Influence of hydrothermal carbonized sewage sludge on coal water slurry performance
Asma Leghari1,2, Yao Xiao1,2, Lu Ding1,2(), Hammad Sadiq3, Abdul Raheem4, Guangsuo Yu1,2,5()
. Institute of Clean Coal Technology, East China University of Science and Technology, Shanghai 200237, China . Engineering Research Center of Resource Utilization of Carbon-containing Waste with Carbon Neutrality, Ministry of Education, Shanghai 200237, China . School of Mechanical and Power Engineering, East China University of Science and Technology, Shanghai 200237, China . Energy and Bioproducts Research Institute (EBRI), Aston University, Birmingham, B4 7ET, UK . State Key Laboratory of High-Efficiency Utilization of Coal and Green Chemical Engineering, Ningxia University, Yinchuan 750021, China
Coal utilization, as a major energy source, raises sustainability concerns and environmental impacts, prompting researchers to explore blending it with other feedstocks. This study discusses hydrochar coal-water slurry (HC-CWS) preparation conditions, emphasizing apparent viscosity and exploring the influence of high ash content on char reactivity. The study highlights that the presence of free water in sludge is moderately influential, while high amounts of free water in raw sewage sludge (SS) and its near absence during hydrothermal carbonization (HTC) of SS are both unfavorable for enhancing the overall performance of coal-water slurry (CWS). HTC reduces the concentration of hydroxyl functional group, enhancing slurry performance and reducing ash content in HC-CWS, indicating that coal complements hydrochar (HC). High-temperature HC preparation is unsuitable for HC-CWS due to increased viscosity and decreased stability. In terms of ash content, the optimal pH and HC ratio for CWS are determined at 30% HC. The gasification reactivity of HC, prepared at 180 °C with a 30% HC ratio in CWS at R0.5 is 6 × 10−3 and at R0.9 is 9 × 10−3. However, increasing HC to 50% diminishes reactivity under CO2 atmosphere. The inhibitory effect was observed with an increasing percentage of HC in CWS and the synergy factor decreased in the following order: 10% HC > 30% HC > 50% HC, i.e., from 1.04 to 0.35. The possible reason is the presence of high ash content and their similar initial gasification rates during its early stages.
Fig.1 Particle size of (a) raw SS and SH coal and (b) HC prepared at 180 °C at 30, 60, and 90 min.
Sample
Ultimate analysis/(wt %, d)
Proximate analysis/(wt %, d)
N
C
H
S
O
Ashd
VMd
FCd
SH coal
0.93
77.22
4.550
0.590
9.320
6.890
32.91
60.20
HC 180-30
1.58
20.54
2.461
0.353
9.116
65.95
27.24
6.81
HC 180-60
1.57
19.80
2.101
0.384
12.315
63.83
28.98
7.66
HC 180-90
1.56
19.61
2.025
0.424
12.951
63.43
30.80
9.37
Tab.1 Proximate and ultimate analysis of HCa)
Sample
SiO2
Al2O3
Fe2O3
P2O5
CaO
K2O
MgO
TiO2
SO3
Na2O
HC 180-30
47.59
18.11
13.02
12.90
2.42
1.68
1.69
0.984
0.772
0.580
HC 180-60
47.21
18.19
13.32
12.70
2.42
1.67
1.67
0.984
0.750
0.605
HC 180-90
47.03
18.09
13.33
13.23
2.35
1.65
1.62
0.985
0.648
0.559
Tab.2 Ash composition of HC
Fig.2 SEM images of HC prepared at different operating conditions: (a) raw SS, (b) 180 °C-30 min, (c) 180 °C-60 min, (d) 180 °C-90 min, (e) 200 °C-30 min, (f) 200 °C-60 min, (g) 200 °C-90 min, (h) 220 °C-30 min, (i) 220 °C-60 min, (j) 220 °C-90 min, (k) 240 °C-30 min, (l) 240 °C-60 min, and (m) 240 °C-90 min.
Fig.3 FTIR spectra of (a) raw SS and SH coal, (b) 180 °C at 30, 60 and 90 min, and (c–e) HC-CWS (30%) against different time at the same temperature.
Sample
SH coal
Raw SS
HC (180 °C-30 min)
HC (180 °C-60 min)
HC (180 °C-90 min)
Specific surface area/(m2·g–1)
4.5648
2.0645
19.1363
19.1399
22.2268
Adsorption average pore size/nm
7.3623
18.7025
16.5532
15.6029
14.1106
Desorption average pore size/nm
8.6057
24.0405
24.5947
22.5801
20.0721
Pore volume/(cm3·g–1)
0.008402
0.009653
0.079192
0.074660
0.078408
Tab.3 Specific surface area, pore size and pore volume of raw SS, HC and SH coal
Sample
Maximum contact angle/(° )
Minimum contact angle/(° )
HC 180 °C-30 min
89.51
49.07
HC 180 °C-60 min
89.17
56.97
HC 180 °C-90 min
87.11
56.90
SH coal
85.45
33.55
Tab.4 Contact angle measurements of HC and SH coal
Fig.4 Apparent viscosities of HC-CWS (a) at different ratios of 180 °C and 30 min HC, (b) at different ratios of 180 °C and 60 min HC, and (c) at different ratios of 180 °C and 90 min HC.
Samples
HC-CWS
Ash (air db)/%
VM
FC
pH
HC
10%
30%
50%
10%
30%
50%
10%
30%
50%
10%
30%
50%
180 °C-30 min
12.20
23.61
36.19
27.50
30.61
29.09
57.90
45.59
32.55
6.37
6.12
5.89
180 °C-60 min
11.76
23.91
34.09
29.90
30.80
29.50
56.97
45.48
36.59
6.20
5.96
5.79
180 °C-90 min
12.29
24.13
33.05
30.21
31.36
31.26
58.21
44.51
37.55
6.94
5.96
5.62
Tab.5 Proximate analysis of HC-CWS with different proportions of HC
Fig.5 (a) TGA and (b) DTG of HC at 180 °C at different holding times.
Fig.6 Carbon conversion curves against gasification time (min).
Sample
R0.5/min–1
R0.9/min–1
Initial gasification rate
Raw SS
3.508 × 10?2
2.230 × 10?2
0.018
SH coal
1.224 × 10?2
1.910 × 10?2
0.039
180-30
2.890 × 10?2
2.250 × 10?2
0.010
180-30-10%
1.233 × 10?2
1.937 × 10?2
0.016
180-30-30%
1.257 × 10?2
1.929 × 10?2
0.014
180-30-50%
6.527 × 10?3
9.950 × 10?3
0.014
Tab.6 Initial gasification rate and reactivity index at R0.5 and R0.9
Fig.7 Carbon conversion curves X against gasification reactivity (min–1) of (a) raw SS and SH coal, (b) 180 °C, 30, 60 and 90 min, (c) different ratios of HC-CWS and (d) synergy index A of HC-CWS.
1
C Numviyimana , J Warchoł , N Khalaf , J J Leahy , K Chojnacka . Phosphorus recovery as struvite from hydrothermal carbonization liquor of chemically produced dairy sludge by extraction and precipitation. Journal of Environmental Chemical Engineering, 2022, 10(1): 106947 https://doi.org/10.1016/j.jece.2021.106947
2
X Yang , B Wang , X Song , F Yang , F Cheng . Co-hydrothermal carbonization of sewage sludge and coal slime with sulfuric acid for N, S doped hydrochar. Journal of Cleaner Production, 2022, 354: 131615 https://doi.org/10.1016/j.jclepro.2022.131615
3
A Mosqueda , K Medrano , H Gonzales , K Yoshikawa . Effect of hydrothermal and washing treatment of banana leaves on co-gasification reactivity with coal. Energy Procedia, 2019, 158: 785–791 https://doi.org/10.1016/j.egypro.2019.01.207
4
H Zhu , Z Yang , Y Yao , X Ju , D Wang , Y Liu , Y Zhang , A Zhou . Preparation of the modified sludge-semi-coke water slurry and analysis of its slurring performance and mechanism. Powder Technology, 2023, 413: 118039 https://doi.org/10.1016/j.powtec.2022.118039
5
L Wang , Y Chang , A Li . Hydrothermal carbonization for energy-efficient processing of sewage sludge: a review. Renewable & Sustainable Energy Reviews, 2019, 108: 423–440 https://doi.org/10.1016/j.rser.2019.04.011
6
M Hu , H Hu , Z Ye , S Tan , K Yin , Z Chen , D Guo , H Rong , J Wang , Z Pan . et al.. A review on turning sewage sludge to value-added energy and materials via thermochemical conversion towards carbon neutrality. Journal of Cleaner Production, 2022, 379: 134657 https://doi.org/10.1016/j.jclepro.2022.134657
7
C Peng , Y Zhai , Y Zhu , B Xu , T Wang , C Li , G Zeng . Production of char from sewage sludge employing hydrothermal carbonization: char properties, combustion behavior and thermal characteristics. Fuel, 2016, 176: 110–118 https://doi.org/10.1016/j.fuel.2016.02.068
8
X Chen , C Wang , Z Wang , H Zhao , H Liu . Preparation of high concentration coal water slurry of lignite based on surface modification using the second fluid and the second particle. Fuel, 2019, 242: 788–793 https://doi.org/10.1016/j.fuel.2019.01.007
9
Y Zhang , Z Xu , Y Tu , J Wang , J Li . Study on properties of coal-sludge-slurry prepared by sludge from coal chemical industry. Powder Technology, 2020, 366: 552–559 https://doi.org/10.1016/j.powtec.2020.03.005
10
R Chu , Y Li , X Meng , L Fan , G Wu , X Li , X Jiang , S Yu , Y Hu . Research on the slurrying performance of coal and alkali-modified sludge. Fuel, 2021, 294: 120548 https://doi.org/10.1016/j.fuel.2021.120548
11
X Jiang , Y Zhou , X Meng , G Wu , Z Miao , F Sun , E Xu . The effect of inorganic salt modification of sludge on the performance of sludge-coal water slurry. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2023, 664: 131146 https://doi.org/10.1016/j.colsurfa.2023.131146
12
W Li , W Li , H Liu , Z Yu . Influence of sewage sludge on the slurryability of coal-water slurry. Fuel, 2009, 88(11): 2241–2246 https://doi.org/10.1016/j.fuel.2009.05.002
13
M Liu , Y Duan , K Bikane , L Zhao . Effect of waste liquid produced from the hydrothermal treatment of both low-rank coal and sludge on the slurryability of coal sludge slurry. Fuel, 2017, 203: 1–10 https://doi.org/10.1016/j.fuel.2017.04.091
14
M K Singh , D Ratha , S Kumar , D Kumar . Influence of particle-size distribution and temperature on rheological behavior of coal slurry. International Journal of Coal Preparation and Utilization, 2016, 36(1): 44–54 https://doi.org/10.1080/19392699.2015.1049265
15
D Li , J Liu , S Wang , J Cheng . Study on coal water slurries prepared from coal chemical wastewater and their industrial application. Applied Energy, 2020, 268: 114976 https://doi.org/10.1016/j.apenergy.2020.114976
16
K Sjöström , G Chen , Q Yu , C Brage , C Rosén . Promoted reactivity of char in co-gasification of biomass and coal: synergies in the thermochemical process. Fuel, 1999, 78(10): 1189–1194 https://doi.org/10.1016/S0016-2361(99)00032-0
17
K Wojtacha-Rychter , N Howaniec , A Smoliński . Investigation of co-gasification characteristics of coal with wood biomass and rubber seals in a fixed bed gasifier. Renewable Energy, 2023, 20: 119725
18
N Howaniec , A Smoliński . Biowaste utilization in the process of co-gasification with bituminous coal and lignite. Energy, 2017, 118: 18–23 https://doi.org/10.1016/j.energy.2016.12.021
19
S Guo , D Xu , X Guo , X Li , C Zhao . Multi-response optimization of sewage sludge-derived hydrochar production and its CO2-assisted gasification performance. Journal of Environmental Chemical Engineering, 2022, 10(1): 107036 https://doi.org/10.1016/j.jece.2021.107036
20
C Gai , M Chen , T Liu , N Peng , Z Liu . Gasification characteristics of hydrochar and pyrochar derived from sewage sludge. Energy, 2016, 113: 957–965 https://doi.org/10.1016/j.energy.2016.07.129
21
X Zheng , W Chen , Z Ying , J Huang , S Ji , B Wang . Thermodynamic investigation on gasification performance of sewage sludge-derived hydrochar: effect of hydrothermal carbonization. International Journal of Hydrogen Energy, 2019, 44(21): 10374–10383 https://doi.org/10.1016/j.ijhydene.2019.02.200
22
S Chen , Z Sun , Q Zhang , J Hu , W Xiang . Steam gasification of sewage sludge with CaO as CO2 sorbent for hydrogen-rich syngas production. Biomass and Bioenergy, 2017, 107: 52–62 https://doi.org/10.1016/j.biombioe.2017.09.009
23
S Khan , K Elkadi , I Janajreh . Investigation of the co-gasification behavior of Kentucky coal and palm woody biomass. Procedia Computer Science, 2023, 224: 314–321 https://doi.org/10.1016/j.procs.2023.09.042
24
J Zdeb , N Howaniec , A Smoliński . Utilization of carbon dioxide in coal gasification—an experimental study. Energies, 2019, 12(1): 140 https://doi.org/10.3390/en12010140
25
A Smoliński , N Howaniec , A Bąk . Utilization of energy crops and sewage sludge in the process of co-gasification for sustainable hydrogen production. Energies, 2018, 11(4): 809 https://doi.org/10.3390/en11040809
26
C Lin , W Zuo , S Yuan , P Zhao , H Zhou . EEffect of moisture on gasification of hydrochar derived from real-MSW. Biomass and Bioenergy, 2023, 178: 106976 https://doi.org/10.1016/j.biombioe.2023.106976
27
M M Yu , M S Masnadi , J R Grace , X T Bi , C J Lim , Y Li . Co-gasification of biosolids with biomass: thermogravimetric analysis and pilot scale study in a bubbling fluidized bed reactor. Bioresource Technology, 2015, 175: 51–58 https://doi.org/10.1016/j.biortech.2014.10.045
28
J Liu , J Wang , C Chen , Y Chen , X Zheng . Preparing coal slurry from organic wastewater to achieve resource utilization: slurrying performance and dispersant suitability. Fuel, 2023, 339: 126970 https://doi.org/10.1016/j.fuel.2022.126970
29
M Cavali , H Benbelkacem , B Kim , R Bayard , N Libardi Junior , D Gonzaga Domingos , A L Woiciechowski , A B Castilhos . Co-hydrothermal carbonization of pine residual sawdust and non-dewatered sewage sludge-effect of reaction conditions on hydrochar characteristics. Journal of Environmental Management, 2023, 340: 117994 https://doi.org/10.1016/j.jenvman.2023.117994
30
P Saetea , N Tippayawong . Recovery of value-added products from hydrothermal carbonization of sewage sludge. International Scholarly Research Notices, 2013, 1: 268947
31
X Yang , B Wang , Y Guo , F Yang , F Cheng . Insights into the structure evolution of sewage sludge during hydrothermal carbonization under different temperatures. Journal of Analytical and Applied Pyrolysis, 2023, 169: 105839 https://doi.org/10.1016/j.jaap.2022.105839
32
M Malhotra , A Garg . Hydrothermal carbonization of sewage sludge: optimization of operating conditions using design of experiment approach and evaluation of resource recovery potential. Journal of Environmental Chemical Engineering, 2023, 11(2): 109507 https://doi.org/10.1016/j.jece.2023.109507
33
M Malhotra , A Garg . Hydrothermal carbonization of centrifuged sewage sludge: determination of resource recovery from liquid fraction and thermal behaviour of hydrochar. Waste Management, 2020, 117: 114–123 https://doi.org/10.1016/j.wasman.2020.07.026
34
Y Tan , X Ma , Z Xu , B Zhang , S M Osman , R Luque . Insights into acid-base properties of hydrotalcite materials during hydrothermal carbonization of sewage sludge. Journal of the Energy Institute, 2023, 110: 101349 https://doi.org/10.1016/j.joei.2023.101349
35
W Zhang , Y He , Y Wang , G Li , J Chen , Y Zhu . Comprehensive investigation on the gasification reactivity of pyrolysis residue derived from Ca-rich petrochemical sludge: roles of microstructure characteristics and calcium evolution. Energy Conversion and Management, 2022, 253: 115150 https://doi.org/10.1016/j.enconman.2021.115150
36
C He , A Giannis , J Y Wang . Conversion of sewage sludge to clean solid fuel using hydrothermal carbonization: hydrochar fuel characteristics and combustion behavior. Applied Energy, 2013, 111: 257–266 https://doi.org/10.1016/j.apenergy.2013.04.084
37
W Huang , R Zhang , A Giannis , C Li , C He . Sequential hydrothermal carbonization and CO2 gasification of sewage sludge for improved syngas production with mitigated emissions of NOx precursors. Chemical Engineering Journal, 2023, 454: 140239 https://doi.org/10.1016/j.cej.2022.140239
38
A Petrovič , Predikaka T Cenčič , L Škodič , S Vohl , L Čuček . Hydrothermal co-carbonization of sewage sludge and whey: enhancement of product properties and potential application in agriculture. Fuel, 2023, 350: 128807 https://doi.org/10.1016/j.fuel.2023.128807
39
W Liang , G Wang , K Jiao , X Ning , J Zhang , X Guo , J Li , C Wang . Conversion mechanism and gasification kinetics of biomass char during hydrothermal carbonization. Renewable Energy, 2021, 173: 318–328 https://doi.org/10.1016/j.renene.2021.03.123
40
A Raheem , L Ding , Q He , F Hussain Mangi , Z Hussain Khand , M Sajid , A Ryzhkov , G Yu . Effective pretreatment of corn straw biomass using hydrothermal carbonization for co-gasification with coal: response surface Methodology-Box Behnken design. Fuel, 2022, 324: 124544 https://doi.org/10.1016/j.fuel.2022.124544
41
J Moon , T Y Mun , W Yang , U Lee , J Hwang , E Jang , C Choi . Effects of hydrothermal treatment of sewage sludge on pyrolysis and steam gasification. Energy Conversion and Management, 2015, 103: 401–407 https://doi.org/10.1016/j.enconman.2015.06.058
42
X Zhang , M Ma , Y Bai , W Su , X Song , P Lv , J Wang , G Yu . Torrefaction of sludge under CO2 atmosphere to improve the fuel properties for high temperature gasification with coal. Thermochimica Acta, 2022, 713: 179249 https://doi.org/10.1016/j.tca.2022.179249
43
J Wei , Y Gong , Q Guo , X Chen , L Ding , G Yu . A mechanism investigation of synergy behaviour variations during blended char co-gasification of biomass and different rank coals. Renewable Energy, 2019, 131: 597–605 https://doi.org/10.1016/j.renene.2018.07.075
44
M Ma , J Wang , X Song , W Su , Y Bai , G Yu . Co-gasification of cow manure and bituminous coal: a study on reactivity, synergistic effect, and char structure evolution. ACS Omega, 2020, 5(27): 16779–16788 https://doi.org/10.1021/acsomega.0c01785
45
H Yang , H Song , C Zhao , J Hu , S Li , H Chen . Catalytic gasification reactivity and mechanism of petroleum coke at high temperature. Fuel, 2021, 293: 120469 https://doi.org/10.1016/j.fuel.2021.120469
46
W Huo , Z Zhou , X Chen , Z Dai , G Yu . Study on CO2 gasification reactivity and physical characteristics of biomass, petroleum coke and coal chars. Bioresource Technology, 2014, 159: 143–149 https://doi.org/10.1016/j.biortech.2014.02.117
47
L Ding , Y Zhang , Z Wang , J Huang , Y Fang . Interaction and its induced inhibiting or synergistic effects during co-gasification of coal char and biomass char. Bioresource Technology, 2014, 173: 11–20 https://doi.org/10.1016/j.biortech.2014.09.007
48
V Satyam Naidu , P Aghalayam , S Jayanti . Synergetic and inhibition effects in carbon dioxide gasification of blends of coals and biomass fuels of Indian origin. Bioresource Technology, 2016, 209: 157–165 https://doi.org/10.1016/j.biortech.2016.02.137
49
Y Zhang , Y Zheng , M Yang , Y Song . Effect of fuel origin on synergy during co-gasification of biomass and coal in CO2. Bioresource Technology, 2016, 200: 789–794 https://doi.org/10.1016/j.biortech.2015.10.076
50
N Howaniec , A Smoliński . Influence of fuel blend ash components on steam co-gasification of coal and biomass—chemometric study. Energy, 2014, 78: 814–825 https://doi.org/10.1016/j.energy.2014.10.076
51
Z Zhang , L Zhang , Y Liu , M Lv , P You , X Wang , H Zhou , J Wang . Co-gasification synergistic characteristics of sewage sludge and high-sodium coal. ACS Omega, 2023, 8(7): 6571–6583 https://doi.org/10.1021/acsomega.2c06962
52
A Mosqueda , J Wei , K Medrano , H Gonzales , L Ding , G Yu , K Yoshikawa . Co-gasification reactivity and synergy of banana residue hydrochar and anthracite coal blends. Applied Energy, 2019, 250: 92–97 https://doi.org/10.1016/j.apenergy.2019.05.008
