Waste management & research : the journal of the International Solid Wastes and Public Cleansing Association, ISWA, Jan 17, 2015
Dry cleaning facilities using perchloroethylene produce a solid waste consisting of spent filteri... more Dry cleaning facilities using perchloroethylene produce a solid waste consisting of spent filtering powders with a high content of residual perchloroethylene, together with dyes and non-volatile residues. Untreated spent powders, classified as hazardous waste, cannot be disposed in landfill and incineration represents the only viable alternative. In this study, together with a full characterisation of the waste, the removal and recovery of the residual perchloroethylene by means of different heat treatments was investigated. In particular, tests of distillation and stripping with air and steam were carried out, evaluating the effectiveness of the treatments by quantifying the residual perchloroethylene in the samples treated. The results obtained show that the spent filtering powders contained about 25% wt. of perchloroethylene and that the maximum perchloroethylene recovery was obtained by steam stripping; approximately 98% after only 50 minutes. However, this treatment accounted f...
Negli impianti di gassificazione di biomassa e di carbone il tar rappresenta un grosso problema p... more Negli impianti di gassificazione di biomassa e di carbone il tar rappresenta un grosso problema perche deve essere eliminato dal syngas ma possiede gran parte del potere calorifico del combustibile di partenza. Per questo motivo e interessante sviluppare un processo che renda il suo recupero vantaggioso. In questo lavoro e stato realizzato un metodo di abbattimento del tar volto al suo recupero: il cracking autotermico dei gas di pirolisi. E’ stata avviata una campagna di sperimentazioni su un impianto di classificazione di laboratorio. L’impianto e costituito da un reattore di gassificazione di tipo up‐draft seguito da un reattore di cracking catalitico a base di allumina. Poiche le reazioni di cracking sono endotermiche, e necessario fornire energia al sistema dall’esterno. Il secondo reattore e quindi riscaldato da una resistenza elettrica esterna. Per aumentare il vantaggio economico ed energetico che deriva dal recupero del tar, si e cercato di rendere il secondo stadio del pro...
Gasification is recognized as one of the most promising technologies to convert low quality fuels... more Gasification is recognized as one of the most promising technologies to convert low quality fuels into more valuable ones. The principal problem related with the use of biomass in gasification processes is the high amount of tar released during the pyrolysis step. It is thus necessary to recover tar and to transform it in lighter combustible gas species such as CH 4 , CO and H 2 . In this work the experimental results of a medium industrial scale plant fed with olive husk and having a capacity of 250 kWt are presented. The gasifier is composed by a up-draft reactor which is followed by a secondary fixed bed reactor filled with alluminium oxide spheres having high porosity dedicated to the tar conversion reactions. The syngas is then used to feed an internal combustion engine with a production of 60 kWe.
Pyrolysis is a widely studied thermochemical process, however the disposal of the produced byprod... more Pyrolysis is a widely studied thermochemical process, however the disposal of the produced byproducts is an unexplored field. In particular, the acqueous phase, characterized by a high organic load (TOC), must be necessarily treated. Aims of this work is to study the potentiality of biochar as adsorbent material for the treatment of this wastewater. For this aim, pyrolysis wastewater and biochar produced in the same plant were used. Two biochars produced at different temperatures (550 and 750 °C) and an activated biochar produced by chemical activation with NaOH of the raw biomass were tested. The study shows that higher temperature in the biochar production leads to higher sorption capacity of the organic compounds due to an increase of the surface area. The activation process further increases the surface area of the biochar that becomes similar to that of a commercial activated carbon while the sorption capacity exceeds that of commercial activated carbon of 2.5 times.
ABSTRACT Pyrolysis is a fundamental step in thermochemical processes of biomass materials, so a s... more ABSTRACT Pyrolysis is a fundamental step in thermochemical processes of biomass materials, so a suitable kinetic model is an essential tool to predict the evolution of the resulting products of reaction. However, many difficulties arise in modeling this process step due to the very high number of the involved reactions. In this work, a new double-Gaussian distributed activation energy model was applied in fitting the experimental data of olive residue pyrolysis obtained by thermogravimetric analysis. 2-DAEM formulation considers two sets of parallel reactions occurring and sharing the same pre-exponential factor, but shows different distributions of the activation energy, described by two separate Gaussian distributions that, in turn, grasp the two pyrolysis steps with a high accuracy. Since it is well known that in fitting all the kinetic parameters the pre-exponential factor results highly correlated with the activation energy, the former parameter was separately estimated as a linear combination of the values obtained for the three main biomass components, cellulose, hemicellulose and lignin.
Waste management & research : the journal of the International Solid Wastes and Public Cleansing Association, ISWA, Jan 17, 2015
Dry cleaning facilities using perchloroethylene produce a solid waste consisting of spent filteri... more Dry cleaning facilities using perchloroethylene produce a solid waste consisting of spent filtering powders with a high content of residual perchloroethylene, together with dyes and non-volatile residues. Untreated spent powders, classified as hazardous waste, cannot be disposed in landfill and incineration represents the only viable alternative. In this study, together with a full characterisation of the waste, the removal and recovery of the residual perchloroethylene by means of different heat treatments was investigated. In particular, tests of distillation and stripping with air and steam were carried out, evaluating the effectiveness of the treatments by quantifying the residual perchloroethylene in the samples treated. The results obtained show that the spent filtering powders contained about 25% wt. of perchloroethylene and that the maximum perchloroethylene recovery was obtained by steam stripping; approximately 98% after only 50 minutes. However, this treatment accounted f...
Negli impianti di gassificazione di biomassa e di carbone il tar rappresenta un grosso problema p... more Negli impianti di gassificazione di biomassa e di carbone il tar rappresenta un grosso problema perche deve essere eliminato dal syngas ma possiede gran parte del potere calorifico del combustibile di partenza. Per questo motivo e interessante sviluppare un processo che renda il suo recupero vantaggioso. In questo lavoro e stato realizzato un metodo di abbattimento del tar volto al suo recupero: il cracking autotermico dei gas di pirolisi. E’ stata avviata una campagna di sperimentazioni su un impianto di classificazione di laboratorio. L’impianto e costituito da un reattore di gassificazione di tipo up‐draft seguito da un reattore di cracking catalitico a base di allumina. Poiche le reazioni di cracking sono endotermiche, e necessario fornire energia al sistema dall’esterno. Il secondo reattore e quindi riscaldato da una resistenza elettrica esterna. Per aumentare il vantaggio economico ed energetico che deriva dal recupero del tar, si e cercato di rendere il secondo stadio del pro...
Gasification is recognized as one of the most promising technologies to convert low quality fuels... more Gasification is recognized as one of the most promising technologies to convert low quality fuels into more valuable ones. The principal problem related with the use of biomass in gasification processes is the high amount of tar released during the pyrolysis step. It is thus necessary to recover tar and to transform it in lighter combustible gas species such as CH 4 , CO and H 2 . In this work the experimental results of a medium industrial scale plant fed with olive husk and having a capacity of 250 kWt are presented. The gasifier is composed by a up-draft reactor which is followed by a secondary fixed bed reactor filled with alluminium oxide spheres having high porosity dedicated to the tar conversion reactions. The syngas is then used to feed an internal combustion engine with a production of 60 kWe.
Pyrolysis is a widely studied thermochemical process, however the disposal of the produced byprod... more Pyrolysis is a widely studied thermochemical process, however the disposal of the produced byproducts is an unexplored field. In particular, the acqueous phase, characterized by a high organic load (TOC), must be necessarily treated. Aims of this work is to study the potentiality of biochar as adsorbent material for the treatment of this wastewater. For this aim, pyrolysis wastewater and biochar produced in the same plant were used. Two biochars produced at different temperatures (550 and 750 °C) and an activated biochar produced by chemical activation with NaOH of the raw biomass were tested. The study shows that higher temperature in the biochar production leads to higher sorption capacity of the organic compounds due to an increase of the surface area. The activation process further increases the surface area of the biochar that becomes similar to that of a commercial activated carbon while the sorption capacity exceeds that of commercial activated carbon of 2.5 times.
ABSTRACT Pyrolysis is a fundamental step in thermochemical processes of biomass materials, so a s... more ABSTRACT Pyrolysis is a fundamental step in thermochemical processes of biomass materials, so a suitable kinetic model is an essential tool to predict the evolution of the resulting products of reaction. However, many difficulties arise in modeling this process step due to the very high number of the involved reactions. In this work, a new double-Gaussian distributed activation energy model was applied in fitting the experimental data of olive residue pyrolysis obtained by thermogravimetric analysis. 2-DAEM formulation considers two sets of parallel reactions occurring and sharing the same pre-exponential factor, but shows different distributions of the activation energy, described by two separate Gaussian distributions that, in turn, grasp the two pyrolysis steps with a high accuracy. Since it is well known that in fitting all the kinetic parameters the pre-exponential factor results highly correlated with the activation energy, the former parameter was separately estimated as a linear combination of the values obtained for the three main biomass components, cellulose, hemicellulose and lignin.
A mathematical CFD model of a biomass packed porous bed system was developed to predict the volat... more A mathematical CFD model of a biomass packed porous bed system was developed to predict the volatiles in terms of tar and light gas as well as char fraction released during the pyrolysis process. In particular, phenol was considered as tar representative while for gas the single species were considered (in particular H2, CO, CO2, CH4 and steam). The model was implemented in a commercial CFD code through several original User Defined Functions (UDFs) to reproduce the source terms in the continuity, energy and chemical species mass fraction equations. Furthermore, both inertial and viscous resistances within the packed bed were modelled and coded to assess the pressure drop in the porous media. Code validation was achieved by comparing the numerical results against experimental data obtained in a small-scale biomass reactor using N2 as carrier gas. To assess the kinetic parameters of the pyrolysis model at different operating conditions, the experiments were carried out by varying, in a wide range, the temperature of both the N2 flux and reactor walls.
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