A Plant to Wash Coal
Photograph by Toby Smith, Reportage by Getty Images
A facility in Inner Mongolia's Ordos processes coal for burning in supercritical power stations, which require better quality coal to maintain high temperature and pressures for an overall more efficient system than conventional subcritical coal plants.
But the coal needs to be washed first, and water consumption and pollution are problems in a nation where 300 million rural residents lack access to safe drinking water, according to the United Nations Development Program.
Energy and water are tightly intertwined. Coal-fired power plants rely on steam to turn their turbines. In general, efficiency increases as the temperature and pressure used to create steam in a boiler increases. In a supercritical boiler system, first developed in the 1950s in the United States, the water is not boiled. Rather, very high temperatures and pressures are used to decrease the density of liquid water until it becomes a vapor (steam).
But there is a constant trade-off between improving efficiency and conserving water. Some measures that cut power plant consumption, such as dry cooling, require more energy. China's 12th Five-Year Plan, announced last year, called for water consumption per unit of value-added industrial output to be cut 30 percent, while energy consumption per unit of GDP is to be cut 16 percent.
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