Humongous Holding Tanks
December 13, 2015
Polish researchers and engineers have designed and built a range of huge, lightweight silos for storing bulk agricultural materials. Some of these silos, though made from steel combined with textiles, are among the most durable in the world, the designers say.
Such large silos, which are sometimes the size of a multi-story apartment building, are used on big farms and in food processing plants. They are intended for the storage of bulk materials such as grain, maize and oilseed plants, including rapeseed and soybeans. This material is stored in silos before being processed into animal feed or biofuel.
The more that steel is used in the construction of such a holding tank, the more expensive it is. The Polish silos are innovative in that their structure has been reinforced while the weight of individual parts has been reduced. They are also easier to empty.
The new range of silos was built jointly by engineers from the Feerum company, based in Chojnice near Legnica in southwestern Poland, and researchers from the Wroc³aw University of Technology. Feerum is carrying out a zl.8 million project called “Innovative Lightweight Silos Made from Steel and Steel-and-Textiles.” The National Center for Research and Development (NCBR) has co-financed it with zl.4.5 million in funds available under the European Union’s Innovative Economy Operational Programme.
Work on the project began in February 2014. The research part of the project will last until the end of 2015. It includes industrial research and development work conducted jointly with the Wroc³aw University of Technology. The strength of six pilot silos has been tested and confirmed by experts from the university’s Faculty of Construction led by Prof. Eugeniusz Hota³a. The implementation stage of the project—whereby Feerum will put all of its silos out on the market—is scheduled to be completed in December 2016.
“Polish agriculture, in terms of both animal breeding and plant production, is developing rapidly—to the extent that we import grain,” says Daniel Janusz, CEO of Feerum. “As a result, demand for silos is growing. More and more producers are ordering tanks capable of holding several thousand tons of grain and other bulk materials.”
The company produces a variety of silos, from small ones intended for storing several tons of grain to huge ones. Its largest silo has a capacity of 20,000 tons, a height of 40 meters and a diameter of 35 meters, which means it is as large as a 12-story apartment building. Such a 20,000-ton monster was produced for a customer in Moldova. In Poland, however, the most popular silos are those with a capacity of just over 1,000 tons.
Companies selling animal feed and meat producers also need such holding tanks. Animal feed, unlike grain, tends to become lumpy and sticks to the walls of the tank, which makes emptying difficult.
The idea to combine steel with textiles for the production of silos originated at the Wroc³aw University of Technology. It is protected by a patent and Feerum has bought a license to use it.
“A silo is usually emptied from the bottom. A plain steel tank is not suitable for storing non-bulk material,” says Feerum’s Janusz. When the bottom layer is removed, the top layer may cave in and destroy the tank. A tank can also be damaged by a lump of dense material, similar in structure to flour, if it falls from a height of several stories to the bottom. That’s why a special textile sack was hung permanently inside the steel tank. This ensures safe storage of about 400 to 500 tons of material.
The use of the textile material makes it possible to deal with the resistance that occurs when the silo is emptied. The stored commodity does not stick to the walls of the silo and there is no need to increase the weight of the tank and reinforce it with steel parts, which would jack up the price.
“Previously steel and textiles were not combined when silos were designed,” says Janusz. “This is a completely innovative idea that has great significance for reducing production costs because it reduces the weight of the silo and the power consumption. Less steel also means the production process is less labor-intensive. As a result, such a tank can be sold at a more attractive price.”
A test steel-and-textile silo with a height of more than 10 meters and a diameter of 8 meters has been built at Chojnowo. It is one of the six pilot silos that were constructed during the project and the only one with a textile layer. The other five are lightweight, thin-walled steel tanks.
“We have been taking part in various innovative projects since the start of the previous decade,” says Janusz. “Back then research institutes led the way. Now it is we who are leading the charge, and universities are doing work for our company. As the leader of this project, we can make a giant leap technology-wise.”
Parts of the structures designed by Feerum are sent to a laboratory at the Wroc³aw University of Technology right after being produced. “The university has the right equipment for crushing steel, which makes it possible to determine the actual strength parameters of whole tanks and their individual parts,” Janusz says. “The market is too demanding and we have too much to lose to sell our structures without such tests.”
In the case of silos, prototypes developed in the research programs become finished products fit for mass production. They only require some minor adjustments following studies which may detect something that needs to be improved or corrected. Theoretical calculations are thus checked in practice, mainly in terms of strength. The grain in the tank puts pressure on its thin walls, which are fastened with bolts. It may tear or bend the silo.
"We have to calculate all that, measure the resistance of the grain,” says Janusz. “We also check just how efficient the process of emptying the tank is. All this is needed to come up with silos as light as possible and at the same time as durable as possible. The product must be safe and competitive in terms of price in relation to those offered by foreign companies. The innovativeness of our tanks is based on the fact that they are more resistant mechanically.”
Feerum produces 24,000 parts from which silos tailored to the needs of an individual customer can be produced. The company’s employees are ready to assemble these on-site. There are about 100,000 large farms in Poland—ranging from several hundred to several thousand hectares—whose owners are potential buyers of Feerum’s silos. The company also has industrial customers who buy grain, store it and produce feed for farm animals from it. Other customers include bioethanol production plants, oil mills, and companies that buy and store commodities for sale later at a higher price, Janusz says.
Feerum was founded in 2002. About 80 percent of its output is sold domestically, but the company also handles orders from customers in Moldova, Mongolia, Belarus, Ukraine, Italy and Germany. Feerum employs 70 engineers in its research-and-development and design department, and has nearly 240 on staff in total.