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| Lehigh Inland Cement produces 1 million tons of cement annually. |
Edmonton, Canada -- Lehigh Inland Cement is a wholly owned subsidiary of Heidelberg Cement. For over 50 years the plant has been producing high quality cement for customers throughout Canada and the U.S. With production exceeding one million tons of cement annually Lehigh has installed the highest quality equipment and systems in their plant.
Because consistency and accuracy are critical in the production of cement, Lehigh Inland relies on Schenck Process weighing and feeding equipment for maintaining a consistent feed to its kiln and to meter fly ash into their finish grinding mill.
Utilizing the Schenck Process Multicor®-S800 Coriolis Mass Flow Meter guarantees precise accuracy for the Lehigh kiln feed system. A Multicor®-S80 Coriolis Mass Flow Meter is installed for metering fly ash in the finish grinding mill for producing a new inter-ground type of cement.
The Process
For Lehigh Cement their process begins at a quarry 190 miles (306 km) away from Edmonton where limestone is mined and crushed into 7.9 inches (20 cm) chunks. The limestone is transported by rail car to the plant in Edmonton. 300 rail cars of the limestone are shipped each week. After the raw material is unloaded and stockpiled it is fed into a hammermill crusher along with clay that is mined at the plant site. The limestone and clay are mixed at a 3:1 ratio.
Now called preblend, this mixture is conveyed to the Preblend Dome where it is stacked by a Radial Arm Stacker in a continuous, circular pile up to 700 layers deep (40 ft or 12 meters high). Further mixing of the preblend is done in this area before being conveyed to the Surge Bin.
The Surge Bin temporarily holds the preblend and feeds the mixture on to a conveyor system where small amounts of sand, bottom ash, iron ore, and more limestone are added if necessary assuring that the limestone and clay are in correct proportion to produce cement. From the Surge Bin the preblend is conveyed to the Roller Mill.
The Roller Mill is comprised of three 27 ton steel wheels that pulverize the preblend into a powder-like mixture resulting in the creation of kiln feed. Over 230 tons of kiln feed are produced each hour. In this stage the kiln feed is sampled multiple times to determine if it meets specification. If low in any of the raw materials, adjustments are made from the additive silos to correct the mixture.
From the Roller Mill, the kiln feed is carried by high pressure air to the homogenizing and kiln feed silos, where it is continually mixed for maintaining a powdery consistency.
Multicor®-S800 Coriolis Mass Flow Meter
After leaving the silos the kiln feed goes into a calibration bin and from there it enters the Schenck Process Multicor®-S800 Coriolis Mass Flow Meter. The S800 offers cement producers a number of key features including, dust containment, compact design, direct weighing technology, repeatability, and accuracy. Lehigh chose the S800 for all the features previously mentioned, but their decision was based primarily on a desire to increase the accuracy and reliability of the system versus the one they had been using.
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| The Multicor-S800 kiln feeding system provides reliability and accuracy. |
The previous kiln feeding system utilized impact flow meters with pneumatics transporting the materials into the flow meters. Air slides were used to deliver the kiln feed to and from the flow meters. The combination of the impact flow meters, pneumatics, and air slides would create pressure and ventilation differences from one side of the system to the other resulting in a sucking action on the flow meter paddle causing it to go down. This would negatively affect the overall accuracy of the system.
With the installation of the Multicor®-S800 Coriolis Mass Flow Meter, Dave Moule, Lehigh Cement Plant Engineering Superintentent, stated “for our particular application the variation in pressures or ventilation did not affect the Schenck Process coriolis meter. We could count on the equipment to give us the same results regardless of any outside forces or plant disturbances.”
The increased accuracies produced by the Schenck Process kiln feed system allowed Lehigh to run at a higher feed rate, which has led to greater production capacity. The Multicor®-S800 Coriolis Mass Flow Meter is capable of feed rates up to 600 tons per hour with accuracies of ±1%.
Continuing the Kiln Feed Process
After being metered from the S800 the kiln feed enters an air slide and then into a high pressure air pump, which conveys the materials to the top of a preheat tower. The material enters the tower at a temperature of 194º F (90º C) and within 20 seconds falls through the tower and emerges from the bottom at a temperature of 1,562º F (850º C). From there the kiln feed enters the kiln where it is heated to 2,552º F (1,400º C), resulting in the creation of clinker.
After cooling, grinding, and milling the clinker into cement the finished product is stored in one of the companies 24 on-site silos. From there it can be easily shipped to customers in bags and bulk form, by rail or truck.
Multicor®-S80 Solids Flow Meter
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| The Multicor-S80 meters fly ash into the finish grinding mill. |
As part of a separate cement manufacturing process within the Lehigh plant another Schenck Process product named the Multicor®-S80 Coriolis Mass Flow Meter is installed for metering fly ash into the finish grinding mill for producing a new inter-ground type of cement.
Moule commented, “This process allows us to reduce the clinker content in the cement product by substituting unclassified ash, which has cement type properties without compromising product quality, resulting in a substantial specific energy savings.”
Traditionally, fly ash has been used in concrete at levels ranging from 15% to 25% by mass of the cementitious material component (Thomas 2007). Because it plays such a vital role in the production of cement the accuracy provided by the Multicor® S-80 is critical.
Fly ash is typically provided to cement plants for little or no cost and if an inadequate amount of the material is metered into the process from the use of inaccurate equipment it reduces the cost savings realized by the use of fly ash for the plant. It also results in producing off spec product. The installation of the Multicor®-S80 has provided Lehigh with a product that has the capability of reaching accuracies of ± 0.5% when metering over two tons per hour leading to precise measurements all in a dust tight compact design.
Moule added, “a short pay back period also made the equipment an excellent investment for Lehigh.”
Results
With the installation of the Multicor®-S800 Coriolis Mass Flow Meter and Multicor®- S80 Mass Flow Meter, Lehigh Inland Cement has been able to increase their kiln feed and fly ash metering accuracies with the added advantages of dust containment and a compact design that meet’s the plant space requirements.
Moule added, “We were not meeting our accuracy and production goals prior to the installation of the Schenck equipment, but with the coriolis meters in place we had the reliability and accuracy that we were seeking.”
Schenck Process
Schenck Process is a manufacturer of belt scales, mass flow meters, kiln feeding systems, pulverized coal feeders, weighfeeders, volumetric and gravimetric feeders, bulk bag discharging systems, fiberglass feeders, controls, and weighing systems for the steel, cement, aggregate, and gypsum industries. Schenck Process can be contacted at 1-800-401-9702 or visit the web site at:
http://www.accuratefeeders.com/
References
Thomas, Michael (2007) “Optimizing the Use of Fly Ash in Concrete”, Portland Cement Association, Skokie, IL
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