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3M: Hutchinson, Minnesota

3M: Letter from Peggy Bartz to Cynthia Cummis

Minnesota Pollution Control Agency

July 23, 1996

Ms. Cynthia Cummis
Project XL Coordinator
United States Environmental Protection Agency
404 M Street Southwest
Mail Code 2126
Washington, DC 20460

RE: 3M Project XL

Dear Ms. Cummis:

I hope this letter addresses the issues you raised in our phone conversation this morning. If necessary, and with some more time, I can get specific information on the variability of operating parameters of the solvent recovery unit at 3M Hutchinson to demonstrate the points made below.

Solvent Recovery Efficiency Used In Actual Emissions Calculations:

Currently, 3M is required to control two of the magnetic coaters in the North Plant due to a New Source Performarce Standard (NSPS) that applies to these coaters. The NSPS requires that they be controlled by the North Plant Solvent Recovery Unit (SRU) which must achieve a 95 percent control efficiency. In 1992, 3M tested the SRU control efficiency using U. S. Environmental Protection Agency (EPA) approved test methods and following Minnesota testing rules and measured an efficiency of 99 percent. So, even though 3M is only required to achieve 95 percent efficiency, when calculating actual emissions for reporting and compliance purposes, 3M is required by Minnesota Pollution Control Agency (MPCA) rules to use a 99 percent control efficiency for the SRU. 3M has measured higher efficiencies (99.6 percent) using on site monitoring devices (Continuous Emissions Monitoring System), but these results have not been verified by the MPCA. Unless those results are verified by the MPCA and the testing conditions meet Minnesota rules, 3M must continue to use the last performance test data that was approved by the MPCA, which is 99 percent as measured in 1992.

Solvent Recovery Efficiency Assumed for Setting Cap:

The rules that require the operation of the solvent recovery (currently NSPS on two magnetic coaters, and in the future, Maximum Achievable Control Technology for all magnetic coaters) require a 95 percent control efficiency. This is based on background information gathered by the EPA to determine what is an achievable control efficiency in the manufacture of magnetic tape. The 3M Hutchinson North Plant SRU is currently achieving atypical control efficiencies relative to other magnetic tape facilities, and even other 3M plants. For example, a 3M solvent recovery unit in operation in Cottage Grove, Minnesota typically achieves a 96 percent control efficiency.

While the 3M Hutchinson plant is currently achieving 99 percent control, this efficiency will most likely not be maintained in the future. The efficiency is dependent on several things that will change over time -- primarily the types of solvents used, but also the concentration of solvents, temperature of gas stream, and the condition and age of the control equipment. Over time, many components of the control unit will degrade and must be replaced. The efficiency drops as this occurs. In addition, one reason for 3M's current high recovery is that the products they make on the magnetic coaters are nearly identical in chemical content, so the equipment is fine-tuned to recover those chemicals. As 3M gets out of the magnetic tape business, it is very likely that the system will need to either, accept a wider variety of chemicals, or recover the same chemicals from less concentrated gas streams; both of these situations will likely result in a drop in efficiency.

Please feel free to contact me at (612)297-8113 if you have questions about this letter or any other issue related to this project.



Peggy Bartz
Staff Engineer
Permit Section
Air Quality Division


cc: Lisa Thorvig, Commissioner's Office
Andy Ronchak, Air Quality Division
Cheri Kedrowski, 3M

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