represents a much higher corrosion rate in the presence of water. Any incineration of H2S-rich gas also generates harmful SOx gaswhich for moderate and large quantities needs special handling.”Many gas treatment processes must treat sour gas components H2S and CO2 differently. H2S features…
For natural gas applicationsthe specification of the export gas is typically 2–4ppmv for H2S and 2.5molepercent for CO2. For refinery off-gasthe feed gas concentrations are typically in the 2–4molepercent range for both the H2S and the CO2with the outlet specification typically set to 50ppmv for H2S. Accordinglywith the less strict regulations set to the outlet CO2 concentrationselective
H2S-removal is a requirement for many sour gas treatment applications.
For moderate and high H2S-fluxessolvent based processes using a selective amine such as tertiary amine MDEA are typically used. Such a solvent reacts (proton reactions) instantaneously with H2Swhereas it undergoes slow intermediate reactions with CO2. Clearlyin order to avoid significant co-absorption of CO2 in the solventthe residence time in the contactor unit should be minimised.
Facing this fundamental issue of efficient selective H2S-removalProPure has developed and qualified its injection mixeroriginally designed for H2S scavenging of sour gasinto a co-current contactor for selective H2S-removal. The development and qualification of the selective H2S removal technologycalled ProCAPProPure Compact Alkanolamine Planthas been sponsored by the industry partners StatoilHydroTotalConocoPhillips and Gaz de France. Pilot testing has been carried out at Gaz de France’s gas storage and processing plant at Chéméry at real natural gas process conditions with pressures 70–100barg and at StatoilHydro’s refinery at Mongstadfor selective H2S removal from refinery off-gas.
Compared to a conventional counter-current absorberthe ProPure co-current contactor unitcomprising injection mixerdownstream contactor pipeline and gas-solvent scrubberis far more compact (Fig.1). In the depicted case designed for a typical sour natural gas application with feed gas 50ppmv H2S and 5molepercent CO2the amine circulation rate is reduced approximately 50percent as compared to conventional technologyand with similar reductions achieved for the weight and energy consumption.
The key feature for the ProPure concept is to reduce the absorption of CO2 such that higher solvent loading capacity of H2S is possible as compared to that of conventional technology. This requires low gas-solvent contactor residence time and large gas-solvent exposure areamade possible by initially establishing a high exposure area between the gas and solvent droplets by the use of a one-shot mixer concept.
In the downstream gas-solvent knock-out scrubberthe exposure between the solvent and the CO2-rich sour gas is minimal so that there is minimal CO2 mass transfer from the gas to the solvent and H2S-flashing from the solvent.o
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Harald Linga is Vice-President Product Development and Bernt H Kalgraff is Senior Process Engineer with ProPure ASNorway (part of ProSep Inc)BergenNorway. www.propure.com
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