			Home About us Contact

Electrical Capacitance Tomography (electrical + capacitance_tomography)

Distribution by Scientific Domains

Chemistry	50%

Selected Abstracts

Advanced Statistical Analysis as a Novel Tool to Pneumatic Conveying Monitoring and Control Strategy Development

PARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 3-4 2006
Andrzej Romanowski
Abstract Behaviour of powder flow in pneumatic conveying has been investigated for many years, though it still remains a challenging task both practically and theoretically, especially when considering monitoring and control issues. Better understanding of the gas-solids flow structures can be beneficial for the design and operation of pneumatic transport installations. This paper covers a novel approach for providing the quantitative description in terms of parameter values useful for monitoring and control of this process with the use of Electrical Capacitance Tomography (ECT). The use of Bayesian statistics for analysis of ECT data allows the direct estimation of control parameters. This paper presents how this characteristic parameters estimation can be accomplished without the need for reconstruction and image post processing, which was a classical endeavour whenever tomography was applied. It is achieved using a ,high-level' statistical Bayesian modelling combined with a Markov chain Monte Carlo (MCMC) sampling algorithm. Advanced statistics is applied to data analysis for measurements coming from the part of phenomena present in the horizontal section of pneumatic conveyor during slug formation. [source]

On the electrostatic equilibrium of granular flow in pneumatic conveying systems

AICHE JOURNAL, Issue 11 2006
Jun Yao
Abstract An analytical methodology involving the concept of "electrostatic equilibrium" is developed for granular flow in pneumatic conveying systems. The methodology can be used for estimation of the electrostatic field distribution at various sections of the system and explanation of the mechanisms involved for various electrostatic phenomena observed. For all cases conducted in the conveying system, there was a "charging time" required for the system to reach the state of "electrostatic equilibrium." Experiments conducted at different sections of the system showed that the time required increased in the order: horizontal pipe, vertical pipe, and pipe bend. Through a physical analysis, it is deduced that electrostatic equilibrium is related to the granules' behavior and local flow characteristics. In general, a longer time duration taken to reach equilibrium corresponds to a process with more complicated granular flow patterns. In the electrostatic equilibrium state, the field distribution shows the highest electrostatic field strength near the pipe wall, and this field strength degrades from the pipe wall to the pipe center. At various pipe sections, the highest strength occurs at the bend, in accord with observations that electric sparking first occurs at that location within the entire pneumatic conveying system. In the vertical pipe, granular distribution was measured using electrical capacitance tomography (ECT), and granular velocities were cross-referenced with those using particle image velocimetry (PIV). The electrostatic force at low air flow rates is found to be the primary cause for granules sticking to the pipe wall and results in the formation of the half-ring or ring structure. The state of electrostatic equilibrium is physically influenced by several elements in conveying systems. In a cyclic conveying system, a new pipe (or low humidity or no antistatic agent) tends to expedite the process to reach electrostatic equilibrium and attain high magnitude of electrostatic current at the state. In a non-cyclic horizontal conveying system, a thin film (pipe) is found to prolong the process duration to reach equilibrium, while the case with charged film (pipe) takes shorter duration to do so. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source]

Application of a Bayesian Approach to the Tomographic Analysis of Hopper Flow

PARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 4 2005
Krzysztof Grudzien
Abstract This paper presents a new approach to the analysis of data on powder flow from electrical capacitance tomography (ECT) using probability modelling and Bayesian statistics. The methodology is illustrated for powder flow in a hopper. The purpose, and special features, of this approach is that ,high-level' statistical Bayesian modelling combined with a Markov chain Monte Carlo (MCMC) sampling algorithm allows direct estimation of control parameters of industrial processes in contrast to usually applied ,low-level', pixel-based methods of data analysis. This enables reliable recognition of key process features in a quantitative manner. The main difficulty when investigating hopper flow with ECT is due to the need to measure small differences in particle packing density. The MCMC protocol enables more robust identification of the responses of such complex systems. This paper demonstrates the feasibility of the approach for a simple case of particulate material flow during discharging of a hopper. It is concluded that these approaches can offer significant advantages for the analysis and control of some industrial powder and other multi-phase flow processes. [source]

Lateral flux and velocity of FCC particles in a CFB riser

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2001
Stefan Malcus
Abstract The radial profiles of the lateral solids mass flux and the lateral solids velocity were determined for FCC particles in a 7 m tall circulating fluidtzed bed riser 0.14 m in diameter by applying a lateral flux probe and electrical capacitance tomography. The external solids mass flux was varied between 148 and 302 kg/(m2.s), while the superficial gas velocity was varied between 3.7 and 4.7 m/s. Under these conditions, a dense bottom region and an upper dilute region coexisted in the riser. Lateral fluxes in the dense bottom region reached 100 kg/(m2.s) at the wall, but fell to 14 kg/(m2.s) at the wall in the upper dilute region. At both axial locations, a net deposition of solids from the core to the annulus occurred, indicating that fully developed flow was never established under these conditions. The lateral fluxes in the bottom region were significantly larger than those found in previous studies. It was further concluded that considering the lateral solids flux to be only a function of solids concentration is an over-simplification. Les profils radiaux du flux massique de solides latéral et de la vitesse de solides iatérale ont été déterminés pour des particules de FCC dans une colonne à lit fluidisé circulant de 7 m de hauteur et de 0,14 m de diamètre, en appliquant une sonde de flux latérale et la tomographic par capacitance électrique. On a fait varier d'une part le flux massique de solides externe entre 148 et 302 kg/(m2.s) et d'autre part la vitesse de gaz superficielle entre 3,7 et 4,7 m/s. Dans ces conditions, une région inférieure dense et une région supérieure diluée coexistent dans la colonne. Les flux latéraux dans la région inférieure dense atteignent 100 kg/(m2.s) à la paroi, mais tombent à 14 kg/(m2.s) à la paroi dans la région supérieure diluée. Aux deux régions axiales, une déposition nette de solides se produit du coeur vers l'espace annulaire, indiquant que un écoulement pleinement développé n'a jamais été établi dans ces conditions. Les flux latéraux sont nettement plus important que ceux trouvés dans les études antérieures. II a en outre été conclu que le fait de considéer le flux de solides latéral uniquement comme étant fonction de la concentration de solides constituait une sur-simplification. [source]