Friday, 12 January 2018

Pulpers | | Function of Pulper in Pulp Making

          Pulper is employed in numoreous industries (Agriculture, paper plants) at different workplaces however here in this topic we discuss regarding the pulper which is employed in Paper Industry. 
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          Pulper is a mechanical machine which is used to produce pulp from cellulose fibrePulper is the heart of the re-pulping operation. Paper pulper is employed for different opeartions like crushing virgin pulp (Slabs and sheets), Waste paper process, machine broke, deinking and pulp purification. The bales of wood pulp or waste paper is loaded on conveyors and passed into a pulper (circular tank) containing water, it breaks the fiber by the action of mechanical operation (by using impellor).           

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          Among different raw materials waste paper processing is important because it contains a lot of dirt, stapler pins, metalic pieces, adhesive tapes, un-dissolved coating and alternative foreign materials like wax, plastic etc., This waste paper ought to be free from these types of undesirable materials. Before entering into pulper these materials are segregated from raw materials however some may remains. If these materials are present in pulp and move into wire section; they harm to wire as well as poor quality of paper occurs. Moreover centi cleaners is also block, increase the paper web breaks, reduces the performance of press felt and dryer screen. Therefore the pulper must has the ability to get rid of most of the contraries like wire, plastic etc.,
          Based on operation pulpers can be classified into two types they are Batch pulper and Continous pulper. In batch mode operation pulp formation is done in batches, by this we can control the size, dry strength of paper, and color by adding some chemicals. For stock deinking and change the color we use Surfacants. The suppliment chemicals of surfacants are Disparcent, Anti-foming agent, Caustic soda, Borax, and Sodium silicates. Waste Paper contains written papers and news paper too, the ink present on them change the color of the paper. Dispercent prevent the ink to diposit on the fibre. While pulper running a lot of foam will form, to reduce foam we use foaming agent. Rest of the three chemicals i.e., Caustic soda, Borax and Sodium silicates enhance the activity of Surfacants.
Pulpers can be classified into a lot of types.

a) Based on power consumption
          1.  Low power consumption 
          2.  Medium power consumption
          3.  High power consumption

b) Based on Consistancy of pulp
          1. Low consistancy
          2. High consistancy

c) Based on model
           1) Hydra pulper
                    a) D-type
                    b) Horizantal
                    c) Vertical
          2) Drum Hydra pulper
          3)  Broke pulper 

Broke pulper: We use these type of pulpers in wet end and dry end of paper machine floor. "Broke is the paper that partially or fully manufactured paper or board". The purpose of broke pulper is dissolving broke from the machine to make the broke suitable for reuse. Broke system is an important fibre source for paper plant because it is fully finished product and also financially helpful. Paper broke form continously while process. The main area's of Broke forming are:

1. Trim cutting in wire section (Coutch pit rolls)
2. During web breaks in paper machine (Presses, size press)
3. While rewinding operation : as trim 
4. Rejected rolls
5. In cutting operations of paper (Sheeters)
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Hydrapulper: Hydra pulpers uses less power and also maintenance is simple. These type of pulpers are dynamically balanced. The impellors use both mechanical and hydro dynamical systems for dissolving pulp. Hydra pulprs again classified into many types for example Vertical Hydra pulper, Horizantal, D-type etc.,
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          D-type pulper is mainly used for old corrugated carton, waste paper and boxes. These type of puplers are present in D-type structure. Compared to traditional hydrapulpers these type of pulpers increases productivity without increasing the volume and momentum. Because of its D-type design it reduces the time of breaking pulp by incresing contact of pulp in less time in a rotation.
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Drum pulper: The more gentle mechanical action of Drumpulpers maintain maximum physical properties of fibre. This is a batch type pulper. This type of pulpers use less water and power.
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