By Gary Rose

The installation of degassing valves above each filter housing provides a novel and efficient solution to several issues associated with a bleach filtration process.

The manufacturing of bleach has come a long way since the early years of the first Industrial Revolution. Back in 1799, Scottish chemist Charles Tennant patented a lime powder that was manufactured by treating lime with water and spreading it thinly over a concrete floor. Chlorine gas was then pumped into the room and absorbed by the lime.

Tennant’s development of bleaching powder as a source of chlorine revolutionized bleaching processes in the textile industry and led to a prolific expansion in the production of more stable, high-quality bleaches. Today, there are numerous chemical companies that produce sodium hypochlorite bleach to meet the increasing worldwide demand for whitening and disinfecting applications. Though the basic chemistry for manufacturing bleach is a matter of common knowledge within the field of chemical engineering, the manufacturing process is quite the opposite. The specific processes of production can be varied, quite complex, and involve numerous patents.

One of the leaders in the industry is Olin Corporation (www.olin.com). Olin has been involved in the U.S. chlor alkali market for more than 100 years and is the third largest producer in the North American chlor alkali market.

Olin’s Chlor Alkali Products Division manufactures chlorine and caustic soda, sodium hydrosulfite, hydrochloric acid, hydrogen, potassium hydroxide and bleach products. In fact, Olin is the largest producer in North America for industrial bleach, with 10 plants located across North America. Recently, Olin spent $11.8 million expanding its bleach production at its Augusta, Ga.; Charleston, Tenn., Niagara Falls, N.Y. plants.

These expansions increased capacity, doubling the number of truck-loading stations, and introduced new production and filtration equipment, storage tanks, controls, infrastructure, and other related equipment.

Olin Addresses Bleach Filtration Issues
Olin Chlor Alkali Products’ Augusta Plant is located in the heart of the Southeastern paper and textile markets, which are heavy users of industrial bleach. The plant’s bleach process engineer, Patrick Hollingsworth, oversees this operation and continually seeks to improve manufacturing efficiencies. A key area of concern for Hollingsworth has historically been the filtering stage that removes any impurities that can discolor the bleach or catalyze its decomposition. This is generally the last stage in the production process before the bleach is shipped to customers.

The filtering stage consists of several CPVC filter housings that contain a manual vent on top of each filter. During the filtration process, the bleach created gas buildup inside each filter housing, ultimately occupying nearly half of the capacity of the housing. This greatly reduced the effectiveness of the filter cartridges, as the bleach was only able to reach the lower half of the filter cartridge, minimizing the filtration effect.

In order to relieve this gas buildup, the filter housings had to be manually vented once per day. This continual problem created numerous issues for Hollingsworth. The first issue was the safety factor of a contained volatile gas. The second issue was the cost of time venting the filters on a daily basis. The third issue was the decrease in flowrate, as the gas would build up within the filter housing, thereby slowing the bleach process as a whole. The last issue was the uneven wear of each filter cartridge. Since the gas prevented the bleach from thoroughly entering the filter housing, only half the cartridge being used.

In an effort to resolve these ongoing issues, Hollingsworth decided to install a CPVC degassing valve (DGV) above each filter housing. The DGV, manufactured by Plast-O-Matic Valves Inc. of Cedar Grove, N.J. (www.plastomatic.com), was isolated between two manual ball valves, which are placed between a tee and connected to the top of the filter. The degassing valve was a normally open valve designed to vent small volumes of gas as gas accumulated at high points in the system while operating and pressurized. As the outgassing from the liquid occurred and accumulated, it also displaced an equal amount of liquid, causing the float to lower/drop and open the orifice to vent the gas.

As the gas was released, the liquid level again rose, lifting the float and closing the valve orifice. This cycle repeated itself as often as the gas accumulated in the valve. The patented Plast-O-Matic DGV represented a continuous and automatic degassing system as opposed to the manual venting method that was previously employed.

According to Hollingsworth, the Plast-O-Matic degassing valves resolved all of the issues he was having with the filtration of the sodium hypochlorite bleach. Since the gas was immediately released through the DGV and dispersed, safety was less of a concern. The elimination of manually venting on a daily basis has saved valuable time as the gas is now continuously and automatically vented. The flowrate has increased due to lack of any restrictions caused by the gas buildup. Finally, the filter cartridges within the filter housings are experiencing normal wear due to the complete filtration of the bleach.

Gary Rose of Rose Industrial Marketing, Inc. assisted Olin”s engineering group in explaining the features and benefits of the Plast-O-Matic Degassing Valve as applied within the bleach filtering process. Rose Industrial Marketing, Inc. has been involved with specification work with engineers over the past 20 years. Mr. Rose can be reached at 800 975-5469 or gcr@roseindmktg.com.