CMA

37 Cement kilns have several features that make them particularly appropriate and efficient for the recovery of minerals and energy from waste fuels and raw materials, for example, high temperature profile in pre-calciner and kiln, high gas residence time of more than five seconds at a temperature higher than 1,000°C (typical incinerator has only 2 seconds), oxidising conditions, alkaline environment, and no residues from the process. Given the differences in temperature between different parts of the process, it is important that waste materials are introduced at the correct point in the process to ensure complete combustion or incorporation and to avoid unwanted emissions. For example, raw materials with volatile organic components may be introduced in the cement kiln at the main burner, in mid-kiln, in the riser duct, or at the precalciner. They should not be introduced with other raw materials except where tests demonstrate that this will have no effect on the off gases. Treatment of AFRs must meet strict environmental, health, and safety standards, and must not impair the quality of the final product. Controlling emissions to the atmosphere from cement manufacture requires precise control of the process, whether using conventional or alternative fuels and raw materials. Particular attention is paid to the specification of the fuel, (specifically its homogeneity, particle size, and flammability) and to the use of best combustion practices, including proper metering, feeding, and burner technology to maintain smooth kiln operating conditions. Cement production is energy and resource intensive and accountable for approximately 7% of man-made CO2 emissions. Half of this is a result of the chemical process involved in the transformation of limestone into clinker; 40% is a result of burning the fuel. The remaining 10% is split between electricity use and transport. Cement production needs more than 700 million tonnes of fossil fuels like coal and more than 6 billion tonnes of virgin raw materials. There are many sources of waste materials and by-products that can be used as alternative fuels, raw materials, and cement constituents. Recycling wastes from one process as raw materials and fuels for another creates a web of relationships between industries that moves society closer to a circular economy. Co-processing is one of the important levers for the cement sector in reducing the CO2 emissions. The table 1 shows the development of thermal substitution rates in different regions of the world, between 1990 and 2019. Table 1. Development of the thermal substitution rates in different regions of the world between 1990 and 2019 (data from GNR 2019) Region 1990 2000 2010 2019 Coverage (%) in 20191 World2 2 % 5 % 12 % 19 % 22 % Europe 3 % 9 % 31 % 50 % 90 % North America 4 % 7 % 13 % 15 % 86 % Central America 0 % 2 % 10 % 17 % 74 % Brazil 5 % 9 % 19 % 31 % 78 % South America ex. Brazil 0 % 3 % 5 % 7 % 69 % CIS3 0 % 0 % 1 % 4 % 21 % Middle East 0 % 0 % 2 % 13 % 14 % Africa 0 % 0 % 2 % 13 % 31 % Asia (n.e.c.)4 + Oceania 0 % 0 % 7 % 11 % 27 % Northeast Asia 1 % 5 % 5 % 6 % 4 % India 0 % 0 % 1 % 4 % 55 % 1. Coverage is percent of cement production covered in the GNR database- https://gccassociation.org/gnr/ 2. Current TSR of world is 6% but because of only 22% coverage the TSR of world in the above table is 19% in 2019. 3. CIS: Commonwealth of Independent States comprising of Azerbaijan, Armenia, Belarus, Kazakhstan, Kyrgyzstan, Moldova, Russia, Tajikistan, Turkmenistan, Uzbekistan and Ukraine. 4. n.e.c : not elsewhere counted: 1.1 Regulatory framework for Co-processing in cement kilns – Examples from India and China 1.1.1 India The MoEFCC in 2016, amended the existing regulatory framework for environmentally sound management of the waste being generated in the country. MoEFCC has notified 6 sets of waste management rules dealing with different kinds of waste: solid waste, plastic, biomedical, construction and demolition, electronic waste, and hazardous waste. These new rules advocate for adopting more scientific, technology driven, sustainable, regulated, and participative environment management.