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March 4, 1994

Mr. Jack Boley
Safety & Environmental Affairs Manager
First City Center
1700 Pacific Avenue
Dallas, TX  75201

                              Re:  Control Requirements for
                                     Glycol Dehydration Units

Dear Mr. Boley:

This letter is in response to the meeting held in Austin on
February 8, 1994 between industry representatives and several
members of the Chemical Section.  The purpose of the meeting
was to discuss the use of condensers as final abatement
control for reboiler vents in glycol dehydration units. 
During the meeting, you and other industry representatives
presented additional testing results on condenser efficiency
at controlling benzene, toluene, ethylbenzene, and xylene
(BTEX) emitted from reboiler vents.  All of the testing
results discussed during the meeting were on condensers which
use rich glycol coming off the absorber as the cooling medium
and have a flash tank upstream.  Therefore, our comments below
will only concern condensers which meet these two
requirements.  We will consider other designs on a
case-by-case basis.

For those individuals who submit PI-8 registrations for
Standard Exemption No. 66, we will review your registration
and send a letter which explains whether or not we agree with
the exemption claim.  If a company proposes to use a condenser
as a final abatement on a glycol reboiler, we will require no
further demonstration as part of the exemption claim, only if
the following conditions are met:  (1)  no more than 80
percent reduction of annual emissions is claimed, (2) the
company completes a one-time efficiency testing on the
condenser to assure that item (1) is being met, (3) 25 tons
per year VOC limitation is not exceeded, and (4) all other
requirements of Standard Exemption No. 66 are met.  

It is our position that if more than 80 percent reduction is
needed in order to meet the 25 tpy limitation, much more
stringent monitoring and testing (i.e., on a continuous basis)
for the condenser would be necessary.  In that case, a
condenser probably should not be used as the final abatement
device.  At those levels, it would be more appropriate to
route the condenser's vent to a combustion device, such as
flare, incinerator, reboiler firebox, or equivalent level of

I hope this letter addresses the concerns that were raised
during our meeting.  We would appreciate if you would share
this letter with all interested parties and industry trade
groups.  If you should have any additional comments or
questions, please contact me. 


Tammy Villarreal
Manager, Chemical Section
New Source Review Program

cc:  Mr. Allan Dees, Texaco Exploration & Production, Inc.
     Mr. Vernon H. Schievelbein, Texaco
     Mr. Curtis O. Rueter, Radian Corporation

bcc: Chemical and Combustion Section Engineers
        Air Program Managers, Regional Offices No. 1 - 15

          Texas Natural Resource Conservation Commission
                      Interoffice Memorandum

To:  Interested Parties
Date:  May 31, 1996
From:  Tammy Villarreal, Chemical Section Chief
Subject:  Control Requirements for Glycol Dehydration Units

Reference: TNRCC Letter, subject as above, dated March 4, 1994, signed by Tammy Villarreal

Many glycol dehydration vent condenser systems are being designed with one or more features
which ensure the uncondensed vent stream fraction is always combusted before it reaches the
atmosphere.  Operators with such units now ask exactly what requirements of the referenced
letter apply to their claim of standard exemption or standard permit.  The simple answer is none.

The March 4, 1994 letter applies to dehydrators whose FINAL vent control is a condenser. 
Systems which direct the uncondensed fraction to the firebox or an afterburner have final control
beyond the condenser.  We typically recognize a destruction and removal efficiency of 98% for
properly designed combustion units such as a dehydrator firebox or flare.  The two percent
uncombusted VOC amount should be determined based on the estimated vent load.  The
estimated vent load may be computed using any of the conservative software programs accepted
by the TNRCC Office of Air Quality or through a rich-lean analysis conducted according to the
protocol prepared by the Gas Research Institute.

No condenser efficiency test is required when the dehydrator still vents are combusted in the
final control step.