| 1. |
- Jönsson, Ann-Sofi, et al.
(författare)
-
Fluid flow in compressible porous media: I: Steady-state conditions
- 1992
-
Ingår i: AIChE Journal. - : Wiley. - 1547-5905 .- 0001-1541. ; 38:9, s. 1340-1348
-
Tidskriftsartikel (refereegranskat)abstract
- This is the first of two articles dealing with fluid flow in compressible porous media. In this article a model describing fluid flow and pressure-induced variations in porosity under stationary conditions is developed. In a forthcoming article the dynamic behavior during filtration and wet pressing of compressible porous media are presented. Fluid flow through rigid porous media is generally described by Darcy's law. The corresponding expression for compressible materials is derived in this article. This expression, the steady-state flow (SSF) equation, allows the steady-state flow to be easily calculated, either numerically, or by using the approximative analytical solutions that are also presented here. In the SSF equation optional empirical and/or theoretical permeability and compressibility relationships may be combined. Further, a new compressibility model which also applies for viscoelastic materials is presented. The influence of the compressibility of the material and the influence of precompression is illustrated.
|
|
| 2. |
- Jönsson, Ann-Sofi, et al.
(författare)
-
Fluid flow in compressible porous media: II: Dynamic behavior
- 1992
-
Ingår i: AIChE Journal. - : Wiley. - 1547-5905 .- 0001-1541. ; 38:9, s. 1349-1356
-
Tidskriftsartikel (refereegranskat)abstract
- This article deals with the dynamic behavior during filtration and wet pressing of compressible porous media. An equation is developed which permits the derivation of the time dependency of porosity and flow at varying locations in a medium subjected to hydraulic pressure and/or mechanical load. Furthermore, a numerical solution that allows the equation to be solved rapidly and with high accuracy on a common PC is presented. The computer program developed in conjunction with this work has been used to illustrate the dynamics of fluid flow in some industrially important applications, such as wet pressing of paper pulp and flow in chromatography columns. The program has also been used to calculate the flow and concentration variations during mechanical impulse loading (that is, a press pulse).
|
|
| 3. |
- Jönsson, Ann-Sofi, et al.
(författare)
-
The influence of nonionic surfactants on hydrophobic and hydrophilic ultrafiltration membranes
- 1991
-
Ingår i: Journal of Membrane Science. - 0376-7388. ; 56:1, s. 49-76
-
Tidskriftsartikel (refereegranskat)abstract
- The influence of different types of surfactants on ultrafiltration membranes has been investigated. A basic approach to membrane-surfactant interactions is also presented. A nonionic (Triton X-100), two anionic (potassium oleate and sodium dodecylbenzenesulphonate) and a cationic (hexadecyltrimethylammonium bromide) surfactant were investigated. The effects on commercial membranes of polysulphone, poly(vinylidene fluoride) and cellulose acetate were studied. The flux reductions of the hydrophobic membranes were found to be much more pronounced than the flux variations of the hydrophilic membranes. Both the material and the molecular weight cut-off were found to influence the performance of the hydrophobic membranes. A drastic influence of hydrophobic impurities was demonstrated. The retention of the nonionic surfactant was low at concentrations below the critical micelle concentration. The retention of the ionic surfactants was quite high, even at low concentrations.
|
|
| 4. |
- Blomgren, Y, et al.
(författare)
-
Concentration of acid hydrolysate by reverse osmosis and mechanical vapor recompression evaporation
- 1991
-
Ingår i: Journal of Wood Chemistry and Technology. - : Informa UK Limited. - 0277-3813 .- 1532-2319. ; 11:1, s. 117-135
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of this project was to investigate possible methods for the concentration of acid hydrolyzate obtained from hydrolyzing wood. A detailed study of concentration of sugar solution by reverse osmosis, RO, has been performed as well as a comparison with mechanical vapor recompression evaporation. The comparison has, in this specific case, shown that RO is currently more expensive. The result is, however, highly dependent on investment costs, and future expansion of membrane technology could mean lower area costs which would favor the technology.
|
|
| 5. |
- Jönsson, Ann-Sofi, et al.
(författare)
-
Fundamental principles of ultrafiltration
- 1990
-
Ingår i: Chemical Engineering and Processing. - 0255-2701. ; 27:2, s. 67-81
-
Tidskriftsartikel (refereegranskat)abstract
- Different theoretical models describing the influence of the operating parameters are treated in this paper. The osmotic pressure, gel layer and resistance in series models are presented. The influence of different operating parameters, such as the operating pressure, temperature, cross-flow velocity and concentration is demonstrated. The complex fouling phenomenon is reviewed. Finally, various pretreatment and cleaning operations are presented.
|
|
| 6. |
- Jönsson, Ann-Sofi
(författare)
-
Influence of shear rate on the flux during ultrafiltration of colloidal substances
- 1993
-
Ingår i: Journal of Membrane Science. - 0376-7388. ; 79:1, s. 93-99
-
Tidskriftsartikel (refereegranskat)abstract
- The shear rate at the surface of a membrane has a distinct influence on the membrane flux in systems containing colloidal substances. If the shear rate is decreased, flux decreases since the thickness of the boundary layer of retained solutes at the membrane surface then increases. When low molecular solutes are used, flux increases again when the shear rate is increased. However, if large solutes are used, polymeric and colloidal substances, for example, it sometimes happens that the flux cannot be increased to its original value again by increasing the shear rate: the flux decline is regarded as irreversible. Experiments, performed in a new type of turbulence-promoting module, which illustrate the influence of shear rate on flux when treating solutions containing colloidal substances, are presented in this paper. It is also shown that a flux decrease which can not be restored by increasing the shear rate, may be completely restored by a temporary interruption of the permeate flow.
|
|
| 7. |
|
|
| 8. |
- Jönsson, Ann-Sofi, et al.
(författare)
-
Ultrafiltration applications
- 1990
-
Ingår i: Desalination. - : Elsevier BV. - 1873-4464 .- 0011-9164. ; 77:1-3, s. 135-179
-
Forskningsöversikt (refereegranskat)
|
|
| 9. |
- Lindau, J, et al.
(författare)
-
Cleaning of ultrafiltration membranes after treatment of oily waste water
- 1994
-
Ingår i: Journal of Membrane Science. - 0376-7388. ; 87:1-2, s. 71-78
-
Tidskriftsartikel (refereegranskat)abstract
- The influences of different types of cleaning agents on a polysulphone ultrafiltration (UF) membrane which had been used to treat oily waste water were investigated. The cleaning experiments were performed with samples of polysulphone membranes removed from a commercial plant in which oily waste water is treated. Five different cleaning agents were used and their influences on the fluxes were investigated. The influence on the flux when cleaning with the different cleaning agents in succession was also studied. Deposits on the membrane surface, before and after cleaning, were analysed using different methods. Most of the analyses were carried out using scanning electron microscopy (SEM) in combination with energy dispersive X-ray (EDX) combined with a micro-analysis system permitting quantitative determination of elements. Some analyses were also performed using Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS).
|
|
