The rapid development of sensor technology provides cement producers with a toolbox of solutions to optimise performance and strengthen market presence. Non-contact volume flow measurement of conveyed materials streamlines the handling process from quarry to final product.
SICK Automation’s bulkscan flow measurement technology had its portfolio broadened recently with the introduction of the low cost Bulkscan LMS111. All versions provide non-contact measurement of volume flow more accurately than mechanical belt scales, while minimising errors in mass and volume flow calculations.
Felix Bartknecht and Michele Savino of SICK, Germany, explain that the movement and handling of bulk materials and packaged cement are tasks mainly carried out by conveyors. In many established cement plants this movement happens unsupervised. Add to this the need for lower production costs and enhanced tracking accuracy, and the need for cement plants to keep up with modern sensor technology becomes obvious. Bulkscan provides automated monitoring and process control all the way from the quarry to the end product.
The cement industry can learn from Industry 4.0 experience in other sectors. One of the key aspects is the ability to take data from process sensors to a centre that can evaluate it and recommend closed-loop process changes. Data can be stored and evaluated over time to spot patterns and determine trends. Attaining this level of accessibility to information increases the potential for process improvements, as well as opening up opportunities to assess and respond to consumer trends and environmental requirements.
Monitoring flow in cement plants
Knowing how much raw material is in the yard is a challenge. It is essential that conveyors provide a nonstop flow of raw materials, additives, fuel, clinker and cement upstream and downstream of the pyroprocess. Mechanical scales measure mass and the volume of material transported is calculated using an average material density.
This process is hindered when material density changes or when a conveyor belt is not properly maintained. Material density is used to convert mass from the weigh scales into volume and vice versa. “When the density is incorrect, the volume and mass calculations are also incorrect,” explains Savino.
Bulkscan flow measurement technology enables the yard manager to measure the contour, volume, height and material distribution through the use of LiDAR (light detection and ranging) technology. The sensors can be mounted over conveyor belts or onto cranes and reclaimers.
Inside the Bulkscan sensor, high-pulse laser beams create a profile of the material on the conveyor which, in combination with belt speed, represents volume flow and calculated mass flow. This measurement principle is based on a laser beam that is deflected internally across a rotating mirror. The sequential order of the laser pulses is synchronised with the rotation frequency of the motor and the desired angular resolution. Generally, the motor rotation speed is determined by the maximum emitted pulse frequency of the laser source and the desired angular resolution. The laser beams scan the surface area of the material on the conveyor and send this information to the measurement device, which compares the data with an empty reference belt.
Bulkscan allows plant operators to measure volume flow on conveyor belts, bucket elevators or drag chain conveyors, outdoors in harsh conditions, as well as inside the cement plant. The scanner can be mounted above the conveyor, measuring volume flow without any material contact, making it virtually maintenance free. The collected data can either inform manual processes, or act as an input to fully-automated systems to drive changes in material flow and composition. When large objects are detected, the plant operator is alerted and an automated stop process is triggered.
Bulkscan helps plant operators to optimise conveyor operation and reduce unplanned downtime. The same laser beams used to measure the bulk flow rate also provide information about the exact height and distribution of the bulk material on the conveyor. In addition, the centre of gravity of the load and the distance between the bulk material and the conveyor edge is measured and provided to a closed-loop system to adjust material distribution on the belt. This process automation helps increase belt life and decrease one-sided roller wear and downtime.
Bulkscan can also be used in conjunction with a weigh scale. The actual bulk density can be determined in real time as the device measures the volume while the weigh scale measures mass. When these values are known, density can be calculated.
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