Fundamental characteristics of solid wastes from calcium carbide industry

Aiming to make full use of three kinds of solid wastes from calcium carbide industry, this paper first investigated elements and mineral compounds of them through inductively coupled plasma and X-ray diffraction (XRD). The three solid waste samples, removed dust (RD), coke dust (CD) and purified dust (PD), have higher Ca/S molar ratios than conventional fuels such as coal. In particular, Ca/S molar ratio of PD unexpectedly achieved 28.05. Calcium in PD is present mainly in the form of calcium oxides, but little calcium carbonates, which was contrary to calcium in RD. In addition, the large proportion of fixed carbon in the samples CD and RD was amorphous carbon. Besides, three former dust samples were mixed at a specific ratio to obtain a new sample, mixed dust (MD), for further experiments as a reference of future industrial applications. Combining thermogravimetric system and Fourier transform infrared spectroscopy system helped to investigate the combustion process of all four samples in air atmosphere. Large amounts of reactive amorphous carbon identified by XRD desorb pollutants adsorbed in retorting process firstly and then help the samples RD, CD and MD ignite easily, which indicates they have potential to be fuels. Besides, the calcium oxide catalyzed the NO x formation during the combustion, which should be inhibited.