Concrete plant owners and operators know the problems of dust collection. From the initial startup permitting and paperwork associated with the dust produced at concrete plants through the ongoing maintenance and replacement of dust filters and equipment years after you have been in business, dust collection and suppression is an important component of the system. The laws and rules regarding dust collection and suppression requirements vary town by town, county by county and even state by state. Additionally you may have various agencies that you need to deal with including local zoning authorities, DNR, EPA and others depending on your location. Fortunately the equipment used for collecting and suppressing dust associated with concrete plants has continued to improve and is now very effective.
Dust collection and suppression must be considered at several different areas of the concrete plant. Some owners will put equipment to collect and control dust in every area where it can be created. Others owners will only put the collection equipment where it is absolutely required. Many owners will use more dust collection equipment then required because they want to be environmentally friendly, appease opponents, or for other reasons. Ultimately the decision on what type of dust collection equipment you need is based on what you are trying to accomplish and what type of concrete plant you have.
At the very minimum concrete plants are sold standard with a dust vent on the cement silos, usually one or more per compartment. When cement is delivered in a bulk tanker it is pneumatically blown from the tanker into the silo. A silo being filled by a bulk tanker without the venting system standard on most silos looks as though the silo is on fire. Cement, fly-ash and slag (the most common materials in silos at concrete plants) are aerated commodities. This means that when air is introduced into the material it becomes lighter and flows easier. When these materials are pumped into the silo’s from a tanker the dust collector keeps the materials from flowing into the environment looking like a thick smoke. In the case of silo dust collectors they actually provide operators with a cost savings because it keeps them from losing large amount of materials being delivered.
Another common place for dust collection equipment is where the materials discharge into the mixer. Precast and product plants will commonly have a dust collection system integrated with their plant mixers. Ready mix plants frequently have a dust collection system that helps contain and control the dust around where the truck connects with the plant. Other areas that are often equipped with dust collectors include weighing hoppers such as a cement batcher. Some locations are even forced to control the dust from trucks on gravel drives and areas using water trucks to keep the area moist and dust under control as trucks travel through.
Obviously understanding the areas on and around your concrete plant that are problem areas for dust creation as well us knowing what the environmental and zoning requirements associated with dust are among the most important factors in selecting dust collectors and suppression equipment. Another important factor is developing the strategy for controlling the dust. Some plants use a different dust collector for every area they need to control. Central dust collectors are also available that use ducting systems to collect dust from multiple areas and vent it to a single centralized dust system. Some concrete plants use a combination of systems. There isn’t necessarily a right or wrong system, it is just selecting the proper system for your application.
Other important factors when considering dust collector are the materials that is being collected and the volume the material will be introduced (in the case of a silo, the number of fill pipes). Different materials have different densities and can require different sizing to ensure the dust collectors work effectively.