Pulping Process Flow
Continuous pulping is the development direction of pulping equipment. The intermittent pulping method is rarely used now. Currently, most paper mills have adopted continuous pulping equipment such as disc mills and conical pulping machines. With the increase in the production scale of papermaking and the improvement of the paper machine speed, a single pulping equipment is often unable to meet the quality requirements of pulping. Therefore, multiple equipment are usually connected in series for pulping. The determination of the pulping process flow is related to the type of paper produced, the selected pulp, and the production scale, as well as the performance of the Polyester Forming Fabric used in the subsequent forming process.
For the production of toilet paper, the requirements are for the paper to be soft and have good water absorption, but the strength of the paper is not highly demanded. Therefore, the pulp mainly consists of disintegration, and only mild pulping is needed. Generally, a single stage of pulping is sufficient. Thus, a single pulping machine can be used for one-stage pulping. For this type of paper, during the forming stage, an appropriate Polyester Forming Fabric is usually selected to ensure the smooth dehydration and formation of the pulp.
For the production of oil-resistant paper, tracing paper, etc., the requirements are for high density and good bonding strength of the paper. Therefore, the pulp needs to have a high degree of pulping, and a multi-stage pulping method is required. For example, using 5-6 stages of pulping. Thus, multiple machines need to be connected for multi-stage pulping. The high degree of pulping is more dependent on the stable water filtration performance and structural strength of the Polyester Forming Fabric to ensure the paper quality under high-speed formation.
In addition, for many paper types, two or more types of pulp are required. These pulps have different pulping characteristics. Therefore, based on the type of production, scale, etc., either separate pulping methods or mixed pulping methods can be selected. Different pulping processes will directly affect the dehydration rate of the pulp on the Polyester Forming Fabric and the uniformity of formation.
The separate pulping process involves pulping the bleached coniferous wood chemical pulp and the bleached broad-leaved wood chemical pulp separately, until the desired pulping degree is achieved. Then, the pulps are mixed in a mixing tank. During the production process, the damaged paper produced undergoes processing such as shredding, and is sent to the damaged paper tank as shown in the figure. It is then subjected to disintegration processing by a disintegrator and enters the mixing tank. The pulping slurry mixed uniformly in the mixing tank is sent to the post-grinding mill (also known as the uniform grinding mill), which helps to make the mixture of different pulps more uniform. This pulping process can effectively control the pulping quality of each type of pulp, but it has a relatively high investment cost. Combining with high-quality Polyester Forming Fabric can further improve the stability and yield of the final paper product.
The mixed pulping process involves blending the bleached coniferous wood chemical pulp and the bleached broadleaf wood chemical pulp in accordance with the process requirements at a specified ratio, and then conducting the pulping. Since broadleaf wood pulp is easier to be fibrillated and sized during the pulping process compared to coniferous wood pulp, this pulping method may result in excessive fibrillation and cutting of the broadleaf wood pulp, while the coniferous wood pulp is still less fibrillated and cut. Therefore, this pulping process has uneven pulping quality, but it has low production power consumption, low investment, and is suitable for paper mills with smaller production scales and lower requirements for paper quality.
