Liquid‐bridge flow in the channel of helical string and its application to gas–liquid contacting process

To solve the problems of the traditional packings, such as high pressure drop, mal‐distribution and short liquid residence time, a helical flow structured packings was proposed. Two different flow patterns, liquid‐bridge flow and liquid‐drop flow were identified when the width of the channel of the helical string was adjusted. Moreover, the characteristics of the helical liquid‐bridge flow including maximum liquid loading, mean thickness of liquid film, mean residence time and effective specific surface area, were examined. And the separation efficiency was studied by the lab‐scale distillation column. In comparison, the effective specific surface area of the helical flow type packings is almost as large as the traditional B1‐350Y structured packings, but with thinner liquid film, longer liquid residence time and finally higher separation efficiency. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3360–3368, 2018     

Kinetics of convective drying of fibre materials based on solution of a diffusion equation

The calculated kinetic curves of convective drying for the moisture, rate, and acceleration of drying are proposed based on the solution of a diffusion equation. The results of the calculation with the equations obtained are compared with the experimental data for convective drying of fibre materials: cotton and viscose fibre and cotton cloth. The universality of the character of the equation of the dimensionless rate of drying as a function of criterion E (dimensionless time of the process) was demonstrated, and this allows generalizing the experimental data on drying of fibre materials. Translated fromKhimicheskie Volokna, No. 6, pp. 53–56,November–December, 1998.     

Drying kinetics and effective moisture diffusivity of purslane undergoing microwave heat treatment

The effects of microwave drying on moisture content, moisture ratio, drying time and effective moisture diffusivity of purslane leaves (Portulaca oleracea L.) were investigated. By increasing the microwave output power (180–900W) and the sample amounts (25–100 g), the drying time decreased from 43 to 12.5 minutes and increased from 27 to 54 minutes, respectively. To determine the kinetic parameters, the drying data were fitted to various models based on the ratios of the differences between the initial and final moisture contents and equilibrium moisture content versus drying time. Among the models proposed, the semi-empirical Midilli et al. model gave a better fit for all drying conditions applied. By increasing the microwave output power and decreasing the sample amount, the effective moisture diffusivity values ranged from 5.913×10⁻¹¹ to 1.872×10⁻¹⁰ m²/s and from 9.889×10⁻¹¹ to 3.292×10⁻¹¹ m²/s, respectively. The activation energy was calculated using an exponential expression based on the Arrhenius equation.     

Effects of dispersant form and amount on the properties of vibrocast periclase-spinel material for making crucibles

The effects have been examined from the form and amount of dispersant on the flow of suspensions based on microgranular periclase, and also the fluidity in the vibration of granular periclase-spinel materials. The best form and amount have been established for dispersants that provide the required flow at various environmental temperatures in the vibration of the granular periclase-spinel materials of water content 5.0–6.5% and working time not less than 3 h. Translated from Novye Ogneupory, No. 12, pp. 24–27, December, 2008.     

Continuous Methanolysis of Palm Oil Using a Liquid–Liquid Film Reactor

A system for the continuous methanolysis of palm oil using a liquid–liquid film reactor (LLFR) was developed and characterized. This reactor is a co-current, constant diameter (0.01 m), custom-made packed column where the mass transfer area between the partially miscible methanol-rich and vegetable oil-rich phases is created in a non-dispersive way, without the intervention of mechanical stirrers or ultrasound devices. An increase in contact area between phases enhances reaction rate while the absence of small, dispersed droplets of one phase into the other diminishes the settling time at the end of the reaction. In this study variations on the concentration of catalyst (sodium hydroxide), flow rate of palm oil and normalized length of the reactor (L/L _max) were explored, keeping constant both the methanol to oil molar ratio and the temperature of the reaction (6:1 and 60 °C). The best experimental results with a reactor of 1.26 m (L/L _max = 1.0) showed a conversion of palm oil of 97.5% and a yield of methyl esters of 92.2% of the theoretical yield, when the mass flow rate and the residence time of the palm oil were 9.0 g min⁻¹ and 5.0 min, respectively. To determine the mean residence time and the degree of axial mixing in the reactor, a residence time distribution (RTD) study was performed using a step-function input. The dispersion model appears to fit well the RTD experimental data.     

Use of polyester monofilaments in the connecting locks of drying screens — “clothing” for paper machines

Different types of frames for joining the ends of drying screens — “clothing” for paper machines were analyzed. A structure for connecting frames for modern fabric drying screens which totally correspond to the technological and service requirements was developed. The optimum types of connecting frames for drying screens include the end segments of the screen fabric forming the sewn flap and the ellipsoidal coil of thick polyester monofilaments mutually connected by a polymer rod. Nevskaya Manufaktura Joint-Stock Company, St. Petersburg. Translated fromKhimicheskie Volokna, No. 5, pp. 45–47. September–October, 1999.     

DRYING OF PULP AND PAPER SLUDGE IN A PULSED FLUID BED DRYER

ABSTRACT

Hydrodynamics and drying kinetics for the pulp and paper primary sludge dried in a pulsed fluid bed dryer with relocated air stream are presented. Batch experiments have indicated that drying of disintegrated sludge to the required 12% moisture content takes place during the first drying period at practically constant material temperature close to the wet bulb temperature with respect to the inlet air conditions. Equations were developed for pressure drop, minimum pulsed-fluidization velocity, dynamic bed height, and volumetric mass transfer coefficient. Continuous experiments under drying conditions determined from the average residence time concept have confirmed that transportation of disintegrated sludge along the dryer follows the plug flow model.

     

Modification of menhaden oil by enzymatic acidolysis to produce structured lipids: Optimization by response surface design in a packed bed reactor

Structured lipids from menhaden oil were produced by enzymatic acidolysis in a packed bed reactor. Response surface methodology was applied to optimize the reaction. Lipozyme IM from Rhizomucor miehei lipase was the biocatalyst, and caprylic acid was the acyl donor. Parameters such as residence time, substrate molar ratio, and reaction temperature were included for the optimization. High incorporation of acyl donor and retention of high levels of eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids in the original menhaden oil were obtained. Good quadratic models were obtained for the incorporation of caprylic acid and for the content of EPA plus DHA retained, by multiple regression with backward elimination. The coefficients of determination (R ²) for the two models were 0.91 and 0.87, respectively. The regression probabilities (P) were below 0.003 for both models. Also, the predicted values from the two models had linear relationships with the observed responses. All parameters studied had positive effects on the incorporation of caprylic acid, but only residence time and substrate molar ratio had negative effects on the content of EPA plus DHA retained. The optimal conditions generated from models were temperature =65°C, substrate molar ratio=4–5, and residence time=180–220 min. Incorporated caprylic acid did not replace DHA, but the content of EPA decreased somewhat with an increase in caprylic acid incorporation.     

Comprehensive analysis of disperse fibre-forming polymers as objects of drying in a suspended bed

The basic elements of a comprehensive analysis of fibre-forming polymers as objects for drying are examined. The basic characteristics and indexes of their effect on the drying process are identified. __________ Translated from Khimicheskie Volokna, No. 3, pp. 24–26, May–June, 2007.     

Modeling the kinetics of drying of viscose fibre

The dependences for describing the kinetics of drying of viscose fibre in restriction of external and internal diffusion with consideration of the period of heating the material are examined. The kinetic dependences are compared with the experimental data for different viscose fibre drying modes and types (convection and microwave with exhaust of vapors). It was confirmed that microwave drying significantly enhances moisture removal. The experimental data on viscose fibre drying kinetics were generalized with a modified quasistationary method. These dependences describe the periods of constant and diminishing drying rates and the heating period with accuracy sufficient for practical calculations. It was shown how to determine the fibre moisture content in any drying zone with the proposed equations. __________ Translated from Khimicheskie Volokna, No. 6, pp. 54–57, November–December, 2006.     

Biodegradation of toluene and dimethyl sulfide in a cocultured biofilter

Biofiltration was performed for 50 days in a perlite-packed biofilter (8 cm I.D.x 105 cm height) for the simultaneous removal of toluene and dimethyl sulfide (DMS). Two strains,Rhodococcus pyridinovorans PYJ-1 andGordonia sihwaniensis PKL-1, were cocultured in the biofilter. Removal efficiencies of toluene and DMS at an empty bed residence time (EBRT) of 3 min were 80–85% and 40–45%, respectively, for an input concentration of 2.5–3.0 mg/L of toluene and 1.5–2.0 mg/L of DMS. The pH of the perlite column was maintained at 7.0–7.2, and the moisture content varied from 61% at the bottom to 51% at the top. Starting from the same initial cell concentration (2.4 x 10₆ CFU/g of wet packing) the number ofR. pyridinovorans PYJ-1 was 2.5 times higher compared with that of G.sihwaniensis PKL-1 after 50 days of operation.     

Condensed combustion products of aluminized propellants. II. evolution of particles with distance from the burning surface

Condensed combustion products of a model propellant on the basis of ammonium perchlorate and aluminum were studied using the sampling technique. The granulometric composition of combustion products and the content of metal aluminum in particles of size from 1.2 μm to maximum were determined within the pressure range of 0.6–7.5 MPa at a distance from the burning surface up to 190 mm. A multimode structure of mass distributions of oxide particles within the size range of 1.2–40 μm was found. An empirical dependence of burnout of metal aluminum from agglomerates on the residence time of particles in the plume of combustion products of the propellant sample was obtained. Translated fromFizika Goreniya i Vzryva, Vol. 36, No. 4. pp. 66–78, July–August, 2000.     

DRYING OF PULP AND PAPER SLUDGE IN A PULSED FLUID BED DRYER

Hydrodynamics and drying kinetics for the pulp and paper primary sludge dried in a pulsed fluid bed dryer with relocated air stream are presented. Batch experiments have indicated that drying of disintegrated sludge to the required 12% moisture content takes place during the first drying period at practically constant material temperature close to the wet bulb temperature with respect to the inlet air conditions. Equations were developed for pressure drop, minimum pulsed-fluidization velocity, dynamic bed height, and volumetric mass transfer coefficient. Continuous experiments under drying conditions determined from the average residence time concept have confirmed that transportation of disintegrated sludge along the dryer follows the plug flow model.     

Use of chemical fibres in drying screens for the paper industry

The basic types of chemical fibres for the development and production of drying screens for paper machines were selected and their properties were determined. Polyester fibres are the most appropriate type for fabrication of drying screens due to their elevated mechanical properties and thermohydrolytic stability. Optimum designs for drying screens based on polyester monofilaments and complex fibres with a polymer coating with defined permeability were developed. To decrease the markability of paper web, it was suggested that the outer supporting surface of the screen be coated with soft fibres or a fibrous layer of Nitron fibres. Translated from Khimicheskie Volokna, No. 2, pp. 43–47, March–April, 1998.     

ANALYSIS OF MECHANICALLY AGITATED FLUID-PARTICLE CONTACT DRYERS

Incorporation of agitation to spouted and fluidized bed dryer result in significant increases in the drying capacity (Q_s ), although product retention persist, which is reduced by increasing the air flow. The physical phenomena occurring in these dryers with several liquid substrates was analyzed and the residence time distributions (RTD) were obtained by the use of dye tracers. The residence time (τ) was found to be a function of the rate of agitation (n) and reaches a minimum at n = n _opt, which was characteristic for each type of substrate, and where maxima also appeared for the drying capacity (Q_s = Q _{s max}) and the heat transfer coefficient (Nu _p = Nu _{p max}). The RTD can be modeled by series of consecutive dryers and a modified Vanderschuren and Delvosalle model can be employed to calculated moisture of the dry product.     

Production of structured lipids in a packed-bed reactor with <Emphasis Type="Italic">thermomyces lanuginosa</Emphasis> lipase

Lipase-catalyzed interesterification between fish oil and medium-chain TAG has been investigated in a packedbed reactor with a commercially immobilized enzyme. The enzyme, a Thermomyces lanuginosa lipase immobilized on silica by granulation (lipozyme TL IM; Novozymes A/S, Bagsvaerd, Denmark), has recently been developed for fat modification. This study focuses on the new characteristics of the lipase in a packed-bed reactor when applied to interesterification of TAG. The degree of reaction was strongly related to the flow rate (residence time) and temperature, whereas formation of hydrolysis by-products (DAG and FFA) were only slightly affected by reaction conditions. The degree of reaction reached equilibrium at 30–40 min residence time, and the most suitable temperature was 60°C or higher with respect to the maximal degree of reaction. The lipase was stable in a 2-wk continuous operation without adjustment of water content or activity of the column and the substrate mixture.     

Pyrolysis of hydrocarbons in a heat-carrier flow with fast mixing of the components

A scheme of autothermal pyrolysis of hydrocarbons in a reactor with fast mixing of the feedstock with a high-temperature heat-carrier flow is considered. The possibility of providing fast mixing of the components is verified in a series of aerodynamic experiments in a model setup, where the optimal geometry of the mixer for operation conditions of the pyrolysis reactor is determined. An experimental reactor is designed and manufactured for verification of the concept proposed. A scheme of the propane pyrolysis reactor is given. Products of combustion of a hydrogen-air mixture are used as a heat carrier. Experimental distributions of the flow temperature and concentration of the injected substance at the exit of the reactor agree with results obtained in the model setup. The mixing time is demonstrated to be smaller than the residence time of the mixture in the reactor mixer by more than an order of magnitude, which allows the process to be arranged under controlled conditions. In addition to experimental research, several detailed kinetic schemes of hydrocarbon pyrolysis are tested on the basis of available experimental data. Results of kinetic calculations for the operation conditions of the experimental setup are presented. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 5, pp. 38–44, September–October, 2008.     

Investigation and calculation of diffusion processes in thin fibre materials and fibre-forming polymers

A solution to the boundary-value problem for diffusion processes in thin fibre materials and fibre-forming polymers is presented. Quantitative estimations for the diffusion coefficients applicable to washing and drying of thin fibre materials and fibre-forming polymers were obtained. __________ Translated from Khimicheskie Volokna, No. 3, pp. 7–8, May–June, 2007.     

Study of an Annular Photoreactor with Tangential Inlet and Outlet: I. Fluid Dynamics

Photochemical reactors tend to exhibit turbulent flow even with low Reynolds numbers. The k‐? model is not always appropriate in this situation. An annular photoreactor was designed with tangential inlet and outlet tubes to investigate this. The fluid flow was characterized by residence time distribution (RTD) experiments, which were reproduced by computational fluid dynamics considering four relevant turbulence models: the k‐?, the k‐ω, the shear stress transport, and the Reynolds stress models. Inlet effects induced helical flow throughout the reactor, switching to plug flow depending on the flow rate and the turbulence model. The k‐ω model properly deals with viscous effects and reproduces the experimental RTD curves with correlation coefficients greater than 0.9566, against 0.8705 from the k‐? model.