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Figure 7 Comparison of net revenue at 400 USD/tonne and 1000 USD/tonne
away from this tried-and-true technology. For example, a high H₂S concentration was assumed, as was a standard feed pressure. Along with the use of a two-bed system rather than a three-bed system, this design represents an aggressively low Capex for a new SRU train. Bear in mind that the sour water used was the same as before the pro- posed expansion. See the sidebars for details on both. Anyone who has worked in a Claus unit knows the unit does not make money. Typically, the sulphur recovered is removed from the facility by a sulphur broker based on an agreed index plus shipping charges. When combined, these charges frequently exceed the costs used to recover the sulphur; however, it is seen as a cost of doing business to keep the rest of the refinery in operation. This is shown in Figure 6 as cumulative net revenue vs a 20-year proj- ect life. The figure is normalised to the cost of the sulphur train. The yellow line begins at time zero by expending the Capex required for the Claus train and then proceeds to lose money over the 20-year project life. The SWSPlus unit, on the other hand, generates cash flow due to the sale of NH3. Using an NH3 price of 400 USD/tonne results in a simple payout of about seven years. If there is an existing sour water stripper and a desire to keep it in service, the Bolt-On SWSPlus option can be used, and the payout is reduced to about five years. The value of NH3 varies as world demand and supply change, and recently the value of NH3 was over 1200 USD/ tonne, as discussed earlier. Using a value of 1000 USD/ tonne, the payout is reduced from about five years for the Bolt-On SWSPlus option to about two years (see Figure 7 ). Conclusions Technology always moves forward. At its inception, SWSPlus (originally known as Chevron’s WWT) solved
a variety of problems seen in downstream SRUs (capac - ity, salt deposition). Current advances take this technology even further by maximising the use of existing SWS assets in a facility to make NH3 recovery even more attractive. The SWSPlus Bolt-On concept offers the benefits of integrating NH3 recovery into an existing facility, including the ability to process heavier crudes (including opportu - nity crudes), adding a revenue stream, and increased SRU capacity. It does all of this while not requiring an air emis- sions permit. All these advantages can be realised at a frac- tion of the capital cost of a new SRU.
SWSPlus is a mark of Bechtel Energy Technologies & Solutions, Inc.
Martin A Taylor is the Manager, Sulphur Technologies for Bechtel En - ergy Technologies & Solutions, Inc. based in Houston, Texas, USA. His experience includes design, troubleshooting, consulting, commission- ing, and start-up of sulphur-related units such as amine, sour water, SRUs, tail gas treating units for the last 20+ years. He has five patents and other patents pending for technologies in and around the sulphur industry. Mr Taylor holds a BS in chemical engineering and an MS in natural gas engineering from Texas A&I University in Kingsville, Texas, USA. Email: mataylo1@bechtel.com Charles L Kimtantas is the Senior Advisor/SME: Sulphur Technology, Carbon Capture, Blue Hydrogen for Bechtel Energy Technology and Solutions, Inc. After gaining over 10 years of refinery experience in process engineering and operations, he has designed, troubleshot, and started up amine (carbon capture), sour water, sulphur, and tail gas treating units and related facilities for over 40 years. He is currently in- volved in blue and green hydrogen production facilities. He holds eight patents and has published or presented 15 papers. He holds a BS in chemical engineering from the University of Florida and an MS in com - puter science from the University of Texas-Dallas. Email: ckimtant@bechtel.com
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