High-Temperature Dust Filter Bags: Enhancing Efficiency and Protecting Against Heat Damage

May 11, 2023
Dust filter bags are suitable for medium to low temperature flue gas (180~290℃), but when the flue gas temperature is high, it is necessary to lower the temperature of the flue gas before it enters the bag filter by using processes such as water cooling or air cooling to protect the filter bags from damage due to high temperature.

In recent years, with the continuous improvement of nitrogen oxide emission standards in China (Due to strong environmental regulation by the government and strict punitive measures, which have increased the emission costs for businesses), the integrated denitrification-dust removal bag filters have started to receive attention. The key technology of this equipment lies in the development of "catalyst-coated filter bags" that are more suitable for bag filters and can meet various operating conditions. This has been driven by the need to develop a new generation of dust filtration products at an accelerated rate.

The current mainstream theoretical view is that catalysts such as manganese-based/vanadium-based catalysts are adhered to the surface of filter bags, and ammonia gas is injected into the interior of the dust collector (or at the inlet of the dust collector). Through the action of the catalyst, the ammonia gas reacts with nitrogen oxides in the flue gas to generate nitrogen gas. This principle is similar to the Selective Catalytic Reduction (SCR) technology, where under the action of a catalyst, the reducing agent NH3 selectively reduces NO and NO2 to N2 under temperature conditions of 180-400°C, while hardly undergoing the oxidative reaction of NH3 with O2. This reduces the consumption of the reducing agent, helps control ammonia leakage, and lowers operating costs.

Over the years, some Chinese experts and scholars have been devoted to the research and development of catalyst-coated filter media. Among them, a group of academicians from the Chinese Academy of Sciences advocate the use of surfactant dispersion method, coating method, and suction filtration method to load manganese dioxide/polyacrylonitrile catalyst onto PPS filter media. The catalyst loading amount is approximately 44g/㎡. Under laboratory conditions, PPS filter bags with catalyst coating achieved a denitrification efficiency of up to 80% at 180°C.

The second viewpoint advocates the in-situ growth of three different catalyst components, namely Mn-CeOx, Mn-SnOx, and Mn-Ce-SnOx, on the surface of PPS fibers through mechanisms related to redox reactions. The results show that the three different catalyst-coated filter media, under laboratory conditions, can achieve denitrification rates of up to 100% when the preparation conditions include a KMnO4/PPS mass ratio of 0.6 and a denitrification reaction temperature of 180°C. Furthermore, even the filter media coated with Mn-Ce-SnOx catalyst can achieve a denitrification rate of 100% at a reaction temperature of 120°C.

In addition, some experts advocate the use of ultrasonic dispersion method to attach 6% MnO2/CNFs catalyst onto the surface of aramid filter media, which can achieve a denitrification efficiency of 80% under laboratory conditions at 180°C after being coated with polydopamine.

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Finally, there are also some viewpoints suggesting the attachment of MnOx onto the filter bags of the baghouse. Research results indicate that when the reaction temperature is 150°C and the flue gas content in the reaction gas is 5%, the removal rate of nitrogen oxides can reach 75%.

Founded in 2005, Yuanchen Technology focuses on technology development and application in the field of environmental protection, pioneering and innovating in industrial flue gas filtration, denitrification, circular economy, intelligent environmental protection, etc. It is committed to the frontier of industry technology and promotes the integration of new business models in the environmental protection industry, and is an enterprise with the qualification of R&D, design and production of high-efficiency filtering materials and SCR denitrification catalysts as well as recycling and reclamation of used catalysts, with CNAS and CMA testing qualification.

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