Multicomponent substitution combustion reaction model of hydrocarbon oxygen-containing derivatives

Hydrocarbons and their oxygen-containing derivatives are often used as fuels or fuel substitutes, most of which are prone to spontaneous combustion. During combustion, high-temperature flames and toxic gases (e.g., carbon oxides and nitrogen oxides) are produced, causing irreversible damage to the surrounding organisms, water bodies, soil, and air. Therefore, quickly and accurately assessing the consequences of accidents caused by their decomposition is a common practical problem in engineering.

This study aimed to characterize the combustion properties of hydrocarbon oxygen-containing derivatives in flammable and explosive hazardous chemicals. A substitute model incorporating multiple components of small molecules was proposed. Based on the ratio of enthalpy changes, the components and proportion coefficients for each multicomponent substitution model were determined, and a library of 120 models was constructed. The following combustion characteristic parameters were selected as indicators: the maximum net heat release rate difference of gas phase reactions, the highest temperature difference of the adiabatic flame, the flame propagation speed difference, the mean square error (MSE) of the H mole fraction, and the MSE of the O₂ mole fraction. The combustion characteristic difference library was comprehensively evaluated using the G1 and TOPSIS methods, along with an improved CRITIC comprehensive weighting approach. The index matching accuracy between small-molecule hydrocarbon substitution models and complex molecular substances was calculated. From this, the optimal substitution schemes and substitution model sets of the same type of substances were selected. Furthermore, the intersection components of the alternative model sets were used as a simple alternative to simulate the combustion reaction kinetics of complex molecular substances. The rationality of these alternative models was verified through high-temperature pyrolysis experiments. Eventually, an alternative model for the combustion reactions of large-molecule complex substances was constructed, characterizing the consequences of hazardous chemical accidents.

(1) Using the selected combustion characteristic indicators effectively identified the best alternative models. (2) The substitution models for alcohols and ethers shared essentially the same components, including: CH₄, C₂H₆, C₃H₈, and C₄H₁₀, and exhibited a very high degree of overlap in their best alternative solutions. (3) The multicomponent substitution model for furan compounds included CH₄, i-C₄H₈, and C₄H₁₀. The analysis results are in agreement with the high-temperature pyrolysis tests. (4) The best alternative model demonstrated low sensitivity to the weights of each indicator. Therefore, the intersection of the alternative models serves as a mandatory and highly reliable component.

The multicomponent, small-molecule hydrocarbon substitution model adopted does not yet encompass all categories of hydrocarbon oxygen-containing derivatives. Some results need further experimental validation. Nonetheless, the research results provide new ideas for constructing combustion reaction kinetic models of hydrocarbons and their oxygen-containing derivatives. This approach enables highly accurate prediction of the consequences of an accident involving complex mixed components (such as gasoline and diesel derived from petroleum).