Effect Of Hydrothermal Carbonization Research Articles

Preparation of Supercapacitor Carbon Electrode Materials by Low-Temperature Carbonization of High-Nitrogen-Doped Raw Materials from Food Waste.

To address the problem of the low nitrogen (N) content of carbon materials prepared through the direct carbonization of food waste, soybean meal and egg whites with high N contents were selected to carry out carbonization experiments on food waste. At 220 °C, the effects of hydrothermal carbonization and microwave carbonization on the properties of supercapacitor electrode materials were investigated. The results show that food waste doped with soybean meal and egg whites could achieve good N doping. At a current density of 1 A·g-1, the specific capacitance of the doped carbon prepared by hydrothermal doping is as high as 220.00 F·g-1, which is much greater than that of the raw material prepared through the hydrothermal carbonization of food waste alone, indicating that the hydrothermal carbonization reactions of soybean meal, egg white, and food waste promote the electrochemical properties of the prepared carbon materials well. However, when a variety of raw materials are mixed for pyrolysis carbonization, different raw materials cannot be fully mixed in the pyrolysis process, and under the etching action of potassium hydroxide, severe local etching and local nonetching occur, resulting in a severe increase in the pore size distribution and deterioration of the electrochemical performance of the prepared carbon materials. At a current density of 1 A·g-1, the specific capacitance of these prepared carbon materials is 157.70 F·g-1, whereas it is only 62.00 F·g-1 at a high current density of 20 A·g-1. Therefore, this study suggests that the hydrothermal carbonization process is superior to the microwave pyrolysis carbonization process for preparing supercapacitor electrode materials with multiple samples doped with each other.

Effect of Hydrothermal Carbonization on Fuel and Combustion Properties of Shrimp Shell Waste

Shrimp shell is a popularly consumed seafood around the globe which generates a substantial quantity of solid wet waste. Hydrothermal carbonization (HTC) could be a viable pathway to convert wet shrimp shell waste into energy-dense hydrochar. The present study aims to assess the fuel properties, physicochemical attributes, and combustion properties of shrimp shell hydrochar generated with a wide range of HTC temperatures (110–290 °C). Results showed that a rise in carbonization rate results in a decline in mass yield to as low as 25.7% with the increase in HTC temperature. Thermogravimetric analysis indicates shrimp shell hydrochars to be more thermally stable than raw dried feedstock. Results from the bomb calorimeter report a maximum HHV of 27.9 MJ/kg for SS-290, showing a 13% increase in energy densification compared to raw shrimp shell. The slagging and fouling indices determined for the hydrochars further assisted in addressing the concern regarding increasing ash content changing from 17.0% to 36.6%. Lower ratings of the slagging index, fouling index, alkali index, and chlorine content for hydrochars at higher temperature indicate the reduced probability of reactor fouling during combustion. The findings of the analysis demonstrate that HTC is a promising approach for transforming shrimp shell waste into a potential fuel replacement.

Improved OER catalytic performance of NiFe-LDH with hydrothermal carbonization microspheres

The electrochemical oxygen evolution reaction (OER) is a fundamental anodic semi-reaction used in the hydrogen energy industry. Herein, we report a novel NiFe-layered double hydroxide (NiFe-LDH)-based hybrid catalyst for the OER, which is promoted by the two-step hydrothermal loading of carbon sphere (CS) onto NiFe-LDH sheets, named as NiFe-LDH@CS. The effects of hydrothermal carbonization (HTC) parameters (such as hydrothermal time and glucose concentration) and the loading ratio of CSs on NiFe-LDH@CS were investigated. The results showed that the two-step hydrothermal synthesis significantly inhibited the interference of the carbonized substances on the lattice formation of NiFe-LDH and successfully achieved a firm combination. By adjusting the HTC process, the surface characteristics and graphitization degree of the carbonized microspheres can be effectively controlled, leading to increased OER performance of NiFe-LDH@CS. Thus, under the optimal process parameters (5 h, 0.6 M, and 5 mL), NiFe-LDH@CS exhibited an excellent overpotential of 292 mV at 50 mA cm-2 and 372 mV at 100 mA cm-2 for the OER. The outstanding OER performance of NiFe-LDH@CS is attributed to the excellent morphology control of the composite, abundant functional groups, and suitable graphitization degree of the hydrothermally carbonized CS, as well as the synergistic effect between the CSs and NiFe-LDH.

Characteristics of Hydrothermal Carbonization Hydrochar Derived from Cattle Manure

The characteristics of hydrothermal carbonization hydrochar derived from cattle manure including excrements and lignocellulosic biomass were analyzed. The effects of hydrothermal carbonization were evaluated by varying the reaction temperatures in the range of 180~240 °C. The hydrochars were evaluated with respect to their usefulness as renewable fuels via physicochemical analysis and pyrolysis processes. As reaction temperatures increased, the fractions of fixed carbon in proximate analyses, carbon elements in ultimate analyses, and higher heating values of hydrothermally carbonized biochars increased in correlation with the primary reactions of coalification. Various correlations were derived with the characteristics of hydrochars in order to be utilized for operating and designing HTC reactors for cattle manure. The correlation between the O/C and H/C ratios was deduced on the basis of a van Krevelen diagram. The interaction equation was represented with the increased fraction of HHV compared to the reaction temperature of hydrothermal carbonization. The ultimate correlation for the estimation of higher heating values was suggested for HTC hydrochars. Moreover, the pyrolysis characteristics and kinetic parameters of the cattle manure and hydrochar were deduced by utilizing a multi-step kinetic model scheme. As the HTC reaction temperature increased, the global activation energy and the pre-exponential factors of hydrochars decreased in the low-temperature section and increased in the high-temperature section.

Multifunctional Loblolly Pine-Derived Superactivated Hydrochar: Effect of Hydrothermal Carbonization on Hydrogen and Electron Storage with Carbon Dioxide and Dye Removal.

Pore modulation via hydrothermal carbonization (HTC) needs investigation due to its crucial effect on surface that influences its multirole utilization of such ultraporous sorbents in applications of energy storage- hydrogen and capacitive- as well as for pollutant abatement- carbon capture and dye removal. Hence, loblolly pine was hydrothermally carbonized followed by KOH activation to synthesize superactivated hydrochars (SAH). The resulting SAHs had specific surface area (SSA) 1462–1703 m2/g, total pore (TPV) and micropore volume (MPV) of 0.62–0.78 cm3/g and 0.33–0.49 cm3/g, respectively. The SAHs exhibit excellent multifunctional performance with remarkably high atmospheric CO2 capture of 145.2 mg/g and high pressure cryogenic H2 storage of 54.9 mg/g. The fabricated supercapacitor displayed substantial specific capacitance value of maximum 47.2 Fg−1 at 1 A g−1 in 6 M KOH and highest MB dye removal of 719.4 mg/g. Higher HTC temperature resulted in increased surface porosity as higher SSA, TPV benefitted H2 storage and MB dye removal while superior MPV favored CO2 capture. Moderate HTC temperature ensured higher mesopore-to-macropore volume ratio favoring electrochemical performance. Isotherm modelling of the adsorbates was compared using models: Langmuir, Freundlich, Langmuir- Freundlich and Temkin.

Effect of hydrothermal carbonization on woody biomass: From structure to reactivity

Hydrothermal carbonization (HTC) pretreatment is an effective method to upgrade the low quality biomass properties. In this work, the pinewood (PIW) and poplar wood (POW) were selected to study the effect of HTC (180–240 °C) on woody biomass structure and reactivity. The results showed that the slight and moderate HTC can make the cellulose structure more ordered, while the severe HTC leaded to the decomposition of cellulose structure. The mesoporous specific surface area and pore volume increased with the HTC temperature, and the pore structure of PIW was more developed than that of POW. The slight HTC had little effect on cellulose structure and the diffusion effect played the dominant role. The severe HTC increased the relative content of lignin and the pyrolysis followed the high order reaction model. The model-free method was used to determine the relationship between T-β-X, and the specific temperature THTC/Traw was calculated. The THTC/Traw value of PIW and POW located in the range of 0.938–1.340 and 0.924–1.422, indicating the HTC pretreatment had great effect on POW pyrolysis reactivity.

Effect of hydrothermal carbonization and eutectic salt mixture (KCl/LiCl) on the pyrolysis of Kraft lignin as revealed by thermal analysis coupled to advanced high-resolution mass spectrometry

The production of graphite requires high temperatures, and fossil petroleum, coal, or nutshells are frequently used as a carbon source. As a replacement, Kraft lignin, a by-product of the pulp and paper industry, is a promising carbon source with a prefigured aromatic network. Biomass-based feedstocks with improved characteristics can be obtained by hydrothermal carbonization, but the chemical nature of this process is not fully understood yet. Moreover, adding a eutectic salt mixture (LiCl/KCl) to the pyrolysis of Kraft lignin and HTC lignin can improve the graphitization at lower temperatures. In this study, thermal analysis with online mass spectrometric detection of the evolved gas mixture was applied to explore the influence of the eutectic salt mixture on the char conversion process. Aside from classical pyrolysis gas chromatography mass spectrometry, thermogravimetry coupled with soft photoionization mass spectrometry allowed to identify phenol, hydrogen sulfide, dimethyl sulfide, and various larger lignin fragments. These larger dimeric/trimeric methoxyphenol derivatives were successfully validated by means of high-resolution mass spectrometry equipped with soft atmospheric pressure chemical ionization. The investigations indicated the catalytic influence of the salt mixture on the production process of the biochars, achieving partially graphitization already at relatively low temperatures (700 °C). On the morphology, Raman spectroscopy and electron microscopy revealed the evolution of the carbon structures and revealed that the materials have typical features for amorphous carbon.

Evaluating performance of pyrolysis and gasification processes of agriculture residues-derived hydrochar: Effect of hydrothermal carbonization

In this study, corn straw and rice husk were hydrothermally carbonized at 180 °C and 240 °C. The effect of hydrothermal carbonization on the biomass/hydrochar characteristics, fate of heavy metals such as As, Cr, Pb, Ti, Cd, Zn, Fe, Cu, and Ni, global reactivity of the pyrolysis and gasification of biomass and hydrochar were investigated in a thermogravimetric analyzer, followed by kinetic modeling and reactivity prediction. Results showed that hydrothermal carbonization temperature 180 °C is more suitable for producing solid fuel in terms of low heavy metals content. Higher hydrothermal carbonization temperature (240 °C) decreased O/C content and improved various characteristics of the hydrochar such as coalification degree, carbon content, higher heating value and the specific surface area. While hydrothermal carbonization conducted at lower temperature of 180 °C, was advantageous for obtaining higher energy yield efficiency and hydrochar yield. The gasification reactivity of hydrochar was more sensitive to the heating rate than the pyrolysis process. The activation energy (Ea) of the pyrolysis process varied significantly with conversion, whereas the gasification activation energy changes were insignificant. Based on the reactivity prediction, the hydrothermal carbonization effect on corn straw and rice husk was almost similar. The hydrochar generated under severe hydrothermal carbonization temperature (240 °C) showed higher thermal stability during pyrolysis in comparison with gasification. Compared with the gasification of rice husk hydrochar, hydrochar gasification of corn straw had lower Ea, hence requires less energy to produce syngas. The results of this research imply that biomass hydrochar is a suitable alternative option to produce pulverized solid fuel.

Effects of hydrothermal carbonization on products from fast pyrolysis of cellulose

In the first step of this study, the hydrothermal carbonization (HTC) of cellulose was performed at 225 and 250 °C for 4, 8 and 12 h. The effect of temperature and residence time on hydrochar (HC) yields and characteristics was investigated, and the highest hydrochar yield had a heating value of 21.06 MJ/kg. In the second step, cellulose and hydrochar-derived cellulose was subjected to fast online pyrolysis at 500, 600 and 700 °C, using a pyrolysis-gas chromatography-mass spectrometry system. The HTC process significantly affected the pyrolysis products. The major decomposition product resulting from the fast pyrolysis of cellulose was levoglucosan, but at all tested temperatures, 2-methylfuran was the major product from hydrochars. Increasing the pyrolysis temperature caused a decrease in the relative yield of 2-methylfuran. Another prominent compound observed in pyrolyzates was 2,5-dimethylfuran. The relative yields of these two compounds decreased when the residence time of the HTC process was increased. The highest 2-methylfuran selectivity was 67.4%, while the highest 2,5-dimethylfuran selectivity among the furanic compounds was 24.0%. This study demonstrated that, by combining HTC and pyrolysis processes, fine chemicals can be produced from cellulose.

Spirulina hydrothermal carbonization: Effect on hydrochar properties and sulfur transformation

The effect of hydrothermal carbonization (Htc) on the hydrochar properties and sulfur conversion for microalgae was investigated. The sulfur species and distribution in solid and aqueous products produced from different temperature (180–300 °C) were evaluated. Results suggested that varying temperature significantly influenced the elemental composition, functional groups of hydrochar, and the sulfur species in the products. With temperature increased, the hydrochar had increased aromatic structure with low H/C and O/C ratio, and more conversion of organic sulfur into liquid as SO42−-S, which acquired the highest concentration (293.31 mg/L) at 300 °C. The thiophene-S, aromatic-S, and thiazole-S accounted for the main sulfur species in bio-oil, while components of thiophene-S and thiazole-S were decreased at high temperature. In addition, elevated temperature resulted in more sulfur forms (i.e. thiophene) in hydrochar and formation of more inorganic-S species like sulfate.

Structure–Reactivity Correlations in Pyrolysis and Gasification of Sewage Sludge Derived Hydrochar: Effect of Hydrothermal Carbonization

Hydrothermal carbonization (HTC) has emerged as a promising way to improve the fuel quality of low-grade energy resource such as sewage sludge (SS) with substantial merits. Thus, it is important to...

Hydrothermal carbonization synthesis and KOH activation of porous carbons from waste marigold flowers

Marigold flower-derived porous carbons were synthesized via hydrothermal carbonization (HTC) and KOH activation. The effect of HTC and KOH activation on the change in morphology, chemical functional group, and surface area were studied and discussed based on the results of scanning electron microscopy, Fourier transform infrared spectroscopy, and N2 sorption analysis, respectively. Both HTC and KOH activation were found to play critical roles in changing morphology and enhancing surface area. Without HTC and KOH activation, carbons had low surface area and lacked porosity. In contrast, with both HTC and KOH activation, a sponge-like morphology with a large specific surface area of 1825 m2/g was obtained. The results serve as a useful guideline for further development and synthesis of porous carbons in certain specific applications.

Effect of hydrothermal carbonization on the properties, devolatilization, and combustion kinetics of Chilean biomass residues

This work evaluates the hydrothermal carbonization (HTC) process as a method to upgrade the quality of biomass residues to be used as fuels in gasification or combustion processes. Seven residues from Chilean biomass were characterized thermochemically before and after being processed by HTC. Additionally, the kinetics of devolatilization and combustion were studied. HTC produces biomass with lower ash content, higher carbon content and higher heating value than the original biomass. Herbaceous wastes showed lower heating values (LHV) around 20% higher after HTC process, while increases around 10% in woody and agroindustrial wastes and corn (even being herbaceous wastes) were observed. The chlorine values obtained after HTC indicate the possibility of using the herbaceous, woody and industrial wastes studied as fuels without chlorine related problems. The activation energy (Ea) values from cellulose and hemicellulose decomposition were higher after HTC process, while lower Ea values from lignin decomposition were found. The combustion characteristic temperatures, ignition temperature (Ti), peak temperature (Tp), and burnout temperature (Tb), were delayed towards higher temperatures with HTC process for all residues. Moreover, the reactivity (R) and combustibility index (S) were lower after HTC, indicating slower combustion for the samples after HTC. Finally, the results show that HTC is a promising process to homogenize the kinetic parameters and the combustion behavior of the samples, thus increasing the interchangeability of the samples in combustion or gasification systems.

Effects of hydrothermal carbonization on catalytic fast pyrolysis of tobacco stems

This study investigated the effects of hydrothermal temperature (HT, 160–240 °C) and residence time (RT, 30–90 min) of hydrothermal carbonization (HTC) on the properties of tobacco stems and their pyrolysis behaviors with catalysts (CaO, HZSM-5). The characterization of hydrothermal products (hydrochars) was carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and 13C superconducting nuclear magnetic resonance (NMR). The pyrolysis experiments of the samples were conducted by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and thermogravimetric analyzer coupled to Fourier transform infrared spectroscopy (TG-FTIR). The experimental results showed that with the increase of HT and RT, the fixed carbon content, high heating value, and energy densification of hydrochar were increasing and the crystallinity index increased first and then decreased, and the aromaticity increased continuously. HTC reduced the contents of acetic acid and ketones in the bio-oil and increased the contents of hydrocarbons and 1,6-anhydro-β-d-glucopyranose. When the HT was higher than 180 °C, excessive aromatization of hydrochar affected the yield of chemical compounds in bio-oil. When HT was lower than and equal to 200 °C, the catalyst HZSM-5 and HTC exhibited combined effects of promoting an increase in the production of aromatic hydrocarbons. When HT was higher than 200 °C, the catalytic effects of the double-layer catalysts were better than that of the single-layer catalyst, and CaO and HZSM-5 exhibited synergistic effects that promoted an increase in aromatic hydrocarbon content.

Effect of hydrothermal carbonization as pretreatment on energy recovery from food and paper wastes

In this study, food waste (FW) and paper wastes were subjected to hydrothermal carbonization (HTC) with a purpose to improve energy recovery potential. FW is suggested as the suitable feedstock for production of hydrochar (HC) having highest calorific value (29.6 MJ/kg). Carbon content in FW derived HC was increased from 50% to ∼72% whereas energy retention efficiency was found to be 5.74 times of that in FW. Wastewater recovered after HTC of FW was rich in carbohydrates with chemical oxygen demand of ∼56,000 mg/L which may further be subjected to anaerobic treatment for biogas generation. Energy balance calculations showed that the solid and liquid fractions recovered after HTC of FW yielded highest energy output (2950 kJ/kg FW) compared to incineration (2217 kJ/kg FW), anaerobic digestion (2605 kJ/kg) and in-vessel composting. HTC process can be adopted as decentralized facility by institutions where highly moisturized wastes are generated.

Thermodynamic investigation on gasification performance of sewage sludge-derived hydrochar: Effect of hydrothermal carbonization

Compared with the conventional thermal drying process, hydrothermal carbonization (HTC) can reduce the energy cost of water removal from sewage sludge prior to its steam gasification. However, less attention is paid on the interactions between HTC and gasification. In this study, the thermodynamic evaluation on hydrochar gasification performance under different operating conditions including HTC duration (τ), HTC temperature (THTC), gasification temperature (Tg), and steam/hydrochar mass ratio (S/C ratio) is performed. Two indicators including carbon conversion rate (CC) and cold gas efficiency (CGE) are used to assess the gasification performance. The results show that elevating both gasification temperature and S/C ratio can enhance the H2 production, which also result in the increase of CC and CGE. The content and gasification activity of fixed carbon increase under moderate HTC duration and temperature, favoring the H2 formation despite of the apparent loss of volatiles species in the hydrochar. Longer HTC duration or higher HTC temperature declines the H2 production due to the sharp reduction of carboxyl and hydroxyl groups, weakening water gas reaction and on-site reforming reaction of tar occurred on the hydrochar surface. In terms of the values of CC = 93.9% and CGE = 64.38%, the optimum HTC conditions of τ = 30min and THTC = 200 °C can be determined. The data provided here favor guiding HTC treatment of sewage sludge targeting gasification and thus promoting the development of this promising waste-to-energy technology.

Effect of bamboo hydrochar on anaerobic digestion of fish processing waste for biogas production

The effect of hydrothermal carbonization (HTC) temperature and bamboo hydrochar (BHC) addition on biogas production in anaerobic digestion of fish processing waste (FPW) was studied. HTC temperature (200–280 °C) had significant effects on methane yield and content, but the BHC had little effects. The maximum biogas yield observed with HTC at 200 °C and a BHC adding ratio of 1:2 (dry mass ratio of FPW to BHC) reached 292 L/kg volatile solids (VS), which were 64% higher than the control group with only FPW, with the maximum methane yield of 219 L/kg-VS and highest net methane energy yield of 3410 kJ/kg-VS. The obtained results can be used to design an efficient anaerobic digestion process for treating and effectively utilizing fish processing waste.

Effect of hydrothermal carbonization on heavy metals in swine manure: Speciation, bioavailability and environmental risk

The speciation, bioavailability and environmental risk of heavy metals (HMs) in the hydrochar derived from hydrothermal carbonization (HTC) of swine manure were investigated in this study. The results indicated that the majority of HMs originally in swine manure were retained in the hydrochar by HTC, and CaO addition substantially reduced the HMs concentration in the hydrochar. HTC especially CaO assisted HTC significantly promoted the HMs transformation from the bioavailable fraction to the relatively stable fraction, and thus decreased their environmental risk in the hydrochar. Moreover, the Toxicity Characteristic Leaching Procedure and diethylenetriamine pentaacetic acid test revealed that the leachability and plant-bioavailability of HMs in swine manure were greatly declined by HTC especially for HTC with 15% CaO addition. The present study suggested that HTC was an effective disposal approach for swine manure from the perspective of HMs immobilization, especially for CaO assisted HTC.

Conversion of organic residue from solid-state anaerobic digestion of livestock waste to produce the solid fuel through hydrothermal carbonization

The solid-state anaerobic digestion (SS-AD) has promoted the development and application for biogas production from biomass which operate a high solid content feedstock, as higher than 15% of total solids. However, the digested byproduct of SS-AD can be used as a fertilizer or as solid fuel, but it has serious problems: high moisture content and poor dewaterability. The organic residue from SS-AD has to be improved to address these problems and to make it a useful alternative energy source. Hydrothermal carbonization was investigated for conversion of the organic residue from the SS-AD of livestock waste to solid fuels. The effects of hydrothermal carbonization were evaluated by varying the reaction temperatures within the range of 180-240℃. Hydrothermal carbonization increased the calorific value through the reduction of the hydrogen and oxygen contents of the solid fuel, in addition to its drying performance. Therefore, after the hydrothermal carbonization, the H/C and O/C atomic ratios decreased through the chemical conversion. Thermogravimatric analysis provided the changed combustion characteristics due to the improvement of the fuel properties. As a result, the hydrothermal carbonization process can be said to be an advantageous technology in terms of improving the properties of organic waste as a solid-recovered fuel product.

Effect of hydrothermal carbonization on storage process of woody pellets: Pellets’ properties and aldehydes/ketones emission

Effect of hydrothermal carbonization (HTC) on the hydrochar pelletization and the aldehydes/ketones emission from pellets during storage was investigated. Pellets made from the hydrochar were stored in sealed apparatuses for sampling. The energy consumption during pelletization and the pellets’ properties before/after storage, including dimension, density, moisture content, hardness, aldehyde/ketones emission amount/rate and unsaturated fatty acid amount, were analyzed. Compared with untreated-sawdust-pellets, the hydrochar-pellets required more energy consumption for pelletization, and achieved the improved qualities, resulting in the higher stability degree during storage. The species and amount of unsaturated fatty acids in the hydrochar-pellets were higher than those in the untreated-sawdust-pellets. The unsaturated fatty acids content in the hydrochar-pellets was decreased with increasing HTC temperature. Higher aldehydes/ketones emission amount and rates with a longer emission period were found for the hydrochar-pellets, associated with variations of structure and unsaturated fatty acid composition in pellets.