Physical and Mechanical Properties of Non-Stoichiometric Cordierite with Treated FGD Sludge Addition Sintered at 1250°C

The effects of addition treated FGD sludge in non-stoichiometric cordierite, by benefiting from its high mechanical strength and good thermal performance, can hold promise for more practical applications of non-stoichiometric cordierite. Treated FGD sludge waste from borosilicate glass industrial were used as a flux to reduce the sintering temperature of cordierite. Cordierite ceramics were prepared using silica (SiO2), alumina (Al2O3), talc, kaolin, magnesia (MgO) and treated FGD sludge via solid-state reaction method. The cordierite were prepared by adjusting the ratio of FGD sludge and magnesia in the cordierite composition, respectively. 4 composition of cordierite with 0%, 1.5%, 3.0% and 4.5% of FGD sludge were prepared to obtain the formation of α-cordierite that can be determine by X-ray diffraction (XRD) analysis. Porosity, density, shrinkage and flexural strength for each of cordierite composition were determined to obtain the best composition of treated FGD sludge required for sintering aids of cordierite. Only FGD 3.0% able to synthesis pure α-cordierite while FGD 1.5 % shows an improvement in both porosity and density. The increasing amount of treated FGD sludge lead to decreasing in mechanical strength of cordierite ceramic due to porous formation.

Dispersion in doublet-type flows through highly anisotropic porous formations

Steady doublet-type flow takes place in a porous formation, where the log-transform $Y = \ln K$ of the spatially variable hydraulic conductivity $K$ is regarded as a stationary random field of two-point autocorrelation $\rho _Y$ . A passive solute is injected at the source in the porous formation and we aim to quantify the resulting dispersion process between the two lines by means of spatial moments. The latter depend on the distance $\ell$ between the lines, the variance $\sigma ^2_Y$ of $Y$ and the (anisotropy) ratio $\lambda$ between the vertical and the horizontal integral scales of $Y$ . A simple (analytical) solution to this difficult problem is obtained by adopting a few simplifying assumptions: (i) a perturbative solution, which regards $\sigma ^2_Y$ as a small parameter, of the velocity field is sought; (ii) pore-scale dispersion is neglected; and (iii) we deal with a highly anisotropic formation ( $\lambda \lesssim 0.1$ ). We focus on the longitudinal spatial moment, as it is of most importance for the dispersion mechanism. A general expression is derived in terms of a single quadrature, which can be straightforwardly carried out once the shape of $\rho _Y$ is specified. Results permit one to grasp the main features of the dispersion processes as well as to assess the difference with similar mechanisms observed in other non-uniform flows. In particular, the dispersion in a doublet-type flow is observed to be larger than that generated by a single line. This effect is explained by noting that the advective velocity in a doublet, unlike that in source/line flows, is rapidly increasing in the far field owing to the presence there of the singularity. From the standpoint of the applications, it is shown that the solution pertaining to $\lambda \to 0$ (stratified formation) provides an upper bound for the dispersion mechanism. Such a bound can be used as a conservative limit when, in a remediation procedure, one has to select the strength as well as the distance $\ell$ of the doublet. Finally, the present study lends itself as a valuable tool for aquifer tests and to validate more involved numerical codes accounting for complex boundary conditions.

Experimental investigation to characterize simple versus multi scaling analysis of hydraulic conductivity at a mesoscale

The spatial variability of the aquifers' hydraulic properties can be satisfactorily described by means of scaling laws. The latter enable one to relate the small (typically laboratory) scale to the larger (typically formation/regional) ones, therefore leading de facto to an upscaling procedure. In the present study, we are concerned with the spatial variability of the hydraulic conductivity K into a strongly heterogeneous porous formation. A strategy, allowing one to identify correctly the single/multiple scaling of K, is applied for the first time to a large caisson, where the medium was packed. In particular, we show how to identify the various scaling ranges with special emphasis on the determination of the related cut-off limits. Finally, we illustrate how the heterogeneity enhances with the increasing scale of observation, by identifying the proper law accounting for the transition from the laboratory to the field scale. Results of the present study are of paramount utility for the proper design of pumping tests in formations where the degree of spatial variability of the hydraulic conductivity does not allow regarding them as “weakly heterogeneous”, as well as for the study of dispersion mechanisms.

Experimental Investigation to Characterize Simple Vs Multi Scaling Analysis of Hydraulic Conductivity at a Mesoscale

The spatial variability of the hydraulic properties of aquifers can be satisfactory described by means of scaling law(s). The latter enables one, among the others, to relate the small (typically laboraory) scale to the larger (typically formation/regional) ones, therefore leading de facto to an upscaling procedure. In the present study, we are concerned, with the spatial variability of the hydraulic conductivity k into a strongly heterogeneous porous formation. A strategy, allowing one to identify correctly the single/multiple scaling of k, is applied for the first time to a real case of a large caiison where a strongly heterogeneous medium was packed. In particular, we show how to identify the various scaling ranges with special emphasys to the determination of the related cut-off limits. Finally, we illustrate how the heterogeneity enhances with the increasing scale of observation, by identifying the proper law accounting for the transtion from the laboratory to the field scale. Results of the present study are of paroumnt utility for the proper design of pumping tests in formations where the degree of spatial variability of the hydraulic conductivity does not allow regarding them as “weakly heterogeneous”, as well as for the study of dispersion mechanisms in solute transport.

Geological controls on brine discharge in Itumbula Salt Dam within the Rukwa Rift in Momba District, Tanzania

The Itumbula salt dam of the Rukwa Rift Basin is a depression formed through extraction of spring-derived salt crystals. Brine yield by springs which is the primary cause of significant amounts of salt in the dam required further geological investigations to understand yield controls. In this study, detailed field geological investigations in the salt dam and its surroundings were conducted to ascertain brine discharge controls. These included documentation of lithology and surface manifestations of brine deposition. Geophysical methods (i.e. magnetic and electric surveys) for studying geologic structures associated with brine deposits, and laboratory analysis of cations and anions (e.g. chlorides, bicarbonates or sulphates) essential to characterize composition of waters were also performed. The information on the springs discharge rate was retrieved from the previous studies. The magnetic profile revealed a very low magnetic anomaly across the salt dam, trending NW to SE direction, which is interpreted to be the main structure that controls fluid movements in the dam. Electric resistivity survey results delineated a low resistivity body in the central part of the dam interpreted as porous formation with saline water. Hydro-chemistry of the hot spring brines indicated high levels of sodium and chloride ions contents than magnesium, calcium, potassium, sulphate, and carbonate and bicarbonate ions, interpreted to be mature water with minimal water mixing. The structurally controlled brines of approximately 2.5 kg/s are discharged in the study area. Keywords: Geologic Structures, Brine, Salt Production, Momba, Rukwa Basin.

A study on the influence of salinity interfaces on borehole seismoelectric wavefields

Previous theoretical and experimental studies on seismoelectric logging suggest that the electromagnetic head wave (EH wave) is much weaker than the electric field accompanying the Stoneley wave (ESt wave). Nevertheless, recent in situ measurements show that the EH wave amplitude can be greater than that of the ESt wave. We have addressed this issue according to the simulation of borehole seismoelectric wavefields and find that the amplitude ratio of EH to ESt waves is sensitive to the salinity contrast at the interfaces. Specifically, the EH wave amplitude can be greater than that of the ESt wave if the salinity of the borehole fluid is much higher than that of the pore fluid in a homogeneous porous formation. When an impermeable mud cake layer is taken into account between the borehole fluid and the formation, the amplitude ratio of EH to ESt waves can be even larger, although the amplitudes of the EH and ESt waves become smaller. For a radially stratified porous formation, the large amplitude ratio of EH to ESt waves also occurs if the salinity of the borehole fluid is much higher than that of the pore fluid in the inner layer, or if the salinity of the pore fluid in the inner layer is much higher than that in the outer layer. The large amplitude ratio of EH to ESt waves has potential for detecting interfaces with high salinity contrast, or it can be used as an indicator of mud cake.