PTQ Q4 2024 Issue

TSS inlet

TSS outlet

PSRI

Bypass

Fines

TSS

Model

Primary cyclone

Feed

Particle size (μm)

design consideration is important, owing to the propensity of fine biochar particles to induce flow issues in the under - flow lines, which the bypass effectively mitigates. Design of primary cyclone and TSS The design of the primary cyclone and the Shell TSS is closely tied to the capacity of the pyrolysis reactor or gasi - fication unit. For larger systems, multiple primary cyclones can be arranged in parallel, like configurations used in FCC units. This parallel design approach allows for scalability and adaptability to specific processing requirements. The Shell TSS is a single vessel equipped with multiple standard-sized swirl tubes. This configuration is tailored to accommodate the necessary processing capacity while ensuring optimal separation performance. A fundamental aspect of the design process is the basis of design, which outlines the core parameters and requirements for both the primary cyclone and the Shell TSS. Table 2 shows the minimum required information. The bypass flow rates are determined by the flux requirements of the Shell TSS underflow lines to ensure optimal perfor - mance and prevent flow issues. Shell TSS designs The key information required for designing a Shell TSS includes reactor vapour mass flow rates, the operating pressure and operating temperature, solids load, the d50 cutpoint (a key measure of how well the hardware sep - arates out erosive particles), the grade efficiency curve, and biochar PSD. The efficiency of the upstream primary cyclone significantly impacts the overall efficiency of the Shell TSS. One critical parameter, the d50 cutpoint, quan - tifies the particle size at which the Shell TSS achieves 50% separation efficiency. A lower d50 cutpoint indicates better separation efficiency, which is a crucial performance metric for the system. The Shell TSS demonstrates high efficiency in remov - ing particles 10 µm and larger, achieving removal rates of 99.95-99.99 wt%. This performance establishes it as a trusted solution for particulate control in FCC operations. The effectiveness of the Shell TSS is supported by Shell Catalysts & Technologies’ proprietary software, which has been refined over decades of field testing and sampling. This software accurately predicts performance, ensuring reliable and consistent operation. Figure 5 PSD as estimated by Shell’s model and PSRI experimental studies

TSS underow

Solids

gas velocities) for commercial designs to minimise biochar attrition. Significant particle attrition was even observed at lower gas throughputs, with coarser cut sizes above 30 µm eroding down to finer sizes below 26 µm. Third, the study showed that the overall pressure drop across the Shell TSS is predominantly a function of volu - metric gas flow rate and is of second-order dependency. Neither inlet solids loading nor the percentage of underflow gas significantly affected the total pressure drop. The fourth key insight from the study is that the overall collection efficiencies of the Shell TSS were essentially the same across all test conditions. Notably, the percentage of underflow, which must be maintained at 3-4% for cata - lyst service, did not impact collection efficiency in biochar service when it was reduced below 3%. Based on these results, an underflow rate of approximately 0.5% is recom - mended for biochar service. Typical configuration Figure 4 shows the typical configuration for the Shell TSS used for biochar separation in a pyrolysis process. This setup incorporates a bypass around the primary cyclone to ensure a minimum flux in the Shell TSS underflow line. This Figure 4 Typical downstream configuration for biochar sep - aration in a pyrolysis process using a Shell TSS, including bypass for efficient vapour management

Minimum required information for designing the primary cyclone and TSS

Reactor effluent

Biochar

P P P P P P P P P P P

Flow rate

Temperature

Pressure Mol. wt

Gas/bulk density Particle density Compressibility Specific heat ratio

Shape factor

Viscosity

Composition/PSD

Table 2

PTQ Q4 2024