#paperpulpmachine

How many can you say about the effect of recycling white water quality on paper making?

The effect of recycling white water quality on paper making

1. For making high-grade paper, the pulp, which is pulp workshop sent to the paper workshop, produce white water, because of the residual chlorine of the white water is high, it affects the paper machine color matching, sizing and so on, generally the white water will directly reuse to the paper workshop, and the water can be recycled to the pulp workshop for reusing.

2. Reuse white water usually contains small fibers, fillers, sizing material and other additives, when the suspended solids is high, will increase the ash content of finished paper, thus affect the paper strength.

3. After repeated recycling of reuse white water, microorganisms in the water multiply in large quantities, easy to cause pulp system appears rotted pulp mass, in the pulp chest and pipe wall will easy to form fog, microorganisms fall off and mix into the pulp, resulting in paper holes and paper machine broken.

4. Due to the use of fillers and other saline materials, calcium and magnesium in the white water increase, water hardness rise, hard water is adverse for paper sizing. For acidic sizing, because Ca2+, Mg2+ in the water will act with saponified sizing material, and form insoluble calcium soap and magnesium soap, thus result in the loss of rosin size.

5. In the white water with AKD sizing, due to the fiber content is higher than the filler surface, sizing material tends to adsorb on the filler surface, the AKD, which is adsorbed on the filler surface, doesn't have a positive effect on the sizing. If the filler is not retained, then the sizing material also will flow into the white water, if this white water reuse again, some of the original sizing material, which is adsorbed by the filler, will redistribute in the fiber surface, after drying to produce sizing chest effect.

6. White water reuse also have a great effect on paper dyeing. On the one hand, due to the white water contains a part of the toner, it is benefit for paper color mixing, and the stability of white water reuse plays an important role in the paper stabilizing. On the other hand, because of the increase of white water hardness, will reduce the dyeing ability of dye.

7. In the process of papermaking, there are wood residue, resin acid, sizing agent, retention aid and other surfactants in the pulp, large number of foam produced in the white water, the gas in the reuse white water will cause the paper machine fluctuation, at the same time is not conducive to the wire part dewatering, the paper appears "needle eye" and eventually affects product quality.

Waste paper furnishes are defiberized by means of continuous turnover (by falling inside the rotating drum). This action separates fibers gently from contaminants, with minimal fiber loss. The contaminants are rejected continuously and automatically. The drum has two sections (pulping and screening): Wetting, chemical impregnation, and defiberizing take place in the pulping section, while fiber recovery and reject separation are assigned to the screening section.

Benefits of the Leizhan Drum pulper

Making pulp

1 Several processes are commonly used to convert logs to wood pulp. In the mechanical process, logs are first tumbled in drums to remove the bark. The logs are then sent to grinders, which break the wood down into pulp by pressing it between huge revolving slabs. The pulp is filtered to remove foreign objects. In the chemical process, wood chips from de-barked logs are cooked in a chemical solution. This is done in huge vats called digesters. The chips are fed into the digester, and then boiled at high pressure in a solution of  Paper sodium hydroxide and sodium sulfide. The chips dissolve into pulp in the solution. Next the pulp is sent through filters. Bleach may be added at this stage, or colorings. The pulp is sent to the paper plant.

Beating

2 The pulp is next put through a pounding and squeezing process called, appropriately enough, beating. Inside a large tub, the pulp is subjected to the effect of machine beaters. At this point, various filler materials can be added such as chalks, clays, or chemicals such as titanium oxide. These additives will influence the opacity and other qualities of the final product. Sizings are also added at this point. Sizing affects the way the paper will react with various inks. Without any sizing at all, a paper will be too absorbent for most uses except as a desk blotter. A sizing such as starch makes the paper resistant to water-based ink (inks actually sit on top of a sheet of paper, rather than sinking in). A variety of sizings, generally rosins and gums, is available depending on the eventual use of the paper. Paper that will receive a printed design, such as gift wrapping, requires a particular formula of sizing that will make the paper accept the printing properly.

Pulp to paper

3 In order to finally turn the pulp into paper, the pulp is fed or pumped into giant, automated machines. One common type is called the Fourdrinier machine, which was invented in England in 1807. Pulp is fed into the Fourdrinier machine on a moving belt of fine mesh screening. The pulp is squeezed through a series of rollers, while suction devices below the belt drain off water. If the paper is to receive a water-mark, a device called a dandy moves across the sheet of pulp and presses a design into it.

The paper then moves onto the press section of the machine, where it is pressed between rollers of wool felt. The paper then passes over a series of steam-heated cylinders to remove the remaining water. A large machine may have from 40 to 70 drying cylinders.

Finishing

4 Finally, the dried paper is wound onto large reels, where it will be further processed depending on its ultimate use. Paper is smoothed and compacted further by passing through metal rollers called calendars. A particular finish, whether soft and dull or hard and shiny, can be imparted by the calendars.

Pulp Varieties

Mechanical Pulp

Stone Groundwood pulp: mechanically grinds the wood into relatively short fibres.  End-use: the resulting pulp is used mainly in newsprint and wood-containing papers, such as lightweight coated (LWC) and super-calendered papers.

Thermo-mechanical pulp (TMP): the wood particles are softened by steam before entering a pressurised refiner.

          End-use: TMP has mainly the same end-uses as Stone Groundwood                   pulp.

Variants of the above two processes are also possible.

Semi-chemical pulp

Semi-chemical pulp: produced in a similar way to TMP, but the wood particles are chemically treated before entering the refiner.

          End-use: this pulp has properties suited to tissue manufacture. Some chemi-thermo mechanical pulp is used in printing and writing grades.

Chemical pulp

Sulphite pulp: produced by cooking pre-cut wood chips in a pressure vessel in the presence of bisulphite liquor. The pulp may be either bleached or unbleached.

          End-use: ranges from newsprint, printing and writing papers, to tissue and sanitary papers.

Sulphate/Kraft pulp: pulp produced by cooking wood chips in pressure vessels in the presence of sodium hydroxide (soda) liquor. The pulp may be unbleached or bleached.

          End-use: widespread uses - pulp used for graphic papers, tissue and carton board, wrappings, sack and bag papers, envelopes and other speciality papers.

Deinked pulp

Paper is made from the cellulose fibres that are present in hardwood and softwood trees . Whether using wood or recovered paper, the first step is to dissolve the material into pulp, and this need pulper equipment. Regardless of the type of pulping process used, the wood or recovered paper is broken down into its component elements so that the fibres can be separated. The pulping results in a mass of individual fibres being produced. The fibres are then washed and screened to remove any remaining fibre bundles. The water is then pressed out and the residue is dried.