Decarbonisation Technology - May 2024 Issue

internal energy mix, fuel gas and steam balance, process configuration, and electricity supply and distribution. For instance, some types of equipment that usually need steam to operate, such as steam ejectors that generate vacuum or steam turbines that drive compressors, can be electrified respectively using vacuum pumps and motors controlled with variable speed drives (VSD). Generally, an electric motor with a VSD is much more energy efficient (around 90-95%) than a condensing-type steam turbine or open-cycle gas turbine (sometimes as low as 25% energy). There are also medium- to large-scale electrification opportunities related to process heating with technologies available today. Equipment that traditionally uses fossil fuels, such as steam boilers, distillation reboilers, hot oil heaters, and fired heaters, can now be replaced with more energy-efficient and zero- emitting electrically powered solutions. The types of electric steam boilers used to generate ‘green steam’ can differ based on steam temperature, pressure, and production flow rate requirements. Electric boilers using either immersed resistive heating elements or electrodes can convert electrical energy into low to high-pressure steam with very high energy efficiency (close to 100%), a very large operability range, and fast ramp-up/down and response times. Electric boilers can become a great asset for incorporating renewable electricity that is either intermittently generated or purchased at a low (or even negative) price. The produced ‘green steam’ can then be distributed across the plant towards consumers using the existing steam network. Another option is to directly electrify steam consumers, particularly small- to medium-scale distillation reboilers or steam-heated process heaters (distillation feed pre-heaters, vapourisers, tank heaters) using electric resistance-based heaters with a tailor-made design that meets specific process requirements. Eventually, small- to medium-sized fired heaters, which are mostly used in catalytic units or as reboilers in some cases, can also be directly electrified with existing technologies to produce lower carbon intensity fuels due to a decarbonised process. A variety of technologies are commercially

available for converting electricity into heat using resistances in direct contact with the process fluid or heating elements radiating heat onto the process coils in a radiant heater. The appropriate technology for each process will primarily depend on factors like heating needs (duty, temperatures) and process fluid characteristics (especially fouling constraints, phase-changing application). Concepts around hybrid heating using various energy sources such as natural gas, hydrogen, and electricity are also under development to benefit from flexibility between energy sources and enhanced reliability. Ways refineries benefit from electrification While refineries’ decarbonisation decisions are primarily spurred by environmental concerns, transforming to a greener refinery brings additional benefits. For instance, electrifying processes brings more opportunities to power with renewable energy, improves air quality by eliminating emissions from burning fossil fuels, reduces maintenance costs compared to some fossil-fuelled equipment, and improves operational safety by reducing the use of gas- fired equipment. Electrification improves energy efficiency Energy efficiency can be increased by more than 20% using commercially available and fit-for-purpose electric heating technologies instead of traditional gas-fired heaters. The efficiency gains occur because electricity can be completely converted to thermal energy with low or no thermal losses. In contrast, flue gas from fired heaters needs comprehensive heat recovery systems to lower energy losses. When operating at a reduced load, electrical heaters will remain highly energy efficient compared with a limited turndown limitation and lower efficiency for fired heaters and steam boilers. Enhancing energy efficiency via electrification can also have substantial financial advantages since energy costs are responsible for approximately 60% of EU refineries’ cash operating costs. This share has doubled in the last two decades due to stricter product standards, escalating energy prices, and increased refinery complexity (Concawe, 2012).