Properties of Granules Based on Ash from Tomsk GRES-2
Abstract Generated abstract
This study evaluates the production of lightweight ash gravel from fly ash generated at Tomsk GRES-2, a difficult-to-swell ash, using small additions of clay, peat, brown iron ore, or magnetite slag. Laboratory granulation, drying, and firing tests compared raw and fired granule properties, including sieve composition, moisture content, density, porosity, compressive strength, drop resistance, bulk density, and water absorption. All tested fired compositions met the applicable standard requirements for expanded-clay gravel and corresponded to grades 500 to 550. The composition containing 90 percent ash, 5 percent clay, and 5 percent brown iron ore showed the best combination of raw-granule mechanical properties and swelling behavior, and is recommended for producing lightweight porous ash gravel.
Full Text
PROCEEDINGS
OF THE TOMSK POLYTECHNIC INSTITUTE NAMED AFTER S. M. KIROV, HOLDER OF THE ORDER OF THE OCTOBER REVOLUTION AND THE ORDER OF THE RED BANNER OF LABOR
Volume 257 1973
PROPERTIES OF GRANULES BASED ON ASH FROM TOMSK GRES-2
G. G. Vergun, V. M. Vitgotin
(Presented by the seminar of the Department of General Chemical Technology)
On the basis of an analysis of Soviet [1, 2, 3] and foreign [4, 5] research and industrial practice, the most promising field of utilization of fly ash from thermal power plants may be considered to be the production of ash gravel. The object of the present study was ash from Tomsk GRES-2, into which various additives were introduced: clay, peat, brown iron ore, and magnetite slag. In terms of chemical composition, the ash from Tomsk GRES-2 belongs to the difficult-to-swell type [3]. The content of iron oxides in it is \(Fe_2O_3 < 7\%\), with a low value of the sum of the oxides \(CaO + MgO\). Clay from the Rodionovo deposit, in an amount of 5%, was introduced as a moisture-capacious additive that improves the process of ash granulation and as a material that swells during firing.
The swelling processes of GRES ashes are at present most often associated with processes of reduction of the oxidic form of iron to the ferrous form, as a result of which the transition of ashes into a pyroplastic state is facilitated. At the same time, capillaries become sealed, and the excess pressure of gases inside the granules leads to swelling. For this reason it appears expedient to introduce brown iron ore and magnetite slag into the compositions of the batches under study. Peat was introduced as a pore-forming additive during firing, facilitating the firing process and reducing the bulk density of the granulate.
Granulation of batches based on ash from Tomsk GRES-2 was carried out on a laboratory disk granulator 1 m in diameter, with a side height of 0.1 m, with an inclination angle of \(45^\circ\), a circumferential rotation speed of 1 m/sec for 15 minutes. The batches were moistened with a 5% CCB solution by means of a spraying nozzle. The compositions of the batches and
properties of the raw granulate are given in Table I.
Table I
| No. | Properties | Batch No. 1 ash 90% clay 5% peat 5% |
Batch No. 2 ash 90% clay 5% limonite 5% |
Batch No. 3 ash 90% clay 5% magnetic sludge 5% |
|---|---|---|---|---|
| 1. | Sieve composition, %: fraction content + 20 mm |
14.47 | 9.13 | 7.35 |
| 1. | Sieve composition, %: fraction content − ″ − + 10 mm |
80.35 | 80.2 | 49.3 |
| 1. | Sieve composition, %: fraction content − ″ − + 5 mm |
— | 7.6 | 36.75 |
| 1. | Sieve composition, %: fraction content − ″ − − 5 mm |
5.18 | 2.87 | 6.4 |
| 2. | Moisture content of granules, % | 39.3 | 33.8 | 32.3 |
| 3. | Bulk density, kg/m³ | 777 | 791 | 813 |
| 4. | Density, g/cm³ | 1.33 | 1.435 | 1.4 |
| 5. | Porosity, % | 49.9 | 45.8 | 47.2 |
| 6. | Compressive strength, g/granule | 620 | 702 | 520 |
| 7. | Number of drops from \(h = 300\) mm |
5 | 4 | 4 |
| 8. | Maximum drop height, mm | 500 | 800 | 800 |
From Table I it is evident that the best mechanical properties are possessed by raw granules obtained from a batch of composition 2. Such granulate is less subject to destruction during transportation from one technological stage to another.
Drying of the granules was carried out in a laboratory drying cabinet at a temperature of 105°C. In this process, strengthening of the granule structure was observed. The compressive strength of the granules was 2000–2500 g/granule. Dry ash granules were fired in a laboratory expanded-clay-type oven
furnace at a temperature of 1250°C for 15 minutes. The properties of the fired ash granules are given in Table 2.
Table 2
| No. | Properties | Batch No. 1 ash 90% clay 5% peat 5% |
Batch No. 2 ash 90% clay 5% brown iron ore 5% |
Batch No. 3 ash 90% clay 5% magnetite slag 5% |
|---|---|---|---|---|
| 1. | Bulk density, kg/m³ | 536 | 402 | 501 |
| 2. | Compressive strength, kg/granule | 90 | 60 | 40 |
| 3. | Water absorption, % | 5.6 | 6.26 | 7.1 |
Ash gravel of all three compositions meets the requirements of GOST 9759–65 for expanded-clay gravel and corresponds to grades 500–550. Taking into account the higher mechanical properties of the raw granulate and the better bloating during firing, batch composition 2 can be recommended for obtaining lightweight porous ash gravel.
References
-
V. M. Ufimtsev, M. F. Chebukov. Production of agloporite gravel from TPP ash by gas firing. Stroitel’nye materialy, 1970, No. 2, pp. 13–14.
-
I. F. Graur, P. N. Dokuchaev, B. A. Is’ko et al. Experience in producing agloporite gravel from TPP ash. Stroitel’nye materialy, 1969, No. 1, pp. 29–30.
-
A. S. Panin, V. G. Grebenkin. Building-material plants based on ash and slag from TPPs. Stroitel’nye materialy, 1968, No. 9, pp. 22–24.
-
V. V. Stel’nikov. Use of fly ash from the combustion of pulverized fuel at thermal power stations. 1969.
-
A. Z. Yurovskii. Session of the expert group on the utilization of ash from solid fuels of the Coal Committee of the United Nations Economic Commission for Europe. Khimiya tverdogo topliva, 1969, No. 6, pp. 132–133.