Concentrated sulfuric acid production from non-condensable gases and its effect on alkali and sulfur balances in pulp mills

The pulp and paper industry often encounters challenges that require process improvements to remain competitive. These challenges may include the requirement to meet more stringent environmental regulations, stricter energy policies, or the need to improve product quality, increase production capacity and profitability. As a result, the pulp mills of today have to focus on becoming more efficient by possessing an effective chemical recovery system and reducing chemical losses. The high degree of closure is beneficial for environment, water consumption and mill economy but can upset the Na/S balance and increase the build-up of non-process elements in the system. Installing an acid plant to convert the sulfur containing Non Condensable Gases (NCG) into sulfuric acid will eliminate the NCG as a sulfur input to the recovery cycle, eliminate purchases of sulfuric acid, reduce caustic purchases, and produce additional steam that will positively impact the mill's heat balance. This paper provides an overview of the OptimumAcid (TM) technology required to produce sulfuric acid in a pulp mill from NCG, presents some of the unique challenges related to feed variability, and discusses some of the technical features of NORAM's sulfuric acid OptimumAcid (TM) process technology and equipment.