Formatted Title
Assessing the Energy Consumption of In Situ Thermal Desorption for Soil Remediation
Background/Objectives
The energy consumption of in situ thermal desorption has raised concerns, with variability stemming from factors like application method, contaminant type, moisture content, and energy source. Over the last 30 years, the overall energy efficiency of ISTD has increased substantially to reach less than 200 KWh/ton of soil, which is comparable to dig and haul options without any soil treatment. This study seeks to comprehensively assess these factors to understand what drives energy consumption and how it can be optimized by design. Real-world projects, like ENI's Gela (Italy) refinery cleanup, where ISTD was applied to clean up more than 100,000 m³ of heavily contaminated soil provide valuable reference points for this assessment.
Approach/Activities
The research employs a methodology utilizing a proprietary UDF adaptation of Ansys-Fluent© modeling on porous multi-phase media. It conducts a detailed simulation of Thermal Desorption's energy consumption, focusing on primary parameters including energy density, type of heating, and energy source. The secondary parameter, heating time, is considered contingent on energy density and power input. Modeling results are then compared to site data to further validate the model and run the different scenarios for understanding the design parameters influencing total energy consumption.
Results/Lessons Learned
Comparative analysis against conventional remediation methods, such as excavation and disposal (typically requiring up to 200 kWh/ton of soil), reveals that optimized energy consumption through careful parameter selection positions ISTD as a more energy-efficient and environmentally responsible alternative. The insights gained from our modeling and real-world experiences contribute significantly to our understanding of the factors influencing energy consumption.
The analysis highlights several key parameters crucial for optimizing energy consumption in ISTD. One of the most critical factors is energy density, representing the interdistance between heating elements. It is evident that higher energy density leads to lower energy consumption. However, it is important to note that there are limitations on energy density, often dictated by the available power supply, particularly when grid electricity serves as the energy source. In such cases, the available power becomes a decisive parameter, and careful consideration is needed to balance energy density with available resources.
Another important parameter is the geometry of the target treatment zone. The surface/volume ratio is directly related to total energy consumption. Shallow, extended treatment areas are suboptimal for ISTD, as they lead to a high thermal loss ratio over the duration of the treatment. Therefore, optimizing the treatment area's geometry is essential for energy efficiency.
Furthermore, ISTD offers the potential for a significantly reduced carbon footprint compared to several alternative soil remediation methods. This reduced environmental impact is primarily due to the efficient energy consumption and the avoidance of extensive excavation and transportation activities associated with traditional soil disposal. By employing ISTD and optimizing its parameters, we can contribute to a more sustainable approach to soil remediation while simultaneously lowering the carbon footprint associated with these critical environmental projects. These findings underline the importance of ISTD in the context of sustainable remediation practices and its potential as a significant contributor to reducing the environmental impact of soil cleanup efforts.
This research contributes to the advancement of ISTD as an environmentally sustainable solution, paving the way for broader adoption all over the world.