Detection of Mixing Dynamics During Pumping of a Flooded Coal Mine

In complex hydrogeological environments the effective management of groundwater quality problems by pump-and-treat operations can be most confidently achieved if the mixing dynamics induced within the aquifer by pumping are well understood. The utility of isotopic environmental tracers (C-, H-, O-, S-stable isotopic analyses and age indicators—14C, 3H) for this purpose is illustrated by the analysis of a pumping test in an abstraction borehole drilled into flooded, abandoned coal mineworkings at Deerplay (Lancashire, UK). Interpretation of the isotope data was undertaken conjunctively with that of major ion hydrochemistry, and interpreted in the context of the particular hydraulic setting of flooded mineworkings to identify the sources and mixing of water qualities in the groundwater system. Initial pumping showed breakdown of initial water quality stratification in the borehole, and gave evidence for distinctive isotopic signatures (d34S(SO4) ~= -1.6‰, d18O(SO4) ~= +15‰) associated with primary oxidation of pyrite in the zone of water table fluctuation—the first time this phenomenon has been successfully characterized by these isotopes in a flooded mine system. The overall aim of the test pumping—to replace an uncontrolled outflow from a mine entrance in an inconvenient location with a pumped discharge on a site where treatment could be provided—was swiftly achieved. Environmental tracing data illustrated the benefits of pumping as little as possible to attain this aim, as higher rates of pumping induced in-mixing of poorer quality waters from more distant old workings, and/or renewed pyrite oxidation in the shallow subsurface.

The Coal Jetty; Shadows

Two new original poems

Coal combustion residues valorisation:Research and development on compressed brick production

This paper presents the results of an experimental investigation on compressive strength of unfired compressed brick obtained with coal combustion residues (CCRs) produced by the Niger Coal Society. Preliminary physical and optical (XRD and SEM) characterisation of coal slag, including lixiviation tests, have been carried out. Cement powder, lateritic clayey soil and sand have been chosen as stabilizing agents for bricks. 12 dosages have been tested and about 300 bricks have been produced with a hand-operated press. Results show uniaxial compressive strengths (UCSs) ranging from 4 MPa to 27 MPa for the highest cement stabilisation ratio. UCS higher than 7.5 MPa have been observed for stabilisation with 20% of laterite +10% cement after 45 days of curing. Obtained bricks showed good mechanical resistance and low weight. No health threat has been detected for the obtained samples. Study developments are oriented towards the analysis of Pozzolanic properties of CCRs, properties of hydrated lime stabilisation, thermal properties and durability assessment.© 2012 Elsevier Ltd. All rights reserved.

Coal Combustion Residuals valorisation through the production of compressed masonry brick

The Niger Coal Society (Societé Nigérienne de Charbon – SONICHAR) produces electricity for local consumption in Tefereyre, 75 km north-west from Agadez, Niger. The coal combustion residuals production is about 150,000 tons per year. In order to reduce this environmental burden and to valorize these by-products, a study focusing on their physical and chemical features as well as on the mechanical resistance of compressed brick has been undertaken. Physical characterization of coal slag, chemical and lixiviation tests have been carried out, assessing the material main parameters, verifying the presence of hazardous composites and elements and comparing the obtained results with the findings of an in-deep literary review. Cement powder has been chosen as stabilizing agent as a preliminary option. Four different dosages have been tested and bricks have been produced with a hand-operated press. Compressive strength has been tested at different days of curing. Results show remarkable uniaxial compressive strengths (UCS) for all the mixes after cure, ranging from 4MPa up to more than 20MPa for the highest stabilization ratio. UCS higher than 5MPa have been observed for 20% and 30% cement stabilization ratios after only 7 days of cure, reaching respectively about 11MPa and 13MPa after 45 days. In conclusion obtained bricks show good mechanical resistance and low weight. No health threat has been detected from the obtained sample. Study developments are oriented towards the feasibility of the utilization of low-cost, locally available stabilization means, notably clay and cohesive soils, and on thermal properties assessment.

Inhibitory Effect of Phosphonium-Based Ionic Liquids on Coal Oxidation

To develop a chemical inhibitor that can efficiently suppress coal oxidation, nine tetraalkylphosphonium-based ionic liquids (ILs) and one imidazolium-based IL [1-allyl-3-methylimidazolium chloride ([AMIm]Cl)] were examined as additives. These ILs were used to treat and investigate the inhibitory effect on the oxidation activity and the structure of lignite coal. Characterization using thermogravimetric analysis showed that phosphonium-based ILs are able to inhibit coal oxidation up to 400 degrees C with the tributylethylphosphonium diethylphosphate ([P-4,P-4,P-4,P-2][DEP]) found to be the most effective. In contrast to the tetraalkylphosphonium-based ILs, inhibition using [AMIm]Cl was only found to be effective at temperatures below 250 degrees C, indicating that the tetraallcylphosphonium-based ILs may be more suitable for the future application of suppressing coal spontaneous combustion over a wide range of temperatures. Fourier transform infrared spectroscopic data showed that the various functional groups change in the coal following IL treatment, which are a decrease in the minerals and hydrogen bonds in all treated coals, while decreased aliphatic hydrocarbon and increased carbonyl bonds only appeared in some samples. During the oxidation of coal, the decomposition of aliphatic hydrocarbon groups is inhibited and the formation of carbonyl groups is delayed, so that the evolved gas concentration decreased, as shown by the temperature-programmed oxidation-mass spectrometry results. The deployment of the [P-4,P-4,P-4,P-2][ DEP] and tributylmethylphosphonium methylsulfate Its as additives also show good inhibitory effect on coal oxidation over the temperature range studied, and a relatively stronger interaction between [P-4,P-4,P-4,P-2] [DEP] and coal is demonstrated by the additive model.

The Coal Jetty

A single poem, presented in the section of the anthology devoted to showcasing the collections shortlisted for the Forward Prize for Best Collection.