Measurement Techniques: Cold Flow Studies

It has been realized in recent decades that a proper investigation of gasification reactor requires the detailed information over the entire flow field, as well as time, at multiple scales. Such detailed information needs the use of sophisticated measuring techniques with capability to provide the required information over the entire flow field, as well as time, at multiple scales. Aside from the mean velocities and volume fractions, information about the flow fluctuations or dynamics (quantified in terms of cross-correlations and auto-correlations) is also desirable. In addition, it is preferable if such techniques are amenable to automation to reduce extensive human involvement in the data collection process. While such data are “stand-alone” sets of information, which can be used for design and scale-up strategies, it also provides information that is crucial to establish the validity of conventional models like phenomenological flow models describing residence time distribution (RTD), as well as more recent and sophisticated models like those based on computational fluid dynamics (CFD). In fact, it almost seems imprudent to validate CFD predictions on overall holdup and flow rates, because these spatial integrals of point properties are simply averages of a complete flow field that a CFD code is designed to and claims to compute. Thus, fair validation must involve validation at multiple scales, for which one needs experimental information also at multiple scales (and not just spatial and temporal averages). Several experimental techniques have been reported in past to quantify the flow field in gas–solid gasification reactors, with each technique having its own advantages and disadvantages. In this chapter, details of pressure, solid velocity, solid fraction, and RTD measurement techniques will be presented. Techniques will be divided majorly in two types, invasive and non-invasive. The postprocessing methods for each technique, advantages, and limitations will be discussed. Finally, some of the recent findings on gas–solids circulating fluidized bed using radioactive particle tracking (RPT) technique will be discussed in detail to explain the use of the experimental techniques for design and scale-up of these reactors.