Carlo Stramigioli

Comparative cradle-to-gate life cycle assessments of cellulose dissolution with 1-butyl-3-methylimidazolium chloride and N-methyl-morpholine-N-oxide

In this paper the expected environmental impacts of the industrial cellulose dissolution with the ionic liquid 1-butyl-3-methylimidazolium chloride (Bmim Cl) were analyzed through a “cradle to gate” Life Cycle Assessment (LCA). In order to weigh up the “greenness” of the process, the analysis was performed through a comparison with the well established environmental friendly N-methyl-morpholine-N-oxide (NMMO)/H2O process. Although dissolution of cellulose in Bmim Cl has not been used for industrial production of cellulose fibers to date, results from LCA suggest that it could be interesting from an environmental point of view since its impacts are similar to those of the NMMO/H2O process. Specifically, the process with Bmim Cl generates a higher environmental load on abiotic resource depletion, emissions of volatile organic compounds and ecotoxicity than the NMMO/H2O process. Conversely it has some environmental advantages with regards to human toxicity. In both cellulose dissolution processes, the major contributions to the environmental impacts come from precursor syntheses. In addition to the comparative analysis of the two cellulose dissolution processes, the paper reports the complete life cycle inventory (LCI) of the two solvents, Bmim Cl and NMMO, and their life cycle impact assessment (LCIA).

A rigorous approach to photochemicals reactors

Abstract The modelling of photochemical reactors has been rigorously treated describing the radiation field within the realm of radiant energy transfer. This kind of approach causes a heavy integro-differential problem to arise any time the reacting species is the absorbing one while the differential nature of the model equations is maintained in the case of photosensitized reactions in a purely absorbing medium. An annular photoreactor has been considered for this last situation and the influence on the absorption process of the most parameters has been investigated for both the cases of a reactor shielded and unshielded by a reflector.

Radiative transfer in an absorbing and anisotropically scattering slab with a reflecting boundary

Abstract Radiative transfer has been considered within a participating plane slab assuming the externallyapplied radiation to impinge normally on one boundary of the slab while the other boundary is assumed to reflect in a diffuse way. The linearly anisotropic and the Rayleigh modes of scattering have been both considered. A rigorous solution is developed following a constructive procedure based on projectional methods: the resulting computational formulae have been numerically processed to obtain the distribution of the physically relevant variables for some significant situations.

Rigorous and simplified approach to the modelling of continuous photoreactors

Abstract Photochemical reactions where the absorption of radiant energy occurs by the reacting species are considered. In this case the radiant energy balance equation can not be decoupled from the mass balance of the reacting species and a highly non linear integro-differential problem arises. Mathematical difficulties have been usually bypassed by modelling the radiation field on the basis of simplified models of questionable physical reliability. A rigorous modelling of the radiation field has not yet been considered for such a class of photochemical processes. An approach based on a rigorous modelling is therefore presented here, the solution being obtained through a transient approach. Results are compared with those obtained on the basis of simplified models in order to investigate the range of the significant parameters where such simple models, which are less computer-time demanding, can be conveniently used.

Effects of scattering and reflection of radiation on batch photochemical reaction in a slab geometry

Abstract Effects of scattering of radiation within the medium, boundary surface reflectivity and initial optical thickness of the medium on the conversion occurring in a batch photochemical reaction in plane-slab geometry are investigated analytically. Results are presented for the local and average conversion within the medium, reflectivity and transmissivity of the medium, and normalized optical thickness of the medium as a function of time. The scattering is found to reduce the conversion and tends to increase the uniformity of the distribution of the reactant within the medium.

The modelling of pool vaporization

Abstract This paper describes a mathematical model which calculates the time dependencies of the flow rate and composition of the vapour emerging from a pool. A large variety of accidental cases can be covered: continuous or instantaneous spills, on confined or unconfined ground, ideal or non-ideal liquid mixtures in boiling or evaporating conditions. The boiling, when present, is modelled through an equation system comprising the Rachford-Rice relation and the energy balance of the pool, which is assumed to be well-mixed. In the case of a volatile pool, interfacial mass rates are determined taking into account the Stefan flux, and the thermal resistance inside the liquid phase is also considered. In all situations, the energy balance includes the contribution of ground, sun and air. Known experimental data have been used to validate the model.

The role of a reflecting boundary in improving the operation of an annular photoreactor

Abstract The influence of a cylindrical reflector on-a photochemical reaction occurring in an annular photoreactor has been investigated for both batch and continuous operations of the reactor. Absorption of radiant energy has been assumed by the reacting species itself and for each of the operating modes both the extreme conditions of mixing have been considered. Results show that a reflecting wall can be effective in enhancing the conversion only when the optical thickness m (based on the initial conditions and on the inlet) is neither too small nor too large, since in these two cases absorption and reflection, respectively, are negligible anyway. In any case conversion has been found to increase when mixing within the reactor is improved.

Radiative transfer in an absorbing-scattering slab bounded by emitting and reflecting surfaces☆

Abstract An exact integral theory of the planar radiative transfer with isotropic scattering and general boundary conditions is presented in the paper. The analytical solution to the problem is numerically processed for two different specializations of the emissivity and reflectivity properties of the bounding surfaces. Results are given for the total and angular radiation intensities as well as for the net radiative flux.

Comparison of alternative flue gas dry treatment technologies in waste-to-energy processes.

Acid gases such as HCl and SO2 are harmful both for human health and ecosystem integrity, hence their removal is a key step of the flue gas treatment of Waste-to-Energy (WtE) plants. Methods based on the injection of dry sorbents are among the Best Available Techniques for acid gas removal. In particular, systems based on double reaction and filtration stages represent nowadays an effective technology for emission control. The aim of the present study is the simulation of a reference two-stage (2S) dry treatment system performance and its comparison to three benchmarking alternatives based on single stage sodium bicarbonate injection. A modelling procedure was applied in order to identify the optimal operating configuration of the 2S system for different reference waste compositions, and to determine the total annual cost of operation. Taking into account both operating and capital costs, the 2S system appears the most cost-effective solution for medium to high chlorine content wastes. A Monte Carlo sensitivity analysis was carried out to assess the robustness of the results.

SUN DRIVEN PHOTOCHEMICAL REACTION IN A HORIZONTAL PLANE SLAB

Abstract The interaction between the solar radiation and a participating-reacting plane medium is studied, and the relevant mass balance and radiative transfer equations are solved by an analytical-numerical procedure. The system simulates a batch photochemical reactor for the exploitation or storage of solar energy. The roles played by the reaction and insolation characteristic times, as well as the effects of geometrical and physical properties of the reactor, are discussed. Some figures, showing the time and space variation of the most meaningful physical quantities, are reported as illustrative examples of the obtained numerical results.