Saving €1.4 million annually: how Rayong Olefins cut energy costs with Alfa Laval heat recovery

The challenge

Ethylene production is energy-intensive, with energy costs constituting a substantial portion of total operating expenses. Even small improvements in energy efficiency can have a dramatic impact on the bottom line. In 2009, Rayong Olefins initiated a project to explore new ways to save energy. At that time, the plant did not utilize compact heat exchangers in its core processes, relying instead on a few in utility positions.

The primary challenge was to recover more heat from the hot quench water used to cool process gas after the cracker. This quench water contained large amounts of energy, but the existing shell-and-tube heat exchanger had poor performance, resulting in significant energy waste. The goal was to increase heat recovery and reduce energy consumption.

Our solution

Alfa Laval, in collaboration with local agent Hydrocarbon Solutions (Thailand) Co., Ltd, presented a range of fully welded compact heat exchangers. After thorough evaluation, Rayong Olefins decided to install a Compabloc 120 heat exchanger in series with the existing shell-and-tube unit. This solution was chosen for its ability to handle high temperatures and pressures, as well as its compact size and high thermal efficiency.

Steam consumption in the deaerator dropped by 43%, from 35 tonnes/hour to 20 tonnes/hour after installing the Compabloc 120. We are also very pleased with the compact size and small footprint of the Compabloc” - says Wirasak Sonamthiang, Aromatic Section Manager.

Process implementation

The implementation process involved several key steps:

1. Evaluation and Approval: Engineers from Rayong Olefins and Alfa Laval conducted a detailed analysis to identify opportunities for using compact heat exchangers in the plant. The Compabloc 120 was selected for its superior performance and compact design.
2. Installation: The Compabloc 120 was installed in series with the existing shell-and-tube heat exchanger. This setup allowed for increased heat recovery from the quench water, which was then used to preheat boiler feedwater.
3. Optimization: The installation resulted in a higher temperature of boiler feedwater entering the deaerator, reducing the amount of heat needed to release oxygen from the water. This optimization led to significant energy savings.

Process overview

Impact and benefits

The installation of the Compabloc 120 heat exchanger brought substantial benefits to Rayong Olefins:

• Energy savings: The company achieved annual energy savings of €1.4 million by increasing heat recovery by 5.5 MW. The payback time, including installation costs, was less than six months.
• Reduced steam consumption: Steam consumption in the deaerator dropped by 43%, from 35 tonnes per hour to 20 tonnes per hour, thanks to the higher temperature of the boiler feedwater.
• Compact design: The compact size and small footprint of the Compabloc 120 allowed for easy installation and integration into the existing system.
• Maintenance-free operation: The highly turbulent flow and design of the Compabloc 120 made it less prone to fouling compared to shell-and-tube heat exchangers. Two years after installation, there was still no need for cleaning, resulting in minimal maintenance requirements.

Conclusion

Rayong Olefins Company's collaboration with Alfa Laval to enhance energy efficiency through the installation of a Compabloc 120 heat exchanger has proven to be a successful initiative. The significant energy savings, reduced steam consumption, and maintenance-free operation have contributed to the company's goal of lean ethylene production, ensuring competitiveness in the global market.