Recycling of municipal solid waste incineration fly ash for ordinary Portland cement production: A real-scale test

The study present in this paper investigates the feasibility of clinker production using water washed MSWI (municipal solid waste incineration) fly ash in addition to cement raw materials. The tested fly ashes were washed and reused as raw material (with dosage of 1% of cement raw material (w/w)). The optimization of the MSWI fly ash washing process was carried out to maximum the extraction of chloride and sulphate. Taking into account economic parameters such as the consumption of water, reaction time and easy operation, the best relation found was a liquid/solid ratio (L/S) of 10/1 during 1/6 h. Pure CO2, used to simulate the cement kiln dust gas, was bubbled into the water effluent to decrease the pH by the formation of CaCO3. In these conditions, the concentration of heavy metals will decrease as a consequence of the co-precipitation with CaCO3. XRD technique was used to monitor the phase formation during the burning of the mixture of MSWI fly ash and cement raw materials. The amounts of trace elements volatilized during clinkerization, as well as leaching behaviours of the clinkers, were also evaluated. After the lab-scale experiments to confirm the efficacy of this technology, a real-scale test (3000 tonnes/day) was conducted. The quality of the resulting cement is sufficient to enable the cement to be put to practical use.