No abstract

No abstract

No abstract

The combined dewatering process and dry separation in a vibration fluidized-bed dryer was developed to upgrade Chinese lignite in terms of moisture and ash for effective utilization in power plants. The influence of operational parameters (fluidizing gas velocity, vibration strength, bed height, and drying temperature) and lignite properties (particle size and moisture content) on the drying or separation characteristics of −6−1 mm lignite was examined in a laboratory-scale vibration fluidizedbed dryer. Both operational parameters and lignite properties had a significant effect on the drying and separation performance. The drying and separation behaviors of a vibration fluidized bed were both enhanced in comparison to the case without vibration under the same operating conditions. Moreover, with the change in gas velocity, the drying and separation processes could be combined in the same vibration fluidized-bed dryer. Both processes achieved promising results compared to those of the fixed gas velocity condition, which was confirmed by the low calorific value analysis. A sequential drying and separation system in a vibrofluidized-bed dryer was also designed on the basis of the separation and drying characteristic results.

Coal is one of the most important primary energy sources worldwide that requires an economic, effective, and clean preparation method. As the shortage of water resources increases, the wet beneficiation technology became questionable. The air dense medium fluidized bed (ADMFB) is a good alternative for dry coal beneficiation processes that require no water. In this account, a pulsating air flow was introduced into the ADMFB system to generate a pulsing dense-phase gas–solid fluidized bed (PDGFB). The effects of the pulsating air flow on the minimum fluidization velocity, stability of the bed density, and motion of the heavy medium were investigated. The pulsating air flow is shown to reduce the minimum of the fluidization velocity, modify the stability of the bed density, and regularize the motion of the heavy medium. Fine anthracite of −6 + 1 mm size is cleaned using PDGFB at elevated separation densities with a true value of 2.03 g/cm3 and probable error (E) of 0.09 g/cm3. In comparison to vibrated fluidized beds, PDGFB has no mechanical vibration and, hence, is advantageous in terms of the mechanical structure, easy operation, and susceptibility to lower failure.

No abstract

No abstract

A Ce-doped Fe−Mn magnetic sorbent (Fe 6 Mn 0.8 Ce 0.2 O y ) was developed using the coprecipitation method. The effects of O 2 , H 2 O, flue gas temperature, SO 2 concentration, and Ce doping on the SO 2 tolerance of the Fe 6 Mn 0.8 Ce 0.2 O y sorbent for mercury removal were explored in a fixed-bed system. Combined with mercury temperature-programmed desorption (Hg-TPD) and X-ray photoelectron spectroscopy (XPS) analysis, the mechanism of mercury removal by the Fe 6 Mn 0.8 Ce 0.2 O y sorbent in the presence of SO 2 was analyzed. The results show that the Fe 6 Mn 0.8 Ce 0.2 O y sorbent is a promising sorbent for circulating mercury removal with high SO 2 tolerance. Ce doping significantly enhances the SO 2 tolerance of the Fe 6 Mn 0.8 Ce 0.2 O y sorbent for mercury removal by protecting the Mn 4+ active sites from SO 2 poisoning. This is because Ce has a stronger affinity with SO 2 compared to that of Mn, and most of SO 2 will preferentially react with CeO 2 instead of MnO 2 to form Ce 2 (SO 4 ) 3 . O 2 in flue gas improves the SO 2 tolerance of the Fe 6 Mn 0.8 Ce 0.2 O y sorbent by timely supplementing the oxygen vacancies. H 2 O coexisting with SO 2 in flue gas further reduces the mercury removal rate because of the competitive adsorption between H 2 O and mercury. Mercury is mainly adsorbed by MnO 2 in the Fe 6 Mn 0.8 Ce 0.2 O y sorbent by the Mars−Maessen mechanism, and SO 2 in flue gas causes the generation of a small amount of Hg 2 SO 4 and HgSO 4 .