Fume control technique

A 13.9 Electrostatic technique of powder painting 13/409 A13.I0 Effluent treatment and fume control 13/4l2... 

Table 13.17 lists some of the important considerations for the different fume capture techniques. From the point of view of cost effectiveness, the usual preference is source collection or a low-level hood, provided an acceptable scheme can be developed within the process, operating, and layout constraints. The cost of fume control systems is almost a direct function of the gas volume being handled. Flence, the lower volume requirements for the source capture or low-level hood approach often results in significant capital and operating cost savings for the fume control system. 

The purpose of the control plant is to maintain a working environment that is acceptable in terms of any statutory regulations and the custom and practice within an industry. The effectiveness of a control system is measured by the amount of dust or fumes it controls. Efficiency, on the other hand, is measured by the amount of power it takes to do the work. It is the job of the dust-control engineer to produce the most effective plant in the most efficient way, and the techniques of control will vary from one industry to another. All control plants will have either four or five elements, as shown in Figure 46.1, i.e. hoods, ducting, fan, collector and disposal. 

The use of aqueous foams to control fume or vapour release from reactive chemicals is discussed. An acid-resistant foam NF2 controlled fume emission from 35% and 65% oleum, and from titanium tetrachloride, but was not effective for sulfur trioxide and chlorosulfuric acid. An alcohol-resistant foam NF1 suppressed ammonia vapour emission by 80%, and Universal fire foam reduced evaporation of ethylene oxide, vinyl chloride and methanethiol, and reduced vapour emission of 1,3-butadiene by 60%. Safety aspects of foam blanketing are discussed [1]. Equipment and application techniques are covered in some detail [2],... 

The volatile organic components that are emitted in the gaseous effluent can be controlled by a variety of technologies including scrubbing techniques, granular-carbon adsorption and fume incineration. The specific technology is selected on a case-by-case basis. 

For the evaluation of the rheology of the silica dispersions, different test methods were applied (a) a shear rate-controlled relaxation experiment at = 0.5 s (conditioning), 500 s (shear thinning), and 0.5 s (relaxation) to evaluate the apparent viscosity, the relaxation behavior, and thixotropy (b) shear yield-stress measurements using a vane technique introduced by Nguyen and Boger [5] (c) low deformation dynamic tests at a constant frequency of 1.6 s in a stress range of ca. 0.5 - 100 Pa. All samples contained 3 wt% of fumed silica. 

The processes used for terminal sterilization are heat, temperatures in excess of 140°C, gamma ray radiation, perchloric acid fumes, and ethylene oxide. These techniques are commonly used for sterilizing metals and plastic tools, medical devices, and instruments. This approach is clearly preferred as it provides a final step that assures sterilization of the product and only demands limited controls prior to that final step. However, unfortunately synthetic organic chemicals, particularly synthetic antibiotics are generally not able to accept these severe conditions without adverse effect on the product. This leads to the need to pursue aseptic processing. 

Surface modification was applied to hydrophilic fumed silica with a BET surface area of 300 mVg. Controlled surface coverage was realized using two different techniques. 

During the preparation of medicines, steam, vapour, aerosols, dust and fumes can be released, which may pose a health risk for the operator. It is not always possible to change the process releasing these hazardous substances. As a consequence it can be necessary to protect operators in preparation or quality control areas from exposure to the product or the active substance. This can be done by active ventilation and exhaust and by filtration in order to protect the environment (see also Sect. 26.4.1). The appropriate equipment may be fume cupboards, moveable exhaust ducts, powder exhaust units, (bio)safety cabinets and isolators. Fumes, gas mixtures and volatiles might be absorbed by special filters, but in pharmacy practice only the technique of exhausting and screen filtration is usually used. 

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