Analysis of MSWI Bottom Ash Reused as Alternative Material for Cement Production

The bottom ash sample was obtained from one of three stably running municipal solid waste incineration plants in Beijing. The major components of bottom ash, i.e. CaO, SiO2, Al2O3, Fe2O3, were similar to that of ordinary Portoland cement, suggesting that bottom ash had the potential for reuse as cement material. In this paper, the smaple was sieved into 8 fractions according to the particle size distirbution. The content of CaO and chloride in the bottom ash almost decreased with the increase of particle size of bottom ash, contrary to the SiO2 content variation in the bottom ash. The Al2O3 and Fe2O3 content were relatively stable in the bottom ash with different particle size. The chloride, which could cause serious corrosion in the cement kiln, in 8 portion of bottom ash were all higher than its allowable limit in raw material for cement production and clinker quality, the dosage of bottom ash used as alternative material for cement production must be stringently controled, and some proper treatment must be used to reduce the corrion caused by chloride. The heavy metals concentration in the bottom ash were relatively high, but met standard requirements for heavy metals concentration in raw meterial. The content of alkaline oxide (K2O, Na2O) and sulphur, also affected cement production, in bottom ash with differernt particle size were all relative high. The bottom ash had the potential to be recycled as alternative material for cement production, but proper treatment measures, such as by-pass system, must be taken to satisfy the cement production, clinker quality and environmental safety.