Heavy oils recovered, recycling

Waste material snch as tank bottoms from crude oil storage tanks constitute a large percentage of refinery solid waste and pose a particularly difficult disposal problem due to the presence of heavy metals. Tank bottoms are comprised of heavy hydrocarbons, solids, water, rust, and scale. Minimization of tank bottoms is carried ont most cost-effectively through careful separation of the oil and water remaining in the tank bottom. Filters and centrifuges can also be used to recover the oil for recycling. 

Isoprene Reactor effluent Isoprene, CTs, Cs s Heavy oil Separation of CTs, Cs s, and isoprene from light gases Stripping is practiced to recover the solute and regenerate the oil for recycling to the absorbent... 

After a residence time of about 0.020 s, the reaction products leave the reaction zone at about 900 C and undergo rapid quench by the injection of a heavy oil in a quench cooler devdoped by the Ozaki Chigh-pressure steam. The quench oil is recovered and recycled, while the cracking effluents are fractionated to separate the naphtha and tars. Tlie gaseous products are then treated m a special compression and treatment system required to remove large amounts of acetylene. CO and H2S obtained in the procsess. The rest of the recovery section is conventional. 

Carbon materials have a large sorption capacity for heavy oils, as explained in Section 111. Also, the sorbed heavy oils can be recovered by a rather simple recycling process, as explained in Section VI. It can be said that carbon materials... 

On the other hand, liquid propane also has a high affinity for paraffinic hydrocarbons. Propane deasphalting removes asphaltic materials from heavy lube oil base stocks. These materials reduce the viscosity index of lube oils. In this process, liquid propane dissolves mainly paraffinic hydrocarbons and leaves out asphaltic materials. Higher extraction temperatures favor better separation of the asphaltic components. Deasphalted oil is stripped to recover propane, which is recycled. 

Temperature-Controlled Residuiun Oil Supercritical Extraction (ROSE) The Kerr-McCee ROSE process has been used worldwide for over two decades to remove asphaltenes from oil. The extraction step uses a hquid solvent that is recovered at supercritical conditions to save energy as shown in Fig. 20-21. The residuum is contacted with butane or pentane to precipitate the heavy asphaltene fraction. The extract is then passed through a series of heaters, where it goes from the liquid state to a lower-density SCF state. Because the entire process is carried out at conditions near the critical point, a relatively small temperature change is required to produce a fairly large density change. After the light oils have been removed, the solvent is cooled back to the liquid state and recycled. 

In the fractionation section, propane that accompanies the propylene feedstock is recovered as LPG product from the overhead of the depropanizer column (2), unreacted benzene is recovered from the overhead of the benzene column (4) and cumene product is taken as overhead from the cumene column (5). Di-isopropylbenzene (DIPB) is recovered in the overhead of the DIPB column (6) and recycled to the transalkylation reactor (3) where it is transalkylated with benzene over a second zeolite catalyst to produce additional cumene. A small quantity of heavy byproduct is recovered from the bottom of the DIPB column (6) and is typically blended to fuel oil. The cumene product has a high purity (99.96-99.97 wt%), and cumene yields of 99.7 wt% and higher are achieved. 

The products leaving the furnace radiatioa zone must be cooled as quickly as possible. This operation is designed in particular to prevent the effluent composition from changing by the formation of heavy polymerization products and the increase in the gasoline content. It is important for the transfer line between the furnace and the quench boiler to be as short as possible to avoid additional residence of the effluents at elevated temperature. The heat of the furnace is first recovered by indirect cooling in the quench boilers, and directly by the introduction in -line of a recycle using a heavy hydroca n cut called quench oil (Fig. Hi). 

The feedstock is introduced into a furnace whose outlet temperature varies from 480°C to 515°C (895-960°F). The heated feedstock enters one of a pair of coking drums where the cracking reactions continue. The cracked products leave as overheads and the coke deposits form on the inner surface of the drum. To give continuous operation, two drums are used while one is on steam, the other is being cleaned. The temperature in the coke drum ranges from 415°C to 450°C (780-840°F) at pressures from 15 to 90 psi. Overhead products go to the fractionator, where naphtha and heating oil fractions are recovered. The heavy recycle material is combined with preheated fresh feed and returned to the reactor. 

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