Syngas Research Articles

Rapid CO detection using MWCNTs/SnO2 hierarchical structure: Synthesis, characterization, and RT gas sensing features

Industrialization, modernization, and heavy car populations cause an extensive release of hazardous gases which impact the environment and human health. In this respect, employing gas sensors for detecting different concentrations of carbon oxides, nitrogen oxides, and other harmful gases is being advanced with much interest and necessity. In our current research, we have feasibly synthesized MWCNTs/SnO2 hierarchical structure through a hydrothermal process. The attained XRD diffraction pattern reflects the crystallinity with a crystallite size <10 nm. The FTIR results signify the presence of the functional group which verifies the successful interaction and connection for the composite network. Morphological features using SEM, HRTEM depict the hierarchical structure persistence. The adsorption/desorption curves are investigated using BET analysis acquiring a surface area of 189 cc/g. Numerous gases were included in the gas sensing study such as ethanol, methanol, acetone, ammonia, CO, and CO2. The sensing performance displays a remarkable result for carbon monoxide (CO) detection. The response time for CO detection was 5 s, while the recovery was 7s for 300 ppm at RT. The improved selectivity of CO amongst ethanol, CO2 and other gases is demonstrated. The proposed CO sensing structure combines feasible approach, low-cost, room temperature operation, and fast response/recovery times. The structure is promising for CO gas detection for versatile industrial applications.

Functional Improvement of NiOx/CeO2 Model Catalyst Active in Dry Methane Reforming via Optimization of Nickel Content

The valorization of greenhouse gases, especially when focused on carbon dioxide, currently belongs to the main challenges of pro-environmental chemical processes. One of the important technologies in this field is dry methane reforming (DMR), leading to the so-called synthesis gas (CO + H2). However, to be efficient and economically viable, an active and stable catalyst is required. Ni-based systems can be recommended in this regard. This research aimed to investigate how nickel content can influence the activity of model NiOx/CeO2 catalysts in DMR. A series of NiOx/CeO2 samples of various nickel loadings (0–10 wt.%) were prepared through dry impregnation. The obtained samples were characterized through XRD, RS, N2-BET, DRIFT, SEM, UV/Vis-DR, and XPS. Nonlinear changes in surface properties of the investigated samples with increasing nickel concentration were found. The observed changes are mirrored both in the determined nickel speciation and in the corresponding catalytic activity. The highest activity was found for the catalyst containing 3 wt.%. of nickel.

Energy efficiency of hydrogen production via gasification from lignocellulosic residual biomass blend

Facing the challenges of environmental sustainability and energy security caused by anthropogenic carbon emissions, there is a need to adopt cleaner energy generation technologies, leveraging Colombia's existing national resources. In this context, hydrogen emerges as a promising source of renewable energy. Therefore, this project explores the use of a blend of residual lignocellulosic biomass as raw material for hydrogen production through gasification for energy purposes. Initially, a screening of residual lignocellulosic biomass in the study region was conducted, a blend was selected, and a simulation of the synthesis gas production process was carried out prospectively using Aspen Plus Dynamics® software. The results revealed that, by using the selected biomass blend, a synthesis gas with a hydrogen molar fraction of 38.7% and an ER of 0.19 was obtained. According to sensitivity analyses, the optimal parameters identified to achieve this hydrogen concentration were: gasification temperature of 707°C, oxygen flows of 484 kg/h, steam at 420 kg/h, and gasification pressure of 1 atm. These findings support the potential of the studied lignocellulosic biomass blend as an alternative for hydrogen production, while also offering an opportunity for the valorization of lignocellulosic residual biomass.

Effect of Equivalent Ratio and Hydrocarbon Ratio on Explosive Characteristics of Synthetic Gas

With the development of society, the importance of energy is increasing day by day, and more and more people realize the importance of energy for social development.Therefore, people began to explore energy utilization, energy exploitation, clean energy and other fields.Therefore, in order to use coal resources cleanly and efficiently and reduce the damage to the environment, the development of clean coal technology is particularly important.As a kind of clean energy, syngas has been paid more and more attention, so people pay more and more attention to the safety application of syngas. This paper explores its influence on syngas explosion by changing the equivalent ratio of syngas and the ratio of hydrogen and hydrogen.The results show that the maximum explosion pressure of syngas occurs near the equivalent ratio 1.2, the maximum explosion pressure rise rate reaches the maximum near the equivalent ratio 1.5, and the maximum explosion pressure time reaches the minimum near the equivalent ratio 1.5.The change of hydrocarbon ratio does not shift the equivalent ratio of the above result, but only changes its value. The prediction equations for predicting the maximum explosion pressure under different equivalent ratios are obtained

Investigation of regeneration cycles with different catalysts on steam gasification of biomass

In this work, agricultural biomass waste was gasified in a two-zone tubular reactor in the presence of steam. Firstly, during preliminary experiments the effect of temperature in the 1st and 2nd reactor zone, as well as the influence of catalysts and steam/raw material ratio was investigated, then the reusability of catalysts was also studied during ten regeneration cycles. Based on the preliminary results, in the 1st reactor zone a lower temperature was used (400 °C), where the yield of carbon dioxide was ∼55 %, which has a positive effect on numerous reactions, also it can be converted to carbon monoxide with proper catalysts with in-situ process. Regarding the temperature, it is important to be mentioned that a significant difference was observed in the yield of synthesis gas at 700 °C thus, the experiments were carried out using 700 °C in the 2nd reactor zone. A natural (Clinoptilolite) and a synthetic zeolite (ZSM-5), a mesoporous alumina (Al2O3) and a carbon dioxide capturing carrier (CaO) were selected and impregnated with nickel for further use and for enhancing the yield of synthesis gas and hydrogen during the gasification process. The utilization of catalysts helped the in-situ reduction of carbon dioxide while their performance in the gasification process during the regeneration cycles was also investigated. Henceforward, the tested Ni/ZSM-5, Ni/Al2O3 and Ni/Clinoptilolite, reduced the amount of carbon monoxide from the 5th regeneration cycles, while the amount carbon dioxide with the four mentioned catalysts was decreased by 15–35 mmol/g raw material, compared to the results obtained during thermal degradation.

Assessment of Syngas Storage Tank Hazards Taking Account of the Domino Effect

In most countries energy needs are satisfied using fossil fuels. Fossil fuel combustion involves environmental pollution and greenhouse gas emissions. The effect of the depletion of natural resources and the growing awareness of the need to protect the environment are the reasons that clean energy and alternative energy sources have been significant research issues. One of the most important technologies enabling efficient generation of low-emission energy is the gasification process of synthesis gas production. Syngas is primarily composed of hydrogen and carbon monoxide, but depending on the feedstock, it can also contain smaller concentrations, e.g., of carbon dioxide, methane and nitrogen. Because synthesis gas contains flammable and toxic substances, it may pose hazards to humans and the environment at every stage of gas production, storage, transport or final utilization if released uncontrollably. This paper presents the results of analyses related to hazards created by an uncontrollable release of synthesis gas during storage. A failure of a syngas system may cause damage to other, subsequent technological systems and facilities located in the neighborhood and containing dangerous substances. The problem gains special significance if syngas is stored in many tanks, where a failure of one may result in damage to subsequent tanks due to the so-called domino effect. The conditions in which the domino effect may occur are analyzed and the effect occurrence probability is determined depending on the mutual location of the tanks.

Higher Alcohol and Oxygenate Synthesis from Synthesis Gas and Ethanol over Supported K-(Co)MoS2 Catalysts: Effect of Novel Ni-Containing Carbon Nanofiber Supports Formed as Byproducts from Methane Decomposition

Higher Alcohol and Oxygenate Synthesis from Synthesis Gas and Ethanol over Supported K-(Co)MoS₂ Catalysts: Effect of Novel Ni-Containing Carbon Nanofiber Supports Formed as Byproducts from Methane Decomposition

ECONOMIC EFFICIENCY OF THE PRODUCTION OF BIOCHAR AND SOLID FUEL BASED ON BIOCAL

Useful disposal of industrial waste and biomass remains is increasingly relevant for Ukrainian enterprises. The purpose of this article is to find additional opportunities for the production of products with greater added value by processing waste and biomass residues to biochar. World prices for biochar are quite high, much higher than for the use of biocoals as fuel, and are around 800 EUR/t, maximum up to 1,800 EUR/t. The main technical characteristics and price offers of equipment for the production of biochar from nine manufacturers from China, Germany, Finland, Norway and the Netherlands were analyzed. The results of feasibility study of the biochar production from sunflower husks on a technological line with an input productivity of 5 t/h for one of the Ukrainian vegetable oils production plants are presented. As the main equipment, a drum-type pyrolyzer heated by synthesis gas, formed during the thermochemical decomposition of biomass, was considered. Byproducts of production are also bioacetic acid and tar oil. The financial indicators in the case of biochar export are attractive enough for implementation. The estimated simple payback period when using granulated husk was about 4 years at a price of biochar of 650 EUR/t and less than one year at a price of 800 EUR/t. When using non-granulated husk, the simple payback period was about 3 years, even at the price of biochar of 450 EUR/t. Possible risks for implementation are the uncertainty regarding market demand and sales opportunities for biochar, quality requirements and the ability of the considered equipment to provide them, insufficient information regarding biochar yield from various biomass, as well as the lack of experience. Enterprises interested in the implementation of such a project are recommended to conduct trial processing of a batch of their raw materials on similar equipment in advance, to determine the share of biochar yield and its quality characteristics, to search for potential buyers to discuss quality requirements and possible prices.

Requirements on synthesis gas from gasification for material and energy utilization: a mini review

Achieving sustainable energy and material use mandates a critical focus on carbon recycling. The imperative for an efficient carbon cycle is paramount in sustainable energy systems and the chemical industry. Syngas, derived from waste and biomass gasification, offers a robust foundation for such recycling efforts. Various technologies, each with unique gas purity requirements, facilitate further refinement of syngas. This study provides a detailed and comparative analysis of the purity specifications necessary for both energetic and material utilization pathways.

Validation of a mathematical model for the simulation of a multitubular and multitask solar reactor

Solar reactors represent an opportunity to obtain chemical reactions at high temperatures, saving costs in energy supply through the concentration of solar energy. Multitubular and Multitask (M&M) solar reactors are one of the options that allow the production of hydrogen and the production of synthesis gas through the gasification of hydrocarbon materials. The complexity of the phenomena involved in this type of reactor requires a robust mathematical model capable of integrating all heat transfer mechanisms. Some previous efforts made for the simulation of reactors use overly complex models that neglect some heat transfer mechanisms such as convection, and despite this have high computational cost, thus reducing the possibility of intensive debugging and the capacity of a sensitivity and uncertainty analysis. In this work, a mathematical model of distributed and transient parameters is presented that considers all the mechanisms of heat transfer by convection, radiation, and conduction in the components of a solar reactor of Multitubular and Multitask type, under a finite difference solution scheme and using the matrix method to calculate the radiation emitted from the components in 2D, offering a code with fast simulation and low computational cost. The model is validated with experimental data from the Multitubular and Multitask solar reactor, satisfactorily reproducing the prediction of the tube and wall temperatures under the conditions to which the reactor was subjected, reaching temperatures close to 1430 K in the tubes. The maximum relative error was equal to −7.4 % in the tube temperatures during a part of the experiment, acceptable given the complexity of the phenomena. The experiment lasted 180 min, and the simulation time spent around 38 s using a commercial computing processor. The model has the ability to quickly and satisfactorily reproduce the behavior of a Multitubular and Multitask type solar reactor, taking into account all the heat transfer mechanisms that had been omitted in previous works.

Mass yields of products and composition of syngas from pyrolysis of Brazilian plastic solid wastes: Combustion simulation and burner design to minimize COx and CxHy emissions

For the first time, the mass yields of products and the composition of synthesis gas (syngas) from pyrolysis of Brazilian plastic solid waste were evaluated for a reactor processing 20 g of plastic at 800 °C. Combustion of the syngas was simulated, evaluating the levels of COx and CxHy emissions, and a burner was designed to minimize emissions during combustion. The main findings highlighted the importance of performing thermogravimetric analyses of waste materials. Higher thermal degradation temperatures (530–900 °C) were obtained for all the plastics, compared to values reported in the literature (300–600 °C). Between 46.7 and 98.0 wt% of syngas was produced, with lower heating values ranging from 10390 to 45684 kJ kg−1, due to differences between the plastics in the fractions of inorganic and hydrocarbon gases produced. The maximum temperatures for syngas combustion, simulated using ANSYS software, were 2000 and 800 °C inside the burner and combustion chamber, respectively. In the burner, higher COx and CxHy levels were related to the syngas composition and incomplete chemical reactions in the flame zone. The CO and CxHy levels decreased towards the combustion chamber, where CO2 was less than 8 wt%, in compliance with the CONAMA 316/2002 regulation.

Bioreduction of chromate in a syngas-based membrane biofilm reactor

This study leveraged synthesis gas (syngas), a renewable resource attainable through the gasification of biowaste, to achieve efficient chromate removal from water. To enhance syngas transfer efficiency, a membrane biofilm reactor (MBfR) was employed. Long-term reactor operation showed a stable and high-level chromate removal efficiency > 95%, yielding harmless Cr(III) precipitates, as visualised by scanning electron microscopy and energy dispersive X-ray analysis. Corresponding to the short hydraulic retention time of 0.25 days, a high chromate removal rate of 80 µmol/L/d was attained. In addition to chromate reduction, in situ production of volatile fatty acids (VFAs) by gas fermentation was observed. Three sets of in situ batch tests and two groups of ex situ batch tests jointly unravelled the mechanisms, showing that biological chromate reduction was primarily driven by VFAs produced from in situ syngas fermentation, whereas hydrogen originally present in the syngas played a minor role. 16 S rRNA gene amplicon sequencing has confirmed the enrichment of syngas-fermenting bacteria (such as Sporomusa), who performed in situ gas fermentation leading to the synthesis of VFAs, and organics-utilising bacteria (such as Aquitalea), who utilised VFAs to drive chromate reduction. These findings, combined with batch assays, elucidate the pathways orchestrating synergistic interactions between fermentative microbial cohorts and chromate-reducing microorganisms. The findings facilitate the development of cost-effective strategies for groundwater and drinking water remediation and present an alternative application scenario for syngas.

Small-Scale Power Plants Based on Organic Rankine cycle (ORC) using Low-Boiling Fluorocarbon Working Fluids when Operating at High Initial Cycle Conditions

The purpose of the work is to develop and analyze the operation of a thermal circuit based on the organic Rankine cycle (ORC) using low-boiling working substances of the fluorocarbon class when operating at high initial cycle parameters. This goal is achieved by energy analysis of single- and multi-stage thermal circuits of power plants with a turbine circuit operating on low-boiling fluorocarbon work-ing substances, such as octafluoropropane C3F8 and decafluorobutane C4F10. It is proposed to integrate the ORC thermal circuit as an extension to a small-capacity gas turbine power plant (GTU), operating on synthesis gas after a biomass gasifier. The most important results of the work are the possibility of implementing a cycle with a low condensation temperature of the medium, which allows, when using low-boiling working fluids, to significantly reduce the temperature of the heat removal process and, consequently, increase the efficiency of the cycle. The possibility of using the listed working substances in power plants with a turbine circuit, which until now have been used mainly as refrigerants for refrig-eration and heat pump systems, has been shown. The significance of the results of the work lies in the fact that, based on the analysis of the energy complex, a circuit solution has been proposed and justified that can increase the energy efficiency of the power supply complex, increasing the volume of generated electrical power and providing a number of technological and environmental advantages.

Fischer-tropsch synthesis: effect of temperature and iron-cobalt ratio in Fe-Co/meso-HZSM-5 catalyst on liquid product distribution

The Fischer-Tropsch synthesis converted hydrogen and carbon monoxide into linear hydrocarbons as liquid fuel. Iron and cobalt were used as polymerization catalyst, that impregnated on HZSM-5. The Fe-Co/HZSM-5 could be applied as bifunction catalyst which combined polymerizing synthesis gas and long chain hydrocarbon cracking for making biofuel. The objective of this study is observing the effect of temperature and composition of iron and cobalt combination, supported by HSZM-5 (Fe-Co/HZSM-5) catalyst on fuel product composition. The results obtained from this study would be used to find optimum condition for various iron and cobalt ratio in the catalyst. The mesoHZSM-5 was prepared from ammonium ZSM-5 over calcination, desilication, and dispersion. The mixed solution consisted of Co(NO3)2.6H2O and Fe(NO3)3.9H2O were used as precursor for incipient wetness impregnation on HZSM-5. The catalyst performance was observed in a continuous fixed bed reactor using Fe-Co/meso-HZSM-5 catalyst with synthesis gas at various composition iron and cobalt ratio (10–40 % wt. Fe in Co), various temperature (225–275 °C) at 20 bars. All catalysts were reduced in situ in the reactor. The 10Fe-90Co/mesoHZSM-5 catalyst was more suitable for FTS at 250 °C with alkane (20.49 %) as the main product and alcohol as the by-product (79.51 %). The others catalysts composition of 20–40 % Fe (by weight) in Fe-Co were more suitable for FTS at 225–250°C because under these conditions, alkanes as the main product were obtained in relatively higher compositions compared to other compounds. The mechanism of paraffins, olefins, aldehydes and alcohols formation in this FTS reaction followed the hydrogen assisted CO dissociation with CO-insertion mechanism

Experimental and numerical investigations of the laminar burning velocities of premixed fuel-rich methane oxy-fuel and oxygen-enhanced flames

In the context of Oxy-fuel combustion, there is a strong industrial interest in highly fuel-rich flames, characterized by an equivalence ratio (Φ) exceeding 2.5, for the production of H2-CO-rich synthesis gas. The validation of existing chemical reaction mechanisms for this specific regime pose a significant challenge due to the scarcity of experimental data for this particular range of equivalence ratio.The scope of this study was therefore the determination of the laminar burning velocity sL of ultra-rich CH4-O2 flames under varying conditions, such as high equivalence ratios and preheating temperatures using the heat flux burner method. The laminar burning velocity was determined for equivalence ratio within the range of 2.3 < Φ < 3.6 and preheating temperature ranging from 300 K to 455 K. Additionally, the impact of the of reducing the oxygen content in the oxidizer on sL was investigated by argon addition in molar percentages ranging from 40 % to 100 %.The results of our study reveal laminar burning velocities ranging from 5 cm/s to 45 cm/s for pure oxy-fuel CH4 flames. Preheating is shown to increase sL and this effect can be represented by a power law correlation sL = sL,0(T/T0)α with α = 1.53. Furthermore, the dilution of the oxidizer with argon leads to a significant decrease in sL of approximately 50 % compared to pure oxy-fuel flames. It is worth noting that detailed reaction mechanisms in combination with molecular transport data are typically not validated within the selected equivalence ratio range.To assess the performance of such reaction schemes in predicting laminar burning velocity under the specified selected conditions, we evaluated 13 different reaction mechanisms sourced from the literature. We compared the laminar burning velocities obtained through calculations of laminar premixed 1D flames and, additionally compared these with experimental data. A sensitivity analysis of the laminar burning velocity were carried out for selected mechanisms. Among the mechanisms, the CalTech2.3 mechanism exhibited the most consistent and accurate performance, particularly at high equivalence ratios.

Study of CH4-H2-CO-Air premixed combustion characteristics based on fractal dimension and flame crack method

The laminar combustion characteristics of CH4-H2-CO-Air are studied in a constant volume combustion chamber with different hydrogen content ratios and the initial conditions of 300 K and 0.2 MPa by schlieren technology. The influence laws of flame instability are analyzed through the influence laws of hydrogen content ratio and equivalence ratio (Φ) on the fractal dimensions of the flame contour and the ratio of the total flame face cracks' lengths to the flame radius (L/R), as well as the influence laws of hydrodynamic instability and thermal-diffusive instabilities on the flames. The results show that L/R is more sensitive to flame instabilities than flame front fractal dimensions due to a wider sampling range. After R exceeds a certain value, for lean and rich combustion conditions with the same distance from the stoichiometric ratio, the L/R is greater during lean combustion, and as the equivalence ratio gradually increases from 0.6 to 1.4, the effect of increasing hydrogen content (Hydrogen mole fraction ranges from 60% to 66.67%) on flame instability gradually shifts from promotion to suppression. This study has certain reference value for the combustion application of biomass synthesis gas.

Biogas upgrading by intensified methanation (SESaR): Reaction plus water adsorption - desorption cycles with Ni-Fe/Al2O3 catalyst and LTA 5A zeolite

This work is conducted within the framework of the Power to Gas (PtG) technologies, focusing on the topic of “biogas upgrading”. The objective is to enhance the CH4 content of biogas streams by utilizing the CO2 present in these streams through the Sabatier reaction, thereby producing a renewable alternative to natural (fossil) gas. Referred to as “SESaR”(Sorption Enhanced Sabatier Reaction), this process employs a catalytic fixed-bed reactor, featuring selective water adsorption using LTA 5A zeolites, as an innovative approach to traditional methanation reactors. The catalyst used comprises Ni-Fe (7.5:2.5 wt/wt) as the active metallic phase supported on γ-Al2O3. Experimental work has been divided in two sets of trials. The first set focuses on the hydrogenation of CO2 as single reactant (H2 also supplied in the inlet with 4:1 = H2:CO2 molar ratio). The second set of experiments was carried out with a synthetic gas mixture representative of a sweetened biogas stream (molar ratio CH4:CO2 = 7:3). Maximum intensification behavior for CO2 conversion was found at 350 °C, also showing that CH4 presence in the inlet gas has negligible influence on the conversion of CO2. Selectivity to CO is minimized at temperatures exceeding 300 °C and remains constant after three consecutive cycles of methanation, water adsorption, and desorption. The Fe-Ni catalyst has demonstrated sustained performance throughout the experimental cycles, exhibiting no significant loss of activity.

Experimental studies and mathematical modeling of the catalytic conversion of biodiesel fuel into synthesis gas

In this work, steam reforming and autothermal reforming of methyl oleate (a model compound of biodiesel fuel) into synthesis gas on a structured Rh-containing catalyst were investigated. It has been shown that the conversion of methyl oleate proceeds through the stage of thermal cracking followed by the conversion of the resulting organic compounds with a shorter carbon skeleton. Based on the experimental results, a mathematical model was developed that takes into account the radial temperature gradient and represents an effective tool for quantitatively describing and optimizing the biodiesel conversion process.

Variation of the shapes of catalytic blocks in the autothermal reforming of hexadecane, propane and methane using mathematical modeling

In this work, mathematical modeling of the autothermal reforming of hexadecane, propane and methane on catalytic blocks of different geometric shapes was carried out. It was shown that the convex shape of the block towards the oncoming reaction flow can increase the maximum temperature in the frontal zone, while the concave shape contributes to a more uniform temperature distribution along the entire length of the catalytic layer. The work also investigated the effect of the reaction flow rate on the change in the temperature gradient, which can subsequently be used to prevent the formation of hot spots and catalyst deactivation. The results obtained can serve as the basis for future research in the field of autothermal reforming and optimization of the geometric parameters of catalysts for the conversion of hydrocarbon fuels into synthesis gas.

Energy, exergy and economic analysis of a poly-generation system combining sludge pyrolysis and medical waste plasma gasification

To optimize the processes of treating medical waste and pyrolyzing sludge, we propose a new integrated system that combines plasma gasification for medical waste treatment, combined cycle power generation, and sludge pyrolysis. The medical waste is first incinerated, and then the synthesis gas from plasma gasification powers a gas turbine to generate electricity in this integrated system. The gas turbine's exhaust gas heats steam and feedwater from the HRSG to achieve a combined gas-steam cycle. Simultaneously, turbine exhaust steam energizes sludge pyrolysis, allowing for efficient conversion of medical waste into electricity in an eco-friendly manner. A hybrid design study was conducted using different methods, including energy, exergy, and economic analysis. The study revealed that the medical waste-to-energy system integration has the potential to attain 66.31% energy efficiency and 66.70% exergy efficiency. Moreover, the medical waste-electricity project has a dynamic payback period of 2.46 years and a relative net present value of 38,949.91k$. These outcomes suggest that this innovative concept is practical, advantageous, and has excellent potential for further development in the field of waste-to-energy conversion.