Acid gas treatment and removal technologies are employed to separate CO2 and H2S, typically referred to as "sour" gases, from natural gas and other process streams. These acid gases are recovered or vented / disposed off, as per process requirement. Acid gas removal system is the core part of all ammonia plants. CO2 in process stream is separated as an undesirable component for ammonia synthesis and use as an intermediate product for urea manufacturing.

Two plants of FFC employ Haldor Topsoe design of the late seventies, featuring UOP Benfield system for removal of carbon dioxide. CO2 of the process gas is absorbed in a          high-pressure potassium carbonate solution with Di-ethanol amine as an activator. The process requires enormous energy for solution regeneration in stripper to separate CO2 and the regenerated solution is recycled back to the absorber. With technological advancement in acid gas removal systems, BASF patent activated Methyl Di-ethanol Amine (aMDEA) process was opted at FFC Plant-II with aim to address corrosive properties of Benfield solution as well as an energy efficient process.

This paper details the successful energy saving retrofits at all three CO2 removal sections of FFC plants. At Plant-I, 'Benfield Lo-Heat Process' proved to be a low cost modification before embarking on extensive scope of work to revamp into aMDEA. This energy saving project later translated into increase in Urea production by utilizing the saved natural gas.

At Plant-II, high load operation was not possible as the system hydraulics and mass transfer areas were limiting. In-house study to increase solvent circulation and adoption of new solvent i.e. OASE Enriched with increased CO2 absorption capacity resulted to address bottleneck of section.

Conventional activator, Di-ethanol amine used in Benfield solution has an inherent problem of solution degradation and thus creates adverse effects on performance of CO2 absorption section. At FFC Plant-III, a project to replace this activator with UOP patent ACT-1 is in execution phase. This will reduce solution circulation rate, decrease regeneration energy in stripper and decrease in CO2 slippage. Replacement of the activator will not only enhance capacity of CO2 removal system but also increase urea production with an attractive payback. This retrofit will be implemented first time in Pakistan and benefits of this advancement will be reaped after its commissioning.