| Tons of Charge. | Sulphur. | Copper. | |||||
|---|---|---|---|---|---|---|---|
| % | Tons. | % | Pounds. | ||||
| First-class ore, | 28,646 | 15·50 | 4,440 | 6·641 | 3,804,555 | ||
| Second-class ore, | 1,913 | 14·60 | 279 | 5·476 | 209,447 | ||
| Lining ore, | 52 | 1·45 | 1 | 3·834 | 3,988 | ||
| B. and B. slag, | 6,667 | .. | .. | 0·797 | 106,325 | ||
| B. and M. slag, | 481 | .. | .. | 1·919 | 18,450 | ||
| Precipitates, | 333 | .. | .. | 58·853 | 392,352 | ||
| Precipitates from old works, | 41 | .. | .. | 68·344 | 56,607 | ||
| Slimes from old works, | 19 | 7·50 | 1 | 4·203 | 1,637 | ||
| Coarse concentrates, | 14,083 | 32·10 | 4,521 | 10·782 | 3,036,802 | ||
| Calcine bearings, | 232 | 4·50 | 10 | 9·321 | 43,230 | ||
| Briquettes, | 27,560 | 15·32 | 4,223 | 4·928 | 2,716,299 | ||
| Reverberatory matte, | 146 | 23·30 | 34 | 35·752 | 104,651 | ||
| Reverberatory slag, | 687 | 1·10 | 8 | 1·566 | 21,501 | ||
| Converter cold matte, | 552 | 18·20 | 100 | 42·675 | 470,839 | ||
| Converter slag, | 9,999 | 1·10 | 110 | 3·018 | 603,429 | ||
| Converter cleanings, | 7,891 | 6·60 | 528 | 16·840 | 2,688,024 | ||
| Lime-rock, | 61,794 | .. | .. | .. | .. | ||
| Coke, 18,766·235 tons, at 14·21 per cent. ash, | 2,667 | .. | .. | .. | .. | ||
| Total charge, | 163,853 | 8·70 | 14,255 | 4·357 | 14,278,136 | ||
| Total production, | 18,447 | 21·13 | 3,898 | 39·483 | 14,567,376 | ||
| To slag, | .. | .. | .. | .. | .. | ||
| Analysis. | |||||
 | |||||
| SiO2 in slag, | 46,081 ÷ 110,810 tons slag | = | Calc. 41·59 % | Actual 41·30 % | |
| FeO in slag, | 21,071 ÷ 110,810 " | = | 19·01 " | 19·00 " | |
| CaO in slag, | 30,693 ÷ 110,810 " | = | 27·70 " | 28·00 " | |
| Total, | 97,845 tons, at 88·30 per cent. = 110,810 tons slag. | 88·30 " | 88·30 " | ||
| Coke consumption, 10·63 per cent.wet weight = 10·96 per cent. dry weight. | |||||
The other constituents used in the charge comprise varying quantities of materials which accumulate round the works, and which, being rich in copper values, it becomes useful and essential to clean up. For the calculating of the furnace charges, the amounts of cupriferous material available at the stock-bins are reported to the blast-furnace department. The quantities decided upon are divided among the number of charges which are considered likely to be worked off during the day, this number averaging about 1,100. The result of this calculation indicates the amount of each kind of material to be weighed for the separate charges; the analysis of each constituent being naturally known. The materials available for smelting are highly siliceous in character, the first-class smelting ore, of which large quantities are treated, giving a strongly acid composition to the charge; copper-bearing basic materials suitable for fluxing are not available in large quantity, and this necessitates the purchase of barren lime-rock, this item being the largest of the blast-furnace charge. In making up the charge sheet, as large a quantity of concentrate as possible is included, since this constituent is not only high in copper values, but owing to a high iron and sulphur proportion, it increases the fuel value of the charge, the influence on the coke consumption being very marked. The concentrate further forms a base for the matte, and introduces iron, of which there is a shortage, into the slag, thus reducing its too-siliceous character and lessening the quantity of lime which it would otherwise be necessary to procure for the purpose.
The briquettes are next worked in to as great an extent at possible, since by this means the large stocks of settling-pond slime and of screened fines are reduced and their 5 per cent. of copper is extracted. The whole stock of old slags and residues is used up on the charge, these materials introducing considerable amounts of copper, whilst being irony, they further help to reduce the acidity of the slag, thus saving the employment of the lime-rock otherwise required for fluxing. The total quantity of copper, iron, and sulphur available being then calculated, and the allowances for sulphur elimination and for the copper loss on smelting (2 to 7 per cent.), as based upon previous experience, being deducted, the amount of iron required to constitute the 45 per cent. copper matte is estimated. From this figure the FeO remaining for slag production is determined. The silica introduced by the above materials is also known, and the amount of lime-rock required to produce an easily running slag is next calculated. The slag which is found by experience to give the most satisfactory running has a composition of about—
| SiO2 | 41 per cent. | |
| FeO, | 19 " | |
| CaO, | 29 " |
Variations from this composition, especially as regards higher silica contents, immediately introduce difficulties, increasing the expense of furnace running, by requiring more fuel and care in working, reducing tonnage, and producing a slag which runs far less freely. So that although the large quantity of siliceous material at hand might tempt the management to work with a more siliceous slag, and so save the procuring of such large amounts of barren lime-rock, the cost of this material is much more than compensated for by the advantages which result from the working with a slag which contains only about 40 per cent. of silica.
The quantities of the charge constituents thus calculated, divided by the likely number of charges to be worked, are entered up on the charge sheet, which is handed over to the charge foreman.
