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[Display omitted] • Supercritical toluene was used to depolymerize e-waste thermoplastics. • STL temperature and time on depolymerization of PA, PC, POM, and PEEK were studied. • STL conversion reached 100% for PEEK but only reached 32.23% for POM. • Depolymerized PA and PC resulted in significant nitrogen containing chemicals. Solvothermal liquefaction (STL) is a thermochemical conversion technique that employs solvents other than water to transform waste plastics into valuable compounds. The objective of this study was to explore the potential use of supercritical toluene, a nonpolar solvent, for the depolymerization of four electrical waste (e-waste) thermoplastics, namely polyamide (PA), polycarbonate (PC), polyoxymethylene (POM), and polyether ether ketone (PEEK), into liquid products. Depolymerization experiments were carried out in batch reactors at three reaction temperatures (325, 350, and 375 °C), and three residence times (1, 3, and 6 h). The findings revealed that increasing STL temperature and extending the reaction time enhances the depolymerization of e-waste thermoplastics. The highest STL conversation (100 %) was observed for POM, and the lowest STL conversation (32.23 %) was observed for PEEK. Additionally, the ultimate analysis showed that the liquid product obtained from STL at 375 °C and 6 h exhibited higher heating values (HHV) within the range of 31.43 to 35.31 MJ/kg. Thermogravimetric analysis (TGA) demonstrated that the boiling point distributions of liquid products are highly dependent on thermoplastic type. Finally, the reaction mechanisms of STL for PA, PC, POM, and PEEK were proposed based on gas chromatography-mass spectrometry (GCMS) analysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • Acidic hydrochar enhances dechlorination of waste PVC during co-HTT. • co-HTT of waste PVC improves energy content of HTT solid residues. • co-HTT solids showed higher ignition temperature and lower burnout temperatures. • co-HTT solids had low slagging, fouling and alkali indices. In this study, the chlorine mitigation from waste polyvinyl chloride (WPVC) during high temperature co-hydrothermal treatment (co-HTT) and the properties of the generated solid products were assessed. WPVC was co-fed with acidic hydrochar (AHC), which was produced via hydrothermal carbonization of pineapple waste in the presence of citric acid water solution. High temperature co-HTT experiments were performed at 300–350 °C, 0.25–4 h of reaction time, and 0–20 wt% AHC loading. Co-HTT solid products (co-HTT_SP) were characterized via proximate analysis, ultimate analyses, combustion analysis, and ash analysis. The results show that the addition of 5% AHC enhances the dechlorination efficiency (DE) of WPVC from 89.35% to 97.66% at 325 °C and 0.5 h. The highest DE, reaching 99.46%, was achieved at 350 °C and 1 h in the presence of 5 wt% AHC. Furthermore, loading 5% AHC improved the higher heat value (HHV) of the solid products from 23.09 to 31.25 MJ/kg at 325 °C and 0.5 h. The maximum HHV (34.77 MJ/kg) of a solid product was achieved at 350 °C, 4 h, in the presence of 5 wt% of AHC. The co-HTT solids shown low slagging indices, fouling indices, alkali indices, and medium chlorine contents. These findings support the viability of WPVC conversion into clean solid fuel via co-HTT. [ABSTRACT FROM AUTHOR]

In this study, carbon dots are synthesized hydrothermally from loblolly pine using top-down and bottom-up processes. The bottom-up process dialyzed carbon dots from hydrothermally treated process liquid. Meanwhile, hydrochar was oxidized into carbon dots in the top-down method. Carbon dots from top-down and bottom-up processes were compared for their yield, size, functionality, and quantum properties. Furthermore, hydrothermal treatment temperature and residence time were evaluated on the aforementioned properties of carbon dots. The results indicate that the top-down method yields higher carbon dots than bottom-up in any given hydrothermal treatment temperature and residence time. The size of the carbon dots decreases with the increase in reaction time; however, the size remains similar with the increase in hydrothermal treatment temperature. Regarding quantum yield, the carbon dots from the top-down method exhibit higher quantum yields than bottom-up carbon dots where the quantum yield reaches as high as 48%. The only exception of the bottom-up method is the carbon dots prepared at a high hydrothermal treatment temperature (i.e., 260 °C), where relatively higher quantum yield (up to 18.1%) was observed for the shorter reaction time. Overall, this study reveals that the properties of lignocellulosic biomass-derived carbon dots differ with the synthesis process as well as the processing parameters. [ABSTRACT FROM AUTHOR]

Dechlorination of waste PVC (WPVC) by hydrothermal treatment (HTT) is a potential technology for upcycling WPVC in order to create non-toxic products. Literature suggests that acids can improve the HTT process, however, acid is expensive and also results in wastewater. Instead, the acidic process fluid (PF) of hydrothermal carbonization (HTC) of orange peel was utilized in this study to enhance the dechlorination of WPVC during HTT. Acidic HTT (AHTT) experiments were carried out utilizing a batch reactor at 300–350 °C, and 0.25–4 h. The finding demonstrated that the dechlorination efficiency (DE) is high, which indicates AHTT can considerably eliminate chlorine from WPVC and relocate to the aqueous phase. The maximum DE of 97.57 wt% was obtained at 350 °C and 1 h. The AHTT temperature had a considerable impact on the WPVC conversion since the solid yield decreases from 56.88 % at 300 °C to 49.85 % at 350 °C. Moreover, AHTT char and crude oil contain low chloride and considerably more C and H, leading to a considerably higher heating value (HHV). The HHV increased from 23.48 to 33.07 MJ/kg when the AHTT time was raised from 0.25 to 4 h at 350 °C, indicating that the AHTT time has a beneficial effect on the HHV. The majority fraction of crude oil evaporated in the boiling range of lighter fuels include gasoline, kerosene, and diesel (57.58–83.09 wt%). Furthermore, when the AHTT temperature was raised from 300 to 350 °C at 1 h, the HHV of crude oils increased from 26.11 to 33.84 MJ/kg. Crude oils derived from AHTT primarily consisted of phenolic (50.47–75.39 wt%), ketone (20.1–36.34 wt%), and hydrocarbon (1.08–7.93 wt%) constituents. In summary, the results indicated that AHTT is a method for upcycling WPVC to clean fuel. [Display omitted] • Acidic process fluid improves dechlorination of waste PVC through AHTT. • AHTT's char has higher ignition temperature and lower burnout temperature. • The char has low slagging, fouling and alkali indexes, and chlorine content. • The HHV of the AHTT's crude oil are between 26.11 and 34.6 MJ/kg. [ABSTRACT FROM AUTHOR]

• The energy analysis demonstrated the first law efficiency of the VRM is 62.1%. • The exergy analysis demonstrated the second law efficiency of the VRM is 34.6%. • The classifier rotor speed increase from 53 to 65 rpm, the particle size decrease significantly. • VRM unit consumes around 9.75 kWh/t more energy to grind raw material than the IBAT unit. In this study, the analyses of energy and exergy were implemented for an industrial-scale vertical roller mill (VRM) of Kerman Momtazan Cement Company (KMCC) of Iran. The energy and exergy analyses demonstrated the first law efficiency of the VRM is 62.1%, while the second law efficiency of the VRM is 34.6%. Comparing to the widely applied ball milling, the second law efficiency is 16.4% higher for the VRM than the ball mill. Results also showed when the classifier rotor speed increases from 53 to 65 rpm, the particle size of the product decreases from P 90µm = 18.2% to P 90µm = 10.8%, but the power consumption of the VRM unit increases from 19.7 to 22.3 kWh/t of raw materials. Finally, the power consumption of the VRM unit compared with 14 raw mill units around Iran and the international best available technology (IBAT). The results demonstrated that the VRM unit consumes around 81% (9.75 kWh/t of raw materials), and 36% (5.8 kWh/t of raw materials) more energy to grind raw material than the IBAT unit and domestic best raw mill (DBRM), respectively. [ABSTRACT FROM AUTHOR]

• The energy and exergy analyses were performed on a cement ball mill (CBM). • The effect of ball charge pattern on the performance of the CBM was investigated. • The effect of cement fineness on the energy consumption of the CBM was studied. • The effect of two additive materials on the CBM was investigated. • Some practical methods to optimize the efficiency of the CBM were presented. Nowadays, ball mills are used widely in cement plants to grind clinker and gypsum to produce cement. In this work, the energy and exergy analyses of a cement ball mill (CBM) were performed and some measurements were carried out in an existing CBM in a cement plant to improve the efficiency of the grinding process. The first and second laws efficiency of the CBM was specified to be 80.5% and 19.9%, respectively. The electrical energy consumption of the CBM unit was specified to be 37.9 kWh/t. The effects of ball charge pattern, cement fineness and two additive materials (limestone and pozzolan) on the performance of the CBM unit and the quality of cement were investigated. The first and second laws efficiency of the CBM increased (81.8% and 20.6%) and the electrical energy consumption of CBM unit decreased (36.5 kWh/t) after modifying the ball charge pattern. Also, the results demonstrated that cement production rate increases (185–224 t/h) and the electrical consumption decreases (41.1–33.1 kWh/t) when cement fineness decreases (3250 –2820 cm2/g). However, the cement compressive strength (3, 7 and 28 days) decreases and the cement setting time (initial and final) increases by reducing the cement fineness. Besides, when the clinker was replaced by limestone or pozzolan, on the one side, the efficiency of the first and second laws of the CBM unit was increased, but on the other side the cement compressive strength was decreased and the cement setting time was increased. [ABSTRACT FROM AUTHOR]

About 40 million tons of plastic waste were produced in the USA in 2021. Waste polyvinyl chloride (WPVC), which is a halogenated material, makes up a significant component of plastic waste. It is vital to design a dependable approach for treating WPVC in a safe and eco-friendly manner without the emission of chlorinated organic chemicals. Dechlorination of WPVC by hydrothermal treatment (HTT) is a viable approach for developing a non-toxic and virtually totally closed WPVC treatment system. According to the literature, noble metal catalysts are often employed to speed HTT. In this study, Pd/C, Ru/C, and Pt/C were used in HTT to promote the dichlorination of WPVC. HTT experiments were carried out using a Hast-C Parr batch reactor at temperatures ranging from 300 to 350 °C for a duration of 0.25 to 4 h. The results indicated that Pd/C, Ru/C, and Pt/C can improve dichlorination efficiency (DE). The maximum DE was 99.1 %, which was achieved at 350 °C and 1 h in the presence of 10 wt% Pd/C. In addition, the HTT solid product has a low chloride content in addition to a high amount of carbon and hydrogen, which results in a much higher heating value (HHV). It indicates that there is a feasible possibility of upcycling WPVC into a clean solid fuel using HTT. [ABSTRACT FROM AUTHOR]

Abstract In this work, firstly the energy audit was performed on the pyro-processing unit of a cement plant in Iran to improve the efficiency of the clinker production process and operating the system. In this plant, fuel combustion is the main source of thermal energy due to generation about 94% of the total heat input energy of system that it used for the clinker production process. The results indicated about 50% of total heat input was consumed for the clinker formation and 48% of it was lost in the form of radiation from the shell of the kiln, grate cooler, preheater, and convection along with exhaust gases from the pyro-processing unit. Also, the thermal efficiency of the pyro-processing unit was 50% that is in the range of modern plants thermal efficiency (50–54%). Secondly, according to the obtained data, the potential of electrical energy production from the exhaust gases of preheater and grate cooler was evaluated through the waste heat recovery power generation (WHRPG) unit. It was found that about 5.2 MWh power can be produced in WHRPG unit. Finally, the economic feasibility showed that the time of return of capital could be about 6.7 years. Highlights • The energy audit was performed on the pyro-processing unit of a cement plant. • An applied methodology for the thermal energy audit was presented. • The potential of electrical energy production from the exhaust gases was evaluated. • The economic feasibility of recovering the thermal energy was investigated. • The results showed that about 5.2 MWh power could be produced in WHRPG unit. [ABSTRACT FROM AUTHOR]

In this study, the equilibrium adsorption isotherms of N 2 , CH 4 and CO 2 on two types of activated carbon adsorbents were measured. The experimental data of the equilibrium adsorption were fitted to the Sips isotherm model at different temperatures. It was found that the Sips model is appropriate to predict the behavior of gas adsorption. Moreover, a method based on the Gibbs energy of desorption of the solid adsorbent was used to estimate the amount of separation factor of binary mixtures at different temperatures. Also, the amount of gas adsorption on activated carbon was predicted by using the artificial neural network-genetic algorithm (ANN-GA) model. The results of the ANN-GA model indicated that the performance of the model for predicting the behavior of gas adsorption is acceptable. Finally, the extended Sips model was used to simulate the multi-component adsorption of three binary mixtures CO 2 /N 2 , CH 4 /N 2 and CO 2 /CH 4 , and the results of this model were validated by experimental data. [ABSTRACT FROM AUTHOR]