Cyclone sampler

W.D. Griffiths, F. Boysan, Computational fluid dynamics (CFD) and empirical modelling of the performance of a number of cyclone samplers, J. Aerosol Sci. 27 (1996) 281-304. 

Using the background information summarized above, a procedure was developed in which the respirable dust samples were ashed, taken up in a suspension and redeposited on a membrane filter. The redeposited membrane filter was used to present the sample to the MIR cyrstal. The cyclone sampler used for collecting respirable dust selectively collects particles less than 10 microns in diameter and no effect was made to grind the particles as no problem in damaging the crystal was encountered. 

Several other types of hand-held vacuum samplers have been used to collect dust from residential surfaces. One of these, the Baltimore Repair and Maintenance Study Cyclone Sampler (BRMCS) (Farfel et al 1994), has been evaluated against the HVFS. The BRMCS uses the same cyclone and catch bottle assembly as the HVS3, but a different nozzle and vacuum source. The vacuumed dust is sucked into the cyclone via a semi-rigid Tygon hose (2.54-cm o.d.) that is notched on the sampling end to simulate a nozzle. Suction is provided by a small, hand-held vacuum device (Royal Hand Vac , Model 553, 2 A). The collection efficiency for the BRMCS was determined to be 44.1 % n =6, s = 3.8) for plush uylou carpet, 61.1 % (n = 6, = 6.7) for level loop carpeting, 71.8-87.8 % n =6, s = 3.5) for upholstery and 84.7 % n = 3, s = 2.3) for wood surfaces (USEPA, 1996b). 

Table 5 PAHs concentration (ng/Nm ) in particulate fractions of the cyclone sampler. Test 2... 

The third atmospheric technique analyses the residual liquid and/or condensate hydrocarbon traces on aerosols carried into the atmosphere by thermals (Barringer, 1981). The aerosols are created by gas bubbles which exsolve into the atmosphere from the sea in areas where microseeps create gas bubbles which reach the sea surface. The aerosols are concentrated from large volumes of air and collected by an airborne cyclone sampler carried aboard an aircraft which is flown at 30 m (100 feet) above the sea surface. Hydrocarbons adsorbed on the aerosols are measured by a flame ionisation detector which yields a total hydrocarbon signal. This system is claimed to produce... 

IBAD The interim biological agent detector (IBAD) is composed of a particle-size sorter/counter, a wet cyclone sampler, a manual identifier, and a flow-through colorimetric ticket assay. Agent identification occurs within 20 minutes. 

Cyclone Samplers. A cyclone is an inertial device that is commonly used in industrial applications for removing particles from large air flows. A particle-laden air stream enters the cyclone body and forms an outer spiral moving downward towards the bottom of the cyclone. Larger particles are collected on the outer wall due to centrifugal force. Smaller particles follow the airstream that forms the inner spiral and leave the cyclone through the exit tube. Application of a water spray to the outer walls of a cyclone facilitates particle collection and preservation. (Boiarski etal., 1995). 

Connect the collection device, tubing, pump and calibration apparatus as shown in Figures 4 and 7, cassette and cyclone samplers, respectively. 

Because a filter sample includes particles both larger and smaller than those retained in the human respiratory system (see Chapter 7, Section III), other types of samplers are used which allow measurement of the size ranges of particles retained in the respiratory system. Some of these are called dichotomous samplers because they allow separate measurement of the respirable and nonrespirable fractions of the total. Size-selective samplers rely on impactors, miniature cyclones, and other means. The United States has selected the size fraction below an aerodynamic diameter of 10 /xm (PMiq) for compliance with the air quality standard for airborne particulate matter. 

An alternative to filtration is the use of inertial samplers, represented by impactors and cyclone separators (Figure 2a and Impaction, a method often used to size... 

Figure 2 Examples of inertial samplers (a) impactor (three-stage) and (b) cyclone separator...

Figure 5. The unmanned plane used to collect and identify aerosolized bacteria in field trials at Dugway Proving Ground, UT. The plane carried a ten-pound payload including a cyclone air sampler and 4-probe fiber optic biosensor.

The fine particle airstream from the cyclone was sampled by two total filters in parallel. A Millipore Fluoropore 47 mm diameter Teflon filter with a 1 pm pore size was used for the first seven samples. Subsequent samples were obtained with a 0.4 pm pore size 47 mm Nuclepore polycarbonate filter because particle absorption measurements and elemental analysis by particle induced X-ray emission (PIXE) were easier and more accurate using the Nuclepore filters. In parallel with the Nuclepore filter, a TWOMASS tape sampler collected aerosol using a Pallflex Tissuequartz tape. The aerosol deposit area was 9.62 cm on the Nuclepore and Millipore filters and 0.317 cm on the Tissuequartz tape. The flow rate was 16-20 1pm through the Nuclepore and Millipore filters and 10 1pm through the Tissuequartz tape. Each Millipore or Nuclepore filter was placed in a labeled plastic container immediately after collected, sealed with Parafilm, enclosed in a ziplock bag, and placed in a refrigerator in the trailer. The tape in the TWOMASS sampler was advanced between samples. The tape sample was removed about once every 8-10 weeks and stored similarly to the Nuclepore filters. The TWOMASS was cleaned at that time. All samples were stored in an ice chest during the return trip to Caltech. Field blanks were handled identically to the samples. Of approximately 100 filter samples collected in 1979, 61 were selected for analysis. The 61 were chosen to span the variation in bjp and to obtain representative seasonal and diurnal samples. Sample times varied from 6 to 72 hours, with an average of 20.1 hours. 

To avoid the problems with vacuum cleaner surface dust sampling a special surface dust sampler, HVS-3, was developed (Roberts et al, 1991). The sampler consists of a nozzle that can be adjusted to a well defined distance to the surface, a cyclone that collects the dust particles, an air pump, and an exhaust filter to capture particles that are not retained in the cyclone. SVOCs may break through the cyclone as vapors and a PUF plug can be inserted after the cyclone. HVS-3 has been modified to ensure a more constant suction pressure and volume, and a known sampled area (Gyntelberg et al, 1994). The design and use of the HSV3 has now been standardized (ASTM, 1997, D 5438-94). 

Instead of using the virtual impactor approach, North American air monitoring programs in the 1980s and later have adopted simpler reference methods that use the weighing of filters in the laboratory. The filters are obtained from samplers equipped with an inlet device that provides for a sharp cut-point in particle entry for samples of particles < 10 xm diameter or <2.5 [im diameter, which are operated over a fixed time period of 24 hours. The inlet fractionation is facilitated either by a carefully designed cyclone or by an impactor. The combination of the two samplers can give estimates of mass concentration for fine-particle and coarse-particle concentrations. 

A mass respirable sampler cyclone is designed to operate at a flow rate of 1.7 L/min. Will the mass respirable concentration that is measured be over-... 

Emission rate. Sampling of particulate emissions was carried out at a stack height of 20 m isokinetic in-stack sampling was achieved with a modified BCURA dust sampling equipment (Airflow Developments, England). The sampler enabled to separate the coarse (> 5 m) and fine particles (< 5 (tm) by means of a cyclone. 

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