Chapter 8 - Combustion of single coal particles in turbulent fluidized beds

Abstract

This chapter provides an overview of combustion of single coal particles in turbulent fluidized beds. A classical bubbling fluidized bed operates in a low velocity regime where discrete bubbles are present. Bubbles cause severe bypassing and back mixing of the fluidizing gas. Bypassing of gas leads to inefficient contact between gas and solid, although bubbles cause solid movement that increases the rate of heat transfer. Though the conventional bubbling fluidized bed technology is widely used in many chemical processes and for coal combustion in boilers, it suffered from certain limitations that did not allow it's scaling up beyond a certain size. The growing need to burn low-quality coal and to meet stringent environmental regulations in utility boilers have forced scientists and technologists to find a viable alternative to the conventional bubbling fluidized bed boilers. Thus, there emerged the circulating fluidized bed boilers, known as the fast fluidized bed boiler, which operates in a completely different regime of fluidization.