一,The main reasons for dust difficulties in the sector and the main problems they cause
The dust issue with moulded pulp packaging arises from the combined influence of material characteristics and process deficiencies:
Not strong enough to connect fibres: A lot of short fibres, too many fillers, or problems with the grinding process (such cutting too many fibres and not enough fine fibres) can make the hydrogen bonding region between fibres smaller, which makes the skeletal structure loose. For instance, one company's ash content was too high (>20%), which allowed filler particles to fill the space between the fibres, which led to a 30% increase in the powder loss rate on the surface of the completed product.
Loss of control over process parameters: There is an imbalance between the specific energy consumption (KWh/T) and the specific edge load (SEL) for grinding. This could cause too much fibre cutting or not enough scouring. If the specific energy consumption of coniferous wood pulp is less than 250 KWh/T, the fibre stiffness drops by 15%. If the SEL value is not 1.65 J/m, the fibre length and adhesion will get much worse.
Interference in the production environment: When the amount of dust in the workplace is more than the standard (>3mg/m ³), electrostatic adsorption and mechanical friction will make the secondary dust pollution worse. A 3C electronic packaging company reportedly had a 12% rise in customer complaints because dust stuck to the surface of its products because it didn't have any mechanisms to get rid of it.
二, A systematic solution: from smart control to process optimisation
1. Improving process innovation: making a fibre strong bonding network
Control of dynamic specific energy consumption: specify up a graded pulping model and specify separate parameters for coniferous wood pulp (250 KWh/T) and broad-leaved wood pulp (80 KWh/T). A company in Shandong has improved the model, which has led to a 15% increase in the tensile strength of finished paper and an 8% decrease in the amount of wood pulp needed to make a tonne of paper.
Improving the design of the grinding disc: a shallow tooth broad groove grinding disc (such the 2.4/2.8/6.1 tooth type) is used to make the fibre broom stronger instead of cutting it. Fernando Mora, a French expert on pulping, said, "The essence of pulping optimisation is to find the golden balance between fibre cutting and pulverisation."
Regulating the concentration gradient: The best concentration of coniferous wood pulp is 4.05%, and the best concentration of broad-leaved wood pulp is 4.55%. To make the pulp more consistent and cut down on dust created by fibre breakage, the concentration of southern pine pulp needs to be cut down to 3.7% because the fibres are long and coarse.
2. Surface enhancement technology: creating a physical barrier to protect the surface
Anionic phenylpropanoid sizing agent: Adding surface sizing agents like JH-WH300 can make a layer on the surface of paper sheets that is resistant to wear and tear and makes the surface 40% stronger. A certain food packaging company used the product, and its temperature resistance went up from -18 to 120 degrees Celsius, and its powder drop rate went down to less than 0.5%.
Nanocoating technology: The sol-gel process puts SiO ₂ nanoparticles on the surface of the packaging to make a thick, water-resistant layer. Tests have revealed that the coating may make the contact angle 152 ° and cut down on dust adhesion by 90%.
3. Smart dust removal system: it can regulate dust during the whole operation.
Source suppression: Put dust coverings on important machines including forming machines and grinding machines, and utilise negative pressure suction devices to keep the dust level below 1mg/m ³. Dongguan Sirui Electronic Equipment Co., Ltd. makes an electrostatic precipitator that removes 99.2% of dust by linking high-pressure cyclone dust collection and negative pressure dust collection.
Finding things online: Use machine vision systems and high-resolution cameras (at least 5 million pixels) along with AI algorithms to find problems like water stains, burrs, and damage in real time. When a certain company put the system in place, the yield rate went from 82% to 97%, and the speed of detection went up to 120 pieces per minute.
End-of-pipe treatment: The combination of "pretreatment, zeolite wheel concentration, and catalytic combustion" is used to treat VOCs and dust from the drying process in a way that works together. After a certain paper company used it, the concentration of non-methane total hydrocarbon emissions was consistent below 20 mg/m³, and the heat recovery rate went up to 85%.
三,Checking the benefits of industry practice
Lenovo ThinkPad uses bamboo fibre moulding packaging for its electronic products. By improving the grinding process (SEL=1.65 J/m) and the way glue is applied to the surface, the strength of the package surface is raised by 30%, the number of complaints about electrostatic adsorption is decreased to zero, and the cost of cleaning dust each year is saved by 2 million yuan.
Food packaging case: A food box company used nano coating technology on their product, which passed FDA certification. The product was 50% more resistant to grease and didn't powder when frozen at -18 °C. It went from 12% to 28% of the market.
Environmental benefits: The China Paper Association says that the full use of dust removal systems in the moulded pulp packaging industry has cut annual dust emissions by 12,000 tonnes, which is the same as saving 18,000 tonnes of standard coal. This has big carbon reduction benefits.
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