Gas sampling from fluidized beds with a newly developed probe: The Venturi probe

摘要

A probe to sample gas from the particle loaded regions of (Circulating) Fluidized Beds was designed, built and tested. Since the Venturi Probe features non-mechanical gas-solids separation, blocking risks and filter maintenance are significantlyreduced. It has a very simple construction and can easily be operated. In gas sampling from commercial-scale fluidized beds, blocking of the probe and filter by solids is a major problem. Some probes apply gas injection in the tip of the probe, creating a cyclone action that separates the solids. To avoid possible dilutionof the gas sample, a novel probe, the Venturi Probe has been designed in which part of the sampled gas itself is used to create the cyclone action. The Venturi Probe consists of a venturi tube at the back of the probe and a cyclone section at the tip. Inthe throat of the venturi a pressure drop is created; the pressure difference between the throat and the back of the probe is used to inject a part of the gas back into the tip of the probe creating the cyclone action. Calculations and experiments show that the venturi can cause a sufficient pressure drop to create a cyclone action. Two prototypes of the Venturi Probe were designed and built. Tests have been performed in a 0.08 m ID cold CFB (DUT), in a 0.96 m{sup}2cold CFB and in a 0.6 m ID hot CFB pilot (both at CERCHAR). Particulate removal efficiencies larger than 90% are feasible when a proper choice of probe dimensions (diameter of venturi, size and location of gas injection ports) is made.