Box Coking Experiments of Charges with a High Content of Kuzbass Gas Coals with the Addition of Finely Ground Coke

I. V. Gebler

In one of the author’s works [1], carried out in the laboratory of pyrogenic-process technology of the Tomsk Polytechnic Institute named after S. M. Kirov, it was shown and theoretically substantiated that, when finely ground coke is added, the coking capacity of gas coals sharply increases, as a result of which their share in charges can be substantially increased without lowering the quality of the coke.

To verify this, experimental coking in boxes was carried out [2].

Boxes made of 5-mm iron were used, with internal dimensions of \(340 \times 340 \times 640\) mm, holding 50 kg of charge. The added coke (dried) had \(A^c = 18.09\%\); \(V^c = 1.46\%\). Grinding—through a sieve of 500 openings/cm².

The bulk density of the charges when freely poured into the box amounted, for charges with coke (5%), to from 800 to 820 kg/m³ and on average may be taken as 810 kg/m³; charges without coke were laid with an average bulk density of 770 kg/m³. Thus, the increase in the bulk density of charges with the addition of 5% finely ground coke does in fact occur and is expressed by a figure of about 5%.

A judgment on the necessary duration of the coking period was made on the basis of the following experiments:

1. A charge containing 94% gas coal, Sh. Pionerka, and 6% coke was coked in old ovens (vertical-flue temperature 1120–1140°) (Table 1, charge No. 1). With a very high amount of volatile matter—36.65%—the coke obtained after the normal coking period (24 hours), established for charges with a volatile content of about 25%, contained 1.46% volatiles, i.e., it was fully mature. Since the coking period increases as the volatile content in the charge increases, it follows that, with the addition of coke, the coking process proceeds at a faster rate and is completed in a shorter time.

2. In one and the same box were placed 25 kg each of charges Nos. 2 and 3 (Table 1); the box was placed near the charging port (old installation) and removed from the oven after 20 hours.

Both charges proved to be not fully coked, with a volatile residue of 14.10% for the second and 19.40% for the third; moreover, both kinds of raw semicoke retained caking capacity. However, the degree of coking of the charge with coke proved to be much greater, since the loss of volatiles for it was

\(30.00 - 14.10 = 15.90\%\),

or 53.0% of the amount of volatiles that had been present in the charge; for the third charge the loss was

\(24.99 - 19.40 = 5.59\%\),

or only 22.3% of what had been present initially. Since both charges, being in one box, were under identical coking conditions and lost different amounts of volatiles over the same period of time, we therefore also have here proof that a charge with coke is coked faster and, consequently, for such charges the period

coking will be shorter. There is an indication of this in the literature [3]. Its actual duration, however, can be established only by a coking experiment with a full oven charge.

Table 1

A more or less accurate calculation of charges assigned for experimental coking was difficult to carry out because of the absence, for the coals to be charged, of indices of caking capacity; this had to be done approximately, according to the average characteristics of coals of various grades.

During the period of the experiments, the following coals were present in the silos:

Gas coals: (\(G_1\)) Kirov mine, Leninskoye deposit;
            Yaroslavsky mine, Leninskoye deposit;
            “A” mine, Leninskoye deposit.

Gas coals (\(G_2\)) Pionerka mine, Belovo-Babanakovskoye deposit.

Coking coals (K) Voroshilov mine, Prokopyevskoye deposit;
            Kalinin mine, Prokopyevskoye deposit.

Lean coking coals (KO)
            Fizkulturnik mine, Anzhero-Sudzhenskoye deposit.

Only the coal from the Pionerka mine (Belovo) was discharged from the gas-coal silos, then coal from the Fizkulturnik mine (Anzherka), and, in addition, Zhirny Osinnikovsky (Zh).

The main guideline in selecting charges with the introduction of finely ground coke was directed toward reducing the deficient coal grades “Zh” and “K” and toward the greatest possible introduction of the most widely available coals “\(G_1\)” and “\(G_2\)” in combination with “KO”¹, which should broaden the assortment of coals going to coking and promote a more correct use of the coking coals of Kuzbass in accordance with their industrial reserves and production volumes.

For coking in the new ovens (battery No. 1—29 ovens)², charges Nos. 5, 6, 7, and 8 were designed, information on which is given in Table 2; in addition, charge No. 4, corresponding in composition to the production charge, was coked in a box under identical conditions, in order to have comparable figures from coke testing on Prof. P. G. Rubin’s small drum. The latter, located at coke sorting, has dimensions: diameter — 1000 mm, width — 500 mm. On the inner surface

the drum has shelves made of iron strips. In testing the coke, the drum was given 150 revolutions over 7–8 minutes (manual rotation), with the aim that the peripheral speed should be more or less close to that of the Sundgren drum. Into the drum were charged 25 kg of coke in pieces larger than 25 mm. After treatment in the drum, the coke was screened on sieves with openings of 70, 40, 25, 15, and 10 mm. The results of testing in the drum and the volatile-matter content in the cokes are given in Tables 2 and 3.

Table 2

As can be seen, experimental charges Nos. 5 and 6, in the yield of classes >25 mm, proved identical with the production charge, but surpassed it in the yield of the largest class >70 mm; charge No. 7 gave coke with a yield of the >25 mm class higher than that of the production charge.

A comparison of the coke from charges Nos. 5 and 6 shows that grinding the additive coke so that it passes through a sieve with 900 openings/cm², as compared with coke ground under a sieve with 500 openings/cm², gives no difference; therefore it may be accepted that the fineness of grinding of the additive coke is necessary and sufficient under a sieve with 500 openings/cm².

The results of the experiments show that, without reducing the quality of the coke, up to 45% of gas coals may be introduced into the charge together with coals of grade “K,” while at the same time reducing the coke coals by half in comparison with the production charge.

In comparison with the latter, such a charge gives coke of better quality, owing to the greater yield of the largest class >70 mm.

Charges Nos. 7 and 8 are of special interest; in the first of them (No. 7), coal of grade “K” is completely excluded, and the amount of gas coals is brought up to 60%; in this case a sufficiently fused, heavy coke was obtained, higher in strength than the production coke.

Table 3

Meanwhile, an analogous charge without a coke addition (No. 8) yielded coke of unsatisfactory quality, with the amount of the class \(>25\) mm after the drum test only 72%, as against 88.8% for the coke from charge No. 7.

Thus, here the highly favorable effect of finely ground coke on the coking properties of charges with a high content of gas coals is revealed quite clearly.

As for the charge for old ovens, here, in accordance with production practice, gas coal from the Belovo-Babanakovo deposit of the Pionerka mine was tested. As is known, it differs from the Leninsk coals by a significantly lower caking capacity; this capacity is almost at the limit of what is required under the coking regime existing in the old ovens.

Therefore, when combined with coke lean coals (Anzherka), enrichment with respect to caking capacity is required by introducing a fat coal from the Osinnikovsk deposit. Tables 4 and 5 give the results of coking in the old ovens. The best charge, which yielded coke of quality above production quality, was charge No. 12 with 50% gas coal from the Pionerka mine.

On the basis of the work carried out, the following conclusions may be drawn.

1. The addition of finely ground coke in an amount of 5% increases the bulk density of charges by an average of 5%.

2. Charges with a coke addition require less time to complete the coking process than ordinary charges, owing to the much greater thermal conductivity of coke as compared with coal.

3. The coking capacity of gas coals (from the Leninsk deposit), when coke itself is added to them in an amount of 8–10%, increases considerably, as a result of which, when coked in modern ovens, it is

Table 4

Table 5

it is possible to introduce up to 60% gas coals into the charges (with 5% coke) without lowering the quality of the coke. At the same time, the amount of coking coals (grade “K”) in the charges can be considerably reduced.

1. For some charges with a high content of the lean mixture “gas coal + coke” (on the order of 65%), coke of satisfactory quality ...

is obtained without the participation of coking coals, but only in combination with the indicated mixture and coals of the “KO” groups in binary charges.

1. The necessary and sufficient degree of grinding of the additive coke corresponds to passage through a sieve with 500 openings/cm².

Literature

1. Gebler I. V. On the question of coking gas coals of the Kuznetsk Basin. Izv. AN SSSR, OTN No. 6, p. 873, 1946.

2. Gluzman L. D. and Edelman I. I. Control of Coke-Chemical Production, p. 75, 1946.

3. Roberts J. and Inkner A. Coking and Low-Temperature Carbonization of Coals, p. 136, 1938.

1. Coals “Zh” and “KO” according to the new technological grouping correspond to “PZh” and “K₂” of the old commercial classification. ↩

2. Temperature of the verticals about 1400°. ↩