Filter Bags For The Future

In the world of filtration, there are many considerations and tradeoffs to be made when choosing the best option to meet the specific application needs of a cement plant. As plants age and the production and environmental demands evolve, it is common for the operation of a filter baghouse in a cement plant to require some improvements to meet these challenges. Different types of fuels, fuel blends, a variety of changing raw materials, and the introduction of new kinds of finished products all put additional demands on the baghouse systems. Air flow, production rate, cleaning pressure, and the overall capability of the baghouse cleaning system logic are some of the variables that need to be taken into consideration when choosing the best possible filter media for a plant’s specific goals.

Cementos y Concretos Nacionales, SA de CV, part of the Cruz Azul Group, is located in the municipality of Tepezalá in the state of Aguascalientes, Mexico, and has an installed production capacity of 2 million tpy of clinker, thus contributing to the presence of the Cruz Azul brand in the Central – Western – Northern region of the country.

For the engineers at Cementos y Concretos Nacionales (CYCNA) a challenge presented itself in 2021. The demand for production was increasing, along with the growing use of co-grinding petroleum coke with coal and the need of a more efficient operation within the coal mill. Additionally, despite the desire for more production, the plant needed to remain confidently compliant with the national emissions standards.

The challenge

The plant had been using GORE® High Durability Filter bags in their coal mill baghouse up until this time. These bags are comprised of a high performance ePTFE membrane laminated to a scrim supported polyester felt substrate weighing 543 g/m². Due to the desire for increased production, the plant began to consider the potential use of a newer class of membrane bags, LOW DRAG Filter Bags. Today, both High Durability and LOW DRAG Filter Bags are used globally in kiln, cooler, finish mill, coal mill, as well as other critical applications in cement plants. High Durability Filters are designed for long life, low emission rates, and low differential pressure under extreme conditions. When Gore introduced LOW DRAG Filters, this innovation allowed cement producers to continue to achieve the longest filter bag life possible, while also reducing particulate matter emissions and increasing airflow compared to other filters, due to having the lowest possible in use filter drag. To clarify, filter drag is defined as differential pressure/air to cloth ratio. Prior to 2021, the coal mill was being operated with High Durability Filter Bags and, although the performance was great, due to the evolution of moving to a high pet coke/coal mix to feed the kilns, the baghouse and filters were pushed to their limit, prompting the plant to seek alternative options.

Since co-grinding petroleum coke with coal often creates a much finer dust load and potentially a wetter dust cake, Gore requested the plant to send a sample of the dust to perform a dust challenge test to both the High Durability and the LOW DRAG Filters. These dust challenge tests include presenting a sample of the dust to the collection side of the filter media, then pulling a strong vacuum across the dust cake and filter media. The filters are then cleaned using a simulated cleaning process to check for residual fine dust on the membrane. The test is then repeated with the addition of moisture by spraying water on the dust cake before the vacuum challenge is implemented. The results with the plant's specific coal/pet coke dust sample showed that, while the High Durability Filter worked well, the LOW DRAG Filters cleaned to an essentially new state. After completing the dust test with positive results, the plant moved forward with the purchase and installation of a complete set of LOW DRAG Filter Bags.

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Read the article online at: https://www.worldcement.com/special-reports/24062025/filter-bags-for-the-future/