Pernis SGHP for Hydrogen and Power_Rev

The Shell Gasification Process for
Power and Hydrogen from Residue
at the
Pernis Refinery
The Netherlands
November, 1997
by the
Gasification and Hydrogen Manufacturing Department
of
Shell International Oil Products
Amsterdam, The Netherlands
The Shell Gasification Process for Power, Hydrogen and Steam from residue
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The Shell Gasification Process for Power, Hydrogen and Steam from residue
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Summary
The conversion of heavy oil residue from the Pernis Refinery into power and hydrogen
has been studied. Shell’s gasification technology converts 1650 tons per day of
residue into 285 t/d pure hydrogen and 117 MWe through IGCC. The combined power
and hydrogen yield is 79.7% on HHV.
Introduction
This publication is prepared by the Gasification and Hydrogen Manufacturing Department of
Shell International Oil Products, Amsterdam. The capabilities of Shell’s gasification
technology for the combined production of electric power and hydrogen are outlined. We
focused on the use of residue from the Pernis Refinery in The Netherlands.
The Shell Gasification Process
SGP is a mature process for converting a wide variety of hydrocarbon feedstocks, including
refinery residues, into clean synthesis gas (syngas) with minimum environmental impact. The
heaviest “bottom of the barrel’ that contains most of the sulphur and heavy metals present in
the crude is converted into syngas. It is a mixture of predominantly hydrogen and carbon
monoxide. The sulphur compounds present in the feed are converted into mainly hydrogen
sulphide that can be converted into saleable sulphur via CLAUS®/SCOT®. The ash present
in the feed is recovered in the Soot Ash Removal Unit (SARU) as a solid metal/ash product
suitable for metals recovery.
Shell’s experience in gasification dates back to the early 1950’s, when the first Shell
Gasification Process was commissioned with oil as feedstock. To date there are more than
150 SGP units licensed world wide. A grand total of 62 million Nm 3 /d CO+H 2 is currently
produced with Shell’s gasification technology. The experience gained from fuel oil and
residue gasification provided the practical base that enabled Shell to be in the forefront of
gasification technology today. In fact, all oil residues produced in refineries can be processed
with Shell’s gasification technology.
The latest developments and findings are incorporated in the Per+ refinery upgrading project
at Shell Pernis (Rotterdam). The combined production of power and hydrogen forms the
cornerstone of the new refinery configuration.
three SGP strings
two HRSG units
Power and hydrogen from residue with
Shell’s gasification technology as
cornerstone of the Per+ refinery
upgrading project at Shell Pernis
(Rotterdam, The Netherlands)
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Basics of the case study - Case study premises
The plant performance reported in this case study is based on a number of premises.
Plant configuration
String concept
Gas turbine type
Gas turbine NO x reduction system
Steam turbine type
Heat Recovery Steam Generator (HRSG)
Oxygen over the fence at gasification
pressure.
Nitrogen supply in-house
3 gasification strings
1 SARU
1 acid gas removal string
1 H 2 manufacturing string (HTS, LTS and
Methanation)
1 sulphur recovery system
2 gas turbines
2 steam turbines
General Electric type MS 6541 B
CO 2 dilution and steam injection
One topping turbine, one extraction/induction
condensing turbine
2 Single pressure HRSG’s with duct burner
Operation conditions/performance
Case study oil residue
Vacuum Flashed Cracked Residue
Power generation
117 [MWe] at full utilisation gas turbines
H 2 production 285 [t/d], purity 98.4 [vol% dry], pressure 47
bara
Oxygen purity
Steam cycle condenser pressure
Gas turbine inlet conditions
99.5 [vol%]
42 [mbar]
15 [ o C]; 1013.15 [mbar]; 65% humidity
Environmental targets
Total sulphur recovery > 99 [%]
NO x emission from gas turbine < 60 [ppm] at 15 vol% O 2
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Performance of the process
The configuration of the combined hydrogen and power production process is given in the
simplified flow scheme below.
electric power
flue
gas
electric power
steam
turbine
HRSG
gas
turbine
gas
conditioning
steam
hydrogen
residual
oil
gasification
O 2
Syngas
Cooler
water
wash
H2S
removal
HTS, LTS
CO shift
CO2
removal
methanation
ASU
over the fence
waste water
treatment
SARU
CLAUS/SCOT
air
waste
water
metals/
ash
sulphur
The residual Vacuum Flashed Cracked Residue (VFCR) enters the gasification preheat
section. The following composition was used:
Composition of residual
oil
wt% as
received
Carbon 83.73
Hydrogen 8.59
Nitrogen 0.50
Oxygen 0.30
Sulphur 6.80
Ash 0.08
Moisture 0.00
Total 100.00
HHV [kJ/kg] 39680
The throughput of the process for residual oil is determined by the required hydrogen (285 t/d
pure H 2 ) and power production (117 MWe). A total residual oil flow of 1650 t/d is needed to
meet this requirement. Today Shell’s gasification technology is applied on 23 sites
successfully processing a total of 20,000 t/d (residual) oil.
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The use of 99.5 vol% pure oxygen and intensive mixing of the reactants (preheated residual
oil, preheated oxygen and steam) creates the characteristic high temperature and turbulent
mass transfer conditions in the entrained flow gasifier. This results in rapid reactions and high
carbon conversion in short residence time.
The gasifier itself is a refractory lined vessel. The
gasifier burner is specially designed to ensure
proper atomisation of the oil and an intimate mixing
of the fuel with the oxygen. This is important for
efficient performance. Also steam is added to the
gasifier through the burner, which acts as a
temperature moderator. The term “partial oxidation”
is used to describe the net effect of various
reactions. It includes the exothermic combustion of
part of the oil to CO 2 and H 2 O and the endothermic
reactions of thermal cracking and steam reforming,
as well as a number of secondary reactions. The
net reaction:
2 CH n + O 2 2 CO + n H 2 (1 < n < 4)
is exothermic, producing a gas containing mainly
CO and H 2 . Depending on the composition of the
feedstock the raw syngas contains small quantities
of CO 2 , CH 4 , H 2 S, N 2 , Ar, etc. In addition a small
amount of soot is present.
The hot reactor effluent enters a specially designed
Syngas Cooler to produce high pressure steam, up
to 110 bars with high thermal efficiency. The raw
syngas leaves the Syngas Cooler at a temperature
approaching the steam temperature and further
heat recovery takes place in an Economiser.
gasifier
Syngas
Cooler
The raw syngas is sent to a water wash/scrubbing unit where soot and trace contaminants
like NH 3 and other water soluble and insoluble contaminants are removed.
The water wash produces a soot slurry. The soot slurry is processed in the Soot Ash
Removal Unit. The SARU was developed for gasification applications processing very viscous
refinery residues. The basic philosophy was off-line processing of soot, e.g. no soot/ash to be
recycled to the reactor and no blending of soot oil into feed as in conventional naphtha based
recovery systems.
The soot is removed from the slurry by filtration. The filter cake is then subjected to controlled
carbon burn off in two Multiple Hearth Furnaces. The ash components are recovered as metal
oxides for use in the metal industry. SARU is successful in operation at two SGP locations.
One of those is located in the Pernis Refinery, The Netherlands. The configuration of the
gasification-, syngas cooling-, and water wash section and SARU is given in the simplified
flow scheme below.
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residue
oxygen
steam
raw syngas
steam
Scrubber
Econ.
Quench
pipe
Reactor Syngas
Cooler
BFW
SARU
Separator
soot
slurry
return water
Slurry filtration
filter cake
Carbon burn off
SGP ash
The performance of the gasification and heat recovery is presented below:
Performance of the Gasification and heat recovery part with residual oil, Pernis
Refinery, The Netherlands
Residual oil input to gasification
Oxygen (99.5 vol%)/oil ratio
Steam/oil ratio
Gasification pressure
Oxygen purity
1650 [t/d]
0.95 [kg/kg]
0.5 [kg/kg]
65 [bara]
99.5 [vol%]
Raw syngas composition ex Scrubber [vol%, wet]
CO 49.4
H 2 43.5
N 2 0.1
CO 2 4.8
H 2 S 1.6
COS 0.1
CH 4 0.3
Ar 0.1
H 2 O 0.1
Total 100.0
Gasifier exit/Syngas Cooler inlet temperature
Raw syngas exit temperature heat recovery &
soot removal system
Steam pressure ex Syngas Cooler
Oil conversion to gaseous products
Soot production on oil
Gross heat recovery HP steam,
% energy in fuel
1300-1350 [°C]
40 [°C]
93 [bara]
99.0 [% wt/wt]
1.0 [% wt/wt
16.2 [% HHV]
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To achieve deep removal of sulphur components from the raw syngas, a methanol based
process (Rectisol®) is used. The characteristics of the syngas treating process are given
below.
Overview of the gas treating section
No of gas treating trains 1
Wet scrubbing
Process
water wash
Removed components soot, trace components, NH 3
Acid gas removal
Process
Solvent
Clean gas properties (wet)
Syngas make
Calorific value
Temperature
Pressure
Rectisol®
methanol
3678 [t/d]
14.9 [MJ/kg, HHV]
35 [°C]
55 [bara]
Clean syngas composition [vol%, wet]
CO 49.3
H 2 43.3
N 2 0.1
CO 2 6.8
CH 4 0.3
Ar 0.1
H 2 O 0.1
H 2 S
0.1 [ppm] (guaranteed)
Total 100.0
Auxiliary systems like the effluent water treating and the sulphur recovery units are designed
for the full plant capacity in single units. Sour off-gases from effluent water streams are
produced by stripping the net water bleed stream. The net water production is produced as
bleed in the wash water loop. These off-gases are combined with the sour off gas from the
acid gas removal regenerator system. Then, they are and sent to the sulphur recovery
system where saleable elemental sulphur is produced. Because of the requirements for
sulphur emissions the system consists of a CLAUS® and SCOT® plant supplemented by a
tail gas incinerator.
Summary on sulphur recovery section and effluent water treating
No. of sulphur recovery units 1
No. of effluent water treating units 1
Sulphur recovery system
Plant configuration
CLAUS® + SCOT® + Incinerator
Elemental sulphur produced
112 [t/d]
Sulphur recovery >99 [%]
Water treating system
Process water stripper 1
Water treating system 1
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Hydrogen production
Most of the clean syngas, i.e. about 67 vol% is used for hydrogen manufacturing for the new
hydrocracker. Steam is added for a one stage High Temperature Shift followed by a Low
Temperature Shift. The CO 2 is removed by the Rectisol® process after which the
methanation step removes the traces of CO and CO 2 left. The product is a hydrogen stream
of 98.4 vol% dry pure hydrogen with 285 t/d hydrogen contained. The hydrogen is generated
at a pressure of 46 bara. Pressure reduction can be applied, if necessary. For this plant LP
(refinery) fuel gas is used in the Heat Recovery Steam Generators as fuel for duct burners to
increase the steam make.
The remainder of the clean syngas is depressurised to turbine inlet pressure and used as
turbine fuel.
Power block
The combined cycle is based on two GE MS 6541B gas turbines and two steam turbines.
NO x emissions in the gas turbines is controlled by CO 2 and, if necessary, steam injection.
The Heat Recovery Steam Generator has one steam pressure level. It contains as main
components an Economiser, an evaporator and a superheater at high pressure. Further
condensate preheat for de-aeration is applied.
In the steam turbine configuration re-heat of the intermediate pressure steam is applied to
ensure a high thermal efficiency. The steam cycle condenser pressure is 42 mbar.
The high pressure saturated steam from the Syngas Cooler is superheated in the high
pressure part of the HRSG - steam turbine cycle
The reliability of the process is high as the gasifiers supply enough hydrogen for the
hydrocracker even when one gasifier is down. Full utilisation of the two gas turbines is arrived
by feeding LPG and natural gas as backup.
Main performance data of combined power and hydrogen production
The quality of the process can be expressed in terms of power+hydrogen yield,
heat/electricity ratio and overall thermal efficiency. The power+hydrogen yield is defined as
(E+F+G)/A × 100. The heat/electricity ratio is defined as (D+F+G+H)/(C+E) and the overall
thermal efficiency is defined as (C+D+E+F+G+H)/(A+B+C+D) All definitions are based on
HHV.
steam recycle D MW
Feed A MW
Utility B MW
IGCC
plant
Electricity E MW
Hydrogen F MW
Steam G MW
Sulphur H MW
Electricity C MW
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Energy balance and Efficiency
The energy balance has been made. The performance of the combined power and hydrogen
production for energy flows (HHV-based) is given in the simplified scheme below. It can be
seen that the overall yield on fuel is over 79%. In terms of overall thermal efficiency 78.4% is
achieved.
steam to SGP reactor
steam
flue gas
residual
oil
100%
clean gas
production
Heat Recovery Steam Generator
steam to CO shift
fuel gas
conditioning
flue gas
gas
turbines
steam
turbine
generator
O
S 2
air
ASU; over
the fence
H2
production
own consumption
hydrogen
64.3 %
electricity
15.4 %
Energy balance
Indicator in figure
Input
Oil 757.8 [MWth HHV] A
Utility 0 [MWth] B
Output
Hydrogen
487.3 [MWth HHV]
HPS steam for export
0 [MWth]
Sulphur 12.0 [MWth HHV] H
Power
Gas turbines
86.1 [MWe]
Steam turbines
40.4 [MWe]
Gross power generation 126.5 [MWe]
Internal consumption
HPS steam
Gasification
Shift
29.7 [MWth]
37.3 [MWth]
Total 67.0 [MWth] D
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Power
Gasification & miscellaneous 10 [MWe] C
Overall performance data of combined power and hydrogen production, Pernis
Refinery, The Netherlands
Oil residue intake
1650 [t/d]
757.8 [MWth HHV]
100.0 [% HHV]
Hydrogen production for export
285 [t/d contained]
98.4 vol% dry 487.3 [MW HHV] F
64.3 [% HHV]
Power production for export 116.5 [MWe] E
15.4 [% HHV]
HPS steam production for export 0 [MWth] G
Hydrogen+power yield 79.7 [% HHV] (E+F+G)/A × 100
Heat/Electricity ratio 4.5 (D+F+G+H)/(C+E)
Overall thermal efficiency 0.784 (C+D+E+F+G+H)/(A+B+C+D)
In relation to the scope of this case study a number of efficiency improvements can be
indicated. We could install for example multi pressure levels in the HRSG in stead of a single
pressure level, a lower steam condenser pressure, an expander to recover energy during
depressurisation of the syngas going to the gas turbines and a high pressure steam ex
CLAUS® in stead of LP steam.
Benefits of the Syngas Cooler
The Syngas Cooler produces High Pressure saturated steam of typically 93 bara. An
evaluation of the added value of the produced high pressure saturated steam that represents
16.2% of the HHV in residual oil has been made. The Pay Out Time of the Syngas Cooler is
less than 2 years, considering the cost of the Syngas Cooler, the additional steam turbine
capacity and a realistic electricity price. Plant experience demonstrates that the lifetime of the
Syngas Cooler internals is more than 10 years.
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Shell International Oil Products B.V. is prepared to arrange for the licensing of the gasification
and syngas treating technology and for the preparation and providing of the basic design
package and related services in connection with the licence.
Question and requests for further information related to the contents of this publication may
be addressed to:
Shell Research and Technology Centre, Amsterdam
Gasification and Hydrogen Manufacturing Department, OGTG
P.O. Box 38000
1030 BN Amsterdam
The Netherlands
Tel: (+31) 20 630 2656/2281
Fax: (+31) 20 630 3964
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