05/07/82

Restatement of Guidance on Emissions Associated with Soot-blowing

                                 MAY 7, 1982


SUBJECT:  Restatement of Guidance on Emission Associated with
            Soot-blowing.


FROM:     Kathleen M. Bennett
            Assistant Administrator for Air, Noise and Radiation


TO:       Directors, Air and Waste Management Divisions
            Regions I-IV, VI-VIII, X
          Directors, Air Management Divisions
            Regions V and IX


     This memorandum restates EPA's guidance on emissions associated
with soot-blowing as it relates to sources under New Source Performance
Standards ( NSPS ) Subparts D and Da and State Implementation Plans
( SIPs ).  Soot-blowers remove ash adhering to heat transfer surfaces in
boilers.  In new and larger boilers subject to Subparts D and Da,
automatic, semicontinuous soot-blowers are used; while in smaller and
older boilers subject to the SIP's, periodic soot-blowing is the
dominant practice.
     As required in 40 CFR 60.8(c), "performance test shall be conducted
under such conditions as the Administrator shall specify to the plant
operator based on representative performance of the affected facility."
Since soot-blowing occurs at regular intervals for each generator,
these emissions cannot be discarded as being a result of an upset
condition.
     Recent data obtained for periodic soot-blowing for smaller
pulverized and spreader stoker boilers show that uncontrolled emissions
increase significantly during soot-blowing, while emissions controlled
to levels of 0.1 lb/106 Btu or less by fabric filters and scrubbers are
unaffected by soot-blowing.  This would indicate that the fraction of
very fine particles is relatively unaffected by soot-blowing and that
other control devices such as "cold side" electrostatic precipitators
should be unaffected, while less efficient systems such as mechanical
collectors may be effected.
     For a source which blows soot on a semi-continuous basis, emissions
can be adequately represented by three sampling runs.


                                      2


For units which do not blow shoot semi-continuously, data suggest that
the source's ability to comply using fabric filters, high-energy
scrubbers, and medium to high efficiency "cold side" ESP's commonly
used to meet design emission levels comparable to Subparts D or Da
should not be adversely affected by the inclusion of soot-blowing.
Testing should thus be done in accordance with previous guidance issued
by DSSE.  A copy of this guidance, dated March 6, 1979 and sent to all
Regions, is attached for your information.
     Relative to SIP limits, demonstrations of attainment and
maintenance of national Ambient Air Quality Standards ( NAAQS ) are
normally based upon continuously achieving the emission levels
prescribed in State Implementation Plans, and the compliance
determinations should be based upon the performance of control devices
over the normal range of boiler operation.  For fabric filters,
electrostatic precipitators, and wet scrubbers, the most stringent test
of their performance occurs at maximum boiler load.  For mechanical
collectors, the most stringent test occurs at low boiler loads.
Therefore, it is recommended that SIP compliance test be made at both
high and low loads, and include soot-blowing per the March 6, 1979
guidance.
     The attached March 12, 1979 guidance noted that it is appropriate
to interpret a never-to-exceed emission limit as requiring control of
soot-blowing emission.  This assumes that the individual SIP does not
specifically address the issue of soot-blowing.  If soot-blowing
provisions are included in the SIP, these SIP provisions will, of
course, take precedence; if provisions are not included, existing
sources should be handled using the same approach as the attached March
6, 1979 determination provides for handling new sources.  ( Of course,
inclusion of provisions in SIPs which provide exemptions in the mass
standard for soot-blowing presupposes a demonstration that such
exemptions will not interfere with the attainment and maintenance of
NAAQS. )
     Sources which are in violation of emission limits during
soot-blowing operations and have not been exempted by the applicable
SIP provisions should be treated as violating sources in accordance
with other guidance.  (See, for example, the definition of a
"significant violator" in my memorandum of December 29, 1981 entitled
"EPA Accountability System---OANR Policy Guidance.")
     Should you have any questions, please contact this office.