Packed Bed

Brown stock washing is an important stage in pulp and paper industry and in fact plays a key role for reducing environmental problems at one hand and helps to get more concentrated black liquor on the other. Usually, it is carried out by using multiple rotary vacuum washers. For better control of the process a mathematical model pertinent to brown stock washing system involving all the parameters needs to be developed because a theoretical analysis may prove helpful to achieve the required objective. Keeping this in view, the general model for cake washing zone of a brown stock washer has been developed. The general model has been simplified by assuming that the longitudinal dispersion coefficient (DL) is zero as in the case of Perron and Lebeau. This model has been solved to find out the concentration of different streams. The efficiency parameters have been given in terms of fundamental parameters. To calculate the performance of the rotary vacuum washer the data of Han and Edward...

A convenient computational approach for solving mathematical model related to diffusion dispersion during flow through packed bed is presented. The algorithm is based on the mixed collocation method. The method is particularly useful for solving stiff system arising in chemical and process engineering. The convergence of the method is found to be of order 2 using the roots of shifted Chebyshev polynomial. Model is verified using the literature data. This method has provided a convenient check on the accuracy of the results for wide range of parameters, namely, Peclet numbers. Breakthrough curves are plotted to check the effect of Peclet number on average and exit solute concentrations.

Azot oksitler (NOX) güçlü emisyon kaynaklarıdır. Zehirleyici özelliğinden dolayı, baca gazlarında bulunan azot oksitlerin uzaklaştırılması gerekir. Bu çalışmada baca gazlarındaki NO2 gazının dolgulu kolonda tutulması araştırıldı. Bu amaçla bakır ile nitrik asit etkileştirilerek NO2 ...

A careful review of the literature reveals that extensive research has been done on the hydrodynamics in packed bed columns using turbulence models. It can be noted that the choice of turbulence model is influenced by the number of phases, type of fluid, Reynolds number range and the type of packing. Thus, comparison of turbulence models for the selection of a suitable model assumes great importance for the better prediction of flow pattern. This is due to the fact that poor prediction of the flow pattern can lead to a limited heat and mass transfer model as the rate of transfer processes in packed bed is governed by the hydrodynamics of the packed bed. The aim of this paper is to give a review of the computational fluid dynamics (CFD)-based hydrodynamics studies of packed bed columns with the primary interest of studying pressure drop and drag coefficient in packed beds. From the literature survey in Science Direct database, more than 48,000 papers related to packed bed columns hav...

The knowledge of airflow resistant of agricultural materials is important to the design of drying and aeration systems and enhances proper fan selection for these systems. This study investigated the pressure drop across a bed of sponge gourd (Luffa cylindrica) seeds at moisture contents in the range of 9.98 to 16.5% (w.b), airflow rate of 0.11 to 0.32 m3s-1m-2, material bed depth (0.2 to 0.8 m) and bulk density (loose, medium, and high). Pressure drop data was fitted to three common airflow resistance models (Shedd’s, Hukill and Ives’s, and Ergun’s models). An empirical equation comprised bulk density, moisture content, and airflow rate was also developed to predict the pressure drop of sponge gourd seeds. Results obtained indicated that the airflow resistance of sponge gourd seeds increased with increase in airflow rate, bed depth but decreased with moisture content. Increased bulk density resulting from loose to densely filled resulted in an increase in resistance to airflow. She...

The thermal conductivity and the particle‐to‐fluid heat‐transfer coefficient for peanut‐shaped polyester particles in a packed bed were determined simultaneously using the pseudo‐random binary noise sequence (PRBNS) response technique. The modified Dispersion‐Concentric (D‐C) model was applied to beds packed with the non‐spherical particles. A time domain method, using the convolution integral, was developed for removing the effects of the bed ends and the transducer time lag on the experimental responses. Parameter estimation was performed in the time domain, using a simplex method to fit the thermal response calculated from the parametric D‐C model to the experimental response curve. The particle‐to‐fluid heat transfer coefficient in the bed was determined to be 106 W/m2. K at an interstitial fluid velocity of 2.0 m/s. The thermal conductivity of polyester was 0.22 W/m. K at 313 K.

The need for effective technologies to remediate the insensitive munitions compound 3-nitro-1,2,4-triazol-5-one (NTO) is emerging due to the increasing use by the U.S. Army and environmental concerns about the toxicity and aqueous mobility of NTO. Reductive treatment is essential for the complete degradation of NTO to environmentally safe products. The objective of this study is to investigate the feasibility of applying zero-valent iron (ZVI) in a continuous-flow packed bed reactor as an effective NTO remediation technology. The ZVI-packed columns treated an acidic influent (pH 3.0) or a circumneutral influent (pH 6.0) for six months (ca. 11000 pore volumes, PVs). Both columns effectively reduced NTO to the amine product, 3-amino-1,2,4-triazol-5-one (ATO). The column treating the pH-3.0 influent exhibited prolonged longevity in reducing NTO, treating 11-fold more PVs than the column treating pH-6.0 influent until the breakthrough point (defined as when only 85% of NTO was removed)....