Solid Products Research Articles

Influence of Hydrothermal Carbonization (HTC) Temperature on Hydrochar and Process Liquid for Poultry, Swine, and Dairy Manure

Hydrothermal carbonization (HTC) is a promising technology for wet manure treatment by converting animal manure into valuable fuels, materials, and chemicals. Among other HTC process parameters, the temperature influences HTC products the most. As various animal manures have different compositions, it is not certain how the HTC temperature influences the hydrochar and HTC process liquid. To evaluate the temperature’s effect on HTC, three different manures (poultry, swine, and dairy) were hydrothermally carbonized at three different temperatures (180, 220, and 260 °C), and solid and liquid products were characterized for their morphology, elemental compositions, and ions. The carbon contents of the hydrochar reached as high as 38.98 ± 0.36% and 40.05 ± 0.57% for poultry and swine manure, respectively, when these manures were treated at 260 °C. Ammonium showed an around 30% increase in poultry manure hydrochar with the increase in the HTC temperature. In contrast, in swine manure, it decreased by around 80%, and in dairy manure, the HTC temperature did not have any remarkable effect on the ammonium content. The process liquids from HTC of dairy manure at 220 °C showed the most balanced distribution of different ions, with 4970 ± 673 ppm of sodium, 4354 ± 437 ppm of ammonium, 2766 ± 417 ppm of potassium, 978 ± 82 ppm of magnesium, 953 ± 143 ppm of calcium, 3607 ± 16 ppm of chloride, and 39 ± 7 ppm of phosphate. These results emphasize the manure-specific effects of the HTC temperature on both solid and liquid products, indicating the need for optimized strategies to enhance HTC processes for various types of animal manures.

STUDY ON ENGINEERING PROPERTIES OF SOIL USING STONE DUST AND BAGASSE ASH

In the discipline of civil engineering, soil stabilization is the process of enhancing and improving the engineering qualities of soil so that it can support large loads without failing. The safe and efficient disposal of waste material without causing harm to society is a significant concern in a well-managed ecosystem. Utilizing solid waste products to stabilize soil has become more popular recently as a successful way to manage trash from many sectors. This paper reviews the usage of various solid waste items that have been applied to stabilize soft soils. However, there are numerous approaches and strategies for stabilizing this soil. This research offers a method for stabilizing soft soil using waste products. An investigation into the stabilizing potential of bagasse ash and sisal fiber for highly compressible clayey soil has been prompted by the rising expense of building traditional stabilizers and the necessity of inexpensively consuming industrial and agricultural wastes for value trade. There is a growing demand for sustainable construction, which is why recent research has concentrated on sustainable resource consumption trends. We can employ natural and biodegradable resources, as well as waste products, to obtain. This study was a large-scale laboratory experiment to explore the use of natural fibers, industrial waste, and agricultural waste to improve the engineering qualities of moderately compressible clay. The purpose of this study was to determine whether Stone Dust and Bagasse Ash were suitable for stabilizing clayey soil. The results of testing for consistency limits, maximum dry density, optimal moisture content, UCS, and (soaked) CBR were obtained using percentages of 10%, 15%, and 20% by weight of dry soil for Bagasse Ash and 6%, 8%, and 10% for Stone Dust. In this work, expansive soil was stabilized using Stone Dust and Bagasse Ash. Bagasse Ash was fixed at 15%, after that Stone Dust was changed to 3%, 6%, and 9%. Key Words: Compaction test, CBR, UCS, Stone Dust, Bagasse Ash

Algal-based biochar and hydrochar: A holistic and sustainable approach to wastewater treatment

Biochar and hydrochar are carbon-rich solid products of algal and terrestrial biomass obtained through various thermochemical processes, mainly hydrothermal liquefaction, pyrolysis, and hydrothermal carbonization. Both are regarded as economical, potent, and environmentally friendly adsorbents for wastewater remediation. The versatile applicability of biochar and hydrochar, which is due to their enhanced surface physicochemical properties, includes efficient metal biosorption, soil fertility enhancement, and carbon sequestration. Consequently, there has been an increase in research for producing and exploiting biochar and hydrochar from algae. Both micro- and macro-algal biomass have strong potential due to their sustainability footprint and distinct properties. This review focuses on a comprehensive account of the synthesis of algal biochar and hydrochar and use in wastewater treatment to develop innovative solutions for efficient mitigation of several aqueous pollutants and heavy metal ions. The review discusses the various thermochemical production routes, biophysical characterization techniques, and modes of mechanism for wastewater bioremediation. Algal-based biochar and hydrochar are reported to have higher porosity and more diverse functional groups such as amines, hydroxyl, and carboxyl compared to their cellulosic and waste-derived counterparts, demonstrating an increased wastewater remediation efficiency. In addition, presence of inorganic metal including sodium, potassium, magnesium, and phosphorus in algal chars facilitates the formation of mesopores and graphite structures, improving their cation exchange capacity. Moreover, algal chars may exhibit pH buffering capacity, which could help stabilize the pH during wastewater treatment processes. Notably, the low O/C content of algal hydrochars enhances the binding and removal of organic pollutants including toxic dyes and antibiotics. The review highlights the development of modified algal chars to enhance the porosity, surface area, structural integrity, and adsorption capacity enabling a higher bioremediation potential.

Pemberdayaan Masyarakat Melalui Inovasi Pembuatan Sabun Padat Bajakah Tampala (Spatholobus littoralis Hassk) pada Masyarakat Kampung Ketupat Samarinda

Bajakah tampala is a plant native to Kalimantan that can be found in forests in the interior of Kalimantan. The use of Bajakah Tampala wood is not widely known by most people. One of the uses of Bajakah Tampala wood is that it can be used as an economically valuable product. This community service takes the form of an empowerment program for PKK and Dasawisma women to provide training in making bajakah solid soap. However, before that, education or outreach was carried out regarding solid soap. Of all participants, 22.2% answered that they knew the process of making solid soap, 44.4% knew about solid soap which has a steel composition, and 20% had an understanding of making solid soap. The results of community service activities showed an increase in the total understanding of participants to 100% answered that they knew the process of making solid soap, 100% answered that they knew about solid soap which has a steel composition, and 100% answered that they understood the process of making solid soap. This activity concludes that all participants can better understand the process of making solid soap products and can feel the benefits of Bajakah solid soap.

The Effect of Residence Time during the Hydrothermal Carbonization Process of Sewage Sludge on the Properties of Hydrochar

The optimal process conditions concerning the hydrothermal carbonization of digested sewage sludge are crucial to the economically effective technology needed to produce a solid product, hydrochar, for energy purposes. Accordingly, different residence times, 0.5 h, 1 h and 2 h, were investigated in order to understand the effect of residence time on the process. Furthermore, the physical and chemical properties of hydrochar were investigated and compared to the raw material. For these reasons, analyses describing fuel properties were performed, including ultimate and proximate analyses, HHV, and TGA analysis. The latter method was employed to study the combustion process of solid samples. In addition, the oxide content of different elements within the ash of solid samples was determined using the XRF method to calculate indices related to operational problems during the combustion process. The results confirmed that time did not matter significantly and the physical and chemical properties of hydrochar were very similar to each other. However, the contact angle for 2 h of residence time confirmed that a longer processing time resulted in a more hydrophobic character of hydrochar and enabled more effective dewaterability of hydrothermal slurry. It was also noted that the hydrothermal carbonization process affected the sewage sludge in a positive way. In brief, the results confirmed that the hydrochar was a brittle, moderately hydrophilic, solid carbon-containing product that provided a different combustion performance than the raw sewage sludge.

Hydrothermal Dissolution of Reactive Silica Materials in Sodium Hydroxide Lyes

AbstractReactive silica materials like vitreous silica or cristobalite were dissolved at temperatures between 100 and 220 °C for up to 7 days in NaOH lyes. The liquid and solid reaction products were analyzed chemically. Sodium water glasses with silica concentrations of up to 27 wt % and molar SiO2/Na2O ratios of up to 3.7 were obtained. The experimental data were evaluated by an approximation algorithm. The initial size reduction rates ranged between 0.1 and 7 µm h−1, depending on the temperature and the choice of starting materials. Correlations between thermodynamics and kinetics were discussed.

An Industrial Perspective for Sustainable Polypropylene Plastic Waste Management via Catalytic Pyrolysis—A Technical Report

Recycling plastics on an industrial scale is a key approach to the circular economy. This study presents a techno-economic analysis aimed at recycling polypropylene waste, one of the main consumer plastics. Specifically, it evaluates the technical and economic feasibility of achieving a large-scale cracking process that converts polypropylene waste into an alternative fuel. Pyrolysis is considered as a promising technique to convert plastic waste into liquid oil and other value-added products, with a dual benefit of recovering resources and providing a zero-waste solution. This study concerns a fast catalytic pyrolysis in a fluidized bed reactor, with the presence of a fluid catalytic cracking catalyst of low acidity for high heat transmission, for an industrial plant with a capacity of 1 t/h of polypropylene waste provided by the Greek Petroleum Industry. From the international literature, the operational conditions were chosen pyrolysis temperature at 430 °C, pressure at 1atm, heating rate at 5 °C/min, and yields of products to 71, 14, and 15 wt.%, for liquid fuel, gas, solid product, respectively. The plant design includes a series of apparatuses, with the main one to be the pyrolyzer. The catalytic method is selected over the non-catalytic because the presence of catalyst increases the quantity and quality of the liquid product, which is the main product of the plant. The energy loops of recycling pyrolysis gas and char as a low-carbon fuel in the plant were considered. The production cost, annual revenue, for 2023, are anticipated to reach €13.7 million (115 €/t) and €15 million (15 €/t), respectively, with an estimated investment equal to €5.3 million. The Payback Time is estimated to 2.4 years to recover the cost of investment. The endeavor is rather economically sustainable. A critical parameter for large scale systems is securing feedstock with low or negligible price.

Unified Solid Solution Product of [Nb][C] in Nb-Microalloyed Steels with Various Carbon Contents.

In this work, the solid solution product of [Nb][C] in the Nb-microalloyed steels with various carbon contents in the range of 0.20~1.80 wt.% was investigated by means of the extraction phase analysis method. The results showed that the Nb content in austenite tended to first decrease and then increase with the increase of carbon content in the steels. A unified solid solution product of [Nb][C] in austenite at different temperatures was obtained according to the results of the experimental steels. The Nb content in austenite of the experimental steels with high carbon contents was lower than that calculated by Ohtani's equation. The existence of NbC precipitates in the case and the core of the specimens carburized at 930 °C and 980 °C were verified by transmission electron microscopy (TEM) observations. The pinning effect of NbC precipitates on austenite grain growth was calculated according to the size and amount of NbC precipitates in the carburized case and the core of the carburized specimens. The calculated results of prior austenite grain sizes were in good agreement with the experimental results, which indicated that the unified solid solution product of [Nb][C] in Nb-microalloyed steels with various carbon contents was applicable for the low-pressure carburizing process.

Unlocking the one-step recovery of solid S8 products through sulfur electro-oxidation in an acidic media

The recognized sulfur oxidation reaction (SOR) is performed in alkaline condition, and its main products of NaSx (x=1–4) are dissolvable, increasing chemical consumption to obtain solid Sx products by the multi-step recovery. Herein, the dopant of atomic carbon on MoS2 nanosheets (C-MoS2) was fabricated by chemical vapor deposition, and it can one-step convert H2S gas to solid S8 products in an acidic solution. Results showed that the yield of S8 product on C-MoS2 reached up to 2.5 kg/m2/d with a Faraday efficiency of 87.1 % at 20 mA/cm2. Moreover, theoretical and experimental studies proved that the electron density surrounding S active site increased with the incorporation of atomic C into MoS2, subsequently improving the adsorption energy of H2S and decreasing the reaction energy to obtain S8 product. Our work provides a new guideline for the SOR research on the one-step conversion of H2S to S8 solid products in acidic condition.

Impact of key parameters on the hydrothermal carbonization process of sewage sludge: A systematic review

The hydrothermal carbonization (HTC) process is a promising green technology for reducing and reusing sewage sludge and can be a powerful tool against the current problems of energy scarcity, climate imbalance, and environmental pollution. Despite its admirable robustness, HTC can be easily tuned by controlling temperature and reaction time, as well as by biomass:water mass ratio and pH. The systematized knowledge of the relationship between these parameters is fundamental to successful innovative research aiming at scaling up the process. In this review, a bibliometric analysis based on ten years of scientific publications was carried out. The PRISMA guidelines were adopted to select forty-seven works as a source of information and critical discussion on key findings of reactions performed in high-pressure reactors. The global scientific community is mainly concerned with solid products (hydrochar) and the study of mechanisms of removal/adsorption of nutrients, minerals, and pollutants. The gaseous phase is in the background, opening up numerous research possibilities. Future outlooks are focused on coupling HTC with biorefineries to strengthen the valorization of sewage sludge, contribute to the production of biofuels and biofertilizers, and benefit communities currently without access to environmental sanitation.

Production of a high-energy solid biofuel from biochar produced from cashew nut shells

The aim of the study is to produce a solid biofuel of high physico-mechanical and energetic quality from heat-treated cashew nut shells. Raw cashew nut shells are heat treated at 300 °C for 120 min at a heating rate of 1 °C/s. The resulting biochar is milled to 74 μm. Sugar cane molasses was incorporated into the biochar powder at a rate of 10% without the addition of water. The mass yields of solid, liquid and gaseous products obtained were 46.5%, 27.6% and 25.9% respectively. The solid biofuel produced has slightly improved physicochemical and energy properties over biochar, except ash and moisture content. Thus, the addition of binder and densification increased the ash and moisture content of the solid biofuel compared to the biochar obtained. With a higher calorific value of 33.02 MJ/kg, the solid biofuel has high water resistance and meets the quality requirements of class A1 of the NF EN ISO 17225-6 standard in terms of density and mechanical strength. Solid biofuel is ideal for use in households and biomass power stations.

The effect of an acidic environment during the hydrothermal carbonization of sewage sludge on solid and liquid products: The fate of heavy metals, phosphorus and other compounds

The pH of sewage sludge is a crucial factor during the hydrothermal carbonization process that influences the characteristics of the resulting products and migration of certain compounds from the solid to liquid phase. Accordingly, this work is focused on examining the pH impact during the HTC process, in particular, pH equals 2, 3, 4, 5 and 6 on the individual hydrothermally carbonized products generated at 200 °C and 2 h residence time. For this reason, the chemical and physical indicators describing the post-processing liquid and hydrochar were determined. For instance, it was observed that the phosphorus content detected in the liquid, derived at pH2, rose significantly by 80%. Furthermore, decreasing the pH of sewage sludge had a significant impact on the ash content and the calorific value of the hydrochar. Additionally, changes in the specific surface area of hydrochar were noticed: pH = 5 and pH = 6 showed an increase of 20–30%, while for lower pH values a decrease of c.a. 26% was achieved. The distribution of heavy metals between the obtained fractions in the HTC process (solid and liquid) indicated that 92 to almost 100% of the tested heavy metals were transferred to the hydrochar. A significant effect of pH on the distribution between these fractions was observed only for Zn and Ni. For instance, for pH = 2, Zn and Ni in post-processing liquid were 34% and 29%, respectively. In addition, the sequential extraction of heavy metals from hydrochar was also performed in order to identify mobile and non-mobile phases. It was noticed that the acidic environment favours a higher amount of mobile heavy metals in hydrochar. The largest effect was observed for Cd, Pb, Cr and Cu, for which, at pH = 2, their respective amounts in the mobile fraction were 2.7; 3.6; 1.8; 6.2 times higher, compared to the hydrochar without pH correction.

Effect of polyethylene terephthalate plastics on nitrogen, sulphur and chlorine contaminants via sludge pyrolysis and Pb/Cu adsorption properties of biochar

ABSTRACT Pyrolysis is an effective process for disposing of municipal sewage sludge (SS). Plastics can affect the SS pyrolysis behaviour and pyrolysis products due to their low ash and high hydrocarbon ratio. The secondary pollutants from the pyrolysis process may also be affected. Therefore, polyethylene terephthalate (PET), a typical plastic, was chosen to investigate the release characteristics of pollutants containing nitrogen, sulphur, and chlorine via SS pyrolysis, and the changes of biochar to adsorb two typical heavy metals, Pb and Cu. The pyrolysis of PET plastics facilitates the migration of N toward solid and liquid-phase products, S and Cl to the gas-phase products via pyrolysis. Oxygenated compounds of pyrolytic volatiles decreased from 38.18% to 28.43%, concurrently promoting the formation of phenolic compounds. The co-pyrolysis improved the quality of biochar and the ability to adsorb Pb and Cu. This systematic study can provide some support for the further improvement of SS pyrolysis technology, and will also be beneficial for subsequent applications.

Development of the wastewater treatment technology for the mine ‘Ternivska’ of the Kryvyi Rih iron ore plant

ABSTRACT Wastewater treatment in mining and mineral processing technology is a topical problem worldwide. The purpose of this study is to substantiate and develop the technology of complex wastewater treatment for the mine ‘Ternivska’ of the Public Joint Stock Company ‘Kryvyi Rih Iron Ore Plant’ with the production of highly purified water suitable for secondary use or ecologically safe discharge into surface water bodies. The proposed technology is based on the sequential application of the following stages: preliminary treatment of contaminated mine waters by coagulation and soda-lime softening methods to remove hardness, suspended solids, and colloidal substances; desalination via reverse osmosis; evaporation and crystallization of reverse osmosis concentrate in a vacuum evaporation unit; dehydration of salt sludge in a centrifuge with drying of salt crystals in a dryer. The treatment of mine water with an initial salinity of 80 g/L will give an annual effect of 1357 thousand m3 of desalinated water with a mineralization of up to 100 mg/L and 739.6 tons of mineral salt mixture. The purified water can serve as an additional source of fresh water for technological needs in industry or alternative purposes. The obtained solid salt product can be used as an alternative reagent for water-softening processes. In general, the proposed processing of mineralized mine water can be considered a zero-waste technology with clean water production and by-product utilization.

On the role of hydrogen inhibition in gas-phase methane pyrolysis for carbon capture and hydrogen production in a tubular flow reactor

The thermal pyrolysis of methane enables economically competitive hydrogen production without direct CO2 emissions. Although several mechanisms for the process have already been proposed, especially the inhibitory effect of hydrogen as well as the process operation at increased pressure have not yet been fully clarified. In this context, the present work investigates the influence of hydrogen and argon as inert gas on product composition, methane conversion, and hydrogen selectivity as a function of temperature (1000 °C to 1600 °C), residence time (1 s to 7 s), molar dilution ratio (1:1–4:1), and pressure (1 bar to 4 bar) in a high-temperature reactor. Within the scope of this work, total differences in CH4 conversion of up to 50 % could be observed at equal process parameters between an argon and hydrogen dilution, underlining the potential impact of diluents on the overall process. Moreover, increasing the pressure from 1 bar to 4 bar reduces the formation of byproducts significantly for both H2 and Ar as diluent, however, with different mechanistic characteristics. The most remarkable difference is the formation of propylene that exclusively takes place in argon-diluted reaction gas mixtures. This occurrence persists unabated, even under elevated pressures and temperatures reaching as high as 1600 °C. We ascribe this phenomenon to the interaction of methyl and ethyl radicals, establishing it as an impasse to further reactions leading to the formation of solid products. Herewith, the study provides novel insights from a reaction engineering perspective as well as from a process development perspective and clarifies the role of the dilution gases hydrogen and argon on the methane pyrolysis reaction.

Copper leaching from complex chalcopyrite-rich ores: Utilizing mechanical activation and wastewater-based sulfuric acid system

Complex chalcopyrite-rich ore is crucial in global copper resources, but is highly refractory in conventional sulfate leaching system. In this paper, we explore the leaching of complex chalcopyrite-rich ores employing a mechanically activated pretreatment combined with wastewater with high concentrations of chloride. The investigation delves into various parameters, including reaction temperature (60 to 90 °C), sulfuric acid concentration (0.005 to 2.0 M), chloride concentration (0 to 1.5 M), liquid/solid ratio (0 to 200), stirring speed (100 to 580 rpm), leaching time (0 to 4 h) and grinding time (0 to 7 h), to evaluate their impact on copper recovery from complex chalcopyrite-rich ores. Furthermore, a comprehensive kinetic analysis of copper leaching behavior was studied, encompassing specific surface area, amorphization degree, grain size, and microstrain. In the sulfuric acid system utilizing wastewater, the presence of mechanical activation and chloride content enhances copper leaching while mitigating the passivating effect of elemental sulfur. Notably, following a leaching period of 4 h at 80 °C, the copper leaching efficiency remarkably reached 89.46 %. In addition, kinetic analysis of copper leaching at temperatures ranging from 60 to 90 °C via a shrinking core model with R2 > 97 %, indicates that the leaching process of copper is primarily governed by solid product layer diffusion, with an activation energy of 54.32 kJ/mol. These findings highlight the efficacy of the proposed approach in optimizing copper recovery from complex chalcopyrite-rich ores, offering insights into the underlying mechanisms driving the leaching process.

Forecasting the waste production hierarchical time series with correlation structure

AbstractContinuous increase in society’s prosperity causes overwhelming growth of the produced municipal solid waste. Circular economy initiatives help to solve this problem by creating closed production cycles, where the produced waste is recycled, or its energy is recovered. An embedment of such principles requires implementation of new waste management strategies. However, these novel strategies must be based on the accurate forecasts of future waste flows. Municipal solid waste production data demonstrate behavior of hierarchical time series. Among all possible approaches to hierarchical times series forecasting, this article is focused on the reconciliation of the base waste generation forecasts. The novel method, that is based on the game-theoretically optimal reconciliation of hierarchical time series, is presented. The modified approach enables to incorporate interdependencies between time series using correlation matrix and to obtain the forecasts corresponding to the unique solution of the optimization problem. The potential of the proposed abstract approach is demonstrated on the waste production data of paper, plastics (both primarily sorted by households), and mixed municipal solid waste from the Czech Republic.

Preliminary strategy and product analysis of microwave pyrolysis of waste printed circuit board

AbstractIn this study, microwave pyrolysis of waste printed circuit boards (WPCBs) was carried out in an inert atmosphere, and the effects of pyrolysis temperature and nitrogen flow rate on the yield and composition of pyrolysis products were investigated. With the increase of pyrolysis temperature, the yield of liquid product increases gradually, and the yield of solid product decreases gradually. At 600°C, the yield of each phase tends to be stable. When the temperature continues to rise, the content of H2 and CO decreases, and the content of C6 ~ C9 in the liquid product decreases. Microwave heating promotes the pyrolysis of brominated epoxy resin, which helps to improve the recovery rate of valuable substances and reduce the environmental impact of waste treatment. This study demonstrates that the microwave pyrolysis of WPCBs in nitrogen atmosphere has great potential in the green recovery process.

Experimental study and prediction method of solid destabilization and production in deep carbonate reservoir during mining

Wellbore instability is one of the significant challenges in the drilling engineering and during the development of carbonate reservoirs, especially with open-hole completion. The problems of wellbore instability such as downhole collapse and silt deposit in the fractured carbonate reservoir of Tarim Basin (Ordovician) are severe. Solid destabilization and production (SDP) was proposed to describe this engineering problem of carbonate reservoirs. To clarify the mechanism and mitigate potential borehole instability problems, we conducted particle size distribution (PSD) analysis, X-ray diffraction (XRD) analysis, triaxial compression tests, and micro-scale sand production tests based on data analysis. We found that the rock fragments and silt in the wellbore came from two sources: one from the wellbore collapse in the upper unplugged layers and the other from the production of sand particles carried by the fluid in the productive layers. Based on the experimental study, a novel method combining a geomechanical model and microscopic sand production model was proposed to predict wellbore instability and analyze its influencing factors. The critical condition and failure zone predicted by the prediction model fit well with the field observations. According to the prediction results, the management and prevention measures of wellbore instability in carbonate reservoirs were proposed. It is suggested to optimize the well track in new drilling wells while upgrading the production system in old wells. This study is of great guiding significance for the optimization of carbonate solid control and it improves the understanding of the sand production problems in carbonate reservoirs.

Thermal reactivity and gas–solid product evolution during coal catalytic combustion: An experimental study

To achieve efficient and clean coal combustion, catalytic combustion technology has received widespread attention. This paper systematically studied the influence of calcium-based compounds on the thermal reactivity and gas–solid two-phase product evolution behavior of different coal using TG-MS and FTIR analysis, combining kinetics and thermodynamics methods, the catalytic coal mechanism was discussed. Results demonstrated that both catalysts improved the combustion reactivity, the burnout temperatures of lignite, bituminous coal and anthracite were reduced by 30.75 °C, 53 °C and 25.5 °C respectively with CaO, as well as decreased by 24.75 °C, 55.5 °C and 29 °C respectively with CaCl2. Meanwhile, it was worth noting that the activation energy of three coals was also reduced. CaCl2 was more likely to bind with the C = O functional group on the surface of coal, forming CO-Ca2+ complexes, resulting in a decrease in the content of C = O and C-O. While CaO tended to absorb volatile matter, causing local overheating and promoting the breakage of side chains and bridge bonds. Besides, the calcium-based compounds advanced the gas evolution peak of combustion and the emissions of CO2, NO2 and SO2 were effectively controlled. These results aimed at providing a new reference direction for further industrial development of clean coal combustion technology.