Regarding the circulating hydrogen volume in the hydrogenation unit
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Gentlemen, in a hydrogenation unit, if all other conditions remain unchanged and only the amount of recycled hydrogen is reduced – with the amount of fresh hydrogen changing accordingly due to system pressure – will the sulfur content of the product increase or decrease? My idea is that, in normal production, if all other conditions remain unchanged, reducing the load on the equipment will naturally lead to a decrease in the sulfur content of the product. The reason is the reduction of the space velocity in the reactor. If I reduce the amount of circulating hydrogen, will the reaction space velocity also decrease? So, under the condition of meeting the minimum requirement for the hydrogen-to-oil ratio, does a lower amount of circulating hydrogen result in better product quality? It’s just the product quality, ignoring all other factors for now
That’s not entirely correct; reducing the feed rate does increase the degree of hydrogenation. However, decreasing the amount of recycle hydrogen does not necessarily result in a lower space velocity, and it may not lead to good outcomes – it’s quite possible that the oil product will not meet the required standards. Hydrogenation reactions require hydrogen to take part, and by reducing the amount of recycle hydrogen, less hydrogen is available for participation in the reaction.
The system pressure hasn’t changed; it’s supplied by the new hydrogen generator, and the pressure throughout the system remains stable. Does that mean the amount of hydrogen available is sufficient?
The system pressure remains unchanged, but the amount of hydrogen is less; as a result, the depth of reaction is not as good as before, and the quality of the product is definitely not as good as it used to be.
The hydrogenation reaction is a reversible reaction; according to chemical equilibrium calculations, an increase in hydrogen partial pressure favors the progression of the reaction in the forward direction. Theoretically, when the hydrogen-to-oil ratio is high, the oil and gas are more evenly dispersed and have better contact with the catalyst, which facilitates the progress of the reaction. My humble opinion
The space velocity is related to the amount of feed oil, and has no direct relationship with the amount of recycled hydrogen.
What do you mean by the low amount of hydrogen? Shouldn’t the amount of hydrogen in the entire system remain unchanged?
Isn’t the space velocity nothing but the residence time? Isn’t the amount of hydrogen plus the amount of feed oil and gas in the entire reactor equal to the total amount of gas used in the reactor?
How exactly should this hydrogen partial pressure be understood? If the amount of recycled hydrogen decreases, but only that amount decreases while the overall system pressure remains unchanged, does that mean that the amount of hydrogen in the system also doesn’t change?
In simple terms, the higher the hydrogen-to-oil ratio, the better the product quality, but the production load increases as well. As the hydrogen-to-oil ratio decreases and the production load drops, the product quality will certainly decline compared to before. This can be seen from the sulfur content of the product.
1. Take a close look at the definition of airspeed. 2. The hydrogen partial pressure does not remain constant just because the system pressure stays the same; it mainly depends on the pressure in the reactor. By reducing the amount of circulating hydrogen, the pressure at the reactor inlet will certainly decrease, as well as the hydrogen partial pressure. A high hydrogen partial pressure facilitates the saturation of aromatics as well as various cyclic hydrocarbons; for compounds that contain aromatic rings or cyclic sulfides, saturation occurs first followed by desulfurization. Therefore, a decrease in hydrogen partial pressure inevitably has an impact on sulfur removal.