Pressure drop cyclone separators

Number of turns made by gas stream in a cyclone separator Pressure drop, Ibs/sq in. 

A defoaming cyclone-type separator is to be installed to prevent excessive foam-related problems in a commercial high-pressure test separator handling a heavy crude feed. We wish to use Eq. (14.4.5) to estimate the submergence required to prevent gas from blowing out the separator s underflow opening. The cyclone s pressure drops and the liquid density at design conditions are ... 

Current designs for venturi scrubbers generally use the vertical downflow of gas through the venturi contactor and incorporate three features (I) a wet-approach or flooded-waU entry sec tion, to avoid dust buildup at a wet-dry pmction (2) an adjustable throat for the venturi (or orifice), to provide for adjustment of the pressure drop and (3) a flooded elbow located below the venturi and ahead of the entrainment separator, to reduce wear by abrasive particles. The venturi throat is sometimes fitted with a refractoiy fining to resist abrasion by dust particles. The entrainment separator is commonly, but not invariably, of the cyclone type. An example of the standard form of venturi scrubber is shown in Fig. 17-48. The wet-approach entiy section has made practical the recirculation of slurries. Various forms of adjustable throats, which may be under manual or automatic control. 

In pressure systems (Fig. 21-12 ), material is dropped into an air stream (at above atmospheric pressure) by a rotaiy air-lock feeder. The velocitv of the stream maintains the bulk material in suspension until it reaches the receiving vessel, where it is separated from the air by means of an air filter or cyclone separator. 

Cyclone Separators Cyclone separators are described in Chapter 7. Typically used to remove particulate from a gas stream, the gas enters tangentially at the top of a cylinder and is forced downward into a spiral motion. The particles exit the bottom while the gas turns upward into the vortex and leaves through the top of the unit. Pressure drops through cyclones are usually from 13 to 17 mm water gauge. Although seldom adequate by themselves, cyclone separators are often an effective first step in pollution control. 

In determining the proper size and number of cyclones required for a given application, two main objectives must be considered. The first is the classification or separation that is required, and the second is the volume of feed slurry to be handled. In the case of hydroclones, before determining whether these objectives can be achieved, it is necessary to establish a base condition as follows Feed liquid - water at 20 C. Feed solids - spherical particles of 2.65 specific gravity Feed concentration - less than 1 % solids by volume Pressure drop - 69 kPa (10 psi) Cyclone geometry - "standard cyclone" as described above. 

Another important objective which must be considered is to provide adequate cyclone capacity for the application. The volume of feed slurry that a given cyclone can handle is related to the pressure drop across the cyclone. The relationship between flow rate and pressure drop for several different sizes of standard cyclones is shown in Figure 56. As shown, the flow rate increases as the pressure drop increases. In order to utilize this graph, the pressure drop used for calculating the separation is used to determine the flow rate for the cyclone diameter which was... 

Figure 4-48. Pressure drop for cyclone separator system. Adapted by permission, Lapple, C. E., Fluid and Particle Dynamics, 1st Ed., University of Delaware, 1954.

Performance of a cyclone separator is determined by flow pattern, pressure drop, and collection efficiency. 

Six-tenths factor, 47 Yearly cost indices, 47 Critical flow, safety-relief, 438 Back pressure, 440 Sonic flow, 438 Critical flow, see Sonic Cyclone separators, 259-269 Design, 260-265 Efficiency chart, 263 Hydroclones, 265-267 Pressure drop, 263, 264 Scrubber, 269 Webre design, 265 Deflagration venting nomographs,... 

Stairmand, C. J. (1949) Engineering 168, 409. Pressure drop in cyclone separators. 

Figure 4-4 shows a typical system under positive pressure. It differs from the vacuum system in that the material enters from one source and is distributed directly to several tanks. In this case no cyclone separator is used the air laden with solids enters the process bins directly. The decrease in velocity of the stream and its change in direction will cause most of the solids to drop out. For this system each receiver must have a filter to remove the remaining solids. Note that the blower is placed at the air entrance, instead of after the filter as in the vacuum system. Should a bag in the fiber filter break, no dust will get into the blower or its motor. Another advantage is that no contaminants from the atmosphere can enter the system when it is under positive pressure, except through the air inlet system. 

The pressure drop in the ductwork is first figured on the basis that no solids are present. This result is then corrected using Figure 8-1 1 to obtain the true pressure drop. The weight ratios of solids to air vary from 1 1 to 20 1. The flow rate of the solids in the positive-pressure system is much greater than for the typical negative system.37 The pressure drop in the fiber filters is generally about 4 in H20 (100 kg/m2), and that in cyclone separator varies from 1 to 3 in HzO (25-75 kg/m2).37... 

---