Improving of Green Sand-Mould Quality using Taguchi Technique

The green sand mould casting is an inevitable process to make large size and complex shape of the industrial components. The quality of green sand in mould is a significant phenomenon on casting quality. In this research, the number of ramming, sand thickness mould, and percentage of additives (western bentonite) mixing with sand have been considered to study the effects on permeability and hardness of mould by L27 orthogonal array. Greensand mould experiments have been conducted in the industry to observe the output parameter variations by Taguchi statistical analysis. It was revealed that the maximum permeability and minimum sand hardness have been obtained from the minimum number of ramming, thin sand thickness, and minimum mixing of additives in the sand. The confirmation tests were conducted to validate the predicted control parameter on responses.

Phase Formation, Microstructure and Permeability of Fe-Deficient Ni-Cu-Zn Ferrites, (I): Effect of Sintering Temperature

We have studied the densification, phase formation, microstructure, and permeability of stoichiometric and Fe-deficient Ni-Cu-Zn ferrites of composition Ni0.30Cu0.20Zn0.50+zFe2-zO4-(z/2) with 0 £ z £ 0.06 sintered at temperatures from 900 °C to 1150 °C. The shrinkage is shifted from 1000 °C for z = 0 towards lower temperatures and reaches its maximum rate at 900 °C for z = 0.02. Stoichiometric ferrites show regular growth of single-phase ferrite grains if sintered at Ts ≤ 1100 °C. Sintering at 1150 °C leads to the formation of a small amount of Cu2O, triggering exaggerated grain growth. Fe-deficient compositions (z > 0) form Cu-poor stoichiometric ferrites coexisting with a minority CuO phase after sintering at 900–1000 °C. At Ts ≥ 1050 °C, CuO transforms into Cu2O, and exaggerated grain growth is observed. The formation of Cu oxide second phases is investigated using XRD, SEM, and EDX. The permeability of the ferrites increases with sintering temperature up to a maximum permeability of µ = 230 for z = 0 or µ = 580 for z = 0.02, respectively, at Ts = 1000 °C. At higher sintering temperatures, the permeability decreases, which is due to the formation of a microstructure with intra-crystalline porosity in large grains, and a non-magnetic Cu oxide grain boundary phase.

Influence of Casting Solvents on CO2/CH4 Separation Using Polysulfone Membranes

Polysulfone membranes exhibit resistance to high temperature with low manufacturing cost and high efficiency in the separation process. The composition of gases is an important step that estimates the efficiency of separation in membranes. As membrane types are currently becoming in demand for CO2/CH4 segregation, polysulfone will be an advantageous alternative to have in further studies. Therefore, research is undertaken in this study to evaluate two solvents: chloroform (CF) and tetrahydrofuran (THF). These solvents are tested for casting polymeric membranes from polysulfone (PSF) to separate every single component from a binary gas mixture of CO2/CH4. In addition, the effect of gas pressure was conducted from 1 to 10 bar on the behavior of the permeability and selectivity. The results refer to the fact that the maximum permeability of CO2 and CH4 for THF is 62.32 and 2.06 barrer at 1 and 2 bars, respectively. Further, the maximum permeability of CF is 57.59 and 2.12 barrer at 1 and 2 bars, respectively. The outcome selectivity values are 48 and 36 for THF and CF at 1 bar, accordingly. Furthermore, the study declares that with the increase in pressure, the permeability and selectivity values drop for CF and THF. The performance for polysulfone (PSF) membrane that is manufactured with THF is superior to that of CF relative to the Robeson upper bound. Therefore, through the results, it can be deduced that the solvent during in-situ synthesis has a significant influence on the gas separation of a binary mixture of CO2/CH4.

Effect of Compaction Banding on the Hydraulic Properties of Porous Rock: Part I—Experimental Investigation

The mechanical behavior and the influence of compaction banding on the hydraulic properties in soft porous rocks were studied. The tested rock was Calcarenite Tuffeau de Maastricht. In the frame of experimental investigations, triaxial and oedometric tests were conducted under dry and drained conditions. The results demonstrated that the rock is forming discrete compaction bands under high confining stresses and steep angle shear bands under low confining stresses. Permeability measurements during the oedometric and triaxial compression tests under drained conditions demonstrated that the axial permeability decreases with increasing axial strain. The maximum permeability decrease was three orders of magnitude for 40% of axial strain.

Impact of Sedimentation on Water Seepage Capacity in Lake Nakuru, Kenya

Accumulation and deposition of sediments in waterbody affect the seepage capacity that could lead to improper water balance and results in the water level rise. This study analysed the influence of sedimentation on seepage capacity in Lake Nakuru and the impact of sediment characteristics to the water seepage and the flow rate formation at the lake bed level. The study was performed by sampling and analysing the sediment cores from two locations in the lake. The sediment hydraulic properties, i.e., moisture and porosity, particle sizes, and hydraulic conductivity, were determined using the oven-drying method, sieve analysis, hydrometer analysis, and falling head tests, respectively. The results showed that the lake sediment sample from location P1 had an average ratio of 39.38% for silty soil, 34.00% for clayey sediment, and 26.63% for fine-sand sediment particles with the maximum permeability coefficient of 3.37 ∗ 10 − 5 cm/s, while the one from location P2 had an average ratio of 63.17% for sand, 20.17% for fine particles, and 16.67% for gravels with the maximum permeability coefficient of 0.010793 cm/s. The hydraulic conductivity of sediment sample from location P1 and P2 increased along the core depth. This could lead to the rise of water level due to the decreases of water movement induced from the sediment cementation in the top layers under the waterbody. Sedimentation affects Lake Nakuru water volume and water balance; hence, there is a need to control the inflow of sediment resulting from anthropogenic activities in the watershed.

Permeability Evolution of Naturally Fractured Coal Injected with High-Temperature Nitrogen: Experimental Observations

The permeability of more than 70% of coal seams in China is less than 1 mD, creating difficulties in recovering underground coal methane. Therefore, a new technology of high-temperature nitrogen (HTN2) injection into the coal seam was proposed to improve the coal permeability and gas extraction rate. In this paper, the effects of the N2 temperature, injection pressure and cycle number on the permeability of naturally fractured coking coal has been investigated. When HTN2 was injected into coal samples, the results indicated that the permeability decreased over time in the beginning, suddenly increased to a large value, and was subsequently maintained in a relatively stable range. The maximum permeability ratio increased with the rise of the N2 temperature and injection pressure. An analysis indicated that the increase of coal permeability was the result of the increase of the global coal strain caused by thermal expansion and the adsorption-induced expansion. The maximum permeability ratios in various cycles of multicycle N2 injection into the coal sample were all greater than 1.0 while progressively declining. Obviously, the alternating stress was conducive to the further expansion of the coal fractures to increase the coal permeability. However, on the basis of the first period of expansion, re-expansion was difficult and required more energy. The effects of multicycle N2 injection on coal permeability have been considerably improved when compared with N2 injection with only one cycle. The research results are helpful for rapidly extracting methane and guaranteeing mine safety.

Experimental Investigation on Permeability Evolution of Dolomite Caprock under Triaxial Compression

In order to study the influence of different confining pressures on the stability and airtightness of dolomite underground gas storage, a permeability test under hydrostatic confining pressure, conventional triaxial compression test and gas–solid coupling test under triaxial compression were carried out on MTS815 test machine. During the tests, an acoustic emission (AE) monitoring system was also employed to estimate the rock damage. The experimental results showed that the relationships between permeability, porosity and hydrostatic confining pressure were exponential function and power function, respectively. Increasing confining pressure reduced the porosity and permeability of dolomite, and increased its triaxial compressive strength, but the addition of nitrogen reduced the compressive strength of dolomite by 10~30%, the higher the confining pressure, the smaller the difference. Compared with the maximum permeability under 15 MPa, confining pressure in the gas–solid coupling experiment, the maximum permeability under confining pressure of 30, 45, and 60 MPa is reduced by 42.0%, 84.4%, and 97.9%, respectively. In addition, the AE activity of dolomite decreases significantly with the increase in confining pressure, which also delayed the arrival of the AE active period.

EFFECT OF AGE ON HEARTWOOD / SAPWOOD RELATIONSHIP, EXTRACTIVE CONTENTE, AND PERMEABILITY OF TEAK WOOD

Due to the physiological differences in the juvenile and adult phases of teak wood, differentiation occurs in the impregnation by extractive materials along the heartwood regions, assuming that there is also a significant variation in the permeability of this material. Thus, the study aimed to evaluate the influence of age on the heartwood / sapwood ratio (H/S), permeability, and extractives content of Tectona grandis L.f wood. Four ages (10, 12, 14, and 16 years) and four trees (repetitions) were evaluated, totaling 16 samples. The H/S ratio, extractive content, and wood permeability were determined, in addition to the average and maximum permeability among all ages selected for calculation of their porosity. The H/S ratio increased over the ages of 10 and 16, and the content of extractive materials increased until the age of 14. There was a high heterogeneity between the permeability values of the wood at all ages analyzed, and one of the possible explanations for this fact is the presence of tyloses in different places on the trunk and the arrangement of the pores around the growth rings.

Experimental Investigation of Water-Inrush Risk Based on Permeability Evolution in Coal Mine and Backfill Prevention Discussion

Induced by coal mining, the fractures constantly occur in geologic strata until failure occurs, which provide channels for water flow. Therefore, it is essential to investigate the permeability evolution of rocks under load. Borehole sampling was conducted in a bedrock layer beneath an aquifer, and the permeability evolution of sandstone specimens under different confining pressures was tested in rock mechanics testing laboratories. The results indicated that the permeability gradually decreases with the increasing confining pressures, while the peak strength increases with the increase of confining pressures. The minimum and maximum permeabilities occurred in the sandstone specimens that were subjected to elastic deformation and strain-softening stages, respectively. The failure, and maximum permeability, of these sandstone specimens did not occur simultaneously. To prevent the flow channel being formed due to the development and failure of rock fractures, a method of backfill gob was proposed and also the influence of backfill on fracture development was discussed.