A. Zabaniotou

Thermal degradation studies and kinetic modeling of cardoon (Cynara cardunculus) pyrolysis using thermogravimetric analysis (TGA)

A key element in the design of sustainable pyrolysis processes is the thermal degradation kinetics of biomass. In this work, pyrolysis tests for cardoon (Cynara carduculus) stems and leaves were performed in a non-isothermal thermogravimetric analyzer (TGA) in order to determine the thermal degradation behavior of both stems and leaves. The kinetic parameters of the process were evaluated using three different kinetic models, the independent parallel reaction model, KAS and OFW iso-conversional model. Good agreement with the experimental TGA data was observed for all models, the best being with the independent parallel reaction model. A variance in the activation energy with conversion was observed when the KAS and OFW models were employed, which reveals that the pyrolysis of cardoon progresses through more complex and multi-step kinetics.

Pyrolysis of used automobile tires and residual char utilization

In the present study the rubber portion of used car tires was transformed by atmospheric pyrolysis into oil, gas and char. The experiments have been performed in a captive sample reactor at atmospheric pressure, under helium atmosphere. The effect of temperature on the products yield was investigated. In a second step, alternative uses of pyrolysis char such as combustion, gasification and active carbons preparation were examined, in order to produce fuels and high added value materials. First, pyrolysis char was burned and its reactivity was measured in function with pyrolysis temperature. Second, char was gasified with Steam and CO2 to produce fuel gases, in a tubular stainless steel reactor. It was also activated to produce high added value materials. It was shown that tire chars present higher reactivity with steam than with CO2 and also active carbons produced from tire chars possess surface areas, comparable with those of commercially available active carbons.

Olive residues (cuttings and kernels) rapid pyrolysis product yields and kinetics

A study of pyrolysis of olive residues (cuttings and kernels) at a temperature range from 300 to 600°C, has been carried out. The experiments were performed in a captive sample reactor at atmospheric pressure under helium. The yields of the derived gases, pyrolytic liquids and char were determined in relation to pyrolysis temperature, at heating rates of about 200°C/s. As the pyrolysis temperature was increased the percentage mass of char decreased whilst gas and oil products increased. The oil products increased to a maximum value of ∼30 wt% of dry biomass at about 450–550°C. The major gaseous products are CO and CO2. A simple first order kinetic model has been applied to the evolution of total losses and gases. Kinetic parameters have been estimated and compared with other reported similar data.

Preparation of activated carbons from agricultural residues for pesticide adsorption.

Activated carbons (ACs) can be used not only for liquid but also for vapour phase applications, such as water treatment, deodorisation, gas purification and air treatment. In the present study, activated carbons produced from agricultural residues (olive kernel, corn cobs, rapeseed stalks and soya stalks) via physical steam activation were tested for the removal of Bromopropylate (BP) from water. For the characterization of the activated carbons ICP, SEM, FTIR and XRD analyses were performed. Adsorption kinetics and equilibrium isotherms were investigated for all biomass activated carbons in aqueous solutions. Experimental data of BP adsorption have fitted best to the pseudo 2nd-order kinetic model and Langmuir isotherm. The study resulted that corn cobs showed better adsorption capacity than the other biomass ACs. Comparison among ACs from biomass and commercial ones (F400 and Norit GL50) revealed that the first can be equally effective for the removal of BP from water with the latter.

Life cycle assessment applied to egg packaging made from polystyrene and recycled paper

Abstract In the present study, the application of life cycle assessment (LCA) for the comparison of two egg packages, from polystyrene and recycled paper, is presented. The input and output streams of mass and energy are examined and the environmental impacts associated with the two systems are analyzed. The application of LCA by using EcoIndicator 95 has made possible the comparison of the environmental impacts of two egg packages. The results of this LCA study are discussed and reveal that the PS packages contribute more to acidification potential, winter and summer smog, while recycled paper egg packages contribute more to heavy metal and carcinogenic substances impact. Nevertheless, it seems that paper eggcups have less environmental impact than the polystyrene ones with the assumption that the accuracy of the results is confined by the credibility of European databases used for primary data.

Soil contamination by heavy metals: Measurements from a closed unlined landfill

The aim of the present study was the characterization of soil samples of a closed unlined landfill located northwest of Thessaloniki, North Greece, in relation to heavy metals values. Samples were obtained by drilling in different depths (2.5-17.5m). Then they were analyzed by atomic absorption spectrophotometry for Cd, Cr, Cu, Ni, Pb and Zn investigation. The chemical analysis showed that the metal values varied over a wide range: from 0.50 to 18.75mg/kg for Cd, 3.88-171.88mg/kg for Cr, 8.13-356.25mg/kg for Cu, 5.63-63.75mg/kg for Ni, 2.50-92.50mg/kg for Pb and 6.38-343.75mg/kg for Zn. The highest values found in three of the six drillings, in depths over 2.5m. Although the area is heavily industrialized, the presented results indicated that local industries have not constituted an extensive metal pollution source for the site. Finally, after all necessary preparatory operations of site cleaning and flattening, surface planting selected and applied as a phytoremediation rehabilitation method of the site.

Process characteristics and products of olive kernel high temperature steam gasification (HTSG).

Exploitation of olive kernel for bioenergy production, with respect to the green house gases (GHGs) mitigation, is the main aim of this work. In this study, olive kernels were used as a solid biofuel, and high temperature steam gasification (HTSG) was investigated, in the fixed bed unit at KTH Sweden, with regard to hydrogen maximization in the produced gasification gas. Experiments were carried out in a temperature range of 750-1050 degrees C, with steam as the gasifying agent. The behaviour of olive kernels, under residence times from 120 up to 960 s, has been studied. At 1050 degrees C, a medium to high calorific value gas was obtained (LHVgas=13.62 MJ/Nm3), while an acquired H2/CO molar ratio equal to four proved that olive kernel HTSG gasification could be an effective technology for a hydrogen-rich gas production (approximately 40%vv H2 in the produced gasification gas at 1050 degrees C). The produced char contained 79%ww of fixed carbon, low chlorine and sulphur content, which enables it for further re-use for energetic purposes. Tar content in the produced gas at 750 degrees C was 124.07 g/Nm3, while a 1050 degrees C at 79.64% reduction was observed and reached the value of 25.26 g/Nm3.

Sustainable valorization of plastic wastes for energy with environmental safety via High-Temperature Pyrolysis (HTP) and High-Temperature Steam Gasification (HTSG)

In the present study the energetic valorization of electric cable shredder residues (mixed plastics) has been investigated. Thermochemical conversion by means of High-Temperature Steam Gasification (HTSG) and High-Temperature Pyrolysis (HTP) was studied. The effects of temperature and reaction time--process parameters--were investigated. Comparison of the results showed that HTSG seems a more suitable process in terms of produced syngas quality (64%, v/v and 13MJ/Nm(3)) than HTP because of higher H(2) yield and lower tar content.

SIMULATION OF FORESTRY BIOMASS DRYING IN A ROTARY DRYER

ABSTRACT Drying of forestry biomass in a rotary dryer has been performed. The raw material used was Erica Arborea belonging to the ever-green, broad leaves ecosystem which covers Central Greece and other Mediterranean countries. The study was part of a project concerning a Greek biomass pyrolysis demonstration plant where drying of biomass is very important in the contribution to the global energy balance and product yields of pyrolysis. The study includes two parts. First, the experimental part concerns the influence of air flowrate, temperature, rotation speed and inclination of a laboratory rotary dryer to biomass residence time and biomass outlet moisture content. The second part concerns the development of a mathematical model for biomass drying in a rotary dryer. Experimental measurements in a rotary dryer were compared to the data from the model, in order to check the validity of the model.

Valorization of cotton stalks by fast pyrolysis and fixed bed air gasification for syngas production as precursor of second generation biofuels and sustainable agriculture.

In the present study, the potential of cotton stalks utilization for H(2) and syngas production with respect to CO(2) mitigation, by means of thermochemical conversion (pyrolysis and gasification) was investigated. Pyrolysis was conducted at temperature range of 400-760 degrees C and the main parametric study concerned the effect of temperature on pyrolysis product distribution. Atmospheric pressure, air gasification at 750-950 degrees C for various lambda (0.02-0.07) was also studied. Experimental results showed that high temperature favors gas production in both processes; while low lambda gasification gave high gas yield. Syngas (CO and H(2)) was increased with temperature, while CO(2) followed an opposite trend. By pyrolysis, higher H(2) concentration in the produced gas (approximately 39% v/v) was achieved and at the same time lower amounts of CO(2) produced, compared to air gasification.