Vertical standpipes

Landfills have two LCRSs a primary LCRS and a secondary LCRS. Any leachate that penetrates the primary system and enters the secondary system must be removed. Vertical standpipes are used... 

The model given here for flows in a vertical standpipe follows closely the approach of Ginestra et al. (1980), Chen et al. (1984), and Jackson (1993). In this model, it is assumed that... 

As mentioned, the flow rate in a standpipe depends on the solid feed device as well as the flow control valve. In this section, we discuss the gas-solid flows in a simple standpipe system where the feed device is a mass flow hopper and the solid flow regulator is a discharge orifice [Chen et al., 1984]. As shown in Fig. 8.15, the entrance of the vertical standpipe is connected to a conical hopper feeder of half angle solids flow patterns are considered. One is a dilute suspension flow, and the other is a solid moving bed. In this case, the following additional assumptions are needed ... 

Mountziaris, T. J The effects of aeration on the gravity flow of particulate materials in vertical standpipes. Ph.D. dissertation, Princeton University, 1989. 

Reddy, Karri S. B., and Knowlton, Ted M. Comparison of Group A Solids Flow in Hybrid Abgled and Vertical Standpipes, in Circulating Fluidized Bed Technology IV (Amos A. Avidan, ed.), pp. 296-301. Somerset, Pennsylvania (1993). 

A standpipe commonly used in the petroleum industry is the underflow vertical standpipe with slide valve at the lower end. In this case the standpipe generates more head than is required and the excess is used across the slide valve in controlling the solids flow. Such a standpipe is used in the fluid catalytic cracking (FCC) unit to transfer solids from the reactor to the regenerator. 

A 10 m long vertical standpipe of inside diameter 0.1 m transports solids at a flux of 100 kg/m s from an upper vessel which is held at a pressure 1.0 bar to a lower vessel held at 1.5 bar. The particle density of the solids is 2500 kg/m and the surface-volume mean particle size is 250 gm. Assuming that the voidage is constant along the standpipe and equal to 0.50, and that the effect of pressure change may be ignored, determine the direction and flow rate of gas passing between the vessels. (Properties of gas in the system density, 1 kg/m viscosity, 2 x 10 Pas.)... 

Chen Y, Rangachari R, Jackson R. Theoretical and experimental investigation of fluid and particle flow in a vertical standpipe. Ind Eng Chem Fundam 23 354, 1984. 

Even though vertical standpipes can transfer solids more efficiently than hybrid angled standpipes, true angled standpipes (those containing no vertical section) are commonly operated satisfactorily in large... 

Karri SBR, Knowlton TM. Comparison of group A solids flow in hybrid angled and vertical standpipes. In Avidan Ar, ed. Circulating Fluidized Bed Technology IV, 1993, pp 253-259. 

The pillow test per GRI-GT15 uses the candidate fabric prefabricated into the shape of a pillow from which a flanged connector and a calibrated vertical standpipe are attached. The fabric enclosure is small and the amount of slurry needed per test is much less than with the hanging bag test. More important, the hydraulic head (converted to inlet pressure) can be monitored over time, resulting in a quantitative assessment of the system including the specific effects of the fabric, slurry, and its additives. A pillow test in progress is shown in Fig. 21.3. 

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