Low Pollutant Emissions Research Articles

Experimental Study of the Pyrolysis of NH3 under Flow Reactor Conditions.

The possibility of using ammonia (NH3), as a fuel and as an energy carrier with low pollutant emissions, can contribute to the transition to a low-carbon economy. To use ammonia as fuel, knowledge about the NH3 conversion is desired. In particular, the conversion of ammonia under pyrolysis conditions could be determinant in the description of its combustion mechanism. In this work, pyrolysis experiments of ammonia have been performed in both a quartz tubular flow reactor (900–1500 K) and a non-porous alumina tubular flow reactor (900–1800 K) using Ar or N2 as bath gas. An experimental study of the influence of the reactor material (quartz or alumina), the bulk gas (N2 or Ar), the ammonia inlet concentration (1000 and 10 000 ppm), and the gas residence time [2060/T (K)–8239/T (K) s] on the pyrolysis process has been performed. After the reaction, the resulting compounds (NH3, H2, and N2) are analyzed in a gas chromatograph/thermal conductivity detector chromatograph and an infrared continuous analyzer. Results show that H2 and N2 are the main products of the thermal decomposition of ammonia. Under the conditions of the present work, differences between working in a quartz or non-porous alumina reactor are not significant under pyrolysis conditions for temperatures lower than 1400 K. Neither the bath gas nor the ammonia inlet concentration influence the ammonia conversion values. For a given temperature and under all conditions studied, conversion of ammonia increases with an increasing gas residence time, which results into a narrower temperature window for NH3 conversion.

A rational design of bimetallic PdAu nanoflowers as efficient catalysts for methanol oxidation reaction* *Project supported by the National Natural Science Foundation of China (Grant Nos. 118740271 and 1774124), Technology Development Program of Jilin Province, China (Grant No. 20180101285JC), and the China Postdoctoral Science Foundation (Grant Nos. 2019T120233 and 2017M621198).

Methanol fuel cells have been intensively developed as clean and high-efficiency energy conversion system due to their high efficiency and low emission of pollutants. Here, we developed a simple aqueous synthetic method to prepare bimetallic PdAu nanoflowers catalysts for methanol oxidation reaction (MOR) in alkaline environment. Their composition can be directly tuned by changing the ratio between Pd and Au precursors. Compared with commercial Pd/C catalyst, all of the PdAu nanoflowers catalysts show the enhanced catalytic activity and durability. In particular, the PdAu nanoflowers specific activity reached 0.72 mA/cm2, which is 14 times that of commercial Pd/C catalyst. The superior MOR activity could be attributed to the unique porous structure and the shift of the d-band center of Pd.

Prospects for the Low Pollutant Emission Control of Circulating Fluidized Bed Combustion Technology

With the pollutant emission standards becoming increasingly stringent and considering the pressure of carbon neutral by 2060, the low pollutant emission potential of circulating fluidized bed (CFB) combustion technology needs to be further exploited, thus to promote the market competitiveness of CFB boilers; this is critical for the clean and efficient utilization of coal as well as for the energy transformation in China. In this article, we summarize the pollutant emission characteristics of CFB combustion, and review the development of major technologies for CFB boiler emission control. Based on the energy development strategies and corresponding policies in China, development suggestions are proposed for reducing pollutant emission of the CFB combustion technology. The most significant approach is to push the limits of original pollutant emission for CFB combustion by re-specifying the fluidization state and through in-furnace combustion adjustment, while the boiler thermal efficiency should be ensured. For the long-term development of coal energy, the new-generation CFB combustion technology with ultra-low emission should be researched and developed while combining with technologies such as supercritical/ultra-supercritical, intelligent operation, carbon capture, utilization, and storage, and energy storage technologies. The existing CFB boilers with small or medium capacity should also be upgraded. Considering the fuel flexibility of CFB combustion, biomass power generation should be promoted to realize low-cost and high-efficiency consumption of low-heat value fuels, urban refuse, industrial wastes, etc. The peak load regulation capacity and low pollutant emission property of the CFB boilers should be promoted to improve operation flexibility and renewable energy consumption. Moreover, the desulphurization ash produced in CFB combustion should be comprehensively utilized, and the N2O emission problem is also significant. The pollutant emission standards and related policies need to be formulated from an overall perspective to guide the healthy development of the energy industry.

Numerical simulation on velocity and temperature of a slotted swirl combustor

Cyclone combustion chamber has the advantages of compact structure, short flame length, good combustion stability, high combustion efficiency and low emissions of pollutants, etc. As one of the key components of the cyclone combustion chamber, the cyclone has a direct impact on the working performance of the combustion chamber. In this paper, we propose a slotted swirler and describe its structure in detail. We simulate the cold state flow field and the hot state temperature field in the combustion chamber of a cyclone with open seam using the CFD method, taking into account the effect of open seam on the air flow field and temperature distribution after the cyclone at different angles. The simulation shows that the temperature distribution in the slotted swirl combustor exhibited a center-focused flame of higher temperature, compared with the non-slotted swirler, the slotted swirler exhibits certain advantages in terms of drag reduction, combustion stability and combustion efficiency, which has a certain guiding effect on the improvement of the working performance of the combustion chamber.

Simulation Research on Battery Energy Management Strategy of Extended Program Based on Cruise

As a new energy vehicle, range-extended electric tractor have the advantages of long driving range and low pollutant emissions. However, at present, most extended battery have problems of insufficient energy management and high consumption.Therefore, it is necessary to study the energy management strategy of the extended-range electric vehicle battery. The additional battery provides power and power for the whole vehicle, realizes on-board charging through the expansion field, provides charging function when parking, and can be connected to the power grid; High voltage power supply safety management function; High voltage battery charger, high voltage power supply device, high voltage circuit current detection function, manual maintenance switch, battery system thermal management system, monitoring system operation status detection function.In order to construct the advanced energy management strategy and carry out the effective simulation analysis, based on the Cruise platform, this paper studies the power system matching and energy management control strategy of the extended battery, and completes the power system matching according to the vehicle dynamic parameters and the basic parameters of the vehicle. In this paper, a Cruise vehicle model of an extended-range extended battery is established on the Cruise professional simulation software platform, and joint simulation experiments are performed based on the energy management strategy model built in Matlab / Simulink. Simulation results show that the control algorithm designed in this paper satisfies the vehicle's driving needs,improves the economy of the vehicle by 6.84%, better controls the change of battery SOC. So as to verify the dynamics and economics of the power system and to evaluate the advantages and disadvantages of using this energy management strategy in different operating conditions, this paper studies the dynamics and economics under different cycling conditions. The vehicle power system matching and energy management strategies designed in this article have better economic characteristics when driving in this cycle.

Electric mobility promoted in Rwanda, environmental and economic impact on Kigali city

Kigali city is one of smart cities in Africa, guiding citizens to a clean orientation with low pollution emissions is a target of the city. Rwanda has intention to reduce the emissions through promoting E-mobility. This paper was intended to assess how ICE-users can shift to e-mobility, they understand the cost of a city to be smart, 64.5 % of respondents agreed to drive e-vehicles,39.9 % of respondents interested to buy e-car but recommend that E-Mobility infrastructures such faster chargers should be available at low cost, 65% of respondents agreed that E-Mobility enable air quality improvement, 68% suggested on station allocation and 69% agreed that the system contribute to energy saving and noise reductions. Chi-square results indicated ICE – vehicle users will shift to electric cars.

Study on combustion irreversibility in turbocharged spark-ignition engines

The direct-injection (DI) and turbocharging strategies are recently adopted for spark-ignition (SI) engines in order to achieve better fuel economy and lower pollutant emissions. A comprehensive analysis is required in order to evaluate the effects of aforementioned strategies on in-cylinder combustion processes. The second law analysis is a proficient thermodynamic tool which is used for identifying irreversibilities and exploring the possibilities of thermal systems optimisation. The present work aims at carrying out an exergetic analysis of a downsized turbocharged DI SI engine. The engine is fuelled with E10 (gasoline with 10% of ethanol content) while experimental data is acquired for different engine operating conditions. The exergetic analysis identified the combustion irreversibilities. Moreover, a comparison between second law analyses of a previously analysed port fuel injection (PFI) naturally aspirated SI engine and turbocharged DI SI engine is also presented. The study concluded with the potential benefits and drawbacks of newly adopted strategies for SI engines.

Study on combustion irreversibility in turbocharged spark-ignition engines

The direct-injection (DI) and turbocharging strategies are recently adopted for spark-ignition (SI) engines in order to achieve better fuel economy and lower pollutant emissions. A comprehensive analysis is required in order to evaluate the effects of aforementioned strategies on in-cylinder combustion processes. The second law analysis is a proficient thermodynamic tool which is used for identifying irreversibilities and exploring the possibilities of thermal systems optimisation. The present work aims at carrying out an exergetic analysis of a downsized turbocharged DI SI engine. The engine is fuelled with E10 (gasoline with 10% of ethanol content) while experimental data is acquired for different engine operating conditions. The exergetic analysis identified the combustion irreversibilities. Moreover, a comparison between second law analyses of a previously analysed port fuel injection (PFI) naturally aspirated SI engine and turbocharged DI SI engine is also presented. The study concluded with the potential benefits and drawbacks of newly adopted strategies for SI engines.

Feasibility analysis of an innovative naval on-board power-train system with hydrogen- based PEMFC technology

The maritime transportation sector is one of the main contributors to global emissions of greenhouse gases (GHGs), volatile organic compounds (VOCs), particulate matter (PM), hazardous air pollutants, NOX and SOX. In particular, it is estimated that the CO2 emissions in this sector are about 1 Gt every year. The International Maritime Organization (IMO) adopted stringent emission limits in its Tier III regulation, most notably on NOX and SOX emissions and pledged to reach a reduction in greenhouse gas (GHG) emissions from international shipments by at least 50% by the year 2050, compared to 2008 emissions. For emission control areas (ECAs) these requirements are particularly strict and will be difficult to meet with traditional diesel engines and bunker fuels. Therefore, ship owners need to adopt solutions to bring emissions within these and other future limits by means of environmentally friendly fuels and high efficiency propulsion technologies. In this context, hydrogen and fuel cells play a crucial role, thanks to their low criteria pollutant and GHG emission. This paper presents a techno-economic feasibility study for replacing the conventional diesel engine powertrain, usually employed in Ro-Pax ferries, with an innovative system based on polymer electrolyte membrane fuel cell (PEMFC) technology. The ferry is actually powered by four diesel engines, which deliver a total output of 37.8 MW. The ferry also has two auxiliary engines which give an output of 4.0 MW and also two 2.0 MW bow thrusters for its manoeuvring. The energy analysis has allowed to define the hydrogen consumption for each cruise, as well as the optimal size of the innovative propulsion system. In particular, The PEMFC powertrain is sized at the same maximum power output as the main diesel engine and, thanks to the modular architecture of fuel cells and their flexible performance at partial load, the auxiliary engines are not contemplated. Moreover, in order to identify the best solution in terms of ship’s weight and space requirements, two hydrogen storage solutions based on compressed hydrogen technology and liquefied hydrogen technology, have been analyzed and compared. The economic assessment has been carried out by estimating the CAPEX and OPEX for each H2 storage technology by considering short-term, mid-term and long-term scenarios (from 2020 to 2050).

Air pollutant variations in Suzhou during the 2019 novel coronavirus (COVID-19) lockdown of 2020: High time-resolution measurements of aerosol chemical compositions and source apportionment.

To control the spread of the 2019 novel coronavirus (COVID-19), China imposed rigorous restrictions, which resulted in great reductions in pollutant emissions. This study examines the characteristics of air pollutants, including PM2.5 (particles with aerodynamic diameters < 2.5 μm), gas pollutants, water-soluble ions (WSIs), black carbon (BC) and elements, as well as the source apportionment of PM2.5 in Suzhou before, during and after the Chinese New Year (CNY) holiday of 2020 (when China was under an unprecedented state of lockdown to restrict the COVID-19 outbreak). Compared to those before CNY, PM2.5, BC, SNA (sulfate, nitrate and ammonium), other ions, elements, and NO2 and CO mass concentrations decreased by 9.9%–64.0% during CNY. The lockdown policy had strong (weak) effects on the diurnal variations in aerosol chemical compositions (gas pollutants). Compared to those before CNY, source concentrations and contributions of vehicle exhaust during CNY decreased by 72.9% and 21.7%, respectively. In contrast, increased contributions from coal combustion and industry were observed during CNY, which were recorded to be 2.9 and 1.7 times higher than those before CNY, respectively. This study highlights that the lockdown policy that was imposed in Suzhou during CNY not only reduced the mass concentrations of air pollutants but also modified their diurnal variations and the source contributions of PM2.5, which revealed the complex responses of PM2.5 sources to the rare, low emissions of anthropogenic pollutants that occurred during the COVID-19 lockdown.

Lean-Burn Natural Gas Engines: Challenges and Concepts for an Efficient Exhaust Gas Aftertreatment System

High engine efficiency, comparably low pollutant emissions, and advantageous carbon dioxide emissions make lean-burn natural gas engines an attractive alternative compared to conventional diesel or gasoline engines. However, incomplete combustion in natural gas engines results in emission of small amounts of methane, which has a strong global warming potential and consequently makes an efficient exhaust gas aftertreatment system imperative. Palladium-based catalysts are considered as most effective in low temperature methane conversion, but they suffer from inhibition by the combustion product water and from poisoning by sulfur species that are typically present in the gas stream. Rational design of the catalytic converter combined with recent advances in catalyst operation and process control, particularly short rich periods for catalyst regeneration, allow optimism that these hurdles can be overcome. The availability of a durable and highly efficient exhaust gas aftertreatment system can promote the widespread use of lean-burn natural gas engines, which could be a key step towards reducing mankind’s carbon footprint.

Systematic Evaluation of a Multi-Lane Green-Driving Algorithm in a Mixed Connected Environment

Vehicles traveling under oscillated traffic have low energy efficiency and high air pollutant emissions. Green driving with the help of connected vehicles (CVs) attracts a lot of research effort to improve vehicle energy efficiency. However, it is very challenging to perform green driving on multi-lane freeways under a mixed connected environment. In the researchers’ previous work, one innovative green-driving algorithm was proposed to solve the multi-lane problem with only one CV. In this study, a systematic analysis of the algorithm is conducted to understand its benefits and limitations on smoothing traffic oscillations. The effect of the steady states and the number of lanes is also analyzed. In addition, the algorithm is extended to a more general scenario with multiple CVs. The extended system coordinates multiple CVs to form multiple moving bottlenecks to mitigate traffic oscillation more efficiently as well as providing more realistic instructions to CVs. The evaluation of the extended system concludes with the most effective strategies to control CVs to smooth oscillations.

Exhaust emissions and engine performance analysis of a marine diesel engine fuelledwith Parinari polyandra biodiesel–diesel blends

The sustainability of biodiesel adoption in diesel engines are dependent on its environmental friendliness relative to lower pollutant emissions. Biodiesel was produced from extracted Parinari polyandra oil via alkali catalyzed methanolysis. Performance and emission analysis of a diesel engine was conducted on a diesel engine, operated under different operating conditions, using varied Parinari polyandra biodiesel blends. Exhaust emissions, like total hydrocarbons, carbon dioxide, carbon monoxide, sulphur dioxide, and nitrogen oxides were measured. The biodiesel properties were found to be similar to fossil diesel. B10 was found to be the optimal blend in improving the engine performance in terms of speed, power and thermal efficiency. B30 demonstrated stable performance characteristics without any modification of the diesel engine. The exhaust emissions from biodiesel blends combustion were found to be lower than that of diesel, except nitrogen oxides. High percentage reduction of greenhouse gases, carbon monoxide and carbon dioxide, was recorded at 81.7% and 65.7%, respectively. The utilization of Parinari polyandra biodiesel for engine application was found to be a viable means of heightening adoption of sustainable biofuels and minimizing pollutant emissions from the combustion of fossil fuels.

Stability study of hydrogen-air flame in a conical porous burner

Porous medium combustion offers several advantages such as extended flammability limits, high burning rates and low pollutant emissions. In this work, laminar premixed flame of hydrogen/air mixture in a conical porous burner is numerically investigated by using OpenFOAM CFD toolbox. An unsteady, two-dimensional mathematical model is constructed. Flame front location within the burner is not predetermined in this model. A baseline case is first investigated using detailed kinetics for hydrogen combustion. Flame stability analysis is then performed and the effect of the burner cone angle on flame location is studied. For this purpose, four different burner cone angles with seven different firing rates are examined. It is observed that the burner cone angle has no considerable effect on flashback and blowout limits. Variation of the flame location in the porous medium with the burner cone angle and firing rate is also investigated. It is concluded that increasing the firing rate for a fixed burner cone angle, moves the flame location downstream in the burner and also increases the length of the preheating zone. On the other hand, an increase in the burner cone angle at a fixed firing rate causes the flame to move upstream and also shortens the preheating zone length.

The Impact of Critical Operational Parameters on the Performance of the Aluminum Anode Baking Furnace

Abstract Minimizing energy consumption and reducing pollutant emissions during the carbon anode baking process are critically important for the aluminum industry. The present study investigates the effects of oxidizer inlet temperature, inlet oxygen concentration, equivalence ratio, refractory wall thermal conductivity, and refractory wall emissivity on the baking process using unsteady Reynolds-averaged Navier–Stokes (URANS)-based simulations in conjunction with the presumed probability density function method. Numerical results are combined with a response surface methodology (RSM) to optimize the anode baking process. The advantage of the coupled method is that it can adequately provide information on interactions of different input parameters. It is remarked that the significance level of the studied parameters varies drastically for different outputs. It is noted that diluting inlet oxygen concentration (from 23% in atmospheric air to 15%) at an elevated oxidizer temperature leads to enhanced furnace fuel efficiency, more uniform temperature distribution, and lower pollutant emissions. A linear model is detected to be adequate for response surface modeling of the anode baking furnace NOx formation. On the other hand, furnace soot formation is modeled with a higher-order model due to the quadratic behavior of the response.

Effects of oxygen partial pressure on physical and chemical characteristics of fuel and deep low NOx emission

The high efficient and clean coal combustion with fundamental deep low pollution emission is extensively explored worldwide. In this work, the Shenmu bituminous coal was preheated in a circulating fluidized bed (CFB) and this modified fuel including the preheated fuel and the coal gas was burned in a down-fired combustor (DFC) under the O2/CO2 atmospheres. The coal char and coal gas produced by preheating raw coal were measured and analyzed to obtain the changes of physical and chemical characteristics and the reduction of NOx original emissions. The results showed that both G band FWHM and IG/IALL of the preheated fuel were lower than those of raw coal, respectively, while both ID1/IG and ID3+D4/IG were significantly higher than those of raw coal, and the intensity of quartz, the anhydrite peaks and the fuel particle size were significantly reduced after preheating process. During the oxygen partial pressure of primary air increasing from 28.6% to 36.0%, and the increase of NH3/HCN from 0.61 to 1.26, NOx emissions decreased from 39.6 mg/MJ to 37.3 mg/MJ (@6%O2). The increased oxygen partial pressure of primary air improved the conversion ratio of fuel-N to coal gas-N. In the period of pulverized bituminous coal preheating, it destroyed and reconstructed the stability of carbon molecular micro-structure and the regularity of crystal structure for modified fuel microphysical morphology.

Influence of pre-chamber structure and injection parameters on engine performance and combustion characteristics in a turbulent jet ignition (TJI) engine

Turbulent jet ignition (TJI) has been proven to effectively improve the burning rate and expand the lean-burn limit of gasoline engines. In this work, based on a single-cylinder engine, injection parameters in the pre-chamber were investigated, combustion characteristics were studied, and pollutant emissions were optimized. Results show that the injection timing in the pre-chamber should be carefully controlled to generate a well-mixed air–fuel mixture and to avoid the diffusion of fuel from the pre-chamber to the main chamber. Therefore, the injection event should be set at the early stage of the compression stroke. Besides, excessive fuel supply in the pre-chamber should be avoided to get optimal engine performance and low pollutant emissions. The lowest indicated specific fuel consumption (ISFC) is achieved when the λ is between 1.5 and 1.6, because lean combustion reduces the heat dissipation but too lean combustion causes more fuel to be burned incompletely. Moreover, to further improve the engine performance and reduce the pollutant emissions, three types of optimized pre-chamber are tested, and results show that with lower pre-chamber volume, better engine performance and lower pollutant emissions are both realized because smaller pre-chamber volume leads to less heat dissipation and less fuel burning around stoichiometric equivalence ratio in the pre-chamber. Furthermore, the pre-chamber with one jet hole is effective to improve the burning rate and to expand the lean-burn limit compared with the 7-hole pre-chamber, and the lean-burn limit of λ is expanded to 2.2 by the optimized pre-chamber, when the minimum NOx of 0.15 g/kWh is achieved.

Low Pollution Emission to Purify Fuel Cell Technology Comprehensively: A Review

In recent decades, scientists have been urged to build the new energy resources by depleting fossil fuel,high-energy demand and pollution. Being one of the principal alternative power devices, Thanks to thehigh energy conversion efficiency, the fuel cells have attracted growing attention, simple operation andlow pollution emissions. This paper surveys the historical backdrop of the power devices, the energy unitactivity, and sorts of energy units, their points of interest, inconveniences and applications.

Spray Characteristics of Air-Assisted Injector Under Different Ambient Pressures

Spray atomization of liquid fuel plays an important role in droplet evaporation, combustible mixture formation and subsequent combustion process. Well-atomized liquid spray contributes to high fuel efficiency and low pollutant emissions. Gasoline direct injection(GDI) has been recognized as one of the most effective ways to improve fuel atomization. As a special direct injection method, the air-assisted direct injection utilizes high-speed flow of high-pressure air at the injector exit to assist liquid fuel injection and promote spray atomization at a low injection pressure. This injection method has excellent application potential and advantages for high performance and lightweight engines. In this study, the hollow cone spray emerging from an air-assisted injector was studied in a constant volume chamber with the ambient pressures ranging from 5 kPa to 300 kPa. External macro characteristics of spray were obtained using high speed backlit imaging. Phase Doppler particle analyzer(PDPA) was utilized to study the microcosmic spray characteristics. The results show that under the flash boiling condition, the spray will generate a strong flash boiling point which causes the cone shape spray to expand both inwards and outwards. The axisymmetric inward expansion would converge together and form a lathy aggregation area below the nozzle and the axisymmetric outward expansion greatly increases the spray width. The sauter mean diameter (SMD) of flash boiling condition can be reduced to 5 μm compared to the level close to 10 μm in the non-flash boiling condition.

Thermal Plasma Treatment of Medical Waste

The harmless treatments of medical waste have significantly drawn people’s attention owing to their risks to health-care staff, the public, and the environment. The traditional thermal technology for processing medical waste may cause indispensable secondary pollution such as dioxin, furan, and heavy metals, and infectious materials that may remain in the solid residual. Thermal plasma technologies offer advantages of effectively treating medical waste due to its high temperature and energy density, lower pollutant emissions, rapid start-up and shut-down, and smaller size of the installation. These benefits play roles in the treatment of medical waste on-site or off-site, especially when somewhere encounters an abnormally sharp increase in medical waste. This paper mainly introduces the typical thermal plasma processes of medical waste and its central component, plasma furnace. Meanwhile, how process parameters influence the formed gaseous and solid products, the performances of mass and volume reduction, pathogen destruction, and energy recovery, are discussed in detail. Finally, the mechanism of the thermal plasma process is also analyzed.