Case Study #2 233

Chapter 14

Case Study #2

T
his case study examines how two refineries discovered savings
within the processing plants by utilizing the waste heat en-
ergy from their gas turbines to increase refinery profitability.

BENEFITS OF INDUSTRIAL GAS TURBINES

FOR REFINERY SERVICES

Bo Svensson, ABB STAL, Finspong, Sweden

Henry Boerstling, ABB Power Generation Inc., North Brunswick, NJ

ABSTRACT

Asea Brown Boveri (ABB) supplied the industrial gas turbines

for cogeneration application in two refineries outside of Athens,
Greece. The Motor Oil Refinery in Corinth and the Hellenic Refinery
in Aspropyrgos are the basis for this paper. These two plants have
been in operation since 1985 and 1990, with a total of 140,000 and
55,000 operating hours, respectively. Topics discussed will include the
integration of cogeneration systems into the refinery operations, tech-
nical details of the cogeneration systems, their applicability to the
users’ specific needs, and the savings realized by the owners.

INTRODUCTION

For years, the oil and gas industry has targeted the well-heads
as the source for maximizing profit. Increasing petroleum exploration
and oil recovery projects around the world exemplify such pursuit.

©2003 by The Fairmont Press. All rights reserved.

 Today, with the maturing of the petro-chemical industry, the quest
for profit has been moving away from the oil and gas fields and into
every comer of the refinery processes.
Driven by a complex environment of regulation and profit moti-
vation, more and more refineries are discovering savings in forgotten
or overlooked areas within their processing plants. In a sense, the
quest is centering on how to use the by-product waste to increase
refinery profitability. The preferred solution is clearly in-plant cogen-
eration systems. The refinery cogen plants are providing savings to
the industry while satisfying growing environmental concerns.
Refinery requirements for electric power and heat are being met
with cogeneration systems consisting of one or more gas turbine-gen-
erators, Heat Recovery Steam Generators (HRSGs) which utilize the
gas turbine waste heat. The generated steam is being used either for
additional power generation and/or process heat for refinery applica-
tion. However, in the volatile climate in which the refineries operate,
the industry must tailor its products to market demand; thus the gas
turbine units must contend with varying types of fuel supply (from
liquid to gaseous, or both simultaneously) and quality (calorific value,
viscosity), as well as the changing electrical and process heat de-
mands throughout its process cycle. Often, this frequent and large
fuel fluctuation presents a major obstacle for better efficiency and
lower operating cost of the cogen system. However, these changing
parameters do not represent a problem for the GT35 and GT10 gas
turbines. The GT35 and GT10 units can utilize multiple fuels of
changing quality and calorific value, including the waste gases de-
rived from the refining process, for the gas turbine combustion pro-
cess. ABB has a sizable fleet of industrial gas turbines installed
throughout the world for refinery application. List of ABB’s petro-
chem applications are exhibited in Figure 14-1.
This paper discusses the benefits of two gas turbine installations
in Greek refineries utilizing the GT10 and GT35 units. These two
medium size gas turbines are ideally suited for industrial cogenera-
tion, because they are compact, heavy-duty industrial machines with
proven reliability and efficiency track-records for operations in harsh
environments.
These two industrial units have since been up-graded in both
performance and emission control. The GT10B is presently ISO rated
at 24.6 MW with a simple cycle Heat Rate of 9,970 Btu/kWh (LHV).

©2003 by The Fairmont Press. All rights reserved.

 Figure 14-1. ABB Gas Turbines for Petro-Chem Services.

Order
Year Customer Location Application
————————————————————————————————
GT35
1968 TPAQ Refinery Turkey Cogen
1977 ELF Norway Power Gen
1979 BP Raffinaderi AB Goeteborg, Sweden Cogen
1981 NPO Refinery Iraq PowerGen
1982 Motor Oil Hellas Corinth, Greece Cogen
1984 BP Development Ltd Ula, Norway Power Gen
1986 Finos Petroleos
De Angola Luanda, Angola PowerGen
1989 Shell Norske AS Draugen Field, Sweden Cogen
1990 Thai Taffeta Co Rayong, Thailand Cogen
1992/3 ESSO Refinery Thailand Cogen

GT10
1984 Imperial Chem
Industries Runcorn, GB Cogen
1986 Arcadian Corp Geismar, LA/USA Cogen
1988 Hellic Aspropyrgos
Refinery Aspropyrgos, Greece Cogen

GT8
1984 Vulcan Chemicals Geismar, LA/USA Combi/Cogen
1984 Shell Nederland
Raffinaderij Rotterdam/NL Cogen
1986 SUN Refinery Marcus Hook, PA/USA Cogen
1987 CHEVRON Refinery Richmond, WA/USA Cogen

GT13
1970 Chemische Werke Huels Huels, Germany Commbi/Cogen
————————————————————————————————

While the GT35 is ISO rated at 16.9 MW with a simple cycle Heat
Rate of 10,665 Btu/kWh (LHV). Both gas turbines are equipped with
ABB’s proprietary EV (Dry Low NOx) burners providing NOx emis-
sions of 25 ppmvd with natural gas fuel. The combustor with EV
burners is depicted in Figure 14-2.

©2003 by The Fairmont Press. All rights reserved.

 Figure 14-2.

REFINERY PROCESSES

The Corinth Motor Oil Refinery

The Motor Oil Refinery is located near Corinth, about one-hour
drive north of Athens along the coast. The refinery was installed in
1972. It is a medium size refinery complex with sophisticated conver-
sion units (i.e., fluid catalytic cracking, alkylation, isomerization, lube
oil processing units), and the traditional distillation, reforming and
hydrotreating units. Presently, the refinery processes 7,500,000 tons
of crude oil per year, and produces 150,000 tons/year of lubrication oil.

©2003 by The Fairmont Press. All rights reserved.

 The Motor Oil Refinery decided to install its own in-plant cogen-
eration plant in early 1980’s with the following objectives:

1. Energy conservation by utilizing the refinery flare gas (11,000

ton/year);
2. Increase refinery productivity by avoiding the costly process
shut-downs due to interruption of electrical power supply;
3. Increase refinery process steam availability and reliability by
utilizing the gas turbine exhaust energy;
4. Reduce refinery operating costs;
5. Reduce refinery pollution.

In 1985, the refinery cogeneration plant, consisting of two ABB

STAL GT35 Gas Turbine-Generator units, was placed in commercial
operation. The two gas turbines exhaust into a single two pressure
Heat Recovery Steam Generator (HRSG) with supplementary firing
capability. The combined electrical output of the two units is 27 MW
and a total 52 tons/hr of high pressure steam for power generation
and 16 tons/hr of low pressure process steam for refinery purposes.
The primary combustion fuel is refinery flare gas originating
from different refinery process streams as waste by-products. It con-
sists essentially of propane and butane in varying proportions rang-
ing from 60% to 100% propane, and 40% to 0% butane by volume.
This by-product flare gas also contains a varying concentration of
H2S, up to a maximum of 10,000 ppm. 20-25 ppm of H2S concentra-
tion is considered a highly corrosive environment for gas turbine ap-
plication. Because the GT35 operates at a low hot blade path tem-
perature profile (exhaust temperature of 710°F) which is below the
melting point of sulfur, it is not affected by the high temperature
corrosion phenomenon; thus making it an ideal machine for refinery
flare gas application.
The flare gas varies in qualities, pressures and temperatures.
Its heating value approximates that of natural gas, i.e. 1,145 Btu/scf.
The cogen plant back-up fuel is gasified LPG (liquefied petroleum
gas) with a heating value of 2,500 Btu/scf.
To use this flare gas for gas turbine combustion, it is initially de-
slugged by a liquid trap which separate the liquid phase from the gas
stream. It is then processed through a low pressure compressor. The
condensates from the compressed fuel gas is further removed by a

©2003 by The Fairmont Press. All rights reserved.

 gas-liquid separator. Finally, the combustion fuel gas is brought to a
pressure of 330 psia by a high pressure compressor. The fuel gas is
fed to the two gas turbines at a temperature of 203°F and pressure of
300 psia. Operating parameters of the cogeneration plant are shown
in Figure 14-3.

Figure 14-3. Corinth Motor Oil Company.

Corinth, Greece
GT35 Operating Parameters
————————————————————————————————
Gas Turbine Units 2 × GT35, ABB STAL
Initial Unit Output 11.5 MW @ 95°F
Up-Graded Unit Output 13.5 MW @ 95°F
Fuels Refinery Flare Gas/LPG
HRSG 1 × Supplementary
High Pres. Steam 52 tons/hr @ 683 psig/788°F
Low Pres. Steam 16 tons/hr @ 36 psig/280°F
————————————————————————————————

The Corinth Cogeneration Plant contributes to the refinery prof-

itability. First, it utilizes its by-product (cost-free) flare gases as the
primary combustion fuel for the gas turbines. By having its own co-
generation system, it dramatically improves the refinery profit profile
by eliminating the costly refinery downtime due to power outages
from the local power grid. The cogen plant also eliminates the ever-
present threat of electrical rate hikes. Lastly, the cogeneration plant
has reduced NOx emissions to an air quality well below the accept-
able limits imposed by the Authority. The cogen plant’s noise emis-
sion is 52 dBA at 400 feet. The cogen plant is viewed positively by the
Greek Authority in the battle against pollution.
The Corinth cogen plant has met all the objectives set by the
Refinery. The utilization of the refinery flare gas has resulted in an
accelerated pay back period for this cogen plant of 2.6 years. Accord-
ing to the Motor Oil Company, the net savings from the cogen plant
for 1992 were US $8,000,000. Profitability is shown in Figure 14-4.

Hellenic Aspropyrgos Refinery

The Hellenic Refinery is located in Aspropyrgos, Greece. It was
installed in 1958, with an initial through-put of 8,500,000 tons per

©2003 by The Fairmont Press. All rights reserved.

 year. This state-owned refinery has been modernized over the years
both in capacity output and plant efficiency.
The Refinery combined cycle/cogeneration plant was placed in
commercial operation on January 19, 1990. The cogeneration system
consists of two GT10 gas turbine-generator units, two dual pressure
Heat Recovery Steam Generators (HRSG) of forced circulation type
with by-pass stack, and one ABB condensing steam turbine-generator
unit. Saturated steam is also produced for general refinery purposes.
Figure 14-5 shows the general arrangement of the Aspropyrgos Co-
generation Plant.
The GT10 unit electrical output is limited to 17 MW per
Customer’s specification. The steam turbine-generator is rated at 15
MW. The combined electrical output of the cogeneration system is 49
MW. The generated high pressure steam of 612 psia/760°F from the
HRSGs operates the condensing steam turbine-generator set. Each
HRSG also produces 18,520 lbs/hr of low pressure steam at 68 psia/
342°F for refinery consumption.
Like the Corinth Motor Oil Refinery, the Aspropyrgos Cogenera-
tion Plant operates normally on refinery flare gas. The primary fuel
for the two GT10s has a heating value range of 18,360 Btu/lb to
23,580 Btu/lb; however, heating values of as high as 29,520 Btu/lb
has been recorded. The gas turbines are also capable of firing pro-
pane, diesel oil, and a mixture of the various refinery by-product gas
streams. The two GT10s start up on diesel oil.
Similar to the Motor Oil Refinery, the factors that motivates the
Hellenic Refinery to install its own in-plant electrical power and
steam plant are the high purchase price of the electrical power and
the unreliability of the local electrical power supply, coupled with the
need to improve refinery efficiency and plant profitability. Since its
commercial operation, the Aspropyrgos Refinery has retired several
gas fired heaters and boilers. The Refinery average electrical con-
sumption is 33,300 kW, and, it exports its excess electrical genera-
tion; thus further improves the Refinery profitability. Cogen plant
reliability has been close to 100% up to its first Major Inspection.
The first Major Inspection of the two GT10s was performed after
25,000 hours of operation (scheduled Major Inspection is 20,000 oper-
ating hours). Unit #2 was inspected and immediately returned to
service. More corrosion was found on Unit #1 then anticipated. It was
overhauled, the first two stages of turbine vanes and blades were

©2003 by The Fairmont Press. All rights reserved.

 Figure 14-4. Corinth Motor Oil Refinery, Corinth, Greece
——————————————————————————————————————————————————
1985 1986 1987 1988 1989 1990 1991 1992
Refinery Power Demand, MWh 156,507 210,028 213,754 211,493 212,424 216,327 223,703 222,074
——————————————————————————————————————————————————
Net In-Plant Power Generation, MWh 149,616 183,128 194,733 172,285 203,526 203,937 215,520 210,530

Purchase Power from Grid, MWh 6,891 26,900 19,021 39,208 8,898 12,390 8,183 11,544

Power Coverage by Cogen Plant, % 0.96 0.87 0.91 0.81 0.96 0.94 0.96 0.95
——————————————————————————————————————————————————
Availability of GTs, %
——————————————————————————————————————————————————
GT#1 90.8 97.8 98.6 78.0 95.4 97.9 99.4 98.2
——————————————————————————————————————————————————
GT#2 87.4 96.7 98.6 91.7 94.8 91.3 99.0 99.0
——————————————————————————————————————————————————
——————————————————————————————————————————————————
INCOMES (1000×$)
——————————————————————————————————————————————————
Saving In Energy Cost $8,019 $12,299 $14,738
——————————————————————————————————————————————————
Credit for Generated Steam $4,155 $2,152 $3,150
——————————————————————————————————————————————————

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 TOTAL SAVINGS $12,173 $14,450 $17,888
——————————————————————————————
TOTAL INVESTMENT IN 1984 US 18,000,000
——————————————————————————————
EXPENSES (1000x$) TOTAL REVENUE, '85-'87 US $20,944,500
——————————————————————————————
Additional Fuel Cost $8,182 $4,650 $6,744 PAYBACK PERIOD 2.6 Years
——————————————————————————————
Purchase Power Cost 353.2 1095.1 1311.4
——————————————————————————————————————————————————
Maintenance Costs
——————————————————————————————————————————————————
Materials 46.3 87 125
——————————————————————————————————————————————————
Labor 39 42 45
——————————————————————————————————————————————————
Personnel 251 276 320 Source: Corinth Motor Oil Refinery Co.
——————————————————————————————————————————————————
TOTAL EXPENSES 8871.4 6149.9 8545.7
——————————————————————————————————————————————————
——————————————————————————————————————————————————
×$)
GROSS REVENUE (1000× 3301.9 8300.2 9342.4
——————————————————————————————————————————————————

©2003 by The Fairmont Press. All rights reserved.

 Figure 14-5. Aspropyrgos GT10 Project.

©2003 by The Fairmont Press. All rights reserved.

 replaced and cracks in the combustor were field repaired.
It is necessary to point out that the two machines operate in a
very polluted environment. Traces of the lead, zinc and natrium were
found in the gas turbine compressors during the Major Inspection.
Furthermore, ABB Field Service personnel have observed, on occa-
sions, that implosion doors of the air inlet plenums were found to be
opened by operators during the plant operation. The subsequent met-
allurgical analysis of the damaged parts indicated that the rapid and
frequent change of fuel quality is also contributed to the damages and
cracks in the combustor.
The spare parts and maintenance cost of the two GT10 turbines
up to the first Major Inspection was US $140,000 for the two units
(for the first three years). For a total of 50,000 operating hours at a
combined output of 34,000 kW, this service cost comes to less than 0.2
mils/kWhr. The estimated total cost of parts and service of the Major
Inspection of Unit #2 was US $1,120,000; which is equivalent to 2.6
mils/kWhr.
Using the same pay back calculation technique that was em-
ployed in the Corinth Motor Oil Project, the pay back of the refinery
cogen plant is estimated at 3.5 years. Figure 14-6 describes the plant
operating characteristics.

Figure 14-6. Hellenic Aspropyrgos Refinery Aspropyrgos, Greece.

GT10 Combi/cogen Operating Parameters

————————————————————————————————
Gas Turbine Units 2 × GT10, ABB STAL
Unit Output 17 MW @ 95°F
Fuels Refinery Flare Gas/Propane/
Diesel Oil

Steam Turbine-Generator 15 MW, ABB Type WG1000

HRSG
High Pres. Steam 30 tons/hr @ 609 psia/770°F

Low Pres. Steam 65 tons/hr @ 55 psia/338°F

————————————————————————————————

©2003 by The Fairmont Press. All rights reserved.

 CONCLUSIONS

The maturing oil and gas industry is finding its refinery pro-
cesses and in-plant utilities to be rich sources of plant improvement
and profitability. Instead of the flaring the by-product waste gases, it
is now harnessing them to power the refinery electrical generation
and process steam production. In so doing, the refineries are becom-
ing more self-sufficient; thus achieving better plant reliability, lower-
ing refinery utility costs and increasing operating profit and improv-
ing the environment.

©2003 by The Fairmont Press. All rights reserved.