Separators cyclone tube

From the tube dryer, fiber drops into a cyclone which separates the fiber from the moist, warm air. The fiber falls from the bottom of the cyclone into a large bin and in then moved to the mat forming line. If machine-blending of fiber with additives is used, it will occur at this point, immediately before the forming line. 

The continuous DCC crystallizer shown in Figure 8.40 has been used for the large-scale production of calcium nitrate tetrahydrate (Cerny, 1963). Aqueous feedstock enters at the top of the crystallizer at 25 C and flows countercur-rently to the immiscible coolant droplets, e.g. petroleum, introduced into the draft tube at 15 °C. The magma, containing crystals of mean size 500 pm, is discharged at 5 °C. The low-density coolant collects in the upper layers and passes to a cyclone to separate aqueous solution droplets before being recycled. 

Figure 4.2 Schematic of main features of fluidized-bed reactor for production of acrylonitrile showing immersed serpentine heat transfer tubing, separate distributors for air and ammonia + propane or propene, and one representative cluster of internal cyclones in series.

In process engineering work the viewpoint is often taken that an improved quality of separation or purification is achieved at a correspondingly higher cost. Empirical relationships are developed which relate the quality of separation achieved to the cost. Not surprisingly this includes both cyclones and swirl tube separators. The measure of the quality of separation is the cut size, X50 or the dimensionless cut size, Stk o, and the cost is the pressure drop required to achieve this, or its dimensionless measure Eu. 

We will be returning briefly to the topic of solids loading in swirl tube separators later. Here, we wish to note that a difference exists between the behavior of cyclones with tangential inlets and swirl tubes equipped with inlet vane assemblies, so that the results shown in these figures cannot be applied to swirl tubes. 

The following sections will show that the vortex end significantly influences the behavior of cyclones and swirl tubes. Its nature, and the factors governing its position, should therefore be well understood by anyone who designs such cyclonic type separators, and this topic should be given high priority in cyclone research at this time. 

The second cyclone body shown in Figure 13.3.4 illustrate a vane-type inlet design that we refer to herein as a swirl tube separator. Vane inlets are the most symmetrical of all inlet designs but are somewhat more comphcated to design and fabricate or, in some cases, to cast. Both the twin inlet and vane inlet cyclone designs described thus far are of the conventional reverse-flow variety. 

Pressure loss. Pressure drop is an important consideration in almost any scrubber installation. The dry scrubbers can be designed for pressure drops varying from several inches of H2O to several psi. Since a minimum actual cubic foot flow/cyclone tube must be maintained to effect good separation, the pressure drop will vary directly as the operating pressure. 

Cyclone inlet section. As the mist-laden gas enters the separator, the entrained liquids and solid particles are subjected to centrifugal force. The gas enters the cyclone tube at two points, designated A, and sets up a swirling motion. Solid and liquid particles are thrown outwardly and drop from the tube at point B. The swirling gas reverses direction at the vortex C and rises through the exit portion of the tube, designated D. See Fig. S-21. 

Fluidized combustion of coal entails the burning of coal particles in a hot fluidized bed of noncombustible particles, usually a mixture of ash and limestone. Once the coal is fed into the bed it is rapidly dispersed throughout the bed as it bums. The bed temperature is controUed by means of heat exchanger tubes. Elutriation is responsible for the removal of the smallest soHd particles and the larger soHd particles are removed through bed drain pipes. To increase combustion efficiency the particles elutriated from the bed are coUected in a cyclone and are either re-injected into the main bed or burned in a separate bed operated at lower fluidizing velocity and higher temperature. 

Both Mitsubishi and Mitsui TLEs differ drastically from other designs. Mitsubishi offers a TLE with an integral steam dmm and cyclone for vapor—hquid separation. The pyrolysis gas flows in the shell side, and is claimed to accomplish the decoking of the furnace and the transferline exchanger in one operation. The Mitsui quench cooler uses three concentric tubes as the tube element, and requires steam—air decoking to clean the TLE (58,59). 

Dust entrained in the exit-gas stream is customarily removed in cyclone cohectors. This dust may be discharged back into the process or separately cohected. For expensive materials or extremely fine particles, bag collectors may follow a cyclone collector, provided fabric temperature stability is not hmiting. When toxic gases or solids are present, the exit gas is at a high temperature, the gas is close to saturation as from a steam-tube diyer, or gas recirculation in a sealed system is involved, wet scrubbers may be used independently or following a cyclone. Cyclones and bag collec tors in diying applications frequently require insulation and steam tracing. The exhaust fan should be located downstream from the cohection system. 

Pneumatic-Conveyor Dryers A pneumatic-conveyor dryer consists of a long tube or duct carrying a gas at high velocity, a fan to propel the gas, a suitable feeder for addition and dispersion of particulate solids in the gas stream, and a cyclone collector or other separation equipment for final recoveiy of sohds from the gas. 

Ball mills or tube mills can be operated in closed circuit with external air classifiers with or without air sweeping being employed. If air sweeping is employed, a cyclone separator may Be placed between mill and classifier. (The principles of size reduction combined with size classification are discussea under Characteristics of Size Classifiers. ) Likewise other types of grinding mill can be operated in closed circmt with external size classifiers (Fig. 20-12), as will be described at appropriate places on succeeding pages. However, many types of grinders are air-swept and are so closely coupled with their classifiers mat the latter are termed internal classifiers. 

FIG. 9 Saponification of alkane sulfochlorides (Leuna technology). 1, Saponification reactor 2, pH control 3, separation tube 4, cooler 5, dilution stirring unit 6, preheater 7, vaporizer 8, cyclone separator 9, condensor 10, cooling roller 11, stirred dissolution tank. 

FIG. 10 Energy-saving evaporation of alkanesulfonate solution. 1, Spiral tube vaporizer 2, cyclone separator 3, heat exchanger 4, rotation film evaporator. 

Fig 1. Schematic diagram of the ICFB gasifier. 1. steam generator, 2. flowmeter, 3. orifice flowmeter, 4. air preheater, 5, gas plenum, 6. draft tube, 7. orifice, 8. gas separator, 9. freeboard, 10. screw feeder, 11. mono-pump, 12. sludge feed nozzle, 13. cyclone, 14. condenser, 15. collector, 16. filter, 17. ID fan. 

Cyclonic filters (and closely related designs such as U-tubes) are employed as an initial gas cleanup step in most gasifier systems because they are effective and relatively inexpensive to operate. In circulating fluidized-bed or entrained-bed gasifiers, cyclones are an integral part of the reactor design, providing for separation of the bed material and other particulates from the gas stream. 

At the bottom of the vortex, there is substantial turbulence as the gas flow reverses and flows up the middle of the cyclone into the gas outlet tube. As indicated above, if this region is too close to the wall of the cone, substantial reentrainment of the separated solids can occur. Therefore, it is very important that cyclone design take this into account. 

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