YINCHUAN, Sept. 28 (Xinhua) -- Gone are the pungent smell of sulphur, the scorched soil and the blue flames leaping from under the ground. Back are trees, daisies and the sound of birds.

    Rujigou Coal Field, a perennial inferno of flames in the eyes of local residents and a major production base of high quality anthracite Taixi Coal, has found peace again after a fire started nearly 180 years ago was extinguished this month.

    Chairman Zhang Wenjiang of the Shenhua-Ningxia Coal Industry Group Co., Ltd. that runs the coal field in northwest China's Ningxa Hui Autonomous Region said that, as a result, at least one million tons of Taixi Coal reserve will be saved each year.

    Dubbed "Heibao", the Chinese for Black Gem, the dense and shiny Taixi Coal whose proven reserve in China stands at 220 million tons - paling in comparison with the country's total coal deposits of one trillion tons - is reputed for its high carbon content and burns with a clean flame. Only Hongji Coal of Vietnam can compare favorably to it.

    The government has imposed an annual ceiling of 5.5 million tons on exploitation and hopes to prolong its service life to at least 40 years. But one major challenge to the objective was the ferocious fire.

    Field surveys by the Yinchuan-based large state-owned enterprise right before a specialized fire-fighting squad was established in 1997 revealed nearly 1.69 million square meters of land had been perennially scorched by fire, incurring an annual economic loss of 40 million U.S. dollars and discharging 90,000 tons of hazardous substances into the atmosphere every year.

    No records show how the fire was started. The common explanation, passed on by word of mouth, tells of a group of ill-treated miners who set their colliery on fire in revenge after bearing a grudge towards their boss more than 100 years ago.

    "It's impossible to prove the legend. But there was a good chance that the fire started from the ground in the first place as miners used to camp on the mining field, lighting fires to cook or warm themselves," Zhang said.

    Poorly-equipped small collieries were believed to be at blame for the ferocious fire as exploitation often triggered accidents and blasts and exposed the coal bed to air, causing oxidization and the accumulation of heat and thus raising the possibility of spontaneous combustion.

    To remedy the situation, the Ningxia Autonomous Region closed down all small collieries on the premise in 2005 and forbade enterprises beginning operation to ditch poor mines for rich ones.

    The battle against the fire has been ongoing but only sporadically by local people until 1997 when the plummeting reserves aroused the attention of the central government.

    An instruction sent directly from Zhongnanhai, the headquarters of the Chinese leadership in Beijing, facilitated the set-up of a specialized fire-fighting squad under the Shenhua-Ningxia Coal Industry. By then, the coal reserves devoured by fire were estimated around 30 million tons, about 10 percent of the then proven deposits.

    Recalling the fierce battle which cost 400 million yuan (about 53.3 million U.S. dollars) over the past decade, Wang Jihai, captain of the 120-person squad, said, "Hazards are everywhere. Perennial combustion has triggered cracks and subsidence, making landslides a frequent risk. I myself witnessed a goat slip into a crack and be incinerated in a few minutes," he said.

    The danger under foot plus the choking air and the altitude sickness hindered the fire-fighting operation. Each fire fighter was only required to be close to the fire for no more than ten minutes at a time on the mountain which is 3,400 meters above sea level.

    An advanced high resolution remote sensing technology was introduced from Germany to help detect the intensity and direction of fire.

    After the fire was put out, the squad enveloped the dark red mountain with earth about one meter thick and built a 14.7 hectare green belt where fast growing poplars planted last year are thriving.

    "We will keep an eye upon hidden fire risks and improve our exploitation technology to avoid wastes," said Ai Yulian, general manager of the Project Management Department of the Shenhua-Ningxia Group.

    Established in December 2002, the state-owned Shenhua-Ningxia Group based in Yinchuan has an annual raw coal output of 16 million tons and boasted a registered capital of three billion yuan and 50,000 employees.