Enhancing efficiency and reducing costs in small scale LNG plants with Compander technology

Overall plant efficiency: The refrigeration compressor is the main power consumer in a small scale LNG plant, alongside pumps and smaller compressors.

Seal leakage rates: Significant process leakage is often linked to the seals of rotating equipment.

Operational flexibility: This is related to the types of compressors and expanders used, and their process characteristics.

Space: The footprint and size of the equipment affect installation costs and CAPEX.

Compander technology in small scale LNG

Atlas Copco Gas and Process Compander technology integrates compressors and expanders on a single gearbox and skid, which is an attractive solution for small scale LNG plants. This approach, already used in other industries such as LNG, has proven to enhance efficiency and reduce costs.

Reduced footprint and costs

The compact design of the Compander reduces the overall plant footprint, which in turn lowers installation and investment costs. When combined with expander turbines on the same gearbox, they utilise a common base frame, including lube oil and seal support systems, controls, and other components. With the compression and expansion processes on a single gearbox, the need for extensive piping, cables, utilities, and insulation is minimised. Additionally, having a single skid setup simplifies the installation process, leading to faster erection times and cost savings.

Nitrogen Brayton cycle and liquefaction

Small scale LNG plants often use either single mixed refrigerant (SMR) or nitrogen Brayton cycles for refrigeration. Smaller plants typically prefer the nitrogen Brayton cycle due to its operational flexibility and ease of operation. The cycle involves expanding compressed, pre-cooled nitrogen to generate cold power, then re-compressing it to the expander inlet pressure. Heat exchange with natural gas occurs in a cold box, cooling the natural gas to near liquefaction temperature.

Proven cooling efficiency

Atlas Copco Gas and Process has been utilising Compander technology in small scale LNG plants since 2002, starting with installations in Norway. These plants have shown significant efficiency gains by integrating the functions of a centrifugal compressor and turboexpander into a compact unit. The use of single or multiple expander cycles allows for tailored optimisation based on local plant conditions.

CAPEX and OPEX benefits

The rotating equipment, a major portion of small scale LNG plant costs, can be optimised using Compander technology. The integration of compressor and expander stages on a single gearbox reduces the need for separate skids, quick shut-off valves, and other components. This integration also allows for pre-fabrication and pre-assembly, further reducing installation costs.

Operating costs are also reduced due to improved process efficiencies. Companders use single dry gas seals (SDGS), which have significantly lower leakage rates compared to traditional seals. This not only reduces the cost of seal-gas make-up procedures but also minimises maintenance requirements.

Maintenance and efficiency

Companders adhere to API 617 standards, and they are designed to operate for up to five years without major overhauls. Moreover, customised maintenance plans and remote monitoring options ensure high availability and efficiency. By tracking equipment performance and replacing parts proactively, plant operators can reduce the risk of production loss.

Conclusion

The example of Norwegian small scale LNG plants demonstrates the significant benefits of integrating compressor and expander functions into a single skid on one gearbox. This setup enhances operational efficiency, reduces capital and operational costs, and meets the stringent requirements of modern small scale LNG plants. Over the years, Compander technology has proven its value in decreasing CAPEX, meeting OPEX targets, and achieving ROI expectations.

To find out more information please visit Atlas Copco Gas and Process.

Click here to find out more about Atlas Copco Compander (TM) integrally geared compressor expander.

Read the article online at: https://www.lngindustry.com/special-reports/23072024/enhancing-efficiency-and-reducing-costs-in-small-scale-lng-plants-with-compander-technology/