4
4
Electricity Fuel + steam
‘2030’ ‘2050’ (zero carbon imports)
3
3
2
Oxo (butanal)
2
1
MeOH
Xylenes
Polyols
1
0
CH
FT
Carbon- ation
Urea
PPC
-1
0
CH
FT
Carbon- ation Xylenes
Urea
PPC
-2
MeOH
Oxo (butanal)
Polyols
either product mandates or high CO2 prices of USD 350/t. Part 1 of this article accounted for the carbon impact of imported electricity and fuel and assumed the hydrogen had a zero carbon intensity (CI). Figure 1 recaptures the carbon utilisation, carbon utilisation intensity (CUI) charts presented for the different technologies. Different power, fuel, and steam emissions factors are assumed for the 2030 and 2050 scenarios illustrated in the bar chart in Figure 1. Part 2 further develops the techno-economics of carbon utilisation by investigating the impact of the CI of green hydrogen, power, and fuel consumed. The capital expenditure for the different technologies is also compared. Utility balance: impact of power, fuel, and steam imports on carbon emissions The carbon utilisation units may import and export electricity as well as steam and/or fuel. However, the balance is primarily determined by the reaction heat, and the heat required for amine regeneration. Exothermic processes have the potential to use the excess heat for steam generation and export. Synthesis processes using hydrogen tend to be highly exothermic. The methanation, Fischer-Tropsch (FT), and xylenes technologies Figure 1 Carbon utilisation intensity (CUI) of the investigated technologies
Figure 2 Import of electricity and fuel/steam
indeed generate considerable amounts of reaction heat, ranging from 1.8 to 2.9 MWh of product for the xylenes and methane processes, respectively. However, this does not always translate into steam exports. Some technologies use medium-level and high-level heat above 120ºC for preheat, while the lower-level heat (<120ºC) is lost in cooling. The intermediate- level heat (150-200ºC) is often used to produce the necessary steam to regenerate the amine solution, which is used to capture CO2. Carbon capture is used in the methanation, FT, and Oxo production processes. Capturing and recycling CO2 are required to avoid large purges of CO2. However, it requires a significant amount of relatively low-level heat for amine regeneration and electricity for the compression and recycling of captured CO2. Ultimately, all technologies are net utility importers except the xylenes process. The xylenes process is a net steam exporter that assumes CO2 capture is optional, and the best technology available for heat integration has been considered, unlike other technologies studied. In addition, caution should be exercised with respect to the xylenes technology because it is still in its infancy. Consequently, the available yield information was limited. KBC anticipates that further improvements in product selectivity will be achieved once the technology matures. Figure 2 shows the net import requirements of electricity and fuel/steam, respectively. The use of import electricity and fuel/steam will lead to emissions that occur outside the carbon utilisation unit. These will be categorised as Scope 1 or Scope 2 emissions depending on whether they occur within a unit located elsewhere on the same production site or
2030
2050
Scenario
Scenario
Green hydrogen
USD 4000 /t
USD 1500 /t USD 200 /t
CO 2 utilisation revenue USD 50 /t
Table 2 Green hydrogen and CO2 price scenarios based on pre-inflation 2021 prices
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