'New' Chlorine Dioxide Method Adapted to Control VOCs

Tiberian Technologies' Process & Equipment Division in March 1999 undertook pilot studies to model the performance of the patented SVP-Pure chlorine dioxide scrubber technology. Its purpose was to optimize performance for the removal of odorous compounds and regulated VOCs at a full-scale rendering plant in Georgia.

Tiberian's research concentrated on optimizing the air flow, liquid recirculation rate, chemical dosage, and pH of the packed towers in an effort to improve the efficiency of existing scrubbers or increase their capacity with minimal capital expense using Eka Chemicals' (Marietta, GA) patented SVP-Pure technology for generating chlorine dioxide on-site.

Current ClO₂ Production Methods
The most popular of two chlorite methods for producing chlorine dioxide mixes a dilute sodium chlorite solution with gaseous chlorine to produce a slightly acidic chlorine dioxide solution. The other method mixes a solution of sodium chlorite, sodium hypochlorite, and hydrochloric (muriatic) acid to produce a solution of chlorine dioxide.

The two-chemical method, although preferred for its control simplicity and favorable economics, suffers the disadvantage of using chlorine gas on-site—a growing problem for facilities wishing to avoid dealing with risk-management plans and process-safety management.

Eka's Sodium Chlorate
The SVP-Pure technology uses sodium chlorate (not chlorite) to produce chlorine dioxide solutions. Sodium chlorate methods to generate chlorine dioxide are not new. In fact, the vast majority of the chlorine dioxide produced (mainly for pulp and paper bleaching), is produced with sodium chlorate. The patented SVP- process is a direct development of Eka Chemicals' 30-yr history with chlorine dioxide in the pulp and paper industry.

Eka's process generates chlorine dioxide gas from a mixture of sodium chlorate, hydrogen peroxide, and sulfuric acid. The process is rapid and better than 95% efficient. The gas is drawn by high vacuum into a water slipstream, producing a dilute chlorine dioxide solution.

Two-month Testing Period
After a two-month testing period using the pilot scrubber, results were analyzed to identify the key variables of the scrubbing process. With this information, Tiberian recommended the application to the plant's existing air scrubbers to establish a comparison between Tiberian's process and the plant's two-year-old chlorite-based process. Minor modifications were made to optimize the system, and the SVP-Pure chlorine dioxide process was implemented.

Highly Favorable Results
Switching to the SVP-Pure chlorine dioxide process produced an almost immediate improvement in performance. Most notable was the reduced odor complaints surrounding the plant.

Subsequently, U.S. EPA compliance testing was performed for VOC emissions. A standardized comparison of the results obtained while operating the optimized scrubbers using the SVP-Pure process versus the compliance test results (using the previous chlorite-based process) produced an average reduction of 52% in VOC emissions.

This reduction enabled the plant to be reclassified as a minor source of VOC emissions.

Other realized advantages were that:

1. the process eliminated the need for chlorine gas while providing a pure chlorine dioxide solution without byproduct chlorine, which can cause unwanted side reactions;
2. the sodium chlorate and hydrogen peroxide are available pre-blended as Purate to minimize the bulk storage needs; and
3. the technology saved on costs.

Additionally, the process is computer controlled to maximize efficiency and safety, while minimizing operator interface.

Contact: Tiberian Technologies Inc., Process & Equipment Division, 1698 Empire Avenue, East Point, GA 30344. Tel: 877-396-9244; Fax: 404-768-9643.

Edited by Paul Hersch