Rice Straw/Sugarcane Bagasse Pulp To Paper Machine
.1.When using rice straw or sugarcane bagasse pulp in a paper machine, here's a general overview of the process:
Preparation of the Pulp
- Rice Straw Pulp: Rice straw first needs to be collected and then undergo a series of pretreatment processes. This includes cleaning to remove dirt, stones, and other impurities. Then, it is usually cooked with chemicals such as sodium hydroxide in a digester to break down the lignin and separate the fibers. After cooking, the pulp is washed thoroughly to remove the chemicals and the dissolved lignin.
- Sugarcane Bagasse Pulp: Bagasse is the fibrous residue left after sugarcane is crushed for juice extraction. Similar to rice straw, it is also cleaned and then subjected to a pulping process. Chemical pulping methods can be used, like the kraft or soda - anthraquinone process, which helps in separating the fibers and removing lignin to a large extent.
Stock Preparation for the Paper Machine
- The prepared pulps are then diluted to a suitable consistency (usually around 0.5 - 1.5% solids content) in a mixing chest. Additives such as fillers (like talc or calcium carbonate to improve opacity and smoothness), sizing agents (to control water absorption of the paper), and retention aids (to help retain the fillers and fibers on the paper web) are mixed in at this stage.
- The pulp slurry is then passed through a series of screens and cleaners to remove any remaining debris or oversized particles that could clog the paper machine or affect the paper quality.
The Paper - making Process on the Machine
- Formation: The pulp slurry is fed onto a moving wire mesh (Fourdrinier wire or a twin - wire former). As water drains through the wire due to gravity and vacuum suction, the fibers start to interlace and form a wet paper web. The speed of the wire and the consistency of the pulp play a crucial role in determining the formation and thickness of the paper.
- Pressing: The wet paper web is then passed through a series of press rolls. These rolls squeeze out more water from the web and also help in consolidating the fiber structure. The pressure applied and the number of press nips can vary depending on the desired paper properties and the type of machine.
- Drying: After pressing, the paper still contains a significant amount of moisture. It is then dried using steam - heated cylinders. The paper passes over a series of these cylinders, and as the heat is transferred, the moisture evaporates, leaving behind a dry paper sheet.
- Calendering: Finally, the dried paper may go through a calendering process. Calender rolls with different surface finishes and pressures are used to smoothen the paper surface and control its thickness and density. This step gives the paper a more uniform appearance and better printability or other end - use properties.
2.Why is pulp quality important for paper making?
The quality of pulp is extremely important for paper making. Firstly, high-quality pulp can enhance the strength of paper. For example, paper used for packaging is prone to damage during packaging and transportation if the pulp quality is poor and the strength is insufficient.
Secondly, the quality of pulp can affect the whiteness and color of the paper. When producing paper with high color requirements such as printing paper, high-quality pulp can make the paper color more uniform and white.
Furthermore, it is also crucial for the smoothness of the paper. Good pulp can make the surface of paper smoother, ensuring smooth writing and clear printing for both writing and printing papers.
3.What types of pulp are suitable for producing?
Mechanical wood pulp
-Suitable for producing news paper. Because mechanical wood pulp contains a high amount of lignin, the paper is prone to yellowing and becoming brittle, but it can retain the original strength of wood fibers, and has high production efficiency and low cost. Newsprint does not have high requirements for paper durability and is mainly used for printing newspapers for short-term reading. The characteristics of mechanical wood pulp perfectly meet the needs of newspaper.
-Suitable for manufacturing writing paper and printing paper. Chemical wood pulp is used to treat wood through chemical methods, removing most impurities such as lignin. The fibers are longer and have high strength, which can give the paper good tensile strength and toughness. When used for writing, the paper is not easily damaged, and when used for printing, it can withstand the pressure and friction during the printing process to ensure printing quality, such as books, magazines, and other paper.
Sulfate wood pulp
-Suitable for packaging paper and specialty paper. Its fiber strength is high, and the paper made from it is tough and durable. In terms of packaging paper, it can withstand a certain weight and pressure to protect the packaging items. For special paper, such as some paper that requires waterproof and moisture-proof functions, through appropriate processing, kraft pulp can meet its special requirements.
Dissolved paper pulp.
-Mainly used for producing artificial fibers, glass paper, etc. Dissolved pulp contains almost no lignin, has high purity, and can be dissolved in specific chemical solvents, and then made into other materials through recycling processes, such as viscose fibers for textiles and glass paper for transparent packaging materials such as food packaging.
Straw pulp.
-Suitable for producing household paper such as toilet paper. Straw pulp has a wide range of sources, low cost, short fibers, and is relatively soft. This characteristic makes the produced toilet paper comfortable to touch, while also meeting its basic requirements for disposable use.
4.What types of grass are used to produce straw pulp for household paper?
There are various types of straw pulp raw materials used for producing household paper.
Reed is one of the common raw materials, and its fiber length is moderate, which can give paper a certain strength. It is also abundant in resources and often grows in wetlands, riverbanks, and other environments.
There is also bamboo, whose fibers are slender, making household paper relatively soft and strong. Bamboo grows rapidly and is a sustainable raw material for papermaking.
In addition, sugarcane bagasse can also be used for pulp production. In the sugar industry, a large amount of sugarcane bagasse is produced, and its fibers can be used for papermaking after treatment, which can reduce costs to a certain extent and is more environmentally friendly.
