High-pressure experiments and modeling of methane/air catalytic combustion for power-generation applications

Abstract

The catalytic combustion of methane/air mixtures is investigated experimentally and numerically at gas turbine relevant conditions (inlet temperatures up to 873 K, pressures up to 15 bar and spatial velocities up to 3 × 10 6 h −1 ). Experiments are performed in a sub-scale test rig, consisting of a metallic honeycomb structure with alternately coated (Pd-based catalyst) channels. Simulations are carried out with a two-dimensional elliptic fluid mechanical code that incorporates detailed transport and heat loss mechanisms, and realistic heterogeneous and homogeneous chemistry description. The methodology for extracting heterogeneous kinetic data from the experiments is presented, and the effects of catalytic activity and channel geometry (length and hydraulic diameter) on reactor performance are elucidated. A global catalytic kinetic step provides excellent agreement (at temperatures below 950 K) between the measured and predicted fuel conversion, over a wide range of parameter variation (channel hydraulic diameter and length, pressure, and inlet temperature). It is shown that, under a certain combination of catalytic activity and channel length, the absolute temperature rise across the catalyst becomes essentially independent of pressure, a feature highly desirable for many practical systems. Even though the computed catalyst surface temperatures remain well below the decomposition temperature of PdO, a significant section of the catalyst-amounting up to 30% of the total reactor length-contributes minimally to the total fuel conversion, suggesting catalytic activity design improvements in the reactor entry.

Supported palladium-platinum catalyst for methane combustion at high pressure

“…Since both catalysts showed similar trends, the pressure impact seemed not to be affected by the type of catalyst used. Carroni et al [14] have also investigated the pressure influence on the activity of palladium catalysts. Their experimentally measured temperature difference over the catalyst is in agreement with our results.…”

Hetero‐/Homogeneous Combustion

“…Superadiabatic surface temperatures can also be of great concern for syngas fuels with high hydrogen contents and also for natural gas combustion due to the slight diffusional imbalance of methane (Le % 0.95). A realistic solution to protect the reactor from overheating is to apply passive cooling [24] by coating only every second channel of the honeycomb reactor (alternately-coated structure), such that the flow in the uncoated channels cools the walls of the active channels. The analysis in Equations 8.1 and 8.2 did not account for gas-phase reactions.…”

“…The kinetic models evaluated in Section 8.4 are implemented in multidimensional codes to assess performance and design issues of gas-turbine catalytic reactors [20,24,26] and microreactors [66]. Examples are provided next that use the kinetic schemes of Section 8.4.…”

Study on the Characteristics of Catalytic Combustion Furnace of Natural Gas and Influence of Its Exhaust Gas to Plant

“…The catalytic combustion of CH4/air mixtures over Pd-based catalysts was investigated experimentally and numerically at gas turbine relevant conditions (pressures up to 15bar and inlet temperatures up to 723K) in a reactor comprising of alternately coated channels. A global catalytic reaction rate was deduced, valid for catalyst temperatures below the PdO decomposition temperature (Carroni et al, 2003). Fibers obtained using the PVB/cerium nitrate reached higher conversions of methane, indicating higher catalytic activity.…”