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Maximizing Sulphur Recovery, Minimizing Stack Emissions, and reducing upset conditions in the SRU

Introduction: A sulfur recovery unit is employed to extract sulfur from crude oils, aiding refiners in producing low-sulfur products to meet emissions mandates. It transforms sulfur compounds like hydrogen sulfide (H2S) into elemental sulfur by oxidizing H2S into SO2. This involves burning 1/3 of the H2S into SO2, constituting a stoichiometric reaction, as adding more air than needed can significantly reduce plant efficiency depending on the levels. The sulfur recovery rate of the Claus process is approximately 95 to 97%. The tail gas, containing unrecovered sulfur, is directed to the tail gas treating unit (TGT). The recovered sulfur undergoes a degassing process to remove H2S before being stored in the sulfur pit and shipped as a product.

Air Demand Analyzer: The pivotal analytical measurement in the sulfur recovery unit (SRU) is a tail gas analyzer or ratio analyzer, crucial for achieving 98% - 99% efficiency. The tail gas treating unit enhances efficiency to 99.98%. Key measurements include H2S and SO2 to calculate air demand.

Tail Gas Treating Unit Analyzer: Installed after the amine absorber or quench tower outlet, this analyzer measures H2 (excess for reduction of SO2 back to H2S) and H2S to assess amine efficiency. The tail gas undergoes catalytic hydrogenation reduction and amine absorption in the TGTU before being directed to an incinerator.

Stack Gas Analyzer: SO2 and O2 are typically measured here for compliance purposes.

Feed Forward Analyzer: While tail gas analysis calculates H2S:SO2 ratio after the furnace for air demand correction, a feed forward analysis system measures H2S concentration in the acid feed gas before the furnace along with total hydrocarbons, CO2, NH3, and H2O. This preemptively adjusts air demand based on real-time feed gas levels, ensuring air demand control with no process lag and preventing efficiency losses.

For more information or a free seminar, please contact Bobby Singh at 225-200-5105


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