A Ferro Silicon Producer in Alabama

Application

A Ferro silicon producer in Alabama was exhausting the gas off a 40 mW furnace through a 12-compartment American Air Filter baghouse (2400 filter bags, 200 bags per compartment).

Optimization Potential

Production and quality were limited due to the high pressure drops in the baghouse, which restricted draft at the furnace. This lack of draft created emission problems from the furnace building. The conventional fiberglass fabric filter bags required sonic horns in addition to the reverse air for cleaning, which disturbed the surrounding community. The bag life of these filters was only two years, after which the pressure drop and baghouse emissions were too high.

Solution

Installed 1680 (140 per compartment) GORE® membrane/acid resistant fiberglass fabric filter bags and eliminated the sonic horns. Expected operating data:

• Air-to-cloth ratio = 1.9 Gross, 2.1 Net    
• Pressure drop = 6" w.g.    
• Emissions = Less than 0.004 gr/cf    
• Bag Life = 8 years

Results

Filter flow resistance (pressure drops) have been significantly reduced, allowing for increase in system gas flow of approximately 20% which has allowed for the increased furnace production. Producer can now operate at a higher furnace power rate, which in turn allows for increased capacity and improved product quality. Community and regulators are pleased because sonic horns have been eliminated and they are achieving extremely low emissions (less than 0.004 gr/acf). Reduced filter resistance has allowed for one fan to be shut down during low load conditions, saving on fan energy costs. Filters have been in operation since April 1993 and are performing as expected.

Installation of GORE® membrane filter bags have enabled the producer to increase and improve Fe-Si production with little capital expenditure and greatly reduce operational costs.