Variation In Pore Size Distribution Research Articles

RO and NF membrane fouling and cleaning and pore size distribution variations

The variations of porosity parameters of some reverse osmosis (RO) and nanofiltration (NF) polyamide thin-film composite membranes were determined in order to explain the changes of membranes' performances caused by membrane fouling and chemical cleaning of the fouled membranes. The pore size distribution curves and the effective number of pores in the membrane surface indicated plugging of the tight network pores in the membrane surface and even their disappearance during fouling. The enlargement of the wider aggregate pores was responsible for the noticed reduction in salt rejection. The initial pore structure of the fouled RO membrane was restored by immediate chemical cleaning. A delay of chemical cleaning of the fouled membranes led to irreversible changes in the porous structure of both the RO and NF membranes, which were caused by a microbial activity.

Hydrothermal Solidification of Wastes withFormation of Zeolites

In order to use waste materials effectively, a possibility of simultaneous solidification of inorganic waste materials and fixation of alkaline ions and heavy metal through formation of zeolite by using hydrothermal processing, was investigated. Fly ash, cinder of sewage sludge, and cinder of rubbish were used as the starting materials. Ca/Si and 2Na/Si molar ratios of the specimens were changed by the addition of CaO and Na\d2CO\d3. These mixtures were formed and hydrothermally processed at 200 C. Various zeolites, such as analcime, Linde B\d1 zeolite, cancrinite, zeolite P-C, and hauyne, were formed at Ca/Si = 0.3 or 0.5 and 2Na/Si = 0.1–1.0. In the case of the fly ash system, although only the zeolite minerals were formed, the flexural strength reached up to 17 MPa when Ca/Si = 0.3 and 2Na/Si = 0.1, and the fixing ratio of Na\u+ ion reached a maximum value of 85% by the formation of zeolites. When cinder of rubbish was used, dissolution of heavy metals from the solidified specimen was scarcely observed. The microstructure and the variation of pore size distribution were also discussed.

ABSTRACT: Variation in pore size distribution with coal rank and composition: potential for substantial resources of free gas in matrix porosity in low rank

ABSTRACT: Variation in pore size distribution with coal rank and composition: potential for substantial resources of free gas in matrix porosity in low rank

Role of Drying Techniques on the Development of Porosity in Silica Gels

Silica gel has been prepared by the hydrolysis of TEOS under three different pH conditions. These gels have been subjected to drying in an air oven, under humidity, and also by exposure to microwaves, followed by further calcination at 500°C under slow heating schedule (3°C/min). Silica samples thus obtained are characterised by B.E.T. specific surface area and pore volume data. The thermal decomposition behaviour of the precursor gels are also reported. The adsorption isotherms of these samples indicate different behaviour related to the method of synthesis. Increase in pH of hydrolysis of the TEOS from 3 to 8 results in increase in specific surface area in tune with the earlier reports. However more significant observation is the variation in pore size distribution as evidenced from adsorption isotherms related to method of drying. Silica gels prepared at pH 3 show Type I behaviour irrespective of the method of drying. However gel prepared at pH 6 shows Type II behaviour when dried under microwave with specific surface area as high as 635 m2/g and pore volume 0.9733 cc/g. The precursor gels prepared at still higher pH exhibit Type IV behaviour when subjected to microwave drying. The pH conditions of synthesis of precursor gels along with drying techniques appear to affect not only the surface areas and porosities but also the resultant adsorption isotherms, in sol-gel silica.

Simulation of Formation Damage in Petroleum Reservoirs

SUMMARY A phenomenological model for prediction of petroleum reservoir permeability impairment by porous media, fine particles and liquid interactions is presented. The combined effects of clay swelling, external particles invasion, fines generation, migration and retention involved in permeability impairment are formulated. Deviation from Darcy flow as the flow paths are plugged and the variation of pore size distribution during plugging are considered. The model is tested for a variety of conditions. The magnitudes of the estimated model parameters are used to determine the relative contributions of various damage mechanisms. The estimated parameter values are shown to be valid beyond the range of the data used to estimate them. The successful match between the measured and predicted values of permeability variation and effluent fines concentration demonstrates the validity and the capability of the formation damage model.

Effect of composition and pore structure on binding energy and effective diffusivity of moisture in porous food

Food samples of different compositions were formulated by extruding mixtures of starch and gluten of different compositions, whereas samples of varying pore structure were obtained through extrusion of durum semolina at 57 and 137°C. Experimental measurement of desorption isotherm of these samples at different temperatures in the range 25–40°C indicated that the water binding ability was fairly insensitive to the pore structure of food samples and was found to be lower for extruded and pregelatinized samples as well as for samples of higher gluten content. Experimental desorption isotherm data were represented by the Oswin equation in order to evaluate moisture binding energy as a function of moisture content and temperature by employing the Clausius-Clapeyron equation. Binding energy was found to be negligible at high moistures (above 0·2 d.b.), increasing at lower moisture contents, lower temperatures and higher starch contents. Effective diffusivity of moisture through the porous food at different moisture contents and temperatures was inferred from drying curves in the temperature range 60–105°C. Effective diffusivity (D eff ) was higher in pregelatinized samples and was found to be much higher through porous puffed pasta than regular pasta. The effect of composition on D eff was confounded by the effect of pore structure as a result of variations in pore size distribution in the extruded samples of different compositions. The decrease in D eff at lower moisture contents was postulated to be due to the decrease in the available free water for diffusion and was explained through a simple model which related the available free moisture to the binding energy.

Relationship between gypsum content, porosity and strength in cement. I. Effect of SO 3 on the physical microstructure of Portland cement mortars

The experimental investigation is part of a wider research programme, addressed to correlating the modifications in the physical microstructure, due to gypsum addition, with the mechanical behaviour of cement mortars. This first paper reports on the examination of a series of mortars manufactured with Portland cement, SO 3 content ranging between 1.5 and 4.5%, cured 3 and 28 days. An outline of the tests procedure is also given. By means of mercury porosimeter analysis it has been pointed out that, in standardized working conditions, a content of about 2–3.5% SO 3 promotes a shifting of the pore size distribution to lower values, ranging between 100 and 1000 Å, as well as a variation in total porosity. This latter appears to be the main factor governing the influence of SO 3 on the compressive strength of Portland cement mortars, since the variation in pore size distribution alone seems confined to a sphere negligibly affecting strength.

Influence of Porosity on the Irradiation Performance of Pyrocarbon Coatings

The pore-size distribution of pyrocarbon (PyC) coatings was measured by small-angle x-ray scattering. The method proved to be a very sensitive means of characterizing the microstructure of PyC's. Variations in deposition conditions--such as temperature, hydrocarbon gas, and gas flux-lead to distinct variations in pore-size distribution. Different pore-size intervals are related to such material properties as density and fracture stress as well as to the irradiation stability and gas permeability of low-temperature isotropic (LTI) coatings. A parametric property, the relative amount of fiber component, is derived from the pore-size distribution and correlated with the microstructural components of LTI coatings as well as with the irradiation performance.

Small-Scale Packing Heterogeneities in Porous Sedimentary Rocks

Packing heterogeneity is defined as local variation in sorting, or more strictly, local variation in pore-size distribution. Small-scale packing heterogeneities essentially determine the amount of liquid which is held as an irreducible wetting phase saturation in a drained porous rock. The so-called irreducible saturations of two unconsolidated core samples were reduced by approximately half after the particles of each core had been well mixed to destroy small-scale packing heterogeneities. Irreducible saturation is proposed as an index of packing heterogeneity, which may reflect depositional environment and post-deposition history.

Evaluation Of Capillary Character In Petroleum Reservoir Rock

Abstract Improved apparatus, methods, and experimental techniques for determining thecapillary pressure-saturation relation are described in detail. In thisconnection a new multi-core procedure has been developed which simplifies theexperimental work in the study of relatively homogeneous reservoirs. The basictheory concerning the Leverett capillary pressure function has been extendedand has been given some practical application. Some discussion is presented toindicate the relationship of relative permeability to capillary pressure, andto provide a new description of capillary pressure phenomena by introducing theconcept of the psi function. Introduction For the purposes of this paper the capillary character of a porous mediumwill be defined to express the basic properties of the system, which produceobserved results of fluid behavior. These basic properties may be classified inthe following manner, according to their relationship to:The geometrical configuration of the interstitial spaces.This involves consideration of the packing of the particles, producing pointsof grain contact, and variations in pore size distribution. The packing itselfis often modified by the secondary processes of mineralization which introducesfactors of cementation, and of solution action which causes alteration of porestructure.The physical and chemical nature of the interstitial surfaces.This involves consideration of the presence of interstitial clay coatings, theexistence of non-uniform wetting surfaces; or, more generally, a considerationof the tendency towards variable interaction between the interstitial surfacesand the fluid phases saturating the interstitial spaces.The physical and chemical properties of the fluid phases in contact withthe interstitial surfaces. This involves consideration of the factors of surface, interfacial and adhesiontensions; contact angles; viscosity; density difference between immisciblefluid phases; and other fluid properties. Fine grained, granular, porous materials such as found in petroleum reservoirrock possess characteristics which are expressible bypermeability,porosity, andthe capillary pressure-saturation behavior of immisciblefluids in this medium. These three measurable macroscopic properties dependupon the microscopic properties enumerated above in a manner which defines thecapillary character. T.P. 2594