| Oxy-coal combustion steam system of near-zero emissions（OCCSS） is a new type of near zero emission power generation system proposed by our research group based on China’s energy structure, which uses coal-based syngas or demineralized coal as fuel. The combustion process has the characteristics of high temperature, high pressure, high water vapor concentration and high oxygen concentration. The key point of this system is to study the combustion characteristics under the complex conditions, as an important part of the combustion characteristics, the study of the flammable limit of syngas has important value for the design and operation of the burner.To meet the experimental requirements, a 20 L spherical explosive device is built according to the related standards. And then the experiment system is debugged and tested to verify the security and reliability. In this study, a 3% pressure rise is used as the criterion which is determined by experiment, and the reliability of the criterion is verified by experiments.Firstly, the influence of the preheating temperature on the LFL of syngas of different components is studied, result shows that the LFL decrease with the increase of preheating temperature. The change trend is more obvious when the temperature is low and the LFL has a liner change when the preheating temperature is more than 150℃. Then, the variation of the LFL with the composition is studied, result shows whether in pure oxygen or with water vapor dilution, the LFL decreases with the increase of H2 content. Fitting the experimental results with the quadratic curve, the fitting degree is above 0.95. In addition, it is proved that when the H2 content is lower, the water vapor has a greater influence on the LEL. Finally the influence of the addition of N2 and H2 O on the LFL of H2/CO mixture is studied, result shows that the LFL began to significantly increase with the increase of N2 concentration when the concentration of N2 is more than 60%. However, with the increase of water vapor, the LFL has different change law with the increase of concentration of the water vapor: when the concentration of water vapor is less than 30%, the LFL increases linearly with the concentration of water vapor; when the water vapor concentration is between 30% and 60%, the LFL remained unchanged; when the concentration of water vapor is more than 60%, the LFL increases again. In addition compared with N2, the influence of water vapor on the LFL is obviously larger, especially when the concentration is lower.In this paper, Le Chatelier rule and the method based on calculated adiabatic flame temperature are used to predict the LFL of the H2/CO mixture. In this paper, we adjust the selection of L1 and L2 in the Le Chatelier formula according to the characteristics of this study and quadratic regression curve is used to select the adiabatic flame temperature. The accuracy is verified based on the experiment datas. The results show that both of the two methods are useful to predict the LFL of H2/CO mixture, the error is less than 10%, the gaps in this field is filled by this research. |
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