Gaseous By-products Research Articles

An efficient approach for the treatment of radioactive waste perfluoropolyether lubricants via a synergistic effect of thermal catalysis and immobilization

Perfluoropolyether (PFPE) lubricants are a kind of high-molecular polymer with many excellent properties. However, the use of PFPEs in the nuclear industry can lead to partial decomposition and carrying radionuclides, resulting in a large amount of radioactive waste PFPE lubricants annually. Moreover, radioactive waste PFPE lubricants are difficult to be effectively treated due to their high stability, the risk of possible leakage of radionuclides, and hypertoxic fluorine-containing by-products. In this study, without any precedent, a strategy of MnO2-catalyzed decomposition and Na2CO3-immobilized conversion was proposed for PFPE lubricant decomposition and fluorine immobilization simultaneously based on the Lewis acid-base and oxygen vacancies concept. A high fluorine conversion efficiency of 95.4% was achieved. Meanwhile, the mechanism of decomposition suggested that MnO2 mainly provided Lewis acid sites and attacked the (basic) fluorine or oxygen atoms in PFPE molecules. The decomposition of PFPE chains was proceed down and volatile fluorine-containing gas was released by partial electron transfer, intramolecular disproportionation reaction, and unzipping fashion. Subsequently, gas by-products could be further oxidized and then immobilized into fluoride salts by carbonate solid absorbents. Overall, this study provides a simple, safe, and potentially practical strategy for the harmless conversion of refractory fluorinated organic wastes, especially perfluoropolymers.

Greenhouse gas reduction and economic cost of technologies using green hydrogen in the steel industry

Reducing greenhouse gas (GHG) emissions from the steel industry is one of the top priorities for mitigating climate change. Although hydrogen has been considered as a key element to accomplish this task, the effects of various hydrogen-using technologies in steel mills have not been analysed and compared to each other. This paper quantitatively analysed the greenhouse gas reduction in steel mills by the use of hydrogen produced from electrolysis with renewable electricity. The four following methods of using green hydrogen were proposed and analysed: 1) use of hydrogen directly in the hydrogen steelmaking process, 2) use of hydrogen to convert byproduct gases produced from steel mills into methanol, 3) use hydrogen to convert the byproduct gases into methane, and 4) sell hydrogen to the hydrogen station and use of oxygen, another product of electrolysis, to reduce the use of air separating unit in steel mills. Not only the greenhouse gas reduction benefits but also the economic cost of these four methods were evaluated. As those results can vary according to country, the economic cost and GHG reduction benefits were determined for the representative steel-producing countries of China, India, Japan, the United States, Russia, South Korea, and Germany. The economic cost was evaluated not only for the present (2020) but also for the future (∼2040) because these methods are more likely to be implemented in the future. Currently, in the representative steel-producing countries, Method 1 was analysed to have the largest GHG reduction among the four methods; but it also showed the largest cost because of its large capital expenditures and electricity cost. Method 2, which converts the byproduct gases into methanol, was shown to offer larger GHG reduction and smaller economic cost than Method 3, which converts the byproduct gases into methane. Comparing Methods 1 and 2, Method 2 offered smaller GHG reduction but a much smaller economic cost than Method 1. Although the cost of Method 4 is currently the smallest, the economic cost of Method 2 is predicted to become lower than that of Method 4 in the future, near 2030, because the future prices of hydrogen and the CO2 allowance are expected to decrease and increase, respectively. These results can be utilized when steelmaking country or steelmaking company make their decision on how to decrease the GHG emissions by using green hydrogen.

Generalizable Synthesis of Highly Fluorinated Ionic Liquids.

The unique chemistry of fluorocarbons (in particular, their weak intermolecular interactions and high degree of intrinsic free volume) makes them promising building blocks for ionic liquids with high gas capacities. Here, we report a generalizable method for the synthesis of fluorinated ionic liquids, which relies on the evolution of gaseous byproducts to drive product formation. This synthetic strategy overcomes solubility challenges that can hinder the synthesis of highly fluorinated ionic liquids via conventional methods and enables a systematic investigation of the effect of fluorination on ionic liquid viscosity and gas solubility.

Life cycle assessment of olive pomace gasification for an up-draft fixed bed gasifier system

Biomass gasification has been considered as an important renewable energy alternative to deal with the environmental problems originating from fossil fuels and climate change effects. Olive pomace as a by-product of the olive oil production process is a significant biomass source. Although gasification technology is accepted as an environmentally friendly power system, the studies to determine its environmental impact via Life Cycle Assessment (LCA) are very limited. LCA is a key tool to evaluate all environmental impacts from the beginning to the end of the process. The aim of this study is to assess the overall environmental impacts of the olive pomace gasification for electricity generation and evaluation of its solid by-products namely biochar and tar. Four scenarios were compared to estimate the environmental impacts of gasification by-products with a LCA approach, following to the cradle-to-grave approach. The production of olive, olive pomace generation during its processing for olive oil production, gasification of olive pomace, construction of the gasifier, gas cleaning system and syngas composition have been included in the evaluations. It is clear from the analysis results that the scenarios have very low impact values in the case of beneficial usage of biochar in different industries. In terms of ozone layer depletion potential (2.74 × 10 −6 kg CFC11 eq) and global warming potential (36.99 GWP100a), the paramount scenario from an environmental viewpoint is the scenario having the biochar and tar usage as a resource in another industry.

The catalytic efficiency of Ru/Mn/Ce-Al2O3 in the reduction of HCN in dry methane reforming with CO2 assisted by non-thermal plasma

This study investigates the catalytic activity of Ru/Mn/Ce-Al2O3 in eliminating HCN via dry reforming CH4 with CO2 in the packed-bed dielectric barrier discharge non-thermal plasma (DBD NTP). A packed bed DBD configuration method was carried out in the non-thermal plasma with Ru/Mn/Ce-Al2O3 catalyst, whereby BaTiO3 beads was the dielectric medium. The carrier gas for dry methane reforming was N2, the peak-to-peak voltage was 24 kV and the total flow rate was 100 sccm with a ratio of 5:5:90 (CH4:CO2:N2), respectively. Gaseous products and by-products were analysed by Fourier transform infra-red (FTIR) spectroscopy. Experimental results revealed that Ru/Mn/Ce-Al2O3 catalyst could eliminate HCN at approximately 82% and had a low selectivity in decomposing NH3. Besides, the conversion of CH4 achieved was approximately 68%.

Using fluoroform in trifluoromethylation reactions

Fluoroform (CF3H), a large-volume industrial by-product and potent greenhouse gas, has emerged as an attractive CF3 source for the development of trifluoromethylation reagents and reactions. This article highlights the recent reports since 2017 on the use of fluoroform in organic synthesis. Topics include direct trifluoromethylation facilitated by organic and inorganic bases, preparation of trifluoromethylation reagents based on transition metals and borazine, and radiolabelled fluoroform.

Enhancing the dechlorination of CuCl residue using a microwave sulfation-roasting method: Process optimization and mechanism investigation

Spent CuCl residue produced from zinc hydrometallurgy is a typical toxic and hazardous solid waste as well as a secondary resource owing to its high contents of chlorine and valuable metals (Pb, Cu, Zn). The removal of chlorine from the CuCl residue and recycling of valuable metals are critical issues for the copper slag resource treatment process. In this study, a novel method of microwave sulfation-roasting under an oxygen atmosphere is used to improve the dechlorination process, and various parameters, such as roasting temperature, duration, sulfuric acid concentration, and liquid/solid ratio, are optimized. First, according to thermodynamic calculations, the addition of H2SO4 can significantly decrease both the roasting temperature and time needed for microwave oxidation-roasting. The dechlorination experimental results reveal that the dechlorination rate of the CuCl residue is as high as 91.91% under a temperature of 250 °C, holding time of 120 min, sulfuric acid concentration of 70%, and liquid-solid ratio of 1.42. The microstructure, chemical composition, and phase changes of the CuCl residue before and after roasting are characterized using scanning electron microscopy coupled with energy-dispersive spectroscopy, X-ray fluorescence and X-ray diffraction; further, the mass contents of the main elements in the roasting product and tail gas absorption solution are determined by chemical analysis, Evidently, the selective heating property of microwaves produces more holes and cracks in the copper slag, which can provide a new reaction channel for H2SO4 and CuCl slag reactions, and almost all CuCl in the copper slag is completely removed by transformation into CuO, CuSO4 and Cu2O(SO4). Simultaneously, a large number of gas by-products produced in the dechlorination process, such as SO2 and Cl2, can be absorbed by the NaOH solution. Therefore, no pollution is generated in the environment. These findings illustrate that microwave sulfation-roasting is an effective method for promoting the treatment and recycling of CuCl waste residues.

Mechanism of Reductive Fluorination by PTFE-Decomposition Fluorocarbon Gases for WO3

Reductive fluorination, which entails the substitution of O2- from oxide compounds with F- from fluoropolymers, is considered a practical approach for preparing transition-metal oxyfluorides. However, the current understanding of the fundamental reaction paths remains limited due to the analytical complexities posed by high-temperature reactions in glassware. Therefore, to expand this knowledgebase, this study investigates the reaction mechanisms behind the reductive fluorination of WO3 using polytetrafluoroethylene (PTFE) in an Ni reactor. Here, we explore varied reaction conditions (temperature, duration, and F/W ratio) to suppress the formation of carbon byproducts, minimize the dissipation of fluorine-containing tungsten (VI) compounds, and achieve a high fluorine content. The gas-solid reaction paths are analyzed using infrared spectroscopy, which revealed tetrafluoroethylene (C2F4), hexafluoropropene (C3F6), and iso-octafluoroisobutene (i-C4F8) to be the reactive components in the PTFE-decomposition gas during the reactions with WO3 at 500 °C. CO2 and CO are further identified as gaseous byproducts of the reaction evincing that the reaction is prompted by difluorocarbene (:CF2) formed after the cleavage of C═C bonds in i-C4F8, C3F6, and C2F4 upon contact with the WO3 surface. The solid-solid reaction path is established through a reaction between WO3 and WO3-xFx where solid-state diffusion of O2- and F- is discerned at 500 °C.

Nanosizing Approach-A Case Study on the Thermal Decomposition of Hydrazine Borane.

Hydrazine borane (HB) is a chemical hydrogen storage material with high gravimetric hydrogen density of 15.4 wt%, containing both protic and hydridic hydrogen. However, its limitation is the formation of unfavorable gaseous by-products, such as hydrazine (N2H4) and ammonia (NH3), which are poisons to fuel cell catalyst, upon pyrolysis. Previous studies proved that confinement of ammonia borane (AB) greatly improved the dehydrogenation kinetics and thermodynamics. They function by reducing the particle size of AB and establishing bonds between silica functional groups and AB molecules. In current study, we employed the same strategy using MCM-41 and silica aerogel to investigate the effect of nanosizing towards the hydrogen storage properties of HB. Different loading of HB to the porous supports were investigated and optimized. The optimized loading of HB in MCM-41 and silica aerogel was 1:1 and 0.25:1, respectively. Both confined samples demonstrated great suppression of melting induced sample foaming. However, by-products formation was enhanced over dehydrogenation in an open system decomposition owing to the presence of extensive Si-O···BH3(HB) coordination that further promote the B-N bond cleavage to release N2H4. The Si-OH···N(N2H4) hydrogen bonding may further promote N-N bond cleavage in the resulting N2H4, facilitating the formation of NH3. As temperature increases, the remaining N-N-B oligomeric chains in the porous silica, which are lacking the long-range structure may further undergo intramolecular B-N or N-N cleavage to release substantial amount of N2H4 or NH3. Besides open system decomposition, we also reported a closed system decomposition where complete utilization of the N-H from the released N2H4 and NH3 in the secondary reaction can be achieved, releasing mainly hydrogen upon being heated up to high temperatures. Nanosizing of HB particles via PMMA encapsulation was also attempted. Despite the ester functional group that may favor multiple coordination with HB molecules, these interactions did not impart significant change towards the decomposition of HB selectively towards dehydrogenation.

Decarbonisation Pathways for the Finishing Line in a Steel Plant and Their Implications for Heat Recovery Measures

Steel production is one of the biggest emitters of greenhouse gas in the industrial sector with about 8% of total global CO2 emissions. Although the majority of emissions can be attributed to primary steel production, there is also potential for reducing CO2 emissions in downstream steel processing. Large industrial furnaces, which are necessary for heating steel, are currently primarily fired with natural gas and by-product gases from primary steel production, offering great potential for heat recovery measures from exhaust gases. However, switching to alternative climate-neutral fuels could change this potential and thus jeopardize the economic viability of heat recovery measures. In the present work, it was therefore examined to what extent a change in energy sources in industrial furnaces affects the potential use of heat recovery in steel processing. For this purpose, an optimization model was used that takes into account heat recovery by means of direct heat transfer, heat pumps and heat distribution systems. Potential future changes in energy supply for industrial furnaces were examined using different storylines. Two different energy price scenarios were also considered to address uncertain developments in energy markets. The results show that heat recovery is a cost-effective and definitely recommendable measure. Switching to alternative fuels has little impact on the use of heat recovery. Electrification and thus the elimination of flue gas, on the other hand, greatly reduces the potential for heat recovery.

CO2 hydrogenation for geothermal energy storage through synthetic natural gas production and byproduct of refrigeration and freshwater using solid oxide electrolyzer cell (SOEC) and methanation reactor; Techno-economic evaluation and multi-objective optimization

A multi-generation geothermal-based energy system is proposed to convert geothermal renewable power into fuel gas and other valuable products such as electricity, cooling, and freshwater. The system is analyzed and optimized from a thermo-economic perspective. This system is constituted of a flash-binary geothermal power plant integrated into an Organic Rankine Cycle, a double-effect Li/Br absorption refrigeration cycle, a multi-stage flash desalination plant (MSF), and a solid oxide electrolyzer cell (SOEC) combined with a Sabatier methanation reactor. The steam leaving the steam turbine are utilized by the SOEC to generate hydrogen, which is used in the Sabatier reactor to hydrogenate CO2 to produce methane. Cooling and Freshwater are respectively produced by the refrigeration cycle and MSF plant that are driven by the steam extracted from the intermediate stages of the steam turbine. The system can produce 22.9 g/s gas fuel with a lower heating value (LHV) of 28453 kJ/kg, of which 53% is methane, 554.4 kW net power, 3715 kW cooling, and 41.35 kg/s freshwater. The SOEC produces hydrogen with a rate of 6.52 g/s; the power demanded to generate this amount of hydrogen is 884.47 kW. The system’s payback period is 7.3 years (regarding the tax). According to the optimization results, compared to baseline design conditions, the payback period and LHV of the generated fuel respectively decline by 18.7% and 35%, and the net output power enhances by 88% at optimum mode when power and payback period are objective functions.

Hydrogen production from coke oven gas using pressure swing adsorption process − a mathematical modelling approach

Coal is playing a major role as a reductant and as an energy source in the present world steel production due to its low cost and widespread distribution around the world. At the same time, being the largest contributor to global CO2 emissions, coal faces significant environmental challenges in terms of air pollution and global warming. Hydrogen is a promising alternative for coal in lowering the steel industry’s CO2 footprint, but the availability of green hydrogen is currently limited by its high production cost. This research study focuses on developing a pressure swing adsorption (PSA) technology that will allow for continued use of coal for a smooth transition towards green hydrogen-based steel production, by better utilisation of its by-product coke oven gas to produce high purity hydrogen. A generic, fast and robust simulation tool for simulating a variety of PSA processes considering both equilibrium and kinetic effects using a detailed non-isothermal and non-isobaric model is developed in the study. The adsorption equilibrium data required for the model are calculated from experimental results using the non-linear regression data fitting method. A series of rigorous parametric studies and breakthrough tests are performed using the developed mathematical model for better understanding of the effects of different factors on the PSA process performance. With the better understanding obtained from the above-mentioned parametric studies, the model is optimised by performing several simulation tests to achieve a high process performance in terms of purity and recovery of the H2 product, productivity of the adsorbents and energy consumption for compression of gases. The optimised 14-step multi-bed PSA cycle developed in this study allows for an improved energy efficiency of coal usage by better utilisation of its by-product coke oven gas by converting it into valuable high purity (>99.999%) hydrogen product with a recovery of over 75%.

A Dynamic Scheduling Framework for Byproduct Gas System Combining Expert Knowledge and Production Plan

Effective scheduling for byproduct gas systems of steel industry is becoming increasingly vital for maintaining their safe operating and improving energy utilization. Considering that the existing studies failed to capture the dynamic changes in the production environment, a novel dynamic scheduling framework is proposed that seamingly integrates expert knowledge with a dynamic programming process. Given the phase characteristics of the steelmaking processes, data series are first partitioned into information granules based on the production plan to form the knowledge-based initial policies. To achieve dynamic scheduling process, a two-stage value function approximation method is proposed, where in the first stage one learns an event-driven Q-function by the fuzzy rule-based states, and then an action fitting strategy is developed for evaluating continuous actions. Considering the difficulties of establishing a mechanism-based model, the state transition process is described by a granular prediction model to simulate taking actions. On their basis, a dynamic compensation for the initial policies is finally achieved. A number of comparative experiments are conducted by utilizing the practical data coming from a steel plant. The results show that the proposed method can deliver effective solutions for long-term scheduling scenarios. Note to Practitioners—Given that the steelmaking process is a discontinuous one and the byproduct gas system can hardly be described by a physical or mechanism-based model, its energy scheduling works is usually performed by manual approach or using static optimization methods, which would lead to low accuracy and a waste of energy. Since a large number of real-time data had been accumulated by the SCADA system implemented in most steel plants, a data-driven dynamic scheduling approach is proposed in this study. The proposed method takes advantages of the expert knowledge and production plan data, and produces dynamic scheduling solutions by utilizing an actor-critic learning process. The application system on the basis of the proposed method can adapt to different scenarios and ensure long-term safety operations of the gas tanks. Furthermore, since there may be missing data or outliners in the acquired data collected by the SCADA onsite, it is necessary to perform data imputation and filtering methods to guarantee the data integrity and reliability. This study avoids the redundant introduction of such preliminary preprocessing methods for the sample data.

Synergistic and Antagonistic Effects of the Co-Pyrolysis of Plastics and Corn Stover to Produce Char and Activated Carbon.

The physicochemical properties of char and activated carbon produced from the co-pyrolysis of corn stover (CS) and plastics, polystyrene (PS) and polyethylene terephthalate (PET), were studied. Non-isothermal gas analysis of the volatiles was conducted using an online mass spectrometer to correlate the thermal degradation of gaseous byproducts to the formation of pores in the char materials. The findings determined that the addition of PS or PET promotes the formation of the solid char product with either higher than average pore sizes or surface areas compared to control samples. The addition of PET to corn stover increases the surface area of the char formed. The char formed from a CS:PET mass ratio of 1:1 produced char with a surface area of 423.8 ± 24.8 m2/g at 500 °C and a duration of 2 h. The surface area of the chars formed from CS and PET decreased as the amount of PET decreased, showing a tendency for PET to increase the surface area of the char materials synergistically. The addition of PS to corn stover promoted the formation of chars with, on average, larger pore sizes than the control char samples. The chars were chemically activated with potassium hydroxide, and the activated carbon that formed had lower surface areas but comparable surface functional groups to the control samples. Vanillin adsorption testing showed that activated carbon from corn stover performed the best at removing 95% of the vanillin after 2 h. In contrast, the activated carbon from the chars produced from the co-pyrolysis of corn stover and polystyrene or corn stover and polyethylene terephthalate removed 45% and 46% of vanillin after 2 h, respectively. The findings suggest that plastics have a synergistic relationship in producing char precursors with improved porosity but antagonistically affect the activated carbon adsorbent properties.

Prediction of gas consumption based on LSTM-BPNN hybrid model

ABSTRACT The economic benefits of iron and steel enterprises require the support of Byproduct gas prediction. A novel hybrid model for data pre-processing is proposed to ensure the stability and accuracy of gas prediction. First, each component obtained from Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (CEEMDAN) decomposition is processed using Sample Entropy (SE), and the members are denoised and restructured by singular spectrum analysis (SSA). Then, the restructured data are predicted by the Back Propagation Neural Network (BPNN) and Long Short-Term Memory (LSTM) and weighted by Particle Swarm Optimization (PSO). Finally, the data are integrated to obtain the final results. The novel hybrid model makes allowances for the linear and nonlinear characteristics of the series and successfully overcomes the limitations of individual models to get accurate and stable prediction results. The results show that the prediction accuracy is improved by 20% on average by adopting the novel hybrid model.

Event-Triggered Adaptive Parameter Control for the Combined Cooling, Heating, and Power System

An industrial integrated energy system gathers a variety of production capacity and energy-related units, which also involves the production, transformation, and consumption of cold, heat, power, gas, etc. The combined cooling, heating, and power (CCHP) system built upon the cascade utilization of energy plays a significant role in improving the utilization rate of multiple energy resources. In this article, a controlled hierarchical relevance vector machine is modeled for identifying the scheduling event in the by-product gas system of a steel industry, which can effectively overcome the disturbance triggered by the changing of operational modes (OMs). Considering the multiple time scales (MTSs) property and the changing of seasons and load conditions of the CCHP, a unified modeling approach is proposed to describe MTSs and multiple OMs of the CCHP by using fuzzy singular perturbation here. Furthermore, an extended <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$Q$</tex-math></inline-formula> -learning approach by incorporating a hierarchical interval type-2 fuzzy system is designed for dynamically choosing the optimal controller’s parameter for the proposed unified model along with the changing of OMs. The performance of the proposed method can be experimentally validated by a series of industrial application cases to highlight the necessity of modeling and self-adaptive parameter of the controller.

Study on preparation of aromatic-rich oil by thermal dechlorination and fast pyrolysis of PVC

Thermal dechlorination and fast pyrolysis experiments of PVC were carried out. Characterizations such as TG, FTIR and 13C NMR were applied to analyze the thermal degradation characteristics and chemical structure evolution characteristics of de-HCl PVC during the dechlorination process. The thermal dechlorination results show that the degree of dechlorination and aromatization of de-HCl PVC is deepened with the increasing dechlorination temperature. The dechlorination efficiency is as high as 99.86% at 320 ℃. Meanwhile, the de-HCl PVC with a chlorine content of 0.22% and the optimal H/Ceff value for aromatics production can be obtained. The de-HCl PVC gradually evolves from a long chain structure with C-C bonds as the skeleton to a long olefin chain structure with partial aromatization during the dechlorination process. The fast pyrolysis results show that the oil generated by the de-HCl PVC (320 °C) pyrolysis has a high aromatic content of 97.32%−99.93%. In addition, there are no chlorine-containing compounds in the oil from de-HCl PVC (320 °C) pyrolysis, while the PVC pyrolysis oil contains chlorinated aromatics with high content of 1.91%−4.02%. During the fast pyrolysis process, the monocyclic aromatic hydrocarbons (MAHs) are mainly formed from the cyclization of polyene fragments released by random fragmentation of de-HCl PVC (320 ℃). Further, the polycondensation reaction is promoted to realize the conversion of MAHs to polycyclic aromatic hydrocarbons (PAHs) under the action of high temperature. The by-products of pyrolysis gas with high HHV and carbon-rich char both can be further utilized. Overall, thermal dechlorination and fast pyrolysis can realize harmless treatment and high-value utilization of PVC.

A facile crush-and-sieve treatment for recycling end-of-life photovoltaics

The shift towards renewable energy mix has resulted in an exponential growth of the photovoltaic (PV) industry over the past few decades. Parallelly, new recycling technology developments are required to address the incoming volume of waste as they gradually approach their end-of-life (EoL) to realize the concept of a circular economy. Typical recycling processes involve high-temperature burning for separation and release of the PV cells for metal recovery processes. However, this thermal process generates gaseous by-products that cause serious health and environmental issues. Eschewing the need for burning, we demonstrate a simple crush-and-sieve methodology to strategically aids the separation of polymeric and metallic contents. The proposed approach showcased the efficient size-selective separation and generated polymer- and metal-rich fractions. More than 90 % of the total polymer present within the studied wastes was found to be retained in larger sized-particle fractions (F1 and F2). Metal content analysis highlighted the enrichment of highly valuable silver into the smallest sized-particle fraction (F4), accounting up to 70 % and 80 % of total silver present respectively for EVAc and MP. The benefits ripe through this simple crush-and-sieve method offers an attractive pathway for PV recycling process to obtain metal-rich fractions and allow focused recovery of valuable materials through an environmentally friendlier manner.

Effects of SCR catalyst breakage on mercury emission properties in coal-fired power plant: field testing and laboratory evaluation

Field testing toward mercury emission properties was conducted at a 300 MW coal-fired power station. Selective catalytic reduction (SCR) was found to reduce Hg content in flue gas significantly through catalyst breakage during the commercial testing in a 300 MW coal-fired power station. Field testing results indicate that the total mercury concentration in flue gas at electrostatic precipitator (ESP) inlet and ESP outlet increase due to SCR catalyst breakage. Correspondingly, mercury content in fly ash decrease and mercury content in gypsum increase. The evolution in laboratory confirmed the Hg0 oxidation capability of commercial SCR catalyst. Catalyst breakage leads to space velocity increasing, so that the lower Hg0 oxidation rates caused the mercury transformation change in flue gas and solid byproducts.

Hydrogen Availability Is Dependent on the Actions of Both Hydrogen-Producing and Hydrogen-Consuming Microbes.

Hydrogen gas (H2) is produced by H2-producing microbes in the gut during polysaccharide fermentation. Gut microbiome also includes H2-consuming microbes utilizing H2 for metabolism: methanogens producing methane, CH4, and sulfate-reducing bacteria producing hydrogen sulfide, H2S. H2S is not measured in the evaluation of gaseous byproducts of microbial fermentation. We hypothesize that the availability of measured H2 depends on both hydrogen producers and hydrogen consumers by measuring H2 invitro and invivo. In the invitro study, groups were Bacteroidesthetaiotaomicron (B.theta, H2 producers), Desulfovibriovulgaris (D.vulgaris, H2 consumers), and D.vulgaris + B.theta combined. Gas samples were collected at 2h and 24h after incubation and assayed for H2, CH4, and H2S. In the invivo study Sprague-Dawley rats were gavaged with suspended bacteria in four groups: B.theta, D.vulgaris, combined, and control. Gas was analyzed for H2 at 60min. In the invitro experiment, H2 concentration was higher in the combined group (188 ± 93.3ppm) compared with D.vulgaris (27.17 ± 9.6ppm) and B.theta groups (34.2 ± 29.8ppm; P < 0.05); H2S concentration was statistically higher in the combined group (10.32 ± 1.5ppm) compared with B.theta (0.19 ± 0.03ppm) and D.vulgaris group (3.46 ± 0.28ppm; P < 0.05). In the invivo study, H2 concentrations were significantly higher in the B.theta group (44.3 ± 6.0ppm) compared with control (31.8 ± 4.3) and the combined group (34.2 ± 8.7, P < 0.05). This study shows that sulfate-reducing bacteria could convert available H2 to H2S, leading to measured hydrogen levels that are dependent on the actions of both H2 producers and H2 consumers.