Packings fluid flow through

The column may be packed or it may be an open tube but in this example, a packed column will be specifically considered. The column is considered to have a length (L) and inlet and outlet pressures and inlet and outlet velocities of (Pi), (Po) (ui) and (uo), respectively. The pressure and velocity at a distance (x) from the front of the column is (Px) and (ux), respectively. According to D Arcy s equation for fluid flow through a packed bed, at any point in the column. 

Filtration is the concentration of solids (or clarification of liquor) from slurry by fluid flow through a permeable medium. This normally takes the form of a membrane, filter leaf or packed bed, which restricts the particles, more than the fluid (Figure 4.4). 

Ergun, S., 1952. Fluid flow through packed colomns. Chemical Engineering Progress, 48, 89. 

A certain amount of information on particle-to-liquid and bed-to-wall heat transfer is available for single-phase fluid flow through a packed bed. It is not clear, however, to what extent this information can be applied to... 

Ergun, S., Fluid Flow Through Packed Columns, Chem Eng. Progress, 48(2) 89-94 (1952)... 

Reproducible correlations for the heat transfer coefficient between a fluid flowing through a packed bed and the cylindrical wall of the container are very difficult to obtain. The main difficulty is that a wide range of packing conditions can occur in the vicinity of the walls. However, the results quoted by Zenz and Othmer(44) suggest that ... 

Ergun, S. Chem. Eng. Prog. 48 (1952) 89-94. Fluid flow through packed columns. 

From d Arcy s Law for fluid flow through a packed bed, at the optimum mobile phase velocity the length of the column is given by,... 

Fixed- or packed-bed reactors refer to two-phase systems in which the reacting fluid flows through a tube filled with stationary catalyst particles or pellets (Smith, 1981). As in the case of ion-exchange and adsorption processes, fixed bed is the most frequently used operation for catalysis (Froment and Bischoff, 1990 Schmidt, 2005). Some examples in the chemical industry are steam reforming, the synthesis of sulfuric acid, ammonia, and methanol, and petroleum refining processes such as catalytic reforming, isomerization, and hydrocracking (Froment and Bischoff, 1990). 

Ergun, S. and Oming, A. A. (1949). Fluid Flow Through Randomly Packed Columns and Fluidized Beds. 1 EC., 41, 1179. 

Dorman, R. G. (1966). Filtration. In Aerosol Science. Ed. C. N. Davies. New York Academic Press. Ergun, S. (1952). Fluid Flow Through Packed Columns. Chem. Eng. Prog., 48, 89. 

In the preceeding section, we have shown how fluid flows through a packed bed may be observed at various levels, leading to completely different interpretations. Actually, when modelling a transport process, it is always necessary to consider at least two observation levels the bed scale and the particle scale. 

Separative flow often occurs in a packed bed—typically a tube filled with a granular material. Chromatography in packed columns is the most important example of packed-bed flow. Similar flow is found in porous membranes used for membrane separation. The fluid flowing through such media can be a gas, a liquid, or a supercritical fluid. 

The Lewis number has been defined by Ray and Hastings (1980) as the ratio of two time constants, ik and tc. The thermal time constant rh is the ratio of the total heat capacity of a unit reactor volume Vto the heat capacity of the fluids flowing through this volume. For an unpacked reactor this time constant equals the residence time, t = VIF. For a packed reactor the thermal time constant can be considerably longer than the residence time. Similarly, the material time constant 7( is the ratio of material holdup in a unit reactor volume to the flow of material through this volume. Again, for an unpacked reactor, v< = t, whereas a packed reactor could have the material time constant much shorter than the overall holdup time due to the space occupied by the... 

The void fraction is the most significant factor determining the loss of pressure during fluid flow through a packed bed. At low flow rates (Re 50) the pressure drop is proportional to... 

In porous solids made of larger elements such as fixed packed beds, where the characteristic dimension of the packing is d (for example the diameter of a packed solid), the frequency of the velocity change is a = v/d (after each flow through an element of the packed bed, the local fluid velocity v changes its direction). Now if we use this value of a in the dispersion coefficient, we obtain the famous relation Pe = (vd)/D = 2, which gives the value of the dispersion coefficient when a fluid flows through a packed bed [4.90]. 

Horvath and Lin, for dispersion in a packed column. 128 Knox, for dispersion in a packed column. 126 mass sensitivity, 172 Poiseuille s, fluid flow through a tube. 132... 

Pressure drop due to fluid flow through a tube or annulus with or without packed beds can be calculated according to the following equation... 

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