Dust Control Systems Using Spray Nozzles | Two Versions of the System
IKEUCHI, The Fog Engineers, a manufacturer of spray nozzles, offers dust control systems using nozzles to create a variety of fogs to effectively suppress dust from becoming airborne and dispersing, as well as dust eruptions.
To design and provide a system suited to the specific environment of a facility, there are two main versions of the system. One is a “soft fog design” that sprays fine and soft fog to settle airborne dust and suppress dispersing. The other one is a “high-velocity fog design” that sprays a large volume of semi-fine fog at high velocity directly at the point where the dust is generated to prevent dust from bursting into the environment.
Both designs are already used in power plants and steel mills in Indonesia, Thailand, Vietnam, South Korea, the United States, Japan, and other countries, to reduce air pollution and improve work environments.
The soft fog design was discussed in the previous article. This article describes a steel mill using the high-velocity fog design.
Problems of Dust Dispersing | Material Yards and Coke Ovens | Steel Mills
There are a variety of sources for dust in steel mills. A large amount of dust comes from the material yards, coke ovens and in blast furnace taphole areas. From there it is spread easily by draft and wind causing unhealthy work conditions inside the mill and complaints from nearby residents outside the mill.
Outside measures to suppress dust were implemented, which include spraying water in the raw material yard to keep the dust from dispersing and renovating the equipment of the coke ovens to reduce dust.
Problems of Dust Eruptions | Blast Furnace Taphole Areas | Steel Mills
However, preventing dust from erupting in the taphole area when the taphole was opened had not been solved and was still causing a worsening of working conditions.
There are two main sources for the dust; one is area right around the taphole, and the other is the main runner that is the flow path of molten iron. Dust is generated around the taphole when the hot metal comes into contact with air and causes dust to escape at the opening, this however can be remedied with the help of a dust collection hood placed above this area.
The molten iron then goes through the main runner to the next process. The main runner is usually covered by main runner cover, each section is approximately eight meters in length. These cover sections keep the molten iron from splashing but are also a shield against heat and prevent the dust clouds from escaping the runner.
These measures generally work well, but the cover section in front of the taphole is removed temporarily to allow the drilling machine to move into position to open the taphole. During these three or four minutes while the taphole is opened, this gap without the cover leaves the pig iron surface exposed to air and allows the dust to rise and escape into the facility on an updraft of hot air. This dust, reaching high up in the facility and then dispersing broadly, cannot be completely captured with the overhead dust hood, and thereby causes a harmful environment.
High-Velocity Fog for Preventing Dust from Erupting
To address this problem, a high-velocity dust control system was proposed. It sprays a large volume of fog at high velocity to suppress the dust from escaping.
Specialized nozzles installed to the upper left and right of the taphole start spraying directly at the taphole as soon as it is opened, suppressing the dust, and keeping it from escaping.
By spraying the fog at a high flow velocity, it is possible to engulf the point of origin of the dust without being affected by the updraft. The fine droplets, approximately 80 µm, will also prevent the surrounding area and equipment from getting wet.
Installation of the system is not a large-scale project, and the only things the customer needs to provide are water and compressed air.
Effectively Preventing Dust in the Blast Furnace Taphole Area
The high-velocity fog can prevent dust from escaping even during the opening of the taphole, drastically lowering the negative effects on the work environment. In addition, several of the nozzles were installed higher up and away from the source of the dust, spraying fog horizontally at areas where dust tends to drift and collect. This layout helps direct the drifting dust towards the intake of the overhead dust collection hood, which supports the control of dust flow, and has improved the efficiency of dust collection.
Summary | Dust Prevention System | High-Velocity Fog Design
Features of the system
- Large amounts of fog sprayed at high velocity envelop the point where dust is generated and prevent the dust from erupting.
- Design of an optimal system for each facility, by selecting nozzles and planning a detailed installation layout for the nozzles, valves, pressure regulators, and other devices of the system, considering the entire area.
- Usage of semi-fine fog does not wet the worksite.
High-Velocity Type | Spray Nozzles Producing a Large Amount of Fog at High Velocity