Air pollution control in kraft pulp mills.

Area of Science:

• Environmental Engineering
• Chemical Engineering
• Industrial Chemistry

Background:

• Industrial emissions, particularly malodorous reduced sulfur compounds and sulfur oxides, pose significant environmental and health challenges.
• Kraft pulping processes are a major source of these sulfurous emissions.
• Effective and economical methods for emission reduction are crucial for sustainable industrial operations.

Purpose of the Study:

• To describe a patented gas scrubbing process for the effective and economical reduction of malodorous reduced sulfur compounds and sulfur oxides from industrial emissions.
• To detail the utilization of recovered sodium salts for pulping applications.
• To review advancements in gas chromatography for analyzing trace sulfur compounds in kraft mill emissions.

Main Methods:

• Scrubbing of stack gases using an alkaline suspension of activated carbon.
• Conversion of reduced sulfur compounds and sulfur oxides into recoverable sodium salts.
• Simultaneous recovery of heat and chemicals during the scrubbing process.
• Review of gas chromatography techniques for trace sulfur compound analysis.

Main Results:

• Effective and economical reduction of malodorous reduced sulfur compounds and sulfur oxides.
• Conversion of sulfur compounds to sodium salts, which are recovered and utilized in pulping.
• Reduction of particulate emissions.
• Elimination of subsequent waste disposal problems.
• Achieved little to zero net cost due to heat and chemical recovery.

Conclusions:

• The described gas scrubbing process offers an effective, economical, and sustainable solution for industrial sulfur emissions.
• The process provides valuable by-products (sodium salts) for pulping, enhancing economic viability.
• Simultaneous recovery of heat and chemicals minimizes operational costs and environmental impact.
• Innovations in gas chromatography aid in precise monitoring of sulfur compounds in emissions.