Feed Forward Analysis

application note

Application Summary

Analysis Point Analyte Typ. Range Suitable Analyzer
acid gas H2S 0-100% OMA H2S Analyzer
NH3 0-50%
CO2 0-50% MicroSpec MCP-200 Infrared Analyzer

Measuring Ammonia in Feed Forward Control

Measuring Carbon Dioxide in Feed Forward Control

Measuring Hydrogen Sulfide in Feed Forward Control

H2S is an extremely dangerous chemical which occurs naturally in fossil fuels and is removed through refining processes. The sulfur recovery unit (SRU) of a refinery converts the H2S to elemental sulfur which can be stored or sold off. A critical point in this process is the furnace which combusts H2S in order to sustain a 2:1 stoichiometric ratio of H2S:SO2 in the subsequent catalytic reaction. The amount of available oxygen in the furnace is carefully controlled to ensure this ratio for the next step. The efficiency of the entire SRU therefore hinges on the ability to continously measure the required amount of oxygen (i.e. "air demand") in the furnace.

While tail gas analysis measures the H2S:SO2 ratio after the furnace to calculate air demand correction, a feed forward analysis system measures the H2S concentration in the acid feed gas before the furnace to preemptively adjust air demand based on the real-time feed gas H2S level. While tail gas analysis provides the most accurate air demand calculation, this measurement occurs after the furnace. Feed forward analysis allows for air demand control with no process lag by immediately detecting sudden changes in acid feed gas composition and preventing any losses in SRU efficiency.