Thermal plasma vitrification process as an effective technology for fly ash and chromium-rich sewage sludge utilization

Waste Dispos. Sustain. Energy

Wei

et al. 2020

Soil pollution (heavy metals and organic matter) is becoming more and more serious, phytoremediation has rapidly become a highly important method to deal with this problem. Therefore, the treatment and disposal of hyperaccumulators have been a topic of concern. In this paper, carambola leaves are selected as feedstock considering that carambola is a potential hyperaccumulator. A series of tests were performed to discuss 6 main influencing factors on total gas yield and metal fixing using a non-thermal arc plasma setup, to investigate the feasibility of plasma treatment of hyperaccumulator and provide a new method to utilize the harvested hyperaccumulator. The maximum total gas yield reached approximately 85% at an airflow rate of 3 L/min, the processing time of 7 min, discharge power of 29.95 W with the addition of water (water: sample = 1:1). A reducing or inert carrier gas or the addition of some specific inorganic additives at optimal conditions were in favor of increasing metal fixing efficiency. However, the effects of these factors usually have two sides, and some factors may have conflicting effects between gas yield and metal fixing, and. It is necessary to optimize these factors for achieving the desired goal. The obtained solid products exhibit the potential to fix metals and act as activated carbon.

Section: Effects Of Metal Salt Additivessupporting

confidence: 86%

Plasma pyrolysis and gasification of carambola leaves using non-thermal arc plasma

Waste Dispos. Sustain. Energy

Wei

et al. 2020

“…For other hazardous wastes, SiO 2 content has been proven to enhance the plasma vitrification process [40,98,104]. It can result in the domination of SiO 4 tetrahedron inside the vitrified slag, and thus traps metals [105]. Also, the hardness of the slag is improved when SiO 2 in the feed is higher [106].…”

Section: The Influence Of Additives and Co-treatmentmentioning

confidence: 99%

“…For instance, in the plasma pyrolysis and gasification, slag is possible not to be formed or formed with a low hardness due to the lack of inorganic matters. Therefore, for some hazardous waste, glass formers such as SiO 2 and CaO are needed to enhance the formation of vitrified slag [ 105 , 124 – 127 ]. For feed continuation, the formed slag must be periodically tapped out of the furnace once the level is close to the maximum of the crucible.…”

Section: Mechanism Of Thermal Treatment Of Medical Wastementioning

confidence: 99%

Thermal Plasma Treatment of Medical Waste

Plasma Chem Plasma Process

2020

The harmless treatments of medical waste have significantly drawn people's attention owing to their risks to health-care staff, the public, and the environment. The traditional thermal technology for processing medical waste may cause indispensable secondary pollution such as dioxin, furan, and heavy metals, and infectious materials that may remain in the solid residual. Thermal plasma technologies offer advantages of effectively treating medical waste due to its high temperature and energy density, lower pollutant emissions, rapid start-up and shutdown , and smaller size of the installation. These benefits play roles in the treatment of medical waste on-site or off-site, especially when somewhere encounters an abnormally sharp increase in medical waste. This paper mainly introduces the typical thermal plasma processes of medical waste and its central component, plasma furnace. Meanwhile, how process parameters influence the formed gaseous and solid products, the performances of mass and volume reduction, pathogen destruction, and energy recovery, are discussed in detail. Finally, the mechanism of the thermal plasma process is also analyzed.

“…The amount of SiO 2 in feedstock composition is regarded as an important factor to determine whether the plasma vitrification is dominant or not. In general, sufficient SiO 2 content can result in the dominance of the SiO 4 tetrahedron inside the vitrified slag . When the bond lengths of X–(O)–Si species are close enough, the metal is believed to be inserted into the silicate matrix.…”

Section: Fundamentals Of Thermal Plasma Treatmentmentioning

confidence: 99%

Thermal Plasma Treatment and Co-processing of Sludge for Utilization of Energy and Material

Wei

2020

Energy Fuels

Thermal plasma treatment of sludge has a significant benefit in converting hazardous waste into renewable combustible gas and inert solid product, which is a workable solution for energy and material recovery. The advantages of this approach also lie in its flexibility, smaller installation, greater compactness, fewer contaminant emissions, and minimization of mass and volume. The present review focuses on various thermal plasma processes for sludge treatment and co-processing. The review starts with fundamental aspects of plasma and mechanisms of thermal plasma sludge treatment and then four basic thermal plasma systems used in previous studies. Five main thermal plasma conversion processes of sludge are classified and discussed, namely, plasma combustion, plasma pyrolysis and vitrification, plasma gasification and vitrification, plasma co-processing, and pre-processing combined with thermal plasma unit. Specifically, key parameters influencing thermal plasma treatment of sludge are distinguished and discussed as well as energy and material recovery. On these bases, the challenges and future research perspectives are addressed.