Are your activated carbon air cleaning device designed with the right interval of residence time ? Does a single panel of filter is workable for any application in LEV system ?

Residence time, filter face area, and thickness of a activated carbon adsorption media are crucial parameters in the design of effective activated carbon air filtration systems. By understanding their significance, we can optimise pollutant removal and balance it with system static pressure losses across the system, ensure cleaner ambient emission, low or zero ground level concentration of the chemical near the stationary source.

In this article, we will explore the importance of residence time and delve into the significance of filter face area and thickness, providing insights on their role in designing air cleaning device with the highest efficacy.

1. Understanding Residence Time:

Residence time refers to the duration that air spends in contact with activated carbon within a filtration system. It directly influences the efficiency of pollutant removal through adsorption process. To define residence time accurately, it is essential to consider the desired level of pollutant removal, specific pollutants of concern, and the adsorption kinetics of those pollutants.

2. Importance of Filter Face Area:

The filter face area, or the surface area of the filter that comes into direct contact with the air, plays a vital role in the design of activated carbon air filtration systems. Here's why the filter face area is important:

   - Airflow Capacity: A larger filter face area allows for reduced face velocity increasing dwelling of airborne hazard longer across the media. This is particularly crucial in applications with high flowrate ventilation requirements or areas with elevated airborne hazard levels. It ensures that the system always maintain the desired or the highest of residence time for effective removal.

   - Pressure Drop: The filter face area influences the pressure drop across the filter. A larger filter face area can distribute the air velocity more evenly, increase dwelling time across the media, reducing the pressure drop and minimizing the energy consumption of the system. It also helps prevent excessive pressure drop, which can negatively impact the overall performance of the filtration system. A fan which operates 365 days a year needs to be running with the lowest possible amp draw to be energy efficient.

   - Residence Time: The filter face area directly affects the residence time by determining the contact area between the air and the activated carbon. A larger filter face area provides more surface area for adsorption, resulting in a longer residence time. This extended contact time enhances the adsorption efficiency and improves the overall effectiveness of pollutant removal. The residence time could vary from 0.03s to >0.3s subjective to the loading capacity which needs to be determined prior to the sizing of the air cleaning device.

3. Significance of Thickness:

The thickness of the activated carbon filter bed or media is another critical parameter in the design of activated carbon air filtration systems. Here's why thickness is important:

   - Adsorption Capacity: The thickness of the activated carbon media directly influences the adsorption capacity. A thicker carbon bed allows for a higher amount of activated carbon, providing a larger adsorption surface area. This increases the total capacity for trapping and removing pollutants from the air. It ensures that the system can effectively handle a higher concentration of pollutants or a longer duration of exposure.

Residence Time: The thickness of the carbon bed plays a significant role in determining the residence time. A thicker bed provides a longer path for the air to pass through the activated carbon, increasing the contact time and enhancing the adsorption efficiency. It allows for a greater opportunity for pollutants to interact with the carbon, resulting in improved removal performance.

   - System Constraints: While maximizing the adsorption capacity is important, it is also crucial to consider the available space within the filtration system. The thickness of the activated carbon filter should be designed to fit within the system constraints while still providing an adequate surface area for effective pollutant removal. This is down via re-simulating several design options based on space available. The face area and the depth needs to be manipulated to meet the much needed residence time to adhere. The residence time will need to be the constant based on loading and not to be made variable to allow as solution for space constraints.

By carefully considering the filter face area and thickness, designers can optimize the airflow capacity, pressure drop, residence time, and adsorption capacity of the activated carbon air filtration system. Finding the right balance between these parameters is crucial to achieving efficient and effective pollutant removal while meeting the specific requirements of the application.

Conclusion :

In the design of activated carbon air filtration systems, residence time, filter face area, and thickness are crucial factors to consider. The filter face area influences the airflow capacity, pressure drop, and residence time, ensuring efficient pollutant removal. The thickness of the activated carbon media directly impacts the adsorption capacity and residence time, optimizing the system's performance. By understanding and carefully defining these parameters during the design process, we can create effective activated carbon air filtration systems that emits cleaner and environment friendly air in various applications.