Diesel upgrading units increase the cetane number of the product
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Dear seniors, I have a 1.8 Mt/h diesel upgrading unit here, with a cold high-pressure of 8.0 Mpa. The feedstock consists of catalyzed diesel and conventional diesel in a 2:8 ratio, and the space velocity is 1. I would like to ask you all: given that the cetane number of the feedstock is around 45, how can we increase the cetane number of the product to above 51? Is it only possible to change the catalyst grading? What kind of gradation can be achieved?
Let’s consider the issue from the following aspects: First, the relationship between the cetane number of diesel and its chemical composition. The cetane number of diesel is determined by its chemical composition; different hydrocarbons have varying cetane numbers, and the general pattern is as follows. (1) Alkanes: Normal alkanes have the highest cetane number, and the higher their relative molecular mass, the higher the cetane number. The cetane number of isomeric alkanes with the same carbon count is lower than that of n-alkanes. For isomeric alkanes with the same relative molecular mass, their cetane number decreases as the number of branches increases. However, monosubstituted and many disubstituted isomeric alkanes have a cetane number between 40 and 70, as well as good spontaneous ignition properties. Alkanes are the main components of diesel; individual alkanes have a high cetane number, and diesel with a higher proportion of alkanes will also have a high cetane number. When the alkane content is low, aromatic characteristics dominate; when the dialkane content is high, alkane characteristics dominate. (2) Olefins: Normal olefins have a fairly high cetane number, but it is slightly lower than that of the corresponding normal alkanes. The effect of branching is similar to that of alkanes. (3) Naphthenes: The cetane number of naphthenes is lower than that of normal alkanes and normal alkenes with the same number of carbon atoms, and naphthenes with side chains have an even lower cetane number than those without side chains. (4) Aromatic hydrocarbons: Aromatic hydrocarbons with no side chains or short side chains have the lowest cetane number, and the higher the number of rings, the lower the cetane number. Aromatic hydrocarbons with longer side chains have a relatively higher cetane number, and this value increases as the length of the side chains increases. Naturally occurring straight-chain alkylaromatic hydrocarbons with the same number of carbon atoms have a higher cetane number than those with branched alkyl groups. The differences in the cetane number of various hydrocarbons mainly reflect their differences in spontaneous ignition properties. As can be seen from the table below, normal alkanes have a high cetane number due to their low auto-ignition temperature, whereas aromatic hydrocarbons have a low cetane number because of their high auto-ignition temperature. II. Process improvement involves modifying the components of the reaction products in order to select an appropriate modification plan.
Thank you for providing the information. Given the current operating conditions of our diesel upgrading equipment, and since we are unable to choose different raw materials, how should we address the issue of low cetane numbers in the products?
Engage a professional design firm to carry out the design and upgrade.
It is recommended to approach the Institute of Rock Mechanics or the Fuyan Research Institute to develop a plan, by sending them information on the properties of the existing raw materials and the size of the reactors, as well as the main process flow diagrams, so that they can prepare a plan!
Could you tell me the 16-cetane number, boiling range, and density of your current products? Including whether there were any attempts to make adjustments later on?
Is the design of this device aimed at modification? Then the catalyst should have the ability to carry out hydrogenation and ring-opening reactions, and proper grading should be taken into account when loading it. If the raw materials cannot be adjusted, the only option is to try increasing the reaction depth. It would be convenient to know what catalyst it is