Emissions Of Hazardous Pollutants Research Articles

A comprehensive review on unleashing the power of hydrogen: revolutionizing energy systems for a sustainable future.

Population growth and environmental degradation are major concerns for sustainable development worldwide. Hydrogen is a clean and eco-friendly alternative to fossil fuels, with a heating value almost three times higher than other fossil fuels. It also has a clean production process, which helps to reduce the emission of hazardous pollutants and save the environment. Among the various production methodologies described in this review, biochemical production of hydrogen is considered more suitable as it uses waste organic matter instead of fossil fuels. This technology not only produces clean energy but also helps to manage waste more efficiently. However, the production of hydrogen obtained from this method is currently more expensive due to its early stage of development. Nevertheless, various research projects are underway to develop this method on a commercial scale.

A mechanistic and kinetic investigation on the oxidative thermal decomposition of decabromodiphenyl ether

The thermal processes of materials containing decabromodiphenyl ether (BDE-209) normally result in the exposure of BDE-209 to high-temperature environments, generating a series of hazardous compounds. However, the evolution mechanisms of BDE-209 during oxidative thermal processes remain unclear. Thus, this paper presents a detailed investigation on the oxidative thermal decomposition mechanism of BDE-209 by utilizing density functional theory methods at the M06/cc-pVDZ theoretical level. The results show that the barrierless fission of the ether linkage dominates the initial degradation of BDE-209 at all temperatures, with branching ratio over 80%. The decomposition of BDE-209 in oxidative thermal processes is mainly along BDE-209 → pentabromophenyl and pentabromophenoxy radicals → pentabromocyclopentadienyl radicals → brominated aliphatic products. Additionally, the study results on the formation mechanisms of several hazardous pollutants indicate that the ortho-phenyl-type radicals created by ortho-C-Br bond fission (branching ratio reached 15.1% at 1600 K) can easily be converted into octabrominated dibenzo-p-dioxin and furan, which require overcoming the energy barriers of 99.0 and 48.2 kJ/mol, respectively. The O/ortho-C coupling of two pentabromophenoxy radicals also acts as a non-negligible pathway for the formation of octabrominated dibenzo-p-dioxin. The synthesis of octabromonaphthalene involves the self-condensation of pentabromocyclopentadienyl radicals, followed by an intricately intramolecular evolution. Results presented in this study can enhance our understanding of the transformation mechanism of BDE-209 in thermal processes, and offer an insight into controlling the emissions of hazardous pollutants.

Plastic and Waste Tire Pyrolysis Focused on Hydrogen Production—A Review

In this review, we compare hydrogen production from waste by pyrolysis and bioprocesses. In contrast, the pyrolysis feed was limited to plastic and tire waste unlikely to be utilized by biological decomposition methods. Recent risks of pyrolysis, such as pollutant emissions during the heat decomposition of polymers, and high energy demands were described and compared to thresholds of bioprocesses such as dark fermentation. Many pyrolysis reactors have been adapted for plastic pyrolysis after successful investigation experiences involving waste tires. Pyrolysis can transform these wastes into other petroleum products for reuse or for energy carriers, such as hydrogen. Plastic and tire pyrolysis is part of an alternative synthesis method for smart polymers, including semi-conductive polymers. Pyrolysis is less expensive than gasification and requires a lower energy demand, with lower emissions of hazardous pollutants. Short-time utilization of these wastes, without the emission of metals into the environment, can be solved using pyrolysis. Plastic wastes after pyrolysis produce up to 20 times more hydrogen than dark fermentation from 1 kg of waste. The research summarizes recent achievements in plastic and tire waste pyrolysis development.

Valorization of food waste into hydrogen: Energy potential, economic feasibility and environmental impact analysis

Hydrogen gas is widely acknowledged as a significant energy carrier worldwide. Hydrogen gas derived from sustainable sources could be used as an alternative to fossil fuel for electricity generation with zero emission of hazardous pollutants. Food waste valorization to hydrogen is a viable energy source with potential economic benefits. The current study examines the economic viability and environmental effect of producing hydrogen from food waste in China using biogas steam reforming for power generation. The key findings show that the steam reforming of biogas from food waste could produce 221.12 billion kg of hydrogen gas. The quantity of hydrogen gas yield could generate 661.97 TWh of electricity. It was found that the consumption of the available electricity from the hydrogen gas could displace 15,482.26 M liters of diesel fuel combustion. The amount of diesel fuel consumption avoided can reduce global warming by 42,041.90 kt CO2e. It was also discovered that hydrogen has an appealing ecological efficiency of 94.64% when used as a source of energy generation. According to the outcomes of the economic analysis, the food waste to hydrogen project is economically feasible in all of China's provinces. The average hydrogen production cost, return on investment, the payback period is $0.814/kWh, 29.8%, and 7.2 years. This study could provide scientific data for investment and decision-making on ecological sustainability in food waste to hydrogen initiatives in China and other emerging nations with a similar culture.

Газовая вредность взрывчатых веществ, применяемых в горнодобывающей промышленности

Reducing emissions of hazardous pollutants that have a negative impact on the environment and human health has been approved as one of the strategic objectives of Russia's development. More than 90% of minerals in mined using blast energy. Despite an increase in the share of non-explosive component mixtures used in mining, blasting still poses a hazard to miners as the gaseous detonation products are potentially dangerous. The composition of blast gaseous products is extremely important in underground blasting because air exchange is difficult under these conditions and the blast products can contaminate the atmosphere of underground excavations, causing illness or poisoning of miners. Currently, there are no uniform requirements for obtaining information on the amount of gaseous blast products that would be hazardous to the human organism. Available documents do not contain information on the permissible amounts of toxic oxides per 1 kg of explosive detonated. The article compares the results of studying gas toxic hazard of industrial explosives obtained by different methods and based on different criteria.

Influence of Nozzle Hole Geometry of CI Engines Performance and Emission Parameters Fuelled by Diesel and Biodiesel-A Review

In the quest to reduce hazardous pollutant emissions and environmental impact, various renewable alternative fuels derived from bio-based sources have entered the market. Biodiesel, a vegetable oil ester, has gained a lot of popularity and attention for diesel engine applications. The performance of diesel engine and emission characteristics are closely linked with fuel atomization and spray pattern of fuel injection nozzles. In modern engines various orifices with different designs are used. In a diesel engine, the shape of the diesel fuel injection nozzle and the fuel flow parameters in the nozzle have a considerable impact on the processes of fuel atomization, combustion, and exhaust emissions. The main focus of this study is to explore how number of nozzle hole and shape affects the performance of diesel engine, combustion, and emissions for both Biodiesel and diesel fuels.

Effects of preheating primary air and fuel size on the combustion characteristics of blended pinewood and corn straw in a fixed bed

This research investigated the effects of preheating primary air and fuel size on combustion behaviors of pinewood and corn straw (50% ratio) in a fixed bed. Primary air temperature (Tair) was ranged in 20–130 °C, and the fuel size was varied in the range of 3–8 cm in length, which affected the whole combustion efficiency, emissions of hazardous pollutants and alkali metals and chloride. Results showed that by increasing Tair the ignition delay time first decreased by 40% and then increased, and both burning and ignition rates increased by 60%; however, the emissions of CO2, CO and CH4 increased first, and then decreased. At the Tair = 85 °C the smallest unburned carbon was left in the ash; the mostly generated N-bearing species was NO followed by HCN, and then by a small of NH3. The higher Tair increased the releases of K (by 16%) to the gas phase and promoted the transfer of Cl to HCl, while mildly effects on Ca. Also, increasing fuel size to 5 cm enhanced the combustion stability and decreased the emissions of NO. Accordingly, mildly increase the fuel size and Tair were found to be well-operating condition, which provide guidance for selections in large-grate boiler during blend combustion.

A Study on the Characteristics of Hazardous Pollutant Emissions in Korea from 2007 to 2016

In this study, trends in hazardous pollution emissions in South Korea for the last decade were investigated to protect people’s health and contribute to the prevention of environmental risks by reducing emissions. It was found that hazardous pollution emissions increased from 47,688,000 kg in 2007 to 57,247,000 kg in 2016. Among them, Xylene and Toluene exhibited the highest proportions. 99% of hazardous pollution were emitted to the atmosphere. Among the Group 1 carcinogens, the top two substances (trichloroethylene, benzene) accounted for more than 80% of the emissions, and trichloroethylene took up the most. Carcinogen emissions also increased, and emissions from major industrial complexes represented approximately 30% of the total chemical emissions from all industrial complexes. Chemical emissions exhibited no significant relationship with particulate matter, cancers, and allergic diseases. It can be said, however, that the use of various chemicals has chemical accident risks. Owing to the nature of chemical accidents, an accident may lead to secondary damage. Therefore, it is necessary to prepare measures for the management of various chemicals and to perform continuous monitoring for reducing chemical emissions.

The Generation and Suppression of NOx and N2O Emissions in the Oxy-Fuel Combustion Process with Recycled CO2 (an Overview)

It is shown that combustion of solid fuels in an oxygen atmosphere with recycled flue gases is an efficient method for capture of CO2. The use of the circulating fluidized bed (CFB) technology in the oxy-fuel combustion process reduces the CO2 capture costs and nitrogen oxide emissions compared with flare combustion. The mechanisms of generation and suppression of nitrogen and nitrous oxides during CFB combustion of solid fuels are considered. The basic reactions that occur during the exit and burning of volatiles and combustion of char resulting in generation of NO, N2O, and N2 are indicated. The effect of the secondary air delivery on nitrogen oxide emissions is studied. It is shown that the degree of converting fuel nitrogen into N2O is reduced when the degree of converting nitrogen into NOx is increased. Comparative analysis that the effect of flue gas recycling and other process factors has on generation of NO and N2O during combustion in air, oxygen, and CO2 has been made. It is shown that, owing to recycling, the fractions of NOx and N2O generated from fuel nitrogen during oxy-fuel combustion are significantly lower than those during combustion in air. Mathematical simulation of various complicated processes related to generation and suppression of hazardous pollutant emissions has recently become a generally accepted method that allows the prediction at relatively low costs of such processes during the combustion of various fuels. However, as applied to new technologies for combustion of various biomass types and cofiring of coal and biomass, these methods have not yet been properly developed. The most preferable mathematical models for calculating nitrogen oxide emissions are provided, and the predicted results are compared with experimental data. The lines of further research, predominantly in the simulation of cofiring of coal and biomass, are outlined. It is shown that comprehensive investigations of generation and suppression of hazardous pollutant emissions during cofiring of coals and biomass of various kinds, in particular, during oxy-fuel combustion with recycled CO2 are of topical interest.

Integral process for obtaining acetins from crude glycerol and their effect on the octane index

The improvement of the combustion process in gasoline spark engines has been a painstaking task focused on developing chemical compounds. These ones have to be capable of bettering the engine performance and meeting standards set by environmental and health regulations aimed at reducing the emission of hazardous pollutants. Among the molecules synthesized for reaching these goals, oxygenating agents have been used to increase the octane number and make more efficient the combustion reaction by reducing the emissions of CO, polyaromatic hydrocarbons (PAHs), and particulate matter. As a result of this quest, MTBE has been used as a solution, but in recent years, negative effects of its use polluting water bodies and, as a consequence, the human health, have proven the opposite. For this reason, alternative oxygenating compounds to MTBE such as alcohols, ethers, and esters are being studied. According to the aforementioned, in the present paper, alternative oxygenating agents belonging to glycerol acetates (GAs) were synthesized from crude glycerol (CG) obtained as a biodiesel by-product and conditioned as starting material to perform esterification reactions with acetic acid or acetic anhydride. In order to assess the performance of these compounds as octane index enhancers, measurements using the same composition of ethanol, MTBE and the as-obtained GAs, in reference gasoline, were made, yielding comparable results that encourage the potential use of acetins as a replacement of MTBE.

Effects of Air Flowrate on the Combustion and Emissions of Blended Corn Straw and Pinewood Wastes

This research investigated the effects of the specific primary (under-fire) air flowrate (m˙air) on the combustion behavior of a 50–50 wt % blend of raw corn straw (CS) and raw pinewood wastes in a fixed-bed reactor. This parameter was varied in the range of 0.079–0.226 kg m−2 s−1, which changed the overall combustion stoichiometry from air-lean (excess air coefficient λ = 0.73) to air-rich (excess air coefficient λ = 1.25) and affected the combustion efficiency and stability as well as the emissions of hazardous pollutants. It was observed that by increasing m˙air, the ignition delay time first increased and then decreased, the average bed temperatures increased, both the average flame propagation rates and the fuel burning rates increased, and the combustion efficiencies also increased. The emissions of CO as well as those of cumulative gas phase nitrogen compounds increased, the latter mostly because of increasing HCN, while those of NO were rather constant. The emissions of HCl decreased but those of other chlorine-containing species increased. The effect of m˙air on the conversion of sulfur to SO2 was minor. By considering all of the aforesaid factors, a mildly overall air-rich (fuel-lean) (λ = 1.04) operating condition can be suggested for corn-straw/pinewood burning fixed-bed grate-fired reactors.

Optical Measurements of a Lower Calorific Values-Combustor Operated in a Micro Gas Turbine With Various Fuel Compositions

In a recent joint research project, a new FLOX®-combustion system was developed to couple a fixed-bed gasifier with a micro gas turbine (MGT). Product gases from biomass gasification exhibit low calorific values and varying compositions of mainly H2, CO, CO2, N2, and CH4. Furthermore, combustion characteristics differ significantly compared to the commonly used natural gas. As the FLOX-technology is considered as efficient and fuel-flexible featuring low emissions of hazardous pollutants, the design of the lower calorific value (LCV) combustor is based on it. It contains a two-staged combustor consisting of a jet-stabilized main stage adapted from the FLOX-concept combined with a swirl stabilized pilot stage. The combustor was operated in a Turbec T100 test rig using an optically accessible combustion chamber, which allowed OH*-chemiluminescence and OH-PLIF measurements for various fuel compositions. In particular, the hydrogen content in the synthetically mixed fuel gas was varied from 0% to 30%. The exhaust gas composition was additionally analyzed regarding CO, NOx, and unburned hydrocarbons. The results provide a comprehensive insight into the flame behavior during turbine operation. Efficient combustion and stable operation of the MGT was observed for all fuel compositions, while the hydrogen showed a strong influence. It is remarkable that with hydrogen contents higher than 9%, no OH radicals were detected within the inner recirculation zone, while they were increasingly entrained below hydrogen contents of 9%. Without hydrogen, the inner recirculation zone was completely filled with OH radicals and the highest concentrations were detected there. Therefore, the results indicate a different flame behavior with low and high hydrogen contents. Although the flame shape and position were affected, pollutant emissions remained consistently below 10 ppm based on 15% O2. Only in the case of 0% hydrogen, CO-emissions increased to 43 ppm, which are still meeting the emission limits. Thus, the combustor allows operation with syngases having hydrogen contents from 0% to 30%.

A Study on the Variation of Hazardous Pollutant Emissions in Korea from 2006 to 2015

A Study on the Variation of Hazardous Pollutant Emissions in Korea from 2006 to 2015

Endoscopic combustion characterization of Jatropha biodiesel in a compression ignition engine

Decline in global resources of petroleum based fuels such as diesel and gasoline have attracted attention of researchers towards alternative fuels which are capable of providing both, energy security and protection against environmental degradation due to emission of hazardous pollutants. As an oxygenated fuel, biodiesel has emerged as a potential alternative fuel, which can be used in diesel engines on large-scale to reduce CO, HC and PM emissions. In this experimental study, Jatropha curcas derived biodiesel (JB100) and its 20% (v/v) blend with mineral diesel (JB20) was tested in a production-grade single cylinder diesel engine for evaluating its combustion characteristics. Since soot and NOx emissions are major concerns in CI engine combustion, it is very important to investigate their in-situ spatial distribution, so that effective control measures can be devised. For this, endoscopic visualization technique was implemented on a modified prototype engine to evaluate the effect of biodiesel blending percentage and engine load on in-situ spatial distribution of in-cylinder soot and flame temperature distributions. Inherent oxygen content of biodiesel helped in achieving superior combustion; as a result, in-cylinder soot formation was lower than baseline mineral diesel. Spatial flame temperature distribution was also relatively lower in biodiesel. Endoscopic visualization technique was found to be effective in evaluating different combustion characteristics in a modified prototype engine.

Characterization of gaseous emissions and ashes from the combustion of furniture waste

Gaseous emissions and ash obtained in the combustion of furniture waste have been studied, with particular emphasis on the emissions of hazardous pollutants, such as PCDD/Fs and dl-PCBS. Two different combustion procedures were carried out, one of them in a conventional residential stove (without an automatic control of combustion air and bad mixing of combustion gases with air), and the other in a laboratory-scale reactor (operating under substoichiometric conditions).Three different experiments were carried out in the residential stove, in which the gaseous emissions and ashes obtained were analysed. The fuel burnt out in two of the experiments was furniture wood waste and in one of the experiments, the fuel burnt out was briquettes composed of a mixture of furniture wood with 10wt.% of polyurethane foam. One of the purposes of these experiments was the evaluation of the possible inhibition effect of the higher nitrogen content on the formation of PCDD/Fs. Slight inhibition of the PCDD/F formation was found although, it is noteworthy that the lowest yield of PAHs, volatile and semi-volatile compounds were obtained in the combustion of these briquettes.In all experiments, the emission factors of polychlorinated dibenzo-p-dioxins and dibenzofurans and dioxin-like polychlorinated biphenyls (PCDD/Fs and dl-PCBs) were between 29 and 74ng WHO-TEQ/kg sample burnt, lower than that obtained by other authors in the burning of pine needles and cones.PCDD/Fs and dl-PCBs emissions from furniture wood waste combustion were also analysed in the laboratory scale reactor at 850°C and the results were compared with the values obtained from the combustion of solid wood (untreated wood). The total equivalent toxicity obtained was 21.1ng WHO-TEQ/kg sample for combustion of furniture wood waste, which is low in comparison with those obtained for other waste combustion in similar conditions.In the laboratory scale reactor, PCDFs were the dominant compounds in the profiles of PCDD/Fs, by contrast, in the combustion in the residential stove, the majority compounds were PCDDs, due to the different operation conditions.

Improving the Energy Efficiency of Stoves To Reduce Pollutant Emissions from Household Solid Fuel Combustion in China

Emissions of air pollutants from household solid fuel combustion in low-efficiency stoves have serious negative impacts on human health and air quality in China. This study compares the thermal efficiency (TE) and emissions from solid fuel combustion in a newly developed under-fire heating stove and a typical traditional over-fire heating stove. The average TEs for burning all tested fuel types (semi-coke, anthracite, briquette, bituminous, lignite, and biomass) were 83 and 42% for the new stove and the traditional stove, respectively. The new stove was effective in reducing CO2 and pollutant emissions per unit energy delivered to a radiator. The average reductions were ∼50% for CO2, 79% for PM2.5, 95% for EC, 85% for benzo[a]pyrene equivalent carcinogenic potency, and 66% for eight selected toxic elements (Pb, Cu, Sb, Cd, As, Ag, Se, and Ni) in PM2.5. Improvements in stove technology are demonstrated as a practical approach for improving TE and reducing emissions of hazardous pollutants and CO2.

Dispatches

Dispatches

The Effects of Compression Pressure Applied on the Manufacture of Carbon Composite Bipolar Plate for PEMFC by Utilizing Graphite Waste Products

Proton electrolyte membrane fuel cells (PEMFC) have near zero carbon dioxide and hazardous pollutant emission. Thus, it is considered as one of energy sources for transportation and other application which can improve environmental performance by decreasing the emission of greenhouse gases and other air pollutant. In accordance with its environmental preservation values, graphite waste product from electric arc furnace (graphite EAF) was chosen as a potential candidate material for bipolar plate for PEMFC. The utilization of graphite waste product is expected to result in light-weight and cost-effective bipolar plates. In this paper, we used graphite EAF as a filler together with carbon black and epoxy resin as a binder. We examined the effects of differential pressure applied on compression molding process on density, porosity, flexural strength and electrical conductivity of the resulting carbon polymer composite bipolar plate. Pressure was applied from 30 MPa - 60 MPa in increments of 5 MPa while maintaining constant temperature operation at 700C for 4 hours. Maximum value of bipolar plate density was achieved at application 55 MPa, of 1.69 g/cm3. At this condition, the flexural strength was measured to be 48 MPa with the porosity of 0.7%, and electrical conductivity of 1.03 S/cm. Taken together, we demonstrated that graphite EAF is a good candidate for the manufacturing of polymer composite bipolar plates.

Fine particle and trace element emissions from an anthracite coal-fired power plant equipped with a bag-house in China

Fine particle and trace element emissions from energy production are associated with significant adverse human health effects. In this investigation, the fine particles and trace elements emitted from the combustion of pulverized anthracite coal at a 220MW power plant were determined experimentally in the size range from 30nm to 10μm with 12 channels. The particulate size distributions and morphological characteristics before and after the bag-house were evaluated. The uncontrolled and controlled emission factors of particles are compared with the calculated values from the US Environment Protection Agency, AP-42. Size-classified relative enrichment factors of As, Hg, Se, Cd, Cr, Cu, Al, V, Zn, Mn, Fe were obtained. Relative distributions of trace elements between bottom ash, fly ash and flue gas are determined by mass balance method. The bag-house collection efficiencies of particles and trace elements in the particulate phase are obtained. Finally, the controlled and uncontrolled emission factors of elements of different particulate size fractions are obtained, which will provide useful information for PM2.5 and PM10 emission inventory development, toxic and hazardous pollutant emission estimates and emission standards established for metal-based pollutants from a pulverized coal-fired boiler.

Catalytic wet-air oxidation processes: A review

Environmental catalysis usually refers to end-of-the-pipe treatment processes that reduce the emissions of hazardous pollutants. Abatement of pollutants in aqueous streams by means of heterogeneous catalysts is an example of such process. This paper reviews the developments in the field of catalytic wet-air oxidation (CWAO). Catalysts are reviewed first, followed by mechanistic speculations and kinetics that have been proposed for the CWAO process. The process is discussed more in detail only in those cases where it is already commercialised or at least foreseen to be in the near future. Particular attention was given to the heterogeneously catalyzed wet-air oxidation of real industrial wastewaters (such as Kraft bleach plant effluents) in batch and continuous-flow oxidation reactors. Finally, the considerable potential of the CWAO process to ultimately destroy organic pollutants in industrial effluents and detoxify them by using novel titania-supported Ru catalysts is presented.