Tandem fluidized bed elutriator-Pneumatic classification of coal particles in a fluidized conveyer

Classification performance as a function of gas velocity. Display omitte

Tandem fluidized bed elutriator-Pneumatic classification of coal particles in a fluidized conveyer

Coal moisture control (CMC) in coking process, which reduces coal moisture before loading the coal into the coke oven, allows substantial reduction in coking energy consumption and increase in coke productivity. The technology is seeking to integrate the coal classification, thus calling it the coal classifying moisture control (CCMC), to separate the fine and coarse coal fractions in the CMC process so that the downstream coal crushing can only treat the coarse fraction. CCMC adopts a reactor that integrates a fluidized bottom section and a pneumatic conveying top section. The present work investigates the pneumatic classification behavior in a laboratory CCMC reactor with such a configuration by removing the coal fraction below a given size (e.g., 3.0 mm) from a 0 to 20.0 mm coal feed. The results show that the coal classification were dominated by the gas velocity in the top conveying section, and the required gas velocity for ensuring the maximal degree of removing a fine coal fraction could be roughly predicted by the Richardson and Zaki equation. The effect of bottom fluidization on the performance of CCMC is also examined. (c) 2012 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved

Research on the Influence of Combustion Methods on NOx Emissions from Co-combustion of Various Tannery Wastes

To further increase combustion efficiency and reduce nitrogen oxide pollution caused by tannery wastes, three raw materials, including tannery sludge, chrome-tanned buffing dust, and chrome shavings, were burned together in a dual-bed model reactor under various conditions. In addition, a thermogravimetric analysis of co-combustion of three tannery wastes was studied in this study, which was conducive to understanding the combustion characteristics and positive effects. The comprehensive combustibility index S, the flammability index K-r, and the stable combustion characteristic index G(b) all increased when the tannery sludge was blended with chrome-tanned buffing dust and chrome shavings, indicating that the combustion behavior was improved by co-combustion. For normal combustion, decreasing the gas volume flow and temperature resulted in a decrease in the oxidation of nitrogen compounds, consequently lowering the NOx emission. During air staged combustion, at an appropriate secondary gas ratio of about 10-40%, the NOx reduction would be increased from 10.9 to 19.3%. By increasing the tertiary gas volume flow from 0.2 to 1.1 L/min in decoupling combustion, an average relative NOx reduction efficiency of 47% was attained compared with normal combustion. The results offered a viable technology that resulted in a lower NOx emission and realized the application of decoupling combustion

Destructive Influence of Cement Dust on the Structure and DeNO(x) Performance of V-Based SCR Catalyst

To investigate the poisoning effects of the cement dust, the commercial V-based catalyst was directly mixed and aged with the real cement kiln dust. It was found that the introduction of cement dust led to the serious deactivation of catalysts, especially for the aged samples above 300 degrees C. The multiple characterization results (X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, NH3-temperature-programmed desorption, and H-2-temperature-programmed reduction) revealed that the alkaline/alkaline earth metal elements (mainly Ca) can react with the active components through solid phase reaction to form inactive surface A(x)V(1-x)O(4) (A=Ca, K, Na, etc.), solid solutions, and the Scheelite phase, bringing about the reduction of the surface acid sites and the passivation of the redox cycle of V5+/V4+. These results implied that the inert solid solutions may form on the industrial flue gas condition, and change the structure and properties of catalytic sites, which may result in the poisoning and inactivation of the selective catalytic reduction catalyst by cement dust

Development of Red Mud Coated Catalytic Filter for NOx Removal in the High Temperature Range of 300-450 degrees C

The red mud (RM) coated catalytic filter was developed as efficient multifunctional material to simultaneously remove NOx and dust in the high temperature range of 300-450 degrees C, which exhibits excellent deNO(x) activity/durability as well as low pressure drop with more than 80% NO conversion in the presence of H2O/SO2. The performance of the RM coated catalytic filter is obviously superior to that of the reference samples of V-W-Ti and Fe-Ti based filter. The multiple characterization data (including XRD, XRF, BET, SEM, TPX and LPSA) reveals the amorphous state of the RM catalyst with high dispersity of Fe active sites accounts for the high adsorption capacity of NH3 and thus excellent deNO(x) performance. Moreover, the prepared colloidal RM slurry is very uniform and stable with the smallest average particle size, which reduces the blocking up of the channel of filter and facilitates the decrease of pressure drop as well as the improvement of deNO(x) activity. The excellent deNO(x) performance, low pressure drop together with the low cost make the RM coated catalytic filter to be promising application prospect for purification of the high-temperature flue gas with high content of dust such as in cement and glass furnaces. Graphic The preparation of RM catalytic filter and the comparison of SCR performance between three kinds of catalytic filters

The simultaneous removal of SO2 and NO from flue gas over activated coke in a multi-stage fluidized bed at low temperature

A multi-stage fluidized bed (MSFB) process was explored to simultaneously remove the SO2 and NOx from flue gas by use of activated coke (AC) as active medium in low temperature range of 100-200 degrees C. The various technological tests (e.g., temperature, feeding rate, superficial gas velocity, bed numbers) were carried out to make clear the removal features of SO2 and NOx in MSFB system. The MSFB process could not only increase both the removal efficiency and capacity of SO2 over AC, but also eliminate SO2 in the first layer of bed to avoid poisoning the AC by ammonium sulphate in upper beds for denitration. 100% desulfurization efficiency and 73.2% denitration efficiency could be acquired over regenerated AC through the four-stage bed at 180 degrees C in the presence of 10 vol% H2O, which was even much more efficient than moving bed process. Moreover, the fresh AC could be activated after the use/regeneration circulation of AC, and the removal efficiency for both SO2 and NO was significantly elevated over the regenerated AC. The multiple structural characterizations (BET, FT-IR, TPD, XPS) revealed that the microporous structure of regenerated AC was expanded with increased surface area and pore volume to provide more adsorption sites for SO2, and meanwhile abundant surface nitrogen/sulfur/oxygen groups were produced as catalytic sites for denitration, accounting for the significantly promoted removal efficiency over the regenerated AC. The demonstrated advantages of MSFB system signify its promising application prospect for the simultaneous removal of SO2 and NOx in industry

The synergistic effect on the product distribution for the co-pyrolysis of tannery wastes

The resource management and decontamination of tannery wastes are greatly desired in the tannery industry. The co-pyrolysis of three tannery wastes (chrome tanned buffing dust (CTBD), chrome shavings (CS), and tanning sludge (TS)) were explored for optimizing the pyrolysis process and product, which significantly increased the yield of tar/gas, the fraction of light tar and the specific surface area of char. The results showed that different materials interacted in the pyrolysis progress, and the influence of the CTBD/CS/TS ratio further confirmed the existence of a synergistic effect. TS played a key role in the co-pyrolysis process, which notably promoted the secondary reaction process of char to tar/gas and upgraded the produced volatiles. Moreover, further investigation into the effect of mineral components revealed that the synergistic effect of co-pyrolysis derived from the catalytic effect of mineral components such as Fe(2)O(3 )and CaCO3 in TS, accounted for the significantly-improved co-pyrolysis performance of tannery wastes. The excellent co-pyrolysis performance of tannery wastes may provide a promising technical route for their resource utilization

Kinetics and Mechanism of Solid Reactions in a Micro Fluidized Bed Reactor

A novel gas solid Micro Fluidized Bed Reaction Analyzer (MFBRA) was developed to deduce reaction rates and kinetic parameters through measuring time-dependent composition changes of evolved gases from the reactions. Application of the MFBRA to the decomposition of CaCO(3) powder resulted in an apparent activation energy of 142.73 kJ/mol and a pre-exponential factor of 399,777 s(-1). This apparent activation energy was much lower than the thermogravimetry-measured value of 184.31 kJ/mol, demonstrating a quicker reaction in the MFBRA. This was further verified by CuO reduction in CO, as accelerated by the fast diffusion and high heating rate in the MFBRA. Measurement of pyrolysis of coal and biomass in MFBRA found that the reaction process was completed in about 10 s, a time much shorter than the literature-reported values in larger fluidized bed reactors. By monitoring the release of gas species from reactions at different temperatures, the MFBRA also allowed deeper insight into the mechanism of pyrolysis reactions. (C) 2010 American Institute of Chemical Engineers AIChE J, 56: 2905-2912, 201

High-quality tar production from coal in an integrated reactor: Rapid pyrolysis in a drop tube and downstream volatiles upgrading over char in a moving bed

A purposely built integrated reactor, which comprised a drop tube and a moving bed assembly located at the bottom of the drop tube, combined rapid pyrolysis and in situ volatiles upgrading over char for the production of high-quality tar from coal. Rapid pyrolysis took place when coal particles flowed through the hot drop tube, and then the produced volatiles and char were introduced into the moving bed for further pyrolysis and volatiles upgrading. The operation parameters of rapid pyrolysis alone in the drop tube were first investigated to ensure a high yield of the initial tar for further upgrading in the moving bed. The effects of the temperature and char bed thickness on further pyrolysis and volatiles upgrading were then determined to obtain the optimized operating conditions in the moving bed. Under the optimized conditions, the tar yield could be as high as 11.4 wt% and reached 89.8% of the Gray-King assay yield. The light fraction in the tar and light tar yield reached 69.0% and 7.9 wt%, respectively, which was much better than that obtained from the rapid pyrolysis alone in the drop tube. The experimental results could confirm the feasibility of the integrated pyrolysis-upgrading process for the production of high-quality tar from coal

The synergistic effect on the product distribution for the co-pyrolysis of tannery wastes

The resource management and decontamination of tannery wastes are greatly desired in the tannery industry. The co-pyrolysis of three tannery wastes (chrome tanned buffing dust (CTBD), chrome shavings (CS), and tanning sludge (TS)) were explored for optimizing the pyrolysis process and product, which significantly increased the yield of tar/gas, the fraction of light tar and the specific surface area of char. The results showed that different materials interacted in the pyrolysis progress, and the influence of the CTBD/CS/TS ratio further confirmed the existence of a synergistic effect. TS played a key role in the co-pyrolysis process, which notably promoted the secondary reaction process of char to tar/gas and upgraded the produced volatiles. Moreover, further investigation into the effect of mineral components revealed that the synergistic effect of co-pyrolysis derived from the catalytic effect of mineral components such as Fe(2)O(3 )and CaCO3 in TS, accounted for the significantly-improved co-pyrolysis performance of tannery wastes. The excellent co-pyrolysis performance of tannery wastes may provide a promising technical route for their resource utilization