Pyrolysis Of Straw Research Articles

Removal of elemental mercury from flue gas over a low-cost and magnetic sorbent derived from FeSO4-flocculated sludge and rice straw

Capture of elemental mercury (Hg0) from coal combustion flue gas by sorbent injection is still associated with challenges, such as high-cost starting materials, difficulty in separation/reuse of sorbent and SO2 poisoning, in its large-scale application. This work highlighted a facile method to prepare a cost-effective and magnetically responsive mercury sorbent by pyrolysis of FeSO4-flocculated sludge and rice straw. Fe3O4, Fe2O3 and short-chain polysulfide in the sorbent were proven to be the main active sites for Hg0 adsorption/oxidation. Appropriate addition of rice straw into sludge boosted the development of porous structure of the sorbent, which facilitated the migration of Hg0 onto the absorption sites. With straw/sludge mixing ratio of 1:1 and pyrolysis temperature of 700 °C, the obtained SR1T7 exhibited good Hg0 capture ability under harsh gas conditions (1000 ppm SO2 and 3% H2O). At 125 °C, the Hg0 adsorption capacity and average adsorption rate were estimated to be 9.63 mg/g and 1.96 × 10−3 mg/(g⋅min), respectively. To extend its service life, the spent SR1T7 could be collected by magnetic separation, followed by thermal regeneration. SR1T7 might be a prospective alternative to traditional carbon-based mercury sorbent, due to its excellent Hg0 capture ability, good recyclability, decent SO2 resistance and low cost.

Coupling effect of pyrolysis temperature and condensing temperature on the enrichment of high value-added phenolic compounds in bio-oil from pyrolysis of crop straw

Pyrolysis experiments were performed using cotton straw and corn straw as raw materials at 723 and 773 K. The variations in condensation efficiency, moisture, and content of important components in bio-oil condensed from pyrolysis vapors were investigated in a water-bath condensation temperature of 313–363 K. The condensing efficiency, moisture, and content of important components of bio-oil increased with increased pyrolysis temperature. The single pyrolysis temperature provided limited control over the quality of bio-oil. The variation in condensing temperature affected the condensing of pyrolysis vapors. As the condensing temperature increased, the moisture in bio-oil was reduced by 200%, and the maximum content of the important components was elevated. The phenol content of the target bio-oil increased by 340.40%. For guaiacol and its derivatives, the relationship between condensing temperature and their content was analyzed using a polynomial fitting function to explore the phase-transition patterns.

The effect of reaction condition on catalytic cracking of wheat straw pyrolysis volatiles over char-based Fe–Ni–Ca catalyst

In this study, the catalytic reforming of wheat straw pyrolysis volatiles over char-based Fe–Ni–Ca catalyst in a fixed bed reactor to investigate the influence of heating rate, pyrolysis temperature and catalyst calcination temperature on the yield of bio-oil, char and pyrolysis gas was presented. Char-based Fe–Ni–Ca catalysts had good activity for the removal of heavy oil, the heavy oil yield is 0.43% with 500 °C pyrolysis temperature and 5 °C/min heating rate. The maximum yield of hydrogen (288.41 mL/g) and combustible gas (hydrogen, methane and carbon monoxide; 403.45 mL/g) were obtained at a pyrolysis temperature of 800 °C and 10 °C/min heating rate. XPS, H2-TPR, XRD, TEM, SEM-EDS and BET were employed to analyze char-based Fe–Ni–Ca catalyst. Characterization results reveal that heating rate, pyrolysis temperature and catalyst calcination temperature had a significant effect on the distribution of active phase. Comparing to 800 °C, the diffraction peaks of Fe, Fe0.64Ni0.36, and Fe2O3 become weak as 500 °C, the particle size changed from 23.17 nm to 24.34 nm. At 500 °C, the power of the diffraction peak decreases successively from Fe2O3, Fe, and Fe0.64Ni0.36. At 800 °C, the highest intensity of the diffraction peak is Fe, followed by Fe2O3. The high activity of char-based Fe–Ni–Ca catalyst is also attributed to the robust adsorption of CO2 forming CaCO3 species facilitated on the oxide ion vacancy site of CaO acting as oxygen exchange site. Also, the char-based Fe–Ni–Ca catalyst can be utilized as an appropriate candidate to crack the bio-oil. The pyrolysis temperature of 800 °C and the heating rate of 10 °C/min can be used as the best reaction conditions for industrial hydrogen production.

In-situ study on structure evolution and gasification reactivity of biomass char with K and Ca catalysts at carbon dioxide atmosphere

The structural evolution and gasification reactivity of biochar prepared from the pyrolysis of wheat straw were investigated by in-situ Raman spectroscopy and thermogravimetric analysis. The Raman spectra consisted of a combination of four Lorentzian bands (D1, D2, D4, G) and one Gaussian band (D3) in the first-order region. The experimental results showed that the addition of catalysts or the presence of ash could improve the CO2 gasification reactivity of biochar and result in a larger ID1/IG ratio and a lower IG/IALL ratio, meaning that the carbon structure was less ordered, and there were also more active sites such as amorphous carbon and cross-linked structures; Ca-based catalysts and K-based catalysts changed the evolution of biochar structure in a different way in CO2 atmosphere, the ID3/ID1 of Ca-based biochar was close to the value of non-catalyst biochar and decreased slowly, indicating that the Ca-based catalysts can stabilize the aromatic rings, while the IG/IALL of K-based biochar decreases significantly and the ID3/ID1 increased significantly, indicating the increase of carbon structure defects and the cracking of large aromatic rings in bio-char into small ones; a scheme of K and Ca reaction with biochar in CO2 gasification process was proposed.

Effect of temperature and fly ash content on the catalytically pyrolyzed rice straw biochar–fly ash composites for methylene blue adsorption

AbstractRice straw and fly ash are the wastes produced in abundance which need immediate attention for their management. In the present study, the in situ pyrolysis of rice straw in presence of fly ash was carried out and the resultant composites were studied for adsorption of methylene blue (MB). Slow pyrolysis of rice straw in presence of fly ash is evaluated using thermogravimetric analysis (TGA) and Coats–Redfern equation for pseudo‐first‐order reaction kinetics, respectively. The activation energy (Ea) for the pyrolysis of rice straw was 41.75 kJ/mol which was lowered to 37.39 kJ/mol in presence of fly ash. Biochar fly ash composites BFA41–3, BFA51–3, and BFA61–3 were prepared at three 400°C, 500°C, and 600°C pyrolysis temperature, respectively, the subscript indicating three different ratios of rice straw and fly ash (1:3, 1:1, and 3:1 w/w ratio). The composites BF4–61–3 were neutral to alkaline in pH, due to the presence of basic oxide and carbonates minerals. BFA4–61–3 was studied for batch adsorption of MB and optimized for pH, dose, and initial concentration of adsorbate. The maximum MB adsorption capacity of 25.91 mg/g was reported for the composite BFA41. MB adsorption efficiency (qe) followed the trend BFA41–3 > BFA51–3 > BFA61–3, which indicates a strong influence of biochar surface functional groups on dye adsorption, as reiterated by the multiple linear regression (MLR) analysis. Stripping of MB was achieved using methanol as a stripping agent for MB‐adsorbed BFA4–61–3 with desorption efficiency of 7% to 11% in the first cycle and 23% to 100% in the second cycle. Thus, the biochar fly ash composite with optimum ion exchangeable functional organic moieties would be suitable for dye remediation and waste generated in the process could find application in soil amelioration.

Thermal influx induced biopolymeric transitions in paddy straw

This is the first article highlighting the bio-polymeric transitions in individual intrinsic bio-constituents during pyrolytic thermal degradation of paddy straw through deconvolution of first order derivative of conversion profile. Non-isothermal slow pyrolysis of raw paddy straw was executed in a thermogravimetric analyzer at different heating rates (β = 10, 20 30 and 40 °C/min). Gaussian deconvolution technique was used to find individual signals related to each intrinsic biopolymers (hemicellulose, cellulose and lignin) in biomaterial. Different heating rates provided varied levels of heat influx to same biomaterial under same the environment which induced the different biopolymeric transitions in biomaterial. The multi-step mechanism was adopted to determine the kinetic triplets of paddy straw by using three different iso-conversional methods; OFW, KAS, and STM. The calculated activation energy from all three methods shows very negligible variations. From reaction mechanisms of three biopolymeric constituents, we established that thermal degradation of raw paddy straw underwent various complex reactions. This particular work found that all bioconsituents commonly followed the trends of diffusion model with no restriction of order of reaction.

Physiochemical characteristics of bio-char derived from pyrolysis of rice straw under different temperatures

Physiochemical characteristics of bio-char derived from pyrolysis of rice straw under different temperatures

Comparative assessment of the biomass solar pyrolysis biochars combustion behavior and zinc Zn(II) adsorption

Biochars from solar pyrolysis of the waste straw, and dried sewage sludge, were assessed to recognize the possible application as unconventional adsorbents and fossils replacements for combustion purposes. The adsorption properties of the biochars were characterized by the BET (Brunauer, Emmett, and Teller) surface area, pore volumes, and the degree of Zn(II) adsorption from aqueous solutions. A higher removal degree of zinc ions of 26% was noted for biochars from dried sewage sludge with a BET area of 40.84 m2/g, compared to the waste straw biochars with a BET area of 1.67 m2/g and a corresponding removal degree of 16%. Both biochars presented more uniform combustion behavior compared to raw biomass, with the ignition and burnout temperatures similar to coal. Solar pyrolysis caused a reduction of the combustion kinetic steps, from multi-step combustion of the raw biomass to a single-step and two-step kinetic mechanisms for the sewage sludge and waste straw biochars respectively. It was found that the waste straw biochars are possible alternative fuels with a higher heating value of 22.6 MJ/kg, while sewage sludge chars presented better zinc adsorption of 2.09 mg/g and a total removal degree of 26%.

Effect of reaction temperature and raw material particle size on the composition of corn straw pyrolysis biological oil

Quartz sand was used as bed material in a small fluidized bed reactor with 1 kg/h feed. Corn straw powder with particle size of 20–40 mesh, 40–60 mesh, 60–80 mesh and 80–120 mesh was used as raw material for rapid pyrolysis at reaction temperatures of 400 °C, 450 °C, 500 °C and 550 °C. The bio-oil obtained after liquefaction of pyrolysis gas was analyzed. The variation trend of bio-oil composition in pyrolysis of corn straw powder with different reaction temperatures and raw material sizes was compared. The results show that: (1) the content of 3-hydroxyl-2-phenyl-2-acrylic acid in bio-oil increases with the decrease of raw material particle size, but it is less at 450 °C; (2) with the increase of reaction temperature, the content of hydroxyacetaldehyde in bio-oil increases at first and then decreases: the content of hydroxyacetaldehyde in bio-oil is the highest at 500 °C when the particle size is 20–40 mesh, and the highest at 450 °C with the other three particle sizes. Compared with other particle sizes, raw material with the particle size of 60–80 mesh is not conducive to the formation of aldehyde compounds; (3) the reaction temperature of 500 °C and the particle size of 60–80 mesh of raw materials are more conducive to the formation of phenolic compounds in bio-oil; (4) the ester compounds with particle size of 20–40 mesh in bio-oil is 20% higher than that of other particle sizes; (5) the reaction temperature and the particle size of raw materials had no significant effect on the formation of ketones, alcohols and alkane compounds in bio-oils.

Pyrolysis as an alternate to open burning of crop residue and scrap tires: Greenhouse emissions assessment and mechanical performance investigation in concrete

In this study, waste from agriculture and industrial sources was transformed into valuable biochar to reduce the environmental threats associated with the open burning of this waste and used as an additive in concrete for the first time to impart superior mechanical characteristics to conventional concrete. Carbonaceous inert particles were derived from the pyrolysis of wheat straw, cotton stalk, and scrap tires. The environmental impact assessment was carried out to gauge the impact of pyrolysis process on char production and the global warming potential for engineered concrete. Based on the analysis, pyrolysis of scrap tires manifested the lowest net global warming potential of −1.285 KgCO 2 -eq. Furthermore, the characterization of synthesized inert particles was carried out by using Laser granulometry, scanning electron microscopy, x-ray diffraction analysis, thermo-gravimetric analysis, and Raman spectroscopy. Thereafter, the mechanical performance of concrete incorporated with synthesized inert particles by 1% of cement weight was evaluated and compared with the reference formulation of concrete having no amount of synthesized inert particles. A significant improvement of 51.42% in terms of flexural resistance was achieved by using pyrolyzed cotton stalk. Fracture toughness index and fracture energy were also improved with the inclusion of these inert particles. To rationalize the improved performance of specimens engineered with synthesized inert particles, fracture path analysis was conducted. In comparison to the reference formulation, composites reinforced with pyrolyzed scrap tires rendered maximum improvement in compressive strength by 43.1%. From the analysis of the emissions to strength ratio of concrete, specimens containing pyrolyzed scrap tires ensued the maximum reduction of 31.31% relative to the reference formulation. • Agricultural residue and scrap tires waste were transfigured to biochar through pyrolysis. • Net negative global warming potential was attained by opting for pyrolysis. • Maximum gain of 51.4% in flexural resistance was obtained with pyrolyzed cotton stalk. • Concrete with 43.1% enhanced compressive strength was made with pyrolyzed scrap tires. • 45.58% increase in strength to emissions ratio was achieved with the addition of pyrolyzed scrap tires.

Effect of acid washing and K/Ca loading on corn straw with the characteristics of gas-solid products during its pyrolysis

Alkali and alkaline earth metallic species (AAEMs) significantly affect the thermal conversion and utilization of biomass. However, the bonding mechanism between AAEMs and biomass carbon substrates is still unclear. In this paper, corn straw with different AAEMs contents were prepared by acid washing and K/Ca loading with impregnation method. A horizontal furnace was used to conduct the fast pyrolysis experiment at 800 °C. The Fourier transform infrared spectroscopy (FTIR) was used to analyse the chemical structural characteristics of corn straw and biochar. The production of pyrolysis gases was online monitored by a synthetic gas analyzer. The main conclusions are as follows: the K/Ca loading promotes the conversion of C–O–C and CO to COO- and C–O in corn straw. K is linked to corn straw mainly through COO- group, and Ca is linked to corn straw mainly through C–O group. Both K/Ca elements are effective in inhibiting the consumption of C–O–C group during corn straw pyrolysis. Besides, K element can catalyze the depletion and decomposition of C–O group during pyrolysis. The K element inhibits the decomposition of the unstable carbon matrix and CO group during pyrolysis, thereby reducing the emission levels of CH4 and CO. K can promote the release of CO2 during pyrolysis, while Ca has no obvious effect. The pyrolysis reactivity of K-loaded corn straw is extremely low, while that of H-form corn straw and Ca-loaded corn straw is at a high level. AAEMs promote the release of H/O elements during corn straw pyrolysis, and the role of K is significantly stronger than that of Ca.

Char structure evolution during molten salt pyrolysis of biomass: Effect of temperature

Pyrolysis of wheat straw in Li2CO3-K2CO3 binary salt was conducted in a fixed-bed reactor, the char structure evolution under different pyrolysis temperatures was analyzed. The results showed that the biochar yield decreased with temperature increasing, the addition of Li2CO3-K2CO3 salt enhanced heat transfer and promoted charring reactions to form more char. At 450–550 °C, the changes in biochar structure from molten salt pyrolysis showed similar trend with those from conventional pyrolysis, the C content increased and the H and O contents decreased, the aromatization degree of biochar increased, the surface functionalities on char surface all decreased. At 600–700 °C, the effect of temperature on biochar structure from molten salt pyrolysis showed significantly different trend. The increase of temperature further decreased H content, but increased O content and decreased C content, the molar ratio of H/C decreased while that of O/C increased. The etching of K salt consumed more C and retained more O in char structure, thus caused insignificant increase in aromatization level of biochar and retaining more CO/COC and –OH functionalities. More porous structures were formed due to the enhanced activation effect of molten salt at higher temperature. The BET surface area of 700MBC could achieve 568.20 m2/g. A functionalized mesoporous biochar with enriched O-containing groups was thus obtained from molten salt pyrolysis of biomass.

RNA-Seq Based Transcriptome Analysis of Aspergillus oryzae DSM 1863 Grown on Glucose, Acetate and an Aqueous Condensate from the Fast Pyrolysis of Wheat Straw.

Due to its acetate content, the pyrolytic aqueous condensate (PAC) formed during the fast pyrolysis of wheat straw could provide an inexpensive substrate for microbial fermentation. However, PAC also contains several inhibitors that make its detoxification inevitable. In our study, we examined the transcriptional response of Aspergillus oryzae to cultivation on 20% detoxified PAC, pure acetate and glucose using RNA-seq analysis. Functional enrichment analysis of 3463 significantly differentially expressed (log2FC >2 & FDR < 0.05) genes revealed similar metabolic tendencies for both acetate and PAC, as upregulated genes in these cultures were mainly associated with ribosomes and RNA processing, whereas transmembrane transport was downregulated. Unsurprisingly, metabolic pathway analysis revealed that glycolysis/gluconeogenesis and starch and sucrose metabolism were upregulated for glucose, whereas glyoxylate and the tricarboxylic acid (TCA) cycle were important carbon utilization pathways for acetate and PAC, respectively. Moreover, genes involved in the biosynthesis of various amino acids such as arginine, serine, cysteine and tryptophan showed higher expression in the acetate-containing cultures. Direct comparison of the transcriptome profiles of acetate and PAC revealed that pyruvate metabolism was the only significantly different metabolic pathway and was overexpressed in the PAC cultures. Upregulated genes included those for methylglyoxal degradation and alcohol dehydrogenases, which thus represent potential targets for the further improvement of fungal PAC tolerance.

Effect of Cd on Pyrolysis Velocity and Deoxygenation Characteristics of Rice Straw: Analogized with Cd-Impregnated Representative Biomass Components.

The pyrolysis characteristics of cadmium (Cd)-impregnated cellulose, hemicellulose, and lignin were studied to elucidate the pyrolysis velocity and deoxygenation characteristics of Cd-contaminated rice straw. The results show that Cd significantly affects the pyrolysis characteristics of a single biomass component. With a heating rate of 5 °C·min−1 and a Cd loading of 5%, the initial pyrolysis temperature of cellulose and hemicellulose decreases while that of lignin increases. The maximum pyrolysis velocity of cellulose, hemicellulose, and lignin is decreased by 36.6%, 12.4%, and 15.2%, respectively. Cd increases the pyrolysis activation energy of the three components and inhibits their deoxygenation. For the pyrolysis of Cd-contaminated rice straw, both the initial depolymerization temperature and the pyrolysis velocity of hemicellulose is reduced, while the pyrolysis velocity of cellulose is accordingly increased. When Cd loading amplifies to 0.1%, 1%, and 5%, the maximum pyrolysis velocity of hemicellulose is decreased by 7.2%, 10.5%, and 21.3%, while that of cellulose is increased by 8.4%, 62.1%, and 97.3%, respectively. Cd reduces the release of volatiles and gas from rice straw, such as CO2, CO, and oxygen-containing organics, which retains more oxygen and components in the solid fraction. This research suggested that Cd retards the pyrolysis velocity and deoxygenation of rice straw, being therefore beneficial to obtaining more biochar.

Enhanced production of hydrocarbons from the catalytic pyrolysis of maize straw over hierarchical ZSM-11 zeolites

The ZSM-11 zeolite has been revealed as an undervalued catalyst for the catalytic fast pyrolysis (CFP) of biomass to produce hydrocarbon-rich bio-oil. However, the importance of hierarchical ZSM-11 in bio-oil production is still unknown. Herein, a series of ZSM-11 with varied morphologies, acidities, and secondary mesopores were synthesized and tested as catalysts in the CFP of maize straw. For the morphology series, ZSM-11 with separate nanorods (Nano-ZSM-11) or aggregated nanosized single-crystal (NS-ZSM-11) performed better in bio-oil production than microsized Micro-ZSM-11. Regarding the NS-ZSM-11 series, optimal acidity facilitated the deoxygenation of biomass vapor, while introduced intracrystal mesopores tended to improve bio-oil yield. NS-ZSM-11(20)-0.3 possessing both adequate acidity and coupling inter/intracrystal mesopores led to a satisfactory bio-oil yield (23.6 wt%) and hydrocarbon selectivity (63.6 area%), which were 1.1 and 1.3 times those for Nano-ZSM-11 (bio-oil yield: 22.0 wt%; hydrocarbon selectivity: 47.8 area%), respectively. NS-ZSM-11(20)-0.3 also showed excellent reusability in regeneration-pyrolysis cycles.

Effect of Pyrolysis Temperature on Removal Efficiency and Mechanisms of Hg(II), Cd(II), and Pb (II) by Maize Straw Biochar

Pyrolysis temperature significantly affects the properties of biochar, which in turn can affect the removal of heavy metal ions and the underlying mechanism. In this work, biochars from the pyrolysis of maize straw at 300, 400, and 500 °C (BC300, BC400, and BC500, respectively) and wheat straw at 400 °C (WBC400) were investigated. The influence of production temperature on the adsorption of Hg2+, Cd2+, and Pb2+ by maize straw biochar was investigated by the characterization of the biochars and by adsorption tests. The adsorption capacities of maize and wheat straw biochar were compared in an adsorption experiment. Biochar BC400 showed the best physical and chemical properties and had the largest number of surface functional groups. The pseudo-second-order kinetic model was more suitable for describing the adsorption behavior of metal ions to biochar. The Langmuir model better fit the experimental data. Biochar BC400 had a higher adsorption speed and a stronger adsorption capacity than WBC400. The sorption of Pb2+ and Hg2+ to maize straw biochar followed the mechanisms of surface precipitation of carbonates and phosphates and complexation with oxygenated functional groups and delocalized π electrons. The adsorption mechanism for Cd2+ was similar to those of Hg2+ and Pb2+, but precipitation mainly occurred through the formation of phosphate. In the multi-heavy-metal system, the adsorption of Cd2+ by BC400 was inhibited by Pb2+ and Hg2+. In summary, BC400 biochar was most suitable for the adsorption effect of heavy metals in aqueous solution.

Enhanced production of monocyclic aromatic hydrocarbons by catalytic pyrolysis of rape straw in a cascade dual-catalyst system of modified red mud and HZSM-5

Catalytic pyrolysis of rape straw was carried out on a dual-catalyst system to produce benzene, toluene, xylene (BTX), realized by promoted cracking of large-molecule pyrolysis vapor over red mud (RM) and followed by selectively catalytic conversion over HZSM-5. With the pyrolysis temperature of 550 °C and the catalyst/biomass mass ratio of 2:1, the yield of BTX in bio-oil reached the maximum of 10.27 wt%. The coking resistance of HZSM-5 in the cascade catalytic system was obviously better than pure HZSM-5. The pretreatment of RM by calcination and acid washing was also performed. The unstable components of RM like cancrinite were decomposed during the calcination. Besides, the content of active metal oxides in RM after acid washing increased by removing Na2O and CaO. Its specific surface area was promoted, due to the new micropores caused by the dispersion of dissolved metal oxides. RM treated with 3 mol/L hydrochloric acid presented the highest specific surface area of 55.24 m2/g while the maximized yield of BTX of 12.91 wt%. Therefore, the dual-catalyst system might be an effective method to dispose and high valued use of rape straw and RM as solid wastes with significant environmental impact to promote carbon neutrality.

Migration of Cl in the process for pyrolysis of corn straw and the influence of catalysis for dechlorination of bio-oil

Migration of Cl in the process for pyrolysis of corn straw and the influence of catalysis for dechlorination of bio-oil

Techno-economic and environmental assessment of decentralized pyrolysis for crop residue management: Rice and wheat cultivation system in India

The current study evaluates a decentralized biorefinery's economic and environmental performance, which uses two-step pyrolysis for converting rice and wheat straw to bio-oil and biochar. The biorefinery was located in Punjab (India), where open burning of residue is prevalent. The decentralized biorefinery was evaluated regarding the energy required for pyrolysis, product yield and applications, and global warming potential (GWP). Pyrolysis of unwashed, water-washed, and acid-washed straws was performed. The net GWP for pyrolysis of unwashed rice straw was −121 kg CO2eq/ton when biochar was used as a carbon sink. But pyrolysis of water-washed (159 kg CO2eq/ton) and acid-washed rice straw (311 kg CO2eq/ton) was a net contributor to GWP, which was undesirable. Similar trends were observed for wheat straw pyrolysis.The GWP of washed rice and wheat straw pyrolysis was higher than unwashed straw because 37–50% biochar generated was used for drying the washed straw, leaving less biochar for further application. Amongst the biochar applications considered, its use as a carbon sink offered more GWP reduction than its use as a substitute for coal in power and heat generation. The net GWP for direct transfer of residues to a centralized refinery for pyrolysis was −75 kg CO2eq/ton for rice straw and −384 kg CO2eq/ton for wheat straw. Therefore, it was environmentally beneficial to treat biomass locally rather than in a centralized unit. Finally, the minimum selling price for biochar was calculated to be 172–623 USD/ton, which was within the range of commercial biochar price. Therefore, the proposed biorefinery was expected to be environmentally and economically viable with an appropriate selection of pretreatment options and end-uses of the products.

Catalytic pyrolysis of biomass with thermal treatment products of spent lithium-ion batteries for the upgrading of bio-oil and syngas

Thermal treatment is an efficient method to recycle spent lithium-ion batteries and the thermal treatment products are rich in valuable metals with catalytic activity such as Co and Ni. Therefore, the feasibility of using the thermal treatment products (PyNCM and PyLCO) of spent ternary lithium batteries (NCM) and lithium cobalt oxide batteries (LCO) as the cheap catalysts for biomass (wheat straw) pyrolysis was explored in this study. The catalytic effect of the typical components of PyNCM and PyLCO (Ni, Co, NiO and CoO) on the biomass pyrolysis process was also investigated for comparison purposes. The results showed that PyNCM and PyLCO could promote the devolatilization process of wheat straw. The Second order model could well describe the catalytic pyrolysis process of wheat straw based on the Coats-Redfern method, and the obtained activation energy was in the range of 79.00 kJ/mol to 83.90 kJ/mol. The PyNCM and PyLCO had good catalytic activity for enhancing the cracking of bio-oil to produce more gaseous products (syngas), especially for PyNCM, whose gas yield increased significantly from 15.70% to 22.26%. As for bio-oil compositions, the PyNCM and PyLCO both promoted the formation of hydrocarbon compounds and reduce the oxygen content of the obtained bio-oils. The increase of the hydrocarbon content was mainly attributed to the NiO and CoO components in PyNCM and PyLCO. In addition, both PyNCM and PyLCO increased the content and yield of H2 in the syngas. Especially for PyNCM, the content and yield of H2 increased 1.6 times and 5.5 times respectively compared with direct pyrolysis of wheat straw without catalyst. The mechanism of biomass catalytic pyrolysis in the presence of PyLCO and PyNCM was proposed and discussed. The catalytic effect of PyNCM on wheat straw pyrolysis was more distinct than that of PyLCO, which might be attributed to the positive synergistic effect of Ni and Co compounds in PyNCM. This study demonstrated that the thermal treatment products of spent lithium-ion batteries could be used as efficient catalysts for biomass pyrolysis products upgrading.