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NPEP Success Story: DuPont Titanium Technologies
DuPont Titanium Technologies Reduces Priority Chemicals at Edge Moor Site
The primary product of DuPont’s Titanium Technologies (DTT) Edge Moor site is Titanium Dioxide (TiO2), a white pigment used in the paper, plastics, and coatings markets. In the United States, DTT has TiO2 manufacturing sites at Edge Moor DE, DeLisle MS, and New Johnsonville TN. DuPont also has international TiO2 manufacturing sites in Mexico and Taiwan. DTT is the world’s largest producer of TiO2 with annual production quantities exceeding over one million tons.
TiO2 is produced via chlorination of Ti-bearing iron ores, followed by oxidation, purification, and finishing steps. Dioxin compounds, for which DTT committed a >50% voluntary reduction, are created as an unintentional byproduct formed during the chlorination step.
DTT's NPEP Goal
DuPont Edge Moor’s voluntary source reduction goal for the NPEP program was to reduce the generation rate of Dioxin and Dioxin Like Compounds (D&DLC), PCBs, and Pentachlorobenzene by >90% by the end of 2008 as compared to 2001 TRI levels. Our goal for hexachlorobenzene was a reduction of 70% by the end of 2008 as compared to 2001 TRI levels. These reductions were achieved by a process modification we term Purge Separation. We constructed the purge separation process in 2006 at a cost of approximately $25 million dollars and the process was activated in 2007. After making process adjustments throughout 2007, purge separation became fully functional in 2008.
Source Reduction and Recycling Alternatives
DuPont’s Research and Development organization did extensive research on the methods of reducing D&DLC and other PBT compounds via source reduction. Longer-term, additional process changes with capability for even further reductions were also studied.
Among the technologies that DuPont DTT studied/evaluated, one involved heating and separating the iron chloride to form metallic iron and chlorine. The heat of the process would simultaneously destroy the D&DLC compounds. Another technological concept was to use filter bags impregnated with catalyst to react D&DLCs in a gas stream. While these options initially appeared to be viable and attractive, the source reduction strategies were ultimately deemed to be the more sustainable, and as a result, we implemented the Purge Separation process.
Hurdles Faced
After making the decision to focus on source reduction strategies, the main hurdle was designing a process change appropriate for DuPont Edge Moor. Many of the changes introduced additional cost as a result of the need to modify equipment. Some other modifications tightened the acceptable ranges for running the process equipment, which required additional process controls. Additional process controls, in turn, required increased training of operators and mechanics. Others involved permit modifications for changes in process emissions. One of the changes involved revising specifications for one of the raw materials to reduce organic precursors that were being introduced to the process. To ensure that this raw material was within the new specification; numerous samples had to be collected and analyzed. The sampling and analytical program not only increased cost, but it also created a demand for on site technical resources to assess and interpret the analytical results. Finally, because the Purge Separation unit was completely new technology, operational hurdles existed after startup. This required us to further optimize process conditions and maintenance for cleaning and repairs. The unit is now achieving 100% operational uptime.
Waste Minimization Results
Reductions achieved through our project were more than originally projected. We source reduced 37 pounds of dioxin/furans, 68 pounds of PCBs, 245 pounds of pentachlorobenzene and 691 pounds of hexachlorobenzene.
In addition to the reduction of PBT chemicals, the quality of our co- product, Ferric Chloride, was actually improved by the changes that were made.
From a cost standpoint, most of the changes implemented resulted in increased cost to DuPont. Some of the changes required capital investment in new equipment but resulted in reduced costs due to improved process yields.
Payback has been a high level of satisfaction internally that we have achieved a significant reduction in dioxins and the betterment of HH&E. And much of this was achieved via science and technology that we had little understanding of 4-5 years ago regarding dioxins. External recognition has been slow but hopefully will come with time.
Lessons Learned
Fundamental science and the use of Six Sigma tools were very important to our success. Appreciating the number of analyses that had to be done to understand baseline conditions, and further to categorize reduction success or non-success, was a huge learning or eye-opener. During the program, and as it continues today, numerous analyses had to be performed. Starting with a superior laboratory, and the better analytical sensitivities therein, proved to be a wise choice as analytical sensitivities and regulatory standards evolved. We also learned that installing a major source reduction project involves many technical uncertainties, which can be minimized with strong teamwork involving the Operations, Engineering, and R&D functions.