Spray technology is used in many different applications in the pulp and paper industry.
In the papermaking process, nozzles are used in every process, from the headbox, the net press section, the drying section to the winding section.
The effectiveness of the nozzles directly determines the quality of the paper and the service life of the various fabrics. Inappropriate selection of nozzles can also lead to paper diseases such as crimping, flooding, wrinkling and pinhole banding.
The following is a brief introduction to several types of nozzles in the application of paper and pulp:
Edge-cutting water jet
A technology widely used in the paper industry, mainly for edge cutting and trimming of paper.
High-pressure water jets are used to cut and chip the edges of paper to achieve precise and flat edges. Due to the high-pressure jet, the edge cutting water jet enables high-speed, effective, precise cutting and trimming of the paper’s edges.
In addition, the use of edge cutting water jet reduces pulp loss and improves the efficiency and quality of paper production.
Water jet usually utilizes a needle-type nozzle, which operates under high pressure conditions, and to increase nozzle life, a core made of high-pressure and abrasion-resistant materials is often used.
Starch coating
One of the most important raw materials.
Starch improves stability in the papermaking process. Starch coating increases strength and durability, improves gloss and smoothness, enhances printability, strengthens moisture resistance as well as raises density and thickness of the paper.
Uniformity of starch coating is very important and starch solution can be applied uniformly through atomizing nozzles. Hollow cone nozzles have good atomization performance and can be used for starch coating.
Chemical antifoaming
The entire pulp and paper industry is affected by foam to varying degrees, which can disrupt normal production, degrade paper quality and, in severe cases, prevent production from continuing.
The affected operations include washing, screening, bleaching, thickening, stock supply systems, surface sizing, coating and black liquor recovery.
Nozzles can spray chemical defoamers uniformly on the surface of the slurry, causing them to spread rapidly and adsorb on the surface of the bubbles, which can change the surface tension and stability of the bubbles, causing them to break up and dissipate quickly to achieve the effect of defoaming.
The nozzle can realize the precise control and adjustment of the chemical defoamer, make its defoaming effect in the pulping process to achieve optimization, so as to improve the efficiency of pulping and product quality.
Usually, full cone nozzles and spiral nozzles are used to complete the operation.
Web cleaning
One of the key parts, responsible for evenly distributing the pulp over the paper machine web, forming the base structure of the paper.
The effect of web cleaning is a critical part of the papermaking process that cannot be ignored. The web needs to be cleaned frequently to maintain its normal operation and production quality, and most of the paper diseases are greatly related to the cleaning effect of the web.
High-quality nozzle products have a significant effect on the cleaning effect and production efficiency. A common net cleaning method is the use of high-pressure nozzles, high-pressure water flow can effectively remove the dirt and fiber residues on the web to keep it clean.
In addition, the spray direction and angle of the nozzle need to be adjusted to ensure that the water spray coverage and intensity is appropriate to avoid damage to the web.
Dry net cleaning
An important part on the paper machine, which bears the role of filtration, pressing and drying of pulp.
After a period of time, the dryer fabric will accumulate a large number of fibers, particles and dirt, these impurities will affect the filtering efficiency and operational stability of the dryer fabric, so it needs to be cleaned.
Usually use high-pressure water jet to clean, which requires high wear-resistant and high-pressure performance of the nozzle.
Low pressure cleaning and lubrication
Generally fan nozzles are used with pressures of 3-5 bar.
The choice of nozzle has a direct impact on water consumption and clogging, the correct choice has a significant effect on water saving, energy saving and spray effect.
High pressure felt cleaning
Felt is a very important part of the papermaking process and needs to be cleaned regularly to ensure it is clean and in good working state.
Using high-pressure nozzles for felt cleaning is an effective method, and it is generally recommended to use 1.0-1.5MPa pressure for continuous spraying during the operation of the paper machine in order to achieve the purpose of effective washing.
At the same time, it is necessary to adjust the movement and speed of the high-pressure spray hose, to avoid streaks caused by overlapping or missed spray.
When choosing nozzles, it is recommended to use fan- nozzles to flush the running surface directly, in order to ensure the uniformity of the spray. This can effectively remove the dirt and impurities on the surface of the felt, and will not damage the fleece on the surface of the felt at the same time.
Humidification in the post-processing section
Humidity control in the paper industry is to control the loss of moisture from the paper after drying.
The moisture on the surface of the paper changes with the surrounding humidity, which can cause problems in the cutting and packaging processes. A paper mill shop needs to control humidity at 45% to 60% to ensure the quality of the paper.
Not only that, humidification can also reduce the concentration of dust in the environment and alleviate the dust flying phenomenon caused by static electricity. Usually use fine atomizing nozzle and air atomizing nozzle to control the temperature and humidity.
Conclusion
In short, the nozzle plays an extremely important role in the papermaking process, the selection of the correct nozzle is the key to achieve the best results.
Professional selection of nozzles can not only effectively guarantee the quality of the product and improve the service life of the equipment, but also to avoid waste and increase in operating costs.
