Solidification of APC residues using PFA

A pulverised fuel ash (pfa) classed as a waste due to high loss on ignition (LoI) was blended with waste alkali and used to solidify air pollution control (APC) residue from a waste incinerator. The resultant samples were tested for compressive strength and characterised using thermogravimmetric analysis (TGA). The effects of various variables including; l/s ratio, APC content, curing temperature and alkalinity of the liquid phase were examined. Results showed that a lower l/s gave higher compressive strength, analogous to that seen for cement mixes. Curing at slightly elevated temperatures were necessary for setting of the mixes within 7 days. An alkaline liquid fraction increased early age strength. The %(w/w) APC content showed no clear correlation with compressive strength results, but some APC was necessary for the mix to set. Resulys suggest the optimum APC content for compressive strength and solidification may be between 10-20%

Factorial Design Applied to Waste Immobilisation in Geopolymer-based Systems

Concentrated alkali, ground glass and air pollution control residues were mixed in various proportions and cured for up to 28 days. These blocks were tested in strength and analysed by thermal gravimetric analysis to assess the success of the geopolymerisation process. A Taguchi factorial design approach was then adopted to investigate the effects of different variables upon the strength development of these blocks

The Behaviour of Finely Ground Bottom Ash in Portland Cement

The aim of this project was to assess the effects of finely ground MSWI bottom ash in Portland cement. Mortar mixes were prepared with 10% and 40% replacement of cement by ground IBA and then tested with regards to their material composition and engineering behaviour. IBA was found not to be inert, but showed some degree of reactivity. Replacement of cement with IBA was found to have no detrimental effects at low concentrations. This was not the case for 40% replacement, where cement replacement greatly affected strength, creep and drying shrinkage

Structure, bonding and morphology of hydrothermally synthesised xonotlite

The authors have systematically investigated the role of synthesis conditions upon the structure and morphology of xonotlite. Starting with a mechanochemically prepared, semicrystalline phase with Ca/Si=1, the authors have prepared a series of xonotlite samples hydrothermally, at temperatures between 200 and 250 degrees C. Analysis in each case was by X-ray photoelectron spectroscopy, environmental scanning electron microscopy and X-ray diffraction. The authors’ use of a much lower water/solid ratio has indirectly confirmed the ‘through solution’ mechanism of xonotlite formation, where silicate dissolution is a key precursor of xonotlite formation. Concerning the role of temperature, too low a temperature (~200 degrees C) fails to yield xonotlite or leads to increased number of structural defects in the silicate chains of xonotlite and too high a temperature (>250 degrees C) leads to degradation of the xonotlite structure, through leaching of interchain calcium. Synthesis duration meanwhile leads to increased silicate polymerisation due to diminishing of the defects in the silicate chains and more perfect crystal morphologies

Studies on microfungi from litter and soil in relation to the ecology of lignin decomposition

The studies reported here on microfungi from litter and soil involved: 1) The behaviour of microfungi in pure culture towards lignin related-phenolic acids. 2) The chemistry and microbiology of Scots Pine litter in relation to lignin decomposition. 3) The decomposition of ferulic acid by mixed populations of microorganisms. Ferulic acid incorporated into agar could be inhibitory or stimulatory to the spore germination and germ hyphal growth of microfungi depending upon its concentration and the fungal species. Within a certain concentration range, the total growth potential of some Angiosperm leaf saprophytes was depressed relative to control whereas there was an increase in the case of conifer needle litter saprophytes and some common soil fungi. Other phenolic acids produced similar patterns of results but the differential effects were generally less marked. The ability of litter and soil microfungi to utilise ferulic acid as a sole carbon source was defined from the decomposition of the substrate after inoculating culture solution with spores. The pattern in the ability to decompose ferulic acid was not related to the effects of this compound on germination on agar or in the liquid medium. Dothichiza pityophila and Fusicoccum bacillare were isolated as the principal primary saprophytes of Scots Pine needle litter while the widespread primary saprophytes of Angiosperm leaf litters, including Aureobasidium pullulans were absent, confirming and reinforcing the results of previous European work. The use of Infra-red spectroscopy of finely divided, but unextracted, Pine needles and humus to follow the course of the decomposition of the litter permitted an evaluation of the role of soil-inhabiting fungi in this process. Burial of litter needles in a deciduous woodland soil or in a field soil led to colonisation by several soil fungi not characteristic of Pine litter, notably Gliocladium roseum and an Actinomycete of genus Nocardia. These two species were able to colonise the needle interior in the presence of needle saprophytes surviving in buried needles whereas Trichoderma viride remained restricted to the needle surface by prior- colonisation. Finally, experiments are described in which Pine needle and soil material from the burial experiments and samples of two other soils of contrasting ligninolytic characteristics were used as inoculum for the decomposition of ferulic acid, the results of these experiments relating to known microbiological and chemical properties of the soils. The importance of phenolic acids released during lignin decomposition in the fungal colonisation of substrates in litter and soil is discussed, and some conclusions are made regarding the validity of phenolic acids as 'lignin model compounds'

The Effect of Co-Combusted Biomass-Coal Fly Ash on the Behaviour Portland Cement

This project has investigated the hydration behaviour of pfa-OPC blended cements, comparing conventional pfa with that obtained from co-firing of coal with biomass (palm kernel expeller). Calorimetry, thermal analysis and electron microscopy have been used to investigate the compositions and microstructures of the hydrated pastes. These have been used to explain the materials’ engineering properties (strength development and workability). The results showed that, in the short term, the behaviour of the co-fired material is comparable with that of conventional pfa, there being no discernable differences between the two systems

Molecular clouds in the centers of galaxies: Constraints from HCN and CO-13 line emission

We have searched for HCN J=1-0 line emission in the centers of 12 galaxies and have detected it in 10 of them. We have obtained complementary data on J=1-0 and 2-1 transitions of CO-12 and CO-13 in these systems. The ratio of integrated intensities, I(CO 1-0)/I(HCN 1-0) = 25 +/- 11 for this sample. We find that HCN emission of this strength can be produced under conditions of subthermal excitation. In combination with the line ratios in CO and CO-13, HCN puts constraints on the mean conditions of molecular clouds and on the mix of cloud types within the projected beam

The GEOS-3 orbit determination investigation

The nature and improvement in satellite orbit determination when precise altimetric height data are used in combination with conventional tracking data was determined. A digital orbit determination program was developed that could singly or jointly use laser ranging, C-band ranging, Doppler range difference, and altimetric height data. Two intervals were selected and used in a preliminary evaluation of the altimeter data. With the data available, it was possible to determine the semimajor axis and eccentricity to within several kilometers, in addition to determining an altimeter height bias. When used jointly with a limited amount of either C-band or laser range data, it was shown that altimeter data can improve the orbit solution

Splicing bioinformatics to biology

A report on the 2nd Symposium on Alternative Transcript Diversity, Heidelberg, Germany, 21-23 March 2006