When it comes to reducing emissions and energy consumption from fuel burning, most people think of switching to alternative fuel sources or end-of-pipe cleanup solutions. But there is also room for improvement at another stage: the combustion process itself, when fuel is burned. Two companies in Beijing are now focusing on improving this process, with impressive results.
Last year Hancunhe village, in Beijing’s Fangshan district, invested almost 20 million yuan (US$2.8 million) in three new heating boilers, which have completely changed the way heat is provided in the area. There is barely a stovepipe in sight and no soot is produced. The villagers can dry clothes or store cabbages in their courtyards without fearing they will collect dirt.
The technology was developed by Beijing Xiongcai Group. In the village boiler room, its chairman, Wang Yongjiang, opens up a small hatch on the boiler and shows me the flame inside. “Normally coal is burned from underneath,” he explains, “but our boilers burn the coal from above, which allows us to collect the soot and burn it again. When the harmful components in the soot are exposed to temperatures over 800 degrees, they are burnt away, massively reducing emissions. The flame inside burns pure blue and translucent, which means the fuel is being burned completely. Yet the coal we use only contains 3,500 kilocalories per kilogram – about half the energy content of fine coal.”
Xiongcai aims to solve some very real problems: how can China make use of its current stock of 4.8 million coal-burning boilers? How can the country cleanly and efficiently burn coal and biomass fuels like chaff, sawdust, leaves and household waste? How can the country utilise commonly discarded low-grade coal such as lignite, coal slurry and gangue, and coal that has not been fully burnt the first time round? These have long been important questions for China’s energy and environmental sectors.
Since 2000 the firm has approached these questions by treating fuel and combustion technology as a single, integrated subject. The company’s patented biomass boiler and “biomass coal” fuel together make up a system for burning biomass combined with lower grade coal, which burns with a heat energy efficiency of more than 80%. Its emissions are on a par with the cleanest of boilers, and the system reduces energy consumption and waste. The “biomass coal” is made up of compressed chaff, tree leaves and branches, household waste, gangue, coal powder and other low-grade coals. The resulting fuel is dense, burns completely, does not produce black smoke and fixes sulphur. When burned in the boiler, it can produce the same heating effect as fine coal. The waste from the boiler also has a number of applications: it can be used in water purification, in building insulation and as fertiliser. Both the biomass fuel and waste from the boilers is transported in sealed packages to prevent any secondary pollution.
Beijing Yanshan Petrochemical installed a Xiongcai biomass boiler system in September 2004. They found they not only reduced their heating costs, but also reduced their pollution emissions. The city then set up several pilot schemes for biomass coal heating systems, which were installed over the winter of 2006 and 2007 in the outlying regions of Fangshan, Yanqing and Shunyi. Satisfaction rates among users were reported to be around 100%. Even in Yanqing, which is colder than most other areas, users said that heating was much improved. The new boilers provided warmth for the farmers, while solving problems with soot, noise and pollution – and its negative health impacts.
Between 2002 and 2007, biomass boilers with a total production capacity of 300 megawatts have been installed in Beijing municipality, resulting in savings of 86,400 tonnes of standard coal. Emissions have been cut by a total of around 223,800 tonnes of CO2, 887 tonnes of sulphur dioxide, 1,729 tonnes of nitrogen oxides and 4,470 tonnes of dust particles. In 2008 the city government will promote clean biomass fuels in Daxing, Pinggu, Miyun, Mentougou, and Yanqing. Heating provision should be expanded by several million square metres.
Another company pioneering new methods of combustion is the Beijing Shenwu Group. “China’s boiler industry is enormous,” says the company’s head of research, Wang Zhenghua. “There’s a huge amount that we can do in this industry because in the past combustion technology has really been far too crude.”
Crude production methods present business opportunities for people who can make real improvements. Shenwu’s chairman of the board, Wu Daohong, says he was “born to work in combustion,” but it was in 1994 he realised that his ideas had a real potential in China. “In the past, people in the countryside burnt firewood for cooking, and in the cities they burnt coal briquettes. Both of these methods only extract a tiny amount of the energy contained within the fuel. We saw massive room for improvement in energy use in all kinds of areas, from the stoves used for heating and boiling water in small companies, to the blast furnaces and kilns used by companies in smelting and industries like thermal power, steel, aluminium and concrete. Saving energy is actually very easy: you just need to change the way you burn the fuel, making combustion more complete, then make more efficient use of the energy produced.”
Wu first had the opportunity to try out his ideas in 1994, refitting a ceramics factory in Xi’an and improving its energy efficiency. The next year Wu started to provide his services to steel companies, ceramics factories and thermal power stations. As he developed the technology further, Wu managed to earn hundreds of thousands of yuan, which he used to set up Shenwu. The company was founded to sell the regenerative burner technology Wu had invented. This burner is highly efficient; it allows for a very complete combustion of fuel and prevents heat from escaping in the process. The result is energy savings of between 30% and 70%, and lower emissions of carbon dioxide and nitrogen oxides.
The regenerative burner uses heat-retaining materials to absorb the heat that is usually emitted along with the smoke. This heat is then used to warm the air entering the combustion chamber. The increase in temperature leads to a fuller combustion. Wu explains: “Just as a sponge absorbs water, certain materials, such as heat-resistant bricks, can absorb heat. When these materials are used to line the outlet channels of the boiler, where temperatures can reach 1,600 degrees, they collect heat. The system alternates in direction of air-flow every 30 or 40 seconds, so hot air from the combustion chamber passes through the outlet and heat is retained in the channel by heat-retaining materials. The direction then changes, so that the outlet is now the inlet. Cold air from outside has to pass through this hot channel to enter the combustion chamber. It flows out the other side, which is also surrounded by heat-retaining materials, and the direction changes again. This not only means that fuel is burnt completely, but also helps to maintain even temperatures throughout the whole boiler.”
When air has passed through the channel lined with heat-retaining materials, it is still at a temperature of around 150 degrees. This heat can still be used. If the system is combined with a condensation system, the air can be used to heat water which can be used for washing. As the fuel has already been burnt more fully, there are far fewer polluting emissions.
Since the company started in 1995, Shenwu have produced 200 energy-saving boilers. The boilers achieve energy savings of over 30% on average, representing annual savings to the country of just over 2 million tonnes of standard coal, and reductions of over 11 million tonnes of carbon dioxide emissions. And these savings are set to rise. In the meantime, Wu’s technology is receiving recognition and praise from far and wide.
Feng Yongfeng is a science reporter for Guangming Daily
Homepage photo by televiseus