Koyama.qxp 1/7/09 3:30 pm Page 74
Computational Fluid Dynamics Simulation on Liquefied Natural Gas Storage Tanks for Safety and Efficiency
Figure 3: Computational Fluid Dynamics Simulation Method Figure 4: Comparison Between Calculated Results and Measurements
Non-linear partial differential equation
Density profiles at tank centre
1. Continuity equation
0
Calc. Meas.
466
Np Np
0.5h
464
Dens ∆
∂
(r
•
ρ ) + (r ρ U) = S
α α α α MS
+ Γ • r = 1
αβ α -1
1h
462
α
∂t
1.5h
460
iβ=1 α=1
2. Momentum equation
2h 458
ty
N
-2
(k
2.5h 456
g m
p Np
4h ∆ ∆ ∆ ∆ 454
∂
(ρU)
•
+ [ρU x U – µ( U + ( U)
T
)] = S
M
– ρ, ρ = r ρ , µ = r ρ
α α α α 452
-
^
∂t
-3
3)
α=1 α=1
450
3. Thermal energy equation 448
Inlet
-4
446
∆ ∆
•∂
(r λ T)] = Q + Sρ h ) [r (ρ Uh – +
α α α α αα 0 5 10 15 20 25 30 35
∂t
α α
4. Turbulence model:
H/D 100 (height)
κ−ε model, etc.
Comparison with measurements
5. Buoyancy: F=∆ρ (T) x g, boil-off gas model, etc.
feed time leads to a larger final density difference; and if the initial
ρ = density; U = velocity; µ = viscosity; S
MS
, S
M
, S = mass, momentum, heat source;
Γ, Q = inter-phase mass, heat transfer; ρ = pressure; h = enthalpy; T = temperature;
depth is low and the feed rate is high enough, the final density
λ = thermal conductivity; t: = time; N
p
= total number of phases;
= subscript refers to phase
difference will be very small.
α, β; r = =olume fraction; g = gravitation vector.
α, β
Discretisation Modelling Numerical
(control volume method) and meshing
Computing
solution
Conclusions
Tank reception procedures with different densities of LNG are studied
General-purpose
Mesh with:
by CFD simulation. A numerical model has been developed and
CFD software CFX
physical properties
boundary properties
verified by actual measurements. A range of case studies indicate that
initial conditions
additional program,
the density difference at the end of the reception depends on the
Mesh
Z
etc.
Z
Y X Y X
initial density difference, the initial depth of heel and the feed rate.
This CFD simulation method has been proved to be effective in
difference; a deeper heel leads to a lower final density difference; a establishing safety guidelines to avoid stratification, making it an
lower feed rate leads to a lower final density difference; a longer essential technology for LNG receiving terminals. ■
Iran to Assist Ugandan Petroleum Value Chain
Iran is to grant financial and technical support for Uganda’s whereby unrefined crude is transported to Kenya, whereupon it
petroleum value chain, including funding a refinery and providing would be refined and exported to global markets from the port of
training for Ugandan petroleum engineers. The agreement is part of Mombasa on the Indian Ocean. Opposing such a plan, Uganda has
a bilateral agreement announced in May following a visit by Ugandan looked to Iran – a nation with which it has considerable historical
President Yoweri Museveni to Tehran, during which he and President ties – for support. The benefits to Iran are not yet clear, since it is
Mahmoud Ahmadinejad agreed wide-ranging collaboration across struggling to develop its own refining capacity and even imposed
energy, agriculture, transport and mining sectors. gasoline rationing in 2006, but the investment may service other
aspects of the bilateral agreement. Iran is particularly interested in
The Ugandan government has sought to develop domestic refining Ugandan uranium, discovered in 2004. Simon Henderson, Director
capacity after exploration and drilling revealed reserves totalling 600 of the Gulf and Energy Policy Program at The Washington Institute,
million barrels of oil in the Lake Albert Rift Basin. Processing the has argued that Iran is expanding co-operation agreements with oil
waxy crude in Uganda will maximise its value and provide jobs. It will and gas customers to complicate the application of sanctions it may
also reduce Uganda’s dependence on petroleum imports since the face as a result of its controversial nuclear programme.
landlocked country relies heavily on road and rail import routes,
which are expensive and vulnerable to disruption (as occurred during With the exception of South Africa, sub-Saharan Africa has
the Kenyan riots last year). “We are more inclined to building a struggled to develop effective domestic refining capacity. Existing
refinery than exporting unprocessed crude oil,” said President refineries are small, ineffective and not fit to meet today’s
Museveni following his visit to Tehran, adding that Uganda could increasingly stringent fuel emissions standards. Capital costs for new
produce a range of petroleum products for transport, power supply refineries are prohibitively high, and foreign oil corporations have
and domestic use. “We don’t want anything raw to get out,” generally not invested because most have refining arms themselves
agreed Energy Minister Hillary Onek, speaking at the 4th East or access to them. The World Bank – an alternative source of
African Petroleum Conference in Mombasa in March. funding for refineries – has been reluctant to invest because Africa
has no comparative advantage and cannot compete with Middle
However, UK-based oil company Tullow Oil and partner Heritage Eastern, European or Asian refining corporations. According to
Oil – who hold major licences in the Lake Albert Rift Basin – have Eleodoro Mayorga-Alba, lead petroleum economist at the World
previously indicated that Ugandan production was not high enough Bank, small domestic markets and weak distribution infrastructure
to justify a refinery of the size the government was desirous of mean refining facilities would actually “weigh heavy on their
(30,000–50,000 barrels per day at a cost of US$1.5 billion). “No-one economies”. However, the desire of Africa’s rising producers to
has ever dreamed of building one of these incredibly complex exert greater control over their oil may result in more collaborations
refineries in the middle of Africa,” said Brian Smith, Vice President of with state-owned oil groups who are better than independent oil
Heritage. Although they have not ruled out the possibility of a corporations at balancing strategic supply interests with short-term
refinery, the two corporations would prefer export-led development profit concerns, according to Sipho Mkhize, CEO of PetroSA. ■
74
HYDROCARBON WORLD VOLUME 4 ISSUE 1
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