Abatement Systems Research Articles

Monitoring the residual capacity of activated carbon in an emission abatement system using a non-contact, high resolution microwave resonator sensor

The accumulation of non-desorbed species or heel buildup reduces the capacity and lifetime of adsorbents used in cyclic adsorption/desorption processes. This study investigates the changes in the physical, chemical, and dielectric properties of beaded activated carbon (BAC) and their relation to the adsorbent residual capacity (i.e., residual lifetime) during cyclic adsorption/desorption using a non-contact, high-resolution microwave resonator sensor. The resonant frequency of the sensor responds to changes in the dielectric properties of the medium surrounding the sensor. BAC samples with different degrees of capacity reduction as indicated by the apparent density, BET surface area, total pore and micropore volumes were tested. A linear correlation (R2 = 0.93) between the apparent density of the BAC samples and the resonant frequency shift of the sensor was observed, irrespective of heel composition indicating that the effect of adsorbent porosity on dielectric property variation is more important than heel composition. The sensor’s ability for fast and continuous measurement makes it an ideal candidate for real-time monitoring of adsorbent capacity status in cyclic adsorption/desorption processes.

Energy, exergy, environmental and economic analysis of hybrid waste-to-energy plants

Recently, studies have been evaluating the thermodynamic performance of new configurations of integrated waste-to-energy/gas turbine cycles, but a question still remains: “Instead of building new natural gas power plants or installing conventional waste-to-energy facilities, should one be investing in flexible efficient hybrid plants?” This article aims at presenting a novel comprehensive approach to help answering this question. The strategy intends to demonstrate how to integrate four known key procedures (energy, exergy, economic and environmental analysis) in an original manner in order to evaluate the feasibility of such systems. The technique consists of a conventional Energy-Exergy analysis followed by a new Environmental-Economic approach. The novelties are in the economic and environmental parts, namely: (i) the use of multiple cost equations for estimating the plant’s initial investment range and (ii) the indirect estimate of the pollution abatement system cost through an energy-ecological efficiency indicator. A case study configuration (similar to the existing plant of Bilbao) is used as exercise to demonstrate the method and its comparability potential, as well as to allow discussion using tangible results. The case-studied plant has a power output capacity of 107 MWe, thermal efficiency of 36%, ecological efficiency of 89%, thermal waste input capacity of 155 MWt and levelized cost of electricity production of US$ 64–89 per MWh. It is compared to several existing single-fueled waste-to-energy facilities and other energy sources, including renewable and non-renewable. As unique findings of this research, it is shown that the proposed economic method allows to predict costs quite accurately and that the specific investment costs of such technology are very attractive compared to existing single-fueled waste-to-energy facilities in Europe and other electricity sources in the Brazilian context. The proposed method proved to be a comprehensive procedure to analytically evaluate the feasibility of hybrid waste-to-energy power plants, which present good potential in the Energy conversion field.

Structured glass catalytic coating on wire mesh for particulate matter (PM) removal by modified sol-gel processing

K-containing soot oxidation catalysts are promising to reduce or replace noble metal usage in combustion engine emission abatement systems. In this paper, we introduce a facile approach for applying a K-containing glass catalyst onto structured wire mesh monoliths to achieve low temperature soot removal. A polyvinyl butyral (PVB) modified sol-gel process was developed to yield a crack-free thickness that is 6 times that of the conventional sol-gel process. An intermediate SiO2 barrier layer was found to be effective to insure stability of the glass catalyst over extended cycling periods. The catalytically coated wire mesh can lower the soot ignition temperature (Tig) to ∼370 °C with O2, and offers catalytic stability for long term combustion cycling.

Metal waste dusts from mechanical workings - explosibility parameters investigation

The reactivity of metal scraps or fine particles, typical residual wastes of mechanical workings, is significantly high to cause violent deflagration when particles disperse in the air in the form of clouds. However, literature information is scarce regarding the explosive risks of mixtures of pure metals, oxides and other impurities (like waste dust) whereas the form the bulk of materials in abatement systems and bag filters in the metal industry. Mechanical working could produce a different type of dust, depending on the process, the source material, and the operating conditions, main differences are in the particle size distribution, oxide content and morphology of samples.The present study investigates several samples of metal/oxide dust mixtures. The results of this work help to recognize the most hazardous dust in term of ignition sensibility when dispersing in clouds. The dust from sanding and welding processes fall into this group, while dust from laser-cutting does not ignite with standard ignition sources (like an electric arc or a hot wire). The work also aimed to establish a correlation between sample properties and explosibility parameters, like KST and Pmax. The results indicate a direct proportionality between these values and the particle size distribution of samples (in particular with the d-tenth percentile of the mass distribution) and with the metal oxide content. Additional research is needed to assess the influence of other variables (morphology, chemical composition) and the actual hazards related to different mechanical workings to prevent and mitigate explosive events.

Effect of the impurity magnesium nitrate in the thermal decomposition of the solar salt

Nowadays, the most matured thermal energy storage (TES) technology for Concentrated Solar Power (CSP) plants is the use of molten solar salts (60 wt% NaNO3 – 40 wt% KNO3), but the thermal decomposition of nitrate salts can result in changes in the composition of molten salts or potential risks of NOx emissions. Up to now, all studies on the decomposition of nitrates in TES systems focus on the effect of the effect of sodium and potassium nitrates in contact with the container material and the NOx emissions formation, but none investigate the effect or contribution of impurities in it. Moreover, although the chemistry of the nitrates decomposition is well known, there is a big uncertainty in commercial solar plants on the production rate of NOx. The only cation in nitrates from mining origin is magnesium, and since it occurs as nitrate, it does contribute to NOx formation. This paper studies the effect of such impurity in the thermal decomposition of the solar salt. The results show that the impurity Mg(NO3)2 is the main source of NOx emissions in solar salts during the commissioning of the plant due to its thermal decomposition during the melting process. But as described this NOx production can be handled by vents and abatement systems if it is needed.

Indirect environmental benefits of a variable set-point for HCl emission in waste-to-energy flue gas cleaning

Hydrogen chloride (HCl) is a typical contaminant generated in waste combustion, whose emission is strictly regulated. In order to cope with severe limits issued by local authorities on the annual mass flow of HCl emitted, several European waste-to-energy plants perform at least a two-stage abatement of the pollutant and operate with a set-point for HCl concentration at stack well below the hourly emission limit imposed by the Industrial Emissions Directive. Even though the operating conditions in a WtE facility are highly variable (both in terms of HCl release from the burnt waste and of operating temperature of the HCl removal system), it is common industrial practice to keep both the set-point for HCl concentration at stack and the set-point for HCl concentration between the two abatement stages at a constant value. However, this might force the abatement system to operate far from its design conditions and from the optimal reactivity window of the adopted HCl removal agent, thus increasing the consumption rate of reactant and the consequent generation rate of process residues. Both the supply chain of reactants and the management of residues generate environmental impacts. The present work demonstrates that the adoption of variable values for both set-points can provide cost savings and indirect environmental benefits, thanks to the reduction of reactant consumption and residue generation. By considering as case study a WtE plant equipped with a two-stage dry HCl removal system, a year of operation of the plant was analysed. The operating costs and life cycle impacts generated by the actual operation of the HCl treatment system with constant set-points were compared with those generated if the plant had operated with variable set-points, simulated with a semi-empirical model for HCl removal tuned on historical process data from the plant. A 13 % reduction of the life cycle global warming impact and an 8 % reduction of the life cycle acidification impact, in addition to 10 % cost savings, were associated to the utilisation of variable set-points.

INCREASING THE EFFICIENCY OF INTERNAL COMBUSTION ENGINES: HEAT RECOVERY FROM EXHAUST GASES BY THERMOELECTRIC EFFECT

The concern related to global warming is generating a legislative pressure on reducing CO2 emissions that is forcing automotive industry to find alternative and more efficient solutions to internal combustion engines. In Europe, the current regulation for passenger vehicles limits the CO2 emissions calculated as fleet average to 130 g/km and fix a target value of 95 g/km to be achieved by 2021. Car manufacturers will have to pay heavy penalties for each registered vehicle exceeding the CO2 limits (€95 per exceeding gram by 2019). Concurrently, the regulations on toxic emissions (CO, NOx, unburned hydrocarbons, particulate matter) is also becoming more and more stringent and requires complex and costly abatement systems to respect the strict limitations imposed on NOx and particulate matter emissions. On the other hand, zero emission electric vehicles, based on batteries, are still not mature enough for a replacement of the internal combustion engine in extra-urban applications, since they are not able to guarantee the driving range required by customers. Hydrogen fuelled vehicles, could meet the same performance of conventional cars, but the cost of materials used in the fuel cell stack is preventing the penetration into the market. Therefore, even though characterized by low energy efficiency, the internal combustion engine will remain, in the short-medium term, the reference technology for the transport industry but the environmental regulations will impose its hybridization with electric systems. Hybrid architectures allow circulating in electric mode in urban areas, limiting the local pollution, and increase the efficiency of the car through energy recovery during breaking phases. An energetic analysis of conventional internal combustion engine reveals that about 70% percent of the chemical energy stored in the fuel is converted in to mechanical energy for traction: the remaining part is dissipated as heat in the exhaust gases (30%) and in the cooling circuit (40%). So a great amount of thermal energy (tens of kW) is available on a car and its effective recovery can dramatically increase the efficiency of the system. Hybrid systems facilitate this task, since the produced electric energy can be stored in the battery pack. Thermoelectric generators (TEGs) offer the possibility to directly convert thermal energy into electricity with a reduced complexity and potential low cost. Even though available semiconducting junctions are characterized by low efficiency and limited operating temperatures, coupling a TEG to the internal combustion engine would allow recovering about 1 kW of electric power on a medium size car, with a reduction of CO2 emissions of about 10 g/km.

Cost estimate of the multi-pollutant abatement in coal-fired power sector in China

Seriously stringent emission regulations are applied in the coal-fired power sector in China. GB13223-2011 standards and ultra-low emission limits are promulgated to improve the application of pollutant abatement systems and reduce emissions, respectively. However, the accompanying problem of additional economic burden may affect the operation of power units and sectors. This study proposed a cost estimate model of multi-pollutant control and designed several scenarios to evaluate the total cost of different emission standards in China's coal-fired power sector. The operating costs of NOx, SO2, and PM control of a typical 300 MW unit were 6.9, 11.7, and 4.3 CNY/MWh, respectively, when meeting the GB13223-2011 emission standard and 8.2, 13.8, and 7.9 CNY/MWh, respectively, when meeting the ultra-low emission limits. Investment, energy consumption, and catalyst greatly influenced the operating cost. The scenarios analysis suggested that the total costs of multi-pollutant control under the GB13223-2011 standards and ultra-low emission limits were approximately 141.79–170.28 and 186.35–221.67 billion CNY per year, respectively. Feasible cost reduction strategies were analyzed on the basis of operation management and sector planning. The economic influence of the application of pollutant abatement systems on coal-fired power units should be evaluated comprehensively.

Energy consumption and energy-saving potential analysis of pollutant abatement systems in a 1000-MW coal-fired power plant

ABSTRACTPollutant abatement systems are widely applied in the coal-fired power sector, and the energy consumption is considered an important part of the auxiliary power. An energy consumption analysis and assessment model of pollutant abatement systems in a power unit was developed based on the dynamic parameters and technology. The energy consumption of pollutant abatement systems in a 1000-MW coal-fired power unit that meets the ultra-low emission limits and the factors of operating parameters, including unit load and inlet concentration of pollutants, on the operating power were analyzed. The results show that the total power consumption of the pollutant abatement systems accounted for 1.27% of the gross power generation during the monitoring period. The wet flue gas desulfurization (WFGD) system consumed 67% of the rate, whereas the selective catalytic reduction (SCR) and electrostatic precipitator (ESP) systems consumed 8.9% and 24.1%, respectively. The power consumption rate of pollutant abatement systems decreased with the increase of unit load and increased with the increase of the inlet concentration of pollutants. The operation adjustment was also an effective method to increase the energy efficiency. For example, the operation adjustment of slurry circulation pumps could promote the energy-saving operation of the WFGD system.Implications: The application of pollutant abatement technologies increases the internal energy consumption of the power plant, which will lead to an increase of power generation costs. The real-time energy consumption of the different pollutant abatement systems in a typical power unit is analyzed based on the dynamic operating data. Further, the influence of different operating parameters on the operating power of the system and the possible energy-saving potential are analyzed.

A comparison of removal performance of volatile organic and sulfurous compounds between odour abatement systems

Three types of odour abatement systems in sewer networks in Australia were studied for 18 months to determine the removals of different compounds. Six volatile sulfurous compounds and seven volatile organic compounds (VOCs) were further investigated. All types of odour abatement systems exhibited good removal of hydrogen sulfide with the biotrickling filters (BTFs) showing the highest consistent removal. Biofilters outperformed BTFs and activated carbon (AC) filters in the removal of dimethyl mono-, di- and tri-sulfide species at the low inlet concentrations typically found. AC filters exhibited little VOC removal with no compound consistently identified as having a removal greater than 0%. Biofilters outperformed BTFs in VOC removal, yet both had high removal variability.

Rare earth ions doped ZnO: Synthesis, characterization and preliminary photoactivity assessment

This work reports the effect of doping zinc oxide with lanthanide ions on structural, EPR and UV visible properties. Bare and doped samples were synthesized using the simple and green hydrothermal process. Different rare earth ions (RE = La, Ce, Pr, Er and Yb) with 1% molar ratio RE/Zn were used. The samples have been studied using X Ray Diffraction, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and UV visible diffuse reflectance spectroscopy. Finally, electron paramagnetic resonance (EPR) spectroscopy, was used to assess the materials photoactivity under UV irradiation, both in solid state, to see the charge carriers’ generation and in solution, evaluating the OH• radical formation using the DMPO (5,5-Dimethyl-1-Pyrroline-N-Oxide) spin trapping technique. The results suggest that the synthesized materials could be interesting systems for the photocatalytic abatement of emerging organic persistent pollutants in wastewater treatment plants.

How to combine CO2 abatement and starch production in Chlorella vulgaris

Microalgae production has gained attention in recent years as promising systems for CO2 abatement as well as a source of proteins, pigments, vitamins, lipids, and carbohydrates. Particularly, starch can be used for bioethanol production in a well-established fermentative process. The aim of this work was to maximize and model biomass productivity and CO2 assimilation in continuous cultures of Chlorella vulgaris. The following culture parameters were studied: dilution rate, pH, temperature, light intensity, and nitrogen supply. The proposed model (r2 = 0.95) predicted a maximum biomass productivity of 0.7 g L−1 d−1 and CO2 assimilation of 1.3 g L−1 d−1. The experimental data agreed with these predictions, resulting in a maximum biomass productivity of 0.67 g L−1 d−1 (resulting in a CO2 assimilation of 1.23 g L−1 d−1). In addition, the starch content was determined, and the results were used as input into a second model, which aimed at predicting starch accumulation during CO2 abatement processes (r2 = 0.84). This second model predicted a daily and continuous production of biomass with a maximum starch content of 0.25 g g−1 d−1 (25% dcw), but under different culture conditions than those found for maximizing biomass productivity and CO2 assimilation. The maximum starch content experimentally determined was 0.2 g g−1 d−1 (20% dcw). Thus, to implement a biological system for CO2 abatement coupled to starch accumulation, it is necessary to find a compromise between these two processes. Hence, although yield in both processes would be reduced, a simultaneous process for CO2 mitigation and starch production would be feasible.

Sewer catchment effects on wastewater and biosolids odour management.

The composition of wastewater in sewer catchments is known to affect the performance of wastewater treatment plants (WWTPs). However, there is limited knowledge as to how catchment characteristics, such as types of catchment industries, impact odour emissions from downstream sludge processing and biosolids management. Odorous emissions from biosolids processing at WWTPs can represent a significant community impact when the local population is exposed to odours. The main odorants emitted from biosolids are volatile sulfur compounds (VSCs), however, volatile organic compounds (VOCs) in emissions may also be perceptable after the removal of VSCs in odour abatement systems. Types of compounds present in emissions throughout biosolids processing at five WWTPs of varying sizes and levels of treatment (primary only and primary and secondary) were analysed. The ratio of total VSCs to VOCs in emissions, and the sensorial importance of each class varied between the sites. As a number of the VOCs in emissions were of industrial origin, this variation is likely dependent on industrial flows into the upstream sewer catchment. The impact of different emission compositions on both activated carbon and biologically based odour abatement systems were discussed.

Factors affecting the adsorption of gaseous environmental odors by activated carbon: A critical review

ABSTRACTActivated carbon has a long history of application to abate gaseous environmental odors; however, design and operating decisions are primarily based on empirical relations and pilot testing, with limited use of fundamental mechanistic knowledge. To support improved abatement outcomes, environmental odorant adsorption was reviewed. While influenced by a range of adsorbate and adsorbent properties and process operating conditions, information about their impacts is often limited or unavailable. Current research has focused on volatile sulfur compounds, with lesser focus on volatile organic compounds and volatile nitrogen compounds. Even within volatile sulfur compounds, most work has focused on hydrogen sulfide and the full range of reduced sulfur compounds (important environmental odorants) remain to be studied. The current narrow window of knowledge does not reflect the complexity of environmental odorants and is limiting development and systematic application of this technology. It has been demonstrated that single component adsorbent characterization does not reflect the adsorption of the complex mixture of odorants and non-odorous compounds that make up environmental odor emissions. Studies to explore adsorption competition in multi-compound systems and develop methods/guidance to account for this in abatement system selection and design are required to achieve cost effective and reliable outcomes.

Radon mitigation during the installation of the CUORE 0νββ decay detector

CUORE—the Cryogenic Underground Observatory for Rare Events—is an experiment searching for the neutrinoless double-beta (0νββ) decay of 130Te with an array of 988 TeO2 crystals operated as bolometers at ∼10 mK in a large dilution refrigerator. With this detector, we aim for a 130Te 0νββ decay half-life sensitivity of 9×1025 y with 5 y of live time, and a background index of ≲ 10−2 counts/keV/kg/y. Making an effort to maintain radiopurity by minimizing the bolometers' exposure to radon gas during their installation in the cryostat, we perform all operations inside a dedicated cleanroom environment with a controlled radon-reduced atmosphere. In this paper, we discuss the design and performance of the CUORE Radon Abatement System and cleanroom, as well as a system to monitor the radon level in real time.

Thermal Abatement of Perfluorocompounds with plasma torches

Perfluorocompounds (PFCs) have long lifetimes and high global-warming potentials. PFCs include CF4, C2F6, C3F8, CHF3, SF6, NF3, etc., which are widely used in the electronic industries. Although the atmospheric concentrations of PFCs are currently much lower than CO2, the annually increasing rate of CF4 and SF6 are 3.3 and 12 times higher than CO2, respectively. A thermal plasma torch can offer an extremely high temperature stream for thermal decomposition of PFCs, and is regarded as a state-of-the-art technology for PFC emission control. In the study a thermal plasma torch is designed and experimentally tested for PFC abatements. Results show that PFC abatements are mainly determined by the plasma power, gas flow rate, and PFC’s concentration. The effects of operational parameters are further evaluated by the multiple regressions and the sensitivity analysis. For CF4, the most significant factor to the removal efficiency is the plasma power, and the flow rate plays a negative role. In addition, the most sensitive factor to the energy efficiency goes to the CF4 concentration. There is a trade-off between abatement efficiency and the energy efficiency. Thermal plasma torches can easily achieve high PFCs abatement efficiencies by an increase of plasma power. From an energy viewpoint, a thermal PFCs abatement system is better operated for streams with higher PFC concentrations. Therefore, installation of a PFCs concentrated unit in front of thermal plasma torch should be a good option in viewpoint of both abatement efficiency and energy efficiency.

Attenuation of low-frequency underwater sound using an array of air-filled balloons and comparison to effective medium theory.

The ultimate goal of this work is to accurately predict the attenuation through a collection of large (on the order of 10-cm-radius) tethered encapsulated bubbles used in underwater noise abatement systems. Measurements of underwater sound attenuation were performed during a set of lake experiments, where a low-frequency compact electromechanical sound source was surrounded by different arrays of encapsulated bubbles with various individual bubbles sizes and void fractions. The measurements were compared with an existing predictive model [Church, J. Acoust. Soc. Am. 97, 1510-1521 (1995)] of the dispersion relation for linear propagation in liquid containing encapsulated bubbles. Although the model was originally intended to describe ultrasound contrast agents, it is evaluated here for large bubbles, and hence low frequencies, as a design tool for future underwater noise abatement systems, and there is good quantitative agreement between the observations and the model.

The impact of light and heavy hydrocarbons on the NH3-SCR activity of commercial Cu- and Fe-zeolite catalysts

Low temperature operation of NH3-SCR systems for NOx abatement in lean burn and Diesel engines poses new demanding challenges due to the necessity of solving issues related to poor catalyst activity, urea injection management and system control. A typical example of these problems is represented by unconverted hydrocarbons (HCs) slip (e.g. during cold start or long idling) onto the SCR catalyst leading to a subsequent decrease of the DeNOx activity. In the present work, a detailed evaluation of the impact of different hydrocarbons (namelyC3H6 and C10H22) on the performances of two new generation commercial zeolite SCR catalysts promoted with Fe and Cu is carried out by means of transient response method (TRM) experiments. Particular attention is devoted to elucidate the interaction between HCs and the typical constituents of SCR feed such as NH3, NO, NO2, O2 and H2O and their influence on the overall reactivity, in order to possibly clarify the associated mechanistic steps.

Very low emissions of airborne particulate pollutants measured from two municipal solid waste incineration plants in Switzerland

A field campaign has been performed in two municipal solid waste incineration (MSWI) plants in Switzerland, at Hinwil (ZH) and Giubiasco (TI). The aim was to measure airborne pollutants at different locations of the abatement systems (including those released from the stacks into the atmosphere) and at a near-field (∼1 km) downwind site, in order to assess the efficiency of the abatement systems and the environmental impact of these plants.During this study, we measured the particle number concentration with a condensation particle counter (CPC), and the size distribution with a scanning mobility particle sizer (SMPS) and an aerodynamic particle sizer (APS). We also sampled particles on filters for subsequent analyses of the morphology, size and elemental composition with a scanning electron microscope coupled to an energy dispersive X-ray spectroscope (SEM/EDX), and of water soluble ions by ion chromatography (IC). Finally, volatile organic compounds (VOCs) were sampled on adsorbing cartridges and analyzed by thermal desorption-gas chromatography/mass spectrometry (TD-GC/MS), and a portable gas analyzer was used to monitor NO, SO2, CO, CO2, and O2.The particle concentration decreased significantly at two locations of the plants: at the electrostatic precipitator and the bag-house filter. The particle concentrations measured at the stacks were very low (<100 #/cm3), stressing the efficiency of the abatement system of the two plants. At Hinwil, particles sampled at the stack were mainly constituted of NaCl and KCl, two salts known to be involved in the corrosion process in incinerators. At Giubiasco, no significant differences were observed for the morphology and chemical composition of the particles collected in the ambient background and at the downwind site, suggesting that the incineration plant released very limited amounts of particles to the surrounding areas.

Corrosion behavior of materials in hydrogen sulfide abatement system at Hellisheiði geothermal power plant

Corrosion tests were conducted in a gas-separation tower of a H2S abatement system at Hellisheiði power plant in Iceland. The susceptibility to uniform corrosion and environmentally assisted cracking of several materials were investigated, including the main construction material of the abatement system i.e., the austenitic stainless steel UNS S31603. The results show that the UNS S31603 and UNS S31803 showed no signs of corrosion damage while UNS S30403 experienced environmentally assisted cracking most likely in the form of stress corrosion cracking. The carbon steel S235JR tested was severely damaged by hydrogen induced cracking, and uniform corrosion.