Patent ID: 8059264

Claim:
A method for monitoring the velocity of growing polymer particles, the method comprising: measuring by means of a photometric instrument a degree of attenuation in the propagation of light in a two-phase stream flowing in a polymerization reactor, the photometric instrument comprising: at least two transmitting optical waveguides connecting at least one light source to said two-phase stream; and at least two receiving optical waveguides connecting said two-phase stream to a light detector, the at least two transmitting optical waveguides and the at least two receiving optical waveguides having reactor-side ends, the polymerization reactor comprising a wall, wherein the reactor-side ends of said transmitting and said receiving optical waveguides are positioned flush with respect to the wall of said reactor, wherein the two-phase stream is a gas/solid or liquid/solid stream, the solid in the solid/gas or solid/liquid two-phase stream comprises polymer particles, and the reactor-side ends of the transmitting and receiving optical waveguides are arranged alongside one another in at least one pair, and wherein the velocity of the growing polymer particles is monitored in a polymerization process and is calculated from the time it takes to cover the distance between the reactor-side ends of the receiving optical waveguides.