CO In Product Gas Research Articles

Catalytic effect and kinetic mechanism of alkali metal carbonates on the reduction reaction of biochar with iron oxide

Previous studies have shown that alkali metals catalyse the pyrolysis and gasification processes of biomass. However, whether alkali metals have the same catalytic effect on the reduction reaction of biochar with iron oxide has not been investigated. In this article, the effect of alkali metals on the reduction behaviour of biochar with iron oxide was investigated. It was shown that adding alkali metal carbonate could increase the reaction rate of CSC reduction stages 1 and 2, but it played an inhibitory role for the first and middle periods of stage 3. Moreover, adding alkali metals resulted in higher total CO2 gas production and reduced total CO gas production for the reduction reaction. The GB1 model was the best mechanistic model for stages 1 and 2 of the CSC-2K and CSC-2Na reduction reactions, while the C1 model was the best mechanistic model for stage 3.

Exploring the factors influencing the low temperature CO gas production characteristics of low-metamorphic coal

CO as an important indicator gas for predicting early spontaneous combustion of coal mainly comes from the oxidation of residual coal in goaf. Low-metamorphic coal has a stronger tendency for spontaneous combustion and is more prone to oxidation to produce CO gas at low temperatures. For example, there are no signs of natural combustion in certain goaf areas of mines, but the CO concentration in the working face continues to exceed the limit, which misleads early natural combustion prediction and warning work. Therefore, taking low metamorphic coal as the main research object, the CO gas production characteristics of different coal samples at low temperatures were determined through temperature-programmed experiments. It was found that the CO gas production rate and concentration of CYM at low temperatures were much higher than those of the other two metamorphic coal samples (approximately 2 times RNM and 3–10 times QM); Determination of content and proportion changes of hydroxyl, aliphatic, Aromatic hydrocarbon and oxygen-containing functional groups in different coal samples before and after heating by Fourier transform infrared spectroscopy. Based on the analysis of CO gas production characteristics of different coal samples, it was found that the intermolecular hydrogen bonds in the hydroxyl groups of CYM and the C-O bonds in the oxygen-containing functional groups decreased significantly. The strongest correlation between intermolecular hydrogen bonds in hydroxyl groups and C-O bonds in oxygen-containing functional groups and the low-temperature CO gas production characteristics of coal is demonstrated; Finally, scanning electron microscopy was used to study the differences in apparent characteristics of different coal samples before and after heating, to determine more complex apparent structures that increase oxygen adsorption sites and promote low-temperature oxidation and CO production of coal during the low-temperature stage. Further guidance will be given to the research on the suppression of intermolecular hydrogen bonds and C-O bonds, as well as the sealing of coal micro pores and crack structures, to improve the targeted application and fire prevention efficiency of fire prevention materials.

Study on the Adsorption/Desorption Characteristics of Protogenetic CO in Coal Seams

ABSTRACT In recent years, abnormal CO gas overruns have often occurred in coal mining workings. CO overruns were thought to be caused by the underground blasting work or spontaneous combustion of coal seams; however, minimal attention has been given to the causes of the desorption and release of adsorbed CO in the coal seams. Additionally, insufficient research has been conducted on the generation, distribution and adsorption and desorption characteristics of protogenetic CO in coal seams. Therefore, a self-built comprehensive testing system for coal seam adsorption and desorption was used to study the characteristics of the depressurization desorption and thermal desorption of coal with different degrees of metamorphism during coal seam mining. The results showed that under isothermal conditions, the amount of CO adsorption and desorption of coal samples increased with increasing pressure; under temperature rise conditions, the gas adsorption-desorption was in a dynamic equilibrium process under certain conditions. When the temperature increased, the equilibrium was beneficial to the desorption direction. The initial temperature range of CO production at different equilibrium pressures was 45–55°C. With increasing pressure, the initial temperature point of CO gas production moves forward and was significantly lower than the initial temperature of coal spontaneous combustion. Our research results further supplement the source of underground protogenetic CO gas and provide theoretical support for the accurate prediction of CO coal spontaneous combustion.

Effects of Functional Groups in Coal with Different Vitrinite/Inertinite Ratios on Pyrolysis Products.

Maceral composition is one of the key factors affecting the liquefaction and gasification of coal, which has attracted extensive attention of researchers working on coal chemical industry. To elucidate the impact of vitrinite and inertinite in coal on pyrolysis products, vitrinite and inertinite were extracted from a single coal sample and mixed to create six samples with varying vitrinite/inertinite ratios. The samples were subjected to thermogravimetry coupled online with mass spectrometry (TG-MS) experiments, and the Fourier transform infrared spectrometry (FITR) experiment was used to determine the macromolecular structures before and after the TG-MS experiments. The results show that the maximum mass loss rate is proportional to the vitrinite content and inversely proportional to the inertinite content, and increased vitrinite content accelerates the pyrolysis process and shifts the pyrolysis peak to low temperatures. Based on FTIR experiments, the sample's CH2/CH3 content, representing the length of aliphatic side chains, decreases significantly after pyrolysis, and the greater the loss of CH2/CH3, the greater the intensity of organic molecule production, indicating that aliphatic side chains are likely to yield organic molecule products. The aromatic degree (I) of samples rises sharply and steadily with increasing inertinite content. After high-temperature pyrolysis, the polycondensation degree of aromatic rings (DOC) and relative abundance of aromatic and aliphatic hydrogen (Har/Hal) within the sample increased significantly, indicating the thermal degradation rate of aromatic hydrogen content is much lower than that of aliphatic hydrogen. When the pyrolysis temperature is lower than 400 °C, the higher the inertinite content, the easier it is to produce CO2, whereas an increase in vitrinite leads to an increase in CO production. At this stage, the "-C-O-" functional group is pyrolyzed to produce CO and CO2. When the temperature exceeds 400 °C, the CO2 output intensity of vitrinite-rich samples is much higher than that of inertinite-rich samples, while the CO output intensity of vitrinite-rich samples is lower, and the higher the vitrinite content, the higher the peak temperature of CO gas production of samples, indicating that when the temperature exceeds 400 °C, the increase of vitrinite inhibits CO production and promotes CO2 production. At this stage, the reduction of each sample's "-C-O-" functional group after pyrolysis is positively correlated with the maximum CO gas production intensity, and the reduction of each sample's "-C=O" functional group after pyrolysis is positively correlated with the maximum CO2 gas production intensity. As a result, the "-C-O-" functional group is more likely to produce CO, whereas the "-C=O" functional group is more likely to be pyrolyzed to CO2. Hydrogen is primarily produced during the polycondensation and aromatization processes, and its production is proportional to the dynamic DOC values after pyrolysis. The higher the I value after pyrolysis, the lower the maximum gas production peak intensity of CH4 and C2H6, which indicates that increasing the aromatic proportion is detrimental to CH4 and C2H6 production. This work is expected to provide theoretical support of the liquefaction and gasification of coal with different vitrinite/inertinite ratios.

Microscopy Investigation of Platinum Ternary Alloy Catalysts on N-Doped Reduced Graphene Oxide Supporter for Direct Ethanol Fuel Cell (DEFC)

Platinum (Pt) is widely used as anode catalyst for direct ethanol fuel cell (DEFC) but toxic CO gas was produced in the system. Pt bimetallic catalysts can increase the reaction rate, current density and reduce CO gas production. However, some bimetallic catalysts are still expensive and give the low reaction rate. Trimetallic catalysts on carbon supporter were represented instead due to their better catalytic activities, long life time of operation and higher current density. In this study, we synthesized trimetallic alloy on N-doped reduced graphene oxide (NrGO) catalysts using as DEFC anode. The percentage of metals composition in the synthesized catalysts was varied. NrGO was prepared by Modified Hummers Method, then reduced by annealing under Nitrogen gas atmosphere and N-added by annealing with melamine. The preparation method for trimetallic alloy catalysts on NrGO was NaBH4 reduction. The X-ray diffraction (XRD) patterns displayed their alloy phase of PtMRu (M = Au, Sn) which compose of Pt main structure and NrGO supporter. Scanning Electron Microscopy (SEM) images showed the dispersion of alloy metal particles on NrGO surface. The composition of catalysts could be confirmed by Energy dispersive spectroscopy (EDS) data and the phase of alloy particles were verified by electron diffraction (SAD) patterns. Transmission Electron Microscopy (TEM) images showed the particle size of PtAuRu and PtSnRu in various specific percentage on NrGO. The approximate particle size for 10Pt2Au8Ru = 4.88±1.02 nm, 10Pt5Au5Ru = 58.45±42.16 nm, 10Pt8Au2Ru = 11.05±2.29 nm, 10Pt2Sn8Ru = 3.31±1.44 nm, 10Pt5Sn5Ru = 3.50±0.73 nm and 10Pt8Sn2Ru = 4.09±0.97 nm. Catalytic activity of these materials related to their particle size.

Experimental study on the effect of mechanochemistry on coal spontaneous combustion

Although the mechanical grinding process is often involved in coal mining and processing, the effect of this process on coal spontaneous combustion has been scarcely investigated in the literature. The changes of the content of oxygen-containing functional groups in coal caused by mechanochemical effect and their effects on coal spontaneous combustion were studied. The low-temperature oxidation experiment, grinding experiment, infrared spectrum experiment, and electron spin resonance (ESR) experiment were carried out. Firstly, the cross-point temperatures (CPTs), CO gas production, and the content of oxygen-containing functional groups of coal with different particle sizes were compared. Furthermore, changes in gas composition and functional groups during the grinding of coal samples under different gas conditions were also analyzed. Finally, the mechanism of mechanochemical reaction was revealed by studying the change of free radical concentration during the grinding process. The experiments have shown that coal will oxidize and generate large amounts of oxygen-containing functional groups under mechanical grinding. The effect of particle size on coal spontaneous combustion is not only caused by the change of surface area which was traditionally considered, but also the mechanochemical action during the crushing and grinding process. The research results can provide a new way for the prevention of coal spontaneous combustion.

Elucidating Singlet Oxygen Production in Li-Ion and Metal-Air Batteries

At high voltages, Li-ion and Li-air batteries undergo unwanted electrochemical reactions that can permanently decrease the performance of the battery. Recent experiments studying off-gassing from NMC cathodes have yielded different results for the trends of O2, CO2, and CO gas production with varying Ni composition. Studies also disagree on the origin of the elements in the gas. Very recently, it was suggested that not only is Li2CO3 on NMC cathodes responsible for the majority of CO2 production [1] but that singlet oxygen is produced when Li2CO3 is bias above 3.82 V [2]. This and other studies suggest singlet oxygen production as a common degradation pathway in Li-ion, Li-air [3,4], and Na-air [5]. With the use of first principles methods, we attempt to reconcile these experimental works and propose a universal mechanism of singlet oxygen production. We will also discuss a way to experimentally verify our mechanism by varying the electrolyte, which we claim will change the onset potential of singlet oxygen production in a predictable way. [1] 1. Renfrew, S. E. & McCloskey, B. D. Residual Lithium Carbonate Predominantly Accounts for First Cycle CO2and CO Outgassing of Li-Stoichiometric and Li-Rich Layered Transition-Metal Oxides. J. Am. Chem. Soc. (2017). doi:10.1021/jacs.7b08461 [2] 1. Mahne, N., Renfrew, S. E., McCloskey, B. D. & Freunberger, S. A. Electrochemical Oxidation of Lithium Carbonate Generates Singlet Oxygen. Angew. Chemie Int. Ed. (2018). doi:10.1002/anie.201802277 [3] 1. Mahne, N. et al. Singlet oxygen generation as a major cause for parasitic reactions during cycling of aprotic lithium-oxygen batteries. Nat. Energy (2017). doi:10.1038/nenergy.2017.36 [4] 1. Wandt, J., Jakes, P., Granwehr, J., Gasteiger, H. A. & Eichel, R.-A. Lithium–Air Batteries Singlet Oxygen Formationduring the Charging Process of an Aprotic Lithium–Oxygen Battery. [5] 1. Schafzahl, L. et al. Singlet Oxygen during Cycling of the Aprotic Na-O2 Battery. Angew. Chemie Int. Ed. (2017). doi:10.1002/anie.201709351

An increase in bed temperature on gasification of dual reactor fluidized bed

One of the main issues using biomass as fuel in air gasification is the dilution of its product gas by the nitrogen in the air. A dual reactor fluidized bed (DRFB) overcomes this problem in which the gasification and combustion reactions are decoupled and conducted in two separate fluidized bed reactors connected by circulating bed material. The DFRB unit made of 304 stainless steel pipe with a height of 100 and 150 cm, and inner diameters (i.d.) of 15.2 and 5.1 cm for gasifier and combustor respectively. The rice husk as fuel and quartz sand as bed material having the same size of 0.4 - 0.6 mm were applied in this investigation. Since the gasification process is an endothermic reaction, gasification temperatures are varied at 600°C to 700°C while combustion reactor were kept at 600°C using the electric heaters enclosed in ceramic cover. The superficial gas velocity in this study was kept constant at 17 m/s using the external air volumetric flux of the blower flow entering the DRFB loop. Gas gasification samples are then examined by gas chromatography to determine syngas content (CO, CH4 and H2). The test results showed that by the increasing temperature of the gasification reactor there was an increase in syngas especially CO gas conentration. The temperature increases in the gasification reactor (600°C, 650°C, 700°C) is able to increase the endothermic reaction in the gasification process which is dominated by CO gas production. The syngas efficiency was found to increase from 40.95% to 43.77%.as the temperature of the gasification reactor increased.

CO Gas Production by CO2 Gas Decomposition in Molten Salt Electrolysis

If CO2 gas can be efficiently decomposed, the produced carbon can be used as the raw material of the reducing agent of iron ore. Oxygen can be also used as the blowing gas into converters. In addition, CO gas can be used as an effective fuel in industrial plants. Thus, all the products arising from CO2 decomposition can become raw materials or energy resources. The decomposition of CO2 gas to carbon or CO gas by electrolysis is examined via the use of a combination of CaCl2-CaO melt as a media and ZrO2 solid-state electrolyte as anode. The schematic of the reactor used in this study is shown in Figure. CO2 gas is injected through the cathodic pipe, and it is reduced near the cathode by metallic Ca that is electrochemically deposited from CaO, leading to formation of carbon or CO gas. However, CO2 gas partially dissolves to form CO3 2- with coexistence of CaO in the melt. CO3 2- precipitates carbon on the cathode. A part of carbon reacts with the blown CO2 gas to form CO gas. These two mechanisms work for effective CO2 decomposition. The anode contained 8 mol% Y2O3 to ensure stability of the ZrO2 cubic crystal structure. By means of utilizing platinum paste as the conductor inside the ZrO2 tube instead of carbon powder, its tube can work as a good anode, and a large amount of CO gas is stably produced in the exhaust gas. At a higher electrolysis temperature, CO2 gas is preferentially converted to CO gas. At 1273 K, the conversion ratio approached the maximum value of 88.2%. The highest concentration of CO gas is generated by application of a cell voltage of 2.55 V, which is lower than the theoretical decomposition voltage of CaO, E 0 CaO (2.65 V at 1173 K). Therefore, CO2 gas decomposes preferentially via the decomposition reaction of carbonate ions.We believe that our approach can contribute in reducing atmospheric CO2. Figure 1

CO Gas Production by CO2 Gas Decomposition in Molten Salt Electrolysis

After complete decomposition of CO2 gas, carbon and oxygen can be used in the steel plant. In addition, CO gas may be used as an effective fuel with easy handling. The preferential decomposition to CO gas is examined by using a combination of CaCl2-CaO melt as a media and ZrO2-8mol% Y2O3 solid-state electrolyte as anode. At a higher electrolysis temperature, CO2 gas is preferentially converted to CO gas. The conversion ratio approached the maximum value of 88.2% at 1273 K. The highest CO concentration was generated at cell voltage of 2.55 V, which is slightly lower than the theoretical decomposition voltage of CaO. Therefore, CO2 decomposes preferentially via the decomposition reaction of carbonate ions. Namely CO2 gas dissolves to form CO3 2- with coexistence of CaO in the melt, CO3 2- precipitates carbon or CO gas bubbles on the cathode, and a part of carbon reacts with the blown CO2 gas to form CO gas.

Steam co-gasification of biomass and coal in decoupled reactors

Steam co-gasification of pine sawdust and bituminous coal was conducted in a lab-scale external circulating radial-flow moving bed (ECRMB) gasification system. The system is composed of three decoupled reactors, i.e., a gas–solid countercurrent moving bed pyrolyzer, a radial-flow moving bed gasifier and a riser-type combustor. Calcined olivine was used as circulating heat carrier and in-situ tar destruction catalyst as well. The influences of biomass blending ratio (BR), pyrolyzer temperature, gasifier temperature and steam to carbon mass ratio (S/C) on the gasification performance were investigated. The results indicated that the gas and tar yields increased with the increase of BR. Synergetic effect based on gas composition was found during co-gasification. At the S/C range of 0 to 1.3, the gas yield and H2 content in product gas increased but CO2 decreased with the increase of S/C. Higher gasifier temperature promoted the gas yield, H2+CO in product gas, carbon conversion and chemical efficiency of the process. A gas yield of 0.60Nm3/kg daf and a tar yield of 5.8g/Nm3 in the gas were obtained at the gasifier temperature of 850°C, BR of 50% and S/C of 1.3. Pyrolyzer temperature at the range of 500 to 700°C had no remarkable influence on the product gas composition.

CO Gas Production by Molten Salt Electrolysis from CO<sub>2</sub> Gas

CO Gas Production by Molten Salt Electrolysis from CO<sub>2</sub> Gas

Coupling Experiment of Compact Integrated Fuel Processors with 75kW PEM Fuel Cells

A compact autothermal reformer suitable for liquid fuel for instance methanol et al. was developed. The fuel reformer was combined with polymer electrolyte membrane fuel cells (PEM FC) and a system test of the process chain was successfully performed. The fuel processor consists of a fuel evaporating step, two-stage reformer and a two-stage reactor of water gas shift (WGS, one for high temperature water gas shift and the other for low temperature water gas shifter) and a four-stage preferential oxidation (PROX) reactor and some internal heat exchanger in order to achieve optimized heat integration. The fuel processor is designed to provide enough hydrogen for 75kWel fuel cells. After the initial step of methanol ATR, CO WGS and CO PROX steps are used for 'clean-up' CO. The exhaust gas from FC anode feedback to the fuel processor to vaporizes the feedstock of methanol and water by a catalytic combusting-evaporator. The hydrogen source system can produce hydrogen 70.5 m3/hr and its specific gravity power and specific volume power reach 255W/kg and 450W/L respectively. During three hours coupling experiment, the fuel processing system and the fuel cells all has been running smoothly. The volume concentration of H2 and CO in product gas (dry basis) was kept in 53% and 20ppm respectively, completely meeting the requirements of PEM fuel cells. The conversion efficiency of the hydrogen producing system based on LHV of fuel and hydrogen can exceed 95.85%. The fuel cells stacks put up strong resistance to CO and its maximum electronic load to the fuel cells reaches 75.5kW. It indicates that it is feasible technically for supplying hydrogen for Proton Exchange Membrane Fuel Cells by catalytic reforming of hydrogen-rich liquid fuel on-board or on-site.

Temperature and Gas Production Distributions on the Surface of a Spherical Model Comet Nucleus in the Orbit of 46P/Wirtanen

A multidimensional comet nucleus model is used to estimate the temperature and gas production distributions on the surface of a comet nucleus in the orbit of 46P/Wirtanen. The spherical model nucleus is assumed to be made up of a porous dust-ice (H2O, CO) matrix. Heat and gas diffusion inside the rotating nucleus are taken into account in radial and meridional directions. A quasi-3D solution is obtained through the dependency of the boundary conditions on the local solar illumination as the nucleus rotates. As a study case, we consider a homogeneous chemical composition of the surface layer which is assumed to contain water ice. The model results include the distributions of temperature and gas production on the surface. For the chosen test case of a nucleus spin axis perpendicular to the orbital plane we found that the CO gas production on the surface is quasi-uniformly distributed in contrast to the nonuniform water outgassing. The mixing ratio at a specific point on the comet nucleus surface is not representative of the overall mixing ratio which is observed in the coma.

15O]H 2O, [ 15O]O 2 and [ 15O]CO gas production, monitoring and quality control system

The 15O gas production system selects the gas production mode, monitors gas delivery conditions and performs quality control needed during the production and delivery of continuous flow radioactive gas for equilibrium and bolus PET studies. Target gas switches choose the appropriate valve positioning for [ 15O]H 2O, [ 15O]O 2 or [ 15O]CO production while flow rate, pressure and radioactivity are constantly monitored. The system also includes an IBM PC interfaced gas chromatograph which provides chemical and radiochemical quality control by on-line, real time, gas sampling of the delivery line.

The influence of CO ice on the activity and near-surface differentiation of comet nuclei

The role of unclathrated CO ice in the activity and near-surface differentiation of comet nuclei is investigated. A computer program used in the authors' previous work (Fanale and Salvail 1987, Icarus 72, 535–554) has been adapted to model a comet nucleus composed of a homogeneous mixture of H 2O ice, CO ice, and dust in a Halley-type orbit. The difference in the volatility of CO and H 2O ices results in greatly different gas production rates, and recession of the CO ice surface occurs, forming a porous surface layer of H 2O ice and dust. Temperatures of H 2O and CO ice surfaces, fluxes of CO and H 2O gases and, depths of the CO ice are presented as functions of orbital position. Also considered are the pressures of subsurface CO as they relate to the stability of the overlying H 2O ice and dust mantle and the possibility of dust or H 2O ice grain emission. Possible pressures are in the range 3 × 10 2 dyn cm −2 to 1 × 10 6 dyn cm −2. These are insufficient to fragment annealed H 2O ice, yet capable of overcoming the lithostatic pressures of many meters of unannealed H 2O ice and emitting free surface grains in the 1-μm range. However, they are comparable to the inferred range of ice-poor mantle strength and may account for episodic regional changes in activity. It has been found that CO ice should always exist within 3 m from the surface and that CO gas production exceeds H 2O gas production beyond 2.5 AU. This has implications for planned in situ elemental analysis of nuclei. CO gas production from “new” comets can be as much as 3 orders of magnitude greater before perihelion. After perihelion there is little difference in CO production for “new” and periodic comets. The results have been found not to depend significantly on the permeability of the water ice mantle or the estimated variability of the mass fraction of CO.