Characteristics of gas back-mixing in micro fluidized bed

Micro fluidized bed (MFB) has been applied to isothermal differential analysis of gas-solid reactions (1), and the fluidized gas and gas product passing through the MFBR is expected to be plug flow. Literature shows that the gas flow is close to plug flow and in low axial gas back-mixing when the gas Peclet number (Pe) is over 50 (2). This work devoted to investigating the effects of inner bed diameter (D), superficial gas velocity (Ug) and static particle bed height (Hs) on axial gas back-mixing in MFB and to distinguishing the conditions for the MFB operation. The experiments of axial gas back-mixing testing are conducted by tracer-gas method in a fluidized bed using air as the fluidized gas and helium as the tracer gas. Fluid catalytic crack (FCC) catalyst particles (Geldart A particles) are selected as the fluidized agent. The mean residence time (), Pe and axial diffusion coefficient (Da,g) of gas are calculated to determine the state of gas flow in MFB. Pe generally decreases with the increase of D and the maximum Pe decreases from 200 to 40 when D increases from 5 to 50 mm as shown in Fig 1. When D of fluidized bed was below 15 mm (i.e. 5 and 10 mm), Pe increased observably from 20 to 200 with the increase of Ug from 10 to 65 times of the calculated minimum fluidization velocity (Umf), but Hs had little effect on it. When D was over 15 mm (15-50 mm), Pe first increased and then decreased to be constant as Ug increased. The higher Hs would lead to lower constant Pe. The suitable operating range and parameters leading to Pe above 50 can be obtained from three-dimensional diagram in which coordinate axis was non-dimensional shown in Fig.2. The empirical equations were further developed to predict the Pe in MFB from the major operating parameters. Please click Additional Files below to see the full abstract

Kdm3a lysine demethylase is an Hsp90 client required for cytoskeletal rearrangements during spermatogenesis

The lysine demethylase Kdm3a (Jhdm2a, Jmjd1a) is required for male fertility, sex determination, and metabolic homeostasis through its nuclear role in chromatin remodeling. Many histone-modifying enzymes have additional nonhistone substrates, as well as nonenzymatic functions, contributing to the full spectrum of events underlying their biological roles. We present two Kdm3a mouse models that exhibit cytoplasmic defects that may account in part for the globozoospermia phenotype reported previously. Electron microscopy revealed abnormal acrosome and manchette and the absence of implantation fossa at the caudal end of the nucleus in mice without Kdm3a demethylase activity, which affected cytoplasmic structures required to elongate the sperm head. We describe an enzymatically active new Kdm3a isoform and show that subcellular distribution, protein levels, and lysine demethylation activity of Kdm3a depended on Hsp90. We show that Kdm3a localizes to cytoplasmic structures of maturing spermatids affected in Kdm3a mutant mice, which in turn display altered fractionation of beta-actin and gamma-tubulin. Kdm3a is therefore a multifunctional Hsp90 client protein that participates directly in the regulation of cytoskeletal components.Publisher PDFPeer reviewe

Synthesis, characterization and catalytic methanation performance of modified kaolin-supported Ni-based catalysts

Kaolin as a raw material for mesoporous support was firstly modified by calcination, add treatment, and then was used to prepare nickel catalysts. The amount of alumina which was activated in kaolin during thermal treatment and then leached out in the acid was different. XRD pattern of the kaolin calcined at 600 degrees C or 900 degrees C exhibited only the diffraction peaks for amorphous silica and quartz while that calcined at 1100 degrees C showed obvious peaks for gamma-Al2O3. Therefore, the nickel-based catalysts exhibited different physic-chemical properties. Atmospheric syngas methanation over the catalysts clarified an activity order of CA-1100 > CA-900 > CA-1400 > CA600 > KA approximate to 0 at temperatures of 350-650 degrees C and a space velocity of 120 L.g(-1). h(-1). Metallic nickel with small diameter which has medium interaction with the modified kaolin and is well dispersed on the support would have reasonably good activity and carbon-resistance for syngas methanation. (C) 2019 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights reserved

synthesischaracterizationandcatalyticmethanationperformanceofmodifiedkaolinsupportednibasedcatalysts

Kaolin as a raw material for mesoporous support was firstly modified by calcination, acid treatment, and then was used to prepare nickel catalysts. The amount of alumina which was activated in kaolin during thermal treatment and then leached out in the acid was different. XRD pattern of the kaolin calcined at 600?°C or 900?°C exhibited only the diffraction peaks for amorphous silica and quartz while that calcined at 1100?°C showed obvious peaks for γ-Al 2 O 3 . Therefore, the nickel-based catalysts exhibited different physic-chemical properties. Atmospheric syngas methanation over the catalysts clarified an activity order of CA-1100?>?CA-900?>?CA-1400?>?CA-600?>?KA?≈?0 at temperatures of 350–650?°C and a space velocity of 120?L·g ?1 ·h ?1 . Metallic nickel with small diameter which has medium interaction with the modified kaolin and is well dispersed on the support would have reasonably good activity and carbon-resistance for syngas methanation

synthesischaracterizationandcatalyticmethanationperformanceofmodifiedkaolinsupportednibasedcatalysts

Kaolin as a raw material for mesoporous support was firstly modified by calcination, acid treatment, and then was used to prepare nickel catalysts. The amount of alumina which was activated in kaolin during thermal treatment and then leached out in the acid was different. XRD pattern of the kaolin calcined at 600?°C or 900?°C exhibited only the diffraction peaks for amorphous silica and quartz while that calcined at 1100?°C showed obvious peaks for γ-Al 2 O 3 . Therefore, the nickel-based catalysts exhibited different physic-chemical properties. Atmospheric syngas methanation over the catalysts clarified an activity order of CA-1100?>?CA-900?>?CA-1400?>?CA-600?>?KA?≈?0 at temperatures of 350–650?°C and a space velocity of 120?L·g ?1 ·h ?1 . Metallic nickel with small diameter which has medium interaction with the modified kaolin and is well dispersed on the support would have reasonably good activity and carbon-resistance for syngas methanation

MP-PIC simulation of the effects of spent catalyst distribution and horizontal baffle in an industrial FCC regenerator. Part I: Effects on hydrodynamics

Improving distribution uniformity of spent catalyst and adding horizontal baffles are two effective measures to improve the regeneration performance of a fluid catalytic cracking (FCC) unit. In this study, an industrial coaxial compact FCC regenerator is simulated using a Eulerian- Lagrangian multi-phase particle in cell (MP-PIC) method. By using the energy-minimization multi-scale (EMMS) drag model based on turbulent flow regime, the MP-PIC simulation predicts the typical solids fraction profile which is in good agreement with industrial data. The Crosser grid (a typical horizontal baffle) is successfully constructed with the help of ?virtual baffles? in simulation. The simulation results show that, after adding Crosser grid (a new horizontal fluidized bed baffle by our group), the bed height increases slightly, the lateral mal-distribution index of solids decreases and the descending flux of spent catalysts decreases significantly. The distribution uniformity of spent catalyst distribution along the bed cross section is more uniform when spent catalyst particles are distributed more uniformly. The presence of gas cushion beneath the Crosser grid allows it to act as a pseudo gas distributor, eliminating gas channeling and decreasing zones of low fluidization quality. The rising bubbles are absorbed by the gas cushion and new small bubbles are generated above the Crosser grid, thereby strengthening the gas?solid contact. The guiding vanes of Crosser grid accelerate the lateral movement of particles. The Crosser grid also proves its stronger suppression on the axial back-mixing of solids

Fuel Process. Technol.

This study is devoted to investigating the potential of producing phenols via pyrolysis of lignin in black liquor (BL) by a fixed bed reactor at 350-550 degrees C. The chemicals in the pyrolysis liquid of both black liquor solid (BLS) and purified lignin (PL) from BL are mainly phenols including 4-methoxyphenol, 3,4-dimethoxyphenol, 2-methoxy-4-alkylphenols and alkylphenols. For pyrolysis of BLS, high temperature facilitated the breakage of methoxyl group(s). The highest liquid yield was 27 wt.% at 450 degrees C, and the content of phenols free of -OCH3 reached 55 wt.% in addition to a small amount of other phenols. The pyrolysis of PL with and without addition of alkali additives of NaOH and Na2CO3 at 450 degrees C verified that the alkali could promote the formation of phenols. The strong alkali of NaOH greatly promoted the production of phenols free of -OCH3, whereas the effect of Na2CO3 in this aspect was much less. Catalyzed by its self-contained alkalis, the pyrolysis of BLS had high contents of alkylphenols and phenol in the tar (organics). This shows the prospective for production of phenols from pyrolyzing black liquor, while the heating value of the pyrolysis residue was above 6300 kJ/kg to further support the cascade utilization of BLS. (C) 2014 Elsevier B.V. All rights reserved.This study is devoted to investigating the potential of producing phenols via pyrolysis of lignin in black liquor (BL) by a fixed bed reactor at 350-550 degrees C. The chemicals in the pyrolysis liquid of both black liquor solid (BLS) and purified lignin (PL) from BL are mainly phenols including 4-methoxyphenol, 3,4-dimethoxyphenol, 2-methoxy-4-alkylphenols and alkylphenols. For pyrolysis of BLS, high temperature facilitated the breakage of methoxyl group(s). The highest liquid yield was 27 wt.% at 450 degrees C, and the content of phenols free of -OCH3 reached 55 wt.% in addition to a small amount of other phenols. The pyrolysis of PL with and without addition of alkali additives of NaOH and Na2CO3 at 450 degrees C verified that the alkali could promote the formation of phenols. The strong alkali of NaOH greatly promoted the production of phenols free of -OCH3, whereas the effect of Na2CO3 in this aspect was much less. Catalyzed by its self-contained alkalis, the pyrolysis of BLS had high contents of alkylphenols and phenol in the tar (organics). This shows the prospective for production of phenols from pyrolyzing black liquor, while the heating value of the pyrolysis residue was above 6300 kJ/kg to further support the cascade utilization of BLS. (C) 2014 Elsevier B.V. All rights reserved

Fuel Process. Technol.

Catalytic upgrading of coal pyrolysis tar was investigated in a dual-stage reactor over char and metal-impregnated char (Co-char, Ni-char, Cu-char, Zn-char). The catalytic upgrading caused the lower total tar yield and the higher non-condensable gas yield but the fraction of light tar (boiling point <360 degrees C) obviously increased to allow slightly higher total yield of light tar. When the catalytic upgrading was at 600 degrees C over a layer of char having a mass of 20% of the tested coal, the resulting light tar fraction in the tar increased by 25% in comparison with the coal pyrolysis only at 600 degrees C Over the metal-impregnated char, which was 5% of the tested coal in mass, good upgrading effect was obtained at 500 degrees C. The catalytic tar-upgrading activity decreased in an order of Co-char > Ni-char > Cu-char > Zn-char, and over Ni-char the realized light tar yield and its content in the tar increased by 17.2% and 32.7%, respectively. The upgrading effect also lowered the contents of element N and S in the resulting tar by 45.6% and 43.5%, respectively. NH3-TPD clarified that the order in acidity of the char-based catalysts was the same as for the upgrading activity shown above. (C) 2014 Elsevier B.V. All rights reserved.Catalytic upgrading of coal pyrolysis tar was investigated in a dual-stage reactor over char and metal-impregnated char (Co-char, Ni-char, Cu-char, Zn-char). The catalytic upgrading caused the lower total tar yield and the higher non-condensable gas yield but the fraction of light tar (boiling point Ni-char > Cu-char > Zn-char, and over Ni-char the realized light tar yield and its content in the tar increased by 17.2% and 32.7%, respectively. The upgrading effect also lowered the contents of element N and S in the resulting tar by 45.6% and 43.5%, respectively. NH3-TPD clarified that the order in acidity of the char-based catalysts was the same as for the upgrading activity shown above. (C) 2014 Elsevier B.V. All rights reserved

Multistep Reduction Kinetics of Fine Iron Ore with Carbon Monoxide in a Micro Fluidized Bed Reaction Analyzer

The reduction kinetics of Brazilian hematite by CO is investigated in a Micro Fluidized Bed Reaction Analyzer (MFBRA) using an analyzing method based on Johnson-Mehl-Avrami (JMA) model at temperatures of 973 K (700 A degrees C), 1023 K (750 A degrees C), 1073 K (800 A degrees C), and 1123 K (850 A degrees C). The solid products at different reduction stages are evaluated by SEM/EDS and XRD technologies. Results indicate that the reduction process is better to be discussed in terms of a parallel reaction model that consists of the reactions of hematite to wustite and wustite to iron, rather than a stepwise route. Meanwhile, the controlling mechanism of the reduction process is found to vary with temperature and the degree of conversion. The overall process is controlled by the gas-solid reaction occurring at the iron/wustite interface in the initial stages, and then is limited by the nucleation of wustite, and finally shifts to diffusion control. Moreover, the reactions of hematite to wustite and wustite to iron take place simultaneously but with different time dependences, and the apparent activation energies of hematite to wustite and wustite to iron are determined as 83.61 and 80.40 KJ/mol, respectively.</p