Volumetric rate

Space Velocity. The space velocity is the ratio of the volumetric rate of gas at standard conditions to the volume of the catalyst. Generally, the percentage of ammonia in the existing gas decreases as space velocity increases however, the same volume of catalyst at the increased space velocities is capable of producing more ammonia (Fig. 4) (27). Normally space velocities for commercial operations are between 8,000 and 60, 000 h . ... 

The sulfur removed via these fixed-bed metal oxide processes is generally not recovered. Rather the sulfur and sorbent material both undergo disposal. Because the sorbent bed has a limited capacity and the sulfur is not recovered, the appHcation of these processes is limited to gas streams of limited volumetric rate having low concentrations of hydrogen sulfide. 

The ratio V,./Vq is of the volume of the reactor to the incoming volumetric rate and has the dimensions of time. It will he compared with the true residence time when the numher of mols changes as reaction goes on, or P and T also change. 

Example 11 Balances of a Semibatch Process The reaction A -l-B Products is carried out by first charging B into the vessel to a concentration Cfco and a volume V,o, then feeding a solution of concentration C o at volumetric rate V for a time t. 

The following terms are generally used to describe the pulse action Frequency is the rate of application of the pulse action, cycles/time. Amplitude is the linear distance between extreme positions of the liquid in the column (not of the pulser) produced by pulsing. Pulsed volume = amplitude X frequency X column crosssectional area = volumetric rate of movement of hquid, expressed as volume/time or vol-ume/(time-area). 

Sege and Woodfield [Chem. Eng. Prog., 50, Symp. Ser. 13, 179 (1954)] provide a good description of the operational characteristics. Refer to Fig. 15-54. Since in many cases the perforations are too small to permit flow owing to interfacial tension of the hquids, the total pulsed volume must ordinarily approximate the volumetric rate of flow of the hquids [Edwards and Beyer, Am. Jn.st. Chem. Eng. J., 2, 148 (1956), show that shghtly higher rates than = pulsed vol-... 

Automated controls for flocciJating reagents can use a feedforward mode based on feed turbidity and feed volumetric rate, or a feed-back mode incorporating a streaming current detector on the flocculated feed. Attempts to control coagulant addition on the basis of overflow turbidity generally have been less successful. Control for pH has been accomplished by feed-forward modes on the feed pH and by feed-back modes on the basis of clarifier feedwell or external reaction tank pH. Control loops based on measurement of feedwell pH are useful for control in apphcations in which flocculated sohds are internaUy recirculated within the clarifier feedwell. 

D is the volumetric rate at which net foamate (net overhead hquid produci) is withdrawn. D = Q/(R + 1). The concentration in the net Foamate is C. In the usual case of total foam breakage (no dephleg-mation), 0 = Cg. 

This program helps calculate the rate of methanol formation in mol/m s at any specified temperature, and at different hydrogen, carbon monoxide and methanol concentrations. This simulates the working of a perfectly mixed CSTR specified at discharge condition, which is the same as these conditions are inside the reactor at steady-state operation. Corresponding feed compositions and volumetric rates can be calculated from simple material balances. 

In practice, however, the liquid velocity relative to fixed particles, Uf, is not very useful. Instead, the velocity of settling relative to the walls of an apparatus, Uf - u, is of practical importance. The volume of the solid phase moving downward should be equal to that of liquid moving upward. This means that volume rates of these phases must be equal. Consider a column of slurry having a unit cross section and imagine the liquid and solid phases to have a well defined interface. The column of solid phase will have a base 1 - e, and the liquid column phase will have a base e. Hence, the volumetric rate of the solid column will be (1 - e)u, and that of the liquid column will be (Uf - u)e. Because these flowrates are equal to each other, we obtain... 

Consider a system of constant volume V through which a stream of fluid is passing at a steady volumetric rate u. If t is the age of elements in the stream at a point or over a region in the system, then the element whose age is between t and t + dt is known as the t-element. The relative frequency of the appearance of t-elements at a point or over a region in the system is an age distribution at the point or over that region. 

Figure 7.7 Microcomputer programming of dosage rate during hatch precipitation. Dosage rate curves linear, q = 0.3 + 3.15 x 10 " t parabolic, q = 0.3 + 9.8 x 10 t exponential, q = 0.73 + 0.00153 exp(0.00153t) where q is the volumetric rate (mL/s) and t is the time (s) after Jones and Teodossiev, 1988)...

A fireball is assumed to bum with a constant temperature in the isothermal fireball model of Lihou and Maund (1982). Combustion is controlled by the supply of air and ceases after a time which is correlated empirically with the mass of flammable gas in the initial vapor sphere. It is assumed that a fraction (1 — /c) of the fuel is used to form soot, and the remaining fractionbums stoichiometrically, producing an increase of /ij moles per mole of flammable gas. The stoichiometric molar ratio of air to flammable gas is p, and dVIdt is the volumetric rate of air entrainment. The rate of increase of volume can now be written as ... 

This further assumption concerning velocity and the volumetric rate of flow restricts flow to the pores and not the full area. Therefore, v is an apparent velocity. The actual velocity, assuming a uniform medium, is... 

The capacity of a pump is determined by the number of plungers or pistons and the size of these elements (bore and stroke). A reciprocating pump is usually designed for a specific volumetric rate capacity and pressure capability. These factors are set by the application. Once the volumetric rate capacity and pressure capability are known, a designer can determine the plunger piston bore and stroke the rotation speed range and the power of the prime mover needed to complete the system. 

The volumetric rate of flow requirements for air drilling operations and unstable foam drilling operations are quite large, on the order of 1,000 actual cfm to possibly as high as 4,000 actual cfm. 

For stable foam drilling operations, much less volumetric rate of air flow is needed (i.e., usually less than 500 actual cfm). Also, the compressor should be capable of variable volumetric rate of flow and variable output pressure. The back pressure must be continuously adjusted to maintain a continuous column of stable foam in the annulus. This continuous adjustment of back pressure requires, therefore, continuous adjustment of input volumetric rate of airflow and output pressure (also, water and surfactant must be adjusted). 

For aerated mud drilling operations, the compressor should also be capable of variable volumetric rate of airflow and variable output pressure. Again, as drilling progresses, the input volume of compressed air and the output pressure are continuously adjusted. 

The approximate volumetric rate of foaming agent (Ib/hr) injected will be q = 0.002(28.5)... 

The results obtained with the P. fluorescerts strain without biochemical manipulation compare well with those reported for a E. cdi strain. Both achieve volumetric rates of 3 g T1 h 1 under normal conditions. So it appears that the efficiency of the process can be increased by a few simple operations increasing the pH and amino donor concentration (aspartic add). 

If the velocity is taken as constant over an annulus of radii s and (,v + d.v), the volumetric rate of flow dQ through the annulus is given by ... 

The volumetric rate of flow of the fluid is the same at sections 1 and 2. 

Two liquids of equal densities, one Newtonian and the other a non-Newtonian power-law fluid, flow at equal volumetric rates per unit width down two wide vertical surfaces. The non-Newtonian fluid has a power-law... 

CHENOWETH and Martin 20,21 1 have presented an alternative method for calculating the drop in pressure, which is empirical and based on experiments with pipes of 75 mm and pressures up to 0.7 MN/m2. They have plotted the volume fraction of the inlet stream that is liquid as abscissa against the ratio of the two-phase pressure drop to that for liquid flowing at the same volumetric rate as the mixture. An alternative technique has been described by Baroczy 22). If heat transfer gives rise to evaporation then reference should be made to work by Dukler et al 23). 

The volumetric rate of flow through the pump Q is equal to the product of the area available for flow at the outlet of the impeller and the radial component of the velocity, or... 

In the usual case h and hf are falling in the direction of flow and Ah and Ahf are therefore negative. Values of frictional pressure drop, — APtpf may conveniently be correlated in terms of the pressure drop —APL for liquid flowing alone at the same volumetric rate. Experimental results obtained for plug flow in a 25 mm. diameter pipe are given as follows by Richardson and Higson(6) ... 

Two immiscible fluids A and B, of viscosities p./t and fin, flow under streamline conditions between two horizontal parallel planes of width b, situated a distance 2a apart (where a is much less than b), as two distinct parallel layers one above the other, each of depth a. Show that the volumetric rate of flow of A is ... 

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