Semichemical pulping article about semichemical pulping by. Pulping chemical preparation and analysis 156 effective alkali ea. It is the mixture of fibers and fiber fragments that gives mechanical pulp the favorable. Pulp is made by heating the chips with steam and mechanically separating the fibers in a pressurized refiner. An important part of the program is the comparison. The pulping process is an important link in the papermaking industry. The sulfite process produces wood pulp thatis almost pure cellulose fibers by treating wood chips with solutions of sulfite and bisulfite ions. 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. 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. 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. There are mainly three modes of production of pulp. Today, only 10% of the world production are obtained by this method.
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. Usually known as kraft pulping which relies on a combination of heat, chemicals and mechanical pulping to convert the wood into a. Kraft pulping is by far the most common pulping process used. Overall view of papermaking from chemical pulp by the kraft process. 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. Valmets fiber technical knowhow provides intelligent, integrated and complete processes for both chemical and mechanical pulping. Preparation of wood pulp by sulfate kraft process nptel. Sulfate or kraft pulping is the main pulping process was invented in germany in 1884 and remains the dominating technology today. The chemical reactions in kraft pulping process pulp paper mill. Many kinds of paper are made from wood with nothing else mixed into them. 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. In the white liquor, sulfidity is the ratio of na2s to the active alkali. Xix automation and control of pulp and paper processes h.
Mechanical pulping involves using machines to grind wood chips into pulp. The four principal processes used in chemical pulping are kraft, sulfite, neutral sulfite semi chemical nssc, and soda. The importance of the sulphite process has decreased steadily over the last years. Advances in chemical pulping processes sciencedirect. 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.
Pulping including cooking or refining, washing, screening and cleaning and. For improved process efficiency and increased business profitability, turn to valmet. This creates pulp, which is then used to make recycled paper. Groundwood pulp was first made in germany in 1840, but the process did not come into extensive use until about 1870. The kraft process alone accounts for over 80% of the chemical pulp produced in the. Possibilities for improving the pulping process peter axegard stfi, swedish pulp and paper research institute peter. Pulp can be classified mainly into two types by the pulping methods.
The fpl was influential in developing the semichemical pulping process as a higher yield offshoot for the kraft process in papermaking. Chemical pulping processes request pdf researchgate. The kraft sulphate pulping process the sulphate or kraft process accounting for ca. Sixta and others published chemical pulping processes find, read and cite all the research you need on researchgate.
A nonfibrous constituent of wood, lignin, binds cellulose fibers together, and is primarily responsible for reducing paper quality and. Unesco eolss sample chapters control systems, robotics, and automation vol. The first three have great potential for causing air pollution. In order to maintain a proper balance of na and s, kraft mills may need to adopt different makeup strategies. Pulp and paper manufacturing process in the paper industry. The pulp obtained is coloured, the degree of colouring depending on the pulping process. Ea is the sum of sodium chemicals that will produce ohduring kraft pulping. The industry utilizes a variety of industrial processes to convert wood into pulp. It has the advantages of low cost, simple paper and pulp production. Tomlinson in the early 1930s, 4 allowed kraft mills to recycle almost all of their pulping chemicals. The 4 processes principally used in chemical pulping are kraft.
It is the mixture of fibers and fiber fragments that gives mechanical pulp the favorable printing properties. Na and sulfur s balances in the kraft pulping process. Pulp and paper mills are highly complex and integrate many different process areas including wood preparation, pulping, chemical recovery, bleaching, and. Semichemical pulping article about semichemical pulping. While high in energy consumption, tmp produces strong fibers, and clean steam can be recovered. Jun 30, 2015 kraft pulping process is the most used pulping process in the world. To make paper from trees, the raw wood must first be turned into pulp. In this process lignin goes into the reactions with the cooking liquor chemicals and split into fragment.
Kraft pulping is by far the most common pulping process used by plants in the u. 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. Hemicellulose plays an important role in fibertofiber bonding in papermaking. 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. Mechanical wood pulp is also known as ground wood pulp. Pulping is done mechanically, thermomechanically, chemically, or with combinations of these treatments. The effect of using a chemical course with nitric acid and a biopulping way using fusarium solani. The effect of chemical and biopulping process on bagasse pulp. These chemicals cleave the bonds between the cellulose and lignin components of the lignocellulose. 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. 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. Chemical wood pulps such as soda and sulfite pulp described below are used when high brightness, strength, and permanence are required. However, a substantial portion of the lignin still remains, and pulp yield 60.
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 paper manufacturing process has several stages. The chips are cooked by heat and pressure in caustic soda and sulphur. The kraft process is the dominating pulping process, which accounts for almost 60% of all mechanical and chemical pulp produced worldwide. Tmp refining has been reported to be the most energy intensive unit. 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 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. Mechanical, semichemical, and sulfite pulp mills differ in detail, particularly in wood preparation, fiber separation, and bleaching, but many of the downstream refining. The kraft process alone accounts for over 80 percent of the chemical pulp produced in the united states. Thermo mechanical pulping tmp chemi thermo mechanical pulping ctmp brightening.
It is the paper pulp made from the fiber raw materials by mechanical grinding method, occupying an important position in the papermaking industry. Pulp and paper manufacturing facilities must report. Stability of wet end for paper machines with dilution headboxes. Commercial processes are generally classified as mechanical, chemical, or semi. For a chemical process to be economically feasible, it has to consist of an efficient recovery system. Tmp refining has been reported to be the most energy intensive unit process in the pulp and paper industry sabourin 2003.
Chips from the storage bins are fed into a digester to which chemicals have been added. Kraft process is the foremost pulping process in the board and paper industry and the biggest lignin supplier. First commercially viable kraft mill, sweden, 1885. 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 white liquor chemically dissolves the lignin that binds the cellulose fibers together.
The choice of pulping process is determined by the desired product, by the wood species available, and by economic considerations. Overview of the process thermomechanical pulping, tmp, is precisely named. Mech 450 pulping and papermaking topic 3b refiner mechanical pulping james a. When recycling paper, the first step is to dissolve the material. Spent cooking chemicals and the energy in the dissolved organic material is recovered. 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. This includes newspapers, magazines and even toilet paper. 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. The category and application of paper pulping process mechanical wood pulp. Pulp and paper chemistry and technology volume 2 pulping. For certain paper grades, the dark pulp has to be bleached. Principal chemical pulping processes include the alkaline sulfate or kraft pulping process, acid.
Kraft pulping process an overview sciencedirect topics. Kraft pulping is the main pulping process together with mechanical pulping used today, and. This process is also the most intensive steam user among pulping. Naoh is completely ionized and for every two sodium atoms of na2s, there will be one ohproduced. 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. The pulping and bleaching processes must be adapted to the final use of the pulp. 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. The process chips are fed to a presteamer and are steamed with. 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 fragments dissolved with the solution and wood disintegrates into fiber. More specifically, it is made from the cellulose fibres in trees. The main chemical reactions in the cooking process can be described as. The purpose of pulping is to reduce wood or other fibrous raw material to individual cellulose fibers. About million tons per year of kraft pulp are produced worldwide bruijnincx et al.
Basic overview of pulp and paper manufacturing process. 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. First commercial process was the rdhprocess of rader rapid. The chemical pulp is produced through the chemical pulping process, while the mechanical pulp is produced through mechanical pulping. Kraft pulping process is the most used pulping process in the world. Lignin is the binding material which holds the cellulose fibres together. It is similar to cellulose in composition and function. 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. 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. Pdf analysis by pineapple leaf in chemical pulping process. Olson pulp and paper centre, department of mechanical. Chemical pulping is the other common pulping process. Modeling of kraft mill chemical balance daniel moreira saturnino. This is achieved by breaking the bonds in the lignin macromolecule.
To increase pulp whiteness and brightness unbleached kraft pulp is usually a dark brown color, and to remove residual lignin, chemical pulps are bleached. Mechanical pulping and chemimechanical pulping comparison. Koivo encyclopedia of life support systems eolss nissinen, a. A typical layout of a mill using the kraft chemical pulping process is shown in figure 21. 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 competing chemical pulping process, the sulfate, or kraft, process, was developed by carl f.
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