Simulação de gaseificação subterrânea de combustível fóssil para a produção de gás de síntese utilizando o aspen HYSYS V8.0

Abstract

Aiming to find new ways of producing energy in a sustainable and efficient form, the present work intends to evaluate a recent hydrocarbon underground gasification model, utilizing n-haxadecane as a source of carbon for producing syngas. It was utilized the Aspen HYSYS V8.0 software to simulate an underground gasification plant, based upon the study of Alshammari and Hellgardt (2014). The feed streams of the well constituted of water and air a. The water stream (100 kg/h, 30℃, 1 atm) passed through a heater for the production of steam (~100℃, 1 atm) then it was compressed by two compressors until the final pressure of 250 bar. The air stream (79% of N2 and 21% of O2, mole) under 30 ℃, 1 atm, passed through a set of two compressors until it reached a final pressure of 250 bar. The utilized piping was comprised of 4 mild steel segments, 1000 m length, schedule 40, inner nominal diameter 50.8 mm, which transported the pressurized streams to the reservoir. A Gibbs reactor (50.000 m3, 150℃) represented the n-hexadecane reservoir, which was fed by at a 500 kg/h e 150℃ flow. The produced gases were carried to the surface through another set of 4 piping segments with the same characteristics of the first ones, then they passed through two expenders and a cooler. Ultimately the stream passed through a two-phase separator. The energy and gasification efficiencies have been analysed at different oxygen/carbon ratios (1; 1,1; 1,2; 1,3; 1,4 and 1,5); water/carbon ratios (2, 3 and 5) and the enrichment of oxygen in the injected air (21, 40, 60, 80 and 100%). The modification in the produced gas components distribution has also been analysed at different ratios (oxygen/carbon; water/carbon) in the reagents streams. It has been concluded that, although the increase in oxygen/carbon created a decrease in the gasification efficiency, the system’s energy efficiency increases due to the increase in temperature of the produced gases. Results also points out that the necessary energy to operate the plant may be balanced by the recovered energy within the produced gases; nevertheless, it is necessary to find a point at which the operational costs are minimized and both efficiencies are maximized, though they are inversely proportional. Future works may be carried out in order to investigate the influence of the changes in oxygen/water ratio as well as the effects of the well production rate to both system’s efficiencies and the analysis of kinetic models.