text
stringlengths
0
1.75k
refineries
was
facilitated
using
Argonne
National
Laboratory’s Greenhouse gases, Regulated Emissions, and Energy
use in Transportation (GREET™) model [19]. The GHG emissions
calculation combines carbon dioxide, methane and nitrous oxide
with their global warming potentials, which are 1, 25 and 298,
respectively, as recommended by the latest Intergovernmental
Panel on Climate Change for a 100-year time horizon [20].
2. Refinery modeling and analysis approach
In the current study, refinery LP modeling was employed to
simulate and compare the operations of 43 US and 17 EU refineries
with individual processing capacity of over 100,000 bbl/day crude
oil. Note that although the 17 EU refineries account for only 25% of
the total EU refining capacity, their operational characteristics
appear to be quite consistent with aggregate average EU refinery
operations (see Table S1).
The
selected
US
refineries
were
located
in
Petroleum
Administration for Defense Districts (PADDs) 1, 2, 3 and 5, while
the selected EU refineries were located in the coastal regions of
Europe. Refinery LP models typically maximize profit by determin-
ing the optimal volumetric throughput and utility balance among
various process units within a refinery under specific market and
operation conditions [21]. The output files from LP model sim-
ulations contain volumetric and mass flow rates associated with
inputs and outputs of process units. Using this information, energy
inputs and outputs can be calculated by using known heating val-
ues of various stream components.
In this study, we grouped the U.S and EU refineries described
above into three different groups according to their average crude
API gravity and HP yield. As shown in Fig. 1, refineries were
J. Han et al. / Fuel 157 (2015) 292–298
293
categorized in the following manner: (1) Low API (API grav-
ity < 29), (2) High API/Low HP (API gravity > 29 and HP < 0.22)
and (3) High API/High HP (API gravity > 29 and HP > 0.22).
Table S2 also shows the operational characteristics of refineries
in each refinery group. Note the almost no overlaps in the key
parameters between the Low API and High API/High HP group.
Among the two High API groups, the Low HP group is clearly more
resource-efficient than the High HP group. It also needs to be noted
that assigning refineries to any of the three refinery groups is not
intended to provide a statistical or physical classification among
refineries; rather it is intended to examine the impacts of resource
and energy efficiencies on life-cycle GHG emissions. Within each
refinery group, three major metrics were evaluated for each refin-
ery: overall refinery efficiency, product-specific refining efficiency
and life-cycle GHG emissions intensity. Based on the volumetric
amounts of refinery inputs and outputs, and purchased electricity
energy
estimated
by
the
LP
modeling,
the
overall
refinery
efficiency was estimated by dividing the total energy output by
the total energy input on a lower heating value (LHV) basis
(see Eq. (1)).
where gLHV is the LHV-based overall efficiency of a refinery. Pn, Cm
and OIoare the amounts of refining product n (e.g., gasoline, jet fuel,
diesel, liquefied petroleum gas [LPG], RFO, pet coke), crude input
m, and other input material o (e.g., normal butane, iso-butane,
reformate, alkylate and natural gasoline) in barrels for liquid prod-
ucts
and
tons
for
pet
coke,
respectively.
NGpurchased;LHV
and
H2;purchased;LHV are the LHV-based energy of purchased natural gas
(NG) and purchased H2, respectively. Electricitypurchased is the energy
in purchased electricity. LHVm, LHVn, and LHVo are the LHVs of
crude input m, refined product n, and other input material o,
respectively, in MJ/barrel for liquid products and MJ/ton for pet
coke.
In order to calculate the GHG emissions intensity for each
refined product, the product-specific efficiency and process fuel
shares need to be determined. This determination is essential as
each product pool is supplied from a different set of process units,
each with different energy and emissions burdens (see Fig. S2).
Since refinery inputs propagate through individual process units
to final products via intermediate products, each intermediate or
final product carries with it certain energy and emissions burdens
of the total refinery inputs, such as crude, natural gas, electricity,