech, 2016) sono utilizzati per sviluppare l’analisi energetica, basata sul metodo del metano netto equivalente, e l’analisi exergetica, basata sull’efficienza exergetica. I risultati ottenuti permettono di definire quale sia la tecnologia di purificazione più conveniente per la produzione di LNG al variare del contenuto di CO2 nel gas naturale grezzo.
Efficient CO2 removal processes for LNG production at different CO2 concentrations in natural gas
PECILE, MASSIMILIANO
2017/2018
Abstract
The ever-increasing world demand of energy predicted by the main international outlooks leads to several new challenges in the energy market. In this scenario, the natural gas is the most promising source of energy to meet the world energy request. Moreover, the increasing demand of natural gas has driven the market to the development of sub-quality, unconventional and remote gas reserves not exploited in the past. The existing technologies for gas processing are not ideal to treat these new natural gas sources because, as the acid gas content increases, the purification of natural gas becomes more and more difficult and expensive. In recent years a lot of studies have been developed to make economically feasible the production of natural gas from these reservoirs and the most promising technologies are the low-temperature ones and the transportation of natural gas in liquid phase. This work aims at studying the energy demand for the purification and liquefaction of several acid natural gas streams composed of CH4 and CO2. These streams differ from each other because of the CO2 concentration, which varies in the range 10-70 % (mol/mol). The conventional amine chemical absorption process, where Methyl-DiEthanolAmine (MDEA) is utilized as solvent, is compared with the recently patented dual pressure low-temperature purification (DPLT) technology for the CO2 removal from natural gas. Two commercial liquefaction technologies are considered in this work for the liquefaction of natural gas: the Mixed Fluid Cascade (MFC) and the Propane Precooled Mixed Refrigerant (C3MR). Both the technologies are analyzed to study if there is an advantage related to the coupling of the DPLT purification and the liquefaction of the sweet natural gas in terms of energy consumptions of the overall process. The results of the simulations developed in Aspen HYSYS® V9 (AspenTech, 2016) are utilized to carry out the energy analysis, based on the net equivalent methane method, and the exergy analysis, based on the second-law efficiency. The handouts allow assessing which is the most convenient acid gas removal technology for LNG production depending on the CO2 content in the raw natural gas.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/142757