PARTICULATE CONCENTRATION ENRICHMENT OF PRIMARY AIR IN PULVERIZED COAL BOILERS

Particulate concentration enrichment (PCE) of primary air favors flame ignition and stabilization, and the reduction of NOx emission in pulverized coal combustion. The methods used for PCE are summarized in five categories: Cyclone PCE, Elbow PCE, Blunt-body PCE, Hydrodynamic PCE and Swirling PCE. Practice of each PCE method is il- lustrated with typical burners and the associated pros and cons are discussed. It is found that the same principle prevails in all PCE methods, that is, due to inertial difference, solid particles preferentially decelerate and separate from the gas stream when the main flow deviates in flow orientation. From analysis of various P-C burners, PCE design is deemed to yet comprise “rule of thumb” practice. Somediscussions regarding PCE application are given.

The Effect of Urban Agglomeration Expansion on PM_(2.5) Concentrations: Evidence from a Quasi-natural Experiment

This study constructs a quasi-natural experiment based on the expansion of the Yangtze River Delta urban agglomeration(YRDUA) of China in 2010 to investigate the impact and inner mechanism of urban agglomeration expansion on fine particulate matter(PM_(2.5)) concentrations through propensity scores in difference-in-differences models(PSM-DID) using panel data from 286 prefecturelevel cities in China from 2003 to 2016. The results show that 1) urban agglomeration expansion contributes to an overall decrease in PM_(2.5)concentration, which is mainly achieved from the original cities. For the new cities, on the other hand, the expansion significantly increases the local PM_(2.5)concentration. 2) In the long term, the significant influence of urban agglomeration expansion on PM_(2.5)concentration lasts for three years and gradually decreases. A series of robustness tests confirm the applicability of the PSM-DID model.3) Cities with weaker government regulation, a better educated population and higher per capita income present stronger PM_(2.5)reduction effects. 4) Urban agglomeration expansion affects the PM_(2.5)concentration mainly through industrial transfer and population migration, which cause a decrease in the PM_(2.5)concentration in the original cities and an increase in the PM_(2.5)concentration in the new cities.Corresponding policy suggestions are proposed based on the conclusions.

Experimental Study on the Effect of Humidification on the Pollution Characteristics of Particulate Matter in the Office

Indoor air quality has a direct impact on human health. Indoor air quality has aroused great concern. This experimental study compares the effects of different water humidification on the indoor particulate pollution characteristics, and analyzes the mass concentration and the particulate number concentration distribution of different sizes of particulates with time under each condition of the purified water humidification, the tap water humidification and the cold boiled water humidification in the office. The results show that under the three kinds of wetting conditions, the concentration of the fine particulates is higher. More minerals are contained in the tap water and the cold boiled water, so the two kinds of humidification have more significant impact on indoor particulate matter. But the purified water humidification has nearly no significant effect on it. The calcium and magnesium ionic compounds are partly removed after the water boiled, so the cold boiled water humidification has less impact on the indoor particulate matter than the tap water humidification. The mass concentration and particulate number concentration of the particle may also be affected due to the frequency of ultrasonic vibration.

Effect of Meteorological Data Assimilation on Regional Air Quality Forecasts over the Korean Peninsula

The Weather Research and Forecasting model coupled with Chemistry(WRF-Chem),a type of online coupled chemistry-meteorology model(CCMM),considers the interaction between air quality and meteorology to improve air quality forecasting.Meteorological data assimilation(DA)can be used to reduce uncertainty in meteorological field,which is one factor causing prediction uncertainty in the CCMM.In this study,WRF-Chem and three-dimensional variational DA were used to examine the impact of meteorological DA on air quality and meteorological forecasts over the Korean Peninsula.The nesting model domains were configured over East Asia(outer domain)and the Korean Peninsula(inner domain).Three experiments were conducted by using different DA domains to determine the optimal model domain for the meteorological DA.When the meteorological DA was performed in the outer domain or both the outer and inner domains,the root-mean-square error(RMSE),bias of the predicted particulate matter(PM)concentrations,and the RMSE of predicted meteorological variables against the observations were smaller than those in the experiment where the meteorological DA was performed only in the inner domain.This indicates that the improvement of the synoptic meteorological fields by DA in the outer domain enhanced the meteorological initial and boundary conditions for the inner domain,subsequently improving air quality and meteorological predictions.Compared to the experiment without meteorological DA,the RMSE and bias of the meteorological and PM variables were smaller in the experiments with DA.The effect of meteorological DA on the improvement of PM predictions lasted for approximately 58-66 h,depending on the case.Therefore,the uncertainty reduction in the meteorological initial condition by the meteorological DA contributed to a reduction of the forecast errors of both meteorology and air quality.

Variation of PM_(2.5) concentration in Hangzhou,China

This observational study investigates the variation of PM2.5 concentration and its ratio against PM10 concentration under different weather systems and pollution types. The study was conducted in Hangzhou on east China＇s Yangtze River Delta using data collected at seven ambient air quality monitoring stations around the metropolitan area between 2006 and 2008 and using weather information in the same period. Nine predominant weather systems affecting the city were classified through careful analysis of the 11- year surface and upper air weather charts from 1996 to 2006. Each observational day was then assigned to one of the nine weather systems. It was found that the PM2.5 concentration varied greatly for different weather systems, with the highest PM2.5 concentration associated with the post-cold-frontal system at 0.091 mg/m^3 and the lowest PM2.5 concentration with the easterlies system at 0.038 mg/m^3, although the PM2.5/PM10 ratio remained consistently above 0.5 for all systems. The post-cold-frontal system typically occurs in autumn and winter while the easterlies system is more a summer phenomenon. Among all types of pollution, the highest PM2.5 concentration of 0.117 mg/m^3 coincided with the large-scale continuous pollution events, suggesting that this type of pollution was more conducive to the formation of secondary particulate matters. The ratio of PM2.5/PM10 was above 0.5 in non-pollution days and all pollution types but one under the influence of dust storms when the ratio decreased to 0.3 or less. The outcomes of this study could be used to develop a rudimental predictive model of PM2.5 concentration based on weather system and pollution type.

Development of a portable reference aerosol generator （PRAG） for calibration of particle mass concentration measurements

The tapered element oscillating microbalance with filter dynamics measurement system （TEOM-FDMS） is an instrument commonly employed by the French air quality monitoring network. This instrument is currently calibrated with calibration weights traceable to SI but having value and mass differences between each of them that are not representative of real atmospheric particle mass measurements. Moreover, these calibration weights do not allow detection of any technical problems associated with either the TEOM-FDMS sampling system upstream of the mass measurement or the intrinsic TEOM-FDMS filtration system. Therefore, a calibration method was developed using a portable reference aerosol generator （PRAG） that produces known and stable particle mass concentrations over time. Here, we present the characterization of the PRAG system in terms of a reference range of particle masses between 30 - 10 and 3456 ± 83 μg at three sampling times. Its coupling with the TEOM-FDMS and a global comparison between the defined reference range of particle masses and the measured masses obtained with each TEOM-FDMS implicated in this study are also presented.

TAKING THE“LEED”IN INDOOR AIR QUALITY:DOES CERTIFICATION RESULT IN HEALTHIER BUILDINGS?

Indoor Air Quality(IAQ)has been an area of growing concern with the increasing knowledge of health hazards associated with contaminants,particularly in high occupancy buildings where residents may be exposed to high levels of nuisance dust and other contaminants.Leadership and Energy in Environmental Design(LEED®)certification,which is awarded to buildings that prioritize sustainability and efficient resource use,has been increasingly sought in new construction.As LEED-certified buildings become more commonplace,it is worthwhile to consider whether these new building practices improve IAQ for its occupants.This study compares particulate matter(PM)concentrations in 12 LEED-certified buildings to 12 analogous non-LEED certified buildings on the University of Utah campus.Real-time air sampling was conducted in each building for PM measurements and a Wilcoxon signed rank test was conducted to compare PM levels.A statistically significant difference was found between LEED certification and PM concentrations,with LEED-certified buildings containing,on average,approximately half the PM of their non-LEED counterparts.These findings suggest that LEED certification is worth the financial investment,as it may lead to improved IAQ for residents.However,further research on other contaminants is warranted,including the characterization and comparison of formaldehyde and carbon dioxide levels.

Quantitative distribution of human exhaled particles in a ventilation room

Respiratory viruses can be attached to human exhaled particles and spread from person to person through respiratory activities.The purpose of this study is to obtain the quantitative description formula of human exhaled particles in the ventilated room through amount number of numerical simulation calculations and regression statistical analysis of the simulated data.In this study,a combination of numerical simulation and laboratory experiments was used,and the results were tallied preferably.Bacillus subtilis was released as a release source to investigate the migration and distribution of bioaerosol.The results show that under the condition of high air supply velocity,due to the disturbance of human respiration and airflow,the diffusion velocity of exhaled particles was faster and the diffusion range is larger than that of low air supply velocity within the same time frame.No matter where the location of the manikin was in the room,the exhaled particles would spread to the whole room in at least 900 s.The method used in this study could be used to predict the distribution of human exhaled particles concentration in different indoor spaces,such as public transport and hospitals.These findings could provide valuable reference for the location of indoor air purifiers,which plays a guiding role in the construction of a healthy indoor environment.