(143e) Development of a New Gas/Liquid Distributing Tray for Catalytic Reactors Operated in Upward Gas/Liquid Flow

Catalytic fixed bed reactors operated in gas/liquid upward flow mode are currently encountered for hydrogenation processes. These reactors are used as finishing reactors to get maximum conversion of di-olefins by keeping a high selectivity for olefins production. In such reactors, the feed is injected at the reactor bottom inlet and hydrogen is injected both into the feed flow line and inside a reactor distribution tray just upstream of the catalyst bed. The fraction of hydrogen flow injected just upstream of the catalytic bed corresponds to the non dissolved fraction of hydrogen and must be correctly distributed in the feed liquid flow over the whole reactor section before flowing through the bed. Since the reactor is used in a finishing step, the amount of injected hydrogen is very low and the main problem is to distribute a small number of gas bubbles in the liquid flow all over the catalyst bed section. In this objective, a new distributing tray has been developed at IFP-Lyon. This development is based on experimental studies on cold mockup and on CFD calculations for scale up at large scale. The concept of distribution has been first validated using a transparency column of 225 mm internal diameter with a short guard bed downstream the distributing device. Then the distribution efficiency has been quantified by measuring gas holdup distribution over the catalytic bed section using a gamma-ray tomographic system in a column of 400 mm internal diameter. The distributing tray performances are compared to those obtained with classical gas spargers (see Figure1). Finally a first example of distributing tray scale up is presented. An industrial distributing tray has been designed, build and installed in a existing industrial unit in 2005. The efficiency of distributing tray is thus validated on a large scale by comparing temperature profiles in the catalytic bed before and after tray installation.