At present, a thermal cracking process is being developed at pilot plant scale at BP's research facilities in Scotland. The process converts a mixture of waste plastic into a hydrocarbon intermediate, which can be used for petrochemical or refinery processes. A problem of the process is the formation and growth of small amount of fibrous carbon in the freeboard space of the fluidized bed, used as the main reactor. The fibres are believed to form on active metallic sites, detach and grow in the recirculating areas in the freeboard. This can be tolerated but there are economic advantages in their reduction. The aim is to characterise the hydrodynamics of the flow in the freeboard to understand and control the growth of the fibres. A cold model of the fluidised bed used in the pilot plant have been constructed, following scaling laws that allow similar hydrodynamics behaviour of the two beds. Particle Image Velocimetry, PIV, a full-field non-intrusive optical velocity measurement technique is used to analyse the gas pattern in the freeboard. Due to the complexity of the flow and the limitations of the technique PIV was implemented using image shifting. The gas flow in the freeboard of a fluidised bed is strongly dependent on bubble eruption at the bed surface. Here, the gas flow above an erupting bubble has been studied by the injection of single bubbles in an incipiently fluidised bed. Gas velocity vector maps of the vertical central plane above the bed surface, i.e. a plane parallel to the direction of the overall flow, have been determined using image shifting. A mechanism has been proposed to describe the process of single bubble eruption.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:664178 |
| Date | January 1999 |
| Creators | Yórquez-Ramírez, María Isabel |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/11963 |
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