Refinery CO2 challenges

How much CO2 can a refinery release into the atmosphere? This is one of the many challenges facing refineries when it comes to reducing CO2 emmisions

R Michiel Spoor, KBC Process Technology Ltd

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Article Summary

Refineries in Europe are facing new challenges, the most important of which is the effect of current legislation on the industry, including:
• How much CO2 can be released into the atmosphere?
• Which units are producing the CO2 in the refinery?
• How are these CO2 emissions measured? Do measuring methods need to change?
• How are CO2 emissions reported and monitored? Is extra manpower needed, or do new tools need to be developed?
• How can CO2 emissions be forecasted? Can the same tools be used, or do the planning tools need to be modified? Is more rigorous simulation required?
• How can CO2 emissions be reduced? What is saved by reducing, and what is the cost involved?
• When looking into the future, what investments should be considered to further reduce CO2 emissions or avoid regret investments for other capital expenditures?

How much CO2 can a European refinery release into the atmosphere? Since the whole European Union has joined the Kyoto community, a framework has been formulated showing how each country can allocate its allowances. Power companies, all refineries and plants that emit more than 25ktpy of CO2 were obliged to join these national allocation plans and were given a fixed amount of credits. Figure 1 shows the emission targets for The Netherlands, with total emissions in year 2010 set at 219Mtpy of CO2. As the Kyoto level is set at 199Mtpy, approximately 20Mtpy is purchased through JI and CDM projects (greenhouse gas reduction projects outside the EU, controlled by the United Nations and UNFCC). The same figure shows that the total contribution to the Kyoto emissions from refineries in The Netherlands is approximately 7%.1

Although these credits were initially provided free, their marginal value is significant. Refinery emissions typically range from 1 million tpy for a typical-sized refinery to 3.5 million tpy for a big, complex conversion refinery. Obviously, extremely large, complex sites may have even more emissions, such as the Shell refinery in The Netherlands with 6.6 million tpy of CO2 credits. The total value of these allocations for a refinery based on the current marginal price of €20 per tonne is €20–70 million each year. The only way to capture this is by shutting down the plant to eliminate the emissions completely.

In the current trading period, up to and including 2007, allocations in some countries were based on actual emissions from previous calendar years, if the refinery could demonstrate that they were already energy efficient. In other countries, the government has forced mandatory cuts in emissions rights, so that refineries have to reduce emissions by reducing capacity, improving energy efficiency or buying the credits on the CO2 market. This has to be done before the closing period of March 2006 to compensate for the emissions in the 2005 calendar year. A penalty of €40 per tonne is imposed for those refineries that cannot deliver sufficient credits.

Countries have to reach their Kyoto level in the target period of 2008–2012, and it is expected that the allocation of credits will be less generous. Up to 10% of the allocations may be auctioned and the total amount of allocated credits may be less than in the previous years. Also, the penalty for non-compliance is significantly higher: €100 per ton of CO2, for which no emissions credits can be delivered.3 Looking even further ahead, the EU is currently reviewing the impact of reducing the CO2 emissions from the Kyoto base level by 60% in 2050.4 If put into legislation, this will significantly impact the refinery business.

What units, what fuels?
What produces the CO2 in the refinery? When comparing CO2 emissions from refineries in Europe, it can be shown that most of the emissions, typically 90%, are coming from a few main units. The two stacked bars in Figure 2 show the emissions of two refineries in Europe: one in South Europe, the other in Scandinavia.

The crude/vacuum heaters account for roughly one-third of the emissions, while the naphtha reformer furnace and the naphtha hydrotreater unit account for up to one-quarter. An FCC regenerator, depending on whether it processes residue or only VGO, will produce 15–20%. Emissions from steam- and power-producing utilities systems are very dependent on the power import situation. A refinery that imports all its power uses typically 15% of the total fuel for utilities; however, when configured with a cogeneration unit, the total CO2 emissions can be as high as 40%. A steam reformer (not shown in Figure 2) is another main source, and it accounts for 15–20% if the refinery has a hydrocracker. This clearly defines the units the refinery should focus on when aiming at CO2 reduction.

It is important to realise that CO2 emissions from heaters and boilers are dependent on refinery fuel. For each ton of CO2 production, 3.1Gcal of heat is produced from refinery fuel oil, 4.3Gcal of heat from natural gas and 4–4.8Gcal from refinery fuel gas. Table 1 shows that a refinery switching from refinery fuel oil to natural gas can reduce its emissions quickly by up to 20%. However, this comes at significant cost.

Measuring CO2

How are CO2 emissions measured? The European Commission has provided guidelines for CO+ measuring and reporting. These guidelines define requirements for the accuracy (or uncertainty) of measuring in tiers, with higher tiers defining higher accuracy. In the current 2005–2007 period, lower tiers are allowed. From 2008 onward, the measurements should fit the highest possible tier, which can lead to certain problems with measurement. For example, heaters, boilers, furnaces and flare fuel rates need to be measured with a 2.5% uncertainty now (tier 3), and with an improved uncertainty of 1.5% in 2008 onward. Another example is that FCC emissions should be calculated from heat and material balance. This may require a rigorous simulation tool linked to the actual rates and feed qualities run during the year. Another cost to the refinery is the special accreditation for the laboratory. The fuel oil and fuel gas to the process units need regular sampling and analysis to determine their calorific values and emission factors from 2008 onwards.

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