Application: Off Gas Recovery

System: Gas Compressor for hydrogen recovery unit

Location: Shell Gothenburg Refinery, Sweden

INTRODUCTION

Meeting the new hydrogen demands imposed by new strict environmental regulations that require reduction in sulphur in both gasoline and diesel, is a challenge all refineries must face in the 21st century.

The unique Hijet Compression System was installed at Shell Gothenburg Refinery, downstream the hydrotreater low pressure separator to compress the hydrogen rich off-gas. The system was commissioned in January 2006.

The system simultaneously reduces the H₂S content and boosts the gas pressure to 28 barg for use in the membrane unit.

THE CHALLENGE

In this project the challenge was to recover the high value hydrogen from the hydrotreater LP separator off-gas.

The off-gas contains a considerable amount of hydrogen, hydrocarbons and high quantities of H₂S.

The viability of such a project can be achieved by using a reliable, maintenance free, low investment cost compressor.

HIJET SOLUTION

The component parts of the system include one Hijector™, separator, scrubber, centrifugal pump and air cooler.

The motive liquid - 30% DEA solution, is circulated with a centrifugal pump and is contacted with the incoming sour gas in the ejector. Thorough mixing of the liquid and gas in the ejector reduces the H₂S concentration from 4% to below 600ppm. Further reduction is achieved with regenerated (lean) DEA that is constantly made-up to the top scrubber mounted on the separator and is equipped with additional contacting surfaces. The separator level is maintained by purging a quantity of (rich) amine to the amine regenerator. The final H₂S concentration is 0 ppm. The treated gas at 28 barg goes to the membrane unit for hydrogen recovery.

The high compression ratio capability of Hijectors™ providing more than 30 bar of discharge pressure in one single stage presents new opportunities to the refining industry. The Shell Gothenburg refinery utilizes the highly reliable Hijet Compression System to recover low pressure, hydrogen rich gases, with low capital and operational costs.

SYSTEM BENEFITS

• Low capital cost compared to reciprocating compressor,
• Reduced operational expense compared with a reciprocating compressor while increasing reliability.