US2186295A - Process of manufacturing tall-oil-free pulp from southern pine - Google Patents

Description

Jm 1940- 'r. HASSELSTROM 2,186.295 I PROCESS OF MANUFACTURING TALL-OIL-FREE PULP FROM SOUTHERN PINE Filed Oct. 50, 1936 INVENTOR. 'TORSTEW #145551. 6'. THO/ 7 ATTORNEY.

Patented Jan. 9, 1940 UNITED STATES PATENT orrlce PROCESS OF MANUFACTURING TALL-01L- FREE PULP FROM SOUTHERN PINE The present invention relates to an improved method of -manufacturing paper and pulp substantially free from tall oil from southern pine woods by the sulfite process, and to the tall-oil- 5 free product resulting therefrom.

Heretofore, it has been a well established principle in the production of paper by the sulfite process that non-resinous woods must be used.

It was commonly believed that rosin in resinous woods was the cause of the so-called pitch trouble and that resinous" conifers could not be pulped v by the standard sulfite method. Various proposals have been made to solve the problem confronting the sulfite pulp industry. It has been suggested that the pitch and beater gum difliculties may be overcome by adding clay or other materials to the pulp to cause a dispersion of the pitch throughout the pulp. Of course, this did not eliminate the pitch, but merely converted the pitch to a form in which it was less obnoxious. An attempt has been made to wash the pulp with alkaline substances in an efiort to remove the pitch. This was very expensiveand merely saponified the pitch without purging it from the system. A further proposal involved storing the finished product before use, but this treatment developed an ofiensive odor similar to that of rancid fat. Another attempt involved the seasoning of spruce to reduce the quantity of pitch but this method was inefiective when applied to southern pine. Still another suggestion involved the storing of the wood as chips and also drying the wood artificially. Neither of these treatments reduced the ether and alcohol extractables sufliciently to enable one to produce pulp from southern pine substantially free from pitch. Thus it has been impossible to produce pulp that contained less than about 1% ether and alcohol extractables, or pitch, from southern pine woods. 40' Although many attempts have been made, none as far as I am aware, has been wholly successful when put into practice on an industrial scale for the production of commercially acceptable products. I have discovered a simple and thoroughly practical method of producing pulp and paper substantially free from tall 011 from southern pine by the sulfite process. I have found that the pitch may be recovered as an exceedingly valuable product which I term tall oil or combined tall oil.

It is an object of the present invention to pro: vide a method of manufacturing comparatively 56 tall-oil-free pulp and paper from southern pine which can be introduced into conventional sulfite systems.

The invention also contemplates the provision of a method of producing substantially tall-oilfree pulp from woods containing large amounts 5 of ether'and alcohol extractables which can be carried .into practice in relatively simple apparatus capable of being coordinated and operatively associated with existing sulfite systems.

Other objects and advantages will become ap- 1o parent from the following description taken in conjunction with the accompanying drawing which illustrates, somewhat diagrammatically, a system of industrial apparatus arranged to carry the present invention into practice on an indus- 15 trial scale.

\ In the operation of conventional pulping systems, it has been the object of the operator to wash as little of the fiber away as was consistent with a reasonable reduction of the pitch and 20 beater gum. With spruce or similar woods this was comparatively simple due to the small amount of pitch present when compared to that present in southern pine woods. In contrast to prior procedures, I have discovered that the pulp from 25 southern pine woods made by the sulfite process can be made substantially free from tall oil by the use of excessive or accentuated washing which removes a substantial amount, herein termed a minor portion, of the fiber. This fiber herein 30 termed reclaimed fiber, which is removedby accentuated washing is subsequently recovered with the combined tall oil. As a result, the process water is rendered practically free fromfiber and the pulp is rendered substantially free from com- 5 bined tall oil. The reclaimed fiber and combined tall oil after recovery are separated. This operationproduces usable fiber practically free from combined tall oil and also produces valuable combined tall oil. By rendering the process water 40 practically free from fiber and combined tall oil, the water may be circulated in a cyclic or closed system with practically no trouble from so-called pitch. Thus, the. mill requirements foruncontaminated water from streams, wells, etc, are 45 reduced with a saving in costs of many dollars' per ton of pulp.

In general, my improved process contemplates washing .raw pulp, by which is meant the pulp as it comes from the blow pits, or pulp which 50 has not been chlorinated, or pulp which has not been re-cooked with caustic soda or other alkaline reagents, preferably-with excessive amounts of water on an inclined screen with about '40 or portions substantially free of combined tall oil and a suspension is formed comprising principally fiber contaminated with combined tall- 10 oil. Thus, there is obtained as a first step, a major portion of the pulp substantially free from "combined tall oil and a minor portion of the pulp contaminated with "combined tall oil and process water containing fiber and combined 15 tall oil." In a second step, the wash water and the water expressed from the pulp is freed from pulp and combined tall oil" producing a water substant ally free of fiber and "combined tall oil" or so-called pitch. Subsequently, the combined a tall oi is removed from the pulp contaminated with combined. tall oil or so-called pitch by means of tall oil extractors which may be of any suitable type. Thus, further amounts of pulpsubstantially free from combined tall oil are 25 obtained and the valuable "combined tall oil may be recovered. In other words, the advantages of my process may be enumerated as follows: (1) my process can be produced from southern pines pulpsubstantially free of combined tall 011', orv

so-called pitch when used in conjunction with sulfite systems; (2) increased amounts of such pulp are obtained; (3) there is a reduced demand for uncontaminated process water from streams or wells or the like with the attendant'economies;

'35 and (4) finally among other advantages the amount of "combined tall oil produced is increased.

' The essential equipment of my improved methd maybe included cooperatively at any suitable 40 place or places in the conventional sulfite systems. The essential object is to wash the pulp substantially tree of combined tall oil. That is the combined tall oil" is reduced to below about 1% ether and alcohol extractables. This 45 may be accomplished, for example, by passing the underfiow of the knotter of the conventional sulfite system over one or more inclined screens or Oliver flltersuntil'substantially tree 0! particles less than about 54; or. of an inch in length, 59 or the discharge from the th ckener may be washed further by similar means. On the other .hand, as indicated in the drawing, the dischargefrom the couch roll of one or more dewatering devices may be washed one or more times. The

a wash waters and the water from the dewatering .devices are combined or treated separately to remove substantially all the fiber and combined tall oil and thus water is obtained for recirculation for processing which is substantially free 00 of fiber and combined tall oil.

For the purpose of giving those skilled in the art a better understanding-of my improved process, it will be described in coniunction with the accompanying drawing. v 06 For example, crude pulp, i. e., pulpcontaining more than 1% combined tall oil,v is pumped to a dewaterer. In this dewaterer, the pulp is dewatered and is removed by a suitable roll 3 and a chute l0 into collector 4. The water drawn 70 oil through filter medium- I is conveyed by means of water outlet 2 and related pipes to aclarifying device I, such as a Dorr clarifier. In clarifier tlie solids, combined tall oil and fiber collect at the bottom to be discharged through a suitable (l valve at outlet I and pipes to the combinedtall area's oil reclaimer 8. The overflow water of the clarifier, which is substantially free oi! combined tall oil and fiber, is returned from the overflow trough 6 to the circulating water system H. Part of this practically uncontaminated circulating water may be used for further washing of the pulp discharged into collector l as by means of conduit II. The remainder of the water may be used in other steps of the process of making pulp, 10 The discharge of the clarifier at outlet 1 is passed to the tall oil reclaimer 8, which may be a conventional plate and frame filter press. In the reclaimer 8, the combined tall oil" and fiber are separated from the water of the suspension. 5 The water practically free of pulp and combined tall oil passes to the water circulation system or to waste. 3 Thefiber and combined tall 0 are removed to the tall oil extractor or extractors 9. r In the tall oil extractor or extractors 9, the combined tall oil" is removed from the fiber by any .well known means. The fiber substantially free of combined tall oil collecting at G may be added to the pulp recovered at IS. The combined tall oil recovered in extractor 9 at H may be further purified, ifdesired.

The pulp produced by my improved process may contain as little as about 0.5% by weight tall oil or less. of the pulp produced by my improved process is not more than about 1% by weight.

As illustrative of the advantages and economies accruing from the improved process, a description of a plant having a capacity oisay one ton of pulp per day will be given in conjunctionwith the drawing.

Starting at inlet l2, which may be at any appropriate place of'a'sulfite paper pulp operation, approximately 2,000 pounds of crude pulp sus- 40 pended in about 72,000 gallons of water are discharged into a suitable dewatering device l3.

' This dewatering device may consist of a rotaryscreen I on the periphery of which the pulp accumulates and is removed by an adjustable. couch roll 3. From the couch roll, about 1900 pounds of pulp, substantially free-from combined tall oil (herein known as tall-oil-iree pulp") and'about 1280 gallons of water are delivered to chute II! where it passes to pulp tank 4; By means of pipe ll, about 3045 gallons of circulation water practically free from combined tall 011 and fiber are added to the contents of pulp collector d for re-washing of the pulp therein. The discharge from collector 4 consists of about 1900 pounds of dewatered novel tall-oil-tree pulp and about 4325 gallons of water. The remaining 70,720 gallons of water, 40 pounds of combined tall oil and pounds of fiber pass through the screen to the cylinder launder or outlet 2 and aredelivered by w suitable means to a clarifler I which may be of any appropriate type, such as a Dorr clarifler. The clar fler' overflow in the amount of 70,620 gallons of practically clear water collects in the overflow trough 6 and is continuously removed through conduit I to be recirculated. I

By the use of the clarifler, a large volume of water is recovered practically free from combined tall oil or so-called pitch and fiber and is ready for recirculation to the processing units. This is of considerable importance where the cost of water is high. In addition, it makes possible and economical the separation and recovery of an additional '60 pounds of fiber and about 40 pounds of talloil from every ton of pulp. The 76 However, in general, the tall oil content 0 recovered fiber and combined tall oil are suspended in about 100 gallons of water. The sus-' pension is discharged from the bottom of the clarifier by the well-lmown means. From the 5 clarifier, the fiber and combined tall oil are transferred by appropriate'conduits to tall oil reclaimer 8 which may be a filter press, such ,as a plate and frame press. The press cake or otherwise dewatered mass consisting of about 60 pounds of fiber and about 40 pounds of combined tall oil and about 5 gallons of water per ton of pulp is conveyed to the tall oil extractor or extractors 9. The filtrate consisting of about 95 gallons oi clear water is returned to the circulating system. Bymeans of the tall oil extractor, the tall 1 is removed from the pulp and about 60 pounds of fiber practically free from combined tall oil are recovered. The reclaimed pulp together with about 5 galolns of water are discharged at outlet G. About 40 pounds of combined tall 011 are removed at outlet H. The pulp obtained at outlet G may be combined with the novel pulp ob-- tained at l5 for delivery to the trade or storage. The 40' pounds of combined tall oil which are recovered at H may be treated or used in a suitable manner known to the art. It is to be observed that all numerical values used in the above illustrative example are in terms of weights or v volumes per ton of .crude pulp.

The clarified tall-oil-free water in conduit II is returned to the pulp mill for recirculation or to any other step where substantially tall-oil-andfiber-free water is desirable. This water amounts to about 70,720 gallons less the 3,045 gallons which are added to the 1,280 gallons in the pulp collector 4 for the purpose of washing the pulp. The eiiluent from the collector I consisting of about 4,325 gallons of water and about 1,900 pounds of novel pulp which is tall-oil-free is delivered by a suitable conduit I! to a dewaterer. (not shown) to befurther dewatered and pressed and processed for shipment or storage. In the drawing, the'eflluent is shown -as coming from a single dewatering device known as a revolving suction filter. In practice, of course, several of these units or other dewatering devices may be usedin series and/orin parallel arrange- 4 ment. The thickened pulp from-the dewatering device passes on as a finished pulp product which is substantially. free from tall oil. -The fluid efiiuent of the dewatering device is processed as described hereinbei'ore, so that practically all of the solids are separated from the water.

It is, or course, understood that materials known to the arts can be added to the-pulp pass-. ing to the dewatering device, to the pulp in the device, or to the emuent from the device, in order to influence theremoval ofthe tall '01] from the bulk of the fiber and/or to assist in the clariflcation of the diluent. The clarified water substantially free from "combined tall oil can be returned to the pulp preparation plant or directly tothe dilution system of the dewaterin devices to maintain the desired dilution. A single white water reclaiming unit is shown in the drawing, but, of course, anytype of suitable equipment may be used in series and/or in parallel arrangement. The thickened solids from the white water reclaiming unit are separated 7 into fractions which consist mainly of fiber as fraction. The. equipment necessary for this step in the processing method can beat types known to the arts such as flotation cells; and/or 7' filtration units, and/or extraction cells, and/or one fraction. and combined tall '01-! as another 3 saponification equipment, and/or centrifuges,

and the like as those skilled in the art will readily understand. Thefiber separated by the tall oil reclaimed and termed reclaimed pulp can be returned to the system and/or passed from the system as a' special product. The combined tall oil can be subsequently reprocessed by a a cyclic system. Moreover, the combined tall oil is reclaimed together with white water fiber.

Although the present invention has been described in connection with a' preferred procedure 'of carrying the invention into practice, it is to be understood that variations and modifications may be resorted to as those skilled in the art will readfly' understand. Such variations and modifications are considered to be within the purview of the specification and scope of the appended claims.

I claim:

1.In the process or manufacturing pulp from highly resinous woods including southern pinewood by the conventional sulflte process involving treating highly resinous wood containing heartwood and sapwood fiber with digesting liquor containing sulphur dioxide in conventionalconcentrations toproduce pulp customarily carrying inore than 1% of tall oil after conventional washing, the improvement which comprises suspending raw sulphite pulp so. obtained and containing more than about.1% combined tall oil in water to form a suspension containing not more than about 3.3% pulp, said suspension over inclined screens having about 40 to about meshes per square-inch to separate fibers containing combined tall oil from saidpulp, repeating the aforesaid operations until said pulp is substantially free from fibers containing combined tall oil, collecting the'water employed in the aforesaid operations contaminated with fiber containing combined tall oil, conveying said collectedwater to settling tanks, separating combined tall oil and fiber from said water to obtain water substantially free from combined tall oil and to obtain fiber containing combined tall oil, and conveying said water substantially free from combined tall oil to a water circulating system for re-use, whereby pulp-from highly resinous wood substantially devoid .of

combined tall oil is obtained in' increased amounts without bleaching and water'used for purifying said pulp is recovered,

2.--In the process of manufacturing pulp by non-alkaline pulping highly resinous wood including southern pinm and customarily carrying .more than about 1% of combined tall oil the improvement which comprises suspending raw pulp containing more than about 1% combined tall oil in water to form a suspension, treating said.

suspension by washing on screen to separate fiber containing combined tall oil, repeating the steps of forming a suspension in water and separating fiber containing combined tall oil from said pulp suspension by washing on screen until the pulp contains less than about 1% combined collected water to obtain clarified water and fiber suspensions and in said separations together with fiber containing combined tall oil, purifying said and water used'for removing combined tall oil is recovered.

'3. In the process of manufacturing pulp from the heartwood and sapwood of highly resinous woods including southern pine wood by the conventional sulfite process involving washing the contents of the digester in the blow-pit with about 25,000 gallons of water per ton of pulp to obtain conventionally washed pulp containing more than about 1% of combined-tall oil, the improvement a which comprises preparing conventional washed sulfite pulp containing combined tall oilin an v amount suflicient to cause defects in the finished commercial pulp, paper and other products, suspending said washed pulp in water in the ratio of about 2000 pounds of conventional pulp containing large amounts of combined tall oil to at least about 72,000 gallons of water to form a suspension, passing said suspension over inclined screens having about 40 to about 100 meshes per square inch, to separate fiber containing combined tall oil from fiber substantially devoid of combined tall oil, continuing said separation in the presence of additional water until said washed pulp is substantially devoid of combined talloil to obtain pulp containing not more than about 1% of combined tall oil and contaminated water containing fiber and combined tall oil, purifying said contaminated water to obtain clarified water and fiber contaminated by combined tall oil, and returning at least a portion of said purified water to a water circulation system for re-use in processing other raw pulp, whereby sulfite pulp substantially devoid of combined tall oil is obtained and water used for purifying said pulp and combined tall oil is recovered.

4. In the process of manufacturing pulp .containing not more than 1% of combined tall 011 from the heartwood and sapwood fiber of highly resinous wood including southern pine wood by the conventional sulfite and groundwood processes involving the washing of highly resinous pulp with an amount of water per ton of pulp sufilcient to obtain conventional raw pulp containing considerably more than about 1% combined tall oil, the improvement which comprises suspending conventionally washed southern pine pulp containing more than 1% combined tall oil in water in a ratio of about 2000 pounds of washed pulp to at least about 72,000 gallons of water, separating a portion of said pulp by screening from said water and washing said separated pulp with further amounts of water relatively free from combined tall oil to obtain pulp -containing not more than about 1% combined tall toil andto obtain contaminated water containing fiber and combined tall oil, purifying said contaminated water to obtain clarified water and fiber contaminated by combined tall oil, and returning said clarified water to a water circulating system whereby pulp containing not more than about 1% combined tall oil is produced and water for purifying said pulp is recovered substantially devoid of combined tall oil and fiber.

tall oil, collecting the water used in forming said 5 In the process of manufacturing pulp containing not more than about 1% of combined tall oil by conventional sulfite or groundwood processes from highly resinous wood including.

southern pine wood involving the washing of raw pulp with a quantity of water per ton ofpulp suflicient to obtain conventional raw pulp containing considerably more than about 1% combined tall oil, the improvement which comprises mixing washed raw pulp containing considerably mor than 1% of combined tall oil with an excessive amount of water, separating said pulp from said water and subjecting said separated pulp to accentuated washing with further amounts of water relatively free from combined tall oil to obtain pulp containing not more than about 1% of combined tall oil and to obtain contaminated water containing fiber and combined tall "011, purifying said contaminated water to obtain clarified water and fiber contaminated by .combined tall oil, and returning said clarified water to a water circulating system, whereby .pulp containing not more than 1% combined tall 011 is produced and water for purifying said pulp is recovered substantially devoid of combined tall oil and contaminated fiber.

6. The process of manufacturing pulp as set forth in claim: 2'in which combined tall oil is extracted from said fiber containing combined tall oil to obtain additional amounts of fiber substantially free from combined tall oil before bleaching. I

7. In the process of manufacturing pulp from highly resinous woods, including southern pine Wood, by the conventional sulphite process involving treating highly resinous wood with conventional sulphite digesting liquor to produce pulp contaminated. by more than about 1% of combined tall oil, the improvement which comprises washing conventional raw sulphite pulp so obtained and containing more than about 1% combined tall oil with water to obtain pulp containing reduced amounts of combined tall oil, re-washing said pulp containing reduced amounts of combined tall oil with additional water to obtain pulp containing less than about 1% of combined tall oil, treating water used in washing the aforesaid pulp to remove combined tall oil and fiber therefrom, and recirculating the thus-treated wash water for re-use whereby pulp from highly resinous wood substantially devoid of combined tall oil is obtained and water used for purifying said pulp is recovered.

8. In the process of manufacturing pulp from highly resinous woods, including southern pine wood, by the conventional sulphite process involving digesting highly resinous wood with conventional sulphite digesting liquor to produce pulp contaminated by more than about 1% of combined tall oil, the improvement which comprises washing conventional raw sulphite pulp so obtained and containing more than about 1% of combined tall oil with water-to obtain washed pulp containing reduced amounts of combined tall oil, re-washing said washed pulp with additional water to obtain pulp containing less than about 1% of combined tall oil, and recirculating the wash water used in washing the aforesaid pulp, whereby pulp from highly resinous wood and containing less than about 1% of combined tall oil is obtained and water used for purifying said pulp is recovered.

TORSTEN I-lASSELSTROM.

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