Hydrodynamics similarities in cold flow model of chemical looping combustors: An experimental study

Abstract

The hydrodynamics of gas-solid flow in chemical looping combustors (CLC) is often studied in cold flow models (CFMs). The opportunity of working at the ambient conditions has been found to be beneficial for scaling purposes. In this study, a 200-kWth demonstration pilot plant CFM–CLC system (the first of its kind in Australia) that is a scaled-up unit of a lab scale 10-kWth unit is designed, fabricated and commissioned. The hydrodynamics similarities of the two units in terms of pressure drop profile and solids circulation rate are investigated. The results showed that the scaling factor for the operating velocity calculated based on the dimensionless relation of the fluidisation gas velocity ratio and the square root of the fluidised bed height ratio (of the air reactor) is 2.36, which was in good agreement with the measured value of 2.55. The same solids circulation rate (SCR) between the units was achieved using the scaling factor of 2.55 whilst maintaining the ratio of normalised total solids inventory of the system equal 1. It was also demonstrated that as the ratio of normalised total inventory increased from 1 to 1.4, the gas velocity to achieve similar SCR needs to be reduced proportionally (in the unit which inventory was increased). Therefore, a simple method of calculating the required gas velocity for achieving the same SCR for systems with non-equivalent normalised total solids inventory is proposed. The prediction results using this method were compared against the experimental data, with an average deviation of less than 10%. The validity of the proposed prediction method (for other cases of non-equivalent normalised total solids inventory) however requires further investigation.