Thermodynamics Irreversibilities Analysis of Oxy-Fuel Diffusion Flames: The Effect of Oxygen Concentration.

Huibo Yan,Zhongnong Zhang,Yuanke Zhou,Guangtong Tang,Chun Lou,Lujiang Li,Chaoyang Wang

doi:10.3390/e24020205

Abstract

In studies on the combustion process, thermodynamic analysis can be used to evaluate the irreversibility of the combustion process and improve energy utilization efficiency. In this paper, the combustion process of a laminar oxy-fuel diffusion flame was simulated, and the entropy generation due to the irreversibilities of the radiation process, the heat conduction and heat convection process, the mass diffusion process, and the chemical reaction process was calculated. The effect of the oxygen concentration in the oxidizer on the entropy generation was analyzed. The results indicated that, as the oxygen concentration in the oxidizer increases, the radiative entropy generation first increases and then decreases, and the convective and conductive entropy generation, the mass diffusion entropy generation, the chemical entropy generation, and the total entropy generation gradually increase.

Highlights

To mitigate the greenhouse effect caused by the emission of carbon dioxide (CO2 ), oxy-fuel combustion technology has been investigated and developed [1,2]
In an oxycombustion process, where a pure or highly enriched oxygen (O2 ) stream is mixed with recycled flue gas, the nitrogen (N2 ) is replaced by CO2, and the oxygen concentration in the flue gas is about 30%, higher than that in air combustion
From Case 1 to Case 5, the oxygen concentration in the oxidizer gradually increased from 30% to 50%

Summary

Introduction

To mitigate the greenhouse effect caused by the emission of carbon dioxide (CO2 ), oxy-fuel combustion technology has been investigated and developed [1,2]. Due to the significant difference in the chemical and physical properties between CO2 and N2 , the efficiency of oxy-fuel combustion and traditional air combustion is different, especially when oxygen concentration is enhanced. It is very useful and important to evaluate energy conversion efficiency in terms of thermodynamics second-law analysis, in which entropy generation is a crucial parameter [3]. Som et al reviewed fundamental investigations on thermodynamics irreversibilities and exergy analysis during combustion processes of various kinds of fuels, and summarized that the local entropy generation in a combustion process is mainly due to the irreversibility of internal heat and mass transfers and to chemical reactions [4]. Yapıcı et al calculated local entropy generation rates in laminar methane-air (CH4 -air) flames and compared the irreversibility of various processes [5]

Methods

Results

Conclusion