Ambuja Cements and ACC, now part of the Holcim Group, operate various cement plants all over India. In last few years monitoring of the impact of the manufacturing process on the environment has become a top priority for most companies. This includes the control on dust emission from various electrostatic precipitators and process/nuisance bag filters.

Cement manufacturers must comply with the Indian regulations concerning environmental protection. In 2006 Ambuja Cements announced putting up a new plant at Rauri near Darlaghat in Himachal Pradesh of 7200 TPD.

Intensiv Filter India deliberates the design, realisation and commissioning of a new pulse jet filter for kiln/raw mill application at Ambuja Cements, Rauri, Himachal Pradesh, the world's largest bag filter for this application.

Conceptualisation of Pulse Jet Bag Filter for Kiln/Raw Mill System

Traditionally Ambuja Cement management, as also ACC, for recent plants have selected Reverse Air Bag Filter over Electrostatic Precipitator for kiln/raw mill application in various plants. However, after Holcim took over management control, Ambuja Cements decided to consider pulse jet bag filter technology over reverse air bag filter due to various advantages.

Factors Considered for Selection of Pulse let Filter Technology

l Holcim operates various plants all over the world and are having good experience of pulse jet bag filter technology for kiln/raw mill l Foot print area of pulse jet bag filter is less compared to Reverse Air Bag House l Filter Media of P-84 and Glass with PTFE membrane are proven for very low emission and this reasonable bag life l Most important aspect of this technology is meeting dust emission level of 10 mg/Nm3 or less. Electrostatic Precipitators and Reverse Air Bag House cannot meet such low levels, and l The plant is located in sensitive area near well known hill station Shimla, hence the environmental norms needs to be strictly complied with.

The process data of bag filter is given below:

Basic Project Data

The technical solution of Intensiv Filter consisted of two parallel pulse jet bag filter units due to space constraint. The filter media was decided as P-84 so that during raw mill shut down, the gases will be cooled up to 190-195?C and will be filtered for gas temperature less than 195?C.

Intensiv Filter has supplied pulse jet bag filter for kiln/raw mill application from 1994 with excellent results (Polysius, Holcim, KHD, Equador, Cemex, Lafarge, Rudniki, Tong-Yang Cements, talcementi, Dyckerhof, Campulung, etc).

Selection of P-84 filter media was due to its capability to filter gases up to 200?C and to offer emission as low as 10mg/Nm3 (measured values for some installations are as low as 2-3 mg/Nm3).

The filter is designed for a gas volume of 22, 00,000 m3/hr when raw mill is down and for a gas volume of 14, 40,000 m3/hr when raw mill is working. This is the largest bag filter for kiln/raw mill application in cement sector.

Due to large volumes and space constraint Intensiv Filter proposed two parallel streams with Twelve compartments each; Twenty Four totally with two separate induced Draught (ID) Fans.Intensiv Filter offered low pressure cleaning technology with the patented - Jet Bus technology for cleaning. As Intensiv has considerable experience of using filter bag as long as 8000 mm, it was decided to consider bag length of 8000 mm. For ease of maintenance a Pent House was installed on bag filter and chain conveyors were considered below bag filter for collection of dust.

Plant layout

As shown in the layout, the dusty gas from the Preheater will go either to the raw mill or to the bag house after dilution. The exhaust gases from raw mill are passed through the bag filter after set of cyclones and raw mill fan. Thus the bag filter will receive the dusty gas either from the Preheater directly or from Roller Mill. The clean gas from the bag filter will be exhausted by two ID fans.

The process filter data and the technical specifications are given in Table 2.

Advantages of the New I\nstallation

Thanks to the new filter technology, a phenomenal reduction in dust emissions is achieved.

The new plant has been designed to guarantee a dust emission rate lower than 10 mg/Nm3 these values were fixed by Ambuja Cements in view of Plants location in Himachal Pradesh, However actual emissions is much lower. Other significant advantages are:

Low pressure cleaning improves bag life. Low compressed air consumption & Possibility of replacing damaged bags when the filter is working.

Conclusion

The plant was commissioned without any problems in January 2010 and has bettered the performance parameters stipulated by Ambuja Cements. The Filtering process is optimised and client is very happy with new filter technology and dust free environment. Needless to mention that this was the first and largest pulse jet bag filter for kiln/raw mill application.

(Contact: Shekhar Joshi Vice President - Technical, Intensiv Filter India Pvt Ltd, Pune. Tel: 020-26634466/8. Fax: 91-20-26634470. Mobile: 094235-85621. Email: shekhar.joshi@intensiv-filter.in)