Breakthrough made in tackling toxic waste gas

Chinese scientists have unveiled a "revolutionary" technology that transforms a highly toxic industrial waste gas into clean-burning hydrogen fuel and high-purity sulfur, potentially solving a century-old environmental headache for the global energy sector.

The project, led by academician Li Can of the Chinese Academy of Sciences, was hailed by industry experts during an evaluation conference in Beijing on Tuesday. Experts recommended an immediate scale-up of the technology to accelerate its industrial use, noting that a pilot plant in Xinxiang, Henan province, has already demonstrated the method's ability to eliminate nearly 100 percent of hydrogen sulfide emissions under ambient conditions.

Hydrogen sulfide is a notorious byproduct of oil refining, natural gas purification, and coal processing. Known for its "rotten egg" smell, the gas is lethal to humans, corrosive to metal equipment, and a primary cause of acid rain.

"Currently, the global energy system faces significant environmental challenges from hydrogen sulfide emissions," Li said. He noted that while China removes about 8 billion cubic meters of the gas annually, the global emission volume exceeds 70 billion cu m, with trillions more held in untapped reserves.

For decades, the industry has relied on the "Claus process" to handle the toxin. This traditional method requires intense heat exceeding 1,200 C and multiple chemical steps.

Even then, it often leaves behind pollutants that require further treatment. Most importantly, the traditional process turns the hydrogen contained within the gas into water, wasting roughly 730,000 metric tons of potential fuel in China every year.

To solve this, Li's team at the Dalian Institute of Chemical Physics spent 20 years developing what they call "off-field electrocatalysis". The breakthrough lies in how the team redesigned the internal "plumbing" of the machine to prevent it from getting clogged.

In standard experimental setups, the chemical reaction happens directly on the surface of the machine's electrical plates. However, when hydrogen sulfide breaks down, it creates solid sulfur — a sticky gunk that quickly coats the plates, "choking" the machine and stopping the electricity from flowing.

The new Chinese technology uses "electron mediators" to carry the electrical charge away from the plates and into a separate tank. By moving the "snapping" of the gas molecules into this separate area, the scientists kept the expensive electrical parts clean. This "off-field" design also prevents tiny hydrogen bubbles from sticking to the machinery and solves the problem of sulfur leaking into sensitive internal filters.

The success of the technology was proven at a pilot facility in Xinxiang, which utilizes waste gas from a nearby methanol plant. Hao Wenliang, general manager of the Shandong Sunway Chemical Group Co, reported that the facility operated for more than 1,000 hours without interruption. The process yielded sulfur with a purity exceeding 99.95 percent and hydrogen gas at 99.999 percent purity, both of which are high-value products for the global market.

Engineers noted that the new facility is "skid-mounted", meaning the components are pre-assembled on a frame and can be easily transported or expanded. This design occupies about 20 percent less space than traditional treatment plants, making it easier to integrate into existing refineries.

The technology arrives as China pushes toward its "dual carbon" goals of peaking carbon emissions before 2030 and reaching carbon neutrality before 2060.

China aims to produce 1.8 million tons of "green hydrogen" before 2030. Li emphasized that recovering hydrogen from waste gas using this method could provide 40 percent of that planned capacity.

limenghan@chinadaily.com.cn