Showing papers on "Packed bed published in 1971"

A comparative study of immobilized amyloglucosidase in a packed bed reactor and a continuous feed stirred tank reactor

Abstract: The catalytic activity of amyloglucosidase covalently attached to DEAE‐cellulose was studied in a packed bed reactor and a continuous feed stirred tank reactor (CSTR) for the reaction maltose → glucose. At low flow rates mass‐transfer limitations in the bed reactor lead to lower conversions for this reactor compared to the CSTR. Simple theoretical expressions for these reactors were compared with the experimental results. There are significant differences between the kinetic parameters and pH profile of the immobilized and free enzyme. The immobilized enzyme also showed greater stability at 50°C than did free amyloglucosidase. The temperature dependence of the reaction rate was the same for immobilized and free enzyme.

Multiple compartment packed bed absorber-desorber heat exchanger and method

Abstract: The invention is a multiple compartment packed bed absorberdesorber heat exchanger. The absorber-desorber heat exchanger includes at least one set of upper and lower compartments containing suitable tower packing. Gas inlets, gas outlets and liquid distributors are provided for each packed bed chamber. The gas flows in the upper and lower compartments are isolated from each other by a liquid seal. The upper and lower packed beds are wetted by a common irrigation liquid or heat exchange fluid which gravitates downwardly through the packed beds to a sump and recycling pump. The dual packed beds can be operated to absorb and desorb gases, to concentrate gaseous contaminants, or to transfer heat and to condense vapors. Preferably, the dual packed bed chambers are of modular construction.

Flue gas recovery method and apparatus

Abstract: The invention is an improved process for the recovery of, for example, sulfur dioxide and heat from hot flue gas employing direct contact packed-bed heat exchangers, a packed bed absorber and desorber and packed bed liquid-liquid heat exchangers of improved design. The process utilizes the thermal energy of the hot flue gas to: desorb sulfur dioxide, preheat combustion air and to reheat absorber tail gas. The formation of a vapor plume and loss in stack gas draft is minimized by operating the absorber at low temperatures and by reheating the absorber tail gases. Heat is extracted from the hot flue gas and cooled by direct contact with an immiscible heat transfer fluid in a packed bed. Moisture is condensed from the flue gas by direct contact with cold heat transfer fluid, and separated from the heat transfer fluid by decantation. Sulfur dioxide is absorbed from the cooled flue gas in a packed bed by direct contact with a cold aqueous sulfite solution to form a bisulfite salt solution. The aqueous bisulfite salt solution is thermally decomposed and the sulfur dioxide desorbed by heating through direct contact with hot heat transfer fluid from the initial flue gas cooling step. Heat is recovered from the stripped sulfite absorption solution by direct contact with heat transfer fluid and used to preheat combustion air. The decomposition of the bisulfite solution during the sulfur dioxide desorption process is aided by the heat transfer fluid which contains an organic acid which is partially miscible with water at elevated temperatures. Improved absorber design is based upon the use of slant packed beds, slant inlet-outlet packed bed access parts and slant packed bed tower internals for reduced bed cloggage, reduced absorber height and ease of packing replacement while the absorbers are in use.

Packed bed electrochemical cell including particulate bipolar electrodes separated by non conducting particles

Abstract: A PACKED BED TYPE OF ELECTROCHEMICAL CELL COMPRISES A LARGE NUMBER OF ISOLATED CONDUCTING UNITS SEPARATED BY NON-CONDUCTING MEANS, THE BED BEING ARRANGED BETWEEN TWO ELECTRODES AND ELECTROLYTE MADE TO FLOW THROUGH THE BED. IN CONSQUENCE THE CELL, IN OPERATION, COMPRISES A MULTIPLICITY OF SMALL BIPOLAR CELLS DISTRIBUTED THROUGHOUT THE BED. THE BED MAY BE CYLINDRICAL OR RECTANGUALR OR OF ANY DESIRED FORM AND MAY COMPRISE A MIXTURE OF CONDUCTING AND NON-CONDUCTING PARTICLES. IF THE PARTICELES ARE OF SIMILAR SIZE OR SIZE DISTRIBUTION, THEN ABOUT TWICE THE QUANTITY (VOLUME) OF NON-CONDUCTING PARTICLES AS CONDUCTING PARTICLES ARE PROBABLY REQUIRED.

Method and apparatus for purifying waste gas

Abstract: Purification of a gas is accomplished by passing the gas through a packed bed having an adsorbent deposited thereon and means are provided for cleaning the bed and depositing fresh absorbent thereon

Pressure drag measurements for turbulent air flow through a packed bed

Abstract: Pressure drag coefficients of spheres in a cubic packing of equal spheres have been determined at Reynolds numbers of 27,000, 10,000, 5,000 and 2,500, where NRe is based on superficial air velocity and a sphere diameter of 7 cm. Two cubic arrangements were used: in the regular arrangement, the mean flow was parallel to one of the principal axes, while in the skewed arrangement, the mean flow made equal angles with the three principal axes of the packing. The pressure drag coefficient of the central sphere has been measured for each of the 12 banks in the regular arrangement, and the effect of bed length has been determined for lengths varying between 1 and 12 banks. The pressure drag coefficient for the central sphere and the overall pressure drop in the skewed arrangement were found to be lower than for the regular arrangement at the same Reynolds number. From the distribution of local pressure measurements, the separation and reattachment points on the central sphere in each bank were determined, indicating that the boundary-layer behavior on a sphere in a packing is similar to that over a single sphere, when allowing for the effects of turbulence and of pressure gradient.

A stochastic model of packed‐bed mixing and mass transfer

Abstract: A new model of packed-bed behavior based on a second-order stochastic process is developed and examined. The model takes as the basis process the transitions of fluid “packets” among allowed velocity states. The observable phenomenon, that is, the spatial distribution of packets, is a projection of the velocity state process. Results from the model compare well with results from experiments for mixing in packed beds. Model parameters are consistent, and correlate with the physical parameters of the systems. Present results under mass transfer conditions are inconclusive but encouraging.

Transport of a fluid through a packed bed

Abstract: The transport of a fluid through a packed bed can be interpreted on the basis of a dispersion model in terms of a dimensionless dispersion number and an effective adsorption capacity for the adsorbent-fluid system. The dimensionless dispersion number is inversely related to the theoretical plate number in the theoretical plate model for the transport of a fluid through a packed bed. The effects of neglecting one of the terms in the solution to the transport equation in the theoretical plate treatment has been examined from the viewpoint of the dispersion model and shown to be significant for adsorbent-fluid systems with dispersion numbers that correspond to low and even fractional theoretical plate numbers. Even for systems with low dispersion numbers that correspond to high theoretical plate numbers, the error is not negligible for values of the concentration of the adsorbate at the outlet of a packed bed that are small compared with the inlet concentration. Experimental data for adsorption systems with dispersion numbers that correspond to small and fractional theoretical plate numbers are compared with the time-dependent equations of the dispersion and theoretical plate models for the transmission of an adsorbate through a packed bed, where the transmission is the ratio of the adsorbate concentration at the outlet of the bed to that at the inlet.

Simultaneous computation of heat transfer and dispersion coefficients and thermal conductivity value in a packed bed of spheres: II. Technique of computing numerical values

Abstract: The method of computing the numerical values is given. It is illustrated with a simulated example to show the high accuracy that is possible, the unknowns being found to four significant figures. The only quantities required are ones that can be measured accurately: the radius of the spherical packing, its volumetric specific heat, and values of the amplitude attenuation and phase angle lag at a minimum of four finite values of the frequency.

Oxidation Adsorption of Sulphur Dioxide in Packed Bed of Activated Carbon

Abstract: 活性炭吸着法による排煙脱硫装置の設計には, 従来, 小規模実験を行なって求めた破過曲線が用いられている。本研究においては, 破過曲線を計算から求める方法を考案した。すなわち, 著者らは前報において, 熱天秤型吸着量測定装置を用い亜硫酸ガスの平衡吸着量や吸着速度を測定し, 実験結果を十分説明しうる吸着反応の速度式を提出したが, この速度式および充填層での物質収支の式を基礎として, 活性炭充填層吸着時の破過曲線を計算し, 実際の固定床による実験結果と比較検討した。その結果, 計算破過曲線と実測値とは, ガス中の亜硫酸ガス濃度および活性炭の種類によらずよく一致することが認められ, 本法による破過曲線の計算法が十分実用できることが確認された。すなわち, 使用する活性炭について, 熱天秤型吸着量測定装置によって, 吸着速度および吸着等温線を測定しておけば, 充填層式吸着を行なう場合の任意のガス濃度, 流速, 活性炭充填量, 装置断面積における破過曲線を計算することができ, これをもとにして吸着装置の設計が行なえることが確認された。

Semifluidization- A Review

Abstract: SEMIFLUIDIZATION is a new and unique type of fluid-solid contacting technique which has been reported recently. In most of the chemical plants we come across situations where a solid phase has to be kept in contact with a fluid phase — for example diffusional operations like drying, adsorption, reaction kinetics, solid catalysed reactions, heat transfer, etc. In all these cases fluid solid contacting is very essential and developments to increase the efficiency of contact are always welcome. Fixed bed or packed bed, batch and continuous fluidization and semifluidization all are two phase phenomena. In case of batch fluidization if the free expansion of the bed is restricted by the introduction of porous disc or sieve and the fluid velocity is increased the particles are fluidized and the expansion starts with further increase in velocity of fluid—the particles will be carried and the formation of a fixed bed results at the top. So by the introduction of restraint some of the particles are distributed to bottom section which is in the form of a packed bed. This is known as semifluidization which can be considered as a new type of solid-fluid contacting method which combines the features of both fixed and fluidized beds. This type of technique overcomes the disadvantages of fluidized bed namely back mixing of solids, attrition of solids and problems involving erosion of surfaces. This also overcomes certain draw backs of packed bed, viz., non-uniformity in temperature in the bed, channel flow and seggregation of solids.

Making ammonium polyphosphate in a packed column

Abstract: HYDROLYSIS OF AMMONIUM POLYPHOSPHATE CAN BE SIGNIFICANTLY DELAYED AND REDUCED WHEN THE HOT FRESHLY MADE AMMONIUM POLYPHOSPHATE REACTION MIXTURE, STILL UNDER PRESSURE, IS PASSED THROUGH A COLUMN CONTAINING AN INERT PACKING E.G. TABULAR ALUMINA, SILICON CARBIDE, OR PORCELAIN.

Frequency response in reacting systems

Abstract: For a packed bed of spherical catalyst pellets, where the intraparticle diffusion resistance is negligible at steady-state operation, frequency transfer function for concentration perturbation of reactant for n-th order reaction kinetics is derived in view of the effects of longitudinal dispersion in moving phase, resistance to diffusion in film on outer surface of pellets, and resistance to intraparticle diffusion according to bimodal pore model. From this function, other frequency transfer functions for various cases are systematically derived. The effects of mass transfer processes on gain and phase shift are examined from numerical evaluations of derived frequency transfer functions for typical values of parameters. From the results, the effects of mass transfer processes on the estimated values of order of reaction and Thiele modulus are discussed.

Gas absorption with chemical reaction in packed column under adiabatic conditions

Abstract: 3) Carberry, J.J. and R. H. Bretton: A.LCh.E. Journal, 4, 367 (1958) 4) Davidson, J. F. and D. Harrisson: \"Fluidized Particles,\" p. 107 Cambridge, University Press, London (1963) 5) Edwards, M.F. and J.F. Richardson: Chem. Eng. Sci., 23, 109 (1968) 6) Evans, E.V. and C.N. Kenney: Trans. Inst. Chem. Engrs., 44, T189 (1966) 7) Gilliland, E.R. and E.A. Mason: Ind. Eng. Chem., 41, 1191 (1949) 8) : ibid., 44, 218 (1952) 9) Hanratty, T.J., G. Latinen and R.H. Wilhelm:

Gas Flow and Heat Transfer in Granular Materials

Abstract: There are numerous possible technological processes for carrying out the reduction of ores by gases containing CO or H2. All conceivable processes are characterized by the common endeavour to achieve in the smallest possible volume the most rapid and complete chemical conversion and heat transfer possible. A uniform circulation of the reducing gases round the ore pieces offers the best conditions. The following sections deal with gas flow in ore charges, with the region of stability for various types of gas flow, and with heat transfer. According to Wicke and Brotz 305), in general, the possible states of a granular material through which a fluid is flowing are those shown in Table 9; from left to right in this table, the states shown correspond to increasing fluid velocity or decreasing grain size. Those of particular importance in the reduction of ores are: a) the static bed, or packed column; b) the fluidized bed; c) particulate fluidization (or fluidized dust).

Porosity fluctuations in a monodisperse granular packed bed

Abstract: 1. Equations were obtained for the absolute and relative fluctuations of the porosity in a monodisperse packed bed. 2. Estimates of these fluctuations were made for various volumes of the packed bed and granules of variable shape.