3M™ Liqui-Cel™ Membrane Contactors for power & steam generation

Controlling dissolved O₂ and CO₂ levels is critical to power plant operation. Both gasses are corrosive and can lead to early piping or component failure which can negatively impact boiler performance. Corrosion control with membrane contactors is ideal for overcoming these issues. High carbon dioxide levels can increase the total ionic load in water, reducing the effectiveness of ion exchange purification technologies.

Historically vacuum towers, decarbonators and chemical injection were common methods used to control gases in make-up and feed water to power plants, heat recovery and storage generators (HRSGs), and other plants with boiler water systems for producing steam. However, these methods can be less efficient, requiring more maintenance and the handling of large volumes of chemicals.

Corrosion products can deposit and plug small process devices, which may cause process heating control and water quality issues, or could be transported back to the boiler in the recovered condensate contributing to boiler water conductivity. Injecting oxygen scavengers after the steam deaerator is also a common practice. Storing the scavengers on site is hazardous. They can be expensive and may contribute to conductivity/TDS in the boiler water. Corrosion products transported to the boiler and using high volumes of chemicals could require higher blow down rates leading to increased make up water use and higher energy losses. Additionally, fouling boiler heat exchange surfaces with corrosion products lowers operating efficiency and puts boiler tubes at risk of failure. Deaerating boiler feed water with 3M™ Liqui-Cel™ Membrane Contactors can help protect capital equipment from corrosion and pitting.

Oxygen removal down to 1 ppb can be achieved with properly designed power generation membrane contactor systems. Compared to a typical vacuum tower or steam deaerator that can achieve 7 ppb, 3M products help reduce the amount of oxygen scavenger used during normal operations and alleviate the need for high dosing when the deaerator is not available. Because the achievable oxygen levels are low with 3M™ Liqui-Cel™ Membranes Contactors, the steam deaerator can be used as a feed water preheater and storage instead of venting off the steam. A plant can realise significant cost savings by reducing the deaerator vent rate.

Lowering dissolved CO₂ levels reduces the total ionic load in water, enhancing the effectiveness of ion exchange purification technologies. This enables a power plant to reduce the frequency of ion exchange resin bed regeneration cycles and increase the service life of deionization equipment, which can save time and cost. Plants using caustic to adjust pH in reverse osmosis (RO) systems may be able to use these steam generation membrane contractors instead of caustic adjustment to help reduce chemical use in the plant.

3M™ Liqui-Cel™ Membrane Contactors used for deaeration can reliably achieve very low dissolved gas concentrations and can operate without chemicals compared with alternative degassing methods. They also offer a solution to mobile water treatment systems with limited available space.