PTQ Q4 2024 Issue

Separation technology addresses challenges in emerging technologies

How a proven technology has been repurposed to offer a versatile solution for separating biochar from hydrocarbon vapours and ash from flue gases

Kusume Srinivasa Rao, Ramkumar Ramanathan and Todd Foshee Shell Catalysts & Technologies

A s the energy transition accelerates, innovative pro- cesses based on pyrolysis, hydropyrolysis, and gasification, among others, are being developed to process lower-carbon and circular feeds, such as biomass and plastic waste. A key challenge in these processes is the effective removal of by-products like biochar from hydrocarbon vapours and ash from gasification flue gases. Addressing these challenges is crucial for improving the efficiency of these emerging technologies. To tackle these challenges, Shell Catalysts & Technologies explored applying the Shell third-stage separator (TSS) beyond its traditional role in refining. For more than 60 years, it has been used to reduce particulate emissions to below 50 mg/Nm³ from fluid catalytic cracking (FCC) unit operations and protect downstream equipment from potential damage. Its research suggests that the Shell TSS offers significant advantages over conventional technolo - gies, like cyclones and candle filters, when used in pyrolysis, hydropyrolysis, and gasification. These advantages include lower costs and, because it has no moving parts, increased reliability and lower maintenance requirements. The potential of the Shell TSS lies in its adaptability from its original function in FCC to these newer applications. In pyrol - ysis and hydropyrolysis, it can efficiently separate biochar from reactor vapours, while in gasification, it can remove ash from flue gases. This use of proven technology demonstrates the Shell TSS’s ability to address contemporary challenges in renewable energy production and waste processing, offer- ing a promising solution for modern energy processes. Separating solids, such as biochar or ash, from gas streams With energy companies striving to reduce the carbon foot - print of the products they sell, processes like pyrolysis, hydropyrolysis, and gasification are becoming increasingly important. These processes can efficiently convert lower- carbon and circular feedstocks, such as biomass and plastic waste, into valuable fuels and chemicals while minimising greenhouse gas (GHG) emissions and improving overall sustainability. Pyrolysis and hydropyrolysis are both thermal decom - position processes that convert biomass or plastic waste into hydrocarbons by heating the material in the absence

of oxygen. A key by-product of these processes is biochar, a low-value byproduct. Efficient separation of biochar from these vapours is crucial for producing high-quality trans - portation fuels, such as gasoline and gasoils. Similarly, gasification transforms feedstocks into syngas by reacting with them a controlled amount of oxygen and steam at high temperatures. One of the challenges in this process is the removal of ash from the flue gas to prevent equipment fouling, ensure efficient operation, and meet emissions standards. Evaluating available separation technologies Several technologies, including single cyclones, two-stage cyclones, and candle filters – and now, the Shell TSS – are available for separating biochar from hydrocarbon vapours and ash from flue gas. Single cyclones, two-stage cyclones, and candle filters – and now, the Shell TSS – are available for separating biochar from hydrocarbon vapours and ash from flue gas A single cyclone can effectively remove the bulk of solids for FCC catalyst particles. However, it is less effective for removing biochar and ash particles, which have a lower particle density and can break into smaller particle sizes more readily in the cyclones than FCC catalyst. For improved separation, a two-stage cyclone system can be used. This system consists of a primary cyclone that handles the bulk of the separation, followed by a secondary cyclone to capture residual particles. Two-stage cyclones used for removing FCC catalyst particles from reactor or regenerator effluent can have a high overall efficiency with a combined d50 cutpoint of around 15 µm. The d50 cut - point is defined as the solid particle size at which 50% of the particles get captured and separated. However, like the single cyclone, biochar and ash parti- cles have a lower particle density and can break into smaller

PTQ Q4 2024