Silica characterisation in the coal seam water train

May 2017May 2020
ARC Linkage Project
Coal seam gas is adsorbed to the surface of coal along fractures and cleats and is released when pressure is reduced by removal of groundwater, which has chemistry peculiar to the region from which it is extracted. Desalination of produced water is severely impacted by mineral scaling on reverse osmosis (RO) membranes.

Silica characterisation in the coal seam water train

The aim of this project is to develop new ways to mitigate silica-associated scaling in CSG water treatment. It investigates how the type and level of silica present in coal seam water behaves at different stages of the water treatment process.

It involves getting a richer understanding of silica/silicate chemistry through the CSG water treatment train, to assist in identification of the most appropriate techniques to mitigate silica-associated scaling. It will concentrate on developing new ways to mitigate scaling by considering silica and silica-rich nanoparticles in concert with cations and organics, with the aim of better managing cations so to facilitate nanoparticle lubrication.

This ensures effective management of existing assets (lower operation expenditure) and potentially enables higher water recovery and reduced brine volumes.

Expected outcomes include more productive and effective use of assets (lower operation expenditure), improved pre-treatment infrastructure to support reverse osmosis operation and the environmental benefits of less chemical waste and higher water recovery, reducing the cost of water processing.

This research project commenced in 2017, following the recommendations of an initial baseline scoping study conducted in 2015.

Background

Due to its relatively high salt concentration, coal seam water often has to be treated before disposal or beneficial reuse. Reverse osmosis (RO) membrane separation is widely used for coal seam water desalination, with the products being useable fresh water and brine. Management of this brine is one of the key challenges for RO desalination plants. The objective is to maximise water recovery and minimise brine volumes.

Part of the cost of CSG water treatment is associated with the maintenance of the water treatment facilities. Silica, which is one elements present in coal seam water, can particularly affect the performance of the RO plant. Silica and/or silicate scaling that precipitates in the RO and brine concentration equipment can result in reduced performance and increased maintenance costs for cleaning, down time, and membrane replacement.

Silica, which is one element present in coal seam water, can particularly affect the performance of the desalinisation plant.

Silica concentrations and the forms that it occurs in fluctuate widely through the water treatment train and can be dependent on the local pressure, temperature and pH conditions. As a result, different techniques may be necessary to effectively manage the silica at different stages of the treatment process. The scoping research sampled and analysed silica/silica-rich particulates through existing water treatment trains.

Project resources:

     

    • Project title: Silica characterisation in the coal seam water train
    • Project status: Underway
    • Project leader: Dr Steven Pratt
    • Research team: Professor Greg Leslie & Dr Greg Birkett & Dr Simon Smart & Ms Deidre Walsh & Dr Jason Dwyer
    • Research group: The University of Queensland School of Chemical Engineering
    • Timeframe: May 2017 - May 2020
    • Project funders: APLNG, Arrow Energy, QGC, Santos, University of Queensland

     

    • Project title: Mitigating silica damage during water treatment (scoping study)
    • Project status: Complete
    • Project leader: Dr Steven Pratt
    • Research team: Dr Greg Birkett
    • Research group: The University of Queensland School of Chemical Engineering
    • Timeframe: January 2015 - December 2015
    • Project funders: APLNG, Arrow Energy, QGC, Santos, University of Queensland