IR!CULTLJ U ROOM
FACILITIES FOR PULP AND PAPE R
RESEARCH AT TH E
U S. FOREST PRODUCTS LABORATORY
Revised July 1960
No. 1499
UNITED STATES DEPARTMENT OF AGR1CULlUR t FORE5f PRODUCTS 1ABORAfOR Y FOREST SERVIC E MADISON 5 . WISCONSI N In Cooperation with the University of Wisconsin L. . FACILITIES FOR PULP AND PAPER RESEARCH AT TH E
U .S . FOREST PRODUCTS LABORATORY-
,By
G : H . CHIDESTER, Chief Division of Pulp and Paper
Introduction.
A completely equipped pulp and paper laboratory is maintained at fhe U .S . Forest Products Laboratory . The purpose of the investigations made in this laboratory is to increase the possibilities of obtainin g economical production, higher yield, and better quality of gulp- from native woods, including those of little or no present utility ;
Research in pulp and paper has the following objectives : (1) To improve yield and quality of pulps obtained with the chemical processes and th e semichemical and mechanical processes ; (2) to develop and improve uni t -operations in chemical and mechanical processing of pulp, such as th e bleaching operation ; (3) to study the relationship of fiber propertie s to the properties of pulps and papers ; (4) to develop processin g conditions for making paper, paperboard, wallboard, and other pulp . and paper products ; and (5) to find means for more efficient utilization of wood species, low grade timber, and manufacturing residues .
To accomplish the objectives of this program, facilities are provide d for conducting investigations and demonstrations through both laboratory . and pilot-plant stages . The equipment consists of machinery for handlin g and preparing wood through the entire sequence of pulp and pape r processing and several laboratories for testing pulps and papers . Thi s equipment serves to meet a major objective in evaluating various specie s of wood for pulp and paper, and.-is also adapted to investigation s designed to improve and perfect techniques in pulp and paper manufacture .
Maintained at Madison, Wis ., by the Forest Service, U .S .-Departmen t .of Agriculture, in cooperation with the University of Wisconsin .
Report No . 1499 (Revised)
Preparation of Wood for Pulpin g
For pulping and papermaking experiments it is often desirable that th e wood be especially selected and cut so that the influence of certai n growth variables can be determined . Data may be taken relative t o growth conditions in the field, such as type of soil, climate, density and character of the stand, and other factors . At the Laboratory , determinations are made of various characteristics and properties, suc h as rate of growth ; specific gravity ; proportions of heartwood, sapwood , springwood, and summerwood ; color ; degree of decay ; chemical composition ; and other, pertinent factors .
If the pulpwood has the bark on when received, it is peeled with han d tools . For both . chemical and semichemical pulping, the peeled wood i s chipped in a small commercial size pulpwood chipper of standard design . The chips are screened to remove fines and over-sized pieces on a screen operating with a horizontal gyratory motion (fig . 1) . The chip s are conveyed mechanically to a chip bin or stored in metal container s until needed for cooking experiments .
Pulping Equipmen t
Chemical and Semichemicaj Pulping
Chemical and) semichemi-cal_ pulping experiments are conducted in vessel s varying. in capacity from beaker-size to a 225-cubic-foot digester . They are designed to operate under the widest possible range of condition s with a high degree of flexibility .
The smallest-scale experiments are made in calorimeter-type bombs, whic h are of stainless steel and have a capacity-of 350 cubic centimeters . The bombs are heated in thermostatically controlled glycerin or oi l baths . Experiments are conducted on this scale when the greates t accuracy is desired or when only a_small amount of•material is neede d for subsequent chemical analysis .
Small-scale digestions for producing 2 to 5 pounds of pulp, sufficien t for making pulp-strength and bleaching tests, are made in autoclaves . Four stainless steel, rotary autoclaves, which have volumes of 0 . 8 •cubic foot and jackets for indirect heating, are used for acid, neutral , and alkaline digestions (fig . 2) . The cooked chips are dumped from the autoclaves . Completely cooked chips are macerated with water in a tank equipped with a propeller-type stirrer . Semichemically softened chip s are fiberized in an 8-inch, single-rotating disk mill . The pulp is the n screened on a diaphragm screen fitted with a slotted screen plate tha t is 9 by 12 inches in size . The screened pulp is dewatered in a hydraulic press, and the pressed cake is shredded in a specially designe d apparatus for the yield determination .
Report No . 1499 (Revised) -2- • - k j
Two rotary digesters having capacities of 13 cubic fee :eaach are available for producing larger quantities of chemical and semichAma al,,pu.lps - (fig . 3) . These digesters have steam jackets and can be heated indirectly or directly . They are constructed for pressures up to 400 pounds pe r square inch . .Qne digester is made from steel plate and is used fo r alkaline digestions ; the other has a stainless steel lining and i s suitable for either acid or alkaline pulping . When the digestion is . completed,-the chemical pulps are blown into a stainless-steel-lined tank equipped with a perforated false bottom for draining off the spent liq or and wash water . The semichemically softened chips are discharged b y dumping into a drain box and are then fiberized in a disk mill, screened, . and wet lapped . Approximately 50 pounds of chemical pulp or T 5:=_p,ouuil s of semichemical pulp can be made in these digesters, which are sufficien t amounts for short papermaking experiments on the Laboratory paper machine .
A digester with a volume of 225 cubic feet (fig . 4) is used torsiappi1iy pulp for extensive papermaking experiments or even for mill-scale paper - making demonstrations . This digester holds the chips from 1 cord of woo d so that approximately 1/2 ton of chemical pulp or 3/4 ton of semi- chemical pulp can be produced from each digestion . It is lined with . stainless steel and is equipped for circulation of the coping ligmir . _through an external heater having stainless steel tubes . The -digester, . - has a working pressure of 200 pounds per square inch . At the-end of a digestion, chemical pulp is blown into a stainless steel taxiklwit h . perforated false bottom in which the pulp is washed . The pulp is the n slushed from the blow tank through pipe lines to stock chests for-snrbi sequent screening and wet lapping . The semichemically softened chips , are discharged through the bottom of the digester onto a dray conveyor , which conveys the chips to a pipeline for flowing them to the chest - supplying the disk mill .
Tanks and other necessary auxiliary equipment are available for liquo r preparation,_pulp washing, and pulp and liquor storage .
Groundwood or Mechanical Pulpin g
The experimental pulpwood grinder -(fig . 5) is a three-pocket,-handfed type with a capacity of approximately 2 tons of air-dry pulp tp :er., .24 _hours . The grinder is of commercial size with regard-t4 t rw;idl s •of the pockets (16 inches) and the diameter of the grindstone (54 inches) . The face of the stone, however, is only 8 inches across . The wood blocks or log sections used for grinding are cut 6 inches in length . The available grinding surface, based on length of wood and width o f pockets, is 288 square inches, which is about one-eighth that of a commercial grinder using wood in 4-foot lengths . Both natural and. artificial pulp-grinder stones of various types are available . -
The grinding pressure is separately controlled in each pocket at any desired pressure up to 100 pounds per square inch of pocket area . The pressure is obtained by oil-operated pistons .
Report No . 1499 (Revised) -3 -
The grinder is powered by a two-speed motor capable of delivering 250 and 330 horsepower at the lower and higher speeds, respectively . The motor is connected to the grinder shaft through a three-speed gear reducer , thus making available six operating speeds of the grinder stone, rangin g from 3,000 to 6,500 peripheral feet per minute .
Power-consumption measurements are corrected for motor efficiency and transmission losses so that the actual energy required to reduce the wood to pulp is closely determinable . The grinder is equipped wit h temperature control for both the shower water and the grinder pit .
The groundwood pulp is screened on a rotary, scraper-type sliver screen , which has a semicircular screen plate 36 inches wide and 18 inches i n radius . Pulp storage tanks are located below the grinder floor level . From these tanks, the pulp passes through a . flat-plate screen of standard design and over an experimental-sized wet machine .
In effect, this grinder is standard in all respects except stone width . In addition, it has features that permit the application of much exaggerated conditions of grinding . Thus the machine is adapted to basi c research as well as standard applied studies .
Asplund Defibrato r
The Asplund mill shown in figure 6 is a laboratory-size, stainless stee l defibrator for producing a coarse type of fiber, such as is used in th e manufacture of roofing and deadening felts, insulating board, and hard - board . It consists of a cylinder of 2-3/4-gallon capacity, fitted wit h an axial shaft from which radiate four steel blades . These blades extend radially to within about 1/8 inch of the cylinder wall but only abou t 1/100 inch from the four equally spaced, steel bedplates that extend th e full length of the cylinder . The chip charge is approximately 1 pound on a moisture-free basis .
In operation, the chips in the cylinder are treated with steam at 17 5 pounds per square inch for 2 or 3 minutes . The defibrator blades ar e then rotated at about 1,700 revolutions per minute for 2 to 4 minutes , after which the pressure is released by exhausting the steam through a cyclone . Then the front of the defibrator is, removed, and the fiberize d material is washed out .
Pulp Cleaning and Dewatering i .1
Pulp Screen s N I .
As mentioned above, small, flat-plate screens (9 by 12 inches) are use d for screening batches of only a few pounds of pulp . A 6-plate commercial- size, flat screen is used for screening both mechanical and chemica l
Report No . 1499 (Revised) -4-
pulps in quantities of 25 pounds or more . This screen can be fitted with , : i plates havingslot openings ranging in width from 0 .006 to 0 .016 inch,, _ depending on the type of pulp and the degree of cleanliness desired . The ; screen is designed, for operation not only in the normal range of pulp - y consistency but also considerably higher owing to a special drive mechanism , (fig . 7) .
Centrifugal! Cleaners,
One 6-inch and two 3-inch centrifugal cleaners are used to remov e undesirable material that is too fine to be taken out-by the screen s (extreme right, fig . 7) .
Wet Machine
A wet machine is available (fig . 7) for converting screened pulp into a form suitable for handling and storage . The capacity of the machin e ranges from 100• to 250 pound s, of ovendry pulp per hour, depending on th e pulp . This machine can be used_to produce lapped or single-web .pulp having a dry-fiber content of about 25 percent .
Pulp Processin g
Screw Pres s
A screw press (three-section, 7-inch-diameter, high-pressure) is availabl e for the initial breakdown or fiberizing of partially, cooked or softene d chips--as, for example, in the production of - cold soda pulp . The action of this press also expresses reaction products and unconsumed cookin g chemicals from the treated chips . The press is shown in figure 8 .
Disk-Mill Refiners
Two 8-inch and . one 12-inch single-rotating disk attrition mills are avail .. able for use in producing small batches of semichemical, cold soda, .chip groundwood, orother high-yield pulps . One is shown in figure 9 . A disk mill of commercial size (fig . 10) is used for producing these kinds of pulp s as well as for refining screen rejects, straw, or,was tepaper . The disk s are fitted with interchangeable processing plates, the_clearance betwee n which can be adjusted to close tolerances . The mill can be operated . either as a single- or as a double-rotating disk mill ." Each disk is rotated at a speed of 1,200 revolutions per minute . When operated as a double-rotatin g disk mill, the disks are driven in opposite directions by individua l l25.-horsepower motors mounted directly on the mill shafts . Stock is fed
Report No . 1499 (Revised) 1-5-
to the mill by means of a screw-type feeding device equipped with a variable-speed drive, and the flow of stock is further aided by shower s of water that control the consistency .
Factors that affect the type and degree of processing obtainable wit h the mill are plate pattern, direction of rotation for the specific plate , clearance between plates, rate of feed, consistency, temperature, powe r load, and speed . Production capacity varies from 5 to 6 or more ton s per day, depending on the material and the degree of processing required . Measurement of power consumption is standard practice .
Beater s
Beaters with capacities of 50 and 125 pounds (fig . 11) are available . The tub design of each beater assures rapid circulation and thorough mixing, the peripheral roll speeds of each being about 1,850 feet pe r minute .
The 50-pound beater has a counterbalanced roll, bronze tackle, and 5/16-inch-wide bars in the roll and 1/4-inch-wide bars in the bedplate . With careful handling, greaseproof stock can be prepared in this beater . The 125-pound beater has corrosion-resistant steel tackle, the bar width in both roll and bedplate being 1/4 inch .
Duration of beating is generally controlled by freeness and strength tests on the pulp .
Conical Refine r
A wide-angle conical refiner with a 12-inch-diameter plug (large end) i s available for continuous- or batch-operation pulp processing experiments . The plug may be fitted with either 1/2-inch cast iron bars of a coarse - grit vitreous material with grooved surfaces . Shells of drilled cas t iron and of coarse-grit vitreous material are available to obtain a range of processing effects (fig . 12) .
Jordan s
Figure 13 shows the Laboratory s two experimental-size jordans . Stock feed lines are arranged so that the jordans may be used individually , in series, or in parallel . The plugs of both jordans are about 15 inche s long, with small and large end diameters of about 8 and 11 inches . The bars are corrosion-resistant steel and are 1/8 inch wide at the face . Adjustable speed drives are used . Plug setting is achieved by a manua l device and each jordan motor circuit contains a current meter for th e determination of power input .
Report No . 1499 (Revised) -6-
Bleaching and Purification Equipmen t
The pulp bleaching and purification facilities include equipment fo r experiments with from 0 .1 to 200 pounds of pulp .
The pilot-plant equipment (fig . 14) is designed for batch operation an d comprises a rubber-lined chlorinator (fig . 14, right foreground), a uni t for either alkaline extraction or hypochlorite treatments (fig . 14, center , rear), a glass-lined stock-dilution tank (fig . 8, rear), and a vacuum washer (fig . 14) . From 60 to 200 pounds of pulp, depending on the kind , can be processed in the chlorinator at consistencies up to 5 percent . From 30 to 200 pounds of pulp can be processed in the unit used for extractio n or hypochlorite treatments with suitable consistency in the range of 6 t o 15 percent . All surfaces of this unit that come in contact with stoc k are type 316 stn•in1-esbs-steel- Steam pressure up to 30 pounds per square inch can be admitted directly at the top . The drum of the vacuum washe r is 3 feet in diameter, has a 12-inch face, and is equipped with a variable-speed drive . A dandy roll is placed just ahead and a press rol l just after the shower . A pin shredder is used to break up the shee t discharged by the washer . All parts of the washer that come in contac t with stock are either rubber-covered or made of stainless steel .
A supply of deionized water is available for use in the production o f dissolving pulps .
Fourdrinier Paper Machin e
The paper machine at the Laboratory (fig . 15) is designed for small-scal e production of a wide variety of papers, ranging from blotting to glassin e and tissue to paperboard . This machine has a wire 18 inches wide, and trims a sheet 12 inches wide . The machine consists of nine sections, th e Fourdrinier forming unit ; three wet presses, the last being a reversin g press ; a smoothing press ; two dryer sections totaling 20 15-inch-diameter , steam-heated dryers ; a combination horizontal and vertical size pres s between the twelfth and thirteenth dryers for applying a wide range o f chemicals ; and two calender stacks and a reel unit . All sections of th e machine are driven by a differential electric drive designed for precisio n control of speed and intersectional variations in speeds, or "draws ." The power units for the sections are energized from a synchronous alternator , which is driven by an adjustable-speed, direct-current motor of 10 horse - power . The speed range is from 11 to 350 feet per minute . Remote controls are provided for draw adjustment of each unit .
The thick stock flow is measured and controlled by a magnetic-type flo w meter to the jordans, from which it is delivered to a mixing box fo r dilution with white water . The diluted stock then flows either directly to the paper machine flow box or to either compartment of a divided four - plate, flat, slotted plate screen (fig . 12, right rear) and then to th e flow box .
Report No . 1499 (Revised) -7-
The Fourdrinier has an adjustable, horizontal-orifice inlet for controllin g the flow of the stock from a streamlined flow box to a 36-foot wire . A secondary headbox is available for making two-ply Fourdrinier sheets . The Fourdrinier is equipped with 36 table rolls (18 rubber-covered alternatin g with 18 brass-covered), 5 flat suction boxes with a dandy roll located between the second and third box and a suction couch . The shake arrange- ment is adjustable for frequency and amplitude . Trays are provided fo r collecting white water for return to the system through a metering uni t leading to the mixing box . A pickup felt arrangement is available for us e when making lightweight papers . A wide range of draw adjustments can b e obtained for creping all weights of paper .
The three press sections have 11-inch-diameter interchangeable rolls , which are of conventional design and loaded pneumatically . Rolls available include those covered with rubber of various hardnesses, neoprene, stonite , brass, granite, and wool felt . One calender stack consists of five large - diameter rolls and the other of seven small-diameter rolls . Each stack i s equipped with an auxiliary pneumatic system for controlling pressure t o achieve various degrees of finish in the paper . The paper can be wound on a reel or on paper-roll cores .
Equipment for Making Laminated-Pape r
Plastics, Wallboard, and Hardboar d
Machine for Impregnating Paper with Resin
Figure 16 shows a machine used for impregnating paper with resin and other chemicals . The internal dimensions of the tower are approximately 9 b y 14 inches, and its height is 11 feet . The heating chamber at the base measures approximately 20 by 20 by 13 inches . Vapors are drawn off from the top of the tower, together with the air that enters at the bottom o f the heating chamber and passes through the tower . The maximum width o f sheet that can be treated is 14 inches .
The resin solution is applied to one or both sides of the paper by mean s of a roller mechanism or a dip tray . The treated paper passes into the top of the drying tower through a 1/4-inch side slot and emerges at the bottom through a similar opening . The paper is pulled through the treate r by a rubber-covered drive roll located at the bottom between the towe r and rewind drum . The control of the drive roll permits a variation o f paper speed from 3 to 10 feet per minute .
Sheets of the resin-treated paper are bonded to the surface of wood , assembled to give a low-density core, or molded in hot presses int o laminated plastics .
Report No . 1499 (Revised) -8-
Formation of Insulating Board and Hardboar d
The combination Defibrator freeness tester and mat-forming apparatus show n in figure 17 is used for making insulating-(board and . hardboard mats.. The. 8-1/2-inch-diameter mat is dewatered and compressed to the desired-thick - ness in a press . Insulating-type boards are dried in a forced-draf.t oven ; hardboards are dried in a hot press .
Presses and Drye r
For pressing insulating board, hardboard, and laminated plastics, severa l . pres-ses are available ; most of which have automatic devices for contro l . of the temperature and pressure . These presses, five in number, rang e in size of platen from 14 by 12 inches to 26-b y. 106 inches . The--larger presses are used for fabricating fiberboard and wood-faced . sandwich panels . A 72- ,by 32-inch Coe dryer, used, primarily for drying veneers , is-also available for drying fiberboard panels .
Corrugating Machine and. Bozmaking,Equipment
Corrugating board made on the Fourdrinier paper machine can be corrugate d and single-faced on a 20-inch corrugating machine (fig . 18) . Facilities are available for fabricating and testing shipping containers- made-o f corrugated fiberboard .- - -
Chemical and Physical Testin,_of Pulps, Papers, and Board s
Facilities are available for making complete chemical analyses of woo d and pulp, including all the standard test s , as well as special tests desired (fig, 19, upper left) .
The physical evaluation of pulp is made by processing it in a 1-1/2- pound-capacity standard test beater (fig . 19, upper right) . - Samples are removed from the beater at regular intervals, the freeness i s . determined (fig . 19, lower), and test sheets are :made on a sheet mold , all by standard procedures .
After the test sheets are dried, they are conditioned and tested-in a room maintained at 7 3 0 ± 3 .5 F . and a relative humidity of 50 ± 2 per - cent (fig . 19, lower) . Physical tests are made on these pulp sheets and on papers made on the Fourdrinier paper machine by means of ;bursting strength testers, tear testers, pendulum-type tensile testers, and folding • endurance te=sters . -
Other equipment, which is used as required, includes a densometer ;. glarimeter, opacimeter, reflectometer, moisture-vapor-transmission cabinet ,
Report No . 1499 (Revised) -9-
abrasion tester, stiffness tester, smoothness . tester, crush resistanc e tester, Instron-type tensile tester, and an apparatus for determinin g the fiber-size distribution of pulp .by street analysis . Analytical work . involving ultraviolet, visible and infrared absorption spectra, an d chromatography can be done as can light and electron microscopy . Sta ndarti machines are available for determining the .strength, stiffness, toughness , dimensional stability, moisture absorption, and b ther properties of wall - board, . hardboard, and laminated plastics .. :
Report No . 1499 (Revised) -10 - 1 .5-30
Figure 2 . -=Small digesters for producing to 5 pounds of pulp. i.
ZM 117 721 Figure 3 . --Digesters used for 50-pound-scale acid and alkaline pulping .
ZM 117 718 Figure 4 . --Digester used for 1, 000-pound-scale acid and alkaline pulping .
ZM 117 715
i Figure 5 . --Pulpwood grthder .
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Figure 9 . --Eight-inch, single-rotating disk., attrition mill .
ZM117648 f 9 Figure 10 . --Thirty-six-inch, single- or double-revolving-disk, attritio n mill
ZM 117 686 •1 1 Figure 11 . --One-hundred;-twenty-five-pound-scale beater . .
- ZM 117 710 ni.
Figure 12 . --Wide-angle conical refiner with 12-inch-diameter plug (large end) . Co Co N N
N -Figure 14 . --Pilot-plant equipment (200-pound capacity) for pulp bleaching and purification .
.i ZM 117 703
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AN Figure 15 . --Experimental Fourdrinier paper machine, viewed from jordan deck .
ZM 117 69 5 Figure 16 . -Equipment for impregnating paper with resins .
ZM 117 784 ; _
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Figure 17 . --Combination Defibrator freeness tester and-mat-formin g machine for insulating board and hardboard stocks .
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t r Figure 19 . --Equipment for chemical and physical testing of pulp and paper . Upper left, chemica l testing laboratory ; upper right, test beater and freeness test apparatus ; lower, physical testin g of pulp and paper .
ZM 117 69 2 ZM 117 693 ZM 117 691 SUBJECT LISTS OF PUBLICATIONS ISSUED BY THE
FOREST PRODUCTS LABORATORY
The following are obtainable free on request from the Director, Forest Product s Laboratory, Madison 5, Wisconsin : List of publications on List of publications on Box and Crate Construction Fire Protection and Packaging Dat a List of publications on List of publications on Logging, Milling, and Chemistry of Wood and Utilization of Timbe r Derived Product s Products List of publications on List of publications on Fungus Defects in Forest Pulp and Paper Products and Decay in Tree s List of publications on List of publications on Seasoning of Wood Glue, Glued Product s and Veneer List of publications on Structural Sandwich, Plastic List of publications on Laminates, and Wood-Base Growth, Structure, and Aircraft Components Identification of Wood List of publications on List of publications on Wood Finishing Mechanical Properties an d Structural Uses of Wood List of publications on and Wood Products Wood Preservation Partial list of publication s Partial list of publication s for Architects, Builders , for Furniture Manufacturers , Engineers, and Retail Woodworkers and Teachers o f Lumbermen Woodshop Practice
Note : Since Forest Products Laboratory publications are so varied in subjec t no single list is issued . Instead a list is made up for each Laborator y division. Twice a year, December 31 and June 30, a list is made u p showing new reports for the previous six months . This is the only item sent regularly to the Laboratory s mailing list . Anyone who has aske d for and received the proper subject lists and who has had his name place d on the mailing list can keep up to date on Forest Products Laborator y publications . Each subject list carries descriptions of all other sub- ject lists .