Pyrolysis of brominated feedstock plastic in a fluidised bed reactor

Fire retarded high impact polystyrene has been pyrolysed using a fluidised bed reactor with a sand bed. The yield and composition of the products have been investigated in relation to fluidised bed temperature. The bromine distribution between the products and a detailed analysis of the oils using GC-FID/ECD, GC-MS, FT-ir, and size exclusion chromatography has been carried out. It was found that the majority of the bromine transfers to the pyrolysis oil and the antimony was detected in both the oil and the char. Oil made up over 89.9% of the pyrolysis products. Over 30% of the oil consisted of benzene, toluene, ethylbenzene, styrene and cumene. The pyrolysis gases were mainly hydrocarbons in the C1-C4 range but some HBr and Br2 was detected

Is the Broido - Shafizadeh model for cellulose pyrolysis true?

The widely accepted Broido-Shafizadeh model describes cellulose pyrolysis kinetics in terms of two parallel (competing) reactions preceded by an initiation step. In spite of the fact that many recent experimental results seem to contradict the predictions of the model, its validity has not been seriously questioned. In this paper we report thermogravimetric analyses of Avicel cellulose involving prolonged thermal pretreatments of small samples (0.5 to 3 mg). The weight loss curves were simulated by modern numerical techniques using the Broido-Safizadeh and other related models. Results were not consistent with the presence of an initiation reaction, but they did strongly confirm the role of parallel reactions in the decomposition chemistry. A subsequent, high temperature (370 °C), pyrolytic degradation of solid intermediates formed below 300 °C was also detected. In the absence of a prolonged thermal pretreatment, only one of the two parallel reactions can be observed. This reaction is first order, irreversible, and manifests a high activation energy (238 kJ/mol). The kinetic parameters of this reaction are not influenced by the large quantity of solid intermediates formed during prolonged, low-temperature thermal pretreatments, indicating that chemical processes are much more significant than the physical structure of the sample during pyrolysis

Cellulose pyrolysis kinetics: Revisited

In the same thermogravimetric analyzer (TGA) under identical conditions, samples of pure, ash-free cellulose (i.e. Avicel PH-105, Whatman CF-11, Millipore ash-free filter pulp, and Whatman #42) obtained from different manufacturers undergo pyrolysis at temperatures which differ by as much as 30 C. Thus the pyrolysis chemistry of a sample of pure cellulose is not governed by a universal rate law, as is the case with a pure hydrocarbon gas (for example). Nevertheless, the pyrolytic weight loss of all the samples studied in this work is well represented by a high activation energy (228 kJ/mol), first order rate law at both low and high heating rates. These results do not corroborate the recent findings of Milosavljevic and Suuberg (1995). For a particular cellulose sample (for example Avicel PH-105), variations in the pre-exponential constant determined at different heating rates reflect uncontrolled, systematic errors in the dynamic sample temperature measurement (thermal lag)

A review on sheet erosion measurements in Hungary

Soil erosion has a significant role in ecology, economy and in environmental protection therefore its quantification and prediction are very important, particul arly on a national level. Although some details can be described using physical equations, the entire soil erosion process is rather complicated and can be determined only empirically, which requires large measured datasets. Because plot measurement is the most convenient and therefore the most popular way of capturing erosion data, we used plot measurement to understand erosion in Hungary. The northern and the western parts of the country are endangered by sheet erosion, which is why the plots were carried out in those areas. Most of the plots were constructed to determin e the “K” factor of the USLE (Universal Soil Loss Equation) under permanently tilled soils without vegetation cover. Additionally the soil protection effect of various field crops and the additiona l land use types (forest, pasture) was measured in the plots. Furthermore descriptive investigations, rainfall si mulations and soil tracer detections were also used to quantify sheet erosion at different environmental conditions and scales. Despite the large amount of measured data collected, only a few of them have since been pub lished. Due to a lack of available data, national erosion research, erosion prediction, and model calibration are less precise and effective Scaling problems among the measured levels also emphasized a de finite need for a larger and more accessible national database. Finally, without the financial base of additional plot measurements , the publication of the previously gathered data is absolutely necessary to continue soil erosion studies in Hungary

Kinetic modeling of biomass pyrolysis : 10 years of a US - Hungarian cooperation

The thermal decomposition of lignocellulosic biomass materials and their major components is discussed. Thermogravimetric and DSC curves at different T(t) heating programs were evaluated by the method of least squares. Pseudo-first order models, parallel, successive and competitive reaction schemes and complex reaction networks were employed in the modeling. The following topics are treated: thermal decomposition of cellulose at low (2°/min) and high (50 - 80°C/min) heating rates; low temperature phenomena; the validity of the Broido – Shafizadeh model; effects of mineral catalysts; cellulose pyrolysis in closed sample holders; thermal decomposition kinetics of xylan, lignin and lignocellulosic plant samples. Keywords: Biomass, Cellulose, Hemicellulose, Lignin, Reaction kinetics, Thermogravimetry, DS

VOICE QUALITY ASSESSMENT DURING VOICE TRANSMISSION\ud BY VARIOUS NETWORK TECHNOLOGIES\ud

This paper deals with the voice quality system assessment including calculation of the noise floor during voice transmission by various network technologies. Voice over Internet Protocol (VoIP) development presupposes solution of the problems related to effective voice transmission with required transmission parameters (Quality of Services - QoS). One of the mechanisms that may be used for assurance of service quality in IP networks is the QoS model. The QoS model is used to evaluate the VoIP quality and to design the VoIP networks. The voice quality may be determined using the passive method – E-model – which respects the used codec, the packet loss and the delay or the jitter. Attention is also paid to the calculation of the noise floor emphasizing the possibilities of the signal-to-noise ratio estimating. This paper also presents results of experimental verification of the designed solution implementation functionality.\ud Описано систему оценки качества голоса включая определение порога шума в течении передачи голоса различными сетевыми технологиями. Развитие передачи голоса интернет протоколом (VoIP) предпочитает решение проблем относящихся к эффективной передачи голоса с требованными параметрами передачи (качество сервиса - QoS). Одним из механизмов, который может быть использован для обеспечения качества сервиса в IP сетях является QoS модель. QoS модели используются для оценки качества VoIP и для проектирования VoIP сетей. Качество голоса может быть определено с использованием пасивного метода – E-модели, которая отражает использован кодек, потерю пакетов, опаздывание и его колебание. Внимание уделяется определению порога шума подчеркивающее возможности оценки отношения сигнал-шум. Приведены результаты экспериментальной проверки функционирования имплементации предложенного решения.\u

Comparison of soil erosion dynamics under extensive and intensive cultivation based on basic soil parameters

The conservation of soil and its elemental feature, t he soil fertility has not just national and agricultural business interest, since the fertile soil is an elemental part of the material turnover in the environment. The soil erosion can reach huge spatial e xtensions and starts with the most valuable part: the upper, fertile layer. So, its research is crucial for our future survival. Our studied area can be found in Gerézdpuszta at the Koppány -valley of Hungary, which is a sensitive erosion area. We sampled the upper 30 cm of soil layer in every 10 meters that resulted 32-32 point samples on the arable and on the grassland, respectively. One sample was taken under the forest as r eference. We analyzed the basic soil parameters: CaCO 3 , pH, AL-P 2 O 5 , AL-K 2 O, Kuron’s higroscopicity, SOM and the particle size di stribution was determined. Besides, we examined the connection between the given results from laboratory soil analyses and the Munsell-type and Google Earth satellite image colors. O ur results show the erosion dynamic on our sample slope, and the main differences in basic soil paramet ers between different intensities. The main indicator of soil erosion dynamic were the CaCO 3 , the SOM, AL-P 2 O 5 and the particle size distribution, where the SOM and CaCO 3 were correlate with the Munsell and Google Earth col or also

A New Method to Measure Portal Venous and Hepatic Arterial Blood Flow Patients Intraoperatively

The intraoperative measurement of the afferent circulation of the liver, namely the hepatic artery flow and portal venous flow was carried out upon 14 anesthetized patients having carcinoma in the splanchnic area, mainly in the head of the pancreas by means of transit time ultrasonic volume flowmeter. The hepatic artery flow, portal venous flow and total hepatic flow were 0.377±0.10; 0.614±0.21; 0.992±0.276 l/min respectively

Application of complex reaction kinetic models in thermal analysis. The least squares evaluation of series of experiments

The complexity of the phenomena which arise during the heating of the various substances seldom can be described by a single reaction kinetic equation. As a consequence, sophisticated models with several unknown parameters have to be developed. The determination of the unknown parameters and the validation of the models requires the simultaneous evaluation of whole series of experiments. We can accept a model and its parameters if, and only if we get a reasonable fit to several experiments carried out at different experimental conditions. In the field of the thermal analysis the method of least squares alone seldom can select a best model or a best set of parameter values. Nevertheless, the careful evaluation of the experiments may help in the discerning between various chemical or physical assumptions by the quality of the corresponding fit between the experimental and the simulated data. The problem is illustrated by the thermal decomposition of cellulose under various experimental conditions

Combustion Kinetics of Corncob Charcoal and Partially Demineralized Corncob Charcoal in the Kinetic Regime

Charcoals produced by a modern, efficient method were studied in the kinetic regime, at oxygen partial pressures of 0.2 and 1 bar by thermogravimetric experiments and their reaction kinetic modeling. The charcoals were ground to an average particle size of 5 – 13 µm. A partial removal of minerals from the feedstock (corncobs) by an acid-washing procedure resulted in ca. 6 times higher specific surface area in the charcoal. In spite of the increased surface area, this sample evidenced a much lower reactivity. A model based on three reactions gave an adequate description over a wide range of experimental conditions. 38 experiments on 4 charcoal samples were evaluated. The experiments differed in their temperature programs, in the ambient gas composition and in the grinding of the samples. Characteristics of the combustion process were determined, including activation energy values characteristic for the temperature dependence of the burn-off; formal reaction orders characterizing the dependence on the oxygen content of the ambient; and functions describing the conversion dependence of the partial processes