Investigation on a gas-solid fluidized bed hydrodynamics using a non-intrusive technology to visualize flow field

The biggest challenge for 21st century is to fulfill global energy demand and at the same time reduce detrimental impact on environment. Gasification technology can meet the requirement and also reduce emission without compromising its performance. In coal gasification, instead of burning coal completely a partial combustion takes place with presence of steam and limited amount of oxygen. In this controlled environment a chemical reaction takes place and produces a mixture of clean synthetic gas. Gas-solid fluidized bed is one type of gasification technology. During gasification mixing behavior of solid (coal) and gas and their flow pattern very complicated to understand. Many attempts have taken in laboratory scale to understand bed hydrodynamics with spherical particle whereas in actual coal are non-spherical. Considering this issue an attempt has taken to investigate fluidized bed behavior using different ranges non-spherical particles and spherical particle as well. Different parameters are controlled during investigation like particle size, bed height, bed diameter and particle shape. Particles used from 355 µm to 1180 µm, bed diameter varied from 2 cm to 7 cm, two fluidized bed with diameter 3.4 cm and 12.4 cm, spherical and non-spherical shape particles were taken into consideration for investigation. Pressure drop was measured with increasing superficial gas velocity. The velocity required to start fluidize the particle is called minimum fluidization velocity. Minimum fluidization velocity is one of the most important parameter to design and optimize gas-solid fluidized bed performance. This minimum fluidization velocity was monitored during investigation with changing factors that affect this velocity. From investigation it has been found that minimum fluidization velocity is independent on bed height for both spherical and non-spherical particles, it decrease with decreasing particle size and it also decrease with decreasing bed diameter. Shadow sizing a non-intrusive technology is also used to visualize flow field inside fluidized bed in dilute section for both spherical and non-spherical particles and also detect the particle size