Lean Flammability Limits of Syngas/Air Mixtures at Elevated Temperatures and Pressures

Abstract

New experimental results for lean flammability limits (LFLs) of syngas/air (H2/CO/air) mixtures have been obtained at temperatures up to 200 °C and pressures up to 9 bar. ASTM Standard E918 (1983) provided the framework for tests at these elevated conditions, using a 1-L pressure-rated test cylinder in which the fuel–air mixtures were prepared and then ignited. The purpose for characterizing the flammability limits for these gaseous mixtures is to facilitate development of appropriate procedures for the safe industrial use of syngas, which contains large quantities of hydrogen and carbon monoxide gas. The LFLs for each gas mixture are found to decrease linearly with increasing temperature at all test pressures. The LFL results at atmospheric pressure are consistent with previous flammability studies, while those at elevated pressures represent new flammability data. An increase in the initial test pressure results in an increase of the LFLs for each test mixture, which also serves to address the lack of syngas/air flammability data at elevated pressures. An empirical formula is derived that allows for the calculation of the LFLs of all syngas/air test mixtures in the temperature and pressure range of the current study in an effort to promote the ease of use in practical applications. Predicted LFL values obtained using Le Chatelier’s mixing rule and an appropriate choice for the lower flammability limit of pure carbon monoxide are consistent with the experimentally determined values near ambient conditions of temperature and pressure.

Flammability Limits: A Comprehensive Review of Theory, Experiments, and Estimation Methods

“…In this table, the emphasis is on experimental work in which the FLs were determined with vessels of different volumes and/or geometries. As observed in Figure , there are 73 works in which cylindrical vessels were used, ,,,,,,− 62 works in which spherical vessels were used, ,,,,− ...…”

“…General characteristics of most common experimental equipment used to determine the flammability limits. (a) Experimental works with cylindrical vessels. ,,,,,,− (b) Experimental works with spherical vessels. ,,,,− …”

Flammability Limits of Combustible Gases at Elevated Temperatures and Pressures: Recent Advances and Future Perspectives

“…The flammability limits of hydrogen, ,, hydrogen/hydrocarbons, hydrogen/carbon monoxide, ,,,,, and hydrogen/carbon monoxide/methane mixtures have been studied experimentally at high temperatures and pressures. In contrast to hydrogen and its mixtures, the flammability limit of ammonia has rarely been studied.…”

“…They found similar results to previous studies, showing an increase in the flammable range (increase in UFL; the LFL decreases as the initial test pressure increases). However, Jaimes et al , found that the lower flammability limits of each mixture ratio of hydrogen/carbon monoxide gradually increased with the initial pressure because the initial pressure had an important influence on the elongation rate of the flame. The initial pressure affects the elongation rate of the flame and then affects the propagation form of the flame.…”

An Investigation of the Kinetic Modeling and Ignition Delay Time of Methanol—Syngas Fuel

“…This method can not only recycle the exhaust heat, but also enable the engine to be closer to the constant volume cycle, and, thus, the thermal efficiency of the engine is improved (Ji et al, 2013). In addition, dissociated methanol gas is rich in hydrogen, and mixing hydrogen with a hydrocarbon fuel for combustion can increase the flame speed (Zhao et al, 2019), and extend the lean-burn limit (Jaimes et al, 2018). Lean combustion enables the fuel to burn completely, which further increases the thermal efficiency, and may reduce the emissions of CO (Liu and Dumitrescu, 2019).…”