Scaling Mitigations for the Binary Plant Vaporizer: Upper Mahiao, the Philippines

Abstract

The Upper Mahiao (UM) binary plant, Leyte the Philippines has two scale deposition problems in the binary fluid vaporizer: (1) the recurring clogging of vaporizer inlet with solid particles and (2) the fouling (mineral scaling) of the vaporizer tubes with silicate scale. After the last plant shutdown in November 2012, a rehabilitation program was conducted in 2015. This study includes additional mitigation and prevention of scaling: (1) calculate the configuration of the heat transfer area of the vaporizer and (2) evaluate silica removal using hydrofluoric (HF) acid solution based on the experience at the Wairakei binary plant, New Zealand.
The calculation of the vaporizer reconfiguration shows that more than 10% of the total number of tubes is plugged so this method will not be followed. Silica scale removal using hydrofluoric (HF) acid solution with the ongoing use of inhibitor is found to be the best silica removal option for the clogged UM brine plant vaporizer with hardened silica deposits. The main advantages of this method are the lower cost and shorter cleaning time compared with water blasting and mechanical cleaning. The study also demonstrates that all environmental concerns for using the acid will be avoided since the chemical will be disposed directly into the reinjection well.