Pressurized Extraction Research Articles

Ultra-high pressure assisted extraction of water-soluble polysaccharides from Moringa oleifera seed husks and their antioxidant activities

ABSTRACT The process conditions and antioxidant activity of ultra-high pressure assisted extraction of polysaccharides from Moringa oleifera seed husks were studied. Taking the yield of polysaccharides as the index, the effects of degree of crushing, extraction pressure, holding pressure time and material-to-liquid ratio on the yield of polysaccharides from Moringa oleifera seed husks were investigated. The optimal extraction conditions were determined by single-factor test and orthogonal test: a holding time of 10 min, a material-to-liquid ratio of 1:25, an extraction pressure of 350 MPa, and a polysaccharide yield of 0.264%. Its antioxidant activity can be determined by measuring the total antioxidant capacity and their ability to scavenge DPPH and ·OH radicals. The results showed that the IC50 of Moringa oleifera seed husk polysaccharides on DPPH and hydroxyl radicals were 0.0662 g/L and 0.0844 g/L, respectively. The total antioxidant capacity was 0.1826 mm/g (expressed as the equivalent concentration of ferrous sulfate). Compared with hot water extraction methods, ultra-high pressure assisted extraction methods can shorten extraction time, improve extraction efficiency. The water-soluble polysaccharides extracted from Moringa oleifera seed husks by ultra-high pressure assisted extraction technology also have higher antioxidant activity than that by hot water extraction method at the same concentration.

Thermal Properties of Seed Cake Biomasses and Their Valorisation by Torrefaction

Seed cakes, by-products from the cold press extraction of vegetable oils, are valuable animal feed supplements due to their high content of proteins, carbohydrates, and minerals. However, the presence of anti-nutrients, as well as the rancidification and development of aflatoxins, can impede their intended use, requiring alternative treatment and valorisation methods. Thermal treatment as a procedure for the conversion of seed cakes from walnuts, hemp, pumpkin, flax, and sunflower into valuable products or energy has been investigated in this paper. Thermogravimetry shows the particular behaviour of seed cakes, with several degradation stages at around 230–280 and 340–390 °C, before and after the typical degradation of cellulose. These are related to the volatilisation of fatty acids, which are either free or bonded as triglycerides, and with the thermal degradation of proteins. Torrefaction at 250 °C produced ~75–82 wt% solids, with high calorific values of 24–26 kJ/g and an energy yield above 90%. The liquid products have a complex composition, with most parts of the compounds partitioning between the aqueous phase (strongly dominant) and the oily one (present in traces). The structural components of seed cakes (hemicelluloses, cellulose, and lignin) produce acetic acid, hydroxy ketones, furans, and phenols. In addition to these, most compounds are nitrogen-containing aromatic compounds from the degradation of protein components, which are highly present in seed cakes.

Research on Denoising Algorithm of Standpipe Pressure Signal in FCC Device Based on Tortuosity and Denoising Intensity.

The pressure signal of the standpipe in the regeneration device for the catalytic cracking reaction is commonly used as a basis for equipment fault diagnosis. The device operates in environments of high temperature, strong vibration, and high flow rate. The standpipe pressure signal is easily interfered with by noise, making it difficult to extract pressure characteristics. In this study, a signal denoising algorithm based on pressure curve tortuosity and denoising intensity is proposed. A power spectrum threshold vector is utilized to filter the pressure in the circulating standpipe, and the denoising intensity and tortuosity after denoising are calculated. Taking the ratio of noise reduction intensity and tortuosity as the objective function, the noise reduction scheme of the pressure signal at different heights of the standpipe is determined. The denoised pressure signals are reconstructed, and the characteristic pressure signals of the circulating standpipe are extracted. The results indicate that the method suppressed the noise, enhanced the significance of characteristic parameters, and improved the accuracy of the fault diagnosis in the FCC units.

Exploration and multi performance evaluation of process intensification for separation of ethyl tert-butyl ether/ethanol from wastewater

Ethyl tert-butyl ether is a green gasoline additive that enhances fuel efficiency and can play an essential role in improving fuel performance. This study explored the separation of wastewater containing ethyl tert-butyl ether and ethanol by changing the pressure and adding reactions based on extractive distillation, using the synergistic effect of the entrainer, pressure, and chemical reaction. By utilizing coupling technology and process intensification concepts, developed a comprehensive series of intensified processes that have clarified the interaction mechanisms between the extractive distillation process (EDP), pressure swing extractive distillation process (PSEDP), and reactive extractive distillation process (REDP). Studying the separation and purification mechanisms of products and intermediates during the reaction process provides theoretical and practical support for optimizing chemical processes. Comparative analysis showed that the reactive extraction pressure swing distillation process (REPSDP) had preeminent economic and environmental benefits. The total annual cost of PSEDP, REDP, and REPSDP was reduced by 5.88 %, 1.68 %, and 10.08 %, respectively, compared with EDP. The gas emissions of PSEDP, REDP, REPSDP, and REPSDP with heat integration process (HI-REPSDP) are all lower than those of EDP. HI-REPSDP saves 47.59 % of gas emissions compared to EDP, highlighting its environmental benefits. HI-REPSDP has the best energy efficiency, reducing energy consumption by 47.58 % compared to EDP, significantly improving the energy utilization rate. It was found that the introduction of heat integration technology had a significant improvement effect. This research has crucial theoretical and practical value and provides guidance and reference for achieving a clean and efficient production process.

Supercritical carbon dioxide chelation extraction of heavy metal ions from drilling fluid waste: Experiment and simulation

This study evaluates the application of supercritical carbon dioxide chelation extraction technology for treating heavy metal ions (Zn2+ and Cr3+) in drilling fluid waste. Through a combination of experimental and molecular dynamics simulation methods, the influence of extraction parameters (temperature, pressure, duration, and chelating agents) on the extraction efficiency are investigated. Findings show that increased duration and pressure significantly improve extraction efficiency, while temperature has a complex effect, initially increasing efficiency but plateauing and slightly decreasing at higher temperatures. The optimum extraction condition with pressure of 220 bar, temperature 348.15 K and an extraction duration of 70 min using ethylene diamine tetraacetic acid (EDTA) as the chelating agent has been determined. Importantly, molecular simulation analysis revealed that citric acid outperforms EDTA in terms of Zn2+ and Cr3+ aggregation by forming larger aggregates with greater numbers of molecules while reducing overall aggregate count. Furthermore, optimization of extraction pressure in the EDTA system shows potential benefits. These results suggest that supercritical carbon dioxide chelation extraction technology has strong potential for environmentally friendly and reliable waste management in the drilling industry. This study represents a significant step forward in developing sustainable solutions for heavy metal removal from drilling fluid waste.

Acoustic Detection of Pipeline Blockages in Gas Extraction Systems: A Novel Approach

Gas extraction is crucial for coal mine safety, yet pipeline blockages by solid slag and water severely hinder efficiency and pose risks. Traditional detection methods are limited by rapid signal attenuation and noise interference. In this study, an acoustic detection technology is introduced for pipeline blockages, utilizing sensors at potential blockage points to collect sound wave data. Experiments with a scaled pipeline model reveal that slag blockages produce characteristic peaks in the 1200 Hz–2000 Hz range, while water blockages show peaks in the 1 kHz–2 kHz and 3.5 kHz–4.5 kHz bands. The longitudinal blockage intensity and extraction pressure significantly affect the sound pressure levels. A reliable fitting model predicts the blockage intensity based on acoustic signals, achieving high accuracy. This novel method enhances blockage identification, offering a non-invasive, cost-effective solution that improves coal mine safety and efficiency.

Study on the Spontaneous Combustion Law of Coal Body around a Borehole Induced by Pre-extraction of Coalbed Methane.

To address the challenges associated with the high gas content, high pressure, and low permeability coefficient in deep coal seams, strategies such as infilling boreholes and increasing the negative pressure of extraction are commonly implemented to alleviate issues related to coalbed methane extraction. However, long-term mining pressure can lead to the development of cracks in the coal seam near the borehole, thereby creating air leakage channels, which could potentially impact the oxygen supply during the extraction process. This leads to secondary disasters such as the spontaneous combustion of coal and gas explosions, considerably impacting the life and health of underground workers. To solve this issue, a thermal-fluid-solid coupling model for the working surface was constructed based on numerical simulation software, taking into account the multimechanism coupling effect of coal seam gas. The laws of coal oxidation and spontaneous combustion induced by coalbed methane extraction around boreholes were studied. The variation laws of the oxygen concentration, coal temperature, and oxidation heating zone around the borehole under different extraction conditions were simulated and analyzed. The findings demonstrate that the negative extraction pressure enables the gas to penetrate the fracture zone of the borehole, leading to an increase in the oxygen consumption rate and coal temperature around the borehole with an increase in negative extraction pressure. The coal gas leakage surrounding the borehole reduces as the sealing depth increases, and both the heating rate of coal and oxygen volume fraction show a downward trend. The fitting relationship between the negative pressure of drainage, depth of sealing, and temperature change in the coal body surrounding the boreholes was identified. It was determined that the negative pressure of 13 kPa for borehole drainage and a sealing depth >18 m are the optimal extraction parameters. The range of the oxidation zone and the position of the boundary line under this parameter were predicted, and the position function of the dangerous area of oxidation heating was defined. The research results have remarkable implications for the coordinated prevention and control of gas and coal spontaneous combustion in coalbed methane predrainage boreholes, as well as for efficient prevention and control of CO in on-site gas extraction boreholes, thus ensuring efficient and safe gas extraction.

Model test of in-situ remediation for heavy metal-contaminated clayey soil by artificial freezing and shaft washing

The low permeability of clayey soil and the pressure of liquid extraction and injection tend to form preferential flow paths in the soil, diminishing the remediation efficiency of shaft washing. Therefore, a new in-situ repair method combining artificial freezing and shaft washing is proposed. Using Pb and Cd contaminated clayey soil as the research object, in-situ model tests of different eluent types, concentrations, and suction modes were conducted to investigate the removal rate of heavy metals and the distribution of temperature and water field. The results demonstrated that the artificial freezing method can effectively induce the water (eluent) migration from the unfrozen zone to the freezing front. Besides, it effectively resolved the issue of poor washing efficiency caused by preferential flow between the extraction and injection wells during the extraction process. After five freeze-thaw cycles, the removal rate of Pb and Cd reached 46.16 % and 59.04 %, respectively. The combination of artificial freezing and plastic drainage plate technology merges artificial freezing and shaft washing methods to achieve the remediation of heavy metal-contaminated soil, providing a reference for the in-situ remediation of heavy metal-contaminated clayey soil.

Fan assisted extraction and low pressure chromatographic system with a phenyl monolithic column for amperometric determination of volatile α-dicarbonyl compounds in coffee brews

In this work, a low pressure chromatographic system featuring a single 0.5 cm length phenyl monolithic column and an amperometric detector was developed to determine volatile ⍺-dicarbonyl compounds in coffee brews. The analytical strategy relied on the extraction of the volatile ⍺-dicarbonyl compounds and their derivatization with o-phenylenediamine, prior to the determination of the resulting quinoxaline derivative compounds in the designed chromatographic system. The studies of the mobile phase composition and electrochemical conditions are presented. The extraction of the volatile ⍺-dicarbonyl compounds was performed resourcing to a recent approach based on the fan assisted extraction system. This system performs the full evaporation technique and allowed the quantitative recovery (>85 %) of diacetyl and 2,3-pentanedione from the coffee brew based on the following experimental conditions: sample volume 30 µL, extraction period 15 min, acceptor solution (water, acetonitrile, 90:10, v/v) volume 400 µL, and sample temperature 50 °C. The developed method showed no matrix effect for different coffee brews and the quantification of the studied analytes can be performed through the external calibration method. Detection limits of 3.6 × 10−6 mol/L for diacetyl and 12.9 × 10−6 mol/L for 2,3-pentanedione were obtained. Sample analysis rate was of 5 h−1 and the acetonitrile consumption was of ca. 450 µL per chromatographic run.

Thermodynamic Analysis of a Marine Diesel Engine Waste Heat-Assisted Cogeneration Power Plant Modified with Regeneration Onboard a Ship

The objective of this study is to perform a thermodynamic analysis on a marine diesel engine waste heat-assisted cogeneration power plant modified with regeneration onboard a ship. The proposed system utilizes the waste heat from the main engine jacket water and exhaust gases to generate electricity and heat, thereby reducing the fuel consumption and CO2 emissions. The methodology includes varying different turbine inlet pressures, extraction pressures, and fractions of steam extracted from the turbine to evaluate their effects on the efficiency, utilization factor, transformation energy equivalent factor, process heat rate, electrical power output, saved fuel flow rate, saved fuel cost, and reduced CO2 emissions. The analysis demonstrates that the proposed system can achieve an efficiency of 48.18% and utilization factor of 86.36%, savings of up to 57.325 kg/h in fuel, 65.606 USD/h in fuel costs, and 180.576 kg/h in CO2 emissions per unit mass flow rate through a steam turbine onboard a ship.

Extraction of polyvinylidene fluoride binder materials for used secondary batteries using supercritical CO2 for an effective battery recycling process

In this study, a polyvinylidene fluoride (PVDF) binder material for secondary batteries was removed using a supercritical CO2 extraction process instead of conventional extraction processes such as leaching and pyrolysis. To determine the optimal process conditions, the phase behavior of the binder in CO2 was studied by measuring the pressure and temperature before the supercritical CO2 extraction. To design an effective extraction process, the extraction time, temperature, and pressure were studied under various experimental conditions using a supercritical extraction system. Various organic cosolvents were used in the experiment to improve the extraction efficiency. According to the experimental result, the optimal extraction conditions were determined to 353.2 K, 10 MPa, and 20 min with dimethylformamide (DMF) cosolvent. Under these process conditions, the removal rate of the binder was 98.8 %. However, there was a significant difference in cell performance such as initial discharge capacity and cycling stability depending on the extraction solvent. Specifically, cycling stability improved in the order of using DMF, NMP, DMSO, and DMAc. The extracted binder material was analyzed by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscope (SEM) to compare the raw and processed materials and evaluate the reusability of the binder material.

Advantages of online supercritical fluid extraction and chromatography hyphenated to mass spectrometry to analyse plastic additives in laboratory gloves

Plastic additives are introduced in plastic material formulations, along with organic polymers, to offer different properties such as stability, plasticity or color. However, plastic additives may migrate from the plastic material to the content (in case of plastic containers) or to the material in contact with the plastic, like human skin. In the case of plastic medical devices, this migration is of particular interest, as plastic additives may be deleterious to health. In the present paper, we examined the interest of combining supercritical fluid extraction (SFE) to supercritical fluid chromatography (SFC) hyphenated to mass spectrometry (MS) in an online system to characterize plastic additives in laboratory gloves, taken as samples of medical devices. A set of target compounds comprising 18 plasticizers, 4 antioxidants and 2 lubricants was defined and their detectability with MS was examined, where it appeared that electrospray ionization (ESI) provided better detectability than atmospheric pressure chemical ionization (APCI). After examining possible stationary phases with the help of Derringer desirability function, an isocratic chromatographic method (CO2:methanol 95:5) was developed on Shim-pack UC Phenyl column. The extraction method was examined with a 3-level full factorial design of experiments to optimize the extraction temperature (40 °C) and pressure (200 bar). The online SFE-SFC-MS method was compared to offline methods where the samples were extracted with liquid solvents at atmospheric pressure or high pressure then analysed with SFC-MS. In all cases, offline methods showed significant contaminants (like the oleamide lubricant) issuing from laboratory plastic materials as nitrogen drying station, syringes and filters, while the online method allowed a complete elimination of laboratory contaminations. Furthermore, the online method saved time, solvents and laboratory consumables. It will also show that transferring a compressible fluid from a loading loop is favourable to high efficiency, as the resulting chromatographic peaks are much thinner than when transferring a liquid. Compared to injecting liquid heptane, the efficiency increase was 3.4-fold, while compared to injecting liquid methanol (a common practice in SFC), the efficiency increase was 13-fold. Finally, the additive composition of different laboratory gloves was compared.

Efficient separation of alcohol ester via extractive distillation and pressure swing distillation based on molecular interaction mechanism analysis

N-amyl alcohol, n-amyl formate, n-propanol and n-propyl formate are all organic solvents with important industrial application value. In industrial production, related alcohol ester azeotropic systems are often generated. Therefore, it is necessary to study the refining process of these substances. The work designed purification processes for two different azeotropic systems of alcohol esters via extractive distillation and pressure swing distillation methods. The required binary interaction parameters were obtained through vapor–liquid equilibrium experiments. Based on experimental data, a suitable entrainer was determined through different methods of analysis. The processes were optimized with the economic cost as the objective. In addition, it evaluated and analyzed different processes from multiple perspectives. This work explores the purification process of alcohol ester systems, providing theoretical guidance for achieving efficient separation of alcohol ester systems.

Study on efficient extraction of saponins from Polygonatum sibiricum by enzyme assisted cold isostatic pressing technology

Saponin is one of the main active ingredients of Polygonatum sibiricum. In this study, the method of enzyme-assisted cold isostatic pressure extraction (EACIP) of Polygonatum sibiricum saponins was established. The effects of different cold isostatic extraction pressures, pressure-maintaining time times, enzymatic temperatures and enzymatic pH on the yield of saponin were investigated, and the factors were simplified by single factor experiments and Box-benhken design (BBD). Under the best extraction conditions, the EACIP method achieved the best possible results and extraction rate was 11.45 % ± 0.017. In addition, SEM-Mapping, XRD analysis and FTIR analysis proved that EACIP treatment increased the extent of cell deformation and improved the mass transfer system between solvent and active substance. Furthermore, by comparing different extraction methods, EACIP was found to have a higher extraction rate due to the synergistic effect of cold isostatic pressure extraction (CIP) and enzymatic hydrolysis extraction (EH). In vitro antioxidant and anti-inflammatory assays demonstrated that EACIP extracts have good antioxidant and anti-inflammatory capacity. Therefore, EACIP is a method to extract natural products from plants with increased extraction rate.

Assessment of Moringa Seed Oil: Fatty Acid Profile, Oxidative Stability and Antioxidant Activity

Moringa oleiferais called the “miracle tree” and it has more vitamins than even some fruits and vegetables like oranges, carrots etc. Objective: To assess functional groups and compare oxidative stability, fatty acid profile, free fatty acid concentration, and antioxidant activity to commercial vegetable oil. Methods: The moringa seed oil was extracted by cold press extraction and solvent extraction by n-hexane and petroleum ether. Functional group, lipid peroxidation, fatty acid profile, antioxidant activity, and FFAs % were analyzed by FTIR, TBARS, GC-MS, DPPH, and titration respectively. Results: The FTIR spectra of prepared samples showed common functional groups of triglycerides, including a sharp peak at 2984 cm-1 for aliphatic C-H stretching. The maximum TBARS value was 0.234 ± 0.03% in T0 at 30 days of storage, whereas the lowest was 0.167 ± 0.04% in T1 at 0 day. The GC-MS analysis of screw press moringa oil showed a high percentage of monounsaturated fatty acids, with 71.38 ± 0.01% oleic acid, 7.01 ± 0.01% palmitic acid, and 1.92 ± 0.01% linoleic acid. At 15 days of storage, FFAs were 2.28 ± 0.06%, showing low hydrolytic rancidity. The Antioxidant Activity in DPPH analysis was 44.46 ± 0.02%, showing high antioxidant properties. Conclusion: The characteristics of moringa seed oil indicate that it could be an effective edible oil and suitable for the production of food items and other edible products in the food and nutraceutical sectors.

Synergistic Impact of Pomegranate Peel Extract and High Hydrostatic Pressure on Controlling Discolouration and Oxidation in Iberian Dry Sausage Throughout Storage

AbstractThis study aimed to assess the impact of high-pressure processing and the inclusion of a pomegranate peel extract (PPE) on colour, antioxidant residual activities and lipid and protein oxidation of dry-cured and uncured sausages during 120 days of refrigerated storage. Nitrite and PPE were added into the sausage formulations following four treatments: (1) 150 mg/kg NaNO2 (C_Pos), (2) 0 mg/kg NaNO2 (C_Neg), (3) 0 mg/kg NaNO2 + 1% PPE (PPE1) and (4) 0 mg/kg NaNO2 + 2% PPE (PPE2). The four dry sausage batches were divided into two groups, one left untreated (0.1 MPa) and the other subjected to high hydrostatic pressure treatment (600 MPa, 8 min). The results revealed significant differences in the initial oxidation levels, with nitrite removal leading to increased lipid peroxidation and protein carbonylation. The pomegranate extract surpasses nitrite in the amount of residual antioxidant activity in the sausages and was comparable to nitrites in controlling lipid and protein oxidation. Despite this, thiols were affected, decreasing their value in batches with added pomegranate extract. Finally, the colour of the dry sausages varied significantly towards more yellowish and less reddish when the pomegranate extract was added.

Biorefinery approach with green solvents for the valorization of Citrus reticulata leaves to obtain antioxidant and anticholinergic extracts

Citrus reticulata L leaves are one of the main post-harvest byproduct, containing bioactive compounds, that are usually undervalued. This work describes the development of a biorefinery process based on the application of supercritical CO2 (SC-CO2) followed by ultrasonic-assisted extraction (UAE) combined with Natural Deep Eutectic Solvents (NaDES) to extract bioactive terpenoids and phenolic compounds from these leaves. Extraction temperature and pressure of SC-CO2 were optimized, obtaining the highest bioactive terpenoids content using 200 bar at 60 °C. A Box-Behnken experimental design showed that 57% of water in NaDES composed of Choline Chloride and Glycerol (1:2) as extraction solvent at 25 °C for 50 min were the optimal UAE-NaDES extraction conditions to obtain the highest bioactive phenolic content from the residue of the optimal SC-CO2 extraction. The optimum extract presented the highest bioactivity and polyphenol content determined by LC-DAD-MS compared with extracts obtained using only water or NaDES as solvent.

The effect of different hydrodistillation times on the composition and yield of bergamot (Citrus bergamia Risso) peel essential oil and a comparison of the cold‐pressing method

AbstractBergamot (Citrus bergamia Risso) is not consumed as fresh fruit as other members of Citrus. Bergamot essential oil has a unique aroma. Bergamot essential oil is a very valuable product used in perfumery, cosmetics, aromatherapy and food industry due to its beautiful scent and functional properties. As with other Citrus species, the composition of bergamot essential oil can vary according to harvest time, climate and extraction technology. Bergamot essential oil could be obtained by cold press extraction or distillation method. Within the scope of the study, the effect of four different hydrodistillation (HD) times (5, 10, 60 and 120 min) on the composition of bergamot essential oil obtained from Turkish fruits was investigated. In the first 60 min, 96.11% of the total essential oil was obtained. Research findings have shown that the distillation time is quite effective in the composition of bergamot essential oil. Limonene, linalool and linalyl acetate, which are the main components of bergamot essential oil, varied in the range, 42.36%–53.25%, 5.59%–12.18% and 20.84%–26.73%, respectively, with respect to distillation time. In cold press method, bergamot essential oil has lower linalool/linalyl acetate ratio (0.15) compared to HD method and a higher quality essence was obtained.

Probing the physicochemical impact of musk melon seed oil on mayonnaise

Owing to high consumption and industrial preparation of musk melon products, most of its byproducts are wasted without effective utilization. Musk melon agro-based waste material (seeds and peels) is an excellent source of antioxidants and phytochemicals. The purpose of this study was to improve the oxidative stability of mayonnaise by addition of musk melon seed oil. The study was conducted to check the physicochemical effect of musk melon seed oil in mayonnaise. Proximate analysis of seeds (i.e. moisture, crude fat, crude fiber, crude protein, ash, and carbohydrate content) was performed. Oil was extracted by using the cold press extraction method, and this oil was tested for different physicochemical analyses (i.e., saponification value, iodine number, specific gravity, 2,2-diphenyl-1-picrylhydrazyl [DPPH] value, viscosity, free fatty acid, and color). Physicochemical analysis was done during the storage period of 0, 20, 40, and 60 days, prior to performing sensory evaluation of mayonnaise. Data obtained from this analysis were further analyzed using statistical tools. A decreasing trend was observed for DPPH and peroxide values of mayonnaise with progression of days, thus showing that addition of musk melon seed oil decreased the production of free radicals. Hence, adding 40% musk melon seed oil showed the best result for overcoming the oxidation of mayonnaise and minimizing the production of free radicals. The data obtained from the statistical analysis indicated that the aroma and texture values of treatment T5 were maximum, and the color and flavor of treatments T4 and T5 were high. The overall acceptability of treatment T5 was high in which 40% of musk melon seed oil was used to combat the production of free radicals. In brief, waste material could be used for producing different types of products in the industry, rather than discarding the same, as it lessened the cost and provide a good quantity of nutrients.

Influence of extraction and injection conditions on the performance of thermal-enhanced soil vapor extraction

Thermal-enhanced soil vapor extraction (T-SVE) is an in-situ remedial technique that can address the limitations of contaminant mass transfer and soil permeability. The relative humidity of the injected air, heating temperature of the thermal well, extraction pressure, and extraction mode are important design parameters of a T-SVE system that determine the temporal and spatial distributions of soil temperature and removal rate. Using a thermal–hydraulic–chemical coupled model with the interphase mass transfer of contaminants and water evaporation/condensation, this study investigated the effects of relative humidity, heating temperature, extraction pressure, and extraction mode on T-SVE performance. The results showed that with an increase in relative humidity, the heating temperature of the contaminated soil significantly improved; however, the removal rate of contaminants decreased, particularly in the late stage of remediation. Considering the heating temperature of the thermal well, a critical air relative humidity value that significantly affects the removal rate of contaminants was observed. The heating temperature of the thermal well must be considered in engineering design; however, the evaluation of the relative humidity of the air cannot be ignored.