1. References
Description of Problem
Background Information
Proposed Sour Water Stripping
Process
Conclusions
Economic Analysis
Plan
Sour Water Stripping: An Alternate Approach
Team 5 Members: Tyler Balding, Justin Milavec, Ben Peterson, Coby Reynolds
Department of Chemical Engineering Senior Design Advisor: John W. Schutte
Proposed Stripping Gases
We were required to consider a flow rate of sour
water, between 20 and 50 GPM, having concentrations
of 300 ppm to 3000 ppm of 𝑁𝐻3 and 5 ppm of 𝐻2 𝑆, and
design a stripping process to remove or reduce the
contaminates. The obligatory concentration of 𝑁𝐻3 in
the stripped water was designated at a maximum of 20
ppm.
Figure 1: A conventional stripper used in new
treatment units.
Currently, sour water
treatment techniques
involve using one or two
columns to either separate
both the 𝑁𝐻3 and 𝐻2 𝑆 into
one stream or to separate
each species into individual
streams. This is typically
accomplished through the
use of air as the stripping
gas, although steam is a common alternative. After
stripping, the gases are then either taken to other parts
of the plants for further processing or flared off. The
processed “sweet” water is then further processed for
use as boiler feed water or sent to a waste water
treatment facility.
• Optimize air, steam, and natural gas stripping
processes using the computer program Aspen Plus
• Conduct analysis based on optimizations to
determine stripping gas for final sour water
stripping process.
• Make assumptions based off of existing plant
specifications.
• Design final process using Aspen Plus.
• Conduct economic analysis on final design taking
into account federal regulations for proposed
design.
• Make conclusions.
• Aspen Plus, V8.6 (32.0.0.29), [Computer Software], Aspen
Technology, Inc.: Aspen Technology, Inc.
• Knorr, Bryce. "Weekly Fertilizer Review." - Farm Futures.
N.p., 9 Mar. 2015. Web. 16 Mar. 2015.
• Lieberman, Norman. "Sour Water Strippers: Design and
Operation." (n.d.): n. pag. Digital Refining. Web. 15 Mar.
2015.
• Weiland, Ralph H., and Nathan A. Hatcher. Sour Water
Stripping Exposed. Proc. of Laurence Reid Gas Conditioning
Conference, Oklahoma, Norman. N.p., 28 Feb. 2012. Web.
15 Mar. 2015.
Air Steam
Steam
Thermo Nat Gas
𝑁𝐻3 ppm 19 14 16 17
𝐻2 𝑆 ppm 1 204 ppb 516 ppb trace
Heat Duty 0 0 0 0
Flow rate 12 cum/min 4 cum/min 0 0.74 cum/min
Vapor Water
Composition 0.302 0.996 0.993 0.042
Figure 3: Data showing compositions of 𝑁𝐻3 and 𝐻2 𝑆 in the “sweet” water after being stripped using
different stripping gases.
Number and type Equipment Cost Module Cost
1x Rotary $24,800 $59,700
1x Fixed, Sheet, or U-Tube $16,300 $104,000
7x Centrifugal $34,140 $219,100
1x Fixed Roof $56,400 $62,000
1x Stainless Steel Sieve Tray $10,900 $49,300
Total Bare Module Cost --> $494,100
Figure 2: Proposed sour water stripping processes utilizing natural gas as the stripping gas and sending the processed sweet water to a boiler.
Figure 4: Base costing of sour water processing without taking into account stripping gas.
After a detailed analysis regarding multiple simulations using alternating
combinations of equipment and striping gases, we recommend a final design that
involves only one stripping column which utilizes natural gas as the stripping gas. We
have found that natural gas is advantageous over the base case due to its superior
stripping to mass flow ratio and its ability to be re-utilized as a boiler fuel gas. This will
lead to a more efficient process saving both economic and utility resources.
Three different stripping gases
were simulated. In all three cases
we were able to strip the
contaminants down to 20 ppm of
𝑁𝐻3 and 1 ppm of 𝐻2 𝑆. Our base
case simulation using air yielded
the least desirable results while
meeting design specifications.
Additionally there was also a
large concentration of 𝐻2 𝑂 in our
distillate, which would be costly
to flare. Natural gas not only gave
us the best separation but also
produced the lowest
concentration of 𝐻2 𝑂 in the
distillate.
The natural gas stripping method was chosen because it
operates more efficiently and uses resources that the are
already in operation. Other methods, such as air and steam,
perform but are not as efficient as the natural gas method.
Operating the stripping process with natural gas when
utilizing a recycling stream is the most economical choice
while ultimately reaching the target concentration of 𝑁𝐻3.
The economic analysis was conducted in reference to
the optimized simulations of different stripping processes.
It was determined that the equipment required for each
respective process was similar when analyzed from an
economic stand point. The true deviation in cost between
the processes was identified within and how each one
must be altered in order achieve the desired separation. It
was discovered that the cumulative energy cost for
compression had surpassed the cost of the natural gas at
around 35,000 𝑈𝑆𝐷 𝑌𝑟.
Recommended Stripping Process