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THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[September, 



The conversion of the pig into bar iron is carried on in various works. In 

 1841 the produce was 263,700 tons of bar iron, of this quantity 146,800 tons, 

 or more tlian half was manufactured with coal, either by the Champagne 

 process with the hammer, or by the Enghsh process ivitli the roller. 



Among the new processes which have been ap[ilied of late years in France, 

 three deserve to be enumerated. These are the use of the hot blast; the 

 substitution of dried or torrefied green wood for charcoal ; and the application 

 of gas in Hast furnaces for refining pig iron and converting it into bar. It is 

 known that the use of hot air was imported from England ; it has not been 

 generalized there ; neither has it in France, it has however extended, and out 

 of 573 blast furnaces, 121, or near a quarter now make use of it. In charcoal 

 furnaces it effects a considerable saving of fuel; it gives more regularity to 

 the process; but it sensibly modifies the quality of the iron by making it 

 more fusible and taking away its tenacity, which seems to imply that it 

 should be abandoned in such charcoal furnaces as arc used for producing bar 

 iron, and should be introduced on the contrary in such as are used for cast- 

 ings. It is also employed with success in blast furnaces, which are worked 

 with green or torrefied wood, or with charcoal and coke mi.\ed, because it 

 remedies the irregularities arising frcm'wantof homogeneity in the combusti- 

 bles employed. In coke furnaces, tlie hot blast seems generally to succeed^ 

 and is frequently adopted. From official returns it seems that of 468 blast 

 furnaces worked with wood, 46 only, or one-tenth use the hot blast ; ol 54 

 with green or torrefied wood, 39 use it ; and of 54 with coal, 36, or two-thirds 

 use it. 



Tlie use of dried or torrefied greenwood has also been introduced within 

 the last ten years. Formerly wood was only used after it had been converted 

 into charcoal, although this operation exhausted many of the combustible 

 elements. Carbonization as practised in the French forests, was at least half 

 the calorific value of wood. This loss is owing to two causes, the imperfec- 

 tion of the processes of carbonization used, and the composition of the wood 

 itself which is such that it is impossible to e.\tract the carbon contained with- 

 out losing a notable quantity, which escapes with tlie steam arising from the 

 water of combination. Several plans have been proposed at different times to 

 ameliorate carbonization and augment the produce ; but these processes, 

 either could not be employed on a large scale in the woods, or when once 

 applied without adequate inspection, no longer gave the habitual results. At- 

 tempts were then made to ascertain how far it was possible to use on the iron 

 manufacture, instead of charcoal, wood in its natural state, or at least only 

 subjected to such incomplete carbonization as would lose only a slight quan- 

 tity of its calorific elements. Many experiments have been made in the last 

 seven or eight years. Some have introduced the daily and habitual use of 

 green wood ; others have dried ; others, and by far the larger number have 

 used a process for preparing it in a close vessel by means of the heat lost 

 from the mouth of the blast furnaces, so as to subject the wood to a less ad- 

 vanced carbonization than that performed in the forests, and producing a 

 combustible intermediate between dried wood and charcoal. The use of green 

 or torrefied wood has not extended so far as might have been wished. Only 

 51 furnaces make use of it, and even this number seems to diminish. Several 

 reasons explain this result. The first is the irregularity produced in the pro- 

 ceedings of the furnaces; the green wood occasions coolings down, which 

 prevent fusion from taking place in a regular manner, and torrefied wood 

 always presenting a very variable degree of desiccation or carbonization pro- 

 duces a similar result. Another and more important cause is that if a true 

 saving of fuel take place by this process, it does not always show itself in 

 money results ; for if the works be at any distance from the woods, then the 

 cost of carriage of the green wood to the furnaces increases. In order for 

 the process to spread, the works would have to be seated in the woods. 

 Whilst the furnaces only consumed charcoal, the endeavour was to place them 

 near mines rather than near forests, for the ore weighs more than the char- 

 coal consumed, but wood weighing more than the ore, the neighbourhood of 

 the forests must be sought, if torrefied wood is to be used with advantage. 

 Besides a great number of furnaces are at the same time distant from both 

 mines and forests, being forced to seek a site where water power was available 

 for the blowing machines. An improvement which has been completely suc- 

 cessful, the use of the heat of the furnace to heat a steam blosviug machine, 

 allows in new works a considerable saving of money to be effected by the use 

 of torrefied wood. Water power for the blowing machines is in fact useless, 

 and as far as the mines allow the works may be placed in the midst of the 

 woods of which they are to consume the produce. 



The third discovery was represented by iron sent by Messrs Trayler and 

 Huillier, and Messrs. D'Andelarre and De Lisa. The term of gas iron was 

 unknown in France three years ago, it is now used in trade, and applied to a 

 class of iron superior to coal made iron, and almost equal for most purposes 

 to charcoal iron. Gas iron is iron manufactured with the gases lost in the 

 blast furnaces, or with those arising from the gasification of combustibles of 

 small value or unfit in their natural state for working iron. This process 

 originated in the woiks of Treveray (Meuse), belonging to Messrs. D'Ande- 

 larre and De Lisa, and is extremely important to works using vegetable fuel. 

 Refining with charcoal has already become impossible in most of the French 



furnaces, on account of the competition of coal, and in a very short space of 

 time it will be so [with the rest. At present coal bar iron produced from 

 charcoal pig is a little better than bar entirely manufactured in the English 

 way, and fetches rather a better price ; but once coal bar master of the field, 

 the difference in quality will not compensate for the great difference in price, 

 and the cheaper article will exclude the other. The gas process on the other 

 hand, if generally adopted, will save the old charcoal works, though it also 

 eff'ects a great saving with regard to coal. An important saving in the gas 

 process is the diminished loss in slag, which is reduced one-half in the pud- 

 dling and balling furnaces. In the Treveray process the gnses lost in the 

 blast furnace, or the gases which have exhausted their physical and chemical 

 influence on the bed of fusion, are collected and sent into the reverberating 

 ovens. These gases before being so used in the subsequent processes are 

 purified from the matters which they may contain, injurious to the iron. 

 This is effected by very simple apparatus, and the pig iron is brought into 

 contact only with a purified gas flame. The arrangement of the gas oven, 

 with jets of hot air and hot gas intermixed, obtains a very high temperature, 

 and perfect combustion, since the turning of a few cocks allows the fire to be 

 regulated at will, not only with regard to the intensity of its temperature, 

 but the chemical nature of its flame, so as to have a neutral, an oxidizing, or 

 a red active flame. The inventors assert that the process is so advantageous 

 as to admit of being applied in other works besides those of iron. Arrange- 

 ments are made so as by very simple means to raise the temperature of the 

 gas to a very great extent before being used. Where there is not a sufficient 

 supply of gas from the works, coal dust is used, turf, anthracite, fee, to make 

 up. The French contend that the process belongs entirely to them, and that 

 a similar process used at Wasseralfingen, in Wurtembuig, has neither priority 

 in lime nor in merit. To France, which is badly ofl' for coal, and is a great 

 wood country, the gas process is of great importance, as so much iron is 

 made by means of wood, of charcoal, and which latter in the competition 

 with coal, has already received many improvements. The charcoal furnaces 

 have been much enlarged, their blowing machinery better constructed, so that 

 furnaces which produced only 400 or 500 tons of pig, now produce more than 

 a thousand, and it is anticipated if the gas process be carried out that the bar 

 iron may be produced with no more expenditure of fuel than is now reijuired 

 for the pig. By the double influence of torrefied wood and the gas process, 

 the iron works dependant on the first have been armed with new resources. 

 It is remarked as singular that while the price of charcoal has tripled in the 

 last fifteen years, that of iron has been constantly falling, so that instead of 

 bar iron being one-third dearer, it is one-third cheaper. 



The iron-works of France may be divided into three principal classes i 

 first, those wliich manufacture pig and bar iron by the exclusive use of 

 mineral fuel ; second, those which manufacture pig with charcoal and coal ; 

 ami third, those which manufacture pig and bar with charcoal only. In this 

 order it may be useful to give a sketch of the works in France which sent 

 specimens to the Exposition. 



The principal works using coal exclusively are those of Alais (GardJ, De- 

 cazeville (Avcyron), the Loire (Loire), all in the south of France ; that of 

 the Creuzot in the centre ; and in the north those of the north and Straits 

 of Calais. These works are established on coal basins, but in general they 

 have not enough ore near them, or at least they have not enough, or have to 

 obtain them from a greater or less distance. They are worked on the Eng- 

 lish plan, or with only the slight difference that pig is sometimes reduced 

 with charcoal. The coal works had much difficulty in establishing them- 

 selves, and languished for a good many years, and have only begun to pros- 

 per since the railway system has opened a new market for their produce. 

 The works of Alais, founded in 1826, encountered great difficulties, and all 

 operations completely stopped in 1834 ; but towards 1836 Messrs. Drouillard, 

 Benoist & Co., having farmed this large establishment, brought their expe- 

 rience and capital to bear for its revivification. The works comprise lour 

 coke blast furnaces, a great forge, the hammers and rollers of which are 

 worked by two engines, severally 30 and 80 h. p. The principal works exe- 

 cuted here are in rails. The Decazeville establishment, also on a large scale, 

 had similar difficulties to encounter. It comprises six contiguous blast fur- 

 naces, a large foundry, three refining furnaces, fifty puddling and reheating 

 furnaces, hammers weighing four tons, and striking 60 blows per minute, 

 puddling rollers and drawers, plate rollers, &c. The total steam power is 

 reckoned 600 h. p. The produce is 12,000 tons of bar iron yearly, and it will 

 soon be carried up to 15,000 or 18,000. More than 2000 work people are em- 

 ployed. It has supplied, among other lines, the Paris and Orleans, Paris and 

 Rouen, and Paris and Belgian with rails. They are said to be remarkable 

 among French rails for tenacity and hardness. The works on the Loire were 

 established to work the beds of coal and iron there, but w hieli were found not 

 so extensive as had been hoped and distant deposits have been had recourse 

 to. Great discouragement prevailed at first, but the construction of the St. 

 Etienne and Lyon railway, the better preparation of coke, the improve- 

 ments introduced, and the reduction in wages have enabled the companies to 

 reach a high degree of prosperity. The £120 shares of the Company of 

 Forges and Foundries of the Loire, whose chief works are at Terre Noire, 



