Emre ÖZKURT / Calderys Turkey Sales Manager (Refractory Engineer)
As known, a material made up of two or more different substances which are physically combined is called mixture. Mixtures are basically divided into two as Homogeneous and Heterogeneous. Thanks to the properties of these mixtures, they are used in different ways in the industry. For example, in one industry the homogeneity of the mixture works although non-homogeneity can be useful in the other industry. In this article, starting from the mixtures thence we will discuss what is deflocculation and how it is used in refractory materials.
Homogeneous mixtures, as the name implies, have the same characteristics at every point, and the substances that made up the mixture appear to be a single substance.
Homogeneous mixture of salt and water
On the other hand, Heterogeneous mixtures, do not have the same properties throughout the mixture and this difference is visible by the naked eye. Heterogeneous mixtures are divided into four as emulsion, suspension, colloid and aerosol.
The emulsion is a heterogeneously dispersed state of another liquid that is insoluble in one liquid.
Olive oil and wateremulsion
The suspension is a heterogeneously dispersed state of a liquid insoluble solid.
Sand and water suspension
Colloid is a mixture of substances suspended in liquid, they appear homogeneous, but this invisible difference can be observed by passing the beam through the mixture.
Movement of light in homogeneous water/salt vs colloid water/flour mixtures
Aerosol mixtures are formed by dispersing solid or liquid in the gas.
Luquid gas aerosol mixture
Colloidal substances may not be wanted in the content of liquid mixtures used in industry. Colloid materials cannot be separated by filtration because they are between 0.1mμ and 1mμ grain size. Separation can be carried out by liquid precipitation using coagulant chemicals. Addition of coagulant to the liquid is called coagulation and the colloid particles, which are destabilized in the liquid, begin to collected by mixing, they turn into larger particle sizes called flocks, this phenomenon is called flocculation.
Colloids try to keep their steady-state by the electrical charges they got in the suspension.
The concentration of the opposite ions on the surface of the colloid particle is very high, the opposite ion concentration decreases as it moves away from the surface, the difference in this ion density creates an electrical potential and this potential on the surface of the particle is called the Zeta Potential. Zeta Potential is measured in mV and the higher this value, the more stable the colloid materials are in suspension and so to be able to resist to flocculation. Rapid coagulation or flocculation occurs between 0 mV and ± 5 mV, Colloids with ± 61 mV Zeta Potential are characterized as excellent stability.
Zeta potential of colloidal particle
After explaining the flocculation, we can say that Deflocculation is the exact opposite of flocculation. In other words; This is the case where the zeta potential of the grains in colloidal solutions is very high and being close to excellent stability, they prevent lumps and form good mud.
As it is known, monolithic refractories are applied by forming a mixture with certain amounts of water. The amount of water to be mixed varies depending on the type of refractory material. The type of RC (Regular Castable), LCC (Low Cement Castable), ULCC (Ultra Low Cement Castable) and NCC (No Cement Castable) mixture water is respectively decrease. This type of monolithic refractory materials can be used with deflocculants to ensure less mixing water and better package systems.
The effect of deflocculants to be used in the material on the viscosity of the sludge to be formed is positive after a certain point, therefore, a good adjustment of the amount of deflocculant is important for the fluency of the application sludge.
Viscosity – Deflocculant Curve
As a Deflocculant LCC monolithic refractory material does not suffer from agglomeration and has a high viscosity, the amount of loss/rebound in gunning applications is minimized.
250mm deep Defloculant LCC refractory application without anchoring system