Ex Situ Treatment of Organic Wastes or Oil-Impacted Soil Using a Smoldering Process

Abstract

An innovative treatment technology has been developed for the treatment of organic wastes. The technology utilizes the waste itself as the primary fuel for treatment via smoldering combustion. The process requires a heat source solely to initiate treatment. Once the process is initiated, treatment is sustained by continuously supplying air. The process may be implemented either ex situ or in situ, with this paper focused on the ex situ application for waste treatment or remediation purposes. This ex situ smoldering combustion treatment technology has been effectively demonstrated at field-scale for the management of oily wastes (e.g. tank bottom sludge, clarifier or pit sludge) and oil-impacted soil. Furthermore, the ex situ application has been demonstrated at pilot scale for domestic and commercial wastes (e.g. biosolids or sanitary sludge, kitchen grease) and ongoing development of the technology indicates other chemicals or wastes may also be effectively treated. If the waste is a combustible organic, or may be mixed with combustible organics, it is possible it may be treated with this technology. The Hottpad configuration is the culmination of collaborative research and technology development between Savron and Chevron. Each Hottpad unit has an engineered and trafficable working surface (or pad) equipped with a heat source to initiate the reaction, and an air distribution system to sustain the smoldering combustion that then propagates upward in the direction of air flow. Each Hottpad system is equipped with an emissions collection and treatment system, as necessary. The technology is cost-effective, robust, and applicable for a broad range of materials. Furthermore, the design is scalable and may be sized to meet project needs (from large centralized facilities, to smaller mobile treatment systems for remote sites). The Hottpad technology is very robust, both in terms of the range of materials that can be treated and from an operations perspective; it is costeffective; it may be implemented on site, reducing off-site transportation, eliminating safety concerns, and reducing the overall remediation carbon footprint; and the treatment will meet stringent treatment or remediation requirements.

Heat losses in a smouldering system: The key role of non-uniform air flux

“…Applications of smouldering combustion are solving a wide range of engineering challenges. Applied smouldering systems represent a simple, economical, and robust thermal conversion option in many contexts, including soil remediation [1][2][3], biomass energy conversion [4,5], wastewater sludge treatment [6,7], resource recovery [8,9],…”

“…Most of these applications require the design and construction of engineered smouldering systems (e.g., batch or continuous reactors). The scale of the reactor is intimately related to the waste-to-energy process, with some systems favouring small reactors [8,11] while other larger systems [3,12]. Thus, scale is a key variable defining the potential of smouldering as a waste-to-energy treatment.…”

“…Currently, nearly every incineration technology uses flaming-based reactors [37][38][39], but for all problematic wastes it is necessary to either preprocess the waste (e.g., moisture removal, chemical treatment) or add supplemental fuel. In these cases it has been shown that these wastes are better handled in smoulderingbased reactors [3,5,8,10,12,29,31,[40][41][42].…”

“…A pilot smouldering reactor demonstrated the ex situ treatment of coal-tar contaminated soil [44], which was similar in size as another smouldering reactor studied for deriving liquid fuel from waste tires [9]. Following [44], a modular, scalable, batch treatment system was developed for contaminated soils and organic sludges [3,12,45].…”

Fuel Gas Production From Self-Sustaining Smouldering Combustion of Lignocellulosic Waste

“…More recently, research advanced onto the application of self-sustaining smouldering (SSS) to soil remediation [3], [11]- [15] with commercial utilization [16], [17], and also as waste treatment method using smouldering reactors in a forced-upward-forward con guration [5]. The latter is the focus of the present work.…”