Valmets fiber technical knowhow provides intelligent, integrated and complete processes for both chemical and mechanical pulping. Pulp can be classified mainly into two types by the pulping methods. Olson pulp and paper centre, department of mechanical. The chemical reactions in kraft pulping process pulp paper mill. It is the component elements of paper the cellulose. Pulp and paper manufacturing process in the paper industry. The main chemical reactions in the cooking process can be described as. Modeling of kraft mill chemical balance daniel moreira saturnino. Mechanical wood pulp is also known as ground wood pulp. Mechanical, semichemical, and sulfite pulp mills differ in detail, particularly in wood preparation, fiber separation, and bleaching, but many of the downstream refining. Chemical pulping processes request pdf researchgate. This is achieved by breaking the bonds in the lignin macromolecule. Kraft pulping is the main pulping process together with mechanical pulping used today, and.
Possibilities for improving the pulping process peter axegard stfi, swedish pulp and paper research institute peter. Semimechanical pulping, as its name implies, is a two stage process that uses a chemical mixture most commonly sodium sulfite and alkaline salts to soften lignin, followed by a disk refiner to fiberize the cooked chips. Koivo encyclopedia of life support systems eolss nissinen, a. Olson pulp and paper centre, department of mechanical engineering, university of british columbia refiner mechanical pulp rmp wood chips are comminuted into fibres by bars on rotating and stationary discs. Semichemical pulping article about semichemical pulping. In the white liquor, sulfidity is the ratio of na2s to the active alkali. Chemical pulping is the other common pulping process. Mechanical pulping and chemimechanical pulping comparison. Stability of wet end for paper machines with dilution headboxes. In the mechanical pulping process, the wood fibers are separated from each other by mechanical energy applied to the wood matrix causing the bonds between the fibers to break gradually and fiber bundles, single fibers and fiber fragments to be released. For improved process efficiency and increased business profitability, turn to valmet. In order to maintain a proper balance of na and s, kraft mills may need to adopt different makeup strategies. Overview of the process thermomechanical pulping, tmp, is precisely named. The effect of using a chemical course with nitric acid and a biopulping way using fusarium solani.
The pulping process is an important link in the papermaking industry. Commercial processes are generally classified as mechanical, chemical, or semi. Unesco eolss sample chapters control systems, robotics, and automation vol. The category and application of paper pulping process mechanical wood pulp. It has the advantages of low cost, simple paper and pulp production. Pulp is made by heating the chips with steam and mechanically separating the fibers in a pressurized refiner.
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. The kraft process is the dominating pulping process, which accounts for almost 60% of all mechanical and chemical pulp produced worldwide. Pulp and paper mills are highly complex and integrate many different process areas including raw material preparation wood debarking and chips preparation. The 4 processes principally used in chemical pulping are kraft. 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. First commercial process was the rdhprocess of rader rapid. Ea is the sum of sodium chemicals that will produce ohduring kraft pulping. Chemical wood pulps such as soda and sulfite pulp described below are used when high brightness, strength, and permanence are required. Tmp refining has been reported to be the most energy intensive unit. The industry utilizes a variety of industrial processes to convert wood into pulp. The four principal processes used in chemical pulping are kraft, sulfite, neutral sulfite semi chemical nssc, and soda. Pdf analysis by pineapple leaf in chemical pulping process.
The pulp obtained is coloured, the degree of colouring depending on the pulping process. Tomlinson in the early 1930s, 4 allowed kraft mills to recycle almost all of their pulping chemicals. 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. It is the mixture of fibers and fiber fragments that gives mechanical pulp the favorable printing properties. When recycling paper, the first step is to dissolve the material. Today, only 10% of the world production are obtained by this method.
Pulping is done mechanically, thermomechanically, chemically, or with combinations of these treatments. The sulfite process produces wood pulp thatis almost pure cellulose fibers by treating wood chips with solutions of sulfite and bisulfite ions. Alternatively, logs can be pressed against grindstones which is why this process is also known as ground. 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. These chemicals cleave the bonds between the cellulose and lignin components of the lignocellulose. Overall view of papermaking from chemical pulp by the kraft process.
Tmp refining has been reported to be the most energy intensive unit process in the pulp and paper industry sabourin 2003. Preparation of wood pulp by sulfate kraft process nptel. The kraft process, which uses sodium hydroxide naoh and sodium sulphide na2s to pulp wood, is the dominant pulping process in the pulp and paper industry. Kraft pulping is by far the most common pulping process used by plants in the u. Many kinds of paper are made from wood with nothing else mixed into them. 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. A method of converting wood chips into paper pulp for use in papermaking accomplished by chemical cooking of the chips, as opposed to mechanical pulping. The purpose of pulping is to reduce wood or other fibrous raw material to individual cellulose fibers. Chemical recovery edit the spent cooking liquor from sulfite pulping is usually called brown liquor, but the terms red liquor, thick liquor and sulfite liquor are also used compared. 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. Kraft pulping process is the most used pulping process in the world. The importance of the sulphite process has decreased steadily over the last years.
It is similar to cellulose in composition and function. The kraft process alone accounts for over 80 percent of the chemical pulp produced in the united states. Usually known as kraft pulping which relies on a combination of heat, chemicals and mechanical pulping to convert the wood into a. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. Naoh is completely ionized and for every two sodium atoms of na2s, there will be one ohproduced. The kraft process alone accounts for over 80% of the chemical pulp produced in the. Principal chemical pulping processes include the alkaline sulfate or kraft pulping process, acid. Kraft process is the foremost pulping process in the board and paper industry and the biggest lignin supplier. Mech 450 pulping and papermaking topic 3b refiner mechanical pulping james a. 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.
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. The chemical pulp is produced through the chemical pulping process, while the mechanical pulp is produced through mechanical pulping. The chemical pulping processes involve reaction or cooking of wood chips with a solution of chemicals in a heated digester vessel for an extended period up to several hours or more followed by mechanical refining. Chips from the storage bins are fed into a digester to which chemicals have been added. There are mainly three modes of production of pulp. 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 kraft chemical recovery process is a mature, effective technology that provides for recycling of the pulping chemicals, efficient generation of steam and electrical power from the fuel value. Pulp and paper manufacturing facilities must report.
Jun 30, 2015 kraft pulping process is the most used pulping process in the world. The kraft pulping process uses an alkaline cooking liquor of sodium hydroxide naoh and sodium sulfide na2s to digest wood, while the similar soda process uses only naoh to digest the wood. The effect of chemical and biopulping process on bagasse pulp. Hemicellulose plays an important role in fibertofiber bonding in papermaking. It is the paper pulp made from the fiber raw materials by mechanical grinding method, occupying an important position in the papermaking industry. The sulfite process does not degrade lignin to the same extent that the kraft process does and the lignosulfonates from the sulfite process are useful byproducts. About million tonsyear of kraft pulp are produced globally, accounting for twothirds of the worlds virgin pulp production and for over 90% of chemical pulp. The paper manufacturing process has several stages. This process is also the most intensive steam user among pulping. To learn why it is important, we have to start from the pulp. Pulping chemical preparation and analysis 156 effective alkali ea.
In this process, pulp is produced by digesting wood chips at high temperature and pressure in a sodium hydroxide solution called white liquor to dissolve the wood lignin and other organic wood substances and. Thermo mechanical pulping tmp chemi thermo mechanical pulping ctmp brightening. To increase pulp whiteness and brightness unbleached kraft pulp is usually a dark brown color, and to remove residual lignin, chemical pulps are bleached. While high in energy consumption, tmp produces strong fibers, and clean steam can be recovered. The choice of pulping process is determined by the desired product, by the wood species available, and by economic considerations. An important part of the program is the comparison. 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. However, a substantial portion of the lignin still remains, and pulp yield 60. Spent cooking chemicals and the energy in the dissolved organic material is recovered. Pulp is a lignocellulosic fibrous material prepared by chemically or mechanically separating cellulose fibres from wood, fiber crops, waste paper, or rags. Sulfate or kraft pulping is the main pulping process was invented in germany in 1884 and remains the dominating technology today. 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.
This includes newspapers, magazines and even toilet paper. Kraft pulping process an overview sciencedirect topics. The fpl was influential in developing the semichemical pulping process as a higher yield offshoot for the kraft process in papermaking. 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. Pulp and paper chemistry and technology volume 2 pulping. More specifically, it is made from the cellulose fibres in trees. About million tons per year of kraft pulp are produced worldwide bruijnincx et al. In the case of mechanical pulp, the wood is processed into fibre form by grinding it against a quickly rotating stone under addition of water.
The pulping and bleaching processes must be adapted to the final use of the pulp. These fragments dissolved with the solution and wood disintegrates into fiber. In this process lignin goes into the reactions with the cooking liquor chemicals and split into fragment. A typical layout of a mill using the kraft chemical pulping process is shown in figure 21. The chips are cooked by heat and pressure in caustic soda and sulphur. A nonfibrous constituent of wood, lignin, binds cellulose fibers together, and is primarily responsible for reducing paper quality and. Pulp and paper mills are highly complex and integrate many different process areas including wood preparation, pulping, chemical recovery, bleaching, and. First commercially viable kraft mill, sweden, 1885. Kraft pulping is by far the most common pulping process used. The continually rising price of electricity and high electrical energy consumption of the process have impaired the profitability of the process. The process chips are fed to a presteamer and are steamed with. It is the mixture of fibers and fiber fragments that gives mechanical pulp the favorable. Na and sulfur s balances in the kraft pulping process.
The pulp, as the name kraft indicates, is also much stronger than pulp produced via other methods and the paper generated from the process runs well on highspeed presses. The white liquor chemically dissolves the lignin that binds the cellulose fibers together. Mechanical pulping involves using machines to grind wood chips into pulp. The first three have great potential for causing air pollution. Basic overview of pulp and paper manufacturing process. Pulping including cooking or refining, washing, screening and cleaning and.
To make paper from trees, the raw wood must first be turned into pulp. For a chemical process to be economically feasible, it has to consist of an efficient recovery system. For this purpose, a dynamic model was developed to predict the na and s balance in. This creates pulp, which is then used to make recycled paper. The kraft sulphate pulping process the sulphate or kraft process accounting for ca.
Lignin is the binding material which holds the cellulose fibres together. Sixta and others published chemical pulping processes find, read and cite all the research you need on researchgate. In addition to energy production, pulping and fiber, paper and board, tissue and biofuels industries, valmet offers solutions to paper converting, mining and chemical industries, food and biotechnology and pharmaceuticals industries, as well as commercial laundries. Groundwood pulp was first made in germany in 1840, but the process did not come into extensive use until about 1870. Xix automation and control of pulp and paper processes h. Semichemical pulping article about semichemical pulping by. For certain paper grades, the dark pulp has to be bleached. Advances in chemical pulping processes sciencedirect.
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