چكيده به لاتين
Hydrogen, as a strategic and valuable gas, plays a vital role in the petrochemical and refining industries. In Isfahan Refinery, hydrogen is extensively utilized in hydrotreating processes for streams containing sulfur and oxygen compounds, as well as in hydrocracking reactions, particularly in the Isomax unit. With the implementation of the development plan in the southern section of Isfahan Refinery, the demand for hydrogen is rapidly increasing, necessitating the establishment of new hydrogen production units to meet this growing demand and enhance production capacity. Among the most economical and cost-effective methods for hydrogen production is the recovery of hydrogen from refinery off-gas streams. This process separates hydrogen from excess process gases, enabling the production of hydrogen at lower costs and higher efficiency. Consequently, hydrogen recovery has become one of the primary solutions for hydrogen supply in the refining industry. This study evaluates the feasibility of hydrogen recovery from various off-gas streams in Isfahan Refinery, including streams from catalytic reforming units (CRU Gas), high-pressure amine (HP Amine), low-pressure amine (LP Amine), and isomerization units (Sweet Gas). These streams, in addition to hydrogen, contain other gases such as methane, ethane, propane, butane, pentane, and hexane. Therefore, a separation process is required to remove impurities from these streams. The separation process was simulated using hydrocarbon solvent absorption in Aspen HYSYS software. Gasoline and diesel were employed as the solvents for absorption, with diesel demonstrating superior performance over gasoline. The purity of hydrogen produced using diesel for the CRU Gas, HP Amine, LP Amine, and Sweet Gas streams was achieved at 0.9887, 0.9766, 0.9882, and 0.9875, respectively. Furthermore, the hydrogen recovery rates from these streams were calculated as 0.9324, 0.9426, 0.9175, and 0.934, respectively. The effects of solvent flow rate, absorption temperature, and process pressure on the hydrogen purity and recovery rates were studied. An economic assessment of the absorption process using selected streams was conducted and compared. The results indicate that hydrogen recovery using the CRU Gas stream is the most cost-effective option, with a production cost of $1.036 per kilogram of hydrogen. Among the streams analyzed, the Sweet Gas stream from the isomerization unit, due to its significant content of propane, butane, and hydrogen, was further investigated for process evaluation and recovery of hydrogen and LPG. The hydrogen purity achieved through the Light Hydrocarbon Recovery (LHR) process was 97 mol%. The annual profit from this process was calculated to be $12,146,024, with a payback period of only one year. Implementing a hydrogen recovery plan for refinery off-gas streams can significantly supply the hydrogen required for the southern units of Isfahan Refinery, reducing the dependency on external hydrogen sources and enhancing overall operational efficiency.
