Lignite drying with solar energy: Thermodynamic analysis and case study

As a clean, free, and nondepleting source, solar energy has become the focus of increasing attention in the drying industry. A lignite-fired power plant integrated with a solar dryer (LPPS), in which solar energy is used to dry lignite and the predried lignite is used to generate electricity, is analyzed theoretically in this paper. The aim of this study is to evaluate the energy performance of solar drying under different system parameters. Thermodynamic models, with which the second-law efficiency of the LPPS could be maximized, were developed. A reference case with three kinds of lignite as input fuel was analyzed to quantify the system performance. The first-law and second-law efficiencies were obtained. The solar-to-electric conversion efficiency in the LPPS is more than 34%. Therefore, solar drying is a potential technology that should be promoted in lignite-deposited areas. Moreover, the influence of main parameters on the performance of system was analyzed. Dryer efficiency is determined to have significant influence on the solar-to-electric conversion efficiency.     

A comparative study on hygroscopic and physiochemical properties of chicken powders obtained by different drying methods

Abstract

Different drying methods (spray drying (SD), vacuum drying (VD), microwave vacuum drying (MVD), and infrared vacuum drying (IFVD)) were applied in order to compare the hygroscopicity behavior of chicken powders. The hygroscopicity curves and glass transition temperature were used to evaluate the influence of ambient humidity and temperature on moisture absorption of powders. The results showed that the chicken powder dried by MVD had the lowest moisture absorption, followed by IFVD, VD, and SD. The hygroscopicity of SD chicken powders was different from other three kinds of chicken powders due to the physical properties of particles and the changes of protein secondary structure as detected by the Fourier transform-infrared spectrometer. For the three vacuum drying methods, the difference of protein secondary structure was the main reason of differences in hygroscopicity. Although MVD chicken powders were slightly inferior to SD chicken powders in taste, MVD chicken powders were the best in terms of smell and color as suggested by instrumental sensory parameter evaluations. It was found that MVD had a positive effect on reducing moisture absorption and maintaining sensory quality of chicken powders.     

假单胞菌复合菌剂对高浓度废水中氨氮总氮浓度降解的研究

在修复工程中,利用微生物处理高浓度氨氮废水.通过对填埋场渗滤液坑底活性污泥驯化,筛选出复合菌剂,在异养硝化培养基或基坑废水中培养25 d后,氨氮平均质量浓度从830.42 mg/L降至38.28 mg/L,去除率最高达95.4％;总氮平均质量浓度从930.03 mg/L降至330.68 mg/L,去除率最高达66.2％...     

Diagnosis of nitrogen deficiency in barley,growing in different rotation systems,by plant analysis

Nitrate concentrations were determined in stems of barley taken at the tillering stage from a 2-year rotational/N fertilizer experiment carried out at 2 locations in Cyprus. In the second year leaf laminae were also analysed for total nitrogen (N) concentration.At sampling maximum dry matter (DM) production was obtained with NO₃-N concentration above 1000 mg kg^–1, which increased with N fertilizer supply. Even though there were differences in DM and NO₃ concentration between rotation treatments the relationship between DM and NO₃ was similar.Nitrate in stems was more sensitive than total N in leaf laminae as an indicator of N nutrition status.     

Effects of different drying methods on the physical characteristics and flavor of dried hawthorns (Crataegus spp.)

ABSTRACT

The objective of this study was to compare the physical characteristics and flavor of dried hawthorns obtained by freeze-drying (FD), microwave freeze-drying (MFD), atmospheric freeze-drying (AFD), and heat pump drying (HPD). The parameters including moisture content, product temperature, rehydration ratio, chroma, hue angle, yellowness index, total color difference, and energy consumption were investigated. The use of fuzzy reasoning for the sensory evaluation of hawthorn quality was also performed. As expected, AFD, FD, and MFD produced better accepted dried hawthorn products than did HPD. Nevertheless, FD consumed the highest energy and had a long drying time, but its product was the best; AFD had a similar energy cost as HPD, but its drying time was the longest; and MFD had a higher energy cost and longer drying time than HPD, but its product quality was similar to that of FD products. As a result, MFD and AFD had potential to replace FD to yield dried hawthorns with high product quality and relatively low cost.     

A comparative study of drying methods on physical characteristics,nutritional properties and antioxidant capacity of broccoli

Abstract

Broccoli is considered one of the attractive raw materials for dehydrated vegetables owing to its high nutritional value. However, information about how drying methods affect the physicochemical and nutritional properties of broccoli is limited. In this study, broccoli pieces were subjected to freeze drying (FD), hot air drying (HAD), microwave vacuum drying (MVD), vacuum drying (VD), MVD combined with HAD (MVD?+?HAD), and MVD combined with VD (MVD?+?VD). Quality attributes of dehydrated broccolis were contrasted in terms of color, texture, volume shrinkage, nutritional components, antioxidant activity, and rehydration capacity. Results demonstrated that FD better preserved the nutrients while HAD displayed the worst effect. The combination of MVD?+?HAD and MVD?+?VD resulted in higher retention of nutritional compositions, better antioxidant activity, and lower energy consumption than that of HAD. Furthermore, combined drying processing exhibited similar rehydration capacity but lower hardness compared to that of HAD.     

Flux decline during ultrafiltration of kraft black liquor using different flow modules: a comparative study

Ultrafiltration of black liquor was studied in three different modules, namely, radial cross flow, rectangular cross flow and stirred cell over a wide range of operating conditions. Effects of different cut-off membranes on the permeate flux and observed rejection were also studied in the stirred cell module. Effects of operating conditions, e.g. pressure difference, Reynolds number and feed concentration on the permeate flux and observed rejection were also investigated. Such comparative study may be useful to select a suitable module, membrane and a set of optimum operating conditions to achieve a desired quantity and quality of permeate flux. A comparative analysis of flux decline for different modules is also presented using a simple resistance-in-series model.     

Comparative study of total lipids in beef using chlorinated solvent and low-toxicity solvent methods

Nine extraction methods (three using chlorinated and six nonchlorinated solvents) were compared for determining lipids in samples of low-(<5%) and high-fat (>20%) ground beef. The nine methods investigated were: Folch, Lees, and Sloane Stanley (FLS); Bligh and Dyer (BD); Bligh and Dyer modified by Undeland, Harrod, and Lingnert (BDU); Bligh and Dyer modified by Smedes (BDS); Hara and Radin (HR); Schmid, Bondzynski, and Ratzalaff (SBR); Roese-Gottlieb (RG); Burton, Webb, and Ingold (BWI); and Soxhlet (SE). The BDS and HR methods do not include solvents such as chloroform and methanol and can be recommended for meat samples that have both low and high fat content. If the use of organic solvents is not critical, the FLS and the BD extraction methods yield the highest results, but the FLS is more expensive owing to the high amount of solvent required. Without considering the toxicity of the solvents, the three BD extraction methods provided the best yields.     

Comparative study on the flavonoids extraction rate and antioxidant activity of onions treated by three different drying methods

Onions, rich in flavonoids, with antioxidant, antibacterial, and other biological activities, are often used as extraction of raw materials to obtain health products with high flavonoids content. However, the amount of raw material consumption is large due to low yield of extracts from fresh onions. As a result, dried onions often are used as extraction materials. The effects of air drying (AD), freeze-drying (FD), and microwave freeze-drying (MFD) on the flavonoids extraction yield of onions were investigated. The most effective and economical method was hot AD. On the other hand, the flavonoids extraction rate of onions dried by MFD was the fastest. FD could also obtain high extraction rate, but it cost the highest energy consumption. In order to obtain relatively rapid, economic, and effective extraction of onion flavonoids, onions can be dried by MFD or AD method.     

高纯氮装置的有效能分析

化工装置的有效能分析是考察流程是否具有先进性、节能潜力是否最大程度利用的工具之一,有效能分析法已经广范应用于能源化工生产当中。常见的分析(即有效能分析)通常包含平衡、损失、效率等基本计算。平衡是指研究系统内部值的守恒原则,但它同时考虑了内部能量的质和量的总体守恒。损失在数值上等于所给系统进出口的值之差,反映了过程内部不可逆损失的情况;效率定义为理想输出与实际输入之比,表示系统对的有效利用率,反映出在过程中的利用程度,是在热力学第二定律的基础上同时结合热力学第一定律提出的更为全面的评价指标。本文重点阐述有效能分析方法、针对高纯氮装置的有效能计算及有效能分析,希望能够促进气体分离行业的发展。     

A comparative study of synthesis and spark plasma sintering of YAG nano powders by different co-precipitation methods

Pure yttrium-aluminum-garnet (YAG) nano particles were synthesized via normal and reverse co-precipitation methods using nitrate starting solutions and ammonium hydrogen carbonate (AHC) as precipitator agent. The impact of titration method on the phase evolution, thermal behavior, precipitate's composition, morphology and chemical bonds of powders were studied by XRD, TG-DTA, FTIR, FESEM, TEM, EDS and BET analysis. The results revealed that in the normal method, the precipitates were composed of relatively dense particles compared with more homogenous fluffy precipitates with higher carbonate content obtained by the reverse method. The precursors achieved by the reverse method formed less agglomerated and smaller size YAG powders after calcination at 900?°C. Calcined nano powders were processed by spark plasma sintering (SPS) technique at 1350?°C for 10?min without any sintering aids or dispersive agents. The sintering of both powders led to a highly dense and fine submicron-structured YAG ceramic. However, the YAG ceramic produced by SPS of reverse co-precipitated nano powders showed higher transparency (43% at 680?nm and 58% in near-infrared range) and finer micro-structure (about 210?nm in grain size) as compared with normal co-precipitated nano particles.     

A comparative study of the synthesis of nanocrystalline Yttrium Aluminium Garnet using sol-gel and co-precipitation methods

Nanocrystalline yttrium aluminium garnet (nYAG) powder has been synthesized via sol-gel and co-precipitation methods using nitrate precursors. Thermal evolution and crystallisation kinetics of both the methods were investigated. The optimised calcination condition for the formation of nYAG was also examined. It was found that a complete transformation to nYAG was observed at 925 °C/2 h and 1000 °C/1 h for the coprecipitation and sol-gel samples respectively. An intermediate YAlO₃ phase was formed at 900 °C in all powders regardless of the synthesis methods. The powder morphologies obtained from TEM revealed very similar particle sizes for the two routes (20–30 nm); whilst the extent of agglomeration was higher for the sol-gel method. It was also observed that by controlling the pH in a narrow range, maintaining the precipitate processing temperature and dehydrating excess OH- ions in the precipitates using n-butanol treatment, the extent of agglomeration was further reduced in the co-precipitated nYAG powder.     

The determination of the degree of hydrolysis in poly(acrylamides): simple methods using C13 n.m.r., and elementary analysis

C¹³ n.m.r. spectroscopy and C, N elementary analysis have been applied to determine the degree of hydrolysis of commercial polyacrilamide samples. The methods proposed do not involve the weighing of the samples, and thus avoid the problems posed by retained water and the presence of inorganic salts. The C¹³ n.m.r. spectrum is sufficiently resolved to allow peak area determinations of the methine carbon in the hydrolysed and non-hydrolysed moieties. Elementary analysis of the solid samples has been applied to obtain the C/N ratio of the polymers, rather than percentage values based on sample weight. A very good correlation is observed between the data obtained via both methods.     

Quantitative study of Portland cement hydration by X-ray diffraction/Rietveld analysis and independent methods

X-ray diffraction (XRD) is a powerful technique for the study of crystalline materials. The technique of Rietveld refinement now enables the amounts of different phases in anhydrous cementitious materials to be determined to a good degree of precision. This paper describes the extension of this technique to a pilot study of the hydration of a typical Portland cement. To validate this XRD-Rietveld analysis technique, its results were compared with independent measures of the same materials by the analysis of backscattered electron images (BSE/IA) and thermogravimetric analysis (TGA). In addition, the internal consistency of the measurements was studied by comparing the XRD estimates of the amounts of hydrates formed with the amounts expected to form from the XRD estimates of the amounts of anhydrous materials reacted.     

Analysis of epoxidized natural rubber. A comparative study of d.s.c., n.m.r., elemental analysis and direct titration methods

A comparative analysis of epoxidized natural rubber samples by ¹H and ¹³C n.m.r., titrimetric, elemental and d.s.c. techniques has been made. Whereas the titrimetric method is only applicable at low epoxy contents (< 15 mol%) both n.m.r. methods give reasonable precision over the compositional range of 20–75 mol%. Elemental analysis appears less reliable. D.s.c. analysis through measurement of T_g provides the highest precision of measurement but requires independent calibration by one or more of the primary methods. The epoxy content may also be related to the polymer density.     

Study on adsorption of nonionic and cationic polymers on silica gel by using total organic carbon analysis

The adsorption behaviour of poly(ethylene oxide) and trimethylammonium glycol chitosan iodide from water onto silica gel is reported. A total organic carbon analytical method was employed to determine precisely the small quantity of polymer remaining after the attainment of adsorption equilibrium. The adsorption isotherms and the curves of equilibrium adsorption against pH were obtained and compared with the ionization properties of the silanol groups investigated by potentiometric titration. The results obtained are discussed in terms of the adsorption mechanism for nonionic and cationic polymers.     

A comparative study on co-combustion performance of municipal solid waste and Indonesian coal with high ash Indian coal: A thermogravimetric analysis

In recent years there has been an increasing utilization of coal blends in the Indian power industry, with Indonesian coal, due to high ash content and shortages in domestic coal production. On the other hand, rapid economic growth is aggravating the municipal solid waste (MSW) related environmental problems. In this study, an attempt has been made to compare the co-combustion characteristics of hydrothermally treated MSW and Indonesian coal with high ash Indian coal, so as to replace the Indonesian coal with MSW. The effect of blending Indonesian coal and hydrothermally treated MSW with Indian coal on ignition behavior was studied. MSW blends of 10%, 20%, 30% and 50% (in wt.%), and an Indonesian blend of 10% with Indian coal were tested in a thermogravimetric analyzer (TGA) in the temperature from ambient to 700 °C with a temperature increase of 10 °C/min. From the results, at 10% of blend, ignition and carbon burnout were similar for Indonesian and MSW blend, analogous to coal combustion and even better than the Indonesian coal blend, which indicated the feasibility for replacing Indonesian coal with hydrothermally treated MSW. Further, the results show a scope to increase the MSW blend in Indian coal up to 20%, as the constituents behave as a single fuel.     

A comparative study of ordinary and mineralised Portland cement clinker from two different production units Part II: Characteristics of the calcium silicates

Portland cement clinkers from two production units were investigated in order to determine the effects of mineralisation on alite and belite; Plant 1: ordinary clinker (P1) and clinker mineralised with CaF₂₊CaSO₄ (P1m); Plant 2: ordinary clinker (P2) and two clinkers mineralised with CaF₂₊CaSO₄ (P2m, P2m′).The polymorphism of alite was studied using synchrotron X-ray powder diffraction (XRD), wavelength 1.5227 Å, and electron diffraction (ED) in a transmission electron microscope. The substitutions of minor elements in alite and belite were determined using electron microprobe analysis. Clinkers P1 and P1m both contained apparent rhombohedral alite (XRD) with an incommensurately modulated structure (ED), while clinkers P2, P2m, and P2m′ all contained monoclinic alite (XRD). The addition of mineralisers in the process caused increased content of fluoride in alite and increased substitution of Si(4+) by Al(3+) and S(6+) in both calcium silicates. The latter effect was most pronounced in clinker P1m due to its high molar SO₃ to alkali oxide ratio (R=2.18).The improved hydraulic activity of P1m compared to P1 was caused by substitutions rather than a change in symmetry. The decreased hydraulic activity of P2m and P2m′ compared to P2 was explained by the high levels of fluorine, which had a retarding effect on the hydration.     

A study of water diffusion, in both radial and axial directions, into biodegradable monolithic depots using ion beam analysis

Water diffusion into cylindrical biodegradable monolithic depots fabricated from extruded mixtures of poly(dl-lactide) and a peptidic drug, goserelin, containing 20, 30 and 40% drug by weight has been studied using an ion beam analysis technique. A series of depots were immersed in a phosphate buffered saline/heavy water solution at 37 °C for times ranging from 1 h to 7 days. One-dimensional radial profiles showing the diffusion of water into the depots were produced at points along the length of the sample and, for some short immersion times, axial profiles were obtained for the cylinder ends. The changes in weight, radius, drug release and water uptake of the depots with time were also studied. Using the water uptake measurements the one-dimensional radial profiles were normalised. From appropriate one-dimensional profiles at the shorter times Fickian diffusion coefficients were obtained for initial water diffusion. The average radial diffusion coefficients were (1.07±0.22)×10⁻⁸ cm² s⁻¹ for the 20% drug-loaded depots, (1.54±0.27)×10⁻⁸ cm² s⁻¹ for the 30% drug-loaded depots and (2.00±0.83)×10⁻⁸ cm² s⁻¹ for the 40% drug-loaded depots—in the ratio of the drug loadings i.e. 2:3:4, implying the water associated with drug during its uptake into the monoliths. The axial diffusion coefficients were found to be of the same order of magnitude as the radial diffusion coefficients, in accord with this hypothesis. At longer times there is a subsequent non-Fickian increase in the water concentration profile. In the case of depots loaded with 40% by weight of goserelin, the substantial fraction of the hydrophilic drug released at times greater than one day is accompanied by a decrease in radius and a decrease in water concentration near the depot surface.