Improving the Quality of Listvyansky Anthracite as a Raw Material for the Production of Electrode Products
Abstract Generated abstract
This study examines dry electromagnetic beneficiation as a means of reducing the ash content of Listvyansky anthracite intended for carbon electrode and block production. Raw and air excluded calcined anthracite, crushed to 3 to 0 and 1 to 0 mm fractions, was treated on a laboratory induction roll magnetic separator, with separation products assessed by yield and ash content. The results indicate that finer grinding improves separation, while preliminary calcination markedly increases the beneficiation effect, apparently by increasing the magnetic susceptibility of iron bearing mineral inclusions. Calcination at 750°C followed by magnetic separation produced concentrates with about 3.4 to 3.6% ash at yields of 75 to 86%, suggesting a practical route for improving thermoanthracite quality for electrode manufacture.
Full Text
IMPROVING THE QUALITY OF LISTVYANSKY ANTHRACITE AS A RAW MATERIAL FOR THE PRODUCTION OF ELECTRODE PRODUCTS
V. M. VITYUGIN, V. A. PROKHOROVICH
(Presented by the scientific seminar of the Faculty of Chemical Technology)
Anthracite is widely used in the manufacture of carbon electrodes and various carbon blocks; the broad use of anthracite is due to its relative cheapness and makes it possible to obtain sufficiently strong and electrically conductive products.
A major obstacle to still broader use of anthracite in electrothermal production is its relatively high ash content. In terms of chemical composition, electrothermal products must have a minimum of mineral impurities, which form ash.
The technology for producing electrode products includes heat treatment of carbonaceous materials at high temperature without access of air and their subsequent grinding to a specified size, depending on the size of the electrode products. Grinding of thermoanthracite before its further use opens up the possibility of reducing mineral impurities by beneficiating it.
This communication presents the results of electromagnetic beneficiation of Listvyansky anthracite, which is a valuable raw material for electrothermal production. The method of dry electromagnetic beneficiation is attractive because of its simplicity and the fairly substantial reduction in ash content of the beneficiated coal [1].
Table 1
Characteristics of the anthracite studied
| Size of anthracite, mm | Determined indices | 3–1 | 1–0.5 | 0.5–0.25 | 0.25–0 |
|---|---|---|---|---|---|
| 3–0 | Yield, % | 70.50 | 10.70 | 8.00 | 11.00 |
| 3–0 | Ash content, % | 5.10 | 7.20 | 10.70 | 14.90 |
| 1–0 | Yield, % | — | 11.10 | 31.40 | 57.50 |
| 1–0 | Ash content, % | — | 5.50 | 6.30 | 7.67 |
For the study, a sample of anthracite from the Listvyansky deposit of the Gorlovka basin was used, obtained from the Leninsk-Kuz-
of the Yenakievo semicoking plant. The anthracite studied was crushed to sizes of 3–0 and 1–0 mm. The screen analysis of these materials and the distribution of ash by size classes are shown in Table 1.
Anthracite was beneficiated on a laboratory induction-roll magnetic separator with bottom feed, intended for weakly magnetic materials. The separator can develop a maximum magnetic-field intensity of 12,000 oersteds at a current of 10 amperes.
The study was carried out both on raw anthracite and on anthracite calcined without access of air. The anthracite was calcined in graphite crucibles with slow heating to specified temperatures and holding at these temperatures for two hours. Magnetic separation of the materials was carried out with recleaning of the nonmagnetic (low-ash) product at settings of 0.5, 8, and 10 amperes, thereby obtaining a nonmagnetic concentrate and magnetic tailings.
Table 2
Electromagnetic beneficiation of Listvyansky anthracite
| Anthracite sample | Size, mm | Beneficiation product | Yield, % | Ash content, % | Reduction in ash content, % |
|---|---|---|---|---|---|
| Raw, with ash content 6.95% | 3–0 | concentrate | 96.50 | 6.40 | 8.00 |
| Raw, with ash content 6.95% | 3–0 | tailings | 0.87 | 54.83 | 8.00 |
| Raw, with ash content 6.95% | 3–0 | losses | 2.63 | 8.00 | |
| Raw, with ash content 6.95% | 1–0 | concentrate | 96.60 | 5.74 | 17.5 |
| Raw, with ash content 6.95% | 1–0 | tailings | 1.01 | 62.00 | 17.5 |
| Raw, with ash content 6.95% | 1–0 | losses | 2.36 | 17.5 | |
| Calcined at 500°C, with ash content 7.13% | 3–0 | concentrate | 84.68 | 6.24 | 12.50 |
| Calcined at 500°C, with ash content 7.13% | 3–0 | tailings | 13.22 | 12.27 | 12.50 |
| Calcined at 500°C, with ash content 7.13% | 3–0 | losses | 2.10 | 12.50 | |
| Calcined at 500°C, with ash content 7.13% | 1–0 | concentrate | 91.75 | 5.10 | 28.50 |
| Calcined at 500°C, with ash content 7.13% | 1–0 | tailings | 5.25 | 32.00 | 28.50 |
| Calcined at 500°C, with ash content 7.13% | 1–0 | losses | 3.00 | 28.50 | |
| Calcined at 750°C, with ash content 7.26% | 3–0 | concentrate | 75.10 | 3.57 | 50.8 |
| Calcined at 750°C, with ash content 7.26% | 3–0 | tailings | 22.90 | 19.10 | 50.8 |
| Calcined at 750°C, with ash content 7.26% | 3–0 | losses | 2.0 | 50.8 | |
| Calcined at 750°C, with ash content 7.26% | 1–0 | concentrate | 86.30 | 3.37 | 53.7 |
| Calcined at 750°C, with ash content 7.26% | 1–0 | tailings | 11.30 | 23.90 | 53.7 |
| Calcined at 750°C, with ash content 7.26% | 1–0 | losses | 2.40 | 53.7 |
The results of beneficiation of Listvyansky anthracite and thermoanthracite by electromagnetic separation are given in Table 2. These data show that, when raw anthracite is separated, the beneficiation effect is in-
is sufficiently high. The reduction in ash content depends on the size of the anthracite. Thus, when the size of the raw anthracite is decreased from 3 to 1 mm, the beneficiation effect doubles.
Treatment of anthracite by preliminary calcination substantially improves the results of magnetic separation. This is explained by the fact that, during heat treatment of anthracite in a reducing medium, the ferric iron of the rock inclusions is reduced to a more magnetic ferrous form. Thus, separation of anthracite calcined at 500°C makes it possible to reduce the ash content by 12.5% at a material size of 3–0 mm and by 28.5% at a size of 1–0 mm. Raising the calcination temperature to 750°C further increases the separation effect and ensures the production of a concentrate with an ash content of 3.4–3.6%, at a yield of 75–86%.
The results of the study show that electromagnetic beneficiation of crushed Listvyansky thermoanthracite will significantly reduce the content of mineral impurities and improve the quality of the products.
REFERENCES
- A. Z. Yurovskii, V. D. Goroshko, V. I. Korshunov, I. D. Remesnikov. In: Technical Directions in Coal Beneficiation. Gosgortekhizdat, Moscow, 104, 1963.