Lignin Gasification Research Articles

Evaluating the role of feedstock composition and component interactions on biomass gasification

Biomass gasification offers a solution to waste concerns while generating clean energy. This study examines the gasification of pine sawdust (PS), used ground coffee (UGC), and wheat straw (WS) under identical conditions. The compositions of the biomass samples are determined, and the gasification of individual components (hemicellulose, cellulose, and lignin) are conducted to understand the process’ dependency on the biomass characteristics. The results suggest cellulose and cellulose-rich biomass (PS) produces more tar and less hydrogen than lignin and lignin-rich biomass (UGC and WS). High lignin and hemicellulose content leave more char. Gasification of PS, UGC, and WS yields 12.7, 15.7, and 17.2 vol% hydrogen, respectively. Additionally, cellulose, hemicellulose, and lignin gasification yield 10.5, 22.1, and 30.4 vol% hydrogen, respectively. Comparing experimental and theoretical values for the three biomass samples reveals significant differences due to component interactions. Thermogravimetry analysis (TGA) indicates significant degradation interactions between hemicellulose-lignin, cellulose-hemicellulose, and cellulose-lignin. It is concluded that high cellulose content biomass shows more predictable results, while high lignin and hemicellulose biomass increases secondary reactions or interactions, exacerbating predictability. These findings assist in estimating gasification performance for better biomass selection.

Comprehensive Evaluation of Fuel Ethanol Production from Poplar Wood Fermentation and its Coupled Pathway with Lignin Gasification Based on Energy-Environment-Economy

Comprehensive Evaluation of Fuel Ethanol Production from Poplar Wood Fermentation and its Coupled Pathway with Lignin Gasification Based on Energy-Environment-Economy

In-situ plasma assisted lithium-ion battery cathodes to catalytically pyrolyze lignin for H2-rich syngas production

In-situ plasma assisted lithium-ion battery cathodes catalysis was investigated to pyrolyze lignin to H2-rich syngas, oil and char. The effects of temperature, cathode to lignin ratio and plasma current on syngas production were investigated by using the typical ternary cathode NCM111 (LiNi1/3Co1/3Mn1/3O2) as catalyst and adopting dielectric barrier discharge mode. Response surface methodology based on BOX-BEHNKEN design was used to analyze the significance and interactions of process factors on the syngas yield. The conditions of 837℃, 10.4 %, and 185 mA for obtaining high-yield syngas (22.58 %) were more stringent; thereinto, from high to low, the intensity of factors on the yield was temperature, plasma current, and cathode ratio. Furthermore, different cathodes (non-cathode, NCM811 (LiNi4/5Co1/10Mn1/10O2), LCO (LiCoO2), and LMO (LiMn2O4)) were applied to decouple the catalytic effects of three metals in the NCM111. NCM111 enhanced both lignin gasification and carbonization by reducing condensable components, and NCM811 further improved gasification, but LCO and LMO had weaker gasification ability. NCM111 increased H2 volume fraction from 22.35 % to 67.31 %, NCM811 elevated the micro-discharge performance, promoting the hydrogasification reactions between energetic H species and char to produce more CH4, while LCO and LMO tended to produce the CO-rich syngas. Besides, in-situ plasma and its synergy with cathodes inhibited the formation of heavy aromatics and produced some high-value bio-oils rich in light aromatics, in which NCM111 achieved 92.30 % selectivity towards MAHs. High Ni ratio was beneficial for improving the char porosity, and the chars obtained by using NCM811 had a surface area of 409.29 m2/g, and a pore volume of 0.401 cm3/g. Comparably, the degree of catalytic lignin gasification for preparing H2-rich syngas could be ranked as Ni > Co > Mn in the ternary cathode.

Effect of Fe and its oxides on steam gasification mechanism of lignin using ReaxFF molecular dynamics simulations

Lignin is an important biomass component and its gasification process has been extensively studied. Iron is widely found in nature, and the corresponding iron-based catalysts have been heavily used in the study of various systems. The advantages are that it is inexpensive and not easy to pollute the environment, and it can also be extracted from the system and reused. However, studies on the effect of iron and its oxides on the steam gasification of lignin are limited, most studies have focused on supercritical water gasification. In this study, the effects of Fe and its oxides on the steam gasification process of lignin dimers were simulated using reactive force field (Reaxff) molecular dynamics (MD). By analyzing the gas products and the evolution of the structures. It was found that low valence Fe greatly improved the efficiency of lignin steam gasification, while higher valence iron oxides were significantly less effective. There were also significant differences in the distribution of gas products for different valence states of Fe. Low-valent Fe greatly improves the yield of combustible gases such as H2 and CO, while high-valent Fe is better at generating CO2. Carbon accumulation occurs on the surface of the catalyst, which reduces the catalytic effect. By comparing the effects of different temperatures on the steam gasification of lignin, it was found that increasing the temperature accelerates the decomposition process of lignin, and that the steam gasification of lignin has a critical temperature at which the yield of the main gaseous products of lignin is the highest.

Experimental and simulation studies of oxygen-blown, steam-injected, entrained flow gasification of lignin

This article presents results from experimental and simulation studies on a laboratory-scale pressurized O2-blown Entrained Flow biomass gasification Reactor (EFR) using pulverized commercial lignin pellets as feedstock. The primary focus lies in the assessment of the EFR’s performance indicators such as the H2/CO ratio, the Cold Gas Efficiency (CGE), and the Carbon Conversion Efficiency (CCE). The gasifier was operated at an absolute pressure of 8.2 bars, with varying amounts of O2 and steam. In the first series of experiments, the O2 equivalence ratio varied between 0.2 and 0.8, with no steam injection. This yielded a maximum CGE of 47%, a CCE of 94%, and an H2/CO ratio within the range of 0.4–0.7. In the last series of experiments, a perforated horizontal steam tube was installed allowing for a variation of the steam-to-biomass ratio (S/B), between 0.5 and 1.5. At a S/B of 1.5, the CGE and the CCE were at their highest levels of 91% and 99%, respectively. Based on the experimental setup, a 3D multiscale Eulerian-Lagrangian computational particle fluid dynamics (CPFD) model for the reactor was developed and validated against the experimental data. This model was then employed to explore the impacts of reactor temperature, S/B, equivalence ratio (λ), and the lignin particle size distribution (PSD) on the gasification process. The findings show that increased reactor temperature enhances H2 and CO production. Higher S/B ratios lead to greater H2 production but reduced CO production. Increased S/B ratios improve both CGE and CCE. Larger particles and higher λ values decrease CO and H2 production. Without steam injection, the peak CGE occurs at λ ≈ 0.45, corresponding to complete CH4 conversion. Beyond this point, as λ increases, reactor temperatures rise while CGEs decrease. Simulations reveal the optimal λ range for steam injection is 0.15–0.35. A sensitivity analysis highlights the significant impact of reactor temperature on H2 and CO production. While λ shows high sensitivity for H2 production, the S/B ratio exerts a greater impact on CO production.

Solid waste of calcium lignin replaces fossil fuel power by gasification to reduce CO2 emissions

Biomass can partially replace fossil fuels for power to reduce CO2 emissions and save non-renewable resources. In the pulp and paper industry, a waste biomass of calcium lignin was obtained by treating chemo-mechanical pulp (CMP) wastewater with calcium oxide. To investigate waste calcium lignin and its potential use in power generation systems in place of fossil fuels, a basic experiment on calcium lignin gasification was conducted. A model of gasification combined power generation was developed. The results showed that, the gasification temperature was 800 °C, the equivalence ratio (ER) was 0.25, the syngas yield was 78.2 wt%, the lower heating value (LHV) of the syngas was 5.15 MJ/Nm3, and the highest cold gas efficiency (CGE) was 57.84%. In the model, the generated electricity and CO2 emissions were 1.10 kg/kWh and 0.62 kg CO2/kWh, respectively. The use of calcium lignin biomass reduced 35.42% of CO2 emissions compared to a traditional coal-fired power plant. In addition, the product value-added was 1.17 RMB per kWh, and this was 82.81% higher than that of the 0.64 RMB of traditional coal-fired power plant.

Alkali and alkaline earth metals catalytic steam gasification of ashless lignin: Influence of the catalyst type and loading amount

This work studies the effects of alkali and alkaline earth metallic species (AAEMs) (Na2CO3, K2CO3, and CaCO3), Na+ impregnation amount (2, 5, and 7 mmol) and sodium salts (NaHCO3, Na2SO4, and NaAlO2) on the gasification characteristics and product distribution of G-type lignin in a fixed-bed system for continuous gasification. The results showed that six catalysts all could improve lignin gasification performance by increasing total gas yields, syngas yields, H2/CO ratios, and carbon conversion rates. Na2CO3 had the strongest catalytic ability, followed by NaHCO3 and K2CO3, while CaCO3, Na2SO4 and NaAlO2 had poor catalytic abilities. Gaseous AAEMs, especially NaOH and KOH, could enhance tar cracking, volatiles reforming, coke gasification, the water-gas shift reaction, and methane steam reforming. The high melting points of CaO and NaAlO2 greatly reduced the catalytic capacities of CaCO3 and NaAlO2. AAEMs could combine with the carbon matrices to form carboxylate structures or phenol/aldehyde structures which might volatilize to catalyze homogeneous reactions. Moderately increasing Na+ impregnation amount to 5 mmol was beneficial to lignin gasification, but excessive impregnation reduced the gasification parameters. In addition, all six catalysts had effects on the tar composition, especially K2CO3 and NaAlO2, which could effectively catalyze tar cracking and reduce heavy compounds.

MATHEMATICAL MODELING AND NUMERICAL STUDY OF BIOMASS FIXED CARBON GASIFICATION IN A DENSE BED AT ATMOSPHERIC PRESSURE. PART 2. ANALYSIS OF NUMERICAL RESULTS

Using the constructed two-dimensional model of aerodynamics, heat-mass transfer and chemical reaction of coke-ash residue in a steam-air mixture at a pressure of 1 atm, taking into account interphase convective heat transfer, radiative-conductive heat transfer of the solid phase, radiative and conductive heat transfer of the bed with the reactor wall, gravitational forces and aerodynamic resistance, the unsteady process of lignin gasification in a fixed bed was theoretically investigated. It is shown that: 1) the maximum value of biomass temperature of 887 °С is reached in the oxidation zone, where exothermic reactions prevail over endothermic reactions; 2) the specified temperature turns out to be lower than the temperature of the beginning of ash deformation of 1050 °С, which indicates the slag-free operation of the gas generator; 3) the largest yield of gasification products occurs in the redox reaction zone, where heat absorption dominates over heat release; 4) a slag pad is formed near the grate, protecting the grate from overheating; 5) the largest changes in discrete phase movement speeds are observed in the oxidizing and reducing zones of the gas generator from –5.791.10−5 m/s до –1.86.10−5 m/s due to the change in particle diameter from 10 mm to 6.83 mm (ash). Bibl. 12, Fig. 6.

Supercritical water co-gasification mechanism of lignin and low density polyethylene into syngas: ReaxFF molecular dynamic simulation and density functional theory calculation study

The supercritical water gasification (SWG) of low density polyethylene (LDPE) and lignin into CO and H2 is a potential path for the conversion of biomass and waste plastics. ReaxFF molecular dynamic simulations are performed to study the supercritical water co-gasification mechanism of lignin and LDPE in the present study. The co-gasification process, the impacts of lignin content and temperature on the co-gasification of lignin and LDPE are analyzed. In addition, the nature of interaction mechanism between H2O and lignin, H2O and phenols in the co-gasification process are studied. The results showed that the primary products are CO and H2, and the proportion of latter is higher than that of former. The first step of the supercritical water co-gasification of lignin and LDPE is the cracking of lignin and LDPE, C5-C10 products and waxes are formed via the cracking of the βO4 bonds and the CC bonds, respectively. The formation of CO and H2 is facilitated by the increase of the feedstock proportion in the reaction system. Hydrogen bond formed between lignin and H2O improves the pyrolysis of lignin. This study provides a viable and green route to convert the biomass and waste plastics to syngas.

Steam reforming of biomass gasification gas for hydrogen production: From thermodynamic analysis to experimental validation

Biomass gasification produces syngas composed mainly of hydrogen, carbon monoxide, carbon dioxide, methane, water, and higher hydrocarbons, till C4, mainly ethane. The hydrocarbon content can be upgraded into richer hydrogen streams through the steam reforming reaction. This study assessed the steam reforming process at the thermodynamic equilibrium of five streams, with different compositions, from the gasification of three different biomass sources (Lignin, Miscanthus, and Eucalyptus). The simulations were performed on Aspen Plus V12 software using the Gibbs energy minimization method. The influence of the operating conditions on the hydrogen yield was assessed: temperature in the range of 200 to 1100 °C, pressures of 1 to 20 bar, and steam-to‑carbon (S/C) molar ratios from 0 (only dry reforming) to 10. It was observed that operating conditions of 725 to 850 °C, 1 bar, and an S/C ratio of 3 enhanced the streams' hydrogen content and led to nearly complete hydrocarbon conversion (>99%). Regarding hydrogen purity, the stream obtained from the gasification of Lignin and followed by a conditioning phase (stream 5) has the highest hydrogen purity, 52.7%, and an hydrogen yield of 48.7%. In contrast, the stream obtained from the gasification of Lignin without any conditioning (stream 1) led to the greatest increase in hydrogen purity, from 19% to 51.2% and a hydrogen yield of 61.8%. Concerning coke formation, it can be mitigated for S/C molar ratios and temperatures >2 and 700 °C, respectively. Experimental tests with stream 1 were carried out, which show a similar trend to the simulation results, particularly at high temperatures (700–800 °C).

Study on the mechanisms of hydrogen production from alkali lignin gasification in supercritical water by ReaxFF molecular dynamics simulation

Lignin is a major polymer in the black liquor of paper mill and one of the most important components of biomass. Supercritical water gasification (SCWG) technology, which is an efficient and clean method for waste lignin treatment, has a good application prospect. To improve the conversion efficiency of lignin, it is necessary to reveal the detail mechanisms of lignin gasification in supercritical water (SCW). Based on the actual molecular structure of lignin, a model of complex lignin was constructed by using Materials Studio (MS). The effects of different reaction parameters on gasification results were analyzed with the reactive force field molecular dynamics method (ReaxFF MD). The simulation results show that higher reaction temperature and lower reactant concentration lead to higher efficiency of lignin gasification in SCW, and lignin has the highest gasification efficiency at 3500 K and 15 wt%. Additionally, the decomposition pathway of lignin and the generation paths of CO2, H2 were clarified. This work will provide theoretical guidance for further research to improve the SCWG efficiency of lignin.

Global warming potential of bio-jet fuel produced by biomass aqueous-phase conversion

High greenhouse emissions from the production of conventional jet fuel plague the aviation industry. Corn stalk as a renewable source for bio-jet fuel production via aqueous-phase conversion can offer a sustainable solution. Based on life cycle assessment method, this study evaluated the greenhouse effects of lignocellulosic biomass aqueous-phase conversion to bio-jet fuel with the different pathways using SimaPro software. The global warming potentials of aqueous-phase conversion routes were compared with that of jet fuel produced from petroleum, and biomass through gasification and Fischer-Tropsch synthesis. The results showed that the greenhouse emissions of the different aqueous-phase conversion routes, including lignin gasification to hydrogen, lignin two-step to cycloalkanes, and lignin one-step to arenes, were from 2672.1 to 3382.1 kg CO2 e/t bio-jet fuel. The integration of lignin one-step conversion to bio-jet fuel with self-supplied hydrogen had the smallest greenhouse emissions, which decreased to 1914.6 kg CO2 e/t bio-jet fuel at the suitable parameters. Compared to petroleum-based jet fuel, the greenhouse emissions of the aqueous-phase conversion routes were reduced by 19.5 %–54.4 %. Moreover, the steam for heat supply and steam for electricity generation in the greenhouse emissions of biomass gasification and Fischer-Tropsch synthesis caused 1953.4 and 1185.9 kg CO2 e/t bio-jet fuel, respectively, relatively lower than that of aqueous-phase conversion. The sensitivity analyses showed that lowering carbon emissions of hydrogen and electricity production, and decreasing chemical consumption (such as sulfuric acid) could further reduce the greenhouse effect. Therefore, biomass aqueous-phase conversion to bio-jet fuel is a feasible routine to mitigate the greenhouse effect, which justifies enterprise spending for environmental benefits.

Investigation on reaction mechanism for CO2 gasification of softwood lignin by ReaxFF MD method

Investigation on reaction mechanism for CO2 gasification of softwood lignin by ReaxFF MD method

Effects of Lignin Gasification Impurities on the Growth and Product Distribution of Butyribacterium methylotrophicum during Syngas Fermentation

This work evaluated the effects of condensable syngas impurities on the cell viability and product distribution of Butyribacterium methylotrophicum in syngas fermentation. The condensates were collected during the gasification of two technical lignins derived from wheat straw (WST) and softwood (SW) at different temperatures and in the presence or absence of catalysts. The cleanest syngas with 169 and 3020 ppmv of H2S and NH3, respectively, was obtained at 800 °C using dolomite as catalyst. Pyridines were the prevalent compounds in most condensates and the highest variety of aromatics with cyanide substituents were originated during WST lignin gasification at 800 °C without catalyst. In contrast with SW lignin-based condensates, the fermentation media supplemented with WST lignin-derived condensates at 1:100 vol. only supported residual growth of B. methylotrophicum. By decreasing the condensate concentration in the medium, growth inhibition ceased and a trend toward butyrate production over acetate was observed. The highest butyrate-to-acetate ratio of 1.3 was obtained by supplementing the fermentation media at 1:1000 vol. with the condensate derived from the WST lignin, which was gasified at 800 °C in the presence of olivine. B. methylotrophicum was able to adapt and resist the impurities of the crude syngas and altered its metabolism to produce additional butyrate.

Lignin Gasification: Current and Future Viability

The consumption of fossil fuels is one of the main drivers of climate change. Lignin derived from biomass is a carbon-neutral raw feedstock, and its conversion into fuels is gaining much attention. The gasification of biomass aims to transform heterogeneous feedstocks into syngas and heat that could be used for various purposes. Lignin is a biomass feedstock of special interest due to its particular properties and its ability to be obtained in abundant quantities as a side product from the paper pulp industry as well as the growing cellulosic ethanol industry. This review explores the existing works regarding lignin gasification from different perspectives and compares the results obtained with other existing thermochemical processes, in addition to providing a perspective on the long-term fate of gasification as a technology compared to other emerging technologies. The analysis indicates that while lignin gasification may grow in importance in the near future due to increased interest in hydrogen production, its potential in emerging applications indicates that lignin may be too valuable to be used purely for energy generation purposes, and applications that take advantage of its inherent chemical compounds are expected to take priority in the long-term.

Gasification of α-O-4 linkage lignin dimer in supercritical water into hydrogen and carbon monoxide: Reactive molecular dynamic simulation study

Gasification of lignin in supercritical water is an efficient and clean way to convert biomass to high value-added fuel. The gasification mechanism of α-O-4 linkage lignin dimer in supercritical water is investigated by using ReaxFF reactive molecular dynamic simulation in this study. The gasification process of α-O-4 linkage lignin dimer, the effects of temperature and α-O-4 linkage lignin dimer/H2O ratio on the gasification of α-O-4 linkage lignin dimer are investigated. The results indicated that the major products of α-O-4 linkage lignin dimer are H2 and CO, and the yield of former is higher than that of latter. The first stage of the gasification process of α-O-4 chain lignin dimers under supercritical water conditions is the pyrolysis of α-O-4 chain lignin dimers, in which the α-O-4 bonds are broken to generate corresponding C5-C10 products. The conversion of C5-C10 and other C1-C4 products to H2 and CO is promoted by the H2O molecules. This work could provide an environmentally friendly, efficient and viable way for the conversion of lignin into high value-added fuel and relieve the stress of energy shortages and environmental pollution.

Gasification of hydrolysis lignin with CO2 in the presence of Fe and Co compounds

The effect of the nature of the metal (Fe and Co) deposited on the surface of hydrolysis lignin, as well as the metal content (1, 3, 5 and 7 wt%), on the process of dry catalytic lignin reforming has been studied. The use of the catalyst led to a twofold increase in the conversion of carbon dioxide at temperatures of 500–800 °C, while both metals showed similar activity. The maximum specific catalytic effect is achieved when supporting 7 wt% of active metals.

Simulation of softwood lignin gasification in supercritical carbon dioxide

Abundant renewable lignin resources have attracted increasing attention. Supercritical carbon dioxide exhibits excellent catalytic gasification properties. In this study, a molecular model for softwood lignin was established as a reactant. The ReaxFF molecular dynamics simulation method was used to simulate the gasification of softwood lignin in a supercritical carbon dioxide environment with platinum nanoparticles as catalysts. A slow temperature increase (80 K/ps) was used, and the system was studied at a constant temperature of 1700 K. The cleavage of different bonds at the initial stage of the reaction was studied, and the different gasification productions under the action of the catalyst in supercritical carbon dioxide were analysed and compared with those under non-catalyst conditions. The results showed that with the addition of the catalyst, the amount of CO2 cracking increased, the number of H2 and CO molecules produced increased, and the reaction rate increased.

Hydrogen production from supercritical water gasification of lignin catalyzed by Ni supported on various zeolites

In the present study, supercritical water gasification of dealkaline lignin catalyzed by Ni supported on different zeolites (3A, 4A, 5A, 13X and ZSM-5) was investigated. Scanning electron microscopy-energy dispersive X‐ray spectrometry (SEM-EDS), N2 adsorption–desorption and X-ray diffraction (XRD) were used to characterize the catalyst. Most of these catalysts enhanced the gasification except Ni/ZSM-5, and the order of their catalytic activity was: Ni/4A > Ni/3A > Ni/5A > Ni/13X > Ni/ZSM-5. The higher activity of Ni/4A was probably because it has mesopores with proper size to disperse Ni and provide more active sites for the reaction. With the catalysis of Ni/4A, the hydrogen selectivity was increased from 27.07% to 42.61%, and the H2 yield increased from 3.14 mol/kg to 5.63 mol/kg. With Ni/4A, the prolongation of reaction time improved the gasification efficiency and hydrogen production, but its impact became less pronounced when it was above 20 min. The increase of the Ni loading amount from 0 to 30 wt% in Ni/4A improved the hydrogen yield by 1.9 times to 6.2 mol/kg, but its further increase from 30 wt% to 50 wt% had less influence.

Hydrogen production by supercritical water gasification of lignin over CuO–ZnO catalyst synthesized with different methods

In this study, lignin was gasified in supercritical water with catalysis of CuO–ZnO synthesized by deposition precipitation, co-precipitation and sol-gel methods. Sol-gel synthesized CuO–ZnO showed the highest catalytic performance, and the gasification efficiency was increased by 37.92% with it. The XRD, SEM-EDS and N2 adsorption/desorption analysis showed that the priority of the sol-gel catalyst was the smallest crystallite size, largest specific surface area and high dispersion. For sol-gel synthesized CuO–ZnO, the increase of CuO/ZnO ratio improved the gasification efficiency but reduced H2 selectivity. And the catalytic activity was reduced with the calcination temperature above 600 °C due to enlarged crystallites and reduced pores. During sol-gel preparation, both the addition of ethanol and PEG in the solvent reduced the agglomeration and improved the catalytic activity. With CuO–ZnO prepared with 1 g PEG + water as the solvent, the highest H2 yield of 6.86 mol/kg was obtained, which was over 1.5 times of that without catalyst.