HTC Process Research Articles

The effect of an acidic environment during the hydrothermal carbonization of sewage sludge on solid and liquid products: The fate of heavy metals, phosphorus and other compounds

The pH of sewage sludge is a crucial factor during the hydrothermal carbonization process that influences the characteristics of the resulting products and migration of certain compounds from the solid to liquid phase. Accordingly, this work is focused on examining the pH impact during the HTC process, in particular, pH equals 2, 3, 4, 5 and 6 on the individual hydrothermally carbonized products generated at 200 °C and 2 h residence time. For this reason, the chemical and physical indicators describing the post-processing liquid and hydrochar were determined. For instance, it was observed that the phosphorus content detected in the liquid, derived at pH2, rose significantly by 80%. Furthermore, decreasing the pH of sewage sludge had a significant impact on the ash content and the calorific value of the hydrochar. Additionally, changes in the specific surface area of hydrochar were noticed: pH = 5 and pH = 6 showed an increase of 20–30%, while for lower pH values a decrease of c.a. 26% was achieved. The distribution of heavy metals between the obtained fractions in the HTC process (solid and liquid) indicated that 92 to almost 100% of the tested heavy metals were transferred to the hydrochar. A significant effect of pH on the distribution between these fractions was observed only for Zn and Ni. For instance, for pH = 2, Zn and Ni in post-processing liquid were 34% and 29%, respectively. In addition, the sequential extraction of heavy metals from hydrochar was also performed in order to identify mobile and non-mobile phases. It was noticed that the acidic environment favours a higher amount of mobile heavy metals in hydrochar. The largest effect was observed for Cd, Pb, Cr and Cu, for which, at pH = 2, their respective amounts in the mobile fraction were 2.7; 3.6; 1.8; 6.2 times higher, compared to the hydrochar without pH correction.

Hydrochar production through co-hydrothermal carbonization of water hyacinth and plastic waste

Abstract The global expansion of the economy and concerns about greenhouse gas emissions and climate change necessitate the exploration of sustainable alternatives to fossil fuels. Water hyacinth (WH) is globally recognized as one of the most problematic aquatic weeds, posing significant challenges to urban management by clogging waterways, polluting water sources, and causing harm to ecosystems. However, water hyacinth is enriched with hemicellulose, cellulose, and lignin, making it a noteworthy and superior biomass resource. Hence, this study focuses on the hydrothermal carbonization of water hyacinth into a renewable fuel source, the hydrochar. Hydrothermal treatment was implemented in this work as it can treat wet biomass, in this case, the water hyacinth, without the need of energy-extensive drying process. Plastic waste (PW), or more specifically low-density polyethylene (LDPE), was added as the co-feedstock during the HTC process with the purpose to boost the higher heating value (HHV) of the end product. The co-hydrothermal carbonization (co-HTC) process of the mixture of WH and PW at various ratios and temperatures were conducted to investigate the optimal HTC condition for high hydrochar yields. As the result, the highest hydrochar yield of 29.23 wt% was obtained with 12.5% LDPE substitution percentage, at 200 °C after a holding time of 90 min. However, in term of energy recovery efficiency (ER), the highest efficiency (27.28%) was achieved with 12.5% LDPE substitution percentage at 260 °C. The HHV value of the hydrochar produced in this work is in the range of 17.71-24.69 MJ/kg. In summary, the co-HTC of WH and LDPE could definitely be a promising alternative to bridge the gap from solid waste to renewable fuels.

Kinetic and combustion characteristics of oil palm empty fruit bunch biochar using thermogravimetric analysis

The usage of renewable energy is a mitigation phenomenon majorly impacting the power sectors, with biomass being one of the sources directly replacing coal in various applications. This leads to the portrayal of biomass having the potential to be a carbonaceous material, namely the Empty Fruit Bunch (EFB) of oil palm. To increase the characteristics of EFB, it can be converted into carbon-based products through thermochemical processes, such as hydrothermal carbonization. Therefore, this study aimed to compare the characteristics of feedstock and biochar EFB using the TGA method. The heating rate used in this study is 10 – 30°C/min at five °C/min intervals. The effect of heating rate on kinetic parameters and thermal (DTG, TGA) and combustion (T ignition, T burn out) characteristics was also determined. This study carried out the HTC process at temperatures of 210ᵒC and 230ᵒC. The results showed that biochar EFB had a higher ignition, burnout temperature, and activation energy than raw EFB. Ignition temperatures for EFB-HT210°C and EFB-HT230°C were 297°C and 298°C; burnout temperatures for EFB-HT210°C, EFB-HT230°C were 407°C and 450°C; and the activation energy for EFB-HT210°C, EFB-HT230°C were 58.84 kJ/mol and 62.16 kJ/mol. Besides the characteristics of biomass, the heating rate also affects combustion. This proved that increased heating rate caused higher ignition and burnout temperature and decreased activation energy. The results also indicated that the difference in heating rate influenced the peak temperature in DTG.

Effect of hydrothermal carbon on biogas production from agricultural waste by anaerobic fermentation

In this study, biogas residue was used as raw material to prepare biogas residue by hydrothermal carbonization at 190℃ with different treatment time. The effects of hydrothermal carbon addition on gas production characteristics during medium temperature anaerobic fermentation (straw, straw + chicken manure, chicken manure) were studied, and the differences of surface formation of biogas residue hydrothermal carbon were observed by SEM. The results showed that the duration of gas generation peak was prolonged in the straw + chicken manure fermentation group and the chicken manure fermentation group after adding biogas residue hydrothermal charcoal, and the total gas production in the 8h, 12h and 24h hydrothermal charcoal groups increased more (P < 0.05), and the total gas production increased 39.2% at most. There was no significant difference in cumulative gas production among groups in straw fermentation group. According to the actual production, the optimal HTC process for anaerobic fermentation is 8 h at 190℃.

Revealing roles of CO2 and N2 in pressurized hydrothermal carbonization process for enhancing energy recovery and carbon sequestration

In this study, CO2– and N2-pressurized hydrothermal carbonization processes were investigated to understand the catalytic effects of CO2 on hydrochar production and its quality (e.g., surface properties, energy recovery, and combustion behaviour). Both CO2– and N2-pressurized HTC processes could enhance the energy recovery (from 61.5% to 63.0–67.8%) in hydrochar by enhancing the dehydration reactions. Nonetheless, the two systems exhibited contrasting trends in volatile release, oxygen removal, and combustion performance as a function of increasing pressure. High N2 pressure enhanced deoxygenation reaction, facilitating the release of volatiles and increasing the hydrochar aromaticity and combustion activation energy (172.7 kJ/mol for HC/5N). Without the contribution of CO2, excessively high pressure may cause an adverse impact on the fuel performance owing to higher oxidation resistance. This study presents an important and feasible strategy to utilise CO2-rich flue gas in the HTC process to produce high-quality hydrochar for renewable energy and carbon recovery.

Fabricating Porous Carbon Materials by One-Step Hydrothermal Carbonization of Glucose

The present study concerned the production of glucose-based porous carbon materials by a one-step acid-catalyzed HTC. The samples were characterized by elemental analysis (EA), scanning electron microscope (SEM), Brunauer–Emmett–Teller (BET), Fourier transform infrared (FTIR) and point of zero charge (pzc). Experimental results showed that the addition of sulfuric acid (SA) with different dosages in the HTC system could improve the yield of products and reduce chemical oxygen demand (COD) of the process water. When the glucose and acid was at a mass ratio of 1:4 (glucose: SA = 1:4), the hydrochar obtained (H-G9) had a larger specific surface area (SBET = 296.71 m2/g) and higher abundance of functional groups on the surface than that of other samples, such as sulfur-containing functional groups and carboxylic groups, belonged to the mesoporous material with highly negatively surface charged. H-G9 exhibited the optimum adsorption for methylene blue (MB). H-G9 adsorbed MB with an initial concentration of 10 mg/L at pH 6 and 25 °C. The adsorption isotherm of MB on H-G9 demonstrated that Freundlich isotherm could be better applied. Regeneration efficiency of 88% was achieved by HTC process for saturated H-G9. This study prepared a porous carbon material by the simple one-step hydrothermal carbonization of glucose in the presence of SA. The maximum monolayer adsorption capacity as high as 332.46 mg/g for MB, which was well beyond that of commercial activated carbon (259.37 mg/g). This indicates that H-G9 has great potential for the removal of MB from wastewater.

Artificial Coalification of Orange Peel for Extraction of Value Added Chemicals

Waste to value added products is the aim of circular economy. Typical waste to value processes such as composting, briquetting, digestion are time consuming and gasification, and pyrolysis only produces energy. In the present research, a thermochemical process called as hydrothermal carbonization process is used to convert the organic wet waste to useful products. The HTC process converts the organic wet waste into coal like high carbon content material called hydrochar and the liquid component called as biocrude. The biocrude is a mixture of chemicals such as 5-HMF, Levulinic acid, Furfural and other chemicals used in pharmaceutical and cosmetic industry. Orange peel waste is processed in a HTC reactor in temperatures ranging between 180 to 220 o C, with the autogenous pressure. The calorific value of hydrochar produced is measured using bomb calorimeter, and is found to have enhancement over the feedstock. The biocrude is analysed using UV spectrometer and gas chromatography and mass spectroscopy to identify the components present. Compounds including anti-fungal, and anti-bacterial molecules are identified and reported.

Coal Discards and Sewage Sludge Derived-Hydrochar for HIV Antiretroviral Pollutant Removal from Wastewater and Spent Adsorption Residue Evaluation for Sustainable Carbon Management

The effects of various parameter interactions on the textural structure of hydrochars produced via hydrothermal (HTC) and co-hydrothermal (Co-HTC) treatments of coal discards and sewage sludge (wastes), as well as the subsequent use of the hydrochars (HCs) synthesized for HIV drug (nevirapine and lamivudine) removal from wastewater, were investigated in this study. The HTC and Co-HTC process improved the carbon content of the raw material by 13.47%, 7.08%, and 30.65% for hydrochar coal tailing (HCT), hydrochar coal slurry (HCS), and hydrochar from coal–sewage blend (HCB), respectively. The Co-HTC-derived HCB had a high SBET of 20.35 m2/g and pore volume of 0.38 cm3/g, leading to significant adsorptive reductions of nevirapine (NEV) and lamivudine (LAM) (97.19% and 93.32%, respectively). HCT and HCS displayed high NEV and LAM adsorption capacities (50 mg g−1, 42 mg g−1 and 52 mg g−1, 41 mg g−1), respectively, despite being less effective than HCB (53.8 mg g−1, 42.8 mg g−1). In addition, the use of spent adsorption residues for energy storage applications was investigated further. The findings showed that spent adsorption residues are an effective carbonaceous material precursor to produce electrical double-layer capacitors (EDLCs).

Adsorption characteristics of lead, copper, cadmium, methylene blue, phenol, and toluene in water using composite synthesized from titanium dioxides and carbon spheres through hydrothermal method

Titanium nanotubes (TNT) are commonly synthesized from TiO2 P25 under hydrothermal reaction (HTR) using 10 M NaOH). Composite adsorbents derived from TiO2 and carbon spheres (CS) were synthesized via a facile two-stage HTR process. CS was firstly synthesized from glucose through HTR. The mixture (CS, TiO2, and NaOH) was then transferred to a Teflon-lined autoclave for another HTC process to generate TNT/CS. The TNT/CS composite was calcined from 300 to 800 °C to evaluate the changes in its surface properties (functional group, morphology, and external charge), textural parameters, crystallinity, cation exchange capacity, and adsorption capacity. Results indicated that the Brunauer–Emmett–Teller surface area and total pore volume of composites were 25.0–131.9 m2/g and 0.099–0.33 cm3/g, respectively. The composites exhibited a negatively charged surface within pH 4.0–9.0, with their zeta potentials at pH 5.0 ranging from −54.60 to −31.1 mV. The result of X-ray photoelectron spectroscopy demonstrated that the main components (%atomic) in the composites were carbon (29.07%–60.75%), oxygen (29.09%–49.16%), titanium (2.93%–17.52%), and sodium (0.56%–9.48%). During the preparation of TNT/CS, CS (its negatively charged surface) can well absorb Na+ ions in the mixture. This phenomenon prevented the performance of tubular morphology in TNT/CS. The synthesized composites were regarded as multifunctional adsorbents for adsorbing various contaminants (Pb2+, Cd2+, Cu2+, cationic methylene blue dye, phenol, and toluene) in water. Equilibrium adsorption at pH 5.0 was carried out to estimate their adsorption capacities toward the selected contaminants. The Langmuir maximum adsorption capacities of Pb, Cd, Cu, methylene blue, phenol, and toluene were 534, 518, 514, 690, 329, 138 mg/g for TNT/CS and 334–523, 384–477, 297–453, 394–677, 303–416, 118–260 mg/g for the calcinated TNT/CS composites, and 26.3, 23.8, 21.4, 285, 239, 188 mg/g for commercial activated carbon, respectively. The adsorption mechanisms were elucidated based on the adsorption experiments and surface characteristics of TNT/CS. Ion exchange was the primary adsorption mechanism for the test cationic contaminants. The van der Waals force was an important adsorption mechanism for phenol and toluene. The developed TNT/CS composite can be employed as an effective adsorbent for adsorbing cationic and non-ionic contaminants in aqueous solutions.

Production of Hydrochars from Lignocellulosic Biomass with and without Boric Acid

AbstractHydrothermal carbonization (HTC) is an important thermochemical process where biomass is converted into coal‐like solid products known as hydrochars. The HTC process is performed in hot‐compressed water under self‐generated pressures. In this work, the HTC of acorn shells was conducted at various temperatures and reaction times with and without boric acid (H3BO3). A high degree of carbonization occurred at 250 °C in non‐catalytic and catalytic 4‐h runs. Hydrochars obtained from non‐catalytic and catalytic runs at 250 °C consisted of spherically carbon particles with diameters ranging from 303 nm to 3.27 μm. Carbon spheres at 200 and 225 °C for 2 h were not observed. The yield and carbon content of the hydrochars were slightly increased by reuse of the process water in thermal runs without catalysts.

Effect of co-hydrothermal carbonization of sugarcane bagasse and polyvinyl chloride on co-production of furfural and solid fuel

The co-production was investigated of furfural and solid fuel using co-hydrothermal carbonization (co-HTC) of sugarcane bagasse (BG) and polyvinyl chloride (PVC) compared with hydrothermal carbonization of sugarcane bagasse alone. The HTC process was studied in the temperature range 180–240 °C and furfural production was studied for reaction times of 20, 40 and 60 min. The residence time for hydrocharproduct was 60 min. The results indicated that the highest furfural yield was achieved at about 88 % of the theoretical pentosan available from sugarcane bagasse at 240 °C and 60 min for the hydrothermal carbonization of sugarcane bagasse alone. The inclusion of PVC with the sugarcane bagasse during the HTC led to decreased furfural formation. The solid fuel characterization results showed that hydrochar derived from both mixing BG and PVC and from BG alone improved the fuel properties.

Process analysis and kinetic modeling of coconut shell hydrothermal carbonization

Hydrothermal carbonization is a promising renewable technology to produce high quality solid biofuel with characters of sterilization, micronization, and homogeneous. In this work, coconut shell was used as feedstock to investigate the products distribution, reaction kinetics and the migration of potassium during HTC process. Experiments were carried out in 180–240 °C with residence time of 0–5 h. The results showed that the content of fixed carbon increased from 20.76 wt% to 49.80 wt%, and HHV increased from 20.75 MJ/kg to 31.77 MJ/kg at 240 °C with the holding time of 3 h. The ratio of H/C dropped from 1.78 to 0.86 and O/C dropped from 0.68 to 0.16 which all indicated the improvement of fuel performance. The effects of increasing temperature and prolonging residence time on the products were in the same direction but different in severity. The properties of the products changed little after the residence time was more than 1 h. In addition, chemical fractionation method was used to investigate migration behavior of potassium. The best removal temperature of potassium was 200 °C which decreased potassium concentration from 2.7 mg/g to 0.6 mg/g specifically. Due to the increase of specific surface and porosity caused by high temperature, the content of potassium rose slightly at 220 and 240 °C. A kinetic model was adopted to predict the products distribution and yield of solid phase and gas phase. The activation energies (Ea) of different reaction paths were calculated and the results showed that Ea of gas formation is greater than that of solid. Migration behavior of potassium and modeling of HTC process is of great significance for design, optimization of industrial HTC reactor and selecting the best time for discharging and feeding to achieve better performance.

Co-hydrothermal carbonization of sewage sludge and coal slime with sulfuric acid for N, S doped hydrochar

In this study, co-hydrothermal carbonization (co-HTC) of sewage sludge(SS) and coal slime(CS) was studied for preparation of N, S doped hydrochar. The effect of blending ratios and temperature was also investigated. The results showed that there existed a synergistic effect during co-HTC, especially at the ratio of 7:3. Compared with the calculated values, the experimental values of the fixed carbon content increased by 51.00%, the carbon content increased by 21.73%, the mass yield increased by 13.52% and the carbon retention increased by 42.34%; while the H/C and O/C decreased by 32.20% and 31.97%, respectively. Furthermore, Raman spectrum and XPS analysis indicated that adding CS could promote the aromatization degree. XPS and FTIR analysis showed that the sulfuric acid could affect the occurrence mode of sulfur and nitrogen and led to abundant oxygen-containing functional groups such as –SO, O–CO and –OH on the hydrochar surface during the HTC process. This study could provide a theoretical basis for the utilization of SS and CS, and also provide a novel method for the preparation of N, S doped hydrochar.

Hydrochar and hydrochar co-compost from OFMSW digestate for soil application: 2. agro-environmental properties

The work concerns the study of the hydrochar from digestate and hydrochar co-compost characterization as amendments. The processes for hydrochar and co-compost production were described in Part 1 of this work (Scrinzi et al., 2022). The amendment properties of hydrochar (produced at 180–200–220 °C for 3 h) and co-composts (25%, 50%, and 75% hydrochar percentage of digestate substitution) were assessed by phytotoxicity, plant growth bioassay, and soil effect. Different seeds species (Lepidium sativum, Cucumis sativus, and Sorghum bicolor sp.) were dosed at increased concentrations using both wet raw amendments and their water extracts. The chemical characterization showed phytotoxic compounds content depending on both the initial feedstock (digestate) and the HTC process; at the same time, the analysis highlighted the reduction of these compounds by composting (organic acid, polyphenols, salt concentration). The dose-response was analyzed by the Cedergreen-Streibig-Ritz model and the half-maximal effective concentration (EC50) was calculated based on this equation. The soil properties and GHG emissions measurements (CH4, CO2, N2O, and NH3) highlighted the effect on N dynamics and on soil respiration induced by substrates. The HC200 soil application determined a significant impact on CO2 and N2O emission and NH3 volatilization (10.82 mol CO2/m2; 51.45 mmol N2O/m2; 112 mol NH3/m2) and a significant reduction of total N and TOC (46% of TKN and 49% of TOC). The co-compost (75%) showed specific effects after soil application compared to other samples an increase of available P (48%), a greater content of nitrogen (1626 mg/kg dry basis), and a reduction of organic carbon (17%). Our results demonstrate the good quality of co-compost and at the same time the validity of this post-treatment for addressing many issues related to hydrochar use in the soil as an amendment, confirming the suitability of HTC process integration for digestate treatment in anaerobic digestion plants.

Synergistic effects of process-generated organic acids during co-hydrothermal carbonization of watermelon peel and high-sulfur coal

Substandard fuel properties and high sulfur levels remained bottlenecks for the utilization of biomass and low-grade coal for energy generation. This work systematically studied the synergistic effects of co-hydrothermal carbonization (co-HTC) of watermelon peel (WP) and high-sulfur coal using process-derived organic acids. Fuel properties, desulfurization efficiency, and combustion behaviors of co-HTC derived hydrochars and fuel blends of WP hydrochar and coal prepared by the typical post-hydrothermal carbonization (HTC) blending technique were compared. The physical and chemical compositions of WP/coal hydrochars were investigated to evaluate their corresponding fuel properties. In addition, flame characteristics were studied via single pellet combustion, while the chemical compositions of residual HTC process water were examined by gas-chromatography mass spectroscopy. Note-worthily, the co-HTC derived hydrochars were characterized by higher heating values in the range of 27.3–28.8 MJ/kg and fuel ratios of 2.67–6.95. HC-3:7, HC-5:5 and HC-7:3 showed higher desulfurization efficiencies (57.9–77.7%) compared to the post-HTC blending method (8.5–33.5%). Moreover, the co-HTC derived hydrochars exhibited lower post-combustion ash contents (8.8–12.0%) compared to CC-3:7 (17.3%), CC-5:5 (17.9%) and CC-7:3 (10.5%). Remarkably, HC-5:5 demonstrated the strongest synergistic effect of 70%. The flame observation results indicated that co-HTC derived hydrochars exhibited more stable combustion flames than the post-treatment blended samples. Hence, co-HTC provides a low-cost and eco-friendly approach for converting WP and high-sulfur coal into cleaner solid fuel.

Valorization of winery and distillery by-products by hydrothermal carbonization

This work aims at finding an alternative strategy to manage the waste generated by the winemaking industry to obtain a solid biofuel and phenolic compounds. The effect of temperature (180–260 °C), residence time (1–7 h), and biomass-to-liquid ratio (0.05–0.25) on the co-hydrothermal carbonization of vine pruning and exhausted grape pomace, by using vinasse as moisture source, is studied. The effect of the variables is investigated and optimized using the Box–Behnken design of response surface methodology to maximize mass yield, fuel ratio, energy densification yield and phenols extraction yield and to minimize energy consumption. The statistical analysis shows that the carbonization temperature is a crucial parameter of the process, decreasing the product yield on one hand and improving the quality of hydrochar on the other. At the optimal conditions (246.3 °C, 1.6 h, 0.066), an hydrochar yield of 52.64% and a calorific value of 24.1 MJ/kg were obtained. Moreover, the analysis of the H/C and O/C ratios of hydrochars demonstrates that carbonisation significantly improves the fuel properties of solid biofuel. Liquid by-products obtained from the HTC process are found to contain high concentrations of organic matter but the BOD/COD ratios suggest their potential valorization by biological methods.

Nanosilver Immobilized in Carbonaceous Particles Derived from Hydrothermal Carbonization of Eleusine indica Leaf Extract

In this study, for the first time, hydrothermal treatment of Eleusine indica leaf extract and silver nitrate produced nanosilver immobilized in hydrothermal carbon synthesized at different reaction times (RT) - 6, 12, 24 and 48 h. The surface morphology of nanosilver hydrochar (AgNP@hydrochar) composites was studied using SEM, while their chemical functionalities were investigated using FT-IR, UV-Vis, XRF and EDX spectroscopy. The AgNP@hydrochar were observed to be agglomerated spherical particles with size ranges from 128 to 171 nm. Varying C=O and C=C IR absorption peaks at different RT suggested that the plant extract reduced Ag+ into Ag0 in solution. Elemental analysis using EDX showed that Ag is dominant in the composite (84.07 %) supported by the Ag spatial distribution as demonstrated by the EDX elemental mapping.
 HIGHLIGHTS
 
 For the first time, hydrothermal treatment of Eleusine indica leaf extract with silver nitrate resulted in nanosilver trapped in hydrothermal carbon
 HTC process of E. indica extract produced composite having agglomerated spherical particles
 EDX elemental mapping showed an abundant silver in the synthesized composite
 
 GRAPHICAL ABSTRACT

Upgrading the fuel properties of hydrochar by co-hydrothermal carbonisation of dairy manure and Japanese larch (Larix kaempferi): product characterisation, thermal behaviour, kinetics and thermodynamic properties

This study investigated co-hydrothermal carbonisation (co-HTC) of dairy manure (DM) and wood shavings from Larix kaempferi, commonly known as the Japanese larch (JL) to enhance the fuel properties of the resulting hydrochar. The JL was mixed with the DM at 25, 50 and 75 wt.% ratios. Co-HTC was conducted at 260 °C for 20 min. The resulting hydrochars were characterised based on the physicochemical properties and the thermal behaviour. Results showed that the hydrochar solid biofuel properties improved as the ratio of JL was increased. The produced hydrochars were in the region of lignite and closed to the region of the coal with increased fixed carbon, carbon contents and lowered H/C and O/C ratios. Hydrochar with ash content of 7.2 ± 0.5% was obtained at 75 wt.% JL. In addition, the HHV of hydrochar increased remarkably to 26.4 ± 0.02 MJ/kg as the mass ratio of the JL was increased. The surface morphology of the hydrochars were altered and became distinct while the specific surface area (SSA) and the total pore volume (TPV) of the hydrochars increased at increasing the mass ratio of the JL. The surface functional groups were also altered by the co-HTC process. A decline in the combustion performance was observed after the HTC process but improved at 75 wt.% JL after the co-HTC process. The kinetic analysis also revealed that the activation energy decreased after the HTC process but increased to a higher value at 50 wt.% JL after the co-HTC process. Therefore, hydrochar production by co-HTC of DM and JL has proved to be an effective and promising solid biofuel source.Graphical abstract

Heat recovery from hydrothermal carbonization slurry product by coupling processes of flash and organic Rankine cycle: Thermodynamic analysis

AbstractHydrothermal carbonization (HTC) is a promising and effective technology for upgrading the fuel quality of high‐moisture organic wastes. However, a large amount of energy is required to heat the feedstock to high temperature for HTC. Therefore, the maximum waste heat should be recovered to increase the energy efficiency of the HTC process. In this work, a flash‐organic Rankine cycle (FSPG‐ORC) system was coupled after HTC to recover the heat contained in the HTC slurry product. Various operating factors including the flashing temperature, the HTC temperature, the solid‐water ratio (S/W) of the feedstock, and the organic working fluids in the ORC section were studied to obtain their influences on thermodynamic performance of the coupled system. Results indicated that the net power (Wnet) of the FSPG‐ORC system increased from 185.64 to 774.30 kW through the increase of the HTC temperature from 160 to 280°C. In addition, the Wnet and exergy efficiency of the FSPG‐ORC system also increased with increasing the flashing temperature of HTC slurry product. The coupled FSPG‐ORC system converted waste heat to electric energy and increased the energy efficiency of the HTC process.

Proposal of a Pilot Plant (2T/day) for Solid Fuel Conversion of Cambodian Mango Waste Using Hybrid Hydrothermal Carbonization Technology

하이브리드수열탄화 (Hybrid HTC) ê¸°ìˆ ì€ 2가지 이상의 ìœ ê¸°ì„±íê¸°ë¬¼ì„ 혼합한 특허 받은 열역학 ê³µì •ìœ¼ë¡œ ê³µì •ì˜¨ë„ 180~250oC, ì••ë ¥ 20~40 bar에서 반응시간이 2시간 이내이며 에너지 소비가 ì ê³ , 폐기물의 부피감소 및 ì• ì·¨ ì €ê°íš¨ê³¼ê°€ 크다. 폐기물 중 대부분의 탄소가 ìµœì¢ ìƒì„±ë¬¼ì— ì¶•ì ë˜ë¯€ë¡œ ìœ ê¸°ì„± 폐기물 ê³ í˜•ì—°ë£Œí™”ì— 가장 ì í•©í•œ ê¸°ìˆ ë¡œ í‰ê°€ë°›ê³ ìžˆë‹¤. 본 연구에서는 하이브리드 ìˆ˜ì—´íƒ„í™”ê¸°ìˆ ì„ 활용하여 캄보디아 ë§ê³ íê¸°ë¬¼ì„ 대상으로 온도 및 반응시간의 변화에 따라 발열량 및 수율 등에 미치는 영향에 대하여 평가하였다. 본 연구를 통해 ê³µì •ë³€ìˆ˜ë¥¼ ìµœì í™”í•˜ê³ , ì „ ê³µì •í”ŒëžœíŠ¸ì˜ 에너지 효율성을 향상시킬 수 있으며, ìˆ˜ì—°íƒ„í™”ê¸°ìˆ ì—ì„œ 분해되어 가스가 생성되는데 이때 수소(H2) 및 메탄(CH4) 등 ì œì¡° 및 ìƒì‚°ê¸°ìˆ ê°œë°œì„ í• ìˆ˜ 있다. 본 연구 결과를 í† ëŒ€ë¡œ ë§ê³ íê¸°ë¬¼(2t/day)실증 물질수지 및 에너지 수지 도출과 함께 ê²½ì œì„±ë„ 평가하였다. Hybrid hydrothermal carbonization (Hybrid HTC) technology is a proprietary thermochemical process for two or more organic wastes.The reaction time is less than two hours with temperature range 180~250℃ and pressure range 20~40bar. Thanks to accumulation of the carbon of the waste during Hybrid HTC process, the energy value of the solid fuel increases significantly with comparatively low energy consumption. It has also a great volume reduction with odor removal effect so that it is evaluated as the best solid fuel conversion technology for various organic wastes. In this study of the hybrid hydrothermal carbonization, the effect on the calorific value and yield of Cambodian mango waste were evaluated according to changes in temperature and reaction time. Through the study, parameter optimization has been sought with improving energy efficiency of the whole plant. It is decomposed in the Hydro-Carbonation Technology to Generate Gas. At this time, it is possible to develop manufacturing and production technologies such as hydrogen (H2) and methane (CH4). Based on the results of the study, a pilot plant (2t/day) has been proposed for future commercialization purpose along cost analysis, mass balance and energy balance calculations. Keywords: Hybrid Hydrothermal Carbonization, Cambodia Mango Waste, Pilot Plant, Bio-SRF, Energy Saving, Reduction