Supercritical water oxidation of a model fecal sludge without the use of a co-fuel

Abstract

A continuous supercritical water oxidation reactor was designed and constructed to investigate the conversion of a feces simulant without the use of a co-fuel. The maximum reactor temperature and waste conversion was determined as a function of stoichiometric excess of oxygen in order to determine factor levels for subsequent investigation. 48% oxygen excess showed the highest temperature with full conversion. Factorial analysis was then used to determine the effects of feed concentration, oxygen excess, inlet temperature, and operating pressure on the increase in the temperature of the reacting fluid as well as a newly defined non-dimensional number, NJa representing heat transfer efficiency. Operating pressure and stoichiometric excess oxygen were found to have the most significant impacts on NJa. Feed concentration had a significant impact on fluid temperature increase showing an average difference of 46.4°C between the factorial levels.

Hydrothermal Oxidation of Fecal Sludge: Experimental Investigations and Kinetic Modeling

“…Price 15 observed minor formation of CH 4 and H 2 , aside from CO 2 and CO in their product gas. Miller and co-workers 19 found that the solids concentration of the feed had an influence on the temperature increase of the reaction. This could also provide an explanation for the slightly lower conversions observed for the experiments with a lower initial TOC content.…”

“…At temperatures of >600 °C, the main part of nitrogen is converted to dinitrogen (N 2 ) and nitrous oxide. Miller et al 19 investigated supercritical water oxidation of a model fecal sludge in a continuous reactor system. They examined different process parameters such as the reactor inlet temperature (500–600 °C), solids concentration of the feed (5–8% by weight), reactor pressure, and oxygen-to-fuel equivalence ratio (1.3–1.5).…”

Characterization of fecal sludge as biomass feedstock for thermal treatment in the southern Indian state of Tamil Nadu

“…Innovative sanitation treatment approaches under development aim to recover energy from onsite waste systems through processes including combustion ( Sellgren et al ., 2017 ), gasification ( Onabanjo et al ., 2016 ), smoldering ( Yermán et al ., 2015 ), hydrothermal oxidation ( Miller et al ., 2015 ) and hydrothermal carbonization ( Afolabi et al ., 2017 ). Key figures of merit for biomass feedstock include total solids (TS) content and calorific content.…”

Copper(II) nanoparticles: an efficient and reusable catalyst in green oxidation of benzyl alcohols to benzaldehydes in water

“…Recently, the development of efficient catalytic systems for oxidations in water or aqueous media has attracted much attention . To achieve selective oxidations, various homogeneous and heterogeneous catalysts have been reported in the chemical literature, the latter of particular interest due to the well‐known and well‐established inherent advantages of heterogeneous catalysis over homogeneous catalysis …”

“…Undoubtedly oxidations in water are superior from known and established points of view . Hydrogen peroxide is an attractive, atom‐economic and environmentally friendly oxidant as it is inexpensive, non‐toxic and commercially available and produces only water as a by‐product …”