Search

The steam gasification kinetics of Zhundong raw coal and the washed coal by deionized water or hydrochloric acid with/without addition of CaO were tested by thermogravimetric analyzer (TGA) at medium temperatures (650–800°C). The cation contents of potassium and sodium in samples were determined by Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES). The Brunauer-Emmett-Teller (BET) surface area of the samples was tested by N2adsorption, and the morphologies of the samples were characterized by scanning electron microscopy (SEM). Experimental results showed that the organic sodium was the main catalyst for the gasification of the pyrolysis char, and the gasification rate of the char could be enhanced further with the introduction of CaO. The inherent alkali metals in coal and the introduced CaO showed a synergistic effect that occurred obviously above 735°C. The char conversion curves with or without CaO were fitted by the modified volumetric model (MVM). The calculated results indicated that the addition of CaO increased the pre-exponential factor obviously, but made little changes on the activation energy. It was proposed that the synergistic effect was resulted from the co-melting of the sodium and CaO, which facilitated the migration of the catalyst ions and the generation of C(O) intermediates for the gasification.

The CO2absorption ability of synthetic calcium-based sorbent modified by peanut husk ash (PHA) was tested by Thermal Gravimetric Analyzer (TGA), and the effects of steam and calcination temperature were investigated. The PHA composition was analyzed by X-Ray Fluorescence (XRF), the apparent morphology was characterized by scanning electron microscope (SEM), and the phases of the sorbent before and after calcination were examined by X-ray diffraction (XRD). The addition of PHA effectively improved the cyclic stability of the calcium-based sorbent. The optimal molar ratio of SiO2in PHA to CaO was around 0.07. Steam had positive effect on keeping porosity of the sorbent at the chemical reaction stage, and improved its CO2absorption ability. Steam also reduced the diffusion resistance of the product layer, and depressed the influence of high temperature calcination. It was also found that the steam hydration after calcination was an effective way to recover the absorption ability of the sorbent, while the hydration duration of 10 min was enough.