American Journal of Oil and Chemical Technologies:
Petrotex Library Archive
American Journal of Oil and Chemical Technologies
Journal Website: http://www.petrotex.us/2013/02/17/317/
CALCULATE VOLUME OF VENTING GAS FROM GAS PIPELINE
IRAN AND USE OF A MOBILE COMPRSSOR FOR SAVE IT
ARASH LAZAR, Farokhi1
1
Chemical Engineering, nigc(national iran gas company), arash_station@yahoo.com
Abstract:
The emissions of natural gas from gas transportation EPA paper was published that is the second factor for green house and
global warming.for this article we try find a way for preventing of waste this source because of economical aspect and
environmental problems.first we calculate the volume of gas venting from pipeline with redlish quank equation and then get
quantity of money value of this gas then we suggest a mobile compressor for saving this gas . buy or renting of this device
was compaired in gas pipeline of iran.
Keyword: mobile compressor,emission,pipeline
1.
Introduction
1.1 Problem description
1.1.1 Greenhouse Effect
The Earth is warmed by radiant energy from the sun.The amount of energy transmitted to the Earth’s surfaceis approximately
equal to the amount of energy reradiatedback into space in the form of infraredradiation, and the temperature of the Earth’s
surfacestays roughly constant. However, the temperature of theEarth is strongly influenced by the existence and composition
of its atmosphere.Many gases in the Earth’s atmosphere absorb infraredradiation that is “re-radiated” from the surface,
trappingheat in the lower atmosphere. Without this natural“greenhouse effect” it is likely that the averagetemperature of the
Earth’s surface would be in theorder of -18° Celsius, rather than the +15° Celsiusactually observed. (IPCC, 1996).
The gases that help trap the Sun’s heat close to theEarth’s surface are referred to as “greenhouse gases.”All greenhouse gases
(GHGs) absorb infrared radiation(heat) at particular wavelengths. It is the absorptive capacity of GHGs that determines their
global warmingpotential (GWP). The most important greenhouse gasesare water vapor (H2O), carbon dioxide (CO2),
methane(CH4), nitrous oxide (N2O), and several engineered gases, such as hydrofluorocarbons (HFCs),perfluorocarbons
(PFCs) and sulfur hexafluoride (SF6).Water vapor is by far the most common GHG, with anatmospheric concentration of
nearly 1 percent,compared with less than 0.04 percent for carbondioxide. Concentrations of other GHGs, such as CH 4and
N2O, are a fraction of that for CO2.
1.1.2 Methane Emissions
Methane emissions originate from three source categories each contributing approximately one-third of CH4 emissions:
energy consumption, waste management and agriculture. Methane emissions from gas systems account for 21 percent of the
anthropogenic methane emissions(1). (INGAA Foundation, 1999), and 8 percent from the total global emissions (USEPA,
2006).While natural gas systems comprise the largest sourceof methane emission within the energy sector, it is the second
largest source of total methane emissions[3]
Figure (1): Percent of Methane Emissions from Anthropogenic Sources (INGAA Foundation, 1999)
2.
Materials and Methods
1.1 Pipeline Pump-down
Pipeline pump-down allows gas pipeline operators to reduce vented methane emissions when they take a section of pipeline offline
for repairs. Normally, for safety reasons, the operator must vent the gas before repair work begins. This can involve the loss of
substantial volumes of gas and money, as well as significant emissions of methane. Instead, with pipeline pump-down, the operator
can use either a portable compressor, in combination with the in-line compressors, to move the majority of the gas to the next
pipeline segment before depressurization. The calculations provided in Table 3 reflect the costs and savings when using a portable
compressor. A portable compressor can pump down a greater percentage of the gas (up to 90%) and can conduct the operation faster
than in-line compressors. However, using in-line compressors involves less capital expense.
In Russia, Gazprom developed and verified a joint implementation project “Use of Mobile Compressor Stations for Pumping
Natural Gas from the Gas Pipeline Section" (1). Gazprom plans to implement the project in the UGSS of Russia applicable for both
existing and projected pipelines with diameters ranging from 700 to 1,420 mm. The project enables gas to be pumped forward from
sections of gas pipelines scheduled for repair. In 2010, pilot (qualification) tests on the mobile compressor stations were made in the
area of the Ust-Buzuluksk trunk line of Gazprom Transgaz Volgograd. The tests consisted of experimental gas pumping using a
mobile compressor made in Russia by the company OOO Gazag. The main technical specifications of the tested mobile compressor
are provided in the Table 1:
Parameter
Installed capacity
Own needs consumption for the whole period
of period of pumping
Volume of gas pumped from the isolated
pipeline section
Number of compressors in the set, required to
pump out one pipeline section
Number of applications per year
Time needed to lower the pressure down to 1
MPA in the section
Unit
kW
m3
Value
2,375
46,777
m3
3,097,476
units
5
hours
18
90
Table 1. Technical Specifications for a Mobile Piston-Type Compressor Station.source(1)
2
Mobile compressors use two typical schemes of gas re-routing, or pump-down, from the withdrawn section of pipeline, as presented
in Figure 2.
Figure 2. Typical Schemes of Application of Mobile Compressor Stations
In the U.S., several EPA Gas STAR partners[4] have successfully used pipeline pump-down. One example is Southern Natural Gas
Company, which reported that it used portable compressors three times at one location over a year to save $228,000 in recovered
gas at a cost of about $68,000. The effort paid for itself in four months; other companies reported even faster payback times (12).
A sutible mobile compressor can gain below item[5]:
-reduce the pressure pipeline under 6 barg
-reduce emmissin until 90%
-reduce the environmental problem
-increace the economical benefit
3. Mathematical Equation
3.1 Volume
We know the mathematical equation of gas [9]
PV=nRT
𝑃1𝑉1
=
𝑍1𝑇2
(1)
𝑃2𝑉2
𝑍2𝑇2
(2)
And the volume of the pipeline
𝜋
4
𝑉 = ∗ 𝐷2 ∗ 𝐿
(3)
And compressibility factor with redlish quank equation is [9]
0.422
(4(
B0 = 0.83 − TR1.6
0.172
B1 = 0.139 − TR4.2
BPC
A = RTC = B0 + 0.008 ∗
P
PR =
(7)
PC
PR
𝐙 = 1 ∗ A ∗ TR
(5)
B1
TR =
(6)
T
TC
(8)
(9)
3
And for calculating the volume of gas in pipeline we see:
π
D2
4
144
V(scm)= ∗
1.01325+P
Z1
1.01325
Z2
∗ L ∗ 3.28084 ∗ (
)∗
∗
T1
T2
∗
1
35.315
(10)
3.1 time of vent
Time for venting gas with this equation is[10]&figure(2):
𝑝2
𝑘
𝑝1
𝑘−1
𝑡𝑐 = 𝑙𝑛 ( ) − (
𝑡𝑣 = 𝑉 ∗
) ∗ 𝑙𝑛 (
𝐴𝑟 =
2
1
𝐾+1 𝐾+2(𝐾−1)
( 2 )
𝑀𝑊
𝐴𝑝
𝐴𝑡ℎ∗𝐶𝑑
Cf = a1 + a2 ∗ log (
)
(11)
(12)
𝐶∗𝐴𝑡ℎ∗𝐶𝑑
𝑍∗𝐾∗𝑅∗𝑇
𝐶=√
𝑘+1
(13)
(14)
f∗L
D
) + a3 ∗ log (
f∗L 2
D
) + a3 ∗ log (
1
1
Ar
Ar
2
f∗L 3
D
)
(15)
1
a1 = 1.0319 − 5.2735 ∗ ( ) + 25.68 ∗ ( ) − 38.409 ∗ ( )
1
1
1
Ar
1 2
Ar
Ar
(16)
Ar
2
Ar
3
1
a2 = −0.26994 + 17.304 ∗ ( ) + 86.415 ∗ ( ) − 144.77 ∗ ( )
3
(17)
Ar
1 3
a3 = 0.24175 − 12.637 ∗ ( ) + 56.772 ∗ ( ) − 88.351 ∗ ( )
1
1
2
(18)
Ar
1
a4 = −0.054856 + 2.6258 ∗ ( ) − 8.9593 ∗ ( ) + 12.139 ∗ ( )
Ar
Ar
Ar
ttot = (tc + ts) ∗ tv ∗ Cf
(20)
3
(19)
For this equation we assume k=1.3 then ts=.7833.and we get friction factor with the table(2) .[10]
Diameter(mm)
Friction factor
26.64 (1" STD)
40.9 (1.5" STD)
52.5 (2" STD)
77.92 (3" STD)
102.26 (4" STD)
154.08 (6" STD)
202.74 (8" STD)
254.46 (10" )
304.81 (12")
336.56 (14" )
387.36 (16" )
438.16 (18" )
488.96 (20" )
590.56 (24" )
742.96 (30")
0.023
0.021
0.019
0.018
0.017
0.015
0.014
0.014
0.013
0.013
0.013
0.012
0.012
0.012
0.011
895.36 (36" )
0.011
Tabel(2):friction factor for pipeline
Ath.d(in)
P2.T2.V
Venting gas
‫گاز‬
L(M)
Ap.D(in)
figure(2): vent in pipeline
4
3.1 mass flow rate of gas vent[8]:
2 𝑘/𝑘−1
If 𝑘+1
𝑝2
≥𝑝1 then we have:
Ms=𝐶𝑑 ∗ 𝐴𝑡ℎ ∗ √𝜌𝑖 ∗ 𝑝 ∗ 𝑘 ∗ (
If
2 𝑘/𝑘−1
𝑘+1
>
𝑝2
𝑝1
2
𝑘+1
𝑃1 1/𝑘
𝑃2
𝑘+1
𝑘−1
)21(
then we have:
MS=𝐶𝑑 ∗ 𝜓 ∗ 𝐴𝑡ℎ ∗ √𝜌𝑖 ∗ 𝑃 ∗ 𝑘 ∗ (
𝜓 =( )
)
𝑃1
∗ √1 − ( )
𝑘−1
𝑘
𝑃2
2
𝑘+1
)
𝑘+1
𝑘−1
(22)
𝑘+1
∗ √(
2
𝑘−1
)∗(
𝑘+1 𝑘−1
)
2
(23)
density of the gas in pipeline is:
𝑃∗𝑀𝑊
𝜌𝑖=8314∗𝑍∗𝑇
(24)
we write a software[12] include of top equatoion that written with visual basic 6 is shown figure(3)
Figure(3):software was written for calculate the volume vent gas
4 choose a portable compressor
A mobile compressor[5] must be have this item:
-Max. capacity, shortest possible transfer time
-Energy source isNatural gas (autonomous unit)
-Built according to applicable European and German codes and standards
-Discharge pressure protection (can be adjusted as required in line with MOP of pipeline)
-Discharge temperature protection
-Gas warning sensor
-Fire extinguishing system (Inergen)
We seggest below mobile compressor was built LMF company for our goal.the Technical details is Figure(4):
5
vehicle: Mercedes MB-1848 LS, 350 kW
Dimensions: Length: 13.5 m; Width 2.55 m; Height: 4.0 m
Weight: less than 40 t
4.1 Compressor :
-Reciprocating compressor (LMF BS 604), two-stage, double-acting, 4x130mm
-640 kW (max.)
-2,200 – 61,000 Nm3/h (dependent on pressure ratio)
-Suction pressure: 69 to 5 barg
-Max. discharge pressure. 70 barg
4.2 Drive:
-Gas engine (CAT G3512LE)
-750 kW (max.) at 1,400 rpm
-Average fuel consumption:150 Nm³/h (250 Nm³/h max.)
Figure(4) mobile compressor lmf
4.3 Installation
-Can be used to connect two different pipelines
-Can be installed on one pipeline
as shown in the figure(5)
-Connecting fittings are retrofitted e.g. by hot tapping
-Min. diameter of connecting piece is 100 mm
-Adapters are available for different connecting pieces
Figure(5) mobile compressor unit
6
Example: Mobile compressor Typical evacuation process below figure(6)
figure(6):time venting gas for example
5. explanation mobile compressor for gas pipeline in iran ( gas transmission region 9)
The best way for choosing mobile compressor is depending on the ventig gas volume and company costs. The
data’s case[11] study is for gas transmission region- 9 Table(5).. we can generalalize for all pipeline of iran.
Gas vent in pipeline and gas station
Name gas station&pipeline segment
ramsar
26680
noor
14680
repaire 30”-60 km
1431789
neka
13450
ghalegigh
10320
sum
1496919
Table(5):gas volume vent in gas transmission region- 9
The price of rent and buy a mobile compressor [4]is table(6)
70 bar
buy
5-3milion
$
40 bar
rent
200.000- 70.000$ per
mounth
buy
1.5-1milion
$
20 bar
rent
50.000- 30.000 $ per
mounth
buy
-500.000
750000$
rent
24.000-15.000$
per mounth
Table(6):mobile compressor buy or vent device
7
In this table(7) compare between buy and rent amobile compressor
buy
rent
Gas vent for region 9
1496919
Gas vent for region 9
1496919
Gas vent for region %90
1349227
Gas vent for region %90
1349227
Velocity of evacuation(m3/h)
6000
Velocity of evacuation(m3/h)
6000
Time for vent(hour)
224
Time for vent(hour)
224
fuel consumption device(m3)
250*224=56217
fuel consumption device(m3)
250*224=56217
Real saving gas(m3)
Equivalent of money for
saving gas(rial)
1293009
1293009
4,522,811,500
Real saving gas(m3)
Equivalent of money for
saving gas(rial)
4,522,811,500
Price of device (million $)
$4
Rent per mounth($)
100.000
Table(7)compare table
6. conclusion
The best way for chossing mobile compressor in iran depending on the gas vent and company cost. to consider
lengh of pipeline figure(7) in iran include 10 zone (pipeline,gas compressors) can guess quantity of vent gas is very
high .in this article we discussed for one zone in norh of iran and it will be benefit for all iran choosing a mobile
compressor in pipeline.and will back investment for many year. for example a project in some country, Value of
natural gas was € 330,000 saved in 2010.And the another project was € 1,870,000 in 2011.
Figure(7): iran’s pipeline grid
8
7. symbol
D
diameter pipe (m)
L
lengh pipe (m)
V
Volume of the pipe being blown down, m3
P1
P2
Atmospheric Pressure, kPa (abs)
Pressure of the gas pipeline, kPa (abs)
𝑡𝑐, 𝑡𝑠
Dimensionless Sonic blowdown time
k
Ratio of Specific heats (Cp/Cv)
𝑡𝑣
Time constant, seconds
c(m/s)
SG
sonic velocity, m/s
Specific Gravity of Gas (Air =1)
T1
gas tempreture 520 rankine
R
Universal Gas Constant (8314 J/kmol-K)
T2
gas tempreture in pipeline
MW
Molecular Weight of the Gas
Blowdown Correction Factor
Z1
compressibility factor 520 rankine
Cf
Z2
compressibility factor in pipeline
f
PC
Critical Pressure 46 bar
Ap(m2)
TC
Critical tempreture 343 rankine
PR
redual pressure gas
Darcy friction factor
C/S area of pipe, m2
Ath(m2)
Blowdown discharge Area, m2
Cd
Blowdown coefficient,
total blowdown time, seconds
TR
redual pressure gas
ttot
ρi (kg/m3)
density of the gas @Pi,T
MS(Kg/s)
massflow rate
8. References:
[1] understanding methane emissions source and viable mitigation measure in the natural gas transmission system:
russian and us. experience
A. Ishkova, G. Akopovab, M. Evansc, G. Yulkinb, V. Roshchankac, S. Waltzerd, K. Romanova, D. Picarde, O.
Stepanenkof, D. Neretinf .
[2]internatioal energy agency (IEA), (2008) natural gas information. http://www.iea.org/stats/prodresult.asp
[3]u.s. environmental protection agency (U.S.EPA), (2006). Global Anthropogenic Non-CO2 Greenhouse Gas
Emissions: 1990-2020. Office of Atmospheric Programs, Climate Change Division
[4] U.S. EPA, Natural Gas STAR Program, (2006). Lessons Learned From Natural Gas STAR Partners. Using
Pipeline Pump-Down Techniques to Lower Gas Line Pressure Before Maintenance
[5] Leobersdorfer Maschinenfabrik GmbH & Co.KG -sales & service representatives
[6] net4gas company. www.net4gas.cz
[7] Methane emissions from natural gas transport. Murrath. March 2009 S. Master of Science – Thesis
[8] Calculating Accidental Release Flow Rates From Pressurized Gas Systems. Milton R. Beychok, Consulting
Engineer Newport Beach, California, USA
[9] Fluid Mechanics, M. Potter, D.C. Wiggart, Schuam's outlines, McGraw Hill (USA), 2008, ISBN 978-0-07148781-8
[10] Simple Method Predicts Gas Line Blowdown Times, by M.H. Weiss, K.K. Botros, W.M. Jungowski, Oil & Gas
Journal, Dec. 12, 1988
[11] data from gas pipeline of iran
[12] calculate volume and time ventig gas.http://cld.persiangig.com/sync.html
[13] Avoiding climate-damaging methane emissions during pipeline repairs. Krakow, Christian Hadick (Pipeline
Intervention) and Axel Scherello .October 14th, 2011
9