Semra Özkan

Energy and exergy analyses of a steam reforming process for hydrogen production

Hydrocarbon steam reforming is an important process for hydrogen production. In petroleum refineries, steam reforming is most commonly used for hydrogen production from naphtha and light hydrocarbon gases (methane, ethane and propane). Since the hydrocarbon steam reforming system is one of the highest energy intensive systems in a petroleum refinery it should be directed to a more efficient use of energy through better process design and analysis, based on accurate thermodynamic analysis via applications of the first and second laws of thermodynamics, and thus, applications of exergy concept. The purpose of this study is to perform the energy and exergy analyses of a natural gas steam reforming process presently in operation at TUPRAS refinery in Yzmit, Turkey. The energy and exergy efficiencies of the steam reformer were found to be 94.33% and 78.23%, respectively, and the lowest exergy efficiency was obtained as 66.81% for steam generator.

Application for pinch design of heat exchanger networks by use of a computer code employing an improved problem algorithm table

In this work, the methods used in pinch design were applied to a heat exchanger network with the aid of an improved problem algorithm table. This table enables one to compose composite and grand composite curves in a simplified way. A user friendly computer code entitled DarboTEK, compiled by using Visual Basic 3.0, was developed for the design of integrated heat exchanger networks and estimation of related capital costs. Based on the data obtained from the TUPRAŞ petroleum refinery at Izmit, a retrofit design of heat exchanger networks was accomplished using DarboTEK. An investment of

DESORPTION OF ETHYL ACETATE-WATER MIXTURE BY USING CROSS-LINKED POLY(VINYLALCOHOL) MEMBRANE AND COMPARISON OF RESULTS WITH PERVAPORATION

3,576,627 is needed which will be paid back in 1.69 years simply by energy conservation due to heat integration.

Pervaporation separation of ethyl acetate–ethanol binary mixtures using polydimethylsiloxane membranes

In this study using poly(vinylalcohol) (PVOH) membranes cross-linked with tartaric acid (Tac) desorption experiments were performed for selected concentrations of binary ethyl acetate (EtAc)-water mixture at temperatures of 30°, 40°, and 50°C to determine sorption of components. Sorption values measured were compared with those estimated by the Flory-Huggins approach. Additionally, desorption results were compared with pervaporation results of another study in terms of solution-diffusion theory, and the effect of thermodynamic interactions on selective transport of the binary mixture and membrane system was investigated. The results obtained show that selective transport of EtAc-water mixture was influenced by increasing temperature and water content in the feed. It is shown that preferential sorption is more effective for pervaporation selectivity than diffusion selectivity.