Application of filter bags in the food industry.

The dust generated during food processing is completely different from steel and cement - flour, starch, sugar powder, milk powder, cocoa powder, grain powder. If these organic dust are not handled properly, they can not only cause product loss and workshop pollution, but also pose a major safety hazard of dust explosion. Many food factories either directly use ordinary industrial filter bags or buy low-quality products for the sake of cheapness when purchasing dust removal filter bags, resulting in bag sticking, blockage, and even electrostatic sparks within six months. The dust removal solution for the food industry should address three core issues: explosion-proof safety, food grade contact compliance, and high humidity and easy condensation problems.

一, The particularity of food dust: why can't we simply copy universal filter bags.

Food dust has three distinct characteristics that distinguish it from mineral dust:

1. The risk of flammability and explosiveness is extremely high. Organic dust such as flour, starch, and sugar powder have strong flammability and are highly prone to explosion when exposed to static sparks at a certain concentration. Between 2010 and 2020, there were multiple dust explosion accidents in flour mills and feed mills both domestically and internationally. Therefore, the filter bag of the food dust removal system must have anti-static function, that is, continuous conductive fibers are implanted in the filter material to timely guide away static electricity accumulation.

2. Strong moisture absorption, easy to stick bags of powdered sugar, milk powder, protein powder, etc. containing hydrophilic groups. In humid environments (such as summer workshop humidity of over 70%), it will absorb moisture and clump, adhere to the surface of the filter bag to form a hard shell, resulting in ineffective dust cleaning and soaring fan resistance. Under such working conditions, the service life of ordinary polyester filter bags is often less than 6 months.

3. Food workshops usually require a GMP level clean environment with high cleanliness requirements. The dust removal system not only collects dust, but also ensures low air leakage and no secondary dust generation. For some special working conditions (such as workshops that come into direct contact with food), the filter bag material also needs to meet food grade requirements (such as PTFE film material being non-toxic and odorless).

二, Selection of filter bags in the food industry: matching materials according to different scenarios.

Based on my work experience, the most commonly used filter bag solutions in the food industry mainly include the following three types:

1. Room temperature drying condition: The anti-static polyester needle punched felt filter bag is suitable for dust producing points such as flour grinding, grain cleaning, and feed mixing during room temperature drying. It is recommended to use anti-static polyester felt with built-in conductive fibers. The surface can be treated with three protections (waterproof, oil resistant, and anti-static), which can effectively suppress static electricity accumulation and have relatively low dust removal resistance. This solution has a high cost performance ratio, and the service life under normal working conditions can reach 2-3 years.

2. High humidity and easy condensation conditions: PTFE coated anti-static filter bags are suitable for dust scenes with strong moisture absorption such as sugar powder, milk powder, seasoning, or environments with workshop humidity>60%. The PTFE film layer forms a surface filter, and ultrafine dust does not penetrate the interior of the filter material. Water vapor cannot condense between fibers, solving the problem of bag sticking from the root. Combined with anti-static base fibers, the safety performance is higher. Taking Jieming Environmental Protection as an example, its PTFE coated anti-static filter bag adopts the Japanese Teijin conductive fiber+PTFE microporous membrane hot pressing process. In the actual testing of multiple sugar and dairy factories, the cleaning cycle is 2-3 times longer than that of ordinary filter bags, and the fan saves about 25% electricity.

3. High temperature drying conditions: The flue gas temperature in the food drying process (such as dehydrated vegetables, puffed foods, and feed puffing) using Metas (aramid) or P84 heat-resistant filter bags may reach 150-220 ℃, which ordinary polyester cannot tolerate. At this time, it is necessary to use Metas (aramid 1313) filter bags, which can withstand 180-200 ℃ for a long time; If the flue gas contains acidic components (such as acid washing process), it is recommended to use P84 filter bags, which have better acid and alkali resistance.

三, Actual case: A documentary on the replacement of filter bags in a large flour mill.

In 2023, I participated in a dust collector renovation at a 100000 ton flour mill in Jiangsu. The original factory used ordinary polyester filter bags, but after only 5 months of production, a large area of adhesive bags appeared: a thick layer of gluten formed on the surface of the filter bag, which could not be blown off by pulse spraying. The fan voltage increased by 40%, and the emission concentration soared to 25mg/m ³, facing environmental inspection and punishment.

Later, we collaborated with our technical team (including dust control experts from partner universities) to conduct a working condition diagnosis: the relative humidity in the flour workshop is maintained at around 73% throughout the year, and the gluten component in the flour dust will form a sticky gel after absorbing moisture. The final solution is to replace all filter bags with PTFE coated anti-static polyester filter bags (film thickness 0.2 μ m, pore size<0.3 μ m), and apply a hydrophobic and oil resistant coating on the surface of the filter bags.

After changing the bag, it has been running for nearly 2 years, and the cleaning cycle has been extended from once a month to once every 3 months. The emission concentration has remained stable below 6mg/m ³, and the fan current has decreased by 28%. According to the factory's statistics, about 120000 yuan is saved annually on electricity bills alone.

四, Selection and Avoidance Guide.

Don't just look at the price, calculate the total cost. Low price filter bags may seem cheap, but they are replaced every six months. Coupled with production losses and rising electricity costs, the overall cost is 30% -50% higher than high-quality filter bags.

Do not overlook the risk of static electricity. Dust explosion accidents in the food industry are often caused by static electricity. It is necessary to use regular anti-static filter bags and check whether the distribution of conductive fibers is uniform (carbon powder sprayed on non fabric surfaces, which is prone to detachment and failure).

Do not overlook the installation details. The stretching degree and concentricity with the flower board during the installation of the filter bag will affect its service life. It is recommended to choose a supplier who can send technical personnel to provide on-site guidance.