Types of pulping process pdf

If the pulp is to be bleached, the kappa number of the pulp before bleaching predicts the bleachability of the pulp. 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 kraft process alone accounts for over 80 percent of the chemical pulp produced in the united states. 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. Know about all types of paper pulping process cnbm.

There are two main types of pulping process for the production of virgin fibre. One common type is called the fourdrinier machine, which was invented in england in 1807. These pulps fulfil the demand for chlorinefree products in the hygiene paper sector and also in printing and writing papers. Pulping is done mechanically, thermomechanically, chemically, or with combinations of these treatments. Sulfite pulps now account for less than 10% of the total chemical pulp production 1 and the number of sulfite mills continues to decrease. This process is also the most intensive steam user among pulping processes. All new pulping processes intend to achieve a closed mill by direct recovery of the. Chemical pulping involves treating wood chips with chemicals to remove the lignin and hemicellulose, thus separating and cleaning the fibers. Pulp from recovered paper poses a different challenge for the papermaker as it often has to be deinked and other contaminants removed. Pulping and papermaking introduction and overview course. It is made primarily out of scrap and kraft paper twede.

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. 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. The 4 processes principally used in chemical pulping are kraft, sulfite, neutral sulfite semichemical nssc, and soda. The category and application of paper pulping process mechanical wood pulp.

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. Thus, we will give a brief on the paper pulping process. Overall view of papermaking from chemical pulp by the kraft process. Wood chips are delignified by harsh chemicals white liquor to produce pulp and spent liquor black liquor. The kraft paper process is particularly efficient because it involves continuous recycling of raw materials. Obviously, there are 3 kinds of paper pulping process, and each of them demands certain machines. Chemical pulping of wood depends on the ability of cooking liquor to flow through the wood. Kraft pulping process an overview sciencedirect topics. The material separated from the pulp is called reject.

There are 2 types of digester systems, batch and continuous. Currently there are four different types of molded pulp based on the manufacturing process and quality of materials put into the process. Process flow diagram of kraft puling and bleaching process is shown in. It is the component elements of paper the cellulose. 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. The first is called thick walled referring to the usual 316 to 38 inch thick walls. Screening of the pulp after pulping is a process whereby the pulp is separated from large shives, knots, dirt and other debris.

Deinking a process in which most of the ink, filler and other extraneous material are removed from printed andor unprinted recovered paper. Chemical pulping processes request pdf researchgate. These are mechanical or groundwood, chemical, thermomechanical tmp and chemical thermomechanical ctmp or semichemical. For a given wood species, there is a single relationship between scattering coefficient and fibre length, from groundwood to refiner pulps to kraft. 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. There are two main types of pulping process for the production of virgin fibre and two intermediate methods. In the sgw process, small logs are ground against artificial bonded stones made of silicon carbide or aluminum oxide grits. The process gives a high yield, but the fibers produced can be very short and often must be combined with. 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. First commercially viable kraft mill, sweden, 1885. 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. This creates pulp, which is then used to make recycled paper. Pulping technology two methods for converting wood to papermaking fibres chemical kraft pulping uses chemical to dissolve lignin from wood to produce nearly pure cellulose fibres 1 ton of tree 0. 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.

Since the source of sodium hydroxide was from caustic soda, this alkaline pulping process was called the soda process. Hemicellulose plays an important role in fibertofiber bonding in papermaking. Delignification gives the fibers greater flexibility, resulting in a substantially stronger paper because of greater contact between the fibers in the finished sheet than can be manufactured from highlignin fibers produced by mechanical pulping. Pulp is a lignocellulosic fibrous material prepared by chemically or mechanically separating cellulose fibers from wood, fiber crops, waste paper, or rags. How to change pulp to paper in paper manufacturing process. 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. 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. Basic overview of pulp and paper manufacturing process. Chemical wood pulps such as soda and sulfite pulp described below are used when high brightness, strength, and permanence are required. 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. Valmets fiber technical knowhow provides intelligent, integrated and complete processes for both chemical and mechanical pulping.

Paper pulp can be classified according to the type of raw material, paper pulping process and pulp yield. 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 sulphite pulping process is an alternative method best suited for speciality pulp which can be easily bleached, generally with hydrogen peroxide. Groundwood pulp was first made in germany in 1840, but the process did not come into extensive use until about 1870. Mech 450 pulping and papermaking topic 3 mechanical pulping james a. It is similar to cellulose in composition and function. The pulping process is aimed at removing lignin without loosing fiber strength, thereby freeing the fibers and removing impurities that cause discoloration and possible future disintegration of the paper. Depending on fibre supply and mill demand, a mill will maintain a 2 to 6 week unscreened.

The screening section consists of different types of sieves screens and centrifugal cleaning. The pulp and paper industry is very diversified, using many types of raw materials to. 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. Chemimechanical pulp aka cmp, including apmp, prc apmp. Dahl, a german chemist, later developed the sulfate or kraft process in 1879 when he replaced the sodium. Pulp and paper manufacturing processes in papermaking industry. Types of pulping processes cepi confederation of european. 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.

The most commonly pulping process used in industry is the kraft or sulfate process 7. When recycling paper, the first step is to dissolve the material. Process water heated to 100f to 110f is also added in this area. The first 3 display the greatest potential for causing air pollution. Deinking requires heat to increase process efficiency like the chemical pulping and papermaking processes. Chemical pulping is the other common pulping process. 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. 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. Pdf the nature of the mechanical pulping process researchgate. There are four main types of mechanical pulping kramer, et al.

For improved process efficiency and increased business profitability, turn to valmet. 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. 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. More specifically, it is made from the cellulose fibres in trees. The fiber from nearly any plant or tree can be used for paper. Commercial processes are generally classified as mechanical, chemical, or semi. The the most common raw material for this process is wood, especially softwood for unbleached. The requirements of the particular pulping process and chip conditions will dictate the duration of chip storage figure 72. The spent liquor is later regenerated to white liquor in the causticizer.

The industry today can be divided into two main sectors according to the types of products manufactured. Pulping and papermaking an overview sciencedirect topics. So we share our knowledge with customers, providing them with samples, specifications, ideas, technical information and a complete range of brochures. 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.

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. Simplified process flow diagram of magnesiumbase process employing chemical. 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. Two chemical pulping methods exist using sodium sulfate kraft and sodium sulfite. 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. This process is also the most intensive steam user among pulping. The following figure is the process flow chart of apmp. However, the strength and quality of fiber, and other factors that can complicate the pulping process, varies among tree species. The result is a pulp which can be used, along with varying percentages of. 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 white liquor chemically dissolves the lignin that binds the cellulose fibers together. This starts with the repulping process, where the paper is defibered and ink is removed from the fiber surface.