Patent ID: 6945287
Filing Date: 2005-09-20
Classification: A23F

Abstract:
1. A gas backflow blocker for use in a process treating a particle mass passing in a substantially continuous flow from a first stage of the process to a downstream second stage, said first stage to be held at a lower pressure than that of the second stage, wherein the particle mass has a density D, a first stage pressure of P h , and a second stage pressure of P l , and comprising: a) an upright duct having an upper end and a lower end, for holding a column of the particle mass flowing therethrough; b) first and second flow restrictors mounted at the upper and lower duct ends respectively, said first flow restrictor for receiving particles flowing from the first stage and limiting particle flow into the duct from the first stage and said second flow restrictor receiving flow from the duct and limiting particle flow from the duct into the second stage, at least one of said flow restrictors having a particle mass flow rate set by a flow rate signal; c) a particle level sensor mounted on the duct adjacent the upper end and providing a level signal indicating the level of particles within the duct; and d) a controller receiving the level signal and responsive thereto, providing a flow rate signal to the one of said flow restrictors to regulate particle flow through said flow restrictor to approximately maintain a predetermined particle mass level H within the duct at the level sensor, said controller regulating H to approximately satisfy the equation H≧(P