628 THE COLLIERY GUARDIAN. CURRENT SCIENCE AND TECHNOLOGY. Melting Brass and Copper with Coal Gas Fuel. Before the Institute of Metals, Messrs. H. M. Thornton and H. Hartley read a paper on coal gas for melting copper and brass in crucible furnaces. They stated that coal gas is a more costly fuel in terms of B.Th.U, than furnace coke, and to attain success with gas-fired metal-melting furnaces an increased thermal efficiency is essential. The thermal efficiency is dependent upon the pouring temperature of the metal, being lower the higher the temperature attained. The over-all efficiency calculated on the basis of the total consumption starting from cold is dependent upon the number of melts put through successively. The steady state efficiency—i.e., the efficiency for individual melts after about the fourth melt—is about 30 per cent, for a pouring temperature of 1,000 degs. Cent., and 25 per cent, for 1,200 degs. Cent., the over-all efficiencies on the basis of six melts being respectively 21’6 per cent, and 17 per cent. The requisite pouring temperature will depend upon the nature of the alloy and the size of the casting. In the experiments with brass quoted in this communication, the pouring temperature has been 100 degs. Cent, above the liquid us for the particular alloy, and probably represents the lower limit of the suitable pouring temperature range. To obtain a pouring temperature 100 degs. Cent, higher than this would involve approxi- mately a 20 per cent, increase in gas consumption. The presence of small amounts of metals foreign to true brass would not be expected to affect the specific heat of the alloy very much, although, of course, they may materially assist in the melting of brass by lowering the liquidus point to a marked extent. Thus, in melting red brass it was poured at 1,090 degs. Cent., and about 20 per cent, more gas was employed than in melting a yellow brass, which was poured at about 100 degs. Cent. For a pouring temperature of 1,000 degs. Cent, yellow brass can be melted at an expenditure of 1,200 B.Th.U. per lb. of metal melted on the basis of six successive melts; with 12 successive melts this reduces to 1,030 B.Th.U., and with 20 successive melts to 960 B.Th.U. Copper ingots have been melted at a con- sumption of 1,908 B.Th.U. per lb. on a basis of six successive melts, the over-all efficiency of the melting process being 17 per cent., the steady state efficiency being 25’5 per cent. By comparing the efficiency result of the copper melt with that obtained during the brass melting, the efficiencies for intermediate pouring temperatures can be calculated, and from these the increase in gas consumption that would be required in order to obtain higher pouring temperatures for brass. The life of the pots obtainable in gas-fired furnaces would appear to be greater than in coke-fired furnaces, and the time required for the completion of the melt would appear to be less in the former case than is general in the solid fuel furnaces. Marked fuel savings result when the furnace is designed so that the metal is preheated before admission to the blast burner. If both the metal and the air are preheated to. the same temperature then greater recuperation results from the brass than fiom the air. On the other hand, data obtained without preheating, and with only metal pre- heating, when Compared with that obtained when there is preheating of both brass and air would appear to indicate that some advantage results in preheating the air on account of its effect on the temperature attained in the combustion zone of the furnace as distinct from the advantage accruing from the mere transference of the thermal energy from the flue, back to the melting chamber. Producer Gas and the Utilisation of Coke Dust. Before the Midland Association of G-as Engineers and Managers, Mr. W. Chaney, of Saltley Gasworks, said (Gas World) that many attempts had been made to utilise coke dust, but this could not be burned satis- factorily in a furnace primarily designed for the burning of coke and breeze. Briquetting was hardly suitable for fast steaming, such as was desired in an electric generating st ition. An outlet might be found for the coke dust by gasification in independent outside producers, and the gas so made utilised for the heating of retort settings, coke ovens, for generating electric current, or other purposes. The producer is similar in design to a water-gas generator, but the bottom is sealed in a water lute, into which the ash and clinker descend. A continuous supply of air and exhaust steam is blown through the producer, the calorific value and the amount of ammonia in the gas so formed being dependent upon the amount of exhaust steam admitted with the air. The gas leaves the top of the producer ata temperature of about 500 degs. Cent., and may be u ed direct, or the ammonia may be recovered with sulphuric acid in an absorber. The highest heating efficiency is obtained when the gas is used direct from the producer, and under non-recovery conditions, otherwise there is a loss of sensible heat due to cooling, etc. Experience, however, has shown that when the gas is taken direct from the top of the producer, tar and dust troubles ultimately develop. The removal of these troubles necessitates the cooling of the gas, but the value of the ammonia recoverable more than compensates for the loss of heat efficiency. The flame temperature of the cold gas is, however, such that for heating purposes some system of regeneration or fire heating is advisable, to obtain the highest efficiency. It is quite possible by this means to obtain a temperature of 1,400 degs. Cent, consistently and regularly. Such a scheme is now in operation at Saltley Gasworks, in connection with the heating of coke ovens, the whole of the coke-oven gas being utilised for town fighting, etc. The fuel usually employed is a coal slack containing a proportion of nuts and about 13 per cent, of ash, the calorific value of the slack being 12,500 B.Th.U. per pound (dry). The dust is of little commercial value, and in many large towns it is necessary to pay tipping charges to dispose of the material. Its calorific value is approximately 10,000 B.Th.U. per pound (dry), and the nitrogen content 1 per cent., the actual sulphate of ammonia recoverable being 451b. to 501b. per ton. At present prices the value of the ammonia recovered per ton of dust is 7s. 2d. By mixing 40 per cent, of coke dust to the producer coal the heating value of the gas is increased to 130 B.Th.U. per cu. ft., and the average price-of the mixture is correspondingly reduced. As regards increased expen- diture of fuel, 12 per cent, for the ordinary internal method of heating retorts would be practically increased to 24 percent, with outside producers, using 40 per cent, of coke dust and 60 per cent, producer coal, so that 2 tons of this producer fuel, costing 2s. 2d., would set at liberty 1 ton of coke at, say, 24s. per ton. The advan- tages of the outside producer are :—The closing down or reduction of the producer gas when standing-off retorts; the utilisation of the coke dust; the recovery of the sulphate of ammonia; the generating of cheaper power; regular heating of producer gas as compared with the variable gas constituent of the ordinary generator ; and less combustibles in ashes and clinker. Colorimetric Determination of Carbon Dioxide in Air. Messrs. H. L. Higgins and W. McK. Marriott (Journal of the American Chemical Society) describe a new colorimetric method of determining the percentage of carbon dioxide in air. The air under examination is passed through a solution of sodium bicarbonate until the solution is saturated with carbon dioxide. The reaction of this solution depends on the relative amount of the alkali bicarbonate and the carbon dioxide present. This, in turn, depends on the pressure of the carbon dioxide in the air under test, and will be inde- pendent of the volume of air blown through, provided saturation has been attained. High pressures of carbon dioxide tend to give an acid reaction, low pressures have the reverse effect; hence the reaction of such a solution is a measure of the pressure of carbon dioxide in the air with which it has been saturated. The reaction is determined by adding as indicator phenolsulfone- phthalein, which shows definite colour changes over a considerable range of reaction, and by comparing the resulting colour with solutions of known reaction con- taining the same amount of indicator. The method is not applicable in the presence of acid or ammonia fumes. As outdoor air always contains practically tbe same percentage (0*03 per cent.) of carbon dioxide, the bicarbonate solution may be easily checked. Estimation of Benzol and Toluol in Coal Gas. Mr. Harold E. Copp, engineer and manager of the Potteries station of the British Gas Light and Coke Company Limited, writes in the Gas World on this subject as follows :— In the ordinary test for the estimation of benzol in coal gas, the gases pass through a series of four bottles containing green oil to a depth of about 14 to 2 inches, the bottles being changed in rotation and the first one charged with new oil from time to time. There are at least two disadvantages about this method:—(1) It is questionable whether the whole of the gas comes into direct contact with the oil; if not, some proportion of the benzenes escape absorption. (2) The accumulated pressure of the meter and absorption bottles amounts in the aggregate to a greater pressure than is often available for naturally forcing the gas through the apparatus, in which case it is necessary to use an aspirator, a water- filter pump being generally used for the purpose. The apparatus employed consists of an ordinary calcium chloride tower or condensing cylinder such as that used in the Referees’ sulphur test, filled with glass beads, a plug of glass wool being placed both at the top and bottom thereof. The oil is gravitated from an ordinary 3-litre aspirator in a downward direction through the beads, the gas after being metered passing upwards through the same. By this method the test for benzol can be com- pleted much more rapidly than with the ordinary method. The average of several tests by both types of apparatus, taken simultaneously, shows that by the method described above an increased absorption of benzol is obtained. Coal Gas Fuel for Melting Non-ferrous Alloys. In a paper read before the Institute of Metals Mr. S. B. Brook stated that some years ago experiments were carried out, in the University of Sheffield, which went to show the material advantage possessed by gas over other fuels for the melting of non-ferrous alloys. The results were sufficiently promising to prompt the author to carry out a severer test, and one of longer duration, on material which demands probably the highest temperature of any industrial non-ferrous alloy—namely, cupro-nickel, for 10 full days of 10 hours each, commercial practice in the size of the ingot, etc., being followed, and a gas-fired pit furnace of a modern type being used. It was found that ordinary coal gas gave a tempera- ture sufficiently high for this alloy, no difficulty at all being encountered in securing a temperature of 1,400 degs. Cent. With regard to the relative cost of melting, the average cost of melting with high-grade metallurgical coke was 36s. 4d. per ton of alloy pro- duced, the cost with gas at ordinary Sheffield rates being 31s. 9d., and at the preferential rate allowed to users of gas for gas engines, 24s. 2d. In relative speed of melting, a great advantage is shown by gas over coke. The same weight of metal can be melted in the gas furnace in 52 minutes which requires 82 minutes in March 30, 1917. ________________ ________ the coke-fired furnace. When this advantage is trans- lated into commercial practice, the advantage is still more striking ; for on two days during the test it was possible to obtain 12 heats in the 10-hour period, whereas the writer was only on very exceptional days able to obtain seven heats from a coke-fired furnace per day. Graphite crucibles, of the same make, have as long, if not a longer, life in properly controlled gas-fired furnaces as in those fired with coke. The lining of the furnace and the burner suffer no serious depreciation. Metal bosses were found to be below the average; and, from the general stability ensured to the crucible, mechanical loss ought to be far less than in the coke- fired type. The labour charges per ton of metal produced are less in the gas-fired furnace, from the fact that a larger number of furnaces can be controlled by the same staff, and the output of such a team of men is higher. In point of quality and product, the cupro- nickel was tested at every stage and was found to be satisfactory. The ultimate test in the production of bullet sheaths showed that the material was equal, if not superior in both quality and minimum failures, to any that had been produced in coke-fired furnaces. The absence of ashes, the elimination of the wasteful process of “ slagging,” the economy of fuel in ease of control, and the reduction of impurities introduced in the process of melting, are factors of considerable importance to the manufacturer, and confirm the writer’s findings that the claims of coal gas as a fuel for the melting of non-ferrous alloys rest on a very sound economic basis. __________________________ SOUTH WALES MIMING TIMBER TRADE. For the week ended March 23, the total quantity of mining timber imported into South Wales and Monmouthshire from foreign destinations amounted to 18,225 loads. The whole of the supplies came from the French ports, very little timber having been received from Spain and Portugal so far this year. To make up for this, larger supplies have been arranged for from France, and, with the increasing use of native timber, quotations have been kept from advancing to higher levels. The imports received from abroad were quickly distributed, and practically no “ free ” wood is avail- able, quotations being nominal, at about 75s. per ton ex ship Cardiff. The actual quantities imported for the week ending March 23 were as follow :— Cardiff, Barry and Penarth: To E. Marcesche......... Budd and Co.......... Lysberg Limited ..... Do. ...... F. R. Howe and Co..... Grant Hayward....... Morgan and Cadogan ... Do. Lysberg Limited ..... Vyvyan Kelly ........ Powell Duffryn Company Morgan and Cadogan ... Lysberg Limited ...... Newport: — T. P. Thomas......... E. Marcesche......... F. R. Howe and Co..... Powell Duffryn Company Swansea: — Lysberg Limited ..... E. W. Cook and Co..... W. Davies and Co...... Do. ..... Budd and Co.......... Evans and Rogers..... Morgan and Cadogan ... E. W. Cook........... From Loads. L’Orient ......... 108 Vannes........... 150 Bayonne ......... 4,560 La Rochelle....... 600 L’Orient ......... 720 Paimpol __........ 108 Bordeaux..................... 816 L’Orient ......... 108 Treguier ......... 74 Bordeaux......... 780 Bordeaux......... 1,200 L’Orient ......... 540 Bordeaux......... 3,000 ______ Total......12,764 La Rochelle........ 960 L’Orient .......... 240 Bordeaux.......... 1,020 Bordeaux.......... 1,650 Total...... 3,870 L’Orient .......... 400 Rochefort......... 168 Bordeaux......... 262 Legue ............ 150 La Rochelle........ 120 Montlier .... ......... 150 Morlaix............ 120 Legue ....... ............ 125 Total...... 1,495 Many sales of standing timber in the South Wales dis- trict have been effected during the past fortnight, but the total yield was unimportant. Maj. G. L. Courthope, presi- dent of the English Forestry Association, recently asked, through the medium of the Press, that information with regard to the supply of home-grown timber, traction power, labour, mills, etc., should be addressed to him. Mr. Finlay A. Gibson, the secretary of the Monmouthshire and South Wales Colliery Owners’ Pitwood Association, points out that the supply of pit wood to the Welsh collieries is of prime national importance, and that information as to the resources of South Wales should be forwarded to the Colliery Owners’ Pitwood Association. This association, representative of the bulk of the coal owners of the district, has spent a good deal of time and money in the endeavour to utilise the district’s timber resources. Mr. Gibson’s plea is generally recognised as the most desirable policy to pursue. The exploitation of the wood resources of South Wales and Monmouthshire for the collieries in the district would lead to an avoidance of unnecessary wastage in facilities. The South Wales dis- trict will require the whole of the growing timber suitable for pit props in the surrounding counties, and, having regard to the national importance of the subject, it would be best if South Wales retained all facilities in the counties imme- diately surrounding the district. Foreign imports cannot be wholly obviated, -and it is stated if cutting proceeds at the present rate for nine months, there will be very little wood left in the counties of Glamorgan, Monmouth, Devon, or Somersetshire. To go further afield means increased trans- port costs. ______________________________ The British Ropeway and Engineering Company Limited, 34, Fenchurch-street, London, E.C., who recently purchased the German business of Messrs. Bleichert and Company, have just secured an order for a ropeway miles long, for hand- ling pit props for the South Hetton Coal Company.