Sustainable high quality recycling of aggregates from waste-to-energy, treated in a wet bottom ash processing installation, for use in concrete products

Nowadays, more efforts towards sustainability are required from the concrete industry. Replacing traditional aggregates by recycled bottom ash (BA) from municipal solid waste incineration can contribute to this goal. Until now, only partial replacement has been considered to keep the concrete workability, strength and durability under control. In this research, the feasibility of a full aggregate replacement was investigated for producing prefabricated Lego bricks. It was found that the required compressive strength class for this purpose (C20/25) could be achieved. Nevertheless, a thorough understanding of the BA properties is needed to overcome other issues. As BA is highly absorptive, the concrete's water demand is high. This workability issue can be dealt with by subjecting the fine BA fraction to a crushing operation to eliminate the porous elements and by pre-wetting the fine and coarse BA fractions in a controlled manner. In addition, a reactive NaOH washing is needed to avoid formation of longitudinal voids and the resulting expansion due to the metallic aluminum present in the BA. Regarding the long-term behavior, heavy metal leaching and freeze-thaw exposure are not problematic, though there is susceptibility to acetic and lactic acid attack and maybe increased sensitivity to alkali-silica reaction

Numerical simulation and controller development for energy transfer in imperfectly mixed fluids

This paper describes the possibility of using Computational Fluid Dynamics (CFD) models for developing Model Predictive Controller (MPC) algorithms. In this work a complex CFD model is combined with a reduced order Data-Based Mechanistic (DBM) formulation so that the low-order model can be used for control applications. To demonstrate the methodology, a Single Input-Single Output (SISO) ventilated installation is used. Initially, a CFD model is used for the installation. At the inlet a step rise in air temperature is applied and temperature responses at 36 monitoring positions are extracted. Then a reduced order model is formulated for the test case and model parameters are identified using the data generated by the CFD model. Finally the reduced order CFD model is used to develop an MPC algorithm. The developed algorithm is found to be robust for disturbance effects and capable of tracking the desired reference temperature trajectory very well.status: publishe

Destruction and formation of PCDD/Fs in a fluidized bed combustor co-incinerating automotive shredder residue with refuse derived fuel and waste water treatment sludge

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Modelling and control of heat transfer phenomena inside a ventilated air space

In this paper a data based mechanistic (DBM) model is proposed using a simplified heat balance formulation for modelling the temperature distribution inside a full scale ventilated room. The model has a number of parameters which are physically meaningful and determined using time temperature data obtained from experiments for several inlet air flow rates. At the inlet a step input in air temperature is applied and temperature responses at 36 sensor locations were recorded. For all ventilation rates used, the parameters of the model are extracted using statistical identification technique. Later, model based predictive control (MBPC) algorithm is developed to control temperature profiles on pre-selected sensor locations. The developed DBM model is compact in structure and found to capture the temperature distribution with high accuracy. The MBPC which is distinguished by explicit use of process models, is robust for disturbance and noise effects. Besides it has high tracking capability of the reference trajectory. (c) 2004 Elsevier B.V. All rights reserved.status: publishe

Comparison of different beneficiation techniques to improve utilization potential of Municipal Solid Waste Incineration fly ash concrete

A large volume of waste is generated in urban areas. Waste treatment techniques are being adopted in developed countries including recycling of wastes (such as paper, plastic, metals, etc.), composting organic waste and incineration of the remaining fraction. Ash generated as a result of incineration processes presently goes mainly into landfill, increasing both land use and resource wastage. Municipal solid waste incineration (MSWI) fly ash could alternatively be used as a supplementary cementitious material (SCM) in cement. The major hurdle that currently prevents its use are the expansion of concrete due to elemental aluminium (Al) and also its non-negligible chloride, sulphate, and heavy metal content. Washing with water is the simplest and most effective technique to remove chloride. To prevent Al expansion washing with water and alkali, or washing with a moderate heat treatment were effective. In this research, MSWI fly ash generated in a fluidized bed incinerator was tested in combination with Portland cement. This paper discusses the conducted experiments with varying parameters and the obtained test results in brief

Modelling mass transfer phenomena and quantification of ventilation performance in a full scale installation

This paper outlines development of a low order model that can be used for control purposes and quantification of ventilation performance in ventilated systems. First informative pollutant transport data is generated using numerical simulations. Later on, identification procedures are followed to build a low order transfer function model from the CFD generated input-output data. The obtained results demonstrate that first order model can sufficiently describe the dominant mass transfer dynamics in the ventilated air space. Afterwards classical mass balance equation is used to explain the objectively formulated model in a meaningful manner. The developed model is compact in structure and accurate in nature making it an ideal input for model based controller algorithm development. Furthermore its model parameter is found to be an inverse of the local mean age of air. Therefore the model can also be used to assess ventilation performance. (c) 2005 Elsevier Ltd. All rights reserved.status: publishe