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Sterling Chemicals, Inc.

Year Submitted: 2003

Process: HCN Waste Treatment

Industry: Chemical Manufacturing

Wastes Reduced: Process Chemicals

Substance: HCN

Equipment: NaOH

Location: Texas City TX

No. of employees: 931

Contact: Sam Chamberlain

Phone: (409) 942-3043


Sterling produces Hydrogen Cyanide (HCN) as a byproduct of its manufacturing process. It is impossible, with current technology, to eliminate the production of byproduct HCN in the Acrylonitrile process. A small percentage (about 20%) of the byproduct HCN has historically been used to produce two other Sterling products: lactic acid and tertiary butyl amine. Even with these units at full capacity, a large excess of HCN existed. Other commercial uses of this material were investigated when Sterling was formed as a corporation in 1986. The majority of this toxic, but potentially useful chemical building block, had been used as a waste that was burned in boilers for heating value. Sterling was faced with the prospect of continuing to burn the HCN or to identify other commercial uses for the material. Although potential off-site users were identified, Sterling's management concluded that transport of this volatile and toxic material via public roads, waterways or pipeline to other manufacturing facilities involved too high a hazard and risk level.

P2 Application:

Sterling's program to convert the remaining HCN waste byproduct stream into a safe and valuable commercial product began to be formulated when Sterling noted that there was a high demand for Sodium Cyanide in the mining and electroplating industry. Sterling chemists recognized that Sodium Cyanide (NaCN) could be produced by the reaction of HCN with sodium hydroxide (NaOH).

Environmental Benefits:

The project has been immensely successful, having converted about 150 million pounds of HCN to Sodium Cyanide since 1989. This means that Sterling has increased from 20% to 85% the amount of excess HCN that is now being utilized in producing a commercial product. An associated 97% reduction in Hydragen Cyanide emissions to atmosphere has been achieved. This achievement is all the more remarkable considering the fact that the capacity of the Acrylonitrile Unit which generates the Hydrogen Cyanide was expanded by about 50% during this same time period.The clear success of the project prompted Sterling to expand the Sodium Cyanide Unit capacity in 1990 by 67% (from 60 million pounds annually to 100 million pounds). Additional work was completed at the Acrylonitrile Unit to improve usage, recovery and destruction of byproduct HCN. These in-process recycling and pollution prevention techniques enabled Sterling to improve HCN utilization and reduce emissions even more by decreasing the amount of excess HCN sent to the boilers. A special team has been assigned to continue to look for ways to market the remaining fraction of excess HCN from the Acrylonitrile process. Over the long term, Sterling expects to further expand the Sodium Cyanide Process or identify additional ways to use excess HCN in the manufacture of other commercial products. Sterling's ultimate goal is conversion of all HCN into product.

Details of Reductions

Additional Information :

The manufacturing and sales of Sodium Cyanide has become a profit center for Sterling Cheicials since 1989, while decreasing Cyanide air emissions by 97%. In addition to the economic benefits to Sterling, employment and economic stimulus to the surrounding community were also generated as a result of this project.

Source: TCEQ

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