Mechanical pulping

This is the final report of Biopulping Consortium I, a 5-year research and information program involving the USDA Forest Service, Forest Products Laboratory (FPL), the University of Wisconsin (UW), the University of Minnesota, and industry. The objective of the Consortium research was to evaluate the technical feasibility of biopulping, defined as the fungal pretreatment of wood for pulping. The research focused on mechanical pulping, specifically on energy savings for the pulping itself, and on paper properties. Past work on biopulping has been minimal, but generally encouraging. In addition to the research objective, the Consortium served an information and education function, interfacing the industrial partners with developments in biotechnology. The overall conclusion of this 5-year research effort is that biopulping works. Through the use of the proper lignindegrading fungi, significant energy is saved in mechanical pulping, and paper strength properties are enhanced. Optical properties are diminished; however, brightness can be restored readily by bleaching. The process appears to be less polluting than chemi-mechanical processes, and the economics look favorable if the process can be performed in a chip pile-based system

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Se ha estudiado el efecto de distintos dosajes en masa de nanofibras de celulosa (CNF), comprendidas entre un 0 y un 6%, sobre las propiedades físico-mecánicas del papel obtenido a partir de las fibras de pasta mecánica de muela de piedra (SGW). Los resultados obtenidos se han comparado con el procedimiento convencional de refinado a distintos grados (de 0 a 2500 RPM). Posteriormente se ha estudiado la incidencia que tiene la aplicación superficial de las CNF en superficie, sobre el papel sin CNF en masa y con CNF en masa. Los resultados obtenidos mostraron que la rigidez del papel y su longitud de ruptura aumentaron con el grado de refino, sin embargo el grado Schopper-Riegler (ºSR) aumentó de forma importante dificultando el drenaje. La aportación de CNF en masa también aumentó el ºSR y la longitud de ruptura, de esta manera el ºSR de un refino a 1500 rev fue equivalente a un contenido en CNF de entre el 4,5 y 6%, pero su longitud de ruptura resultó ser sensiblemente superior. Puede concluirse que la aplicación de CNF en masa puede contemplarse como una alternativa al refino mecánico y que la aplicación superficial de CNF permite dotar al papel de mejores propiedades sin afectar a la capacidad de drenaje.

AGRIS record. Record number, US9509107. Titles, Biopulping: a glimpse of the future? Personal Authors, Kirk, TK,Koning, JW Jr.,Burgess, RR,Akhtar, M.,Blanchette, RA,Cameron, DC,Cullen, D.,Kersten, PJ,Lightfood, EN,Myers, GC. Publication Date, Dec 1993. AGRIS Subj. Cat. ...

Shear and compression are probably the main types of fibre deformation occurring in refiners for collapsing and fibrillating fibres into a suitable pulp. In current refiners, the repeated mechanical action of the bars is almost random on the fibres and consumes large amounts of energy. A more suitable application of shear and compression forces during the refining process could be a way to develop fibres at a lower energy demand. These ideas have been studied in this work trying to find new ways of saving energy in the mechanical pulping process. One way of application of the shear/compression treatment is by producing wood shavings instead for wood chips. Reductions of the energy demand in refining involving a limited shear combined with compression forces could also be achieved by a pre-treatment of wood chips in a roll nip prior to refining or by an intermediate stage of mechanical treatment of 1 st stage refined TMP coarse fibres.

The potential of a new mechanical pulping strategy to enable the separate development of earlywood and latewood fibres has been evaluated in a pilot plant study. In this study, wood chips were treated with a low energy application to produce a primary-stage pulp containing a high proportion of shives. Conventional “fractionation technologies” were then used to separate the shives from the liberated fibres so that these two streams could be given separate refining treatments. The key observations from this study were; Fractionating a low energy feed pulp containing 57% shives is difficult as this type of pulp dewaters and thickens very quickly resulting in blocked pipes and valves. However, processing the pulp at 0.5% consistency produces an accept pulp containing 5 % shives and rejects with 73 % shives. Pressure screens are more “efficient” in removing shives from the single stage pulp than hydrocyclones. The fibre dimension data obtained from the screening stage provided support fo...

Non-wood raw materials are an essential fiber source in regions where forest resources are limited. Therefore, chemimechanical high-yield bagasse pulp was prepared and then bleached with a dithionite bleaching agent. Oneand twostage bleaching of the pulp was carried out by using sodium dithionite (Y) as a sole bleaching agent, or after bleaching with hydrogen peroxide to achieve high brightness for the prepared pulp. Different parameters, such as consistency, concentration, temperature, time and pH were investigated. The effect of various additives, such as diethylenetriaminepentaacetic acid (DTPA) as chelating agent or Zn compounds and hexamethylenetetramine to stabilize the bleaching solution, was studied. The effect of dissolved oxygen in liquor was also considered.

In a mechanical pulping process, (TMP) wood is refined to pulp in a process with very high wood utilization. However, the power demand in the process is high. Thus efficient energy recovery, especially steam recovery, is very important. In high consistency (HC) refining the pulp wood is refined at high temperature (140°C) and pressure. The high temperature makes it possible to recover process heat with usable steam properties. One strategy to decrease the power consumption is to split the refining into two stages, one HC-stage and one low consistency (LC) refining stage. This kind of system is quite common today. One drawback with LCrefining is that it operates at a low temperature normally below 100°C. Hence, the steam recovery potential from conventional LC-refining is limited. In this project, we analyse three concepts of steam recovery in LC-refining by increasing the temperature in the LC-stage. Two base cases: Conventional HC refining only and conventional HC/LC refining is compared with three steam recovery cases: Pulp/Pulp heat exchanging, Screw Press Dewatering combined with process water re-circulation and finally Pulp/Water Heat Exchanging. The study shows that it is possible to recover steam from the LC-stage and, hence, increase the energy efficiency of a combined HC/LC refining system. The screw press case has the highest steam recovery potential of the HC/LC configurations. An initial economic estimate indicates that steam recovery in LC-refining is profitable compared to a conventional HC/LCconfiguration.

The relationship between various Norway spruce wood fiber properties and TMP fiber properties was studied in order to find alternative energy-property combinations for mechanical pulping. The results show the large differences in the wood fiber property distributions between the different wood lots. The shape of the distributions and the interaction between the fiber properties and the defibration impacts acting on them are stated to have a significant effect on the deformation of the fibers. By selecting Norway spruce wood raw material by the growth rate and the position in the stem the energy-property combinations of TMP could be widely influenced.

One of the major cost factors in mechanical pulp production is the electrical energy input. Much of the research in this field has therefore been devoted to an understanding of the mechanisms in the refining process and, consequently, to find ways of reducing the electrical energy consumption. Shear and compression are probably the main types of fibre deformation occurring in refiners for collapsing and fibrillating the fibres into a suitable pulp. In current refiners, the repeated mechanical action of the bars on the fibres consumes large amounts of energy in a treatment of mechanical fibres that is almost random.

Wood chips used in the thermomechanical pulping (TMP) process were originally designed to suit the chemical pulping process. The production of small wood pieces more suitable for the TMP process could lead to an energy saving in this energy-intensive process. This paper discusses the potential benefits of using wood shavings instead of chips as the raw material for TMP production. In some exploratory trials, wood shavings with a thickness of about 2 mm and wood chips were refined in two steps under normal TMP process conditions in a pilot refiner. The first-stage refining was performed under pressurized conditions at 130°C. The second-stage refining was performed at atmospheric pressure at approximately 100°C at four different energy levels. The quality of the pulp produced from wood shavings was found to be better than that of the pulp produced from wood chips, with respect to both strength properties (except tear index) and optical properties at comparable energy levels. The potential for energy savings at a given tensile index using wood shavings instead of the traditional chips is estimated to be about 25%.

When wood undergoes an acidic or alkaline chemical action or a moderate thermal action, acetyl groups are easily removed. As deacetylation favourably increases the accessibility of the cell wall and the fibre swelling, mechanical properties of wood and responses of wood to pulping are modified. In this paper, the importance of the deacetylation effects in alkaline pulping is highlighted. It is shown that it is very useful to analyse acetyl content profiles in eucalyptus wood for determining the level of alkali impregnation. Global deacetylation can be a parameter that can be practical for determination of the effectiveness of alkaline impregnation of chips. In alkaline chemi-mechanical pulping of poplar, the deacetylation level that takes place during pre-treatment can establish the bonding capacity of the pulp developed afterwards in the refiner. Acetyls can be very reactive under conditions of peroxide bleaching of chemi-mechanical pulps and, as a consequence of this reaction, alkali concentration in the process and final pulp properties can be notably affected. Konsequenzen der Deacetylierung in Zellstoffprozessen Zusammenfassung Wenn Holz einer sauren oder alkalischen chemischen Behandlung oder einer gema¨ßigten thermischen Behandlung unterworfen wird, werden Acetylgruppen leicht abgespalten. Da eine Deacetylierung vorteilhaft die Zuga¨nglichkeit der Zellwand und die Faserquellung erho¨ht, werden die mechanischen Eigenschaften des Holzes und das Verhaltung des Holzes beim Aufschluss vera¨ndert. In dieser Arbeit wird die Bedeutung der Deacetylierung beim alkalischen Zellstoffaufschluss hervorgehoben. Es wird gezeigt, dass es sehr nu¨tzlich ist, Profile des Gehalts an Acetylgruppen in Eukalyptusholz zum Bestimmen des Ausmaßes der Im-pra¨gnierung mit Alkali zu analysieren. Die Gesamt-Deacetylierung kann ein Parameter sein, der nu¨tzlich ist, die Wirksamkeit der alkalischen Impra¨gnierung der Spa¨ne festzulegen. Im alkalischen chemo-mechanischem Aufschluss von Pappelholz kann das Deacetylierungsniveau wa¨hrend der Vorbehandlung die spa¨tere Bindungskapazita¨t des Zellstoffs im Refiner bestimmen. Acetylgruppen ko¨nnen sehr reaktiv sein unter den Bedingungen der Peroxydbleiche des chemomechanischen Zellstoffs, und als Folge dieser Reaktion ko¨nnen die Alkalikonzentration im Prozess sowie die Eigenschaften des resultierenden Zellstoffs beeinflusst werden.

Se ha estudiado el efecto de distintos dosajes en masa de nanofibras de celulosa (CNF), comprendidas entre un 0 y un 6%, sobre las propiedades físico-mecánicas del papel obtenido a partir de las fibras de pasta mecánica de muela de piedra (SGW). Los resultados obtenidos se han comparado con el procedimiento convencional de refinado a distintos grados (de 0 a 2500 RPM). Posteriormente se ha estudiado la incidencia que tiene la aplicación superficial de las CNF en superficie, sobre el papel sin CNF en masa y con CNF en masa. Los resultados obtenidos mostraron que la rigidez del papel y su longitud de ruptura aumentaron con el grado de refino, sin embargo el grado Schopper-Riegler (ºSR) aumentó de forma importante dificultando el drenaje. La aportación de CNF en masa también aumentó el ºSR y la longitud de ruptura, de esta manera el ºSR de un refino a 1500 rev fue equivalente a un contenido en CNF de entre el 4,5 y 6%, pero su longitud de ruptura resultó ser sensiblemente superior. Puede concluirse que la aplicación de CNF en masa puede contemplarse como una alternativa al refino mecánico y que la aplicación superficial de CNF permite dotar al papel de mejores propiedades sin afectar a la capacidad de drenaje.

Non-wood raw materials are an essential fiber source in regions where forest resources are limited. Therefore, chemimechanical high-yield bagasse pulp was prepared and then bleached with a dithionite bleaching agent. Oneand twostage bleaching of the pulp was carried out by using sodium dithionite (Y) as a sole bleaching agent, or after bleaching with hydrogen peroxide to achieve high brightness for the prepared pulp. Different parameters, such as consistency, concentration, temperature, time and pH were investigated. The effect of various additives, such as diethylenetriaminepentaacetic acid (DTPA) as chelating agent or Zn compounds and hexamethylenetetramine to stabilize the bleaching solution, was studied. The effect of dissolved oxygen in liquor was also considered.

The relationship between various Norway spruce wood fiber properties and TMP fiber properties was studied in order to find alternative energy-property combinations for mechanical pulping. The results show the large differences in the wood fiber property distributions between the different wood lots. The shape of the distributions and the interaction between the fiber properties and the defibration impacts acting on them are stated to have a significant effect on the deformation of the fibers. By selecting Norway spruce wood raw material by the growth rate and the position in the stem the energy-property combinations of TMP could be widely influenced.

Se ha estudiado el efecto de distintos dosajes en masa de nanofibras de celulosa (CNF), comprendidas entre un 0 y un 6%, sobre las propiedades físico-mecánicas del papel obtenido a partir de las fibras de pasta mecánica de muela de piedra (SGW). Los resultados obtenidos se han comparado con el procedimiento convencional de refinado a distintos grados (de 0 a 2500 RPM). Posteriormente se ha estudiado la incidencia que tiene la aplicación superficial de las CNF en superficie, sobre el papel sin CNF en masa y con CNF en masa. Los resultados obtenidos mostraron que la rigidez del papel y su longitud de ruptura aumentaron con el grado de refino, sin embargo el grado Schopper-Riegler (ºSR) aumentó de forma importante dificultando el drenaje. La aportación de CNF en masa también aumentó el ºSR y la longitud de ruptura, de esta manera el ºSR de un refino a 1500 rev fue equivalente a un contenido en CNF de entre el 4,5 y 6%, pero su longitud de ruptura resultó ser sensiblemente superior. Puede concluirse que la aplicación de CNF en masa puede contemplarse como una alternativa al refino mecánico y que la aplicación superficial de CNF permite dotar al papel de mejores propiedades sin afectar a la capacidad de drenaje.

Se ha estudiado el efecto de distintos dosajes en masa de nanofibras de celulosa (CNF), comprendidas entre un 0 y un 6%, sobre las propiedades físico-mecánicas del papel obtenido a partir de las fibras de pasta mecánica de muela de piedra (SGW). Los resultados obtenidos se han comparado con el procedimiento convencional de refinado a distintos grados (de 0 a 2500 RPM). Posteriormente se ha estudiado la incidencia que tiene la aplicación superficial de las CNF en superficie, sobre el papel sin CNF en masa y con CNF en masa. Los resultados obtenidos mostraron que la rigidez del papel y su longitud de ruptura aumentaron con el grado de refino, sin embargo el grado Schopper-Riegler (ºSR) aumentó de forma importante dificultando el drenaje. La aportación de CNF en masa también aumentó el ºSR y la longitud de ruptura, de esta manera el ºSR de un refino a 1500 rev fue equivalente a un contenido en CNF de entre el 4,5 y 6%, pero su longitud de ruptura resultó ser sensiblemente superior. Puede concluirse que la aplicación de CNF en masa puede contemplarse como una alternativa al refino mecánico y que la aplicación superficial de CNF permite dotar al papel de mejores propiedades sin afectar a la capacidad de drenaje.

In this work, the physical and mechanical properties of bleached Eucalyptus pulp reinforced with nanofibrillated cellulose (NFC) are compared with those of traditional beaten pulp used in the making of writing/printing and offset printing papers. For this purpose, three different types of hardwood slurries were prepared: beaten pulps, unbeaten pulps reinforced with NFC, and slightly beaten pulps also reinforced with NFC. Physical and mechanical tests were performed on handsheets from these different slurries. The results showed that adding NFC to unbeaten pulps results in physical and mechanical properties similar to those in pulps used for printing/writing papers. Nevertheless, the best results were obtained in slurries previously beaten at slight conditions and subsequently reinforced with NFC. These results demonstrate that the addition of NFC allows a reduction in beating intensity without decreasing the desired mechanical properties for this specific purpose.

Se ha estudiado el efecto de distintos dosajes en masa de nanofibras de celulosa (CNF ), comprendidas entre un 0 y un 6%, sobre las propiedades físico-mecánicas del papel obtenido a partir de las fibras de pasta mecánica de muela de piedra (SGW). Los resultados obtenidos se han comparado con el procedimiento convencional de refinado a distintos grados (de 0 a 2500 RPM). Posteriormente se ha estudiado la incidencia que tiene la aplicación superficial de las CNF en superficie, sobre el papel sin CNF en masa y con CNF en masa. Los resultados obtenidos mostraron que la rigidez del papel y su longitud de ruptura aumentaron con el grado de refino, sin embargo el grado Schopper – Riegler (ºSR) aumentó de forma importante dificultando el drenaje. La aportación de CNF en masa también aumentó el ºSR y la longitud de ruptura, de esta manera el ºSR de un refino a 1500 rev fue equivalente  a un contenido en CNF de entre el 4,5 y 6%, pero su longitud de ruptura  resultó ser sensiblemente superior. Puede concluirse que la aplicación de CNF en masa puede contemplarse como una alternativa al refino mecánico y que la aplicación superficial de CNF permite dotar al papel de mejores propiedades sin afectar a la capacidad de drenaje.

High-yield bagasse pulp was prepared by soaking bagasse in 10 % cold
sodium hydroxide for 24 hours and then refluxing for two hours at 95 °C.
Optimization of dithionite bleaching was attained by investigation of different
parameters as consistency, temperature, time and pH. Effect of additives such as
chelating agent (DTPA) or stabilizing of bleaching solution using Zn compounds
and hexamethylene tetramine was considered. The effect of dissolved oxygen in
liquor was also studied. One- and two-stage bleaching of the pulp were
investigated by using sodium dithionite (D) as a sole bleaching agent or after
bleaching by hydrogen peroxide to attain high brightness for the prepared high
yield pulp.