Hybrid Filter– innovative solution to reduce emissions

Introduction:

Clair had the opportunity to work with an esteemed client in Tamil Nadu to convert an existing ESP. The existing ESP was designed to handle flue gases from a 15 TPH boiler handling fuels such as coal, rice husk and briquettes. The existing ESP is of 2 field and was designed to meet an outlet emission of ≤ 100 mg/Nm³. Clair was assigned the task to revamp the ESP as the existing ESP was not able to achieve the designed outlet emissions. Based on the input details provided, Clair proposed to install a Hybrid filter considering the critical nature of the application, the fuels being used and the layout restrictions. Hence, the ESP internals in the 2^nd field were removed and converted to a bag filter.  The basic specifications are given in Table 1.

Hybrid Filter is a combination of ESP and Bag filter. The dust particles in the flue gases are first charged in the ESP field. Majority of the dust is normally collected in the 1^st field. The balance charged dust then moves to the Bag filter zone. As the dust particles are electro-statically charged, they form a porous cake over the fabric surface. This leads to a lower pressure drop across the filter. As the majority of dust is collected in the ESP field, the cycle time of pulse rates to the bags is very long with respect to normal Bag filter. This calls for less flexing of the bag and leads to longer bag life.

CFD Analysis was performed to ensure uniform gas distribution across the hybrid filter.Since the commissioning of the bag filter, the system has been running successfully achieving the desired emission levels of ≤ 30 mg/Nm³.

Data/ Table:

Table 1:Basic specifications of Hybrid filter

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