EFFECT OF DRYING METHOD ON MESOPOROSITY OF RESORCINOL–FORMALDEHYDE DRYGEL AND CARBON GEL

Resorcinol–formaldehyde hydrogels were synthesized by sol–gel polycondensation of resorcinol with formaldehyde in a slightly basic aqueous solution. RF cryogels, RF xerogels, and RF xerogels (MW gels) were respectively prepared from RF hydrogels by freeze drying, hot air drying, and microwave drying. Carbon cryogels, carbon xerogels and carbon MW gels were subsequently obtained by pyrolyzing RF drygels in an inert atmosphere. Freeze drying and microwave drying were effective to prepare mesoporous RF drygels and carbon gels. RF cryogels and carbon cryogels showed high mesoporosity over wide ranges of the molar ratio of resorcinol to catalyst (R/C) and the ratio of resorcinol to water (R/W) used in sol–gel polycondensation. Although RF xerogels had a few mesopores, carbon xerogels had no mesopores. RF MW gels and carbon MW gels showed mesoporosity if appropriate values of R/C and R/W were selected.     

EFFECT OF HEATING MODES ON INTERNAL STRAIN–STRESS FORMATION DURING DRYING OF MOLDED CERAMICS

Parametric analyses in drying processes of molded ceramics are performed to investigate the influence of heating modes on the formation of drying-induced strain–stress as well as the drying characteristic. The transient three-dimensional problem of strain–stress and heat and moisture transfer in a slab is solved simultaneously by the finite element method. Three modes of hot air, intermittent and internal heating are compared by modeling in the normalized parameters. The tensile and compressive stresses fluctuate, and fall remarkably during the low Biot number period when the slab is heated intermittently. In the internal heating mode, the drying rate is the fastest but stress formation is maintained at the lowest level among the three modes. This effectiveness of the internal heating is investigated experimentally by employing the microwave heating as well.     

DIFFUSION MODELS OF PAPAYA AND MANGO GLACe’ DRYING

ABSTRACT

The objective of this research was to develop diffusion models for papaya and mango glace’ drying. Effective diffusion coefficients of papaya and mango glace’ were evaluated by regression analysis of the experimental data to drying kinetic equation. Models 1 and 2 were developed by assuming that effective diffusion coefficients were constant and varied proportionally with the moisture ratio. Model 3, which the Arrhenius factor was a second-degree polynomial function of moisture content, was developed by assuming that the value of effective diffusion coefficient was constant over a short time interval. Model 4, which was similar to Model 3, was developed by considering the effect of volume shrinkage during drying. Four diffusion models were compared and it was found that the predicted values of moisture contents calculated by using Models 1 and 2 were close to experimental values during the early period of drying. Models 3 and 4 were able to have better predictions particularly towards the final period of drying. However, Model 4 was complicated. Therefore, Model 3 was recommended for calculating drying curves of papaya and mango glace’ drying.     

CONVECTION HEAT TRANSEER COEFFICIENTS AT CONVECTIVE DRYING OF POROUS MATERIALS∗

ABSTRACT

Our measurements proved that the convective heat transfer coefficient (h) has a larger value h_wet at the constant drying rate period and after that it falls down to a minimum one: h_dry in the equilibrium dried state (see Fig.1). Our measurements showed also that the heat of vaporisation in the last phase of the falling drying rate period is far greater than it was in the constant drying rate period (see Fig.10).

Our first measurements were made on a gypsum plate. Afterwards we carried out measurement research with fine glass powder and cement-perlite plate and determined h_wet and h_dry heat transfer coefficients as function of Reynolds number. All of these measurements confirmed our establishment that h_wet is far greater than h_dry .     

DRYING CHARACTERISTICS OF OSMOTICALLY PRETREATED CRANBERRIES—ENERGY AND QUALITY ASPECTS*

ABSTRACT

This study reports on finish drying of osmotically pretreated (dehydrated and sugar-infused) cranberries. The halved fresh berries pretreated in a standard osmotic solution (67.5 Brix at 50°C for 5 h) were then freeze-dried, vacuum-dried and air-dried in various dryers (cabinet-air-through, fluid bed, pulsed fluid bed, and vibrated fluid bed dryers) in order to identify the best drying technology. Energy consumption and product quality were chosen as the comparison criteria. The best product quality, quantified by the anthocyanins content, rehydration ratio, color and taste, was noted for freeze-dried berries. As all other drying methods gave similar, albeit slightly lower quality products than freeze-drying, the selection of a drying method could be based on the unit heat consumption. The vibrated fluid bed and the pulsed fluid bed should be favored because of the highest energy efficiency. Even though sugar infused into cranberries during osmotic pretreatment reduces drying rates during the second drying period as compared to untreated berries, osmotic dehydration reduces the total energy consumption on top of the preferential sensory characteristics of the final product.

     

areviewof: A Comprehensive Review of the Book DRYING’85

This work studied the effects of drying temperature on the quality and drying kinetics of betel leaves (Piper betle L.). As the drying process applies heat on the product, this might lead to the degradation and decomposition of valuable phytochemicals within the herbs. In this study, the effect of drying temperature on the quality of dried leaves was studied by analyzing the change of major phytochemicals found in the leaves, which are hydroxychavicol and eugenol. The results indicate that the content of major compounds increased with temperature from 40 to 70°C but underwent decomposition when the leaves dried at 80°C. Besides that, the drying kinetics for different drying temperatures also studied. The kinetics results show that the increase of drying temperature shortened the total drying time. Five thin-layer models were selected in describing the drying process of betel leaves. The logarithmic model was found to be the most suitable one.     

新百货 COME ON

<正>提及百货公司,就会忆起上世纪90年代妈妈们在人头攒动的国营商场里购物的情形。多年过去,一节节玻璃柜台变成了开放式售架,货柜后面的售货员也换作了年轻优雅的妙龄女郎,独栋的百货商场,也变身成应有尽有的大型购物中心,灯火通明,人山人海。但近些年来,在外有电子商务、内有租金压力等因素的影响下,传统百货公司正逐渐步入尴尬的境地,人们开始习惯网络购物,商场不再人来人往,若想留住顾客,转型是百货公司唯一的路,     

EXPERIMENT ON METHANE GAS HYDRATE FORMATION

1　INTRODUCTIONMethanegashydrates (MGH )aresolidphasecrystallineinclusioncompounds (alsocalledclathrates)thatconsistofahostwaterlatticewithcavitiesinwhichmethanegasiscagedasaguestgas Methanegashydratemightcontain 164volumes(atstandard pressureandtemperatu…     

STUDY ON THE INFLUENCE OF ANNULAR SPACE WIDTH ON THE AXIAL MIXING IN PULSED-SIEVE-PLATE EXTRACTION COLUMN

1 INTRODUCTIONAnnular pulsed-sieve-plate extraction column is an unique extraction equipment that can beused to ensure critical safety in reprocssing of irradiated nuclear fuel,The study of this kind ofextraction column has been carried out and some results were published in resent years [1—9]. It is known that axial mixing is one of most important parameters effecting column be-     

THE INFLUENCE OF PROCESS PARAMETERS ON THE INTERFACIAL CHEMISTRY OF γ-GPS ON ALUMINIUM: A REVIEW

Within the “International Collaborative Programme on Organosilane Adhesion Promoters” (ICOSAP), scientists from the U.S. and Europe contributed to the understanding of an organosilane primer process, based on an aqueous solution of γ-glycidoxypropyl trimethoxysilane (γ-GPS), used currently for aerospace repair purposes. Parameters such as temperature of cure, ageing time, and concentration of the aqueous solution have been investigated, and this work reviews the effect that each variable has on the process, and the resulting integrity of the GPS/aluminium interface. The aim of the work was to provide a more environmentally friendly replacement for pretreatments containing Cr(VI) that are currently used, such as chromic acid anodising and acid etching employed for the structural adhesive bonding of aluminium.

The formation of covalent interfacial bonding is shown to be a function of the hydrolysis and condensation of the silane molecules in solution as well as the type of solvent used. The curing temperature of the aqueous film on the aluminium is also shown to have an effect on the chemistry of the resulting primer film and its efficacy as an adhesion promoter. All these parameters must be optimised to obtain durability that matches that obtained by a phosphoric acid anodising pretreatment. This work reports on the various studies performed towards this aim carried out within the remit of the ICOSAP initiative, with a particular emphasis on the interfacial chemistry between γ-GPS and the aluminium substrate, and indicates the manner in which the results point the way towards a viable, environmentally friendly pretreatment for the adhesive bonding of aluminium for aerospaceapplications.     

STUDY ON THE SCALE-UP EFFECT OF CYCLONES

The scale-up effect, which is a key factor controlling the performance of industrial cyclones, is conventionally estimated through grade efficienty curves. A new principle based on the centrifugal separation factor (CSF) is proposed to improve the scale-up procedure in designing industrial cyclones.     

STUDY ON EBULLIOMETRIC METHOD AND LEANING EBULLIOMETER

The relation between the gravimetric liquid concentration (χ_(10)) and equilibrium one (χ_1) is developed for the system within an ebulliometer or a still operating steadily. From the relation, the necessary and sufficient condition for χ_(10)→χ_1, and a new equation for calculating limiting activity coefficient (γ~∞) are deduced. This equation proves more accurate than that proposed by previous researchers. The leaning ebulliometer, a new apparatus, is designed to measure bubble points and γ~∞ without composition analysis, its operating line (T, P, χ_(10)) proves a good approximation to the bubble-point line (T, P, χ_1): |(χ_(10)-χ_1)/χ)|<0.005|K_1-1|, where K_1=y_1/χ_1 is the K-value.     

KINETICS ON EPOXIDATION OF PROPYLENE WITH ETHYLBENZENE HYDROPEROXIDE

In the range of 76° to 1200C,Dalin and others studied the kinetics on molybdenum-catalyzed epoxi-dation of propylene with ethylbenzene hydroperoxide,proposed a mechanism model of this reaction andsuggested that effective concentration of catalyst is constant during the process of epoxidation.In thispaper the reaction has been studied experimentally based on Dalin's investigation.After analyzing thedata obtained in our experiment and those of Dalin,it is shown that the effective concentration of thecatalyst is not a constant but a variable,and its rate of consumption behaves in accordance with the firstorder reaction.Thus,the authors have modified the mechanism model in literature [3] and pointed outthat the deactivation mechanism of the catalyst is different from the inhibition mechanism described byFarberof.     

STUDIES ON GAS-LIQUID-SUSPENDED SOLID MULTIDECK GAS LIFT REACTOR

Following the work on gas lift reactor (Pachuca tank) for gas-liquid-suspended solid 3-phase reaction,multideck gas lift reactors have been developed.This type of reactor has many unique advantages suchas realization of counter-current operation between gas and slurry,reduction of gas consumption and lower-ing of the amount of volatile components of the liquid which has to be recovered from the exit gas.The stability of the overflow tube of the reactor was studied.A semiempirical equation was derived tocalculate the flooding point of the reactor.The operating range of the overflow tube was also deter-mined.This multideck reactor has been operated successfully in a pilot plant of ammonia leaching of copperore.Results agree reasonably well with those predicted from small scale batch experiments.The extractionof vanadium from soda roasted steel slag in a 5-deck reactor with carbon dioxide in the gas phase wasalso satisfactory.Experimental results obtained from the continuous flow 5-deck reactor and those calcu-lated from batch experimental data with CSTR model were in agreement.     

ADSORPTION OF H_2PtCl_6 ON ALUMINA

The adsorption kinetics and equilibrium of H_2PtCl_6 on various types of alumina were studied,and IRSand DRS were used to characterize these supports before and after impregnating with H_2PtCl_6 solution.Thedata indicated that the uptake of H_2PtCl_6 on supports strongly depends on the Lewis acidity of alumina andthat the adsorption rate is controlled by pore diffusion for supports of high adsorption capacity.Relationshipbetween uptake and acidity is interpreted in terms of active hydroxyl groups on alumina.     

INFLUENCE OF CHEMICAL ADDITIVES ON GAS HYDRATE FORMATION

One surfactant as sodium dodecyl sulfate (SDS) and one synthesized sample as gas hydrate inhibitor are introduced in this paper. Through experiments we prove sodium dodecyl sulfate can accelerate the formation rate of gas hydrate and the synthesized sample can inhibit the formation and growth.     

KINETIC STUDIES ON SUSPENSION POLYMERIZATION OF VINYL CHLORIDE

A kinetic model dC/dt=a βC~(1/3)for suspension polymerization of vinyl chloride was developed.Kineticstudies on such polymerization were carried out in a stainless steel tube reactor in the presence of high-,medium-,or low-activity initiators at different concentrations,and at temperatures ranging from 50 to 62~C.Twenty-six sets of kinetic data were obtained under different conditions.According to these experimentalresults,the acceleration behavior of vinyl chloride polymerization was discussed in detail.It is proposed thatthe auto-acceleration effect is due to the decrease of the termination rate constnat in the polymer-rich phaseand to the increase of initiator concentration owing to volume contraction during polymerization with aninitiator of lower activity.All plots of dC/dt against C are nonlinear during the two-phase stage,while dC/dtversus C~(2/2)curves show much better linearity up to 60—70% conversion.The proposed model can beused to explain satisfactorily why the reaction order of initiators is between 0.5 and 1.0.     

A STUDY ON SUPERCRITICAL FLUID EXTRACTION OF L-PROLINE

The extraction of L-proline from the fermentation broth filtrate with the supercritical fluid was studied. It has been proved that L-proline and most amino acids are hardly dissolved in the pure supercritical carbon dioxide fluid. When the methyl alcohol was added as an entrainer in L-proline solution or carbon dioxide fluid, the solubility of L-proline in the supercritical fluid would be greatly increased, but ethyl alcohol was unsatisfactory as an entrainer.The influences of extraction pressure, temperature, time, flow rate of fluid, concentrations of L-proline and entrainer on the yield of L-proline have been investigated for searching the optimal extraction conditions.