A method for removal of solid contaminants and for predistribution of liquid to a fine distribution tray in a catalytic reactor vessel with concurrent downflow of vapor and liquid , said liquid being the liquid fraction of a process stream entering through a top nozzle of said catalytic reactor vessel , the method comprising the steps of: Providing a scale collection and predistribution tray inside said catalytic reactor vessel above said fine distribution tray ; Passing said liquid through a scale collection zone on said scale collection and predistribution tray for settling and deposit of said solid contaminants ; wherein a permeable upstanding wall forms said scale collection zone and wherein said liquid is filtered as it flows through said permeable upstanding wall ; or wherein said scale collection zone comprises flow restrictions such as baffles, grids, wire mesh, packed beds of particles, or packing like random or structured packing, providing a calm flow zone with low flow velocities and low flow turbulence to allow said solid contaminants to settle and deposit in said scale collection zone; Passing said liquid from said scale collection zone towards a weir located at the rim of said scale collection and predistribution tray ; directing said process stream through said scale collection zone in a general flow direction being radially outwards toward said weir , and providing a liquid trough between said scale collection zone and said weir to even out liquid level differences in order to obtain an equal liquid height above each of apertures , wherein said apertures are provided in the tray plate of said scale collection and predistribution tray downstream of said scale collection zone, or in said weir ; Passing said liquid through said apertures to said fine distribution tray ; and Passing vapor from the space above said scale collection and predistribution tray through the flow area between said scale collection zone and the wall of said vessel and through the flow area between said weir and the wall of said vessel to said fine distribution tray . Providing a scale collection and predistribution tray inside said catalytic reactor vessel above said fine distribution tray ; Passing said liquid through a scale collection zone on said scale collection and predistribution tray for settling and deposit of said solid contaminants ; wherein a permeable upstanding wall forms said scale collection zone and wherein said liquid is filtered as it flows through said permeable upstanding wall ; or wherein said scale collection zone comprises flow restrictions such as baffles, grids, wire mesh, packed beds of particles, or packing like random or structured packing, providing a calm flow zone with low flow velocities and low flow turbulence to allow said solid contaminants to settle and deposit in said scale collection zone; Passing said liquid from said scale collection zone towards a weir located at the rim of said scale collection and predistribution tray ; directing said process stream through said scale collection zone in a general flow direction being radially outwards toward said weir , and providing a liquid trough between said scale collection zone and said weir to even out liquid level differences in order to obtain an equal liquid height above each of apertures , wherein said apertures are provided in the tray plate of said scale collection and predistribution tray downstream of said scale collection zone, or in said weir ; Passing said liquid through said apertures to said fine distribution tray ; and Passing vapor from the space above said scale collection and predistribution tray through the flow area between said scale collection zone and the wall of said vessel and through the flow area between said weir and the wall of said vessel to said fine distribution tray . <EOS>