Aldo Muntoni

Application of accelerated carbonation on MSW combustion APC residues for metal immobilization and CO2 sequestration.

The present study focuses on the application of an aqueous phase accelerated carbonation treatment on air pollution control (APC) residues from municipal solid waste combustion, aimed at assessing its influence on the environmental behaviour of the residue under concern, as well as the potential of the process in terms of sequestration of the CO2. APC residues are considered hazardous waste and must be treated before final disposal in order to achieve the immobilization/mobilization of critical contaminants such as heavy metals as well as mobilization of soluble salts. The treatment applied proved to be effective in reducing the mobility of Pb, Zn, Cr, Cu and Mo, the optimum final pH for the carbonated APC residues being in a range of 10-10.5, whilst a mobilization effect was noticed for Sb and no effect was assessed for chlorides. The effect of carbonation treatment on the contaminant release was further evaluated by means of a sequential extraction procedure, indicating that the distribution of contaminants on water soluble, exchangeable and carbonate fraction was modified after treatment. The CO2 sequestration potential assessed for the APC residues showed that the carbonation technology could be a technically viable option in order to reduce emissions from WtE plants.

Compressor surge active control via throttle and CCV actuators. A second-order sliding-mode approach

In this paper we address the problem of active surge control in compressor systems by using a Close-Coupled Valve (CCV) and a Throttle Valve (TV) as actuator devices simultaneously acting on the compressor. With reference to the Moore-Greitzer compressor model, we suggest the use of a second-order sliding-mode (2-SM) technique. We show that the proposed control system can stabilize any desired operating point belonging to some region in the state plane by rejecting a significant class of persistent pressure and flow disturbances acting on the system. The perfect knowledge of the compressor and load characteristics is not required to design the controller, and, furthermore, the unmodelled actuator dynamics are taken into account explicitly in the stability analysis.

Compressor Surge Suppression by Second-Order Sliding Mode Control Technique

Abstract Surge is one of the two main dynamic instabilities that can occur in compressor systems (the other is the rotating stall) preventing their satisfactory operation and being potential cause of serious damages. In this paper we consider a Close Coupled Valve (CCV) as actuator, and we suggest the use of a second-order sliding-mode (2-SM) technique for the active control of the surge phenomenon. We refer to the Moore-Greitzer model with cubic compressor characteristics, and we show that the proposed technique can drive the system towards a stable operating point by rejecting a significant class of persistent pressure and flow disturbances acting on the system. Furthermore, the perfect knowledge of the compressor and load characteristics is not required to design the controller.

Use of stone wool by-products in the construction of sanitary landfills and tailing dams.

Abstract The delay of the introduction of a used item or residual material in the “waste circuit” is a key factor of an effective and environmentally sound waste management policy. This principle has been fully adopted by the European legislation and consequently, in most of the member countries. In the same time, re-use of low cost materials or, even better, by-products in environment protection works (sanitary landfills, mineral processing residues dams, etc.) could make easier the effective implementation of an environmentally sound waste management policy, especially in developing countries. However, the assessment of the recovery options has to be performed on the basis of proper technical specifications concerning the kind of reuse proposed and of an accurate investigation on the technical and environmental properties of the residue. The present article reports the results of a research programme aiming at evaluating the feasibility of use of stone wool by-products, usually directly disposed in landfills, as construction materials for sanitary landfills and tailing dams.