Dusting problems

For most appHcations, bismuth vanadate is not thermally or chemically stable enough, and it has to be encapsulated with a dense, amorphous shell of sihca (40,41). It is recommended that bismuth vanadate be granulated to improve its handling and eliminate any dusting problems. 

Because they are fine and light, dusting problems might occur and therefore careful housekeepiag is necessary. Most carbon blacks are peUetized, which not only reduces dusting problems, but because of the higher bulk density, peUetization also lowers the cost of shipping. 

Handling of alumina and coke presents dusting problems. Hoods and exhaust systems collect the dust, which is then separated from the exhaust air either by cyclones, electrostatic precipitators, filter bags, or a combination of these methods, and recycled to the process (see Air pollution control PffiTHODS). 

Cost-effective control of dust problems arising from bulk materials handling requires an initial examination of the overall handling operations. Factors influencing dust generation and dispersion must be understood in order to achieve a proper design. 

Attrition of particulate materials occurs wherever solids are handled and processed. In contrast to the term comminution, which describes the intentional particle degradation, the term attrition condenses all phenomena of unwanted particle degradation which may lead to a lot of different problems. The present chapter focuses on two particular process types where attrition is of special relevance, namely fluidized beds and pneumatic conveying lines. The problems caused by attrition can be divided into two broad categories. On the one hand, there is the generation of fines. In the case of fluidized bed catalytic reactors, this will lead to a loss of valuable catalyst material. Moreover, attrition may cause dust problems like explosion hazards or additional burden on the filtration systems. On the other hand, attrition causes changes in physical properties of the material such as particle size distribution or surface area. This can result in a reduction of product quality or in difficulties with operation of the plant. 

The carbon black industry takes extreme efforts to confine product during all stages of manufacture (45). Highly efficient bag filters are used to collect the product. After collection the fluffy carbon black is densified and pelletized to minimize dusting problems during shipping and use. 

Most residues are finely divided solids that, when dry, create dust problems and. when wet. gradually release metal ions in solution that may contaminate the environment. 

Work surfaces may be wetted with a fine spray to prevent creation of dust. Dusty materials being conveyed may also be sprayed. This practice not only minimizes the problem of airborne dust, but simultaneously reduces product loss. Spray heads may be located at as many locations as have dust problems because the equipment required is moderate in cost and there is no hazard to personnel from Aerosol GPG Surfactant. 

The residence time is 20 min. The speed is 3-4 rpm. On the average, 7.5% of the cross section is occupied by solid. Because of dusting problems, the linear velocity of the air is limited to... 

The discovery of C60 by Kroto and coworkers (1985) was motivated in part by the interstellar dust problem. C60 would seem to be an ideal candidate, as it is spherical and graphite-like, it forms spontaneously in harsh environments with carbon dust, and is stable in intense radiation fields, a condition analogous to that found in the diffuse ISM (Kroto and Jura 1992). In fact, the observation of two DIBs at 957.7 and 963.2 nm are tentatively considered the first evidence of C60+ in interstellar dust (Foing and Ehrenfreund 1997). Moreover, a mixture of hydrides of C60 is shown to exhibit spectral features remarkably similar to those seen in the unidentified infrared emission (Stoldt et al. 2001). The UV absorption spectrum of synthetic C60H36 was also observed to possess abroad bump at 217.5 nm (Cataldo 2003). 

Other powder issues are also important in delivering the food powder, and these include the ability to handle and transport ingredient powders, dust problems, dust fire and explosion hazards, allergy problems, creation of desirable powder particle properties, and the ability to dissolve these powders when required. Many of these issues are in common with other powders and much can be leamt from other industries dealing with powders. 

Small particle sizes of raw batch materials accelerate melting and homogenization via an increase in the reaction area between raw materials. However, the use of very fine raw materials has an associated dusting problem along with the added cost of particle size reduction. In the following, simultaneous thermal analysis in conjunction with x-ray diffraction were used to determine the fusion path in a typical glass composition as a function of particle size. 

Edwin Lightfoot I would take heart from that, John, because only a few years ago, a meteorologist predicted that we were going to have an ice age because of the dust problem. So, if we make enough dust, we can solve the greenhouse problem. 

The principal anode performance problem of Soderberg cells is the low-baked anode carbon. This results in preferential attack on binder coke and creates some level of filler dust problem as a standard operating condition. For VS Soderberg anodes, there is additional performance loss for the lower-quality pinhole carbon, which fills the space created when pins are reset. This is due to porosity created when pinhole paste is baked in place by the existing excessive heatup rates, VS Soderberg anodes are also adversely affected if the carbon has a high sulfur content. Conductor pin tips will become coated with an iron sulfide scale, which interferes with electrical conduction in the anode. 

The residue consists of mainly carbon and has a high heating value, as shown in Table 26.12. However, applications could not be found and the residue was landfilled as waste, after cosily packaging in a flexible container because the residue was a fine dry powder and caused dusl problems upon handling. The codevelopment work with Sapporo city successfully utilized the residue in the sludge incinerator as supplementary fuel. However, dust was still a problem in this application. To resolve the problem and to find belter applications, pelletizing facilities for this residue were installed in April 2004. As a result, the dust problem was solved and better applications are expected. 

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