Patent Application
20240173758
This patent application claims the benefit and priority of Chinese Patent Application No. 202211501188.9, entitled “METHOD FOR LOWERING TEMPERATURE IN THERMAL REMEDIATION OF CONTAMINATED SOIL” filed on Nov. 28, 2022, the disclosure of which is incorporated herein by reference in its entirety.
The present disclosure relates to the field of soil and groundwater remediation technologies, and in particular to a method for lowering temperature in thermal remediation of contaminated soil.
Petroleum is one of the indispensable energy sources for the national economy and daily lives, as well as the most important fuel and chemical raw materials in modern society. With the rapid development of social economy, the demand for petroleum products has increased significantly. However, a large amount of petroleum hydrocarbons (PHCs) leak into the underground environment during the extraction, transportation, processing, storage, and application of petroleum products, causing serious soil contamination. The PHCs include long-chain alkanes and polycyclic aromatic hydrocarbons (PAHs), which are structurally stable and challenging to degrade, causing persistent and irreversible barm to the ecological system and posing a severe threat to human health. Therefore, it is necessary to find effective ways to remediate PHCs contaminated soil.
At present, thermal desorption technology, including in-situ and ex-situ, is widely used for remediating PHCs contaminated soil due to its effective results, short time and wide applicability. In-situ thermal desorption is the process of increasing the temperature of contaminated area by heating, and thereby changing the physical and chemical properties of the contaminants (the vapor pressure and solubility increase, while the viscosity, surface tension, Henry's constant, and soil-water partition coefficient decrease). Through this process, the concentration of contaminants in the gas or liquid phase is increased, ultimately leading to the removal of contaminants via liquid-phase or gas-phase extraction. The in-situ thermal desorption has attracted widespread attention due to its advantages of eliminating the need to excavate soil and removal contaminants in-situ, and has been implemented in a large number of engineering applications at real sites in recent years. The ex-situ thermal desorption is a process to heat the contaminated soil to above the boiling point of the target contaminant using either direct or indirect heating, where gasification and volatilization of the target contaminant are selectively promoted by controlling the system temperature and the material residence time. The outcome is that the target contaminant is separated from the soil particles and subsequently removed. Currently, thermal desorption generally requires electricity or fuel for heating, which has the disadvantage of excessive energy consumption. So, reducing energy consumption in thermal desorption remediation and simultaneously improving remediation efficiency is an urgent demand that requires immediate attention.
An objective of the present disclosure is to provide a method for lowering a temperature in thermal remediation of contaminated soil. The method could reduce the energy consumption of thermal remediation, leading to a decrease in overall remediation costs.
To achieve the above objective, the present disclosure provides the following technical solutions:
The present disclosure provides a method for lowering a temperature in thermal remediation of contaminated soil, including the following steps: injecting an entrainer into PHCs contaminated soil for remediation by thermal desorption; where the entrainer includes ethanol at a volume percentage of 10% to 50%.
In some embodiments, the entrainer is injected with sufficient quantity to at least saturate the PHCs contaminated soil.
In some embodiments, temperature of the thermal desorption is not lower than 120° C.
In some embodiments, the temperature range of the thermal desorption is from 120° ° C. to 200° C.
In some embodiments, duration of the thermal desorption is at least 6 hours.
In some embodiments, PHCs in the PHC's contaminated soil include diesel hydrocarbons.
In some embodiments, the entrainer has 10% to 40% of ethanol by volume.
In some embodiments, the entrainer has 20% of ethanol by volume.
In some embodiments, the remediation by thermal desorption is achieved via in-situ or ex-situ methods.
In some embodiments, a heating process of the soil remediation by thermal desorption is preferably electricity resistance heating (ERH) or thermal conduction heating (TCH).
The present disclosure provides a method for lowering the temperature in thermal remediation of contaminated soil, including the following steps: injecting an entrainer into PHCs contaminated soil for remediation by thermal desorption; where the entrainer includes ethanol at a volume percentage of 10% to 50%. The method is based on the azeotropic principle, and the removal temperature of PHCs, especially diesel hydrocarbons, can be significantly lowered by adding the entrainer. Since the boiling points for diesel of different constituents can range from 180° ° C. to 370° C., soil remediation by thermal desorption without the entrainer needs to reach at least 250° C. to achieve the desired removal effects. The entrainer of the present disclosure may lower the azeotropic point of the diesels to 100° ° C. to 120° ° C., which has a significant energy-saving effect, and shows a desirable removal effect.
The present disclosure provides a method for lowering temperature in thermal remediation of contaminated soil, including the following steps: injecting an entrainer into PHCs contaminated soil for thermal remediation; and the entrainer is ethanol at a volume percentage of 10% to 50%.
In the present disclosure, PHC's in the soil include preferably diesel hydrocarbons. There is no special requirement on the type of the diesel hydrocarbon, and any diesel hydrocarbon well known in the industry can be used, specifically for example, #0 Diesel.
In the present disclosure, the entrainer is preferably obtained by mixing ethanol and water. The entrainer has preferably 10% to 40%, specifically 10%, 20%, and 40% of ethanol by volume.
In the present disclosure, there is no special requirement for an injection process of the entrainer. Specifically, an injection vehicle or a water pump can be used for the injection.
In the present disclosure, the entrainer is preferably injected in an amount sufficient to make moisture of the PHCs contaminated soil to be remediated saturated.
In the current disclosure, soil remediation by thermal desorption is accomplished by either in-situ or ex-situ thermal desorption, preferably in-situ thermal desorption. There is no special limitation on the implementation of the in-situ thermal desorption and the ex-situ thermal desorption, which can be conducted according to processes well known in the art.
In the current disclosure, soil remediation by thermal desorption is carried out for a minimum of 6 h at temperature of ideally between 120 and 200° C. There are no particular requirements for the exact heating duration, which is determined by the size of the restoration site and the concentration contaminants.
In the present disclosure, a heating process of soil remediation by thermal desorption is preferably resistance heating or conduction heating. There are no unique requirements for ERH or TCH methods, and well-known heating methods can be employed.
The method is based on an azeotropic principle, and the removal temperature of PHCs, especially diesel hydrocarbons, may be significantly lowered by adding an entrainer. Since the diesel hydrocarbons have a boiling point of 180° ° C. to 370° ° C., soil remediation by thermal desorption without the entrainer needs to reach at least 250° ° C. to achieve a removal efficiency. The entrainer of the present disclosure may lower an azeotropic point of the diesel hydrocarbons to 100° ° C. to 120° C., has a significant energy-saving effect, and shows a desirable removal effect.
The method for lowering temperature in thermal remediation of contaminated soil provided by the present disclosure is described in detail below with reference to the examples, but these examples may not be understood as a limitation to the protection scope of the present disclosure.
PHCs with a saturation rate of 30% (ratio of the volume of PHCs to the volume of pores) was added in a porous medium to simulate contaminated soil, 125 g of 40 mesh to 80 mesh quartz sand was added into a three-neck flask, and 10 mL of #0 Diesel and 20 mL of entrainer (with 50% of ethanol by volume, specifically including 10 mL of the ethanol and 10 ml of ultrapure water) were added. A temperature thermocouple, a condenser tube, and a glass stopper were connected to the left, middle, and right openings of the three-neck flask in sequence, tightened, and subsequent devices were connected tightly in sequence. The condensation water switch was turned on, followed by the heating power supply, to allow heating to a preset temperature of 120° ° C. Temperature changes were recorded every 2 s with a temperature detector to record the changes in temperature over time. The results are shown in
As shown in the heating curve in
1.5 kg of non-contaminated ground soil was weighed, diesel was dissolved in 1:1 (V/V) n-hexane/acetone, and the resultant combination of diesel and n-hexane/acetone was then combined with the non-contaminated soil and agitated frequently until all of the acetone evaporated. The mixed soil was aged for 1 week and then sealed and stored for later use. The contaminated soil had a total petroleum hydrocarbon (TPH) concentration of 26,300 mg/kg.
50 g of prepared contaminated soil was added to a three-neck flask, and an entrainer with 10% of ethanol by volume was added to the contaminated soil until the soil was fully submerged. The heating device was started at a set temperature of 200° C.′, and the temperature changes were recorded every 2 seconds with a temperature detector.
This example differed from Example 2 only in that the entrainer had 20% of ethanol by volume.
This example differed from Example 2 only in that the entrainer had 40% of ethanol by volume.
This example differed from Example 2 only in that the heating was conducted at 120° C.
This example differed from Example 3 in that the heating was conducted at 120° C.
Control Group 1
This control group differed from Example 2 in that the contaminated soil with saturated moisture was directly heated at 200° ° C. without adding ethanol.
Control Group 2
This control group differed from Example 2 in that the contaminated soil with saturated moisture was directly heated at 120° ° C. without adding ethanol.
The heating time-temperature curves obtained according to Examples 2 to 4 are shown in
It can be seen from the above examples and comparative examples that adding an entrainer in the present disclosure may not only significantly lower the azeotropic interval temperature of the PHCs in soil, but also improve the removal efficiency of contaminants. This is extremely beneficial in terms of saving energy consumption, lowering remediation costs, or enhancing remediation effects, and provides a new perspective for the remediation of high-boiling point contaminants.
The above descriptions are merely preferred embodiments of the present disclosure. It should be noted that a person of ordinary skill in the art may further make several improvements and modifications without departing from the principle of the present disclosure, but such improvements and modifications should be deemed as falling within the protection scope of the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202211501188.9 | Nov 2022 | CN | national |
