Nathan Schindler, Evonik Corporation, explores the importance of evaluating the total cost of ownership of filtration equipment when controlling clinker cooler particle emissions.
The clinker cooler is a critical component in the production of quality clinker in a cement plant. As the cement industry continues to optimise clinker to meet more stringent quality requirements and reduce CO2 emissions from plants, proper and consistent cooling takes on greater importance. The cooler also has a significant impact on overall efficiency as the effective use of tertiary and secondary air improves efficient operation of the kiln and preheater, while heat lost from escaping cooler vent air reduces efficiency. In a new system, the cooler can be balanced for the fuel, production rate, quality of raw material, quality of product, and other factors. However, these factors change over the life of modern cement plants, frequently leading to a constant battle among competing priorities. These changes increase the total cost of ownership of operating and maintaining the cooler vent baghouse responsible for complying with strict particulate control emission limit.
Considerations in pulse-jet baghouse design for clinker cooler
Gas composition and particulates
Cooler baghouses need to be designed to handle the particular air and dust composition in the cooler vent airstream. Cooler vent air is fairly simple in its composition – hot air and fine, abrasive clinker dust. While most of the high temperature (up to 1500°C) leaving a modern clinker cooler is recovered and used in making clinker, the cooler vent air can be up to 300°C. Prior to entering the filter, the vent air needs to be cooled from 300°C to approximately 170°C, as 300°C is too hot to effectively dedust in a filter system. Clinker dust is abrasive and consists of mainly the finer particles carried off the cooler grate. Filter bags must be able to handle both the operating temperature of the baghouse and the loading of fine particles to operate efficiently and economically with long-life.
Cooler operations and performance
Over the life of a cement plant, it is common for raw materials, fuels, production levels, and product criteria to change over time. This is particularly true as cement plants seek ways to reduce their carbon footprint. These changes often require operators to attempt to adjust the flow to the cooler vent, increasing flow and/or temperature of the vent system. The filter operation and bag-life are frequently impacted by these changes resulting from higher air-to-cloth ratio, excess abrasive particulate, or higher operating temperatures. Upsets in the clinker cooler can cause catastrophic damage to filter bags. Snowmen, red rivers, and popcorn can cause excessive temperatures or dust loading to the filter. Uncontrolled hot air can destroy m-aramid filter bags in a matter of minutes. Excessive dust can penetrate the bags and cause a permanent increase in pressure drop through the baghouse, increasing operating costs of the filter.
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