Technology to reduce CO2 emissions during cement production (1990s, Taiheiyo Cement)

Technology to reduce CO2 emissions during cement production (1990s, Taiheiyo Cement)
In the 1990s, global warming emerged as a serious policy issue in Japan, and the Kyoto Protocol of 1997 made CO2 reduction an international obligation, requiring energy-intensive industries to take drastic measures. The cement industry is considered to be a particularly large source of CO2 emissions, accounting for approximately 5% of Japan's industrial CO2 emissions. In the cement manufacturing process, limestone is calcined at high temperatures to produce clinker, which generates not only CO2 from fuel, but also CO2 directly from calcination of limestone. This is an unavoidable emission in the process, and the core of the technological development was how to reduce it.
Against this backdrop, Taiheiyo Cement promoted research and development of a new calcination process that simultaneously achieves energy conservation and CO2 emission reduction in cement calcination. A typical example is the improvement of firing efficiency by upgrading the pre-heater and pre-calciner. By preheating the raw powder using high-temperature exhaust gas in a cyclone heat exchanger before feeding it into the kiln and partially calcinating it in the precalciner, the amount of heat required in the main kiln can be significantly reduced. This results in lower fuel consumption and consequently reduced CO2 emissions.
In addition, the use of alternative fuels to coal and heavy oil has been promoted. The use of waste tires, waste plastic, paper waste biomass, etc. as heat sources has reduced dependence on fossil fuels and created a zero-emission process that links the waste treatment and manufacturing processes. The cement kiln was highly evaluated as an appropriate waste treatment device because it is capable of high-temperature, long-term treatment and does not generate toxic components.
Furthermore, low-temperature firing of clinker and optimization of mineral composition were considered, and by adding an auxiliary agent to lower the firing temperature, the necessary crystal structure was formed at a lower temperature, saving energy and reducing CO2 emissions. These efforts have provided the foundation for Japan's cement industry to achieve a high level of energy efficiency, even by global standards, and have become a leading example of how to build a recycling-oriented society.