Turbine agitator

Figure 5-5H. A typical radial Impeller agitator. Operates as agitating turbine or a conventional propeller, wide range of applications. Courtesy of Struthers-Wells Corp., Warren, Pa.

Agitator Turbine, 3.6 HP, 1750 rpm, XP rated motor, variable speed drive Circulating pump Viking series HL124, 2 HP, 1745 rpm, XP rated motor Micro Motion mass flow meter stainless steel 316L, 0-80 lb/min mass flow range, accuracy of 0.4% of range, XP rated with electronics unit mounted separately in nonhazardous area. 

Type of agitator/turbine/propeller. The actual design of agitator will depend on the speed of agitator Whether gearbox is required... 

A 2-m-diameter agitated tank contains 6200 kg (dilute aqueous solution). The agitator (turbine of diameter 0.67 m) operates at 2.33 r/sec. If the jacket uses steam condensing at 110°C and the fluid is at 40°C, what is the heat transfer coefficient ... 

In this accident, the steam was isolated from the reactor containing the unfinished batch and the agitator was switched ofiF. The steam used to heat the reactor was the exhaust from a steam turbine at 190 C but which rose to about 300°C when the plant was shutdown. The reactor walls below the liquid level fell to the same temperature as the liquid, around 160°C. The reactor walls above the liquid level remained hotter because of the high-temperature steam at shutdown (but now isolated). Heat then passed by conduction and radiation from the walls to the top layer of the stagnant liquid, which became hot enough for a runaway reaction to start (see Fig. 9.3). Once started in the upper layer, the reaction then propagated throughout the reactor. If the steam had been cooler, say, 180 C, the runaway could not have occurred. ... 

Monomer emulsions ate prepared in separate stainless steel emulsification tanks that are usually equipped with a turbine agitator, manometer level gage, cooling cods, a sprayer inert gas, temperature recorder, mpture disk, flame arrester, and various nossles for charging the ingredients. Monomer emulsions are commonly fed continuously to the reactor throughout the polymerisation. 

Until recently most industrial scale, and even bench scale, bioreactors of this type were agitated by a set of Rushton turbines having about one-thind the diameter of the bioreactor (43) (Fig. 3). In this system, the air enters into the lower agitator and is dispersed from the back of the impeller blades by gas-fiUed or ventilated cavities (44). The presence of these cavities causes the power drawn by the agitator, ie, the power requited to drive it through the broth, to fall and this has important consequences for the performance of the bioreactor with respect to aeration (35). k a has been related to the power per unit volume, P/ U, in W/m and to the superficial air velocity, in m/s (20), where is the air flow rate per cross-sectional area of bioreactor. This relationship in water is... 

The two procedures primarily used for continuous nitration are the semicontinuous method developed by Bofors-Nobel Chematur of Sweden and the continuous method of Hercules Powder Co. in the United States. The latter process, which uses a multiple cascade system for nitration and a continuous wringing operation, increases safety, reduces the personnel involved, provides a substantial reduction in pollutants, and increases the uniformity of the product. The cellulose is automatically and continuously fed into the first of a series of pots at a controlled rate. It falls into the slurry of acid and nitrocellulose and is submerged immediately by a turbine-type agitator. The acid is deflvered to the pots from tanks at a rate controlled by appropriate instmmentation based on the desired acid to cellulose ratio. The slurry flows successively by gravity from the first to the last of the nitration vessels through under- and overflow weirs to ensure adequate retention time during nitration. The overflow from the last pot is fully nitrated cellulose. 

The stabihty of the emulsions further permits them to be compounded in simple Hquid-blending vessels by means of agitators, eg, marine-type propellers, paddles, or turbines. The adhesives can be adapted to any type of machine appHcation, ie, from spray guns to rollers to extmder-type devices. Different appHcators are fairly specific in their viscosity requirements, as are the various substrates receiving the adhesive. 

Flooding of Agitator Impellers A review of impeller flooding has been done by Sensei et al. [AlChE Symp. Series No. 283, 89 (1993)] and they have offered the following flooding correlation for a six-bladed disk-type turbine. 

Flynn and Treybal [Am. Inst. Chem. Eng. J., I,. 324 (1955)]. Continuous extraction of benzoic acid from toluene and kerosine into water baffled vessels, turbine agitators. Stage efficiency is correlated with agitator energy per unit of liquid treated. 

Ryon, Daley, and Lowrie [Chem. Eng. Ftog., 55(10), 70, (1959), U.S. AFC ORNL-2951, I960]. Continuous extraction of uranium from sulfate-ore-leach liquors and kerosine -t- trihiityl phosphate and di(2-ethylhexyl)-phosphoric acid baffled vessels, turbine agitated. There is strong evidence of the influence of a slow chemical reaction. 

Ryon and Lowrie (U.S. AEC ORNL-3.381, 1960). Batch and continuous extraction of uranium from aqueous sulfate solutions into kerosine -t- amines, stripping of extract with aqueous sodium carbonate baffled vessels, turbine agitated. A detailed process study. 

The power for agitation of two-phase mixtures in vessels such as these is given by the cuiwes in Fig. 15-23. At low levels of power input, the dispersed phase holdup in the vessel ((j)/ ) can be less than the value in the feed (( )df) it will approach the value in the feed as the agitation is increased. Treybal Mass Transfer Operations, 3d ed., McGraw-HiU, New York, 1980) gives the following correlations for estimation of the dispersed phase holdup based on power and physical properties for disc flat-blade turbines ... 

FK . 15-22 Uqiiid agitation by a disc flat blade turbine in the presence of a gas-liquid interface a) without wall baffles, (h) with wall baffles, and (c) in full vessels without a gas-bqiiid interface (continuous flow) and without baffles. [Couitesy Treyhal, Mass Transfer Operations, 3rd ed., p. 148, McGraw-Hill, NY,... 

FIG. 15-23 Power for agitation impellers immersed in single-phase liquids, baffled vessels with a gas-liquid surface [except curves (c) and (g)]. Curves correspond to (a) marine impellers, (h) flat-blade turbines, w = dj/5, (c) disk flat-blade turbines witb and without a gas-liquid surface, (d) curved-blade turbines, (e) pitcbed-blade turbines, (g) flat-blade turbines, no baffles, no gas-liquid interface, no vortex. 

Pitched-blade turbines (Fig, 18-3) are used on top-entering agitator shafts instead of propellers when a high axial circulation rate is desired and the power consumption is more than 2,2 kW (3 hp), A pitched-blade turbine near the upper surface of liquid in a essel is effecth e for rapid submergence of floating particulate solids,... 

Close-Clearance Stirrers For some pseiidoplastic fluid systems stagnant fluid may be found next to the -essel walls in parts remote from propeller or turbine impellers. In such cases, an anchor impeller maybe used (Fig, 18-6), The fluid flow is principally circular or helical (see Fig, 18-7) in the direction of rotation of the anchor. Whether substantial axial or radial fluid motion also occurs depends on the fluid iscosity and the design of the upper blade-supporting spokes. Anchor agitators are used particularly to obtain irnpro ed heat transfer in high-consistency fluids,... 

---