Big and beautiful
The new cement manufacturing facility of Holcim (US) at Ste. Genevieve with a production capacity of four million tonnes per year went on stream mid-2009 and is one of the most environmentally-efficient cement plants in the Holcim Group. It is 40 percent more energy-efficient than the Holcim (US) plants that were closed in 2009 and emits 10 to 25 percent less CO2.
The Danish FLSmidth was awarded the contract for the engineering and the supply for the main processing equipment for this new giant plant. In a cement plant airflows are often hot and contain dust. Crushed limestone and clay is grinded and dried by vertical roller mills. The high moisture of the raw material require more than normal gas flow quantities through the mill for drying. The power consumption for the mill fan is about 60% of the total power consumption of the grinding system. The aim was to control and minimize the air flow through the mill. Before the Genevieve project was launched Holcim tried measurement of the differential pressure across the fan, the dp across the cyclone and fan power consumption to estimate the air flow in a cement plant but without satisfactory results. Mecontrol Air flowmeters were installed directly in the duct of the fan to establish whether this new technology is suitable for flow measurement under these harsh conditions. After some month of operation the PROMECON technology proved itself to be accurate, drift and almost maintenance free.
The MECONTROL Air system makes use of unique patterns of electrical noise generated by particles passing the receiver rods. By correlating these patterns the time of flight between the receiver rods can be accurately measured. Since the principle is based on time measurement it is absolutely drift free.
For the new grassroots plant Ste. Genevieve, Missouri HOLCIM decided after several years of experience with MECONTROL´s correlation technology based instrument systems to select PROMECON as the preferred supplier for the vital air flow measurements in the process. PROMECON provided the gas flow measurement for the four cement mills, two raw mills, and two coal mills. Also the downcomer gas flow is measured by the Mecontrol Air system.
Economical and clean
Significant power and cost savings and increased plant availability have been achieved due to modern plant design and sophisticated instrumentation - overall a great success.