PTQ Q4 2022 Issue

times the size of current world-scale hydrogen plants for hydroprocessing clean fuels. They require large capital investment, substantial supporting infrastructure, and pro - cessing of the off-gases that have become a significant part of the fuel used in refinery process heaters as an alternative to flaring. When looking at the process units across a refinery, the hydrogen plant and FCC produce flue gas streams contain - ing the highest concentrations of CO₂ and make significant contributions to overall refinery emissions (see Figure 2 ). CO₂ capture is an obvious way to address CO₂ emissions from flue gases but has complexities associated with deployment across different process units. Aside from the hydrogen plant and FCC, other process units and crude unit emissions are fragmented across a refinery site and present challenges in collection and capture. For FCC flue gases from the unit and the regenerator, there are development technologies that address the particulates and unique impurities in the process like nitrogen, sulphur, and carbon monoxide to concentrate and capture the CO₂ emissions. In contrast, the existing steam methane reformer (SMR) hydrogen plant, one of the largest single-point sources in the refinery, has existing, ready now and tested technology solutions to reduce emissions. A carbon capture- focused hydrogen plant revamp offers a compelling place to start significantly reducing refinery CO₂ emissions today. Accelerating climate payback There are several options for revamping an existing plant, and it is important to keep in mind several key criteria, includ - ing future hydrogen production requirements and existing refinery site constraints. A relatively low investment option is to use next-generation reforming catalysts that provide a step change in heat utilisation within the existing SMR- based hydrogen plant, reducing CO₂ emissions and firing within the SMR. While low capital cost and risk, the scale of emissions reduction is low at 10-20%. Another option, pre-combustion carbon capture, has been practised on ammonia plants for decades, with more recent experience on refinery hydrogen plants. Relatively high pressure, high CO₂ concentration, and minimal impuri - ties enable pre-combustion capture to provide flexible mid- level emission reduction at 50-60%. As refinery hydrogen plants cycle through hydroprocessing demand of as much as 40-50%, the flexibility of pre-combustion capture is of additional value. To achieve the many ‘low carbon’ capture targets

11%

SMR FCC Crude distillation Other process units Power

29%

19%

22%

19%

Where to start? Early focus in refineries has been on carbon replacement strategies replacing fossil fuel with hydrogenated vegetable oil (HVO) biogenic feed processing creating biofuels. This biofuel production to biodiesel and SAF receives incentives in many regulatory environments, which makes strong busi - ness cases for these projects. More sustainable cellulosic- based sources of biogenic feeds are being developed along with their processing techniques to meet the high volume of renewable fuels projected in the next few decades. In the near term, the availability of HVO feeds is reaching its peak as the volume of projects progresses, limiting the decarboni - sation potential of this approach. Burning fossil fuels in furnaces and combined heat and power plants across the refinery is responsible for most emissions across a refinery but is a hard area to tackle due to high energy demand, low CO₂ concentrations, and a high number of distributed point sources. Substantially reducing emissions from power will take a green grid, which is still some time away. Green hydrogen solutions at existing elec - trolyser scales are only 5-10% of the size needed for energy replacement in a refinery, and it will take the rest of this decade to create the 300-500 MW scale needed to replace the main energy source of existing refineries. Grassroots hydrogen production with carbon capture, such as the LCH technology, can meet this energy scale and address not only the hydroprocessing hydrogen required but also provide additional hydrogen as a low-carbon fuel for the refinery. These grassroots energy scale plants are two to three Figure 2 Relative contribution of units across a refinery to Scope 1 emissions, based on IEAGHG 2017 base case for 220,000 BPSD refinery⁸

Next-generation reforming catalyst

Pre-combustion

Post-combustion

Enhanced carbon capture /CleanPace technology

capture

Capital cost Operating cost

Plot plant requirements Production disruption Production rate flexibility

Additional hydrogen production CO 2 emissions reduction potential

Table 2 Comparison of carbon capture options for an existing SMR hydrogen plant and their relative performance

PTQ Q4 2022