Chinese scientists use small boilers, new tech to beat smog

PUBLISHED : Monday, 08 June, 2015, 4:00pm
UPDATED : Thursday, 08 March, 2018, 6:04pm

Scientists in China have taken another step forward in the fight to reduce smog by finding a cleaner way to burn coal, the major source of air pollution in the country in winter.

The latest breakthrough could make coal as clean as natural gas when it comes to producing heat for rural areas by using small boilers that operate horizontally instead of vertically, the team claims.

“Mankind has tried to reduce pollution by building huge power and heating plants, but things have just become worse,” said professor Liu Xinhua, lead scientist of the project.

“It’s time to go small. The key to getting rid of bothersome smog can be found in small boilers.”

During tests in Hebei province, which surrounds Beijing, the researchers eliminated nitrogen oxide, fine particulate matter and most major air pollutants that are created when the fossil fuel is burned.

The experiment, which was conducted in a village in the province last winter, produced encouraging data, according to the researchers at the Chinese Academy of Sciences’ (CAS) Institute of Process Engineering.

“Coal can be as clean as natural gas. It depends on how you burn it,” said Liu.

From its use in kitchen stoves to enormous coal-fired power plants, the way in which coal is burned has not changed in centuries.

It is burned from the base up, with fresh coal added on top to provide enough air flow while generating sufficient heat.

The process produces nitrogen oxide and other pollutants that can trigger smog due to a series of photochemical reactions.

But scientists at the CAS institute decided to challenge tradition by having their boiler lie on the ground instead of standing upright.

The coal was then burned from side to side, a process they called “decoupling combustion”.

At its simplest, this involved adding coal into a low-heat chamber on the right-hand side, where it was converted to gas under controlled temperatures of less than 400 degrees Celsius.

This was then passed over to a chamber on the other side that could handle higher temperatures, where it was burned at up to 1,000 degrees with little pollutants emitted.

“It was simple in theory, but extremely difficult in practice,” Liu said.

The team took nearly two decades to get the technology from the lab to the field. A major challenge was maintaining the delicate chain reaction of combustion between the two chambers, it said.

However, several hurdles may impede the tech’s widespread application.

First, the boilers are more expensive and sophisticated than their precursors. Second, a centralised heating system for a Chinese village would demand an investment of several million yuan, as a new heating plant and pipelines would be needed.

As such, projects like this are not considered realistic without notoriously hard to obtain government subsidies.

At the other end of the spectrum, local farmers proved useful to the researchers in developing the new tech. Their simple suggestions led to the improvement of sophisticated algorithms in computer simulations and lab experiments, Liu said.

“Now they love what we’ve done,” said Liu, giving the example of one 700kw “decoupling boiler” the team installed at a village in the province’s Gu-an county.

It now provides about one-third of the local population with central heating at a low cost with minimum pollution.

Each family there paid less than 2,000 yuan (US$322) for their winter heating bills, making it a cheaper alternative than their old home boilers. The infrastructure was paid for by the local provincial government.

Liu said China has discouraged the use of small boilers in the past in a bid to reduce pollution, but that this was possibly misguided.

“The discrimination against small boilers will be consigned to history with the advancement of science and technology,” he said.