Minimizing dioxin emissions from integrated MSW thermal treatment.

The combustion of wastes has very significant benefits in reducing the volume of waste materials and producing energy. However, combustion processes produce emissions, which must be below the Best Practical Means (BPM) specified legislative limits. Several wastes, such as tires and meat meal, have been successfully combusted in cement kilns, up to 20% w/w, while retaining emission standards well below legislative limits. In the case of municipal solid waste (MSW) the introduction of large amounts of MSW into cement kilns is not practical because the additional kiln volume required is too great, the large amounts of ash generated will affect the cement clinker quality, and it would be difficult to sustain the required very high clinkering temperature of 1500 degrees C with large quantities of low calorific value MSW. A completely novel process, termed the Co-Co process, has been developed, integrating MSW combustion in a synergistic fashion with the cement production. This process is based on combining the cement "front-end" calcination reaction and incorporating it with a high temperature, at 1200 degrees C, combustion process, providing a giant acid gas scrubber. A pilot plant was designed, constructed, and operated to demonstrate the benefits of the Co-Co process. The pilot plant achieved emissions minimization: dioxins were typically 0.5-1% of the European BPM limits, HCl, SOx, NOx, and particulates were 15, 10, 20, and 25% of BPM limits, respectively. Heavy metals were typically below 25% of BPM limit values.