legislation refer in their waste management practice to tyres in the waste management hierarchy. This sets the priorities of what to do with scrap tyres. This is: recycle, re-use, production of crumbs and strips, de-polymerisation, energy recovery and disposal.
The most important uses of cement are as an ingredient in the production of mortar in masonry, and of concrete, a combination of cement and an aggregate to form a strong building material.
The use of wastes in cement production can be interesting for two main reasons:
• Natural mineral resources may be substituted if these minerals are also contained in the ash component of the waste
• Fossil fuels may be substituted in case the autonomous incineration of the waste under the process conditions occurs at a sufficiently high combustion temperature.
The calorific value of waste can be used to differentiate between waste elimination and waste recovery in the cement industry. This differentiation is important for a process manager when considering the acceptance of waste, but also as a regulatory tool. The chemical composition of the waste is calculated to find the total contribution to the process. A complicating factor hindering the practical, user-friendly application is that one always needs to calculate the combustion temperatures from the composition of the materials considered.
The use of alternative fuels and raw material is common practice in the cement industry. Over 1 billion tyres are sold worldwide each year, which causes around 1 billion tyres to be scrapped. Despite in increase in the service life of tyres, volumes are growing constantly because of the increased vehicle use worldwide.
Tyres have a complex composition. Depending on their size and intended use they may vary in design, construction and total weight. The main component of a tyre is rubber compound and the compositions of the tyres produced by different manufacturers are very similar. Tyres are generally homogeneous. They are 100 % recyclable and a valuable resource. Many countries with environmental
In cement plants, tyres are used as a secondary fuel source. In order to calculate the benefits from substitution of primary fuels the following considerations have to be taken into account: the Calorific value, and the Biomass / CO2 value. The calorific content value of tyres is between some 6450 Cal / Kg and 8000 Cal / Kg. To substitute 1 ton of coal around 0.76 – 0.95 ton of scrap tyres is needed. Compared to pet coke the substitution factor is slightly more. Around 1.03 – 1.27 ton of scrap tyres is needed to substitute 1 ton of pet coke.
Hence the energetic utilization of tyres has clearly a better CO2 balance than the incineration of fossil fuels as the emission factor for coal is 96 ton CO2 / TJ.
The use of tyres as a fuel in cement production influence kiln operation and clinker composition.
The use of alternative fuels to replace conventional fuels, in particular coal, is a widespread practice and can contribute to improving the global warming impact and total environmental footprint of the cement industry. The DDS Calorimeter range plays a small part in this process to determine the best possible materials to use.
The use of alternative fuels to displace coal reduces reliance on fossil fuels, reduces emissions of carbon dioxide and other pollutants, and contributes to long-term cost savings for cement plants. Further, due to their high burning temperatures, cement kilns are well-suited for accepting and efficiently utilizing a wide range of wastes that can present a disposal challenge.
alternative fuel in kilns
The types of fuels that can be used as alternative fuels in cement manufacturing( focusing on energy and environmental considerations) include: agricultural biomass, non-agricultural biomass, chemical and hazardous waste, petroleum-based fuels, and miscellaneous alternative fuels.
• Non-Agricultural Biomass
• Agricultural Biomass
• Petroleum-Based Fuels
• Chemical and Hazardous Waste
• Miscellaneous Fuels
DDS Calorimeters | Feb / March 2017 Issue www. ddscalorimeters. com