45
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35
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30
6
25
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20
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15
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0
H S in v ent gas ppm Linear (H S in v ent gas ppm )
Inlet gas H S v ol% Linear ( i nlet gas H S v ol%)
Sulphur production LTPD Poly. (Sulphur production LTPD)
Figure 3 Sulphur data for Navy 210 unit
Typical performance measures about 15 ppmv, which maintains the unit within environmental permit requirements. Navy 210 was designed for 3.0 vol% H₂S in the feed gas, but H₂S levels have never exceeded 2.8 vol%. Today, inlet H₂S has declined from an average of 2.0 vol% to about 1.0 vol%. At start-up, Navy 210 initially produced sulphur at rates of 4-6 LTPD with spikes up to 7.2 LTPD. Over time, average sulphur production declined to 3-4 LTPD. The start-up and operations experience from Navy 1 helped the start-up and operation of Navy 210. Initially, the H₂S in the vent gas averaged 15 ppm with occasional spikes ranging from 30-40 ppmv. Since 2007, the vent gas H₂S has averaged less than 10 ppm with occasional spikes up to 20 ppm. Despite these spikes, the treated gas has consistently complied with environmental permit requirements. Solution maintenance In general, Lo-Cat units offer robust, consistent performance that meets unit design criteria over a wide range of operating conditions, including varying inlet gas flow rates and composition. This performance is possible by maintaining
the working catalyst solution within a defined range of alkalinity, catalyst concentration, and sufficient regeneration. Trending daily solution analysis results helps operations keep the solution within an optimum range. However, rapid changes in the inlet gas rate and composition can cause excursions that could result in off-specification treating. Additional solution testing immediately after measurable inlet gas changes helps operations maintain solution chemistry during the ‘upset’ and mitigate any adverse treating effects. Merichem recommends detailed monthly analysis, but Coso decided to send a sample to Merichem every two weeks. This generated a large amount of operating data for analysis. Merichem’s detailed analyses show that the proprietary chemicals solution concentrations have stayed relatively stable throughout the years of operating both Lo-Cat units. Coso measures the alkalinity and oxidation- reduction potential (ORP) of the regenerated Lo- Cat solution daily. This ensures the unit operates reliably because these measurements determine the chemical addition rates needed to keep the solution chemistry within the required guidelines. Coso also performs a shake test that measures
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