MechChem Africa January-February 2024

Metso launches upgraded Evaporative Cooling Tower Metso Corporation has released an upgraded and more efficient dry gas cleaning solution for furnace off-gas, which offers improved cooling efficiency and excellent

M etso’s newly launched upgraded Evaporative Cooling Tower is an efficient dry gas cleaning solution designed to cool down hot furnace off-gases by means of evapora tion. The Evaporative Cooling Tower, which is normally followed by a hot electrostatic precipitator or a bag filter, cools the gas from about 600-700 °C to about 200-350 °C. The tower operates dry, meaning that all water added is evaporated. The small droplets in the tower evaporate rapidly, which reduces the retention time and length needed to ensure complete evaporation. “We are excited to introduce the enhanced Metso Evaporative Cooling Tower. Its unique design enables efficient and even cooling. We have many decades of experience with cooling towers, and we have now improved both the design and the process control. The advanced model-based automatic control, for instance, allows for accurate control of cooling during startup and varying process conditions; this is important for protecting the tower and the downstream equipment,” explains Leif Skilling, director, Gas Cleaning at Metso. Benefits of the Metso upgrade include: • Controllable outlet tem

perature coupled with advanced model based automatic control for startup and varying process conditions. The even temperature profile reduces the risk of condensation, protecting the tower and downstream equipment from corrosion. Efficient gas distribution by means of guiding vanes in the inlet. • Rapid liquid evaporation of small drop lets through the use ofusing atomising air. • A large turn-down ratio and lower air consumption can be achieved in the tower design through the selection of nozzles and the number of headers. Metso has 60 years of experience with evaporative cooling towers and about 30 units installed. All this extensive knowledge is incorporated in the new versionlatest ver sion of the Metso Evaporative Cooling Tower. Operating principle The hot process gas enters the tower from the top. The gas is evenly distributed by means of guiding vanes in the inlet. The top of the tower separates the cross-sectional area of the in coming gas duct from the evaporative zone. This is specifically designed not to disturb the gas profile downstream of the guiding vanes. Special two-media nozzles are placed at the inlet part of the tower, in which the water is atomised with compressed air to form small droplets. The nozzles are placed to create a uniform spray pattern that covers the entire cross-sectional area of the tower. This minimises the risk of partial cooling of the gas. The small droplets evap orate quickly using the heat from the hot gas, reduc • •

The amount of water injected into the tower is determined by a control loop based on the outlet temperature. As the temperature increases, more water is sent through the nozzles and vice versa. The control circuit of the water injection ensures that the gas leaving the cooling tower will have a steady temperature around the set point needed for downstream equipment such as bag filter or hot ESPs. To handle varying flow conditions, during a start-up, for example, the temperature con trol is supplemented by an advanced model based automatic control, which ensures that the water injection adapts quickly to even large fluctuations in the heat load, keeping the operation steady and reducing the risk for over or under cooling. In addition, any dust that settles at the bottom of the tower is continuously removed by a scraper conveyor and a rotary feeder. The Evaporative Cooling Tower can treat gases from any type of metallurgical furnace. It has commonly been used for example with Peirce Smith converters and anode furnaces. In addition to furnaces, Metso can also supply excellent hood systems for the gas uptake, where, for example, the converter hood sys tem provides adjustable dilution air intake, giving the operator control of both gas com position and temperature. www.metso.com/portfolio/

ing the tem perature in the process. These small droplets have a large surface area, reducing the retention time and length of the evapora tive zone needed to ensure

Metso’s recently upgraded Evaporative Cooling Tower can treat gases from any type of metallurgical furnace and is commonly used with Peirce Smith converters and anode furnaces.

complete evaporation.

26 ¦ MechChem Africa • January-February 2024