Sinter production makes use of a combination of iron ore, heat and coke to prepare iron ore for steel manufacturing. This application is typical of a large number of such applications in the ore processing industry which are very similar to steel making and coal power plants applications. These applications present a combination of challenges to silo level measurement.
Application Example
Details of an application at a customer facility as shown in Figure 1 are provided below:
- The silos were all geometrically lined up with common height of 18 m
- Several conveyors and tripper cars load the silos independently at the same time
- Several of the silos were constantly being filled or emptied at the same time
- There is always a situation of “rat-holing” of the product in the silos. The rat holing at times only leaves a tiny percentage of the silo flowing, especially in the constantly filling silos.
- There is a wide range of particle sizes from fist-size rocks to powder
- The materials with small particle size create dust.
- Extreme peaking and slumping of the material
- Diverter plates can greatly vary the location of the falling fill stream
- Product color and dielectric constant vary greatly
- High Vibration when silo vibrators are turned on
Figure 1. Steel manufacturing facility
The customer tried several radar, capacitance and ultrasonic transmitters for several years without any success. The most recent sensors installed were capacitance level switches which had all failed in the application for a variety of reasons and required the staff to monitor the silos visually 24 hours a day.
Reasons for the failures were easy to see and understand, and included the following:
- Moving location of the Rat-holes
- Worn through Sensor cables
- Changing dielectrics due to material and moisture changes
- Uneven Coatings
- Peaking and slumping of the material
Solutions Offered by ABB
ABB LM80 laser level transmitters, as shown in Figure 2, were tested and were successful in providing level readings on the silos.
Figure 2. ABB LM80 laser level transmitters
The signal from the LM80 was connected to the DCS, and used to adjust the speed of the conveyors, and turn on the vibrators on the silos when rat-holing was excessive. Particle size, dust and color were not an issue for any of the silos, including the powdered limestone, with the exception of the recycled fines, which has the consistency of fly ash. In this environment, the LM80 cannot penetrate the dust beyond a distance of about 10 m and can be used for close up measurements alone.
For redirecting the LM80 in case the feed conveyors are relocated, adjustable mounts are used. Heavy dust mode with some fine tuning of parameters is required for this application. Vibration from the silo vibrators caused no false indication of movement in the LM80 readings.
Such sites typically also have large stacker/reclaimer machinery in addition to the silos and are good targets for LM200 laser positioning applications.
At this specific location, production rate is 10,000 mt per day of sinter ore. The customer is the Philippine Sinter Corporation, a subsidiary of Kawasaki Steel Corporation of Japan. They have agreed to act as a reference site.
About ABB Analytical Measurements
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This information has been sourced, reviewed and adapted from materials provided by ABB Analytical Measurements.
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