Chelating agents for diluted geothermal brine reinjection

Area of Science:

• Geochemistry
• Environmental Engineering
• Materials Science

Background:

• Blue energy generation utilizes salinity gradients between geothermal fluids and freshwater.
• Reinjecting diluted geothermal fluid can cause injectivity issues due to mineral precipitation.
• Chelating agents are investigated to mitigate these issues.

Purpose of the Study:

• To identify optimal chemicals for preventing mineral precipitation in geothermal brine reinjection.
• To evaluate the effectiveness of synthetic (oxalic acid, EDTA, EDDS) and natural (humic acid) chelating agents.
• To ensure reservoir injectivity in SaltPower systems.

Main Methods:

• Speciation simulations were performed to predict metal-ligand complex formation.
• Isothermal titration calorimetry (ITC) experiments quantified complex formation heat.
• Evaluated chelating agents in a rock + geothermal brine system.

Main Results:

• Complexing degree strongly depends on pH and chelating agent type.
• Complex formation heat followed the order: EDTA > EDDS > oxalic acid > humic acid.
• EDTA demonstrated significant potential in preventing Fe(III) oxide, calcite, and dolomite precipitation.

Conclusions:

• EDTA is a promising agent for managing mineral precipitation in diluted geothermal brine.
• Effective chemical selection is crucial for maintaining injectivity in blue energy systems.
• This research supports sustainable geothermal fluid management for SaltPower operations.