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Oh DY, Kim D, Choi H, Park KY. Syngas generation from different types of sewage sludge using microwave-assisted pyrolysis with silicon carbide as the absorbent. Heliyon 2023; 9:e14165. [PMID: 36923894 PMCID: PMC10009543 DOI: 10.1016/j.heliyon.2023.e14165] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2023] [Revised: 02/21/2023] [Accepted: 02/23/2023] [Indexed: 03/05/2023] Open
Abstract
In this study, the pyrolysis of sewage sludge was explored through microwave-assisted pyrolysis. Three kinds of sludge (primary sludge, waste-activated sludge, and digested sludge) from a sewage treatment process were used. All three kinds of sewage sludge had a low microwave absorption capacity; therefore, an absorber was added to enable microwave-assisted pyrolysis. By using silicon carbide as the heating element, it was possible to increase the temperature within a short time by applying microwaves. During the microwave-assisted pyrolysis of sewage sludges, the amount of gas generated and the H2 and CO fraction of the produced gas increased as temperature increased. The pyrolysis of waste-activated sludge produced the greatest quantity of gas. However, the primary sludge produced the highest amount of syngas in terms of H2 and CO, which indicate the high-quality of the syngas.
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Affiliation(s)
- Doo Young Oh
- Department of Civil and Environmental Engineering, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 05029, Republic of Korea
| | - Daegi Kim
- Department of Environmental Technology Engineering, Daegu University, 201 Daegudae-ro, Jillyang-eup, Gyeongsan-si, Gyeongsangbuk-do 38453, Republic of Korea
| | - Hanna Choi
- Taeyoung E&C, 111 Yeouigongwon-ro, Yeongdeungpo-gu, Seoul 07241, Republic of Korea
| | - Ki Young Park
- Department of Civil and Environmental Engineering, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 05029, Republic of Korea
- Corresponding author.
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Lin J, Cui C, Sun S, Ma R, Yang W, Chen Y. Synergistic optimization of syngas quality and heavy metal immobilization during continuous microwave pyrolysis of sludge: Competitive relationships, reaction mechanisms, and energy efficiency assessment. JOURNAL OF HAZARDOUS MATERIALS 2022; 438:129451. [PMID: 35777144 DOI: 10.1016/j.jhazmat.2022.129451] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Revised: 06/03/2022] [Accepted: 06/21/2022] [Indexed: 06/15/2023]
Abstract
To realize the efficient resource utilization of sewage sludge, this work explored the competitive relationship and reaction mechanisms between syngas quality optimization and heavy metals (HMs) immobilization. The results showed that continuous microwave pyrolysis (CMP) technology with an instantaneous temperature increase could shorten the pyrolysis time, and the biogas yield and syngas concentration reached 51.68 wt% and 83.6 vol%, respectively. Although a higher pyrolysis (750 °C) temperature could optimize the syngas quality, the HMs immobilization efficiency was reduced due to the deep pyrolysis of the biochar. The moderate pyrolysis temperature (650 °C) facilitated the rapid formation of biochar with abundant surface functional groups and pore structure, thus enhancing HMs immobilization. Furthermore, the HMs could also form more stable crystalline compounds with inorganic components (SiO2, Al2O3, inorganic sulfur). By optimizing the process parameters, the risk factor of HMs in the sludge decreased from 117.36 to 62.5 while obtaining high-quality syngas. The energy utilization efficiency of microwave pyrolysis also increased significantly from 11.20% to 82.01%. This work provided new insight into the efficient resource utilization and environmentally friendly treatment of sludge, and demonstrated that CMP technology has significant potential for future industrial applications as an alternative to traditional pyrolysis.
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Affiliation(s)
- Junhao Lin
- School of Environment, Harbin Institute of Technology, Harbin 150090, China
| | - Chongwei Cui
- School of Environment, Harbin Institute of Technology, Harbin 150090, China
| | - Shichang Sun
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen 518060, China; Research Center for Water Science and Environmental Engineering, Shenzhen University, 518055, China
| | - Rui Ma
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen 518060, China.
| | - Weichen Yang
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen 518060, China
| | - Yi Chen
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen 518060, China
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Kocbek E, Garcia HA, Hooijmans CM, Mijatović I, Kržišnik D, Humar M, Brdjanovic D. Effects of the sludge physical-chemical properties on its microwave drying performance. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 828:154142. [PMID: 35227715 DOI: 10.1016/j.scitotenv.2022.154142] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Revised: 01/31/2022] [Accepted: 02/21/2022] [Indexed: 06/14/2023]
Abstract
Thermal drying is an effective sludge treatment method for dealing with large volumes of sludge. Microwave (MW) technology has been proposed as an effective and efficient technology for sludge drying. The physical-chemical properties of the sludge depend both on the origin of the sludge, as well as on the treatment process at which the sludge has been exposed. The physical-chemical properties of the sludge affect the performance and the subsequent valorisation and management of the sludge. This study evaluated the effect of certain physical-chemical properties of the sludge (moisture content, organic content, calorific value, porosity, hydrophobicity, and water-sludge molecular interaction, among others) on the MW sludge drying and energy performance. Four different types of sludge were evaluated collected from municipal wastewater treatment plants and septic tanks. The performance of the MW system was assessed by evaluating the sludge drying rates, exposure times, energy efficiencies and power input consumed by the MW system and linking the MW drying performance to the sludge physical-chemical properties. The results confirmed that MW drying substantially extends the constant drying period associated with unbound water evaporation, irrespective of the sludge sample evaluated. However, the duration and intensity were determined to depend on the dielectric properties of the sludge, particularly on the distribution of bound and free water. Sludge samples with a higher amount of free and loosely bound water absorbed and converted MW energy into heat more efficiently than sludge samples with a lower amount of free water. As a result, the sludge drying rates increased and the constant drying rate period prolonged; hence, leading to an increase in MW drying energy efficiency. The availability of free and loosely bound water molecules was favoured when hydrophobic compounds, e.g., oils and fats, were present in the sludge.
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Affiliation(s)
- Eva Kocbek
- Department of Biotechnology, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, the Netherlands; Department of Water Supply, Sanitation and Environmental Engineering, IHE-Delft Institute for Water Education, Westvest 7, 2611 AX Delft, the Netherlands; Tehnobiro d.o.o., Heroja Nandeta 37, 2000 Maribor, Slovenia.
| | - Hector A Garcia
- Department of Water Supply, Sanitation and Environmental Engineering, IHE-Delft Institute for Water Education, Westvest 7, 2611 AX Delft, the Netherlands
| | - Christine M Hooijmans
- Department of Water Supply, Sanitation and Environmental Engineering, IHE-Delft Institute for Water Education, Westvest 7, 2611 AX Delft, the Netherlands
| | - Ivan Mijatović
- Tehnobiro d.o.o., Heroja Nandeta 37, 2000 Maribor, Slovenia
| | - Davor Kržišnik
- Department of Wood Science and Technology, Biotechnical Faculty, University of Ljubljana Jamnikarjeva 101, SI-1000 Ljubljana, Slovenia
| | - Miha Humar
- Department of Wood Science and Technology, Biotechnical Faculty, University of Ljubljana Jamnikarjeva 101, SI-1000 Ljubljana, Slovenia
| | - Damir Brdjanovic
- Department of Biotechnology, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, the Netherlands; Department of Water Supply, Sanitation and Environmental Engineering, IHE-Delft Institute for Water Education, Westvest 7, 2611 AX Delft, the Netherlands
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Lin J, Sun S, Luo J, Cui C, Ma R, Fang L, Liu X. Effects of oxygen vacancy defect on microwave pyrolysis of biomass to produce high-quality syngas and bio-oil: Microwave absorption and in-situ catalytic. WASTE MANAGEMENT (NEW YORK, N.Y.) 2021; 128:200-210. [PMID: 34000690 DOI: 10.1016/j.wasman.2021.05.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 04/20/2021] [Accepted: 05/02/2021] [Indexed: 06/12/2023]
Abstract
This paper proposed to use ferric oxide (Fe2O3) and ferroferric oxide (Fe3O4) as catalysts with both microwave absorption and catalytic properties. Carbon dioxide (CO2) was introduced as the reaction atmosphere to further improve the quality of biofuel produced by microwave pyrolysis of food waste (FW). The results showed the bio-gas yield and the syngas concentration (H2 + CO) increased to 70.34 wt% and 61.50 mol%, respectively, using Fe3O4 as the catalyst. The content of aliphatic hydrocarbons in bio-oil produced with the catalyst Fe2O3 increased to 67.48% and the heating value reached 30.45 MJ/kg. Compared with Fe2O3 catalyst, Fe3O4 exhibited better microwave absorption properties and catalytic properties. Transmission electron microscopy (TEM) and Electron paramagnetic resonance (EPR) characterizations confirmed that the crystal surface of Fe3O4 formed more oxygen vacancy defects and unpaired electrons. Additionally, according to the X-ray photoelectron spectroscopy (XPS) analysis, the content of lattice oxygen in Fe3O4 was 14.11%, a value that was much lower than Fe2O3 (38.54%). The oxygen vacancy defects not only improved the efficient utilization of microwave energy but also provided the reactive sites for the reaction between the volatile organic compounds (VOCs) and CO2 to generate CO. This paper provides a new perspective for selecting catalysts that have both microwave absorption and catalytic properties during the microwave pyrolysis of biomass.
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Affiliation(s)
- Junhao Lin
- School of Environment, Harbin Institute of Technology, Harbin 150090, China
| | - Shichang Sun
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen 518060, China; Research Center for Water Science and Environmental Engineering, Shenzhen University, 518055, China
| | - Juan Luo
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen 518060, China
| | - Chongwei Cui
- School of Environment, Harbin Institute of Technology, Harbin 150090, China.
| | - Rui Ma
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen 518060, China.
| | - Lin Fang
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen 518060, China
| | - Xiangli Liu
- Shenzhen Engineering Laboratory of Aerospace Detection and Imaging, Department of Materials Science and Engineering, Harbin Institute of Technology (Shenzhen), Shenzhen 518055, China
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Zhang C, Ho SH, Chen WH, Eng CF, Wang CT. Simultaneous implementation of sludge dewatering and solid biofuel production by microwave torrefaction. ENVIRONMENTAL RESEARCH 2021; 195:110775. [PMID: 33497681 DOI: 10.1016/j.envres.2021.110775] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Revised: 01/13/2021] [Accepted: 01/18/2021] [Indexed: 06/12/2023]
Abstract
Sludge dewatering is a matter of great concern to reduce the volume of sludge, stabilize its organic components, and achieve resource utilization. This study investigates sludge dewatering by microwave torrefaction along with the production of sludge solid biofuel at 480-800 W combined with durations of 5-25 min. Proximate analysis, calorific value analysis, thermogravimetric analysis, and scanning electron microscopy observations are employed to evaluate the dewatering degree, fuel properties, and energy efficiency of the torrefaction process. The independent parallel reaction (IPR) model and particle swarm optimization (PSO) analysis are also adopted for sludge pyrolysis kinetics calculation. The results show that microwave torrefaction is efficient for sludge dewatering with a short duration. The produced sludge solid biofuel is similar to stone-like coal, and can be used for civil or industrial boilers after flotation or just co-firing with briquette. The ash content of sludge solid biofuel shows a declining trend and the surface characteristics change from smooth to rough and fluffy with increasing the torrefaction severity. The bio-oil is mainly composed of phenols, siloxanes, and cholesterol. In addition, hydrogen is detected in the torgas. Furthermore, it is found that lower torrefaction power with a shorter duration yields a higher energy efficiency of the torrefaction process.
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Affiliation(s)
- Congyu Zhang
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin, China
| | - Shih-Hsin Ho
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin, China.
| | - Wei-Hsin Chen
- Department of Aeronautics and Astronautics, National Cheng Kung University, Tainan, 701, Taiwan; Research Center for Smart Sustainable Circular Economy, Tunghai University, Taichung, 407, Taiwan; Department of Mechanical Engineering, National Chin-Yi University of Technology, Taichung, 411, Taiwan.
| | - Chun Fong Eng
- Department of Aeronautics and Astronautics, National Cheng Kung University, Tainan, 701, Taiwan; International Master Degree Program on Energy, National Cheng Kung University, Tainan, 701, Taiwan
| | - Chin-Tsan Wang
- Department of Mechanical and Electro-Mechanical Engineering, National I-Lan University, I-Lan, 260, Taiwan
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Luo J, Lin J, Ma R, Chen X, Sun S, Zhang P, Liu X. Effect of different ash/organics and C/H/O ratios on characteristics and reaction mechanisms of sludge microwave pyrolysis to generate bio-fuels. WASTE MANAGEMENT (NEW YORK, N.Y.) 2020; 117:188-197. [PMID: 32861081 DOI: 10.1016/j.wasman.2020.08.017] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2020] [Revised: 07/17/2020] [Accepted: 08/11/2020] [Indexed: 06/11/2023]
Abstract
To study the effects of different ash/organics and C/H/O ratios on bio-fuel characteristics and energy efficiency, four kinds of sludge with different properties were used for microwave pyrolysis (800 °C). Moreover, the microwave pyrolysis reaction mechanisms of different sludge were also explored. The results showed that high-ash sludge could accelerate the frequency of polar molecule rotation in the microwave field due to the presence of oxides with dielectric properties in ash, thereby achieving faster heating rates and higher temperatures. However, compared with high-organic sludge, high-ash sludge exhibited lower bio-gas yield and higher bio-char yield. As the H/C ratio increased from 0.127 to 0.148, the bio-gas yield increased from 15.41% to 40.01%, and the content of H2 in bio-gas and aliphatics in bio-oil increased to 36.69 vol% and 26.54 wt%, respectively. When the O/C ratio was reduced to 1.31, the content of CO and oxygenated compound in bio-oil increased to 31.25 vol% and 40.04 wt%, which lowered the quality of the bio-oil. Those consequences also determined that a mixture of sludge with different ash/organic ratios could be pyrolyzed to obtain high-quality bio-fuels and high energy efficiency. Differences in C/H/O ratios in the mixed sludge greatly affected the microwave pyrolysis heating process, which affected the pyrolysis reactions and the quality of the bio-fuels. Therefore, this study provides a theoretical basis to elevate the quality of bio-fuels and reduce microwave pyrolysis costs.
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Affiliation(s)
- Juan Luo
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen 518060, China
| | - Junhao Lin
- School of Environment, Harbin Institute of Technology, Harbin 150090, China
| | - Rui Ma
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen 518060, China
| | - Xing Chen
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen 518060, China
| | - Shichang Sun
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen 518060, China; Research Center for Water Science and Environmental Engineering, Shenzhen University, 518055, China.
| | - Peixin Zhang
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen 518060, China
| | - Xiangli Liu
- Shenzhen Engineering Laboratory of Aerospace Detection and Imaging, Department of Materials Science and Engineering, Harbin Institute of Technology (Shenzhen), Shenzhen 518055, China
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