Prediction of the dewatering of selected inorganic sludges

2001 ◽  
Vol 44 (10) ◽  
pp. 191-196 ◽  
Author(s):  
P.J. Harbour ◽  
A.A.A. Aziz ◽  
P.J. Scales ◽  
D.R. Dixon
Keyword(s):  
Volume Fraction ◽  
Efficient Operation ◽  
Capillary Suction ◽  
Laboratory Techniques ◽  
Dependent Parameter ◽  
Solid Liquid ◽  
Solid Liquid Separation ◽  
Separation Devices ◽  
Different Sources

There are a number of laboratory techniques traditionally used in the characterisation of sludges for the prediction of the efficient operation of dewatering processes such as centrifugation and filtration. In industry, capillary suction time and specific resistance to filtration measurements are common. Whilst useful in predicting trends, they do not assist in the design and optimisation of devices from first principles. Recent work in our laboratories has developed a technique for the fast measurement of the permeability and compressibility of sludge. This information, when coupled with first-principle models is useful for the prediction of the performance of solid-liquid separation devices. The work has shown that a single volume fraction dependent parameter, namely the solids diffusivity, calculated from permeability and compressibility, is able to fully characterise the dewaterability of sludge. This allows different sludges to be compared in an unequivocal fashion. Data will be presented for a range of sludges from different sources showing vastly different dewatering properties. The dewaterability of the different sludges is easily compared and the true role of flocculants in dewatering is highlighted.

scholarly journals From colloidal dispersions to colloidal pastes through solid-liquid separation processes

2005 ◽  
Vol 77 (8) ◽  
pp. 1369-1394 ◽  
Author(s):  
J. B. Madeline ◽  
M. Meireles ◽  
J. Persello ◽  
C. Martin ◽  
R. Botet ◽  
...  
Keyword(s):  
Silica Nanoparticles ◽  
Volume Fraction ◽  
Cell Model ◽  
Solid Particles ◽  
Fractal Structures ◽  
Particle Volume ◽  
Liquid Separation ◽  
Separation Processes ◽  
Solid Liquid ◽  
Solid Liquid Separation

Solid-liquid separation is an operation that starts with a dispersion of solid particles in a liquid and removes some of the liquid from the particles, producing a concentrated solid paste and a clean liquid phase. It is similar to thermodynamic processes where pressure is applied to a system in order to reduce its volume. In dispersions, the resistance to this osmotic compression depends on interactions between the dispersed particles.The first part of this work deals with dispersions of repelling particles, which are either silica nanoparticles or synthetic clay platelets, dispersed in aqueous solutions. In these conditions, each particle is surrounded by an ionic layer, which repels other ionic layers. This results in a structure with strong short-range order. At high particle volume fractions, the overlap of ionic layers generates large osmotic pressures; these pressures may be calculated, through the cell model, as the cost of reducing the volume of each cell. The variation of osmotic pressure with volume fraction is the equation of state of the dispersion. The second part of this work deals with dispersions of aggregated particles, which are silica nanoparticles, dispersed in water and flocculated by multivalent cations. This produces large bushy aggregates, with fractal structures that are maintained through interparticle surface-surface bonds. As the paste is submitted to osmotic pressures, small relative displacements of the aggregated particles lead to structural collapse. The final structure is made of a dense skeleton immersed in a nearly homogeneous matrix of aggregated particles. The variation of osmotic resistance with volume fraction is the compression law of the paste; it may be calculated through a numerical model that takes into account the noncentral interparticle forces. According to this model, the response of aggregated pastes to applied stress may be controlled through the manipulation of interparticle adhesion.

The role of interparticle forces in colloidal aggregates: local investigations and modelling of restructuring during filtration

2006 ◽  
Vol 53 (7) ◽  
pp. 25-32 ◽  
Author(s):  
J.B. Madeline ◽  
M. Meireles ◽  
R. Botet ◽  
B. Cabane
Keyword(s):  
Scaling Laws ◽  
Particle Distribution ◽  
Model Systems ◽  
Separation Processes ◽  
Interparticle Forces ◽  
Colloidal Aggregates ◽  
Solid Liquid ◽  
Solid Liquid Separation ◽  
Applied Stresses

Industrial solid–liquid separation processes, such as pressure filtration or membrane processes, involve the application of pressure to suspensions. In response, some water is extracted, the suspension volume is reduced, and the dispersed aggregates start to form a network. In recent works, we aimed to make a prediction for the response of aggregates to stress which occurs during a filtration. We chose model systems made of aggregated silica nanoparticles. Some of these systems offer a strong resistance to applied stresses, and retain their permeability; others yield and collapse. We used small angle neutron scattering by which we can locally quantify the particle distribution within the network to determine the processes by which particles reorganise during collapse: we found that reordering processes at the scale of 1 to 10 particle diameters control the course of collapse and the loss of permeability. Finally we constructed a numerical model for describing the processes by which colloidal aggregates are compressed. This model predicts that the response of such networks to pressure follows some scaling laws, which depend only on the elastic vs. dissipative nature of interparticle bonds.

scholarly journals Assessment of different saccharification and fermentation configurations for ethanol production from Agave lechuguilla

BioResources ◽  
2017 ◽  
Vol 12 (4) ◽  
pp. 8093-8105
Author(s):  
Thelma K. Morales-Martínez ◽  
Deniss I. Díaz-Blanco ◽  
José A. Rodríguez-de la Garza ◽  
Jesús Morlett-Chávez ◽  
Agustín J. Castro-Montoya ◽  
...  
Keyword(s):  
Simultaneous Saccharification And Fermentation ◽  
Ethanol Concentration ◽  
Attractive Alternative ◽  
Industrial Implementation ◽  
Separate Hydrolysis And Fermentation ◽  
Enzyme Dosage ◽  
Solid Liquid ◽  
Solid Liquid Separation ◽  
Separation Devices ◽  
Simultaneous Saccharification

Different strategies were assessed for the production of ethanol from Agave lechuguilla that was pretreated by autohydrolysis. Separate hydrolysis and fermentation (SHF) was compared against simultaneous processes including simultaneous saccharification and fermentation (SSF) and prehydrolysis and simultaneous saccharification and fermentation (PSSF) using different solids (15%, 20%, and 25% w/w) and enzyme loadings (15 FPU/g, 20 FPU/g, and 25 FPU/g glucan). The results showed that the maximum ethanol concentration (53.7 g/L) and productivity (1.49 g/L h-1) was obtained at 36 h in the SHF configuration at the highest solids and enzyme loadings (25% w/v and 25 FPU/g glucan, respectively). The ethanol concentration and productivity obtained in the PSSF configuration at the same time were 45 g/L and 1.25 g/L h-1, respectively. The SSF configuration exhibited the lowest ethanol concentration and productivity (10.4 g/L and 0.29 g/L h-1, respectively) at 36 h. The enzyme used, Cellic CTec3, allowed for high glucose yields at the lower enzyme dosage assessed. The SHF configuration exhibited the best results. However, the PSSF configuration can be considered an attractive alternative because it eliminated the need for solid-liquid separation devices, which simplifies the industrial implementation of the process.

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