Deposition Efficiency Research Articles

10 Validation of an Aerosol Exposure-Air Liquid Interface (AE-ALI) System to Facilitate Realistic Hazard Identification of Nano-Sized Aerosols

Abstract To facilitate hazard characterisation for inhaled engineered nanomaterials we have established an aerosol exposure air-liquid-interface (AE-ALI) system, incorporating a Cultex RFSTM cell exposure system. While offering potential benefits in terms of more realistic aerosol exposure mode over traditional submerged in vitro models and being in-line with the principles of the 3Rs, (replace, reduce and refine animal use), detailed system characterisation is required to produce reliable and reproducible results. As such, this work looked to fully characterise our AE-ALI system with a view to optimising cell viability of system controls and deposition quantity, uniformity, and reproducibility for engineered nanomaterials. Using a nano-CeO2 aerosol, the effects of exposure conditions and system parameters (e.g. temperature, electrostatic precipitator voltage and airflow) on deposition efficiency, pattern and reproducibility were investigated using ICP-MS. While results showed that appropriate choice of operating parameters can produce broadly uniform deposition, reproducibility was low, and dose monitoring during exposures is recommended. After initial optimisation of the system for deposition, the effect of exposure duration, well size and flowrate on cellular responses (e.g. cytotoxicity (LDH) and selected gene expression (IL-8, CXCL1, HMOX1, SPP1) of system controls (H2O aerosol) was investigated using human lung alveolar (A549) and primary small airway epithelial cells. Results indicate that even after optimisation for cell health, the system itself is “toxic” to cells in comparison to incubator controls, with increasing effects observed with exposure duration meaning exposure durations must be minimised. Results from this study highlight the need for detailed characterisation of AE-ALI systems prior to use.

"H" sprayer effect on liquid deposition on cucumber leaves and powdery mildew prevention in the shed.

To clarify the effect of droplet size on solution deposition and powdery mildew control on greenhouse cucumber leaves, the effect of volume median droplet diameter (VMD) on solution deposition and maximum retention, as well as the effect of flusilazole on powdery mildew control on cucumber, was determined using the stem and leaf spray method. The VMD of the typical fan nozzles (F110-01, F110-015, F110-02, F110-03) of the selected US Tee jet production differs by approximately 90 μm. The results showed that the deposition of flusilazole solution on cucumber leaves decreased as the VMD of the droplets increased and that the deposition of the solution in the treatments with VMD of 120, 172, and 210 μm decreased by 22.02%, 10.37%, and 46. 97%, respectively, compared to that observed with treatment with 151 μm VMD. The deposition of the solution on cucumber leaves showed the highest deposition efficiency of 63.3% when the applied solution volume was 320 L/hm2, and the maximum stable retention of the liquid on the leaves was 6.6 µl/cm2. The control effects of different concentrations of flusilazole solution on cucumber powdery mildew differed significantly, and the best control effect was achieved at the dosage of 90 g/hm2 of the active ingredient, which was 15%-25% higher than that observed at the dosage of 50 and 70 g/hm2 of the active ingredient per hectare. A significant difference in the effect of droplet size on the control of cucumber powdery mildew was observed at any specific liquid concentration. Nozzle F110-01 showed the best control effect when the dosage of the active ingredient was 50 and 70 g/hm2 per hectare, which did not differ significantly from that observed with nozzle F110-015 but differed significantly from those observed with nozzles F110-02 and F110-03. Hence, we concluded that the use of smaller droplets with VMD of 100-150 μm, i.e. the choice of F110-01 or F110-015 nozzles, for application on the leaf parts of cucumber in the greenhouse under conditions of high liquid concentration, can significantly improve the effective use of pharmaceuticals and the disease control effect.

Computational fluid-particle dynamics modeling of ultrafine to coarse particles deposition in the human respiratory system, down to the terminal bronchiole

Background and objectivesSuspended respirable airborne particles are associated with human health risks and especially particles within the range of ultrafine (< 0.1 μm) or fine (< 2.5 μm) have a high possibility of penetrating the lung region, which is concerned to be closely related to the bronchial or alveoli tissue dosimetry. Nature complex structure of the respiratory system requires much effort to explore and comprehend the flow and the inhaled particle dynamics for precise health risk assessment. Therefore, this study applied the computational fluid-particle dynamics (CFPD) method to elucidate the deposition characteristics of ultrafine-to-coarse particles in the human respiratory tract from nostrils to the 16th generation of terminal bronchi. MethodsThe realistic bronchi up to the 8th generation are precisely and perfectly generated from computed tomography (CT) images, and an artificial model compensates for the 9th-16th bronchioles. Herein, the steady airflow is simulated at constant breathing flow rates of 7.5, 15, and 30 L/min, reproducing human resting-intense activity. Then, trajectories of the particle size ranging from 0.002 – 10 μm are tracked using a discrete phase model. ResultsHere, we report reliable results of airflow patterns and particle deposition efficiency in the human respiratory system validated against experimental data. The individual-related focal point of ultrafine and fine particles deposition rates was actualized at the 8th generation; whilst the hot-spot of the deposited coarse particles was found in the 6th generation. Lobar deposition characterizes the dominance of coarse particles deposited in the right lower lobe, whereas the left upper-lower and right lower lobes simultaneously occupy high deposition rates for ultrafine particles. Finally, the results indicate a higher deposition in the right lung compared to its counterpart. ConclusionsFrom the results, the developed realistic human respiratory system down to the terminal bronchiole in this study, in coupling with the CFPD method, delivers the accurate prediction of a wide range of particles in terms of particle dosimetry and visualization of site-specific in the consecutive respiratory system. In addition, the series of CFPD analyses and their results are to offer in-depth information on particle behavior in human bronchioles, which may benefit health risk assessment or drug delivery studies

High-Temperature Oxidation Behaviour of CrSi Coatings on 316 Austenitic Stainless Steel.

In this study, a closed-field unbalanced magnetron sputtering system, which is environmentally friendly and has high deposition efficiency, was used to deposit CrSi coatings on 316 austenitic stainless steel. This system utilised separate Cr and Si targets, and the appropriate content of Cr and Si of the coatings was adjusted by changing the currents applied to the targets. A series of CrSi coatings with different Si/Cr ratios were produced, and their oxidation behaviour at elevated temperatures was investigated. By analysing the weight gain, surface morphology and microstructure, composition and phase constituents, the oxidation behaviour at 600 °C, 700 °C and 800 °C was investigated and the optimized coating to protect the stainless steel has been identified. The outcome of the research indicated that a small amount of Si (between 4-7 at.%) in Cr coatings is effective in protecting the austenitic stainless steel against oxidation at high temperatures, while a high Si content (around 10 at.% or more) makes the coating more brittle and prone to cracking or delamination during oxidation at 800 °C.

Cold sprayed AlNiCoFeCr–TiB2 metal matrix composite coatings

In this work, the mechanically alloyed AlNiCoFeCr high entropy alloy (HEA) was used as matrix to develop metal matrix composite (MMC) coatings. Dense and thick AlNiCoFeCr – 30 wt % TiB2 MMC coatings were firstly fabricated by solid-state cold spraying (CS) technique at the low pressure of 0.9 MPa, and temperature of 300 and 450 °C. The effect of compressed air flow temperature and pressure parameters on structure and mechanical properties of coatings were established. As a low-temperature deposition process, CS completely retained the phase composition and nanostructure in the coatings without any phase transformation. With an increase in pressure up to 0.9 MPa a refinement of the coating structure and a double increase in the fraction of TiB2 particles in the coating were detected. An increase in temperature at least to 300 °C breaks down the oxide layers of the particles, multiplying the deposition efficiency and the properties of the coatings. The coatings fabricated at a spraying temperature of 450 °C and a compressed air flow pressure of 0.9 MPa exhibit the average thickness of 1110 μm, as well as a good combination of high microhardness (6.9 GPa) and sufficient indentation fracture toughness (3.8 MPa∙m1/2).

Prediction of Deposition Rate in Meniscus‐Confined Electrodeposition Based on Parameter Optimization Algorithm

Meniscus‐confined electrodeposition (MCED) is a potential approach to fabricate 3D metallic microstructures and can be used in microelectromechanical systems, optoelectronics, and flexible electrical interconnections. However, deposition efficiency and the quality of the microstructures obtained by this method on optimal parameters are identified by a large number of comparative experiments, resulting in high cost and inefficient practices. For this reason, herein, the fabrication process of metal microstructures by MCED simulation and optimizes parameters affecting deposition quality and rate is investigated. First, the finite‐element method is used to simulate the voltage and copper ion concentration identifies the target range. Then, the electrodeposition rate 1 × 10−7 m s−1 is set as the target value. The best applicable values of 0.29 V and 0.46 m are obtained after optimizing the voltage and copper ion concentration that affects the quality of deposited microstructures and rate of MCED based on the genetic algorithm (GA), cuckoo search (CS) algorithm, and support vector regression (SVR) algorithm. Finally, simulations and experiments are carried out according to the optimized parameters values. The results show that the maximum error of deposition rate is 7.9%. This study pioneers a new approach to achieving efficient and high‐quality deposition by MCED.

Study on Process Parameters of Aluminium Alloy Oscillating Laser Double-wire Additive Manufacturing

To improve the deposition efficiency and forming quality of laser fuse additive manufacturing, this paper combines the advantages of oscillating laser and double-wire additive manufacturing to realize oscillating laser double-wire additive manufacturing. The feasibility of the scheme is verified through experiments, and a corresponding three-dimensional simulation model is established. Through the comparison of experiment and simulation, the forming fit is good and the accuracy of the model is verified. Finally, the forming effects under different laser oscillating frequencies and oscillating amplitudes are studied through the simulation model. The results show that the appropriate oscillating amplitude can preheat the substrate and improve wettability. The laser oscillating frequency is inversely proportional to the forming width, and a high oscillating frequency can improve the forming effect.

Effect of surfactant concentration in modifying solution on corrosion properties of the coatings based on vinyltrimethoxysilane (VTMS) and poly(3,4-ethylenedioxythiophene) (PEDOT)

This paper presents an analysis of the structure and physicochemical properties of coatings based on an organofunctional silane (VTMS), a conductive polymer (PEDOT), and a surfactant (polyoxyethylene glycol monolauryl ether BRIJ).The coatings were deposited on X20Cr13 stainless steel and glassy carbon specimens using sol-gel immersion. The obtained coatings were characterised in terms of topography, microstructure, roughness, adhesion to the steel substrate, thickness, and corrosion resistance. Corrosion tests were conducted in sulfate environments with pH = 2 without or with the addition of Cl- ions.The use of different surfactant concentrations in the modifying solution is intended to improve the deposition efficiency and increase the degree of dispersion of silane and conducting polymer.The tested coatings were found to slow down the corrosion of the steel substrate, thus effectively protecting it from this phenomenon. The use of a surfactant compound is intended to increase the degree of dispersion of silane and polymer in the modifying solution to improve deposition efficiency.Test carried out in corrosive media have shown that the coatings proposed in the above work, based on VTMS silane, PEDOT polymer and BRIJ surfactant, significantly increase the corrosion resistance of the tested materials, which confirms their effectiveness and possibility of application in various industries.The novelty of this paper is the use of silane (VTMS), polymer (PEDOT) and surfactant (BRIJ) as components of the anticorrosion coating.

Hydrodynamics and Nucleosynthesis of Jet-driven Supernovae. I. Parameter Study of the Dependence on Jet Energetics

Rotating massive stars with initial progenitor masses M prog ∼ 25–140 M ⊙ can leave rapidly rotating black holes to become collapsars. The black holes and the surrounding accretion disks may develop powerful jets by magnetohydrodynamics instabilities. The propagation of the jet in the stellar envelope provides the necessary shock heating for triggering nucleosynthesis unseen in canonical core-collapse supernovae. However, the energy budget of the jet and its effects on the final chemical abundance pattern are unclear. In this exploratory work, we present a survey on the parameter dependence of collapsar nucleosynthesis on jet energetics. We use the zero-metallicity star with M prog ∼ 40 M ⊙ as the progenitor. The parameters include the jet duration, its energy deposition rate, deposited energy, and the opening angle. We examine the correlations of the following observables: (1) the ejecta and remnant masses; (2) the energy deposition efficiency; (3) the 56Ni production and its correlation with the ejecta velocity, deposited energy, and the ejected mass; (4) the Sc–Ti–V correlation as observed in metal-poor stars; and (5) the [Zn/Fe] ratio as observed in some metal-poor stars. We also provide the chemical abundance table of these explosion models for the use of the galactic chemical evolution and stellar archeology.

Experimental optimization of physicochemical factors for spontaneous deposition of 210Po using newly designed deposition kit

A simple spontaneous deposition kit for 210Po determination using alpha spectrometry was newly designed, and polonium deposition characteristics under various physicochemical conditions were evaluated using it. The high-purity silver disc (99.99%) showed high deposition efficiencies of over 85.1% in the HCl concentration range of 0.01–6 M. Optimal physicochemical factors were determined to be a temperature of 90 °C, deposition time of 90 min, and the use of ascorbic acid as a reducing agent in an amount similar to that of the interfering element (Fe).

Highly efficient electroextraction of gold and simultaneous iodine regeneration using ionic liquid 1-ethyl-3-methylimidazolium dicyanamide

The iodination method is a cyanide-free and efficient gold-leaching process, but a large amount of electric energy is consumed for hydrogen evolution during the process of gold recovery by electrodeposition in the iodide/H2O system. Herein, [C2MIM][N(CN)2] ionic liquids were developed as electrolytes to overcome the limitations of water-based solvents for higher current efficiency by extending the electrochemical window. And the three-dimensional carbon felt with a high surface area and abundant active sites was selected as the cathode material to enhance the deposition rate. Cyclic voltammetry test demonstrated that both Au+ reduction and I- oxidation are irreversible processes controlled by diffusion with the diffusion coefficients of 1.48 × 10-7 cm2/s and 2.91 × 10-7 cm2/s at 20 °C, respectively. The optimal current efficiency (88.03%), specific energy consumption (216.37 kWh/t) and recovery of gold (95.77%), and iodine (85.75%) were obtained by regulating the electrodeposition parameters, including applied potential, temperature, and stirring speed. Moreover, the gold leaching and deposition efficiency were stable at approximately 93% and 95% with 0.2% iodine supplement for four cyclic leaching-electrodeposition. SEM-EDS, XRD, and XPS analysis showed the deposits on the carbon fibers had good uniformity, and the deposit composition contained Au0, Cu0, and CuO. [C2MIM][N(CN)2] ionic liquid is an attractive alternative to non-concentrated aqueous electrolytes for high-efficiency and low-power electrodeposition applications.

A unified model of slagging particle deposition behavior with thermophoresis and dynamic mesh based on OpenFOAM

This study used a unified algorithm to calculate the deposition process of slagging particles by coupling five sub-models and revising thermophoretic force and particle adhesion models based on dynamic mesh technology. The model predicted deposition thickness with an error of 7.66%. Results showed that thermophoretic forces can extend slagging particle transport range and facilitate the impact of particles below 18 μm on the probe, with impact and deposition efficiencies of 55% and 15%, respectively. Particles sized 25–40 μm and with 0.004–0.007 mJ energy are easily captured by the probe, and escaped particles have a temperature 100 K lower than deposited particles. Moreover, the deposition process of slagging particles is significantly staged with the properties of the deposited particles at different stages corresponding to the initial and sintered deposition layers. Average particle size within the second stage (40–100 min) was higher than that of the first stage (0–40 min) with 32 and 27 μm, but the average particle temperature was lower than that of the first stage with 1280 and 1320 K, which is an important reason of deposition stratification.

Coacervate-Enhanced Deposition of Sprayed Pesticide on Hydrophobic/Superhydrophobic Abaxial Leaf Surfaces.

Deposition of high-speed droplets on inverted surfaces is important to many fundamental scientific principles and technological applications. For example, in pesticide spraying to target pests and diseases emerging on abaxial side of leaves, the downward rebound and gravity of the droplets make the deposition exceedingly difficult on hydrophobic/superhydrophobic leaf underside, causing serious pesticide waste and environmental pollution. Here, a series of bile salt/cationic surfactant coacervates are developed to attain efficient deposition on the inverted surfaces of diverse hydrophobic/superhydrophobic characteristics. The coacervates have abundant nanoscale hydrophilic/hydrophobic domains and intrinsic network-like microstructures, which endow them with efficient encapsulation of various solutes and strong adhesion to surface micro/nanostructures. Thus, the coacervates with low viscosity achieve high-efficient deposition on superhydrophobic abaxial-side of tomato leaves and inverted artificial surfaces with a water contact angle from 170° to 124°, much better than that of commercial agricultural adjuvants. Intriguingly, the compactness of network-like structures dominantly controls adhesion force and deposition efficiency, and the most crowded one leads to the most efficient deposition. The tunable coacervates can help comprehensively understand the complex dynamic deposition, and provide innovative carriers for depositing sprayed pesticides on abaxial and adaxial sides of leaves, thereby potentially reducing pesticide use and promoting sustainable agriculture.

Optimization of CO2 laser drilling process parameters of GFRP/Al2O3/perlite composites

Glass Fiber Reinforced Polymer (GFRP) composites have excellent mechanical characteristics and are extensively used in aerospace and marine applications. Drilling GFRP composite through conventional methods leads to delamination and taperness, causing quality loss and imprecision. CO2 laser drilling, an unconventional method to drill GFRP composites, is adopted in this study to reduce the delamination and taperness. This work aims at optimizing the process parameters of CO2 laser drilling. Hybrid S-glass/Al2O3/Perlite powder composite is used in this study. Laser drilling parameters: laser power (P), cutting speed (N), focal length (L), and hole diameter(d) were studied to reduce the hole delamination and hole taperness. These results were achieved through mathematical modelling and optimization using Response Surface Methodology (RSM) and Multi-Objective Genetic Algorithm (MOGA). The optimum process parameters were found by minimizing the objective function upon considering the drilled holes economic features, deposition efficiency, geometric features, and hole diameter at larger and smaller sides. The most critical output factors, delamination and taper responses, had a deviation from the objective by less than 3%. The optimum process parameters laser power, cutting speed, and focal length is found to be 80.795 W, 7.9089 mm/sec, and − 1.9641 m respectively. From the experimental confirmation study, the optimum process parameters effectively reduced the hole delamination and taperness.

Holistic Strategies Lead to Enhanced Efficiency and Stability of Hybrid Chemical Vapor Deposition Based Perovskite Solar Cells and Modules

AbstractHybrid chemical vapor deposition (HCVD) is a promising method for the up‐scalable fabrication of perovskite solar cells/modules (PSCs/PSMs). However, the efficiency of the HCVD‐based perovskite solar cells still lags behind the solution‐processed PSCs/PSMs. In this work, the oxygen loss of the electron transport layer of SnO2 in the HCVD process and its negative impact on solar cell device performance are revealed. As the counter‐measure, potassium sulfamate (H2KNO3S) is introduced as the passivation layer to both mitigate the oxygen loss issue of SnO2 and passivate the uncoordinated Pb2+ in the perovskite film. In parallel, N‐methylpyrrolidone (NMP) is used as the solvent to dissolve PbI2 by forming the intermediate phase of PbI2•NMP, which can greatly lower the energy barrier for perovskite nucleation in the HCVD process. The perovskite seed is employed to further modulate the kinetics of perovskite crystal growth and improve the grain size. The resultant solar cells yield a champion power conversion efficiency (PCE) of 21.98% (0.09 cm2) with a stable output performance of 21.15%, and the PCEs of the mini‐modules are 16.16% (22.4 cm2, stable output performance of 14.72%) and 12.12% (91.8 cm2). Furthermore, the unencapsulated small area device shows an outstanding operational stability with a T80 lifetime exceeding 4000 h.

Efficient depositing aluminum alloy using thick strips through severe deformation-based friction rolling additive manufacturing: processing, microstructure, and mechanical properties

Solid-state additive manufacturing is a promising technology for production of high-strength aluminum alloy components. However, most solid-state AM technologies use thin foils or powder as feeding materials, limiting the deposition thickness of each layer and thus restricting deposition efficiency. This study is the first to utilize 2-mm-thick 5052-H32 aluminum alloy strips as feed material for a severe deformation-based friction rolling additive manufacturing (FRAM) method. In this study, the effect of process parameters such as rising height, transverse speed, and rotational speed, on the forming quality, microstructure, and mechanical properties of the resulting part were investigated. The results indicated that macroscopic forming defects can be avoided by selecting appropriate process parameters. A non-planar lamellar microstructure of fine and ultra-fine equiaxed grains densely embedded in each other was obtained without porosity or unbound defects; although the deposited material was not composed of completely equiaxed grains, the anisotropy of mechanical properties was small. The ultimate tensile strength and elongation in both the longitudinal and build directions of deposited material were higher than those of the raw feeding strips owing to the non-planar lamellar microstructure and grain refinement, with maximum values of 215 MPa and 32%, respectively. Through this microstructure analysis, the mechanism behind the formation of the lamellar microstructure was elucidated. The concepts investigated here regarding defect-free, high strength, and high elongation lamellar materials by FRAM with thick strips as feeding material, provides a methodology for future preparation of laminated composites using FRAM.

Efficiency determination of J-PET: first plastic scintillators-based PET scanner

BackgroundThe Jagiellonian Positron Emission Tomograph is the 3-layer prototype of the first scanner based on plastic scintillators, consisting of 192 half-metre-long strips with readouts at both ends. Compared to crystal-based detectors, plastic scintillators are several times cheaper and could be considered as a more economical alternative to crystal scintillators in future PETs. JPET is also a first multi-photon PET prototype. For the development of multi-photon detection, with photon characterized by the continuous energy spectrum, it is important to estimate the efficiency of J-PET as a function of energy deposition. The aim of this work is to determine the registration efficiency of the J-PET tomograph as a function of energy deposition by incident photons and the intrinsic efficiency of the J-PET scanner in detecting photons of different incident energies. In this study, 3-hit events are investigated, where 2-hits are caused by 511 keV photons emitted in e^+e^- annihilations, while the third hit is caused by one of the scattered photons. The scattered photon is used to accurately measure the scattering angle and thus the energy deposition. Two hits by a primary and a scattered photon are sufficient to calculate the scattering angle of a photon, while the third hit ensures the precise labeling of the 511 keV photons.ResultsBy comparing experimental and simulated energy distribution spectra, the registration efficiency of the J-PET scanner was determined in the energy deposition range of 70–270 keV, where it varies between 20 and 100%. In addition, the intrinsic efficiency of the J-PET was also determined as a function of the energy of the incident photons.ConclusionA method for determining registration efficiency as a function of energy deposition and intrinsic efficiency as a function of incident photon energy of the J-PET scanner was demonstrated. This study is crucial for evaluating the performance of the scanner based on plastic scintillators and its applications as a standard and multi-photon PET systems. The method may be also used in the calibration of Compton-cameras developed for the ion−beam therapy monitoring and simultaneous multi-radionuclide imaging in nuclear medicine.

High-Performance Pure Aluminum Coatings on Stainless Steels by Cold Spray

Aluminum target material is an important target material and is widely used in preparations of semiconductor films, integrated circuits, display circuits, protective films, decorative films, etc. In this study, pure aluminum coatings were deposited on stainless steel substrates by cold-spray technology as part of an overall project to produce large-size pure aluminum sputtering target materials. The results show that pure aluminum coatings exhibit high adhesive strength (~98 MPa), high deposition efficiency (~95%), and low porosity (~0.3%) on stainless steel substrates. The bonding mechanisms of pure aluminum coatings on stainless steel are a combination of metallurgical and mechanical interlocking. The evolutions of microstructure and mechanical properties of pure aluminum coatings under different heat treatments were also studied. With the increase of heat treatment temperature, it is found that cold-sprayed aluminum coatings become more homogenous in microstructure, the microhardness is reduced, and the adhesive strength seems to be slightly reduced. Overall, this study demonstrates significant advantages of cold-spray technology in depositing high-performance pure aluminum coatings on stainless steels.

Variations of inhalation risks during different heavy pollution episodes based on 3-year measurement of toxic components in size-segregated particles

Toxic metals (TMs) and polycyclic aromatic hydrocarbons (PAHs) in size-segregated particles during common days (CD) and different heavy pollution (HP) episodes were measured during 2018–2021 in a Chinese megacity. The Multiple Path Particle Dosimetry Model (MPPD) was performed to estimate deposition efficiency, and then inhalation risks in the human pulmonary region during different types of HP were assessed and compared. The higher pulmonary deposition efficiency of PAHs and TMs during all types of HP than those during CD was confirmed. The accumulative incremental lifetime cancer risk (ILCR) of different HP were 2.42 × 10−5, 1.52 × 10−5, 1.39 × 10−5, 1.30 × 10−5 and 2.94 × 10−6 for HP4 (combustion sources HP), HP1 (ammonium nitrate HP), HP5 (mixed sources HP), HP3 (resuspended dust HP) and HP2 (ammonium sulfate HP), respectively. The accumulative hazard quotient (HQ) during different HP episodes decreased in the order of HP4 (0.32) > HP3 (0.24) > HP1 (0.22) > HP5 (0.18) > HP2 (0.05). The inhalation risks were dominated by Ni and Cr, what's more, the HQ of Ni and ILCR of Cr during the five HP episodes shared a similar size distribution pattern. However, the characteristic components during different HP episodes and their size distributions of them were distinctive. The size distribution of inhalation risks of the related components (Ni, Cr, BaP, and As) from the combustion process during HP4 peaked at fine mode (0.65–2.1 μm). The size distribution of inhalation risks of the dust-related components (Mn and V) and the components (As and BaP) that are likely to volatilize and re-distribution peaked at coarse mode (2.1–3.3 μm) during HP3. Notably, Mn and Co as catalysts at fine mode could increase the degree of secondary formation and toxicity.

Numerical simulation and mathematical models of ash deposition behavior considering particle properties and operating conditions

A unified model is proposed considering thermophoresis, erosion, dynamic mesh techniques and mixed particle adhesion model based OpenFOAM open-source software. The effects of particle concentration, particle size distribution, flow velocity, probe and air temperature were discussed. Results show that the unified model predicts the deposition thickness at the probe with an average error of 7.66%. Deposition and impact efficiency always show opposite trends to factor changes, which are dominated by particle temperature and size distribution, respectively. Impact efficiency is distributed in 50–65% and the deposition efficiency is 5–25%, which get the efficiency of forming deposition of any ash particles in the boiler may be 2.5–16.25%. Different factors affect the deposition efficiency by influencing the particle temperature, the average particle temperature rises by 30 K with a double increase in flow rate. Also, a change of 10 to 30 K in particle temperature corresponds to a change of 100 K in air temperature. Mathematical models of PCA and BP neural networks based on broad data were proposed, which predict the maximum deposition thickness and probe deposition morphology with an error of 15% and 8.9%. The results of this study can provide a monitoring method and reference for boiler operators and researchers.