Ineos bought Grangemouth as part of a £6 billion acquisition of assets from BP in 2006, with the plant supplying industries with raw materials for making everything from cars to detergents.
The refinery receives crude oil from two pipelines - Forties from the North Sea and Finnart from Argyll, which carries imported oil from tankers.
Once the gases are separated out, 200,000 barrels per day are converted into products including petrol, diesel, jet engine fuel and naptha. The naptha and some of the Forties gas are diverted to the petrochemicals plant, where they are converted through a process called cracking into various chemicals.
Both the refinery and petrochemical businesses are going through tough times. Refining always struggles in recessions because demand for fuels falls - two UK refineries have gone bust since 2008.
But where the chemicals business has often compensated for refinery lows in the past, this time has been different. Like its 40-odd European rivals, Ineos is suffering from cheaper products coming to the UK from the US, Middle East and China. Most analysts are predicting that many of Europe's plants will close in the next few years.
Grangemouth has an extra problem and an extra advantage. Its advantage is that its modern "cracker" system runs on ethane, a light gas that is much more profitable to crack than the naptha used at virtually all the European plants. Its problem is that the ethane comes from the North Sea and it is running out.
Ineos's solution is to import shale gas ethane from the US (cutting gas costs by 30% in the process), which is why it needs the new terminal. It is doing something similar at its site in Norway.
Yet the whole Grangemouth plant is still profitable in the meantime, even if the company's complex web of accounts makes it impossible to nail down the exact position. And much of the investment that allows Ineos to say that the plant is loss-making is from spending about £120m on the cracker so that it can also cope with heavier gases (for which it is receiving another £7.5m from the Scottish Government). This project finishes in early 2015, at which point the old naptha cracker will close down and the whole operation will become much more profitable.
Gerry Hepburn, chief financial officer of Ineos Chemicals Grangemouth, says the plant will still be losing money after investment, because a planned £300m terminal is in the equation. Overall it will make enough money to have paid off this loan by about 2020.
This is why some question why Ineos would have wanted to shut the plant, but Hepburn says you have to factor in the risks inherent in the new cracker building project.
Richard Murphy, a former auditor who advises the STUC, questions the company's pessimism. Having looked closely at the accounts, he points to a statement in which the company says it expects to make sufficient profits to cover a deferred tax bill. This, he says, suggests it will make at least £500m over the next five years.