September 11, 1914 _______________________________________________________________________________________________________ THE COLLIERY GUARDIAN. b&1 Table VI.—Heating oe Coal in Air calculated from Table III. (assuming no Heat Loss). Time, Temperature, in hours. Degs. Cent. 0 .......... 30 3 .......... 35 7 .......... 40 13 .......... 45 18 .......... 50 23 .......... 55 27 .......... 60 31 .......... 65 35 .......... 70 40 .......... 75 Time, Temperature. in hours. Degs. Cent. 43 .......... 80 45| .......... 85 48 .......... 90' 50 .......... 95 511 .......... 100 52 .......... 105 521 __________ 110 54 _____.......... 130 55 .......... 180 After which the coal heats very rapidly indeed. It is clear from Table VI. that the absorption of oxygen from the air is quite sufficient to cause the coal to fire, provided that no heat is lost during the reaction. The mere heating of the air absorbs very little heat; but a far more serious source of heat loss is the evaporation of water contained in the coal. The Barnsley Hards contain about 5 per cent, of moisture when fresh, so that to heat 100 grammes of coal above 100 degs. Cent, it is necessary to supply about 2,800 calories for the evaporation of the contained water. The cooling effect due to this cause does not become very serious below 70 degs. Cent., provided just as much air is supplied to the coal that all the oxygen is absorbed. At 70 degs. Cent., however, half the oxygen absorbed from the air current (when the issuing stream contains no oxygen) will be required ;to evaporate. 4he water. At 80 degs. Cent, all the oxygen in the ais supply is needed to evaporate water, and hence the temperature could not rise above this point until all the water has disappeared. Provided that the temperature survived this interval, it would afterwards begin to rise rapidly again, increasing in rapidity until the coal fired, as is shown by Table VII., which is based on the assumption that all the oxygen is absorbed from the air stream, which is saturated with moisture when it leaves the coal. Table VII.—Rate of Heating of Barnsley Hards. Hours Hours Temperature. (water evaporating (no evaporation Degrees Cent. from the coal). taking place). 30 0 0 35 3 3 40 7 7 45 13 13 50 18 18 55 23 23 60 28 27 65 35 31 70 44 35 75 60 40 80 79 43 85 161 45J 90 171 48 95 178 50 100 183 5H 105 186 52 110 188 52J 115 189 — 120 190 — 130 ’ .. 191 (8 days) 54 The difference between the two rates indicates how “ exact ” the conditions have to be for a small mass of coal actually to fire. The air current must be regulated to a nicety, and the mass must be well heat-insulated. Up to 60 degs. Cent, very little heat is carried away from the coal, even if the air current is comparatively large, so large, for example, that it contains about 15 per cent, of oxygen after passing over the coal. Above this temperature, however, the air current has a tremendous cooling effect, and if it exercises this effect, the coal may easily be cooled to 40 degs. Cent..again, from which temperature very little heating can occur a second time, since the quantity of oxygen that the coal has already absorbed is about sufficient to saturate it at 40 degs. Cent. A series of experiments is now being made to’ test these conclusions, by measuring the actual rise in temperature when coal dust is allowed to absorb oxygen from the air, and a fuller discussion of the mechanism of the heating will then be possible. (To be continued.) _____________________________ Immingham Coal Exports.—The quantity of coal exported from Immingham during the week ended September 4 is shown by the official return to be as follows :—Foreign : To Gefle, 4,431 tons; Helsingborg, 2,963; Oxelosund, 2,824; Rotterdam, 5,765; Stockholm, 3,323-7—total, 19,306 tons, compared with 38,508 tons for the corresponding week of last year. There were no exports to coastwise destinations either this year or last for the week ended September 4. Hull Coal Exports.—The official return of the exports of coal from Hull for the week ending Tuesday, September 1, 1914, is as follows:—Antwerp, 129 tons; Alderney, 173; Archangel, 9,973; Bandholm, 1,432; Buenos Ayre^ 3,181; Christiania, 764; Drontheim, 359; Gothenburg, 459;.Har- lingen, 1,670; Liulea, 2,901; Malmo, 2,871; Naples, 1,709; Oxelosund, 6,374; Odense, 1,908; Randers, 600; Rotterdam, 10,401—total, 44,904 tons. Corresponding period September 1913—total, 85,160 tons. Imports of Pit Props in August.—According to the tables published by the Board of Trade, only 184,258 loads of pit props and pitwood were imported into the United Kingdom in August, the value being £238,551; in August 1913, 422,206 loads were imported, valued at £600,340; and in August 1912, 425,737 loads, valued at £578,257. Imports had previously been somewhat short, as 1,727,833 loads were imported in the eight months ended with August, the value being £2,032,577, as compared with 2,106,118 loads, valued at £2,636,351 in August 1913, and 1,875,705 loads, valued at £2,287,321, in August 1912. UNKNOWN CLAYS IN COAL MINES,* By J. W. Mellor, D.Sc. A great many papers have been read at various times with the object of directing attention to the waste of materials which Nature has provided in but limited stores. This question will, however, become of vital importance only when the end of the world’s stock becomes more clearly defined, and mines begin to “ peter out ” one after the other. The abandonment of an exhausted mine in a particular district—the graphite mine in Cumberland, for example—may be a local disaster; but it is not generally serious when plenty more can be found elsewhere. The writer has no message to deliver concerning the conservation or the preservation of our natural resources, his object being rather to invite the co-opera- tion of the members in the quest for new supplies. He has the feeling that coal miners are missing the chance of conferring a great benefit on many industries. There is a great demand for high-grade fireclays, and if a good supply of such a clay were discovered in any locality, a new and lucrative industry would most certainly soon be flourishing. As an example, the writer may mention the Stourbridge district, which has probably built its name on the so-called “ Old Mine ” fireclay; and in Germany the long-famed Hessian crucibles are made from the Almerode clay. In modern times, when the manufacturing i ndustries employ fiercer heats than were formerly in vogue, engineers are clamouring for high-grade refractories. So greatly are the metallurgical and gas industries dependent upon firebricks, that any marked improvement in their refractoriness would be immediately followed by better and more efficient methods of manufacturing the corresponding products. The pottery industries, too, complain that their sagger clays are poor, and that many types of pottery cannot be made here because of the inferior quality of these clays. Geologists assert that the North Staffordshire district is an exceedingly promising place to look for good fire- clays. There are certainly indications that in the coal mines one or more good fireclays are being passed by as useless, which if brought to the surface would be as valuable as, or more valuable than, coal. The simul- taneous mining of coals and fireclay is no new matter. There are coal mines which bring up coal and clay simultaneously; and there are exhausted coal mines which are being re-worked for fireclay. So far as the writer knows, the fireclays associated with the coal are not mined in this district. Why? If it be certain that all the clays passed by are of an inferior grade, the answer is obvious; but, so far as the writer has been able to ascertain, the true answer is that no one has given the subject much attention. The writer has made preliminary tests on a very small number of samples which have come into his hands ffom local mines, and these have been very satis- factory. A few years back Mr. Frank Rigby kindly presented a furnace for testing clays, and some thousands of clays from different parts of the country must have been treated therein, but of local clays very few. Most of the fireclays which crop out in the local surface mines, and are used in making saggers and firebricks, would be classed as second-grade fireclays; and some would not be called fireclays at all, if judged by the standards adopted in some of the industries. The refractory or fire-resisting quality of a clay is tested by moulding it in the form of a little four-sided cone, and heating it on a gradually rising temperature alongside a number of similar cones (called Seger’s cones) made from definite mixtures of china clay, alumina, etc., and designed by the manufacturer to collapse at definite temperatures, when heated under certain definite conditions. The cones are numbered, say, 26, 27, 28, 29, up to 40. Cone 26 “ squats ” at approximately 1580 degs. Cent., or 2876 degs. Fahr.; cone 27 at 1610 degs. Cent., or 2930 degs. Fahr., and so on. If, therefore, a cone made from the clay be heated with Seger’s cones 26, 27, 28, 29, and if cone 26 squats before the clay, it follows that the clay resists a higher temperature than 1580 degs. .Cent.; but if the clay stands while cone 29 squats, and squats while cone 30 stands, the refractoriness of the clay is described as cone 29. Some corporations have agreed to define a fireclay as one which squats at about 26; ands a first-grade fireclay as one which squats at not less than cone 30. The average sagger marl in the North Staffordshire dis- trict squats at about cone 27, and is therefore uncom- fortably near the lower limit. The writer will exhibit a fireclay taken from a mine in this country which squats at cone 33. An average British fireclay squats at about cone 30 or cone 31. The new clay is quite a superior clay, and if the seam where it was found is sufficiently thick—and the writer is told that it is—he anticipates that it will have a bright commercial future before it. A good fireclay, it may be mentioned, is worth about 10s. per ton at the surface. \ The writer knows that several clays, at different times, have been brought up from mines, mixed with perhaps quite unsuitable material, and made into bricks, which after trial were condemned. These reports are very unsatisfactory. Every clay requires “humouring” in order to get it to give the best results. Such reports as the writer has heard are quite inadequate; the clay has not had a fair chance, and consequently has been condemned on evidence that is perhaps worse than valueless. 'the writer has tried to show that good fireclays are a valuable commercial asset; and that we may or may not be ignorantly passing by valuable fireclays in our * From a paper read before the Institution of Mining Engineers. coal mines. He has also shown how to make a pre- liminary test on the refractoriness of a fireclay. It now rests with mining engineers to confirm or dispel the suspicion that they are passing by good money. ________________________ AMERICAN COAL AND THE WAR. The United States coal operators continue their prepara- tions for an extension of the export trade in coal, and efforts are also being made to develop the sales of by-products. In a recent communication, Mr. Franklin K. Lane, Secre- tary of the Interior, after alluding to the fact that the United States is now producing 40 per cent, of the world's supply of coal, and the reserves yet to be drawn upon exceed, so far as known, those of all the rest of the world combined, added that it is not generally known to what an extent America has been depending upon Europe, principally Germany, for many of the chemical products derivable from coal, and which we have been permitting to go to waste, in the most reckless manner. The chemical industries dependent upon coal tar as a raw material have had little development in the United States. Imports of coal tar products in 1913 were valued at 11,000,000 dols. at initiating points, and when they reached the ultimate consumer probably cost double that amount. If the present war continues any length of time the American consumer will have to do without aniline colours and dyes, certain drugs, and numerous other coal tar products, or the American manufacturers will undertake to supply these essential commodities which have hitherto carried the label, “Made in Germany/’ The following is a comparative statement of imports and exports in the United States for June 1913-14, and for the 12 months ending June 1913-14, in long tons:— 12 months. June. ( Imports from : 1913. 1914. 1913. 1914. United Kingdom 9398.. 11,025... 648... 341 Canada 1,336,387.. . 1,005,693... . 80,533... 67,511 Japan Austria and Tas- 79,072... 85,689.. 260... 1,838 mania 150,150.. . 251,977... 9,325... 21,896 Other countries 3,257.. 3,618.. — ... 5 Total 1,578,264.. . 1,358,002.. . 90,766... 91,591 Exports : Anthracite — Canada 4,545,976.. . 3,897,365.. . 414,901... 427,710 Uruguay — 84... — — Other countries 79,505.’ 61,665.. ‘ [5,764... 5,546 Total 4,625,481.. . 3,959,114.. . 420,665... 433,265 Bituminous— Canada 11,981,443.. .11,472,397 . 1,418,113... 793,856 Panama 483,974.. 362,427.. 40,725... 25,810 Mexico 443,884.. . 296,392.. 37,635... 15,866 Cuba 1,273,945 . . 1,129,954.. . 106,264... 81,575 West Indies 601,431.. . 577,541.. . 51,376... 45,433 Argentina — .. 139,409.. — 9,977 Brazil — . 239,082.. — 10,023 Uruguay — 62,452.. — 6,200 Other countries 1,298,424 ’. . 1,425,312.. . 237,458... 196,826 Total .....16,083,101...15,704,966 .. 1,891,571...1,185,566 Bunker coal ... 7,350,404... 7,811,913... 683,910... 687,386 The Coal Age says (August 29) the export trade at Baltimore remains a negligible quantity. “ Foreign purchasers, mostly through London connections, are making cable enquiries, but the fact that no cash exchange has been arranged for this side is apparently holding up a business that will probably develop a little later.” On the other hand, enquiries are in the market at Hampton-road for large quantities of coal for export. The enquiries for export coal are coming from both European and South American ports usually supplied with Welsh coal, and already sales have been made and shipments moved. It is difficult to ascertain at what prices the export coal is being sold, but it is not believed quotations have been over 2*85 dols., though perhaps some may have been made at 2’90 dols. The Journal of Commerce says the demand for tonnage to carry coal to South America and Mediterranean countries continues active, and rates have eased up. A charter made for coal carriage, September loading, from Virginia to Rio de Janeiro, was closed at 5’40 dols. Quite a few boats have been fixed to carry coal to Las Palmas and Italian ports. American coal exporters state that New River, Pocahontas and other high-grade coals have been sold in large quantities for early shipments. Spain, Portugal and Egypt have sent in large buying orders, as well as Italy and South American countries. Operators are insisting that shippers have bills payable in New York on the surrender of the proper documents. To a certain extent, where coal is urgently needed, this has been done. Coal charters have been reported as follow:— Vessel. From To Tons, Navisbrook... Atlantic Range... Bahia .........1,965...6’00 Egda ..... Baltimore ..... Puerto Barrios... 1,610... — Kennebec ... Baltimore _____ Boston .......1,913... -r- ....... Van Allens Boughton .. Philadelphia... Boston .............1,909... — Kelbergen ... Norfolk ....... Rio de Janeiro...2,974.. 6’36 Josephine ... Philadelphia... Halifax ....... 842... 1’74 ....... Chehaw ... Port Reading... Savannah ..... 982 .1’10 ..... Hugin ..... Baltimore ..... Havana ......................1,174... — J. E. Bignon Philadelphia... Savannah ...... 4^8... — Rob Roy ... Philadelphia ___..... Charleston ... 684.. — Romera ... Virginia ....... Rio de Janeiro...3,189 — Jethou..... Norfolk ‘....... Mediterranean..2,781..5’40 Special attempt is being made to facilitate the financing of South American business generally, and the under- standing now is that a substantial degree of success has been attained in making these arrangements. It is asserted at the Department of Commerce that particular enquiries are already being made in South America concerning the details of conditions surrounding the sale and shipment of consignments of fuel. There is every.reason to suppose that the War Risk Insurance Bill will be adopted, thereby eliminating the probability of losses due to the seizure of fuel which is in process of transit from the United States to foreign buyers. More resistance is being offered to the passage of the Ship Purchase Bill, but that also is believed likely to become law in some form for a great while. With the improving outlook as to foreign exchange, this is expected to relieve the export situation materially.