Experimental studies into the effect of air pressure on the atomization characteristics of coal-water slurries

The paper studies the effect of atomizing agent pressure on the spray characteristics after spraying coal-water slurry that contains small additives of liquid waste from the pyrolysis of industrial rubber goods and used engine oil. The conducted experiments used automobile tires as the indicated rubber products; spraying was carried out employing an internal mixing pneumatic atomizer. Following the atomization of considered fuels, droplet size changes were studied using the interferometric particle imaging (IPI) technique. The spray angle was determined by means of a Photron high-speed camera. In addition, coal-water slurry containing liquid waste from the pyrolysis of industrial rubber goods and used engine oil (3–12 wt%) was sprayed to study the effect of atomizing agent pressure on the spray characteristics. A decrease in air pressure was found to reduce the spray angle by less than 6%, which resulted in the formation of rather large droplets exceeding 600 µm in size. It is experimentally confirmed that more fine droplets are formed at similar fuel and air pressures when using a spraying device equipped with an internal mixing chamber for slurry and air. The number of droplets, in this case, is 2–9% higher as compared to a typical two-component coal-water slurry fuel, with the spray angle of the sprayed coal slurry having the greatest value. When using an atomizer having an internal mixing chamber for slurry and an atomizing agent, fuel droplet breakup occurs due to the aerodynamic drag forces of the environment. Thus, the use of such atomizers reduces the number of possible breakup mechanisms for sprayed fuel droplets.

Observational Evidence Points at AGB Stars as Possible Progenitors of CEMP-s and CEMP-r/s Stars*

The origin of enhanced abundance of heavy elements observed in the surface chemical composition of carbon-enhanced metal-poor (CEMP) stars still remains poorly understood. Here, we present detailed abundance analysis of seven CEMP stars based on high-resolution (R ∼ 50,000) spectra that reveal enough evidence of asymptotic giant branch (AGB) stars being possible progenitors for these objects. For the objects HE 0110−0406, HE 1425−2052, and HE 1428−1950, we present for the first time a detailed abundance analysis. Our sample is found to consist of one metal-poor ([Fe/H] < −1.0) and six very metal-poor ([Fe/H] < −2.0) stars with enhanced carbon and neutron-capture elements. We have critically analyzed the observed abundance ratios of [O/Fe], [Sr/Ba], and [hs/ls] and examined the possibility of AGB stars being possible progenitors. The abundance of oxygen estimated in the program stars is characteristic of AGB progenitors except for HE 1429−0551 and HE 1447+0102. The estimated values of [Sr/Ba] and [hs/ls] ratios also support AGB stars as possible progenitors. The locations of the program stars in the absolute carbon abundance A(C) versus [Fe/H] diagram, along with the Group I objects, hint at the binary nature of the object. We have studied the chemical enrichment histories of the program stars based on abundance ratios [Mg/C], [Sc/Mn], and [C/Cr]. Using [C/N] and 12C/13C ratios, we have examined whether any internal mixing had modified their surface chemical compositions. Kinematic analysis shows that the objects HE 0110−0406 and HE 1447+0102 are thick-disk objects and the remaining five objects belong to the halo population of the Galaxy.

An Index for Quantitative Evaluation of the Mixing in Ethanol Precipitation of Traditional Chinese Medicine

(1) Background: Ethanol precipitation is widely used in the manufacturing traditional Chinese medicines (TCMs). Insufficient mixing of ethanol solution and concentrate usually results in the coating loss of active ingredients. However, there is no index for quantitative evaluation of the mixing in ethanol precipitation. Therefore, this study aimed to define an index for quantitative evaluation of the mixing effect in ethanol precipitation of TCMs. (2) Methods: The concept and requirements of a mixing indicator were proposed. The mass percentage of concentrate fully mixed with ethanol solution (well-mixing ratio, WMR) was used as an index to evaluate the mixing effect. The formula for calculation of WMR was derived. The utility of the WMR was evaluated on stirring devices and a micromesh mixer. (3) Results: Increasing stirring speed, decreasing total solid content of the concentrate, and decreasing the diameter of the ethanol solution droplets all resulted in higher retention rates for lobetyolin and higher WMR. The WMR increased with the increasing flow rate of the concentrate and ethanol solution in the micromesh mixer. The mixing of ethanol solution and concentrate was better when using a micromesh mixer with a smaller internal mixing zone. The results revealed that WMR could be used to quantitatively characterize the mixing of concentrate and ethanol solution, although it has some limitations. (4) Conclusions: The proposed index WMR could guide quality control of the TCM ethanol precipitation process. This study represents a new contribution to improving ethanol precipitation equipment, optimizing process parameters, and enhanced properties of concentrate for TCM enterprises.

An Experimental Study on the Dielectric Properties of Rubber Materials

According to specific formulas, the mixing of rubber samples occurs by two methods: open mixing and internal mixing. The effects of frequency, mixing process, carbon black (CB) content, zinc oxide (ZnO) content, and stearic acid (SA) content on the dielectric properties of rubber materials were studied. The results showed that the effects of the mixing process on the dielectric properties of the rubber samples cannot be ignored, and the appropriate mixing process should be selected when preparing the required rubber materials. The dielectric constant and loss factor of the rubber samples vary depending on the frequency. The dielectric constant had a peak and valley value, while the loss factor only had a peak. The dielectric constant and loss factor of rubber samples were significantly affected by the content of CB, ZnO, and SA. The peak frequency decreased with the increase in CB content, however, the dielectric constant increased with an increase in CB content. The higher the ZnO content, the lower the peak frequency. In addition, the dielectric constant and loss factor increased with an increase in ZnO content. The higher the SA content, the greater the peak frequency. In addition, the dielectric constant and loss factor decreased with an increase in SA content. It is hoped that the experimental results obtained can provide guidance for the study of the dielectric properties, microwave absorption properties, and microwave heating characteristics of rubber polymers.

The impact of aerosol size-dependent hygroscopicity and mixing state on the cloud condensation nuclei potential over the north-east Atlantic

We present an aerosol cloud condensation nuclei (CCN) closure study over the north-east Atlantic Ocean using six approximating methods. The CCN number concentrations (NCCN) were measured at four discrete supersaturations (SSs; 0.25 %, 0.5 %, 0.75 % and 1.0 %). Concurrently, aerosol number size distribution, sub-saturation hygroscopic growth factor and bulk PM1 chemical composition were obtained at matching time resolution and after a careful data validation exercise. Method A used a constant bulk hygroscopicity parameter κ of 0.3; method B used bulk PM1 chemical composition measured by an aerosol mass spectrometer (AMS); method C utilised a single growth factor (GF) size (165 nm) measured by a humidified tandem differential mobility analyser (HTDMA); method D utilised size-dependent GFs measured at 35, 50, 75, 110 and 165 nm; method E divided the aerosol population into three hygroscopicity modes (near-hydrophobic, more-hygroscopic and sea-salt modes), and the total CCN number in each mode was cumulatively added up; method F used the full-size-scale GF probability density function (GF–PDF) in the most complex approach. The studied periods included high-biological-activity and low-biological-activity seasons in clean marine and polluted continental air masses to represent and discuss the most contrasting aerosol populations. Overall, a good agreement was found between estimated and measured NCCN with linear regression slopes ranging from 0.64 to 1.6. The temporal variability was captured very well, with Pearson's R value ranging from 0.76 to 0.98 depending on the method and air mass type. We further compared the results of using different methods to quantify the impact of size-dependent hygroscopicity and mixing state and found that ignoring size-dependent hygroscopicity induced overestimation of NCCN by up to 12 %, and ignoring a mixing state induced overestimation of NCCN by up to 15 %. The error induced by assuming an internal mixing in highly polluted cases was largely eliminated by dividing the full GF–PDF into three conventional hygroscopic modes, while assuming an internal mixing in clean marine aerosol did not induce significant error.