Alberto Malandrino

Hydrodynamics of circulating fluidized beds with risers of different shape and size

Abstract The hydrodynamics of risers of CFB units have been studied by means of a transparent column having a 0.120×0.012 m rectangular cross-section and two cylindrical columns having 0.120 m i.d. and 0.400 m i.d. Several solids, ranging in size from 48 μm to 300 μm and ranging in density from 1 330 kg m −3 to 2 600 kg m −3 , were tested. Instantaneous pressures were measured at several points along the risers by means of pressure transducers. Their output signals were processed to provide instantaneous and time-averaged voidage profiles. Unit flow structures made of ‘plugs’ and ‘slugs’ were detected in dense and transition regions of the risers, regardless of the size and the shape of the column and the type of solids. The dense and transition regions as a whole appear to form the inlet section of the risers. A descriptive model has been proposed to estimate the length of the dense and transition regions in terms of the risers design and operating variables. The model is based on Taylor instability at the interface between ‘plugs’ and their upstream ‘slugs’.

DME synthesis via catalytic distillation: Experiments and simulation

Abstract This paper regards the field of the chemical engineering that is commonly identified as Process Intensification (PI) . The main objective of PI is to improve processes and products to obtain technologies more safe and economic. ENI and the University of Pisa are partners in the European project INtegrating SEparation and Reactive Technologies (INSERT) that considers the integration of the two key steps common to conversion processes (reaction and separation) , to develop new configurations with advanced performances respect to the conventional ones. It has been chosen to apply Catalytic Distillation, the most promising application of the intensification principles, to the synthesis of dimethyl ether (DME) from methanol. This is one of the seven industrial case studies being investigated to test and validate the INSERT methodology.

One-Step-Hydrogen: a new direct route by water splitting to hydrogen with intrinsic CO2 sequestration

Publisher Summary The One-Step-Hydrogen process is aimed to produce hydrogen from water splitting and also to tackle the carbon management issue targeting a zero carbon emission at lower costs than allowed by the Best Available Technologies (BAT). Well known water possesses an oxidizing potential which can be utilized in a simple water splitting application where it reacts with selected metals to give pure hydrogen. So combining in a cycle the water oxidative potential and the reverse action by a reducing agent like hydrocarbons, it allows the hydrogen production and as well as the intrinsic carbon dioxide sequestration. This chapter proposes this new process. In the first step, a suitable oxide takes up the oxygen from water splitting producing hydrogen. The solid acts as an oxygen storage medium. Such “lattice” oxygen is in turn released through one or more elemental steps. The overall reaction is endothermic and an energy supply is needed to close the energy balance. The decoupling of the overall reaction into three separated reactions allows the process to overcome the thermodynamics constraints of the overall equilibrium. The major breakthrough is however the exit of the two main products—hydrogen and carbon dioxide—from two different vessels, so that the carbon dioxide, once water is condensed, is pure and ready to be buried.