Ash deposition during the co-firing of bituminous coal with pine sawdust and olive stones in a laboratory furnace

This article describes an experimental study on ash deposition during the co-firing of bituminous coal with pine sawdust and olive stones in a laboratory furnace. The main objective of this study was to relate the ash deposit rates with the type of biomass burned and its thermal percentage in the blend. The thermal percentage of biomass in the blend was varied between 10% and 50% for both sawdust and olive stones. For comparison purposes, tests have also been performed using only coal or only biomass. During the tests, deposits were collected with the aid of an air-cooled deposition probe placed far from the flame region, where the mean gas temperature was around 640 degrees C. A number of deposit samples were subsequently analyzed on a scanning electron microscope equipped with an energy dispersive X-ray detector. Results indicate that blending sawdust with coal decreases the deposition rate as compared with the firing of unblended coal due to both the sawdust low ash content and its low alkalis content. The co-firing of coal and sawdust yields deposits with high levels of silicon and aluminium which indicates the presence of ashes with high fusion temperature and, thus, with less capacity to adhere to the surfaces. In contrast, in the co-firing of coal with olive stones the deposition rate increases as compared with the firing of unblended coal and the deposits produced present high levels of potassium, which tend to increase their stickiness.

Molecular mobility, composition and structure analysis in glycerol plasticised chitosan films

This study was developed with the purpose to investigate the effect of polysaccharide/plasticiser concentration on the microstructure and molecular dynamics of polymeric film systems, using transmission electron microscope imaging (TEM) and nuclear magnetic resonance (NMR) techniques. Experiments were carried out in chitosan/glycerol films prepared with solutions of different composition. The films obtained after drying and equilibration were characterised in terms of composition, thickness and water activity. Results show that glycerol quantities used in film forming solutions were responsible for films composition; while polymer/total plasticiser ratio in the solution determined the thickness (and thus structure) of the films. These results were confirmed by TEM. NMR allowed understanding the films molecular rearrangement. Two different behaviours for the two components analysed, water and glycerol were observed: the first is predominantly moving free in the matrix, while glycerol is mainly bounded to the chitosan chain. (C) 2013 Elsevier Ltd. All rights reserved.

An SEM investigation of the pozzolanic activity of a waste catalyst oil refinery

The most active phase of the fluid catalytic cracking (FCC) catalyst, used in oil refinery, is zeolite-Y which is an aluminosilicate with a high internal and external surface area responsible for its high reactivity. Waste FCC catalyst is potentially able to be reused in cement-based materials - as an additive - undergoing a pozzolanic reaction with calcium hydroxide (Ca(OH)2) formed during cement hydration [1-3]. This reaction produces additional strength-providing reaction products i.e., calcium silicate hydrate (C-S-H) and hydrous calcium aluminates (C-A-H) which exact chemical formula and structure are still unknown. Partial replacement of cement by waste FCC catalyst has two key advantages: (1) lowering of cement production with the associated pollution reduction as this industry represents one of the largest sources of man-made CO2 emissions, and (2) improving the mechanical properties and durability of cement-based materials. Despite these advantages, there is a lack of fundamental knowledge on pozzolanic reaction mechanisms as well as spatial distribution of porosity and solid phases interactions at the microstructural level and consequently their relationship with macroscopical engineering properties of catalyst/cement blends. Within this scope, backscattered electron (BSE) images acquired in a scanning electron microscope (SEM) equipped with Energy-Dispersive Spectroscopy (EDS) and by X-ray diffraction were used to investigate chemical composition of hydration products and to analyse spatial information of the microstructure of waste FCC catalyst blended cement mortars. For this purpose mortars with different levels of cement substitution by waste catalyst as well as with different hydration ages, were prepared. The waste FCC catalyst used is produced by the Portuguese refinery company Petrogal S.A.