Thermal Remediation Research Articles

Ultra-Slippery Hydrophilic Surfaces by Hybrid Monolayers.

Slippery solid surfaces with low droplet contact angle hysteresis (CAH) are crucial for applications in thermal management, energy harvesting, and environmental remediation. Traditionally, reducing CAH has been achieved by enhancing surface homogeneity. This work challenges this conventional approach by developing slippery yet hydrophilic surfaces through hybrid monolayers composed of hydrophilic polyethylene glycol (PEG)-silane and hydrophobic alkyl-silane molecules. These hybrid surfaces exhibited exceptionally low CAH (<2°), outperforming well-established homogeneous slippery surfaces. Molecular structural analyses suggested that the remarkable slipperiness is due to a unique spatially staggered molecular configuration, where longer PEG chains shield shorter alkyl chains, thus creating additional free volume while ensuring surface coverage. This was supported by the observation of decreased CAH with increasing temperature, highlighting the role of grafted chain mobility in enhancing slipperiness by self-smoothing and fluid-like behaviors. Furthermore, condensation experiments demonstrated the exceptional performance of the hydrophilic slippery surfaces in dew harvesting due to superior condensation nucleation, droplet coalescence, and self-sweeping efficiency. These findings offer a novel paradigm for designing advanced slippery surfaces and provide valuable insights into the molecular mechanisms governing dynamic wetting.

Numerical modeling and parametric analysis of temperature distribution in soil based on water content variation under radio frequency heating for in-situ thermal remediation

Radio frequency heating (RFH) is recognized as an efficient and economical method for volatilizing organic pollutants from contaminated soils. Although some numerical simulations have been conducted to predict temperature changes during RFH, models that account for effects of water content (WC) variation on dielectric properties and temperature evolution in soil were rarely reported. To address this, a three-dimensional numerical model integrating electromagnetic-thermal conversion, heat transfer, and mass transfer was developed with coupling dynamic changes in WC and corresponding impacts on soil properties. The effects of soil types and RFH engineering parameters on temperature evolution and energy utilization were evaluated. The model's temperature prediction was validated using experimental data, indicating that temperature decreases outward from hot electrode, with high-temperature regions forming at the top and bottom regions near electrode. Water evaporation in soil causes a temperature plateau with >76.25 % of energy utilized for heating and evaporating water during 60-d RFH. Moreover, higher soil WC could increase electromagnetic-thermal conversion capability, counteracting the negative impact of increased specific heat capacity on temperature rise. Thermophysical properties of soil are crucial in RFH: sand, with lower specific heat capacity and higher thermal conductivity, results in faster heating rates. While, clay, with higher density and specific heat capacity, results in lower heating rates but greater energy utilization efficiency. Low-power RHF and wider well spacing improve the uniformity of temperature distribution but require more time to reach target temperatures. Moreover, input power influences the magnitude and timing of optimal energy utilization efficiency, while well spacing primarily affects timing. The models developed in this study provide essential guidance for RFH-based soil remediation projects.

Effects of simulated low-temperature thermal remediation on the microbial community of a tropical creosote contaminated soil.

In the search for more sustainable remediation strategies for PAH-contaminated soils, an integrated application of thermal remediation and bioremediation (TEB) may allow the use of less impacting temperatures by associating heating to biological degradation. However, the influence of heating on soil microbiota remains poorly understood, especially in soils from tropical regions. This work investigated the effects of low-temperature heating on creosote-contaminated soil bacteria. We used culture-dependent and 16S rRNA sequencing methods to compare the microbial community of soil samples heated to 60 and 100 oC for 1h in microcosms. Heating to 60°C reduced the density of cultivable heterotrophic bacteria compared to control soil (p < 0.05), and exposure to 100°C inactivated the viable heterotrophic community. Burkholderia-Caballeronia-Paraburkholderia (BCP) group and Sphingobium were the predominant genera. Temperature and incubation time affected the Bray-Curtis dissimilarity index (p < 0.05). At 60°C and 30 days incubation, the relative abundance of Sphingobium decreased and BCP increased dominance. The network of heated soil after 30 days of incubation showed fewer nodes and edges but maintained its density and complexity. Both main genera are associated with PAH degradation, suggesting functional redundancy and a likely potential of soil microbiota to maintain biodegradation ability after exposure to higher temperatures. We concluded that TEB can be considered as a potential strategy to bioremediate creosote-contaminated soils, allowing biodegradation in temperature ranges where thermal remediation does not completely remove contaminants. However, we recommend further research to determine degradation rates with this technology.

Synergistic approach of GCW-ISTR for enhanced remediation of semi-volatile organic contaminants in groundwater: Modeling and experimental validation

The poor remediation performance of groundwater circulation well (GCW) on semi-volatile organic contaminants (such as aniline) has severely limited its practical application. To address the challenges posed by the low volatility and solubility of these contaminants, an innovative integration of GCW with in-situ thermal remediation (ISTR) was proposed to create a thermal enhanced circulation well (GCW-ISTR) in this study. Laboratory experiments and model simulations were performed to evaluate the heat transfer and enhanced remediation effect by GCW-ISTR. Results demonstrate that the heat transfer process is controlled by the water circulation around GCW-ISTR and is influenced by factors such as aeration flow rate, groundwater velocity and aquifer permeability. Heating area is directly proportional to the seepage velocity of groundwater which can be analyzed by multiplying the water head difference between the upper and lower screens with the aquifer permeability. Therefore, the heat transfer model, based on Darcy's seepage theory and the energy conservation equation, effectively simulates the heat transfer with an error margin of less than 10%. Compared to individual GCW, GCW-ISTR exhibits a 25.8% improvement in aniline remediation efficiency, resulting in a decrease in the average concentration from 97.95 mg/L to 0.168 mg/L within 48 h, effectively mitigating the occurrence of tailing phenomena. This study provides a feasible method of enhancing the remediation of GCW on semi-volatile contaminants and is anticipated to broaden the applicability of GCW in site application.

Macroscopic and molecular scale assessment of thermal effects on soil-water interactions of unsaturated diesel-contaminated soils

The soil-water interactions of unsaturated diesel-contaminated soil are crucial for assessing pollution transport during thermal remediation. This paper aims to improve our understanding of this issue by measuring the matric suction of unsaturated contaminated kaolin and carrying out molecular dynamics simulations under thermal conditions. Results show that the increase in pollutant concentration could reduce the water retention capacity of diesel-contaminated kaolin due to changes in electrochemical properties and pore characteristics of samples, as well as a decrease in interfacial tension. On the other hand, pollutants formed a protective film on the kaolinite surface to act as a liquid bridge and prevent water loss at higher temperatures, as confirmed by Fourier transform infrared spectroscopy. With rising temperatures (50–60 °C), kaolin matric suction generally decreased with higher pollutant concentrations, but this trend was not very evident at lower pollution concentrations (0–10,000 mg/kg). In addition, molecular dynamics simulations were used to demonstrate the validity of these findings. The presence of pollutants might strengthen the interaction energy between kaolinite and water (for example, increasing from 276.52 kcal/mol (25 °C) and 267.95 kcal/mol (40 °C) at 8000 mg/kg to 296.54 kcal/mol (25 °C) and 292.46 kcal/mol (40 °C) at 10,000 mg/kg), thereby enhancing the water retention capacity of kaolin. In short, the study revealed that the coating of pollutants on kaolinite could act as a protective film, which binds water molecules through van der Waals and electric field forces and thereby reduces the sensitivity of water retention capacity to temperature.

Sodium alginate grafted phase-changing electrolyte for energy-efficient thermochromic and electrochromic synergy with uniquely tunable optical states and simultaneous Vis-NIR modulation

Conventional smart windows, limited by their single-stimulus response, often fail to meet diverse practical needs, and cannot achieve zero transmission across the Visible-NIR spectrum. Integrating thermochromic, electrochromic, and synergetic-responsiveness into a single device is both challenging and essential for effective light modulation and energy efficiency. Herein, we present a novel green phase-changing electrolyte integrated with a versatile chromogen, to create an “all-in-one” smart window. This device autonomously switches functions and can also simultaneously respond to dual-stimuli, achieving an absolute private state. The device’s tunable performance in optical contrast, switching kinetics, coloration efficiency, and cyclic stability, influenced by lattice water concentration is also meticulously assessed. Our comprehensive study highlights the device’s robust multifunctional properties, including thermal insulation, lifestyle interventions, and environmental remediation. These features make the smart window a highly energy-efficient solution with exceptional climate adaptability, such as shutting down light transmission with environmentally-benign operations and on-demand color changes. This innovative approach transforms smart windows from mere energy savers to versatile, energy-efficient systems for modern buildings. By bridging the gap between advanced materials and practical applications, our “all-in-one” smart window represents a significant advancement, paving the way for broader adoption in various environmental and energy-saving contexts.

Long term impact of electrical resistance heating on soil bacterial community based on a field test

Thermal remediation is an effective technology for organic contaminant remediation. However, the application of thermal remediation may have negative effects on soil properties and ecological functions, which requires further investigation. Based on a pilot test of electrical resistance heating remediation (ERH), soil samples were collected at different locations after heating for 116 days. Most soil physicochemical properties were less affected by the heating temperature difference. Application of high temperature increased microbial abundance but inhibited alpha diversity of the bacterial community. More significant changes in microbial communities were observed at temperatures above 60 °C. The genera mainly affected by heating temperature included Flavobacteria, Brockia, and S085, while the increase in temperature also inhibited the abundance of nitrochlorobenzene functional genes. At 140 days after the end of the pilot test, the bacterial community affected by thermal remediation could recover effectively, and the recovery of the bacterial community was not affected by temperature difference during the heating period. This study provides valuable field evidence of the long term impact of soil ERH treatment on soil properties and microbial communities, and provides further references for optimization of remediation performance with coupled technologies.

Feasibility of microwave remediation of simulative crude oil-contaminated soil assisted by bluecoke-based modifiers

Microwave (MW) remediation of organics-contaminated soil technology offers the advantages of high efficiency and minimal damage, representing a new approach of soil thermal remediation. However, soil, being a weak MW-absorbing medium, struggles to convert MW energy into thermal energy, thus failing to attain the necessary temperature for thermal remediation. This paper prepared two new bluecoke (BC)-based modifiers (KHCO3@BC and KHCO3/MnO2@BC) to address temperature problem of MW remediation, as well as enhance soil quality. Their composition, structure and electromagnetic properties were analyzed to investigate their role in assisting with the MW remediation of an artificially crude oil-contaminated soil were investigated. Additionally, the industrial feasibility of MW remediation was addressed for the first time. The results showed that the KHCO3 and MnO2 particles in the two modifiers were covered on the BC surface and exhibited local agglomeration. Their carbon crystalline grain size increased, and the electromagnetic properties were weaker than those of the BC. Following 10 min of MW remediation assisted by KBC or KMnBC, the remediation temperatures exceeded 300 °C, with the removal rates of PHs reaching 76.16% and 88.31%, respectively. The organic matter content, soil potassium and mechanical fraction of the remediated soil were improved, but soil acidification still needed to be further addressed. The industrial application analysis indicated that the technical process and techno-economics of MW remediation of crude oil-contaminated soil were feasible, suggesting significant potential for the large-scale industrial application.

Influence of Thermal Desorption Technology on Removal Effects and Properties of PAH-Contaminated Soil Based on Engineering Experiments

Polycyclic aromatic hydrocarbon (PAH) contamination in soil poses a serious threat to ecological safety, human life, and health. Thermal desorption is commonly used to remediate PAH-contaminated soil. Current thermal desorption research primarily focuses on parameters for engineering designs through in-house simulations. In this study, based on a PAH-contaminated site thermal desorption remediation project, the removal efficiency of PAHs in soil (S1, S2) after disposal at different heating temperatures (400, 450, 500, 550 °C) and different residence times (20, 25 min) was investigated, and changes in soil properties before and after disposal were analyzed. The removal rate of 16 PAHs from soil at two concentrations reached 100% after 20 min at 500 °C and 550 °C, respectively. The three-phase structural distances of S1 and S2 soils, respectively, increased by 1.65 and 2.99 times after disposal, sand content increased by 3.20% and 8.27%, water-stable macroaggregates decreased by 8.14% and 2.06%, organic carbon content decreased by 7.27% and 27.05%, heavy fraction organic carbon increased by 33.68% and 5.12%, pH decreased from 10.00 and 10.35 to 8.81 and 8.69, and cation exchange decreased by 13.79% and 26.65%. Soil nutrient content such as TP, AP, TK, and AK increased after thermal desorption, and TN content decreased; approximately 1.0 mg/kg of NO3−-N remained. Our results are expected to support the design of programs for soil reuse after disposal.

Evolution of soil DOM during thermal remediation below 100 °C: concentration, spectral characteristics and complexation ability

Evolution of soil DOM during thermal remediation below 100 °C: concentration, spectral characteristics and complexation ability

Remediation effectiveness of aging diesel-contaminated soil using thermochemical treatment: Soil microstructure transformation and reusability

This study investigated the microstructure transformation observed in an aging diesel-contaminated soil after thermochemical treatment (DT150°C + PS) to explore its impact on engineering reusability. Three thermal remediation procedures (i.e., DT150°C, DT350°C, and DT550°C) were selected as the control group. The results show that: (a) Pyrolytic carbon was produced in the DT350°C and DT550°C, while none was produced in DT150°C and DT150°C + PS; (b) Iron-based minerals and organic matter in DT150°C + PS, DT350°C, and DT550°C were combusted and decomposed to release the Fe(II) substances; under stronger oxidation environments, Fe(II) substances would further transform into more stable Fe(Ⅲ) substances; and (c) Halloysites and illites were formed in DT350°C, palygorskites and cordierites were formed in DT550°C, and oxidation in DT150°C + PS produced the sulfate minerals. The formed sulfate minerals in the DT150°C + PS sample filled pores and provided the skeleton strength, resulting in high unconfined compressive strength and poor permeability. Using a self-developed assessment model, only the DT150°C + PS sample showed an improvement (calculated as 2.96 × 10−5) in engineering performance and other methods led to the deterioration of soil mechanical properties. Thermochemical treatment is more suitable for engineering reuse, and this study can provide a theoretical basis for evaluating the greener reusability of contaminated soil after thermal or thermochemical remediation.

Machine learning models for predicting thermal desorption remediation of soils contaminated with polycyclic aromatic hydrocarbons

Among various remediation methods for organic-contaminated soil, thermal desorption stands out due to its broad treatment range and high efficiency. Nonetheless, analyzing the contribution of factors in complex soil remediation systems and deducing the results under multiple conditions are challenging, given the complexities arising from diverse soil properties, heating conditions, and contaminant types. Machine learning (ML) methods serve as a powerful analytical tool that can extract meaningful insights from datasets and reveal hidden relationships. Due to insufficient research on soil thermal desorption for remediation of organic sites using ML methods, this study took organic pollutants represented by polycyclic aromatic hydrocarbons (PAHs) as the research object and sorted out a comprehensive data set containing >700 data points on the thermal desorption of soil contaminated with PAHs from published literature. Several ML models, including artificial neural network (ANN), random forest (RF), and support vector regression (SVR), were applied. Model optimization and regression fitting centered on soil remediation efficiency, with feature importance analysis conducted on soil and contaminant properties and heating conditions. This approach enabled the quantitative evaluation and prediction of thermal desorption remediation effects on soil contaminated with PAHs. Results indicated that ML models, particularly the RF model (R2 = 0.90), exhibited high accuracy in predicting remediation efficiency. The hierarchical significance of the features within the RF model is elucidated as follows: heating conditions account for 52 %, contaminant properties for 28 %, and soil properties for 20 % of the model's predictive power. A comprehensive analysis suggests that practical applications should emphasize heating conditions for efficient soil remediation. This research provides a crucial reference for optimizing and implementing thermal desorption in the quest for more efficient and reliable soil remediation strategies.

Study on numerical model of thermal conductivity of non-aqueous phase liquids contaminated soils based on mesoscale

The thermal conductivity of soils is an important factor affecting the efficiency of in-situ thermal desorption remediation of contaminated sites. Restrict the selection of in-situ thermal desorption repair methods and heating parameters. The existence of non-aqueous phase liquids (NAPLs) pollutants affects the original thermal conductivity of the soils. To obtain an accurate and efficient method to study the thermal conductivity of NAPLs-contaminated soils. In the paper, the NAPLs-contaminated soils models are established by the four-parameter random generation method, and the thermal conductivity is calculated based on the Lattice Boltzmann Method (LBM). Explore the impact of NAPLs-contaminated soil model on its thermal conductivity calculation results, and propose an optimized NAPLs-contaminated soil model. Finally, the numerical simulation results are compared with the experimental results, and a large number of calculations and statistical analyses are carried out on the thermal conductivity. The results indicate that it is feasible to combine the four-parameter random generation method with LBM to study the thermal conductivity of NAPLs-contaminated soils. The calculation accuracy of the two-dimensional model of NAPLs-contaminated soils is lower than that of the three-dimensional model, while the calculation of the three-dimensional model is too time-consuming. The optimized NAPLs-contaminated soils three-dimensional model has the characteristics of high computational accuracy and efficiency. Saturation and Nz have a great influence on the calculation time of thermal conductivity. The thermal conductivity of the two-dimensional model is more sensitive to anisotropy. With the decrease of model anisotropy, the increase of saturation, and the decrease of porosity, the calculation accuracy of thermal conductivity of two-dimensional and three-dimensional models is similar, otherwise, the calculation accuracy of two-dimensional model is lower. The influence of porosity and NAPLs content on thermal conductivity should be paid special attention to when in-situ thermal desorption.

Understanding of Co-boiling between Organic Contaminants and Water during Thermal Remediation: Effects of Nonequilibrium Heat and Mass Transport.

In situ thermal desorption (ISTD) provides an efficient solution to remediation of soil and groundwater contaminated with nonaqueous phase liquids (NAPLs). Establishing a relationship between the subsurface temperature rise and NAPL removal is significant to reduce energy consumption of ISTD. However, the co-boiling phenomenon between NAPL and water poses a great challenge in developing this relationship due to the nonequilibrium heat and mass transport effects. We performed a systematic experimental investigation into the local temperature rise patterns at different distances from a NAPL pool and under different degrees of superheat by selecting four representative NAPLs (i.e., trichloroethylene, tetrachlorethylene, n-hexane, and n-octane) according to their density and boiling point relative to water. The patterns of temperature rise indicated that the underground temperature field can be divided into three zones: the zone of local thermal equilibrium, the nonequilibrium zone affected by co-boiling, and the zone unaffected by co-boiling. We developed a pattern-recognition-based approach, which considers the effects of local heat and mass transport to establish a qualitative correlation between the temperature rise and NAPL removal. Our results give deeper insights into the understanding of subsurface temperatures in ISTD practice, which can serve as the guideline for more accurate and sustainable remediation.

Impact of organic matter on transformation during thermal remediation of pyrene-contaminated substrates

Thermal remediation (TR) is a broadly applicable technology that is effective at removing volatile and semi-volatile contaminants from soil. However, TR can be costly and inefficient in practice, with underlying removal and transformation mechanisms poorly understood. To better understand the role organic matter plays in removal, a series of experiments was performed with a humic substance, humic modified silica, and a natural soil in the presence of pyrene from 100 to 500 °C and compared to prior experiments using pure minerals. Detection of by-products confirmed that pyrene was removed by transformation in addition to volatilization. Oxidation via hydroxyl radical formation and reductive hydrogenation were both indicated as possible reaction mechanisms promoted by organic matter. Because the presence of bulk water did not impact the extent of pyrene degradation or transformation, it is hypothesized that hydroxyl radicals were produced from soil organic matter functional groups, such as carboxyl and phenol groups, and possibly bound water at elevated temperatures in dry experiments. Additionally, the average oxidation state of carbon in detected by-products increased with temperature in experiments with humic modified silica and soil but not humic substance alone, though the extent of degradation did not significantly change. This shift in oxidation state may indicate that attachment of organic matter to another surface may increase interaction between reactive species. The results of this study show that contaminant transformation in soils during TR significantly contributes to removal, even at temperatures lower than those used in traditional treatment. This information will help to guide the design and operation of TR systems, potentially reducing energy requirements and highlighting the necessity of testing for transformation by-products.

New insights into thermal desorption remediation of pyrene-contaminated soil based on an optimized numerical model

Thermal desorption (TD) is known as an effective technique to remediate PAHs-contaminated sites. However, effectively removing PAHs using TD while saving time, and energy, and minimizing soil damage remains a challenge. In this study, we examined the combined effects of various factors on the removal efficiency of pyrene (PYR) by TD and developed an optimal numerical model based on conducting a series of soil experiments. The results showed that temperature (T) and time (t) promoted the desorption of PYR, while water (Sw) and organic matter (fom) were just the opposite. Besides, water and organic matter had a synergistic effect proportionally. It was found that adjusting the soil-water ratio (which can be controlled by organic matter) maximized the desorption rate of PYR. An ideal Sw/fom 1.56 and a minimized recommended temperature (173 °C) were proposed based on the model. Finally, the efficacy of the optimized scheme was validated in real-world site soil. These findings not only mechanistically revealed the desorption behavior of PYR under the influence of various factors, but also provided an optimized scheme for efficiently removing PAHs using TD, thereby accelerating the remediation process and reducing energy consumption. The modeling ideas and conclusions obtained may be applicable to other PAHs, guiding the effective remediation of PAHs-polluted sites.

Development of Predictive Model for Wax Formation in Deep-water Pipeline Using Machine learning

Wax deposition in deep sea pipelines can affect oil and gas production. It happens when the pipeline temperature drops below the wax appearance temperature, causing the wax to solidify and stick to the pipeline walls. This paper discusses the limitations of current models in predicting wax deposition in pipelines and proposes the development of more complex, intelligent models that are accurate, resilient, and adaptable to novel input-output scenarios. It also highlights various methods for preventing wax deposition, including the use of chemical inhibitors and thermal remediation techniques. The paper aims to develop a neural network modeling approach for predicting wax deposition potential in producing reservoirs to prevent accumulation before removal. The parameters that were used are wax molecule concentration gradient at pipe wall, temperature gradient at pipe wall, reported wax deposition rate, the pipe wall shear stress, and crude oil viscosity. The radial basis function neural network (RBFNN), is based on the machine learning technique. RBFNN is a good choice for building a predictive wax deposition rate model because it is highly accurate, robust to noise and outliers, computationally efficient, can model complex nonlinear relationships, suitable for real-time applications and requires less training data. The RBF neural network is constructed using MATLAB. The outcomes and experimental data are consistent with a 1.5 percent relative inaccuracy when compared to prior studies. The R^2 value was 0.9906, R value was 0.9953 and the RMSE value was 0.8598. The RBF neural network-based approach for predicting wax deposition rate was successful.

Best management practices for minimizing undesired effects of thermal remediation and soil washing on soil properties. A review.

The use of remediated soils as end-of-life materials raises some challenges including policy and regulation, permits and specifications, technological limitations, knowledge and information, costs, as well as quality and performance associated with using them. Therefore, a set of procedures must be followed to preserve the quality and fundamental properties of soil during a remediation process. This study presented a comprehensive review regarding the fundamental impacts of thermal desorption (TD) and soil washing (SW) on soil characteristics. The effects of main operating parameters of TD and SW on the physical, chemical, and biological properties of soil were systematically reviewed. In TD, temperature has a more remarkable effect on physic-chemical and biological characteristics of soil than heating time. Therefore, decrease in temperature within a suitable range prevents unreversible changes on soil properties. In SW, more attention should be paid to extraction process of contaminants from soil particles. Using the right dosage and type of chelating agents, surfactants, solvents, and other additives can help to avoid problems with recovery or treatment using conventional methods. In addition, this review introduced a framework for implementing sustainable remediation approaches based on a holistic approach to best management practices (BMPs), which, besides reducing the risks associated with different pollutants, might provide new horizons for decreasing the unfavourable impacts of TD and SW on soil.

Insight into heat dissipation in fractured rock influenced by groundwater influx and heat source configurations using numerical analysis

The characterization and evaluation of heat dissipation effects in fractured rock is becoming a priority topic with respect to the potential application of low-temperature thermal remediation in these settings. A three-dimensional numerical model was utilized to investigate heat dissipation-related thermo-hydrological processes in an upper fractured rock layer and a lower impermeable bedrock layer. To identify the factors controlling spatial temperature variances in the fractured rock layer accounting for a scaled heat source and variable groundwater flow, global sensitivity analyses were conducted on the variables using three categories: heat source, groundwater flow, and rock properties. A discrete Latin-hypercube-one-at-a-time method was used to conduct the analyses. A heat dissipation coefficient was proposed to evaluate the correlation between heat dissipation effects and transmissivity based on a case study using the hydrogeological setting of a well-characterized Canadian field site. The results show a significance ranking of three sets of variables controlling heat dissipation processes in both the central and the bottom areas of the heating zone: specifically, heat source > groundwater > rock. The groundwater influx and heat conduction in the rock matrix are key factors determining heat dissipation at the upstream and bottom areas of the heating zone, respectively. The heat dissipation coefficient is closely associated with the transmissivity of the fractured rock in a monotonic relationship. A significant growth rate of the heat dissipation coefficient appears when the transmissivity is between 1 × 10−6 and 2 × 10−5m2/s. The results suggest that the low-temperature thermal remediation can be a promising technique to adapt the significant heat dissipation in highly weathered fractured rock.

State of the Practice Worldwide: Complex Installation for In Situ Thermal Remediation Beneath an Active Manufacturing Facility

AbstractIn situ thermal remediation (ISTR) was used to treat a vadose‐zone source of trichloroethylene present at depths of 60 to 125 ft. below an occupied building at an active manufacturing facility. ISTR required innovative methods to install 135 steel casings from inside the building that included access limitations, space constraints that required angled borings and pre‐modeling of rig mast positions, control measures to manage exhaust from up to four drill rigs operating simultaneously, adjustments to heater wiring to limit temperatures in shallow soils leading to indoor air heating and potential for vapor intrusion, and ensure proper positioning and trajectory of closely spaced heaters. The installed heater casings were surveyed using a Devi‐Flex™ tool to monitor heater placement in casings that ranged from 87 to 196 ft. at angles between 90° and 30° from horizontal and periodically had to compensate for deflections caused by cobbles and boulders. Additional casings were installed to ensure adequate heater spacings in cases where deviations exceeded design parameters. ISTR was conducted using custom‐built thermal conduction heaters designed to minimize heat output in the shallow vadose zone and inside the building while temperatures in the lower vadose zone were maintained near boiling. Cables, vapor extraction pipes, and exhaust ducts were routed overhead and through the building roof to minimize disturbance to manufacturing operations. To expedite remediation, three groups of heaters and vapor recovery wells were installed and operated in overlapping periods. The major challenges and solutions for ISTR design, construction, and operation are presented. Operations and remedial results are covered in a companion paper.