Test Rig Experiments for Silica Scaling Inhibition

Abstract

A sophisticated test rig has been constructed and operated to test a number of silica scaling inhibition methods. The test rig is fully instrumented and controlled and can simulate either double or triple flash regimes or a binary/heat exchanger operation. Silica scaling is measured on a number of test pipe sections throughout the test rig, and in a packed bed. The test rig has been operated at the Kawerau and Rotokawa geothermal fields in New Zealand, and has elucidated some of the design parameters and operating conditions for new power stations at these locations.

As a result of the experiments, both new power stations have been designed with pH modification to suppress silica scaling in the brine. However, tests are continuing using organic silica dispersants to control silica scaling. Arsenic and antimony either as sulfides or the elements were the principal non-silica scales that were produced at lower temperatures and lower pH.