Pierre River Mine Project

AIR AENV SIRS 6 – 14
Question No. 12
Section 11.1
River Mine plant site shown in that response illustrate that the difference between
the original 1995 CALMET data set and the corrected data set is negligible.
Request Volume 2, SIR 250b i-ii, Page 20-43.
Shell indicates that the failure of the SO2 control equipment is expected to be
once in every 17 years, and that the determination of this probability is consistent
with the technique outlined in the EPRI FGD Redundancy Development
document cited in the question.
12a Provide supporting information on the calculation of SO2 control equipment
failure probability, and demonstrate that the method used to estimate failure rate
probability is consistent with the EPRI document.
Response 12a The SO2 control equipment failure frequency was estimated by an engineering
contractor engaged by Shell. Based on a preliminary equipment scope, Shell
worked with an equipment manufacturer to incorporate industry experience on
FGD reliability performance. Although this is not necessarily consistent with the
EPRI document as stated in the response to SIR 250bii in the May 2009 Pierre
River Mine, Supplemental Information, Volume 2, Shell believes that this level
of reliability is achievable and reasonable at this stage of the process design. The
level of design detail required by EPRI would typically be dealt with during the
detailed engineering phase of the project.
Question No. 13
Despite this preliminary scope, it is expected the SO2 control equipment will
have a high availability (see the response to ERCB SIR 40). In addition, the
boiler and burner design will be capable of switching to natural gas on short
notice (about 15 minutes) if the FGD system fails.
Request Volume 2, SIR 250e, Page 20-47.
An equipment failure rate of once in 17 years would not be considered an
“unlikely” event based on the EPRI method of evaluating SO2 control systems
because it means that the equipment is likely to fail at least once during the life of
the facility. Furthermore, a probability of equipment failure of once in 17 years
does not mean that the equipment will fail only once in every 17 years. For
example, the equipment could fail twice in a 10 year period, and then not again
for the next 25 years and still remain within the 1-in-17 year probability failure
rate.
11-12 Shell Canada Limited April 2010
CR029