MACHINERY

A pair of Lepol-type horizontal rotary kilns for the production of artificial cement, each with a nominal production capacity of 250 tons/day, manufactured by the Polysius-Neubeckum firm (formerly Polysius-Deasau) in 1955 and 1959, respectively. The kiln tube of each Lepol is 32 ml long, with a diameter of 2.80 mt and an incline of 3.5%. The tube is supported on two rolling stations equipped with two rollers each; the upper station also includes two vertical-axis thrust rollers. Pa.Vo. (acronym for Pazienza [Patience] and Volontà [Willingness]) and Fo.Co. (acronym for Forza [Strength] and Coraggio [Courage]) produced cement clinker from marly and tuffaceous limestone that had been appropriately mixed, ground and homogenized. Equipped with a mobile grate heat exchanger that prepared the material for sintering and then burning by pragmatically using the heat from the combustion fumes, for the same production yield the Lepol kilns operated with greater thermal efficiency and a shorter kiln tube than the standard rotary kilns at that time. They were innovative in that they could also be powered by methane.

Started up in 1969, the ARES1 burning line (known as Trilo) was initially a small, experimental system comprising a stacked, horizontal rotary, dry process Polysius prekiln and kiln. The prekiln tube (upper) is 16 mt long with a diameter of 2.1 mt and an incline of 5%, the kiln tube (lower) is only 7 mt long with a diameter of 3.4 mt, and no incline. On the other hand, the ARES2 burning line (known as Bosco) was an industrial-sized system with a production capacity of 250,000 cubic meters/year of expanded clay. Started up in 1976 and also a dry process system, the line comprises a clay dryer from the German firm BSH (Büttner-Schilde-Haas AG) that is 15 mt long with a diameter of 2.6 mt and an incline of 2.5%, a BSH prekiln tube that is 32 mt long, with a diameter of 2.8 mt and an incline of 2.5%, and a kiln tube from the Italian firm Bosco di Terni that is 17 mt long, with a diameter of 3.4 mt and an incline of 1%. The layout on the stand shows the dryer and prekiln side-by-side and stacked on top of the kiln. The process involved crushing the raw clay in lump crushers, which was then dried and ground in a ball mill with the addition of fuel oil and pyrite ash. Stored in silos, the meal was reclaimed and passed through a grain plate, where the grains were formed with the addition of water (by sprayers). The grain size was regulated by the amount of water, the spray point and the incline of the plates, yielding grain sizes between 1 to 20 mm at the end of burning. The pellets then passed through the prekiln where they were heated to about 900°C. After reaching the final temperature, they passed into the actual furnace below, where they were expanded at 1120-1150°C. The degree of expansion was governed by the temperature in the kiln and the amount of time the grains remained in the kiln. Different types of expanded clay with different densities were also produced, i.e., with the strengths required for their various uses either as a sealant (very light) or as a replacement for the natural aggregates in structural concretes (denser and therefore stronger). The expanded clay was first cooled in a fluidized bed, and then conveyed by metal cassette conveyor belts to the screens and divided into the different grain sizes.

The 12-deck vertical kiln for drying marl was used for the production of artificial pozzolan for Cemento Pozzolanico. It is 18 mt high, has a diameter of 6.5 mt and was fired by 16 remotely regulated methane burners. It had a burning temperature of around 950° C and a production capacity of 200 tons/day. It was built in 1959 by the Del Monego firm of Legnano (MI) under an exclusive license from the Pacific Foundry Company LTD of San Francisco in California. The kiln comprises a load-bearing shell supported on columns in sturdy steel frames equipped with ladders and service walkways and 2 inspection doors for each deck. Inside the kiln is a structure consisting of a rotating central shaft equipped with 16 primary agitator rakes in alloy, together with teeth, 8 additional agitator rakes in cast iron on decks 1-2-11-12 of the kiln, and a set of agitator rakes with an automatic feeder on the preheating deck. The raw material was fed into the kiln through 3 inlet mouths, also equipped with an automatic feeder. The central structure was cooled by air fans. The rotating shaft, arms and agitator teeth were made of a special, highly pyrometric resistant alloy and could be removed without having to cool the kiln, so it could be used continuously over 24 hours. The Pacific was incorporated into the centralized control system that also governed the grinding units of the finished product.