812 SODA.— Black-ash. Revolving Furnace.
the almost insuperable difficulties which their ballsoffered to lixiviation, their invention remained use-less, till Messrs. Stevenson and Williamson, ofthe Jarrow Chemical Works, South Shields , madevery considerable improvements both in the me-chanical and in the working details, which wereultimately crowned with perfect success. This was,however, a question of time, and up to a few yearsago it might be truly said that, although the revolv-ing ball-furnaces were undoubtedly a success, theiradvantages over the ordinary hand-worked furnacedid not seem so apparent as to warrant their verymuch higher expense. For the last few years,however, the advantages of the “ revolvers ” overthe hand-furnaces have been preponderating, andthey have been made still more apparent by in-creasing the size and strengthening the workingparts; the expense both of working and of re-pairing the revolvers has also been materiallyreduced. Three of the largest works on the Tyne ,and several in Lancashire , have entirely abolishedliand-furnaces and replaced them by revolvers; andmany others both on the Tyne and in Lancashire are doing part of their work with them. It seemsthat in a few years in all but the smallest alkaliworks there will be no ball-furnaces found exceptrevolving ones. The advantages claimed by thepatentees, as follows, seem to be borne out by thefacts, viz.:—
1. The whole of the contents of the furnace areheated with such uniformity that no portion everbecomes hot enough to cause a serious loss of sodaby volatilization.
2. The atmosphere inside the furnace is alwaysdeoxidising, as the furnace never requires to beopened during the mixing and fluxing.
3. As one revolving ball-furnace does the work ofseveral (at first three, now four or five) hand-furnaces, less skilled labour is required to turn outthe same quantity of work, and a more completedecomposition of the sulphate of soda is effectedby the more perfect mixing of the materials.
4. There is less absorption of soda into the brick-work than in the beds of the ordinary furnaces,and less wear and tear, as no coals are used in theprocess.
After' many years’ practical work it is possibleto make more positive statements from experience,and to summarize the advantages of the revolversover the hand-furnaces, thus: less labour (skilledand otherwise), less fuel, stronger ash (becauseof the better decomposition of the sulphate),fewer repairs. The one drawback urged up to thelatest time against the revolvers, viz., smaller yield ofash, has now been overcome so far that it can be saidwith certainty that their yield of available sodiumcarbonate (and nothing else is paid for by the cus-tomers) is considerably larger than that of hand-furnaces.
The early plan of revolving furnaces has been com-pletely superseded in everything except the leadingfact, that the working part of the furnace consistsof a brick-lined cylinder of iron plates. The dia- |
grams given in Plate IY. represent a furnaceand pans embodying the latest improvements, asconstructed by Messrs. Carrick and Wardale, ofGateshead-on-Tyne, and erected in several alkaliworks. The revolving furnace proper consists of acylinder of boiler-plate, half an inch thick, lined withfire-bricks. The wrought-iron shell is 15 feet 6 incheslong, and has an inside diameter of 10 feet 2 inches,properly fitted with strips, gussets, and stays. Allthe seams are broken-jointed, butted, lapped at bothsides, and double-rivetted. In each end thereis a hole (“eye”), 4 feet in diameter, protectedwith strong angle irons; and in the circular partof the shell there is a charging hole of 18 inchesdiameter, with a door. This shell is strengthened bytwo very strong cast-iron rings, rivetted firmly toit, and hooped with solid cast-steel tyres, 6 inchesby 2 inches in section. These steel tyres are accu-rately turned and shrunk hot on to the cast-ironrings, and firmly secured by a sufficient number ofturned tapered bolts. These tyres are afterwardsturned to work in Carrick and Wardale’s patent“ V’d ” rollers in the furnaces erected by them.The steel tyres are always in one piece; but thecast-iron hoops are sometimes made in severalpieces, whose joints run obliquely across the sectionof the hoop, the object being to allow of someexpansion and contraction without a breakage of thehoop. A large spur wheel, 7-J- inches broad, runsround the circumference of the cylinder, and issecurely bolted to a carrying ring, and rivetted tothe shells. The revolver runs upon four strongcarrying wheels or rollers, 3 feet diameter, whichare provided with cast-steel tyres, or even madeentirely of cast steel. These are accurately boredto receive short shafts, which are keyed into them,and woi’k in carriages, fitted with the proper meansof adjusting the cylinder in a perfectly level andtrue position. Those made by Carrick and War-dale are of cast steel or ofdrilled cast iron, and called Fi s- 23.
“V’d” rollers, from the shapeof their periphery, which re-sembles a very flat V (Fig.
23). The object of this de-pression (a quarter of an inchdeep), which is ground per-fectly true with emery, andto which the steel tyres areperfectly fitted, is to keep thefurnace running truly without any side motion.Previous to this, the plain or coned ordinary railwaywheel tire was used, which had the disadvantagethat the furnace ran from side to side until it wasbrought up by either flange.
The revolver is driven by a vertical steam engine,with inverted cylinder 12j inches diameter and 14inches stroke, and so arranged that the speed of therevolver can be varied from about five turns perminute to one turn in five minutes. The engineis fitted with link motion, so that it can be quicklystopped or reversed by levers within easy reach ofthe platform. It drives directly a spur pinion on a.