Stručni rad
INCREASING HYDROGEN PURITY BY ABSORPTION
Zoran Adžamić
Senad Bešić
Sažetak
Abstract High environmental standards are nowadays being growingly adopted as requirements of the market and, subsequently, hydrotreating is gaining priority in oil processing. This, first of all, refers to sulphur content in fuels, which ultimately endangers the future existence of many refiners worldwide. This was the main reason for constructing the new plant for HDS/MHC of heavier oil fractions at the Rijeka Refinery. Hydrogen quantities and its purity have become a very significant parameter in optimizing the Refinery’s operation. The availability of sufficient hydrogen and its purity not only influence the level of process utilization but are also the key factor in meeting the highly severe requirements on sulphur content in oil products. In Rijeka Refinery, like in many others, the Platformer unit is the only hydrogen producing unit. The purity of hydrogen ranges from 65 to 75% vol., depending on process parameters in the existing platformers. Since hydrogen purity proved to be quite a limiting factor for hydrotreating and hydrocracking processes, the ways of enriching platformer “net-separator gas” were sought for. The Refinery experts are well acquainted with the processes for the production of pure hydrogen from light and heavy oil fractions and natural gas. However, construction of such process units would involve significant additional costs and time. The same applies to processes for purification of hydrogen-rich gases. These facts have triggered the search for the optimum solution leaning on the Refinery’s own resources. The results were not only the optimization of the Platformer unit but also the utilization of a part of the existing refinery’s process equipment for the generation of higher purity hydrogen. The conceptual design was developed and theoretical, technological and technical documents elaborated to support the realisation of the process for the production of higher purity hydrogen by means of absorption, which should take place on the 17 C-1 column. It should be mentioned that the 17 C-1 column is physically incorporated into the Tatoray process and has been out of service for some 12 years. Thus, the 17 C-1 column becomes the absorber in the technical-technological sense, absorbing light hydrocarbons from “net-separator gas” produced on Platformer 2. In our case, the absorbent is the stabilized and cooled down platformate showing high absorbing characteristics. By connecting the 17-C1 column with the Platformer 2 stabilizer, the stabilizer has taken over the role of stripping the absorbed hydrocarbons from the absorbent (cooled platformate) which is separated as dry gas and LPG at the stabilizer overhead vessel. The inclusion of the continuous absorbtion column into the Platformer 2 process has proved to have multiple favourable effects: 1. The main target has been achieved: that of upgrading the Platformer 2 gas to contain over 83% vol. of hydrogen; 2. Through absorbtion of valuable hydrocarbons from the platformer gases (C3 and C4) the LPG yields at the Platformer unit have been significantly increased; 3. The gas purity with over 83% vol. of hydrogen content has enabled us to run the HDS/MHC plant in both modes at its maximum capacity and operating severity, yielding optimum quality products; 4. The plant run in HDS mode produces the maximum quantity and quality of gas oil, i.e. of diesel fuel; 5. MHC mode generates the maximum quantity and the required quality of the FCC feed. By processing the properly hydrotreated feed, additional favourable effects are achieved. These are, first of all, increased yields of gasoline, LPG and LCO at the expense of less valuable decanted oil and dry gas. All FCC products show the minimum sulphur level which ultimately has a favourable influence on the blending of commercial products.
Ključne riječi
platformate gas; platformate hydrogen for HDS/MHC; absorption tower of platformer plant; hydrogen purification by absorption; hydrodesulphuration/mild hydrocracking HDS/MHC; INA Oil industry Rijeka Refinery
Hrčak ID:
7370
URI
Datum izdavanja:
29.8.2003.
Posjeta: 3.521 *