Factory Floor
What is intended here is not to treat the manufacture of fluting paper to exhaustion, but to expose the knowledge experienced and shared on the factory floor, from the entry of raw material, with regard to recycled shavings and other items, until the industrialized paper, ready to be shipped to customers.
Chapter I
Recycling
Recycling takes place everywhere where paper is consumed, or at least that is what should happen in all homes, offices, factories and commercial houses.
Of all the paper produced in the industries, just over 30% comes back in recycled form. It is very little compared to the Brazilian paper production.
If a better awareness were made, starting first in homes, then in schools and then in all places of consumption, this percentage of collection would possibly increase on a large scale.
Also contributing to this gap is the fact that the prices of pulp and paper in general are unstable, not only in the domestic market but also abroad. If the price of finished paper falls in price, the industries are forced to lower the price of the raw material in the case at hand, the scrap. This leads to a disincentive for the people involved in the collection of these materials, which are paper collectors, scrap dealers and apparitionists.
Each factory recycles a certain type of cuttings, depending on the product it processes. Here we will deal with the corrugated board shavings whose final product will be the fluting paper.
The process for making the fluting paper follows several steps that we enumerate below and will be treated in detail in their own chapters:
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chip breakdown;
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purification or cleaning of the obtained paste;
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refining the paste;
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addition of chemicals.
Benefits of Recycling:
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noticeable improvement in the quality of the collected chips;
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job creation in the sector;
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saving the area to be reforested;
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saving wood for papermaking (1 ton of shavings corresponds to a planted area of 100 to 300 m2 of trees, depending on the type of paper to be manufactured);
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energy saving;
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saving reforestation area;
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waste reduction in large urban centers;
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saving water used in the process;
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There will be no need for new cellulose plants;
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increase in the collection rate from 25 to 30% to 60 to 70%.
Chapter II
Recycled Corrugated Cardboard
After telephone contact with suppliers, informing them of the price and quality to be sent, the purchase is contracted.
The trucks are received at the entrance of the industry where each one receives the order of unloading.
The truck enters the fraud-proof electronic scale, where it is weighed. Then it is positioned inside the unloading shed where it is removed. Then the person in charge of receiving arrives. This person must be directly connected to the board and be of the utmost confidence.
The recipient looks at the gross weight, observes the type of truck and the way it is loaded, sees the bales being pressed and then counts them. This is the first a priori sampling that the recipient has when making contact with the goods.
By the weight of the truck, the size, pressing and the number of bales, the first idea is formed. The next step is to randomly take three bales out of the truck and open them. Once again, the person in charge of receiving and inspecting will observe the degree of prohibitive material found in the burden. The prohibitive material can be water in the form of moisture, broken glass or porcelain, old clothes, Styrofoam, sand, stone and others that unscrupulous people can put on without our suppliers knowing, because they often buy from third parties. Three samples are taken that enter the greenhouse to know the moisture content.
Once the discharge is agreed with the supplier, the recycled chips are unloaded from the truck using modern forklifts that stack them by sector, according to the degree of purity, that is, if the bales contain more or less corrugated cardboard, because what matters for the production of fluting paper is long fiber and it is precisely in the corrugated board.
Chapter III
Preparation Of The Pasta
Breakdown
The bales of recycled scraps are removed from the pile by the forklift's valet and placed close to the conveyor so that the wires can later be removed and can be dragged to the conveyor that will transport the cardboard sheets to the disintegrator.
The disaggregator or hidrapulper is a cylindrical equipment with a rotor at its bottom that very much resembles a giant blender and its capacity can vary from five to forty cubic meters, according to the productive capacity of the industry.
The chips, through the centrifugal force, are sucked up to the rotor together with the water previously added and will form a homogeneous paste with some degree of hydration and with the consistency of 4 to 7%, that is, in 100 liters of water there will be, thick way, 4 or 7 kilos of cardboard already broken down.
Not all recycled paper found in the bales is of the same texture and quality. At least 10% receipt of other types of paper is acceptable. Due to the various differences in the quality and strength of the papers, their break-up time will also be different. For this reason, in order to have a good mixture, it is necessary that the contents of the hydrapulper, made by batch, remain in it for at least 20 minutes in constant movement before it is thrown into tank I.
Chapter IV
Paper Pasta Cleaning Or Cleaning
Despite the choice received, the recycled scraps arrive at the factory with some degree of impurities such as old fabric, plastics, pieces of iron, pieces of ceramic and glass, styrofoam, string, the staples of the boxes themselves, etc.
In order for all of these non-papermaking materials to be purified, there is a device called contaminex that extracts both heavy and light bodies.
We will make a light sketch of the operation of this machine: the hidrapulper is composed in its bottom part by a sieve, usually made of stainless steel with a 3/8 ”hole, so that only the paper mass can pass through, and everything above that measure remains there. withheld.
When the purification is not continuous, after four or five batches have been broken down, the pulper is cleaned. All the mass found in it is pumped into tank I, leaving only plastics, old fabrics, some pieces of metal and larger clips. This material is then washed by diluting it with plenty of water, and afterwards, an open rotor pump sucks out all of this content. The heavy bodies fall into a separator built for this purpose and the light ones are transported to the contaminex through an 8 ”pipe, where they are thrown in a horizontal press where they are baled to be later loaded into a truck that will transport them to to the landfill.
Part of the purification was carried out in the previous description, at least as far as the thickest part is concerned, but as we know, the paper after disintegrating becomes a tangle of fibers that intertwine and drag with them little pieces of plastic, undefibrated paper bags, Styrofoam , glass, ceramic, wood, small clamps and mainly microscopic sand. To eliminate all these wastes, some equipment is needed. In order to extract sand, glass, staples and pieces of wood, high-consistency clones are generally used, which work by centrifugation with the mass entering tangentially pressurized into the top of the clone, while back pressure water enters the bottom making the differential the pressure to bring all the heavy material down to a chamber. The acceptance is sent to the plastic strip that we will see below.
The accepted pulp that comes from the clones is received by the plastic strips that work at atmospheric pressure and contain cylindrical hole sieves inside where they retain the plastic, the undefibrated paper bags and some pieces of wood that later fall on a mat that leads to a container and the partially cleaned mass is deposited by gravity in tank II.
From the tank, a pump raises it to a level box that is higher than another mixing pump that has the purpose of changing the consistency from 4% to 0.8 to 1% so that tiny particles of sand disentangle themselves from the fibers and can be removed in the three stages of low consistency cleaners that work like high clones. After all this process, the recycled paper pulp is practically free of all impurities and there is, therefore, a need to raise it again to 4%, for this another pump throws it in thickeners that separate it from the water. In this way it is ready to be refined.
Chapter V
Refining
We believe that the use of the word refining for those who work with recycled material is not very appropriate, it gives us the impression that we are cutting even more a fiber that has already been processed several times. It would be more interesting to use the terms: comb, open or why not say goose bumps so that it can be hydrated. To refine and cut it would be to make it shorter, which would contradict our type of manufacturing which requires the use of long fibers. There are modern equipments for the treatment of recycled fiber, called triconic refiners, where the fibers are massaged in such a way that they are highly apt to be hydrated and ready to reach the ideal “shop reagler” level for the manufacture of “fluting” or “ test liner ”.
It is worth remembering that for the disintegration, purification and cleaning sector, a forklift operator is used that feeds the conveyor, a pulper operator and a helper and in the refining sector only one operator which makes four men per shift hours. We can say that in industries with a little efficiency it is reasonable to accept 6.5 ton./man/month.
Chapter VI
Chemicals Addition
Starch
There is a chemical station next to the paper-making machine where the glue is made by cooking the cassava starch that is released before the machine's inbox.
The strength and stiffness of a paper is usually conferred by the quality of the fibers that make it up, but in the absence of it some chemicals are used, including cationized corn or cassava starch. In addition to the internal resistance, the addition of starch in the dough provides better smoothness, difficulty in penetrating liquids in the sheet, greater rigidity and also prevents the formation of dust. In most modern machines, surface bonding using a device called “Size Press” or a size press is normal. Here the starch is applied superficially on the already formed and practically dry leaf.
The surface bonding gives the sheet, among other characteristics, the greatest difficulty in penetrating liquids, increasing the mechanical qualities and in the case of papers to print a better printability.
Breu Cola
The product used is pitch resin which, after being treated, is soluble in water and the emulsion is added to the paper mass to give it a low “cob”, that is, little penetration of liquids.
For the glue to produce the desired effects, it is necessary that the medium where it will act must be with an acidic PH, in the scale of 4 to 6. The PH is corrected with aluminum sulfate.
Humectants
The sulphate used in pH correction enters the composition of the leaf and is in contact with the drying battery forms sulphate crystals that are highly hygroscopic, which impairs the strength and stiffness of the leaf. In order to maintain its mechanical characteristics, wet and dry humectants are used.
Chapter VII
Paper Machine
The paper machine consists of several parts. First comes the input box, then the flat table or forming table, then the presses and finally the drying.
Input Box
The inbox is a pressurized paste container, of the same width as the forming screen, made of stainless steel, with two lips and the upper lip is adjustable so that its opening is adjusted to the lower or higher speed of the mesh.
The suspension enters the rear of the box through a conical pipe and is received by diffusers that are across the entire width.
At the front, a perforated distributor roll is responsible for homogenizing the fiber, avoiding its flocculation and agglutination, and may impair the good formation and uniformity of the sheet.
The jet of fiber suspension as soon as it leaves the inbox and passes through the previously regulated lips flows into the forming screen.
Flat Table
The flat table or forming table is the width of the inbox or slightly more. The length can have several measures, depending on the production you want to achieve. It consists of a bedside roller coated with ebonized material and a rubber-coated suction roller. These two pieces keep the screen taut, but the tension itself is given by the tensioner roller.
Right after the bedside roll and a few centimeters from the bottom lip of the box, under the forming screen, there is the “form bord”.
It is usually said that it is in this space that the formation of the leaf occurs.
Continuing at the top of the flat table and after the "form bord" there are some rulers and dewatering boxes with their lips positioned in the opposite direction to the movement of the screen so that they can extract the maximum amount of water from the solution on it. The suction boxes also make up the forming table. The number of rulers and dewatering boxes as well as suction boxes depends on the length of the screen and the productivity of the machine. To guide the screen and support it, there are screen guides coated with ebonite. In the past the screen was kept in place and guided manually, as the speed of the machines was low, today due to the high speeds the pneumatic screen guides do the job perfectly.
Training Table Operation
The fiber suspension, which is at 08% consistency, (that is, 800grms of dry fiber in 100lts of water), passes through the lips of the inbox and flows into the forming screen that is in motion.
As the screen is made of synthetic yarns of 24 mesh when passing through the drainage elements the suspension is retained on it and the water passes through the mesh and falls on a tray. This water, as it is rich in fiber, will feed the machine through the mixing pump, it also feeds the pulpper and the leftovers will be filtered to feed the showers. It was said that the suspension leaves the lips of the box at 0.8% consistency, now after leaving the vacuum boxes with the sheet formed the consistency is 15 to 16 and when passing through the suction roller it is 25 to 27 It should be noted that the screen has two movements, one longitudinal and the other transverse that is made by the shaker. The combination of these two movements is the reason for the good interlacing of the fibers and, therefore, for the good formation of the sheet. This is finally detached from the suction roller and goes to the press section. In order to keep the screen clean and to receive a new suspension on the way back, there are fan showers and needle showers, those with constant incidence and intermittent ones.
Chapter VIII
Press
Modern paper machines have two or three sections of presses and their rolls can vary from 0.5m to 1.20 m in diameter. Both rollers are coated with a hard rubber and the lower rollers are provided with a blind hole. The presses are embraced by needles made of synthetic material. One that embraces the first upper press and the other the lower one. The same is true with the second press. Felts have two functions. One is to transport the paper and the other to carry water that has been extracted at the nip of the presses. Also in the press section there are the felt-guide rollers, the felt-guide, the fan and needle showers and the suction tubes to condition the felts and keep them clean in order to transport the paper and load the water again.
Press Functioning
The paper sheet leaves the suction roller with 74% water, passes through the first press where it receives a nip pressure of 120 to 180 kg per linear cm, due to this pressure part of the water is transferred from the sheet to felts and can leave the first press up to 43% consistency or 57% water. It enters the second press and receives a nip pressure that can vary from 200 to 300 kg by linear cm, at the exit the sheet will be more or less with 53% consistency or 47% water. Then the sheet enters the drying batteries.
Chapter IX
Drying
The drying of a machine is made up of as many drying cylinders as you want to achieve in production. They work with saturated steam. This is nothing more than the heat transport vehicle to the cylinders that work with a pressure of 4 to 5 kg, reaching up to 12 kg and from 1 to 2 kg when the steam is "flax".
The temperature can vary, but a good number to be adopted would be 160 to 200 degrees. Generally, cylinders are grouped in batteries that work in a cascade system.
"Flax" steam is used where there is a need to just heat the sheet while live steam is used to evaporate water from the sheet. All dryer cylinders are dressed with 80 Mesh synthetic fiber dryer screens and between them and the dryers' smooth surface passes the sheet. The screens not only serve to transport it, but also to keep it pressed against the walls of the dryer so that there can be a greater transfer of heat to the sheet. When leaving the last cylinder for the reel, the humidity varies from 6 to 7.5%. The mother roll leaves the reel by means of an overhead crane and is transported to the rewinder where it receives the processing so that it can meet customers' requests.
Laboratory
The fluting paper factory has a modern laboratory for analyzing the physical and mechanical properties of the manufactured paper. The market demands are such that the product has to arrive at the customer's door with approved quality and excellent service.
The tests required by packaging manufacturers are:
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Concora test (burst or burst)
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RCT (wave crush)
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Moisture test (acceptable from 5 to 7.5%)
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Shop Reagler test (degree of refinement)
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Cob test (greater or lesser penetration of liquids in the paper)
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Consistency test
Effluents
Water is vital for making paper. The industrial plant must necessarily be located near a river with a reasonable flow from where the water will be pumped into a settling pond and from there to the industry. As we saw in the previous description, all the manufacturing water precipitated in the flat table tray contains fiber. After being collected in tanks, part of it goes to the machine, another to the disintegrator and the remainder is directed to the treatment of effluents to be filtered and later used in showers.
Nowadays most of the paper industries have the industrial water circuit almost completely closed when this does not happen there are two ponds, one aerobic and another for settling. All the excess water from the final bottleneck goes to the aerobic lagoon, where several aerators inject oxygen from the atmospheric air to feed the bacteriological flora that will consume all the fiber or tiny particles of paper fibers. In order for the lagoon environment to be very conducive to bacteria, aluminum sulfate for pH correction and urea for food are added to the white water. Doing a test on the final spillway, taking two samples, one from the river and the other from the effluent, it is noted that the sample of the effluent is more conditioned to be thrown into the stream than its own water. Of course, this would not happen if there was not a great awareness of the industry in preserving the environment, continuing its purpose of recycling.
Monitoring is carried out 24 hours a day, by trained people, assisted by a modern laboratory where some tests are carried out, including COD (chemical oxygen demand).
Author
Luís Filipe Figueiredo da Silva
December 09, 2002
Bibliography
Garden, NS Town waste
Kimoto, S. Recycling x waste
The world of paper. SL: Pirahi.sd
Pinto, CMS aspts. tecs. and rec ecns.
Di Sarno-Paper recycling in Brazil
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