HCN Catalyst Impregnated Ceramic Filter Treats NO_x Particulate and Acid Gases (FF 2003)

The H&CN Co., Ltd. in Korea offers ceramic filter technology to remove hazardous gases and dust simultaneously.

This technology consists of the manfuacturing of a catalyst impregnated ceramic filter and of its application. This technology can simultaneously treat NO_x and dust and acid chemicals by injecting absorbents into the inflow duct. Thus this technology combines all the conventional dust collecting equipment (electrostatic precipitator, baghouse) as well as gas treatment facilities (absorption tower, scrubber) into one single process.

The life span of the filter is extended due to the high wear and tear resistance of the material used. The filtering rate of the filter is three times as high as that of existing textured fabric filters. Furthermore, this filter is very light and has a highly porous structure with a porosity of 80~90 percent. The prohibition of corrosive gas condensation is possible due to the use of a high operation temperature dust removal process using on-line pulse jets.

This process displays a fast reaction at high temperature and has the same NO_x removal efficiency as that of existing SCR process. Moreover, as a result of this process, the recombustion process becomes unnecessary. In addition, this technology results in the formation of cake through the use of lime, as well as the simultaneous and highly-efficient removal of dust and hazardous gases (NO_x, SO_x, HCl) at high temperature (340-450° C).

This filter is highly efficient, collecting fine dust (0.3 µm) and simultaneously removing hazardous gases (over 90 percent for NO_x, 80 percent for SO_x, 50 percent for HCl).

The costs associated with the maintenance of the plant as well as the necessary area are reduced as a result of the possibility of using a simultaneous high temperature treatment in conjunction with this compact equipment.

Use of chemically-stable materials makes the safe operation and maintenance of this technology possible.

This filter is applicable to most air pollutant emitting plants, and especially recommended for high temperature and dust containing flue gas emitting plants. It is applicable for glassware, melting, casting, incineration, electric power plants, as well as for carbonization processes.

Catalyst Impregnated Ceramic Filters Remove Particulates and NO_x  (2006 FF)

The simultaneous removal of particulates and NO_x using catalyst impregnated fibrous ceramic filters was studied by Ajou University, Suwon (Republic of Korea) in cooperation with Myoungji University, Yongin (Republic of Korea).

The research focused on the development and commercialization of high efficiency, cost-effective air pollution control systems, which can replace in part air pollution control devices currently in use. In many industrial processes, hot exhaust gases are cooled down to recover heat and to remove air pollutants in exhaust gases. Conventional air pollution control devices such as bag filters, ESPs. and adsorption towers withstand operating temperatures up to 300° C. Also, reheating is sometimes necessary to meet temperature windows for SCR. Since oxidation reactions of acid gases such as SO₂ and HCl with lime are enhanced at high temperatures, catalyst impregnated ceramic filters can be a candidate for efficient and cost-effective air pollution control devices. Catalytic ceramic filters remove particulates on exterior surface of filters and acid gases are oxidized to salts reacting with limes injected in upstream ducts. Oxidation reactions are enhanced in the cake formed on the exterior of filters. Finally, injected reducing gas such as NH₃ reacts with NO_x to form N₂ and H₂O interior of filters in particulate-free environment. Operation and maintenance technology is similar to conventional bag filters except that systems are exposed to relatively high temperatures ranging 300-500° C.

Korea Looks for Multi-Pollutant High Temp. Clean Up  (2003 FF

The energy for Korea's economic and industrial growth is primarily based on fossil fuel combustion. To counter the ill effects this has on the environment the government has been imposing increasingly stringent emission standards on these energy sources.

Research teams at Ajou University and Myoungji University are investigating methods to effectively and simultaneously remove multi-pollutants. At the 5th International Symposium on Gas Cleaning at High Temperatures, Jon In Choi of Ajou University, Suwon, Korea, presented results of work targeting simultaneous removal of particulates and HAP using catalyst impregnated fibrous ceramic candle filters. Catalytic ceramic filters used in this study were impregnated with CuO/Al₂O₃, V₂O₃/TiO₂, or V₂O₅/TiO₂/SiO₂-Al₂O3.

Untreated fibrous ceramic candle filters are commercialized and successfully used at many industrial processes including semiconductor manufacturing processes and pyrolysis, etc. for particulates removal alone. For 16 months of continuous operation, pressure drops were stable and collection efficiencies were over 99.5 percent in removing submicrometer SiO₂ particulates in semiconductor etching processes. Ceramic filters are suitable for the treatment of air pollutants at high temperatures in small scale processes where a heat recovery system is unnecessary.

For SO₂ and HCl removal tests with lime injection, SO₂ removal mechanisms are similar to conventional dry scrubbing systems except that operating temperatures are relatively higher. Ceramic filters can withstand up to 500° C, enhancing oxidation reactions with limes in the duct and on the dust cakes formed on the ceramic filters. As operating temperatures are raised to 500° C, SO₂ conversion rates are increased up to 90 percent, an efficiency seldom obtained in conventional dry scrubbing systems. Similar phenomenon occurred for HCl oxidation reactions with limes.

A longer term test was performed using a 1-m long ceramic candle filter to remove PM, NO_x, and SO_x simultaneously. The test lasted two months with NO removal tested for the first 30 days and SO_x and NO_x removal tested for the last 10 days. Reducing agent and limes were injected intermittently averaging two hours a day and hot gas flowed for the rest of the operating time.

One meter-long candle type ceramic filter tests show that simultaneous removal is as effective as conventional separate air pollution control devices. Removal efficiencies of particulates, NO_x, SO_x and HCl are over 99.5 percent, 90 percent, 75 percent, 50 percent at optimum test conditions. Catalysts were slightly degraded after two months of operation for the simultaneous removal of particulates and NO_x. Developed technology can be best applied to hot gas cleaning systems such as glass melting, semiconductor manufacturing, carbonization and pyrolysis processes.

Future testing will apply the technology to the removal of VOCs and dioxins utilizing different catalysts and sorbents.