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Volume 28, 1895
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Art. LXXII.—Iron from the Titaniferous Sand of New Zealand.

[Read before the Wellington Philosophical Society, 18th December, 1895.]

At starting Mr. Purser desires me to say that until about three years ago the author had no special knowledge of the subject of this paper, but about that time he conceived the idea of separating the refractory from the metallic portion of the sand by magnetism and then forming it into a hard briquette suitable for the smelting-furnace. He asks that you will make due allowance from a scientific point of view when discussing this paper, he relying more on a practical direction.

Mr. Purser says the component parts of the titaniferous sand that is found in such enormous quantities on the west coast of the North Island consist of magnetic oxide, titanium, olivine, and silica, the most refractory of which is titanium. The proportion of magnetic oxide varies according to the local surroundings, that found in the vicinity of the Breakwater at New Plymouth being heavily charged with silica, which comes down from the surrounding hills of grey sand. The same drawback is also found at Waitara, and many other parts of the Taranaki District; while the richest deposits are generally found at the mouths of the rivers, and always on the north side of them. The best deposits the author has observed are at the Waiwaki, in Taranaki Province, and the Awakino and Mokau Rivers, in Auckland Province. On the north shores of these rivers there is practically an unlimited supply of very rich sand, which averages about 88 to 90 per cent. of magnetite; and equally good sand has frequently been found in thick layers far inland whilst well-sinking. The origin of these deposits is to a certain extent shrouded in mystery; in all probability Mount Egmont was the parent of them, and those found as far north as Onehunga and Kaipara have probably been carried in that direction by sea-currents.

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The object of the author's invention is to eliminate all the refractory constituents of the sand by magnetism, and to make the cleaned portion up into a hard briquette suitable for the smelting-furnace. He also claims that the product made from separated sand is far superior and more malleable than it would otherwise be if the titanium was fused with the magnetite, in which case titanic acid would be absorbed in the iron and be nearly as potent in producing “red short” as phosphorus; while some of the specimens laid before you this evening, made from separated sand, are comparatively malleable, even although they have not been puddled or treated by any second process whatever.

Separation.—This is accomplished by passing the sand underneath magnetized drums; and the author thinks it prudent, in order to avoid complications, to embrace the two principles of magnetism—namely, electro and permanent. The electro-magnet is made with equal sections of magnetized skins and insulation alternately, and is so arranged that at each quarter-revolution the current is broken and discharges the magnetic sand accumulated; while in the permanent magnet-drum its periphery comes in contact with a fixed brush, which sweeps the sand into a receptacle provided for it: but, as the author is in attendance with drawings and the means of practically demonstrating the process, it is needless that I should take up the time of the meeting by attempting to describe it.

The Briquette.—As it is impossible to smelt loose sand in a blast or cupola furnace, it becomes necessary to put it into some solid form in order that it may be subjected to the fullest possible action of the fuel, and also stand the weight of the furnace during fusion. This is accomplished by mixing the separated sand with a glutinous substance made to the strength of ordinary size, of about one part of ordinary carpenters' glue to twenty-two parts of water. Even when using the glue of commerce this would not be an expensive article, as it takes a very small quantity to saturate a large body of sand; but this cost is further reduced by making the size from the waste by-products of the butcher's slaughterhouses. After being well mixed it is spread on sheets of iron to the thickness of ½in., and blocked out into oblong briquettes about 5in. by 3in. These are then dried with a gentle heat for about thirty minutes, when they become perfectly hard and are ready for the smelting-furnace. It is further claimed that by the use of this glutinous organic substance for binding the sand a double object is attained—that of becoming a supplier of animal charcoal in one direction and of carbonic oxide in another; in fact, it acts as a very useful flux, which greatly assists conversion. The total cost of the finished

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briquette is estimated at 3s. 3d. per ton, including separation of the sand; and 1 ton of good fuel will smelt 8 tons of them.

These briquettes smelt as readily in a cupola furnace as ordinary pig-iron does, and with the same amount of fuel as previously stated; while the proportion of slag is only slightly in excess of that found in remelting pig-iron, or at the outside 25 per cent. This very low percentage is not to be wondered at when it is remembered that all extraneous matter has been eliminated from the sand by separation, and the glutinous substance used in making the briquette has all the cleansing properties of a flux. The author considers that, while separation is necessary in order to produce malleable iron, this briquette is really the key to the position for producing the highest class of metal at (as will be shown later on) the lowest cost of any iron-producing country known.

This is saying a good deal; but it must be remembered how wonderfully Nature has endowed New Zealand with the richest of raw materials for the manufacture of iron, costing next to nothing to mine; and in this condensed form it is so easy to handle that New Zealand should not only supply her own wants, but at an early date (having in view the very superior quality) should soon become a large exporter, even to Europe itself.

Cost of Production.—It is quite anticipated, it will be granted, that the reduction of this ore is an easy matter, and that the product is superior to any iron on the market—in fact, from the low percentage of carbon and the high percentage of iron it is apparent that we have the raw material of steel lying at our feet; but the all-important question is, What will it cost to produce? The author has gone very carefully into this matter, and cannot make the cost per ton come to more than £1 10s., as follows:—

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£ s. d.
Elevating the sand 0 0 9
Separating 0 1 0
Making briquettes 0 1 6
Labour 0 6 7
Fuel 0 9 0
Flux 0 4 0
Loss of weight 0 5 0
Interest on capital 0 2 2
£1 10 0

This is probably lower than ordinary pig can be produced for in Europe, and, surprising as it may appear, it is still a fact, considering the advantages we have in the raw material

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already referred to, as against the heavy work of mining the ordinary iron-ore of Europe. Then, also, outside calcining requires about 1 ton of coal to each ton of ore (in order to get rid of only a portion of the extraneous matter prior to its going into the furnace); and finally there is the handling of 3 ½ tons of ore, and, moreover, the consumption of fuel sufficient to fuse these 3 ½ tons in order to produce an output of 1 ton of pig-iron: while the balance, 2 ½ tons, until recently was not only absolutely valueless, but necessitated a still further expense for handling. Now, while the cost of fuel and labour in New Zealand is in advance of these items in Europe, this extra cost is more than counterbalanced by the richness of our oxide, and the production of a metal which, at its first stage, would probably fetch double the price of No. 1 pig, owing to its very superior quality.

Analysis.

It will be seen by the following analysis that iron made from New Zealand sand is superior to even the highest quality known in Europe—viz., Swedish pig—being higher in the good elements and lower in the refractory ones:—

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(Sir Lowthian Bell.)
Swedish Pig-iron.
Carbon 4.50
Silicon 0.50
Sulphur 0.03
Phosphorus 0.15
Manganese 1.80
Iron 93.02
100.00

[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]

(Mr. Skey, Government Analyst, 14th April, 1895.)
New Zealand Iron.
Carbon 2.21
Silicon 0.84
Sulphur Trace
Phosphorus 0.20
Titanium 0.34
Iron 96.41
100.00

From another sample assayed on the 16th July, 1895, with a view to find what percentage of carbon was in combination and what quantity of titanium (if any), Mr. Skey reported: “The total quantity of carbon in the iron No. 6958 is 1.71, of which 1.34 is in combination with the iron. I found traces of titanium only.”

It is further interesting to note that, while pig-iron made from New Zealand ironsand contains only about one-half the carbon found in the best brands of European manufacture, even a large percentage of this is in combination, as stated above, while the only other metal I can find carrying any carbon in combination is that used by Bessemer for making steel, which stands thus:—

Carbon combined 0.50 4.10
Carbon graphitic 3.60
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Prospects of the Industry.

By reference to the Statistics of New Zealand, page 171, 1893, it will be seen that the imports of certain descriptions of iron, the whole of which could be manufactured in New Zealand from the titanic ironsand at a much cheaper rate, were as follows:—

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£
Rails and railway-bolts 48,037
Pig-iron, wrought, wire, &c. 358,511
Nails 24,773
Steel and steel rails 14,484
£445,805

Or, in other words, these items represent one-fourteenth of the entire imports of the colony for that year.

As an evidence of the easy manner in which the briquette melts, perhaps it would not be out of place if I were to submit a few certificates from ironfounders who have conducted experiments in small cupola furnaces.

The following are the results of practical trials that have been made with Mr. Purser's process:—

Blenheim, 20th February, 1895.

I smelted about 5cwt. of ironsand briquettes made under Mr. E. Purser's patent process on the 8th February. The mode of smelting was in a small cupola furnace; from the time of putting them in until they were melted was about twenty minutes; and the quantity of fuel requisite seemed similar to that used for smelting pig-iron.

I find that that portion of the briquettes which was run off in the time mentioned—viz., twenty minutes—the metal was not thoroughly converted, while the last charge, which I let down with the fuel by letting down the bottom of the furnace, and allowed to cool gradually, produced a malleable metal of very superior quality, much resembling mild steel.

William Fairweather

,
The Foundry, Blenheim.

New Plymouth, 16th April, 1895.

About 5cwt. of Mr. Purser's briquettes were made in my foundry, and afterwards smelted in my cupola furnace, with the following results: The briquettes smelt easily; they will flow in about thirty minutes, but at that stage it looks a great deal like slag, but by putting it through the furnace again a considerable quantity of iron was obtained, although it was not sufficiently liquid to flow freely. This was owing to the furnace being too short, and not giving the material sufficient time to absorb carbon. Fortunately, there was sufficient slag intermixed with the metal to allow it to be cut out, which was done as soon as the furnace was cool enough, and the following day it was cast into ingots, wheels, &c. The metal is very close-grained, and resembles very superior steel.

F. W. Okey

,
Taranaki Foundry.

Wellington, 19th June, 1895.

I assisted Mr. Purser when smelting a quantity of ironsand briquettes, made under his patent process, at Mr. Seager's foundry, Wellington. They smelt with great rapidity (the time being thirty-five minutes) in a small cupola furnace, and conversion takes place in about half an hour

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after they reach the melting-point. Ran out castings of tools and ingots, but the rapidity (which is peculiar to steel) with which it cooled on the hearth of the furnace prevented utilising the whole of the product for casting purposes on that day. The metal is remarkably tough and very fine in the grain, and in my opinion it is a high-class steel.

J. Neal

,
Smelter, Antimony Department of Mr. E. Seager, Wellington.

In addition to these certificates Mr. Purser has made several other experiments, all of which confirm what can be successfully accomplished even under the disadvantage of having only a small cupola furnace and crucibles to work with; and it must be remembered that a cupola is not constructed on lines suitable (nor was it ever intended) to smelt ore, but manufactured iron, such, for instance, as scrap, cast, or pig, for making castings.

It will be seen that in these cases the briquettes flow from the tap-hole at from twenty to thirty minutes, according to the pressure of the blast; but in order to absorb sufficient carbonic oxide to come to complete conversion the liquefied mass must remain on the hearth of such a furnace for a further time before conversion takes place. Now, when it is remembered that the height of the cupola-furnaces used was only 10ft. from the twyers, and that an ordinary blast-furnace would be quite 40ft. high, it is absolutely clear that conversion would take place before the molten briquettes reached the hearth of this kind of furnace, practically from the greater length of time the charge would take in coming down a distance of 40ft. in a blast-furnace of that height, as against only 10ft. in a cupola.

In conclusion, if New Zealand is to become the great nation which nature intended her to be, by the rich endowments of mineral wealth, the time is none too soon when we should make a great effort to develope them; and, above all, her iron deposits are the most valuable, for not only could we keep £500,000 a year in the colony which is now being sent out of it, out, owing to the vastly superior article got from the titaniferous sand, it is not hoping for too much that at an early date New Zealand will become a powerful competitor with the world in the production of both iron and steel. While giving employment to a large portion of the population, the spending-power of the people would be such as to justify the manufacture locally of many classes of goods that are now imported.