HISTORY of FPL COLD SODA CMP PROCESS: 1950 - PRESENT the Purposes of This Report Are: 1

TAPPI proceedings of the 1988 pulping conference; 1988 October 30-November2; New Orleans, LA. Atlanta, GA: TAPPI Press; 1988: 641-648. Book 3. HISTORY OF FPL COLD SODA CMP PROCESS: 1950 - PRESENT The purposes of this report are: 1. To record the circumstances of the origin and development of the J. N. McGovern E. L. Springer FPL cold soda CMP process; 2. To note the growth University of Wisconsin U.S. Forest Products Lab. and decline of commercial cold soda pulping in the Madison, WI 53706 Madison, WI 53705 U.S.; 3. To point out the short time �or transfer of the experimental technology into mill practice; ABSTRACT 4. To discuss the nature and mechanism of the cold soda process from new experimental information; and The first report on the so- called FPL cold soda 5. To review recent literature on the process. pulping process was published in 1950. The feasi bility of the process for commercial operation was Historical demonstrated by continuous production in a Wisconsin NSSC mill, making corrugating board, in 1951-52. A cold soda- type process was patented in Germany in This was the first application of chemimechanical 1919 by Erich Opferman for producing pulp from straw, (CMP) pulping. In 1956 the first custom- designed reeds and ocher nonwood plant materials by simul mill started up in New York State. The product was taneous treatment with alkali at ambient temperature printing paper. This CMP process was developed to and mechanically fiberizing in a kollergang, stamp produce pulp at near- groundwood yield with strength, mill or other fiber separation means (4). In 1935 processing capability and potential for softwood Robert Woodhead patented in Australia a chemical- groundwood substitution. mechanical pulping process based on treatment of wood chips (specifically Australian eucalyptus) with Within 10 years (1960) there were nine CMP mills in an alkali or alkaline salt (specifically caustic the U.S. and an equal number in foreign countries. soda) with simultaneous or subsequent disintegration By 1969 however, alternative methods of hardwood of the chips in a rod or ball mill (including a pulping had been developed and only one U.S. mill kollergang) to produce a coarse pulp for wrappings remained in operation along with several foreign and news (using 2% NaOH) and a fine pulp for mills. Despite chis decline, a cold soda CMP mill printings and writings (using 8-10% NaOH) (5). started operation in Spain in early 1980's making Although the patent also mentions the beater and pulp for coated papers. jordan as Fiberizing equipment, the disk refiner, the heart of the modern semichemical- type processes, Research and development on the process continues was not recognized. As far as is Known, neither and certain results and a chronology of the rise the Opferman nor the Woodhead processes were ever and decline of cold soda CMP operations in the U.S. developed commercially (6). arc given. FPL Cold Soda Pulping Process Development Studies INTRODUCTION FPL publications on cold soda pulping in the period A research program directed toward utilization of of 1950-1958 involved extensive investigations of hardwoods by producing papermaking pulps at near the variables of the process as outlined below groundwood yields but with processing potential was (2, 7, 8, 9). undertaken at the Forest Products Laboratory (FPL) in the immediate post- WorldWar II period. This Independent Variables: program continued the FPL investigations that had led to the FPL semichemical pulping process. Wood - Aspen and 17 northern, southern and western hardwoods, spruce, northern fir; chip size; The first study in the program, begun in late 1947, chip moisture content. involved treatment of wood chips with water and Treatment - Presteaming; time, temperature, pressure steam followed by fiberizing in a disk refiner. The (including vacuum impregnation) and alkali pulps were suitable for application to corrugating concentration; liquor/wood. medium as reported in May, 1949 (1 ). A preliminary Fiberizing - Degree (freeness), disk refiner; roll- study of pulping with mineral acids at low tempera type fiberizer. tures started at the same time proved unpromising. Brightening - Brightening agents (calcium hypo- chlorite, sodium peroxide, sulfur dioxide in Another research project, which started in late water, sodium hydrosulfite, zinc hydrosulfite). 1948, considered the use of caustic soda of Paper Products - Printing and newsprint; corrugating. moderate strength on wood chips at ambient tempera ture. This project resulted in the development of Dependent Variables: the so- called " cold soda semichemical" (CSSC) process, more properly designated as cold soda Pulp - Yield; chemical consumption; freeness; pulp chemimechanical process (cold soda CMP). The first strength properties; optical properties; fiber publication on this process appeared in August, classification; chemical composition. 1950 (2 ). This process was successfully demon Paper Products - Strength properties; optical strated in a trial at the NSSC mill of Green Bay properties; special use tests. Pulp & Paper Co., Green Bay, Wisconsin, and was subsequently used there commercially from 1951 to Mill Application of FPL Cold Soda CMP Process 1952 (3 ). The product was corrugating board. This was the first CMP operation. The FPL cold soda process moved into full commercial production about six years after the first publica tion in 1950 with the exception of the 1951-1952 temporary, partial production in the NSSC mill noted previously. The chronological order of the 1988 Pulping Conference / 641 establishmen: of the nine U.S. mills in the period Pressing in screw pressers for prefiberizing and of 1950-1960 is given in Table 1. Nine cold soda spent liquor recovery. mills were also started up and operated in foreign Fiberizing in vertical disk refiners in one to countries, including Australia (Tasmania), Japan, three stages. Argentina, Colombia and Italy (10). Screening and cleanings with standard equipment. Brightening hardwood cold soda pulps from the Increased utilization of hardwoods from a fiber brightness range of 40-45%, depending on the resource standpoint was an important factor in the wood species, to a brightness level of 60-70% U.S. industry during the 1950- 1960 period. This by the application of sodium chlorite (yield circumstance was favorable to considering the cold loss of 2-5%), peroxide, sodium or hydrogen soda process as a means for increasing :he use of with appropriate buffering, and sodium hydro hardwoods in northern and southern mills. sulfite in methods adapted from groundwood brightening. The U.S. and foreign mills differed considerably in Spent Liquor Recovery and Disposal. Cold soda their pulping systems, as described below, although pulping operations in 1960 generally fortified all involved the two- stage, semichemical- type con spent caustic treatment reagent for subsequent figuration of impregnation and fiberizing steps. reuse. Wash water was usually recycled as dilution water at the refiners, screens and Chronology. A chronology of the FPL publications on cleaners. The reactions products, once the cold soda pulping and the U.S. mill applications system was in equilibrium apparently passed out over the 1950-1960 period is given in Table 1. in the white water or, as discussed below, in the pulp itself. Since the mills mostly had The records of longevity of the cold soda operations low pulp capacity (Table 1), the environmental cannot completely be established, but it is known effect was ignored. An exception was a that by 1969 only one of the original U.S. cold soda relatively large mill of 200 tons per day, mills was still in operation (27 ) and this mill employing a cross recovery arrangement with its terminated its cold soda pulp production in 1986 associated kraft mill (36). The caustic spent (19). The three mills in Tasmania (the first in liquor and the necessary sulfuric acid were 1957 (29, 30, 31)) and others in Japan have con added to the concentrated black liquor as a tinued operating to this day (32, 33, 34). A cold replacement for salt cake makeup. The BOD5 for soda pulping operation in Spain, making pulp for use cold soda pulping is reported as being 200 in coated papers, was patented in 1981 with lb/ton of pulp (26). operation in 1984 (35). Continuing Investigations of Cold Soda CMP Pulps Hardwood utilization, The FPL publications showed and Pulping that the cola soda process was flexible as to hard wood species (7). This facility was important to The cold soda CMP process is still under investi mills dependent on softwoods and wanting to gation after nearly 40 years since the initial diversify their fiber base into the hardwoods. studies. These investigations cover such aspects as Thus. the northern mills used aspen (poplar), beech, the chemical composition of the pulp, the morphology maple and birch and the southern mills pulped gum of its fibers and process developments. and oak. The Tasmanian mills used eucalyptus and the Japanese cold soda mills used indigenous mixed Chemical Composition of Pulps. The first FPL hardwoods. The new Spanish mill also uses publication on cold soda CMP pulping of aspen showed eucalyptus (35 ). the yield loss, which increased with increased alkali consumption, was concentrated in the hemi Pulping systems. The nine cold soda pulp mills as cellulose fraction (2 ). The solution of wood sub of 1960 (Table 1) used a variety of systems for stances by the cold soda reagent has also been special chip preparation, impregnation of the described as being small amounts, 5-10% of lignin caustic reagent, pressing for prefiberizing and and carbohydrates, with a pulp yield of 90-93% spent liquor recovery and fiberizing in one to three (uncorrected for fiber fragments) (37). Another stages. This same variety extended to the reference claims the loss of a small amount of brightening of the pulp as required by the products. lignin but mostly hemicelluloses (other than The screening and cleaning and washing and extractives), largely acetyl groups; sodium ions thickening before papermaking used the screens and may exchange for calcium ions (38 ).

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