Horizontal elutriator

A high-volume sampler has an airflow rate of 30 ft3/min. Design a horizontal elutriator (settling chamber) that could be placed upstream from the sampler to eliminate those particles greater than 10 pm in diameter. Assume a particle specific gravity of 2.3. What diameter particles would be reduced by a factor of 50 percent in this unit ... 

If we are interested in what reaches the lower lung then sampling devices should collect dust on the same basis. Sampling devices have been designed which do this, such as the horizontal elutriator as the reference device (heavy and bulky), and the mini-cyclone (lightweight and portable). 

As in sedimentation, the concentration of the particles in the elutriators affects the results of measurement. Also the velocity in the elutriators tends to be parabolic rather than uniform and thus introduces errors in measurement. Centrifugal force can also be applied like that in the sedimentation to enhance the performance. Different designs, including horizontal elutriators, are available. 

In horizontal elutriators a stream of suspension is passed over a reservoir of clear fluid. The larger fineparticles leave the suspension stream and are collected at the bottom of the settling chamber. The fractionation efficiency of this device is not good since some fineparticles of all sizes will leave the suspension stream as it moves over the clear fluid in the collection chamber. The solids concentration of the feed stream must be kept low, otherwise, bulk penetration by the feed layer into the fluid in the container will occur (see discussion of the stability of the line start suspension system in Chapter 4). It is possible to use a more dense fluid in the reservoir to improve the stability of the system but this system has not been used in size characterization studies. Fineparticles that drop through the full height of the fluid stream in the time taken for the fluid stream to move across the elutriating chamber are completely removed from the feed stream. 

The cross-flow classifier shown in Figure 5.10, developed by various investigators, is an industrial-scale horizontal elutriator [24,25,26]. Fineparticles to be fiaaionated are entrained in a high-speed air jet, which is fired across a winnowing stream of air. 

A schematic diagram of the experimental apparatus is shown in Fig. 1. A rotating fluidized bed composes of a plenum chamber and a porous cylindrical air distributor (ID400xD100mm) made of stainless sintered mesh with 20(xm openings [2-3]. The horizontal cylinder (air distributor) rotates around its axis of symmetry inside the plenum chamber. There is a stationary cylindrical filter (ID140xD100mm, 20(o.m openings) inside the air distributor to retain elutriated fine particle. A binary spray nozzle moimted on the metal filter sprays binder mist into the particle bed. A pulse air-jet nozzle is also placed inside the filter, which cleans up the filter surface in order to prevent clogging. 

Both washed and unwashed cottons were processed through a blender feeder, a No. 12 horizontal opener, and a two-beater picker and made into picker laps. The carding was conducted in our model cardroom at 18,2 kg/h, and dust levels were determined by use of vertical elutriators. The cottons were spun into 19.7 mg/ m yarn of 38.2 twist factor at 13000 rpm spindle speed in a 4536 spindle-hour test. 

Elutriator A device used to separate respirable and non-respirable particulates such as the cyclone or horizontal types. 

When the thirty-six hours were expired, the whole was allowed to cool, after which tire pots were removed and broken, and the vermilion which was ineruBted -within them, and chiefly in their upper parts, collected, ground with water between horizontal stones, then passed through sieves, and thereafter elutriated and. dried. The usual loss in converting the black sulphide by this process into vermilion, was nearly three per cent. 

Some ash and elutriated bed media particles are removed by settling in the horizontal pass, and the cyclone located downstream of the horizontal pass provides additional particle separation. Gas and small particles not separated by the cyclone are discharged into a vertical ceramic-lined exhaust duct drawing laboratory air for dilution and cooling. When the reactor is functioning as a gasifier, the product gas is flared in the duct at the cyclone stack. 

Optimum size distribution is important for a fluid bed reactor (Bergoug-nou). Models based on bubbles are not yet capable of predicting the wall effect (Wen). Vertical baflles are most effective in breaking up large bubbles (Volk). The height of the bottom ends of vertical tube bundles above the grid will set the attainable bubble size at the bottom of the bundle. The bundles then essentially maintain the bubble size (Zenz). Horizontal perforated baflle plates reduce the mean residence time of elutriable fine particles in a fluidized bed (Buckham). Observations on attrition in cyclones indicate that it is an exponential function of velocity (Tenney). 

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