Feed pipe diameter

Torbaeke and Rasmuson (2001) report the empirieal influenee of different seales of mixing in reaetion erystallization of benzole aeid in a loop reaetor. The authors infer that the proeess is mainly governed by mesomixing in terms of liquid eireulation rate but find anomalous behaviour in respeet of feed pipe diameter. 

The mesomixing time t , is the time for "significant mixing of an incoming jet of feed liquid with the surrounding fluid. A formula for estimating f , is the time for turbulent diffusion to transport liquid over a distance equal to the feed pipe diameter d0. 

In terms of the Corrsin development, for mesomixing the initial scale is set by the inlet conditions (e.g., feed pipe diameter), not by the local turbulence. The first term of eq. (13-13) accounts for the mesomixing effect, and the second term is related to the micromixing effect large values of the first term occur when an unmixed plume is evident. 

If an in-line mixer is not feasible and a stirred vessel is to be used, the design shown in Figure 13-11 is recommended to provide (1) high shear and micromixing at the lower turbine with proper placement of the feed line in the impeller discharge at the point of maximum energy dissipation rate, and (2) good circulation from the upper pitched blade. Prediction of applicable feed pipe diameter and feed velocity must be evaluated by methods described in Section 13-4.1.4 and in Jo et al. (1994). 

Baldyga, J., J. R. Bourne, and Y. Yang (1993). Influence of feed pipe diameter on meso-mixing in stirred tank reactors, Chem. Eng. ScL, 48, 3383-3390. 

D = inlet diameter, feed pipe ft f = fanning friction factor dimensionless tj) = average value of tj)... 

A liquid hydrocarbon is fed at 295 K to a heat exchanger consisting of a 25 mm diameter tube heated on the outside by condensing steam at atmospheric pressure. The flow rate of the hydrocarbon is measured by means of a 19 mm orifice fitted to the 25 nnn feed pipe. The reading on a differential manometer containing the hydrocarbon-over-water is 450 mm and the coefficient of discharge of the meter is 0.6. 

The critical feed time t it depends on the location and number of feed pipes, stirrer type, and mixing intensity, and increases with increasing reactor volume. When a constant power-to-volume ratio is preserved, ta-u is proportional to and where D., is the stirrer diameter and Vr the reactor volume (Bourne and Hilber, 1990 Bourne and Thoma, 1991). The productivity of the reactor expressed as the amount of product formed per unit time becomes almost independent of reactor volume. The reason is that the reaction goes to completion in the zone nearby the stirrer tip. The size of this zone increases independently of the tank size it only depends on the velocity of the liquid being injected, the location of the nozzle, and the stirrer geometry and speed of rotation. Accordingly, for rapid reactions, the feed time will also be the reaction time. 

A process liquid is pumped from a storage tank to a distillation column, using a centrifugal pump. The pipeline is 80 mm internal diameter commercial steel pipe, 100 m long. Miscellaneous losses are equivalent to 600 pipe diameters. The storage tank operates at atmospheric pressure and the column at 1.7 bara. The lowest liquid level in the tank will be 1.5 m above the pump inlet, and the feed point to the column is 3 m above the pump inlet. 

Toluene is to be pumped between two vessels using a centrifugal pump with a flowrate of 30t h 1. The pipe diameter is 80 mm (internal diameter 77.93 mm). The pipeline is 35 m long, with 4 isolation valves (plug cock), a check valve and 5 bends. The discharge tank is 3 m in elevation above the feed tank. The density of toluene is 778 kgrn 3 and viscosity of 0.251 x 10 3 N-s-rn 2. 

In the formulation of Bickel et al. (B7) which appears to be the most general formulation on this problem to date, both the feed and delivery conditions (temperature, pressure, flow rate, and composition) are specified. As before, the decision variables include the pipe diameters. But in addition, the number, placement, suction, and delivery pressures of compressors may also be varied within the constraints of overall pipeline lengths and network... 

Consider the reaction used as the basis for Illustrations 10.1 to 10.3. Determine the volume required to produce 2 million lb of B annually in a plug flow reactor operating under the conditions described below. The reactor is to be operated 7000 hr annually with 97% conversion of the A fed to the reactor. The feed enters at 163 C. The internal pipe diameter is 4 in. and the piping is arranged so that the effective reactor volume can be immersed in a heat sink maintained at a constant temperature of 160 °C. The overall heat transfer coefficient based on the... 

The feed pipes connecting the reactors were 28 inches in diameter. Because only 20-inch pipe stock was available at the plant, the connections to reactor 4 and reactor 6 were made using flexible bellows-type piping, as shown in Figure 1-10. It is hypothesized that the bypass pipe section ruptured because of inadequate support and overflexing of the pipe section as a result of internal reactor pressures. Upon rupture of the bypass, an estimated 30 tons of cyclohexane volatilized and formed a large vapor cloud. The cloud was ignited by an unknown source an estimated 45 seconds after the release. 

Govier et al. (G5, G6, B14) have correlated flow patterns in terms of the location of the two minima and the maximum observed in the pressure drop vs. gas-liquid volumetric feed ratio (12 ) curves (cf. Fig. 2). Gas-liquid ratios, gas flow, liquid flow, pipe diameter and gas-phase density were investigated for the air-water system in isothermal flow. From the correlations presented (as against a function, when n varies... 

However, the vent collection system that served the low-pressure feed tank also served a nearby distillation column that operated at nearly 15 psig and contained a toxic component. Physically the low-pressure tank was on the vent piping between the distillation column and the flare stack. During a distillation column upset, there was an increased flow to the flare. The vent header pressure increased. The vent piping diameter between the distillation column and the flare proved to be too small. Toxic fumes from the higher pressure system column were released from the low-pressure tank emergency tiffing lid. 

In the Table 6-3, D and T are the impeller and tank diameter, respectively, G is the distance from the feed pipe to the impeller, and is the recommended minimum ratio... 

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