Silica Geochemistry
and Scaling...
Silica
scaling is a special problem in geothermal power development.
Unlike many other minerals, silica can form a colloid when brines
become oversaturated. Typical silica colloids are shown above as
spherical particles. The colloids have diameters ranging from 5nm
to >5000nm. The colloid properties depend on the individual
brines, and the method by which the brine became oversaturated.
Each geothermal field is different, and therefore field-specific
experiments are necessary to define the characteristics of the
colloid. We have developed special equipment to measure the
polymerisation of silica to a colloid at any temperature and
pressure. This data is essential in defining the likelihood of
silica deposition in surface plant and reinjection wells. The
equipment can also measure the polymerisation characteristics
when the pH is altered. pH adjustment is one commonly used method
of coping with silica deposition.
In the pre-development stage, we can calculate likely silica
concentrations, and the likelihood of silica deposition. This can
greatly assist in the definition of turbine inlet pressures and
separation pressures.
