Dry Gas Seals for the First Supercritical CO2 Power Cycle Plant

In Houston, Texas, the first commercial power plant using the Allam oxy-fuel cycle has been operating on a 50 MW scale with a supercritical CO2 (sCO2) compressor. The sealing solution for this compressor is an example of a dry gas seal in new conditions.

Operating conditions

According to John Crane, the selected seal is Type 28XP, which must operate with CO2 at pressures up to 178 bar and temperatures up to 204 degrees C in the seal area. Supercritical CO2 has a very high density, posing a challenge for the gas seal.

Design approach

• A single seal configuration with a polymer ring as the secondary seal is used, since CO2 is non-toxic.
• Due to the high temperature in the fourth compression stage, the seal is designed with an additional internal labyrinth, allowing for the injection of cooling gas to create a thermal barrier.
• The remaining leakage must be carefully handled.

Results

According to the article, the dry gas seals were successfully put into operation and ran smoothly, meeting design expectations.

Significance

The supercritical CO2 cycle and carbon capture are creating new conditions for seals, and dry gas seals are the chosen solution.

Reference

Pumps and Systems (June 2023), a case study by John Crane. The article was compiled and reinterpreted by SNS-VN; brand names belong to their respective owners.