PINGDINGSHAN, China—On the edges of an old and depleted mine on the rugged outskirts of Pingdingshan in central China’s Henan province, workers sift through dunes of low-grade coal, looking to extract every last calorie of energy from the city’s crumbling seams. But despite an unexpected energy crunch that left authorities scrambling to guarantee coal supplies over the winter, it is still mostly business as usual for Henan’s old mining regions. “Our workload hasn’t changed,” said Guo Xianguo, 50, a truck driver queuing at a coal depot in eastern Pingdingshan’s Liangbei district. Coal prices in China surged to record levels this year, giving the industry a new short-term lease of life, with the major coal producing region of Inner Mongolia increasing daily output by 420,000 tonnes since the beginning of October. But the Chinese regime has been trying to restrain price rises to help struggling power plants build up stockpiles for …