Technické aspekty výroby elektřiny a tepla ze zplynění odpadní biomasy z jihomoravské pily

The paper presents results of tests on a pilot plant using waste from the process timber. Experiments presented were obtained from the gasification of different biomass fuels, as well as various types of reactors. Presented biomass gasification technology shows the optimization process of converting fuel to its energy use in cogeneration unit. Installation requires few refinements of various gas purification components and the preparation of a long work to obtain the best possible economic effects.Příspěvek prezentuje výsledky testů na pilotním zařízení určeném pro využití odpadního dřeva z pilařského průmyslu. Prezentovány experimenty byly získány ze zplyňování různých paliv, v různých typech reaktorů. Prezentovaná technologie zplyňování biomasy ukazuje optimalizaci procesu přeměny pevného paliva na plyn a jeho energetické využití v kogenerační jednotce. Instalace vyžaduje vylepšení systému čištění plynu a přípravu dlouhodobého provozu pro získání co nejlepších ekonomických výsledků

Modelování jílovitých výsypek

MODELLING OF LUMPY CLAY FILLS Jan Najser Abstract An extensive open cast mining of brown coal has been taking place in NW Bohemia since 1940's. During the mining process, overburden clay is placed in the form of irregularly shaped lumps of typical dimensions up to 500 mm into large spoil heaps. The total thickness of the lumpy clay landfills is usually 20-50 m. Their material has a double porosity structure: the porosity of intact clay (intragranular porosity) and the voids between clay lumps (intergranular porosity). The total porosity of the fresh fill can be up to 70%. This soil presents special challenges for geotechnical design, primarily because of its high and non-uniform settlement. Further, the progressive tranformation from the "granular" to "fine-grained" material makes the lumpy clay difficult to characterise and model. The aim of the presented thesis is to describe the behaviour of the landfill and the change of its structure by means of field measurements, the centrifuge and numerical modelling. During site investigation for a motorway over a 20-30 years old landfill, two trial embankments were built and monitored over the period of 3 and 6 years respectively. The subsoil of the embankments was instrumented by hydrostatic levelling profiles, pore pressure transducers and depth reference points...MODELOVÁNÍ JÍLOVITÝCH VÝSYPEK Jan Najser Abstrakt Od 40. let minulého století probíhá v severních Čechách rozsáhlá povrchová těžba hnědého uhlí. Odtěžený nadložní jíl se ukládá na výsypky ve formě hrud o průměru do 500 mm. Průměrná výška výsypek dosahuje 20 až 50 m. Charakteristickou vlastností výsypek je jejich dvojí pórovitost, která je dána vnitřní pórovitostí jílových hrud (intragranulární pórovitost) a mezerovitostí (intergranulární pórovitost). Celková pórovitost čerstvé výsypky může dosáhnout až 70%. Vysoká a nerovnoměrná stlačitelnost výsypek komplikuje jejich budoucí využití pro zakládání staveb. Dalším problematickým faktorem je změna struktury výsypek v čase, při které dochází k jejich homogenizaci a přeměně původně sypkého materiálu na zeminu s mechanickým chováním odpovídajícím jílu. V důsledku těchto faktorů jsou mechanické vlastnosti starých výsypek obtížně předpověditelné. Cílem práce je popis mechanického chování výsypek a změn jejich vnitřní struktury na základě analýzy terénních měření, fyzikálního modelování v geotechnické centrifuze a numerického modelování. V souvislosti se stavbou dálnice D8 byly v letech 1998 a 2001 v plánované trase dálnice vybudovány dva pokusné násypy. Násypy, postavené na 20-30 let staré vodou nasycené výsypce, byly monitorovány po dobu 3 a 6 let. Podloží násypů...Institute of Hydrogeology, Engineering Geology and Applied GeophysicsÚstav hydrogeologie, inž. geologie a užité geofyzikyFaculty of SciencePřírodovědecká fakult

Construction of Motorway on Double Porosity Clay Fill

The paper describes the mechanical behaviour of double porosity clay fills. A trial embankment had been constructed on a 20-30 year-old landfill and monitored for 3 years. The embankment was instrumented by hydrostatic levelling profiles, surveying reference points, pore pressure gauges, inclinometers and depth reference points. Centrifuge modelling of the embankment behaviour on the consolidated landfill was carried out in the geotechnical centrifuge at ETH Zürich in Switzerland. The models were instrumented similarly to the real embankment with pore pressure transducers and a newly developed tool called “system of straws” for measurement of deformation at different depths. Surface deformations were measured by laser scanning. The results of centrifuge modelling are compared with in-situ data. The degradation of the double porosity structure in the vertical profile of the landfill, and its influence on the permeability of the soil is discussed

Vanadium – Valuable and toxic element in coal combustion ash: An overview

The paper evaluates all important aspects related to V present in coal and its behaviour during coal combustion with particular attention paid to its potential extraction from ash and slag wastes. Due to great environmental benefits of co-combustion of coal and wastes, these alternative fuels and corresponding ash and slag counterparts were also taken into evaluation. Specifically, the paper summarizes V levels in world coals, in other related materials (alternative fuels, additives etc.) and in ash and slag residues including V speciation and discussion of its valence states. Theoretically predicted (equilibrium-based) calculations and species are compared with experimental results; due to a significant effect on mitigating CO2 emissions, attention is paid also to oxy-fuel combustion conditions. With the aim to extract V out of the ash and slag residues, physical, chemical, and biotechnological separation methods are discussed in detail along with dominant affecting factors. The paper includes also concluding remarks and highlights the most promising trends and limitations thereby providing suggestions for future research.Web of Science17294092

Gasification of Miscanthus x giganteus Pellets in a Fixed bed Pilot-scale Unit

Gasification of Miscanthus x giganteus (Mxgig), is highly promising due to the high efficiency of the process and the many advantageous properties of this crop. Pilot-scale, fixed bed gasification studies were performed utilizing this fuel at three temperatures (750, 850, and 950 degrees C) to determine the process effects of temperature on gas quality and tar yields. Simple thermodynamic equilibrium modeling was successfully applied to the pilot-scale gasification process. The Mxgig crop performed well, with best process stability reached at temperatures of 800 degrees C or higher. Average calorific values of the product gases were highest at around 850 degrees C at 5.2 MJ.m(-3). Tar yields gradually increased with increasing temperature and dropped after 900 degrees C. The presented thermodynamic equilibrium model conformed well with experimental results, deviating little in terms of O-2, CO2, H-2, and CH4 and no more than 8.1% in the case of CO. This indicates that simple modeling methods can be utilized to predict gas compositions for the pilot-scale.Web of Science6art. no. UNSP 9

On the possibility of cleaning producer gas laden with large quantities of tars through using a simple fixed-bed activated carbon adsorption process

The study presents the results of research on using fixed-bed, activated carbon (AC) adsorbers in the cleaning of heavily tar-laden producer gas from the gasification of biomass. The efficiency of removal of organic compounds as well as the remaining adsorption capacity of the bed were determined using a spectrum of commonly applied diagnostic methods, including qualitative and quantitative analyses of the adsorbed compounds and changes in the pore volume of the bed material (IN, MN). The authors compare these lab quantifications with a simple technique which is based on the analysis of the changes in the position of temperature front in the bed. The main benefit of the latter is the possibility of performing the diagnostics of the bed "online" and using low-cost temperature measurements. The test was performed using a commercially available AC Desotec AIRPEL 10-3 and real producer gas obtained through the gasification of alder chips. For tar, VOC and C-2-C-5 compounds, the removal efficiencies reached respectively 74.5%-wt., 52.8%-wt., and 85.5%-wt. Obtained results indicate that depending on the final application of the gas, the use of dry adsorption systems is an interesting alternative to the well-established but complicated, cumbersome, and costly wet scrubbers. Moreover, a concept for in situ regeneration of the adsorbent, coupled with direct reforming of the tars, is presented and discussed.Web of Science1519art. no. 743

Analysis of the effect of catalytic additives in the agricultural waste combustion process

This paper presents the research results of the effect of using calcium oxide and potassium permanganate on the combustion of pellets from wheat bran and beet pulp. The measurements were performed in the technical laboratory of the Centre of Energy Utilization of Non-Traditional Energy Sources in Ostrava. The research examined the effect of the use of chemical substances on the amount of air pollutants from biomass thermal conversion in a low-power boiler and the process temperature. First, we performed technical and elementary analyses of agricultural waste. The raw material was then comminuted, mixed with a selected additive, pelletized, and finally burned in a low-power boiler. The additive was added in three proportions: 1:20, 1:10, and 1:6.67 (i.e., 15%) relative to the fuel weight. The combustion process efficiency was measured using a flue gas analyzer and three thermocouples attached to the data recorder. From the measurement results, we were able to determine the percentage reduction of pollutant emissions into the atmosphere (CO, NOx, and SO2) due to the use of additives. Because emission standards are becoming increasingly stringent and fuel and energy prices are rising, the results presented in this article may be useful to agri-food processing plants that want to manage these materials thermally.Web of Science1510art. no. 352

Selection of appropriate symbolic regression models using statistical and dynamic system criteria: Example of waste gasification

In this paper, we analyze the interpretable models from real gasification datasets of the project "Centre for Energy and Environmental Technologies" (CEET) discovered by symbolic regression. To evaluate CEET models based on input data, two different statistical metrics to quantify their accuracy are usually used: Mean Square Error (MSE) and the Pearson Correlation Coefficient (PCC). However, if the testing points and the points used to construct the models are not chosen randomly from the continuum of the input variable, but instead from the limited number of discrete input points, the behavior of the model between such points very possibly will not fit well the physical essence of the modelled phenomenon. For example, the developed model can have unexpected oscillatory tendencies between the used points, while the usually used statistical metrics cannot detect these anomalies. However, using dynamic system criteria in addition to statistical metrics, such suspicious models that do fit well-expected behavior can be automatically detected and abandoned. This communication will show the universal method based on dynamic system criteria which can detect suitable models among all those which have good properties following statistical metrics. The dynamic system criteria measure the complexity of the candidate models using approximate and sample entropy. The examples are given for waste gasification where the output data (percentage of each particular gas in the produced mixture) is given only for six values of the input data (temperature in the chamber in which the process takes place). In such cases instead, to produce expected simple spline-like curves, artificial intelligence tools can produce inappropriate oscillatory curves with sharp picks due to the known tendency of symbolic regression to produce overfitted and relatively more complex models if the nature of the physical model is simple.Web of Science119art. no. 46

Influence of the use of permanent catalytic systems on the flue gases emission from biomass low-power boilers

The paper presents the research results on the use of permanent catalytic systems applied to the surface of a low-power boiler deflector. The tests were carried out on a standard 15 kW retort boiler. The boiler was powered by three types of biomass pellets (wood pellets, wheat straw pellets, and hemp expeller). In the research cycle, the influence of the catalysts on the emission of individual compounds, CO, NOX, particulate matter (PM), polycyclic aromatic hydrocarbons (PAH), and volatile organic compounds (VOC) and the influence on the temperature in the combustion chamber were examined. The tests used an exhaust gas analyzer, a dust meter, a two-channel aspirator, and a laboratory gas chromatograph stand with a flame ionization detector. Four catalysts (copper, manganese, titanium, and platinum) were prepared for the analysis. Each catalyst had three variants of the active substance concentration on the ceramic support surface: 17.5 g, 35 g, 52.5 g for CuO, TiO2, MnO2, and, respectively, 0.05 g, 0.1 g, and 0.15 g for platinum. Concerning the deflector surface, this concentration corresponded to 140, 280, and 420 g center dot m(-2) for CuO, TiO2, and MnO2, and 0.4, 0.8, and 1.2 g center dot m(-2) for platinum catalysts. All the catalysts used contributed to an increase in the combustion temperature and a reduction in pollutant emissions. The results presented in the paper will allow the implementation of the developed solutions in the industry producing low-power boilers and in already-existing heating installations. The factor that motivates the introduction of changes may be continuously tightening European emission regulations.Web of Science127art. no. 71

Analysis of the effect of Fe2O3 addition in the combustion of a wood-based fuel

A comparative study was carried out of emissions from the catalytic combustion of pellets made from furniture board waste and pellets made from wood mixed with Fe2O3 . The mass content of the Fe2O3 catalyst in the fuel was varied from 0% to 5%, 10%, and 15% in relation to the total dry mass weight of the pellets. The average flame temperature in the boiler was between 730 and 800 ◦C. The effect of the catalyst concentration in the fuel was analysed with respect to the contents of O2, CO2, CO, H2, and NOx in the flue gas and the combustion quality of the pellets in the heating boiler. Changes in the CO2 content and the proportion of unburned combustible components in the combustion residue were assessed. It was established that an increase in the Fe2O3 content of the prepared fuels had a positive effect on reducing NOx, CO, and H2 emissions. However, the proportion of iron oxide in the tested fuel pellets did not significantly influence changes in their combustion quality. A strong effect of the addition of Fe2O3 on the reduction of the average NOx content in the flue gas occurred with the combustion of furniture board fuel, from 51.4 ppm at 0% Fe2O3 to 7.7 ppm for an additive content of 15%. Based on the analysis of the residue in the boiler ash pan, the amount of unburned combustibles relative to their input amounts was found to be 0.09–0.22% for wood pellets and 0.50–0.31% for furniture board waste pellets.Web of Science1521art. no. 774