Use of waste as alternative fuel in cement production
For more than 10 years, the use of waste as alternative fuel in cement production has been a well-established process in most of the European cement industry. However, this was not the case in Bulgaria. On October 8, 2003, Zlatna Panega Cement AD became the first plant in Bulgaria to install an alternative fuel facility. As an environmentally conscious company, Zlatna Panega recognized that the use of alternative fuel in cement production could bring multiple environmental benefits, such as reducing the need for natural resources, and allowing for proper disposal of community waste.
Cement is produced by heating raw materials such as lime, silica, alumina and iron in kilns to produce a fused material called clinker. Clinker is then ground with small quantities of gypsum into a fine powder to form cement. This production process is characterized by an extremely high-temperature combustion process, necessary for heating and fusing the raw materials. The fuels most commonly used for this combustion process are coal and natural gas.
Alternative fuels are materials such as used tires that are rich in energy and that can replace coal or natural gas as a source of thermal energy in the cement manufacturing process. The thermal energy released from burning one tonne of tires is equal to the thermal energy released from burning one tonne of high quality coals and 0.7 tones of mazut. Additionally, alternative fuels often contain lime, silica, alumina or iron oxides, which are primary components in the production of clinker.
Using waste as alternative fuel is not only an excellent source of thermal energy in the cement manufacturing process, but it is also an intrinsically safe method to dispose of community waste. Because of the relatively long residence times and the high temperatures required in the kiln burning zone (1450-1500°C), the cement manufacturing process creates very favourable conditions for a complete combustion of organic material such as community waste.
The new alternative fuels facility at Zlatna Panega will be used mainly to dispose of solid waste such as tires, plastics, sewage sludge, etc. Initially, priority will be given for the disposal of used tires since, as part of the National Programme for Waste Management in Bulgaria, the company has committed to collect and burn 7,000 to 9,000 tonnes of used tires annually.In the cement manufacturing process, the use of alternative fuels brings multiple environmental benefits. First, the use of alternative fuels limits the depletion of non-renewable natural resources such as coal, natural gas or other fossil fuels, which are normally used in the manufacturing process. And by reducing the use of fossil fuels, alternative fuels also contribute to lower emissions of associated greenhouse gases. Furthermore, since alternative fuels contain lime, silica, alumina and iron oxides, which are primary components in the production of clinker, they also contribute to limit the depletion of these other natural resources. Finally, since they are substitutes for fossil fuels such as coal, alternative fuels contribute to reduce the environmental impact associated with coal mining.
The use of alternative fuels also brings major environmental benefits in terms of community waste management. Cement kilns are a very safe and effective alternative for disposal of waste compared to conventional disposal of waste in landfills or in dedicated waste incinerators, where ash or energy may not be fully recovered. The use of alternative fuels maximizes the recovery of energy from waste that would otherwise have been incinerated and would have produced harmful emissions. The process also maximizes the recovery of the non-combustible part of waste and eliminates the need for disposing of slag and other residues, since the inorganic part of waste is used as a substitute for raw material in the production of cement.
Since the start of its alternative fuel installation on October 8, 2003, Zlatna Panega was able to burn more 1,200 tonnes of used tires. During that same time, the company was able to receive and maintain certification according to ISO 9001:2000 Quality Management Standard and ISO 14001:1996 Environment Management Systems. Such accreditation is a proof of Zlatna Panegas good environmental management and a confirmation of the environmental benefits of using alternative fuels.
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