Identification of key parameters of magnetite deposition on steam generator surfaces—Modeling and preliminary experiments

Deposition of Colloidal Magnetite on Stainless Steel in Simulated Steam Generator Conditions—Experiments and Modeling

“…The kinetic model of deposition and consolidation has been already described in detail in our previous paper [9], therefore, only a short overview is given here. A simplified scheme of the processes considered in the model is presented in Figure 1.…”

“…In addition, the detachment rate of a particle that has undergone consolidation by the JMKA mechanism is considered to be zero. To summarize, the following general equation for the deposition and consolidation process was proposed [9]:…”

“…where m d (t) is the deposited mass as a function of time (kg m −2 ) and m p is the mass concentration of particles in the fluid (kg m −3 ). The rate constants of deposition (k a ) and detachment (k d ), as well as the fraction of particles that consolidate (α) are expressed as follows [9]:…”

“…In these equations, d p is the diameter of the depositing particle (a typical value is in the order of 100 nm); η is the dynamic viscosity, Φ b = U max , the value of the repulsion maximum estimated via differentiation of the total interaction energy vs. distance curve; Φ min = U min is the value of the attraction minimum estimated via differentiation of the total interaction energy vs. distance curve; h min is the location of the minimum on the distance axis; k c is the rate constant of consolidation; and n is the exponential factor. The total interaction energy per unit area between a planar surface and a spherical particle (separated by a distance h) is computed as a sum of the retarded Van der Waals (VdW), Lewis acid-base (AB) and constant potential electrostatic double layer interaction energy (EDL) expressions [9]:…”

“…Despite considerable research efforts on the subject in recent years [5][6][7][8][9][10][11][12], currently, no generally applicable models of sludge deposition and consolidation processes have been proposed. The development of this type of model would include a quantitative assessment of the possibilities of minimizing the formation of magnetite particles and their deposition on the SG surfaces by optimizing the water chemistry and hydrodynamics (assessing the influence of different types of amines, the use of dispersants, etc.).…”