This made wood fibers the main raw material in paper, instead of textile fibers. Burst strength is determined by applying pressurized and packaging purposes. The white water systems of the paper machine can be coupled countercurrently to the white water system of the mechanical pulping process. This type of pulp is globally widely used for paper and board production. These include chlorine dioxide, chlorine gas, sodium hypochlorite, hydrogen perioxide, and oxygen. Application Young, David A. Tillman, in Encyclopedia of Physical Science and Technology (Third Edition), 2003. by Louis Robert in France in 1799. and finish quality, is important for many applications. The process gives a pulp that is generally characterized by high yield that ranges from about 92 to 96%, and has high bulk, stiffness, opacity, and softness. and thermo-mechanical pulp (TMP) that does not remove lignin from the fibers in contrast Mechanical pulp is very different from the pulp produced in the chemical processes (the sulfite process and the Kraft process). The problem in mechanical pulping is its high energy consumption. By continuing you agree to the use of cookies. Production of paper was introduced to Europe in the 12th century. The main advantage of this kind The same comparison cannot be used for whiteness. air to the surface of the sheet. Here the steam and volatile materials are tubed off. 10.13. The bleaching agents and the sequence in which they are used depend on a number of factors, such as the relative cost of the bleaching chemicals, type and condition of the pulp. HSh3mtY
qLC'w60|H. Due to the "brute force" nature of mechanical pulping, both whole and partial fibers are created. extra shiny for special applications, such as art papers. Figure6.4. Tensile indexes of biomechanical pulps were higher in comparison to reference pulps. The majority of the waste in the process is black liquor - but these facilities typically operate in a "closed loop" system. The disadvantages are that the fibers produced are very short and often must be combined with strong but expensive chemical fibers in order to be strong enough to pass through the paper machine, coaters, and printing processes. Some digesters operate continuously with a constant feed of chips (furnish) and liquor are charged intermittently and treat a batch at a time. This results in a higher, longer-fiber content and a much lower-shive content. Products such as cellulose acetate, rayon, cellulose esters that are made from cellulose will be used for packaging films, explosives. This process steams wood chips to soften them before putting them through the same machine that is used in the refiner process. as it passes through a specially designed series of drum type rolls as a result of other lignocellulosic materials such as cotton, rice or wheat straw for writing, printing The goal is to extract the fibers, and this is accomplished either using a chemical or mechanical process. Using warm water for grinding and chip washing helps soften lignin and promotes fiber separation, reducing mechanical energy requirements. Here is more detail on each one of these steps: Pulp is mixed with water as well as additional fillers and additives and then pumped onto a belt. As the pulp lines include storages where the pulp can be stored for 8h without affecting its quality, the increased production capacity can be utilized as a demand response without jeopardizing continuous paper or board production. The second one is For a TMP mill (capacity 400t/day), NCASI (2001) has estimated total cost savings because of steam as $585,200 per year and net reduction in carbon dioxide emissions as 17,055 ton carbon dioxide per year. The specific energy consumption in mechanical pulping is 10004300kWh/ADt pulp for different mechanical pulping methods (SGW, RMP, TMP, or CTMP) (European Commission, 2013). For writing purposes whiteness of paper is important, therefore, pulp is bleached A sufficiently smooth surface is a basic requirement for most printing papers for Mechanical pulping can further be classified into two subgroups, namely ground pulping Papers are made with the pulp of the woods, which is an Eco-friendly product. Mechanical pulping relies more so on mechanical actions to separate and develop wood fibers, rather than using chemical means. and to convert the material into fiber bundles. and newspaper, wrapping and tissue paper, and other special papers. This is where paper goes through a series of rollers that squeese the paper to make it really flat. coloring of the fibers, and later to form paper sheet in a Fourdrinier machine. This excess material becomes a biomass energy source to help power the paper mill. I hope you enjoyed learning how paper is made. The inorganics (chemicals) are recovered and re-used for the next batch of paper, while the remainder of the liquid (natural biomass) is converted to energy to operate the plant. Mechanical pulps can be produced by grinding logs or refining chips. These are commercial technologies, but their application to effluents from mechanical pulp mills was relatively unproven until the 1990s. Comparisons are made taking account of bleached vs. unbleached materials, and materials made from virgin chemical pulp, virgin mechanical pulp and recycled fibres. Pectinase did not show a significant effect on energy consumption. The cellulase, xylanase, and pectinase pretreatments have been examined by KCL, STFI-Packforsk, CTP, VTT, Holmen Paper, Stora Enso, UPM-Kymmene, and Metso. groups: simulating the printing process by pressure on the surface and determining in both directions in specially designed equipment, such as a Taber Instrument. 10.13). Two basic approaches have been tried to achieve zero discharge. These logs are cut into small chunks of wood that are about 1/2" to 1" long, and 1/4" to 1/2" thick. Sodium Hydroxide, a strong alkali is used to extract the dissolved lignin from fibers surface. After that, this cooked pulp is returned to the chemical recovery cycle. A comparison of different food packaging options that value freshness and convenience and are also environmentally sustainable. If the pulp is brightened, the additional pollution load from the chemical brightening operation is roughly related to the amount of brightening chemicals used. Brazilian researchers biotreated Eucalyptus grandis wood chips with Ceriporiopsis subvermispora in a 50-t chip pile and evaluated for TMP and CTMP processing on a mill scale (Guerra etal.,2004,2005,2006). The stylus profilometer that falls in the second group presents an original They applied two pectinase treatments (Pectinex 3XL, Novozyme 863) to TMP of black spruce (Picea mariana) wood chips. Articles, Training, Videos, Tips, eBooks, and More! It is also used as the middle layer in cardboard because of its stiffness. The chips were allowed to react for a period of 2.5h at an average temperature of 4748C. The remaining fiber is cleaned in a variety of ways and sometimes bleached to ensure purity. Although biotechnology has been successfully used in some pulp and paper production processes, it has been quite challenging in the pretreatment of wood chips. liquor is a by-product of the production, which is washed from cellulose fibers to The specific energy consumption was reduced by 9 and 9.6%, respectively. [4] In the mechanical pulp mills the majority of the electricity is converted to heat, creating steam which is utilized in the paper machines. What makes a paper "supercalendared" are a series of chrome rollers that spin faster than the paper is moving. The most common of trees that paper comes from are: In most cases, the best parts of these trees are used for construction, and less desirable portions are used in pulp. While the felt used to be made of wool, these days synthetics are more normal. Effluent treatment of this nature usually removes in excess of 95% of the BOD and produces a nontoxic effluent. Owners of livestock and poultry in Oklahoma may have interest in marketing their animals, a portion of their animals or the meat/poultry from those animals directly to consumers. are most commonly used species in North America. Several enzymes have been used for pretreatment of wood chips (Girard etal.,2006; Wang etal.,2007). heated up to 200oF (93oC) to ensure the sheet has an approximate 4-5% moisture content. 10.14). Speed of the sheet in the machine ranges from 1,200 fpm (13.6 mph) Chemical pulping is used to produce higher quality paper with more expensive Most mechanical pulp mills use primary and secondary biological effluent treatment to reduce the impact of their discharges on receiving waters. Much like wood, paper has a grain direction. The mechanical pulps are primarily used in newspaper and magazine paper and the chemimechanical pulps for cardboard and soft paper. The wood chips are placed into a giant machine that combines them with really hot water and chemicals. Beating Because biological pretreatment is an additional operation, operations and maintenance costs also increase compared to costs of mechanical pulping without biological pretreatment (Scott etal.,1998; Swaney,2002; Swaney etal.,2003a). The use of mechanical pulps is confined mainly to nonpermanent papers such as newsprint and catalog paper. This process takes small logs and grinds them against artificial bonded stones. Lignin is modified by sunlight, making paper produced from mechanical pups susceptible to yellowing and becoming brittle. production of various types of papers, such as writing and drawing papers, printing This provides a board with maximum stiffness at minimum grammage. In the "Wet Press Section," the pulp moves off of the mesh belt onto a felt belt. An example of this type of paper is newsprint. In the case of CTMP pulps with similar CSF, energy consumption was 1038kWh/t and 756kWh/t for control and biotreated wood chips, respectively (27% of energy saving in the pulping process). The mechanical pulping process uses significantly more energy than is produced by the biomass power generated by the bark. Most CTMP is produced in Canada. Raw pulp contains an appreciable amount of lignin and other discoloration, it must be bleached to produce light colored or white papers preferred for many products. Capital costs will depend on how the two white water systems are coupled. Use of chemicals for controlling these undesired substances could increase. Table12.4. Novozyme 863 was a more aggressive enzyme preparation produced by a selected strain of A. aculeatus. Coupling the paper machine and mechanical pulping white water systems will reduce total carbon dioxide emissions. In areas of the world where the resource base is dwindling, the increased yields offered by newer mechanical pulping techniques are highly desirable. to evaluate tearing resistance. Debarked logs are forced against rotating stone grinding wheels in the stone ground-wood procedure. PGW is important in Scandinavia but has limited production outside this region. Papers made from mechanical pulps are also known as "groundwood fiber papers" and are typically very cost effective. Figure 3. Fiber separation in mechanical pulping is less dramatic. Patrick, K., 1998 Primer of Pulp and Paper Making: Technologies and Production Practices. is reduced first using suction units, called the wet press area, and later by drum rotating steel discs having different types of profiles. Bleaching of mechanical pulp is designed to minimize the removal of the lignin that would reduce fiber yields. Some bleed of white water from mechanical pulping may also be necessary. Mechanical pulping produces pulp through the use of mechanical energy instead of chemicals. Sabourin and Hart (2010), however, obtained positive results with pectinases. In such situations, mills designed to operate with no effluent discharges may be the only alternative. The orentation of the fibers on this belt dictates the "grain direction" of the paper. Papermaking and Paperboard Making. and burst resistance are some of the mechanical properties of paper. It has been largely replaced by chemical pulping, is still used for lower grade papers such as newsprint, and is the only process used for recycled paper (Casey,1983a). Volume 2. Improvements are constantly being made, and considerable gains have been made in adapting different types of wood and different forms of wood (sawdust versus chips) to mechanical pulping via advanced process control techniques. Light-colored, nonresinous softwoods and some hardwoods are often the fiber source. Softwoods and hardwoods are used for paper-making and are sometimes mixed to provide both strength and print ability to the finished product. Net energy consumption during refining was 745kWh/ton1 and 610kWh/ton1 of processed pulp for control and biotreated wood chips, respectively. The main steps of typical paper manufacturing. After the 1h treatment, the pulp was then washed thoroughly with distilled water through a 75m sieve until all the sodium hydroxide was eliminated and the pulp was alkali free, as determined by checking the pH periodically using pH paper. Figure 3 shows the main steps of typical paper manufacturing. This pulp is generally used for the making of newspapers, books, and magazines. Opacity, the measurement of light passing through a sheet of paper and brightness an original surface profile. Used paper is also recycled, and after purifying and sometimes deinking, it is often blended with virgin fibers and reformed again into paper. [2] Today the groundwood pulping mills are few, but the mechanical pulping processes employing refiners are still important in the Pulp and paper industry. Mechanical pulp can also be bleached to increase the brightness, but retaining the lignin in the pulp.[1]. Hardwoods produce a weaker paper as they contain shorter fibers. Once the pulp enters the "Dryer Section," it has started to take the shape of paper. Electricity consumption is estimated to be about 2041kWh/t pulp (Jaccard and Willis,1996) while average steam consumption for this process is estimated at 0.9GJ/t pulp. .l;Kxz4N The pulp moves through a series of high pressure rollers designed to push the liquid into the felt. Chemicals used for bleaching mechanical pulps selectively destroy coloring impurities but leave the lignin and cellulosic materials intact, These include sodium bisulfite, sodium or zinc hydrosulfite (no longer used in the United States), calcium or sodium hypochlorite, hydrogen or sodium peroxide, and the Sulfur Dioxide-Borol Process (a variation of the sodium hydrosulfite method). The average energy consumption for producing TMP pulps with 450470 Canadian standard freeness (CSF) was 913kWh/t and 745kWh/t for control and biotreated wood chips, respectively (18% of energy saving in the pulping process). Mechanical pulping is the process in which wood is separated or defibrated mechanically into pulp for the paper industry. A conical refiner machine to improve pulp quality. The last part of the machine is called the "Calendar Section." |LM,X(GhVGrE]]TW_ZTPc"d@lSn}|= Refiner-mechanical pulping (RMP) was introduced in order to use wood in chip rather than in log form. Supercalendaring is used to add gloss to less expensive papers made from mechanical pulp, while coatings are used to add brightness and shine to higher quality stocks. So far, this technique has been examined in laboratory and pilot plant scale. production cost than that of mechanical pulping. force perpendicular to the plane of the paper required to tear several pieces is used Using warm water has other benefits, like quality and production improvements in the groundwood mill. A number of different mechanical processes exist:[5], "Types of Pulping Processes | CEPI - CONFEDERATION OF EUROPEAN PAPER INDUSTRIES", https://en.wikipedia.org/w/index.php?title=Mechanical_pulping&oldid=968742345, Creative Commons Attribution-ShareAlike License 3.0, This page was last edited on 21 July 2020, at 07:06. This leaves wood fibers, and a liquid called "black liquor.". Figure 2. The heat generated in mechanical grinding or refining processes can be utilized in the paper mill area. It can be seen that, in general, recycled fibres are stronger than mechanical fibres but less strong than chemical fibres. Estimates of the energy consumption of this process vary widely throughout the published literature depending upon furnish species and desired freeness. It is similar to cellulose in composition and function. Salim Hiziroglu. Project Management, Training and Consultancy, Recycling / Deinking Technologies and Equipment, Industrial Engineering solutions and Services Providers, Water Treatment and Environmental Control. These materials and processes are discussed in detail later (Fig. The chemical pulping processes can often generate enough energy (steam and electricity) to make the mill energy self-sufficient. Accordingly, 18.5% net energy saving could be achieved. and the percentage of light reflected from the surface of paper are two physical characteristics Salim Hiziroglu FAPC Value-added Wood Products Specialist. produce pulp. Later the chemical pulping processes started dominating for many paper types. Few zero-effluent bleached chemi-refiner mechanical pulp mills started up in Canada in the early 1990s: Louisiana-Pacific Canada Ltd. (purchased by Tembec Ltd.), Chetwynd, British Columbia (June 1991); and Millar Western Pulp Ltd., Meadow Lake, Saskatchewan (February 1992). Typical ranges of energy consumption are shown in Table12.4. type dryers. A drawback with the mechanical pulping processes are that they require a high amount of electrical power. This energy is generated from wood leftovers (bark and chips) and from black liquor, which in principle is 50% of the incoming wood (as the yield is less that 50% and a majority of the rest ends up in the black liquor). 1970. The specific energy consumption in mechanical pulping is dependent on the particular pulping process, the properties of the raw material (wood species), and, to a large extent, the quality requirements (freeness) of the pulp set by the end product. Mechanical pulping produces pulp through the use of mechanical energy instead of chemicals. If we compare four properties of mechanical and chemical fibres it can be seen that, density increases as the amount of chemical pulp increases, stiffness increases by increasing the amount of mechanical pulp, strength increases with increased chemical pulp content. TAPPI. They have low strength because the lignin interferes with hydrogen bonding between fibers when paper is made. The Pulp and Paper Manufacture. But the overall costs of mechanical pulping with biological pretreatment technology are lower than the costs without biological pretreatment because of the large amount of energy saved with biopretreatment. At this point it is worth considering some general comparisons of different types of paper and paperboard as shown in Figs10.1310.15. paper production involves two main processes: the treatment of raw material, which Reductions will result from a drop in mill water heating (reduced steam generation and fuel consumption) and increases in process efficiency. The dilute slurry is then cleaned in cyclone cleaners and screened in centrifugal screens before being fed into the wet end of the paper-forming machine. Refiner pulp and thermo-mechanical pulp are produced by chips. The fiber extracted from any plant can be used for paper. Additional piping, pumps, and tankage will be required. pulping. Mechanical pulping is one of the most electricity-intensive processes in the pulp and paper industry, consuming 23.5MWh of energy per ton pulp, depending on raw material and process conditions (ETEPS,2007; CAI,2009). Mechanical pulping is primarily used in paper products with relatively short life span, such as news paper, books or brochures, but also in coated paper grades for magazines and catalogs. A benefit from the mechanical processes is that they have a high yield, usually between 90 and 98%, which means that nearly all the wood is used. Thermomechanical pulping produces the highest grade of pulp from mechanical pulping. The addition of enzymes to the wood chips between the first and second refiner can hydrolyze the hemicellulose and improve the fiber freeness of the cellulose fibers. In a refiner operation the coupled white water could be used for chip washing. The dilute stock passes through a head-box that distributes the fiber slurry uniformly over the width of the paper sheet to be formed. However, lignin is retained in the pulp resulting in fibers of high lignin content and accordingly they have low strength and brightness (Biermann, 1993). surface appearance is improved by increasing the amount of chemical pulp. The energy costs were reduced by 33% from $121/t to $81/t (Swaney etal.,2003a). machine of Louis Robert. In this process, wood chips are ground between two grooved discs. under the condition of a fixed weight of measuring head, is a typical example of the This is becauseof the size incompatibility between the enzyme molecules and the dimensions of pores (Bajpai,2012). Many papers include different types of recycled content. to chemical pulping. This helps remove air pockets so that the chips will break down into fibers more easily. The Technical association of the Pulp and Paper Industry. The process starts with an impregnation of sodium sulfite and chelating agents. Pulp is combined with water and placed on a paper making machine where it is flattened, dried, and cut into sheets and rolls. Yields are nearly as high as other mechanical processes. Currently, all zero discharge mills utilize evaporation as the primary separation method. This part of the machine weaves the web of paper through a series of heated rollers. If you can think of these rollers as tires on a car, and the paper as a road, then the rollers are doing a "burn out" on the paper. A subsequent step involved an industrial test performed with 10-t of fresh wood chips inoculated and maintained at 373C for 39 days in a biopulping pilot plant. Stiffness is determined by bending a small sample The principle behind all mechanical pulping is to take a raw material and grind it down into individual fibers. process. The total yield is about 90%98%. Mechanical pulp is pulp produced by using only mechanical attrition to pulp lignocellulosic materials; no chemicals (other than water or steam) are used. Heat in the white water is used to offset the heating of fresh water with steam. first group. It is the least energy intensive using approximately 1650kWh/t pulp (Jaccard and Willis,1996). Some of the important production processes and properties These include: Although many fibers were mentioned above, forestry products (logs from trees) are the source of most fiber in paper pulp. This belt is typically made of a mesh that encourages all of the fibers to go in one direction. Paper sheet continuously runs through a series of stainless steel drums Mechanical pulping relies more so on mechanical actions to separate and develop wood fibers, rather than using chemical means. This energy efficiency improvement also enables significant grinder production increase of some 30% without additional investments. These include supercalendering and coatings. These chips are ground by passing them through rapidly rotating in both processes. Biopulps contained lower shive content and had improved strength properties compared to control pulps. The fibers are further delignified by solubilizing additional lignin from the cellulose through chlorination and oxidation. Brazilian researchers further investigated biopulping of E. grandis wood chips with Phanerochaete chrysosporium RP-78 under nonaseptic conditions in a laboratory and a mill woodyard (Masarin and Ferraz,2008; Masarin etal.,2009). Natural fibers such as cotton are used in some cases because its fibers are very strong. To accomplish this, the animals must be slaughtered and processed and prepared as finished meat/poultry cuts. Bark does not work well for making paper, so the first step in the mechanical pulping process is to remove the bark from the logs. a more commonly used method to produce paper with low strength properties. If you enjoyed this article, you could also read our other informative articles about paper: Or if you want to talk to our professional team of experts about what paper choice would be a good fit for your next print project, go ahead and hit that bog "Talk to an Expert" button below. The characteristics of the treated effluent will generally satisfy the regulatory requirements of most jurisdictions.
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