Patent ID: 7904271

Claim:
A method for determining activity of a catalyst in a polymerisation process, said polymerisation process comprising the steps of feeding a catalyst and a diluent into a storage vessel, to form a concentrated settled catalyst, feeding said concentrated settled catalyst into a mixing vessel equipped with mixing means and feeding hydrocarbon diluent into said mixing vessel, to form a diluted catalyst slurry, feeding said diluted catalyst slurry into a polymerisation reactor via a volumetric pump, and feeding at least one monomer into said polymerisation reactor to form a polymer, wherein said catalyst activity is determined by measuring the density of the diluted catalyst slurry between an outlet of the mixing vessel and the volumetric pump, determining the amount of catalyst fed into the polymerisation reactor based on the measured density of the diluted catalyst slurry, and comparing the amount of catalyst fed into the polymerisation reactor to the amount of the polymer formed to determine the activity of the catalyst and wherein the amount of catalyst fed into the polymerisation reactor is determined as the average of the amount determined based on the measured density of the diluted catalyst slurry, and at least one of the values selected from the group consisting of the amount determined based on a flow-rate of diluent entering the mixing vessel and a concentration of the diluted catalyst slurry, the amount determined based on flow-rate of the volumetric pump, and the amount determined based on a flow of a hydrocarbon diluent used for further diluting the diluted catalyst slurry and a flow of the further diluted catalyst slurry.