gasfluidised

Gasfluidised refers to a state in which solid particles are suspended in a gas stream, behaving as if they were a fluid. This phenomenon is achieved when the upward velocity of the gas flowing through a bed of solid particles exceeds the minimum fluidisation velocity. At this point, the drag force exerted by the gas on the particles overcomes their gravitational force, causing them to lift and move freely within the gas. The resulting mixture exhibits fluid-like properties, such as the ability to flow, level out, and exert hydrostatic pressure.

The key characteristic of a gasfluidised bed is the intense mixing of gas and solid phases. This leads to excellent heat and mass transfer rates, making gasfluidised beds highly effective in various industrial applications. The uniform temperature distribution within the bed is another significant advantage, preventing hot spots and promoting efficient reactions. Common applications include catalytic cracking in the petroleum industry, combustion of fuels, drying of solids, and coating of particles.

The behaviour of a gasfluidised bed is influenced by several factors, including particle size and shape, gas velocity, and the properties of the gas and solid materials. Different flow regimes can be observed within a gasfluidised bed, ranging from bubbling fluidisation, where discrete bubbles of gas rise through the bed, to turbulent fluidisation and fast fluidisation, which exhibit more vigorous mixing and higher particle entrainment. Understanding these regimes is crucial for optimising the design and operation of gasfluidised systems.