摘要:

AbstractNous avons caractérisé par voie chimique les résidus solides issus de la liquéfaction par fractionnement en milieu aqueux de deux essences tropicales. Le procédé de fractionnement est constitué des étapes suivantes: préparation de la suspension aqueuse, préchauffage à 135°C, décharge à travers une restriction (ΔP= 17,2 MPa), réaction entre 180 et 230°C, puis refroidissement rapide.Les solides résiduels ont été analysés selon les deux méthodes suivantes:i)hydrolyse acide: cette technique permet de quantifier les monosaccharides présents dans le résidu et de suivre ainsi la solubilisation des hémicelluloses et de la cellulose.ii)analyse élémentaire: cette technique s'est révélée ětre un indice de la solubilisation connexe des hémicelluloses et de la lignine.Par chromatographie gazeuse nous avons détecté le CO2comme étant le seul gaz formé à des températures inférieures à 230°C.Deux modèles cinétiques de premier ordre relatifs à la solubilisation des hémicelluloses et à la formation du dioxyde de carbone ont été dév

ISSN:0008-4034    

DOI:10.1002/cjce.5450650112

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractThe hydropyrolysis of hardwood and softwood derived black liquor was studied to develop material balance data and to investigate the potential yield of phenolic oils that might be obtained as chemical by‐products of a kraft pulp mill. Hydropyrolysis reactions on softwood liquors were found to be more efficient in char formation than those on hardwood liquors. The yield of extractible phenolic oils was low, around 20–30 percent of black liquor organics, but the yields of simple phenols determined by gas chromatography were found to be even lower at 1–5 percent on black liquor org

ISSN:0008-4034    

DOI:10.1002/cjce.5450650113

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractAn experimental investigation was conducted to ascertain the contribution of thermal reactions in the hydroprocessing reactor of two‐stage liquefaction processes. Various solvent/residuum feedstocks were reacted in the absence of a catalyst at temperatures ranging from 655K to 728K. Detailed characterization of the composite and fractionated feedstock and product samples was performed to ascertain the extent of residuum conversion, heteroatom removal, and hydrogen rearrangement. The results showed that hydrogenation of the solvent portion of the feedstock neither enhances residuum conversion nor results in the transfer of hydrogen from the solvent to the residuum. Higher reaction temperatures also had little effect on the reactions involved. These results suggest that the conversion of residuum in the hydroprocessing reactor of two‐stage liquefaction processes must occur catalytically rather than therma

ISSN:0008-4034    

DOI:10.1002/cjce.5450650114

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractCoal is successfully gasified in the presence of a pilot flame in a modified fluidized bed. Except for the pilot flame, no external heat is required to operate this gasifier. The results showed that increasing the solid‐to‐air ratio in the feed increased the temperature and the products, carbon monoxide and hydrogen. About 95% of the volatile materials and 80% of the fixed carbon of the feed coal could be gasified by this pilot‐flame gasification method. The ash could be efficiently separated during gasification by a distributor within the dead‐zone collector of this g

ISSN:0008-4034    

DOI:10.1002/cjce.5450650115

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractA model is developed for the purpose of analyzing the performance of the ring furnace and the effect of various operational parameters on energy consumption, furnace behavior and product quality. The model combines an energy balance on the gaseous stream and a calculation of heat transfer inside the solids. The process is a semi‐continuous counterflow heat exchange, further complicated by other phenomena such as air infiltration into the flue, evolution of volatile matter, and heat losses. Several simulation runs are made which succeed in reproducing the various real‐life operating conditions, and predicting furnace behavior and efficiency for other conditions. The model proves to be a useful tool for the analysis of this important and costly equipment of the aluminium indus

ISSN:0008-4034    

DOI:10.1002/cjce.5450650116

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractIt is shown that a CSTR is essential for the correct evaluation of kinetic parameters in the Fischer‐Tropsch (FT) synthesis. Furthermore, a rather complicated expression is required in order to extract the correct growth probability at low carbon number in cases where a “break” is observed in the Anderson‐Schulz‐Flory (ASF) distribution.It is shown that if product molecules can readsorb and continue to grow on a variety of locations where competing processes occur, the linearities of the ASF plot are preserved but the slopes of the plot no longer have a simple interpretation in terms of processes governing chain growth on the surface.Finally, results obtained using an integral Plug Flow Reactor (PFR) are shown to yield “growth probabilities” which have no fundamental significance and are a function of the level of conversion and of the inpu

ISSN:0008-4034    

DOI:10.1002/cjce.5450650117

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractThe influence of viscoelasticity on gas hold‐up and the volumetric mass transfer coefficient in a bubble column is discussed and examined experimentally. It was found that the gas hold‐up increased due to an increase in the number of entrapped very small bubbles formed because of the elasticity of the liquid. On the other hand, a decrease in volumetric mass transfer coefficient due to the fluid elasticity was observed. Qualitative effects of an antifoam agent and a draft tube on the performance of the bubble column with viscoelastic fluids were also exami

ISSN:0008-4034    

DOI:10.1002/cjce.5450650118

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractFischer‐Tropsch Synthesis (FTS) was studied on a precipitated Fe/K catalyst in a bubble column slurry reactor (10 cm in diameter, suspension height ≤ 150 cm) with a perforated plate sparger. The rate data for syngas consumption obtained at low H2to CO inlet ratios (<0.8) cannot be described by first order kinetics. However, a multicomponent model which considers rate inhibition by CO2chemisorption gives an excellent description of the data. The optimized kinetic parameters are in agreement with recent findings from an autoclave unit. The multicomponent model and the kinetic parameters can be successfully applied to describe previous results from a bench‐scale pilot plant. The results indicate the importance of rate inhibition by CO2if syngases of low H2to CO ratio from advanced gasifiers are converted by FTS. Two‐stage processes with intermediate CO2absorption are reco

ISSN:0008-4034    

DOI:10.1002/cjce.5450650119

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractThe synthesis of para‐tolunitrile (PTN) and terephthalonitrile (TPN) by reacting nitrogen monoxide with para‐xylene was studied in presence of three chromium oxide catalysts. The Cr2O3—Al2O3catalyst was prepared under the form of aerogel or xerogel and shows excellent selectivities in nitriles along with good stability. However, the unsupported Cr2O3catalyst showed much less performance and, in particular, produced no TPN. The beneficial action of alumina was explained in terms of stabilization of the Cr5+species. Kinetic results seemed to indicate a redox‐type mechanism of the reaction. Moreover the PTN was shown to be an intermediate in TPN fo

ISSN:0008-4034    

DOI:10.1002/cjce.5450650120

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractThe present paper relates to the treatment of crude wet‐process phosphoric acid with ammonium nitrate and hydrofluoric acid to precipitate aluminum and magnesium impurities in the form of an easily separable phase: (NH4)xMgyAlz(F, OH)6.2 H2O. To check the effect of some concentration factors on this reaction, an orthogonal central composite design is realized with three variables: %Al3+, %NH4+and %F−. It is concluded that the amount of aluminum in acid is the limiting factor of magnesium precipitation. Thus complete removal of magnesium, which is a major impurity in wet‐process phosphoric acid, can be obtained by adding to the crude acid extra soluble aluminum salt simultaneously with hydrofluoric acid and ammonium ni

ISSN:0008-4034    

DOI:10.1002/cjce.5450650121

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY