2nd Best Innovators Prize
The Yemen LNG plant, located in the heart of a country ravaged by conflict, was forced to switch to preservation mode in April 2015. To ensure the survival of the liquefaction site and the restarting of an LNG train (using APCI technology), the teams left on-site successfully managed to use the cryogenic heat exchanger to produce ethane from the refrigeration circuit: an unprecedented technical achievement. This is their story.
On April 4th 2015, the spreading conflict in Yemen and growing insecurity around the Balhaf site led to Yemen LNG (YLNG) to stop production.
The site switched to “preservation” mode, with a reduced team of 50 volunteer employees in charge of operating the utilities (electricity, nitrogen, water, etc.) and maintaining the units in good working order.
At YLNG, the gas emitted from the LNG tanks is used to produce electricity for the plant on-site. This is now the only power source available in a region where there are no other remaining electricity production and distribution grids. However, now LNG levels in the storage tanks are beginning to drop due to natural evaporation, as are ethane levels in the refrigeration circuits of the LNG trains. With no political end to the conflict in sight, months went by with the plant in “preservation” mode, until the reduction in LNG stock reached worrying levels and threatened to jeopardize ongoing electricity production.
We needed to find a solution to keep the power on, and we needed one quickly. Finding enough diesel to generate the 15 MW needed was expensive and complicated in a war-torn country. Connecting the plant’s pipeline to the gas network directly would have put us at risk of sabotage, and would have turned the pipeline into a 320 km-long target. Restarting a production train to restore the LNG stores we were using as an energy source was the best course of action.
However, this was a difficult plan to put into action because there was no way to store the ethane used in the refrigeration loop. With the boiling pressure at ambient temperature exceeding the design pressure of the sphere, the gas evaporated to the flare. We had planned to import the ethane, as we did in 2009 when YLNG was started up for the first time. Back then, the 100 tons of ethane needed for the site were delivered from the US in special containers kept at -100 °C. Unfortunately, there was no way we could repeat that now given how long it would take (4-6 months), how much it would cost (over $1 million), and how difficult it would be in a country at war.
Ethane production using the cryogenic heat exchanger and APCI technology
There was only one option left to us: restart an LNG train and try to produce ethane on-site. After much research, the YLNG technical team found inspiration in an article they found online summarizing how the Australian company Woodside managed to start up a Pluto LNG train in 2012, with Linde technology, using the cryogenic heat exchanger to generate ethane. The YLNG teams conducted several thermodynamic simulations to see if the idea could be adapted to and work with an APCI (Air Product Chemicals Inc.) process.
Their calculations swiftly showed that not only was this solution possible at the Yemen LNG plant, but that it was also compatible with the composition of the natural gas there. They therefore set to work designing a new operating procedure for producing ethane on-site with the APCI process, a world-first. This was quickly validated by Total headquarters.
YLNG was able to restart train 2 just before the LNG reached a critically low level in the tanks. The train was restarted with gas on October 7th 2015, after six months of total shutdown. The two refrigeration compressors were restarted on October 11th and 12th. Ethane production with the refrigeration circuit began in the afternoon of October 12th, in line with the new procedure. In the morning two days later, the unit reached production levels of LNG and the desired concentration of ethane in the refrigeration loop. Train 2 was kept in operation until the LNG and ethane stocks were replenished, thus ensuring energy independence for another eight months. It was put back in “preservation” mode on October 25th, marking the success of what was a crucial and instructive operation.
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