Silica separation from reinjection brines at Monte Amiata geothermal plant, Italy

A process for the separation of silica from geothermal reinjection brines is reported, in which the phases of coagulation, sedimentation and filtration of silica are involved. The effectiveness of lime and calcium chloride as coagulating agents has been investigated and the separating operations have been set out. Attention has been focussed on Monte Amiata reinjection geothermal brines, whose scaling effect causes serious problems in the operation and maintenance of reinjection facilities. The study has been conducted using different amounts of added coagulants and at different temperatures, to determine optimal operating conditions. Though calcium chloride was revealed to be effective as a coagulant of the polymeric silica fraction, lime has also proved capable of removing monomeric dissolved silica at high dosages. Investigation on the behaviour of coagulated brine has revealed the feasibility of separating the coagulated silica by sedimentation and filtration.