Wood pyrolisys using aspen plus simulation and industrially applicable model

Over the past decades, a great deal of experimental work has been carried out on the development of pyrolysis processes for wood and waste materials. Pyrolysis is an important phenomenon in thermal treatment of wood, therefore, the successful modelling of pyrolysis to predict the rate of volatile evolution is also of great importance. Pyrolysis experiments of waste spruce sawdust were carried out. During the experiment, gaseous products were analysed to determine a change in the gas composition with increasing temperature. Furthermore, the model of pyrolysis was created using Aspen Plus software. Aspects of pyrolysis are discussed with a description of how various temperatures affect the overall reaction rate and the yield of volatile components. The pyrolysis Aspen plus model was compared with the experimental data. It was discovered that the Aspen Plus model, being used by several authors, is not good enough for pyrolysis process description, but it can be used for gasification modelling

Thermo-catalytic pyrolysis of polystyrene in batch and semi-batch reactors: A comparative study

Thermo-catalytic pyrolysis is considered as a promising process for the chemical recycling of waste polymeric materials aiming at converting them into their original monomers or other valuable chemicals. In this regard, process parameters and reactor type can play important roles for an enhanced recovery of the desired products. Polystyrene (PS) wastes are excellent feedstocks for the chemical recycling owing to the capability of PS to be fully recycled. In this respect, the present work deals with the thermo-catalytic pyrolysis of PS in batch and semi-batch reactor setups. The main goal was to perform a comprehensive study on the depolymerisation of PS, thereby investigating the effect of reactor type, catalyst arrangement, feed to catalyst ratio and residence time on the yields of oil and styrene monomer (SM). A further goal was to identify the optimum operating conditions as well as reactor type for an enhanced recovery of oil and SM. It was demonstrated that the semi-batch reactor outperformed the batch reactor in terms of oil and SM yields in both thermal (non-catalytic) and catalytic tests performed at 400 degrees C. Furthermore, it was shown that the layered arrangement of catalyst (catalyst separated from PS) produced a higher amount of oil with higher selectivity for SM as compared to the mixed arrangement (catalyst mixed with PS). Moreover, the effect of carrier gas flowrate on the product distribution was presented.Web of Scienceart. no. 0734242x2093674

Influence of Miscanthus rhizome pyrolysis operating conditions on products properties

Waste from the Miscanthus production cycle may be a promising source of material for the pyrolysis and biochar production. The biochar can be used to enrich the soil on which the crop grows, thus increasing productivity. A sample of Miscanthus rhizomes was used as a raw material in a series of experiments in order to find the most suitable conditions for the preparation of biochar. Miscanthus biochar was prepared in a laboratory unit using four different temperatures (i.e., 400, 500, 600 and 700 degrees C). All pyrolysis products were subsequently evaluated in terms of their quality and product yields were determined. For a temperature of 600 degrees C and a residence time of 2 h, the appropriate properties of biochar were achieved and the process was still economical. The biochar contained a minimal number of polycyclic aromatic hydrocarbons and a high percentage of carbon. Surface area was measured to be 217 m(2)/g. The aqueous extract of biochar was alkaline.Web of Science1410art. no. 619

Hematites precipitated in alkaline precursors: Comparison of structural and textural properties for methane oxidation

Hematite (alpha-Fe2O3) catalysts prepared using the precipitation methods was found to be highly effective, and therefore, it was studied with methane (CH4), showing an excellent stable performance below 500 degrees C. This study investigates hematite nanoparticles (NPs) obtained by precipitation in water from the precursor of ferric chloride hexahydrate using precipitating agents NaOH or NH4OH at maintained pH 11 and calcined up to 500 degrees C for the catalytic oxidation of low concentrations of CH4 (5% by volume in air) at 500 degrees C to compare their structural state in a CH4 reducing environment. The conversion (%) of CH4 values decreasing with time was discussed according to the course of different transformation of goethite and hydrohematites NPs precursors to magnetite and the structural state of the calcined hydrohematites. The phase composition, the size and morphology of nanocrystallites, thermal transformation of precipitates and the specific surface area of the NPs were characterized in detail by X-ray powder diffraction, transmission electron microscopy, infrared spectroscopy, thermal TG/DTA analysis and nitrogen physisorption measurements. The results support the finding that after goethite dehydration, transformation to hydrohematite due to structurally incorporated water and vacancies is different from hydrohematite alpha-Fe2O3. The surface area SBET of Fe2O3_NH-70 precipitate composed of protohematite was larger by about 53 m(2)/g in comparison with Fe2O3_Na-70 precipitate composed of goethite. The oxidation of methane was positively influenced by the hydrohematites of the smaller particle size and the largest lattice volume containing structurally incorporated water and vacancies.Web of Science2315art. no. 816

Vliv kvalitativních parametrů černouhelné smoly na texturní vlastnosti uhlíkatého materiálu

Import 11/03/2010Prezenční617 - Katedra chemieNeuveden

Hydrodynamics of Multiphase flow Reactors

Import 15/01/2013Reaktory s vícefázovými toky jsou široce zastoupeny v mnoha odvětvích nejen chemického průmyslu. Oblastí zájmu předkládané práce je vícefázový probublávaný reaktor s vnitřní cirkulační smyčkou hnanou sací trubicí, označovaný jako Pachuca. Pachuca zpravidla slouží pro loužení kovů z rud a hornin nebo z metalurgických odpadů. Předmětem disertační práce je studium hydrodynamického chování vícefázového toku uvnitř reaktoru se sací trubicí (s vnitřní cirkulační smyčkou). Prvním cílem práce byl návrh a konstrukce laboratorního reaktoru. Při studiu chování dvoufázového toku v laboratorním reaktoru se měřily tlakové diference na sestavených manometrech s obrácenou U-trubicí. Měření byla podle místa odběru interpretována jako základní hydrodynamické parametry: zádrž plynu, hustota disperze, cirkulační rychlost kapaliny a koeficient ztrát. Z experimentů bylo zjištěno, že geometrie sací trubice, vyjádřená poměrem průměru sací trubice k průměru reaktoru (ddf /dc) má zásadní vliv na tyto hydrodynamické parametry. S klesajícím poměrem ddf /dc vzrůstá cirkulační rychlost kapaliny v sací trubici a zároveň klesá zádrž plynu v mezikruží. Dalším zkoumaným parametrem, který ovlivňuje vícefázovou hydrodynamiku, byla poloha sací trubice v reaktoru. Tato poloha je vyjádřena bezrozměrnými vzdálenostmi konců sací trubice od dna a od hladiny. Při experimentech byly rovněž identifikovány typy cirkulačních režimů bublin, které řídí hydrodynamiku uvnitř reaktoru se sací trubicí. Vzhledem k existenci velkého počtu možných nastavitelných proměnných parametrů a časové náročnosti vlastních experimentů, byl navržen jednoduchý numerický model popisující mezní situace při dvoufázovém toku. Pro CFD simulaci byl použit model bublinového toku programu COMSOL Multiphysics. Výsledky experimentů s různými poměry ddf /dc byly srovnány s výsledky CFD simulace. Srovnání přineslo poznatky o možnosti využití tohoto modelu pro hledání optimální geometrie pro třífázový tok. Na základě výsledků studia dvoufázového toku byla navržena vhodná geometrie reaktoru s třífázovým tokem. V reaktoru s třífázovým tokem byl nalezen hysterezní charakter tlakové diference, ze které byly stanoveny kritické průtoky plynu pro suspendaci částic při vzrůstajícím nebo klesajícím průtoku plynu.The multiphase flow reactors are widely used in the chemical and other process industry. Multiphase flow reactor with internal circulation loop called Pachuca was in focus of interest of my thesis. The Pachuca tank is a typical hydrometallurgical reactor for leaching of ore, other minerals, or metallurgical wastes. Study of hydrodynamic behavior of multiphase flow in reactor with a draft tube (with internal circulation loop) was the main topic of my PhD thesis. Design and construction of laboratory reactor with the draft tube was first aim of my work. The hydrodynamics parameters such as gas hold-up, density of dispersion, liquid circulation velocity and loss coefficient were determined from measured pressure differences. The inverse U-tube manometers were used for the measurement of the pressure differences. The geometry of equipment was characterized by the dimensionless ratio of diameter of the draft tube to the diameter of reactor (ddf /dc). This ratio had a primary influence to the hydrodynamics parameters. Increasing of liquid circulation velocity in the draft tube (riser) simultaneously with gas hold-up in annulus (downcomer) decreasing as a function of decreasing ratio ddf /dc was observed. Position of the draft tube was further parameter, which affected the hydrodynamics of multiphase flow. These positions were characterized by the dimensionless ratio of the draft tube upper end and the liquid level heights, and by the dimensionless ration of the draft tube lower end and the bottom of reactor. Patterns of the bubbles circulation regimes to the hydrodynamic in the laboratory reactor were observed besides of the quantitative parameters. Large number of geometry configurations can be varied and the measurement is time consuming. For these reasons, simple numerical model was suggested. The COMSOL Multiphysics software with bubbly flow model was used for CFD simulation. The results of experiments and results of CFD simulation were compared for three magnitudes of ratio ddf /dc. Agreement between the respective results proved that the numerical simulation is suitable tools for investigation of three-phase flow. Optimized design of three-phase flow reactor was suggested on the base of the results for the two-phase flow. Hysteresis of the pressure difference was found in three-phase flow reactor and then, critical gas volumetric flows for suspended solid particles have been determined for increasing and decreasing gas volumetric flow, respectively.Prezenční617 - Katedra chemievyhově

Synthesis of Carbon Sorbents with the Ordered Porous Structure

Import 01/09/2009Prezenční619 - Katedra fyzikální chemie a teorie technologických pochodůvýborn

Wet flue gas desulphurization using a new O-element design

Scrubbing by liquid sprayingis one of the most effective processes used for removal of fine particles and soluble gas pollutants (such as SO2, HCl, HF) from the flue gas. The primary function of venturi scrubber, which represents the first stage of the wet flue gas cleaning processes, such as in waste incineration plants, is to capture fine particles as well as remove HCl, HF or SO2 as a result of the decrease in the flue gas temperature before entering the absorption column. In this paper, a newly developed four-branch O-element is proposed as a replacement for venturi scrubber. By means of this device, sulphur dioxide (SO2) removal efficiency and pressure loss and temperature drop were experimentally calculated. The dependence of these variables on liquid–gas ratio was monitored. The simulated flue gas was prepared by the combustion of the carbon disulphide solution in toluene (1:1 vol.) in the presence of the flame in the reactor. Such prepared flue gas with temperature around 150 °C was processed in the laboratory-designed O-element scrubber. Water was used as an absorbent liquid. The maximal efficiency of SO2 removal achieved by this process was up to 70 %, which is far better in comparison with the commonly used venturi scrubbers. The pressure drop of our proposed newly designed wet scrubber is similar to that of the commonly used venturi scrubbers; nevertheless, the influence of the amount of the liquid on pressure drop is not so significant. In parallel, a mathematical model describing the mass transfer, enthalpy balance and pH change of the absorbing solution was also developed. Enthalpy balance was calculated by numerical iteration to determine the unknown outlet liquid temperature. Mass transfer calculation was used for the determination of complete Henry constant from all the subsequent SO2 absorption reactions.Web of Science19242641

Influence of potassium hydroxide and method of carbonization treatment in garden and corn waste microwave pyrolysis

After initial selection, the samples of garden and corn waste were activated by potassium hydroxide and processed by microwave pyrolysis using both single-step and double-step methods. Experiments were carried out in a self-made microwave reactor for 20 min at the power of 440 W. The distribution and quality of the resulting products were evaluated. The gaseous components were analysed discontinuously by gas chromatography. The concentration of measured hydrogen (activated corn waste 54.4 vol %, non-activated corn waste 18.8 vol %) was strongly influenced by activation and material selection. The char with a heating value of 33.3 MJ kg(-1) suggested the direction of its further use as fuel. Optimum conditions of sorbents production from garden waste material with a surface area of 530m(2) g(-1) with regard to the influence of the activation were determined.Web of Science118454

The removal of CO2 from biogas using a laboratory PSA unit: design using breakthrough curves

The production of biomethane from biogas offers the possibility to obtain chemical resources fuels from combustion engines, gas turbine and fuel cells. However, each biomethane application requires specific treatment. This work is focused on the removal of CO2 from biogas as a fundamental step in biogas treatment. A laboratory scale PSA unit is introduced in this paper. The extruded activated carbon was used to construct the fixed bed adsorption layer. The maximum sorption capacity of CO2 was determined from the adsorption isotherm of pure CO2 carried out in a high pressure thermogravimeter. Breakthrough curves of CO2 and CH4 were determined for different volumetric flows of feed. The results were applied for the optimisation of PSA time in order to maximalize the suppression of CO2 from upgrading CH4. The concentration of CH4 is more than 98 % after the upgrading process. The total efficiency of the process was 77 %.Web of Science1751289128