HWC Operating Limit Determination for Lone Star Industries Greencastle Facility

David Gossman, David Constans and Jim Woodford of Gossman Consulting, Inc.

IMPACT OF “AVERAGE OF RUN AVERAGES” ON OPERATING ENVELOPE SPECIFIC TO GREENCASTLE

Using actual 2000 ROC test the differences in establishing the various parameters are demonstrated.

ELEMENT FEEDRATE LIMITS

The set point for the SVM, LVM, Hg and chlorine feedrate limits under the HWC MACT is the average of the three run average HRA input rates. In this case, the 2000 ROC mercury data is insufficient to provide an input rate limit primarily due to concentration values less than detection limit, especially for the raw feed materials.  Under BIF it was unnecessary to have a precise input value for mercury from raw materials.  HWC requirements are however more stringent.  HWC does still have a provision similar to BIF’s Tier IA.  See 63.1207(m) where an MTEC may be calculated.  Amendments to the HWC MACT have also been made which ease the requirements on how non-detects are handled. See FR 66 No. 128 page 35098.    Clearly the 12 HRA will flatten the data. 

ADDRESSING EACH MONITORED PARAMETER IN TURN:

Minimum Combustion Chamber Temperature – The lower the value the better.  The ideal would be to run as low of a temperature as possible during both the DRE and PCDD/PCDF tests.  At the same time however we would want to maximize flue gas flow rate (or production), HWF feed rate and during the PCDD/PCDF test maximize the APCD inlet temperature. (Although maximizing production rate as an alternate for maximum flue gas flow rate will likely be difficult and still minimize combustion chamber temperature.)  This should be possible but it will be necessary to sit down and work out the desired values, compromising as required, and plan out how this can be done.

Maximum Flue Gas Flow Rate – This will be somewhat easier because the limit is to be a HRA less than the average of the maximum HRA of the test runs.  Here a large amplitude cycle will be an advantage.

Maximum HWF Feed Rate – Because of the way the limit is set the only thing that can be done is to feed at a high rate throughout the test runs.  This can be a conflicting parameter with minimizing combustion chamber temperature for some kilns.

Maximum APCD Inlet Temperature – There is no upper limit on this value if the PCDD/DF is below 0.2 ng/dscm TEQ.  Even if it is necessary to comply with the >0.2 but <0.4 ng/dscm at 7% O2 and therefore limited to a maximum of 400 F (per the HWC MACT rule, 63.1204(a)(ii)) it is worth while, if possible, to establish a set of  “average of run averages” above 400 F so that 400 F is indeed the limit and not some value less than that like 398 F.  If however, it is necessary to be at, say 300 F, to be below 0.4 ng/dscm@7% O2 it is still worth while to maximize this temperature limit to provide as much operating envelope as possible.

Element Feed Rate – The 12 HRA limit flattens the data however it is still possible to exceed the limit, particularly if there is a pronounced cycle in the metals feedrate which is not accommodated in the run start and stop times.  Consistently feeding these elements at as high a rate as is allowable throughout the runs would be best.       

CONCLUSION

Waste Combustor MACT versus BIF makes little or no difference for maximum raw material feedrate, ID fan rpm, liquid HWF feedrate or maximum HWF feedrate.  There is clearly an impact on minimum combustion chamber temperature, maximum ESP inlet temperature and maximum by-pass APCD inlet temperature.  Clearly, a facility has more flexibility under the new rules, but each facility will still have to decide which operating parameter they choose to dictate operations.

Key Words

Boilers, Cement, HWC, EPA, MACT, DRE, Burning, Hazardous Waste