The development and future prospect of pulp and paper technology



The invention of paper technology brought the spread and inheritance of human civilization into a new era, and the carrier of characters changed from heavy bamboo slips to light and easy to carry paper. It can be said that the emergence of paper changed the way of cultural transmission, so that the culture and historical materials of thousands of years ago can be preserved until now. However, due to the limitation of the technical level, the quality of paper was very poor when paper was just invented. With the continuous development of human science and technology, papermaking technology is also constantly changing, and the quality of paper is getting higher and higher, and the functions are getting more and more. At present, China has become the world's leading country in the manufacture and consumption of paper products, so it has become an urgent problem to study and solve to further improve the pulping technology to control production costs, improve paper quality and environmental pollution caused by the production process. As a papermaking industry practitioners, we must strive to innovate, absorb domestic and international advanced papermaking technology, further innovate the existing papermaking technology, and improve the quality and efficiency of papermaking.

1. Introduction

Pulping has a great impact on the quality of paper molding, so if you want to obtain high-quality paper, you must improve the quality of the pulping process. Generally speaking, pulping includes mechanical pulping, chemical pulping and semi-chemical pulping. Pulping generally refers to the pulp required to make wood into paper, and the use of special methods (generally referring to the use of mechanical, chemical or a combination of two ways) to make natural pulp or further bleaching of fiber raw materials extracted from trees and other plants. In the nearly one thousand years after the production of paper technology, due to the limited technical level, more mechanical pulping is used, and in recent years, with the development of science and technology, chemical pulping is more and more widely used, which greatly improves the efficiency of pulping and the quality of pulp. This paper mainly introduces the more and more widely used chemical pulping technology, and introduces the more advanced chemical bleaching methods, and analyzes the advantages and development prospects of chemical pulping technology.

2. Types and uses of chemical pulping technology

The common methods of chemical pulping technology are alkali process and sulfite process, of which the alkali process mainly includes caustic soda method and sulfate method, and the sulfite subprocess usually includes acid bisulfite method, bisulfite method, slightly acidic sulfite method, neutral sulfite method and alkaline sulfite method. Chemical pulping technology is an advanced technology that has developed rapidly in recent years, which is mainly used to make high-grade cultural paper, paper bag paper, national defense paper and fiber composite materials. In order to improve the quality of papermaking, save production costs and solve the environmental pollution problems caused by papermaking, all countries in the world are trying to innovate pulping technology, at the end of October 2014, the ninth China International Papermaking Chemical Technology and pulping equipment Exhibition was held in Shanghai World Expo Exhibition Center. In this exhibition, the more advanced chemical pulping raw materials and equipment in various countries are displayed, and the application of papermaking chemicals in the papermaking industry is introduced, as well as the major impact on controlling production costs, improving environmental pollution and improving the quality of papermaking, so that people deeply understand the important role of chemical pulping process on papermaking technology.

3. Development status of chemical pulping technology

As we all know, pulping is short for a series of processes, mainly including raw material selection, cooking separation of fibers, concentration, grinding, storage of logs, sawing, peeling, knotting, chipping, cooking, washing, screening, purification, bleaching, dipping and grinding to obtain this color paste board. With the development of chemical science and technology, more and more chemical technology has been applied to these production processes, which has made a significant contribution to the development of the paper industry. The following is an introduction to the application of chemical processes in several production processes. In the cooking of wood, the tower continuous cooking system and low-energy replacement intermittent cooking and other equipment are generally used, and the appropriate amount of caustic soda is added in the cooking process to increase the rate of dewood-removal, and most of the lignin is removed and continuously diffused into pulping, while also slowing down the dissolution of carbohydrates. However, it should be pointed out that the acquisition rate of using this method is low, generally around 50%.

In the previous grinding process, whether it is disk grinding or stone grinding, logs or wood chips are simply placed into the mill or stone grinder, and physical pressure is applied to promote the separation of fibers. Such a processing method is less efficient, and the construction investment is large, the most commonly used method is to carry out chemical pretreatment first, the use of chemical agents to make the structure of the log more relaxed, but also to soften the fiber. After chemical pretreatment, the grinding process becomes much simpler, and it also greatly improves the efficiency and quality of the processing, and improves the yield.

Bleaching is also a common process in the paper industry, in the ancient bleaching technology has not yet been born, the quality of paper is poor. We all know that lignins and extracts are the reason for the other colors of the pulp, and the purpose of bleaching is to add chemicals to improve the whiteness of the pulp. There are two common bleaching methods, one is to only let the chromophore group decolorization and retain the lignin, such bleaching is commonly used disulfite and sodium borohydride. The other type does not retain the lignin, and uses bleach to oxidize and dissolve the lignin. The two kinds of bleaching methods are that the former has a higher yield, but the whiteness of the obtained pulp is not high; The latter has a large loss and a low gain rate, but can obtain high whiteness pulp. In the actual production process, bleaching methods can be reasonably selected according to the different paper yield and whiteness.

In addition to the above two categories of traditional bleaching methods, hydrogen peroxide bleaching method has been more and more widely used in recent years. In the traditional bleaching methods, most of them use the reducibility of chloride ion for bleaching, and hydrogen peroxide, as a chlorine-free bleaching agent, has its unique advantages. The use of hydrogen peroxide as a bleach agent is to use its HOO- functional group, passivating and even eliminating the chromophore group, but can maintain the original structure of lignin. Because of its unique chemical properties, it is sometimes used as a multi-stage bleaching process to change the structure of the hair base group and maintain the whiteness of the pulp. However, its disadvantage is that the improvement performance of hydrogen peroxide for pulp whiteness is very limited, generally about 8%-10%.

4. Application prospect of chemical pulping technology

The role of chemical science and technology in improving pulping technology is self-evident, and with the continuous development of science and technology, new technologies will continue to be applied to pulping technology. Objectively speaking, although China is a large country in the manufacture and consumption of paper products, there is still a certain degree of gap between China's equipment manufacturing industry and Western developed countries, and the pollution problem caused by the paper industry is still severe. Simple use of mechanical pulping, the efficiency is relatively low, the production cost investment is large, and will inevitably cause more serious environmental pollution, so it is foreseeable that chemical pulping technology is bound to be more and more applications. The scientific concept of development requires us to develop environmentally friendly industries, as an industry with large environmental pollution, the paper industry needs to continue to innovate, analyze various problems in the paper making process, and use chemical methods to solve them. In general, chemical pulping technology is bound to get more and more broad development and application prospects in the future.

5. Conclusion

Whether the pulping technology is mature determines the quality of the paper, so it is very important to improve the pulping technology. Compared with traditional mechanical pulping, chemical pulping technology has its unique advantages, but we should also pay attention to absorb the advantages of mechanical pulping technology in the production process, integrate the advantages of chemical pulping technology and mechanical pulping technology, and constantly improve the pulping technology, catch up with the international advanced level, constantly improve the pulping level, and improve the quality of paper making. Solve the problem of environmental pollution caused by the papermaking process and develop environmentally friendly industries. Research on chemical agents in the process of cooking and bleaching should be carried out to improve the yield and further improve the method of pulping whiteness. Practitioners in the paper industry should constantly improve their professional literacy, improve professional quality, constantly understand and learn advanced foreign pulping technology and apply it to production, strive to achieve greater development of China's paper industry at a smaller cost, and constantly improve China's existing pulping technology.