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PPC Lime Acres baghouse

Conversion project is in the bag

In a move to enhance its environmental performance, PPC Lime has successfully converted the filtration equipment on its Lime Acres kiln (LK 9) from an electric precipitator system, to a state-of-the art bag-house operation.

“This R20 million project will significantly reduce the facility's overall dust emissions to be well within permit stipulations and meet European standards. In addition, the increased fan capacity will improve the kiln efficiency.” Says PPC's chief operating officer, Dr Orrie Fenn.

Of the four rotary kilns operated at PPC's Lime Acres operation, LK 9 is the largest with a capacity of more than 1400 tons per day.

The conversion is part of PPC's ongoing plans to improve the dedusting of kiln off-gas, the hot air from the kilns containing fine dust particles, at its Lime Acres facility.

In 2002, PPC Lime's capital programme to improve dedusting commenced with the first electrostatic precipitator to bag-house conversion taking place on the Lime Acres kiln 7. The conversion brought the operation in line with permit requirements.

The latest conversion on Lime Acres kiln 9 has reduced the total amount of dust released into the atmosphere from all kilns at the Lime Acres facility by at least 50% from the pre-2002 levels.

The cladded structure of the existing electrostatic precipitator needed 370 tons of steel plates, wiring and wrapping gear removed before two plenums (rooftop-like structures) were built on top of the building. The plenums were then filled with over 4 000 filter cages containing fine mesh filter bags to trap the dust. The use of a dedicated tower crane led to the project taking only eight weeks to complete.

The Lime Acres team used the downtime during the refurbishment project to carry out additional maintenance work on the plant.

How does a bag-house work?

• Kiln off-gas is drawn through the bag-house, a large volume vessel, by a bag- house fan.

• Once air enters the bag-house, its air flow speed is reduced substantially causing large particles to drop out of the off-gas before it makes contact with the filter bags. This reduces bag wear and extends bag life.

• The filter bags are made from a special coated, glass fiber material which collects the dust.

• The clean air flows through the bags to the bag-house fan, and is vented to atmosphere through a kiln stack.

• When an optimum amount of dust has been collected, the bags are cleaned with a blast of air. The kiln dust is collected in a dust bin, slaked and disposed of in an environmentally friendly manner.

As the kiln off-gas cannot bypass the bag-house, all the off-gas from the kiln is cleaned in the bag-house before being released into the atmosphere.

“Dust emissions are monitored continuously to ensure the bag-house operates efficiently,” Fenn concludes.



1. Building two new plenums on top of the structure.

2. Installing the filter cages which trap the dust particles.

3. The entire structure has been cladded to create a virtually dust-free environment.


Issued by : Joanne Smith
Meropa Communications
Tel: (011) 772-1000

On behalf of: PPC Cement
Contact: Beth Harris
Tel: (011) 386-9095

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