Raschig rings
Multi-hole cylinders
Q uadralobe
Katalco 57-4MQ
Katalco 57-4Q
intrinsically impacts the thermal efficiency of the process and pressure drop over the SMR. Catalyst pellets often have domed faces to avoid stacking, which results in the formation of large voids during loading. The length- to-diameter (L:D) ratio is also an important characteristic of the pellet geometry. The L:D ratio significantly influences the pellet orientation during the loading. Pressure drop can be reduced by decreasing the L:D ratio to <1; however, this can negatively affect mass and heat transfer properties if overexploited. A higher L:D ratio increases relative pressure drop but improves radial gas mixing and enhances heat transfer; this is an increasingly important factor as reformer tube sizes have grown over time. Sustaining performance over the lifecycle Catalyst shape not only affects the initial pressure drop at the start of the run but also influences how the pressure drop evolves over time. During start-up and shutdown, SMRs undergo thermal cycling, which causes the tubes to expand and contract. This mechanical stress can lead to fragmentation of the catalyst pellets. Traditional pellets may break into fines, creating zones of reduced voidage. This leads to increased pressure drop and higher energy demands for gas compression. Modern pellets are precision-engineered with designed break points. As a result, when subjected to mechanical stress, these pellets fracture into larger secondary fragments rather than fines (see Figure 2 ). The porosity of the support is also designed for a specific distribution, which ensures a high surface area for dispersion on the active Ni, minimising Figure 2 Finite stress analysis of a cross-section of the Quadralobe pellet
K atalco 57-4GQ
K atalco 57-4XQ
Increasing activity
Balancing efficiency and throughput Steam reforming catalysts are typically composed of shaped ceramic supports impregnated with active nickel (Ni) species. Modern catalyst designs must balance multiple performance variables: activity, pressure drop, heat transfer, and mechanical integrity. Shape remains one of the most important features of the catalyst. Multi-channel designs, such as Johnson Matthey’s Quadralobe Figure 1 Depiction of the improvements in steam reforming catalyst shapes, and the balance of activity and pressure drop “ Catalyst shape not only affects the initial pressure drop at the start of the run but also influences how the pressure drop evolves over time ” catalysts, increase the geometric surface area available for reaction, enhancing both mass and heat transfer. These advanced shapes have been engineered to maintain high strength and optimum activity, while allowing higher gas velocities and lower energy consumption (see Figure 1 ). The traditional method to increase geometric surface area is to reduce the pellet size; however, while smaller pellet sizes and textured surfaces offer a higher surface area per unit volume, it is at the cost of increased pressure drop. Pellet geometry also impacts the packing characteristics of the catalyst, which
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