Pyrolysis and Ignition Characteristics of Pulverized Coal Particles

Abstract

Pyrolysis and ignition characteristics of pulverized coals were examined under similar burning conditions to those of industrial burners. In the early stage, fine particles (less than 37 μm) were mainly pyrolyzed by convective heat transfer from surrounding gas. The coals ignited when pyrolyzed volatile matter mixed with surrounding air and formed a combustible mixture. Pyrolysis of large particles was delayed, but accelerated after ignition by radiant heat transfer from coal flames. The effects of radiant heat transfer were strong for intermediate-size particles (37–74 μm). Ignition temperature was examined analytically by using a modified distributed activation energy model for pyrolysis. The calculated results agreed with experimental ones obtained from both laboratory-scale and semi-industrial-scale burners.

Fundamental Experiments of Coal Ignition for Engineering Design of Coal Power Plants

“…We assumed that L was in inverse proportion to the amount of pyrolized volatile matter Figure 11 compares estimated L values based on the pyrolysis calculation with measured values. The pyrolysis rate constant was fitted by thermogravimetric analyses [27]. The estimated values agreed with the experimental values.…”

“…Figure 18(a) reproduces instantaneous photos and (b) is the averaged photo. Coal particles were ignited around 150mm downstream from the burner exit [27,35]. Burning coal www.intechopen.com particles were not observed from the burner exit to 150mm downstream.…”

“…We developed an experimental apparatus to evaluate lift-off height of continuous coal flames, and LES (large eddy simulation) results were verified with the experimental results [23]. Figure 17 shows schematic drawings of the pulverized coal jet flame experiment [27]. The mixture of coal and air was injected through a primary nozzle installed at the centreline of www.intechopen.com the preheated gas flow and ignited by the surrounding preheated gas.…”

“…12(b) shows time changes of the particle temperature. The method of calculation has been shown elsewhere [27]. Heat balance of particles was written as…”

“…The relationship between heating time and amount of pyrolized volatile matter was calculated when the particle was heated at a rate of 20000K/s. The distributed activation energy model (DAEM) was used for the pyrolysis [24][25][26][27][28][29]. The pyrolysis rate dV/dt was calculated by Eq.…”