The Dominion Cove Point LNG Terminal on the western shore of the Chesapeake Bay in Maryland, US, has been in existence for approximately 40 years. Since its reactivation in 2003, it has been ready to accept LNG from around the world, regasify it and deliver it to hungry US markets. Then the unexpected happened.
The birth of large natural gas shale plays in the eastern US, brought about by advanced drilling technologies, changed the economic equation for LNG very quickly. The US Energy Information Administration (EIA) reports that there was no natural gas flowing from the Marcellus five years ago. Today, Marcellus produces approximately 13 billion ft3/d and production is climbing. In fact, the EIA expects supply to exceed US demand in 2016.
This abundant supply and eventual surplus has lowered the price of US natural gas to between US$ 3 and US$ 5 per million ft3, depending on seasons and peak demand periods.
So instead of approximately 85 import vessels arriving at Cove Point each year to drop off their LNG, the facility receives a few ships each year with only enough LNG to maintain the availability of the facility.
Dominion Resources, one of America’s largest energy companies and owner-operator of the Dominion Cove Point LNG Terminal, saw all of this as an opportunity. During its January 2011 quarterly report to its investment community, Dominion Chairman Thomas F. Farrell II said that the company was considering adding export capabilities at Cove Point.
The advantages were obvious. The Cove Point LNG Terminal already existed with storage tanks, piping systems, a pier to accept ships and skilled employees. In 2009, Dominion increased the capacity of the pipeline, added new storage tanks, and, in 2011, updated the offshore pier so it could handle the larger, modern tankers. Ship capacity rose from 148 000 m3 to 267 000 m3.
Furthermore, the 47-mile transmission pipeline loop that was built during the expansion to take regasified LNG to the interstate natural gas pipeline system already connected the facility to other interstate pipelines and could be converted to deliver surplus natural gas to Cove Point for liquefaction and export.
So in June 2012, Dominion notified the US Federal Energy Regulatory Commission (FERC) that it would seek to add a liquefaction and export facility at Cove Point, at an estimated cost of US$ 3.4 billion - US$ 3.8 billion. By 2013, the US Department of Energy (DOE) had approved the export of LNG from Cove Point to countries with and without Free Trade Agreements (FTAs) with the US. The company is awaiting the FERC’s decision and permits and approvals from about 50 other agencies. Construction is scheduled to start by mid-2014 and the terminal is expected to begin operating in 2017, pending all approvals.
The challenge for the Dominion Cove Point project was to engineer and build a large train of liquefaction capability within the footprint of the facility’s 131-acre industrial boundary and not encroach on a surrounding 800-acre conservation easement with the Sierra Club and the Maryland Conservation Council, a local environmental organisation. Only 69 acres within the existing footprint were available for development. Dominion also had to ensure that it could still import LNG to meet the terms of existing contracts.
Dominion awarded the engineering, procurement and construction (EPC) contract to IHI/Kiewit Cove Point, a joint venture between IHI E&C International Corp. of Houston and Kiewit Corp. of Omaha, Nebraska, following completion of the front-end engineering and design work.
The key pieces of the export puzzle include:
- A liquefaction train.
- A process that incorporates gas turbines to drive the refrigeration compressors to liquefy the natural gas.
- A power block utilising waste heat recovery on the refrigeration gas turbines to help produce steam to power two steam turbine generators to make electricity for the facility.
- Pre-treatment operations to remove water and other trace impurities from the pipeline-quality natural gas that will arrive at Cove Point.
- Incorporation of dry cooling and water recycling to minimise water use.
- Utilising a state-of-the-art Zero Liquid Discharge (ZLD) system to eliminate process water discharges from the plant.
- Offsite areas for large equipment arrival, lay-down yard and parking for approximately 1500 workers (average at peak).
Dominion Cove Point will consist of a large LNG train. The base LNG production capacity of the designed facility is 5.25 million tpa, based on conservative assumptions regarding ambient air temperatures, the quality of gas received at the LNG terminal and a design margin used for equipment and pipe size selections.
However, a review of production capability for global liquefaction plants shows that actual capacity will exceed design capacity by as much as 10%. So Dominion has filed for authorisation for production capacity of up to 5.75 million tpa.
Dominion selected the Air Products split-C3/MR process as its liquefaction technology. The process utilises refrigeration to chill the natural gas and produce LNG; it uses a propane pre-cooling system, a mixed-refrigerant refrigeration system and Air Products’ proprietary spiral-wound main cryogenic heat exchanger. The liquefaction train will be composed of two parallel and identical refrigeration compressor strings, each driven by a gas turbine assisted by a helper motor. Each compressor string will be composed of a propane compressor, a low pressure mixed refrigerant (MR) compressor, a medium pressure MR compressor and a high pressure MR compressor.
The capacity of the facility is fully subscribed, with signed 20-year terminal service agreements. Pacific Summit Energy LLC, a US affiliate of Japanese trading company Sumitomo Corp., and GAIL Global (USA) LNG LLC, a US affiliate of GAIL (India) Ltd., each have contracts for half of the marketed capacity of 770 million ft3/d.
Dominion Cove Point will use two General Electric (GE) Frame 7 EA natural gas-fired turbines to drive the main refrigeration compressors to get the natural gas to -260°F and liquefy it in the main cryogenic exchanger. Each gas turbine will drive mixed refrigerant compressors and a propane compressor.
Current load calculations indicate that approximately 80 MW of electrical power will be needed for the liquefaction facility. This will be provided by two 65 MW steam turbine generators, which will utilise the waste heat from the natural gas-fired turbines that are used to compress the natural gas to produce steam and generate electricity. Cove Point generates its own electrical power today and is not connected to the transmission grid.
Dry cooling and water recycling will be used to minimise the amount of water that is needed for the facility processes. These cooling and recycling processes are a necessary part of the state-of-the-art ZLD system, which concentrates the few impurities in the facility’s well water in a crystalliser and removes most of the remaining water. The removed water is recycled back into the purification process.
Pre-treatment of natural gas
Equipment will be installed to remove water and other trace impurities from the natural gas supply stream. These impurities have corrosive potential and could crystallise during the liquefaction process. Pre-treatment will include the following components:
- Inlet gas receiving and metering to pre-heat the feed gas, control its pressure and meter the flow.
- Two parallel mercury removal beds to remove any potential mercury in the feed gas to protect the aluminium heat exchangers in the liquefaction process.
- Acid gas removal unit to extract essentially all carbon dioxide and hydrogen sulfide.
- Dehydration unit to reduce water content of the feed gas to 1 ppmv.
- Heavy hydrocarbon unit will extract the heavier hydrocarbons.
Offsite areas for lay-down yards and workers
At the peak of the 2009 expansion activities, approximately 750 construction workers were on site and they drove to the terminal. Pending approval, the liquefaction and export facility work will require thousands of jobs over a three-year period, with about 1500 at peak, plus 50 - 75 workers involved in support activities at offsite equipment lay-down yards. Labour representatives have estimated that 50 - 60% of the required workforce that currently commutes outside the region for work is expected to stay closer to home to work on this project instead.
To reduce local traffic impacts, construction workers will park 1.6 miles from the terminal and will take shuttle buses to the job site. Turning lanes and traffic lights are being added to existing intersections to ensure safe and efficient vehicle travel. A lay-down yard will also be built at the offsite parking location. Larger equipment will be barged to another offsite area on the Patuxent River from where it will be loaded and moved 6.3 miles to the terminal construction site during the night to reduce further impacts to traffic.
Upon its projected completion in 2017, the Dominion Cove Point LNG Terminal will be an import-export facility with an unparalleled environmental footprint – within today’s fence line, with low air emissions meeting strict federal and state regulations, with waste heat from its natural gas-fired turbines generating electricity via a steam turbine and all within an 800-acre conservation easement.
The full version of this article is available in the April issue of LNG Industry.
Written by Diane Leopold. Adapted to house style by Ted Monroe
Read the article online at: https://www.lngindustry.com/liquefaction/21042014/diane_leopold_looks_at_the_dominion_cove_point_lng_terminal/