Andres Fullana

Analysis of the pyrolysis and combustion of different sewage sludges by TG

Abstract The pyrolysis and combustion of seven samples of sewage sludge were studied by TG dynamic runs carried out at 15°C min −1 . Two different behaviors were observed. For some samples, considering the variations of weight loss versus temperature or time, the combustion thermograms are similar to those of pyrolysis but with a displacement of the corresponding curves of combustion to temperature intervals less than those of the pyrolysis runs. For the other samples, the pyrolysis thermograms coincide with the combustion thermograms, except in the last part of the combustion thermogram where a final decomposition appears as a consequence of the combustion of the char previously formed. The different behavior can be associated to aerobic stabilization of the samples. Some runs were also done with acid-washed samples to test the influence of the metal content.

Kinetic model for the combustion of tyre wastes

Abstract The decomposition of tyre wastes at different heating rates in an oxidizing atmosphere is explained by means of a kinetic model including a first step of pyrolysis, which assumes three organic fractions not forming residues, and a step of combustion. The atmosphere used varied from 10 of oxygen to 20% (v/v). The activation energy for the step of combustion is in the range 221–235 kJ/mol, and there exists a dependence of the rate of decomposition on the partial pressure of oxygen.

Thermal decomposition of meat and bone meal

Abstract A series of runs has been performed to study the thermal behavior of meat and bone meal (MBM) both in inert and reactive atmosphere. Although they are actually burned, the thermal decomposition of such MBM wastes has not been studied from a scientific point of view until now. The aim of this work is to present and discuss the thermogravimetric behavior of MBM both in nitrogen and air atmospheres. A thermobalance has been used to carry out the study at three different heating rates. A kinetic scheme able to correlate simultaneously (with no variation of the kinetic constants) the runs performed at different heating rates and different atmospheres of reaction is presented.

Pyrolysis and combustion kinetics and emissions of waste lube oils

Abstract The present work studies first the kinetics of the global primary thermal decomposition of raw waste lubricant oils in helium atmosphere conditions and with different proportions of helium:oxygen by TGA. In addition, pyrolysis and partial oxidation runs were carried out in a tubular reactor at 723 and 1123 K, where the volatiles and semivolatiles evolved were quantified by gas chromatography. TGA analysis shows nearly no difference between helium and helium–oxygen atmosphere, yielding no appreciable residue. Primary decomposition, which takes place between 450 and 700 K, can be modeled with two different processes: the main one (92.6% of the initial material) is an evaporation of the motor oil (with apparent zero order and a kinetic constant dependent on the mass and heating rate) and a small contribution of a typical solid carbonoceous pyrolysis. In the tubular reactor, gases evolved in pyrolysis at 773 K corroborate TG findings that the process is mainly an evaporation, with little changes with respect to the original chemical structure of the oil. Nevertheless, the gas composition changes completely in the presence of air, where the partial oxidation in the gas phase after evaporation yields lower chain paraffins and olefines. Gas evolution at 1123 K is completely different, yielding showing typical cracked flue gas composition: light gases with abundant olefins and poly-condensed aromatics.

Pyrolysis study of polyurethane

Abstract The thermal decomposition of a polyurethane in an inert atmosphere has been studied. Three different apparatus, a thermobalance, a pyroprobe and a laboratory furnace, were use to study the kinetics of decomposition and the evolution of gas and volatiles. The kinetics were studied using a thermobalance and four heating rates. The experimental results were described satisfactorily by a two parallel reaction models. The kinetic parameters, that is, the pre-exponential factors, activation energies, reaction orders and maximum production of volatiles at infinite time were also obtained. The formation of hydrocarbons at different nominal temperatures was studied using a coil pyroprobe. An increase of the yield of light hydrocarbons (methane, ethylene, etc) was observed as the pyrolysis temperature increased. The secondary products from the formation/cracking reactions of the different primary compounds were identified by passing the pyrolysis products through a furnace prior to detection. The recovery of chemicals from the pyrolytic degradation was then studied. Toxic compounds were determined by carrying out thermal degradation in a Nitrogen atmosphere. Gas chromatography/mass spectrometry (GS/MS) was used to identify volatile and semivolatile organic compounds generated by the thermal degradation reactions.

Kinetic law for solids decomposition. Application to thermal degradation of heterogeneous materials

Abstract The kinetic expressions considered for the decomposition of heterogeneous solids, with several reactions and inert compounds, are discussed. Proposals of the best way for expressing the kinetic equations are presented, as a consequence of the mathematical analysis used. A discussion on the number of parameters that can be obtained in the correlation of experimental data is also presented. In addition, a method for comparing the kinetic constants is proposed. This analysis is applied to thermal decomposition data of several wastes where potential laws have been considered.

Interrelation between the kinetic constant and the reaction order in pyrolysis

Abstract A numerical method for calculating the kinetic constants of the thermal decomposition of heterogeneous solids is proposed, considering the interdependence between the pre-exponential factor and the reaction order. This method is applied to the pyrolysis of poly-(ethylene terephtalate) with satisfactory results. The kinetic constants calculated with this method during the optimization goes preferably to parameters with correct physical meaning, and therefore, a lower number of iterations in the optimization calculation system is needed. The interdependence of the pre-exponential factor and the reaction order restricts the possible solutions of the calculations, and produces more valid solutions in the calculation procedure.

Hydrothermal carbonization of industrial mixed sludge from a pulp and paper mill.

Mixed sludge from a pulp and paper mill was hydrothermally carbonized at 180-260°C for 0.5-5h with the use of HCl or NaOH for determining the effect of acid and base additions during sludge carbonization. Based on the results carbonization was mainly governed by dehydration, depolymerization and decarboxylation of sludge components. Additive type had a statistically significant effect on hydrochar carbon content and carbon and energy yield, of which especially energy yield increased through the use of HCl. The theoretical energy efficiencies of carbonization increased with decreasing reaction temperature, retention time and the use of HCl and suggested that the energy requirement could be covered by the energy content of attained hydrochar. The BOD5/COD-ratios of analyzed liquid samples indicated that the dissolved organic components could be treated by conventional biological methods.

Formation of polychlorinated compounds in the combustion of PVC with iron nanoparticles

The influence of iron nanoparticles in the fuel-rich combustion of PVC has been studied in this work. Dynamic runs for PVC and the mixture PVC and iron nanoparticles were firstly carried out by TGA-MS in order to study the influence of iron on the compounds evolved in the thermal degradation of PVC. To complete the study both PVC and a mixture of PVC and iron nanoparticles were burnt in a laboratory reactor under two different operating conditions: at 850 degrees C and in two stages, the first one at 375 degrees C and the resulting char cooled and subsequently burnt at 850 degrees C. Carbon oxides, light hydrocarbons, PAHs, chlorophenols, chlorobenzenes and PCDD/Fs were analyzed. It was observed that the mixture of PVC with iron nanoparticles at 375 degrees C greatly enhances the formation of light hydrocarbons and polychlorinated compounds, probably indicating that the presence of iron during the thermal decomposition of PVC causes the formation of iron chloride which may have a high catalytic effect.

Pyrolytic products from tannery wastes

Abstract Pyrolytic products evolved from the thermal degradation of tannery wastes have been studied using a Pyroprobe 1000 with a secondary reactor and a small furnace. Main primary and secondary products have been analyzed as a function of the operating temperature, using the Pyroprobe 1000 with the secondary reactor at low temperatures (primary reaction in the Pyroprobe 1000) or at high temperatures (primary reaction in the Pyroprobe 1000 and secondary reaction in the secondary reactor). In addition, some runs were carried out in a small furnace to consider the minor products evolved from the primary decomposition and from the primary decomposition+secondary tar cracking.