Some cases of air purification from toxic hazards
Sometimes when deleting local exhaust significant amounts of toxic hazards is necessary to clean the air before throwing it out. In practice, ventilation, such cases relatively few, as opposed to process emissions are rarely! high concentrations of harmful substances.
Questions on cleaning ventilation emissions of gases, fumes and aerosols are solved or local health surveillance, or by the designers of ventilation. Only for certain especially harmful substances (for example, chromium, mercury and lead), there are direct indications of the need for clean air emissions.
Quite often used cleaning ventilation air, at which gases and vapors react and are neutralized. It is used as an absorption process in which hazards are absorbed by the solids
Neutralization of air containing gases and vapors - special issue. Designing wastewater treatment plants are usually handled by gas treatment. We therefore consider here only the simplest and most common cases.
If the hazard or water-absorbing solution, we can apply the simplest, albeit bulky device. Here it is sufficient to achieve adequate exposure to air pollution with an absorbing liquid, and the problem resolved. To achieve this contact, contaminated air is passed through the scrubber, ie, a hollow cylinder with a nozzle, irrigated with water solution of PLI.
Contact the contaminated air with water IPT solution is also achieved by sparging air through a bed of mortar. You can use the filter-bubbler.
Cleaning the air of gases and vapors, does not absorb water and does not react with the solutions of (carbon monoxide) are very difficult. Currently, no effective technique of case and sinks of carbon monoxide. Used for this purpose preparation of manganese oxide (gopkalit), although it absorbs carbon monoxide, but quickly "work". In addition, when exposed to moisture absorber loses its activity.
Also mention the clean air of the volatile solvent vapors. With a significant evaporation of the solvent in the room (20-30 kg / h) is the meaning of his capture, not only with health, and in economic terms. It can be used absorptive capacity of activated charcoal and silica gel. The air is passed through a layer of absorbent powder, cleaning usually takes place in the so-called "fluidized bed".
When large scale soldering lead or alloys of the PIC in the air, local exhaust removed, contains appreciable amount of aerosols of lead and its oxides. In some cases, this air must be cleaned before its release into the atmosphere.
Aerosols of lead and its oxides are well captured by filters very fine filter, such as fibrous tissue or FPP filter cardboard type FMN. But in the air, away from the soldering except aerosols lead, still contained a pair of condensing flux. These pairs, in particular resin, can condense on the surface of the fabric or cardboard and clog them.
To increase the longevity of fine filters recommended to pass air through the strainer, which ends up condensing Nara scheme similar setup is shown in Figure 17.
Strainer is a framework of tight corners with them fine grid (cell 2X2 mm). Lively cross-section of such a grid is approximately 40-50% of the dimensions. At a load of filter parameters m/ch-m1 3000, ie at a rate in the living section of the grid about 2 m / sec, the resistance of the filter in a pure state is about 3 kg/m2. As fouling nets settling substances increases its resistance. When resistance 10 ks/m1 nets should be replaced.
The data presented should be considered as indicative, as the operating experience of similar treatment plants are not yet available. Issues of air purification from vapors and gases in some detail in the book by VN Uzhova "Sanitary protection of air, to which we refer interested.