The recently completed $155-million expansion at Phoenix Park Gas Processors Ltd.'s Point Lisas, Trinidad, plant has nearly doubled inlet capacity and more than doubled capacities to produce, store, and export NGL (OGJ, Apr. 26, 1999, p. 30).
Moreover, says the company, the project realized a host of cost savings; among them:
- In the fractionation expansion, integrating the train and utilities saved $2.5 million (US), compared to original plans for an independent-train process in the expansion.
A revised plant layout, to reduce plot size and shorten pipe racks to new flare stacks, saved $1.5 million in capital cost and $24,000 annually in lease payments. - The new substation, still under construction, will reduce the plant's electricity rate (in $/kw-hr) by 40% by purchasing at a higher voltage.
- In the storage and export expansion, Phoenix Park used an alternate method of dredge disposal to reduce dredging costs by $750,000, and extended the jetty peninsula with excavated material to shorten jetty structure to the dock platform, reducing capital costs by $125,000.
The company also conducted additional pile tests to increase allowable piling load, reducing the gasoline tank foundation cost by $100,000. And Phoenix Park modified the tank outlet nozzle configuration, saving $75,000. - The Phase II expansion of the gas plant used a proprietary Ortloff process that reduced capital cost by $600,000 (through optimizing the heat exchanger configuration) and increased propane recovery by 2%.
The entire expansion was completed in only 14 months, says the company, 4 months ahead of schedule to take NGL from Atlantic LNG as soon as the liquefaction unit began operation.
Phoenix Park's expansion increased gas input capacity to 1.35 bcfd from 750 MMcfd and NGL production capacity to 33,500 b/d from 13,500 b/d. The company more than doubled NGL storage capacity, to 750,000 bbl, and added a second port, a deepwater terminal, for exporting NGL.
The entire expansion project consisted of the following:
- Expanding the inlet capacity of the plant along with the inlet-gas pipeline feeding the plant.
- Expanding the liquids fractionation, storage, and export capacities as well as installing a new NGL pipeline feeding the plant's liquids facilities.
- Upgrading by replacement of the plant's distributed control system (DCS).
Caribbean operations
Phoenix Park began operations slightly more than 8 years ago as one of the largest gas-processing plants in Latin America (OGJ, Oct. 28, 1991, p. 42): 650 MMcfd with 98% propane recovery.
Initially, company ownership consisted of the National Gas Co. of Trinidad & Tobago Ltd. (NGC) 49%, Conoco Inc. 41%, and Pan West Engineers & Constructors 10%. At the time of the latest expansion, however, NGC owned 51% and Conoco 39%.
In 1991, as now, unprocessed natural gas arrived, via a transmission system operated by NGC, from oil and gas fields offshore southeast Trinidad. It moved to Point Lisas, on the west side of the island, for processing, thence to industrial consumers.
Recovered NGL under the original scheme moved through a series of towers that recovered propane, butane, and a C5+ stream. Propane and butane moved into tank storage in anticipation of export through a marine terminal. The C5+ stream moved off site via pipeline sales.
Product storage under the initial design was in a 100,000-bbl, 100-ft diameter butane tank and a 150,000-bbl, 120-ft propane tank.
Before the recent expansion, a 1-mile, 10-in. insulated product line connected the plant with the LPG-loading terminal and loading dock built in the Gulf of Paria.
Initially, the dock could handle ocean-going LPG tankers of up to 70 m x 154 m.
Initial inlet capacity of 650 MMcfd was increased in 1996 to 750 MMcfd in response to increased gas demand by energy-based industries on Trinidad.
The modifications for this expansion fell into three categories: increasing gas processing capacity, increasing liquid recovery, and effecting several operational improvements.
NGL recovery at the plant continued to use Pan West's proprietary process. Construction began in June 1995 with commissioning of the plant occurring in January 1996.
Other major work at the plant has included installation of a 150,000-bbl C5+ storage tank (118 ft x 78.4 ft), supplied by Pitt-Des Moines Inc., Pittsburgh.
The tank was made convertible to butane storage and commissioned in July 1994.
Later, to handle rich gas from the Soldado fields, operated by Petroleum Co. of Trinidad & Tobago (Petrotrin) and Texaco, on southwestern side of the island, Phoenix Park added a compressor station within the plant fence.
Installed were three Ariel JGK/4 compressors, rated at 17.1 MMcfd each and driven by three Caterpillar 3606 TQ engines, rated at 2,400 hp each.
The compressor station project was designed for 42 MMcfd of wet gas and was commissioned in October 1995.
Fig. 1 presents an overview of the plant with major areas identified.
Inlet, processing expansion
To bring increased natural gas production and to feed increased capacity of the Phoenix Park plant, a new 1-mile, 48-in. inlet pipeline was installed from Phoenix Park's valve station at the interconnection with NGC's 30-in. line.
Line pipe was supplied by Europipe GMBH, Ratigen, Germany; engineering and procurement were by Mustang Engineering Inc. and Conoco, Houston.
In addition, existing facilities at the interconnect were modified to segregate low-yield dry gas and allow it to by-pass the plant en route to distribution by NGC in the more populated northwestern part of Trinidad.
Pipe-spool fabrication took place in December 1998 and January 1999 by Weldfab Ltd., Claxton Bay, Trinidad, and in December 1998 through March 1999, Harbert International Establishment SA, Brimingham, Ala., installed the 48-in. pipeline.
The new pipeline allowed increased volumes of feed gas to the 600 MMscfd additional cryogenic processing capacity installed to complement the existing 750-MMscfd plant.
Phoenix Park says the new train uses the Ortloff Improved Overhead Recycle process scheme to recover 98.6% of the propane (design) from the gas stream with little external energy utilization (refrigeration or gas compression) and 100% of the butane and natural gasoline (design).
Fig. 2 identifies and dates the stages in the plant's evolution.
Improvements and optimizations to the base process design during detailed engineering saved more than $1.2 million in equipment cost and reduced construction time.
This included savings in regeneration compression, in negotiation of a contract with the Black & Veatch-Tarmac joint venture saving time and cost in the bidding process, and in the schedule effects of having two separate major contractors on the same site.
Also as part of the expansion project, Phoenix Park installed a new 15.9 MMbtu/hr regeneration gas heater to supply dehydration regeneration for the new plant and parallel inlet and residue piping and metering facilities for the new train.
Major equipment includes three dehydrators (Beard Industries, Shreveport, La.), each 162 in. ID x 20 ft; a cryogenic absorber tower, 102 in. (ID) x 114 ft; a stripper tower (McIver and Smith, Houston), 198 in. (ID) x 58 ft; a 5,400-hp expander-compressor (Mafi Trench Corp., Santa Maria, Calif.); and a 108 MMbtu/hr gas-gas exchanger (Altec, LaCrosse, Wis.).
Overall EPC contractor was a joint venture between Black & Veatch Pritchard Inc., Overland Park, Kan., and Tarmac Construction (Caribbean) Ltd., Couva, Trinidad. The two companies split duties for primary engineering-procurement contractor (Black & Veatch) and primary field construction contractor (Tarmac).
Field construction began in February 1998 and was completed by Mar. 26, 1999, when commissioning began.
Liquids handling, processing
As significant as the inlet processing-plant expansion is the expansion of Phoenix Park's fractionation facilities. This was undertaken to take advantage of increased liquids yield from the increased gas throughput and to accommodate increased liquids feed from the newly built Atlantic LNG plant at Point Fortin.
That plant started up operations in January 1999 (OGJ, Apr. 26, 1999, p. 30).
To feed liquids from the LNG plant to the new fractionation facilities, Phoenix Park installed a new 8-in., 35-mile pipeline, together with metering at Point Fortin. Initial throughput is 12,000 b/d, which can be increased to 25,000 b/d to accommodate planned future expansion of the Atlantic LNG facilities (OGJ, Aug. 9, 1999, p. 24).
The line was fusion-bonded epoxy coated; 80% of the line pipe is 0.250-in. WT, 15% is 0.312-in. WT, and 5% is 0.375-in. WT.
Main engineering contractor on the NGL pipeline was TI Energy, Houston; the line was installed by Brown & Root Murphy LLC, Houston; and Conoco Inc. was in charge of procurement. Geneva Steel, Provo, Utah, supplied the line pipe.
The line was installed February-September 1998; commissioning was completed in March 1999.
Gene Morrison, Phoenix Park's general project manager, says construction of the line required a great deal of directional boring and drilling through environmentally sensitive swampy areas. He says the line is typically buried to 4 ft, but in some areas burial goes as deep as 5 ft.
At the plant, NGL fractionation increased by 20,000 b/d to 33,500 b/d with design production set at 16,500 b/d propane; 9,000 b/d butane, and 8,000 b/d natural gasoline (C5+).
Design recoveries are:
- Propane: 2% ethane and CO2; and 2.5% C4+.
- Butane: 3% propane in iso-butane; 2% C5+.
- Natural gasoline: 2% butane.
The fractionation scheme for the plant is a conventional, three-tower distillation process.
To achieve these figures, Phoenix Park added the new 8-in. pipeline, as discussed, a new depropanizer (102 in. x 120 in. x 120 ft); three NGL surge bullets of 90,000 gal each; a 7.1 MMbtu/hr product chiller; 1,800 hp of refrigeration compression; a 38 MMbtu/hr hot-oil system; and a new process flare.
The revised process includes two flares designed to be smokeless by use of air-assisted combustion. Both flares (LPG and process) have air blowers at the base of the stacks to supply the air assist.
Also, the company converted the existing depropanizer into a debutanizer.
Referring to the economies wrung during the design and construction phases, Morrison says, for example, "We went from early planned 60 days shutdown [to make necessary connections and tie ins] to 42 days then to 18 days. Once we started the shutdown, we saw that, through cooperation of contractors, we were able to reduce that to 14 days."
As stated, the main overall contractor was a joint effort of Black & Veatch Pritchard and Tarmac.
Phoenix Park identified major equipment suppliers as McIver & Smith for the depropanizer; Beard Industries, for the surge bullets; Smithco Engineering Inc., Tulsa, for the refrigeration coolers, depropanizer condenser, and C5+ product cooler; Energy Exchanger Co., Tulsa, for the refrigeration compression economizers; Gas Packagers Inc., Denver, for the refrigeration compressors, along with T. H. Russell Co., Tulsa, and Afton Pumps Inc., Houston.
To accommodate the increased liquids production, new storage tanks were added and the export capacities of the existing dock expanded.
Storage was expanded to total 750,000 bbl: butane, 150,000 bbl (converted from C5+ storage); propane, 250,000 bbl (including conversion of 100,000 bbl butane storage); and natural gasoline, new 350,000-bbl tank.
Bhim Roopnarine, Phoenix Park's superintendent for instrumentation and electrical, says the challenge of operating during construction "was to keep the [tanks' product] inventories as low as possible before the shutdown period so that as little product as possible was in the tanks during conversion."
Product loading rates were increased as well. At the existing dock, product can be loaded at 5,000 bbl/hr; at the new deepwater dock, at 10,000 bbl/hr. The new deepwater port was needed to accommodate larger vessels and thus the trebled amount of NGL being produced for load out.
The new 350,000-bbl C5+ storage tank was built by CBI Co. Ltd., Houston.
Construction began in late 1997; new storage and offloading facilities were commissioned by December 1998; and final tie-ins to the plant were made in January 1999.
Table 1 presents recent history of NGL shipments.
DCS upgrade
Looking ahead to future plant expansions, the company decided to upgrade the plant's distributed control system (DCS), selecting Honeywell's Total Plant Solutions (TPS), says Roopnarine and Keith Ridgway, lead instrumentation engineer for the project.
Phoenix Park says it selected this product based on the system's ability to be expanded and the ease of future upgrading. Another key was the system's ability to interface with third-party devices (that is, programmable logic controllers-PLCs, process analyzers, electric power systems, motor-protection relays, and flow computers) and to bridge process information from operations to administration.
TPS included Honeywell fail-safe controllers, the new vintage global user stations, and a process-history database. The software prioritizes the most important loops of the process. The fail-safe controllers manage shutdown functions.
The operating system used in the distributed control system, Windows NT, is compatible with Phoenix Park's administration operating system. This system provides process information for reports by use of spreadsheets and other administration network tools.
The control system uses serial communication links to interface with the various third-party devices mentioned earlier.
The control equipment was assembled in prefabricated buildings. This provided the opportunity fully to test the control system before shipment to site. After installation of the buildings at site with the tested system, field cabling was routed from the end devices to the control equipment and then connected to the plant control room via fiberoptic cable.
Redundant fiberoptic cable provides process data from the remote input/output units at each of the two export loading facilities, a couple of miles from the central control room.
Control functions for the process equipment are distributed to the process equipment itself. Allan-Bradley 504 PLCs control such packaged equipment as the refrigeration compressors, heaters, and turboexpander. Process measurement functions are distributed to the Omni 6000 flow computers.
The NGL pipeline metering station 34 miles from the Phoenix Park plant is controlled by a Modicon system with dedicated communication links to the Honeywell control system.
The transfer of 1,250 points from the plant's existing control system to the new Honeywell DCS system was accomplished by a "hot cutover" process. This allows the plant to stay on line during the conversion.
This hot cutover process was completed in October 1998, a month ahead of the scheduled completion, and required 5 months.
The expanded fractionation, storage, and export facilities added 750 points, and the Phase II gas processing plant added approximately 400 points to the system for a total of nearly 2,400 input/output points.
