Nanostructured MnO_2 synthesized via methane gas reduction of manganese ore and hydrothermal precipitation methods

A three-stage methane gas （CH4） reduction of manganese ore, dissolution, and precipitation from solution procedure was conducted to synthesize MnO2 nanorods. Methane gas reduction was carried out at 850, 875, 900, 925, and 950℃ for 120 min. Precipitation of the a-MnO2 nanorods was performed in the temperature range of 25-90℃with a constant reaction time of 90 min. The morphology and particle size of the products were determined from scanning electron microscope （SEM） images and X-ray diffraction （XRD） patterns. The BET and BJH of the products were found out by the surface area analyzer. Reduction results indicated that MnO-rich phase is significantly formed at 950℃ as MnO2 phase disappears. Precipitation results also showed an average diameter size of - 50 nm for the embedding a-MnO2 nanorods with BET surface area of 174 m^2/g.

Implementation of a greenhouse gas reduction roadmap for steel producing companies

This paper shall show an economic feasible approach to implement greenhouse gas(GHG) reduction measures into steel companies. The goal to improve energy consumption is directly linked to the reduction of GHG emissions and therefore directly in correlation with the economic viability. A baseline scenario of the considered reference system and of the respective reference year has to be defined, mapped and analysed. In a second step an analysis of the same operation using available and prospected best available technology (BAT) processes is carried out to generate a basis for a benchmark system. The identified reduction potentials are reported and the GHG emission reductions are put into relation to the investment cost of the new process technologies/process adaption to be implemented.This economic feasibility calculation is necessary to realise a cost efficient GHG reduction roadmap implementation into the company's business operations. The GHG reduction roadmap is developed using the abatement curve concept to get an indication of ' low hanging fruits' and for establishing a sequence for implementing carbon emission reductions measures. The scope of that approach can be extended by including further important environmental parameters like NOx, SO_2,CO,dust,heavy metal emissions in air as well as production residues.That gives in the end a broader picture and more starting points to improve the overall environmental performance of steel producing companies beyond the GHG emissions and energy consumption.

CFD simulation of effect of anode configuration on gas–liquid flow and alumina transport process in an aluminum reduction cell

Numerical simulations of gas–liquid two-phase flow and alumina transport process in an aluminum reduction cell were conducted to investigate the effects of anode configurations on the bath flow, gas volume fraction and alumina content distributions. An Euler–Euler two-fluid model was employed coupled with a species transport equation for alumina content. Three different anode configurations such as anode without a slot, anode with a longitudinal slot and anode with a transversal slot were studied in the simulation. The simulation results clearly show that the slots can reduce the bath velocity and promote the releasing of the anode gas, but can not contribute to the uniformity of the alumina content. Comparisons of the effects between the longitudinal and transversal slots indicate that the longitudinal slot is better in terms of gas–liquid flow but is disadvantageous for alumina mixing and transport process due to a decrease of anode gas under the anode bottom surface. It is demonstrated from the simulations that the mixing and transfer characteristics of alumina are controlled to great extent by the anode gas forces while the electromagnetic forces(EMFs) play the second role.

Thermodynamic behaviors of SiCl_2 in silicon deposition by gas phase zinc reduction of silicon tetrachloride

The modified Siemens process,which is the major process of producing polycrystalline silicon through current technologies,is a high temperature,slow,semi-batch process and the product is expensive primarily due to the large energy consumption.Therefore,the zinc reduction process,which can produce solar-grade silicon in a cost effective manner,should be redeveloped for these conditions.The SiCl2 generation ratio,which stands for the degree of the side reactions,can be decomposed to SiCl4 and ZnCl2 in gas phase zinc atmosphere in the exit where the temperature is very low.Therefore,the lower SiCl2 generation ratio is profitable with lower power consumption.Based on the thermodynamic data for the related pure substances,the relations of the SiCl2 generation ratio and pressure,temperature and the feed molar ratio（n（Zn）/n（SiCl4） are investigated and the graphs thereof are plotted.And the diagrams of Kpθ-T at standard atmosphere pressure have been plotted to account for the influence of temperature on the SiCl2 generation ratio.Furthermore,the diagram of Kpθ-T at different pressures have also been plotted to give an interpretation of the influence of pressure on the SiCl2 generation ratio.The results show that SiCl2 generation ratio increases with increasing temperature,and the higher pressure and excess gas phase zinc can restrict SiCl2 generation ratio.Finally,suitable operational conditions in the practical process of polycrystalline silicon manufacture by gas phase zinc reduction of SiCl4 have been established with 1200 K,0.2 MPa and the feed molar ratio（n（Zn） /n（SiCl4）） of 4 at the entrance.Under these conditions,SiCl2 generation ratio is very low,which indicates that the side reactions can be restricted and the energy consumption is reasonable.

Mitigation of greenhouse gases released from mining activities:A review

Climate changes that occur as a result of global warming caused by increasing amounts of greenhouse gases(GHGs)released into the atmosphere are an alarming issue.Controlling greenhouse gas emissions is critically important for the current and future status of mining activities.The mining industry is one of the significant contributors of greenhouse gases.In essence,anthropogenic greenhouse gases are emitted directly during the actual mining and indirectly released by the energy-intensive activities associated with mining equipment,ore transport,and the processing industry.Therefore,we reviewed both direct and indirect GHG emissions to analyze how mining contributes to climate change.In addition,we showed how climate change impacts mineral production.This assessment was performed using a GHG inventory model for the gases released from mines undergoing different product life cycles.We also elucidate the key issues and various research outcomes to demonstrate how the mining industry and policymakers can mitigate GHG emission from the mining sector.The review concludes with an overview of GHG release reduction and mitigation strategies.

Effective goaf gas capture design at Ravensworth Underground Mine

This paper highlights a reliable goaf gas capture system developed and used at Ravensworth Under-ground Mine since its trial in 2009. The method utilises horizontal holes drilled from underground sites and connected to an underground gas pipeline. This system incorporates a gas suction and flaring plant designed specifically for this method. The current method has captured effectively a total longwall, and adjacent goaf gas accounts for over 85%. The design of the holes drilled has been the success of the gas flow reliability. The flow is extraordinarily consistent and predictable. The management of the under-ground pipeline determines the overall reliability of flow. The design has resulted in Ravensworth Man-agement being confident to remove a gas bearing bleeder roadway and still manage the existing tailgate roadway for allowing access as required. The reduction of CO2 equivalent emissions recorded is approx-imately 0.35 ？ 106 tons annually. This design has further improvements to be added to allow use at any other site with gas in the overlying strata.

Carbon nanotubes loaded with vanadium oxide for reduction NO with NH_3 at low temperature

The catalytic activity of carbon nanotubes-supported vanadium oxide(V_2O_5/CNTs) catalysts in the selective catalytic reduction(SCR) of NO with NH_3 at low temperatures(<250℃) was investigated.The effects of V_2O_5loading,reaction temperature,and presence of SO_2 on the SCR activity were evaluated.The results show that V_2O_5/CNTs catalysts exhibit high activity for NO reduction with NH_3 at low-temperatures.The catalysts also show very high stability in the presence of SO_2.More interestingly,their activities are significantly promoted instead of being poisoned by SO_2.The promoting effect of SO_2 is distinctly associated with V_2O_5 loading,particularly maximized at low V_2O_5 loading,which indicated the role of CNTs support in this effect.The promoting effect of SO_2 at low temperatures suggests that V_2O_5/CNTs catalysts are promising catalytic materials for low-temperature SCR reactions.

Gas adsorption in shaped zeolitic imidazolate framework-8

Zeolitic imidazolate framework-8(ZIF-8) was prepared through a solve-thermal reaction method and then shaped using different additives. The in fluence of the shaping conditions on the microstructure of the shaped samples was characterized by the XRD, BET, and SEM techniques. The results demonstrate that the compressive strength of the various shaped tablets is greatly increased and capable of meeting the industrial requirements compared to the unshaped ZIF-8 and that the loss rate of speci fic surface areas was maintained at 10% after the addition of 10%(by mass) binder and 10%(by mass) solvent. The adsorption isotherms of CO2, CH4, C3H8, and C3H6 on powdery ZIF-8and the shaped tablets(T-shaped ZIF-8, C-shaped ZIF-8, and N-shaped ZIF-8) were determined through volumetric measurements under different pressures and temperatures(298.2, 323.2, and 348.2 K). The adsorption capacities of the gases on both the ZIF-8 powder and the shaped tablets follow the order C3H6 N C3H8N CO2 N CH4. Furthermore,the results show that the adsorption capacities of the gases on the shaped tablets are lower by approximately 10%–20% than those on the powdery ZIF-8. In fact, the adsorption equilibrium isotherms for CO2, CH4, C3H8, and C3H6 on both powdery and shaped ZIF-8 can be well described by the Langmuir equation.

Ecological Footprint of Hydropower Development in China and the Associated Reductions of Greenhouse Gas Emission

Hydropower, next to coal, is the second most important source of electric power supply in China. It amounted to 20.4% of the nation＇s total installed capacity of electricity generation in 2011. To provide a comprehensive picture of the development of hydropower in China and its potential environmental impacts, this study calculates the ecological footprint and greenhouse gas emission reduction of hydropower development in China over the past 60 years. The ecological footprints include the energy ecological footprint and arable land occupation footprint. The energy ecological footprint is calculated in terms of the area of the land which would be used for reforestation in order to assimilate CQ emissions from fossil energy consumption for hydropower development. The arable land occupation footprint is calculated in terms of the area of the land to be inundated by hydropower development. The calculated energy ecological footprint was 502 422 ha in 2010 or about 0.3% of total arable land in China and the calculated inundated land was about 1.42×10 6 ha or about 1.2% of total arable land in China. The regional power grid baseline method was used to calculate the greenhouse gas emission reduction. Results indicated that CQ emission reduction from hydropower development was increasing rapidly since 1949 and reached 5.02×108 tons of COe emission in 2010, with an accumulative total of 6.221×109 tons of CQ emission during the period 1949-2010.

Carbon Productivity Analysis to Address Global Climate Change

Developing low-carbon economy and enhancing carbon productivity are basic approaches to coordinating economic development and protecting global environment, which are also the major ways to address climate change under the framework of sustainable development. In this paper, the authors analyze the annual rate of carbon productivity growth, the differences of carbon productivity of different countries, and the factors for enhancing carbon productivity. Consequently, the authors clarify their viewpoint that the annual rate of carbon productivity growth can be used to weigh the efforts that a country takes to address climate change, and propose policies and suggestions on promoting carbon production.

Thermodynamic Analysis and Experimental Investigation into Nonflame Combustion Technology(NFCT) with Thermal Cyclic Carrier

The utilization of fossil fuels causes serious negative impacts on the environment and human life. To mitigate greenhouse gases and other pollutants, a novel combustion process-the nonflame combustion technology with a thermal cyclic carrier of molten salt is introduced. In this technology, a whole combustion is divided into two steps, i.e., the section of producing oxide and the section of combustion. In the first step, oxygen is separated from air, and pure N_2 is simultaneously formed which is easily recovered. In the other step, the fuels react with lattice oxygen in the oxides formed in the first step, and at the same time, thermal energy, CO_2 and H_2O vapor are produced. It is noted that the CO_2 is easily separated from water vapor and ultimately captured. Theoretically, there are no environmental-unfriendly gases such as CO_2, NO_x and SO_2 discharged in the whole combustion process. Some metal oxides scattered into molten salts play the roles of oxygen carriers in the combustion system, and they can constantly charge and discharge oxygen element from air to fuels during the combustion process. A nonflame combustion system with Li_2CO_3+K_2CO_3+Na_2SO_4 as the molten salt system, CH_4 as the fuel and CuO as the catalyst was experimentally investigated. The experimental results show that the combustion process proceeded as it was theoretically analyzed, and CO_2 with a high volume fraction of 77.0%_95.0% and N_2 with a high volume fraction of 91.9%_99.3% were obtained. The high concentration of CO_2 is favorable for capturing and storing subsequently. Therefore, the potential of reducing CO_2 emissions of this nonflame combustion technology is huge.

Adsorption of methane on biochar for emission reduction in oil and gas fields

To contribute to the reduction of methane emissions,using low-cost biochar as adsorbents for capturing and storing methane in oil and gas fields is investigated.This work presents results of methane adsorption on four biochars made from forestry wastes in comparison with the results of three commercial activated carbons.Although the adsorption capacity of the biochars is lower by over 50%than that of the activated carbons,thelow-cost and potential environmental benefits provide the incentive to the investigation.Moreover,it is shown that biochar can store more methane than vessels of compressed gas up to the pressure of 75 bar,suggesting the possibility of avoiding high-pressure gas compression and heavy vessels for cost savings in oil and gas fields.The thermodynamic and kinetic behaviors of the adsorption are studied and implications for the targeted application are discussed.

Research and Experience Reference on London’s Response to Climate Change in the Twenty-first Century

London’s approaches to tackling climate change after the 21st century are multifaceted and relatively systematic.The aim of this research paper is to analyse London’s actions in response to climate change and to draw out what valuable lessons London has for the world in terms of its response to climate change.This paper provides an in-depth analysis of London’s policies and actions on climate mitigation in the areas of“greenhouse gas emissions”and“energy infrastructure”,and climate adaptation actions in the areas of“city green belt and urban afforestation”,“UHI and thermal crisis management”and“water supply infrastructure and sustainable drainage”.It then examines the positive aspects of these actions to determine what London has to say about climate change to the rest of the world and other cities.This paper also discovers that to effectively mitigate and adapt to climate change,London has not only established carbon reduction targets,but also created a large academic research network,represented by the LCCP.At the same time,London has developed a scientific climate change adaptation planning framework(P2R2)that focuses on four key areas:Economic,environmental,health,and infrastructure sectors,and three types of risks:Flooding,heat,and water supply,and emphasizes the dynamics and flexibility of each adaptation strategy.

Investigation on the application of reformed coke oven gas in direct reduction iron production with a mathematical model

To investigate the application of reformed coke oven gas （COG） in producing the direct reduction iron （DRI）, we simulated a countercurrent gas solid moving bed reactor in which the iron ore pellet was reduced by reformed COG. An ordinary differential equation （ODE） was set based on the unreacted shrinking core model considering both mass and energy balances of the reactor. The concentration and temperature profiles of all species within the reactor were obtained by solving the ODE sys tem. The solid conversion and gas utilization were studied by changing gas flow rate, solid flow rate, reactor length, and the ratio of O/CHa to guide the practical application of COG in DRI production. Model results showed that COG was suitable for the DRI production. In order to meet the requirement of the industrial production, the minimum gas flow rate was set as 130,000 Nm3/h, and the maximum production was 90 t/h. The reactor length and the mole ratio x（O）： x（CH4） were depended on the actual industrial situations.

Physicochemical principles of hydrogen metallurgy in blast furnace

Based on the stoichiometric method and the free energy minimization method,an ideal model for the reduction of iron oxides by carbon and hydrogen under blast furnace conditions was established,and the reduction efficiency and theoretical energy consumption of the all-carbon blast furnace and the hydrogen-rich blast furnace were compared.The results show that after the reduction reaction is completed at the bottom of the blast furnace,the gas produced by reduction at 1600℃still has a certain excessive reduction capacity,which is due to the hydrogen brought in by the hydrogen-rich blast as well as the excess carbon monoxide generated by the reaction of the coke and the oxygen brought in by the blast.During the process of the gas with excessive reduction capacity rising from the bottom of the blast furnace and gas reduction process,the excessive reduction capacity of the gas gradually decreases with the increase in the dydrogen content in the blast.In the all-carbon blast furnace,the excess gas reduction capacity is the strongest,and the total energy consumption per ton of iron reduction is the lowest.This shows that,for the current operation mode of the blast furnace,adding hydrogen in the blast furnace cannot reduce the consumption of carbon required for reduction per ton of iron,but rather increases the consumption of carbon.

Disposal of zinc extraction residues via iron ore sintering process:an innovative resource utilization

Zinc extraction residue,a solid waste generated from the treatment of zinc-containing dust in rotary kilns,is commonly stockpiled in steel companies for extended periods.It poses significant disposal challenges and environmental pollution risks.So far,research on the treatment of zinc extraction residues has been slow,inadequate,and sporadic.For this gap,a novel approach was proposed to effectively treat the zinc extraction residue via the iron ore sintering process.It was feasible to add 1 wt.%of zinc extraction residues to the sintering raw materials.The more adequate mineralization reaction resulted in higher yield and tumbler indexes,despite a slight decrease in sintering speed.Although this may result in a slight decrease in sintering speed,the more complete mineralization reaction leads to improved sintering yield and tumbler index.Interestingly,the addition of zinc extraction residues reduced the CO and NO_(x) concentrations in the sintering flue gas.Thus,the iron ore sintering process provided a viable solution for resource utilization and environmentally friendly treatment of zinc extraction residues.

Orderly defective superstructure for enhanced pseudocapacitive storage in titanium niobium oxide

Artificial defect engineering in transition metal oxides is of important terms for numerous applications.In the present work,we proposed an in-situ gas reduction strategy to introduce ordered defects into titanium niobium oxide embedding on vapor grew carbon fibers(Ti_(2)Nb_(10)O_(29-x)@VGCFs).High-resolution transmission electron microscopy(HRTEM)and fast Fourier transform(FFT)simulation indicate that the ordered oxygen defects locate at interval layers,which leads to a new superstructure in Ti_(2)Nb_(10)O_(29).The ordered defects could provide extra active sites for lithium-ion storage and modulate ionic migration,resulting an enhanced pseudocapacitive performance.In addition,the excellent structural stability of the superstructure was proved by in-situ HRTEM under a harsh electrochemical process.Our work provides a directly observation of orderly defective superstructure in transition metal oxide,and its functionality on electrochemistry was revealed.