Collection devices

Sample Handling System. Venous or capillary blood, urine, and cerebrospinal fluid are specimens routinely used in medical diagnostic testing. Of these biological fluids, the use of venous blood is by far the most prevalent. Collection devices such as syringes and partial vacuum test tubes, eg, Vacutainer, are used to draw ten milliliters or less of venous blood. At collection time, the test tubes are carefully labeled for later identification. 

Cement plants in the United States are now carehiUy monitored for compliance with Environmental Protection Agency (EPA) standards for emissions of particulates, SO, NO, and hydrocarbons. AH plants incorporate particulate collection devices such as baghouses and electrostatic precipitators (see Air POLLUTION CONTROL methods). The particulates removed from stack emissions are called cement kiln dust (CKD). It has been shown that CKD is characterized by low concentrations of metals which leach from the CKD at levels far below regulatory limits (63,64). Environmental issues continue to be of concern as the use of waste fuel in cement kilns becomes more widespread. 

Gas pressure drop, cm of water across wet scrubber collection device... 

The selection of the optimum type of particulate collection device (i.e., ESP or fabric filter oaghouse) is often not obvious without conducting a site-specific economic evaluation. This situation has been brought about by both the recent reductions in the allowable emissions levels and advancements with fabric filter and ESP technologies. Such technoeconomic evaluations can result in application and even site-specific differences in the final optimum choice (see Piecip New.sLetter, 220, June, 1994 and Fabric Filter Newsletter, 223, June, 1994). 

Particulate Emissions To meet environmental regulations, AFBC boilers, and some PFBC boilers, use a back-end particulate collector, such as a baghouse or an electrostatic precipitator (ESP). Compared to PC units, the ash from FBCs has higher resistivity and is finer Decause the flue-gas path contains cyclones. Both factors result in reduced ESP collection efficiency with AFBC units, but good performance has been achieved with PFBC units, where the SO3 present in the flue gas lowers the ash resistivity. In general, however, bag-houses are the preferred collection devices for both AFBC and PFBC apphcations. 

Wood-fired power boilers are generally found at the mills where wood products are manufactured. They are fired with waste materials from the process, such as "hogged wood," sander dust, sawdust, bark, or process trim. Little information is available on gaseous emissions from wood-fired boilers, but extensive tests of particulate matter emissions are reported (19). These emissions range from 0.057 to 1.626 gm per dry standard cubic meter, with an average of 0.343 reported for 135 tests. Collection devices for particulate matter from wood-fired boilers are shown in Table 30-21. 

Particulate Matter Collection Devices for Wood-Fired Boilers... 

Several separating systems are used for particulate sampling. All rely on some principle of separating the aerosol from the gas stream. Many of the actual systems use more than one type of particulate collection device in series. If a size analysis is to be made on the collected material, it must be remembered that multiple collection devices in series will collect different size fractions. Therefore, size analyses must be made at each device and mathematically combined to obtain the size of the actual particulate in the effluent stream. In any system the probe itself removes some particulate before the carrying gas reaches the first separating device, so the probe must be cleaned and the weight of material added to that collected in the remainder of the train. 

Extreme care should be taken in transporting and storing the samples between the time of collection and the time of analysis. Some condensable hydrocarbon samples have been lost because the collection device was... 

Attach the collection device (filter cassette, charcoal tube, etc.) to the shirt collar or as close as practical to the nose and mouth of the employee). Employee exposure is that exposure which would occur if the employee were not using a respirator. The inlet should always be in a downward vertical position to avoid gross contamination. Position the excess tubing so as not to interfere with the work of the employee. 

Remove the collection device from the pump and seal it as soon as possible. The seal should be attached across sample inlet and outlet so that tampering is not possible. 

Connect the collection device, tubing, pump, and calibration apparatus. 

Four precautions must be observed when this type of collection device is used ... 

PM Control - An impingement-plate scrubber is a vertical chamber with plates mounted horizontally inside a hollow shell. Impingement-plate scrubbers operate as eountercurrent PM collection devices. The scrubbing liquid flows down the tower while the gas stream flows upward. Contact between the liquid and the particle-laden gas occurs on the plates. The plates are equipped with openings that allow the gas to pass through. Some plates are perforated or slotted, while more complex plates have valve-like openings. 

Run-off/Run-on Control (Diversion or Collection Devices) Temporary Cover... 

The fields of application are wide involving computational fluid dynamics (CFD), flow in ducts and pipes, pumps, fans, collection devices, pollution dispersal, and many other applications. 

Decontamination factor A logarithmic scale used to measure the collection efficiency of a particulate collection device. 

Deposit gauge A collection device that records the deposition rate of solid or liquid particulate matter from the air. 

Efficiency, particle size The ability of a collection device to remove particles of a specified size or size range. 

Inertial impaction This is the predominant mechanism used in all particle collection devices. 

Interception A special case of impingement, in which a particle is trapped on a fiber due to the effect of Van der Waals forces rather than inertia. The interception of a particle in a particle collection device occurs when the particle follows a gas streamline round a collector at a distance less than the radius of the particle. 

Personal sampler A collection device attached to a person that obtains samples of air to be tested for radioactive, chemical, or biological agents. 

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