Dust loading

Loading dust The selected synthetic dust used to determine the dust-holding c t-pacity of a filter. 

Lorius et al. (1990) performed a simple multivariate analysis in which they correlate the temperature changes of the past 160 kyr (as recorded in the Vostok SD record) with changes in five forcings atmospheric CO2 plus CH4, ice volume, aerosol loading (dust and sepa-... 

Grain loading (dust concentration) is less than 10 grains/fT. 

Bag filter very efficient removal of small-diameter and small-particle loadings dust diameter... 

The adsorption of dioxins and furans on activated carbon generates a PCDD/F-loaded dust stream. In order to prevent the explosion risk in the bag filter, mixing of the activated carbon with lime may be needed. This will increase the total amount of residue for disposal and will limit the possibility to re-use the filter dust. 

Settling basin dust diameter > 100 [tm feed concentration 2 to 75 g/m temperature < 400 °C gas phase Ap = 3 to 7 kPa power usage 0.04 to 0.7 kW/m /s. Bag filter very efficient removal of small diameter and small particle loadings dust diameter 0.5 to 70 [tm feed concentration 0.01 to 100 g/m temperature... 

The dust may be deposited on a surface by free settling. The specially designed apparatus showri in Fig. III. 18 may be used to apply dust to a plate. A rubber membrane 5 is fitted onto the end of a tube, and a weighed quantity of dust is placed in the hollow of this membrane. When the bulb is squeezed, the membrane blows out, and the particles are sprayed out and settle on the horizontal plates 4. This apparatus can also be used to load dust onto vertical and horizontal plates, either by free settling or with various velocities of particle collision with the plate the latter is achieved by rotating the disk 3 by means of an electric motor 2 [11]. The screen 7 eliminates possible effects of air-flow perturbations on the process of covering the surfaces with dust as the disk moves. 

Table 12.2 identifies the failure modes and their causes for cyclonic separators. Since there are no moving parts within a cyclone, most of the problems associated with this type of system can be attributed to variations in process parameters, such as flow rate, dust load, dust composition (i.e., density, si2e, etc.), and ambient conditions (i.e., temperature, humidity, etc.). 

Bag filters. Bag filters, as discussed in Chap. 3 and illustrated in Fig. 3.66, are probably the most common method of separating particulate materials from gases. A cloth or felt filter material is used that is impervious to the particles. Bag filters are suitable for use in very high dust load conditions. They have an extremely high efficiency, but they suflFer from the disadvantage that the pressure drop across them may be high. ... 

Some empirical equations to predict cyclone pressure drop have been proposed (165,166). One (166) rehably predicts pressure drop under clean air flow for a cyclone having the API model dimensions. Somewhat surprisingly, pressure drop decreases with increasing dust loading. One reasonable explanation for this phenomenon is that dust particles approaching the cyclone wall break up the boundary layer film (much like spoiler knobs on an airplane wing) and reduce drag forces. 

Table 7. Dust Loadings and Cyclone Inlet Velocities above Which Erosion Is Excessive ...

A low incidence of explosions has been reported when precipitation is effected without a nucleating agent and during the screening process. Precautions must be taken during detonator loading to prevent dusting and to maintain a scmpulously clean operation. 

Air cleaning systems are often used to remove dust or vapors from plant or process exhaust streams. Dust collecting systems such as filters or electrostatic precipitators that handle heavy loads of dust are usually designed to be self-cleaning, but it is stiU. necessary to enter the air cleaner periodically for inspection or repair. Dust deposits inside the equipment are likely to be stirred up and inhaled by unprotected workers. Baghouses are particularly likely to cause exposure because large amounts of dust may be retained in the cloth and released when the bags are handled. 

Pitch. Pitch used to be stored in solid form at the tar distillery in open bays, from which it was removed by small explosive charges. Loading of the lump pitch by mechanical shovel created a dust ha2ard both at the tar installation and at the customer s, where the lumps had to be ground before use. In the 1990s, pitch is stored in tanks heated by superheated steam or circulating hot-oil coils and transported in fiquid form in insulated rad, road tankers, or ships. When transport as a hot fiquid is not feasible, not acceptable by the customer, or for small amounts, the pitch is converted into a dust-free particulate form, ie, short rods termed pencils, pastilles, or flakes. 

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