Sewage sludge charcoal production by N 2 - and CO 2 -torrefaction

Hernández, Ana Belén Roig; Okonta, Felix; Ntuli, Freeman

doi:10.1016/j.jece.2017.08.001

Cited by 17 publications

(6 citation statements)

References 22 publications

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“…The torrefaction process not only reduces the mass of sewage sludge but also removes the NOx, SOx and other pollutants and improves the heating value and C/H ratio of sewage sludge [93,94]. The solid torrefied sewage sludge upon combustion at 900°C gives significant reduction in NH3 (46%) [95]. Also, torrefied sewage sludge or biomass can also be used with each other to produce a mainly bio-char product.…”

Section: Torrefaction and Htcmentioning

confidence: 99%

Thermochemical conversion of sewage sludge: A critical review

Quan

Kamran

Williams

2020

Progress in Energy and Combustion Science

452

117

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Section: Torrefaction and Htcmentioning

confidence: 99%

Thermochemical conversion of sewage sludge: A critical review

Quan

Kamran

Williams

2020

Progress in Energy and Combustion Science

452

117

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“…Sewage sludge (with ash content ranging from 12% to 43% d.m.) was torrefied, resulting in biochar with HHVs of 11.43 to 19.86 MJ·kg −1 [26,[30][31][32][33]. Research on the effects of high ash content is required to build a database informing and enabling the SS torrefaction applicability to SS with a wider range of properties.…”

Section: Sewage Sludge Torrefactionmentioning

confidence: 99%

Torrefaction of Sewage Sludge: Kinetics and Fuel Properties of Biochars

et al. 2019

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We propose a 'Waste to Carbon' thermal transformation of sewage sludge (SS) via torrefaction to a valuable product (fuel) with a high content of carbon. One important, technological aspect to develop this concept is the determination of activation energy needed for torrefaction. Thus, this research aimed to evaluate the kinetics of SS torrefaction and determine the effects of process temperature on fuel properties of torrefied products (biochars). Torrefaction was performed using high ash content SS at six (200~300 • C) temperatures and 60 min residence (process) time. Mass loss during torrefaction ranged from 10~20%. The resulting activation energy for SS torrefaction was 12.007 kJ·mol −1 . Initial (unprocessed) SS higher heating value (HHV) was 13.5 MJ·kg −1 . However, the increase of torrefaction temperature decreased HHV from 13.4 to 3.8 MJ·kg −1 . Elemental analysis showed a significant decrease of the H/C ratio that occurred during torrefaction, while the O/C ratio fluctuated with much smaller differences. Although the activation energy was significantly lower compared with lignocellulosic materials, low-temperature SS torrefaction technology could be explored for further SS stabilization and utilization (e.g., dewatering and hygienization). Energies 2019, 12, 565 2 of 10 J.A.K.; validation, J.P., A.B., J.A.K.; investigation, J.P.; resources, J.P., A.B., P.M.; data curation, A.B., J.A.K.; writing-original draft preparation, J.P., A.B.; writing-review and editing, A.B., P.M., J.A.K.; visualization, J.P., A.B., J.A.K.; supervision, A.B., P.M., J.A.K.

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“…Other research on SS torrefaction was performed on materials characterized by ash content between 12 to 43%. Produced biochars calorific value ranged between 11.43 to 19.86 MJ•kg −1 [36][37][38][39][40], with one research indicate extremely high devolatilization in the temperature range between 260~300 • C resulting in biochars with the lower heating value (LHV) from 6.50 to 3.88 MJ•kg −1 [41].…”

Section: Introductionmentioning

confidence: 99%

Waste-to-Carbon: Is the Torrefied Sewage Sludge with High Ash Content a Better Fuel or Fertilizer?

et al. 2020

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Sewage sludge (SS) recycling is an important part of the proposed ‘circular economy’ concept. SS can be valorized via torrefaction (also known as ‘low-temperature pyrolysis’ or ‘roasting’). SS can, therefore, be considered a low-quality fuel or a source of nutrients essential for plant growth. Biochar produced by torrefaction of SS is a form of carbonized fuel or fertilizer. In this research, for the first time, we tested the feasibility of torrefaction of SS with high ash content for either fuel or organic fertilizer production. The research was conducted in 18 variants (six torrefaction temperatures between 200~300 °C, and three process residence times of 20, 40, 60 min) in 5 repetitions. Fuel and fertilizer properties and multiple regression analysis of produced biochar were conducted. The higher heating value (HHV) of raw SS was 21.2 MJ·kg−1. Produced biochar was characterized by HHV up to 12.85 MJ·kg−1 and lower H/C and O/C molar ratio. Therefore, torrefaction of SS with high ash content should not be considered as a method for improving the fuel properties. Instead, the production of fertilizer appears to be favorable. The torrefaction increased C, N, Mg, Ca, K, Na concentration in relation to raw SS. No significant (p < 0.05) influence of the increase of temperature and residence time on the increase of biogenic elements in biochar was found, however the highest biogenic element content, were found in biochar produced for 60 min, under the temperature ranging from 200 to 240 °C. Obtained biochars met the Polish regulatory criteria for mineral-organic fertilizer. Therefore SS torrefaction may be considered a feasible waste recycling technology. The calculation of torrefaction energy and the mass balance shows energy demand <2.5 GJ∙Mg−1 w.m., and the expected mass yield of the product, organic fertilizer, is ~178 kg∙Mg−1 w.m of SS. Further investigation should consider the scaling-up of the SS torrefaction process, with the application of other types of SSs.

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Sewage sludge charcoal production by N 2 - and CO 2 -torrefaction

Cited by 17 publications

References 22 publications

Thermochemical conversion of sewage sludge: A critical review

Thermochemical conversion of sewage sludge: A critical review

Torrefaction of Sewage Sludge: Kinetics and Fuel Properties of Biochars

Waste-to-Carbon: Is the Torrefied Sewage Sludge with High Ash Content a Better Fuel or Fertilizer?

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