The Mechanical Handling and Storing of Material

STORING OF COAL AND OTHER MINERALS 663 On the ground floor is a movable automatic weighing machine that can be brought into contact with any of the silo outlets, the coal being thus automatically withdrawn and weighed at the same time. This refers to the nine silos only. The remaining six, for coal to be screened, extend to the ground, and are connected with two band conveyors. These deliver the coal to another elevator which takes it up to the top of the building, from which it is conveyed by a band to the screening appliances, and thence into a series of smaller silos ready for loading into vehicles. The whole installation is driven by electricity, and when in full work only consumes 120 H.P., which is generated by a vertical engine of 150 H.P. coupled direct to the electro- motor. A similar engine, but of only 45 H.P., is held in reserve for use when only a portion of the plant is required. In these stores great care is taken to record the temperature at regular intervals, and thermometers enclosed in iron pipes are fixed in the different silos for this purpose, as a means of guarding against spontaneous combustion. This installation is the design of G. Luther, of Brunswick, by whom it was erected, and to whom the author is indebted for the description and illustrations given above. In Continental ports like Hamburg, coal stores either on this or a similar system are absolutely necessary, and they are also becoming popular in all great industrial centres. General Remarks concerning the Warehousing of Coal.—With regard to the storage of coal largely imported from Great Britain, for the use of gasworks in Germany, the practice is to heap such coal up in the bin, or sometimes in little hillocks, 50 ft. high or more. German coal, however, could not be dealt with in this way. The English Gasworks at Berlin make a practice in the winter of storing 60,000 tons of English coal in one uncovered yard, and no instance of spontaneous combustion is on record. On the other hand, German coal, which is used in the City Gasworks of Berlin and Charlottenburg, and also in the power house of the Berlin Electric Co.’s works, is stored in much thinner layers; but in spite of this precaution explosions have often taken place, and serious loss has occurred from this cause. Westphalian coal, on account of the high proportion of sulphur it contains, seems more exposed to this risk than Silesian coal. In each store house where German coal is kept in any quantity some precautions must be taken against fire risks. The civic authorities of Berlin require gasworks provided with railway sidings to maintain in store 30 per cent, of one year’s requirements, but works which are dependent for their supply on water and canal traffic are compelled to keep about 70 per cent, of a year’s consumption in stock on account of the possibility of obstruction of the waterways by frost. As land is very dear in cities, it is clear that instead of spreading such coal on the ground, or packing it away in covered sheds, it will be more profitable to store it in silos which can be filled to a great depth. But as the higher coal is stacked, the greater the risk of combustion, some means must evidently be adopted to guard against this danger. The following is the plan devised by Professor Buhle, town architect of Charlottenburg.1 To reduce the depth of the layer of coal, the silos are divided into two or more sections, placed one over the other. These sections are completely separated, and are filled, emptied, and aerated quite independently. The coal is brought by boat, and carried by a gravity bucket conveyor to the top of the silos, and may be passed as desired by a shoot to an upper bin, or by way of a second spout into a lower bin. The spouts 1 Zeitschrift des Vereines deutscher Ingenieure, 9th July 1900.