February 2, 1917. THE COLLIERY GUARDIAN. 229 the recbanigul’ar shape. The essential features of the beehive oven are a circular vaulted brick chamber with a port hole in the top, through which the coal may be charged,, and the products of combustion escape. An arched opening is. left at the bottom to admit the, air necessary for combustion, and for the quenching and withdrawal of the coke, such being temporarily bricked up during the coking process, with the necessary air vents so manipulated that the supply is more or less under control all the time. The opinion is held that this type of oven is best for high-class coals. The rectangular ovens are really a modification of the old Belgian type, and were evolved primarily to com- pensate for unskilled labour and higher costs. The name indicates' the shape, and they are built to various patterns, the main differences being the flue arrange- ments, by which heat is applied to the charge, and mechanical discharge of the coke. Some are built with side flues, in which the evolved gases are burnt whilst passing between the oven walls; others have bottom flues only, with a similar object; whilst a. third type are fitted with both side and bottom flues, thus assuring a more general distribution of the heat. This arrangement also enables the waste gases to be used in the heating of boilers for steam power produc- tion, which amounts to from 12 to 20 horse-power per coke oven. Up to the present, in New South Wales, only one coke works has adopted this source of steam power, but another company are constructing ovens with the same object in view. There appears to be very little doubt that the rect- angular oven will continue to be used , in New South Wales, and it is apparent that they have many advan- tages. Amongst the claims made for the rectangular ovens are increased yield, a better product, and lower cost of operation, but the more conservative consumers in other countries are inclined to favour the product from the older type of ovens. There may be a certain amount of justification for this opinion, but the writers’ investigation of the literature on coke production leads them to the belief that if such is the caise, it is more applicable to by-product coke, as compared with bee- hive, than to coke made in rectangular ovens. The third type of oven has been adopted by only two coke work in the State, namely, the Broken Hill Pro- prietary Company’s Steel Works and the Australian Coking and By-Products Company. The first of these has only been running a little over six months, and the second were erected about 3| years ago, but up to the present has not proved a success. This would appear to be largely due to faulty material and construction, and an effort to remedy these evils is now being contem- plated by the company. Burning Periods. The period occupied in burning a. charge of coke varies not only with the size of the charge and the nature of the coal, but also with the amount of air admitted into the oven. In New South Wales, with the ordinary type of rectangular oven, it is, as a rule, found most advan- tageous to arrange, the burning period on a *72 and 96 hour basis, in order to tide the works over a Sunday shift. In many cases an increased quantity of duff is charged for the longer period, namely, an increase, say, from 15 to 20 per cent., but this does not seem essential, and by regulating the air supply either a longer or shorter period of burning may/give practically the same result. f' Breeze and Black Ends. The breeze in New South Wales coke occasionally amounts to as much as 5 per cent, of the total charge", and as there is practically no sale for it at. present, it is a more or less serious loss to the coke producer. In some cases (the Broken Hill Proprietary By-Pro- duct Coke Ovens, Newcastle') the black end appearing at the rear of the charge is not pushed clear of the oven, but left to be re-burnt in the following charge, but this, however, is. only a partial remedy, for one “ end ” passes to the consumer, and the other to be “ over- cooked ” in the following burn off, when loss still ensues from burnt coke ash. Another remedy practised is to allow the ends to burn off to some extent after opening the doors, and before discharging; but here again, the remedy is accompanied by an equally undesirable action from the producer’s standpoint, for the “ ripe ” coke suffers from oxidation, with a resultant increase in coke ash. Black ends are more pronounced in the wide rect- angular beehive ovens owing to the surface area of the ends exposed to cooling influences being greater than in a narrow but longer oven, and it frequently happens that an otherwise good batch of coke- is somewhat spoiled by a noticeable quantity of black end. Several remedies have been tried in other parts of the world, such as recessed doors, flued doors, etc., but the former lessens the output of the oven somewhat, and the adaptability of the latter would appear to depend upon a complete flue arrangement throughout the ovens. Many New South Wales coke ovens are not provided with flues, but the possibility of cavity doors, which will overcome the difficulty to some extent, presents itself. The general principle might be worked out on the basis of openings being left at either side in the upper portion of the oven, these to coincide with corre- sponding openings on the inside of the cavity door, thus enabling the burning gases to pass through from one side to the other, a draught being created by a small opening at the top of'the door, over the cavity. About an hour’s extra burning under favourable con- ditions has been found sufficient to remedy the black end. trouble, and it should be possible by a system of dampers to so regulate matters that sufficient extra heat is applied to the front and back of the charge during the latter stage of the burning only. Physical Properties of New South Wales Coke. Speaking in general terms, the cokes produced in New South Wales may be classified as follow, but it must be remembered that different producing conditions vary the nature of the coke even from the same coal. The Southern Coke Works, using Buili. seam coal, produce a coke less porous than is obtained from the Borehole seam coal within the Northern coal field, but with considerable hardness in the cell walls, whilst coke from the Lithgow seam in the Western coal field might be placed midway between the two. Rix’s Creek coal yields a hard, very porous coke of low ash percentage, and apparently suited for blast furnace purposes. Coke produced from seams Nos. 2 and 3 within the Southern coal field is more of the nature of the Bore- hole seam coke, but exhibiting greater strength in the cell walls, and here again we have evidence of the pro- bable advantage of blending coal from these seams with the Buili seam coal, with every prospect of producing a hard, porous coke, well suited to the metallurgist. Coke Production. The following comparative table with regard to the coke industry of New South Wales places much of the available information in a condensed form. Where possible, the ash content is that supplied by the various companies, and represents the commercial basis as between supplier and consumer :— Comparative Table. Coal No. Men Coal Coke Average ash. Company. Locality. used. of em- consump- produc- (Seam.) ovens. ployed. tion, 1915. tion, 1915. Northern— Tons. Tons. Per cent. Broken Hill Proprietary Co *s Newcastle Borehole 66* 135 71,160 43,968 16’2 S eel Works 67f (6 months) (6 months) Co-operative Coal and Coke Co. Wall sen 4 (Plattsburg) 9 9 14 13,020 7,161 . 12’0 The Great Cobar Co. Rix*s Creek, Singleton 1 26f 8 —• — 11’5 Wallsend Purified Coal and Jtsmond (Wallsend)... 9 9 76f 45 44,000 21,14411 13’0 Cote Co. Southern— Buili 115J The Broken Hill Associated Bellambi 71 73,581 53,102 16’5 Sme ters Buili Colliery and Coke Works Buili 541 25 31,704 22,872 16;5 Ltd. 40J 15’0^ Corrimal-Balgownie Collieries Ltd. The Federal Coke Co. Ltd Corrimal 9 9 — — — Wollongong 99 451 40 65,000 44,000 14’7 Illawarra Coke Co. Ltd. Coal Cliff 99 501 — _• 16’0 Mount Lyell Co. Ltd Port Kembla 36J 40X 45 36,300 27,400^[ 16’0 Mount Pleasant Coke Co. Wollongong 99 22 50,350 35,294 14’5 (Figtree and Sons') North Buili Coke Co Cohdale 106J 50 70,000 50,000 17’0 South - lifton Coal and okeCo. Western— Scarborough Lithgow 66f 93t 30 21,725 16,300 15’5 17’6 G-. & C. Hoskins* Steel Works Lithgow 30 — — Oakey Park Coal and Coke ( 40t) 25 26,687 16,007 18 0 J 3 i on C l Co. Ltd. I 32§ ) 952 540 258,769 * Semet Solvay by-product ovens. f Beehive ovens. J Rectangular beehive ovens. § Ordinary beehive ovens. || Made from washed coal. 51 Made from washed coal and charges stamped. Mount Lyell Coke Works. The coking plant at Port Kembla (opposite No. 2 jetty) was established in 1899, and has been running ever since, apart from suspension of work owing to labour troubles. Whilst the desired end is attained in producing a coke up to the standard required by the smelting company, the. coal used at present is far from ideal in its normal state, and considerable care must be exercised in producing an economical and satisfactory coke. The position of the works afford exceptional opportu- nities for economic shipment, and whilst practically the whole of the present output is absorbed by the owners, when the production of coking coal extends south from Mount Kembla, these works should be in an ideal posi- tion for the manufacture of large quantities of coke •suitable for export. The coal used (all slack or small coal) is obtained from the Mount Kembla Colliery, distant some four miles by rail from the works. Analyses of coal from this colliery, as published recently by the Department of Mines, are as follow, the coke in each case being firm, not swollen, with a dull lustre :— Percent. Percent. Hygroscopic moisture ...... 1’01 ... 1’00 Volatile hydrocarbons.... 23’41 ... 23’20 Fixed carbon ............. 63’30 ... 66’39 Ash .................... 12’08 ... 9’41 100 00 ... 100’00 Sulphur .................. 0’237 ... 0’310 Specific gravity ......... 1’382 ... I’3b6 Coke..................... 75’58 ... 75’80 Calorific value.......... 12’04 ... 12’07 ' An elaborate -system of washing or concentration has been installed. The coal is received in a storage bunker holding about 600 tons, from which it is delivered by scraper conveyors to the washing plant with a minimum of handling. On reaching the washery, the coal is mechanically graded into four sizes, the finest dust being withdrawn by ia centrifugal blower, and fed direct into the mixing chamber, where, being in a dry state, it helps to reduce the moisture percentage in the mix. The-two sizes over the T3g in. gauge are dealt with in two nut coal pulsating washers, whilst the remaining finer material goes to felspar jigs, of which there are 5, but 3 are usually sufficient to deal with the output. The product from the nut coal washers is partially dried over a reciprocating screen, and passes ’to the Stedman grinder, whilst the fine coal from the felspar jigs is similarly drained. A quantity of fine sludgy coal . and water flows over the face of the coal lying next to the screen, and this is saved by a -system of settling vats. The “ tailings,” or extracted dirt consists for the most part of carbonaceous clay shale and calcite or “spar.” A cleaner “ wash ” could be ensured, but it means that an appreciable proportion of highly carbonaceous material useful in the charge is lost, and it is found more economical not to concentrate too thoroughly, even at the cost of a slightly , higher ash percentage in the finished product. The drainage system after wash- ing, together- with the addition of the dry coal dust, reduces the' moisture to about 10 per cent., which is found most satisfactory in' the stamping machine and subsequent kiln charge. The results obtained by washing the coal is evidenced by the two following proximate analyses, the ash in both cases being light grey in colour and semi-granular :— Hygroscopic moisture . Unwashed. Per cent. 0’77 ... W ashed. Per cent. 0’72 Volatile matter 22’30 ... 23’36 Fixed carbon 6“’8l ... 63’62 Ash 16’12 ... 100’00 ... 12’10 100’00 Sulphur 0’266 ... 0’269 Specific gravity 1’406 ... 1’385 The washing process removed 4’02 per cent, of shale, &c. From’the mixing chamber the coal is elevated to and distributed in the charge storage bunker, holding about 180 tons, and placed at a sufficient elevation to deliver to the Buchanan ramming and charging machine. This machine (fig. 1), which travels on a,track of four rails, also carries the ram for discharging the ovens, 'and suffi- cient coal for three separate charges. It weighs about 60 tons without the charges, and is operated by steam power. The coal is fed from the feed bin in layers of about 12 in. to a thickness of about 4 ft. into a box 29 ft. long and 1ft. 10 in. wide, along which a Caledonian stamping machine travels, fitted with two stampers, each weighing 3|cwt., with a drop of 12 in., and falling 32 strokes per minute. Whilst a coke charge is being pushed out by the ram, the new charge of about 6 tons 10 cwt. is being stamped to- be pushed into the oven on the floor of the box, which is then withdrawn, the coal being retained in position during this operation by lowering the back door of the oven until its rests on the floor of the charge box, and is there wedged in position. The doors are finally fastened, and luted with clay, and .burning proceeds, usually occupying 48 hours. The- ovens, of which there are 36, are 30 ft. long at the floor, average 2 ft. 7| in. in width, and are 7 ft. high, each oven being isolated from its' neighbour by a -solid wall 16 in. thick, so that repairs can be effected with a minimum of interference to adjoining ovens. The walls are of South Coast firebricks, and the floor of Hurstville dry pressed bricks, with a horizontal flue system designed to produce uniform heating throughout. The quenching platform is level with the floor of the ovens, and about 7 ft. above the coke platform. The coke, before falling on to the latter, passes between a • cage sprayer, which sprays a considerable quantity of water against the coke, so that very little watering has to be done on the coke platform. - The surplus water runs back into the dam, and is re-used when cool. The coal charged to ovens during the year 1915 was 36,300 tons, and the coke produced approximated 27,400 tons. Almost the whole of the coke produced is used in the blast furnaces of the company’s plant at Queens- town, Tasmania, being bagged and shipped at Port Kembla. The waste gases from the ovens are used under the boilers, and practically meet all steam require- ments. The working conditions are undoubtedly good at these coke works, and the number of men employed averages 45. The following is the result of an analysis of a sample of coke from these works :— Per cent. Hygroscopic moisture........... 0’73 Volatile matter................. 1’14 Fixed carbon..................... 81’87 Ash.............................. 15’95 Sulphur ....................... 0’31 100 00 Specific gravity............... 1’812 Ash, slight reddish tinge, semi-granular. Coke, dull grey in colour, very dense, hard rough surface. Should readily stand handling without breaking, and bear a heavy burden for smelting purposes. The ash con- • tained : Moisture at lOOdegs. Cent., 0’07 per cent.; silica, 54’11; alumina, 33-46; ferric oxide, 4’75; and lime, 1’92 per cent. (To be continued.)