Abstract
This paper presents a planned heating control strategy applied for a natural gas thermal desorption system for polluted soil to achieve the dynamic adjustment of the heating time and energy consumption. A lumped-parameter model for the proposed system is established to examine effects of the natural gas mass flow rate and the excess air coefficient on the heating performance of the target soil. The control strategy is explored to accomplish the heating process as expected with constant temperature change rate or constant volumetric water content change rate at different phases by adapting the natural gas flow. The results demonstrate that the heating plan can be realized within the scheduled 36 days and the total natural gas consumption can be reduced by 24% (1487 kg) compared to that of the open-loop reference condition, which may be widely applied for other thermal remediation systems of the polluted soil.
Highlights
Over the past few decades, soil contamination has become an increasingly prominent concern owing to accelerated industrialization and urbanization in China and all over the world [1,2,3]
Among all kinds of hazardous substances released by industrial activities, heavy metals make a significant contribution to soil pollution [6] which are covert, persistent and irreversible [7]
The results proved that the carefully designed gas thermal desorption system (GTDS) may have a broad prospect of application for contaminated soil remediation
Summary
Over the past few decades, soil contamination has become an increasingly prominent concern owing to accelerated industrialization and urbanization in China and all over the world [1,2,3]. In situ thermal desorption (ISTD) is one of the remediation technologies for polluted soil and has attracted great research interest in recent years This method uses fluid injection or heating elements to heat the contaminated site at sufficient temperature without excavation. Energies 2020, 13, 642 of suitability to various types of pollutants, a short remediation period, high efficiency and no secondary pollution [11,12,13] For all this, it has been applied at a great many contaminated sites via different heating modes such as steam-enhanced extraction (SEE), electrical resistance heating (ERH) and thermal conduction heating (TCH). A planned heating control strategy of a natural gas thermal desorption system (GTDS) is proposed aiming to effectively heat the contaminated soil within the specified heating time with less energy consumption. The results proved that the carefully designed GTDS may have a broad prospect of application for contaminated soil remediation
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