A shake-up in global coal trading has delivered some oxygen to the struggling American mining industry, driving up exports to energy-hungry countries. But the relief may not last.

United States coal sales abroad over the first three quarters of the year surpassed exports for all of 2016, according to government figures. Energy experts project an increase of 46 percent for the full year, adding more than $1 billion to coal companies’ revenues.

Those are crucial dollars for an industry trying to stabilize itself after nearly a decade of declining prices, expanding competition from natural gas and wind and solar energy, and bankruptcies. Domestic coal-fired power plants continue to close despite promises of regulatory relief by the Trump administration, making the exports all the more critical.

The upturn in exports has been particularly helpful to Appalachia, where production is up 11 percent this year. Coal executives attribute the increase mostly to exports, especially of coal for making steel, known as coking coal.