THERMOCHEMICAL SOLIDIFICATION: LARGE LABORATORY TESTING AND SCALEUP

摘要

Thermochemical solidification (TCS) has considerable potential to provide substantial benefits in terms of performance and reliability of thermal technologies applied to the management of dense non-aqueous phase liquids (DNAPL), such as coal tar residues found at former manufactured gas plant sites (MGPs). In particular, it is expected that the technology will be applicable to the treatment of concentrated DNAPL in shallow and in deep subsurface locations. Using TCS technologies, rapid and effective removal of light fraction can be achieved in coal-derived DNAPL in treatment zones of appreciable depths. Conventional methods of applying thermal desorption to achieve quantitative in situ removals of coal-based DNAPL have been partially successful due to the inability to reach the required target temperature range of 400-700oC using commercial heating hardware. Barriers to reach such temperature in subsurface include: 1) The heat of vaporization due to high moisture condition of many sites with shallow water tables, and 2) The loss of heat transfer efficiencies in soils that lose virtually all moisture. These limitations point to the need for a new strategy for the effective use of thermal treatment at lower temperatures. A new technology from the Gas Technology Institute (GTI) called thermochemical solidification (TCS) was proposed for testing that was based on an improved fundamental understanding of the nature of coal-derived DNAPL gained through a number of critical experiments on MGP site materials. The TCS technology is the application of thermochemical treatment techniques to strategically remove the light fraction of the DNAPL so that the majority of the DNAPL mass will solidify, thereby reducing the release rates of the contaminants of concern.