|
Featured on the cover and as the lead
story in the April 1999 Pipeline & Gas Journal and December
1999 Pipeline & Gas Industry magazines: New system design
reduces project costs, shortens project schedule, simplifies
operation, and provides local municipal utility with economic
peak shaving supply.
Northstar Industries provides the only
cost efficient, premanufactured M & R, LNG, and Inline Heater
Replacement Modular Systems on the market today.
Staffed by professional ex-utility
engineers, Northstar offers innovative single and multi-building
stations to meet all your growing needs.
We're Hiring! New opportunities
at Northstar Industries.
Providing a Modular Systems Approach
To The Controls, Systems & Measurement Industry.
Northstar Completes Innovative LNG
Plant In Greenville, NC.
Typical sites we provide.
©1999 Northstar Industries, Inc.
Northstar Industries is a registered trademark of Northstar
Industries, Inc., Reg. U.S. Pat. and Tm. Off. The American Gas
Association is a registered salesmark of The American Gas
Association. All other trademarks are the property of their
respective owners.
|
Northstar Industries
is a Massachusetts based company specializing in
the premanufacturing of city gate stations,
LNG facilities, odorization, SCADA and
distributed power systems for natural gas,
industrial and power clients. Northstar's
staff is comprised of gas ex-utility managers and
workers teamed with professional engineers and
environmental scientists for approvals and
permitting (click on photo for
detail).
Northstar Industries
Provides Modular System Design To Bring LNG
Facility On Line.
The Greenville
Utilities Commission (GUC) is a municipal gas,
water, sewer, and steam company located in
Greenville, North Carolina. The Gas Department
serves 14,950 customers and has experienced a
130% growth since 1990 due to the positive
business environment and the fine quality of life
in the region. Historically, GUC's Gas Department
has relied on pipeline capacity from its supplier
.The price of this capacity is based upon a
demand charge and a commodity charge. The load
characteristics of GUC's gas system resulted in
very expensive peak volumes (click here to learn
more about LNG).
Greenville Utilities
had begun exploring several options. During the
1996-97 heating season, they conducted a pilot
project involving a portable LNG vaporization
unit. Based on that project's success, Greenville
Utilities decided to move ahead quickly with a
project to install a permanent satellite LNG
peakshaving facility. To economically meet the
peak day requirements of the 1997-98 peaking
season, the permanent facility would have to be
operational by November 1997.
According to Tom
Quine, Northstar's president, several steps
needed to occur in order to guarantee project
success. A project team was formed by GUC's
management to manage an extremely fast track
regulatory and insurance approval, finance,
siting, long-lead-time equipment
definition/procurement, design and construction
contractor management process (click on photo for
detail).
Also, GUC's Gas
Department's Operations personnel played a
significant role in the project's actual
construction and coordinating the local
contractors. Northstar's experiences in obtaining
siting permits, regulatory approval and working
with contractors experienced in LNG construction
proved to be invaluable constructing a satellite
LNG facility in eight months that meets all
of the regulatory requirements.
In March 1997, GUC
developed specifications for the LNG tanks with
assistance from various industry experts and
received the bids for the two tanks in April.
This step was necessary to take in advance of
consultant's selection to ensure the tanks would
arrive before November 1997. Of course, this put
more pressure on the consultant to design and
construct a facility with the tank design and
bids completed. In April 1997, GUC selected Northstar
Industries, Inc. for the project design,
procurement and construction management of the
project. To meet the deadline, Northstar provided
prefabricated skids for various portions of the
facility. Essentially it would be an 18-month
project condensed into an 8-month time-frame.
The LNG plant designed
by Northstar consists of five major modular
systems integrated into a total system. The
systems are as follows: storage, heating,
odorant, emergency and SCADA systems. These
systems are integrated to provide a plant that
can be operated with a minimum number of people
and remotely without compromising the safety of
the personnel (click on
photo for detail).
Two shop fabricated
55,000-gallon stainless-steel cryogenic storage
tanks were provided by Process Engineering Inc.,
Plaistow, New Hampshire. The majority of existing
factory fabricated LNG storage tanks in the
United States were manufactured by Process
Engineering in Plaistow, NH. Ken Paul of Process
Engineering has been a major participant in the
LNG industry since the 1960's. A six-sided,
precast, concrete building served as the basis
for most control equipment, and the boiler
system. It was pre-fitted with a major portion of
the control system and odorant system, and moved
to Greenville for final assembly and connection.
Outfitting the building ahead of time reduced
travel cost, reduced time on site, and helped
achieve an aggressive project schedule.
The vertical,
shell-and-tube vaporizer was provided by Henry
Bivens of Chicago Power & Process, Inc., and
has a peak hourly send-out rate of 500,000
standard cubic feet/hour.
Other components were
acquired from Flow Safe, Goddard, ACD, Fisher,
Teledyne-Laars and Worcester.
PECO Energy Co., West
Conshohoken, PA, was chosen to supply LNG.
Jack B. Kelley,
Amarillo, Texas, was selected to provide the
overland transportation. Nine deliveries of
approximately 90,000 gallons of LNG from
Pennsylvania had been received in mid-December
for the facility's initial fill. The first
vaporization took place one day later.
In the past, every
time the gas system exceeded this set limit they
were subjected to a penalty by the pipeline
supplier. The supplier recently installed a flow
controller on GUC's city gate stations that
mechanically limit Greenville's firm supply MDQ.
Greenville's current limit is 13,500 DT's/day.
LNG is making up the difference.
Project Economics
The economics of a
peakshaving plant are typically based upon
avoided pipeline demand charges along with a
component of avoided capital cost for some
alternative pipeline solution. Pipeline capacity
is commonly purchased for $1,000,000-$4,000,000
per year for each 10,000 dekatherms/day of
capacity. Small LNG peakshaving facilities can
typically be constructed for a one time capital
cost of $1,000,000-$4,000,000. The annual
carrying costs for these facilities are derived
from ($Financing + $O & M). If a $2,000,000
plant has an annual carrying cost of $300,000 per
year, and it can avoid $1,000,000 per year in
demand charges from the pipeline, then it is easy
to understand the economic justification of
peakshaving.
The economics of a
base-load facility are somewhat different. The
economics of base-load facilities are generally
driven by cost of the base-load LNG vapor as
compared to alternative fuels available. The
facilities can be installed at industrial sites
or a stand alone utility system. Many operators
are unaware of the great potential at the
industrial sites for volumes of sales. An
industrial customer running three shifts at 100
dekatherms per hour can use 800,000 dekatherms
per year of load. LNG can be produced for prices
of $3.00-$4.00 per dekatherm. Transport can
commonly cost between $.50-$2.00 depending on
travel time. The simplified cost per dekatherm of
vaporized LNG is now determined by ($Fuel Cost +
$Annual Financing + $Annual O & M + $ Annual
Profit) annual load.
Despite the fact that
the Greenville Utilities' project was
accelerated, Northstar's design has many unique
characteristics. The simple process design was
based upon the preheating designs utilized by
Northstar as well as the extensive vaporizer
replacement experience of the design team.
Codes and Standards
All systems have been
designed and constructed in accordance with the
following codes and standards:
- 49
CFR Part 193: Liquefied Natural Gas
Facilities: Federal Safety Standards
- NFPA
59A: Standard for the Production,
Storage, and Handling of Liquefied
Natural Gas (LNG)
- NCSBC:
North Carolina State Building Codes,
Volume I, General Construction, 1996
Edition with 1996/1997 Revisions.
- NCSBC:
North Carolina State Building Code,
Volume I-A Administration and Enforcement
Requirements, 1996 Edition.
System Description
The site plan and
process flow diagram illustrate the layout of
components, required distances and the input and
output of the new facility.
The site has two
double wall 55,000 gallon tanks that contain the
equivalent of approximately 8,250 dekatherms of
storage. These tanks will be normally operated at
85 psig. This pressure sufficiently overcomes the
50 psig distribution pressure downstream without
the use of a send-out pump. The tanks were
factory fabricated with liquid level indication,
pressure indication and the appropriate liquid
and vapor nozzles.
The tanks are located
within a containment system that is designed to
direct an LNG spill away and into a remote
concrete impoundment pit. The entire site 6 acre
facility is enclosed within a security fence with
vapor slats to contain the vapor from a design
spill. This arrangement minimizes site size and
minimizes the exclusion zones.
The site design was
faced with some challenges as well. Much of the
area surrounding the site is in a coastal flood
plain. Because of this and as a result of
requests from Greenville's insurance carrier,
Factory Mutual System, the control building,
storage tanks, access road and major equipment
were raised to be on foot above the 500-year
flood elevation. This required significant impact
on the site design, particularly regarding LNG
spill containment.
An LNG transport
unloading skid is provided with vapor and liquid
connections and pressure controls for top and
bottom fill of the tanks.
Vaporization is
located within the impoundment system. This
vertical shell and tube heat exchanger is
provided with a tube arrangement surrounded by a
single shell. The vaporizer is operated based on
flow control. The desired flow rate is obtained
by operating the LNG flow control valve. Liquid
differential is measured using an orifice plate
and the liquid flow rate is converted to Mcfh.
For example, 100 gpm = 500 MSCFH.
To raise or lower the
flow the operator need only change the desired
output. Pressure control will still remain as an
override. A pressure building heat exchanger
mounted on each tank, is designed and utilized to
maintain a desired pressure in the vapor space of
the tank which allows for transfer of fluid (click on photo for
detail).
Heat for the send-out
gas is supplied by water/glycol pumped from the
water/glycol heater room in the modular control
building containing three parallel units. A
water/glycol skid is located in the heater area.
The prefabricated skid had a stop/start panel as
well as valves, strainer, and expansion tank
built in. The water/glycol supply and return
lines, along with the gas send-out piping, are
carried from within the impoundment dike to the
building above ground on common pipe supports.
The two water/glycol pipes terminate in the
water/glycol heater room of the control building
and the gas send-out piping outlets into the
distribution system after odorization.
The NJEX odorant
system (located in the odorant room of the
modular control building), injects the requisite
levels required for detection in the State of
North Carolina. Fuel gas for the water/glycol
heaters (domestic gas) is taken from a tap on the
distribution system piping which is downstream of
the odorizer.
A single 21' x 63 '
monolithic concrete building has been located on
site. It is located outside the vapor fence. One
nonhazardous room contains the electrical motor
control center. Another nonhazardous room
contains the personal computer, rest-room,
control RTU and SCADA interface. A third room
contains the three glycol water heaters, pump
skid and pneumatic system for instrument air. A
fourth hazardous room contains the odorant
injection system and send-out piping.
The boil-off system is
designed as a back pressure regulator set for the
desired tank pressure which will vent the design
boil-off through the vaporizer and into the
distribution system.
A stainless steel
temperature safety valve is located prior to the
transition to carbon steel. This is the required
temperature shutdown valve for the plant. The
outlet of the vaporizer is all stainless steel,
up to the shutdown valve. This arrangement
effectively protects the downstream carbon steel
piping systems from gas temperatures above or
below their design rating which is not expected
to occur other than during an upset condition.
An ESD (Emergency Shut
Down) 50 foot valve on the outlet of each tank
can be operated remotely and locally with local
and remote indication of valve position. This
valve isolates the tanks from the downstream
piping and equipment.
Thermal radiation and
vapor dispersion analysis confirm the
acceptability of the final configuration.
Pipe supports are
constructed of reinforced concrete and stainless
steel to provide low maintenance cryogenic
supports.
A check valve prevents
a back-flow and a manual block on the discharge
will allow for total isolation of the
vaporization unit.
System control and
safety interlocks for the new system are
accomplished with a process controller. This
interlock logic control resides within the ROC
364, located on-site in the control building,
which is programmed to protect the plant
according to logic that has been developed in the
Interlock Logic Diagram.
In accord with the
future of such facilities, the Greenville
Utilities satellite facility can be operated
either locally, from GUC's Gas Department office
via its SCADA (Supervisory Control and Data
Acquisition) system. As the project was designed
for fail-safe automatic shutdown, the facility
only has to be manned for truck unloading. The
Greenville facility exceeds both the NFPA 59A
codes and the new DOT 193 requirements (click on photo for
detail).
Dry Instrument air is
provided by electric compression and drying with
dry nitrogen gas as a backup.
Pneumatic and electric
controls and electrical power conduits are run
from the control room and motor control center to
the heater and vaporizer areas on above-ground
supports.
All electrical
equipment is installed in accordance with the
area classification in which it operates.
A Factory Mutual
Approved fire and gas detection system, complete
with the requisite audible and visual alarms, is
installed in the vaporizer area, the water/glycol
heater area, truck loading, storage, and control
areas.
The perimeter security
system is comprised of microwave transmitters and
receivers connected to the SCADA system.
In summary, the
storage tanks receive liquid natural gas from
highway transports via the pump skid and store
the liquid to give a ready reserve of about eight
million cubic feet of natural gas.
When extra gas is
needed in the distribution main, liquid natural
gas is forced out of the tank toward the main by
a tank pressure created and/or maintained by a
pressure building coil, which is higher than main
pressure. En route to the main, the liquid is
evaporated and the resulting gas is warmed and
flows to distribution.
If either tank's
pressure approaches its safety valve setting, a
back-pressure regulator will open to allow a
small flow of vapor from the top of the tank to
the warming coil, and to the main, thus holding
tank pressure at a safe level without discharging
gas to the atmosphere. This operation will be
automatic at all seasons, manually shut off only
if a need for maintenance arises.
Project Impact
Greenville's current
MDQ is 13,500 Mdf/day from the pipeline at a
premium price. Their system load has grown beyond
the pipeline supply. LNG is making up the
difference.
With the growth in the
customer base, Greenville expects the reliance on
LNG to grow. Near term plans call for two more
55,000-gallon storage tanks and an additional
vaporization train.
Future planning is
being completed for a larger facility with
liquefaction.
The increased use of
LNG as long-term supply for peakshaving is
economically and financially justified above the
existing 13,500 dekatherm maximum daily quantity
(MDQ) of Greenville's firm gas supply contract,
and is projected to provide significant cost
savings to GUC's customers in future years.
The true success of
the project can be witnessed by the fact that the
operators can easily operate the new facility on
their own and reduce their cost of gas
significantly.
With the completion on
the project, ERG and Northstar Energy Corporation
continue their relationship with Greenville
Utilities in undertaking strategic planning work
for the future expansion of the facility and
other LNG-related projects.
|
