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Applications
The ADIP process is a regenerative process developed to selectively reduce H2S in gas to very low concentrations, while a good selectivity for H2S in the presence of CO2 can be achieved. The ADIP process uses an aqueous solution of di-isopropanol amine (DIPA) and an aqueous solution of methyldiethanol amine (MDEA). MDEA is used for those applications in which high selectivity for H2S is required. Depending on operating conditions 20 - 60% of the CO2 is co-absorbed if DIPA is used as the ADIP solvent, while this can be reduced to 10 - 30% if MDEA is used as the solvent. The ADIP process can also be used for enrichment of acid gas feed to a sulfur recovery plant, to achieve a higher H2S content. Integration of gas treating with the SCOT solvent system is an option.

Description
The H2S containing gas is contacted counter-currently in an absorption column with ADIP solvent. The regenerated solvent is introduced at the top of the absorber. The H2S loaded solvent (rich solvent) from the absorber is heated by heat exchange with regenerated solvent and is fed back to the regenerator, where it is further heated and freed of the acid gases with steam.

The acid gases removed from the solvent in the regenerator are cooled with air or water, so that the major part of the water vapor is condensed. The sour condensate is reintroduced into the system as a reflux.

The acid gas is passed to the sulfur recovery plant (Claus plant) in which elemental sulfur is recovered from the H2S.

The gas feed from the hydrotreating units enter the bottom section of the absorber column. The regenerated and cooled lean solvent enters the column at the top. The flow of the lean solvent to the absorber is flow-controlled. The treated gas passes from the absorber to the treated gas knock-out drum, where any entrained solvent is separated from the gas. The rich solvent containing H2S leaves the bottom of the absorber under level control and is pumped by the rich solvent pump towards the lean/rich heat exchanger. In the lean/rich heat exchanger the rich solvent is heated by the hot lean solvent from the regenerator. Regeneration takes place in the regenerator column, which is equipped with a stripping section and one wash section in the top. The rich solvent from the lean/rich heat exchanger enters the regenerator below the wash sections and is stripped counter-currently with steam. The steam is generated in the reboiler. Low-pressure steam is used as heating medium. The top gas from the regenerator is cooled in the overhead condenser. Practically all steam present in the overhead gas is condensed. The acid gas and condensate are passed to the reflux drum from which the condensate is pumped back to the top of the regenerator by a reflux pump, in order to remove entrained solvent from the overhead gas. The acid gas, which also contains some hydrocarbons, is fed to the Sulfur Recovery Unit under pressure control. The hot lean solvent leaves the bottom of the regenerator and is pumped to the lean/rich heat exchanger by the lean solvent pump. The lean solvent is further cooled in the lean solvent cooler. Then the cooled lean solvent is sent to the absorber.

Operating Conditions
Absorber operating pressure can be up to 150 bar. Gas temperature can vary from ambient up to 60 C.

Features
   Reduction of H2S to very low concentrations.
   Low steam consumption and solvent circulation.
   Carbon steel equipment.
   Resistant against degradation (DIPA).
   No reclaimer required.
   Good selectivity for H2S in the presence of CO2.
   Reduced investment and operating costs compared to conventioanl designs.

References
More than 450 ADIP units ranging in capacity from 1.900 Nm3/d to 12.200.000 Nm3/d and 19 t/sd to 7700 t/sd liquid hydrocarbons are in operation throughout the world, demonstrating the reliability of the process

Licensor
Jacobs Nederland B.V., Leiden, The Netherlands, is one of the three authorized licensors on behalf of Shell Research Ltd. since 1981.

Streams to be Treated
Contaminants Removed
Refinery gases: e.g. from HDS and cracking units
Natural gases
Reduced Claus tail gas (SCOT process)
Gas from oil or coal gasification in combined-cycle power stations
Claus feed gas enrichment
    H2S
   H2S, CO2 (partly)
   H2S, CO2 (partly)
   H2S, CO2 (partly)
   H2S, CO2 (partly)
 

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