Development of an asymmetric composite PPS-based bag-filter material through membrane laminating and superfine fiber blending: Lab test, field application and development of numerical models.

Dedusting is crucial for air pollution control, and nonwoven needle felt (NWNF) bag-filters are widely applied for this purpose. Surface treatment of the filter materials can enhance NWNF's performance, but the large discrepancy in pore size between the surface and NWNF layers causes interface effects, impairing reverse cleaning and shortening service life. In this study, a novel PTFE membrane-laminated asymmetrical composite bag-filter was developed, by blending superfine polyphenylene sulfide fiber (PPS) in the original NWNF structure. Image analysis shows a gradual increase in pore size from the surface to the downstream layer. In standard lab-scale tests, the novel M-PPSF-S filter showed moderately higher resistance, significantly longer service life, higher dedusting efficiencies and better cleaning performance, compared to filters without surface laminating and/or superfine fiber blending. Numerical modelling was performed, and the flow fields and pressure distribution in these filter materials were visualized, confirming that M-PPSF-S' unique structure facilitated the alleviation of interface effect and non-steady flow. M-PPSF-S was further scaled up to treat real flue gas from a coal-fired power plant, where constant good performance was observed over 5 months. This study offers a novel and practical way to develop low-cost, high-performance filter materials for high temperature flue gas treatment.

Development of Hydrotaea spinigera (Diptera: Muscidae) at Constant Temperatures and Its Significance for Estimating Postmortem Interval.

Hydrotaea spinigera Stein is a necrophagous species, widely distributed in Oriental and Australasian regions. Considering that the postfeeding larvae or puparia of this species can still be found in abundance at the advanced decomposition stage or even the skeleton stage of remains, it can serve as a good supplementary indicator for estimating the minimum postmortem interval (PMImin). This could also extend the range of PMImin when the primary colonizers are no longer associated with the corpse or have emerged as adults. This study investigated the development duration, accumulated degree hours, and larval body length changes of H. spinigera at seven constant temperatures ranging from 16 to 34°C, and established three development models for estimating PMImin, including isomorphen diagram, isomegalen diagram, and thermal summation model. At 16, 19, 22, 25, 28, 31, and 34°C, the development durations of H. spinigera from egg to adult stage were 1,412.6 ± 62.9, 867.4 ± 14.9, 657.1 ± 22.9, 532.3 ± 10.1, 418.8 ± 21.3, 379.8 ± 16.6, and 340.0 ± 20.3 h, respectively. The lower developmental threshold L0 was estimated as 10.50 ± 0.20°C, and the thermal summation constant K was 7,648.83 ± 146.74 degree hours. Using regression analysis, equations were obtained modeling the change of larval body length with time after hatching at different temperatures. This study provided basic data based on the growth and development of H. spinigera for the estimation of PMImin in forensic science.