Loop circulation

Axial-Flow (Propeller) Pumps (Fig. 10-44) These pumps are essentiahy very-high-capacity low-head units. Normally they are designed for flows in excess of 450 mVh (2000 gal/min) against heads of 15 m (50 ft) or less. They are used to great advantage in closed-loop circulation systems in which the pump casing becomes merely an elbow in the line. A common installation is for calandria circulation. A charac teristic cui ve of an axial-flow pump is given in Fig. 10-45. 

Figure 5-5. The ICI low-pressure process for producing methanol " (1) desulfurization, (2) saturator (for producing process steam), (3) synthesis loop circulator, (4) reactor, (5) heat exchanger and separator, (6) column for light ends recovery, (7) column for water removal.

The ammonia vaporizer receives liquid ammonia from the adjacent plant at - 15°C and 1240 kPa and vaporizes it at 35°C using warm water. The warm-water loop circulates water from the ammonia vaporizer to the secondary cooler. Water enters the ammonia vaporizer at 80°C and exits at about 50°C. 

Turbine pumps mix features of a simple propeller (axial flow) pump with a centrifugal pump and are often referred to as units with mixed flow. A simple turbine pump carries curved vanes on a central rotating spindle. Such pumps are often immersed in the liquid and find use in closed-loop circulation systems, in condenser circulating water, and in sumps and wells. Turbine pumps have noteworthy pumping capacity, and like positive displacements pumps are often used for heads up to about 100 ft/stage with capacities of up to several hundred gallons/minute. 

The two phase mixture then passes to the methanol catchpot where the two phases are separated. After an inerts purge is taken, the gas passes back to the suction of the loop circulator. 

Absorption refrigeration utilizes low grade heat and may be employed to chill compressor suction and hence reduce compressor horsepower. Similarly it may be used to chill the loop circulating gas and increase the conversion per pass. This would lead to a reduction in the circulator power of up to 10%. 

P-1 MAIN LOOP CIRCULATING PUMP TR-3 LOWER PHASE S02 OFF-GAS LN2 TRAP... 

Table 4 presents the direct construction costs for the two plants. Equipment costs must be adjusted to account for hydrogen production these costs include the intermediate heat exchanger ( 56 M), reactor-process piping ( 38 M), primary helium circulator ( 33 M), and intermediate loop circulator ( 22 M) (for a total of 149 M). These costs are added to Account 22. On the other hand, 84% of the Fixed Capital Investment of the S-I hydrogen production facility ( 571.53 IM x 0.84 = 480 M) in account 23 (Chemical Facility) replaces account 23 (Turbine-Generator). Also, the initial chemical inventory (primarily iodine) is equal to 114.8 M x 0.84 = 96 M. (Although there is an implicit assumption in [13] that all iodine is recycled, this assumption is challenged in [14].)... 

The polymer s loop circulation is set up and defined by the pressure balance between the two polymerization zones. As it flows dovm under gravity, the downcomer polymer bed pumps the gas downwards and recovers the head losses developed in the riser, the gas/polymer separator and all other sections of the... 

The blood circulatory system of the body acts the same way. If not for the looping circulation of the blood, all the nutrients and oxygen could be used by the first tissues contacted by the blood, and downstream tissues would be exposed to metabolic wastes produced by the upstream tissues. A circulation system is a good technique for supplying constantly fresh fluid to a range of remote locations. 

Palladino, J.L., Mulier, J.P., and Noordergraaf, A. 1997. Closed-loop circulation model based on the Frank mechanism. Surv. Math. Ind. 7 177-186. 

The first loop circulates Freon-12 through a pump, reservoir, heating coil, test section, condenser, and back to the pump. The second loop circulates hot water, which is pumped from the heater to the annular space between the Freon and hot water tube. In the test section the Freon and hot water flow counter-currently. 

The loop circulating reactor outlined above expresses in chemical engineering terms, the characteristics of a perfect mixer. This type of reactor presents the following characteristics required for the neutralisation step ... 

Kim J. Hydrodynamic behavior of solid transport for a closed loop circulating fluidized bed with secondary air injection. Korean J Chem Eng 16 840-842, 1999. 

Bischi, A., Langdrgen, 0., Saanum, I., Bakken, J., Seljeskog, M., and Bysveen, M. (2011) Design study of a 150 kWth double loop circulating fluidized bed reactor system for chemical looping combustion with focus on industrial applicability and... 

The final energy input is power for the three gas-compression duties synthesis gas compression, synthesis loop circulation, and ammonia refrigeration. The power required for these duties depends, for example, on synthesis pressure and on converter design. Refrigeration power is strongly dependent on ambient temperature. However, typical figures for a modern 1000 ton per day low-pressure... 

Layouts (b—e) were not recommended due to unpredictable water chemistry regimes at various locations throughout the thermodynamic cycle. Layout (a) with the secondary steam reheat required high pressures and temperatures in the primary loop. Circulation pumps with different parameters (power and pressure) would have to be used to feed common header upstream of the channels of the primary group. In this respect, Layout (a) was considerably more complex and expensive than Layout (f). Activation of SHS, which could occur in Layout (f), was not considered to be posing any significant complications to the turbine operation and hence remained a viable option (Dollezhal et al., 1958). 

Pressurizer. A small sidestream of fuel solution is continuously directed into the pressurizer, where it spills through a distribution header and drips down through an oxygen gas space to the liquid reservoir in the bottom of the vessel. The pressurizer liquid return line is connected to the suction side of the primary-loop circulating pump. Oxygen is added batchwise to the pressurizer to keep the fuel saturated at all times to prevent precipitation of uranium. As fission-product gases accumulate in the pressurizer, they are vented to the off-gas system, also in a batchwise operation. 

With the total absence of any boiling, all heat entering the liquid, by radiation, conduction or convection, is absorbed by primary natural convection currents which carry the heated (strictly superheated with respect to To) liquid to the surface, in an open loop circulation (Fig. 2.2). 

It is easy to see that the reference time is nothing but the loop circulation time. and are respectively the length average hydraulic diameter and flow area of the loop and the total circulation length, Lt=ELi. In case of negligible local pressure losses, Z(Leff)i becomes equal to the total circulation length, Lt of the loop. The non-dimensional equations can be expressed as ... 

FIG. 11. Experimental two-phase FIG. 12. Steady state flow in a two-phase natural natural circulation loop. circulation loop. 

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