Texas Eastern Products Pipeline Co., Houston (Teppco), this month has begun segregating butane streams at the company's Mont Belvieu and Baytown, Tex., terminals (Fig. 1) according to fluoride and olefin contents.
The company says that no other products pipeline company is segregating butane streams for specific end users. Product-quality standards of certain end users have driven the project, which received company approval in November 1992.
Streams containing fluoride or an olefin content greater than 1 ppm (or both) currently flow into Teppco's south Mont Belvieu terminal. Those fluoride-free streams with less than 1 ppm of olefins flow to its north Mont Belvieu terminal.
It has been a major undertaking, says Teppco, comparable to adding an entirely new product to the system.
Major producers and end users of butanes transported by Teppco include Amoco Oil Co., Exxon Co. U.S.A., Shell Oil Co., Coastal Refining & Marketing Co., Phillips 66 Co., and Mobil Oil Co.
During 1992, butane movements along Teppco's Gulf Coast system averaged nearly 33,000 b/d.
TWO TYPES
To meet requirements of the Clean Air Act (CAA) amendments of 1990, gasoline producers will need to add oxygenates (such as methyl tertiary butyl ether-MTBE) to their gasoline pools.
Even though gasoline blending currently accepts butanes with higher fluoride and higher olefin contents, the process used to make the MTBE additive for reformulated gasoline requires a fluoride-free, low-olefin butane.
Butane processed through an isomerization unit yields isobutane, a key component in MTBE. But high-fluoride butane from crude-oil refineries using hydrofluoric (HF) acid alkylation units cannot be used to produce MTBE because fluoride will damage isomerization units' process catalysts.
Olefins also affect the efficiency of isomerization units, says Teppco, but less critically than fluorides. Their presence is higher in refinery product than in fractionated NGL.
To extend the life of their process catalysts and to maximize yields, producers (including MTBE and isomerization unit operators) are specifying low-fluoride butanes developed from natural-gas fractionators or from refineries that do not use an HF process.
SPLITTING THE STREAMS
Teppco modified its Baytown and two Mont Belvieu terminals, installing dedicated tines to segregate the butanes based on fluoride and olefin content.
Previously, says Teppco, butane streams flowed to either Mont Belvieu storage cavern, effectively making all streams high-fluoride streams.
In order to maintain the critical integrity of the fluoride-free, low-olefin product, the butane system is now split into two separate streams. That capability also allows specific crediting of the two butanes to customer accounts.
Since the two butane types originate from different sources, Teppco can specifically credit shippers' accounts with whatever butane types they deliver into the system. This specific crediting is important because the price difference between the butane types can vary significantly on a seasonal basis.
Late last year, Teppco representatives met with all its butane suppliers to complete plans for how the system was to be modified and how product was to be batched through certain receipt lines.
The project plan called for dedicated service lines for each product between Baytown and Mont Belvieu, and between Teppco's two terminals at Mont Belvieu.
The butane line running between Baytown and suppliers on the Houston Ship Channel is used as a batched, multiple-product line. It carries cycles of fluoride-free and higher-fluoride butane, in addition to isobutane.
Use of the multiple-product line requires close monitoring to keep the fluoride-free product isolated, says Bob McKnight, Teppco's manager of Gulf Coast LPG services.
Key to the segregation program is an on-line program to monitor the butane quality. This program includes gas chromatography to monitor the specific olefin and hydrocarbon content.
Teppco monitors fluorides, for which no on-line chromatographic capabilities exist, through a continuous sampling and testing program. This monitoring is performed at the Baytown and the two Mont Belvieu terminals.
Copyright 1993 Oil & Gas Journal. All Rights Reserved.
