TOWARDS A ZERO (NET) CARBON REFINERY
Author:
Michael Stockle
Chief Engineer, Refining Technology
Business Solutions Group
Foster Wheeler
The well-to-wheel emissions for petrol and diesel can be split into three main parts; oil
production and transportation, oil processing and transportation, and emissions from the
consuming engine.
In order to reduce emissions and meet government targets for carbon reduction it is likely
that all three parts of the chain will need to make some contribution.
Whilst the processing of oil in the refinery only contributes around 5-10% of the total well-towheel emissions, the opportunities for reducing these are significant due both to the nature
of the processes used, the fuels available and the fact that these are large-scale fixed
location processes making applications such as carbon capture and storage (CCS) more
practical than they would be on individual vehicles.
This paper will look at the main sources of carbon emissions from a refinery and look at a
range of options for reducing the carbon impact of the refinery, starting fuel substitution and
energy efficiency then moving on to look at how technologies such as CCS and renewable
power generation could be integrated into the refinery.
The paper will look at the impacts on refinery economics of making these changes and show
one possible solution that, at a sufficiently high carbon price, could see a net zero carbon
refinery.
Introduction
Processing of crude oil in a refinery typically counts for about 5-10% of the well to wheel
emissions associated with extracting crude, converting it into transport fuels and burning
those fuels.
To maximise the use of fossil fuels and get the most from each drop of oil we need not only
to use oil efficiently in the vehicles we drive but also to process the oil as efficiently as
possible. By making our refinery efficient and by looking for ways to decarbonise the fuels
used in the refinery we can start to look at how we can move towards a zero net carbon
refinery and make a significant contribution to reducing the well to wheel emissions of fossil
fuel powered transport.
Sources of Carbon Dioxide in the refinery
The sources of carbon dioxide in the refinery can be grouped into four main groups;
•
•
Fuel to process units
Steam and power production
•
•
Hydrogen production
FCC Coke (where applicable)
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The emissions of an individual refinery depend on a number of factors. The configuration of
the refinery is a key factor, as complex upgrading refineries produce more CO2 than simple
hydroskimming configurations, but they also produce more of the fuels society demands.
The fuels used in the refinery also have an impact, as do the crudes processed, heavy sour
crudes require more energy to process than light sweet crudes.
In order to quantify the relative sizes of the emissions we can look at a typical refinery
configuration and the carbon dioxide emitted from it. In this paper we have considered a
European FCC-based refinery processing 150,000 BPSD of Ekofisk crude that generates all
power and steam on site from refinery fuel gas and fuel oil. The diagram below shows the
main configuration of this refinery.
LPG
LPG Merox
LPG
Naphtha
H2
Lt Nap
SFG
H2
CDU
Nap
Naphtha
Naphtha HDT
CCR
Ref
Hvy Ref
Hvy Nap
Kero
Gasoline
Splitter
SFG
H2
Crude
C4’s
Reformate
FG
H2
Splitter
Isom
ISOM
LPG
Kero HDT
Diesel
Jet
SFG
H2
Diesel
Diesel HDT
H2
SFG
LPG
LCO
H2
Atm Res
VGO
FCC
VDU
SFG
FCC Nap
HDT
Naphtha
Treated Gasoil
LCO/DCO
WN
Visbreaker
V Res
Atm/Vac Res to Fuel Oil
SFG
HSFO
Gas Oil
Residue
Kero to Fuel Oil
Diesel to Fuel Oil
SFG
Amine Treatment
FG
Legend:
SFG Sour Fuel Gas
FG
Fuel Gas
H2S
Fuel Gas System
Sulphur
SRU
LPG
Hydrogen Plant
H2
Block Flow Diagram:
FCC & Visbreaker Configuration
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The emissions from this typical refinery are shown below.
6,000.00
5,000.00
4,000.00
Utilities
TPD of CO2
HPU
SRU
Visbreaker
3,000.00
FCC
DHT
Naphtha Block
CDU /VDU
2,000.00
1,000.00
Base Sources
Options for reducing refinery carbon emissions
There are a number of ways of reducing the carbon emissions of a refinery, ranging from
relatively simple low-cost options to complex, capital-cost-intensive options. The options can
be grouped into a number of areas and we will consider each area in turn.
Energy efficiency
As we look to reduce carbon emissions the first focus area is energy efficiency. The other
options we pursue will tend to be more expensive than the current energy sources in the
refinery (if they were cheaper they would already be being used) and so making the most of
energy we do use will become even more important.
Even refineries that consider themselves good performers in terms of energy efficiency can
do more and this is illustrated by a recent study Foster Wheeler and AspenTech jointly
completed for a top quartile performing refinery in northern Europe. This study resulted in
operational improvement and investments being identified that saved around 10% of the fuel
used on the refinery and were expected to deliver a payback of less than 18 months.
This clearly demonstrates that in a world where crude price are sustained above $100/bbl
energy efficiency is something every refinery should be looking at again. In our example we
will assume our base case refinery has already achieved a high level of efficiency and will
focus on other options to reduce the emissions from the refinery.
Fuel substitution
Hydrocarbon fuels contain significantly different levels of carbon and result in significantly
carbon emission for the same level of energy requirement. The table below compares the
impact of different fuel sources on carbon emissions.
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Table 1: CO2 emissions for typical fuels
Fuel
Calorific value
(kJ/kg)
50,000
47,500
46,300
47,200
40,000
119,900
Methane
Ethane
Propane
Ethylene
Fuel Oil
Hydrogen
CO2 tonnes/
tonne
2.75
2.93
3.00
3.14
3.21
0
CO2 tonnes/
FOE tonne
2.20
2.47
2.59
2.67
3.21
0
The graph below shows the total refinery CO2 emissions from a 150,000 BPSD refinery
assuming all heat and power is generated on site, compared to the level of emissions if
natural gas was imported for power generation.
6,000.00
5,000.00
Utilities
TPD CO2
4,000.00
HPU
SRU
Visbreaker
3,000.00
FCC
DHT
2,000.00
Naphtha Block
CDU /VDU
1,000.00
Base
Nat Gas Firing
Moving from fuel oil firing to natural gas firing reduces emissions from the refinery by about
13%.
Of course, the economics of this option are very dependent on the relative prices of natural
gas and fuel oil. In the US, where the differential between natural gas and crude price has
widened considerably, then natural gas firing will be increasingly attractive. In Europe the
incentive will be lower but will still generally favour natural gas firing where available. The
graph below shows the natural gas price required to breakeven on energy cost versus fuel
oil at varying carbon prices.
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Break even natural gas price versus fuel oil price at varying carbon price
30.0
Natural Gas price $/MMBTU
25.0
20.0
15.0
10.0
5.0
0.0
50
60
70
80
90
100
110
120
Fuel oil Price $/bbl
$/tonne CO2
0
25
50
Green heat and power
In our example refinery we have assumed that all the refinery’s power requirements are
generated on site. On e way to reduce the emissions associated with the refinery would be
to generate this power from low carbon sources, either on site or by purchasing green power
over the fence.
If we replace all of the onsite power generation we can with imported low carbon power then
emissions drop as shown in the graph below.
6,000.00
5,000.00
Utilities
HPU
TPD CO2
4,000.00
SRU
Visbreaker
3,000.00
FCC
DHT
2,000.00
Naphtha Block
CDU /VDU
1,000.00
Base
Elec Purchase
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This option reduces on-site emissions by 28%, but is dependent on a reliable supply of
green power.
If power was required to be generated on-site, options such as wind and solar could be
evaluated, but again the dependability of these sources may be an issue, and investment is
likely to be required in backup systems (which won’t offer a carbon saving) or energy
storage.
If we combined natural gas firing and low carbon power purchase then we can reduce
emissions by almost 40% from the original base case.
To make further reductions in emissions, other, less conventional options, need to be
investigated. These could include
•
•
•
Renewable sources of heat, such as heat from CSP or electrical heating from green
power.
Carbon capture
Use of biomass derived or other low net carbon fuels
There are several potential renewable sources of heat that could be used in a refinery, green
power could be used in electrical heaters and CSP or geothermal power could be used as
sources of heat to generate steam. These options have not been considered in detail in this
paper, but could offer real benefits for refiners with easy access to abundant sources of
these types of energy.
Carbon Capture
There are a number of ways that carbon capture can be integrated into the refinery. All three
of the commonly proposed capture schemes can be used in the refinery with precombustion, post-combustion and oxyfuel capture schemes all viable in some areas of the
refinery.
Capture can typically recover up to 90% of the carbon in the fuel and can enable a refinery
to get much closer to a zero carbon target. We will look at two options; the first is to change
all of the fired heaters in the refinery to fire on hydrogen and capture the carbon dioxide
produced in making the hydrogen, for the second, post-combustion capture can be added on
all sources of carbon from the refinery.
Base Case Emissions Compared to Capture Cases
3,000,000
2,500,000
TPA CO2
2,000,000
1,500,000
Captured
Emitted
1,000,000
500,000
Base
Full Post capture
Precomb Capture
(except FCC)
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Carbon capture can deliver a large reduction in emissions but it still cannot achieve 100%
carbon-free processing in the refinery. Even combining capture with the other options
considered, using natural gas as fuel, importing power and implementing CCS, around 8% of
the carbon emitted in the base case is still emitted.
To achieve a net emission of no fossil-derived carbon we need alternative fuel sources that
are not derived from fossil fuels. The obvious choice is biomass-based fuels. The carbon
from these sources has been captured from the atmosphere and will be captured again as
plants grow absorbing the emissions. An alternative option could be using hydrogen
produced from electrolysis using green electricity, but the costs of this are high and
significant levels of power are required.
A number of biomass-based fuels could potentially be used in the refinery with everything
from wood chips to algae being potential fuels for the utilities boilers. For the process units
converting to solid fuels would be more challenging so in order to keep the assumptions
simple we will look at an example where some the purchased natural gas is replaced by bioderived methane. This could be produced from anaerobic digestion or by methanation of bioderived syngas.
The production of the biogas uses energy and because this is not all carbon-free there are
still some emissions associated with using this gas. In our example where we combine
power import, natural gas import and full post combustion capture our refinery still emits
around 140,000 TPA of CO2. To get to a net zero carbon refinery this amount would need to
be equivalent to the bio-derived content of the biogas.
The graph below shows the emissions on the net zero refinery
CO2 From The Net Zero Carbon Refinery
1,600,000
1,400,000
1,200,000
TPA CO2
1,000,000
Bio derived
800,000
Captured
600,000
400,000
200,000
0
Carbon Emmisions
The table below shows the level of biogas-firing required at different levels of carbon
reduction achieved by the biogas.
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Net Emissions when
using Biogas
Biogas
emissions
as % of
Nat Gas
% of Natural Gas from Biomass
20%
50%
70%
10%
100%
0%
68,830
886
- 202,944
-
338,830
-
542,660
20%
82,418
28,064
- 135,000
-
243,710
-
406,774
50%
102,801
68,830
- 33,085
-
101,029
-
202,944
80%
123,184
109,595
68,830
41,652
886
From the table we can see that at high rates of replacement of natural gas with biogas it is
possible to actually achieve negative overall emissions from the refinery and in effect
decarbonise some of the product, although the impact on products is small with even the
most optimistic case only reducing emissions from the products by about 2.5%.
Conclusions and Summary
We have seen that a number of options exist for refiners to reduce the carbon emissions
from their refineries. The technologies already exist to develop a refinery that has net zero
emissions. The challenging in achieving this not technical, but commercial, with refiners
requiring sufficient incentive to invest and sufficient protection against the impacts lower
carbon emissions could have on their competitive position.
The current high oil prices mean that the returns on energy efficiency are good and most
refineries are likely to find some attractive investments in this area.
Where natural gas is available, changing from fuel oil firing to natural gas firing is also likely
to be attractive.
Steps beyond these options are generally less attractive financially unless there is
sufficiently high carbon price or appropriate level of government subsidy.
Previous Foster Wheeler studies have shown a carbon price of around $60/tonne CO2 is
required to justify the investment in carbon capture. The higher cost of biomass-derived fuels
means that similar or higher levels of subsidy / carbon tax are required to make this option
economically attractive.
This results in hierarchy of actions for any refiner looking to reduce carbon emissions.
1. Maximise design efficiency and operate efficiently
2. Minimise the carbon in the fossils fuels you use
3. Capture the carbon you cannot avoid and/or move to low carbon fuels and power
The right solution will of course depend upon the specific circumstances and business
objectives of a particular refinery, and the full range of options need to be studied in order to
develop a robust technical solution and optimised investment plan.
© 2012 Foster Wheeler. All rights reserved.
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