Vapor Recovery System Analysis and Engineering
R. A. Nichols Engineering has been serving the Oil and Gas
Industry for 30 years. We provide engineering services that range from
troubleshooting problem systems to complete terminal design. We have experience
in designing and overseeing the installation of Cone Roof and Floating Roof
Vapor Control Systems. To simplify our analysis, we have adopted the methodology utilized by major oils for
evaluating economic data. This methodology has also been presented in EPA literature The
resulting trade-offs are used to determine the system configuration of greatest cost
effectiveness. Many variables are considered
to achieve the most accurate capital, operating and maintenance costs and the highest
return on investment.
The most important operating variables to consider are the vapor concentration and
the flow rates from the rack. Both variables
dictate your equipment sizing and process capabilities, and your Return on Investment.
With very little information, we can provide an accurate model of what you can expect from
our equipment.
We generate a Terminal Average Vapor Concentration Calculation Sheet using fraction
vapor balance, SS Stage I on truck deliveries and fraction diesel / gasoline loaded in the
terminal as parameters. The Terminal Average Vapor Concentrations and the Terminal Yearly
Throughput are used to predict for any proposed system, System Efficiency and Return on
Investment. We have included our
formula, so that you can understand how we achieved these findings. Some companies simply assume a vapor concentration
of 40%; this is well above saturated and highly unlikely to occur under normal conditions.
For example, Gasoline is typically blended to have a vapor concentration of 35%. With 100%
Stage 1 and 100% gasoline loading, a vapor concentration of 33.43% could be collected at
the rack; this is well below the assumed 40% saturation. Such unreasonable assumptions are
used to justify huge costs for recovery equipment.
We use your rack truck loading profiles to calculate the maximum cf of vapor
generated in any time period. By measuring refueling rates and measuring the number of
trucks refueled / hour, vapor return rates from truck loading can be estimated. Assuming equipment sizes we estimate Process
Rates, Ave. CFM, Process time / truck, and Vapor Holder Surge and necessary Holder
capacity in CF @ VRU Process Rate. A
carbon system size is usually based on its four hour process rate. The run time / day for the VRU can be calculated. A vapor holder is sized to handle minimum run time
and to store the surge volume. A 300 cfm
process unit with a 5,000 cf vapor holder and burner can handle throughputs of 1.5M
gal/day, with a VRU run time of 11.4 hours. For
a medium size terminal, loading 24 hours a day, this run time is about 1/2 of a on-line
carbon or refrigeration unit.
We hope that this information and the attached diagram,
showing the interconnection of our VRU Equipment,
can answer your questions regarding our information.
If you would like some pictures, some further information, or a system
quote, please give us a call.
