/ Issued June 11, 1912. U. S. DEPARTMENT OF AGRICULTURE, FOREST SERVICE. HENRY S. GRAVES, Forester. FOREST PRODUCTS LABORATORY SERIES. EXPERIMENTS WITH JACK PINE AND HEMLOCK FOR MECHANICAL PULP. BY J. H. THICKENS, . ?snr y Chemical Engineer in Forest Products. WASHINGTON: GOVERNMENT 'PRINTING OFFICE. 1912. Rwsest ef*Ic5* W^S.^Ifi.cf AgriooJture jVlechanical Pulp PLATE I. FIG. 1 .MOTOR GENERATOR SET AND SWITCHBOARD. FIG. 2. -GRINDER AND WET-MACHINE ROOM. Issued June il, U. S. DEPARTMENT OF AGRICULTURE, FOREST SERVICE. HENRY S. GRAVES, Forester. FOREST PRODUCTS LABORATORY SERIES. EXPERIMENTS WITH JACK PINE AND HEMLOCK FOR MECHANICAL PULP. BY J. H. THICKENS, // Chemical Engineer in Forest Products. WASHINGTON: GOVERNMENT PRINTING OFFICE. 1912. LETTER OF TRANSMITTAL UNITED STATES DEPARTMENT OF AGRICULTURE, FOREST SERVICE, Washington, D. 0., December 13, 1911. SIR: I have the honor to transmit herewith a manuscript entitled " Experiments with Jack Pine and Hemlock for Mechanical Pulp," by J. H. Thickens, chemical engineer in forest products, and to recommend its publication. Respectfully, HENRY S. GRAVES, Forester. Hon. JAMES WILSON, Secretary of Agriculture. 2 CONTENTS. Page. Need of a substitute for spruce pulp wood 5 Results of experiments 6 Why jack pine and hemlock have not been used for pulp 7 Equipment used in the experiments 8 Electrical equipment 8 Pulp machinery and auxiliary equipment 8 Methods employed .* 10 Qualitative and quantitative tests 10 Commercial tests 10 Treatment of the wood before grinding 10 Grinding 11 Losses in grinding 12 Fiber study 12 Calculation of results 12 Comparison of yields 13 Factors which influence quality and production 15 Speed and pressure 15 Surface of stone 16 Temperature 18 Undetermined factors 18 Microscopic comparison of experimental pulps and commercial standards 18 Standard pulps 18 Jack pine pulp 20 Hemlock pulp 21 Mixed pulps 21 Samples of paper produced 22 Summary of data 23 3 477631 L LUSTRATIONS. PLATES. Page. PLATE I. Fig. 1. Motor generator set and switchboard. Fig. 2. Grinder and wet-machine room Frontispiece. II. Fig. 1. Natural surface of stone (jack pine run No. 2). Fig. 2. Ten to the inch solid, straight-cut burr (hemlock run No. 0). Fig. 3. Eight to the inch solid, spiral burr (hemlock run No. 43) 8 III. Fig. 1. Three to the inch solid, straight-cut burr (hemlock run No. 46). Fig. 2. Three to the inch solid, straight-cut burr, cut over with 12 to the inch solid, spiral burr (hemlock run No. 51). Fig. 3. Six to the inch diamond-point burr (jack pine run No. 17-1) . . 8 IV. Fig. 1. Spruce sulphite standard. Fig. 2. Spruce ground wood, No. 1 standard 16 V. Fig. 1. Spruce ground wood, No. 2 standard. Fig. 2. Spruce ground wood, No. 3 standard, coarse ground 16 VI. Fig. 1. Spruce ground wood, No. 4 standard, medium ground. Fig. 2. Spruce ground wood, No. 5 standard, fine ground 16 VII. Comparison of hemlock pulps ground at different speeds. Fig. 1. 100 revolutions per minute (run No. 35). Fig. 2. 150 revolutions per minute (run No. 36). Fig. 3. 200 revolutions per minute (run No. 37) 16 VIII. Comparison of jack pine pulps ground at different speeds. Fig. 1. 152 revolutions per minute (run No. 19). Fig. 2. 205 revolu- tions per minute (run No. 20-1) 16 IX. Fig. 1. Jack pine ground wood (run No. 14-1). Fig. 2. Jack pine ground wood (run No. 13-1) '. . ' 16 X. Fig. 1. Jack pine ground wood (run No. 7-1). Fig. 2. Jack pine ground wood (commercial run No. 24) :V 16 XI. Fig. 1. Hemlock ground wood (run No. 41). Fig. 2. Hemlock ground wood (commercial run No. 14-1) 16 XII. Fig. 1. Hemlock ground wood (commercial run No. 8). Fig. 2. Hemlock ground wood (run No. 2) 16 XIII. Fig. 1. Hemlock ground wood (commercial run No. 30). Fig. 2. Hemlock ground wood (commercial run No. 50). (Used in accom- panying paper sample) 16 XIV. Fig. 1. Ground-wood pulp, one-third spruce, two-thirds hemlock (run No. 46a). Fig. 2. Ground-wood pulp, all hemlock (run No. 466). Fig. 3. Ground-wood pulp, all spruce (run No. 46c) 16 XV. Mixed ground-wood pulps (used in accompanying paper samples). Fig. 1. One-third spruce, two- thirds hemlock (commercial run No. 46a). Fig. 2. One-third hemlock, one-third jack pine, one- third spruce (commercial run No. 51). Fig. 3. One-third jack pine, two-thirds hemlock (commercial run No. 52) 16 TEXT FIGURE. FIG. 1. Portion of a chart from a recording wattmeter, showing decreased power consumption after removal of load from pocket and pocket binding. . . 14 4 EXPERIMENTS WITH JACK PINE AND HEMLOCK FOR MECHANICAL PULP. NEED OF A SUBSTITUTE FOB SPRUCE PULPWOOD. Few well-established industries have expanded as rapidly as has the pulp and paper industry. In less than a decade the amount of raw material used annually has more than doubled. During 1900 l there were consumed in the United States 1,986,310 cords of pulp- wood. The ground-wood process used 598,229 cords of domestic spruce, 120,820 cords of imported spruce, and 67,791 cords of other woods, such as hemlock, jack pine, poplar, and balsam, or a total of 786,840 cords. During 1909 2 the amount of wood used in all proc- esses was 4,001,607 cords, the ground-wood process using a total of 1,246,121 cords, which consisted of 806,282 cords of domestic spruce, 317,289 cords of imported spruce, and 122,550 cords of other miscel- laneous woods. Thus the increase in the total amount of pulpwood used during this period was 101 per cent, while the amount of pulpwood of all kinds used for ground wood increased 58J per cent. The domestic spruce consumption for this purpose increased 35 per cent and the con- sumption of miscellaneous woods 80.5 per cent. But the largest increase was in the use of imported spruce, the consumption of which increased 162 per cent. The price of spruce has increased at a very rapid rate. In 1900 the average cost of spruce used in all processes in the United States was $4.83 per cord for domestic spruce and $6.50 for imported, while in 1909 the average price of domestic spruce was $9.32 and of imported $11.34 per cord. This increase has been reflected in the cost of ground-wood pulp. The manufacturing cost of pulp, as determined by the Tariff Board, 3 increased from $10.84 per ton in 1900 to $16.58 in 1909, 93 per cent of this increase being accounted for by the greater cost of the wood used. Manifestly, therefore, it is almost essential, if the ground-wood i Twelfth Census of the United States. a " Pulpwood consumption, 1909," Bureau of the Census. 3 Report by the Tariff Board relative to pulp and news print paper industry, Senate Document No. 31, Sixty-second Congress, first session. 5 8 JACK PINE AND HEMLOCK FOR MECHANICAL PULP. industry is to centime, that substitutes be found for spruce pulp, especially in the manufacture of news, wrapping, and other of the cheaper grades of paper. To determine whether there are not other domestic species which will produce a commercial grade of ground wood suitable for the purpose, etc., the Forest Service, in cooperation with the American Pulp and Paper Association, began an extensive series of tests on several of the woods which occur in large quantities in the United States, particularly in the Lake States. The woods which have been tried up to the present are hemlock and jack pine, together with a small amount of spruce, for the purpose of comparison. The experiments were conducted at Wausau, Wis., under the general supervision of the director and assistant director of the Forest Products Laboratory, and an advisory committee of the American Pulp and Paper Association, composed of Messrs. G. F. Steele, chairman Nekoosa-Edwards- Paper Co.; W. G. McNaughton, secretary Nekoosa-Ed wards Paper Co. ; D. C. Everest, Marathon Paper Mills Co.; W. L. Edmonds, Wausau Paper Mills Co.; A. M. Pride, Tomahawk Paper Co. ; and Wm. Eibel, Rhinelander Paper Co. RESULTS OF EXPERIMENTS. Not only have very promising sheets of pulp been obtained from both the hemlock and jack pine, but paper has been made from them on commercial machines, operating at high speed, and under all other conditions of actual commercial practice, which has the strength, finish, and appearance of standard news paper. The production per grinder, the horsepower consumption per ton, and the yield per cord approximate the averages which obtain in the grinding of spruce. Again, pulps composed of mixtures of hemlock, spruce, and jack pine in different proportions have been obtained, which compare very favorably with the ordinary spruce ground wood. Hemlock ground wood has a decided reddish tinge, though this is not very noticeable, even in an all-hemlock sheet of news paper. Jack pine pulp is also slightly off in color, but is not nearly as dark as hemlock pulp. Careful study by experts should make it possible to bring the color of the paper produced from these pulps more nearly to the usual white. As it is, the sheets of news paper which have been secured are only slightly off color, though they are the result in each case of but a single attempt to secure the standard degree of whiteness. Since the experiments on hemlock have brought out a number of points in favor of the grinding of that wood, two paper-mill com- panies have signified their intention of using it in their cheaper grades of paper. One of these mills has already begun to do so, and is well satisfied with the pulp obtained. JACK PINE AND HEMLOCK FOR MECHANICAL PULP. 7 WHY JACK PINE AND HEMLOCK HAVE NOT FEEN USED. There is much doubt as to exactly why the pulp industry has neglected to use hemlock and jack pine for the cheaper grades of paper. It seems to be the general impression that hemlock grinds so fine and short that there is a great loss in conversion. It has been said that the yield obtained is in many instances only three-fifths of that from an equal amount of spruce. This loss in grinding hemlock has not been in evidence during the tests. The pitch in jack pine is undoubtedly responsible for the lack of attention paid to that wood. This, however, can be removed by steaming or soaking, and such treatments will be taken up in future experiments. In all the experiments the yields secured from the different woods were in direct proportion to their bone-dry weight per cubic foot. It is therefore to be expected that the yields from jack pine and hemlock will be less per unit of volume than those from spruce, since the two first woods are considerably lighter in weight. On the basis of weight, however, there appears to be relatively little more loss in converting hemlock or jack pine into pulp than in converting spruce. The fiber obtained from the ground hemlock and jack pine has been considered unsatisfactory on account of its shortness. Yet it has been found long enough for use in cheap papers. . One who is accustomed to handling spruce ground wood will not be favorably impressed with the appearance of either hemlock or jack pine pulp. This is particularly true of the hemlock sheet. Both pulps are somewhat softer in texture than spruce, and, alto- gether, are not as pleasing in appearance as the present commercial product. Another point which may account for the lack of attention paid to hemlock and jack pine is the care which must be exercised in grinding them. It is possible to obtain a grade of pulp from spruce which is suitable for most purposes without using a great deal of care in the preparation of the surface of the pulp stones. In the grinding of jack pine and hemlock, especially hemlock, on the other hand, great care must be exercised in bringing the stone to the correct degree of sharpness, since these woods will grind to powder if the surface is as sharp as the one ordinarily employed in grinding spruce. Yet notwithstanding certain shortcomings the fact remains that it is possible to obtain hemlock and jack pine pulps commercially which are suitable for the cheaper grades of paper. 8 JACK PINE AND HEMLOCK FOR MECHANICAL PULP. EQUIPMENT USED IN THE EXPERIMENTS. ELECTRICAL EQUIPMENT. To study accurately the fundamental variables of grinding it was necessary to install an elaborate electrical drive and apparatus for control and manipulation. There has also been provided a system of recording instruments for the determination of speed, pressure, and load fluctuation. The electrical apparatus consists of a motor- generator set and a direct-current variable-speed motor. The variable-speed motor, direct connected to the pulp grinder, is rated at 225 horsepower at 100 revolutions per minute and 500 horsepower at 300 revolutions per minute, with a 50 per cent overload capacity at all speeds. However, it is possible to obtain about 25 per cent more capacity than the rating. Variation in speed is obtained by variation of voltage applied to the motor armature, and by means of a rheostat in the field circuit of the generator it is possible to maintain this voltage at any point desired, thus giving a very con- stant speed. The efficiency of the grinder motor has been determined for all values of speed and load throughout the range of usage. Conse- quently, the power applied to the grinder at any value of peripheral speed or at any pressure on the cylinders can be calculated. Individual motor drives have also been installed for the various other pieces of pulp-making machinery and their auxiliary apparatus. The machines for wood preparation and the wet-machine vacuum pump are the only ones which are not direct connected to indi- vidual motors. In several cases variable-speed motors have been installed to permit adjustment of speed to the most effective value. PULP MACHINERY AND AUXILIARY EQUIPMENT. The pulp-making machinery, machines for wood preparation, and the auxiliary pieces of apparatus are all of standard commercial types and were loaned by the following manufacturers or others interested in the work of the laboratory: Grinder Friction Pulley and Machine Works. Wet machine Improved Paper Machinery Co. Flat screen Harmon Machine Co. Ruth centrifugal screen H. L. Orrman & Co. 5 by 8 inch triplex pump Goulds Manufacturing Co. 4 by 6 inch triplex pump Do. 5-inch centrifugal pump Do . 4-inch centrifugal pump Do. Storage tank Valley Iron Works. Barker. . . .'..... Green Bay Foundry and Machine Works. Forest Service, U. S. Dept of Agriculture Mechanical Pulp. PLATE II. FIG. 1. NATURAL SURFACE OF STONE. (JACK PINE RUN No. 2.) FIG. 2. TEN TO THE INCH SOLID; STRAIGHT-CUT BURR. (HEMLOCK RUN No. 0.) FIG. 3. EIGHT TO THE INCH SOLID; SPIRAL BURR. (HEMLOCK RUN No. 43.; Forest Service, U. S. Dept. of Agriculture Mechanical Pulp. PLATE III. FIG. 1. THREE TO THE INCH SOLID; STRAIGHT-CUT BURR. (HEMLOCK RUN No. 46.) FIG. 2. THREE TO THE INCH SOLID; STRAIGHT-CUT BURR. CUT OVER WITH TWELVE TO THE INCH SOLID; SPIRAL BURR. (HEMLOCK RUN NO. 51.) FIG. 3. Six TO THE INCH DIAMOND POINT BURR. (JACK PINE RUN No. 17-1.) JACK PINE AND HEMLOCK FOR MECHANICAL PULP. 9 Swing cut-off saw American Pulp and Paper Association. 3-ton scale Paper (Inc.). 2 Ash ton relief valves Do. 1 pulp truck W. A. Lounsberry & Co. 1 wood truck Do. 1 54 by 27 inch pulp stone Manufacturers' Paper Co. 12 42-inch screen plates Union Screen Plate Co. 1 wet-machine felt Albany Felt Co. 1 wet-machine felt Appleton Woolen Mills. 1 set barker knives Dowd Knife Works. 1 set sectional and solid burrs. .Ticonderoga Machine Works. Plate I shows a portion of the pulp-making equipment. The grinder (PL I, fig. 2) has three pockets, the cylinders are 14 inches in diameter, and it is designed for a 54 by 27 inch pulp stone. Each of the grinder cylinders is equipped with a pressure gauge, and the pressure line between the triplex pumps and the grinder is provided with Ashton relief valves, which make it possible to obtain very uniform pressures up to 100 pounds per square inch. A recording thermometer gives a record of the temperature in the grinder pit. From the grinder pit the pulp is passed through a mechanically agitated sliver screen, then pumped to a storage tank by means of a 6-inch centrifugal pump, and from there pumped to a centrifugal screen. A variable-speed motor direct connected to the screen makes it possible to obtain speeds of rotation from 400 to 600 revolutions per minute. Throughout the tests, however, the speed was maintained at 500 revolutions per minute. The plate in the centrifugal screen is perforated with holes 0.065 inch in diameter. The tailings from it are led by gravity to a 12-plate horizontal dia- phragm screen, the plates of which are the Union Screen Plate Go's, type B, cut with 0.012-inch slots. The good pulps from the centrifugal and the plate screens are united in the vat of the wet machine, which is direct connected to a variable-speed motor giving felt speeds ranging from 75 to 115 feet per minute. The wet machine is provided with a small triplex pump by which the cylinders connected to the press rolls are operated, the dryness of the pulp being determined by the pressure applied to the cylinders. A vacuum of from 10 to 15 inches, produced by a rotary suction pump, is maintained on the felt, and this, too, assists in obtaining the desired dryness of the pulp. The white water from the wet-machine vat is pumped back to the grinder sliver screen by a 4-inch centrifugal pump. White water from the felts is run directly to the sewer, as is also the white water from the felt suction. Plate I, figure 2, gives an idea of the general arrangement of the pulp- making machinery. A 40-inch swing cut-off saw and a Green Bay wood barker are used to prepare the wood. 10 JACK PINE AND HEMLOCK FOR MECHANICAL PULP. METHODS EMPLOYED. QUALITATIVE AND QUANTITATIVE TESTS. In order to cover the field in a reasonable length of time, short tests ranging up to two hours in length were run. In these tests no attempt was made to cover every point, the object being to touch only such as were thought to have a marked effect on the quality of the product. The surface of the stone, the pressure on the grinder cylinder, and the peripheral speed of the stone were the variables which received most attention. No especial attention was given to economic con- siderations. Tests were made with pressures of from 20 to 75 pounds per square inch on the cylinder, corresponding to from 8.2 to 30.8 pounds per square inch of pocket area. The speed of rotation of the stone was varied from 84 to 225 revolutions per minute, corresponding to a range in peripheral speed of from 1,173 to 3,150 feet per minute. In studying the effect of the surface condition of the stone it was necessary to utilize burrs of many different types and designs. These ranged in fineness of cut from 12 to the inch to 3 to the inch. The style of cut differed also, spiral cut, diamond points, and straight cut being employed. The power applied to the grinder ranged from 87.3 to 520 horsepower, while the rate of production of bone-dry pulp varied from 1 ton to 7.3 tons in 24 hours. It should be under- stood that neither the two minimum nor the two maximum values were necessarily obtained from the same test. When the power applied to the grinder was 87.3 horsepower, for instance, it does not necessarily follow that the production was 1 ton per day. The horse- power consumption per ton under the given conditions was found to vary from 68.3 to 196 in 24 hours. The samples of pulp obtained during the qualitative and quanti- tative tests were examined and commented upon by members of the advisory committee of the American Pulp and Paper Association, and those runs considered most promising were duplicated later in commercial tests. COMMERCIAL TESTS. TREATMENT OF THE WOOD BEFORE GRINDING. All of the wood used in the tests was cut either in Wisconsin or Michigan and was representative of the species. In some cases the wood was secured directly from the forest, while in others it was shipped to the laboratory from near-by mills. Upon arrival at the laboratory the logs were closely piled on skids. An attempt was made to keep the material green by painting the ends with paraffin, but this proved unsatisfactory, because the paraffin peeled off. The wood tested was taken directly from the piles for all tests up to and includ- JACK PINE AND HEMLOCK FOB MECHANICAL PULP. 11 ing run No. 52 of the hemlock series, with the exception of runs Nos. 49, 50, and 51, the wood for which was soaked in the pond for approxi- mately two months before being used. The only jack pine soaked was that used in the commercial test on seasoned wood of that spe- cies run 14. The jack pine and spruce used in tests on mixed pulps were in all cases dry before grinding. The wood for the tests was prepared approximately 2 cords at a time, sawed into 2-foot lengths, barked, weighed, and piled up for the grinding process. To determine accurately the yield, the bone-dry weight per cubic foot of wood, as well as the percentage of moisture present, was determined in each commercial test. All weighings were made in 500 or 1,000 pound lots, and the wood was used as soon as ground. No attempt was made to remove knots or punky portions of the wood. In fact, all of the tests were carried on in accordance with the usual commercial practice. GRINDING. Before commencing the grinding tests an impression of the surface of the stone which had been selected was taken by means of a piece of carbon paper and a sheet of coated paper. This impression was later photographed, as shown in Plates II and III. In these the black dots represent projecting points and the white portions between them depressions in the stone. The surface shown in Plate III, figure 2, is particularly interesting, since it is the result of dressing with two different kinds of burrs. Before starting the tests the recording thermometer and all of the other recording instruments were placed in operation. The pockets of the grinder were filled, the pressure adjusted to the proper value, and the grinder started. For the purpose of check and control, regular readings were taken of the various switchboard instruments, the indicating tachometer, the pressure gauges, and the recording thermometer. On short tests up to 2 hours in length these readings were recorded at 5-minute intervals, but on longer tests the interval was increased to 15 minutes. The speed, pressure, and other variables were maintained as nearly constant as possible. For instance, when one of the grinder pistons was raised the speed was brought back to the desired value by manipulation of the rheostat controlling the motor armature voltage. During the qualitative and quantitative tests the pulp stone did not have an opportunity to heat up, and, in consequence, some of the data on power consumption and production may be more or less questionable. In the commercial tests, however, all of which were made under the hot-grinding process, the stone was brought up to a high temperature, which was maintained throughout the run; con- sequently these more nearly approximate commercial conditions. 12 JACK PINE AND HEMLOCK FOR MECHANICAL PULP. LOSSES IN GRINDING. To determine approximately the losses occurring in the conversion of wood to pulp, the bone-dry weight of screenings obtained from a known amount of bone-dry wood was determined. The loss in the white water was then taken as the difference between the bone-dry weight of the wood ground and the bone-dry weight of the pulp secured plus the screenings. FIBER STUDY. During each test the character of fiber obtained was examined by means of an apparatus for microscopic study. This consists of an ordinary stereopticon provided with a specially constructed carrier for microscopic slides. Samples of wet pulp were taken from the wet-machine vat and slides were made by first removing the water by drying, then staining with Bismarck brown, and moistening with glycerine. The mixture of glycerine and fiber was teased out to cover the area of an ordinary microscopic cover glass, which was placed over the mixture. Evaporation or leakage was prevented by means of a thin strip of shellac around the edge of the cover glass. With this apparatus it was also possible to compare different samples of pulp with the commercial standards used, the latter being selected from a large number of samples submitted by American manufacturers of ground- wood pulp. CALCULATION OF RESULTS. To give a clear understanding of the method employed in calcu- lating the various items in connection with a test, all the calculations for a representative run, No. 50, Table 4, are given here. Consid- erable data taken during the tests have been eliminated from the compilation, since they have no direct bearing on the study. The test mentioned required 3.42 hours to complete, and during that time 3,388 pounds of hemlock wood were ground. For com- parison all of the figures on weight of wood were brought to a bone-dry basis. The bone-dry weight of wood was secured by drying a known volume of wood to constant weight and calculating the weight per cubic foot. By calculating the bone-dry weight of a log of measured volume and subtracting this amount from the actual weight of the log, the' moisture content of the wood was determined. The bone-dry weight of this wood, per cubic foot, was 24.84 pounds, and the moisture content was 46.5 per cent; consequently the amount of bone-dry wood ground was 53.5 per cent of 3,388, or 1,810 pounds. This is equivalent to 72.9 cubic feet of solid wood ground during the JACK PINE AND HEMLOCK FOR MECHANICAL PULP. 13 given period; or, in other words, the grinding was carried on at the rate of 512 cubic feet of solid wood in 24 hours. The amount of wet pulp obtained during the test was 3,795 pounds, and this upon analysis was found to have a moisture content of 60.22 per cent. Consequently, 1,507 pounds of bone-dry pulp were obtained during the period of test, corresponding to a production of or 5 - 3 tons * n 24 hours. To grind the wood and pro- duce this pulp it was necessary to apply to the grinder motor power which averaged 338 kilowatts. This value was obtained by dividing the total number of kilowatt hours used, as given by a watt-hour meter, by the length of the test in hours. Figure 1 shows a section of a wattmeter record obtained during this test, and illustrates how the power used by the grinder varied upon the removal of the load from one of the grinder pockets. The entire recording wattmeter curve was averaged by means of a planimeter, in order to check the value of power consumed as given by the watt-hour meter. By using curves which show the losses in the motor it was found that 15.3 kilowatts were required to supply the heat losses in the grinder-motor armature and 7.1 kilowatts to supply the stray power losses, making a total of 22.4 kilowatts lost in converting the power from electrical to mechanical. This amount subtracted from 338 kilowatts gives 315.6 kilowatts which were furnished to the grinder pulpstone, and 315.6 divided by 0.746 1 gives the value of 422J horse- power applied to the grinder. In order, then, to obtain 5.3 tons of bone-dry pulp in 24 hours it was necessary to apply to the grinder over that period 422 J horsepower, or the horsepower consumption per ton was 422J divided by 5.3, or 79.7 horsepower per ton in 24 hours. The yield from 100 cubic feet of solid wood was obtained by dividing the amount of pulp produced during 24 hours, 5.3 tons or 10,600 pounds, by the number of hundreds of cubic feet of wood ground in 24 hours, viz, 5.12. The result is 2,070 pounds. The average temperature of grinding was determined by reading the recording thermometer every five minutes, adding these values, and dividing by the total number of readings. COMPARISON OF YIELDS. Much importance is attached to the amount of pulp obtained from a cord of wood, because this represents the efficiency of con- version. Commercial practice in the manufacture of spruce ground wood requires a yield of approximately 2,300 pounds per cord of i A horsepower is equivalent to 0.-746 kilowatt. 14 JACK PINE AND HEMLOCK FOR MECHANICAL PULP, rossed wood, or 1,800 pounds per cord of rough wood. The average yields which have been obtained for hemlock and jack pine, together KILOWATTS. FIG. 1. Portion of chart from recording wattmeter, showing decreased power consumption after removal of load frojuti pocket and pocket binding. with those obtained for two different shipments of spruce, are given in Table 1. JACK PINE AND HEMLOCK FOR MECHANICAL PULP. TABLE 1. Average yields from spruce, hemlock, and jack pine. 15 Species. Weight per 100 cu. ft. bone-dry. Yield per 100 cu. ft. of solid wood. Efficiency of conversion. Spruce Pounds. 2,840 Pounds. 2 480 Per cent. 87 3 Do 2,270 2,000 88 2 Hemlock 2,480 2 100 84 8 Jack pine 2 540 2 200 86 7 One hundred cubic feet of solid wood was selected as the basis of yield, since it eliminates the variable loss in barking, and represents fairly well the amount of solid wood in a rossed cord. The yield, as will be seen, is directly proportional to the bone-dry weight of the wood. The loss in conversion has been found to range between 12 and 15 per cent of the original weight of the bone-dry wood. Ap- proximately 6 per cent can be accounted for in the white water and 1 per cent in screenings. The manner in which the remaining losses occur has not been determined, but will be studied in future tests. The storage capacity for white water in the laboratory was very limited, and this may to some extent account for the low yields. The continuous use of the white water and the use of save-alls would undoubtedly tend to increase the yields and result in saving a great deal of fine pulp. The loss in barking jack pine and hemlock, so far as has been determined up to the present time, is practically the same as the loss in the barking of spruce. There are a great many knots in both hemlock and jack pine, and it is possible that this may cause a some- what greater loss in barking these species. However, on account of the small amounts of the various woods used, no reliable data on loss were obtained. FACTORS WHICH INFLUENCE QUALITY AND PRODUCTION. SPEED AND PRESSURE. The effect of speed on the quality of pulp can best be illustrated by the magnified fibers shown in Plates VII and VIII. In grinding these pulps the pressure and surface of the stone were maintained constant, and the speeds were, respectively, 100, 150, and 200 revolu- tions per minute for the hemlock, and 152 and 205 revolutions for the jack pine. There is little difference in the fibers ground under these different conditions of speed; especially those run at 150 and 200 revolutions per minute. Speed probably has very little effect on the quality of pulp. With satisfactory pressure and curface of stone, it is possible to obtain good grades of pulp at any speeds within reasonable limits. Commercially, it is practically impossible to main- 16 JACK PINE AND HEMLOCK FOR MECHANICAL PULP. tain the speed constant at all times. When the pressure on a pocket is removed the speed is bound to rise considerably, especially when the water wheels or turbines are operated without a governor. When hemlock wood was ground at low speed and low pressure it was impossible to obtain anything more than a powder. Also when this wood was ground at low pressure and high speed the product was extremely short, but the pressures at which these results were obtained are considerably lower than those ordinarily employed commercially, and the results have little significance. If the stone is what is ordi- narily called sharp, it is necessary to use a lower pressure, and when dull, a higher one, but it is impossible to obtain the same quality of pulp under both conditions. Speed and pressure affect quantity rather than quality, and by the proper adjustment of both the maxi- mum efficiency of grinding is attained. If a certain speed is selected there must be a corresponding pressure which will yield the greatest amount of pulp in 24 hours with the least consumption of power. By the term " constant pressure/' wherever used in this report, is meant constant pressure on the grinder cylinders. The pressure per square inch of wood in contact with the grinding surface varies con- siderably, chiefly with the size of wood ground and the area of the pocket. Again, the length of the wood is not at all a constant quantity, and this, too, can only result in a variable pressure per square inch of wood. The pressure of the wood on the stone varies throughout certain limits with any pressure on the grinder cylinder, and the ranges of pressure of the wood on the stone are raised or lowered by raising or lowering the cylinder pressure. This pressure variation, however, can hardly be controlled commercially, and therefore has not been considered in the test's discussed in this report. There is also more or less pressure variation due to binding of wood in the pockets, and this, too, is difficult, if not impossible, to control. Figure 1 shows a measure of the power applied to the grinder. The effect of pocket binding and the withdrawal of pressure from one of the pockets will be noted. At one end of this chart the power con- sumed is approximately 360 kilowatts, falling off gradually to 280 kilowatts, due to pocket binding. After raising the pistons and read- justing the wood in the different pockets, the power to the grinder motor had to be increased to 350 kilowatts on account of the added load produced by eliminating the pocket binding. SURFACE OF STONE. The most efficient grinding condition is one where there is a maxi- mum amount of grinding surface, and still a sufficient amount of depression in the stone to allow for the carrying away of the ground wood, or, as this is commonly called, for the clearing of the stone. Forest Service, U. S. Dept. of Agriculture Mechanical Pulp. PLATE IV. FIG. 1. -SPRUCE SULPHITE STANDARD. '-.^^m^^stm FIG. 2. SPRUCE GROUND WOOD, No. 1 STANDARD. Forest Service, U. S. Dept. of Agriculture Mechanical Pulp. PLATE V. . :. \ FIQ. 1. SPRUCE GROUND WOOD, No. 2 STANDARD. FIG. 2. SPRUCE GROUND WOOD, No. 3 STANDARD, COARSE GROUND. Forest Service, U. S. Dept. of Agriculture Mechanical Pulp. PLATE VI. FIG. 1. SPRUCE GROUND WOOD, No. 4 STANDARD, MEDIUM GROUND. m FIG. 2. SPRUCE GROUND WOOD, No.- 5 STANDARD, FINE GROUND. Forest Service, U. S. Dept. of Agriculture- Mechanical Pulp. PLATE VII. FIG. 1.-100 R. P. M. (RUN No. 35.) FIG. 2. 150 R. P. M. (RUN No. 36.) - *. , - "- FlQ. 3.-200 R. P. M. (RUN No. 37.) COMPARISON OF HEMLOCK PULPS GROUND AT DIFFERENT SPEEDS. Forest Service, U. S Dept. of Agriculture Mechanical Pulp. PLATE VIII. fflnBi 3IP4, ^XM^^mMm FIG. 1.-152 R. P. M. (RUN No. 19.) FIG. 2. 205 R. P. M. (RUN No. 20-1.) COMPARISON OF JACK PINE PULPS GROUND AT DIFFERENT SPEEDS. Forest Service, U. S. Dept. of Agriculture Mechanical Pulp. PLATE IX. FIG. 1. JACK PINE GROUND WOOD. (RUN No. 14-1.) FIG. 2. JACK PINE GROUND WOOD. (RUN No. 13-1.) Forest Service U. S. Dept. of Agriculture Mechanical Pulp. PLATE X. mm i - I * \r .' ,\> FIG. 1. JACK PINE GROUND WOOD. (RUN No. 7-1.) FIG. 2. JACK PINE GROUND WOOD. (COMMERCIAL RUN No. 24.) Forest Service, U. S. Dept. of Agriculture Mechanical Pulp. PLATE XI. FIQ. 1. HEMLOCK GROUND WOOD. (RUN No. 41.) '-'--'-^^ - , -^., - " '>--*. 'l*- -' FIG. 2. HEMLOCK GROUND WOOD. (COMMERCIAL RUN No. 14-1.) Forest Service, U. S. Dept. of Agriculture Mechanical Pulp. PLATE XII. .: J^fegj FIG. 1. HEMLOCK GROUND WOOD. (COMMERCIAL RUN No. 8.) FIG. 2. HEMLOCK GROUND WOOD. (RUN No. 2.) Forest Service, U. S. Dept. of Agriculture Mechanical Pulp. PLATE XIII. ' FIG. 1. HEMLOCK GROUND WOOD. (COMMERCIAL RUN No. 30 ) FIQ. 2. HEMLOCK GROUND WOOD. (COMMERCIAL RUN No. 50.) USED IN ACCOMPANYING PAPER SAMPLE. Forest Service, U. S. Dept. of Agriculture Mechanical Pulp. PLATE XIV. FIG. 1 .GROUND-WOOD PULP, ONE-THIRD SPRUCE, TWO-THIRDS HEMLOCK. (RUN No. 46 A.) FIG. 2. GROUND-WOOD PULP, ALL HEMLOCK. (RUN No. 46e.) /. "%, IMfei^ ^^/^ - / (^^* ^i ~y- FIG. 3. GROUND-WOOD PULP, ALL SPRUCE. (RUN No. 46c.) Forest Service, U. S. Dept. of Agriculture Mechanical Pulp. PLATE XV. FIG. 1. ONE-THIRD SPRUCE, TWO-THIRDS HEMLOCK. (COMMERCIAL RUN No. 46A.) *V3 FIG. 2. ONE-THIRD HEMLOCK, ONE-THIRD JACK PINE, ONE-THIRD SPRUCE. (COMMERCIAL RUN No. 51.) ^Ti&^i? ^A--. '?;* -. .vvt- '^ i-^ .-m .-^JW,-- '** -v t :: J '^ V^SI S W:^^' s>^^ -<, ; v- .*;-,' :v'..jf3^r/> iV-^k r v >. FIG. 3. ONE-THIRD JACK PINE, TWO-THIRDS HEMLOCK. (COMMERCIAL RUN No. 52.) MIXED GROUND-WOOD PULPS USED IN ACCOMPANYING PAPER SAMPLES. JACK PINE AND HEMLOCK FOR MECHANICAL PULP. 17 Throughout the experiments, particularly the commercial tests, it was found that the pulp of same appearance as regards fiber and of the same apparent strength can be obtained by using burrs of different design and fineness of cut, provided the grit of the stv, is in each case the same. For example, during the commercial tests the stone was burred at different times with different types of burrs, and the grinding in each case was found to require the consumption of the same amount of power. The production per day was the same also, provided the grit was brought to the same condition of sharpness and the other variables were kept constant. During some of the preliminary tests the surface of stone was dulled with a fire brick, as is often done in mills. This appears to have been unnecessary ; in fact, the result is detrimental rather than beneficial. Better pulp was obtained and the production was increased slightly by crushing the tops of the ridges formed in burring by means of a solid, smooth bush roll. This method does not smooth off the indi- vidual particles of sand on the stone as duUing with the brick does, but rather sharpens them . During the tests conducted on mixed woods a surface obtained by the use of a three- to- the- inch straight-cut solid burr and a 12-cut spiral burr was used. The stone was first dressed with a three-to-the-inch burr, forming grooves in the stone approxi- mately one thirty-second inch deep; then the portion of the stone between these depressions was roughed with a 12-cut spiral burr. This caused the grit to stand out and gave a maximum of useful grinding surface. The pulp obtained with this surface was almost entirely free from shives, and the fibers were long and fine. The sur- face of stone used during these tests is shown in Plate III, figure 2. A great deal of experimentation still remains to be done, not only with burrs of different cut and design, but more especially with stones of different grits, since it appears that the grit is more responsible for the quality of pulp obtained than any other variable feature in its production. Where the pulp stone is deep burred, however, the grit is not so important a factor of quality. When the power consumed in making a ton of bone-dry pulp is as low as 50 to 60 horsepower, the added production which must be secured to bring the power to this low value is obtained through the action of the ridges on the stone and not through the grit. When it is desired to manufacture a pulp of high quality, however, it is the grit of the stone and the manner of raising it which must be considered. The type of burr used and the depth of dressing both influence production, but it is only the latter that influences the quality. When the pulp stone has been dressed so as to provide just sufficient depression to carry away the ground 23688 12 2 18 JACK PINE AND HEMLOCK FOR MECHANICAL PULP. wood a high-grade pulp will be produced, providing the grit of the stone is suitable, irrespective of the style of the burr and within ~vable limits of the pressure used. It is not impossible to con- jf an artificial stone which could be used continually without n, Jig, which would clear itself without having depressions or ridges, and which would have the correct size and kind of grit to give the maximum production and best quality. TEMPERATURE. The temperature of grinding, it is said, has much to do with the quality and quantity of pulp obtained, and many manufacturers insist that it is impossible to secure a tough, strong fiber with anything but the hot grinding process. It was noted in the experiments that the rate of production was not nearly as great at a low temperature as it was after a high one was reached. However, it was impossible to detect microscopically any difference in the fibers themselves. As has been said, the only observations made on cold grinding were while the stone was warming up, and on this account it is impossible to say definitely what particular advantages or disadvantages, if any, lie in the hot grinding process. UNDETERMINED FACTORS. Since the experimental work on hemlock, jack pine, and spruce was started a number of factors which more or less influence the quality and the rate of production of pulp have made themselves evident. These are the rate of growth of the wood, moisture content of the wood, size of wood ground, temperature of grinding, the thick- ness of stock in the grinder pit, and the grit of the pulp stone, the last undoubtedly being the most important. All of these variables will be studied in future experiments, though the grit of the pulp stone is the one which will probably receive the greatest attention. It is doubtful whether this very important item in the production of ground wood has been given sufficient consideration by manufacturers. MICROSCOPIC COMPARISON OF EXPERIMENTAL PULPS AND COMMERCIAL STANDARDS. STANDARD PULPS. Since it was necessary to have some means of comparing the experimental pulps produced with commercial products, portions of the samples obtained from manufacturers were photographed, in an endeavor to classify the fibers according to their quality. It was found that there is a more or less regular grading of the material from long, fine fiber to pulp which is almost a powder. It is probable JACK PINE AND HEMLOCK FOR MECHANICAL PULP. 19 thai/ each of the various grades of pulp has its particular use in cer- tain qualities of paper, though no attempt has been made to classify them according to uses. The standards selected are shown . ites IV, V, and VI; in each case the fibers are enlarged 15 time For the purpose of comparison the spruce sulphite standard fiber is shown in Plate IV, figure 1, and the No. 1 spruce ground- wood standard in figure 2. It is indeed very seldom that a sample of pulp is obtained which corresponds to the No. 1 spruce ground- wood standard. As will be noted, the fibers are very similar to the sulphite fibers, although there is a certain amount of short material and coarse fiber present which does not occur in the sulphite pulp. Plate V shows the No. 2 ground- wood standard and No. 3 coarse ground- wood standard. The No. 2 differs from the No. 1 standard only in the amount of short fiber and coarse fiber present, the No. 2 having larger amounts of these two kinds. The coarse standard needs no description. It is a kind of fiber often made by mills during their low-water periods in order to maintain production with less power consumption. The No. 4, medium ground-wood standard, and the No. 5, fine ground-wood standard, seem to follow in logical sequence those pre- viously given. The No. 4 standard has the appearance of being a mixture of No. 3 and No. 5. The No. 5, as will be noted, contains an extremely small amount of fiber and is composed largely of dust and short-fiber particles. Table 2 gives the data furnished by the manufacturers of the various pulp samples selected as standards. These data, for the most part, are only approximate, but they will serve to give some idea of the conditions under which the material was produced. TABLE 2. Conditions of manufacture of spruce ground-wood standards. Number of stand- ard. Make of grinder. 1 Size of cylinders. & * o i" 3 35 40 45 60 90 Equivalent pres- sure on 14-inch cylinder. Kind of stone. Kind of burr. Size of stone. Number o ets. 3 ~> i d s>> i 1 mlock sulpr uce ground ^S 1 I 0. ight per rea 24 by 36 erage thicki p fl o 1 "& erage stretc] erage load o trip 18 b .65 cm. !! <3 d erage stretc erage load o trips 18 b .65 cm. p 03 fcjQ g o> r3 B > > Wl-< >-~ !> > WH * ' r-l O w 00 w ^ 5 M CQ accounted for by the fact that although the same kind of burr )d, the stones were of different sharpness. s been found difficult to duplicate in one test the surface of si^ , used in another under the same conditions and obtain the same production with the same power consumption. In fact, the pro- duction factors vary greatly over short periods as a result of the vary- ing attention given by the grinder man. On this account the power and production data in the tables can be applied to commercial plants only approximately. If a grinder is operating under the conditions of any of the commercial tests shown in Tables 5, 6, and 7, however, the data given will closely approximate the actual working conditions. TABLE 4. Qualitative and quantitative tests on jack pine Power consumption and production. Kind of stone. Run number. Kind of burr. Pressure on 14-inch cylinder. Pressure per square inch, pocket area. Revolutions per minute. Peripheral speed per minute. Average horsepower to grinder. Bone-dry pulp in 24 hours. Horse power per ton bone-dry pulp in 24 hours. Bone-dry pulp per 100 cubic feet borie- dry wood. Weight per cubic foot bone-dry wood. Average tem pera- ture'bf grinding. Size of screen slots. Manufac- turers'. Do 1 2 Natural sur- face, do Lbs. 20.0 30.0 Lbs. 8.20 12.30 151. 151.0 Feet. 2,100 2,100 Tons. Lbs Lbs. JK 140.0 147.0 Inch. (i) Do 3 do 39 10.00 150 2,090 176. (i) Do 3-1 do .. 39.3 16. 10 151.0 2,100 176.0 (i) Do 4 do 50 20.50 150.6 2,100 196. (i) Do 5 do ... 60.0 24.65 151.0 2, 100 199. (i) Do 6 do 60 24. 65 171.0 2,380 196.0 (i) Do 6-1 do 60.0 24.65 171.0 2,370 201.0 (i) Do 7 do 50 20.50 171.0 2,370 199.0 C 1 ) Do 7-1 do 50.0 20.50 172.0 2.380 256.0 1.305 196.2 1,820 25.27 197.0 0. 012 Do 7-2 do 50.0 20.50 172 2,380 245 1.263 193. 6 2, 150 25. 57 183.0 .012 Do 8 do 60 24 65 203 2,810 198.0 (i) Do 8-1 do 60.0 24. 65 203. 2,810 191.0 (i) Do 9 do 50 20. 50 202 2,800 205.0 (i) Do 10 do.... 75.0 30.80 202.0 2,800 185.0 (i) Do Do 11 11-1 Diamond point, 6 to the inch, do 60.0 60.0 24. 65 24. 65 152. 5 154.0 2,100 2,100 380.5 360. 5 6.075 59.3 148.0 146.0 .012 .012 Do do 50 20 50 152 5 2 100 350 5 225 67 145.0 .012 Do 12-1 do!!! '!!.... 50.0 20.50 154.0 2,100 359.0 7.030 51.0 179.0 .012 Do 13 do. . 40.0 16.40 152.5 2,100 260. 3.028 85.9 138. 2 .012 Do. .. Do 13-1 14 do do 40.0 50.0 16. 40 20.50 153. 5 173.0 2,100 2,380 299.0 324.0 2. 670 4.7K 112.0 68.8 195.0 154.0 .012 .012 Do 14-1 do 50.0 20. .50 174.0 2,380 398.0 5. 046 78.8 166.0 .012 Do 15 do 60.0 24.65 173. 2,380 395. 5 6.290 61.8 138. .012 Do 15-1 do. . 60.0 24. 65 174.0 2,380 461.0 5.500 83.8 158.0 .012 Do. .. Do. .. Do 16 16-1 17 do do do 40.0 40. ( 40.0 16.40 16. 40 16. 40 203. 5 205. 173.0 2,800 2.800 2.380 362. 5 375.0 289. 5.450 5. 360 3.834 66.4 70.0 75.5 147.0 200.0 143. .012 .012 .012 Do 17-1 . do 40.0 16.40 174.0 2,380 332.0 4. 350 76.3 178.0 .012 Do 18 do . 50.0 20. -50 204.0 2,800 407.5 6.910 59.0 143.0 .012 Do 18-1 ...do.... 50.0 20.50 205.0 2,800 414.0 6.360 65.0 193 t O .012 Do 19 do 30 12 30 15 5 2 100 201 2.045 98 3 149.0 .012 Do 20 do 30.0 12.30 205.0 2,800 313.0 5 320 58.8 178.0 .012 Do Do. 20-1 21 do do.... 30.0 30.0 12.30 12.30 205. 174.0 2,800 2,380 304.0 269. 5 3.620 4.810 83.8 56.0 2,370 24.90 198.0 172.0 .012 .012 Do 22 do 60.0 21. 64 205. 2,800 481.0 7.320 65.8 1S5. .012 Do Lombard 23 24 do 40.0 { 40.1 16. 40 16.40 205.0 J175. 2,800 2,445 249.0 395. 4.110 4.305 84.9 91.8 2,220 25.60 206. 176.3 .012 .012 \ 45. 18. 46 / 1 Unscreened. JACK PINE AND HEMLOCK FOR MECHANICAL PULP. 25 TABLE 5. Qualitative and quantitative tests on hemlock Power consumption and production. Kind of stone. m number. Kind of burr. essure on 14-inch cylinder. essure per square ich, pocket area. evolutions per minute. ripheral speed per minute. ^erage horsepower to grinder. >ne-dry pulp in 24 hours. C fl !* a= E 111 o M P | d t m 1! *! HI to &o 0> p v jo C 1 g o o> tf Pi (2 < PQ W (2) Do 21 do .. (50 24.65 100.6 1,100 281.0 2. 810 100.0 160.0 2 Do 22 do 50 20 50 150 ? 090 366 3 815 96 161 5 w Do 23 D i a m o n d- 40 16.40 175.0 2,440 347.0 3. 360 103.2 159.0 M Do 24 pointcut, 10 to the inch, do 50 20 50 175 2,440 394.0 5.065 77 7 157. ( 2 ) Do.... Do 25 26 do do 60 30 24. 65 12 30 100.0 200 1,390 2,782 291.5 315.0 3.312 2 945 88.0 107 156.0 163.0 Do 27 do 50 2J. 50 200.0 2,782 432.0 5.400 80.0 160.5 M Do 28 do 60 24. 65 101 1,408 290.0 168.0 (2) Do Do 29 30 do Straight cut: 4 to the inch. 50 1 40 20.50 16. 40 175. 175.0 2,435 2,435 372.0 319.0 3.900 81.8 187.0 145. 0) (2) Do 31 10 to the inch do f 60 24 65 100 1 390 269 3 330 80 9 145 (2) Do Do 3? 33 do do 6( 50 24. 65 20 50 100 175 1,390 2, 435 298.0 376 3. 120 4 000 95.5 94 155.0 163.0 ( 2 ) ( 2 )' Do Do 34 35 Spiral cut, 8 to the inch, do 60 60 24.65 24 65 100.0 100 1,390 1 390 297.0 284 4.35C 2 915 68.3 97 5 135.0 147 ( 2 ) (2) Do.. .. 36 do . 60 24.65 150.0 2,090 417.0 5. 130 81.4 152. (2) Do 37 do 60 24 65 200 2 782 50 6 890 75 5 154 (2) Do 38 do 50 20.50 84.3 1,173 212.0 2.660 79.7 154.0 M Do 39 do 60 24 65 85 1 183 271 2 955 91 8 150 M Do 40 do 50 20.50 100.0 1,390 285. 3 0?5 94 3 156.0 ( 2 ) Do 41 do 50 20 50 150 2 090 379 4 450 85 2 155 () Do 42 do.. 50 20.50 175. 2,435 429.0 5.295 81.1 155.0 (2) Do 43 do 50 90 50 200 2 782 439 5 4^5 80 9 145 (2) Do Lombard . . Do.... 44 45 47 do Straight cat, 3 to the inch, do 40 40 55 16. -10 16.40 22.60 175.0 200.0 200 2, 435 2..800 2,800 359.0 340.0 516.0 4.225 2. 91f 5.370 85.0 116.5 96.2 158.0 159.0 161.0 H (2) Do 48 . . .do 50 20.50 225.0 3,145 510. 6.235 81.8 164.0 Do...... 50 Straight cut, 3 to the inch; spiral cut, 12 to the inch. 50 20. 50 175.0 2,445 422.5 5.300 79.7 2.070 24.84 170.6 ( 2 ) 1 Unscreened. 2 Size of screen slots, 0.065 and 0.012. 26 JACK PINE AND HEMLOCK FOR MECHANICAL PULP. TABLE 6. Commercial tests on jack pine Power consumption and production. GREEN MATERIAL. | S, i 1 i f$ olutions minute. pheral sp per minute. rage horsepo^ to grinder. e-dry pulp ir hours. sepower per ne-dry pulp hours. o! S i "S &.g S'S v, C I &o f,r t, &! 3 2 ^ '.Q > % "3 S <8 G > g 0^^ - S S 3 & H O'D I o fi P4" 1 X P-i 4 m w m 4 CO CO Lbs. Lbs. Feet. Tons. Lbs. Lbs. op Lbs. Incli. Manufac- 14 D i a m o n d- 50 20.5 169 2,380 435 5.380 80.9 2,200 24.9 153 (i) turers'. point cut, 6 to the inch. Do 14 .. do.... 50 20.5 171 2,400 458 G. 650 68.9 2 070 24.9 150 (i) Do 14 do 50 20. 171 2,400 430 6. 850 62.7 2, 130 24. 9 145 H Do 14 .. do... 50 20. 171 2,400 416 7.040 69. 1 24.9 149 m Do... 14 do. .. 50 20. 171 2,400 430 6. 610 65. 24.9 149 Do.... 14 .. do.... 50 20. 171 2,400 4 ''7 7. 070 60.4 2,190 25.8 150 ( c) Do 14 do 50 20. 171 2,400 447 7. 550 59.2 25. 8 150 Do 14 .. do 50 20. 171 2,400 df\C 8.300 55.3 25.8 147 n Do 14 do 50 20. 171 2,400 441 7.700 57.3 2,190 25.1 147 i Do 14 .. do 50 20. 171 2,400 jor 7.420 58.0 2,075 25. 1 151 i) Do 11 do 50 20 171 2 400 4^1 4 960 85 2 025 25 1 154 ll Do. . . 14 .. do 50 20. 171 2,400 6.035 76.0 2,180 25. 1 162 i) Do 14 50 20 1 7 1 2 400 446 6 635 67 3 2 200 25 1 150 Do... . 14 . do.... 50 20. 2,400 445 7. 135 62 5 2, 190 25.1 147 t < Do 14 do .. 50 20 171 2,400 462 7 440 62 2 2 160 25 4 143 j\ Do 14 .. do 50 20. 171 2,400 6,860 66.0 2,153 25.4 14S (1) Do 14 do. 50 20. 171 2,400 484 7 560 64 2,155 25 4 142 Do 14 do 50 20. 171 2,400 467 7.335 63.7 2,235 25.4 137 0) Weighted av- 436 7.030 2.170 148 erages. Size of screen slots, 0.065 and 0.012. SEASONED MATERIAL. Manufac- 14 Diamond 50 20.5 171 2,400 457 5.140 89.0 2,125 25.4 147 /0.065 1 019 turers'. point, cut 6 1 . Ul^S to the inch. Do 14 do 50 20.5 171 2,400 451 5.570 81.0 2,170 25.6 142 ' . 065 i .012 Do 14 do 50 20.5 171 2,400 468 6.780 69.0 2,210 25.6 140 / .065 i .012 Do 14 do 50 20.5 171 2,400 455 7.050 64.5 2,260 25.6 136 / .065 \ .012 Do 14 do . 50 20.5 171 2,400 460 7. 365 62.4 2,233 25.6 142 .065 .012 Do 14 do.... 50 20.5 171 2,400 490 6.160 79.5 2,150 25.6 154 .065 .012 Do 14 . do 50 20.5 171 2,400 3S6 3.995 96.6 2,095 25.6 152 . 065 .012 Do 14 do 50 20.5 171 2,400 421 6.240 67.6 2,225 25.6 144 .065 .012 Do 14 do 50 20.5 171 2,400 444 6.340 70.0 2,320 25.6 152 .065 .012 Do 14 do 50 20.5 171 2,400 417 5,990 69.7 25.6 146 .065 \ .012 Weighted' av- 447 6. 2SO 72.7 2,210 145 erages. SEASONED MATERIAL. Lombard . 24 Straight cut, 3 to the inch; 40 16.4 175 2,445 385 4.190 91.9 2,220 25.6 169.4 10.065 \ .012 spiral cut, 12 to the inch. {/u>e Do 24 do 45 IS. 46 175 2,445 404 4. 100 91.8 2,220 25.6 182.0 .012 Weighted av- 395 4. 305 91. 8 2,220 25.6 176.3 14.9 erages. T\OK PINE AND HEMLOCK FOR MECHANICAL PULP. 27 TABLE 7. Quantitative and commercial test on mixtures of spruw, jack pine, and hemlock Power consumption and production. ^ . g 4 .2 4 3 f i .a 1 4 3 a i Ig ^ I 2 Kind of stone. rcial run num Kind of burr. 4 g e per square pocket area. tions per mini ?ral speed per i W SH p ry pulp in 24 1 ower per ton pulp in 24 hot ry pulp per 1(X bone-dry woe per cubic fool dry wood. II Qgs per 100 cut bone-dry wooc screen slots. a a 1 I | i i s ra II o 1*" i M O t> ! "3 3 i! PH PS PH < PQ n PQ F J & w $ spruce; hem- lock: Lbs. Lbs. Ft. Tows. Tb- g C3 a, & > 3 CM 3 3 -H^ +2 S-S 'I ftjg k a s$ wl? P ll I i Kind of stone. un numbei Kind of burr. f If evolutions ute il |a ft i 11 if > |1 i orsepower bone-dry 24 hours. 1! r eight per c bone-dry G) So C3 o P 1!| g > 5 g PH PH PH PH PH oo 2 795 394 4 175 94 4 166 7 Weigh ted 402 4 120 97 5 2 012 22 72 168.0 13 75 averages. Straight cut 20 8 2 175 2 445 101 1 215 157.0 2,300 27.66 163.0 9.82 3 to the inch; spiral cut, 12 to the inch. 4 do.. 40 16.4 175 2,445 333 3.025 110.0 2,408 27.66 166.5 17.8 5 ....do. 60 24.65 1 75 2, 445 454 5.255 86.4 2,415 27.66 152.2 18.6 TABLE 10. Furnish to beater on basis of 1,000 pounds of stock Experimental and commercial papers. EXPERIMENTAL PAPER. 1 1 a a 1 PH h a S ti 3 jr ,a 3 03 3 P & w CO w CO ^ o PH CO P O r,fc, 'Lint. Lbs Lfefc Lbs Lbs. Lbs. 02. 0?, 02. 02. 0^. Commercial 1 A 50 950 8 8 20 067 3.33 Do 250 750 8 8 20 067 3 33 Do 24 750 8 8 20 3.6 0.15 Do 46 250 250 500 8 8 20 4 15 Do 50 250 750 8 8 20 3 7 20 Do 51 250 250 250 250 8 8 20 4 1 15 Do 500 250 8 8 20 4.3 .15 COMMERCIAL PAPER. No 2 white manila 210 395 395 8 s 2 8 Butchers manila <>10 263 527 >n ^0 26.7 2.75 0.83 O UNIVERSITY OF CALIFORNIA LIBRARY UNIVERSITY OF CALIFORNIA LIBRARY BERKELEY Return to desk from which borrowed. This book is DUE on the last date stamped below. 20Apr'50F;