Safe solutions to sticky situations
Published by Alfie Lloyd-Perks,
Editorial Assistant
World Cement,
One of the most critical aspects of successful cement production is the consistent flow of materials. Yet accumulations in ducts, chutes, cyclones and vessels often chokes the movement of materials, causing bottlenecks that create expensive impediments to plant performance, process efficiency, productivity and profitability. Buildup needs to be manually cleared with alarming regularity – unless, of course, the right technology is employed to keep things flowing smoothly.
Go with the flow
Preheater towers, in some form, have been in operation since the 1920s, and today’s cement plant designs can include as many as six stages in towers reaching up to 12 storeys (120 ft/35 m) tall. Preheaters operate on a tried-and-tested principle: the mix flows down a chute into a splash box, where it is lifted by the hot airflow of the riser duct into the top of a cyclonic collector. From there, the material passes through a valve to the next preheater stage, repeating this process until the material reaches the kiln feed inlet.
Effective as this process is, one of the biggest contributors to material buildup is the high heat and material velocity. As material gets hotter, it gets stickier, clinging to the sides of the flow chutes and splash box, as well as in the riser duct and elsewhere.
With the increased use of a range of waste-derived fuels, plus alternative raw materials such as shale replacements, in many cement plants around the world there is evidence of increasing hard buildup causing reduced and unstable flow. Large accumulations can even completely block the outlet of a cyclone. If left unchecked, clogs can form quickly, stopping the material flow, leading to unscheduled downtime and lost production.
Lancing the boil
To make matters worse, poor material flow also takes its toll on maintenance teams, not only diverting them from core activities but also presenting serious health and safety risks.
That is because the traditional way of dislodging buildup is to implement regular cleaning schedules, assigning workers with water lances extended through access holes. A worker ascends the tower and dons a thick full-body suit of high-heat personal protective equipment (PPE).
Lancing the material with high-pressure water clears the blockage and restores proper flow. Despite the risks, this procedure is typically done while the preheater is still in operation, causing a tremendous amount of heat and some molten material to blow back. The exposure to heat, manual handling, awkward and confined spaces and even the PPE itself makes preheater cleaning one of the most unpleasant jobs in a cement plant.
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Read the article online at: https://www.worldcement.com/special-reports/23102024/safe-solutions-to-sticky-situations/
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