Investigation of the porous structure of heat-treated peat-ore materials
Abstract Generated abstract
This study examines how heat treatment and iron oxide additions affect the porous structure of peat-based moldings. Samples of high-moor peat and peat with finely dispersed iron oxide were heated in a laboratory shaft furnace, then analyzed by mercury intrusion porosimetry over an effective pore-radius range of 60 to 360000 Å. The results indicate that adding iron oxide changes the pore-size distribution by partially filling large pores and increasing the number of smaller pores and distribution maxima, while subsequent heating shifts pore development differently in peat-ore material than in peat alone. The authors conclude that iron oxide additions reduce total porosity but promote finer pore formation, and that higher treatment temperatures in peat-ore material contribute to pore burnout through oxygen supplied by the oxides.
Full Text
STUDY OF THE POROUS STRUCTURE OF HEAT-TREATED PEAT-ORE MATERIALS
N. G. ANTONOV, G. L. MARKELOVA
(Submitted by the scientific-methodological seminar of the organic departments
of the Faculty of Chemical Technology)
Changes in the porous structure of fuels during interaction with oxidizing agents in various processes have a substantial influence both on the kinetics of these processes and on the properties of the solid residue. At the same time, the influence of pores on the properties of the latter is not the same.
In the present work, a study was made of the porous structure of peat and peat-ore moldings obtained from high-moor peat (degree of decomposition 20–25%, moisture content—88.18%, \(A^c = 4.85\%\)) and peat with additions of iron oxide in an amount of 24.84% on a dry-substance basis. Heat treatment of the samples was carried out in a laboratory shaft furnace at a heating rate of \(5^\circ/\text{min}\) and with a one-hour hold at the end of the coking interval. After cooling, the samples were crushed, and the 0.2–0.6 mm fraction, in an amount of 0.2–0.5 gram, was investigated by the mercury-intrusion method according to the Plachenov procedure on a mercury porosimetric apparatus. The interval of pores studied, with effective radius, was from 60 to 360000 Å.
It is evident from Figs. 1 and 2 that samples of peat and peat-ore materials have pores of all sizes. The introduction of iron oxides into the peat mass promotes an increase in the number of pores in the investigated interval in comparison with peat without additives. The incorporation of fine mineral particles into pores larger than 360000 Å partially fills them; “fragmentation” of large pores into smaller ones occurs, as a result of which the porosity in the interval of pores with radius 360000–60 Å increases, and the number of porosity maxima also increases. Thus, if in the initial sample without \(\mathrm{Fe_2O_3}\) there are three porosity maxima corresponding to pores with effective radii: 1—more than 50000 Å, 2—50000–13000 Å (\(\lg r = 4.7—4.1\)), 3—13000–1600 Å (\(\lg r = 4.1—3.2\)), then in the peat-ore material there are six of them.
The structure-forming processes occurring during heating of peat and peat-ore material (POM) have substantial differences. In POM, with increasing treatment temperature, all porosity maxima shift into the region of larger pores. The pores develop. In samples without \(\mathrm{Fe_2O_3}\), the first maximum shifts into the region of larger pores, while the second shifts into the region of small pores and merges with the third.
Thus, the introduction of finely dispersed iron oxides into the peat mass promotes a change in the character of pore distribution by
in size. The total porosity of the material decreases as a result of the penetration of iron oxide particles into the large pores. The consequence of this is an increase in the number of pores of smaller radius. An increase in the heating temperature
Fig. 1. Distribution of pore volume by radius for solid peat residues. 1 — initial peat; 2 — 400° C; 3 — 800° C; 4 — 1200° C
Fig. 2. Distribution of pore volume by radius for solid residues of TPM. 1 — initial TPM; 2 — 400° C; 3 — 800° C; 4 — 1200° C
of the peat-ore material promotes the burnout of pores due to the oxygen of the oxides.