Fluidized beds display a degree of structure which it is vital to unde
rstand in any design and scale-up of equipment. This paper is on the e
mployment of chaos theory to describe this structure. The measuring te
chnique of electrical capacitance tomography is used to determine the
local porosity of a gas-solids fluidized bed and to monitor its fluctu
ation with time; These raw data are translated into invariants charact
eristic of the structure mentioned, such as the Kolmogorov entropy. In
itial measurements have shown a strong variation in these chaotic inva
riants with bed position and operational parameters. First results are
compared with earlier data from pressure measurements.