Thermal Pretreatment Temperature Research Articles

Enhancing volatile fatty acid production from food waste by H2O2-moderate temperature thermal pretreatment: Treating waste with waste in coal mining areas

Supplementing carbon sources in sewage treatment plants with organic matter from food waste is crucial for resource recycling in coal mining areas. In this study, a moderate-temperature H2O2 method was used to pretreat food waste from a coal mining area. The changes in the properties of the pretreated food waste and their influence on volatile fatty acids (VFAs) production during anaerobic fermentation were investigated. Additionally, the nitrogen and phosphorus removal rates obtained when glucose and fermentation slurry of food waste (FSFW) were used as carbon sources in the sewage treatment system were compared. Compared with untreated food waste, the soluble chemical oxygen demand (SCOD) increased by 58 % after pretreatment with 0.25 % H2O2 at 60 ℃, and the viscosity and oil content decreased significantly, which caused VFAs production to increase from 15,267 mg COD/L to 50,774 mg COD/L. When the H2O2 concentration increased to 2.0 %, the SCOD increased to 153 %, and the viscosity and oil content further decreased, but the VFAs production decreased to 7477 mg COD/L. This occurred because large quantities of ammonia nitrogen was formed at higher H2O2 doses, which inhibited VFAs formation. Moreover, the nitrogen removal rate was higher when FSFW was used as a carbon source than when glucose was used as a carbon source.

Increasing the Biomethane Yield of Hazelnut By-Products by Low Temperature Thermal Pretreatment

Biomethane energy, which has the status of renewable energies, has the potential to be produced from all kinds of organic wastes, as well as from lignocellulosic materials, which are the most common in nature. In this study, hazelnut shells (HS), one of the hazelnut by-products, were used for biomethane production. In order to obtain higher yields from HS, thermal pre-treatments were applied at temperatures of 60°C, 80°C and 100°C. Pretreatment effects were controlled by lignocellulosic substance amount determinations. As a result of thermal pretreatment at 100°C for 2 h, cellulose and lignin removals occurred approximately 15% and 30%, respectively. While the cumulative biomethane yield of raw HS was 32.3 mL•g total solids (TS)‒1, the cumulative biomethane yields of 100°C pretreated HS were measured as 132.3 mL•gTS‒1. As a result of different pretreatment temperatures, different cumulative biomethane yield curves were successfully simulated with the Modified Gompertz equation and R2 values were found to be between 0.9962 - 0.9985.

Effect of the Pretreatment on the Properties of Cement-Based Recycled Powder

Three pretreatment methods including calcination, carbonization, and a carbonization-calcination combined pretreatment were studied to understand the pretreatment mechanisms for cement-based recycled powder (CRP). The mineral and microstructure of the CRP sample were investigated through X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermal gravity (TG) analysis, and scanning electron microscopy (SEM) after exposure to different thermal temperatures (400 °C, 600 °C, and 800 °C), carbonization times (6 h, 1 d, and 3 d), and pre-carbonization for 1 d followed by heating at 800 °C. The results showed that the optimal thermal pretreatment temperature was approximately 720–800 °C. Through the process of calcination, the C-S-H, Ca(OH)2, and CaCO3 minerals in the CRP sample underwent decomposition to produce CaO or C2S. During carbonation, the pretreatment not only results in the increased production of CaCO3 owing to the reaction of the C-S-H gel and Ca(OH)2 with CO2, but also enhances its properties and the strength of chemical bond between CaCO3 and the post-hydration products. Both CaCO3 and CaO were present after the combined pretreatment, which indicates that the CaCO3 mineral formed superior stability after it had been pre-carbonated. Due to fewer impurities in CRP, the positive effect of the pretreatment on CRP was significantly better than that on recycled powder derived from construction and demolition waste.

Enhancing Biomethane Production from OFMSW: The Role of Moderate Temperature Thermal Pretreatment in Anaerobic Digestion

Enhancing Biomethane Production from OFMSW: The Role of Moderate Temperature Thermal Pretreatment in Anaerobic Digestion

Effects of thermal pretreatment and biotin supplementation on the anaerobic digestion of pineapple (Ananas comosus) wastes, kinetics of methane production, and statistical analysis

The anaerobic digestion (AD) of pineapple wastes (PW) was employed to understand the effects of design parameters, namely thermal pretreatment (TP) temperature (X1) and reaction time (X2), and biotin concentration (X3), to methane production. Kinetic parameters were evaluated by utilizing sigmoidal growth functions, whereas modified Gompertz (MGM) and Logistic function (LF) best described the system among all batch assays. Principal components analysis (PCA) and Pearson correlation matrix were used to understand the correlation and relationship between the design parameters, evaluated kinetic parameters, methane yield (Y), and process performance parameters, wherein it was found that the significantly statistical correlations were Rm-A, λ-X1, A-Y, A-%VS reduction, A-%pH change, Rm-Y, Y-%VS reduction, Y-%pH change, and %VS reduction-%pH change. Furthermore, the cumulative methane production profile in all reactors showed an increase of 19.2–169.2 % in Y compared to the control, suggesting that TP and biotin supplementation were suitable for the optimization of Y from the AD of PW. The Y among all reactors followed the order of A0 <A1 <A2 <A4 <A7 <A3 <A5 <A8 <A6 wherein the lowest Y from pretreated PW was observed at A1 (77.6478 mL/gVS), while the highest was recorded at A6 (175.3053 mL/gVS). The ANOVA results demonstrated that the contribution of main and interaction parameters to Y (X3 >X1X3 >X2X3 >X1 >X2 >X1X2) were statistically significant (p < 0.05), and therefore relevant in the microbial syntrophies during the AD of PW. From the regression analysis, a surrogate mathematical model was constructed with a goodness of fit R2adj= 0.998. Herein, the optimum design conditions in the methane production from AD of PW were found to be X1 = 80ºC, X2 = 120 min, and X3 = 0.25 mg/L.

Influence of thermal pretreatments on dimensional change and humidity sensitivity of densified spruce and poplar wood

The effect of thermal pretreatments on the dimensional change and humidity sensitivity of densified spruce (Picea orientalis) and poplar (Populus nigra) wood were investigated. A thermal pretreatment was applied on the wood specimens at 140 °C, 160 °C, 180 °C, and 200 °C for 7 h and 9 h. Wood specimens were then compressed at ratios of 20 % and 40 % at a temperature of 150 °C. The results showed that spring-back and thickness swelling increased in all specimens (thermally pre-treated and untreated) depending on the increase in compression ratio. However, set-recovery was determined higher at 20 % compression ratio. The equilibrium moisture content values ​​of untreated specimens and thermally pre-treated specimens at low temperatures (140 ºC and 160 ºC) were found lower than uncompressed specimens. The impact of compression ratio on equilibrium moisture content was not clear. Thermal pretreatments significantly affected the dimensional stability and hygroscopicity of densified specimens (especially poplar wood). Depending on the increase in thermal pretreatment temperature and duration, spring-back, set-recovery and thickness swelling in wood specimens decreased up to 31 %, 67 % and 62 %, respectively. In addition, equilibrium moisture content and water absorption decreased with the increase in thermal pretreatment temperature and duration. Moreover, the thermal treatment temperature was more important than duration on the investigated properties.

Strategies for designing hydrophobic MnCe-montmorillonite catalysts against water vapor for low-temperature NH3-SCR

The H2O resistance of low-temperature NH3-SCR catalysts is a key factor for practical applications. This work aims to strategically enhance the hydrophobicity of catalysts by intercalating surfactants into montmorillonite (M) via its cation exchange capacity. Various thermal pretreatment temperatures and chain lengths of surfactants have been used to enhance the hydrophobicity and interlayer spacing of montmorillonite, respectively. As a result, MnCe-M8-600 (with thermal pretreatment at 600 °C and the chain length of surfactant = 8) exhibits good low-temperature NH3-SCR performance and H2O resistance due to its labile oxygen, hydrophobicity, and structural stability. It is worth noting that the hydrophobicity of MnCe-M8-600 weakens the interaction between –OH and the catalyst, thereby continuously maintaining the redox ability and transferring electrons between Mn4+ and Ce3+. The results of the H2O resistance test showed that the NOX conversion of MnCe-M8-600 decreased by only 6% in the presence of 10% H2O, and its activity was fully recovered after turning off H2O. Hence, MnCe-M8-600 shows high activity and H2O resistance and is a promising catalyst for low-temperature NH3-SCR system applications.

Insights into thermal hydrolysis pretreatment temperature for enhancing volatile fatty acids production from sludge fermentation: Performance and mechanism

To reveal the impact of thermal hydrolysis pretreatment (THP) temperature on the unclear mechanisms of volatile fatty acids (VFAs) production, four groups were established with different temperatures (100, 120, 140 and 160 °C), and high throughput sequencing technology was utilized. The results indicated that the optimal VFAs production occurred at 140 °C. Moreover, as the THP temperature increased, the proportion of acetic acid also increased, accounting for 10.8% to 26.7% of the VFAs, compared to only 4.9% in the control group. Mechanism investigations revealed that THP facilitated the hydrolysis and release of biodegradable organic matter. Moreover, the abundance of VFAs production and hydrolytic microorganisms and related metabolic functional genes expression were evidently improved by THP. Overall, this study deepens the understanding of the mechanisms through which different THP temperatures stimulate the production of VFAs through acidogenic fermentation, providing technical support for future THP application in sludge treatment.

Torrefaction at low temperature as a promising pretreatment of lignocellulosic biomass in anaerobic digestion

The lignocellulosic structure of agricultural biomass, which makes it resistant to microbial attack, is the main obstacle in its anaerobic digestion. However, not all biomasses behave the same in the face of anaerobic digestion. Instead, depending on their composition in terms of lignin, cellulose and hemicellulose content, the anaerobic digestion process may be more or less favoured, although a pretreatment stage is usually necessary. This paper presents the results of a laboratory scale batch experiment to study the effect of thermal pretreatment (torrefaction) on the anaerobic digestion of two biomass materials: barley straw and vine shoot. For this, thermal pretreatment temperatures of 100, 130, 180 and 210 °C, with a residence time of 24 h, were studied for both biomasses and the results were compared with the material without pretreatment. Significant differences in biogas production were observed for both biomasses depending on the pretreatment temperature. The highest biogas yields of 458 and 213 mL/gVS for straw and vine shoot, respectively, were observed from biomass pretreated at 100 °C. Barley straw pretreated at 100 °C showed 275% higher methane yield compared to untreated straw. In the case of the vine shoot, the increase was 210%. Furthermore, FTIR-ATR analysis and thermogravimetric analysis coupled with a pseudocomponent kinetic model revealed changes in the lignocellulosic composition of both biomasses while SEM analysis revealed also structural changes. The modified Gompertz model fitted the production data well and predicted shorter lag time and higher biogas production at pretreatment temperatures from 100 to 180 °C compared with the untreated materials. From there, a reduction in methanogenic activity is observed when the pretreatment temperature increases. In general, the change in the lignocellulosic structure and the decrease in the hemicellulose content could be considered as the main reasons to improve the biogas production.

Hydrolysis kinetics for solubilizing waste activated sludge at low temperature thermal treatment derived from multivariate non-linear model

Low temperature thermal pre-treatment is a low-cost method to break down the structure of extracellular polymeric substances in waste activated sludge (WAS) while improving the sludge biodegradability. However, previous models on low temperature thermal pre-treatment did not adequately elucidate the behaviour of sludge hydrolysis process for the duration ranging from 5 to 9 h. Therefore, this work had developed an inclusive functional model to describe the kinetics of sludge hydrolysis for a wide range of treatment conditions (30 °C–90 °C within 0 and 16 h). As compared with treatment duration, the treatment temperature played a greater impact in solubilizing WAS. Accordingly, the 90 °C treatment had consistently produced WAS with the highest degree of solubility. Nonetheless, the mediocre discrepancies between 90 °C and 75 °C may challenge the practicality of increasing the treatment temperatures beyond 75 °C. The effects of treatment duration on soluble chemical oxygen demand, soluble carbohydrate and soluble protein were only significant during the first 4 h, except for humic substances release that continued to increase with treatment duration. Finally, a good fit with R2 > 0.95 was achieved using an inclusive multivariate non-linear model, substantiating the functionality to predict the kinetics of sludge hydrolysis at arbitrary treatment conditions.

An Insight into the Separation of 1,2-Propanediol, Ethylene Glycol, Acetol and Glycerol from an Aqueous Solution by Adsorption on Activated Carbon

Glycerol conversion processes such as aqueous phase reforming and hydrogenolysis generate value-added compounds highly diluted in water. Because distillation is a high energy demand separation step, adsorption could be an attractive alternative to recover these chemicals. Adsorption isotherms of 1,2-propanediol, acetol, ethylene glycol and glycerol onto activated carbon were determined by batch adsorption experiments. These isotherms were fitted slightly better to the Freundlich equation than to the Langmuir equation. Acetol is the compound with the highest adsorption at concentrations smaller than 1 M. Properties of the adsorbate such as the −OH group number, chain length, molecular size and dipole moment, besides characteristics of the adsorbent such as the surface area, oxygen and ash content, are considered to explain the observed results. Moreover, adsorption experiments were performed with mixtures of compounds and it was determined that the molar amount adsorbed is less than predicted from the adsorption isotherms of the individual compounds treated separately. In addition, the influence of the activated carbon thermal pre-treatment temperature on the adsorption capacity has been studied, the optimum being 800 °C. An analysis of the influence of the activated carbon characteristics showed that the most important parameters are the total pore volume and the ash content.

The effect of thermal pretreatment temperature on the diameters and mechanical properties of asphaltene-derived carbon fibers

The effect of thermal pretreatment temperature on the diameters and mechanical properties of asphaltene-derived carbon fibers

Pretreatments for enhanced biomethane production from buckwheat hull: Effects on organic matter degradation and process sustainability

Buckwheat manufacturing produce a large amount of lignocellulosic residue (buckwheat hull), which could be used as substrate in anaerobic digestion, even if hard lignocellulosic structure represents the main obstacle for its degradation. This study presents the results of a laboratory experiment conducted to evaluate the effects of different pretreatments on buckwheat hull anaerobic digestion. To achieve the aim, five pretreatments (alkaline, thermo-alkaline, microwave, ultrasonication and low temperature thermal pretreatment) were studied and the results were compared to non treated buckwheat hull. Cumulative biomethane yields significantly increased after alkaline and thermo-alkaline pretreatments (+61% and +122% with respect to non treated hull, respectively). These results were mainly related to organic matter solubilisation (+772% and +859% of soluble reducing sugars, respectively) and lignin, hemicellulose and cellulose degradation. Overall, process parameters behaviour and digestate quality were not affected by the pretreatments. Alkaline and thermo-alkaline pretreatments were evaluated for their energetic and economic affordability, showing that combination of thermal and alkaline pretreatments ensures significant advantages.

Germination of tucumã (Astrocaryum aculeatum G. Mey.) as a function of thermal pretreatment and stratification temperature

Abstract: Germination of tucumã (Astrocaryum aculeatum G. Mey.) seeds is slow and although the removal of the endocarp favors the speed of the process, the time is still considered long. Thus, this study aimed to investigate the effects of different pretreatment and stratification temperatures on the germination of tucumã seeds. Two experiments were set up. The first experiment was conducted using a completely randomized design in a factorial scheme and seedling emergence was evaluated as a function of the pretreatment of diaspores at different temperatures (27, 30, 35, and 40 °C) during different periods (20, 40, and 60 days). The second experiment was also conducted in a completely randomized design and seed germination was evaluated as a function of seed stratification at constant (25, 30, 35, and 40 °C) and alternating temperatures (26 - 30, 26 - 35, and 26 - 40 °C). Germination decreased progressively in all tested periods as the pretreatment temperature increased. Seed stratification at different constant and alternating temperatures showed different results. The pretreatment of diaspores at different temperatures for different periods was not effective in overcoming the dormancy of tucumã seeds. Seed stratification at alternating temperatures, with the highest thermal amplitude (26 - 40 °C), favored the overcoming of dormancy and the germination of tucumã seeds.

Study on Dissolution Characteristics of Excess Sludge by Low-Temperature Thermal Hydrolysis and Acid Production by Fermentation.

To investigate the dissolution characteristics of low-temperature thermal pretreatment conditions and the process of sludge fermentation to produce acid, the influence of thermal pretreatment temperature on the dissolution of excess sludge organic composition and the mechanism of cell crushing of sludge thermal pretreatment were analyzed by an experimental method, and the performance of acid production was explored by sludge fermentation after pretreatment at different temperatures. The performance of acid production by sludge fermentation after pretreatment at different temperatures was measured. The results proved that the soluble chemical oxygen demand (SCOD) shows the largest increase in dissolution rate (11.92%) at 70 °C and in dissolution quantity (6518.33 mg/L) at 90 °C. However, at 80 °C, the solubility of total organic carbon (TOC) is the highest (3224.47 mg/L), and at 70 °C, the best dissolution conditions for soluble carbohydrate (SC) and soluble protein (SP) reached 340.07 and 80.92 mg/L, respectively. The degree of sludge breaking starts to increase at 70 °C. Correlation analysis shows that dissolved organic matter is mainly derived from the cell wall and intracellular material and SP is mainly derived from intracellular material. Excitation–emission matrix spectra and parallel factor analysis (EEM-PARAFAC) divides the sludge dissolved organic matter (DOM) into five fluorescent components, including C1 (318/366) tyrosine, C2 (418/470) UVA humic acid, C3 (282/334) tryptophan substances, C4 (322/430) UVC humic acids, and C5 (314, 382, 454/526) UVA humic substances. Fermentation acid production experiment shows that the peak concentration is highest at 80 °C, the arrival time is 2 days, and the acid production type is butyric acid fermentation. Thus, it is proved that low-temperature thermal pretreatment promotes the process of acid-producing fermentation and has no effect on the type of fermentation. The optimal condition for hydrolytic dissolution and acid production under low-temperature thermal pretreatment is 80 °C.

Waste paper valorization for bioethanol production: Pretreatment and acid hydrolysis optimization

ABSTRACT The dramatic fluctuations of oil cost and climate change have together concentrated political and scientific attention on the search of alternative fuels. The aim of this work is to recycle waste paper for producing bioethanol. The production process includes two main stages: the conversion of polysaccharides into simple sugars and the fermentation of these sugars into ethanol. In order to maximize the total sugars content, the parameters of both thermal pretreatment and acid hydrolysis steps are optimized by using the response surface methodology combined with Box–Behnken design. In the thermal pretreatment stage, temperature (100–140°C), residence time (20–60 min), and paper–water ratio (0.5–1.5% w/v) are adjusted. For acid hydrolysis step, temperature (60–100°C), reaction time (20–60 min), and amount of sulfuric acid (1–3% v/v) are the investigated parameters. Total sugars evolution is monitored during fermentation reaction using the yeast Saccharomyces cerevisiae under the optimal parameters of both pretreatment and acid hydrolysis steps. The optimum of thermal pretreatment step was found for the following operation conditions: Temperature = 100.46°C, time = 20.11 min, and paper–water ratio = 1.45% (w/v) with a yield of 48.69% (w/v) of total sugars while the best conditions for the acid hydrolysis step: Temperature = 96.31°C, time = 20.64 min, and amount of sulfuric acid = 1% (v/v), which led to a yield of 79.65% (w/v) of total sugars. Moreover, physicochemical and thermodynamic characteristics of the produced bioethanol (purity degree of 90% v/v) have shown a good agreement with the standards.

New insights into impact of thermal hydrolysis pretreatment temperature and time on sewage sludge: Structure and composition of sewage sludge from sewage treatment plant

This work investigated the effects of THP temperature (140–200 °C) and time (10–60 min) on the surface morphology, pyrolysis properties, and soluble compounds of dewatered sludge. Results indicate that higher temperature and longer pretreatment time considerably improve organics hydrolysis (the SCOD content increased 1.4–2.46 times, increasing 2.46 times at 200 °C). In addition, high temperature also improved the sludge pyrolysis efficiency (the highest at 200 °C), and reduced the harmful gas release, especially HCN. Moreover, the surface morphology of the sludge changed, the gap and floccules on the surface of the sludge increased. The carbohydrate content increased the highest; approximately 91.9% at 170 °C. THP promoted the decomposition of the nitrogen compounds in the sludge and facilitated their transition to a liquid phase. The total nitrogen and ammonia nitrogen content doubled, and the organic nitrogen content decreased by 50% with time increased from 10 to 60 min.

In situ preparation of CaTiO3 and its effect on CO2 sorption performance of nano-CaO–CaTiO3 adsorbent

ABSTRACT The aim of this work is to prepare the nano-CaO–CaTiO3 adsorbents with both high CO2 sorption capacity and high durability. A series of nano-CaO–CaTiO3 adsorbents with different CaTiO3 grain sizes were in situ prepared by the reaction between TiO2 and nano-CaO with variation of the preparation methods, doping contents and thermal pretreatment conditions. The results showed that the CaTiO3 grain size would decrease by adopting the adsorption phase reaction method, reducing the doping content as well as thermal pretreatment temperature and time properly. Moreover, smaller CaTiO3 grain size was favourable for increasing sorption capacity of the adsorbent, while larger CaTiO3 grain size was more helpful for improving the durability. Under the consideration of the benefit of both the sorption capacity and the durability of adsorbents, the optimal CaTiO3 grain size was got as 23.5 nm and its sorption capacity remained 8.52 mol/kg at the 50th cycle under the actual severe regeneration condition.

Effects of low temperature thermal pretreatments in solubility and co-digestion of waste activated sludge and microalgae mixtures

A low temperature thermal pretreatment was applied to three different ratios of waste activated sludge (WAS) and microalgae mixtures to increase their solubility. The performance of three organic flocculants was assessed in order to select the best flocculant for previous microalgae harvesting. The effect of the following variables in the solubilisation were evaluated: ratio of the mixture of WAS and (flocculated and non-flocculated) microalgae (50:1, 25:1 and 10:1, in v:v basis), incubation time (24, 48 and 72 h) and temperature (37 and 60 °C). A cationic polymer of diallyl dimethyl ammonium chloride free of acrylamide was selected for microalgae flocculation due to its high harvesting efficiency (95%). In pretreatments at 37 °C, effect of temperature and time in the solubilisation of the mixtures was negligible. However, results showed a high increase in solubilisation pretreatments at 60 °C using both flocculated and non-flocculated microalgae in the mixtures. Initial soluble chemical oxygen demand in the mixtures containing WAS and flocculated microalgae was higher in comparison with that in the mixtures of the same ratio without previous flocculation of the microalgae. According to the results, the optimal pretreatment conditions were incubation of the mixtures during 24 h at 60 °C in a 25:1 (WAS:microalgae, in v:v basis) mixing ratio. Thus, these optimal mixtures using flocculated microalgae and non-flocculated microalgae were chosen to assess the effect of the pretreatment in the biogas yield. The anaerobic co-digestion of the selected mixtures indicated a lack of proportionality between the soluble chemical oxygen demand attained during the pretreatment and the methane yield obtained (51 and 34% lower in comparison to the control, respectively). This behaviour could be explained by the high organic matter consumption in the low temperature thermal pretreatment before the anaerobic co-digestion, which could have been fostered by the enzymatic activity of the sludge.

Optimization of temperature and pretreatments for methane yield of hazelnut shells using the response surface methodology

In this study, NaOH pretreatment, H2SO4 pretreatment, thermal pretreatment and production temperature were optimized to ensure maximum methane yield from hazelnut shells (HS) using the response surface methodology (RSM). A Box-Behnken design was achieved with four different independent variables and one dependent variable (methane yield). A total of 29 tests were performed after pretreatment according to the RSM design and to different production temperatures, suggesting optimum values for NaOH pretreatment, H2SO4 pretreatment, thermal pretreatment and production temperature were 3.5% w/v, 2.56% v/v, 145.66 °C and 34.65 °C, respectively. Under these conditions, the RSM-predicted methane yield was 215.896 mL/g volatile solid (VS). The high R2 value (0.9904) showed that the model could be applied effectively in the digestion of HS for the predicted methane yield according to the production temperature and pretreatments. In addition, lignocellulosic solubilisation was tested after pretreatment of the reactors according to the RSM operating conditions, which showed that the highest cellulose, hemicellulose and lignin solubilisation that could be achieved was 38.7% w/w (R10), 36.9% w/w (R22) and 50.5% w/w (R10), respectively. The modified Gompertz model supported the experimental cumulative methane yields (CMYs).