Agglomeration in fluidized beds: Detection and counteraction

Agglomeration in fluidized beds: Detection and counteraction

Bartels, M.

Kapteijn, F. (promotor)

Applied Sciences

2008-11-11

Fluidized beds comprise a quantity of solid particles that is suspended by an upward flowing gas. They are used for a variety of processes in the chemical industry, such as catalytic reactions, drying, coating and energy conversion. A major problem in industrial practice is the occurrence of unwanted agglomeration, i.e. solid particles adhering to each other and forming larger agglomerates. The formation of agglomerates is a consequence of the presence of a liquid phase that results in increased particle stickiness. If this effect is not detected and counteracted it can eventually result in defluidization of the bed and subsequent costly shut-down of the whole installation. In energy conversion processes, typically combustion and gasification, agglomeration is often one of the main bottlenecks in the course of switching from fossil fuel to biomass as a regenerative energy source. This work aims at identification and application of suitable methods for the early detection of and counteraction against agglomeration in fluidized bed energy conversion processes. The attractor comparison method has been developed previously for monitoring multiphase hydrodynamics. This method is based on a relative comparison of the state-space projections of pressure fluctuation measurements and indicates significant changes in the hydrodynamics. In this work, the method is investigated for its suitability to detect agglomeration and small changes in particle size in circulating fluidized beds. The method has shown to be sensitive to agglomeration on lab-scale and sensitive to small particle size changes on both lab-scale and industrial scale. It is therefore considered a cost-saving tool for industrial practice. Moreover, a screening methodology has been developed that allows the efficient identification of signal analysis methods that are sensitive for and selective to agglomeration. This screening methodology has been successfully applied to identify suitable methods for several case studies in different scale bubbling and circulating fluidized beds. Defluidization of the bed has shown to be successfully prevented using the attractor comparison method in combination with suitable agglomeration counteraction methods on both lab- and pilot plant scale. The suitability of different agglomeration counteraction methods has been assessed.

fluidized beds
agglomeration
detection
counteraction
pressure measurements
monitoring

http://resolver.tudelft.nl/uuid:9fff7a86-97d2-4a62-9b0e-1e2d5de128e7

978-90-8570-311-2

Institutional Repository

doctoral thesis

(c) 2008 M. Bartels