Page:Encyclopædia Britannica, Ninth Edition, v. 13.djvu/362

 34(5 IRON as a lining material for the converter, and found that when a &quot; basic &quot; lining of this description was substituted for ganister a removal of phosphorus to a greater or lesser extent was actually brought about in the converter just as it is in the puddling furnace ; for some few years, how ever, this method was not applied on a commercial scale, but subsequently the subject was again examined by Thomas and Gilchrist, who finally succeeded in reducing the principles of Snelus s patent to successful practical operation, finding that by the use of a &quot; basic &quot; lining to the converter, and especially the addition of a small amount of lime, or lime mixed with &quot; blue billy &quot; or some other form of iron oxide such as mill scale, to the charge together with the continuance of the blow for some short period after the decarbonization is complete, the elimination of phosphorus (even from highly phosphorized pig, containing 1 5 to 2 per cent, of phosphorus) could be very largely effected, some 80 to 90 per cent, at least of the total phosphorus present becoming oxidized and converted into phosphates, this action chiefly taking place during the &quot;after blow&quot;; provided that the cinder is sufficiently basic, the iron does not oxidize during this after blow as it does in the ordinary &quot;acid lined&quot; converter process. Owing to the success of these operations, the &quot;basic&quot; process has been more fre quently spoken of as the &quot; Thomas-Gilchrist process &quot; than as being what it substantially is, the principle of Snelus s earlier patent in a somewhat but not very largely modified form. Warned probably by the disasters of previous in ventors, the rival competitors for the honour (and profit) of the practical production of ingot metal of fair quality from phosphorized pig have coalesced and united their forces, instead of opposing one another in costly litigation. Processes baaed upon the general principle of making the cinder of the Bessemer converter more or less &quot;basic,&quot; but considerably different in details from the basic lining method of Snelus, Thomas, and Gilchrist, have been proposed at one time or another by various inventors ; thus, in the earlier patents of Bessemer himself, the admixture of steam with air in the blowing operation was included, whilst steam had been previously employed as an adjunct in the refinery, the action being the formation of iron oxide (with evolu tion of hydrogen). Somewhat analogous uses of steam have been sub sequently proposed by others, in some cases the phosphorus being alleged to be evolved as phosphoretted hydrogen (?), e.g., in Bull s process, in which the ordinary air blowing of a Bessemer converter or the effect of an oxidizing blast in a Siemens hearth, &c., on cast iron is first used to remove silicon and carbon, and then a jet of uteam used to remove phosphorus. The direct incorporation of oxide of iron (blue billy, &c. ) alone with the material (by blowing into the converter along with the blast) has also been proposed by Pettitt ( 24), the object in all cases being to assist the formation of phosphate, and thereby remove phosphorus from the iron by making the cinder highly basic. During the oxidation of phosphorus a large amount of heat is evolved, so that the temperature rises during the after blow just as it does during the oxidation of silicon. According to various experimenters the heat of combustion of phosphorus is a little short of 6000, so that, as that of silicon is near to 8000, 4 parts of phosphorus are thermally about equivalent to 3 of silicon. Plence if a pig containing 2 per cent, of silicon will furnish sufficient heat to keep the blown metal and slag fluid, the same result will be attained by means of a pig containing about 5 per cent, of silicon and 2 - per cent, of phosphorus, i.e., if the radia tion loss be the same, and also the diminution in heat evolution due to separating the non-metal from the iron, 1 as well as the fusibility of the slag. In actual practice the &quot;basic&quot; method is found to take a little longer time than the ordinary &quot; acid &quot; blow, so that the radiation loss is a 1 The experiments of Troost and Hautefeuille show that this is not the case, the heat evolution during the union of silicon and iron being much less than that taking place when phosphorus and iron combine together ; so that considerably more than four parts of phosphorus would be requisite to produce the same amount of heat as three of silicon if both non-metals are severally combined with iron. little greater ; the calcareous cinder too is somewhat less fusible than the ferrous silicate cinder of the ordinary ganister-lined converter ; so that a practical inconvenience is apt to be occasioned owing to the frothy mass of imper fectly fused cinder formed foaming up to the mouth of the converter and there solidifying, whilst the greater extent of the foaming causes more material to be ejected than is usual with the ordinary converters. To remedy this, it has been proposed to add the basic matter in a highly heated or even molten state, and to make the air used for blowing traverse a chamber filled with coke on to which petroleum is allowed to drop, so that combustible vapours are blown into the converter along with the air, thus raising the tem perature considerably, and preventing the blocking of the converter-mouth by solidification of cinder, and the pro duction of metal too little heated to remain fluid during the pouring of the ingots, and consequently solidifying in the ladle forming a &quot; skull.&quot; Wilks finds that the action of this arrangement is very satisfactory and effective in preventing &quot; cold blows &quot; from, occurring. The same result is also producible by means of coal dust or other freely divided combustible matter blown in along with the blast. With silicious pig iron the lining is apt to be attacked by the silica formed during the first part of the blowing operations ; this is partly but not wholly avoided by the addition of heated lime to the charge. Harmet has proposed, and at Witkowitz attempts have been made, to blow phosphorized and siliciuretted pig suc cessively in two converters, one acid-lined for removing silicon and carbon, and the other basic-lined to get rid of the phosphorus, the blown metal being transferred from the one to the other ; much cooling of the metal was thus produced, and the operation was pro longed some fifteen minutes, so that the method was speedily abandoned. According to Tiinner, in order to produce 100 parts of pure ingots of blown metal 122 5 parts of pig are requisite with &quot;basic &quot; converters, and only 1187 with the ordinary &quot;acid &quot; ones (waste in remelting being included in each case ; when the metal is used direct from the blast furnace, only 112 parts are required with acid converters) ; hence an extra loss of nearly 4 per cent, of metal is experienced in the basic process. The following analyse?, by Miiller, of specimens taken during a prolonged investigation at Horde illustrate the non-removal of phosphorus and sulphur during the earlier part of the blow, and indeed their slight increase (in percentage amount) owing to the oxidation of manganese, silicon, and carbon ; and also the rapid remoral of phosphorus during the after-blow : Time in Minutes .... -&amp;lt; 0. Original Metal. 41. t- iU. 13. 2-97 2-480 0-811 0-049 ... 0-53 0-009 nil nil 1-22 1-230 1-320 0-786 6-021 0-61 0-247 01-23 Sulphur 0-15 0-206 0-262 0-26-2 0-206 Copper Iron by difference J 0-111 95 697 I 97-607 ) 98 903 ( 0-119 99-531 100-00 ,100-000 100-000 100-000 100-000 The composition of the slag produced during the basic process differs greatly from that of the ordinary method ; the following analyses illustrate the difference : Ordinary Process. Basic Process. A. Tamm. Scheercr. Pattinson and Stead. Pink. I ( Particulars From Westanfors Charcoal Pig : no Spiegel- eisen used. Crystalline Siag ft om Horde, West phalia. Middles- borough Slag. Horde Slags : some 15 per cent, of Lime added to Converter. I 15-62 20-59 32 : 74 1-53 0-17 44-73 12-21 1-17 4-76 40-08 10-65 2-50 15-20 12 23 6 : 12 7-24 1-5(3 6-16 59-35 5-01 traces 9-50 9-76 0-87 8-90 1-75 4-40 50-21 9-84 traces 11-10 12-43 1-15 Maneanesc oxide 86-83 0-70 traces 3-94 42-85 0-015 Silica Phosphoric anhydride Calcium sulphate Sulphur 99-955 99-76 98-9-2 99-45 99-78
 * 94-52