Rich Oil Cracker Design Based On RQL Principle

Currently, with the wide applications of gas turbines and the increasingly serious environmental pollution problems, the pollutant emissions of gas turbines and the need of environmental protection is more and more obvious, therefore the low pollution emissions combustion has became one of the central topics of gas turbines combustion technology. RQL（Rich-burn / Quick-quench / Lean-burn） combustion technology is the leader of many low emissions combustion technologies, but there are still some shortcomings which are, such as,difficulty of cooling and combustion organization in oil-rich combustion zone. Therefore, for the above problems, it carried out the following research works in this paper:（1） According to the working principle of the RQL combustion chamber, the oil-rich combustion zone was reformed, the total equivalence ratio of the oil-rich cracker with above 10 was designed. The simulated fuel of the gas turbine was n-heptane, and taking advantage of the endothermic cracking characteristics of n-heptane could, on one hand, control the range of the core high temperature and reduce the overall temperature level of the cracker, on the other hand,it is easy to organize the second combustion when the endothermic large molecules n-heptane pyrolysised into the small molecules of gaseous mixtures.（2） In order to take advantage of the endothermic cracking characteristics of n-heptane,the low temperature reaction process of the n-heptane during the reaction, the reaction process of large molecules pyrolysising into smaller molecules and the high-temperature reaction process were analyzed in the paper, and the framework of the mechanism was built,the model of a simplifying n-heptane chemical kinetics was built based on it. With CHEMKIN-PRO, the simplified mechanism built, the detailed n-heptane reaction mechanism and the known simplified n-heptane mechanism were compared to verify their simulated accuracy under the design condition of the paper. The NOx reaction mechanism was added in the chosen model to construct the n-heptane reaction mechanism required finally.（3） According to the known conditions, the one-dimensional design was made with CHEMKIN-PRO to analyze the main parameters of affecting the n-heptane combustion pyrolysis in the cracker under the ideal condition and determine the basic geometry sizes of the cracker; afterwards, many cracker cases were designed and these kinds of structures of combustion performance ware simulated numerically with Fluent. The results showed that in the first case, it could meet the basic need of combustion, but increasing the amount of intake air or oil would both cause the temperature level of the wall and outlet beyond the material restriction; in the second case, the usage of the basic concept of stratified combustion of oil and gas, the oil-rich combustion of the core oil road and the endothermic pyrolysis way of the outer oil road could control the range of the core high temperature zone well and lower the wall temperature, but its main drawback is the amount of the intake air is small, and the capacity of processing fuel is lower; in the third case, the way of oil layered was still used, a the single air inlet was used, its intake air amount is large, the capacity of dealing with fuel is higher, but the intake pressure is a little bit larger. Ultimately the second case was chosen as the cracker model.（4） The way of the CFD coupling simplified reaction mechanism was used to simulate the combustion of the two-dimensional cracker model and the endothermic cracking condition of the n-heptane, and the short carbon chain components, which is like CH₄、C₂H₄、C₃H₄,was monitored in the outlet to verify the feasibility of cracker. The conditions of intake oil and air were changed, and the variation regulation of the cracker outlet components was examined and the effect of the variation of the equivalence ratio to the temperature distribution of the cracker was most obvious.（5） The three-dimensional cracker model was districted partly with ENERGICO, the ERN network diagram was created, the detailed reaction mechanism of the n-heptane was imported,the combustion emissions performance was calculated, and the emissions performance of the two-dimensional coupling simplified mechanical calculation was compared and analyzed to verify the feasibility of analyzing the combustor emissions performance with ENERGICO.