Relative Humidity Control • DEC.RHC™

Relative Humidity Control
DEC.RHC™

The efficiency of activated carbon in adsorbing Volatile Organic Compounds (VOCs) is a cornerstone of industrial gas phase solvent recovery plants. However, the presence of humidity in the Solvent Laden Air (SLA) presents a significant challenge, often diminishing the adsorbent's capacity. The intricate relationship between humidity and the adsorption of common industrial solvents [e.g. Ethyl Acetate, Ethanol, Isopropanol, and other fast-evaporating volatile solvents], on activated carbon requires the adoption of sophisticated and efficient adsorption algorithm: the DEC.RHC™ • Relative Humidity Control system, an integral part of DEC.SRU™ • Solvent Recovery Units.

Activated Carbon's vast, porous surface area provides a multitude of sites for VOC molecules to adhere to through physical adsorption, a process driven by van der Waals forces. However, in industrial air streams, these sites are also attractive to water molecules (humidity), leading to a competitive adsorption scenario that can significantly hinder VOC capture.

DEC.RHC™ • Relative Humidity Control is a sophisticated control strategy integrated into our state-of-the-art DEC.SRU™ • Solvent Recovery Units. This algorithm, powered by the DEC.AIP™ • Artificial Intelligence Platform, is transforming traditional gas phase activated carbon solvent recovery by dynamically optimizing processes in real-time, leading to significant cost savings, reduced emissions, and enhanced operational reliability.

The integration of AI/ML through the DEC.AIP™ platform enables the DEC.RHC™ to perform its two primary functions: prediction and dynamic adjustment. By anticipating changes in the process stream, the algorithm can proactively modify DEC.SRU™ • solvent recovery parameters, rather than reactively responding to suboptimal conditions.

DEC.RHC™ • adsorption sites, affinity, polarity

The competition between VOCs and water is fundamentally a battle of molecular affinities and polarities. Water, a highly polar molecule, readily forms strong hydrogen bonds with the functional groups often present on the surface of activated carbon. This strong affinity allows water molecules to occupy and block adsorption sites that would otherwise be available to VOCs. The general trend observed is that the more polar the VOC, the more susceptible it is to the negative impacts of humidity due to the similar nature of the intermolecular forces at play with water.

Adsorption isotherms, such as the Langmuir or Freundlich models, graphically represent the relationship between the concentration of a substance and the amount adsorbed on a surface at a constant temperature. In the presence of humidity, the shape of the VOC adsorption isotherm changes, reflecting a lower adsorption capacity at any given partial pressure of the VOC. The isotherm for water itself on activated carbon is typically Type V, indicating weak initial interactions followed by multilayer formation and capillary condensation at higher relative humidities. This surface condensed water can further block the microporous structure of the activated carbon, rendering a significant portion of the adsorption sites inaccessible to larger VOC molecules.

Recognizing the critical impact of humidity on SRU performance, DEC has developed a sophisticated, AI-driven engineered solution that proactively manages moisture to optimize VOC adsorption. This system integrates the DEC.RHC™ • Relative Humidity Control module with the powerful resources granted by the DEC.AIP™ • Artificial Intelligence Platform.

The DEC.RHC™ module is a key component of DEC.SRU™ • Solvent Recovery Units. Its primary function is to continuously monitor and control the relative humidity of the solvent-laden air (SLA) stream before it enters the activated carbon beds. By varying the relative humidity the SLA inlet stream, the DEC.RHC™ system effectively lessens the competitive load on the activated carbon, thereby preserving its adsorption capacity for the target VOCs. This is achieved by varying the adsorption temperature profile: by strategically adjusting the temperature of the incoming air, we modify its relative humidity, creating a more favorable environment for VOC adsorption.

DEC.RHC™ • an innovative approach

The true innovation lies in the integration of the DEC.RHC™ with the DEC.AIP™ platform. This AI-engineered system acts as the central nervous system of the SRU, leveraging machine learning algorithms to achieve a level of process optimization previously unattainable.

The DEC.AIP™ platform continuously analyzes a multitude of data streams from the DEC.SRU™ • solvent recovery Unit, including:

RH humidity data: a dew-point transmitter is continuously monitoring humidity in the SLA;

VOC concentration data: the total concentration of Volatile Organic Compounds (VOCs) in the incoming solvent laden air stream is a primary determinant of the required adsorption capacity. Interfaced with the DEC.EMS™ module, the system provides a continuous, real-time measurement of the total VOC load;

VOC composition data: the specific mix of solvents being treated has a profound impact on the required adsorption parameters. The DEC.GCX™ module automatically samples and analyzes the process stream to determine its precise chemical composition;

SLA temperature data: the temperature at which the carbon beds are adsorbing is a critical factor.

This comprehensive data is fed into the DEC.PDA™ • Predictive Dynamic Algorithm, an additional core component of the DEC.AIP™ • Artificial Intelligence Platform platform.

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DEC.RHC™ • benefits

The implementation of the DEC.RHC™ offers a multitude of advantages for facilities operating Solvent Recovery Units, focusing on process efficiency and performance:

Enhanced VOC adsorption capacity: by actively varying the relative humidity of the incoming SLA (Solvent Laden Air), the system minimizes water molecule competition, allowing the activated carbon to adsorb significantly more VOCs;

Optimized adsorption and regeneration cycles: by dynamically adjusting adsorption and desorption cycles based on real-time VOC load and humidity data. This prevents both premature regeneration and costly VOC breakthrough;

consistent performance: the system maintains high efficiency regardless of fluctuating ambient or seasonal weather conditions or process variations that can alter air stream humidity.

Furthermore DEC.RHC™ delivers consequent economic and financial advantages:

Significant Energy Savings: the algorithm calculates the precise amount of energy needed for regeneration, avoiding the waste associated with fixed-cycle, high-temperature regeneration and/or low-temperature condensation. This directly lowers thermal energy and electricity consumption;

Reduced Operational Costs (OPEX): the combined savings from lower energy use, extended carbon life, and maximized solvent recovery lead to a substantial reduction in overall operating expenditures;

Maximized Solvent Recovery: by improving adsorption efficiency, more solvent is captured and recovered for reuse, further increasing DEC.SRU™ • solvent recovery overall efficiency.

DEC.RHC™ • a paradigm shift

The influence of humidity on the activated carbon adsorption of VOCs is a significant and complex challenge. The competition for adsorption sites, governed by principles of affinity and polarity, can severely compromise the efficiency of solvent recovery systems.

DEC.RHC™ • Relative Humidity Control module with the DEC.AIP™ • Artificial Intelligence Platform represents a groundbreaking approach to mitigating this issue. By moving from a passive to a predictive and dynamic mode of operation, this technology not only enhances the adsorption capacity of activated carbon but also significantly reduces energy consumption and improves overall system reliability. The synergy between precise humidity control and intelligent, data-driven optimization paves the way for a more sustainable and economically viable future for industrial solvent recovery.

Contact DEC!

For more information on DEC's VOC sustainable emission control solutions, powered by DEC.RHC™ • Relative Humidity Control, please contact DEC.