A machine-learning reduced kinetic model for H2S thermal conversion process

H2S is becoming more and more appealing as a source for hydrogen and syngas generation. Its hydrogen production potential is studied by several research groups by means of catalytic and thermal conversions. While the characterization of catalytic processes is strictly dependent on the catalyst adopted and difficult to be generalized, the characterization of thermal processes can be brought back to wide-range validity kinetic models thanks to their homogeneous reaction environments. The present paper is aimed at providing a reduced kinetic scheme for reliable thermal conversion of H2S molecule in pyrolysis and partial oxidation thermal processes. The proposed model consists of 10 reactions and 12 molecular species. Its validation is performed by numerical comparisons with a detailed kinetic model already validated by literature/industrial data at the operating conditions of interest. The validated reduced model could be easily adopted in commercial process simulators for the flow sheeting of H2S conversion processes.

Mathematical modeling and multiobjective optimization complex catalyst hydroalumination reaction of olefins with diisobutylaluminium hydride

A mathematical model for the catalyst hydroalumination reaction of olefins with diisobutylaluminium hydride has been developed. In solving the direct kinetic problem applies multi-step method Gere variable order. When solving systems of ordinary differential equations in chemical kinetics, it is necessary to fulfill the balance relations at each sampling point. That ensures the fulfillment of the law of conservation of matter and the convergence of the numerical method. For the catalytic reaction of hydroalumination olefins in the presence of the organoaluminum compound diisobutylaluminum hydride, the problem of multicriteria optimization reaction conditions was solved based on a detailed kinetic model. The solutions found make it possible to optimally select the reaction conditions to achieve the maximum yield of target products, which can be based on the subsequent introduction of the laboratory reaction into production.

Optimization of Methanol Synthesis under Forced Periodic Operation

Traditionally, methanol is produced in large amounts from synthesis gas with heterogeneous Cu/ZnO/Al2O3 catalysts under steady state conditions. In this paper, the potential of alternative forced periodic operation modes is studied using numerical optimization. The focus is a well-mixed isothermal reactor with two periodic inputs, namely, CO concentration in the feed and total feed flow rate. Exploiting a detailed kinetic model which also describes the dynamics of the catalyst, a sequential NLP optimization approach is applied to compare optimal steady state solutions with optimal periodic regimes. Periodic solutions are calculated using dynamic optimization with a periodicity constraint. The NLP optimization is embedded in a multi-objective optimization framework to optimize the process with respect to two objective functions and generate the corresponding Pareto fronts. The first objective is the methanol outlet flow rate. The second objective is the methanol yield based on the total carbon in the feed. Additional constraints arising from the complex methanol reaction and the practical limitations are introduced step by step. The results show that significant improvements for both objective functions are possible through periodic forcing of the two inputs considered here.

Ignition Studies of C1-C7 Natural Gas Blends At Gas-Turbine Relevant Conditions

New ignition delay time measurements (IDT) of natural gas mixtures enriched with small amounts of n-hexane and n-heptane were performed in a rapid compression machine to interpret the sensitization effect of heavier hydrocarbons on auto-ignition at gas-turbine relevant conditions. The experimental data of natural gas mixtures containing alkanes from methane to n-heptane were carried out over a wide range of temperatures (840-1050 K), pressures (20-30 bar), and equivalence ratios (f = 0.5 and 1.5). The experiments were complemented with numerical simulations using a detailed kinetic model developed to investigate the effect of n-hexane and n-heptane additions. Model predictions show that the addition of even small amounts (1-2%) of n-hexane and n-heptane can lead to an increase in reactivity by ~40-60 ms at a temperature of 700 K. The IDTs of these mixtures decrease rapidly with an increase in the concentration of up to 7.5% but becomes almost independent of the C6/C7 concentration >10%. This sensitization effect of C6 and C7 is also found to be more pronounced in the temperature range 700-900 K compared to that at higher temperatures (>900 K). The reason is attributed to the dependence of IDT primarily on H2O2(+M)??H+?H (+M) at higher temperatures while the fuel-dependent reactions such as H-atom abstraction, RO2 dissociation, or Q OOH+O2 reactions are less important compared to the temperature range 700-900 K, where they are very important.

Ignition Studies of C1–C7 Natural Gas Blends at Gas-Turbine Relevant Conditions

New ignition delay time measurements of natural gas mixtures enriched with small amounts of n-hexane and n-heptane were performed in a rapid compression machine to interpret the sensitization effect of heavier hydrocarbons on auto-ignition at gas-turbine relevant conditions. The experimental data of natural gas mixtures containing alkanes from methane to n-heptane were carried out over a wide range of temperatures (840–1050 K), pressures (20–30 bar), and equivalence ratios (φ = 0.5 and 1.5). The experiments were complimented with numerical simulations using a detailed kinetic model developed to investigate the effect of n-hexane and n-heptane additions. Model predictions show that the addition of even small amounts (1–2%) of n-hexane and n-heptane can lead to increase in reactivity by ∼40–60 ms at compressed temperature (TC) = 700 K. The ignition delay time (IDT) of these mixtures decrease rapidly with an increase in concentration of up to 7.5% but becomes almost independent of the C6/C7 concentration beyond 10%. This sensitization effect of C6 and C7 is also found to be more pronounced in the temperature range 700–900 K compared to that at higher temperatures (> 900 K). The reason is attributed to the dependence of IDT primarily on H2O2(+M) ↔ 2ȮH(+M) at higher temperatures while the fuel dependent reactions such as H-atom abstraction, RȮ2 dissociation or Q.OOH + O2 reactions are less important compared to 700–900 K, where they are very important.