Electricity + Control September 2016

SENSORS, SWITCHES + TRANSDUCERS

How to work smarter, not harder

Jan Gerritsen, Endress+Hauser

A cement company mastered the challenge of dust formation, abrasion and high temperatures for reliable level measurement in clinker silos with the help of a self-learning smart sensor.

C ement is a fundamental part of life, and demands are high in respect to the quality of this construction material. Different varieties are created by joint grinding of the basic clinker with a gypsum anhydrite mixture, with gypsum rock or blast furnace slag and other aggregates. The current construction market situation demands a high level of flexibility and fast switching of varieties from production plants. This is why system availability and storage capacity in the clinker silos are becoming more and more important. However, clinker silos differ from typical bulk solids silos in terms of their size and the stacking and discharge systems associated with this. This means that it is fairly common for a central column to be incorporated in the silo, with various openings. As well as being abrasive, clinker typically forms fine dust clouds during storage. As the clinker is transported directly out of the kiln and into the silo via the cooler, the bulk solids have a high residual heat – temperatures which may exceed 100°C. All these factors make reliable level meas- urement very challenging. This is particularly true as the installation location for themeasuring technology is often defined by local factors. Challenging conditions for measuring technology One clinker silo at a Cement Factory presented particularly challeng- ing application conditions for measuring technology. In addition to dust formation, abrasion and high temperatures, massive structures impeded reliable level detection. Strong false echoes occurred caused

by the filling device via a flanged central column in the clinker silo with various openings. To date, these problems were frequently resolved by means of an electromechanical plumb line system. The disadvantage of this contact-based measurement system as far as abrasive media are concerned is the high amount of maintenance required. To reduce this, ultrasound devices are frequently used which are contact-free. But this technology in turn has its physical limitations in terms of very strong dust formation. Solution The solution for this cement factory: The Micropilot FMR57 bulk solids radar measuring device from Endress+Hauser. Because this free-space radar device combines the no-contact approach and the resistance to dust. False echoes are also no problem for the smart sensor which features multiple echo detection and uses clever evalu- ation algorithms to compensate for these disruptive factors. The self-learning software algorithms in the Micropilot are capa- ble of monitoring and characterising up to 20 microwave reflections

simultaneously: • Level signals • Interfering signals • Doppler signals • Ground signals

Electricity+Control September ‘16

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