15.01.2009 | Editor: Marcel Dröttboom
Global competition and higher production costs mean that the energy intensive cement industry in particular needs effective solutions for reducing the cost of energy. Dwindling resources and the resulting spike in raw materials’ prices are lending ever more weight to the call for the use of alternative sources of energy.
The advantages of using used tires over traditional types of fuel are obvious: tires offer high heating value, which is comparable to coal or oil. At the same time, the cement industry in particular benefits from the opportunity to use the scrap iron content of the tire carcasses as mineral additions in their products. This removes some or even all of the need for adding other ferrous correctives. Other studies, including research by the Federal Environmental Agency, have proven that the use of substitute fuels is a positive development, in particular with a view on protecting the climate.
With over 50 solutions for transporting and batching used tires and tire shreds already installed worldwide, the Beumer Group can look back on 30 years of experience with the technology. With this know-how, the company is constantly improving the operating reliability and efficiency of the technology as well as its ability to meet the increasingly tough requirements for environmental protection, emission limits and other country-specific standards. In the course of its research work, the company has also developed systems for conveying and batching ground tires (tire shreds) for feeding rotary kilns.
Pre-ground tires offer the advantage of easier batching compared to whole tires. The higher density of the material and the consequent savings in its transportation are a further argument for the choice of ground tires as fuel.
One option for using Beumer systems for the use of tires as fuel in the cement industry could be the following (Fig. 1):
The tires are delivered by lorry and stored in a whole tire bunker of sufficient size to cover any potential supply issues with a few days’ reserves. A polygon crane feeds these tires into a shredder that cuts them to a desired size, before removing the discharge box that captures the tire shreds. This box can also be used as a feeder for tire shreds if the operator of the plant receives pre-cut tires shreds in place of whole tires. An intermediate storage unit for the shredded material offers enough buffer space if fuel supply has to be halted for a period of time. The batching unit is kept in constant supply from this storage buffer, where a stable flow of fuel can be adjusted to the amount of fuel required within the defined limits. A conveyor belt transports the exactly batched amounts of fuel to the heat exchanger for feeding into the calciner through a triple-gate valve.
The fuel fed into the calciner has a considerable impact on the combustion process and needs to be measured out exactly. A lack of precision at this stage can lead to varying levels of quality in the end product. The batching procedure developed by Beumer meets the needs of the end user in every aspect. The great number of renowned reference clients from the cement industry is proof of the innovative technology and the thorough know-how offered by Beumer. The specialist for intralogistics has already supplied many conveyance installations for alternative fuels, including solutions for the Heidelberger Cement-Group, Cemex and Ciment Quebec.
Important fuel cost reductions are being enjoyed by the internationally active cement producer Ciment Quebec Inc., based in St. Basile, Quebec, Canada. Since early 2006, the company has been using a highly complex Beumer solution for receiving and conveying tires as fuel in the production of cement. When the contract was awarded in June 2004, the client expected Beumer to install a system that supplies its calciner with alternative fuels. These were expected to include whole and shredded tires as well as other automotive fluff, shredded plastics and wood. The finished installation has delivered all the elements that ensure the reliable and constant supply of alternative fuels for the production of cement.
The delivered shredded tires are dumped and stored in a walking-floor type storage bunker from which a belt conveyor removes the required amounts of fuel. Ultrasonic sensors monitor the required levels on the belt. A counter-rotating scraper produces an even distribution of the tire shreds on the belt conveyor. The flow of material is batched gravimetrically by means of a single-roller belt weigher coupled with the speed control of the conveyor belt system. The even discharge of the material into the calciner is managed by a winch roller, which stops oversized or stuck batches from entering the kiln.
For the burning of whole tires, a conveyor system was designed in parallel to the shredded line system that uses special sensors to identify and exclude strongly deformed tires or wheel rims. Material that is unusable for burning is automatically conveyed to a discharge point. In order to avoid leak air entering the calciner during the feeding process, the calciner feed point was equipped with a triple rotary gas lock. Three consecutive gas locks made from special steels allow only minimal heat loss as a result of their material and special design. This maintains a highly leak-tight system.
When deciding on a supplier, Ciment Quebec was looking for a company offering experience with handling solid waste fuels. The global presence of the company, their on-site service and the comprehensive service package offered were further aspects in favour of Beumer. The company has been established in the U.S. with its subsidiary, the Beumer Corporation in Branchburg, NJ, since 1977.
BEUMER Maschinenfabrik GmbH & Co. KG
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