Paper pulp machine

A paper pulp machine (or paper making machine) is an industrial machine used in the pulp and paper industry to make paper in large quantities at high speed. Modern paper machines are based on the principles of the Fourdrinier Machine, which uses a moving woven mesh to create a continuous paper path by filtering the fibres held in a paper stock and producing a continuously moving wet fibre mat. This is dried in the machine to produce a strong paper web.
The basic process is an industrialized version of the historical process of hand paper making, which could not meet the requirements of the development of modern society for large quantities of a printing and writing substrate. The first modern paper machine was invented in Britain by Henry and Sealy Fourdrinier and patented in 1806.
The same process is used to produce cardboard on a cardboard machine.

Process sections

Process componentsPaper machines usually have at least five different operational sections:
Forming section, usually called the wet end, is a continuously rotating mesh that extracts water from the paper by vacuuming it out of the suspension.Pressure section, where the wet end goes between large, high-pressure loaded rolls to squeeze out as much water as possible.Drying section, where the pressed plate partially passes a series of steam heated drying cylinders in a serpentine manner. Drying removes the water content to a level of about 6%, where it remains indoors under typical atmospheric conditions. Infrared dryers are also used in addition to cylinder drying where necessary.Size Press section, where the semi-dry paper is applied with a thin layer of starch and/or other chemicals to improve various paper properties, reduces dust generation and air permeability, increases stiffness, burst strength and compression over short distances.Calendar section, where the dried paper is smoothed under high load and pressure. Only one sip (where the sheet is pressed between two rolls) is needed to hold the sheet, which shrinks through the drying section and is kept under tension between the press section (or the crusher stack if used) and the calender section. Additional nipples provide better smoothness, but at some cost to the stiffness of the paper.Roll section, where the paper coming out of the machine is wound on individual spools for further processing.There can also be a coating section to adjust the surface properties with coatings such as porcelain stoneware.
HistoryBefore the invention of continuous paper making, paper was made in separate sheets by stirring a container with pulp waste and pouring it into a cloth sieve, which is called a leaf shape, or by dipping the leaf shape and lifting it out of the vat. While it was still on the fabric in the sheet mould, the wet paper was pressed to remove excess water. The sheet was then lifted to be hung over a rope or a wooden rod to dry in the air.
Fourdrinier machineIn 1799, Louis-Nicolas Robert of Essonnes, France, was granted a patent for a continuous paper machine.[1] At the time, Robert worked for Saint-Léger Didot, with whom he fought over ownership of the invention. Didot believed that England was a better place to develop the machine. But in the turbulent times of the French Revolution he could not go there himself, so he sent his brother-in-law, John Gamble, an Englishman living in Paris. Through a chain of acquaintances Gamble is introduced to the brothers Sealy and Henry Fourdrinier, stationaries of London, who agree to finance the project.
With the help of Bryan Donkin, a skilled and ingenious mechanic, an improved version of Robert's original was installed in Frogmore Paper Mill, Apsley, Hertfordshire, in 1803, followed by another in 1804. A third machine was installed at Fourdriniers' own mill at Two Waters. The Fourdriniers also bought a mill at St Neots to install two machines, and the process and machines continued to develop.
Thomas Gilpin is usually credited for making the first American paper machine in Brandywine Creek, Delaware in 1817. This machine was also developed in England, but it was a cylindrical forming machine. The Fourdrinier machine was not introduced in the US until 1827.[2].
Similar designsRecords show Charles Kinsey of Paterson, NJ already had a patent on a machine for making continuous paper in 1807. Kinsey's machine was built locally by Daniel Sawn and in 1809 the Kinsey machine successfully made paper in the Essex Mill in Paterson. The financial stress and potential opportunities created by the Embargo of 1807 eventually persuaded Kinsey and his financiers to change the focus of the mill from paper to cotton, and Kinsey's early paper-making successes were soon overlooked and forgotten.[3][4].
Gilpin's 1817 patent was similar to Kinsey's, as was the John Ames patent of 1822. The Ames patent was challenged by its competitors, who claimed that Kinsey was the original inventor and that Ames had stolen the ideas of others, proving that Daniel Sawn was working on his machine.
Related inventionsThe method of continuous production demonstrated by the paper machine has influenced the development of continuous rolling of iron and later steel and other continuous production processes.
Pulp types and their preparationsMain article: Pulp (paper)The vegetable fibres used for pulp consist mainly of cellulose and hemi-cellulose, which tend to be

Shaping section or wet end

A worker inspecting wet, bleached wood pulp for an old-fashioned Dutchman pulp or "knocker".From the machine box, the stock is pumped to a main tank, also called "headtank" or "stuff box", which aims to keep a constant head (pressure) on the fibre slurry or stock while it feeds the basic weight valve. The stuff box also provides a means of releasing air bubbles. The consistency of the pulp-sludge at the stuff box is in the range of 3%. The flow of the stuff box is by gravity and is controlled by the base weight valve on its way to the suction of the fan pump, where it is injected into the main flow of water to the fan pump. The main flow of the water pumped by the fan pump comes from a wild water box or tank that collects all the water discharged from the forming part of the paper machine. Before the fiber flow from the box is introduced, the wild water is very low in fiber content. The white water is constantly recirculated by the fan pump through the headbox and is recovered from the wire pit and various other tanks and crates that receive drainage from the forming wire and vacuum assisted drainage from the suction boxes and wet fiber web treatment rollers. On its way to the headbox, the pulp sludge can pass through centrifugal cleaners, which remove heavy contaminants such as sand, and sieves, which break down fibre lumps and remove oversized debris. The fan pump ultimately feeds the delivery box, regardless of whether or not centrifugal cleaners or sieves are present.[7]
The purpose of the headbox is to create turbulence to prevent the fibres from clumping and to distribute the slurry evenly across the width of the wire. Wood fibres tend to attract each other to form clumps, which is called flocculation. Flocculation is reduced by lowering the consistency and/or by stirring the slurry; however, flaking becomes very difficult at a consistency much higher than 0.5%. Minimising flocculation during forming is important for the physical properties of paper.
The consistency in the headbox is typically less than 0.4% for most papers, where longer fibres require a lower consistency than short fibres. A higher consistency causes more fibres to be oriented in the z-direction, while a lower consistency promotes fibre orientation in the x-y direction. A higher consistency promotes higher callibration (thickness) and stiffness, a lower consistency promotes higher tensile strength and some other strength properties and also improves formation (uniformity). Many feather properties continue to improve below 0.1% consistency; however, this is an impractical amount of water to process. (Most paper machines have a higher consistency than optimal because they have accelerated over time without replacing the fan pump and headstock. There is also an economical trade-off with high pump costs for lower consistency).
The stock slurry, often called white water at this point, leaves the backbox through a rectangular opening with adjustable height called the slice, the white water flow is called the jet and it is pressurized on high-speed machines to gently land on the moving dust loop or wire at a speed usually between plus or minus 3% of wire speed, called "rush" and "drag" respectively. Excessive rush or resistance causes more orientation of the fibres in the machine direction and gives different physical properties in the machine and cross direction; however, this phenomenon is not completely avoidable on a Fourdrinier machine.
On machines with a lower speed of 700 feet per minute, gravity and the height of the stock in the headbox provide sufficient pressure to form the beam through the slice opening. The height of the stock is the head, which gives the headbox its name. The speed of the beam in relation to the speed of the wire is known as the ratio between the beam and the wire. When the radius-thread ratio is less than the unit, the fibres in the flask are pulled out in the direction of the machine. On slower machines where sufficient liquid remains in the stock before it is discharged, the wire can be driven back and forth by a process known as shaking. This gives some degree of randomisation of the direction of the fibres and gives the sheet a more uniform strength in both the machine and transverse direction. In fast machines, the stock does not stay on the wire in liquid form long enough and the long fibres are in line with the machine. When the beam-thread ratio is greater than the unit, have

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