Substitution of sulfuric acid used for re-pulping process in a paper company
An old paper company innovated its process for pH adjustment in the recycling process. After numerous laboratory and on-site trails, liquid carbon dioxide was used efficiently instead of sulphuric acid.
Carbon dioxide (CO2) is not classifies as toxic.In closed enclosures there is however the risk of suffocation by large amounts of CO2 licks. If the CO2 is not from recycled sources or separated form the atmosphere, it contributes to the carbon footprint of the company, as it is a known greenhouse gas. Physical hazards relating to installations using liquefied gases need to be controlled.
For hazards of the initial substance see Substance information.
The oldest paper manufacturer in North America makes products that require highly technical specifications. The paper is mostly made of cotton and other natural and synthetic fibres and the company is proud that it was used to announce the inauguration of the Statue of Liberty.
The company innovated its paper reclaiming process as part of a toxic use reduction process. To reuse paper that does not meet requirements or was reclaimed from finishing operations, the paper must be reprocessed into slurry. Many papers made by the company have a high degree of permanent wet strength. This requires the use of alkalis and high temperatures, followed by a pH adjustment before reusing the slurry.
The pH of the slurry used to be adjusted with sulphuric acid. The research unit of the company proposed to use liquid carbon dioxide (CO2) instead. Initial laboratory tests were carried out at room temperature but had less than 50% efficiency. Pilot tests followed, using mobile CO2 sources and after several changes to the process and equipments the united teams of the company and the CO2 supplier proved that the substitution was a viable option even under ambient conditions.
The use of carbon dioxide as alternative to sulphuric acid improved the process control stability and reduced chemical risks. The project resulted in an overall 3% reduction in pulp production costs.
The implementation of the substitution needs significant technological changes and training of operators. It eliminates the use of a very corrosive substance and the measures to manage it properly during transportation, storing and use. Hazards due to liquid CO2 need to be properly controlled.
Type of information supplier
Commonwealth of Massachusetts, Executive Office of Environmental Affairs, Office of Technical Assistance (OTA)
The description is based on the document ‘Crane & Company, Inc. Toxics Use Reduction Case Study Substitution with Carbon Dioxide Eliminates Major Use of Sulfuric Acid” published by the Office of Technical Assistance (OTA), a branch of the Massachusetts Executive Office of Environmental Affairs on its website in 2003.Type of publication and availability
Internet presentation, freely available.
Original document: click here
Publication or last update: January 2013