| In the petroleum refining process,3?8% of petroleum resources are converted into refinery tail gas, most of which contains great amounts of high-value components such as hydrogen, ethane, ethene, propane, propene and butane. Recovering the high-value components in the refinery gas could improve the production efficiency of petroleum industry, and the key to the problem is the separation process of those components. However, the composition of the refinery gas is complex, when single separation technology is applied, the limited operating conditions, singular target, low recovery and high operating consumptions are the major drawbacks. Thus, petroleum industry usually applies multiple separation technologies for comprehensive recovery, and the integration of different separation process becomes the most important aspect of process design. Aiming to optimize the integrated process of refinery gas recovery, this work targets the two key factor of refinery recovery process, i.e., hydrogen recovery and methane removal from hydrocarbons. Based on the investigations of separation technology, this work proposed an analytical tool for the matching of different separation targets/technologies and production energy consumptions. The target components are separated individually and separately through the optimization of each unit operation, achieving high product purity, high recovery and low operating consumption of hydrogen and hydrocarbons. In addition to the proposed method, several case studies of refinery plants are investigated and optimized by the proposed step-principle of process design. The proposed step-recovery processes for those plants have achieved multi-target separation of hydrogen, ethane, LPG and naphtha.Conventional analytical tool for energy efficiency can not fully meet the demand of industrial applications. This work proposed a novel analytical tool for energy consumption, which thoroughly considers the energy exchange between systems and energy dissipations of separation units. By defining the energy efficiency ratio, this work employed it as a criterion for energy efficiency, and derived a quantitative index for the energy consumption of separation process and recovered components. Take the desulfurized hydrogen tail gas from hydrocracking process as an example, the proposed method provided more accurate results for the energy consumptions of separation processes. The comparisons of energy efficiency ratio between different separation technologies and processes showed that, when the hydrogen purity requirements are lenient (97?99%), single PSA or membrane process could meet the separation target, and PSA are 28% improved than membrane. While hydrogen requirements are altered (99.9%), single technology could not achieve the separation target, and hybrid process of PSA and membrane should be applied. The results showed that, the energy consumption of membrane unit increases with the increase of hydrogen recovery. When membrane was employed and pre-enrichment unit for PSA, the energy efficiency ratio of the hybrid process could be further increased by 40%, comparing to PSA/membrane process.Hydrogen-rich tail gases are common byproducts of petroleum industry, and the recovery of hydrogen is the key to synthetic recovery of refinery gases. Conventional PSA/membrane hybrid process focuses on hydrogen recovery, while the purity issues are compromised. This work optimized the separation sequence, operational parameters of PSA and membrane, and achieves both high purity and recovery of hydrogen product for feed stream of 62.57% hydrogen. The PSA/membrane hybrid process could achieve 94% recovery with the hydrogen product purity of 99.9%, while membrane/PSAcould achieve 97% recovery due to the pre-enrichment effect of front-installing membrane unit. The proposed hybrid process is implemented in a refinery in Zhejiang by updating current VPSA. The hydrogen product of the updated process are increased from 99.5% to 99.9%, hydrogen recovery is also increased by 7%. More importantly, the hybrid process is more robust for operation, and the operational flexibility is also improved. The process investment is recovered in less than 8 months.Despite of hydrogen recovery, the methane removal from vapor gas mixtures are another key aspect of refinery gas recovery. Conventional processes such as low-temperature rectification have energy issues for refrigeration and compression. The vapor stream from the top stage of towers are usually fed to vapor membranes for recovery. This work proposed novel two-membrane hybrid processes to improve the separation efficiency of methane removal process, which are able to achieve high methane removal (less than lppm in product) and low hydrocarbon loss (less than 4%). The results showed that, the rectification/two-membrane hybrid process could endure 10? higher condensation temperature of top stage, and the compression load could be reduced by 87%. The two-way enrichment effect also enabled the hybrid process could produce 85% purity hydrogen, and effectively improved the efficiency of energy and resources. By employing rectification-PI-PDMS process to a refinery in Shandong, the energy consumption of the separation process was reduced by 18%, and provided 300Nm3/h hydrogen with 85% purity. The process investment was recovered in 13 months.The synthetic analyze and utilization of energy and resources of refinery plants are still below the expectations. This work proposed an integrated process by employing multiple separation technologies through the analysis of energy efficiency ratio. The proposed process was able to separate hydrogen, ethane, LPG and naphtha synthetically. The hydrogen recovery of the proposed process achieved 98.25%, ethane recovery achieved 98.32%, hydrocarbon recovery achieved 99.97%, and naphtha recovery achieved 99.98%. The process achieved high-efficiency separation of refinery tail gas, and could also meet the complicated requirements of product purities, pressures and other operational conditions. An illustrating process was implemented in a refinery of Guangdong. The operational results showed that, the total investment cost was 140 million CNY, and the product value exceeded 3 billion CNY, indicating that the investment was recovered in less than 6 months. |
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