This process is also the most intensive steam user among pulping. The category and application of paper pulping process mechanical wood pulp. Chemical pulping involves treating wood chips with chemicals to remove the lignin and hemicellulose, thus separating and cleaning the fibers. This creates pulp, which is then used to make recycled paper. Mechanical pulping fibres mechanically removed from wood matrix chemical pulping lignin holding fibres together is dissolved lignin fibres in addition to fibre removal, fibres are broken and fines fibres pulping process.
Kraft pulping process 155oc 900 kpa a td kraft pulp mill 0 500 1500 2000 2500 3000 chemicals wood dissolved organics fibre chemicals td black liquor pulp 8000 10,000 td weak black liquor produces 1500 td bl d. It is the component elements of paper the cellulose. This starts with the repulping process, where the paper is defibered and ink is removed from the fiber surface. Depending on fibre supply and mill demand, a mill will maintain a 2 to 6 week unscreened. Obviously, there are 3 kinds of paper pulping process, and each of them demands certain machines. For improved process efficiency and increased business profitability, turn to valmet. Since the source of sodium hydroxide was from caustic soda, this alkaline pulping process was called the soda process. Basic overview of pulp and paper manufacturing process. Thus, we will give a brief on the paper pulping process. The sulphite pulping process is an alternative method best suited for speciality pulp which can be easily bleached, generally with hydrogen peroxide. The most commonly pulping process used in industry is the kraft or sulfate process 7. Kraft pulping process an overview sciencedirect topics. How to change pulp to paper in paper manufacturing process.
However, the strength and quality of fiber, and other factors that can complicate the pulping process, varies among tree species. For a given wood species, there is a single relationship between scattering coefficient and fibre length, from groundwood to refiner pulps to kraft. On the process of paper manufacturing process, in order to finally turn the pulp into paper, the pulp is fed or pumped into giant, automated papermaking machines. The kraft pulping process is the dominant manufacturing process by which wood chips are transformed into pulp, the intermediate material from which a very broad spectrum of finished or semifinished paper products are made. When recycling paper, the first step is to dissolve the material. This process is also the most intensive steam user among pulping processes. Process flow diagram of kraft puling and bleaching process is shown in. The process gives a high yield, but the fibers produced can be very short and often must be combined with. Mechanical pulping is the process in which wood is separated or defibrated mechanically into pulp for the paper industry the mechanical pulping processes use wood in the form of logs or chips that are mechanically processes, by grinding stones from logs or in refiners from chips, to separate the fibers. Process water heated to 100f to 110f is also added in this area. Chemimechanical pulp aka cmp, including apmp, prc apmp.
The spent liquor is later regenerated to white liquor in the causticizer. Groundwood pulp was first made in germany in 1840, but the process did not come into extensive use until about 1870. Pulping refers to the production process that uses chemical methods, mechanical methods or the combination of two methods to make the plant fiber materials dissociate into unbleached or bleached pulp. Types of pulping processes cepi confederation of european.
Pulp and paper mills are highly complex and integrate many different process areas including wood preparation, pulping, chemical recovery, bleaching, and papermaking to convert wood to the final product. Pulping is done mechanically, thermomechanically, chemically, or with combinations of these treatments. The kraft process also known as kraft pulping or sulfate process is a process for conversion of wood into wood pulp, which consists of almost pure cellulose fibers, the main component of paper. Olson pulp and paper centre, department of mechanical engineering, university of british columbia mechanical pulping comparison of mechanical and chemical pulps debarking stone groundwood refiner mechanical pulp thermo mechanical pulping tmp.
Steps in the pulp and papermaking process raw material preparation wood received at a pulp mill may be in several different forms, depending on the pulping process. Today, the kraft process is the dominating chemical pulping process worldwide due to the superior pulp strength properties compared with the sulfite process, its application to all wood species, as well as to the efficient chemical recovery systems that have. Simplified process flow diagram of magnesiumbase process employing chemical. There are four main types of mechanical pulping kramer, et al. The composition of spent liquors depended strongly on the type of wood and chemicals used in the pulping process as well as the pulping conditions sixta 2006.
The the most common raw material for this process is wood, especially softwood for unbleached. Wood chips are delignified by harsh chemicals white liquor to produce pulp and spent liquor black liquor. Dahl, a german chemist, later developed the sulfate or kraft process in 1879 when he replaced the sodium. Commercial processes are generally classified as mechanical, chemical, or semi.
Pulp and paper manufacturing process in the paper industry. Kraft pulping process the recovery process figure 2 shows a simple flowsheet of the kraft chemical recovery process. It is similar to cellulose in composition and function. Chemical pulping is the other common pulping process. Hemicellulose plays an important role in fibertofiber bonding in papermaking. Mech 450 pulping and papermaking topic 3 mechanical pulping james a. Overall view of papermaking from chemical pulp by the kraft process. Pulping and papermaking introduction and overview course. It is made primarily out of scrap and kraft paper twede. These are mechanical or groundwood, chemical, thermomechanical tmp and chemical thermomechanical ctmp or semichemical. The paper making process, the fifth technical brochure from sappi idea exchange idea exchange sappi is committed to helping printers and graphic designers use paper in the best possible way. Pulping and papermaking an overview sciencedirect topics. One common type is called the fourdrinier machine, which was invented in england in 1807.
Pulp is a lignocellulosic fibrous material prepared by chemically or mechanically separating cellulose fibers from wood, fiber crops, waste paper, or rags. Depending on fibre supply and mill demand, a mill will maintain a 2 to 6 week unscreened chip inventory, usually in large outdoor chip piles. There are two main types of pulping process for the production of virgin fibre. Mixed with water and other chemical or plantbased additives, pulp is the major raw material used in papermaking and the industrial production of other paper products. Depending upon the furnish, small quantities of caustic soda, bleach, or surfactants may be added to speed the repulping process, for example, one gallon per halfton batch of pulp. The industry today can be divided into two main sectors according to the types of products manufactured.
More specifically, it is made from the cellulose fibres in trees. Chemical pulping of wood depends on the ability of cooking liquor to flow through the wood. All new pulping processes intend to achieve a closed mill by direct recovery of the. Pulp from recovered paper poses a different challenge for the papermaker as it often has to be deinked and other contaminants removed. Deinking a process in which most of the ink, filler and other extraneous material are removed from printed andor unprinted recovered paper. There are two main types of pulping process for the production of virgin fibre and two intermediate methods. The following figure is the process flow chart of apmp.
The first 3 display the greatest potential for causing air pollution. There are 2 types of digester systems, batch and continuous. If the pulp is to be bleached, the kappa number of the pulp before bleaching predicts the bleachability of the pulp. The material separated from the pulp is called reject. Process flow of thermomechanical pulping pretreatment soaking, thermomechanical pulping and yield all three biomass types were soaked in water at room temperature the night before at a liquidtobiomass ratio of 10. The first is called thick walled referring to the usual 316 to 38 inch thick walls. The requirements of the particular pulping process and chip conditions will dictate the duration of chip storage figure 72. The kraft paper process is particularly efficient because it involves continuous recycling of raw materials. Know about all types of paper pulping process cnbm. Deinking requires heat to increase process efficiency like the chemical pulping and papermaking processes. Valmets fiber technical knowhow provides intelligent, integrated and complete processes for both chemical and mechanical pulping. A high kappa number, indicating a greater amount of retained lignin, is common for unbleached pulps used in the production of linerboard or bag paper. This, along with the ability of the kraft process to accept a wider variety of types of wood and produce stronger fibers made the kraft process the dominant pulping process starting in the 1940s.
Mechanical pulping fibres mechanically removed from wood matrix chemical pulping lignin holding fibres together is dissolved lignin fibres in addition to fibre removal, fibres are broken and fines fibres of pulp mass is in form of fines. Sulfite pulps now account for less than 10% of the total chemical pulp production 1 and the number of sulfite mills continues to decrease. In the sgw process, small logs are ground against artificial bonded stones made of silicon carbide or aluminum oxide grits. Pdf the nature of the mechanical pulping process researchgate. Mechanical pulp yields over 90% of the wood as fiber is produced by forcing debarked logs, about two meters long, and hot water between enormous rotating steel discs with teeth that literally tear the wood apart. So we share our knowledge with customers, providing them with samples, specifications, ideas, technical information and a complete range of brochures. The white liquor chemically dissolves the lignin that binds the cellulose fibers together.
Two chemical pulping methods exist using sodium sulfate kraft and sodium sulfite. What is pulp, what is pulping process, how is pulp made, how to make pulp, how to make wood pulp, all this questions will be explained in this column. The kraft process alone accounts for over 80 percent of the chemical pulp produced in the united states. Chemical wood pulps such as soda and sulfite pulp described below are used when high brightness, strength, and permanence are required. Paper pulp can be classified according to the type of raw material, paper pulping process and pulp yield. The fiber from nearly any plant or tree can be used for paper. The result is a pulp which can be used, along with varying percentages of. The kraft process also known as kraft pulping or sulfate process is an industrial process for conversion of wood into wood pulp consisting of almost pure cellulose fibers treatment of wood chips with a mixture of sodium hydroxide and sodium sulfide, known as liquor, that breaks the bonds that link lignin to the cellulose. These pulps fulfil the demand for chlorinefree products in the hygiene paper sector and also in printing and writing papers. The pulp and paper industry is very diversified, using many types of raw materials to. Pulp and paper manufacturing processes in papermaking industry. Chemical pulping processes request pdf researchgate. The kraft process entails treatment of wood chips with a hot mixture of water, sodium hydroxide naoh, and sodium sulfide na 2 s, known as white liquor, that breaks the bonds that link lignin. Pulp and paper pulp is the fibrous mass that results when a pulping process ruptures the bonds in the wood structure that hold the woody cells together.
458 523 1298 1452 1018 1557 1198 1102 1510 392 134 614 1568 244 609 805 113 117 989 121 791 710 1460 850 1204 1539 46 285 990 411 195 8 63 514 210 710 1244 541