Reaction regimes in coal oxidation

Abstract

A series of seven coals were oxidized in a fixed bed reactor to determine the controlling reaction regimes during mild coal oxidation. The effects of coal porosity and particle size, reactor temperature, and oxygen partial pressure were evaluated. The results show that coal‐oxygen reactions are controlled by the rate of internal gaseous diffusion for most coals, and by the rate of chemical reaction for the most porous coal of the set tested. Particle size effects also suggest internal diffusional control. Determinations of cumulative oxygen deposition indicate that surface areas several orders of magnitude greater than the superficial surface can participate in oxidation reactions, putting in doubt the applicability of the model previously derived by Kam et al. (1976a) for external mass transfer control.

Oxidation Behavior and Caking Property of Coal under the Atmosphere at Low Oxygen Concentration.

“…These results show that the oxidation reaction of Go coal is controlled by the rate of internal gaseous diffusion. Similar results were reported by Avison et al, 10) Karsner and Perlmutter 11) and Mahajan et al 12) On the other hand, Kaji et al 13) reported that the oxidation rate evaluated by CO 2 and CO formation rates during oxidation was not affected by the coal particle size. One of the reasons for the contradiction may be due to used coal rank.…”

“…In this case, because the oxidation reaction is controlled by the rate of internal gaseous diffusion, the chemical structures and some properties of coal may depend on the part in the coal particle. So far, a number of works on the low temperature oxidation of coal were performed and some researchers [15][16][17] reported that the oxidation rate depended on the coal particle size. However, no clear evidence on the difference in chemical structure and properties between exterior part and inner part of coal particle were obtained.…”

Effect of Oxidation Period on Helium Density, Specific Energy and Acidity Values in Oxidation of Coal and Correlation for Prediction of Specific Energy

“…Mazumdar et al [2] reported that oxidation of coal may become useful route for bulk production of series of chemicals. Karsner et al [3] found that the pore structure of coal played an important role in coal oxidation. In a oxidation study of Japanese Taiheyo coal Ouchi et al [4] found that the yield of humic acids increases with increase of oxidation time.…”

Comparisons between sulfide flash smelting and coal combustion—with implications for the flash smelting of high-grade concentrate

“…The mass of dilution nitrogen required formed in the shaft is reduced to FeO in the settler by reaction to carry excess combustion heat is then determined by the with the FeS in the matte phase and is also suppressed by furnace heat balance (Eq. [5]), assuming no air infiltration SiO 2 in the fayalite slag. Some of the relevant overall reacinto the furnace.…”

“…Third, the porous structure of coal particles is important in determining the overall rate of oxidation for conditions where the intrinsic kinetics of the reaction are controlling, such as at low temperature and small particle sizes. [5,6] Naturally occurring sulfide minerals are nonporous and only form a porous structure upon release of their volatile sulfur. This structure is short lived as the particle reaches its melting point and forms a nonporous molten sphere.…”