Process Water Research Articles

Anaerobic digestion of process water from hydrothermal treatment processes: a review of inhibitors and detoxification approaches.

Integrating hydrothermal treatment processes and anaerobic digestion (AD) is promising for maximizing resource recovery from biomass and organic waste. The process water generated during hydrothermal treatment contains high concentrations of organic matter, which can be converted into biogas using AD. However, process water also contains various compounds that inhibit the AD process. Fingerprinting these inhibitors and identifying suitable mitigation strategies and detoxification methods is necessary to optimize the integration of these two technologies. By examining the existing literature, we were able to: (1) compare the methane yields and organics removal efficiency during AD of various hydrothermal treatment process water; (2) catalog the main AD inhibitors found in hydrothermal treatment process water; (3) identify recalcitrant components limiting AD performance; and (4) evaluate approaches to detoxify specific inhibitors and degrade recalcitrant components. Common inhibitors in process water are organic acids (at high concentrations), total ammonia nitrogen (TAN), oxygenated organics, and N-heterocyclic compounds. Feedstock composition is the primary determinant of organic acid and TAN formation (carbohydrates-rich and protein-rich feedstocks, respectively). In contrast, processing conditions (e.g., temperature, pressure, reaction duration) influence the formation extent of oxygenated organics and N-heterocyclic compounds. Struvite precipitation and zeolite adsorption are the most widely used approaches to eliminate TAN inhibition. In contrast, powdered and granular activated carbon and ozonation are the preferred methods to remove toxic substances before AD treatment. Currently, ozonation is the most effective approach to reduce the toxicity and recalcitrance of N and O-heterocyclic compounds during AD. Microaeration methods, which disrupt the AD microbiome less than ozone, might be more practical for nitrifying TAN and degrading recalcitrant compounds, but further research in this area is necessary.

IoT-Enabled Water Quality Monitoring and Alum Dose Determining System

The water treatment process involves a series of physical, chemical, and biological techniques and methods designed to remove contaminants, impurities, and undesirable substances from raw or untreated water to make it safe, clean, and usable. Adverse weather conditions, such as rainy seasons and floods, present significant challenges, and difficulties to the water treatment process. Alum is mainly used for reducing the turbidity of the water in the treatment process. In Sri Lanka, all water treatment plants use the Jar Test to determine the Alum dosage manually. They conduct Jar Tests to measure raw water quality in their laboratories. The Alum addition valve is set to a pre-determined quantity and the value is decided based on the experience of the technicians. Since there is no specific formula, the presence of an experienced technician is required to determine alum dosage using the Jar test. Thus, this study intends to propose an automated system for determining the optimum Alum quantity to be added to a given raw water sample. This is achieved by designing an Internet of Things (IoT)-enabled sensing device for measuring the water quality, which feeds data to a Machine Learning Model trained to predict the Alum quantity to be added. The task of the Machine learning model is to identify the pattern of raw water parameters and Alum dosage. By doing this, a could be provided a guideline for determining alum dosage instead of a manual Jar test and removed the necessity of experienced technician support always. A user-friendly web interface will allow the operators to customize the parameters according to the requirement and display a detailed analysis report. The predetermined quantity of Alum is transmitted to the output Alum adding value, to enhance its performance as an automated control rather than doing the addition process manually. This is a conceptual study on how to determine the Alum dosage using Raw water parameters and past experiment results.

A Combination of UV and Disinfectant for Inactivating Viable but Nonculturable State Pseudomonas aeruginosa: Efficiency and Mechanisms

Conventional disinfection techniques, relying on a single disinfection step, often fail to directly eliminate microorganisms, instead causing them to enter a viable but nonculturable (VBNC) state. However, microorganisms in the VBNC state retain metabolic activity and can reactivate under suitable conditions, representing a “hidden source of contamination” that threatens drinking water safety. This study fundamentally assessed the feasibility of combined disinfection methods by integrating UV254 with disinfectant (NaClO, PAA, and PDS) for inactivating Pseudomonas aeruginosa (P. aeruginosa), an opportunistic pathogen that has been widely detected in water supply systems. The number of culturable cells was determined using the heterotrophic plate counting (HPC) method, and the number of VBNC cells was quantified using our recently developed qPCR approach. Quantitative analyses showed that combined disinfection methods can effectively reduce both culturable and VBNC cells by several orders of magnitude compared to a single disinfection step. Notably, VBNC P. aeruginosa, after 30 min of UV/NaCIO treatment, was below the detection limit (3.191 log CFU/mL) of PMA-qPCR. The reactivation experiment also confirmed that VBNC P. aeruginosa did not reactivate for 16 h after 30 min of UV/NaClO treatment under controlled laboratory conditions. The higher disinfection capacity of combined methods can be attributed to the generation of reactive radicals. This study highlighted combined disinfection as a promising approach for the inactivation of bacteria in the VBNC state, yet further studies are needed before an application can be considered for minimizing VBNC reactivation in city utility water processing or high-risk building water distribution systems.

Advances in Research and Technology of Hydrothermal Carbonization: Achievements and Future Directions

Hydrothermal carbonization (HTC) has emerged as a pivotal technology in the battle against climate change and fosters circular economies. Operating within a unique reaction environment characterized by water as a solvent and moderate temperatures at self-generated pressures, HTC efficiently converts biomass residues into valuable bio-based products. Despite HTC’s potential—from the management of challenging biomass wastes to the synthesis of advanced carbons and the implementation of biorefineries—it encounters hurdles transitioning from academic exploration to industrial implementation. Gaps persist, from a general comprehension of reaction intricacies to the difficulty of large-scale integration with wastewater treatments, to the management of process water, to the absence of standardized assessment techniques for HTC products. Addressing these challenges demands collaboration to bridge the many scientific sectors touched by HTC. Thus, this article reviews the current state of some hot topics considered crucial for HTC development: It emphasizes the role of HTC as a cornerstone for waste management and biorefineries, highlighting potentialities and challenges for its development. In particular, it surveys fundamental research aspects, delving into reaction pathways, predictive models, analytical techniques, and HTC modifications while exploring HTC’s crucial technological applications and challenges, with a peculiar focus on combined HTC, wastewater integration, and plant energy efficiency.

Biowaste management by hydrothermal carbonization and anaerobic co-digestion: Synergistic effects and comparative metagenomic analysis

The feasibility of anaerobic co-digestion in semicontinuous mode of two major urban biowaste, food waste (FW) and garden and park waste (GPW) (75 % FW and 25 % GPW) as well as the co-digestion of FW with the process water originated from the hydrothermal carbonization of GPW (95 % FW and 5 % process water), both on a COD basis, has been assessed. The effect of varying organic loading rate (OLR) from 1.5 to 3.5 g COD/L·d on methane yield, gross energy recovery, and microbiome population was evaluated. For comparison, anaerobic digestion of FW was also conducted to determine the best strategy for sustainable biowaste management. This study showed an optimal OLR of 2.5 g COD/L·d. Acetic and propionic acid content increased as OLR raised for each condition studied, while methane yield decreased at the highest OLR tested indicating overloading of the system. The anaerobic co-digestion of FW and process water showed a 10 % increase on methane production compared to anaerobic digestion of FW (324 vs. 294 mL CH4 STP/L·d). Moreover, it enhances the process due to a greater abundance and diversity of hydrolytic and acidogenic bacteria belonging to Bacterioidota, Firmicutes, and Chloroflexi phyla, as well as promotes the hydrogenotrophic pathway under higher propionic concentrations which is not usually favoured for methane production. The integration of hydrothermal carbonization of GPW with the anaerobic co-digestion of 95 % FW and 5 % of process water results in the highest potential energy recovery and could be a good strategy for sustainable management of urban biowaste.

A contribution to understanding ion-exchange mechanisms for lithium recovery from industrial effluents of lithium-ion battery recycling operations

Industrial effluents or process waters generated from spent lithium-ion batteries (LIBs) recycling operations often contain high concentrations of lithium ions (Li+). This study characterizes the composition of process water obtained from pre-treatment and concentration operations of LIBs recycling. Ion-exchange experiments are conducted using synthetic lithium solutions (1g/L) and industrial waters to understand Li+ recovery. Employing four commercial cationic resins, fast Li+ exchange kinetics are observed fitting the pseudo-second order model. The equilibrium isotherm data corresponds to the Langmuir adsorption model and reveals a Li capacity of 30-32mg/g using AmberliteTM IRC 120 H, 70mg/g using Lewatit® TP 308 H, 37-40mg/g using Lewatit® TP 208 Na, and 37-41mg/g using Lewatit® TP 260 Na. While the resins initially demonstrate moderate affinity for Li+, this can be significantly enhanced by increasing the Li+ concentration. Notably, as LIBs recycling operation effluents typically contain minimal competing ions, these results underscore the potential of employing ion exchange as a viable method to recover and concentrate lithium before precipitation into lithium salts.

Distribution of Per- and Polyfluoroalkyl Substances (PFASs) in a Waste-to-Energy Plant─Tracking PFASs in Internal Residual Streams.

Per- and polyfluoroalkyl substances (PFASs) constitute a diverse group of man-made chemicals characterized by their water- and oil-repellent properties and persistency. Given their widespread use in consumer products, PFASs will inevitably be present in waste streams sent to Waste-to-Energy (WtE) plants. We have previously observed a subset of PFASs in residual streams (ashes, treated process water, and flue gas) from a WtE plant. However, the transport and distribution of PFASs inside the WtE plant have remained unaddressed. This study is part of a comprehensive investigation to create a synoptic overview of the distribution of PFASs in WtE residues. PFASs were found in all sample types except for boiler ash. The total levels of 18 individual PFASs (Σ18PFASs) in untreated flue gas ranged from 5.2 to 9.5 ng m-3, decreasing with 35% ± 10% after wet flue gas treatment. Σ18PFASs in the condensate ranged from 46 to 50 ng L-1, of which perfluorohexanoic acid (PFHxA) made up 90% on a ng L-1 basis. PFHxA was also dominant in filter ash, where Σ18PFASs ranged from 0.28 to 0.79 ng g-1. This study shows that flue gas treatment can capture some PFASs and transfer them into WtE residues.

Effect of Solvent Ratio (Ethylene Glycol/Water) in the Synthesis of Pt/C Cathode Catalysts on PEM Fuel Cell Performance

Abstract The ethylene glycol (EG)/water mixture composition of an alkaline one-step polyol synthesis for Pt/C catalysts was systematically investigated and optimized for a low ethylene glycol content with regards to resulting Pt particle size and electrochemical performance of membrane electrode assemblies tested as proton exchange membrane (PEM) fuel cell cathode catalysts. Beginning test fuel cell data show a possible reduction of the required EG amount per gram of synthesized catalyst by up to 98% without significantly compromising the initial electrochemical performance. Taking catalyst durability into account, a Pt/C catalyst synthesized with 40 vol% H2O and 32 mM Pt precursor concentration showed a decent initial electrochemical performance (716 mV at 1 A cm-2) as well as an accelerated stress test-derived stability similar to an internal reference catalyst, obtained with 100 vol% EG. In summary, our study shows that optimizing the amount of water and platinum precursor in the synthesis process can lead to catalysts with excellent performance for PEM fuel cells while contributing significantly to cost reduction by using less EG during synthesis.

Comprehensive characterization of organics in oil sands process water in constructed mesocosms utilizing multiple analytical methods

This study aims to provide a thorough characterization of dissolved organics in oil sands process water (OSPW) in field-based aquatic mesocosms at both molecular and bulk measurement levels using multiple analytical methods. In a 3-year outdoor mesocosm experiment, the analysis of naphthenic acid (NA) species was conducted using ultra-performance liquid chromatography time-of-flight mass spectrometry (UPLC-TOFMS). The results revealed the removal of both total NAs (38% and 35%) and classical NAs (O2–NAs, 58% and 49%) in undiluted and half-diluted OSPW, respectively. The increased ratios of oxidized NAs (O3–O6 NAs) to classical NAs suggested a transformation trend. The results also indicated that O2–NAs with higher carbon number and lower double bond equivalent (DBE) were more easily degraded in the mesocosm systems. Biomimetic extraction using solid-phase microextraction (BE-SPME) measurement displayed 26% (undiluted OSPW) and 30% (half-diluted OSPW) decrease in total bioavailable organics over 3 years. Naphthenic acids fraction compounds (NAFCs) obtained by liquid-liquid extraction (LLE) were also determined using Fourier transform infrared spectroscopy (FTIR). Reduction in acute toxicity for undiluted (43%) and half-diluted (26%) OSPW was observed over 3 years, which are well correlated with the decreases of NAs and BE-SPME concentrations. Moreover, BE-SPME values were found to be linearly correlated with total NAs concentrations (r = 0.96) and NAFCs (r = 0.96). Additionally, the linear relationships of individual O2–O6 NA species and BE-SPME concentrations unveiled the changes in the relative abundances of O2–O6 NA species in total bioavailable organics over time in the mesocosms. The present study has provided comprehensive insights by integrating various analytical methods, contributing valuable information for assessing the effectiveness of aquatic mesocosm systems in studying the temporal changes of organics in OSPW.

The Modelling of the Evapotranspiration Portion of the Water Footprint: A Global Sensitivity Analysis in the Brazilian Serra Gaúcha

Water footprints have been widely used to illustrate the consumption of water in many situations, for instance, in products, processes, or regions of interest. In this work, we analyzed—using a sensitivity analysis approach—the effect of some variables in the calculation of the water footprint in the viticulture in the Brazilian Serra Gaúcha (the major producing region of Brazilian wine). The classical Penman–Monteith model for evapotransporation was considered, with uncertainties in some parameters (dead mulch covering a fraction of the vineyard, maximum temperatures for some months, the altitudes and latitudes of the site). A sensitivity analysis was conducted using the SAFE toolbox under Octave framework. The results indicated that the the portion of the water footprint corresponding to evapotranspiration is more sensitive to the values of the mulch-covered fraction and the altitude of the site in comparison with the latitude and the maximum temperatures.

Design of Production Line of 2000 Tons of Fermented Milk Beverage with Annual Output of Whole Bean

The whole soybean fermented milk beverage designed by this production line is a beverage made of soybean as raw material and fermented under the fermentation action of compound probiotics. The design optimizes the production line of whole soybean fermented milk beverage with an annual output of 2000t and strictly refers to the relevant national regulations to determine the process design, material balance, equipment selection, water and electricity estimation, and workshop design of the whole soybean fermented milk beverage production line. Finally, the technical and economic analysis of the scheme shows that the fixed investment of the project is 7.95 million yuan, the annual production cost is 15193.72 million yuan, the total profit after tax reached 16.80628 million yuan, the construction period is 1 year, and the payback period is expected to be about 2 years.

Clarification of Mining Process Water Using Electrocoagulation

Clarification of Mining Process Water Using Electrocoagulation

Lean and sustainability assessment in the sawmill industry using Sus-VSM: A case study in the context of Fiji

Waste from the perspective of lean manufacturing and sustainability has a huge influence on economic, environmental, and societal aspects. The inefficiency of the current manufacturing systems poses a huge risk to small and medium size sawmills going out of business as current prices of fossil fuel and associated emissions continue to rise at an alarming rate. In this case study, a local sawmill has been investigated to improve process efficiency using sustainable value stream mapping in the context of Fiji. The produced timber with the highest demand is selected as the product and a complete assessment is done on the downstream operation to compile data and develop the current state map. The current state map incorporates sustainability pillars to address the lacking factors such as energy and water consumption, raw material usage, labor physical load, and workspace noise level along with standard lean manufacturing time-based metrics. Sustainable value stream mapping allowed the research team along with a panel of experts to identify processor 2 as the root cause of bottlenecking, unnecessary material movement/transportation, and high physical load index score. Implementing a multi-blade horizontal bandsaw in place of processor 2 reduces; energy consumption for transport, energy consumption for processing, VAT, NVAT, process water consumption, raw material usage, and carbon emission by; 34.9%, 8.72%, 6.37%, 20%, 24.71%, 3.05%, and 10.33% respectively without compromising productivity. The findings of this research suggest evaluating and assessing sustainability performance using Sus-VSM in the sawmill industry unveils potential economic, environmental, and societal benefits.

Isolation and Identification of Bitter Compounds in Ginseng (Panax ginseng C. A. Mey.) Based on Preparative High Performance Liquid Chromatography, UPLC-Q-TOF/MS and Electronic Tongue

As a traditional Chinese medicinal herb, ginseng (Panax ginseng C. A. Mey.) is commonly used to treat common diseases, for example, esophageal cancer and myasthenia gravis. Furthermore, ginseng is also processed into a functional food additive that is utilized to improve the freshness of chicken soup and make health wine. Unfortunately, ginseng (Panax ginseng C. A. Mey.) has already shown a noticeable bitterness during its application process. In this research, the bitter substances in ginseng (Panax ginseng C. A. Mey.) after two common preparation processes (water extraction and ethanol extraction) were separated, purified and identified by preparative high performance liquid chromatography (prep-HPLC), high performance liquid chromatography with diode array detector (HPLC-DAD), ultra-performance liquid chromatography coupled with high-resolution quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS) and an electronic tongue. The results indicated that compared with the other four bitter compounds, the ginsenoside Rb1 had the highest bitterness value, followed by 20(S)-ginsenoside Rg2, ginsenoside Rg1, ginsenoside Rf and ginsenoside Rb3. Upon the evaluation of results to reduce the bitterness of ginseng extract, we found that the composite embedding system of chitosan adsorption in the ginseng carrageenan gel microsphere (K/MC/MCG) could effectively reduce the bitterness.

Continuous wet air oxidation of aqueous phase from hydrothermal liquefaction of sewage sludge

The conversion of organic waste into advanced fuels through hydrothermal liquefaction (HTL) is a promising route. However, for the commercialisation of HTL technology, treatment and valorisation of the generated aqueous by-product are required for its economic viability. This study investigates subcritical non-catalytic continuous wet air oxidation (WAO) for the treatment of the aqueous phase from hydrothermal liquefaction (HTL-AP) of sewage sludge. A custom-made tubular reactor was used at temperatures and residence times similar to the HTL process (300-350 °C; 6-50min), with excess air equivalent to 1.5-2 times the oxygen demand. The WAO process removed up to 95.3% of the chemical oxygen demand and 91.8% of the total organic carbon, generating volatile fatty acids, mainly acetic acid, as intermediary compounds from the oxidation reactions, and CO2 and H2O from the pollutant’s complete degradation. The process effectively eliminated almost all of the organonitrogen compounds, generating NH4+, which reached values of up to 97% of the total nitrogen. Comprehensive molecular characterization performed by FT−Orbitrap MS analysis revealed that the main basic organonitrogen compounds in HTL-AP are distributed in the O1N1, N2, O1N2, N1 classes. For neutral to acidic organonitrogen species, O3N1 is the most representative chemical class. The energy consumption for heating the WAO reactor was up to 40% lower using HTL-AP compared to blanks experiments. Despite good process water clean-up, autothermal operation was not achieved, and improvements in the reactor design are suggested.

The occurrence and human health risk assessment of microcystins in diverse food matrixes during production

Globally, the presence of cyanotoxins in water supplies and food has been widely investigated for over a decade. Cyanotoxins are harmful metabolites produced by toxic cyanobacterial genera. These metabolites belong to diverse chemical classes, with a variety of physicochemical properties, chemical structures, and toxic activities. The present study seeks to investigate the occurrence of cyanotoxins in water supplies destined for food processing and assess the human health risk from exposure to cyanotoxins. To achieve this, a simple, sensitive, and reliable analytical method was developed for the determination of microcystins (MC-RR, MC-LR, MC-YR) in process water, raw maize meal, and cooked maize (porridge) at ppb (parts per billion) levels. These compounds were extracted using Solid Phase Extraction (SPE) with optimized parameters; thereafter, Liquid Chromatography-tandem Mass Spectrometry (LC-MS/MS) was used for the rapid determination of the analytes selected for the present study. The method developed was applied to samples collected from the meal grinding station located in Mawoni village in South Africa; and was able to detect and quantify all the target cyanotoxins. MC-LR, MC-YR and MC-RR were detected at concentrations ranging from 10 to 11.2 μg/L, 9.1–9.4 μg/L, and 2.3–3.5 μg/L, in water samples, respectively. However, MC-YR was not detected in ground water sample. Moreover, MC-LR, MC-YR, and MC-RR concentrations in maize and porridge samples ranged between 9.2 and 11.2, 5.5–8.6, and 6.3–9.3 μg/kg dry weight, respectively. The hazard quotient index (HQi) levels found in the present study ranged between 2.2 – 8.4 and 0.11–8.9 for adults and children, respectively, representing potential risks to human health. Findings from LC-MS/MS reveal that cyanotoxins can be transferred from water to food during food processing using cyanotoxins contaminated water. Furthermore, the methods developed can be used by environmental and health agencies to strengthen the monitoring of cyanotoxins in water and food.

Effect of baking conditions on resistant starch: Model systems and cake formulations

Five ingredients rich in RS (resistant starch) were assessed in a model system simulating baking process (water addition 30–50%, 180 °C/35 min) and in reformulated cakes (50% replacement of wheat flour). Moreover, two enzymatic methods used for RS determination (official and rapid) were compared. The combined effect of heating and water addition (50%) significantly decreased the RS content in all ingredients. Reformulated vegan cakes presented significantly lower RS values than those theoretically expected, according to the RS value of raw ingredients. The highest RS amount was observed for Hi Maize, which kept 84% and 72% of the initial RS content in the model systems and cake, respectively. Only the cakes made with Hi Maize reached the criteria for the health claim related to the reduction of post-prandial glycemic response (European Union regulation). Finally, differences between the official and rapid methods were less significant in the cakes than in the model systems.

Trade‐Off Between Light Deprivation and Desiccation in Intertidal Seagrasses Due To Periodic Tidal Inundation and Exposure: Insights From a Data‐Calibrated Model

AbstractSome seagrass species thrive in shallow intertidal zones globally, adapting to periodic tidal inundation and exposure with distinctive physiological traits and offering crucial ecosystem services. However, predicting the responses of intertidal seagrasses to external stressors is hampered by the complexity of the dynamic and harsh environments they occupy. Intertidal seagrass growth models, especially those incorporating dynamic physiological responses, are scarce in the literature. Our study comprehensively collated relevant data from the literature to parameterize the relationship between air exposure, seagrass leaf water content and photosynthetic efficiency to inform new growth rate functions for generalizable intertidal seagrass growth models. We tested the applicability of these model formulations for scenarios with varying physiological process assumptions, seagrass species, tidal conditions, meadow elevations and water turbidity. We found that neglecting air‐exposed physiological responses (i.e., leaf water content loss and reduced photosynthetic efficiency) can substantially overestimate seagrass growth rates. We also observed a trade‐off between light deprivation and desiccation on intertidal seagrass growth under specific tidal ranges and turbidity conditions. This can yield an “optimal” elevation where overall stress of desiccation (increasing with meadow elevation) and light deprivation (decreasing with meadow elevation) are minimized. The predicted optimal elevation, that is, the most suitable habitat for intertidal seagrass, moves upward as water turbidity increases. Our study provides conceptual and quantitative guidance for ecological modelers to include air exposure responses of intertidal seagrasses in coastal ecosystem models. The model also helps to evaluate the viability of intertidal seagrass habitats and inform decisions on coastal ecosystem management under changing environmental conditions.

Electrochemical reclamation of oil sands process water: Two and three-dimensional electrode configuration systems structured with different anode materials

Several studies have indicated the potential of the electrochemical advanced oxidation process in oil sands process water (OSPW) reclamation; however, the variations in different electrode configuration systems and anode materials remain elusive. This study assembled a two-dimensional electrode system (2-DES) and a packed bed electrode reactor (PBER) for OSPW reclamation, of which boron-doped diamond (BDD) (non-active anode), dimensionally stable anodes (DSA-RuO2 and DSA-IrO2) and graphite (active anodes) were selected as the anode materials, while in PBER, spherical activated carbon (SAC) was added as the third electrode. Within the 2-DES, BDD achieved over 60% removal of chemical oxygen demand (COD) due to its excellent •OH generation ability, while DSAs generated the most active chlorine and were quickly consumed by organic matter during the first 30 minutes. However, mass transfer limitation restricted the 2-DES treatment efficiency regardless of the anode materials employed, particularly resulting in limited removal of naphthenic acids (NAs). Compared to 2-DES, PBER significantly improved the OSPW treatment under identical electrolysis conditions, achieving over 91% COD and 99% NAs removal using DSA-IrO2 + SAC. Because of the contribution of the third electrode in PBER, the performance differences between various anode materials were less substantial than in the case of 2-DES. Packed SAC enhanced the mass transfer performance and generation of radical oxidants during OSPW electrolysis, improving the OSPW electrochemical treatment process. Additionally, SAC adsorbed most free chlorine from the liquid phase, avoiding the formation of halogenated organic compounds in reclaimed OSPW.

Research on the co-combustion characteristics and kinetics of rice husk hydrochar with anthracite

Co-combustion of anthracite and hydrochar derived from hydrothermal carbonization with process water recirculation was proposed as an effective way to achieve a transition to low-carbon energy in industries that rely heavily on coal combustion. In this study, thermogravimetric analysis and model-free methods were employed to investigate the co-combustion characteristics and kinetics of anthracite and hydrochar. The results demonstrate that the carbon content of hydrochar is lower than that of anthracite, but the volatile content is higher than that of anthracite, indicating that hydrochar has better combustion performance. There is a synergistic effect in the co-combustion reaction of hydrochar and anthracite. With the increase of the hydrochar addition ratio, the ignition and burnout temperatures of anthracite decrease gradually. With the increase of temperature rise rate, the combustion reaction is enhanced and the combustion performance of anthracite is improved under the fixed mixing ratio. According to the calculation of combustion activation energy by Flynn-Wall-Ozawa and Kissenger-Akahira-Sunose methods, the apparent activation energy of the mixed samples gradually decreases with the increase of combustion conversion rate. When the addition of hydrochar is 60%, the average apparent activation energy of the mixed sample is the lowest, which is 66.51 kJ·mol-1 and 54.62 kJ·mol-1, respectively.