Are you ready to start your paper pulp plant? It is important to be prepared to know the answer to some common questions in the wood pulp process. Answering these common questions can be a smart strategy. You can figure out what really is paper pulping process, and makes your wood pulp production smoothly.
1. What is paper pulping?
Paper pulping refers to the processing that changes wood fiber or other fiber materials into the fibrous matter. To be specific, paper pulping use chemical method, mechanical method or both of them to separate paper pulp from fiber materials. The basic pulping production line can be summed into 6 steps, materials preparation, pulp cooking, pulp washing, pulp screening, pulp bleaching and pulp storage. Common paper pulper machines for paper pulping include pulp digester, blow tank, vacuum drum washer, twin roll press, single screw press, disc filter, etc.
2. What are advantages of diluting white liquor with black liquor?
Black liquor: the waste liquor produced by the pulp cooking of the paper pulping process. The black liquor contains the inorganic substance, lignin, hemicellulose, organic acid, etc. and it is black brown.
White liquor: white liquor is a common name for cooking liquor in the paper and pulp industry. It usually consists of sodium hydroxide and sodium sulfide.
The cooking liquor is largely required in the real paper pulp production line. From the view of energy conservation and recovery, it is practicable to add certain content of black liquor into the white liquor. Specific advantages as following:
- Reduce the concentration of white liquor, less cellulose degradation;
- Achieve the goal of dilution without increasement of waste evaporation;
- Reuse the residual alkaline and heat of waste liquor;
- The hemicellulose of black liquor has lubrication action.
3. Why is the residual alkali needed in the alkaline cooking?
If the residual alkaline of black liquor is insufficient, at the end of cooking process, the organic acid produced from carbohydrate decomposition will reduce the pH value. If the pH value is less than 12, dissolved matters will be absorbed on the fibers, meanwhile, lignin of paper pulp will increase over time, and it will have the bad influence on next step. Besides, these dissolved matters are hard to remove in the pulp bleaching process. Especially when the pH value is equal to 6, sedimentation of lignin will reach its peak. So that is why we should control alkaline capacity.
4. What is the H-factor? What is the use of it? How to calculate it?
Definition: H-factor is a parameter that combines cooking temperature and cooking time.
Use: For same raw material, when the alkaline content, sulfidity, liquor ratio are all same, make the H-factor same and the pulp yield and lignin content of pulp will be same too. In another word, if you control the H-factor at same value, you can get pulp with same quality.
Calculating method: H-factor equals to product of average reaction rate and time interval under certain temperature. H=KR×△t
5. Why relieving in the alkaline cooking?
- Avoid the temperature error produced by false pressure;
- Relieving will boil the liquor, also reduce the temperature difference and concentration difference in the digester, good for liquid permeability and even cooking;
- In the pine cooking, relieving also discharge the turpentine and other volatile matters, recovery the turpentine.
6. What are differences between KP pulp and SP pulp?
- KP pulp has higher strength than SP pulp;
- KP pulp has lower whiteness than SP pulp;
- KP pulp has good applicability, apply for various kind of paper manufacture; SP pulp has long and soft fiber, but the applicability is bad.
- KP pulp has dark color, higher whiteness requires multiple bleaching processing; SP pulp basically has no need of bleaching treatment.
- Compared to KP pulp, SP pulp is easier to washing and be manufactured into paper.
7. How to decide the degree of vulcanization? Does bigger mean better?
According to the transition relation of alkaline content and sulfidity, when the alkaline content is, the sulfidity directly affect the numbers of sodium sulfide. Because the sulfide is directly applied to the delignification, the sulfidity has impact on cooking speed, pulp yield, and pulp quality.
In general, increase sulfidity within limits can shorten the cooking time, decrease lignin content and ensure high pulp yield. But too high sulfidity value will produce a negative impact on following aspects:
- Produce bad smell and environmental pollution;
- Increase the corrosion of paper pulper machine;
- When sulfidity over a certain value, the NaOH content can’t meet the requirement of delignification;
- The sulfidity is limited by alkaline recovery;
In conclusion, the sulfidity is not the bigger the better.
8. What are advantages of high temperature and low concentration in the defibrination?
- Due to the low concentration of defibrination, which means grindstone is easy to keep clean and reduce affection from regrinding and pasting;
- Full separation will increase the content of log fiber, reduce short fiber, improve pulp quality and increase the strength of paper;
- uniform load and stable production;
- The higher temperature of whitewater reduces the temperature difference between spray water and grindstone and prolongs the service life of grindstone.
9. What is the resource of pulp color?
The color of paper pulp comes from unsaturated group. Besides, there is another group that is called auxochrome, it can deepen the color of pulp. The combination of chromophore and auxochrome decide the color of paper pulp, chromophore directly decides the shade of color.
10. Why chemical pulp has least lignin content but darkest color?
To chemical pulp, although most of the lignin is removed, the degradation group of lignin, cellulose, and hemicellulose are mostly unsaturated group, and they still exist in the paper pulp. To mechanical pulp and other kinds of pulp, lignin content is large, but the functional group of most lignin is auxochrome, so they have a light color.
After learning the basic questions, do you want to know the cost-benefit analysis of paper pulp plant? As a paper pulp making machine manufacturer, CNBM has rich experience in providing paper pulp solution and paper pulper machine. if you have any question about paper pulp production line, welcome to contact us!
