New technology halves cost of recycling activated carbon for removing harmful substances

A research team from the Korea Institute of Energy Research has developed a technology that efficiently manages volatile organic compounds (VOCs) emitted from small-scale businesses and recycles them with lower energy consumption compared to existing methods. Notably, this technology can be applied to automotive painting businesses located in and around cities, significantly reducing the burden on businesses caused by emission regulations. The findings were published online in October 2024 in the journal Energy Conversion and Management: X.

VOCs, which include carcinogenic substances such as benzene, are primarily generated from paint, new furniture, and industrial processes, contributing to fine dust and unpleasant odors. To remove these pollutants, activated carbon, known for its air-purifying effects, is commonly used. In particular, regulations mandate that small-scale businesses emitting 10 tons or more of air pollutants per year use activated carbon to control VOC emissions.

Automotive painting businesses, commonly found in cities, are also subject to regulations if their facility size exceeds approximately 400 square meters. Under these regulations, such businesses must install monitoring sensors in pollution control facilities, which consist of filters and activated carbon, and manage their operation in real time.

However, VOC sensors are expensive, so businesses rely only on current and differential pressure sensors. Without accurately measuring VOC concentrations, it is challenging to properly manage pollution control facilities. As a result, small-scale businesses, burdened by the costs, struggle to implement effective measures.

In response, the research team developed a technology that allows the replacement cycle of activated carbon to be determined even with low-cost sensors, as well as a method to regenerate used activated carbon. This innovation has successfully reduced the replacement cost for small-scale businesses to about half the price of new activated carbon.

The research team developed an algorithm that enables accurate measurements even with low-cost sensors by calculating the difference between VOCs measurements from high-performance and low-cost sensors and analyzing the environmental conditions causing these discrepancies with Kwangwon University. With this algorithm, the measurement accuracy of low-cost sensors improved to 92%, allowing businesses to determine the optimal replacement cycle without relying on high-performance sensors.

The research team addressed the high cost of replacing activated carbon by developing a recycling technology specifically designed for air purification applications. Activated carbon is generally categorized into two types: one for water purification and the other for air purification.

Although both types are typically regenerated through high-temperature heating to remove adsorbed substances, water purification carbon requires heating up to 1,000°C, while air purification carbon can be regenerated at just 200°C. However, due to a lack of specialized facilities for recycling air purification carbon, businesses have had to rely on high-cost facilities intended for water purification carbon, resulting in significantly higher heating expenses.

In contrast, the research team successfully developed a specialized 200°C facility for regenerating air purification activated carbon, reducing process energy consumption by over 70% compared to conventional methods. This newly developed system removes VOCs by supplying steam while continuously moving the activated carbon. The regenerated activated carbon retains 90% of its original performance, making it reusable for businesses.

Notably, during the removal of VOCs, a certain amount of synthetic gas is generated, which can be used to power a generator and produce electricity. The electricity generated is then fed back into the process, helping to reduce both the recycling costs and the expenses incurred by businesses that request recycling services.

The research team predicts that if multiple small-scale businesses share the newly developed facility, the cost of activated carbon replacement could be reduced to approximately half the price of new activated carbon.

In addition, the research team is developing a method to produce hydrogen, an eco-friendly energy source, using VOCs. Currently, VOCs are typically incinerated for disposal, leading to the emission of carbon dioxide, a greenhouse gas. To address this issue, the researchers aim to reform the hydrocarbons in VOCs into hydrogen and carbon monoxide, creating a sustainable process that reduces carbon emissions throughout the entire recycling cycle.

Dr. Dong Hyuk Chun of KIER, who led the study, stated, “This study is significant in that it effectively manages VOCs emissions from small-scale businesses, reduces operating costs through the regeneration of used activated carbon, and realizes the energy utilization of waste gases such as VOCs.

“In the future, this technology will contribute to the expansion of eco-friendly public management systems and the realization of carbon neutrality.”

Meanwhile, this research was conducted with support from the Ministry of Environment’s project on intelligent optimization and management technology for fine dust reduction at industrial sites.