Pulp and Paper Production
Paper, which is an important material in meeting the communication needs of societies, has maintained its importance since the first day it was discovered. The need for paper products has increased since the first times they started to be used and this increase is expected to continue in the future.
Today, worldwide paper consumption has exceeded 400 million tons/year. The contribution of paper in the field of technological and cultural development of countries is great.
The pulp and paper industry is classified as a heavy-scale manufacturing industry that requires intensive capital and energy.
The paper industry uses woody and herbaceous lignocellulosic material and waste paper as a raw material source and transforms it into cellulose and pulp as an intermediate product by mechanical, chemical or a combination of these. Finally, these intermediate products are converted to paper.
When examined from this point of view, paper production is one of the processes in which the highest benefit is obtained from plant material and it is transformed into products with high added value.
Nowadays, the paper industry, in which the most advanced technological approaches are used, has a very high investment and operating cost. It turns out that about five billion particles per second (fiber, fillers and additives, etc.) considering that Decoupage occurs between these particles by laying them at a speed of 60-80 km/ h from the ruler mouth, and paper with a length of about two km per minute can be produced from a paper machine, one can get an idea of how precise and technological this production technology is.
Thousands of paper products can be produced for many different uses. Paper and cardboard products can be classified in many different ways depending on the raw material properties used, the technological approach chosen and the end product properties.
The following classification can be given as the most general and simplified. These main paper classes are further divided into several subgroups:
According to their weight: Low, medium or high weight papers.
According to color properties: Colored, white, bleached or unbleached (brown) papers.
According to end use: Industrial, cultural and food papers.
According to the raw material properties used in its production: Papers produced from woody, herbaceous or secondary fibers.
According to the applied surface treatment properties: Super calendered papers with or without surface coating.
Sources of Raw Materials Used in Paper Production
Cellulose, which is the main skeletal element of the paper sheet structure and is 70-100% by type, is one of the most important natural polymers produced by living plant organisms on earth. The structure of cellulose is formed by the formation of β-1-4 glycosidic bonds of D-glucose sugars.When examined in this aspect, cellulose is a homopolymer. Cellulose is produced on earth from primitive plants (algae, moss, ferns, etc.) it has a very wide spread, ranging from highly organized plants (wood) and some bacteria. Although it is very common in the plant world, it is most commonly found in the cotton plant in its pure form. It can also be found in other ligno-cellulosic plants (wood, agricultural plants and herbs) at a rate of 30-70% along with chemical compounds such as lignin, hemicellulose and extractives. In plants such as algae and algae, which have less morphological development, there is a much smaller proportion (10-40%). It is preferred from a commercial point of view that it is obtained in significant quantities and in pure form from plants where it has a high spread, so that its chemical properties do not deteriorate.
Chemical Pulp Production (Cellulose Production)
One of the basic conditions for the production of quality paper and cardboard products with high physical and mechanical properties besides the degree of purity is the complete and effective removal of lignin, which is the most common in lignocellulosic plant cells after cellulose. This is only possible with the application of full chemical processes followed by multi-step bleaching processes. Worldwide, two full chemical cellulose production methods are most commonly used.
These are;
- Acidic sulfide full chemical pulp (Cellulose) production method.
- Alkaline sulfate (Kraft) full chemical pulp (cellulose) production method.
Mechanical Pulp Production (Cellulose Production)
Unlike chemical pulp production, these methods are used in the production of cheap paper and cardboard products with low physical and mechanical properties, where the degree of purity does not matter. Because, in this approach, the goal is not to remove lignin from the cell wall, but mechanical effects (crushing, scrubbing, shearing, etc.) with the help of which it is aimed to individualize the vegetable fibers. Two main mechanical pulp production methods are most widely used throughout the world.
These are;
- Stone mechanical pulp production (SGW).
- Refinery mechanical pulp production (RMP).