PTQ Q1 2023 Issue

immediate future. The breakdown of Scope 1, 2 and 3 emissions is shown in Table 2 . Scope 2 emissions relate to electricity import. Scope 3 emissions represent emis- sions related to the combustion of motor fuels only, ignoring other contributors. Scope 3 emissions can be drastically reduced if a greater fraction of the refinery products is worked up to petrochemicals. Improving energy efficiency has a direct impact on Scope 1 and possibly Scope 2 emissions. While it has always been the goal of a refin - ery operator to reduce fuel consumption, the enforcement of a CO₂ tax gives further impe - tus to this. Techniques previously regarded as uneconomical may now prove to be attractive. Energy efficiency can be improved by operational and technical means. Operational means include operating distillation columns at their lowest possible pressure, minimising furnace excess air, avoiding reprocessing of CO₂ abatement measures Improved energy efficiency

CO₂ reduction and associated cost for selected measures, 2019 Western European pricing

Item

CO₂

Invest-

€/t CO₂ avoided

reduction,

ment

KTA

M€

(30% higher utility prices)

Energy efficiency Furnace revamp/replacement Fuel substitution Steam drivers to e-motors on green electricity 1

-4

-44

3 0

299

384

Green electricity 2 Blue hydrogen firing Green hydrogen firing5

271 273 370 370

3813

2384

261

514 121

996 457

1273

Electric heating 6

584

1. It is assumed the refinery has 10 steam turbines in the 40-2000 kW range 2. The refinery has a power import of 82 MW. ‘Green’ electricity implies that this power is now coming from renewable sources. 3. Two furnaces of 100 MW each, new blue hydrogen plant 4. Excluding cost of CO2 disposal 5. Electrolyser stack cost of 650 €/kW, Two furnaces of 100 MW each 6. Two heaters of 100 MW each

Table 3

streams, avoiding cooling and subsequent reheating of streams, minimising tank heating, use of more efficient catalysts that allow operating temperature or pressure to be reduced, preventive maintenance/cleaning, and so on. Technical means include installing additional or more effi - cient heat exchangers, implementing variable speed drives on pumps, applying heat pumps, swapping steam-driven ejectors for liquid-driven ejectors, and/or additional instru- mentation to monitor key variables and maintain them at optimum values. 2, 3 Operational and technical measures often go together, such as installing instrumentation to measure furnace flue gas O₂ content and ensuring this information is used to adjust the air rate to the burners. Energy efficiency improve - ment projects reduce CO₂ emissions, have a positive pay - back, and a negative CO₂ avoidance cost. A comprehensive review was carried out to determine the cost/benefits of revamping/replacing several stand- alone furnaces/boilers to achieve a 90% thermal efficiency. In preparing a hypothetical case, the refinery has a few fur - naces with efficiencies as low as 60%, which will need to be replaced. A number of other, higher-duty furnaces with efficiencies of around 80% will be revamped (for example, by installing air preheaters). For the hypothetical case, the total investment amounts to 97 M€. The 44 MW reduction in natural gas firing duty reduces Scope 1 CO₂ emissions by 74 KTA (4% of the original Scope 1 emissions). Without CO₂ tax, this project would, assuming 10% disbursement per year and a natural gas price of 375 €/t, have a payback time of close to 10 years and would not qualify for project sanctioning. The cost per ton of CO₂ avoided is -4 €/t, dropping to -44 €/t at a 30% higher natural gas price. The cost per ton of CO 2 avoided takes into account investment disbursement and changes in operating cost between the as-is situation and

the future situation also considering any changes in Scope 3 emissions where relevant. Fuel substitution Another way to reduce Scope 1 and 2 emissions is to con- vert steam drivers to electric motors and swap all electric consumers to green power. As a supplemental step in fuel substitution, furnaces could be converted to hydrogen fir - ing using green hydrogen produced via water electroly- sis or blue hydrogen from a new auto thermal reforming (ATR)-type hydrogen plant equipped with pre-combustion CO₂ capture. Some heating services (such as steam boil - ers) may be replaced by electric heat exchangers using green electricity. The estimated cost of these modifications, their impact on CO₂ emissions, and the cost per ton of CO₂ avoided (based on typical 2019 Western European pricing) are reported in Table 3 . The CO₂ avoidance costs are heavily dependent on the utility prices used. The last column in Table 3 shows the CO₂ avoidance cost at 30% higher utility prices. For all measures except furnace efficiency improvement, the cost of CO₂ removal goes up with higher utility prices. Replacing steam turbines with electric motors is not attractive as natural gas is still fairly inexpensive (in our cost basis) compared to electric power. This does not reflect current circumstances. ‘Green electricity’ implies all users have changed to elec- tricity from renewable sources at a higher cost than grey electricity. Electric and hydrogen (especially green hydrogen) firing have a high CO₂ avoidance cost. Feedstock substitution Replacing crude oil with renewable feedstocks such as vegetable oil (processed in an hydrotreated vegetable oil

PTQ Q1 2023