Lined valves provide long-term safety benefits to chemical plant

Paul Boughton

The Anderson Development Companya wholly-owned subsidiary of Mitsui ChemicalsInc of Japanis a speciality chemicals company located in MichiganUSA.

In 1995Mitsui decided to move into the production of chemicals to support the semiconductor industry.

As part of this movethe company built a new production facility in AdrianMichigan to mirror an existing Nitrogen Trifloride (NF3) plant in Japan.
Nitrogen Trifloride is a high-purity gas (99.9999 pure) that is used in the semiconductor industryprimarily for etching computer chips and cleaning out chemical vapor disposition ovens.

Liquid crystal displays

The gas is also used in the fabrication of liquid crystal displays. There is a tremendous growth in the use of Nitrogen Trifloride use due its use as an alternative to ozone-depleting gases such as CF4.

The production of Nitrogen Trifloride involves the handling of extremely corrosive and toxic chemicals.

The process involves bringing in the raw material of anhydrous hydrofluoric acid by rail car or truck.

Once the raw material enters the plantit is hydrated and becomes hydrofluoric acidwhich needs to be transported through a number of processes in the plant.

Handling corrosion

During the planning of the new plantthe customer was looking for ball valves that could handle the corrosion and permeation of the acid.

According to Dan Ellis of Engineered Process Solutions Group“The flourine molecules in the hydrofluoric acid are extremely small and they tend to make their way through valve linings over time.”

The customer had a choice of using a high-alloy valve – which can be very expensive – or use a PFA-lined (perfluoroalkoxy) valve product.

Scott TatroPlant Manager for Anderson said that: “There are not many materials that can withstand the corrosive effects of hydroflouric acid. We also have to make sure that we keep it in a liquid form and free from contamination.”

Ellis noted that the: “Customer was looking for corrosion and permeation resistance. They were concerned about emissions from the stem area of the valve because hydrofluoric acid is a dangerous material and be lethal.”

Containment system

In the construction of the plantAnderson built a state-of-the-art chemical handling and containment system.

Tatro said: “We were looking for the best materials of construction at the lowest cost. When we looked at valveswe looked at what would be the total life cycle cost of the valves in addition to service and delivery.”

ITT EPSG came to Anderson with PFA-lined KNA ball valves with a superior stem packing arrangement that met the customer’s requirements.

During the production of Nitrogen Triflouridethe hydrofluoric acid is combined with ammonia to form ammonia biflouride.

Using electrolysis and a series of purification stepsthe high-purity Nitrogen Triflouride gas is produced.

According to the customerPFA-lined valves are used in applications that have anything to do with the flow of hydrofluoric acid through the plant. These applications include unloadingsampling portssealing around instrumentationand waste handling in the electrolyte process where they are used in pump-out applications. The valves are used at temperatures ranging from 60°F to about 150°F.

Acid-indicating paint

As part of the safety regime at the plantthere are leak detectors and monitors as well as acid-indicating paint.

Tatro noted that: “We’ve had excellent sealswith some of these valves in operation for over eight years. Some of these valves only get actuated about four times per year and are inspected once per year.”

During the construction of the plantboth PFA-lined and stainless steel valves were used in certain applications.

The customer reported that the stainless steel valves tended to freeze up if they were not actuated frequentlywith the consequence that the entire process would need to be shut down to replace the valve.

These stainless steel valves are now being replaced with Richter PFA-lined valves.
The Anderson plant started out as a small facility – producing about 25metric tons of Nitrogen Triflouride. The facility has since grown to produce over 130metric tons per year. The plant is currently undergoing an expansion that will include new Richter valves.

As a testament to the safety of the Richter valvesthe Nitrogen Trifloride plant was the recipient of one of three Responsible Care Achievement Awards given by the Synthetic Organic Chemical Manufacturers Association (SOCMA) to the Anderson Development Company.

Responsible Care programme

The award recognises chemical manufacturing facilities that have demonstrated a strong public commitment to environmentalhealthsafetyand security excellencewhich is encouraged by the industry’s voluntary Responsible Care programme.
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