Flexsorb process

Exxon s Flexsorb process [669], [670] uses a sterically hindered amine as an effective promoter of a hot potash system. A lower energy requirement and less solution makeup than in other processes are claimed. So far it has been successfully used in several large plants. 

Others. ExxonMobil also offers two mixed hindered amine/physical solvent versions of the Flexsorb process. The Hybrid Flexsorb SE Process employs a solution of the Flexsorb SE amine, water, and an unspecified physical solvent. Two plants are in operation. The Flexsorb PS solvent consists of a different hindered amine, water, and a physical solvent. Five of these plants are believed to be operating.198,199... 

A number of processes have been developed using hot potassium carbonate plus an activator. The activator, which may be DEA, boric acid, or a hindered amine, serves to accelerate the rate of absorption, thus reducing absorber and regenerator sizes. Catacarb, Benefield, and Flexsorb HP are examples of proprietary processes of this type. 

A number of absorption processes use a mixture of amines and physical solvents to take advantage of the best characteristics of both types. A mixed solvent is generally a compromise between H2S selectivity and the degree of the physical solubilities of the other sulfur compounds. Among the most numerous applications of such processes used commercially are Sullinol (Shell) and Flexsorb.58 189... 

Figure 2.22 Schematic of Exxon Flexsorb solvents process. Source [38].

Song, Cook C., et al. 1992. Conversion of CO2 Removal Process for Flexsorb HP Solvent, Ammonia Safety Symposium,... 

Exxon Research and Engineering Co., 1994, Flexsorb Solvents, in Gas Processes 94, Hydro. Process., April, p. 80. 

Hot Potassium Carbonate (Benfleld) Process, 334 Catacarb Process, 363 Flexsorb HP Process, 369 Giammarco-Vetrocoke Process, 371... 

The Flexsorb HP Process is a promoted hot potassium carbonate process developed and licensed by Exxon Research and Engineering Company. Four commercial plants using the process were reported to be in operation in 1992 (Exxon, 1992). The proeess is similar, with regard to flow schemes and general applications, to the activated Benfield and Cataearb proeesses. It is characterized by the use of a sterieally hindered amine as the activator. 

Removal of hydrogen sulfide om the hydrogenation reactor off-gas in the presence of carbon dioxide is accomplished by use of a selective amine such as Exxon s Flexsorb SE Plus or Union Carbide s UCARSOL HS-103 (see Chapters 2 and 3). Regeneration of the selective amine produces a hydrogen sulfilde-rich gas which is sent to a sulfur recovery unit. In the Parsons FGC process, the Recycle Selectox process (see Chapter 8) is used for sulfur recovery. 

Several processes have been developed based on the oxidation approach, but, with some exceptions, such as the Linde Clintox process (Heisel and Marold, 1992) these have not been commercial successes because of the complexity of SO2 recovery processes and their comparatively low SO2 removal efficiencies. Hydrogen sulfide, on the other hand, can be removed at very high efficiency by a number of processes, including the selective amine processes discussed in Chapter 2. Processes that involve the conversion of Claus plant tail gas sulfur compounds to H2S and the removal of this H2S are discussed in the following sections. Processes reviewed include Parson s Beavon Sulfur Removal (BSR) process. Shell s SCOT process, FB and D Technologies Sulften process, the TPA Resulf process, and the Exxon Flexsorb SE Plus process. 

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