Feedstock recycling di plastiche: recupero di monomero da polietilene e polistirene mediante trattamenti termici

By this work, we want to emphasize the importance of the chemical waste recycling, since it allows the reprocessing of the polymer waste into raw materials, which can be utilized again in the refineries or in the petrochemical industry: turning a polymer back into monomers, amenable to further polymerization, closes the life-cycle of the material. Unfortunately, selective depolymerization is not easy to achieve for the largest class of polymers, i.e. those obtained by free-radical polymerization. Polyolefins belong to this category and xxPE and PP together are the largest production of synthetic polymer. Decomposition of polyolefins into olefins can be thermally achieved indeed, but the process is expected to operate through a random, rather uncontrollable, free-radical reaction mechanism. Products distribution is dramatically affected by temperature and residence time. A serious analysis of the state of the art in the waste recycling field and the reutilization of plastics in Europe, and particularly in Italy, shows that feedstock recycling is still little developed. Consequently recycling could be an interesting support in the traditional methodology of mechanical and energetic recycling. Nowadays, the integrated waste management of plastics seems the best solution to safeguard the word environment. With the target of demonstrating the chemical recycling effectiveness, the tests in laboratory have taken place starting from the depolymerization of plastic waste by heating in absence of oxygen: we gave great attention especially to the non-catalyzed pyrolysis of polyethylene, considering the great presence of this polymer in solid urban waste, due to the versatility and to the many uses allowed by this plastic. Pyrolysis is a process of thermal decomposition in inert atmosphere (nitrogen, helium, argon) of a substrate, usually solid, and generally characterized by a fairly elevated molecular complexity. This substrate, thanks to the heating action, produces a solid fraction (called char), a liquid fraction (formed by products called tars, which condense at room temperature) and gases. During the experiment we tested different plant configurations in order to final out the best operating conditions to maximize the yield in the base monomer which constitutes the fed polymer. Since we worked with polyethylene, it was obvious for us to try to maximize the productivity in ethylene. In this line of action, we also tried to look for optimal contact-time of the polymer in the reactor and optimal operative temperatures. In fact, operating on some parameters, it is possible to improve the selectivity of some compound instead of others: this is the reason why we tried to identify the right level of heating, the suitable temperature of cracking and the appropriate contact-time in order to find out, more specifically, the thermal decomposition reaction towards the desired olefins . Beside the study of the best plant processing, we also optimized the gas-chromatographic sampling technique, with the purpose to obtain a quality and quantity analysis of the gas mixture, produced by the pyrolysis reaction

New approaches to leadership: from vertical to horizontal organizational vision

openQuesto elaborato nasce dalla lettura dell’opera “Horizontal Organizing” di A. Bekman (Bekman, 2016), in cui l’autore spiega il pensiero, se non addirittura la filosofia, sui cui principi opera la sua azienda di consulenza, IMO International, fondata nel 2005, focalizzata sulla trasformazione orizzontale della struttura organizzativa delle aziende. Nel primo capitolo vengono analizzati, sinteticamente, le prospettive teoriche in cui i due diversi modelli di leadership, verticale e orizzontale, mettono radici. Quindi, si dà prima uno sguardo alle teorie classiche, alla base della organizzazione gerarchica, e poi si passa alla teoria del sensemaking, su cui si fonda l’idea di leadership orizzontale. Vengono sottolineate quali sono le principali criticità del modello classico, e come le idee racchiuse nel management orizzontale ne costituiscano possibili soluzioni. Nel secondo capitolo viene analizzato l’approccio più efficiente, per le organizzazioni, di avvicinarsi ad un modello di management orizzontale, ovvero quello di svilupparlo all’interno di progetti, e in quale contesto è più probabile che questo succeda, ovvero durante la gestione del cambiamento. Dopo un breve excursus sulla definizione di progetto e di change management, si analizza il rapporto tra questi due elementi, ovvero viene messo in luce il ruolo che spesso, all’interno di un’organizzazione, viene affidato ai progetti: la gestione del cambiamento. Il cambiamento è spesso il motivo scatenante di una crisi della leadership, che può portare alla riprogettazione della stessa, legandolo a doppio filo con l’idea stessa di management orizzontale, soprattutto quando pensato come soluzione ai limiti del management verticale; da qui il rapporto tra l’ambiente organizzativo del progetto e il management orizzontale. Inoltre, si comprende, in questa parte dell’elaborato, come, nella realtà dei fatti, più che la realizzazione di una vera e propria leadership orizzontale estrema, ci si trovi di fronte ad una leadership bilanciata, ovvero all’incontro e alla convivenza dei due modelli manageriali. Infine, nell’ultima parte dell’elaborato, sono presentati quattro case study esemplificativi che supportano la tesi espressa nel capitolo precedente, che mostrano come la leadership orizzontale esista e sia applicata, ma in modalità diluita, ovvero come leadership bilanciata, e circoscritta ad esperienze di progetto. Infine, viene brevemente menzionata l’influenza che la cultura nazionale e la cultura organizzativa hanno sullo svolgimento dei progetti.This paper stems from the reading of A. Bekman's work "Horizontal Organizing" (Bekman, 2016), in which the author explains the thought, if not even the philosophy, on the principles of which his consulting firm, IMO International, operates. founded in 2005, focused on the horizontal transformation of the organizational structure of companies. The first chapter briefly analyzes the theoretical perspectives in which the two different leadership models, vertical and horizontal, take root. So, we first take a look at the classical theories, at the base of the hierarchical organization, and then we move on to the sensemaking theory, on which the idea of ​​horizontal leadership is based. The main criticalities of the classic model are underlined, and how the ideas contained in horizontal management constitute possible solutions. The second chapter analyzes the most efficient approach for organizations to approach a horizontal management model, i.e. to develop it within projects, and in which context this is most likely to happen, i.e. during the management of change. After a brief excursus on the definition of project and change management, the relationship between these two elements is analyzed, that is, the role that is often entrusted to projects within an organization is highlighted: change management. Change is often the trigger for a leadership crisis, which can lead to the redesign of the same, tying it in two ways with the very idea of ​​horizontal management, especially when thought of as a solution to the limits of vertical management; hence the relationship between the organizational environment of the project and the horizontal management. Furthermore, in this part of the paper, it is understood how, in reality, more than the realization of a real extreme horizontal leadership, we are faced with a balanced leadership, or rather the meeting and coexistence of two managerial models. Finally, in the last part of the paper, four exemplary case studies are presented that support the thesis expressed in the previous chapter, which show how horizontal leadership exists and is applied, but in a diluted way, i.e. as balanced leadership, and limited to experiences of project. Finally, the influence that national culture and organizational culture have on the development of projects is briefly mentioned

Two-steps selective thermal depolymerization of polyethylene. 1: Feasibility and effect of devolatilization heating policy

Aiming at controlling the selective depolymerization via the thermal route, we investigated a two-stage process, where volatiles are produced in a low temperature (800 degrees C, residence time <1.3 s). Splitting the process allows to control the reaction times independently and circumvent limitations of a multiphase reacting system, where melting contrasts a rapid heating. The two-stage process with independent melting can dramatically improve the olefins yield, and particularly that of ethene. A proper heating policy in the 1st thermal decomposition affects the species distribution in the intermediate product (oils and waxes). The following gas phase, short contact time thermal cracking takes advantage of a 'tailored' feedstock, to drive the products distribution towards a larger amount of ethene. With the two-stages sequential process we achieved cumulated ethene yields from LLPDE in excess of 45 wt.% with respect to polymer fed. While gas yield approaches 85 wt.%, up to 75 wt.% of the gas can be ethene at suitable conditions. Indications to improve the interesting results are discussed. (C) 2010 Elsevier B.V. All rights reserved

Onset and propagation of smouldering in pine bark controlled by addition of inert solids

We investigated the smouldering onset and propagation in a biomass (pine bark) bed to mitigate or control the process. By the addition of sand, the bed porosity has been modified. Sand of different average particle size, in different arrangements and proportions (from 30 to 70%) has been used, modifying the bed porosity (between 0.44 and 0.67). Experiments have been carried out in a flow reactor, with controlled O2 content in the feed. The packed bed was large enough to allow the development of a reaction front, as expected in large scale applications. Pressure drop measurements revealed as a useful indication to monitor the smouldering onset and the front evolution. The process appears always controlled by the flux of O2, as expected for smouldering. Properly tuning the bed porosity with inert solids, allows to control the self-heating propagation, in view of its exploitation for low temperature heat production with simultaneous controlled conversion. The addition of sand supports a well-defined reaction front. The inert solid preserves the bed texture when the biomass is progressively consumed and allows to evenly distribute O2 to the biomass, thus regulating the heat dissipation and keeping the smouldering front confined

Improved compaction of dried tannery wastewater sludge

We quantitatively studied the advantages of improving the compaction of a powder waste by several techniques, including its pelletization. The goal is increasing the mass storage capacity in a given storage volume, and reducing the permeability of air and moisture, that may trigger exothermic spontaneous reactions in organic waste, particularly as powders. The study is based on dried sludges from a wastewater treatment, mainly from tanneries, but the indications are valid and useful for any waste in the form of powder, suitable to pelletization. Measurements of bulk density have been carried out at the industrial and laboratory scale, using different packing procedures, amenable to industrial processes. Waste as powder, pellets and their mixtures have been considered. The bulk density of waste as powder increases from 0.64 t/m3 (simply poured) to 0.74 t/m3 (tapped) and finally to 0.82 t/m3 by a suitable, yet simple, packing procedure that we called dispersion filling, with a net gain of 28% in the compaction by simply modifying the collection procedure. Pelletization increases compaction by definition, but the packing of pellets is relatively coarse. Some increase in bulk density of pellets can be achieved by tapping; vibration and dispersion filling are not efficient with pellets. Mixtures of powder and pellets is the optimal packing policy. The best compaction result was achieved by controlled vibration of a 30/70 wt% mixture of powders and pellets, leading to a final bulk density of 1 t/m3, i.e. an improvement of compaction by more than 54% with respect to simply poured powders, but also larger than 35% compared to just pellets. That means increasing the mass storage capacity by a factor of 1.56. Interestingly, vibration can be the most or the least effective procedure to improve compaction of mixtures, depending on characteristics of vibration. The optimal packing (30/70 wt% powders/pellets) proved to effectively mitigate the onset of smouldering, leading to self-heating, according to standard tests, whereas the pure pelletization totally removes the self-heating hazard