10481-BCL-AKSX-PR-REP-0001-A0
NNPC
Nigerian National Petroleum Corporation
Ajaokuta Kaduna Kano
Gas Pipeline Project
PROCESS DESIGN BASIS
06-01-2021
Project Management Consultant
EPC Contractor
BRENTEXCPP Limited
Ajaokuta Kaduna Kano Gas Pipeline Project
10481-BCL-AKSX-PR-REP-0001-A0
PROCESS DESIGN BASIS
REVISION
A0
06-01-2021
5
01-11-2020
4
13-08-2020
3
18-07-2020
2
10-06-2020
1
AFC – Approved for Construction
Prateek
Sheikh
Luo Yexin
Prateek
Sheikh
Luo Yexin
Prateek
Sheikh
Luo Yexin
Nadeem
Sheikh
Luo Yexin
IFA - Issued for Approval
Shakeel
Sheikh
Luo Yexin
06-05-2020
IFR - Issued for Review
Shadab
Sheikh
Luo Yexin
0
22-03-2020
IFR - Issued for Review
Shakeel
Sheikh
Luo Yexin
Rev.
Date
Status Description
Originator
Checked
Approved
IFC - Issued for Construction
IFC - Issued for Construction
IFA - Issued for Approval
10481-BCL-AKSX-PR-REP-0001_A0_AFC_Process Design Basis
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TABLE OF CONTENTS
1
GENERAL
7
2
PURPOSE
7
3
DEFINITIONS AND ABBREVIATIONS
8
3.1
Definitions
8
3.2
Abbreviations
8
3.3
Referenced Documents
10
3.4
Metric System Used
12
3.5
Codes and Standards
14
4
5.0
6.0
OVERVIEW OF THE AKK PIPELINE SYSTEM
16
4.1
Key System Requirements
16
4.1.1
Early Gas Phase
16
4.1.2
Phase 1
16
4.1.3
Phase 2
16
4.2
Pipelines
17
4.3
Block Valve Station
17
4.4
Pigging Stations
18
4.5
Terminal Gas Stations
18
4.6
Design Life
18
4.7
Project Battery Limits
18
4.8
Environmental Conditions
19
4.7.1
20
Reference Conditions
PROCESS DESIGN DATA
22
5.1
AKK pipeline sections design conditions
22
5.2
Gas Composition
23
5.3
Gas Properties
27
5.4
Gas Flow Rates
28
5.5
Battery Limit Conditions
29
PROCESS DESCRIPTION FOR SOW
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30
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PROCESS DESIGN BASIS
7.0
INSTALLATIONS AT OFF-TAKE GAS METERING STATION
31
8.0
PROCESS AND MECHANICAL EQUIPMENT
32
8.1
Pig Launcher and Receiver
32
8.2
Filter Separator
32
8.3
Line Heaters
34
8.4
Gas Metering and Control Package (PCV)
34
9.0
PROCESS UTILITY SYSTEMS
37
9.1
Vent System
37
9.1.1
Piping System
37
9.1.2
Knock Out Drum
38
9.1.3
KO Drum Level Control System
38
9.1.4
Cold Vent Stack
38
9.1.5
Vent Gas Metering System
39
9.2
Fuel Gas System
39
9.3
Compressed Air System
40
9.4
Nitrogen System
41
9.5
Gas Engine Generator
41
9.6
Diesel Fuel System
42
9.7
Diesel Generator
42
9.8
Utility Water System
43
9.8.1
Pipes
43
9.8.2
Water wells
43
9.8.3
Submersible pumps
43
9.8.4
Raw water tank
43
9.8.5
Potable water treatment unit
43
9.8.6
Disinfection units
44
9.8.7
Potable water tanks
44
9.8.8
Pump units (booster unit)
44
9.9
Closed Drain System
9.10 Open Drain System
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46
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10.0
11.0
9.10.1 Pipes
47
9.10.2 Oil water separators
47
9.11 Simulations
47
KADUNA & KANO FACILITIES DESIGN BASIS
48
10.1 Criteria for sizing of station piping
48
10.2 Criteria for orifice meter sizing
48
10.3 Criteria for Relief System Sizing
49
10.3.1 Relief causes
49
10.3.2 General Design Criteria
49
10.3.3 Emergency isolation and blowdown system
51
10.3.4 Manual depressurization
51
HOLD LIST
52
FIGURES
Figure 1
AKK (Segment 2) Overall Pipeline Route
Figure 2
AKK Section Overview Map
Figure 3
Project Overview Map
Figure 4
Block Flow Diagram for AKK Pipeline (Segment 2)
TABLES
Table 1
Units of Measurement
Table 2
List of applicable Codes and Standards
Table 3
Pipelines of the AKK Section within the AKK pipeline system [Ref 2]
Table 4
Block Valves of Pipeline Section within the TNGP System [Ref 27]
Table 5
Location of Pigging Stations [Ref 27]
Table 6
Location of Terminal Gas Stations [Ref 27]
Table 7
Environmental Conditions for the AKK Project area [Ref 2, 28]
Table 8
Pipelines operating and design conditions
Table 9
Specification for Eastern Gas Supply System [Ref 2]
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Table 10
West African Gas pipeline (WAGP) Specification [Ref 2]
Table 11
OB3 Pipeline Gas Composition [Ref 2]
Table 12
Gas composition at Ikot Abasi Metering station [Ref 2]
Table 13
Gas Composition at Ikot Abasi Metering Station (Thermochemistry) [Ref 2]
Table 14
Gas specification and composition used for simulations. [Ref 2]
Table 15
Trans Nigeria Gas Pipeline Project gas properties [Ref 2]
Table 16
Summary of Gas volumes supplied withdrawn
Table 17
Trans Nigeria Gas Pipeline Project pressure requirements at battery limit [Ref 4]
Table 18
Design conditions for Pig Launcher and Receiver
Table 19
Filter Separator Separation Efficiency - Kaduna & Kano TGS [Ref 14, 15]
Table 20
Filter Separator Design Conditions- Kaduna & Kano TGS [Ref 14, 15]
Table 21
Line Heater Design Conditions – Kaduna & Kano TGS
Table 22
Gas Metering and Control Skid Design conditions- Kaduna & Kano TGS
Table 23
Vent System Design Conditions
Table 24
Fuel Gas System Design Conditions
Table 25
Compressed Air System Design Conditions
Table 26
Inlet Oil water parameters
Table 26
Design Requirements for Station piping
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1
GENERAL
The Nigerian National Petroleum Corporation (NNPC), hereby referred to as the OWNER
has awarded the contract to Brentex CPP Limited for the Engineering, Procurement and
Construction of Ajaokuta Kaduna Kano (AKK) Gas Pipeline and Stations Project (Segment
2) from Block Valve Station 12 (outer line of the fence) to Kano Terminal Gas Station with
a distance of about 318.66 km of the Trans Nigeria Gas Pipeline and stations. The pipeline
runs from BVS12 roughly northern towards Kano TGS as illustrated in Figure 1 below:
Figure 1
AKK (Segment 2) Overall Pipeline Route
This document covers the technical requirements for engineering works and services, including all items such as pipelines, crossings, stations, BVS, ancillary installations, temporary installations, etc.
2
PURPOSE
The purpose of the document is to provide the basis for developing the process deliverables for the AKK (Kaduna to Kano Section) scope of work. The scope of work is limited to
KADUNA and KANO TGS stations along with the pipeline section from Block Valve Station 12 (outer line of the fence) to Kano Terminal Gas Station with a distance about
318.66km of the Trans Nigeria Gas Pipeline and stations. Therefore, this document will
contain the design basis for KADUNA and KANO stations TGS facilities and pipeline. In
addition to the requirement specified in this document, the relevant statutory authority
requirements must be observed wherever applicable.
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3
DEFINITIONS AND ABBREVIATIONS
3.1
Definitions
3.2
PROJECT
Ajaokuta Kaduna Kano Gas Pipeline Project.
OWNER
Nigerian National Petroleum Corporation (NNPC).
PMC
NETCO-ILF Consortium.
CONTRACTOR
Brentex CPP Limited.
SUBCONTRACTOR
The party(s) which carries out all or part of the engineering,
design, survey and geotechnical investigation as specified by
the CONTRACTOR.
SUPPLIER
The company or factory that designs and manufactures the
Equipment and provides it to the OWNER of this Project.
SUB-SUPPLIER
The company or factory that subcontracts the design and
manufacture of the equipment and provides to SUPPLIER for
this Project.
Shall
Indicates a mandatory requirement.
Should
Indicates a strong recommendation.
Abbreviations
AG
Above Ground
AKK
Ajaokuta – Kaduna – Kano
API
American Petroleum Institute
bara
Absolute pressure in bar
barg
Gauge pressure in bar
BDV
Blowdown Valve
BL
Battery Limit
BVS
Block Valve Station
CCR
Central Control Room
CS
Compressor Station
DP
Design Pressure
DPR
Department of Petroleum Resources
EIA
Environment Impact Assessment
EGP
Early Gas Phase
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ELPS
Escravos-Lagos Pipeline System
EPC
Engineering, Procurement and Construction
ESD
Emergency Shutdown
F&G
Fire and Gas
FCV
Flow Control Valve
FOC
Fiber Optic Cable
FEED
Front End Engineering and Design
GA
General Arrangement
GC
Gas Chromatograph
GCV
Gross Calorific Value
GGS
Gas Generator Set
GP
Gas Plant
HC
Hydrocarbons
HHV
High Heating Value
IA
Instrument Air
ICAO
International Civil Aviation organization
ILF
ILF Consulting Engineers
KP
Kilometer Point
LHV
Lower Heating Value
LMLS
Load Management and Load Shredding system
MCC
Motor Control Centre
MMscfd
Million Standard Cubic Feet per Day
MS
Metering Station
NGC
Nigerian Gas Company
NNPC
Nigerian National Petroleum Corporation
OB3
Obiafu/Obrikom to Oben Pipeline
Ob/Ob
Obiafu/Obrikom
OUA
Obigbo-Umuahia-Ajaokuta
PCV
Pressure Control Valve
PP
Power Plant
PPM
Parts Per Million
PS
Pigging Station
PSD
Process Shutdown
QIT
Qua Iboe Terminal
ROW
Right of Way
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3.3
RTU
Remote Terminal Unit
SA
Service Air
SCADA
Supervisory Control and Data Acquisition
SCR
Station Control Room
SOW
Scope of work
SDV
Shutdown Valve
TGS
Terminal Gas Station
TNGP
Trans Nigeria Gas Pipeline
TUCO
Turbo compressor
VTC
Vendor to confirm
WAGP
West Africa Gas Pipeline
WT
Wall Thickness
Referenced Documents
Ref.
1
Document No.
Document Title
10481-BCL-AKSX-PR-DWG-0001
Trans Nigeria Gas Pipeline System
Flow Diagram for Segment 2
2
Deleted
3
10481-BCL-AKS4-PR-REP-0001
Heat and Material balance for Kano
Terminal Gas Station
4
10481-MOM-NETCO-ILF-OSL0008
MOM-Steady State Hydraulic Simulation Alignment Meeting
5
10481-BCL-AKSX-PR-PHL-0005
Relief & Venting Philosophy
6
10481-BCL-AKSX-ME-SPC-0004
Specification for Fuel Gas Skid
7
10481-BCL-AKS4-PR-DAT-0001
Process Equipment Data Sheet- Fuel
Gas Package Kaduna TGS
8
10481-BCL-AKSX-ME-SPC-0012
Specification for Air Compressor Package & Air Dryer Package
9
10481-BCL-AKS2-PR-CAL-0005
Process Calculation for utility system
for Kaduna TGS.
10
10481-BCL-AKS4-PR-CAL-0005
Process Calculation for utility system
for Kano TGS.
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Ref.
Document No.
Document Title
11
10481-BCL-AKSX-PP-SPC-0002
Piping Material Class Specification
12
10481-BCL-AKS2-PR-CAL-0002
Process Calculation for Relief Load for
KADUNA TGS
13
10481-BCL-AKS4-PR-CAL-0001
Process Calculation for Relief Load for
KANO TGS
14
10481-BCL-AKS2-PR-DAT-0001
Process Equipment Data Sheet-Inlet
Filter Separator Kaduna TGS
15
10481-BCL-AKS4-PR-DAT-0002
Process Equipment Data Sheet-Inlet
Filter Separator Kano TGS
16
10481-BCL-AKSX-EL-SPC-0007
Low Voltage Diesel Generator Set
Specification
17
10481-BCL-AKSX-EL-SPC-0006
Low Voltage Gas Generator Set Specification
18
10481-BCL-AKSX-ME-SPC-0003
Specification for Filter Separator
19
10481-BCL-AKPL-PR-PFD-0001
Process Flow Diagram For The Pipeline System for Segment 2
20
Deleted
21
Deleted
22
10481-BCL-AKS2-PR-REP-0002
Depressurization study Report for Kaduna TGS
23
10481-BCL-AKS4-PR-REP-0002
Depressurization study report for Kano
TGS
24
10481-BCL-AKS2-PR-CAL-0001
Line sizing calculation notes Kaduna
TGS
25
10481-BCL-AKS4-PR-CAL-0004
Line sizing calculation notes Kano
TGS
26
O027-TQ-BCL-ILF-0051-TQ
TQ Reply for Technical Clarification on
Scope Of Work
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Ref.
3.4
Document No.
Document Title
27
10481-BCL-AKPL-PE-REP-0004
Pipeline Station Location Selection Report
28
10481-BCL-AKGE-PR-REP-0005
Nigerian Meteorological Data Report
Metric System Used
The units used for all calculations and referenced on all drawings and documentation are
given in SI units except piping diameter which will be given in inches, pressure given in
bar, flow rate given in million standard cubic feet per day (MMscfd) and water content given
in pounds per million standard cubic feet(lb/MMscfd). Any gas specifications and data provided by the Owner will be used in original units to maintain easy reference to the source
[Ref 2].
Table 1
Units of Measurement
Designation
Length
Time
Pressure
Differential Pressure
Area
10481-BCL-AKSX-PR-REP-0001_A0_AFC_Process Design Basis
Unit
Abbreviation
Kilometer
km
Meter
m
Centimeter
cm
Millimeter
mm
Year
y
Day
d
Hour
h
Second
s
bar absolute
bara
bar gauge
barg
bar,
bar,
Millibar
mbar
Square meter
m2
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Designation
Unit
Abbreviation
Volume
Cubic meter
m3
Temperature
Degree Celsius
o
Viscosity (Dynamic)
Centipoises
cP
Viscosity (Kinematic)
Centistokes
cSt
Flow rate (Mass)
Kilogram per hour
kg/h
Flow rate (Volume for Gas)
Million Standard Cubic MMscfd
feet per day
Flow rate (Volume for Gas)
Standard Cubic Feet per SCFH
hour
Flow rate (Volume for Gas)
Standard Cubic Feet per SCFM
minute
Flow rate (Volume for liquid)
Cubic meter per hour
m3/h
Flow Velocity
Meter per second
m/s
Force
Kilonewton
kN
Energy
Joule
J
Kilojoule
kJ
Megajoule
MJ
Revolution per minute
rev/min
Rotation Speed
C
rpm
Electrical Voltage
Electrical Current
Electrical Frequency
10481-BCL-AKSX-PR-REP-0001_A0_AFC_Process Design Basis
Volt
V
Kilovolt
kV
Millivolt
mV
Ampere
A
Kilo ampere
kA
Milliampere
mA
Hertz
Hz
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Designation
Unit
Electrical Power
Stress
Abbreviation
Kilowatt
kW
Kilovolt-ampere
kVA
Pounds per Square inch
psi
Newton per square Milli- N/mm2
meter
MPa
Mega Pascal
kPa
Kilo Pascal
Weight
3.5
Kilograms
kg
Pounds
lb
Angles
Degree
O
Velocities
Meter per second
m/s
Acceleration
Meter per square second
m/s2
Codes and Standards
Table 2
Sr. No.
List of applicable Codes and Standards
Standard
Description
1
API 5L
Specification for Line Pipe
2
API 6D
Specification for Pipeline valves.
3
API STD 520
Sizing, Selection, and Installation of Pressure-Relieving
Devices in Refineries, Part I.
4
API RP 520
Sizing, Selection, and Installation of Pressure-Relieving
Devices in Refineries, Part II.
5
API STD 521
Pressure Relieving and Depressuring Systems.
6
API STD 530
Calculation of Heater-Tube Thickness in Petroleum Refineries
7
API RP 535
Burners for Fired Heaters in General Refinery Services
8
API STD 560
Fired Heaters for General Refinery Services
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Sr. No.
Standard
9
API STD 619
Rotary – Type Positive Displacement Compressors
10
API STD 661
Air-Cooled Heat Exchangers for General Refinery Service
11
API STD 680
Packaged Reciprocating Plant and Instrument Air Compressors for General Refinery Services
12
ASME B16.47
Large Diameter Steel Flanges
13
ASME B16.5
Pipe Flanges and Flanged Fittings
14
ASME B31.3
Process Piping
15
ASME B31.8
Gas Transmission and Distribution Piping Systems
16
ASTM D1785
Standard Specification for Poly (Vinyl Chloride) (PVC)
Plastic Pipe, Schedules 40, 80, and 120
17
ASTM D3350
Standard Specification for Polyethylene Plastics Pipe
and Fittings Materials
18
ASTM F714
Standard Specification for Polyethylene (PE) Plastic
Pipe (DR-PR) Based on Outside Diameter
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Description
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4
OVERVIEW OF THE AKK PIPELINE SYSTEM
4.1
Key System Requirements
The AKK Gas Pipeline Project (as part of the planned Trans Nigerian Gas Pipeline network) needs to be constructed to accommodate future gas demands and supplies. The
design pressure of the future gas pipeline supplying the gas to future consumers and
connected downstream TGS will be at the same value as a design pressure of the TGS.
The project development phases are identified and captured in the time frame of three
expansion phases:
4.1.1
Early Gas Phase
Early Gas Phase is driven by availability of two main gas sources Oso Platform (gas delivered via Qua Iboe Terminal) and existing Cawthorne Channel, Alakiri and Obigbo satellite gas plants and the need of gas supply to the Escravos Lagos Pipeline (Western Gas
Transmission System). Gas from QIT will be transferred through new QIT-Obigbo-Ob/Ob
pipeline to Ob/Ob metering station upstream of the inlet to the OB3. Gas from Cawthorne
Channel and Alakiri will be transferred through new Cawthorne Channel-Obigbo pipeline.
4.1.2
Phase 1
Phase 1 is driven by availability of additional gas supplies from Assa Gas Plant and the
need of gas supply to the Northern / Eastern States through new Obigbo-UmuahiaAjaokuta pipeline and new Ajaokuta-Kaduna-Kano pipeline.
4.1.3
Phase 2
Phase 2 accounts mainly for additional gas supplies from a further increased capacity of
Oso Platform via QIT. Gas from QIT in addition to the QIT-Obigbo-Ob/Ob pipeline will be
evacuated through new QIT-Uyo-Umuahia pipeline.
Phase 2 is not within the scope of work of this project. However, the system has to be
designed in such a way that allows for expansion to phase 2 when additional gas volumes
will be available and will need to be transported. Therefore, the station inlet and outlet
headers as well as the linear pipeline section shall be designed for phase 2 flow rates.
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4.2
Pipelines
The pipeline project scope is summarised in the following table:
Table 3
Pipelines of the AKK Section within the AKK pipeline system [Ref 2]
Development
Phase
Pipeline
Phase1
Station Name
Section Size
Ajaokuta – Kaduna - Block Valve Station
Kano Gas Pipeline
12-Kaduna TGS
40”
Kaduna TGS – Zaria
PS and future tie-in
for TGS
40”
Zaria PS- Kano TGS
40”
In general, the operation of pipeline will be one direction.
4.3
Block Valve Station
The block valve stations in the project scope are tabulated as follows (spacing is according
to ASME 31.8 and local regulations if more stringent requirements are applicable):
Table 4
Development Phase
Phase1
Block Valves of Pipeline Section within the TNGP System [Ref 27]
Pipeline
Station Name
KP
Block Valve Station 13
333.955
Block Valve Station 14
361.328
Block Valve Station 15
380.334
Block Valve Station 16
411.548
Ajaokuta –Kaduna –
Block Valve Station 17
445.362
Kano Gas Pipeline
Block Valve Station 18
473.491
Block Valve Station 19
525.633
Block Valve Station 20
554.654
Block Valve Station 21
577.159
Block Valve Station 22
598.061
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4.4
Pigging Stations
Following pigging stations are foreseen in the Segment 2 pipeline system (in accordance
with Pigging philosophy Doc. No 10481-BCL-AKGE-PM-PHL-0002)
Table 5
Development Phase
Phase1
4.5
Location of Pigging Stations [Ref 27]
Pipeline
Station name
KP
Kaduna Pigging Station
KP 402.443
Ajaokuta –Kaduna –
Zaria Pigging Station
KP 496.408
Kano Gas Pipeline
Kano Pigging Station
KP 623.27
Terminal Gas Stations
The terminal gas station will be designed to measure gas flow rate, to reduce gas pressure
accounting for the full range of expected downstream gas volumes and pressures. The
station shall be self-supporting with full process and utilities systems within the plant battery limit.
The Segment 2 pipeline system configuration accounts for terminal gas stations as detailed in the following table:
Location of Terminal Gas Stations [Ref 27]
Table 6
Development
Phase
Phase1
4.6
Pipeline
Station name and location
Ajaokuta –Kaduna Kaduna Terminal Gas Sta– Kano Gas Pipe- tion
line
Kano Terminal Gas Station
KP
KP 402.443
KP 623.27
Design Life
The entire Pipeline System including equipment, such as block valve stations, pigging stations and metering stations, shall be designed for a life time of twenty-five years.
4.7
Project Battery Limits
The battery limits of the Ajaokuta-Kaduna-Kano Gas Pipeline system are:
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According to the project scope of work, AKK Project (Segment 2) concerns only with Early
Gas Phase (EGP) and Phase 1. However, analysed system has to be designed in a way
that allows for expansion to Phase 2, when additional gas volumes will be available and
will need to be transported.
Ajaokuta Kaduna Kano (AKK) Gas Pipeline and Stations Project (Segment 2) start from
Block Valve Station 12 (outer line of the fence) to Kano Terminal Gas Station.
At BVS 21, an offtake towards Kano IPP (17.6 km 24” spur line) is to be provided for future
provision. A flow rate of 270 MMscfd shall be foreseen for the Phase 1 / 2 offtake. While
this additional spur line is out of scope for the project, the additional 270 MMscfd will have
to be considered in the hydraulic simulations.
4.8
Environmental Conditions
Topography: Rather flat /hilly, raising to the north after Izom city
Climate: Tropical savannah (wet and dry) climate (Aw acc. to Köppen-Geiger classification)
Temperatures: High
Rainfall: High during wet season (April to November)
Humidity: Low.
Soil pH: from 5.6-6.0 (moderately acid) to 6.1-6.5 (slightly acid) from Kaduna to Kano.
The environmental conditions for the AKK Project area are presented in Table 7.
Table 7
Environmental Conditions for the AKK Project area [Ref 2, 28]
Location
Northern Part (AKK)
Design wind velocity (Kaduna)
50 km/hr (14 m/s/27Knots)
Design wind velocity (Zaria)
55.6 km/hr (15.4 m/s/30 Knots)
Design wind velocity (Kano)
50 km/hr (14 m/s/27Knots)
Design Wind Speed for Structural Design
144 km/hr (40 m/s)
Mean maximum ambient temperature (Kaduna)
41.7 °C
Mean Minimum ambient temperature (Kaduna)
14.2 oC
Mean maximum ambient temperature (Zaria)
38.5 °C
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Location
Northern Part (AKK)
Mean Minimum ambient temperature (Zaria)
13.1 oC
Mean maximum ambient temperature (Kano)
41.0 °C
Mean Minimum ambient temperature (Kano)
8.4 oC
Black Bulb Temperature
60°C
Minimum average relative humidity
60%
Ground Temperature
25°C
Maximum relative humidity
98%
Mean annual total rainfall (period of the year)
700 mm
Design average annual rainfall (period of the
year)
700 mm
Design mean maximum hourly rainfall
70 mm
Prevailing wind direction
south-west
Seismic zone according to Modified Mercalli
scale (MM)
Zone 0: MM V and below
4.7.1
Reference Conditions
The reference pressure and temperature for “standard cubic feet” are defined as 1.013
Bara and 15.56°C respectively [Ref 2].
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Figure 2
Figure 3
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AKK Section Overview Map
Project Overview Map
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5.0
5.1
Process Design Data
AKK pipeline sections design conditions
Figure 4
Block Flow Diagram for AKK Pipeline (Segment 2)
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Table 8 Pipelines operating and design conditions
Pipeline
Maximum Operating
Pressure
Ajaokuta–
Kaduna–
Kano Gas
Pipeline
94 barg
5.2
Design
Pressure
Maximum
design
temperature
Minimum
underground design temperature
Minimum
above
ground design temperature
Supply
Temperature From
Segment 1
98 barg
60˚C
0˚C
-29˚C
25˚C
Gas Composition
Gas supplied to Trans Nigeria Gas Pipeline System is considered as dry, sweet gas that
meets NGC’s gas quality specification. The gas specification for Eastern Gas Supply Systems (for Obigo Node, Alscom, Ibom Power etc.) is presented in Table 9 below.
Table 9
Specification for Eastern Gas Supply System [Ref 2]
Composition
Minimum
Maximum
Hydrocarbon Dew Point
0
10°C
Water Content
0
7lbs/MMscf
Methane
82%
96% Vol
Ethane
0.1%
10% Vol
Propane
0.1%
8% Vol
Butanes
0
5% Vol
Pentanes
0
1.10% Vol
Hexane- Plus
0
1.0% Vol
Total inert gases
0
15%
CO2
0
10%
N2
0
3% Vol
H2S
0ppm
10ppm
Total Sulphur
0ppm
28ppm
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Composition
Minimum
Maximum
O2
0ppm
10ppm
Higher heating Value (GCV)
950btu/scf
1150btu/scf
Wobbe Index(HHV basis)
47 MJ/m3
52 MJ/m3
Delivery Temperature
20°C
50°C
The gas specification for West African Gas Pipeline Specification (for ELPS, Oben Node,
Ajaokuta etc.) is presented in Table 10 below:
Table 10
West African Gas pipeline (WAGP) Specification [Ref 2]
Composition
Minimum
Maximum
C1
84% Vol
95% Vol
C2
-
10%
C3
-
8%
C4+paraffin
-
5%
CO2
-
4%
N2
-
3%
H2S
-
4ppm by volume
Total Sulphur
-
28ppm
O2
-
10ppm
H2O
-
7lb/MMscf
HC Dew Point
-
10°C
Higher Heating Value
1000 btu/scf
1150btu/scf
Wobbe Index
47 MJ/m3
52 MJ/m3
1281 (based on
btu/scf)
1396 (based on
btu/scf)
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OB3 Pipeline Gas Composition (for the fields around Obite Gas Plant) is presented in Table 11
Table 11
Obite
GP
OB3 Pipeline Gas Composition [Ref 2]
AgipEbocha
AgipIdu
AgipAgb
ainbiri
AgipAkri
Assa
North
Central
CPF
Ready
beyond
2015
Volume
(MMscfd)
165
50
150
100
20
1000
(>2016)
6000
Component
Mole %
Mole %
Mole %
Mole %
Mole %
Mole %
Mole %
C1
83.874
85.370
94.6
88.960
80.280
89.77
98.8
C2
6.887
6.701
3.26
5.260
8.680
3.95
0.92
C3
3.423
4.091
0.250
2.700
4.900
2.64
0.1
C4
1.596
2.206
0.150
1.140
2.230
1.20
0
C5
0.518
0.994
0.050
0.310
0.680
0.35
0
C6+
0.423
0.000
0.130
0.280
0.250
0.36
0
CO2
3.220
0.506
1.439
1.218
2.852
1.65
0
N2
0.058
0.130
0.120
0.130
0.130
0.08
0.2
Total
100
100
100
100
100
100
100
Gas composition of the sample taken from the Ikot Abasi Metering Station is presented in
Table 12 and 13 below
Table 12
Gas composition at Ikot Abasi Metering station [Ref 2]
Sr. No
Compound
Symbol
Mole %
1
Methane
C1
86.85
2
Ethane
C2
5.33
3
Propane
C3
3.54
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Sr. No
Compound
Symbol
Mole %
4
Normal butane
n-C4
1.05
5
Iso Butane
i-C4
0.62
6
Normal Pentane
n-C5
0.28
7
Iso Pentane
i-C5
0.30
8
Hexane
C6+
0.14
9
Carbon Dioxide
CO2
1.85
10
Oxygen
O2
0.00
11
Nitrogen
N2
0.04
Table 13
Gas Composition at Ikot Abasi Metering Station (Thermochemistry) [Ref 2]
Thermochemistry
Parameters
Value
Unit
Avg. Molecular Wt
19.43
g/mole
Specific gravity
0.673
SG
Hydrocarbon Dew
Point Temperature
N/A
°C
Water Dew Point temperature
N/A
°C
Moisture Content
4.50
lb/MMScf
Higher Heating value
1150.45
btu/Scf
Lower Heating Value
1040.84
btu/Scf
Wobbe Index
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For the purpose of the simulations, gas compositions as per FEED Stage Heat and Mass
Balance – Kano TGS (Document No: G791-ILF-AKS4-PR-CAL-0002 REV. 1) shall be
taken, since the available gas specification provided by NNPC (Eastern Gas Supply Systems and WAGP Gas Specification) are adjusted in a way to cover the range of C6+ at a
higher possible level, keeping the gas specification requirements i.e. water dew point, hydrocarbon dew point and heating value to account for any liquid components that may be
seen during pipeline and stations operation. The gas specifications are given in Table 14.
Table 14
5.3
Gas specification and composition used for simulations. [Ref 2]
Component
Unit
Gas Composition
used for simulations
C1
% mol
84.04
C2
% mol
6.79
C3
% mol
3.42
i-C4
% mol
0.82
n-C4
% mol
0.74
i-C5
% mol
0.31
n-C5
% mol
0.25
C6+
% mol
0.27
N2
% mol
0.15
CO2
% mol
3.21
H2O
lb/MMscf
7
HC Dew
Point
°C
9.9
MW
kg/kmol
20.03
Gas Properties
The gas properties as defined in Table 15 shall be used in equipment specifications for
the Project. Values are extracted from the Eastern Gas Supply System gas specifications
provided.
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Table 15
Trans Nigeria Gas Pipeline Project gas properties [Ref 2]
Component
Unit
Gas Source
Eastern Gas Supply
System
C1
% vol
82-96
C2
% vol
0.1-10
C3
% vol
0.1-8
C4
% vol
0-5
C5
% vol
0-1.1
C6+
% vol
0-1
CO2
% vol
0-10
N2
% vol
0-3
H2O
% vol
-
H2S
ppm
0-10
Water Content
lb/MMscfd
0-7
Water Content
mg/m3
0-112
HC Dew Point
°C
Maximum 10
HHV
Btu/scf
950-1150
Wobbe Index
MJ/m3
47-52
Btu/scf
1261-1396
5.4 Gas Flow Rates
The Table 16 summarizes the gas volumes supplied to and withdrawn from the AKK pipeline system at the battery limit of each pipeline section.
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Table 16
Facility
Summary of Gas volumes supplied withdrawn
In-take
Cumulative
gas in-take/gas withdraw (MMscfd)
Off-take
Early Gas
Phase
Phase 1
Phase 2
Ajaokuta – Kaduna – Kano Gas Pipeline (AKK)
Kaduna TGS
-
175
280
Zaria TGS
-
0
140
Kano IPP
-
270
270
Kano TGS
-
50
50
Total Intake
from Segment
1
-
495
740
5.5 Battery Limit Conditions
Battery Limit conditions at the TGS are provided below in the table.
Table 17
Trans Nigeria Gas Pipeline Project pressure requirements at battery limit [Ref 4]
Selection Criteria
AKK Gas Pipeline
Min. gas arrival pressure at Kaduna TGS: 43 barg
Min. gas arrival pressure at Zaria TGS: 43 barg
Min. gas arrival pressure at Kano TGS: 43 barg
Min. gas outlet pressure at Kaduna TGS : 39 barg
Min. gas outlet pressure at Zaria TGS : 39 barg
Min. gas outlet pressure at Kano TGS : 39 barg
Erosional velocity / Design velocity: 18 m/s / 9 m/s
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6.0
Process Description for SOW
Gas from AKK Gas Pipeline will be partially transferred to the Kaduna Terminal Gas Station, while the surplus gas will be further transported to Kano Terminal Gas Station through
the AKK pipeline which is a termination point for the AKK pipeline.
Gas will arrive at the respective TGS and will flow to the process trains for treatment before
sending the gas to the off-takers.
Inlet Filter Separators will be the first stage of the gas conditioning to remove any solid and
liquid particles from the gas stream. Next the gas will be transferred to the Line Heaters
for heating. The heater outlet temperature shall compensate for the following gas cooling
at the metering and control skid caused by the Joule Thomson effect”.
After passing through the line heaters, the heated gas will flow to the Gas Metering and
Control Skid. The PCV which is part of the metering and control package will maintain a
constant gas pressure at the TGS outlet header and at the same time will restrict the flow
to limit the gas drawn (pressure control with flow-rate override). The export gas drawn from
the TGS system will be measured and recorded by the metering system, which will be
installed upstream of the pressure control valve.
The metering and control package will provide custody transfer rates between AKK Gas
Pipeline and gas off-takers downstream the TGS will reduce gas pressure and control gas
flow to the gas off-takers and will transmit the AKK system boundary conditions data (actual pressure and flow) to the SCADA and Pipeline Leak Detection System.
The Kaduna-Kano pipeline section will be equipped with intermediate Pigging stations.
Kaduna and Zaria Pigging station will be each equipped with Pig Launcher and Receiver,
whereas Kano TGS will be equipped with only a Receiver. The design of the launcher will
be capable to perform intelligent pig launching operation.
The SDV valve will be provided at the station inlet and outlet. In case of an emergency
event the SDV valves will cut off the gas supply from the AKK and to the off-takers.
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7.0
Installations at Off-Take Gas Metering Station
There are several gas in-takes and off-takes of the analysed pipeline system. The gas
volumes supplied to the network and off-taken from the system are based on “The System
Selection Report [Ref.20] and based on the new future offtake towards Kano IPP (17.6 km
24” spur line) with a flow rate of 270 MMscfd.[Ref 26]
According to the project scope of work, AKK Project concerns only Early Gas Phase (EGP)
and Phase 1. However, analysed system has to be designed in such a way that allows for
expansion to Phase 2, when additional gas volumes will be available and will need to be
transported. Ajaokuta Kaduna Kano (AKK) Gas Pipeline and Stations Project (Segment 2)
starts from Block Valve Station 12 (outer line of the fence) to Kano Terminal Gas Station.
This section covers the process facilities required at Kaduna and Kano Off-Take Gas Metering Stations. The process facilities at Off-Take MS will include:
•
Pig Launcher(to be provided at Kaduna TGS);
•
Pig Receiver (to be provided at Kaduna & Kano TGS);
•
Filter Separator Skids;
•
Gas Line heaters
•
Gas Metering and Control Packages;
Utility Systems including:
•
Vent System
•
Instrument Air System
•
Fuel Gas Conditioning System
•
Nitrogen system
•
Fire Fighting System ( includes Fire Water Pump Package)
•
Utility Water System
•
Diesel Fuel System
•
Diesel Generator Set
•
Gas Engine Generator Set
•
Utility Air System
•
Closed Drain System
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8.0
Process and Mechanical Equipment
8.1 Pig Launcher and Receiver
Pig Launcher shall be designed for use of intelligent pigs (6 m maximum length). Design
code for Pig Launcher will be ASME B31.8 or ASME Section VIII Div 2 and shall be confirmed later. In case of ASME B31.8 use, a design factor depending on the location but not
less than Location Class 2 shall be taken. The same corrosion allowance for the
launcher/receiver as for the pipeline shall be considered.
The quick opening closure shall be equipped with a mechanical interlocking system to
prevent opening of a pressurized vessel. Pig signallers will be installed on both sides of
the pig launcher/receiver outlet valve to provide confirmation that the pig was successfully
launched/ received and passed through the pig trap valve.
Provision shall be made in layout for pig trays with handling and lifting facilities for pig
inserting/removal operations.
The hazardous fluids drained from the pig launchers and receivers containing flammable
or hazardous substances will be drained to the closed drain system.
Table 18
8.2
Design conditions for Pig Launcher and Receiver
Design Pressure
(barg)
Design Temperature
(°C)
98
-29 to 60
Filter Separator
Inlet gas arriving at stations is specified as a dry gas with a maximum hydrocarbon dew
point of 10°C and a minimum inlet temperature of 20°C. It is therefore assumed that condensation of gases at station inlet does not occur and under normal operating conditions
only minor amounts of solids may be expected. In case of off-spec gas and/or during commissioning, gas might condensate, leading to liquids in the lines. Thus, for protection of
the downstream equipment, 2-stages, horizontal Filter Separators shall be installed.
The horizontal filter separator vessels shall contain two separation sections and separate
condensate collection sumps located below. It is envisaged that the filters shall be cartridge type at 1st stage and vane type at 2nd stage. The filters will be installed in parallel
with a filtration capacity sufficient to treat the maximum nominal gas flow rate at 0.5 bar
maximum pressure drop (clean). The criterion for separation efficiency of the filter
separator has been shown in table 19[Ref 14, 15]. The filters will be equipped with differential
pressure monitoring and automatic liquid discharge to the closed drain system. Potential
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overfill and gas break through shall be monitored and automatic PSD measures shall be
in place to protect the subsequent systems [Ref 2].
Filter Separator Separation Efficiency - Kaduna & Kano TGS [Ref 14, 15]
Table 19
Separation
Efficiency
Liquid Droplets
Solid Droplets
≥1 μm
99%
≥3μm
100%
≥1 μm
99%
≥3μm
100%
Filter separators and all other pressurized components shall be designed, fabricated,
welded and tested in accordance with ASME VIII Division 1. The filter separators shall be
designed and manufactured to ensure low-maintenance, long-lasting and reliable operation. [Ref 14, 15]
The quick opening closure shall be equipped with a mechanical interlocking system to
prevent opening of a pressurized vessel. Filters shall be equipped with manual venting
facilities. The design and operating conditions of filter separator at Kaduna and Kano TGS
are as follows [Ref 2, 14, 15]:
Table 20
Filter Separator Design Conditions- Kaduna & Kano TGS [Ref 14, 15]
Parameter
Value for KADUNA TGS
Value for KANO TGS
Design Pressure
98 barg
98 barg
Design Temperature
-29/60°C
-29/60°C
175MMscfd
50 MMscfd
Number of Filter Separator
2x100%W
2x100%W
Maximum pressure drop
clean
0.5 bar
0.5 bar
Maximum pressure drop
dirty
1.0 bar
1.0 bar
Operating Capacity
Each Filter Separator
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8.3 Line Heaters
The Line Heaters shall be provided at stations where gas pressure reduction is required
before gas is transferred to gas off-takers. The gas temperature shall be set at a level to
compensate for the J-T effect (gas temperature reduction during gas pressure reduction)
and to provide gas superheating about 15°C above HC dew point temperature at the TGS
outlet. Thus, the gas shall be heated in indirect water bath line heaters.
The Line Heater shall be provided with atmospheric expansion tank, manual drain; main
burner; pilot burner; fuel gas and combustion air system. The gas heating coil will be immersed into the hot water contained in the boiler. The temperature of the gas delivered to
the TGS outlet header will be controlled by a temperature control loop using the heater by
pass. The design pressure in combination with the design temperature may require ASME
Class 900 flanges [Ref 2].
The design and operating conditions of line heaters at Kaduna and Kano TGS are as follows:
Line Heater Design Conditions – Kaduna & Kano TGS
Table 21
Parameter
Value for KADUNA
TGS
Value for KANO TGS
98 barg
98 barg
-29°C - 100°C
-29°C - 100°C
25oC
25oC
Number of Line Heater
1W+1S
1W+1S
Maximum pressure drop clean
0.5 bar
0.5 bar
Design Pressure
Coil Design Temperature
Gas Temperature
PCV
Downstream
8.4 Gas Metering and Control Package (PCV)
The Gas Metering and Control Package shall be provided, designed for gas pressure and
volume flow control and custody transfer rates between the stations. The gas metering
and control package shall be designed as package-unit, skid-mounted, with all necessary
ladders and platforms provided.
Gas Metering and Control Package shall consist of four main functions:
•
Gas metering – meters installed within the skid;
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•
Online proving - master meter (meter prover) installed on the separate prover run
within the skid;
•
Downstream pressure control – PCV installed within the skid;
•
Gas analysis – separate Gas Chromatograph delivered with the skid.
For metering, orifice meters (e.g., senior orifice & Ultrasonic) compliant to custody transfer
certification by DPR are planned which allow for fast and simple exchange of orifice plates
under pressure without flow interruption. These metering runs (custody transfer) will be
provided with a separate, dedicated prover run and a gas chromatograph (GC) recording
gas composition data. The GC shall meet requirements of the DPR “Guidelines for the
Determination of Quantity and Quality of Gas at Custody Transfer Points”.
The gas chromatograph shall be located close to the Gas Metering and Control Skid to
allow for the shortest practical sampling route between the sampling point and analyser.
Water dew point analysis shall be implemented in form of dedicated water dew point analyser. Single sampling point shall be provided for each fiscal metering skid. sampling probe
/ sensor shall be designed such that it is possible to be retracted under operating pressure.
Analyser shall indicate water dew point and moisture content as a minimum. Water dew
point measuring system shall be equipped with automatic compensation of pressure and
temperature. The whole uncertainty of the water dew point calculation shall be ±0.5 °C or
better.
The Gas Metering and Control Package will be also used to transmit AKK system boundary
conditions data (actual pressure and flow) to the SCADA and pipeline leak detection system.
The pressure control valves shall be installed downstream each meter lines to cover control requirements of the station design conditions. The turn-down ratio of the control valves
shall be the same or better than that of the metering equipment [Ref 2].
The gas metering and control skid design conditions at Kaduna and Kano TGS are as
follows:
Table 22
Gas Metering and Control Skid Design conditions- Kaduna & Kano TGS
Parameter
Value for KADUNA TGS
Value for KANO TGS
Design Pressure
98 barg
98 barg
Design Temperature
-29/60°C
-29/60°C
Required min. pressure
downstream PCV
45 barg
45 barg
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Parameter
Value for KADUNA TGS
Value for KANO TGS
175 MMscfd
50 MMscfd
2 (1W+1S)
2 (1W+1S)
Size of Meter Run (Inch)
16 (VTC)
8(VTC)
Size of
(Inch)
16(VTC)
8(VTC)
Operating Capacity
Number of Meter Run
Meter
Prover
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9.0
Process Utility Systems
The process utility systems described below shall be provided at each Metering Station.
9.1 Vent System
Vent system shall provide safe and reliable method for disposal of flammable gases during
the following scenarios:
•
Relief due to fire in the pipeline system;
•
Relief due to malfunction of process equipment, process upsets, utility failure,
blocked outlet, etc.;
•
Emergency depressurization (either manual or activated by the ESD system);
•
Maintenance depressurization.
The vent system shall comprise of the following main components shortly described in
paragraphs below [Ref 22, 23]:
•
•
•
•
9.1.1
Piping system (tail pipes, sub-headers and main header);
KO drum;
KO drum level control system (Level control valve and drain pipes);
Vent stack package including vent stack tip and vent stack riser.
Piping System
Cold vent collection headers are required to collect relief, blowdown and venting loads
from the facility and route them to the knock out (KO) drum.
Materials of cold vent system piping shall account for the most extreme release conditions
and any temperature drop which may occur during depressurization process due to the
Joule-Thomson effect.
The design shall be done on a basis of maximum allowable mach number or maximum
allowable back pressure (whichever is more stringent). The velocity in the cold vent piping
shall not exceed Mach number of 0.6 in the main headers and 0.7 in the tail pipes. The
velocity in the cold vent stack shall not exceed 0.5 Mach for peak flow. The maximum
allowable back pressure shall not reduce relieving capacity of any of the pressure relieving
device and shall be lower than pressure rating of piping materials [Ref 5].
Vent header shall be self-draining with no low points towards to the KO drum. The piping
between cold vent stack and KO drum shall be sloped to the drum. The minimum slope
in both cases shall be 1:500 [Ref 5].
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The cross-sectional area of cold vent piping in each section shall not be lower than that in
the preceding section.
Lines from individual relief valves should be sized for the PSV rated flow.
The main header, sub-headers, KO drums, cold vent stack and cold vent tips shall be sized
to handle the maximum coincidental emergency loads. Since the simultaneous occurrence of two or more unrelated contingencies is unlikely, unrelated contingencies should
not be used as a basis for determining the maximum system load.
9.1.2
Knock Out Drum
From main header gas will flow through the knock-out drum to collect liquid droplets (if
any) and further to the cold vent stack.
Knock out drum is required to separate condensed liquids from gas in inlet stream and to
hold the maximum amount of liquid that can be relieved during an emergency depressurization. Collected liquids shall be routed to the closed drain system [Ref 5].
KO drum shall be installed as close as possible to the cold vent stack. Possibility of personnel access for maintenance on KO drum shall be taken into consideration in case of
cold vent systems with automatic depressurization [Ref 5].
KO drum shall be sized for maximum gas relief case and case at which maximum liquids
(if any) may appear. KO drum shall be sized so that maximum size of exiting droplets will
not be larger than 600 microns as per API 521.
9.1.3
KO Drum Level Control System
KO drum shall be equipped with Level control system used for removing accumulated liquid from the drum. The capacity of KO control valve shall be sufficient to drain out the liquid
between high level to low level within 10 minutes. The level control valve shall open at high
level on KO drum and close on low level. This will avoid the ESD level 2 tripping in TGS
which will be activated on high-high liquid level in KOD [Ref 5, 12].
9.1.4
Cold Vent Stack
Cold vent stack shall be sized so that dispersion of gas into the atmosphere will not be
harmful to the personnel. Location of the cold vent stack shall be downwind or crosswind
of personnel accommodation and/or work areas based on the prevailing wind conditions.
The location of the vent stack(s) shall be in a safe distance from process facilities, fence
line and occupied buildings at the station [Ref 5].
The height and location of the vent stack shall be selected so that the concentration of
vapour at a point of interest is below the lower flammable limit of the vapour. The height
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and location shall also be selected taking possible unintended ignition of the vented gas
into account [Ref 5].
Aircraft warning lights shall be installed at the cold vent stack structure (45m or above) as
per ICAO requirement.
Lightening arrestors shall be foreseen in the cold vent system design.
This is applicable to Kaduna, Kano, Zaria Stations and Block Valve Stations.
9.1.5
Vent Gas Metering System
Vent gas metering device shall be provided on vent lines upstream of cold vent stack
(downstream of KO drum, if any). The metering devices shall be suitable for high turndown
ratios. The volume of vent gas shall be recorded in station control system and transferred
to SCADA [Ref 5].
Any gas releases due to the operational upsets, gas venting or ESD operation shall be
measured as per DPR requirements. Thus, metering will be provided as a part of cold vent
stack system.
Table 23
Description
Vent System Design Conditions
Vent KO Drum
Design Pressure
(barg)
FV/10
Design Temperature
(°C)
-46/80
Vent Stack
FV/10
-45/210
9.2 Fuel Gas System
Fuel gas conditioning sequence is described as follows:
•
Removal of liquids and solids by filtering;
•
Temperature controlled pre-heating upstream the pressure reduction valve;
•
Pressure reduction to required pressure level;
Fuel gas system mainly consists of filtering system, gas metering system, gas pre-heating,
pressure reducing, protection with safety shut-off valves and relief valves, isolation valves
and piping components with fittings, flanges and bolting materials. Fuel gas system shall
be configured as 100% redundant. One train in operation and one train stand by. Each fuel
gas unit skid shall be designed according to the fuel gas system specification [Ref 6]
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The filters shall be able to remove 99% of solid particles down to 10 microns and larger
[Ref 7].
The fuel gas system take off shall be downstream of the station filter separators for normal
station operation, however, alternative supply from the pipeline for the station start-up
and/or upset shall be considered in the design. The fuel gas system shall supply high
pressure consumers (turbines) and low-pressure gas consumers including gas generators.
Table 24
Fuel Gas System Design Conditions
Equipment
Design Pressure
(barg)
Design Temperature
(°C)
Coalescer
98
(-)29 - 60
Electric Heater
98
(-)29 - 100
9.3 Compressed Air System
A station instrument air (IA) and utility air (UA) facility including a distribution system shall
be provided.
The compressed air system mainly serves for the reliable and cost-effective supply of compressed air for the compressor stations. Mainly block and control valves with pneumatic
actuators are supplied with compressed air.
The compressed air system shall consist of air compressors, buffer tanks, dryer pack-ages
with relevant filters, air receivers (storage tank) and relevant piping system. Instrument air
unit shall be skid mounted [Ref 8].
The IA and UA facilities will be located under a common sun shed.
To prevent condensation in the supply piping and instruments, the dew point of the compressed air at operating pressure shall be at the level required by the nitrogen generation
package and instrument gas consumers’ Vendor but at least 10 °C below the lowest expected ambient temperature [Ref 2].
Table 25
Compressed Air System Design Conditions
Design Pressure
(barg)
10
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Design Temperature
(°C)
80
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9.4 Nitrogen System
Nitrogen bottles shall be provided to purge the vent system and for maintenance purging
of process equipments.
For the purpose of vent header purging, nitrogen bottled package is provided with permanent connect to vent header. An adequately sized restriction orifice alongwith isolation
valve shall be provided at the vent header for operator to sweep-through purge the vent
header to reduce oxygen concentration upto allowable limit (6% as per API-521), to remove air ingresses in to vent system for prevent formation of flammable mixture in and to
minimise nitrogen loss during purging.
In scenario of accidental fire at the vent stack, nitrogen package can also utilize for extinguishing the fire. This shall be done using fire snuffing connection at the vent header (in
the downstream of KOD). An adequately sized restriction orifice alongwith isolation valve
shall be provided at the vent header for operator to extinguish the fire.
For maintenance of process equipment, the purging of process equipment shall be performed to reduce oxygen concentration upto allowable limit (6% as per API-521) for
maintenance and prevent any chance of accidental fire during ventilation of process equipment. The vessel purging shall be done using mobile bottles by connecting directly to the
vessel.
9.5 Gas Engine Generator
Each GGS shall consist of the following main parts:
•
Gas engine;
•
Generator;
•
Starter equipment;
•
Fuel system;
•
Lubrication system;
•
Air intake and exhaust system;
•
Acoustic enclosure;
•
Auxiliary power distribution system;
•
Protection, control and monitoring system.
Gas generators sets (GGS’s) will operate as a local power plant (PP) providing primary
power supply for the Kaduna & Kano TGS.
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Each PP will operate in 1+1 philosophy with 1 GGS’s operating as primary unit and 1 GGS
operating as a stand-by unit at one time. Each GGS will be utilized as a primary and standby unit rotationally. Changeover sequence will be automatically performed by the Power
Plant Control System (PPCS) through load management and load shredding system
(LMLS)in order to ensure equal, annual operation time of each unit.
PP shall operate in such way that there will always be at least 15% of single GGS nominal
power available in a system as a spinning reserve. If there is not enough spinning reserve
in the system, then additional GGS will be started immediately.
In case of any abnormal condition in the running gas generator viz. overheating, failure of
auxiliaries, overload scenarios etc, the standby gas generator is capable to take full load
automatically of TGS (within a span of 1-2 min approx.) to provide uninterrupted power
supply & prevent TGS shutdown due to power supply failure.
Generators shall operate with their star points directly grounded.
Gas engine and generator shall be placed on a common base frame and connected with
a dry flexible coupling. The GGS’s shall be installed in the acoustic enclosures [Ref 17].
9.6 Diesel Fuel System
Diesel fuel shall be used for the back-up diesel generator sets. Diesel will be delivered by
road tanker to site and stored in a storage tank. The diesel storage tank capacity shall be
determined based on the fuel consumption of the diesel generators. As a minimum diesel
fuel for 7 days uninterrupted operation at emergency load of the generator will be provided
[Ref 2].
9.7 Diesel Generator
The diesel generator sets shall consist of the following main parts:
•
Diesel engine,
•
Generator,
•
Starter equipment,
•
Fuel system,
•
Lubrication system,
•
Air intake and exhaust system,
•
Control and monitoring system,
•
Acoustic enclosure.
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Diesel engine and generator shall be placed on a common base frame and connected with
a dry flexible coupling. The DGS set shall be integrated in the DGS equipment container.
The DGS sets shall be provided in a manner such that 15 sec after initiation of start the
full load can be taken over [Ref 16].
9.8 Utility Water System
9.8.1
Pipes
Water distribution network shall be made of High-Density Polyethylene (HDPE), class A50
of Piping Classes Specification (G791-ILF-AKGE-PP-SPC-0001).
9.8.2
Water wells
The minimum total capacity of all operating wells shall be the cumulative of the following
consumption rates:
•
Raw water average daily consumption for the manufacture of potable water, plus,
•
Loss of water from the manufacture of potable water, plus,
•
Raw water average daily consumption for process, plus,
•
Raw water for filling Fire Fighting Tank;
9.8.3
Submersible pumps
Submersible pump shall be suitable for operation under submerged condition in raw water;
Submersible pump shall pump raw water to a raw water tank. The pump shall be
controlled by a signal of the raw water tank filling level;
9.8.4
Raw water tank
The minimum storage capacity of raw water shall be cumulative of the following
consumption rates :
•
Daily consumption of 120 LPDPM,
•
Demand for process,
•
5 days of reserve.
9.8.5
Potable water treatment unit
Potable water treatment system shall produce potable water quality according to WHO
standards. Potable water treatment unit shall be selected on the basis of the raw water
characteristic and treatment needs.
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Potable water treatment unit shall consist of following basic components :
•
Raw water line valve – valve that allows to cut off raw water supply line;
•
Pre-filter(s) - filter(s) used to remove sand silt, dirt and other sediment. The prefilter(s) shall be sediment type;
•
Reverse osmosis membrane – the membrane shall be spiral wound, made of the
CTA (cellulose tri-acetate) which is chlorine tolerant;
•
Post filter – shall be made of carbon (either in granular or carbon block form). Post
filtration process removes any remaining tastes and odors from water;
•
Automatic shut off valve – installed to conserve water. When the potable water
tank is full this valve stops any further water from entering the reverse osmosis
membrane, thereby stopping the water production. By shutting off the flow this
valve also stops water from flowing to the drain;
•
Check valve – prevents the backward flow;
•
Flow restrictor – the device maintains the flow rate required to obtain the highest
quality potable water;
•
Drain line – the line shall run from the outlet end of the reverse osmosis membrane
housing to the drain. This line shall be used to dispose of the impurities and contaminants found in the water well.
9.8.6
Disinfection units
Disinfection unit shall be designed to be added, at the relevant dosing point, the requested amount of disinfectant;
Disinfection unit shall be designed for manual operation ;
9.8.7
Potable water tanks
The potable tank shall be built from materials approved for potable water. The capacity
of potable water tank shall be sufficient to meet potable water consumption requirements dimensioned according to below values:
•
Daily consumption of 120 LPDPM,
•
2 days of reserve.
Potable water tank shall be equipped with water level controlling device connected
with automatic valve (valve equipped with electrical actuator);
The water mirror will be adjusted through the emergency overflow drains directed into
an open drain system ;
9.8.8
Pump units (booster unit)
Pump unit shall be used to refilling potable water tank and firefighting water tank and
to supply users. Pump unit shall be approved for potable water;
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Pump unit shall be controlled by a signal from pressure switch.
Pump unit shall consist of minimum two operating pump (2x50%) and one standby
pump and one standby pump (1 x 100%)
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9.9 Closed Drain System
The closed drain system shall be designed for collecting any liquids containing flammable
or hazardous substances in Kaduna, Kano and Zaria TGS respectively.
The main items system shall include:
A closed drain vessel, to be installed in a concrete pit, equipped with truck loading connection; main header for collecting and draining condensate toward the closed drain vessel.
All closed drain lines shall be routed to the header drain by gravity with a minimum slope
of 1:100. The liquid content in the header shall be sloped to the closed drain vessel, from
where it shall be pumped out using vacuum truck connection.
The closed drain system shall account for reliable disposal of the drain fluids at the remote
locations without possibility of arrival of vacuum trucks.
Drainage flowrate shall not be bigger than the one resulting from draining largest item from
the low-low liquid level to the bottom within one hour & drain drum shall be sized to accommodate this volume [Ref 5].
The drain operation shall be executed manually in controlled manner except for the filter
separator skids and knock out drum in Kaduna and Kano Stations with automatic liquid
discharge to the closed drain system.
The minimum manual drain connection shall be 2” and minimum drain header size shall
be 4”.
9.10
Open Drain System
Non-hazardous water (storm water) shall be directed to open ditch with evacuation outside
station. The surface water shall be collected in open channels and routed outside the station through concrete & stone run-off located around the station.
Hazardous Open Drain System shall collect potentially contaminated water from process
areas. Each process unit shall contain a sump which shall be sized to contain the rainfall
lasting 15 minutes. Excess water shall be diverted into the non-hazardous open drain system.
The Hazardous Open Drain collection header shall be routed to the hazardous open drain
sump, where the collected oil will be separated and depending on location disposed locally
or collected by vacuum trucks.
the clear water from the sump will be discharged to non-hazardous open drain system [ref
5].
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9.10.1 Pipes
Non-hazardous (storm water) open drain system shall be made of uPVC per ASTM D1785;
or RTR (fiberglass) ;
Hazardous open drain system shall be made of High-Density Polyethylene (HDPE) per
ASTM D3350and ASTM F714.
9.10.2 Oil water separators
For inlet oil water parameters see below table:
Table 26
Inlet Oil water parameters
Oil content
600 ppm (expected)
Oil specific gravity
0.885 kg/dm3
Hydrocarbon condensate
content
Hydrocarbon condensate
specific gravity
Total suspended Solids
traces (accidental)
Temperature (min/max)
5/60ºC
0.529 – 0.602 kg/dm3
100 ppm (expected)
Oil water separators shall be sized to provide a hold up of 15mins. Oil separators shall be
designed in accordance with API PUB 421 or the Design and Operation of Oil water separators or other acceptable references;
A central oil-water separator shall be provided;
Collected oil shall be evacuated by vacuum truck while clean water shall be diverted to the
storm water system;
Waste oil and oily sludge shall be disposed-off in a waste disposal facility as approved by
the OWNER.
9.11
Simulations
Steady State simulation shall be performed using Aspen HYSYS to verify the Heat & Material Balance and developing the input required for steady state hydraulic study.
The design gas specification as stated in section 5.3 Table 14 shall be used.
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10.0
Kaduna & Kano Facilities Design Basis
10.1
Criteria for sizing of station piping
Table 27
Design Requirements for Station piping
Max △P
[bar/100m]
Service
Max gas velocity
[m/s]
Single phase gas process line
0≤P≤35barg
0.11
20
35≤P≤140 barg
0.25
20
The line sizing to be performed for two different scenarios which covers the operating envelope of the station:
Minimum Pressure
Scenario developed to account for operating conditions of the
station which are determined by minimum required gas pressure
at the station inlet. The minimum inlet pressure is 43 barg.
Maximum Pressure
Scenario developed to account for operating conditions of the
station which are determined by maximum gas pressure at the
station inlet. The maximum inlet pressure of 94 Barg shall be
considered for TGS sizing only. However, this pressure shall not
be the normal operating Scenario.
Diameter of piping shall be selected based on worst case scenario which is minimum pressure. Diameter of single HF train shall be selected with assumption that 30% of total gas
flow rate will be transported via HF, 70 % of total gas flow rate will be transported via bypass [Ref 24, 25].
10.2
Criteria for orifice meter sizing
The metering runs shall be designed based on the requirements stated in DPR (Department of Petroleum Resources), “Procedure Guide for the Determination of Quantity and
Quality of Gas and Gas Derivatives at Custody Transfer Points”, 2006.
Requirements concerning orifice meter are as follows:
•
Design flow of metering runs and thereby orifice meters shall result from the criterion that maximum operating flow is 80% of design flow.
•
Beta ratio
•
Maximum allowable pressure drop across orifice meter shall be 1000 inch of H2O
shall not be higher than 0.6
Sizing shall be carried out for worst case operating conditions (minimum operating pressure and maximum operating temperature) [Ref 9, 10].
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10.3
Criteria for Relief System Sizing
10.3.1 Relief causes
The relief causes considered in this report as per API STD 521 are as follows [Ref 12, 13]:
•
Gas expansion in the filter separators due to the fire;
•
Pressure rise in the closed drain vessel due to gas breakthrough through the filter
separators’ condensate system;
•
Gas expansion in the line heaters with continued heat input while the process side
is blocked;
•
Thermal expansion of trapped fluids in the pig receiver.
The other sources of relief connected to the vent system are as follows:
•
Emergency depressurization of inventory trapped between shutdown valves;
•
Manual depressurization of facilities installed within the station;
•
Manual depressurization of pipeline.
10.3.2 General Design Criteria
The following design criteria shall be followed in the design [Ref 12, 13]:
•
Pressure safety valves installed on each filter separator to be sized for fire case
scenario;
•
Pressure safety valves installed on closed drain vessel to be sized for gas breakthrough through the filter separators condensate system;
•
Pressure safety valves installed on inlet line to line heaters to be sized for over
pressurization due to outlet blockage with the continued heat input;
•
Pressure safety valves installed on pig launcher and pig receiver to be sized for
thermal expansion of trapped fluids;
•
Maximum accumulated pressure in the vessel equipped with pressure safety
valves for non-fire case: 110% of design pressure;
•
Maximum accumulated pressure in the vessel equipped with pressure safety
valves for fire case: 121% of design pressure;
•
Incremental pressure loss in the PSV inlet line caused by the flow through the PSVs
shall not exceed 3% of set pressure;
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•
The PSV outlet line design shall be done on a basis of maximum allowable Mach
number or maximum allowable back pressure (whichever is more stringent). The
velocity in the cold vent piping shall not exceed Mach number of 0.6 in the main
headers and 0.7 in the tail pipes. The velocity in the cold vent stack shall not exceed
0.5 Mach for peak flow. The maximum allowable back pressure shall not reduce
relieving capacity of any of the pressure relieving device and shall be lower than
pressure rating of piping materials [Ref 5].
•
Back pressure in the outlet piping downstream relief valve shall not exceed 10% of
set pressure in case of conventional PSV and 50% of set pressure in case of balanced PSV.
•
Superimposed pressure in the vent system resulting from relief of other source
shall not exceed 10% of set pressure in case of conventional PSV and 50% of set
pressure in case of balanced PSV (only if simultaneous relief of these sources is
credible)
•
The materials of discharge piping and vent stack shall be selected that are compatible with the expected minimum temperature during relief.
•
Exit velocity from vent stack for peak flow rate shall be 150m/s (recommended by
API STD 521).
•
Emergency depressurisation shall allow for depressurisation of each ESD section
from design pressure down to 50% of design pressure within 15 minutes [Ref 20].
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10.3.3 Emergency isolation and blowdown system
ESD System shall be provided as a primary overpressure protection.
Process plant shall be segregated into different blowdown sections separated by ESD
valves. ESD valves shall be provided as a minimum in the battery limits and HP/LP system
boundaries. Each of the ESD section shall be equipped with blowdown valves (BDV).
Blowdown valves shall be automatically actuated by signal from F&G system (fire and gas
detection system) or manually by the operator. Facilities shall be provided to enable the
operator to manually initiate blowdown.
Blowdown system shall be sized for the fire scenario as it is more stringent scenario. Depressurization rate for the fire scenario shall results from reducing pressure at initial conditions to a level equivalent to 50% of the design pressure within approx. 15 minutes.
Material of piping downstream of the BDV shall withstand cold temperatures occurring
during depressurization due to Joule-Thompson effect.
BDV and restriction orifices shall be installed at the highest point. [Ref 5].
10.3.4 Manual depressurization
Pipeline
Each pipeline sections separated by block valve stations shall be manually depressurized
in case of an emergency through the vent stack located at stations or vent stack located
at block valve stations. A throttling valve (globe valve) and a properly sized restriction orifice shall be used as restriction element for depressurization to ensure re-leased gas flow
and temperature are within desired limits (max 0.7 Mach flow and min temperature with
LTCS limit of -46 deg C). The throttling element shall be sized such that depressurization
will be carried out within a reasonable time.
In order to limit the pipeline depressurisation time within 5 days, linear section depressurisation shall be conducted via upstream & downstream vent system simultaneously..
In order to minimise loss of gas & emissions during depressurisation, Each BVS & TGS is
provided with mobile compressor connection across Station isolation valve (Gas operated
Valve). After a section of pipeline is isolated by valves, and prior to blowdown, the pressure
in the line can be reduced by using a mobile compressor(s) to transfer gas from that section to a downstream section of the pipeline.
Further, The BVS vent system is provided with positive isolation to prevent any gas leakage & loss of gas during normal operation.
Pig Launcher / Pig Receiver
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Pig launchers / receivers shall be depressurized manually only. Automatic blowdown
valves are not necessary as pig launchers / receivers shall be depressurized during normal operation. A throttling valve (globe) and a properly sized restriction orifice shall be
used as restriction element for depressurization to ensure released gas flow and temperature are within desired limits.
Terminal Gas Station
The process equipment shall be manually depressurized if any maintenance activities are
required. All vents from each isolated section shall be collected into one sub-header connected to the main cold vent collecting header. A throttling valve (globe) and a properly
sized restriction orifice shall be used as restriction element for depressurization to ensure
released gas flow and temperature are within desired limits.
11.0
HOLD List
1. Deleted.
2. Deleted.
3. Deleted
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