Kerosene production

Example 15.2 A crude oil stream is to be preheated by recovering heat from a kerosene product in a shell-and-tube heat exchanger. The flowrates, temperatures and physical properties (at the mean temperatures) are given in Table 15.5. 

Jet-A This is a narrow cut kerosene product. This is the standard commercial and general jet fuel available in the United States. It usually contains no additives but anti-icing chemicals may be added. 

The reflux ratio is 3.71. At Stage 6, some liquid is withdrawn and fed to a 4-stage stripper. Open steam (3300 Ib/h) is used to strip light material from the liquid leaving the main column. A kerosene product is produced from the bottom of the stripper. It has ASTM 5% and 95% boiling points of 396 and 502 F, respectively. 

What could we learn from this material balance The first observation is that 1.6% extra kerosene is produced than expected. This has a simple explanation because the tower was operated to maximize kerosene production as kerosene was more valuable in the local market at that certain time. In contrast, 4.3% less of diesel was made, which was surprising. Two plausible causes were thought of by the process engineer responsible for the tower operation. One reason was that kerosene cuts 1.6% deep... 

I was called to a refinery to help determine why kerosene production had declined 3,000 B/SD. The refinery manager explained that a process engineer had spent six months on the problem and had run several computer simulation analyses on 16 different crude oils, including complete tray-to-tray heat and material balances for three operating modes. 

The result of the involved simulation study led to the recommendation that improved tower control, using advanced, feed-forward computer control and increased operator attention would maximize kerosene production. 

I found that the instrument air tubing connection to the kerosene-draw control valve was loose. That valve controls the flow of kerosene from the crude tower to the side-stream stripper. The control valve simply wasn t getting enough air to open fully. I tightened the connection, and kerosene production rose to the normal rate. 

Hydrogen partial pressure has an impact on the saturation of aromatics. A decrease in system pressure or recycle gas purity has a sharp effect on the product aromatic content. This will be especially true for kerosene aromatic content, which will in turn affect the kerosene product smoke points. 

The example of the petrochemical industry, which provides the model for the biorefinery, offers an interesting illustration. The petrochemical industry did not start by identifying exact structures of compounds wanted from the crude oil raw material. Rather, the product slate developed as fundamental research was carried out on crude oil to find those broad technologies most applicable to the properties of the raw material, and identifying the structures most easily made from these technologies. Kerosene production led to thermal cracking, steam... 

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