DUST CONTROL

The presence of dust can cause serious problems in many dry cleaning plants and in the pretreatment sections of wet cleaning plants. In addition, dust containment is an integral part of aU thermal drying units. The need for dust collection arises because of air pollution control, safety- and health-hazard elimination, and reduction of equipment maintenance costs. 

In addition to the economic and health hazards, coal dust can present serious explosion hazards. Certain bituminous coals and anthracites also continue to release measurable quantities of methane gas for days, and sometimes weeks, after they have been mined, which increases the possibility of explosion. Provision of efficient ventilation and restriction of electrical or thermal sources of ignition are required by regulation. 

Other sources of dust are windblown losses from storage piles and from railcars during loading and transportation. Various chemical treatments are available for stockpile sealing and are being used for spraying the tops of railcars active stockpiles present an almost insurmountable problem. 

---

Dust control Dust control agent Dusts... 

In addition to the previously noted safety factors associated with these processes, there are additional needs for dust control and ventilation for dissipation of various vapors from pressing, tempering/heat treatment, and machining and finishing operations. 

The health and safety issues outlined herein for particleboard also apply to MDE. A special note should be made of the fact that, because the MDF raw material is of dry fiber base, there exists in MDF a large component of very small, broken, dust-like wood fibers. These contribute to the dust concerns in the manufacturing areas, requiring exceUent dust-control systems, good housekeeping, and personal protection. 

Other Applications. Polyacrylamides are used in many additional appUcations including soil modification (138), dust control (139,140), humidity control (141), protein purification (142), removal of barium from wastewater (143), and removal of arsenic from hydrocarbons (144). Polyacrylamides have been used for many years in sugar manufacture and textile treatment. 

Sealant Manufacturing. Most sealants use mineral-based fillers which may contain small amounts of crystalline siHca. If crystalline siHca is present, dust control is important to prevent inhalation of these particles. Crystalline siHca is a known cause of siHcosis, a debiHtating disease of the lung. Another common safety concern in sealant manufacturing is the use of flammable materials. Not all sealants use flammable ingredients, but for those that do, proper inerting and grounding are needed to prevent potential explosions. 

In recent years, several wet milling operations have been initiated with obvious advantages in dust control and potential advantages in the separation of mineral contaminants from the fiber product. On the other hand, large-scale industrial wet classification methods are not in use at present. 

Roadbed Stabilization/Dust Control. One of the earliest uses of calcium chloride was for dust control and roadbed stabilization of unpaved gravel roads. Calcium chloride ia both dry and solution forms are used both topically and mixed with the aggregate. When a calcium chloride solution is sprayed on a dusty road surface, it absorbs moisture from the atmosphere binding the dust particles and keeping the surface damp. Calcium chloride does not evaporate, thus this dust-free condition is retained over along period of time. 

Economic Aspects and Uses. Total production of calcium chloride in 1989 was 873,000 tons (31). Most of this was produced from Michigan brines. The principal use of calcium chloride is to melt snow and ice from roads. It is also used in dust control, concrete setting control, and various industrial uses. 

For dust-control work, it is recommended that a preliminary quah-tative examination of the dust first be made without a detailed particle count. A visual estimate of particle-size distribution will often provide sufficient guidance for a preliminaiy assessment of reqmrements for collection eqmpment. 

Rubber Industry Advisory Committee - A New Practical Guide to Complying with COSHH in the Rubber Industry Dust Control in Powder Handling and Weighing Dust and Fume Control in Rubber Mixing and Milling Control of Solvents in the Rubber Industry... 

Recycle condensates, rainwater, and excess process water for washing, for dust control, for gas scrubbing, and for other process applications where water quality is not of particular concern. 

Give preference to fabric filters over wet scrubbers or wet electrostatic precipitators (ESPs) for dust control. 

Furnaces should be enclosed to reduce fugitive emissions, and dust from dust control equipment should be returned to the process. 

Recycling should be practiced for dust control and gas scrubbing, as well as for cooling water, condensates, rainwater, and excess process water used for washing. 

Ranking equipment and teehnology options for an intended applieation then beeomes a matter of seleeting those projeet options with the shortest paybaek period. So, for example, if we compare a baghouse versus an electrostatic filter for a dust control application, an overall payback period for each option can be determined based on the capital investment for each piece of equipment, operating, maintenance, power costs, and other factors. 

Air con Corp. Site markets air pollution systems including dust control systems and equipment, http //aircon-corporation.com... 

Fortress Designs Supplier of dust control equipment, baghouses, dust collectors, fabric filters, dust filters, bin vents. http ll vww. fabricfilters.com... 

This discussion will address needs, applications, performance characteristics, and design considerations for LVHV exhaust ventilation. The applications are primarily for dust control. LVHV systems can be effective for protecting workers from dust exposures and for recovering valuable process materials. The equipment, excepting the nozzles, involves technology that is the same as for large central vacuum cleaning systems. 

LVHV nozzles can create problems that may be sufficiently severe as to prevent their use, usually in the form of ergonomic encumbrances and excessive noise. These problems can be dealt with, to limited extents, and LVHV applications can be effective. It must also be understood that dust control by 1..VHV systems is ultimately limited. No ventilation control measure can ensure sufficient worker protection down to extraordinatily low acceptable dust levels. Worker protection must always be confirmed by industrial hygiene monitoring and evaluation, and administrative control measures such as respiratory protection may be necessary. 

If well designed and properly used, LVHV applications have the primary advantage of effective dust control. LVHV systems also require much less replacement airflow than conventional ventilation systems. This can result in significant savings in operating costs to condition the replacement air. These savings can help to offset the typically high installation costs for LVHV systems,... 

FIGURE 10.27 Examples of LVHV exhaust nozzles for dust control on hand-held tools. ... 

Peripheral dust captured Fine dust controlled Heovy particles... 

FIGURE 10.29 ACGIH VS-Print for designing a multiple-nozzfe LVHV exhaust system for dust control ir. foundry operations. ... 

Exhauster and Motor Air movers for LVHV systems are not conventional fans. The low static pressures needed to operate LVHV systems can be generated by multiple-stage centrifugal (turbine-type) exhausters. These utilize high-precision rotating blades that can be damaged by dust. Consequently, it is always necessary to have an air cleaner in an LVHV dust control system to protect the fan. The low static pressures also require air volume flow rates to be corrected to standard conditions for exhauster selection. 

A list of important variables affecting dust control during clamshell unloading was established as follows ... 

The original design was based on a control velocity recommended by dust control design manuals. The original design of 28 m s exhaust flow induced an inward velocity of about 0.5 m s" through the enclosure entrance and trolley shots. This was not sufficient to overcome plume trajectories aimed outward, or to overcome the effect of moderate wind levels. 

A design based on the enclosure open-area control velocity does not consider all the other variables listed as affecting dust control. Calculation procedures to predict many of the other variables would be very complicated if not impossible to perform. Physical modeling of the problem and solution w as therefore used as the basic design tool. 

---