Paper Production Process

The paper production process is totally different for each factory and is not the same.

In Iran, each factory uses the technology based on their establishment date. Another important point that influences in paper production line lay out, is the type of output paper which is produced as final product in factories and supplied to market. The combination of this issues, determines the machinery arrangement in paper production line and the equipment to be used in paper production process. In this article, we have completely reviewed these issues. Please be with us.

 

Paper Production Steps

In general, the process of paper production can be summarized in 9 phases as follows.

 

1st Step: Process of Paper and Pulp

At the beginning of paper production process, recycled paper or wastages are poured to a large stainless steel to be mixed with water and prepare the initial paper pulp. This large container is called a pulper device. Impurities and coarse additives in the primary dough are removed from the dough by passing through filters in the pulper. This helps the process to produce higher quality paper.

 

2nd Step: Paper Pulp Dilution

During this process, in different stages, a certain amount of water is added to the paper pulp to dilute the final pulp and form a better formation. In fact, it can be said that at the end of the pulping process, the pulp contains 1% fiber and the remaining 99% is water. For proper refining, the pulp goes through several machines, to regulate the density of fibers and sort them, meanwhile, its impurities and wastes will be removed. We have discussed more regarding these devices in upcoming topics.

 

3rd Step: Wire Section

After passing the pulp through different machines for several times and completely separating impurities and wastages, it is time for wire section. In this section, the pulp with proper density spreads over wire surface through head box so that the excess water is removed and uniform homogenized fibers are remained. This section is done on fourdrinier table through forming wire, dewatering foil, and vacuum boxes.

 

4th Step: Press Section

The next step to dewater the pulp is using a press. In this machine, the pulp passes through a series of rollers so that water exits of the flat below it and only a certain percentage of moisture remains in it. In this way, the paper fibers become more compact and interlaced. Once the moisture volume reaches to about 45 to 55%, the pulp can form a dense and even sheet of paper. In this stage, proper pressing pressure helps to strengthen the mechanical properties of the paper.

5th Step: Dryers Section and Sizing

The dryer section is used to dry the paper, which increases the temperature of its cylinders up to about 150 Centigrade degrees, due to the line speed and gramage of the paper. In the pre-dryer stage, the paper dries completely. Adding starch and other additives is done at this stage. This helps very much to strengthen the bond between the paper fibers.

Depending on the produced paper type, if it needs sizing, the paper is heated again by passing through the size press machine and adding starch and other strengthening materials and by passing through after dryer machine. So that its humidity will be re-adjusted again. The humidity is generally adjusted in the range of 4-7% according to the customers’ needs.

 

6th Step: Calender

In paper calendaring, surface of paper gets smooth and even. This makes the paper ready for writing or printing and makes the surface even. At this stage, the paper is rolled through smooth, hard or soft rollers to remove all uneven surfaces on it.

 

7th Step: Quality Control

Quality control is an important step in the paper making process that examines the quality of the final product and the output paper. At this stage, the sheets of paper are checked by scanners or manually to confirm that the gramage, color and etc. of product are under control.

 

8th Step: Paper Packaging

At this stage, the produced paper is placed in the winder machine to be cut to the desired dimensions according to customer orders and sent to the intended customers.

 

9th Step: Paper Testing

The taken samples are regularly sent to specialized laboratories, in order to examine and evaluate the quality of produced papers. Cobb test, grammage test, RCT, Burst and etc. are some of the steps which are done in this stage.

 

The Equipment and Main Steps in Packaging Paper Production

In general, an almost certain process can be considered for producing packaging papers. Packaging papers are brown, non-white papers that include various types like fluting, testliner and liner papers.

 

 

The First Stage of Paper Making: Pulp Production and Refining

 

  1. Collecting Waste Papers

A similar procedure is followed in production of these types of paper, as the other types. Firstly, the waste papers i.e. the recycled paper and brown cartons are collected of around the city and taken to the paper manufacturing factories. In first station, pulper machine is used to make pulp. According to the technology and capacity of the factory, pulper machine can vary to one of its types such as: drum pulper, D pulper, hydro pulper, horizontal pulper, vertical pulper, etc.

 

Below, the most popular machines used in paper making line are introduced briefly:

 

  1. Pulper Machine for Making Pulp

With the entrance of waste (recycled) paper into this machine as the first step of the paper making process, recycled papers are combined with water and form the primary paper pulp. Inside the pulper device there is a filter on which there are distinctive meshes or holes. The pulp passes through this filter and a series of particles such as coarse plastics, stones and any wastes in general that may have entered the pulp for various reasons, is separated from the pulp. It is noteworthy that the wastes separated from the pulp at this stage, are particles that are larger than the size of the holes in this filter and cannot pass through it.

 

  1. Cleaner Machine

In next stop, the paper pulp enters the ponds that are placed in the path of factory production line. Once the pulp passes these ponds, it is time to cleaner machine. In general, 3 types of cleaner machines are available in paper production: HD Cleaner (High Density Cleaner), MD Cleaner (Medium Density Cleaner) and LC (Low Density Cleaner).

Since the density of pulp is high, in first stage of paper production process, the MD cleaners are used (centrifugal cleaners). At this stage, based on the cleaner mechanism and its design type, coarse particles like sand, stapler needle, gravels, etc. that have passed through the pulper mesh, will be re-separated from the pulp. Thus, the pulp is refined in several stages until the output paper quality comes to an acceptable level. During the paper refining process, impurities are separated from the pulp in several stages.

 

 

 

  1. Turbo-Separator Machine

After completing the process in HD cleaner, it is time to turbo-separator machine. In this stage as well, some amounts of impurities like plastics are removed from the pulp. Some factories, use also reject sorter machine in their paper production line. This machine, re-checks the output wastage of this stage again and separates paper pulp from impurities more accurately. As such, a part of paper pulp that had been removed along with plastic wastages by mistake, returns to production line.

Also, depending on the type of paper production line, some additional machines such as: deflaker, fine screen, coarse screen, etc. can be used in paper making process. All of these machines are aimed to separate fibers and pulp impurities. Depending on the mesh size that has been applied in the screen basket of these equipment, impurities and wastages in different sizes and dimensions are separated from paper pulp.

In this process, MD and LD cleaners will be used again in order to remove the smallest particles from the paper pulp.

 

  1. Pressure Screen Machine

The last stage of paper making process, is done in pressure screen machine. The pulp is entered to the inner chamber of the machine in high pressure. Thanks to the very tiny mesh (0.2~0.35 mm) on the baskets in this device, the paper pulp is refined thoroughly and no trace of particles or contaminants will remain. In fact, the mesh size on this machine is determined in such a way that, only very small particles can pass and even Styrofoam may not pass through it. Therefore, there would not remain any particle that can harm the quality of final pulp and produced paper.

 

The Second Stage of Paper Production Process: Making Paper

Up to know, we discussed the processes done for pulp making. Once the pulp is ready, it is time to Approach System or Paper Machine. In fact, his stage means completing the pulp making and refining process and the paper making procedure is started.

 

1.Dewatering through Forming Wire

In this stage, the pulp is poured on fourdrinier through head box inlet. Fourdrinier machine, dewaters paper pulp, based on the wire installed on it. Formation of the paper pulp is also done in this step. Considering the dewatering foils and vacuum boxes installed on fourdrinier, an average of 25% of excess water will be removed in this stage.

 

 

2.Press machine

In next step, the dewatered pulp, enters press section. At this stage, due to one or two strollers of the press, the paper is pressed. According to the type of the machine (single or double press), paper is pressed. It can be said in fact, this is the first step, in which; the paper is truly pressed mechanically in order to get its physical properties. The second step of paper dewatering is done in this section as well. Ideally, the moisture of the paper should reach to less than 50%, or more precisely to about 40 to 45% after passing through the press section, so that it can enter the dryers (dryer section).

 

3.Dryers

In dryer section, temperature of the cylinders is adjusted between 40-180oC, according to the line speed and produced grammage, in a specific cycle. Passing through these cylinders, the paper will lose the remaining moisture.

In production of papers like testliner, fluting or top white and etc. which need the sizing process, size press is used after dryer or pre-dryer step. This machine provides the necessary conditions for adding liquid AKD (SSK), dye, starch and other additives for paper sizing. This helps to strengthen the properties of the paper.

In case of using size press machine in paper making process, paper should get dried again by passing through the after dryer machine, because of absorbing additives such as starch, liquid AKD (SSK) and etc. Generally, dryer screen is used for rotating the cylinders. Since the humidity here reaches to maximum 20~25 percent, dryer machine has fewer cylinders.

 

4.Reel Drum Machine for Paper Packaging

The next step belongs to reel drum machine which makes the paper ready for packaging. Usually, the humidity of paper in this stage, should be between 6-8 percent which may vary due to the paper making process in each factory.

After paper being rolled in reel drum, it is time to last step. If the produced paper is meant to be top white paper or any printable paper, coating process is also needed. Calender or ironing is also another stage of paper making that helps the surface of the paper to be smooth and even. It should be mentioned that, this stage also varies in production lines of different factories.

In this stage, a machine called winder or re-winder is also used. This device trims the paper prepared in previous section. This procedure includes trimming the paper edges, cutting rolls to the width requested by customers, coating, etc. So the packaged paper is cut to smaller rolls the measures of it is specified according to the customers’ needs.

 

 

Scanner Machine in Paper Production Line

Scanner machine is used in production line of some factories. This machine, scans paper grammage every moment, during paper making process and controls the width grammage of the paper by a command given to head box at the beginning of line. Thus, we can ensure the paper will not exceed its standard and original grammage. All these depend on the process level and applied technology in paper production line of each factory.

All Rights are Reserved. | Designed and developed by Darkoob.