(Luận văn thạc sĩ) co hydrothermal carbonization of sludges and kitchen waste for energy and resource recovery

VIETNAM NATIONAL UNIVERSITY, HA NOI VIETNAM JAPAN UNIVERSITY TRUONG QUOC DAI CO-HYDROTHERMAL CARBONNIZATION h OF SLUDGE AND KITCHEN WASTE FOR ENERGY AND RESOURCE RECOVERY MASTER’S THESIS VIETNAM NATIONAL UNIVERSITY, HA NOI VIETNAM JAPAN UNIVERSITY TRUONG QUOC DAI CO-HYDROTHERMAL CARBONNIZATION OF SLUDGE AND KITCHEN WASTE FOR ENERGY AND RESOURCE RECOVERY h MAJOR: ENVIRONMENTAL ENGINEERING CODE: 8520320.01 RESEARCH SUPERVISORS: Associate Prof Dr CAO THE HA Dr NGUYEN THI AN HANG Hanoi, 2022 COMMITMENT I have read and understood the plagiarism violations I pledge with personal honor that this research result is my own and does not violate the Regulation on prevention of plagiarism in academic and scientific research activities at VNU Vietnam Japan University (Issued together with Decision No 700/QD-ĐHVN dated 30/9/2021 by the Rector of Vietnam Japan University) Author of thesis Truong Quoc Dai h ACKNOWLEDGMENTS This research would not have been possible without the direction, support, and patience of several people, with whom I have had the pleasure of interacting and learning over the past years Firstly, I'd want to convey my sincere gratitude to Assoc Prof Cao The Ha and Dr Nguyen Thi An Hang for their passionate instruction and encouragement during my thesis implementation at VNU Vietnam Japan University (VNU-VJU) Secondly, I'd like to take this occasion to acknowledge all of the professors, lecturers, and students at the Master’s Program in Environmental Engineering for their support and inspiration during my study at VNU-VJU, which is greatly appreciated Thirdly, I am grateful to the financial support from the research project [QG.22.26] of Vietnam National University, Hanoi Finally, my special thanks go to my friends Huong, Duc and Trang for their assistance h and encouragement throughout this lengthy process TABLE OF CONTENTS h COMMITMENT ACKNOWLEDGMENTS TABLE OF CONTENT LIST OF TABLES i LIST OF FIGURES ii LIST OF ABBREVIATIONS iv CHAPTER 1: INTRODUCTION 1.1 Research background 1.2 Research significance 1.3 Research objective 1.4 Thesis structure CHAPTER 2: LITERATURE REVIEW 2.1 Municipals solid waste in the world and in Vietnam 2.1.1 Environmental concerns and potential use of sludge 2.1.2 Environmental issues and potential use of kitchen waste 12 2.1.3 Municipal solid waste treatment technologies 14 2.2 Technologies for energy and nutrient recovery from sludge and kitchen waste 20 2.2.1 Hydrothermal carbonization (HTC) 20 2.2.2 Anaerobic digestion (AD) 27 2.2.3 Combination of AD and HTC 28 2.2.4 Crystallization of MAP (struvite) 31 CHAPTER 3: MATERIALS AND METHODS 34 3.1 Materials 34 3.1.1 Sewage Sludge 34 3.1.2 Kitchen waste 34 3.2 Experiment setup 36 3.2.1 Co-hydrothermal carbonization of sewage sludge and kitchen waste 36 3.2.2 Determination of composition and energy properties of raw materials and synthesized hydrochars 37 3.2.3 Crystallization and characterization of MAP from HTC process water 37 3.3 Measurement and calculation methods 39 3.3.1 Moisture removal 39 3.3.2 Volatile matter 39 3.3.3 Ash content 40 3.3.4 Fixed Carbon 41 h 3.3.5 High Heating Value (HHV) 41 3.3.6 Energy densification 42 3.3.7 Hydrochar yield 42 3.3.8 Energy recovery 42 3.4 Environmental parameter analysis 42 3.4.1 pH 42 3.4.2 Total Nitrogen 42 3.4.3 Total Phosphorus 44 3.4.4 Chemical Oxygen Demand (COD) 45 3.4.5 Ammonia 45 3.4.6 Phosphorus 47 3.5 Statical data analysis 48 CHAPTER 4: RESULTS AND DISCUSSION 49 4.1 Energy potential of hydrochar 49 4.1.1 Characteristics of hydrochar 49 4.1.2 Energy potential of hydrochar 52 4.2 Nutrient recovery from HTC process water 54 4.2.1 Characteristics of HTC process water 54 4.2.2 MAP crystallization 58 4.3 Economic feasibility study of energy and nutrient recovery – a case study 65 4.3.1 Energy recovery 68 4.3.2 Nutrient recovery 71 4.3.3 Technical economic analysis (TEC) 74 CHAPTER 5: CONCLUSION AND RECOMMENDATION 82 5.1 Conclusion 82 5.2 Recommendation 83 REFERENCES 84 APPENDIX A 91 LIST OF TABLES Table 2.1:The total number of domestic wastewater treatment facilities and the estimated sewage sludge generation in the different provinces of Vietnam (The World Bank, 2018) .8 Table 2.2: Vietnam's policies of building a sustainable lifestyle 10 Table 2.3: Composition of solid waste components in Vietnam (% weight) (Ministry of natural resources & environment, 2019) .13 Table 2.4: The pros and cons of the existing technologies for solid (Kaza & Bhada-Tata, 2018) 15 Table 2.5: Waste-to-Energy Recovery Methods (Oladejo et al., 2019) .18 Table 2.6: A summary of the literature on HTC 23 h Table 2.7: A summary of the literature on HTC process water 26 Table 2.8: AD's energy recovery and GHG reduction potential (Tyagi et al., 2018) 28 Table 2.9: Optimum pH for MAP crystallization from HTC process water 32 Table 4.1: Conditions and results of the experiment 60 Table 4.2: Concentration of nutrients in HTC process water before and after Kjeldahl conversion 61 Table 4.3: Conditions and results of the experiment 63 Table 4.4: Conditions and results of the experiment 64 Table 4.5: Mass flow rates entering the HTC plant 66 Table 4.6:Capital cost estimate of bare-module equipment for the HTC plant 69 Table 4.7: Total capital investment for HTC plan 69 Table 4.8: UASB tank operating parameters 70 Table 4.9: Capital cost of UASB (steel carbon) 70 Table 4.10: Capital cost of struvite production 71 Table 4.11: quantity and price of chemicals for each scenario 72 Table 4.12: The annual economic evaluation of the process 72 Table 4.13: Mass balance of co-HTC 2h with SS 3KW .74 i LIST OF FIGURES Figure 2.1: Reduce, reuse, and recycle hierarchy (Oyenuga, 2015) Figure 2.2: Sewage sludge recovery routes in Europe in 2017 (Gillman 2019) Figure 2.3: Untreated sludge discharged into the environment Figure 2.4: Mechanisms of anaerobic digestion process (Al Mamun, 2015) 27 Figure 2.5: Module for zero waste disposal by using AD and HTC 30 Figure 2.6: SEM image of MAP recovered from desorption solution at the optimal condition (Nguyen 2015) .33 Figure 3.1: Samples of sludge before and after moisture content 34 Figure 3.2: (a) My Dinh dormitory and (b) Sampling place 35 Figure 3.3: Collecting and sorting kitchen waste 36 h Figure 3.4: Hydrothermal carbonization reactor with Teflon inner compartment and stainless-steel outer cover 36 Figure 3.5: Furnace (CWF 12/13, Carbolite, England) 37 Figure 3.6: Jar test equipment (JT-M6C, Daihan, Korea) for MAP crystallization .38 Figure 3.7: Experiment to MAP crystallization 38 Figure 3.8: The bomb calorimeter (6200 Isoperibol, Parr, USA) 41 Figure 3.9: UV-vis spectrophotometer S2150UV 43 Figure 3.10: Calibration curve for TN determination 43 Figure 3.11: Calibration curve for TP determination 44 Figure 3.12: Calibration curve for determination of COD 45 Figure 3.13: Calibration curve for determination of N-NH3 46 Figure 3.14: Calibration curve for determination of P-PO4 48 Figure 4.1: Raw materials for HTC process 49 Figure 4.2: Hydrochars with different mass ratios of feed materials (a) Sewage sludge (1:0), (b) sewage sludge + kitchen waste (3:1), (c) sewage sludge + kitchen waste (1:1), (d) sewage sludge + kitchen waste (1:3), and (e) kitchen waste (0:1) 49 Figure 4.3: The percentage of volatile matter in the feed materials and hydrochars 50 Figure 4.4: The percentage of ash in the feed materials and hydrochars .50 Figure 4.5: The percentage of fixed carbon in the feed materials and hydrochars 51 Figure 4.6: Effects of mixing ratio and HTC time on HHV values of the feed materials and hydrochars .51 Figure 4.7: Effects of mixing ratio and HTC time on the mass yield of hydrochars 53 Figure 4.8: Effects of mixing ratio and HTC time on the energy density of hydrochars .53 ii Figure 4.9: Effects of mixing ratio and HTC time on the energy yield of hydrochars 53 Figure 4.10: Effects of mixing ratio and HTC time on the pH concentration in the HTC process water 54 Figure 4.11: Effects of mixing ratio and HTC time on the COD concentration in the HTC process water 55 Figure 4.12: Effects of mixing ratio and HTC time on the TN concentration in the HTC process water 56 Figure 4.13: Effects of mixing ratio and HTC time on the TP concentration in the HTC process water 56 Figure 4.14: SEM (JSM-IT100, JEOL, Korea) 58 Figure 4.15: Image of the precipitate obtained from experiment 59 Figure 4.16: SEM images of MAP recovered from experiment .59 Figure 4.17: Kjendahl digestion unit (DK6, Velp, EU) .61 Figure 4.18: Image of the precipitate obtained from experiment 62 Figure 4.19: SEM images of MAP recovered from experiment .62 Figure 4.20: The image of the precipitate obtained from the experiment 64 Figure 4.21: The SEM image of the precipitate obtained from the experiment 64 Figure 4.22: Schematic flow sheet of the HTC plant 67 h Figure 4.23: Mass and energy balance of SS and KW at 2000C thermal treatment 75 iii LIST OF ABBREVIATIONS Anaerobic Digestion American Society for Testing and Materials Chemical Oxygen Demand Direct cost Dry Matter Electrical Conductivity Energy, waste and food Food and Agriculture Organization Fixed Carbon Hydrochar Higher Heating Value Hydrothermal Carbonization Greenhouse gas Kitchen waste Magnesium ammonium phosphate Municipal solid waste Million tonnes of oil equivalent National Council for Air and Stream Improvement Organic fraction municipal solid waste Pinewood saw dust Primary sewage sludge Scanning Electron Microscope Standard Methods for the Examination of Water and Waste Water Sewage sludge Total capital investment Total depreciable capital Technical economic analysis Total Nitrogen Total Phosphorus Urban Environment Limited Company United States Environmental Protection Agency Volatile Matter Vietnam Television Waste mixed Waste to Energy Wastewater treatment plants h AD: ASTM: COD: DC: DM: EC: EWF: FAO: FC: HC: HHV: HTC: GHG: KW: MAP: MSW: MTOE: NCASI: OFMSW: PS: PSS: SEM: SMEWW: SS: TCI: TDC: TEC: TN: TP: URENCO: US EPA: VM: VTV: WM: WtE: WWTPs: iv h Figure 4.23: Mass and energy balance of SS and KW at 2000C thermal treatment 75 The COD concentration after the AD stage was 69% of the entire starting concentration, indicating that the majority of the COD may be degraded by energy production, such as biogas or hydrochar combustion Due to its high nutritional content, the residual liquid waste may either be utilized for irrigation or recycled into the thermal treatment if extra liquid is necessary for co-processing sewage sludge with another biomass Because KW samples mostly include vegetation, they absorb nitrogen and phosphate from waste water The majority of the nitrogen dissolved during heat treatment was in the form of ammonium (NH4+), which could be utilized to precipitate struvite Previous research has shown that the proteins in sewage sludge hydrolyze during heat treatment, releasing ammonium into the process fluids (Aragón-Brico et al., 2021) The majority of the phosphorous, on the other hand, remained in the solid fraction The phosphorus after the HTC process increased from to 0.97 kg in process water showed organic phosphorus molecules (complex phospholipids, DNA, and phosphate monoesters) break down into phosphate during the heat process, phosphorus is solubilized (Aragón-Brico et al., 2021) From Figure 4.22, providing the amount of h MgO to raise the pH to can save chemical costs compared to NaOH and MgCl 2, and showed the great potential struvite production with 5.5 per tonne of sludge treated respectively CHP unit is used to provide both thermal and electrical energy from AD technical A CHP plant consists primarily of an electrical generator and equipment for collecting and using the heat generated by the generator A prime mover, such as a gas turbine or a reciprocating engine, may be used as the generator It might also be a steam turbine that generates electricity from high-pressure steam generated in a boiler CHP systems may achieve efficiencies of over 60%, which indicates that at least 40% of the heat produced by burning fuel is lost, and frequently much more, compared to 50% for traditional systems, by collecting and using heat that would otherwise be wasted and limiting distribution losses (e.g., conventional electricity generation and an on-site boiler) (Breeze, 2018) Assuming the energy capture efficiency of CHP is 40-50%, it’s recover 479.6 kWhel/h and 539.5 kWhth/h According to Circular 32/2015/TT-BCT dated 8-1080 2015 of the Ministry of Industry and Trade, surplus power may be sold for $0.091/kWh as an incentive for comprehensive waste treatment: Energy of electrical consumption for HTC plant each hour: 368𝑘𝑤ℎ𝑒𝑙 /𝑑 24ℎ + 16.2kwhel/h = 31.53 kWhe/h Energy of electrical production from HTC plant: 479.6 kWhe/h Net energy gained: 479.6 – 31.53 = 448.07 kWhe/h Profits from selling energy by day: 448.07 kWhe/h × $0.091/kWh × 24h = $978/day So can profit from this HTC-AD activity When biogas generation is the sole energy source in the suggested systems, the net energy output decreases dramatically when hydrochar is introduced as an energetic source As a result, including hydrochar as a fuel source inside the system is critical in order to make it more self-sustaining Regardless of the quality of the hydrochar samples, h including the energy produced by hydrochars as a low-grade fuel improves the net energy output in each scenario The HTC of sewage sludge combined with AD resulted in a good overall energy recovery (1025.5 MJ per tonne treated), with hydrochar accounting for 47 % of the potential energy recovered 81 CHAPTER 5: CONCLUSION AND RECOMMENDATION 5.1 Conclusion This study investigates the effects of the SS:KW mixing ratio and HRT reaction time on the energy and nutrient properties of the hydrochar and co-HTC process water In addition, the potential of nutrient recovery from the co-HTC process water was examined at the lab-scale Finally, the techno-economic feasibility of a case study on energy and nutrient recovery from SS and KW using a hybrid HTC-AD-MAP recovery process for a city of 100,000 people was evaluated It was found that the HHV values of the synthesized hydrochars were increased with the decline in the SS:KW mixing ratios The highest HHV value (17 MJ/kg) was obtained with the SS:KW mixing ratio of 1:3, indicating the key role of KW in enhancing HHV values of co-substrate derived hydrochars The extension of the HTC reaction time from to 4h led to a slight increment in the HHV value (2-3 MJ/kg) h The SS:KW mixing ratio of 1:3 resulted in the highest nutrient concentrations in the coHTC process water The longer HTC reaction time led to the decline in nutrient concentrations of the co-HTC process water, owing to the formation of secondary char and adsorption of nutrients on the generated hydrochar The optimal conditions for nutrient recovery from co-HTC process water at the lab-scale were the Mg: NH4: PO4 molar ratio of 1:1:1; addition of suspension MgO, and pH of The maximum N and P recovery efficiencies were 49% and 91%, respectively The integrated HTC-AD process resulted in a reduction in COD concentration in the effluent up to 69% Moreover, it produced a positive energy balance in all scenarios, with a maximum net energy output of 1025 kWhth and 479,6 kWhel per ton of treated sludge if the hydrochar is employed as a fuel source As long as the struvite (MAP) production line becomes a part of this integrated system, it may generate a revenue of up to $45,000/year 82 5.2 Recommendation Due to the adverse impacts of COVID-19 pandemic, during my thesis implementation, the access to MEE lab was occasionally restricted Consequently, this research could not be fulfilled with further investigations e.g., low heating value (LHV), elementary analysis, etc It is expected that future work can address these limitations In an attempt to improve the energy properties of hydrochar and nutrient recovery efficiency from co-HTC process water, more research should be done on the process optimization that consider various influential factors (e.g., feed materials, reaction time, temperature, mixing ratio, etc.) This study studied the nutrient recovery from co-HTC process water at the lab-scale and evaluated techno-economic feasibility of a proposed, large-scale, integrated AD-HTCMAP crystallization process for energy and nutrient recovery, which was based on the inputs from various studies, which may be different in the scale and application conditions Therefore, additional study on a pilot-scale hybrid system, which integrates h HTC, UASB and MAP production in one system, is needed in the future 83 REFERENCES h Ahammad, S Z., & Sreekrishnan, T R, 2016 Chapter 20 - Energy from Wastewater Treatment In M N V Prasad (Ed.), Bioremediation and Bioeconomy (pp 523-536): Elsevier Al-Rumaihi, A., McKay, G., Mackey, H R., & Al-Ansari, T, 2020 Environmental Impact Assessment of Food Waste Management Using Two Composting Techniques Sustainability, 12(4), 1595 Retrieved from 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5th edition: YH = 0.08 g VSS/g COD bH = 0.03 g VSS/g VSS×d, fd =0.10 g VSS cell debris/g VSS biomass decay Methane production at 0°C = 0.35 L CH4/g COD Energy content of methane at 0°C = 39,700 kJ/m3 Percent methane in gas phase = 65% Height of reactor process volume = 8.5 m Height of clear zone above the sludge blanket = 0.50 m Height of gas-solids separator 2.5 m Reactor length:width ratio = 2.0 10 Maximum reactor upflow velocity = 1.0 m/h 11 Average solids concentration in process volume = 180 kg VSS/m3 (180,000g VSS/m3) 12 Heat-transfer coefficient of carbon steel: Dry earth embanked for entire depth, U = 0.91 W/m2.oC Floor of digester in moist earth, U = 2.85 W/m2.oC Carbon Steel Roof exposed to air, U = 0.91 W/m2.oC 13 Temperatures: Air 25 oC Incoming sludge = 35 oC Earth below floor = 15°C Process water contents in digester = 35 oC 14 Specific heat of process water = 4200 J/kg.oC Solution 1) Determine the reactor proc volume a) Use the max upflow velocity A = Q/v, and Vv = H(A) 91 Cross section A (m2): 𝐴= 𝑄 = 𝑣 3000𝑚3 /𝑑 (1𝑚/ℎ)(24ℎ/3) =125 m2 Reactor volume, Vv (m3): Vv = A(H) = 125 × 8.5 = 1062.5 m3 b) Use the organic loading rate (m3) 𝑉𝑂𝐿𝑅 = 𝑄𝑆0 𝑂𝐿𝑅 = 3000𝑚3 /𝑑×51kgCOD 10𝑘𝑔 𝑚3 /𝑑 =15300 kg COD/m3/d 2) Determine the process HRT (d) V/Q = 15300𝑚3 3000 𝑚3 /𝑑 = 5.1𝑑 h 3) Determine the reactor dimensions a) Total reactor height HT = process hgt + clear zone hgt + separator list hgt =11.5 m b) Reactor area = 2πr×(r+hgt) Area (m2) = V/H = 1800 m2 Number of tanks: (The option to use stainless steel metal is considered expensive when the reactor built in large scale) Area each tank: 600m2  R= 6.4 m 4) Determine the reactor SRT a) From equation (1): X(V) = Px(SRT) b) From equation (2), c) Substituting Eq (2) into Eq (1), (S0 – S) = 0.7S0 = 0.7(51000 g COD/m3) = 35,700 g COD/m3 (30,000 g VSS/m3)(15,300 m3) = (3000 𝑚3 𝑉𝑆𝑆 35700𝑔𝐶𝑂𝐷 )( )(𝑆𝑅𝑇)[1+0.1(0.03𝑔/𝑔×𝑑)(𝑆𝑅𝑇)] )(0.05 𝑑 𝑔𝐶𝑂𝐷 𝑚3 1+(0.03𝑔/𝑔×𝑑)(𝑆𝑅𝑇 𝑚3 + (3000gVSS/m3)( 3000 )SRT 𝑑  SRT = 86.3 d 5) Determine the daily sludge production rate 𝑋 (𝑉) (30,000 𝑔𝑉𝑆𝑆/𝑚3 )(15300𝑚3 )(1𝑘𝑔/103 𝑔) 𝑃𝑋,𝑉𝑆𝑆 = 𝑉𝑆𝑆 = = 3191.1 kgVSS/d 𝑆𝑅𝑇 86.3 𝑑 6) Determine the excess sludge daily waste volume PX,VSS = QXe + XQw 31911.9 kgVSS/d−(3000𝑚3 /𝑑)(120𝑔𝑉𝑆𝑆/𝑚3 ) 180,000 g VSS/m3 = 175.289 m3/d 7) Determine the CH4 gas production rate by COD balance a) COD removal = methane COD + biomass COD 92 b) PX,bio = PX,VSS - nbVSS(Q) PX,bio = 3,191×1000g VSS/d - 3000 g VSS/m3(3000 m3/d) = 2,291,100 gVSS/d c) from a): Methane COD = COD removed - biomass COD CH4 COD/d = 3000m3/d(35,700g COD/m3) - (1.42g COD/g VSS)( 2,291,100 g VSS/d) = 7,456,505 gCH4COD/d d) At standard conditions, methane production rate at oC = (7,456,505 g CH4 COD/d)(0.35 L CH4/g COD)(l m3/103 L) = 2,609 m3 CH4/d (273+35)°C e) Methane production rate at 35°C = (2,609 m3 CH4/d) × 273°C = 2,942 m3 CH4/d 8) The total gas production rate; Percent CH4 = 65% = 0.65 Total gas production = 2,942 𝑚3 CH4 /d 0.65𝑚3 CH4 /𝑚3 gas = 4,529 m3 biogas/d 9) Energy content of methane production Energy = (39700 kJ/m3)(45,295 m3 CH4/d) = 1,036,081.400kJ/d = 287,800kWh/d (1 kWh = 3.6 MJ = 3600 kJ) 10) Compute the heat requirement for the sludge q = (114,000 kg/d)[(35 - 35)°C](4200 J/kg.°C) = J/d 11) Compute the area of the walls, roof, and floor Wall area = (6.4) (8.5) = 171 m2 h Floor area = (11.5) [11.52 + (11.5 – 8.5)2]1/2 = 429 m2 Roof area = (11.52) = 415 m2 12) Compute the heat loss by conduction using q= UA T a) Walls: q = 0.91 W/m2.°C (171m2)(35 - 25°C)(86,400 s/d) = 1.34*108 J/d b) Floor: q = 2,85; W/m2-°C (429 m2)(35 - 15°C)(86,400 s/d) = 12.12*108 J/d c) Roof: q = 0.91 W/m2.°C (415 m2)[35 -25°C](86,400 s/d) = 3.26*108 J/d d) Total losses: q t = (1.34+ 12.12 + 3.26) *108 J/d = 16.72*108 J/d 13) Compute the required heat-exchanger capacity Capacity = heat required for sludge and heat required for:digester = (0 + 16.72)*108 J/d = 16.72*108 J/d = 456 kWhth 93