Cement, Energy and Environment

debris can be reused as a cement raw material after being pulverized in a raw material mill, and metals such as iron and aluminium can be collected in an unoxidized condition for recycling, as they process value. Environmental consideration . . ' . , The CKK design prevents odours from being emitted by introducing an air-tight waste pit with negative pressure. Dioxins and . '·',/J-·J ~·~ .,, . ~ ' .. . 'lJJ:JU4J~._.,..f:n~ -rl .• · ~J .' ~' .. • ·, ,·, '. ' ,,' ~ /-:J';/: Figure 1.The process flow of CKK system. residue disposal or other post-processing is not required; no new exhaust gas disposal is required. • Reduced fuel consumption - utilize energy from waste as fuel and use incinerator ash as raw material for cement. • Maintain cement quality - there must be no negative impact on the final product. After considering the above from various angles KHI decided to apply gasification melting furnace technology that has previously been supplied in Japan. This meant attaching a fluidized-~ed type gasification furnace to gasify the waste before beginning the cement manufacturing process, with the gases generated used as fuel for high-temperature cement processing. At the same time, a detoxificaion system was developed. The system's characteristics are described here and pictured in Figure 1. Process flow for CKK system MSW collected by truck is dumped into the waste pit and stored temporarily. After being crushed and uniformed, MSW is put into the fluidized-bed type gasification furnace. Under a low-temperature reduced atmosphere (bed temperature: approx. 500 - 600 °C, air ratio: 0.2- 0.4), combustibles are set into the cement production as pyrolysis gas and unburned char, and become a fossil fuel replacement. Ash generatd through the gasificaton process can be used as a raw material in cement production. Incombustibles are expelled from the base of the gasification furnace and are recycled. The other harmful substances emitted by MSW are sent to the cement manufacturing process with the odours and are decomposed at high temperature (800 - 1400 °C) before being released into the air. Furthermore, there is no effect on cement quality, since the CKK System includes a chlorine bypass system that can extract chlorine and alkali (sodium and potassium contained in MSW. Figure 2 CKK building seen from SP tower. 64