Utilization Of Syngas Research Articles

Catalytic influence of alkali and alkali earth metals in black liquor on the gasification process: a review

AbstractDuring the pulping process, either alkali or alkali earth metals are added in a cooking solution to turn wood chips into pulp, and these alkali and alkali earth metals (AAEMs) end up in the black liquor. These AAEMs are known to catalyze the gasification process, by lowering the reaction temperature and degrading tar in the syngas. Of the various black liquor valorization methods, gasification is a promising process that can be integrated into existing pulping processes to recover the process energy via syngas utilization. It is, therefore, important to firmly understand how AAEMs in black liquor catalyze the gasification process. This review paper also discusses how black liquor is generated from both the Kraft pulping and the sulfite pulping process. The paper also examines advances that have been made in terms of an integrated gasification process into the existing pulping process. The paper explores the supercritical water gasification of back liquor and syngas as fuel in the pulp and paper industry. A discussion of the co-gasification of black liquor with either fossil fuels or biomass, focusing on the catalytic effect of AAEMs in the co-gasification process as well as the synergistic effects of fossil fuels and biomass is presented.

Unlocking high-performance HCl adsorption at elevated temperatures: the synthesis and characterization of robust Ca–Mg–Al mixed oxides

The presence of HCl and SO2 gas imposes limitations on syngas utilization obtained from household waste in a wide range of applications. The hydrotalcite-like compounds (HTLs) have been proved that could remove HCl efficiency. However, the research on impact of synthesis conditions of HTLs and SO2 on HCl removal was limited. In this study, a range of Ca–Mg–Al mixed oxide sorbents was synthesized by calcining HTLs, with variations in crystallization temperature, solution pH, and the Ca/Mg molar ratio. These sorbents were examined for their effectiveness in removing HCl at medium–high temperatures under diverse conditions. The adsorption performance of selected sorbents for the removal of HCl, SO2, and HCl-SO2 mixed gas at temperature of 350 °C, 450 °C, and 550 °C, respectively, was evaluated using thermogravimetric analysis (TGA). It was observed that the HTL synthesis parameters significantly influenced the HCl adsorption capacity of Ca–Mg–Al mixed oxides. Notably, HTLs synthesized at 60 °C, a solution pH of 10–11, and a Ca/Mg ratio of 4 exhibited superior crystallinity and optimal adsorption characteristics. For individual HCl and SO2 removal, temperature had a minor effect on HCl adsorption but significantly impacted SO2 adsorption rates. At temperatures above 550 °C, SO2 removal efficiency substantially decreased. When exposed to a mixed gas, the Ca–Mg–Al mixed oxides could efficiently remove both HCl and SO2 at temperatures below 550 °C, with HCl dominating the adsorption process at higher temperatures. This dual-action capability is attributed to several mechanisms through which HTL sorbents interacted with HCl, including pore filling, ion exchange, and cation exchange. Initially, HCl absorbed onto specific sites created by water and CO2 removal due to the surface’s polarity. Subsequently, HCl reacted with CaCO3 and CaO formed during HTL decomposition.Graphical abstract

The effect of CH4 addition on high-H2 syngas combustion characteristics under N2/CO2 dilution

The composition of biomass gas is complex, in order to promote the more extensive and efficient utilization of low-calorific syngas, it is necessary to master the basic combustion characteristics of low-calorific syngas under different compositions. In this paper, the effects of addition of CH4 (0% – 20%) on the combustion characteristics of laminar flow flame of high-H2 syngas (H2:CO = 3:1) were studied by experiments and numerical simulations under the dilution of N2 and CO2 (40%). The laminar burning velocity (LBV) and Markstein length are obtained by experiments. CHEMKIN-PRO software package was used to compare the prediction results of the four mechanisms with the measured data. Finally, GRI3.0 mechanism was selected as the simulation mechanism in this paper. The experimental results indicate that the LBV of N2 dilution is higher than that of CO2 dilution, and the flame is more stable, with adding CH4, the LBV of syngas mixtures is decreased, and the LBV of rich-fuel mixtures is decreased faster, but the stability of premixed flames of syngas is improved. Numerical simulation shows that the dominant branch chain reaction changes from R99 to R38 after CH4 is added, and the mole fraction of H, O decreases while the mole fraction of OH, CH3 increases. The dilution of CO2 results in a lower concentration of active radicals than N2 because CO2 inhibits the important reaction R99. The GRI 3.0 mechanism was used to simulate the formation of NO: the addition of CH4 promoted the formation of hot NO. The NO production of NNH and N2O intermediate mechanism is decreased, and a new way of N2 and CH reaction to HCN is increased. The dilution of CO2 can reduce NO emission more than that of N2. The insights gained from this study have practical implications in a variety of production applications. For example, optimizing mixture equivalence ratios can improve combustion efficiency, thereby increasing energy efficiency and reducing environmental emissions.

Tar Formation in Gasification Systems: A Holistic Review of Remediation Approaches and Removal Methods.

Gasification is an advanced thermochemical process that converts carbonaceous feedstock into syngas, a mixture of hydrogen, carbon monoxide, and other gases. However, the presence of tar in syngas, which is composed of higher molecular weight aromatic hydrocarbons, poses significant challenges for the downstream utilization of syngas. This Review offers a comprehensive overview of tar from gasification, encompassing gasifier chemistry and configuration that notably impact tar formation during gasification. It explores the concentration and composition of tar in the syngas and the purity of syngas required for the applications. Various tar removal methods are discussed, including mechanical, chemical/catalytic, and plasma technologies. The Review provides insights into the strengths, limitations, and challenges associated with each tar removal method. It also highlights the importance of integrating multiple techniques to enhance the tar removal efficiency and syngas quality. The selection of an appropriate tar removal strategy depends on factors such as tar composition, gasifier operating and design factors, economic considerations, and the extent of purity required at the downstream application. Future research should focus on developing cleaning strategies that consume less energy and cause a smaller environmental impact.

Experimental and numerical study on the explosion characteristics of syngas under different venting conditions

To explore ways to mitigate the harm and damage caused by syngas explosions and provide a theoretical basis for the safe and widespread use of syngas, the explosion characteristics of syngas under different venting conditions were experimentally and numerically investigated in our work. Five venting configurations were established based on the location and size of the lateral vent. The combined effects of venting conditions and hydrogen concentrations on explosion characteristics were concerned. Results showed the lateral vent significantly impacted the flame front structure, flame propagation velocity, and overpressure. Moreover, the formation and development of tulip flame could be affected by the lateral vent and hydrogen concentration. The presence of a lateral vent reduced both the flame propagation velocity and overpressure. With increasing hydrogen concentration, the drop ratio of the maximum flame propagation velocity did not increase, whereas the drop ratio of the maximum overpressure increased for the same venting condition. Finally, the internal mechanism of syngas venting explosion under different venting conditions was revealed by numerical simulation. In short, the research results provided the theoretical basis for the safe utilization of syngas in the industrial production field.

Effect of dual port-direct injection of syngas in a rotary engine

Using syngas as a primary fuel for internal combustion engines with spark ignition is a bridge technology for transitioning from carbon-based to hydrogen-based energy sources. There are two different ways of syngas delivery into combustion chamber: port injection or direct injection. In this study, the combination of these methods is considered for integration benefits of each injection technology and promotion of syngas utilization in rotary engines. In the novel concept of syngas dual injection, part of the fuel is delivered by a port injector during the induction stroke, while another part is directly injected during the compression stroke. The ratio of fuel mass delivered by port and direct injection is changed within the range of 0.0 (direct injection only) to 1.0 (port injection only) and chosen as a key parameter of concentration stratification. This study aims to investigate the optimal fuel injection strategy with numerical simulation of mixture formation, ignition, and combustion processes. It was shown that dual injection strongly influences turbulence intensity and mixture heterogeneity. The turbulence lengthscales generally increase with dual injection ratio growth. The direct injection case demonstrates maximum performance characteristics. However, the case with a small portion of directly injected fuel (10%–25%) increases fuel conversion efficiency by 5%–7% and decrease fuel consumption by 4%–6% with lower level of CO emission. The results show that the dual injection strategy provides flexibility in controlling the combustion process and emission reduction.

A study of co-pyrolysis of sewage sludge and rice husk for syngas production based on a cyclic catalytic integrated process system

To address the challenges of low yield and low heating value of syngas, high yield of tar via pyrolysis, and to promote the resource utilization of syngas, this study prepared high-quality syngas through the secondary cracking of tar in cyclic catalytic pyrolysis steam based on a novel cyclic catalytic integrated pyrolysis system. In this study, the cyclic catalytic integrated pyrolysis system process parameters were synergistically optimized based on the pyrolysis syngas yield and lower heating value as indicators. The results showed that the optimal mixing ratio of sewage sludge and rice husk was 25:75 w/w. The optimal cycle speed and catalyst dosage was 1050r/min and 2.5g respectively. Compared to the normal pyrolysis system based on sewage sludge pyrolysis, the liquid phase product yield reduced 6 wt%, and the gas product yield increased 27 wt%. Regarding energy recovery, the syngas lower heating value increased 41.55%. The sewage sludge and rice husk have a synergistic effect and the long residence time promotes secondary cracking of the tar via pyrolysis, thus improving the yield and quality of the syngas. This study provides a new idea for the co-pyrolysis of different biomass to produce high quality syngas, and is very important for the preparation of renewable energy from biomass for application in power generation systems.

Kinetic Study of Carbon Deposition in Solid Oxide Fuel Cells (SOFCs)

Owing to many irreplaceable advances, solid oxide fuel cells (SOFCs) have a promising and competitive potential in the application of green power supply and greenhouse gas reduction. Especially the utilization of biomass-derived syngas shows a high efficiency potential for the overall system. However, carbon deposition at the anode is a major challenge for the practical application. Once carbon deposited at the anode, the degradation of SOFC performance is permanent and irreversible to a certain extent. The carbon deposition is closely associated with the inner temperature distribution and fuel gas composition within the SOFCs, which is determined by complex chemical and electrochemical reactions. In this study, competing kinetic rates for carbon deposition and regasification are analyzed based on CFD methods for typical biomass-derived syngas compositions. Based on this method, reasonable operating conditions and flow field configuration can be recommended, which reduce the kinetic rate of carbon deposition at the SOFC anode. It is also worth mentioning that the specific anode area where carbon deposition occurs firstly will be detected numerically under different fuel gas components, operating temperatures and flow filed configurations. In summary, an effective method is provided to reduce the carbon deposition at the anode and improve the life expectancy of SOFCs, which is meaningful for SOFC design and operation in practical applications.

Plasma-Catalytic CO2 Reforming of Toluene over Hydrotalcite-Derived NiFe/(Mg, Al)O x Catalysts.

The removal of tar and CO2 in syngas from biomass gasification is crucial for the upgrading and utilization of syngas. CO2 reforming of tar (CRT) is a potential solution which simultaneously converts the undesirable tar and CO2 to syngas. In this study, a hybrid dielectric barrier discharge (DBD) plasma-catalytic system was developed for the CO2 reforming of toluene, a model tar compound, at a low temperature (∼200 °C) and ambient pressure. Periclase-phase (Mg, Al)O x nanosheet-supported NiFe alloy catalysts with various Ni/Fe ratios were synthesized from ultrathin Ni-Fe-Mg-Al hydrotalcite precursors and employed in the plasma-catalytic CRT reaction. The result demonstrated that the plasma-catalytic system is promising in promoting the low-temperature CRT reaction by generating synergy between DBD plasma and the catalyst. Among the various catalysts, Ni4Fe1-R exhibited superior activity and stability because of its highest specific surface area, which not only provided sufficient active sites for the adsorption of reactants and intermediates but also enhanced the electric field in the plasma. Furthermore, the stronger lattice distortion of Ni4Fe1-R provided more isolated O2- for CO2 adsorption, and having the most intensive interaction between Ni and Fe in Ni4Fe1-R restrained the catalyst deactivation induced by the segregation of Fe from the alloy to form FeO x . Finally, in situ Fourier transform infrared spectroscopy combined with comprehensive catalyst characterization was used to elucidate the reaction mechanism of the plasma-catalytic CRT reaction and gain new insights into the plasma-catalyst interfacial effect.

4-E analyses of plasma gasification integrated chemical looping reforming system for power and hydrogen co-generation using bakelite and acrylonitrile butadiene styrene based plastic waste feedstocks

The present work studies a novel hybrid system of reforming using chemical looping technology integrated plasma gasification for the generation of hydrogen and electricity (via gas, air and steam turbines). Different power plant scenarios using two feedstocks such as electrical switch wastes (ESW) and computer keyboard plastic wastes (CKPW) working at two pressure levels (1 bar and 15 bar) were considered. A detailed investigation of the proposed process was performed using Aspen plus software based on 4-E (energy, exergy, economic and environmental) analyses. Sensitivity analyses were conducted to analyze the impact of feed ratio (feed gas/metal) in fuel reactor (FR), steam reactor (SR) and air reactor (AR) on their respective gas and metal oxide flow rate, and operating temperature. Based on the simulated results, the preferred ratios in terms of complete utilization of syngas, steam and air, and the high purity hydrogen in FR, SR and AR is 0.063, 0.5 and 0.188, respectively. It was found that the net overall energy efficiency is found higher for CKPW (72.35 %) than ESW (64.92 %) at the base case (i.e. 0 % excess OC or air concerning all plant scenarios), while the net overall exergy efficiencies were lower by 15 % for ESW and 3 % for CKPW on average, compared to energy efficiencies. In addition, the cost of electricity for all cases remains below 111 $/MWh for ESW and 76 $/MWh for CKPW while the LCOH lies in the range of 1.7–2.3 $/kg for ESW and 0.8–1.7 $/kg for CKPW. Likewise, the power plants fed with CKPW assured higher sustainability from the ecological point of view as all carbon was captured and stored.

Preliminary Experimental Results and Modelling Study of Olive Kernel Gasification in a 2 MWth BFB Gasifier

Gasification is a promising and attractive thermochemical method for biomass-to-energy conversion, with fluidized bed reactors being one of the best options for large-scale operations. Olive residues in particular are potentially excellent candidate biomass fuels in the Mediterranean area, due to the region’s increased capacity in olive oil production. Herein, the gasification experiments of olive kernels in a 2 MWth air-blown, bubbling fluidized bed reactor located at CENER’s facilities (BIO2C) in Navarra, Spain are presented. Even though technical issues were demonstrated due to the operation of the plant with a high-density biomass fuel and given the scale of the process, a quasi-steady-state and isothermal 12 h operation at an equivalence ratio of 0.25 ± 0.03 was attained. Given the satisfactory experimental results, an Aspen Plus simulation model of the process was also attempted. Notably, the proposed methodology agrees well with the experimental results and can be regarded as a starting point in future studies examining the gasification of relevant biomass in a MW-scale unit. Next, the effect of equivalence ratio and residual biomass moisture content were also evaluated, with the scope of designing future experiments that require minor modifications in the already existing apparatus. Finally, a syngas utilization route through the provision of energy for district heating purposes in the nearby village of Aoiz was proposed.

LaNixFe1−xO3 as flexible oxygen or carbon carriers for tunable syngas production and CO2 utilization

The current study reports LaFe1−xNixO3−δ redox catalysts as flexible oxygen or carbon carriers for CO2 utilization and tunable production of syngas at relatively low temperatures (∼700 °C), in the context of a hybrid redox process. Specifically, perovskite-structured LaFe1−xNixO3−δ with seven different compositions (x = 0.4–1) were prepared and investigated. Cyclic experiments under alternating methane and CO2 flows indicated that all the samples exhibited favorable reactive performance: CH4 and CO2 conversions varied between 85% and 98% and 70–88%, respectively. While H2/CO ratio from Fe-rich redox catalysts was ~2.3:1 in the methane conversion step, Ni-rich catalysts produced a concentrated (~ 93.7 vol%) hydrogen stream via methane cracking. The flexibility of LaFe1−xNixO3−δ to produce syngas (or hydrogen) with tunable compositions was found to be governed by the iron/nickel (Fe/Ni) ratio. Redox catalysts with higher Fe contents act as a lattice oxygen carrier via chemical looping partial oxidation (CLPOx) of methane whereas those with higher Ni contents function as a carbon carrier via chemical looping methane cracking (CLMC) scheme. XRD analysis and temperature-programmed reactions revealed that both types of catalysts involve the formation of La2O3 and Ni0 /Ni-Fe phases under the methane environment. The ability to re-incorporate La2O3 and Ni/Fe into a perovskite structure gives rise to oxygen-carrying capacity whereas stable Ni0 or Ni/Fe phases would catalyze methane cracking without lattice oxygen exchange in the reaction cycles. Temperature programmed oxidation and Raman spectroscopy indicated the presence of graphitic and amorphous carbon species, which were effectively gasified by CO2 to produce concentrated CO. Stability tests over LaFe0.5Ni0.5O3 and LaNiO3 revealed that the redox performance was stable over a span of 50 cycles.

Thermo‐Economic Analysis of a Plasma‐Gasification‐Based Waste‐to‐Energy System Integrated with a Supercritical CO2 Cycle and a Combined Heat and Power Plant

Herein, a novel hybrid design that combines hazardous waste plasma gasification, gas turbine, supercritical CO2 cycle, absorption heat pump, and coal‐fired combined heat and power (CHP) plant is proposed. In the integrated scheme, medical waste and concentrated solution of desulfurization wastewater are sent to the plasma gasifier and converted to syngas, which is conveyed into the gas turbine system after the necessary treatment. In terms of waste heat utilization of syngas and flue gas, some are used to drive the supercritical CO2 cycle, some are used by the absorption heat pump for heating, and the rest are used to heat the feedwater of the coal‐fired CHP plant directly. Based on a typical coal‐fired CHP plant, the benefits of this system are examined in terms of both thermodynamics and economics. Once the heat supply and the net electricity from coal remain the same, the net power generated by the waste in the hybrid design is 18.45 MW, while the net waste‐to‐electricity efficiency reaches 47.40%. In just 4.76 years, the initial investment in the proposed system is recouped, and in its 25 year lifetime, the system achieves a net present value of 150,491.81 k$.

Sorbents for high-temperature removal of alkali metals and HCl from municipal solid waste derived syngas

Impurities such as alkali metals (NaCl and KCl) and hydrogen chloride can limit downstream syngas utilization. In this study, a highly-active sorbent based on alumina containing active components for alkali metals and HCl sorption was synthesized for simultaneous removal of alkali metals and HCl from syngas at high temperatures of 750–850 °C in a reactor and compared with other sorbents (kaolin and γ-Al2O3). Results revealed that the removal efficiency of the developed sorbent for NaCl, KCl and HCl was the highest compared to kaolin and γ-Al2O3. At optimized conditions, the simultaneous alkali metal and HCl removal efficiencies were >80% and >70%, respectively (≤850 °C). Experimental data and thermodynamic calculations suggest that the removal of alkali metals was predominantly governed by physical sorption, while the removal of HCl was governed by chemical sorption. The physicochemical adsorption interactions between the sorbent and NaCl, KCl and HCl contributed to the simultaneous removal of alkali metals and HCl.

On the Efficiency of Utilization of Hydrogen and Syngas in a Spark-Ignition Engine

On the Efficiency of Utilization of Hydrogen and Syngas in a Spark-Ignition Engine

Co-gasification of different biomass feedstock in a pilot-scale (24 kWe) downdraft gasifier: An experimental approach

Co-gasification is considered as a useful technique for post-treatment of anaerobic digestion residues. The present study has dealt with the efficiency parameter of 24 kWe downdraft biomass gasifier with 50% mixture ratio of wood chips + corn cobs and 50% ratio of sugarcane bagasse + coconut shells. The performance of the gasification process was assessed with respect to biomass ratios on gasification efficiencies, reactor thermal profiles and equivalence ratio on specific yield of syngas composition and tar contents. Trials were conducted at a temperature range of 650–950 °C using equivalence ratios from 0.15 to 0.30. The biomass feeding rate was maintained between 35 and 40 kg/h. The total volume of gas obtained from co-gasification of wood chips + corn cobs was low (75.6 m3) than the mixture of sugarcane bagasse + coconut shells (94.33 m3) of gas at 5% moisture content. The average yield of syngas produced from the mixture of 1 kg wood chips + corn cobs and sugarcane bagasse + coconut shells were 2.52 and 3.14 m3, respectively. These results have shown that the mixture of wood chips + corn cobs produced almost 4238.6 mg/m3 tar impurities compared with the co-gasification sugarcane bagasse + coconut shells that produced 3767 mg/m3 with LHV of 3.8 MJ/Nm3 and 4.56 MJ/Nm3 at 5% moisture content respectively. This research concluded that co-gasification of sugarcane bagasse + coconut shells were found to be a suitable feedstock mixture for gasification and utilization of syngas for power generation depends on tar production, the flowrate of syngas, and performance in a downdraft gasifier.

Effect of alkali additives on desulfurization of syngas during supercritical water gasification of sewage sludge.

Amount of H2S and SO2 were generated during the SCWG of sewage sludge. It is essential to reduce the sulfur concentration in syngas for depth utilization of syngas from SCWG of sewage sludge. The syngas desulfurization ability of five additives (KOH, K2CO3, NaOH, Na2CO3, AC) were tested and the result indicated that K2CO3 had the best syngas desulfurization effect while KOH could significantly promote the yield of syngas at 450°C and 4% loading. Increasing KOH and K2CO3 loading to 12% could reduce around 90% of sulfur in syngas comparing to no additives. The XPS analysis results indicated that alkali additives promoted the cyclization and oxidation of unstable sulfur compounds in raw sludge, which can convert it into stable sulfur compounds such as thiophene, sulfone and sulfate. The sulfur in liquid was mainly in the forms of sulfate, and the effect of alkali and AC additive on sulfur in liquid was relatively weak.

Large eddy simulation of n-heptane/syngas pilot ignition spray combustion: Ignition process, liftoff evolution and pollutant emissions

The utilization of syngas in the internal combustion engine is one way to reach low carbon emission engine. The n-heptane/syngas pilot ignition spray combustion is simulated here by high fidelity model with different syngas compositions. It is found that the ambient syngas suppresses the ignition by diluting the ambient oxidizer (non-chemical effect) and by affecting the chemical reactions (chemical effect). The consumption of OH radicals through H2+OH = H + H2O and CO + OH = CO2+H in low temperature combustion (LTC) stage is shown to be the main reason for the suppression of ignition. Cool flame propagation into the rich mixture in the mixing layer of n-heptane jet is observed during the transition process from LTC to high temperature combustion (HTC). CO is found to assist the transition to HTC through CO + HO2 = CO2+OH. On the contrary, H2 slows down the cool flame propagation and narrows down the cool flame flammability range, which retards the onset of HTC. The effects of syngas compositions on the flame structure and emission formation are discussed in detail. Due to the upstream auto-ignition, a cool/diffusion/hot flame structure is identified at the liftoff position in dual-fuel case, which drastically changes the flame structure. And more soot formation in early stage is found in dual-fuel cases due to the naturally richer mixture.

In situ growth of LaSr(Fe,Mo)O4 ceramic anodes with exsolved Fe–Ni nanoparticles for SOFCs: Electrochemical performance and stability in H2, CO, and syngas

Fe–Ni nanoparticle–decorated LaSr(Fe,Mo)O4 Ruddlesden–Popper (R–P) perovskite anodes, named R–LSFMNx, were prepared in situ by reducing perovskites La0.5Sr0.5Fe0.9Mo0.1–xNixO3–δ (LSFMNx; x = 0.03–0.07) under SOFC anode operating conditions. Electrolyte–supported single cells with a configuration of R–LSFMNx|La0.9Sr0.1Ga0.8Mg0.2O3–δ (LSGM)|Ba0.5Sr0.5Co0.9Nb0.1O3–δ were used to evaluate the electrochemical performances and redox/long–term stability of the R–LSFMNx anodes fuelled by H2, CO, and simulated syngases (x% H2/CO; x = 50–10). EIS analyses indicated that the increased Ni level in the exsolved Fe–Ni nanocatalysts significantly promotes fuel diffusion/adsorption/dissociation, which plays a rate–limiting role in the anode fuel oxidation. Furthermore, the incremental Ni in Fe–Ni alloy also enhances the anode redox/long–term stability and carbon resistance/tolerance, and the R–LSFMN0.07 anode, i.e., Ni level in Fe–Ni alloy attaining ∼14 mol.%, displays the optimal stability and carbon resistance/tolerance. Finally, the potential of the R–LSFMN0.07 anode for direct utilization of syngas was demonstrated by the characterization of the electrochemical performance and stability based on the R–LSFMN0.07 anode cell.

Outlook for the coal industry and new coal production technologies

Outlook for the coal industry and new coal production technologies