Transactions
American Institute of Mining, Metallurgical, and Petroleum Engineers
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In the flue connecting the main dust chamber to the chimney, no provision was made for removing the accumulated dust, the bottom being simply a level dirt floor, as shown in section E-E. Openings 3 ft. 3 in. by 5 ft., provided with hinged cast-iron doors, are located about every 1 10 ft. on the east side and about every 240 ft. on the west side. It will be noted from the general plan that this flue branches near its upper end, so as to enter the chimney at two points 90° apart. The openings in the base of the chimney are each 36 ft. high by 15 ft. wide. From the point where the flue branches, each leg grows narrower and higher as so to maintain a practically uniform sectional area. Section F-F shows a view of one branch, at a point near the chimney entrance. VI. Main Dust Chamber. A cross-section and partial longitudinal section of the main dust chamber is shown in Plate XV. These sections are taken near the upper end of the chamber, in order to show special features of construction such as wire-shaking arrangement, cold-air pipes, etc. Other details of construction are the same throughout. Plate XVI shows a hopper plan of the dust chamber. The part within the dotted lines is hung with steel wires spaced at about 2.3 in. center to center, there being a total of about 1,200,000 wires, each of which weighs about 1 lb. As indicated on the plan, these wires are hung in two groups or divisions, there being about 47 ft. of clear flue between them. It will be noted that a clear space is left at the inlet end, affording an unobstructed passage for the gases to distribute themselves equally over the full width of the chamber. The total average length of flue filled with wires is approximately 317 ft. There are two sizes of wire used in the first group or division. For a distance of about 51 ft. from the inlet end, No. 8 W. & M. wires, 16 ft. long are used, the rest being No. 10 wires, 20 ft. long. The second division is hung with No. 10 W. & M. wire 20 ft. long. At the upper end of the first division of wires, there are 22 pipes for the admission of air in case it should be desired to lower the temperature of the flue gases, with a view to condensing fume. These pipes are shown on Plate XV and by photograph on Plate XVII, which plate also shows dther structural details. The open space between the two groups of wires is provided in order that a thorough intermingling of the cold air and gases can take place before entering the second division. 606 THE GREAT FALLS FLUE SYSTEM AND CHIMNEY, It will be noted that 11 of these air pipes enter from the top, or roof, of the flue and 11 through the bottom. A brick partition wall, on the F line of columns, divides the chamber into two parts, there being six panels on the east and five on the west side. At each end of the chamber a line of butterfly dampers is provided Plate XVII. — View of Cold-Air Pipes, Expansion Joints, and Hoppers. so that either side, or the whole, of the chamber may be closed to the passage of gases. Plate XVIII shows these dampers partially erected. They are made of heavy cast-iron plates which are carried by a vertical shaft. The step bearing at the bottom is below the floor plate, where it is free from dust and can be oiled and inspected. The upper end of the shaft passes out through the roof of dust chamber, each one being equipped with a worm wheel, worm, and hand wheel for operating the damper. THE GREAT FALLS FLUE SYSTEM AND CHIMNEY. 607 Guided by the observations made in the experimental flue, which showed that the dust and condensed fume collected on the wires at tem- peratures about 400° and below, the upper division of wires in the new chamber was equipped with a device for shaking them in order to remove the condensed fume and dust. We estimated that the temperature in the first or lower division of wires would be above the point where the fume would condense and collect on the wires, but in this we were in error. The improved draft conditions provided by the new system resulted in the entrance of so much more cold air at the various furnace Plate XVIII. — View of Dampers at Inlet End of Dust Chamber (Partly erected). and flue openings than under the old system, that a temperature of under 400° F. exists in the first division of wires with the result that there is an accumulation of solid matter upon them. In order to remove this dust, connections were made to the old stone dust chamber which carries the hot reverberatory gases that are normally passed around the new chamber. At intervals the lower dampers on one side at a time of the new chamber are closed and these gases are turned into that side. This results in volatilizing and disintegrating the material on the wires so that it breaks up and the greater part of it falls off. Plate XIX shows the manner in which the wires are suspended. Crimped iron screen cloth 1^-in. mesh is stretched along the bottom of the roof purlins. Flat bars 2.5 in. by 5/16 in., bolted to the purlins, 608 THE GREAT FALLS FLUE SYSTEM AND CHIMNEY. hold the screen in place. The warp or longitudinal wires are No. 8 W. & M. gauge, while the woof or cross wires are No. 10 W. & M. gauge. The baffle wires are provided with a hook in the form of a shepherd's crook on one end and are suspended from alternate intersecting points on the screen. This arrangement has the effect of staggering the wires which are about 2.25 in. apart, making the baffling action more effective. The device for shaking the upper division of wires consists of angle-iron I wmm warn Plate XIX.— Method of Supporting Baffle Wires. frames suspended from the roof beams by hangers about 10 ft. in length, thus bringing the frames at about the middle point of the baffle wires. On these frames a wire netting having a 4 by 7 in. mesh is stretched, through which the baffle wires pass. The frames are 10 ft. wide and extend from the side walls to near the partition wall. A connecting rod attached to each frame passes out through the flue wall and is connected to a bell-crank lever which is actuated by an eccentric, giving the frame £i stroke of 9.5 in. The frames make about 60 strokes per minute. Line shafts, carrying the eccentrics on each side of the flue, are operated THE GREAT FALLS FLUE SYSTEM AND CHIMNEY. 609 by electric motors. The eccentrics are set at different angles in order to prevent vibrations which might be produced in the structure if the com- plete group of wires was moving in unison. The wires are shaken for a period of about 30 min. at intervals of from 60 to 90 days as may be required. While the shaking device on one side of the chamber is in operation all gases are passed through the other side. The upper dampers are closed on the side where the wires are being shaken, thus guarding against the loss of any dust removed from the wires. Plates XX and XXI show the wire-shaking device during construction. Plate XX. — Device for Shaking Wires. (Baffle wires not in place.) VII. Some Details of Construction. Throughout the flue system a structural steel framework is used. The inner columns are of box section, being built up from plates and channels, while the columns in the outside wall are 12-in. I-beams, between which a brick curtain wall 11 in. thick is laid. The main roof beams resting on top of columns are chiefly I-beams, channels being used only at the expansion joints. The roof consists of steel I-beam purlins between which brick arches 5 in. thick are sprung. Special perforated bricks were made for this purpose, the skewback brick being molded to fit the I-beams, while all others were made radial to suit the arches. The valleys between the skewback brick and top of I-beams were filled with concrete (see Fig. VOL. XLVI. — 25 610 THE GREAT FALLS FLUE SYSTEM AND CHIMNEY. 1, Plate XXII) and, when the roof was completed, it was given two coats of a one-to-one concrete wash, in order to fill up all cracks and prevent leakage of air or water. For the walls of the flue, which are 11 in. thick, special perforated brick were also made. These brick were 11 in. long by 5% in. wide by 4^8 m- thick. They are laid up to break joints, one row of headers to Plate XXI.— Wire-Shaking Machinery and General View of Flue System. four of stretchers, and were all made at the plant which was constructed for the manufacture of brick for the chimney. Each column in the dust chamber, for a distance of about 18 D ft. from the inlet end, was provided with a hole in the base and another near the top, so that it could be cooled by allowing cold air to blow through it into the flue, in case the temperature should become high enough to endanger its strength. We have never found it necessary to use these openings. THE GREAT FALLS FLUE SYSTEM AND CHIMNEY. 611 612 THE GREAT FALLS FLUE SYSTEM AND CHIMNEY. In a structure of this size and character, where a goodly part of the steel is exposed to high and varying temperatures, we considered it very essential to the life and maintenance of the structure to make ample provision for the expansion and contraction of the steel. We were also advised by our friends in Anaconda, who had experienced some mis- fortunes with similar structures, to make all parts of good heavy construc- tion. We believe that it is to the exercise of these precautions that we SECTION ON LINE E-F SECTION ON LINE C-D ! -Jflinimuii figure l'i%^-^] Jrf \lU R. J-l —4— k^J&Core 1% Hole la SIDE ELEVATION Plate XXIII. — Hopper Gate and Valve. are able to say at this time, after the flue has seen four years of continuous service, that it stands as true and plumb as upon the day it was erected. To provide for this expansion the framework is built in units of from three to seven panels each. The middle panel is securely braced, which holds it plumb, the expansion taking place in both directions from this central point. The roof beams are riveted to the tops of all columns except the one midway between the braced panels, where they are suspended from the columns by links as shown in Plate XXII, Fig. 1. The roof between the purlins on each side of this expansion joint is made of No. 10 steel, bent as shown in the figure. These joints extend across the full width of the flue. THE GREAT FALLS FLUE SYSTEM AND CHIMNEY. 613 To take up the expansion in the purlins which extend across the flue two expansion joints are provided running the full length of the dust chamber, thus dividing the roof into three sections as indicated in the sectional elevation Plate XV. The middle panel in each of these sections is securely braced, so that the expansion is taken up at the joint, a detail of which is shown in Fig. 2, Plate XXII. The main-hopper beams are 15-in. channels, which are riveted to the sides of the lower columns. A detail of the expansion joints in these beams is shown in Fig. 3, Plate XXII. In the longitudinal section shown in Plate XV it will be seen that Plate XXIV. — Hoppers Under Dust Chamber. there are two hoppers to each longitudinal panel, the center line of the hoppers coinciding with the center line of the panel and of the columns. The object of this arrangement is to allow the expansion of the cross- hopper beams to be taken up by the spring in the main longitudinal beams. A crimped plate covers the space between the main channel beams as shown in Fig. 4, Plate XXII. A part of the structure which might seem of minor importance, but which is operated more frequently than any other single element, is that of the gate on the bottom of the hoppers. When it is considered that there are 1,042 hoppers under the main dust chamber, 100 under the cross- take flue, 74 under the blast-furnace flue, 12 under the MacDougall flue 614 THE GREAT FALLS FLUE SYSTEM AND CHIMNEY. Plate XXV. — Trackage Under Dust Chamber. Plate XXVI. — Interior of Dust Chamber During Erection. THE GREAT FALLS FLUE SYSTEM AND CHIMNEY. 615 and eight under the uptake, some of which are being operated every day, the desirability of an efficient and easily operated hopper gate is appreciated. Plate XXIII shows the gate which was designed for this work. It has given extremely good satisfaction. It is made of cast iron, all holes being cored so that it required no machine work of any kind. The essential feature of this gate is that there are no closed slots to fill up with dust and cause the slide to stick or to prevent it from closing. The hoppers and tracks under the dust chamber are shown in Plate Plate XXVII. — Interior of Dust Chamber, Showing Wires and Cold-Air Pipes. XXIV, and Plate XXV shows a portion of the track system before any steel was erected. The total length of trackage under the dust chamber is about 8,900 ft, Dust is transferred from the main dust chamber to the furnaces in hopper-bottom cars of about 80 cu. ft, capacity. The over-all length of each car is just equal to the span on one hopper, so that one spotting only of the train is necessary for each loading. Some additional details of dust-chamber construction are shown on Plates XXVI and XXVII. 616 THE GREAT FALLS FLUE SYSTEM AND CHIMNEY. VIII. The Chimney.1 Having decided upon the construction of a chimney 506 ft. high and 50 ft. inside diameter at the top, the contract for furnishing the brick and building the chimney was let to the Alphons Custodis Chimney Construction Co., of New York, who designed and erected the structure. The foundation was put in by the owners, the design and construction having the approval of the chimney contractor, who is responsible for the stability of the whole structure. The chimney is designed to withstand a wind velocity equivalent to 33 1/3 lb. per square foot diametral projection. The total estimated weight of brickwork in the completed chimney is 17,000 tons. The thickness of the shell is so proportioned that the combined dead and wind load do not exceed 21 tons per square foot at any point. There is no tension at any point on the windward side. Specifications for the brick of which the chimney is constructed required that they withstand a test pressure of not less than 3,750 lb. per square inch of total sectional area, including perforations. General drawings of the chimney and of some details of construction are shown on Plate XXVIII, while Plate XXIX. is a view of the completed structure. The whole of the interior is circular in section. The exterior is octagonal for a height of 46 ft. above the base, the remainder being circular. The profile of the chimney presents four separate tapers as follows: The upper 180 ft. is 2 per cent, taper (1 per cent, batter); the next lower 100 ft. is 4 per cent, taper (2 per cent, batter); the next lower 180 ft. is 7 per cent, taper (3.5 per cent, batter); and the octagonal base 46 ft. in height is 8 per cent, taper (4 per cent, batter). The wall thickness varies by steps of 2 in., the sections of constant thickness being of variable heights, ranging from 10 ft. at the bottom of the circular section, where the wall is 54 in. thick, exclusive of lining, to 50 ft. at the top, where the wall is 183^ m- thick. The chimney is lined throughout with a 4-in. course of hard-burned brick laid in acidproof mortar, the joints being made as thin as possible. This lining is what is known as sectional construction, each section resting on a corbel ring built out from the inner wall of the main chimney shell. Xo section of lining exceeds 20 ft. in height. An air space of 2 in. is left between lining and main chimney shell. Fig. 1, Plate XXVIII, shows a detail of corbel and lining. The top brick of the corbel is molded with a lip for the purpose of forming a drip outside of the lining. In order to 1 New 506-ft. Chimney at Great Falls Smelter, Engineering and Mining Journal, vol. LXXXVII, p. 150. The World's Largest Chimney, Engineering News, vol. LX, p. 583. The Chimney of the B. & M. C. C. & S. M. Co., Engineering Record, vol. L VIII, p. 600. The World's Largest Chimney, Mines and Minerals, vol. XXX, p. 257. —,'r- Two only. Copper Cables on opposite side of Chimney. Each Cable consists of 49 No.13 B. & S. Copper wires. Belt cable of same size connects rods to main cable DETAIL SHOWING CORBEL AND METHOD OF SUPPORTING LINING Copper Wire Screen Anchor . m 4 Mesh 18 long spaced every 7 6 HALF SECTION & ELEVATION OF CHIMNEY & FOUNDATION Plate XXVIII. — Details of 506-ft. Chimney. 618 THE GREAT FALLS FLUE SYSTEM AND CHIMNEY. prevent any dust or condensed fume from settling in the space between lining and chimney wall, this space was filled with mineral wool for a depth of about 2 ft. at the top of each section. The acidproof mortar, which is composed of silicate of soda, asbestos wool and other ingredients, is a very slow-setting material and, when fresh, acts as somewhat of a Plate XXIX. — Great Falls Chimney, 506 Ft. High. lubricant between adjacent courses of brick. It is, however, extremely hard when thoroughly set and dry. In order to hold the lining course in place until the mortar had set, small sections of copper wire netting were built into the main shell and lining at intervals of 7 or 8 ft. The mortar used in the main part of the chimney was a 1 :2 :5 cement- lime-sand mixture. For a distance of 50 ft. down from the top, all out- side joints in brickwork were pointed up with acidproof mortar and the top 3 ft. of the main wall was laid with this mortar throughout. THE GREAT FALLS FLUE SYSTEM AND CHIMNEY. 619 The top of the chimney is corbeled out in steps of 0.75 in. to a thickness of 42 in. The cap is composed of specially shaped radial interlocking terra-cotta tiles laid in acidproof mortar. Fig. 2, Plate XXVIII, shows the general design and arrangement of this cap. For protection against lightning, 16 rods are provided, each of which extends 5 ft. above the chimney top. They are made of 1-in. round copper rod, lead coated for protection against acid, and tipped with a platinum point 1.25 in. high. These rods are all connected to a copper cable which encircles the chimney a few feet below the top. From this encircling cable two ^-in. copper cables lead to the ground on opposite sides of the chimney. The lower end of each cable is fastened to a copper plate about 6 sq. ft. in area, which is buried several feet under ground and at a distance from the foundation, at a point where moisture is usually present. The cable band, as well as the vertical cables for a distance of about 100 ft. down from the top, are lead covered. The cables are composed of 49 No. 13 B. & S. gauge copper wires. Fig. 2, Plate XXVIII, shows the general arrangement and method of supporting the lightning rods. An outside ladder built into the brickwork extends from the base to the top. It consists of one-piece rungs made of 0.75-in. round iron, which stand out 6 in. clear from the chimney wall. The hooked ends of these rungs extend 6 in. into the chimney wall. They are placed at every third joint, or about 15 in. apart. At every second rung there is a guard rung or loop made of 1-in. round iron. The hooked ends extend 8 in. into the brickwork, and the loop is 16 in. outside of the ladder rung and is 28 in. wide inside. For a distance of 100 ft. down from the top, the ladder and guard rungs are lead covered. At each corbel point on the circular portion of the chimney, a flat steel cable about 5 in. wide by 0.5 in. thick is laid in the brickwork. These are for the purpose of reinforcing the shell at the corbel points, where a small portion of it is exposed to the heat of the gases. The cables used were old hoisting cables that had been discarded at the mines. There are four openings in the base of the chimney, each of which is 36 ft. high by 15 ft. wide. The brickwork across the top of each of these openings is carried by seven 9-in. 21-lb. I-beams, which rest on 1-in. plates at each end, and are protected from the acid fumes by special brick fitted over the flanges. Only two of these openings are in use at the present time, the other two being bricked up with double curtain walls which are flush with the inside and outside of the chimney walls. The outside, or facing, course of brick in all flue openings is laid in acid- proof mortar, and a course of brick 1 ft. thick, laid in the same material, covers the floor of the flue openings and protects the concrete base at this point. Plate XXX is an interior view at the base of the chimney, 620 THE GREAT FALLS FLUE SYSTEM AND CHIMNEY. Plate XXX. — Chimney Base Interior. FLUE .BRICK MO. 936 12-14-00 Plate XXXI. — Brick Used in Chimney and Flues. THE GREAT FALLS FLUE SYSTEM AND CHIMNEY. 621 showing the flue entrances. It also shows several corbel rings and a portion of the paved floor which is described later. In order to break joints and also to obtain the required variations in the thickness of the walls, five sizes of brick were used in the main chimney shell. These are known as perforated radial brick. The holes are about 1 in. square and are in a vertical position when the brick are laid. Plate XXXI shows the various sizes and shapes of brick used in the con- struction of the chimney and flues. To supply these brick, a plant was erected near the chimney site, equipped with the necessary grinding pans, etc., an auger machine of over 100 tons capacity in 8 hr., a drier which is arranged to use either direct or waste heat, and eight circular beehive kilns, independently fired. Altogether, the plant has a capacity of 100 tons per day and is being operated at the present time for the manufacture of such products as paving brick, fire brick, hollow tile, drain tile, etc., as well as common and perforated building brick. The shale of which the brick was made was quarried with steam shovel, near the plant. An analysis of this shale is as follows: Loss on Ignition Insoluble SiOz AI2O3 FeO CaO MgO SO3 8.02 77.8 58.3 19.0 6.3 1.2 2.3 0.74 Crushing tests were made on several samples of brick, with results as shown in the following table. In all cases pressure was applied parallel to the perforations. In calculating the crushing weights, the gross area of the brick was used, no deduction being made for the area of holes. Pressure in Lb. per Sq. In. First Crack Ultimate Hard burned 3,033 3,064 2,766 7,173 Medium burned Soft burned 4,255 3,949 Chimney Foundation. The chimney foundation is shown on Plate XXXII. It is composed of concrete, and is annular in shape, the inside being circular, and the outside octagonal. It contains 4,300 cu. yd. of concrete composed of a 1:2.3:4.5 mixture of cement, tailing sand from the concentrator, and broken slag from the smelter. A drainage gutter near the top having a slope of 3^8 m- Per foot 622 THE GREAT FALLS FLUE SYSTEM AND CHIMNEY. SECTION A-A 6"Perforated Brick laid in Acid Troof Mortar - 2-Layers P 1 Tar Felt,- Laid in Tar 6 Concrete 1-4-7 - Fill above Screen with Mineral Wool 6 Vitrified Pipe SECTION B-B Plate XXXII.— Foundation for 506-ft. Chimney. THE GREAT FALLS FLUE SYSTEM AND CHIMNEY. 623 was built as a part of the foundation. The footing on which the founda- tion rests is a hard shale. A loading test was made on the bottom of the excavation to determine whether it would withstand the required maximum pressure which it was estimated would be 5.25 tons per square foot. Four cast-iron plates 2 ft. square by 3 in. thick were set in a thin Flue System — Construction Data. Excavation: Cu. Yd. Main dust chamber 90,354 Connecting flue 14.800 Chimney 5^500 Track to smelter 10,000 Total 120,654 Concrete : Chimney 4,300 Flue system 7,933 Total 12,233 Steel and Iron Work: Tons Structural steel 3,412 Wire baffles (1,200,000) 600 Wire netting (89,400 sq. ft.) 35 Castings 203 Total 4,250 Equivalent in Brickwork: Cu. Ft. Tons Common Brick Blast-furnace dust chamber 15,968 926 351,000 MacDougall dust chamber 6,505 377 143,000 Uptake 13,100 760 288,000 Cross-take 7,977 463 176,000 Main dust chamber 63,356 3,675 1,394,000 Connecting flue 91,866 5,328 2,021,000 Cu. Ft. Chimnev 293,104 17,000 6,441,000 Shell." 261,429 Lining 29,948 Floor 1,727 Totals 491,876 28,529 10,814,000 Trackage: Ft. Under dust chamber (40-lb. rail) 8,900 Dust chamber to smelter (55-lb. rail) 4,300 Under blast furnace flue (40-lb. rail) 700 Total 13,900 cement grout and at equal elevations. These plates were at the corners of a rectangle 6 ft. 6 in. by 16 ft. 6 in. Plate girders were then sym- metrically placed on these plates, and the whole loaded with rails sufficient to produce a load 6.5 tons per square foot of bearing area of the cast-iron plates, being about 24 per cent, in excess of the maximum calculated pres- sure. The test was continued for a period of 20 days, during which time 624 THE GREAT FALLS FLUE SYSTEM AND CHIMNEY. heavy rains flooded the excavation to a depth of several inches over the bearing plates, making the test an especially severe one. The total settlement of the bearing plates was 0.058, 0.058, 0.075, and 0.088 ft. respectively, from which it was decided that the footing material was safe for the required loading. To prevent' possible damage to the concrete foundation by the action of leachings from dust on the floor or sides of the chimney, in case the plant should be shut down for an extended period, the floor was given a slope of 0.5 in. per foot to the center, from which a vitrified pipe laid in acidproof cement leads to the outside of the foundation. The floor itself is constructed from the bottom up as follows: 6 in. of concrete footing; two layers of No. 1 felt with a good coating of tar under, between, and on top of same; 4 in. of sand to act as a bed for brick flooring and also to prevent the heat of gases from damaging the tar and felt; and 6 in. of good quality perforated brick laid in acidproof mortar. The details of this construction are shown on Plate XXXII. IX. — Operation of New Flue System. The new flue system was put into operation on June 12, 1909. It has been in service continuously ever since, with the exception of a period of about 40 days in December, 1909, and January, 1910, when the plant was shut down on account of a strike among employees of the railway company, which stopped the delivery of ore and other necessary material. From June 12, 1909, to Jan. 1, 1913, the total amount of dust collected in the various parts of the system, as well as the average analysis of the dust covering the whole period of 41 months, is shown in Table VIII. Table VIII. — Quantity and Analyses of Flue Dust. Tons Dust Cu Per Cent. Ag Oz. per Ton Au Oz. per Ton Insol. Si02 FeO A1203 CaO Name of Flue Total for 41 Mo. Aver- age per Mo. S Blast furnace MacDougall fur- Uptake and cross- Main dust cham- Connecting fiueQ. 87,020 18,741 17,360 64,048 4,000 2,122 457 423 1,562 98 8.08 10.22 12.59 8.61 3.09 2.7 3.6 4.1 3.3 3.1 0.019 0.023 0.026 0.020 0.012 34.7 37.6 34.8 33.3 12.6 26.8 29.0 26.0 23.6 8.5 33.0 27.1 27.2 14.5 5.4 7.1 7.5 7.2 8.0 4.0 1.7 0.3 0.7 0.7 0.1 16.1 21.3 19.5 11.8 10.6 Total 191,169 4,662 a Weight estimated. Average analysis is from sample taken in June, 1912, at different points from dust chamber to chimney. A comparison of the dust recoveries from the old and new flue systems, with relation to the amount of original cupreous material treated, may be of interest, and is shown in Table IX. THE GREAT FALLS FLUE SYSTEM AND CHIMNEY. 625 Table IX. — Comparison of Dust Recoveries from Old and New Flue Systems. Old Flue System New Flue System Oct. 25, 1903, to June 12, 1909, 68 Months June 12, 1909, to Jan. 1, 1913, 41 Monthsa Tons new cupreous material treated at MacDougall furnaces Tons new cupreous material treated at blast furnaces Total tons new cupreous material treated at MacDougall and blast furnaces 1,213,890 1,663,498 2,877,388 50,604 104,239 3.04 3.62 579,545 898,481 1,478,026 87,020 191,169 9.69 12 93 Tons dust recovered from blast furnace dust chamber. . .. Tons flue dust recovered from entire system Dust recovered from blast furnace dust chamber in per cent, of total new cupreous material to blast furnaces.. Total dust recovered from entire system in per cent, of total new cupreous material treated a Plant not operating during December. 1909, and part of January, 1910. The experimental brick-flue tests indicated that 3.7 per cent, of the new cupreous material charged to the MacDougall roasters was being lost through the old chimney and flue system. Also, that 2.57 per cent, of the new cupreous material charged to blast furnaces was lost in the same way. Applying these percentages to the respective tonnages of new cupreous material treated by the two departments, when operating with the old flue system, and adding to these results the tonnage of dust recovered, we find that 6.66 per cent, of the new cupreous material charged to the furnaces was carried into the flues as dust. Assuming that at present a practically complete recovery of all dust is made, it will be seen that with the new conditions the amount of dust produced is about twice as much as under the old system. There are several reasons why this is so, two of which are well defined: First, as will be shown later, there is a greatly increased volume of gas passing through the new system per ton of material treated. This, of course, is the result of a much stronger draft, together with improve- ments in flue construction which have largely eliminated draft hindrances. In this connection it may be of interest to note that the top of the new chimney is 751 ft. above the blast-furnace charging floor, while the top of the old chimney was only 419.5 ft. above the same floor. Second, since the new system has been in operation, a considerable tonnage of fine concentrate has been charged to the blast furnaces, a practice which was not in vogue under the old system. The curve on Plate XXXIII may be designated as a cumulative plot of the dust collected and drawn from the wire-baffled dust chamber. lin '.III 81 60 O 50 40 LJ a- 30 20 / / / Dottc areas baffle d lines e filled wi s. lclose ,h wire \ \\ i \ \ *' ? 1U 15 40 SO 20 25 30 35 HOPPER NUMBER Plate XXXIII. — Cumulative Plot of Dust Drawn from Dust Chamber. 20 25 30 HOPPER NUMBER Plate XXXIV. — Plot Showing Relative Deposition of Dust Through Dust Chamber. THE GREAT FALLS FLUE SYSTEM AND CHIMNEY. 627 That is, it shows the dust collected from the inlet end up to any given point, in per cent, of the total dust collected in the chamber. The super- imposed outline sketch of the dust chamber, showing the wire-baffled areas within the dotted lines, makes clear the cause of changes in the slope of the curve at various points. The curve or plot on Plate XXXIV shows the relative actual total amounts of dust drawn from the different cross rows of hoppers in the dust chamber. The outline sketch of the dust chamber is again super- imposed on this plate to show the location of the maximum dust settlement. From these two plates it will be noted that about 77.5 per cent, of the total dust deposited is obtained before reaching the upper end of the first section of wires. On account of the low percentage of copper in the dust from the upper part of the chamber, it is evident that the proportion of values collected in the first section of wires is a greater percentage of the total than is indicated by the amount of dust. Table X shows how the analysis of the dust changes from the inlet end of the dust chamber up to the base of the chimney. Table X. — Analyses of Dust from Inlet End to Base of Chimney. Dust Chamber Cu Insol. SiOj FeO AhOj CaO s Hopper Nos. 1-7 8-12 13-17 18-24 10.05 9.17 8.72 7.43 6.83 5.83 5.17 3.73 32.8 32.1 31.6 28.15 27.1 22.7 21.0 16.3 23.7 22.6 23.35 20.6 19.3 15.7 14.4 10.85 17.4 15.2 17.2 13.45 12.0 9.7 8.7 6.5 7.8 7.7 7.5 7.2 7.4 6.5 6.7 4.6 0.3 0.4 1.1 1.1 1.2 1.1 1.0 1.1 14.3 13.1 13.1 11.7 25-29 11.2 30-38 10.9 39-45 10.7 46-52 10.3 Connecting Flue. Door No. 7-E 9-E 10-E 12-E Base of chimney 4.13 17.4 11.5 7.2 5.6 0.1 3:13 12.9 8.8 5.4 3.6 0.1 3.64 15.0 10.5 6.4 4.1 0.1 2.36 9.2 6.1 4.1 3.8 0.1 2.21 8.4 5.4 3.8 2.8 0.1 10.7 10.6 10.3 10.3 10.7 Plate XXXV shows the relative deposition of dust across the dust chamber. In making this plot the total weight of dust from hoppers 4 to 43 inclusive was taken, since all other hoppers are in converging portions of the chamber. The view is taken facing the chimney and 628 THE GREAT FALLS FLUE SYSTEM AND CHIMNEY. shows that a fairly uniform rate of settlement is effected over the full width of the chamber. The marked irregularity in adjacent rows of hoppers in this as well as in Plate XXXIV is due chiefly to the manner in which the dust is drawn. The arrangement of tracks under the hoppers is such as would lead to a result of this kind unless strict supervision is exercised over the operators. Plate XXXVI shows the distribution of dust collected in the blast- furnace flue, with relation to the furnace locations and furnace days in 6 z It* as ~ s 5. Q 1— CO 1 i Uj U. o co Z> 1 I 2 < > H i u 1 0 - ... , 23 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2- 1 HOPPER ROWS Plate XXXV. — Relative Deposition of Dust Across Dust Chamber. operation, from June 12, 1909, to Jan. 1, 1913. The increase in the amount of dust from hopper No. 1 is doubtless due to the flow of dust from the uptake when it is partially filled up from dumping cross-take dust into it. Recent observations made by drawing out several wires from the central portion of both the upper and lower groups of wires show that in the first or lower group there is a light accumulation of dust on each wire which readily falls off when gently rapped. A cross-section through this accumulated dust is wedge shaped, the point of the wedge facing the current of gas being almost as thin as a knife edge. The depth of the THE GREAT FALLS FLUE SYSTEM AND CHIMNEY. 629 % fa < « p fa H 01 PQ suox ^ o ^ o lO o o © o o lOO "**"*£ COCO 1^i>| rH rH © NMvya isna ivioi- jo in30 U3d rs o 630 THE GREAT FALLS FLUE SYSTEM AND CHIMNEY. wedge is from 1 to 2 in. and the back in which the wire is located is about Y% in. thick. In the upper section of wires, the overall diameter of dust on wire is about 0.25 in., after shaking. These dimensions differ little, if any, from similar dimensions taken a year or more ago, which indicates that an indefinite increase in the permanent accumulation of dust on the wires is not to be feared. X. Temperatures and Drafts. The average temperature of the gases entering the wire-baffled dust chamber, exclusive of reverberatory gases, is about 325° F. = 163° C. The temperature at the upper end of dust chamber just after entering the connecting flue averages about 275° F. = 135° C. In the connecting flue, just before it branches to enter the chimney, the average temperature is 325° F. = 163° C. This includes reverberatory gases. Temperatures are also taken at about the central point of the blast- furnace flue. These vary considerably depending upon the number of furnaces in operation and the conditions under which they are working. A fair average temperature when three furnaces are running is about 375° F. = 191° C. These temperatures are taken with Bristol pyrometers having seven- day charts. Recording draft gauges are connected at the same points where temperature readings are taken. A typical set of draft and tem- perature curves covering the months of February and March, 1911, are presented in Plate XXXVII. Table XL- — Draft Readings on New Flue System. Location of Reading Elevation Temperature in Flue F.° Temperature of At- mosphere F.° Draft Readings In. Water Impact Tube Static Tube A — Blast furnace 3,338 3,361 3,413 3,413 3,413 3,570 391 419 358 346 312 310 80 80 80 70 70 70 1.12 0.94 0.88 0.94 2.20 1.80 1.16 B — MacDougall D — Cross-take 0.98 0.97 D — Cross-take 1.01 L — Connecting flue LT — Near chimney 2.26 1.84 Special draft readings taken on the new flue system at points A, B, and D (see Plate XIII) and at two points on the connecting flue, one of which was near dust chamber, designated as L, and the other near chimney, designated as U, are presented in Table XI. Simultaneous observations were made at points A, B, and D and at D, L, and U. During this time there were three blast furnaces, nine 'Blast Furnace Flue Crosstnke February 1911 ***** Plate XXXVII.— Draft and Temperature Curves. 19G 632 THE GREAT FALLS FLUE SYSTEM AND CHIMNEY. MacDougalls, three 12-ft. converters and three reverberatories in opera- tion. Gases from two of the reverberatories were being bypassed around the main dust chamber. In taking these readings, Pitot-tube elements were used, the impact- and static-pressure ends being read independently. Using these observations, the total draft energy on the MacDougall furnaces is calculated, and also the loss in draft through the various sections of the flue system. The lower hearth of the MacDougall furnaces is at an elevation of 3,313, while the top of chimney is at an elevation of 4,054 ft. Difference in Elevation Ft. Average Temperature F.° Draft Loss In. Water Lower hearth of MacDougalls to cross-take Cross-take through wire baffles to connecting flue. Connecting flue near dust chamber to near chimney Connecting flue near chimney to top of chimney.. 100 0 157 484 460 329 311 300 1.40 1.26 0.25 0.06 Totals 741 2.97 It should be explained that the loss through the wire-baffled dust chamber shown in the above tabulation is higher than normal, because of the fact that the upper section of wires had not been shaken for about four months and also that there was an accumulation of several feet of dust in the lower group of wires. A comparison of draft readings at similar points on the old and new systems may be of interest. Readings, of course, vary rather widely, depending upon furnace and other conditions, but in general are about as follows: Old system. Xew system. Draft Readings — In. Water Blast Fur- nace Flue 0.50 1.15 MacDougall Flue 0.25 0.90 Reverb. Flue Near Furnaces 0.90 1.50 On Flue Near Chimney 0.60 1.85 XI. Velocities and Volumes. During March and April, 1911, tests were made to determine the velocity and volume of gases passing through the various parts of the new flue system. From these tests also, the amount of gas per furnace and per ton of cupreous material treated has been calculated. Pitot tubes were used in making velocity determinations, nine impact THE GREAT FALLS FLUE SYSTEM AND CHIMNEY. 633 points being inserted into the flue, representing as many equal rectangular areas. Bristol pyrometers were used for obtaining temperatures, and other instruments and methods were the same as have been described earlier in this paper. Plate XXXVIII. -Construction* axd Arraxgemext of Pitot Tubes ix Reyer- beratory flue. During this test the reverberatory gases were bypassed around the dust chamber through the old Xo. 3 flue, in which velocity readings were taken with five Pitot points as indicated on Plate XXXVIII. The furnaces referred to in the tables below are of the following sizes: Blast furnaces. 56 by ISO in. at tuyeres. MacDougall furnaces. 1-4 ft. 6 in. inside of lining: six hearths. Reverberatories. gas fired. 42 ft. 4 in. by 15 ft. 9 in. Converters. 12 ft. upright. 634 THE GREAT FALLS FLUE SYSTEM AND CHIMNEY. Table XII. — Velocities, Volumes, Average Temperatures and Weights of Gases. ; 8X A B C G E2 D2 Date, 1911 Apr. 6-8... Apr. 6-8 ... Apr. 6-8... Mch. 21-24 Apr. 6-8... Mch. 21-24. Mch. 21-24. Apr. 10. Apr. 10. Aver- Clear No. and age Area Kind of Temp- of Furnaces erature Flue F.° Sq. Ft. 4 B. F. 10 MacD. 5 Conv. 2 Rev. 4 B. F. 10 MacD. 5 Conv. 4 B. F. 6 MacD. 5 Conv. 4 B. F. 6 MacD. 5 Conv. 2 Rev. 4 B. F. 10 MacD. 5 Conv. do. 345 352 303 496 331 286 290 401.6 169.0 78.5 152 . 5 636 977 311 977 977 322 : 636 Vel. in Ft. per Sec. , Vol. at Ob- served Tempera- ture Cu. Ft. per Min. Pounds Gas per Min. 17.26 415,960 18,510 17.50 253,500 10,980 50.37 213,630 9,840 43.34 396,700 14,530 21.80 859,300 38,190 15.51 901,400 42,280 21.03 1,234,900 56,110 15.54 910,950 42,270 22.74 867,760 38,700 Pounds Gas per Furnace 4,630 1,100 1,970 7,270 Tests A, B, and C on the individual department flues show a total of 39,330 lb. of gas per minute. The gases from these flues unite in the cross-take on which a simultaneous test was made showing 38,190 lb. per min., thus checking within about 3 per cent. Tests Di and Ei taken at the inlet and outlet end respectively of the main dust chamber cannot be compared directly, since they were made on different days, and a different number of furnaces were in operation. Tests D2 and E2 may be compared since they were taken on the same day and under the same conditions. Lb. D2 — Gas entering main dust chamber through cross-take flue. 38,700 E. — Gas leaving main dust chamber through connecting flue. 42,270 Leakage of air into main dust chamber 3,570 Leakage in per cent, of gas entering main dust chamber 9.2 percent. THE GREAT FALLS FLUE SYSTEM AND CHIMNEY. 635 The temperature of the atmosphere on the day of the test was 54° F. Calculating the temperature which would result from mixing 3,570 lb. of air at 54° F. with 38,700 lb. of gas (considered as air) at 322° F., we obtain a temperature of 299°. Since the air leaving the dust chamber was at a temperature 290°, the loss due to radiation was 9° F. Sum- marizing we have: Temperature of gases entering chamber through cross-take flue . 322° F. Temperature of gases leaving chamber through connecting flue. 290° F. Temperature of outside air 54° F. Drop in temperature of gases in passing through chamber 32° F. Drop in temperature of gases caused by leakage of cold air 23° F. Drop in temperature of gases caused by radiation 9° F. Per cent, of total drop due to leakage of cold air 71 .9 Per cent, of total drop due to radiation 28 . 1 A further check on the accuracy of the tests may be made by comparing the sum of tests Ei and G with test F. Test Ei, which includes blast furnace, MacDougall and converter gases plus test G, which covers re- verberatory gases only, show a total of 56,810 lb. per minute. Test F on the connecting flue near the chimney, where all furnace gases were combined, shows a total of 56,110 lb. gas per minute, being a difference of about 1.25 per cent. Based on the amounts of gas for the various department flues, as presented in Table XII, Table XIII is presented to show the volume and weight of gas for one furnace of each kind when operating on the new flue system. Table XIII. — New Flue System. Amount of Gas per Furnace and per Ton of Charge. Kind of Observed Temperature Corresponding to Given Volume F.° Rate per Min. Rate per 24 Hr. 