What is the relationship between the circulating hydrogen volume and the hydrogen partial pressure in a hydrogenation unit?
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I’m a bit confused – how should the relationship between the circulation hydrogen volume in a hydrogenation unit and the hydrogen partial pressure be expressed?
Do we still need to include the purity of the recycled hydrogen?
The hydrogen partial pressure is related to the purity of hydrogen and the amount of recycled hydrogen
Hydrogen partial pressure = Total system pressure × Purity of recycled hydrogen
When the system pressure is high, the flow rate relative to you is greater; the hydrogen partial pressure is the system pressure multiplied by the hydrogen purity
The effect of reaction pressure is manifested through the hydrogen partial pressure. The hydrogen partial pressure determines the operating pressure in the system, the hydrogen-to-oil ratio, the properties of the feedstock, the purity of the recycled hydrogen, and the gasification rate of the feedstock. Increasing the hydrogen partial pressure facilitates the progress of hydrogenation reactions and accelerates their rate. A higher hydrogen partial pressure is beneficial for catalytic reactions; it can suppress coking reactions and reduce the rate of catalyst deactivation. Additionally, it enhances the removal of impurities such as S, N, and metals, while also promoting the hydrogenation and saturation of polycyclic aromatic compounds. Therefore, the hydrogen partial pressure in the reaction system should be increased as much as possible, within the limits permitted by the equipment and operating conditions. Increasing the hydrogen-to-oil ratio raises the partial pressure of hydrogen in the reactor, thereby increasing the number of hydrogen molecules available for the reaction. This is beneficial for enhancing the degree of reaction, suppressing hydrocondensation reactions, reducing coke formation on the catalyst surface, maintaining catalyst activity, and prolonging its service life. However, an excessively high hydrogen-to-oil ratio increases the load on the recycle hydrogen compressor and the gas-liquid separation system, leading to higher energy consumption, greater power usage, and increased operating costs. Therefore, it is necessary to select an appropriate hydrogen-to-oil ratio based on specific circumstances.
Increasing the amount of circulating hydrogen raises the hydrogen partial pressure