───────────────────────────────────┬────────┬─────────────────
│ Time. │ Composition.
├───┬────┼─────┬────┬──────
│Hrs│Mins│ Cu. │ Au.│ Ag.
───────────────────────────────────┼───┼────┼─────┼────┼──────
│ │ │ % │ Oz.│ Oz.
11.52 am Charged No. 1 blast matte,│.. │ .. │46·08│0·15│ 31·50
11.54 am Blow commenced. │ │ │ │ │
12.04 pm Sample No. 1 blowing, │.. │ 10 │46·02│0·17│ 31·80
12.14 pm Sample No. 2 blowing, │.. │ 20 │51·46│0·18│ 35·80
12.18 pm Punched 3 minutes. │ │ │ │ │
12.24 pm Sample No. 3 blowing, │.. │ 30 │53·27│0·20│ 37·80
12.25 pm Punched 7 minutes. │ │ │ │ │
12.34 pm Sample No. 4 blowing, │.. │ 40 │56·29│0·21│ 40·80
12.40 pm Punched 2 minutes. │ │ │ │ │
12.44 pm Sample No. 5 blowing, │.. │ 50 │59·90│0·22│ 43·70
12.45 pm Punched 2 minutes. │ │ │ │ │
12.54 pm Sample No. 6 blowing, │ 1 │ 00 │62·67│0·23│ 44·90
12.55 pm Punched 6 minutes. │ │ │ │ │
1.04 pm Sample No. 7 blowing, │ 1 │ 10 │67·89│0·25│ 49·20
1.07 pm Punched 3 minutes. │ │ │ │ │
1.12 pm Blow stopped. │ │ │ │ │
1.13 pm Skimmed. │ │ │ │ │
1.14 pm Blow resumed. │ │ │ │ │
1.14 pm Sample No. 8 blowing, │ 1 │ 20 │73·97│0·27│ 54·90
1.17 pm Punched 2 minutes. │ │ │ │ │
1.21 pm Blow stopped. │ │ │ │ │
1.22 pm Skimmed. │ │ │ │ │
1.25 pm Blow resumed. │ │ │ │ │
1.25 pm Sample No. 9 blowing, │ 1 │ 30 │77·82│0·28│ 57·30
1.34 pm Sample No. 10 blowing, │ 1 │ 40 │74·16│0·26│ 54·30
1.44 pm Sample No. 11 blowing, │ 1 │ 50 │81·72│0·15│ 57·60
1.54 pm Sample No. 12 blowing, │ 2 │ 00 │98·50│0·78│107·70
2.02 pm Punched 1 minute. │ │ │ │ │
2.04 pm Sample No. 13 blowing, │ 2 │ 10 │98.57│0·40│ 81.60
2.05 pm Punched 2 minutes. │ │ │ │ │
2.08 pm Blow stopped, test for Cu.│ │ │ │ │
2.09 pm Blow resumed. │ │ │ │ │
2.10 pm Blow finished. │ │ │ │ │
Converted copper, │ 2 │ 16 │99.08│0·38│ 83·80
Total time punching, │.. │ 28 │ .. │ .. │ ..
Total time of blow, │ 2 │ 16 │ .. │ .. │ ..
Actual time of blow, │ 2 │ 09 │ .. │ .. │ ..
───────────────────────────────────┴───┴────┴─────┴────┴──────
───────────────────────────────────┬────────┬────────────────────────
│ Time. │ Composition.
├───┬────┼──────┬─────┬─────┬─────
│ │ │Insol-│ │ │
│Hrs│Mins│ uble │ Fe. │ S. │ As.
───────────────────────────────────┼───┼────┼──────┼─────┼─────┼─────
│ │ │ % │ % │ % │ %
11.52 am Charged No. 1 blast matte,│.. │ .. │ 0·15 │24·30│24·70│0·22
11.54 am Blow commenced. │ │ │ │ │ │
12.04 pm Sample No. 1 blowing, │.. │ 10 │ 1·30 │23·70│22·95│0·07
12.14 pm Sample No. 2 blowing, │.. │ 20 │ 0·30 │20·50│23·10│0·06
12.18 pm Punched 3 minutes. │ │ │ │ │ │
12.24 pm Sample No. 3 blowing, │.. │ 30 │ 1·10 │18·70│22·15│0·06
12.25 pm Punched 7 minutes. │ │ │ │ │ │
12.34 pm Sample No. 4 blowing, │.. │ 40 │ 1·30 │16·20│21·85│0·06
12.40 pm Punched 2 minutes. │ │ │ │ │ │
12.44 pm Sample No. 5 blowing, │.. │ 50 │ 0·90 │13·70│21·95│0·06
12.45 pm Punched 2 minutes. │ │ │ │ │ │
12.54 pm Sample No. 6 blowing, │ 1 │ 00 │ 1·30 │11·40│21·35│0·06
12.55 pm Punched 6 minutes. │ │ │ │ │ │
1.04 pm Sample No. 7 blowing, │ 1 │ 10 │ 0·65 │ 7·60│21·15│0·05
1.07 pm Punched 3 minutes. │ │ │ │ │ │
1.12 pm Blow stopped. │ │ │ │ │ │
1.13 pm Skimmed. │ │ │ │ │ │
1.14 pm Blow resumed. │ │ │ │ │ │
1.14 pm Sample No. 8 blowing, │ 1 │ 20 │ 0·25 │ 3·40│20·10│0·05
1.17 pm Punched 2 minutes. │ │ │ │ │ │
1.21 pm Blow stopped. │ │ │ │ │ │
1.22 pm Skimmed. │ │ │ │ │ │
1.25 pm Blow resumed. │ │ │ │ │ │
1.25 pm Sample No. 9 blowing, │ 1 │ 30 │ 0·15 │ 0·90│19·60│0·04
1.34 pm Sample No. 10 blowing, │ 1 │ 40 │ 3·30 │ 2·60│16·60│0·04
1.44 pm Sample No. 11 blowing, │ 1 │ 50 │ 0·25 │ 0·20│15·35│0·04
1.54 pm Sample No. 12 blowing, │ 2 │ 00 │ 0·017│trace│ 0·78│0·050
2.02 pm Punched 1 minute. │ │ │ │ │ │
2.04 pm Sample No. 13 blowing, │ 2 │ 10 │ 0·052│ 0·01│ 0·78│0·033
2.05 pm Punched 2 minutes. │ │ │ │ │ │
2.08 pm Blow stopped, test for Cu.│ │ │ │ │ │
2.09 pm Blow resumed. │ │ │ │ │ │
2.10 pm Blow finished. │ │ │ │ │ │
Converted copper, │ 2 │ 16 │ 0·017│trace│ 0·01│0·033
Total time punching, │.. │ 28 │ .. │ .. │ .. │ ..
Total time of blow, │ 2 │ 16 │ .. │ .. │ .. │ ..
Actual time of blow, │ 2 │ 09 │ .. │ .. │ .. │ ..
───────────────────────────────────┴───┴────┴──────┴─────┴─────┴─────
Samples taken each 10 minutes from beginning of blow until finished.
In general character, this colour sequence, during the bessemerising
of the ordinary class of copper mattes—_i.e._, those consisting
largely of iron, copper, and sulphur, with but moderate quantities of
impurity—does not vary very markedly, but the body and luminosity of
the flame depend to a great extent on the nature of the charge and on
the working conditions. The colours are intensified by very hot metal,
large charges, heavy blast, and rapid working, and particularly by the
presence of secondary constituents, such as zinc, lead, or arsenic,
which liberate dense white fumes, and so increase the luminosity of the
flame.
There are generally four main variations in the appearance of the flame
from the acid-lined converter:—
┌─ ─┐
│Oxidation of secondary │ Dark reddish-brown
At commencement ─┤ constituents, ├─ flame.
of blow, │Burning of iron, sulphur,│ Accompanied by much
└─ and coal, ─┘ smoke.
Slagging stage, Iron-sulphide oxidation, Apple-green flame.
White metal stage, Copper oxidation in White-blue flame.
presence of slag,
Blowing to blister Sulphur oxidation, Thin red-purple flame.
copper,
The changes in composition of the charge during a converter blow have
been traced by Mathewson, who assayed samples during the various
stages; some of these results are indicated in Table xii. and in Fig.
66. For full record see _Trans. Amer. Inst. Min. Engineers_, 1907.
In general, of the constituents present in the matte, iron and sulphur
are removed very readily, 96 per cent. of the former and 53 per cent.
of the latter in the slagging stage of the blow, whilst the elimination
of the injurious impurities is high, bismuth and arsenic being removed
to the extent of upwards of 90 per cent., and of the antimony,
selenium, and tellurium, from 40 to 70 per cent. are eliminated (see p.
217).
_Working of a Typical Charge in Silica-lined Converter._—The Anaconda
converter plant is now being operated with basic linings. The former
practice at this works was representative of the best type of
acid-lined working, and the following description, based upon this
practice, is typical of the method in general use. There were in
operation twelve converter stands of the dimensions previously given.
Normal working was to convert the 45 per cent. copper matte to white
metal, to pour off slag, blow to blister copper, and pour the resulting
metal—in regular sequence.
The colour-changes in the flame during bessemerising are indicated in
the colour-photographs reproduced in the frontispiece.
[Illustration: Fig. 66.—Composition of a Charge during Bessemerising
Operation.]
[Illustration: Fig. 67.—Pouring Slag, Anaconda.]
Seven to 8 tons of matte at an average temperature of 900° C. are
charged into the converter, which is in an upright position with the
blast on (16 lbs. per square inch). The operation of charging occupies
three minutes. A few lumps of coal are thrown in, a vigorous action
commences, copious and heavy white fumes and smoke and a full red to
red-brown flame being emitted. The converter is now turned slowly back,
so as to bring the tuyeres more completely under the charge and ensure
more rapid and efficient oxidation, and the blow proper then commences.
The flame drops for a time, continuing to be of a red to red-purple
colour for two to eight minutes, after which, green commences to show
in the red smoky flame (A), indicating that the first or slag-forming
period of the blow is beginning. The green colour becomes more
prominent and continues for 40 to 45 minutes (B). A preliminary pouring
off of slag is then usually made, owing partly to the danger of violent
or even explosive interaction which might otherwise occur between
matte and slag, and also with the object of keeping down the copper
losses in the slag by removing the greater portion of the latter at as
early a stage as possible. The blowing is then continued. Flashes of
blue now occasionally appear in the flame, and gradually increase in
number until the flame becomes blue-white (C), which indicates that
most of the iron has been slagged off and that the white metal stage
is reached. The blue-white colour of the flame is to be attributed
to the production of copper silicate, owing to the tendency of the
copper oxide formed by the air blast at this stage, to flux off, and
to produce the silicate rather than attack the copper sulphide. This
formation of copper-silicate is particularly liable to occur in the
presence of much slag and at high temperatures, factors which are well
known to encourage this selective combination, and which prevail at
this stage.
The blowing up to white metal takes about one hour.
Slag is then poured off again, until an iron rabble held under the
stream commences to show signs of “metal” which give an appearance
of spots of grease on the blade. The charge is then usually “doped.”
“Dope” consists of highly cupriferous scrap, cleanings, slags,
residues, also some siliceous material, added partly for the purpose of
cooling down the charge which tends to become overheated at this stage.
The converter is turned up again and the blowing is resumed in order to
convert the white metal to blister copper.