API Publ 4679:1999 pdf download.Amine Unit Emissions Model
The system consists of two major operations: absorption and regeneration. A natural gas stream or a natural gas liquid stream containing acid gases (H2S andor COz) is introduced into an absorber column where the stream is counter-currently contacted with an amine solution. The acid gas contents are removed through chemical reactions with the amine. After the treatment, the natural gas or the natural gas liquid becomes suitable for consumer use or for further chemical processing. This process is often referred to as a gas sweetening process, and treated gas or liquid is called sweetened gas or liquid. On the other side, the amine solution, referred to as rich amine solution after selectively absorbing the acid gases from the stream requires regeneration before it can be used to sweeten sour gas again. The regeneration column serves the function of stsipping absorbed acid gases from the rich amine solution. A flash tank is usually installed at the outlet of the absorber to permit the recovery of the dissolved and entrained hydrocarbons and to reduce the hydrocarbon contents of the acid gas product. The flash gas from the flash tank and the stripped acid gas from the regenerator in amine units have the potential to emit hazardous air pollutants (HAPS), and therefore, the unit operators may be required to quanti% and report the emissions. The regulatory report may include both Hazardous Air Pollutants (HAPS) and Volatile Organic Compounds (VOCs). As a consequence, the American Petroleum Institute (API) supported the development of a comprehensive software package for the estimation of emissions from amine sweetening units.
The absorption of acid gases into an amine solution is a gas-liquid mass transfer process accompanied by complex chemical reactions. The rate of absorption is strongly influenced or enhanced by the rate of chemical reactions taking place in the liquid phase. The occurrence of the chemical reactions has two distinct effects on the overall behavior of the system. The first effect is to maintain a high driving force for mass transfer in the liquid phase. When component A is absorbed into the liquid phase, it is consumed by the chemical reactions and therefore its concentration in the bulk of the liquid is kept low. This implies that the driving force for absorption remains higher than it would be if no chemical reactions were taking place. The second effect is subtler. At a given level of driving force, the actual rate of mass transfer may be significantly larger when chemical reactions are talchg place than it would be in the absence of chemical reactions. The rate of enhanced mass transfer may be very large (up to two orders of magnitude or even more).
API Publ 4679:1999 pdf download
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