Thermochemical Conversion Processes Research Articles

An Overview of the Thermochemical Valorization of Sewage Sludge: Principles and Current Challenges

With the increase in the world population and economic activity, the production of sewage sludge has grown, and its management has become an environmental problem. The most traditional method of managing sewage sludge is to dispose of it in landfills and on farmland. One way to valorize sewage sludge is to use thermochemical conversion processes to produce added-value products such as biochar, biofuels, and renewable gases. However, due to the high moisture content, thermochemical conversion using processes such as pyrolysis and traditional gasification involves multiple pre-treatment processes such as material drying. Hydrothermal thermochemical processes usually require high pressures, which pose many challenges to their application on a large scale. In this work, the advantages and disadvantages of the different existing thermochemical processes for the recovery of sewage sludge were analyzed, as well as the resulting industrial and environmental challenges. A SWOT analysis was carried out to assess the different thermochemical processes in terms of technical feasibility, economic viability, and broader market considerations.

Synergistic effects on properties of biofuel and biochar produced through co-feed pyrolysis of Erythrina indica and Azadirachta indica biomass

Co-feed pyrolysis is a thermochemical conversion process that entails the simultaneous or sequential decomposition of various feedstock in an oxygen-free environment, concurrently improving the quality of the end products. The technique is widely used to produce a range of valuable products, including biofuels, chemicals and biochar, capitalizing on the synergies between various feedstock. The current study focuses on the synergistic effects of co-feed pyrolysis of Erythrina indica (EI) and Azadirachta indica (AI) biomass at different co-feed ratios (EI:AI) of 1:4, 1:3, 1:2, 1:1, 2:1, 3:1 and 4:1 on weight basis. The reactions were carried out at a temperature of 600 °C under a pressure of 1 bar using nitrogen as inert atmosphere. The bio-oil yield produced through the co-feed pyrolysis reactions ranged from 29.51 to 32.40 % by weight, while the biochar and non-condensable gases yields ranged from 38.25 to 42.48 % and 26.90 to 30.73 % by weight, respectively. Positive synergistic effects of co-feed pyrolysis led to a notable enhancement in physicochemical properties of the fuel phase, especially by virtue of calorific value, density and presence of low mol. wt. components when compared to their individual counterparts. Specifically, the fuel phase obtained at 1:1 co-feed ratio exhibited the peak calorific value of 36.80 MJ/kg along with lowest density of 0.82 g/ml and pH of 3.58 which is the pinnacle accomplishment of this work; and comparable with commercial gasoline. Gas chromatography and mass spectroscopy of biofuels revealed alkanes, alkenes, alcohols, aromatics, esters, nitro compounds and organosilicons as their main compounds. Specific compounds, including cyclopentane, methyl-, 1-cyclohexyl-2-propen-1-ol and 1-pentene, 3-methyl, are the most significant compounds at co-feed ratio of 1:1. Biochar produced at co-feed ratio of 1:1 also depicted excellent physiochemical properties with the highest elemental carbon of 79.23 wt % and lowest oxygen and hydrogen contents of 18.49 wt % and 2.28 wt %, respectively with a maximum calorific value of 29.23 MJ/kg; which can be utilized as solid fuels. The biochar produced from the co-feed pyrolysis reactions also possesses highly porous structure which can be useful as a soil conditioner, carbon sequestration water filtration or wastewater treatment. Additionally, non-condensable gases composed of 7.45 vol % hydrogen, 34.26 vol % carbon monoxide, 21.32 vol % methane and 36.97 vol % carbon dioxide when co-feed ratio is 1:1.

Experimental investigation on utilization of Sesbania grandiflora residues through thermochemical conversion process for the production of value added chemicals and biofuels

All the countries in the world are now searching for renewable, environmentally friendly alternative fuels due to the shortage and environmental problems related with the usage of conventional fuels. The cultivation of cereal and noncereal crops through agricultural activities produces waste biomasses, which are being evaluated as renewable and viable fossil fuel substitutes. The thermochemical properties and thermal degradation behavior of Sesbania grandiflora residues were investigated for this work. A fluidized bed reactor was used for fast pyrolysis in order to produce pyrolysis oil, char and gas. Investigations were done to analyze the effect of operating parameters such as temperature (350–550 °C), particle size (0.5–2.0 mm), sweeping gas flow rate (1.5–2.25 m3/h). The maximum of pyrolysis oil (44.7 wt%), was obtained at 425 °C for 1.5 mm particle size at the sweep gas flow rate of 2.0 m3/h. Fourier transform infrared spectroscopy and gas chromatography-mass spectrometry methods were used to examine the composition of the pyrolysis oil. The pyrolysis oil is rich with aliphatic, aromatic, phenolic, and some acidic chemicals. The physical characteristics of pyrolysis oil showed higher heating value of 19.76 MJ/kg. The char and gaseous components were also analyzed to find its suitability as a fuel.

Hydrothermal co-liquefaction of microalgae, sugarcane bagasse, brewer's spent grain, and sludge from a paper recycling mill: Modeling and evaluation of biocrude and biochar yield

Biomass can be used as an energy source to thermochemical conversion processes to biocrude production. However, the supply and dependence on only one biomass for biocrude production can be an obstacle due to its seasonality, availability, and logistics costs. In this way, biomass waste and agroindustrial residues can be mixture and used as feedstock to the hydrothermal co-liquefaction (co-HTL) process as an alternative to obtaining biocrude. In this sense, the present paper analyzed the biocrude yield influence of the co-HTL from a quaternary unprecedented blend of different biomasses, such as sugarcane bagasse, brewer's spent grain (BSG), sludge from a paper recycling mill (PRM), and microalgae (Chlorella vulgaris). In this way, a simplex lattice design was employed and co-HTL experiments were carried out in a 2000 mL high-pressure stirred autoclave reactor under 275 °C for 60 min, considering 15% of feedstock/water ratio. Significant effects in each feedstock and their blends were analyzed aiming to increase biocrude and biochar yield. It was found that the addition of microalgae is only significant when considered more than 50% into the blend with BSG and PRM sludge to increase biocrude yield.

Effect of Bone Char Application on Soil Quality, Soil Enzyme and in Enhancing Crop Yield in Agriculture: A Review

Soil quality, in contrast to air or water, exhibits a heightened level of heterogeneity and necessitates closer examination due to its impact on the well-being of flora, fauna, and human beings. Organic carbon is considered a fundamental indicator of soil quality, as it plays a significant role in strategies aimed at mitigating climate change. The generation of bone char arises from a thermochemical conversion process involving defatted bones. Specific attention is focused on the solubility of P compounds, which serves to classify bone chars as potential slow-release P fertilizers. The introduction of P into the soil can be enhanced through an "internal activation" process facilitated by the adsorption of reduced S compounds. Additional properties of agronomic significance originate from the porosity of bone char, which promotes water retention and provides a habitat function for soil microorganisms. The evaluation of soil quality has been a longstanding practice, involving an examination of physical and chemical characteristics such as pH, nitrogen levels, soil organic carbon, bulk density, accessible water, aggregate stability, particle size distribution, and soil structure. Recently, the concept of soil quality has been expanded to encompass the notion of soil health, which is perceived as a finite, non-renewable resource that undergoes constant change. Research also demonstrates the crucial role of soil biota in the assessment of soil quality, as they exhibit rapid responsiveness to disturbances. Animal bones undergo a process of defatting, degelatinization, and subsequent incineration at temperatures ranging from 600-800°C to produce bone char (BC). Reports indicate that typical BC contains 152 g P kg<sup>-1</sup>, 280 g Ca kg<sup>-1</sup>, and 6.5 g Mg kg<sup>-1</sup>, with carbon content typically falling below 100 g kg<sup>-1</sup>. The solubility of bone char in the soil depends on factors such as pH and the soil's capacity to absorb P, situating it within the range between rock phosphate and triple super phosphate (TSP). The application of bone char to the soil can enhance soil health, resulting in increased crop yield and improved quality.

Floating Aquatic Macrophytes in Wastewater Treatment: Toward a Circular Economy

Floating aquatic macrophytes have a high level of proficiency in the removal of various contaminants, particularly nutrients, from wastewater. Due to their rapid growth rates, it is imperative to ensure the safe removal of the final biomass from the system. The ultimate macrophyte biomass is composed of lignocellulose and has enhanced nutritional and energy properties. Consequently, it can serve as a viable source material for applications such as the production of bioenergy, fertilizer and animal feed. However, its use remains limited, and in-depth studies are scarce. Here, we provide a comprehensive analysis of floating aquatic macrophytes and their efficacy in the elimination of heavy metals, nutrients and organic pollutants from various types of wastewater. This study offers a wide-ranging scrutiny of the potential use of plant biomasses as feedstock for bioenergy generation, focusing on both biochemical and thermochemical conversion processes. In addition, we provide information regarding the conversion of biomass into animal feed, focusing on ruminants, fish and poultry, the manufacture of fertilizers and the use of treated water. Overall, we offer a clear idea of the technoeconomic benefits of using macrophytes for the treatment of wastewater and the challenges that need to be rectified to make this cradle-to-cradle concept more efficient.

Energy potential of biomass from rice husks in bangladesh: An experimental study for thermochemical and physical characterization

Rice husks, abundant leftovers from rice production, offer immense potential as a renewable energy source through thermochemical conversion processes. However, their efficient utilization hinges on understanding their unique thermal properties and reaction kinetics. This study addresses a critical gap by meticulously analyzing four prominent Bangladeshi rice husk varieties: BR22, BRRI Dhan46, BRRI Dhan47, and BRRI Dhan49. Through rigorous experimentation, we unveil a comprehensive dataset encompassing their physical, chemical, and thermochemical characteristics. Our investigation reveals favorable alignment of moisture content with various conversion technologies, alongside suitable bulk density for efficient handling. Proximate analysis sheds light on crucial components like ash, volatile matter, and fixed carbon, vital for optimizing combustion efficiency. Furthermore, elemental analysis not only highlights the presence of ash-forming elements but also assures low nitrogen and sulfur content, suggesting potential environmental benefits compared to conventional fuels. Delving into thermochemical characteristics, we measured higher heating values ranging from 13.31 MJ/kg to 14.42 MJ/kg, confirming the viability of these rice husk varieties for energy conversion. Thermogravimetric and kinetic analyses further illuminate their unique decomposition behavior, with BRRI Dhan47 exhibiting the highest decomposition rate, emphasizing the distinct reactivity profiles of different varieties. This extensive dataset empowers researchers and industry professionals with valuable insights for informed decision-making. By understanding the unique attributes of each rice husk variety and their behavior during conversion, we can optimize operational parameters for various thermochemical methods. Ultimately, this study bridges a critical research gap and paves the way for more efficient and sustainable utilization of rice husks as a renewable energy source, contributing to a greener future.

Enhancing biomass Pyrolysis: Predictive insights from process simulation integrated with interpretable Machine learning models

Waste biomass pyrolysis is a promising thermochemical conversion process for the production of biofuels and sustainable materials. However, it is challenging to accurately predict the properties and yield of products formed during pyrolysis. Machine learning (ML) is a useful tool for predicting the performance of a process. In the present study, ML algorithms integrated with process simulation were explored to accurately model waste biomass pyrolysis based on properties such as H/C, O/C, oil yield, gas yield, and char yield. Six different ML models including Random Forest (RF), Gradient Boosting Regressor (GBR), eXtreme Gradient Boosting (XGBoost), Adaptive Boosting (AdaBoost), Artificial Neural Network (ANN), and Stochastic Gradient Descent (SGD) were used to model pyrolysis process. It was found that the out-of-the-box (without optimization) models for RF, XGBoost, ANN, and GBR performed the best and did not benefit from hyperparameter optimization. The GBR was identified as the most effective among various ML models. It accurately predicted yields of gas, biochar, bio-oil yields, and their H/C and O/C compositions. GBR effectively demonstrated the complex relationships between these variables. The box plot showing the root mean squared logarithmic error (RMSE) revealed that the GBR model had the best overall performance with a value less than 0.03. Also, the partial dependence plot and SHAP feature importance were evaluated to better understand each feature's effect on the output. Lastly, a shareable graphical user interface (GUI) was created to enable researchers explore and predict pyrolysis yield.

Artificial intelligence methods for modeling gasification of waste biomass: a review.

Gasification is a highly promising thermochemical process that shows considerable potential for the efficient conversion of waste biomass into syngas. The assessment of the feasibility and comparative advantages of different biomass and waste gasification schemes is contingent upon a multifaceted combination of interrelated criteria. Conventional analytical approaches employed to facilitate decision-making rely on a multitude of inadequately defined parameters. Consequently, substantial efforts have been directed toward enhancing the efficiency and productivity of thermochemical conversion processes. In recent times, artificial intelligence (AI)-based models and algorithms have gained prominence, serving as indispensable tools for expediting these processes and formulating strategies to address the growing demand for energy. Notably, machine learning (ML) and deep learning (DL) have emerged as cutting-edge AI models, demonstrating exceptional effectiveness and profound relevance in the realm of thermochemical conversion systems. This study provides an overview of the machine learning (ML) and deep learning (DL) approaches utilized during gasification and evaluates their benefits and drawbacks. Many industries and applications related to energy conversion systems use AI algorithms. Predicting the output of conversion systems and subjects linked to optimization are two of this science's critical applications. This review sheds light on the burgeoning utility of AI, particularly ML and DL, which have garnered significant attention due to their applications in productivity prediction, process optimization, real-time process monitoring, and control. Furthermore, the integration of hybrid models has become commonplace, primarily owing to their demonstrated success in modeling and optimization tasks. Importantly, the adoption of these algorithms significantly enhances the model's capability to tackle intricate challenges, as DL methodologies have evolved to offer heightened accuracy and reduced susceptibility to errors. Within the scope of this study, an exhaustive exploration of ML and DL techniques and their applications has been conducted, uncovering existing research knowledge gaps. Based on a comprehensive critical analysis, this review offers recommendations for future research directions, accentuating the pivotal findings and conclusions derived from the study.

Nanoarchitectonics of self-supporting porous carbon electrode with heteroatoms co-doped: For high-performance supercapacitors

Wood possesses a uniform hierarchical porous structure and high mechanical strength, rendering it an excellent precursor for the preparation of self-supporting carbon electrodes without binders and conductive agents. This paper presents an efficient method for synthesizing a self-supporting carbon electrode (HCW-0.7) with high specific surface area, hierarchical pore structure and abundant surface functional groups, utilizing simple hydrothermal pre-treatment and one-step thermochemical conversion process. The HCW-0.7 electrode demonstrates remarkable electrochemical performance, achieving an excellent specific capacitance of 298.52 F g−1 under a current density of 0.5 A g−1. The wood-based symmetrical supercapacitor (HSC) constructed with HCW-0.7 as the electrode has excellent energy density, power density and rate performance. At the power density of 287.5 W kg−1, HSC demonstrates an energy density of 9.43 Wh kg−1, exhibits its excellent electrochemical performance. Notably, even when subject to a higher power density of 5750 W kg−1, the energy density remains at 5.16 Wh kg−1. Furthermore, even after 20,000 charge and discharge cycles, HSC demonstrates a remarkable capacity retention rate of 96.24 %.

Comparison of Waste Biomass from Pine, Eucalyptus, and Acacia and the Biochar Elaborated Using Pyrolysis in a Simple Double Chamber Biomass Reactor

Using waste biomass is considered one of the ways to reduce climate change. Arboreal waste biomass from pine, eucalyptus, and particularly invasive plants (Acacias) would make it possible to transform this natural resource, but needs to be adjusted to current and innovative technologies. The production of high fixed carbon biochar with this biomass would improve not only environmental aspects, but also the use of currently not susceptible materials for other types of exploitation. The objective of this study is to develop biochar from three different waste biomass materials and compare their parameters with those of the original biomass. Thermochemical conversion processes were used in a simple double chamber reactor developed for this study. Temperatures between 400 and 500 °C during 280 min were achieved and allowed to transform the initial biomass in a biochar with a high content of fixed carbon. By comparing the original biomass with the final biochar through tests of humidity, density, calorific values, fixed carbon, and cationic and elemental analysis, an increase in the parameters was confirmed. Fixed carbon of 70%, 77%, and 71% with pine, acacia, and eucalyptus biomass have been obtained, respectively, with yields between 30% and 40%. The results are favorable, particularly with acacia invasive plants, and could help in their difficult silviculture management.

Experimental strategy for the preparation of adsorbent materials from torrefied palm kernel shell oriented to CO2 capture

In this study, an experimental strategy to obtain biochar and activated carbon from torrefied palm kernel shell as an efficient material for CO2 removal was evaluated. Biochar was obtained by slow pyrolysis of palm kernel shell at different temperatures (350 °C, 550 °C, and 700 °C) and previously torrefied palm kernel shell at different temperatures (220 °C, 250 °C, and 280 °C). Subsequently, activated carbons were prepared by physical activation with CO2 from previously obtained biochar samples. The CO2 adsorption capacity was measured using TGA. The experimental results showed that there is a correlation between the change in the O/C and H/C ratios and the functional groups –OH and C=O observed via FTIR in the obtained char, indicating that both dehydration and deoxygenation reactions occur during torrefaction; this favors the deoxygenation reactions and makes them faster through CO2 liberation during the pyrolysis process. The microporous surface area shows a significant increase with higher pyrolysis temperatures, as a product of the continuous carbonization reactions, allowing more active sites for CO2 removal. Pyrolysis temperature is a key factor in CO2 adsorption capacity, leading to a CO2 adsorption capacity of up to 75 mg/gCO2 for biochar obtained at 700 °C from non-torrefied palm kernel shell (Char700). Activated carbon obtained from torrefied palm kernel shell at 280 °C (T280-CHAR700-AC) exhibited the highest CO2 adsorption capacity (101.9 mg/gCO2). Oxygen-containing functional groups have a direct impact on CO2 adsorption performance due to electron interactions between CO2 and these functional groups. These findings could provide a new experimental approach for obtaining optimal adsorbent materials exclusively derived from thermochemical conversion processes.

Thermochemical Conversion of Animal-Derived Waste: A Mini-Review with a Focus on Chicken Bone Waste

Food waste, particularly animal-derived waste, presents a significant challenge globally, prompting the need for sustainable management strategies. In 2022, the amount of food waste per capita reached 131 kg/capita in the EU (European Union), which is why the search for environmentally friendly ways to manage food waste through thermochemical conversion processes has gained momentum in recent years. Animal-derived waste is a good source of organic matter (proteins, lipids, and polysaccharides) and mineral compounds (calcium phosphate, mostly hydroxyapatite). This composition makes animal-derived waste valuable for the extraction of chemical compounds, such as hydroxyapatite (HAp), which constitutes up to 70 wt% of animal bones; keratin; collagen; and hyaluronic acid (HA), to produce pharmaceutical, medical, or industrial by-products. The thermochemical conversion of chicken bones through pyrolysis and gasification creates a new opportunity to valorize this type of waste by reintroducing valuable by-products into the economy and thus achieving sustainable waste management objectives. The results of this study showcase the multiple applications of the pyrolysis of chicken bone waste products (as adsorbents in aqueous mediums, catalysts, fertilizers, and biomedical applications) and the necessity of a better exploration of the gasification process of chicken bone waste. Therefore, this study explores the properties of animal-derived waste and discusses the pyrolysis and gasification of chicken bone waste, the influence of process conditions on product yields, and the catalytic enhancement of these thermochemical processes.

Comparative Assessment of Hydrothermal Gasification and Anaerobic Digestion using Aspen Plus and SuperPro

Wet biomass is gaining increasing attention as an energy source globally. Various wet biomass materials like macroalgae, microalgae, sewage sludge, cattle manures, and food waste, are of high moisture contents, typically around 70% or more. There are two routes of high potential for converting these wet biomasss resoures to gaeous fuel, which are biomethanation and supercritical water gasification (SCWG). Biomethanation is conversion of wet-organic residues to biogas using via anaerobic digestion process. SCWG is a thermochemical conversion process, taking place in supercritical water producing enriched CH4 and H2 gases. In this study, the two processes are comperatively investigated using different process simulation softwares. Aspen Plus was employed for SCWG, while the biomethanation process was simulated with SuperPro. Various raw materials were used as input. We calculated the energy efficiency of the biomethanation process using experimental yields from the literature. For the SCWG process, we determined the higher heating value based on the simulated composition of the methane-enriched gas. Additionally, we conducted an economic analysis to compare the two processes, taking into consideration specific criteria relevant to the Norwegian context.

Application of machine learning in optimizing thermochemical conversion processes with pre-treatment to get higher bio-oil yield from biomass waste

Application of machine learning in optimizing thermochemical conversion processes with pre-treatment to get higher bio-oil yield from biomass waste

The effect of hydrogen peroxide treatment on functional properties of paddy husk biochar and its application for wastewater treatment

Paddy husk is one of the biomass raw materials and byproducts of the rice production and processing industry. It is very much abundant in Sri Lanka, which is readily available as an energy source. Paddy husk contains silica as a special characteristic component. Application of paddy husk is novel in Sri Lanka. Though it has perceived implications, the process may impose limitations in its application. Appropriate knowledge of the functional properties of paddy husk is required for applying them in thermochemical conversion processes like pyrolysis. The ultimate objective of this study is to identify the effectiveness of wastewater treatment using biochar, derived from H2O2-treated paddy husk. The changes in functional properties: moisture content, proximate analysis, true density, bulk density, and porosity of paddy husks, before and after H2O2 treatment were evaluated in this study. Two main variables: concentration of H2O2 and treatment temperature, were considered. The H2O2 treatment method was investigated to remove the lignin distributed in the lignocellulosic matrix of paddy husk. The results obtained from this experimental study showed that there was a significant difference in the functional properties of the paddy husk after H2O2 treatment. The biosorbent adsorption process is the finest treatment method, for the removal of methylene blue dye. The use of H2O2-treated paddy husk bio sorbent as an alternative cost-effective adsorbent in the removal of methylene blue has been extensively studied and compiled. Biochar as a firm carbonaceous material shows reasonable potential to oversee wastewater contaminants, due to induced pore spaces that are responsible for the removal of contaminants.

Unveiling radical pathways in the pyrolysis of eugenol: Experimental and computational insights

Understanding the lignin pyrolysis mechanism holds significant importance for enhancing thermochemical conversion processes and advancing the refinement of biofuels. In this paper, a mechanism study was conducted on the pyrolysis of eugenol within the temperature range of 450 to 750 °C, utilizing synchrotron photoionization mass spectrometry coupled with density functional theory. 5-allyl-2-hydroxyphenoxyl radical (m/z 149) and other major radicals were detected experimentally during eugenol pyrolysis for the first time. The cleavage of the O-CH3 bond was confirmed as the main initial unimolecular pyrolysis pathway compared with other hemolysis and isomerization reactions. Radical-assisted bimolecular reactions initiated by CH3 and H atoms, such as ipso substitution and abstraction reactions, were well discussed. Radical-assisted abstractions made the most contribution to the formation of main radicals and products at high temperatures. Furthermore, quinone-type products were determined and their formation pathways were discussed. This research provides insights into eugenol pyrolysis, shedding light on the fundamental mechanisms of thermochemical conversion of lignin.

Valorisation of Cranberry Residues through Pyrolysis and Membrane Filtration for the Production of Value-Added Agricultural Products

Pyrolysis is a thermochemical conversion process producing biochar, gas, and bio-oil at high temperatures in an oxygen-free environment. Specific pyrolysis conditions enable a significant production of the aqueous phase of bio-oil, commonly known as wood vinegar. Wood vinegar contains organic compounds such as acetic acid and phenols derived from bio-oil. These compounds have herbicidal properties against weeds and biostimulant properties for plant growth. This study reveals the potential for efficient management of cranberry residues consisting of stems and leaves by producing wood vinegar through pyrolysis at 475 °C with a humidity level of 20%. Membrane separation of wood vinegar, using nanofiltration (NF) and reverse osmosis (RO) membranes, yielded phenols in the retentate and acetic acid in the permeate with respective yields of 44.7% with NF membrane and 45% with RO membrane. Biostimulation tests using 2% of the retentate showed significant germination rates for basil, sage, and parsley plants. Additionally, using 40 mL of the wood vinegar permeate (30 mL injected at the base and 10 mL sprayed on the leaves) resulted in leaf damage, measured by conductivity (leakage of electrolytes released by the leaves), of 62.3% and 20.5% respectively for quack grass and white clover, two weeds found in cranberry production.

An experimental investigation of high-temperature thermochemical conversion of oil shale residues into valuable materials

Oil shale residues, a solid waste produced during oil shale mining, extraction, and refining processes, pose a significant challenge to the environment and sustainability. This study aims to develop a thermochemical conversion process to transform oil shale residues into valuable composite materials. Experiments are conducted to investigate the effects of reaction temperature, time, and reactant composition on the reaction behavior and resulting product characteristics. The results demonstrate that mullite-rich composite materials can be prepared at reaction temperatures of around 1300 °C with reaction times of 5 min. Industrial aluminum ash can be used to supplement the aluminum needed for the complete conversion of excess SiO2 in oil shale residue, but it must be thermally treated to eliminate the NaCl content, which hinders mullite formation. Overall, this study offers a viable approach to converting solid waste into valuable resources while simultaneously addressing the environmental concerns associated with oil shale residues.

Study on waste tire pyrolysis product characteristics based on machine learning

Tire pyrolysis is a highly complex thermochemical conversion process that transforms waste tires into high-value products such as pyrolysis oil, pyrolysis gas, and pyrolysis char. This process significantly mitigates the environmental issues caused by waste tires and reduces reliance on fossil resources. The physicochemical properties of tires and pyrolysis operation parameters have a significant impact on the yield of the three-phase products, thus affecting the industrial viability of tire pyrolysis to a large extent. Traditional prediction methods such as computational fluid dynamics and process simulation often fail to provide satisfactory results. However, data-driven machine learning (ML) models have demonstrated their ability to handle complex nonlinear problems and offer more reliable predictions of pyrolysis products yield. This study employed a collected database of tire pyrolysis to develop tire pyrolysis product prediction models based on five ML models. These models were further optimized using Particle Swarm Optimization (PSO), and their prediction performances were quantitatively evaluated to identify the optimal model. Shapley analysis and one-way partial dependence analysis were conducted to explore the impact of input features on the output responses. Furthermore, an industrial-grade software was developed for accurate prediction of tire pyrolysis three-phase products yield. The results revealed that Gaussian process regression (GPR) and random forest regression (RFR), both optimized with PSO, demonstrated impressive prediction performance. Among them, the GPR model achieved the highest prediction accuracy with coefficient of determination (R2) values of 0.964, 0.924, and 0.86 for oil, char, and gas yields respectively, during the testing stage.