January/February 2014 | Volume 33, No. 1

Smog and Haze Lead to High Demand for Filter Materials in China.
By Jason Chen, China Correspondent


Smog and haze is not uncommon around industrial hubs in Northern China, leading to a demand for filter materials.

In the past few months, public concerns over China’s severe air pollution forced the government to take a series of new measures to tackle the ever-growing environmental challenges. Production of filtration fibers in the Chinese market will be boosted by the new governmental plans and reach 1,5 million tons by 2020, according to industry experts.

Smog and Haze
The market for air filtration is booming in China as the country has been shrouded for months in thick smog and haze. In eastern China, where most of the country’s manufacturers are located, the Air Quality Index (AQI) kept rising during most of 2013. An AQI of 0 to 50 is regarded as excellent, 101 to 150 is considered light pollution, and above 300 is severe pollution. But the AQI in Beijing constantly sat between 400 or 500 during the entire 2013, and in Shanghai, China’s commercial center, the AQI even reached 700, a level deemed “poisonous” in early December 2013.

To tackle the hiking air pollution, the Chinese central government set up a series of measures late last year, including limiting car driving according to license plate numbers and phasing out polluted production capacity. They also included a project with a total investment of 1,750 billion RMB ($290 billion), which aims to reduce the smog and haze and improve air quality in the country’s three most important economic zones by introducing advanced technologies, new products, and new mechanisms during the next five years. These three zones include Beijing circle (Beijing, Tianjin, and Hebei Province), Shanghai circle (Yangtze River Delta Region), and Guangzhou circle (Pearl River Delta Region). This project will also reach the final goal of eliminating all the heavy air pollution (AQI 251 to 300) in China by 2023. Chinese industry experts expect the investment will boost the growth of the country’s filtration industry, especially of those for high-temperature waste gases reduction.

PM2.5 and filter materials
In China, the main harmful material in the air is particulate matter 2.5 (PM2.5). With a small diameter of only 2.5 micrometers, a PM2.5 spreads through the air and can directly enter the human alveoli of lungs, which can cause severe health problems. PM2.5 mainly come from fossil fuels in vehicles, power plants, and manufacturing industries. Among these sources, high-temperature waste gases from power plants and manufacturing industries such as cement and steel contribute to most of China’s PM2.5 emissions, according to the government.

Electrostatic precipitators, bag filters, and electrostatic and bag compound filters are used to eliminate high-temperature waste gases in China. But most of the products currently used in China have a low efficiency, according to Sun Maojian, president of the Yantai Tayho Advanced Materials Co., Ltd. (Tayho).

“Electrostatic precipitators (used by Chinese manufacturers) can only catch around 60% of the particulate matters, which diameters are smaller than 10 micrometers. On the other hand, most of the Chinese companies still use traditional materials such as glass fibers as the main materials in bag filters, which have problems such as short life span, low accuracy, low abrasion resistance, and wastes pollution,” said Sun.

Professor Liu Jingxian of the Filter Materials Testing Center (FMTC) of Northeastern University also admitted electrostatic precipitators can’t catch PM2.5 effectively, though they can catch 99% of the dust. He said bag filter had become the main stream in China’s high-temperature filtration efforts.

According to recent research from FMTC, main filter materials currently used in China to eliminate PM2.5 emissions include:

For coal-fired power plants
Currently, more than 80% of China’s power consumption is supplied by coal-fired power plants. The main filter material in these plants is polyphenylene sulfide (PPS) needle punched felt. A PPS needle punched felt filter can catch around 78% of the PM2.5 in the waste gases, according to the FMTC research. Some filter companies use spunlace process to increase the efficiency. A filter made of spunlaced PPS felt can catch up to 85% of the PM2.5 in a coal-fired power plant.

As the government seeks to tighten the PM2.5 emission limit, polytetrafluoroethene (PTFE) membrane PPS felt will be more widely used by power plants. PPS needle punched felt is dipped, laminated, or coated with PTFE to improve high temperature resistance, corrosion resistance, and the ability to catch small particulate matters. The PTFE-laminated filter material can catch more than 99% of the PM2.5.

For cement plants
Bag filters have been used in China’s production of cement since early 2000 and have dominated the market since early 2010. The main filter materials for the cement industry include polyimide fibers, also known as P84 fibers. China-made P84 filters can effectively catch PM2.5 in the environment of high temperature, according to a recent report of the Jiangsu Aoshen Advanced Materials Co., Ltd.

But today most of the Chinese cement producers still have dust emissions of much more than the national standard, which is 10mg per cube meters of gases emissions. This means many cement producers still don’t use bag filters made of P84 fibers and other advanced materials to reduce gases emission.

For the steel industry
In China, more than 90% of the filtration products in the steel industry are bag filters, according to Liu. Main filter materials include glass fibers and their composites with other fibers such as P84 fibers and aramid. Glass fiber-based bag filter can catch up to 97% of the PM2.5 emissions in steel production.

Aramid filters
Comparing to most other products for high-temperature waste gases filtration in China, aramid bag filters have better performance, according to Sun. He said a bag filter made of aramid fibers could catch 98% to 99% of the particulate matters, with diameters as small as one micrometer. But currently only 5% of the filtration products for high-temperature waste gases are made of aramid in China. As the governmental efforts to tackle air pollutions will force the manufacturers to use more efficient filters, Sun estimated China would consume 50,000 metric tons of aramid fibers for producing new bag filters to replace the current electrical precipitators and glass-fiber bag filters in the next few years. This would be a billion-dollar market, said Sun.

But the high cost of aramid fibers will still be the main obstacle to slow this replacement process. Currently China’s supplies of aramid fibers are dominate by global brands such as Du Pont and Teijin, and most of the Chinese manufacturers prefer to use the relatively cheaper filter materials such as glass fibers.

The government’s 1,750-billion-RMB investment could help Chinese manufacturers reduce the aramid cost. Chinese government subsidizes domestic companies for technological innovation and other efforts that fit the government’s plan. The subsidies could reduce the cost of usage of aramid bag filters.

Another possible momentum will be the decrease of aramid prices. As Chinese aramid fiber manufacturers have started to expand their production capacity, the prices of aramid fibers are expected to decline, and aramid bag filters will have better cost performance in the market. Currently, Tayho is China’s largest para-aramid producer, with an annual capacity of 1,000 metric tons. China’s total para-aramid capacity was only 1,500 metric tons by 2013. But the capacity will reach, respectively, 5,000 metric tons in 2015 and 16,000 metric tons in 2020, according to Ye Yongmao, chief consultant of the China Chemical Fibers Association (CCFA).

Filtration fibers
In China, the main filtration fibers include polyester, nylon, polypropylene, polyacrylonitrile, PTFE, aramid, glass fiber, P84, and PPS. Polyester fibers account for around 70% of China’s filter materials consumption, but it can’t be used in a high-temperature environment. For high-temperature filtration, the main materials are PTFE, aramid, glass fiber, P84, and PPS.

China’s production of filtration products consumed 740,000 metric tons of fibers in 2012, a 14% growth rate from the 2011 level, according to China Nonwovens & Industrial Textiles Association (CNITA). CNITA estimates that the annual growth rate will continue at double digits in the following eight years, which means the country’s consumption of filtration fibers could overtake 1.5 million metric tons by 2020.

The market of each fiber is described in the following:

Polyester fiber will continue to be the largest sector. China’s consumption of polyester for filtration purposes was about 500,000 metric tons in 2012. By 2017, the annual consumption of filtration polyester fibers could reach 760,000 metric tons.

Aramid will be one of the fastest-growing sectors. In 2013, more than 60% of China’s annual para-aramid consumption of around 8,400 metric tons was imported from the United States, Japan and Europe. Para-aramid will remain an average annual growth rate of around 15% between 2012 and 2020. According to Ye Yongmao, by 2015 domestic fiber manufacturers will supply half of China’s annual para-aramid fiber consumption of 10,000 metric tons; by 2020 domestic fiber makers will supply 80% of the annual para-aramid consumption of 20,000 metric tons in China.

PPS fibers will welcome a strong growth in the next few years. China’s capacity of PPS resins and PPS fibers reached, respectively, 30,000 and 20,000 metric tons by middle 2013. The demands from bag filters in power plants have started to boost the consumption of PPS fibers. Zhang Daming, CEO of China Lumena New Materials Corp. (Lumena) expected China’s annual PPS fiber consumption will remain at more than 20,000 metric tons in the next few years. Lumena is one of China’s largest PPS fiber suppliers, with an annual capacity of 30,000 metric tons of PPS resins and 5,000 tons of PPS fibers. Zhang said Lumena had high gross profits and strong bargain power for their PPS fibers, as sales were good since 2012. On the contrary, China’s PPS fiber sales were weak before 2011, while PPS fiber manufacturers’ operating rate was usually below 50%.

China’s output and consumption of glass fibers reached, respectively, 2.9 million and 1.7 metric tons in 2012, according to the China Composites Industry Association (CCIA). CCIA estimated 11% of the domestic glass fiber consumption was for industrial textiles, including filtration.