Production on a coking furnace at Sanxing Coal Gasification in Taiyuan, Shanxi province, was closed on Nov 10. It marked the phaseout of the company's outdated facility to meet stricter environmental requirements.

"It's time to say goodbye to this coking furnace, which had been working for thousands of days," said Xiong Youwen, a Sanxing executive in charge of the furnace.

"We see the furnace as an 'old friend' of ours, as we have worked with it from the very beginning."

According to Xiong, Sanxing is one of the advanced coking gas producers in Taiyuan. The company was among the first to use the processes of desulfurization and denitrification in Shanxi to make sure that its waste gas discharge met environmental standards of the times.

However, Taiyuan's industry and information technology bureau as well as environmental protection bureau released a joint regulation at the beginning of the year to require the shutdown of coking furnaces with a coking chamber height of less than 4.3 meters. The new measures meant companies like Sanxing would need to meet even stricter pollution-control standards.

"By the end of November, all the 4.3-meter-and-below coking furnaces in Taiyuan had been shut down, eliminating outdated capacity totaling 5.21 million metric tons a year," said Cui Junlin, chief of Taiyuan's industry and information technology bureau.

In Shanxi as a whole, outdated coking furnaces with an annual capacity totaling 11.92 million tons were shut down in 2019. And the number has reached 10.79 million tons to date this year, according to the Shanxi Provincial Department of Environmental Protection.

The coking industry has been an economic pillar in Shanxi province, which is known for its rich coal resources. However, it has been a major source of air pollution in the province over the past decades.

In recent years, Shanxi authorities have required local coking enterprises to raise pollution-control standards by phasing out outdated facilities and promoting more environmentally friendly manufacturing.

According to insiders in the coking industry, the height of the coking chamber is a determining factor in pollution control. A higher furnace means a larger volume in the coking chamber, which allows for full combustion of coal and leads to better coking efficiency and less emissions.

In China, the height specifications for coking chambers are 4.3, 5.5, 6 and 7.65 meters.

"About 70 percent of the coking chambers in China are 4.3 meters at present," said Liu Junwei, a researcher at Jinhuan Keyuan, an environmental protection research company based in Taiyuan.

Coking furnaces with higher coking chambers have been increasingly used in Shanxi in recent years.

According to Liu, 5.5-meter-and-above furnaces accounted for 25.5 percent of the province's total by the end of 2017. The ratio increased to 38 percent by the end of 2019. He predicted the number will rise to 50 percent by the end of this year.

"The phaseout and replacement of outdated coking furnaces is of great significance in the green development in Taiyuan and in Shanxi as well," Liu said.

However, local officials said closing and replacing outdated facilities is not the ultimate goal. It is a means for the industrial transformation and green growth in Shanxi.

Back at Sanxing Coal Gasification, employees are not worried about whether they will retain their jobs.

The entire company will be relocated to the Qingxu Fine Chemicals Industrial Park in the suburbs of Taiyuan, Xiong said, in hopes of engaging in an industry with higher added value and lower emissions.

Like Sanxing, Gengyang Investment, a Taiyuan-based company, has also moved its coking-related operations to the park.

"We used to produce coke tar that could sell at about 2,000-3,000 yuan ($300-$460) per ton," said Mi Jingxuan, vice-president of Gengyang. "Now at Qingxu park, we have installed new facilities to produce needle coke products, which can sell at 20,000-30,000 yuan a ton."

Longhui Coal Gasification is another company that recently moved to Qingxu park. It will maintain its coking operation at a much more advanced level.

A coking furnace of 7.65 meter, which represents the highest level in the world, will soon be completed at the company's new site. Longhui executives said they are confident that the company can become a role model for advanced, clean coking production in Shanxi and in China.

Guo Yanjie contributed to this story.