Tar analysis from biomass gasification by means of online fluorescence spectroscopy

Optical methods in gas analysis are very valuable mainly due to their non-intrusive character. That gives the possibility to use them for in-situ or online measurements with only optical intervention in the measurement volume. In processes like the gasification of biomass, it is of high importance to monitor the gas quality in order to use the product gas in proper machines for energy production following the restrictions in the gas composition but also improving its quality, which leads to high efficient systems. One of the main problems in the biomass gasification process is the formation of tars. These higher hydrocarbons can lead to problems in the operation of the energy system. Up to date, the state of the art method used widely for the determination of tars is a standardized offline measurement system, the so-called “Tar Protocol”. The aim of this work is to describe an innovative, online, optical method for determining the tar content of the product gas by means of fluorescence spectroscopy. This method uses optical sources and detectors that can be found in the market at low cost and therefore it is very attractive, especially for industrial applications where cost efficiency followed by medium to high precision are of high importance.     

The rate of gasification by CO2 of chars from waste

Three chars and an activated carbon were gasified by reaction with CO₂ in a fluidised bed of sand, at 800–1050 °C. The chars were produced from (i) dried sewage sludge, (ii) car tyres, and (iii) a bituminous coal. For the conditions used, the rate of CO₂ + C → 2CO was largely determined by chemical kinetics; there was a small effect from mass transfer for the most reactive char, derived from sewage sludge. The rate of CO formation, r, differed greatly for these chars, but was well described by:

The reactivity of a char depends on: (i) its pore structure, (ii) catalytic activity of the associated ash, and (iii) the activity of the char’s carbon. The sewage sludge char was the most reactive, on the basis of either BET area or mass by 2 orders of magnitude. The activated carbon had the lowest reactivity per unit BET surface area, indicating that the area in its micropores is comparatively unreactive.     

Effect of pyrolysis conditions on gasification reactivity of woody biomass-derived char

The effect of pyrolysis conditions on char reactivity has been studied using Raman spectroscopy. This paper reports on the relationship between the properties of biomass char and the gasification rate. The gasification kinetics of biomass char have been revealed by measuring the rate of weight loss during its reaction with CO₂ as a function of temperature. First-order kinetic rate constants are determined by fitting the weight loss data using a random pore model. The relationship between the char structure and CO₂ gasification reactivity was investigated in the range of 15–600 °C/min at a constant pyrolysis pressure (0.1 MPa), and 0.1–3.0 MPa at a constant heating rate (15 °C/min). The experimental results reveal that the reactivity of biomass char is determined by the pyrolysis condition. The CO₂ gasification rates in char generated at 0.1 MPa exhibited approximately twice the values as compared to those obtained at 3 MPa. This is because the uniformity of the carbonaceous structure increases with the pyrolysis pressure. The uniformity of carbonaceous structures would affect the CO₂ gasification reactivity, and the decreasing uniformity would lead to the progression of cavities on the char surface during the CO₂ gasification process. The gasification rate of biomass char increases with the heating rate at pyrolysis. This is due to the coarseness (surface morphology) of biomass char and rough texture, which increases with the heating rate.     

Temperature and fiber optic spectroscopy composition measurements of heated propanol–acetone droplets

Time-dependent temperatures and compositions within individual fiber-supported droplets initially from about 2–3 mm in diameter were investigated. In the experiments, droplets were composed of mixtures of 1-propanol and acetone. The droplets evaporated in room air, where the air was heated by placing an electrically heated coil underneath the droplets. The experiments employed thin optical fibers to carry light from a UV–vis light source into and out of a droplet. The time-dependent UV absorption spectrum of the liquid between the fiber ends was measured using a spectrometer coupled to one of the fibers. This spectrum yielded real-time information on the composition of the liquid. Droplet temperatures were simultaneously measured using a thermocouple that was immersed into the liquid. Results demonstrate that droplet evaporation follows a multi-stage process and that acetone is preferentially gasified from a droplet.     

Sequential hydrothermal gasification of biomass to hydrogen

A new technology, in which a renewable biomass is used to produce hydrogen fuel, is described. This hydrogen can be used as a feed for fuel cells to generate electricity or in other energy-producing processes. Degradation and gasification of cellulose-based biomass in compressed water was studied in the 100–400 °C temperature range. Phase behavior of the cellulose in subcritical water was studied in a diamond-anvil cell, coupled with optical microscopy, at heating rates of 1 and 5 °C/s. Homogeneous conditions of a single water-cellulose phase were established. Complete dissolution of the cellulose was achieved at 333 °C. The evolution mechanism based on a rapid hydrolysis of the cellulose to oligomers and glucose is suggested. Glucose was then used as a model compound to characterize the chemistry of biomass gasification. A 0.1-M glucose solution was fed into a continuous-flow reactor at a pressure of 100 bar using an HPLC pump. Catalytic effects of Pt/Al₂O₃ on the gasification temperature were determined. Gas product composition was analyzed using online GC-TCD. A mixture of H₂, CO₂, and CH₄ gas was produced. Quantitative analysis of the total organic carbon in the liquid residue indicated 67% carbon gasification efficiency at 330 °C. Qualitative analyses of liquid residues showed that the main decomposition products in the liquid phase were alcohols and carboxylic acids. It was shown that the hydrogen fuel could be efficiently generated from biomass.     

酿造酒的激光拉曼光谱

用激光拉曼光谱的方法对市场销售的几种酿造酒进行了研究，对酿造酒的拉曼光谱的归属进行了设定，并指出了拉曼光谱对鉴别酒的质量所具有的意义     

Spatially and temporally resolved IR-DFWM measurement of HCN released from gasification of biomass pellets

For the first time, to the best of the authors’ knowledge, nonintrusive quantitative measurement of hydrogen cyanide (HCN) released during the devolatilization phase of straw pellets gasification is demonstrated with high spatial and temporal resolution. Mid-infrared degenerate four-wave mixing (IR-DFWM) measurements of HCN were performed by probing the interference-free P(20) line in the v₁ vibrational band at around 3?µm and the IR-DFWM signal was detected with an upconversion-based detector, providing discrimination of thermal noise and increased sensitivity. A novel single-pellet setup consisting of a multi-jet burner was used to provide hot flue gas environments with an even and well-defined temperature distribution, for single straw pellet gasification at atmospheric pressure. The environments had temperatures of 1380?K, 1540?K and 1630?K with a constant oxygen concentration of 0.5?vol%. In order to quantify the amount of HCN released during the devolatilization of straw pellets, calibration measurements were performed in well-defined HCN gas flows. Selected hot water lines were probed with IR-DFWM in the interrogated volume to obtain the instantaneous temperature, which were used to correct the temperature effect. HCN concentrations up to 1500?ppm were detected during the devolatilization stage, and the results indicate a strong temperature dependence of the HCN release.     

FTIR和Raman用于盐酸曲马多的结构分析

采用AVATAR 360型傅里叶变换红外光谱仪和RM-1000型激光共聚焦拉曼光谱仪测定盐酸曲马多的红外光谱和拉曼光谱。拉曼光谱和红外光谱中均显示出了盐酸曲马多的特征峰,都能够用于其结构鉴别。采用红外、拉曼光谱这两种方法互相印证,互相补充,可增强鉴定的准确性、可靠性。     

Nd-Fe-B永磁合金腐蚀产物的拉曼光谱研究

本文应用拉曼光谱法,研究了Nd—Fe—B永磁合金在NaCl,NaHSO_4水溶液及大气环境中的腐蚀产物组成及其变化。测定结果表明,Nd—Fe—B合金大气腐蚀产物的主要组成为:Nd(OH)_3,γ—FeOOH,α—FeOOH,Fe_3O_4及B_2O_3,在NaCl溶液中则有NdCl_3生成。在不同PH值的NaHSO_4溶液中,锈层的组成有所变化。据此,对Nd—Fe—B合金的腐蚀过程与机理进行了探讨。     

The investigation of single bacteria by means of fluorescence staining and Raman spectroscopy

The successful combination of Raman spectroscopy and fluorescence labelling of single bacterial cells is presented. The results show that the selected dyes (DAPI, SYTO 9, CFDA, SYTOX blue and PI) in most cases do not influence the Raman spectrum of a labelled bacterium significantly compared to an unstained bacterium spectrum. The labelling of bacteria offers the possibility of live/dead or biotic/abiotic differentiation prior to a Raman identification step. Copyright © 2007 John Wiley & Sons, Ltd.     

激光拉曼光谱法无损鉴别人参及其伪品

利用激光拉曼光谱技术并结合二阶导数拉曼光谱,对人参及其拟伪品峨参、北沙参、桔梗进行了鉴别。人参及其伪品均在拉曼光谱中出现了1 460,1 130,1 086,942,483cm-1等拉曼振动峰,根据这些拉曼位移可以判断出在人参及其伪品中都含有糖类物质。北沙参的拉曼谱图中出现了不同于其他三种药材的2 206cm-1的拉曼特征峰。峨参中出现了1 050和1 869cm-1相对应的链状酯类化合物的拉曼振动峰。桔梗中出现了1 227,600,691cm-1等明显不同于其他三种药材的拉曼振动峰。利用这些拉曼振动峰的差异可将人参及其伪品进行很好的区分。再利用二阶导数拉曼光谱图对人参及其伪品的鉴别结果进行进一步的补充说明。此鉴别方法与常规的光谱法相比具有更直接、快速,并且具有不破坏样品的原性质的特点。     

拉曼光谱法结合薄层层析分析红酵母色素

利用薄层层析色谱法分离红酵母色素,结果显示,红酵母细胞能合成至少三种色素,即β-胡萝卜素、红酵母红素、圆酵母红素;采集三种色素的拉曼光谱,光谱数据经过背景扣除、基线校正、三点平滑等方法预处理,统计不同色素的平均光谱,结果表明三种色素的CC拉曼位移不同,并且β-胡萝卜素的拉曼位移最多,红酵母红素和圆酵母红素的含量较多;定量分析色素特征峰高比值,各色素峰高比值差异不大,峰高比值能用作参数,为深入研究活体细胞内色素的相对含量提供参考。以上结果表明,拉曼光谱法结合薄层层析能够分析红酵母色素,可以提供红酵母色素的丰富信息,是研究色素的有效方法。     

光镊捕获金福菇孢子的拉曼光谱分析

使用光镊拉曼光谱系统俘获悬浮在生理盐水中的单个金福菇孢子,激发并收集其拉曼信号,结果显示单个金福菇孢子的拉曼光谱基本能呈现其内含物的组成和结构信息,脂类物质是其主要成分。同种栽培方式的3个不同菌株单个金福菇孢子的平均拉曼光谱信号基本一致,分别对其进行多元统计分析(PCA),无法区分其拉曼光谱信号;同一菌株不同栽培方式的单个孢子平均拉曼光谱的差异光谱表明其主要成分相同,都以脂类物质为主;而源自于脂类1743、1655、1442、1125、1080、1070、876、728cm-1等峰的信号强度基本一致,说明其脂类的含量基本相同。从单细胞拉曼光谱角度初步分析金福菇孢子,为光镊拉曼光谱技术研究食用菌孢子萌发机理提供有意义的参考。     

High-resolution spectroscopy of ethylene by means of a spin-flip-Raman laser

By means of a cw spin-flip-Raman-laser operating in the spin saturated regime the spectrum of the P-branch of thev ₇ +v ₈ parallel vibration of ethylene was investigated. The K-doubling of the rotational-vibrational transitions which is due to the slight deviation of the molecule from a symmetric top was observed.     

甲苯的激光拉曼光谱研究

采用激光拉曼光谱技术获得了甲苯的振动拉曼光谱,结合群论方法及退偏度测量,指认了其中16条振动谱线,为有机混合物中对甲苯的识别提供了依据．选择甲苯全对称环呼吸振动（1008.8cm－1）为检测谱线,对不同浓度的甲苯／四氯化碳样品进行了分析．研究结果表明：在200．1～2．61g／L浓度范围内,甲苯／四氯化碳振动拉曼光谱强度比与甲苯浓度呈良好的线性关系,线性相关系数为0.997．为甲苯的定量分析提供了一种有效的研究方法．     

Investigating the formation of an adduct of formamide with dioxane by means of Raman spectroscopy

Raman experiments of formamide (FA) and p‐dioxane (DX) mixtures at different compositions were carried out. A red shift of the C O stretching band of DX was observed upon dilution, while blue shifts were observed for the C H stretching and C O C bending bands. In this latter region, the new band at ∼441 cm⁻¹, whose intensity shows large dependence on the FA concentration, has been assigned to an FA–DX adduct and it is reported for the first time in the literature. The spectral changes observed in the C O C bending region allowed to determine a proportion of 4:1 FA–DX and this experimental evidence is also presented for the first time by Raman spectroscopy. The present work shows an excellent agreement with our previous investigation, where the 2:1 FA—THF (tetrahydrofuran) adduct was characterized. Copyright © 2008 John Wiley & Sons, Ltd.     

Laser ablation of powdered samples and analysis by means of laser-induced breakdown spectroscopy

The presented work proves the capacities of laser-induced breakdown spectroscopy (LIBS) as a fast, universal, and versatile technique for analysis of complex materials as ceramics. This paper reports on the analysis of ceramic raw materials (brick clays and kaolin) submitted to laser ablation in the form of pressed pellets. Spectrographic study was provided by standard single-pulse LIBS technique and orthogonal reheating double-pulse LIBS. It was found that both methods are comparable in terms of analytical performance, if adequate experimental parameters and signal detection systems are used.     

Quantitative analysis of cement powder by laser induced breakdown spectroscopy

Determination of elemental composition of cement powder plays an important role in the cement and construction industries. In the present paper, Laser induced breakdown spectroscopy (LIBS) is used for measuring the concentration of cement ingredient. Cement powder samples are pressed into pellets. Laser pulses are focused on the surface of pellets. A microplasma is formed in the front of samples. The plasma emission contains information about the elemental composition of the samples. By assumption of local thermodynamic equilibrium (LTE) and using several standard cement samples, a calibration curve is prepared for each element. The major and minor elements of cement such as Ca, Si, K, Mg, Al, Na, Ti, Mn and Sr are qualitatively and quantitatively determined. For verification of LTE conditions, plasma parameters such as plasma electron temperature and electron density are computed. According to the obtained results, the LIBS technique could be a suitable method for determination of elemental composition in the cement production industries.     

Terahertz laser velocity modulation spectroscopy of ions

Velocity modulation spectroscopy has been investigated in the terahertz region, employing pure rotational transitions of ArH⁺ and rotation-tunneling transitions of H₃O⁺ to study the competition between pressure broadening and Doppler broadening on the lineshapes, neutral suppression, and modulation efficiency. Velocity modulation is demonstrated to be effective to frequencies as low as 60 cm⁻¹, yielding S/N values for ArH⁺ (770/1) that surpass published terahertz FM results by an order of magnitude.