Climate change, in our day, is an ever-present and important topic. One of the main causes is certainly the increase in the production of carbon dioxide which, ending up in the atmosphere, increasing the concentration more and more and in this way the heat does not leave the earth and the temperature increases. This increase in temperature damages the planet and we need to look for technologies that replace, improve efficiency or new techniques to do what we already do today but avoiding the production of greenhouse gases.
A very important slice of greenhouse gas production in Europe is attributable to the industrial sector. Indeed, Figure 1.1 shows that 33% of greenhouse gas emissions derive from the industrial sector. One third of total emissions is attributable to the industrial sector. Although greenhouse gases are not composed solely of CO2, CO2 is one of the main ones; it is one of the major gases present in the atmosphere and occupies a portion equal to 10-20%.
Figure 1.1: Greenhouse gases emissions from different sources in Paper mills
1%
Chemicals
3% Glass works
2%
Cement works 8%
Other 4%
Steelworks 8%
Refineries 7%
Energy and heating
67%
It must also be remembered that CO2 is present in the atmosphere also for natural causes. In recent years, however, man's anthropogenic activity has meant that the concentration of CO2
has increased considerably, and governments have had to intervene with laws and new taxes to avoid its uncontrolled production.
We have seen how much the industrial sector impacts compared to the energy production sector. Now from Figure 1.2 you can see the impact of greenhouse gas production from each sector in 2017. It is immediately evident that 17% derives from the industrial sector, if we add 18% of transport to this, it becomes a large slice that derives from the combustion of fossil fuels such as oil.
In this work, I will study the refinery and its impact on CO2 production, which, according to the article "Overview of the refining industry in the European Union Emissions Trading System (EU ETS)", is responsible for 7% of emissions of greenhouse gases in Europe. It is therefore important to try to limit this quantity. Furthermore, the refinery sector is chosen as a starting point as there are few studies regarding this topic as the available waste heat is almost absent and therefore new techniques to reduce CO2 emissions are still being studied.
It will be explained in the following chapters that the most convenient technique for limiting CO2 emissions is post-combustion as many European refineries have been working for years and it would not make sense to change the process upstream. Post-combustion is a minimally invasive technique from the plant engineering point of view, in fact it only requires the presence of space to build the suitable equipment.
Figure 1.2: GHG emissions by sector in Europe in 2017. [1]
Chapter 1
The CO2 capture process, as will be seen below, requires the need to produce heat. This heat can come from hot streams or it can be produced on purpose. In the second hypothesis, further CO2 will be produced and therefore it is more convenient to use waste heat that comes from processes that would otherwise be lost. In the paper "Process evaluation of CO2 capture in three industrial case studies" three types of industries are compared: a kraft pulp mill, an oil refinery and an aluminum mill. In this article, available waste heat is calculated as the heat that can be extracted from flue gas. What emerges is that in the aluminum plant the recovery heat covers 60% of the heat necessary to have a CO2 capture efficiency of 85%; in the case of the pulp mill there is not enough heat available (low quality heat) while in the case of the refinery, the waste heat covers 25% of the total demand. This fact makes us think:
the heat available in the refineries is scarce as the processes have an excellent synergy and the heat is recovered to have very high process efficiencies. The same article also analyzes a new generation power plant where the available heat is almost infinite as there will be spills from the turbine which, however, will affect the production of mechanical energy.
Furthermore, the quality of the recovery heat in this case is very high even if we cannot properly speak of recovery heat. The boiler does not have to produce extra heat, it is the turbine that will see less steam flow. In this case, the heat is sufficient to cover the heat demand of the CO2 capture process even if part of the work produced will be renounced.
Quoting the article "Fuel specification, energy consumption and CO2 emission in oil refineries" it can be estimated that in a refinery from 7 to 15% of the crude oil input is used to supply heat to the necessary refinery processes. Over the years, however, this situation has changed, in fact the environmental laws that impose a better quality of oil products and shift towards low-grade crude oils in the world refining industry have meant that the thermal demand increases more and more. The increase in the quality of petroleum products results in low sulfur contents which normally require more energy. Consequently, to produce a cleaner diesel and gasoline, more energy is required and therefore more emissions of carbon dioxide which is a greenhouse gas as seen above.
Therefore, new roads are born that the refinery must follow in the medium term: alternatives are needed to avoid wasting the energy produced or the implementation of new processes that replace the existing ones. In the 27 European countries, 97.8 Mt of carbon dioxide were emitted in 2018 for fuel combustion in refinery. Figure 1.3 shows how these emissions are divided between the various European states.
This study is keen to point out that this sector is constantly expanding and will continue to expand in the coming years. Indeed, it emerges from numerous articles where many studies of future scenarios still hypothesize the presence in large quantities of oil products in energy production and transport.
From the annual report "BP Statistical Review of World Energy 2020" prepared each year by the British Petroleum oil company, it emerges that, although in many countries CO2
production has decreased, in many others it has increased, bringing to the annual total (2019) an increase of 0.5% compared to 2018 and increased 1.1% compared to the last decade (2008-2018).
Again, in accordance with BP's annual report, CO2 emissions from electricity generation increased by 0.5% as well as oil demand increased by 0.9% compared to 2019. Even though refinery utilization dropped dramatically by 1.2%, daily production still increased leading to little or no change in oil demand. In Table 1.1 you can see how the demand and production of the main countries has varied.
Figure 1.4 shows the trend of recent years in the production of CO2 by the American oil industry, the image is taken from the United States Environmental Protection Agency. It is immediately evident how the production of CO2 from refineries has remained almost constant for many years; it is therefore interesting to study ways to break this trend.
Figure 1.3: Percentages of CO2 emissions of EU member states compared to 97.8 Mt/a (2018).
Chapter 1
Table 1.1: Top five increases and decreases in oil consumption and production.
Also citing "World Energy Outlook 2020", four future scenarios are described taking into consideration the covid19 pandemic that has affected the whole world and all sectors, in fact the refinery industry has suffered as well as the price of oil leading to an economic crisis.
The first two scenarios are the most realistic while the last two are the most optimistic. These scenarios are:
Oil consumption Annual change (thousand b/d) Oil production Annual change (thousand b/d)
Increases Increases
China 681 US 1685
Iran 183 Brazil 198
India 159 Canada 150
Algeria 37 Iraq 148
Russia 35 Australia 135
Decreases Decreases
Mexico -88 Iran -1266
Italy -59 Venezuela -556
Pakistan -52 Saudi Arabia -429
Taiwan -52 Mexico -150
Venezuela -47 Norway -115
Figure 1.4: Emission trend of CO2 from the refineries sector from 2011 to 2019. [5]
• Stated Policies Scenario (STEPS): is based on current policy and on the basis that the covid19 pandemic is controlled by 2021. GDP returns to pre-crisis value in 2021 while the global energy demand comes back in 2023.
• Delayed Recovery Scenario (DRS): this scenario is almost like the previous one but increases the damage caused by the pandemic. In this future, the global GDP is not recovered until 2023 while the demand for energy returns the same only in 2025.
• Sustainable Development Scenario (SDS): it is a scenario in which short-term investments are required to reduce emissions by more than 10 Gt in 2030 compared to the STEPS scenario. It is a very ambitious scenario as it requires a major transformation of the energy production sector.
• Net Zero Emissions by 2050 (NZE2050): it is a utopian scenario, which is used to see how it is possible to reduce emissions to 0 in 2050. In this scenario, the measures to be taken to have a future with zero emissions by 2050 are explored. A great acceleration is needed to reach this goal in the development of new renewable energy sources.
Figure 1.5 shows the scenarios with the relative composition of the future energy park in 2030 for the different scenarios. It can be seen how the demand for oil will increase in the case of the STEPS scenario while in the DRS scenario the demand will remain unchanged.
Only coal will go down.
Furthermore, the trend in fuel demand is also analyzed in the scenarios. Oil will always be the most used fuel until 2040 in the STEPS scenario; in the SDS scenario, the demand for fuel deriving from oil decreases even if it remains high. Figure 1.6 shows the request for oil fuel for the most current scenario (STEPS).
According to Figure 1.7 the demand for fuel will increase until 2040. The fact that the demand for fuel oil will increase is not linked to CO2 emissions in the refinery, however it is understood that crude oil must be processed before reaching the market. Processing takes
Figure 1.5: Future energy park in 2030 [6]
Chapter 1
place in refineries and by increasing demand, it will also result in an increase in the current production capacity of the refineries. The increase in demand for crude oil distillates suggests how important the role of the refinery is. It was also seen in Figure 1.5 that even on the energy production side, oil will always be present, forcing refineries to work and occupy an important slice of the industrial sector for the next years