Performance of a large-scale greenhouse solar dryer integrated with phase change material thermal storage system for drying of chili

ABSTRACT

Large-scale greenhouse solar dryers have been used for drying various products and this type of dryer is usually equipped with LPG burner as auxiliary heater, which creates more operating cost. To overcome this problem, phase change material (PCM) thermal storage was proposed to substitute for the LPG burner. In this work, the performance of a large-scale greenhouse solar dryer integrated with a PCM as a latent heat storage for drying of chili was investigated. Experimental studies were conducted to compare the performance of this dryer with that of another large-scale greenhouse solar dryer without the PCM thermal storage and open sun drying. Chili with an initial moisture content of 74.7% (w.b.) was dried to a final moisture content of 10.0% (w.b.) in 2.5 days, 3.5 days, and 11 days using the solar dryer integrated with the PCM thermal storage, the solar dryer without the PCM thermal storage and the open sun drying, respectively. The performance of the solar dryer integrated with the PCM thermal storage was also evaluated using exergy analysis. The exergy efficiency of the drying room of the solar dryer integrated with the PCM thermal storage and the solar dryer without the PCM thermal storage for drying of chili was found to be 13.1% and 11.4%, respectively and the thermal storage helps to dry chili during adverse weather conditions. The results of exergy analysis implied that the exergy losses from the dryer with the PCM should be reduced.     

Determination of particulate polycyclic aromatic hydrocarbons in ambient air by gas chromatography-mass spectrometry after molecularly imprinted polymer extraction

A solid phase extraction procedure (SPE) is described for the quantitative analysis of polycyclic aromatic hydrocarbons (PAHs) in atmospheric particulate matter (PM), as ubiquitous environmental pollutants routinely measured in air quality monitoring. A SPE cartridge was used based on a molecular imprinted polymer (MIP-SPE) properly tailored for selective retention of PAHs with 4 and more benzene fused rings. The performance of the clean-up procedure was evaluated with the specific concern of selective purification towards saturated hydrocarbons, which are the PM components mostly interfering GC analysis of target PAHs. Under optimized operative conditions, the MIP-SPE provided analyte recovery close to 95% for heavier PAHs, from benzo(α)pyrene to benzo(ghi)perylene, and close to 90% for four benzene rings PAHs, with good reproducibility (RSDs: 2.5%-5.9%). Otherwise, C₁₇-C₃₂ n-alkanes were nearly completely removed. The proposed method was critically compared with Solid Phase Micro Extraction (SPME) using a polyacrylate fiber. Both methods were successfully applied to the analysis of ambient PM_2.5 samples collected at an urban polluted site. Between the two procedures, the MIP-SPE provided the highest recovery (R% ≥ 93%) for PAHs with 5 and more benzene rings, but lower for lighter PAHs. In contrast, SPME showed a mean acceptable R% value (∼ 80%) for all the investigated PAHs, except for the heaviest PAHs in the most polluted samples (R%: 110%-138%), suggesting an incomplete purification from the interfering n-hydrocarbons.     

洱海沉积物重金属地球化学相及其污染历史研究

高原封闭、半封闭型湖泊是气候和环境演化的敏感指示器，其沉积物记录具有连续性、敏感性和高分辨率的特点。高原湖泊沉积记录在恢复和重塑各种短时间尺度（千年、百年、十年）的气候和环境演化序列上，具有其它自然历史记录无法替代的优势，尤其在揭示近代环境污染历史方面更有其独到之处。本文通过对洱海沉积物重金属地球化学相的研究，利用因子分析方法，识别了沉积物重金属的主要来源和影响其分布的主要因素，即：流域侵蚀作用、大气沉降作用、工业废水与生活污水的排放，以及早期成岩作用。同时，结合沉积物柱芯210PBex计年结果，本文初步评价了洱海150多年来的重金属污染历史：1958年以来．因为化石燃料使用量的增加．洱海湖区大气污染日趋严重；1982年后，由于西洱河水电站的建成运行和湖区植被的破坏，流域侵蚀作用显著加强，应当引起重视。     

Numerical simulation of stratified turbulent two phase flow in aquatic environment

Ｉｎｅｓｔｕａｒｙ,ｄｅｎｓｉｔｙｓｔｒａｔｉｆｉｅｄｆｌｏｗｅｘｉｔｓｗｉｄｅｌｙｂｅｃａｕｓｅｆｒｅｓｈｗａｔｅｒｊｏｉｎｓｉｎｔｏｓｅａｗａｔｅｒａｎｄｔｈｅｄｅｎｓｉｔｙｏｆｆｒｅｓｈｗａｔｅｒｉｓｄｉｆｆｅｒｅｎｔｆｒｏｍｔｈａｔｏｆｓｅａ?..     

环境水样中邻苯二甲酸二辛酯GC测定固相萃取条件优化研究

借助于均匀设计法合理安排试验,再应用计算机回归技术进行C18柱固相萃取条件的设计和优化研究,建立相关的数学模型,找出了各因素对回收率的影响规律。成功地确定(正己烷:丙酮)配比17∶1、洗脱体积2.0m l、洗脱速率6.0m l.m in-1、上样速率9.0m l.m in-1为优化的萃取条件,此时得到DEHP和DnOP的回收率分别为91.98%、107.3%。     

裂隙地下水中残留LNAPL物理驱替冲洗实验

利用透明复制裂隙模型，选择两种典型LNAPL（轻非水相液体）-邻二甲苯和十二烷残留体，开展一系列水流驱替冲刷和SDS（十二烷基磺酸钠）表面活性剂增强驱替实验，直接获取了裂隙内部LNAPL残留体几何形状与分布情况，结果表明：水流驱替冲刷和SDS驱替裂隙内残留体的去除率分别为8.3%~12.3%和65.9%~82.1%.残留体累积去除率随着驱替流体雷诺数的增加而增加.水流驱替冲刷条件下，残留体离散为小液滴，数量比初始残留状态增加1.3~2.2倍.SDS表面活性剂降低了"LNAPL-水"间的界面张力，能够有效去除裂隙内较大残留体，驱替后仅残余单个面积为1mm²左右的微小液滴.由于粗糙裂隙的非均质性，水流冲刷易导致系统内的"LNAPL-水"有效界面面积增加，对LNAPL污染修复不利，表面活性剂增强修复是一种更有效的方法.     

有利于环境的催化方法

载体催化剂在许多有机反应中已证明可作为对环境有利的催化剂而取代传统催化剂（一般有腐蚀性，毒性或极难分解和重整并产生大量废物）。综述了近年来固体酸催化、固体碱催化剂和其它载体催化剂的特性及液相有机化学反应中的应用成果，催化机理及发展趋势。     

气相色谱法测定蔬菜中有机磷农药残留的前处理方法比较

采用液-液萃取、索氏提取和基质固相分散3种不同的方法对青椒样品进行前处理，用毛细管气相色谱法对处理后样品中的DDV、甲拌磷、甲基-对硫磷和马拉硫磷等农药残留进行测定，并对不同前处理方法的回收率和精密度进行比较。结果：3种方法的回收率和RSD相当，但基质固相分散操作较为方便简单、溶剂消耗量少。     

土壤中麦草灵残留的固相萃取—高效液相色谱测定

土壤中麦草灵用酸性乙醇提取，采用固相萃取技术用Ｓｅｐ－Ｐａｋ Ｃ１８柱净化浓缩，以反相离子抑制高效液相色谱分离测定，方法简便、快速、在土壤中的检出下限为０．０４ｍｇ·ｋｇ＾－１回收率范围在８３．８－８５．８％之间。     

环境样品前处理技术及其进展（二）

在前文中讨论了环境样品的制备、前处理的概况，以及超临界流体萃取法。本文将继续报导近年来环境样品制备与前处理领域中其他一些新技术和新方法，包括固相萃取（ＳＰＥ）、微波溶出（ＭＷＤ）和液膜萃取（ＳＬＭ）法，阐述了这些方法的基本原理、操作过程、各种实验参数的影响，及其在环境样品制备与前处理中的应用，并探讨了该领域的发展动向。