Acetylene is formed as a byproduct in the manufacture of ethylene. It is removed by selective hydrogenation using noble metal catalysts (see, for example, US 7,453,017). A particular catalyst achieves 90% acetylene saturation with 50% hydrogen selectivity for acetylene at a weight hourly space velocity of 800 h 1 based on ethylene. Design a reactor to remove 1% acetylene from ethylene in a plant that produces 1.5 million metric tons per year of ethylene using this catalyst.