Article written by Kurt Gieselman, Jim Cahill on 10/21/2021 – Read the Original Article
Advanced automation technology from Emerson is helping to solve a range of solids level measurement challenges at a large lime processing plant in the US.
The need to reduce costs and increase operational efficiency is driving greater adoption of automation technology. For producers of lime, limestone and clay products, automation is key to continuous production. However, due to the processes involved and the nature of the products, conditions in lime processing plants are particularly harsh, which creates a challenging environment for instrumentation. In a Powder & Bulk Solids magazine article, ‘Meeting the level measurement challenges at lime processing plants’, Kurt Gieselman, a senior field sales specialist for Rosemount™ measurement products at Emerson, explains that:
…In general, the biggest instrument challenge producers face is obtaining reliable and accurate level measurements of solid materials. That includes measurement of the crushed and powdered limestone, coal in silos that feed kilns, and hydrated lime as it is produced. All these applications have challenging operating conditions due to the weight of the material, dust, and low reflectivity of the surface.
The article describes several challenging solids level measurement applications at a large lime processing plant in the US. The first involved a hydrated lime surge bin, through which finished product passes before being conveyed to large storage silos. Achieving a stable level measurement was challenging because the material tended to compress in some areas and create gaps and bridges in others. Kurt explained that:
…To prevent this, pneumatic vibrators are used to shake and re-distribute the material. Previously, a capacitance probe had been used to perform the level measurement, but its measurements were erratic and slow to respond to level changes. In addition, the high vibration shortened the lifespan of the capacitance unit to only a few months. As the surge bin is only four feet tall, this made guided wave radar the ideal choice.
A Rosemount 5303 guided wave radar (GWR) level transmitter from Emerson was selected to replace the capacitance probes. The device is available with a remote housing extension for mounting the transmitter head away from the probe, which protects the electronics from the vibration, helping to extend the lifespan of the device. A critical advantage of GWR devices is their ability to provide accurate measurements in small tanks with rapidly changing levels, which is essential for this application. The Rosemount 5303 is proving to be reliable and maintenance-free, and the improvement in measurement accuracy has allowed the process to become more stable.
Another challenge involved two 112ft silos that store coal used to heat the kilns. Accurate level measurement is required for inventory purposes, as coal is pulled from the two silos simultaneously and the measurements are used to determine when to order more coal. The silo must be ready to receive the full amount of coal from the barge when it arrives, as receiving only a partial load is costly and inefficient, so good inventory management is essential. The article explains that…