Above: A few seconds before the dump, Fog is already ON.
The Raring Corp (TRC) has been in the dust control business for the last 37 years, mostly helping its industrial clients to solve their dust issues, writes Gonzalo Campos Canessa, TRC CEO. It has carried out over 670 projects in all five continents, and it has used either water spraying systems or its ADSTM Dry Fog. The water spraying systems increases the moisture of the material in order to reduce its ability to generate dust.
On the other hand, ADSTM Dry Fog systems (active dust control) create a cloud of extremely small droplets that are in the same size range as the airborne respirable dust. Key to the reliable delivery of fog into the system is the design of TRC’s FP-series acoustic nozzles, which use compressed air to create high frequency sound waves that shatter water into the fog-sized droplets needed while retaining adequate kinetic energy to project the fog where it’s needed and penetrate through opposing air flows. These water droplets agglomerate with the dust particles, make them heavier, and settle them back to their source.
Most of TRC’s projects come from hard rock mining, coal mining, coal-fired power plants, frack sands and ports. The bulk materials being handled in those facilities can be quite different and the same facility can process a variety of materials. The features of bulk materials can vary depending on the exact location where their deposits are located. Within the same country and even in two closes by deposits, the ores can be different, and TRC considers all these factors within its designs.
Another important factor to consider when designing and supplying a dust control system is the applications/equipment where the bulk material is being transferred. There are some parts of the material handling processes that are more intensive on generating dust, so understanding how the whole process works it is a key factor for designing a successful dust control system.
Above: During the dump.
Also relevant is the importance of passive dust control and its effect on the overall performance of the dust control system. Passive dust control is that one that doesn’t require energy to operate and gives retention time, residence, and collection surface to help the ADSTM Dry Fog to agglomerate the dust providing an adequate dust control solution. The passive containment is as important as the active dust control, and it is easier to implement in transfer points than on truck (or front-end loader) dump hoppers. On the first one you need to consider a head box, sealed chutes, conveyor covers, conveyor skirts and adequate baffles. On the dump
hoppers, a three-walled and roofed stilling shed with rubber curtains, both inside and on the entrance of the stilling shed; also baffles around the hopper will help to provide ideal conditions to work together with ADSTM Dry Fog.
ADSTM Dry fog is particularly well suited to most containable dust sources, it is sometimes the only choice that has a chance of success — and in some cases, it cannot be used. In most plants, a well-thought-out combination of technologies is the best solution. TRC’s ADSTM Dry Fog requires small amounts of water, and it doesn’t increase the moisture content of the bulk material by more than 0.1%.
Even though TRC has vast experience controlling dust issues generated by different kinds of bulk material — in different environments, in a diverse pool of industries and in different countries — the food industry is reluctant to use water-based solutions which may increase the moisture of their bulk materials, causing the following issues:
- growth and spread of microorganisms;
- reduction in quality; and
- packaging issues
Allowing regular maintenance to TRC’s systems and installing the fog nozzles at the correct locations ensures that none of those issues can be expected.
TRC’s dust control system sold through PEBCO (TRC’s REP within the USA) to a food-grade facility in the southern part of the country, comprises several transfer points and hoppers. Before installing and commissioning this dust control system, the dust generated a dense cloud of fine particles inside of the factory, which made visibility scarce.
The reduced visibility was dangerous for the operator’s health and created safety issues inside the building. The point where most of the dust was generated was at the front-end loaders’ dump hopper. Even though this is a batch process, the amount of material being dumped in a short period of time created a dense cloud of dust per dump.
During August 2021, TRC started-up and commissioned an ADSTM Dry Fog system on this food facility, handling corn, wheat and soy. The ADSTM system included nozzles on different hoppers and transfer points along the plant. As expected, the system worked very well on the transfer points where passive containments were present. On the secondary hoppers, there was no chance to add passive containment and TRC was expecting these to generate more dust than they actually did, a factor that facilitated the dust control work.
The main concern was the dust control at the front-end loader discharge, which feeds the whole processing facility — no containment was available around the pocket. This kind of application is always a challenge since a huge amount of bulk material dumps in a few seconds. This process accelerates the particles in two directions, first when they are falling down and second, when they try to go up and out of the hopper’s boundaries after they hit the bottom of the hopper. In this case, the Fog nozzles were installed around the hopper, creating a dense cloud to help agglomerate the dust particles and controlling the dust. It was crucial to the success of the project to start spraying fog inside of the hopper a few seconds before the dump actually occurs, which helps the dust to interact with the dense cloud of fog as soon as the dump happens.
TRC was able to successfully achieve the two main goals of its client: to control the dust issues inside their facility without increasing the bulk material’s moisture at all.
Dry Cargo International