Lube Plants

Internal reflux is induced by means of externally cooled liquid pumparounds. A pumparound simply removes hot liquid from the tower, pumps it through a heat exchanger and then introduces this cooled liquid into the tower a few trays above. Use of pumparounds allows a better distribution of tower loadings than if all the heat were removed from the VPS using an overhead condenser. Four to six trays between sidestreams and two pumparounds are normally specified for a lube VPS. The three liquid sidestream products to be used as lube plant feed stocks are steam stripped to remove lighter boiling components which condense with tire sidestreams. 

The state of the art, today, is based on an all catalytic lube plant, which does not rely on solvent processing. An example of such a plant is Mobil s Jurong plant located in Singapore (11). The configuration of the plant relies on the use of a lube hydrocracker, coupled with a selective catalytic dewaxing unit (Fig. 8.2). 

Fig. 8.2 All Catalytic lube plant 8.3.3 Hybrid lube plants...

Production of base oils by this route is sometimes described as lubricant oil hydrocracking because it is really a variant of the common refinery process of hydrocracking to make light fuel products from vacuum distillate feedstocks. It is not a complete process for making base oils. Distillation, de-waxing and usually also hydrofinishing steps are needed, just as in a conventional lube plant. 

Sulfur Sulfur is present in all lube plant feedstocks fractionated from crude oil and its content may be up to several percentage points. Solvent refining removes some but not all, therefore such stocks with no further treatment can contain up to several mass percent of sulfur. Hydrofinishing of solvent refined stocks can reduce this level substantially. Base stocks from conversion processes will have sulfur levels in the low parts per million (ppm) range since sulfur is relatively easily removed in severe hydroprocessing. 

In this chapter we will discuss a number of commercial lube plants whose purpose is to make base stocks by hydrocracking and whose design basis has been outlined in papers from either the company that developed the specific technology or by a licensee. In the case of a licensee, the technology would have been adapted (and developed) as needed to meet that company s circumstances, including capital available, feedstocks and their qualities, existing refinery infrastructure, and eventual product marketplace. 

FIGURE 7.6 Schematic for Shell s lube plant at Petit-Couronne, France. 

Physical and Chemical Changes in Second-Stage Hydrotreating at Petro-Canada s Lube Plant... 

FIGURE 7.12 Plant schematic for Chevron s Richmond, California, lube plant when started. Source T. R. Farrell and J. A. Zakarian, Lube Facility Makes High-Quality Lube Oil from Low-Quality Feed, Oil and Gas Journal May 19 47-51 (1986). With permission. 

Properties of Alaskan North Slope Feeds to Chevron s Richmond, California, Lube Plant... 

Low investment by integration with existing solvent lube plant. 

Lube Plant and One Using a Lubes Hydrocracker Solvent Refined Plant Lubes Hydrocracker ... 

If you examine arty layout sketches in hirrdsight it seems apparent that the Natiorral Gtrard Camp which included family hoirsing arrd other residential homes were located too close to the flashing flammable liqirids in the facility. The lube plant was too close also. 

O Donnell reported that nearly all of the falahties were non-refinery workers living or working outside of the refinery ferrce. A rrumber of sorrrees estimate there were 47 deaths. One refirrery employee was reported to have died arrd five employees at an adjacent lube plant had died. The sad fact that the rest of the deaths were of local residents. 

Lube plant feedstocks are taken fi om the bottom of the crude barrel (see Figure 1). 

Figure 1. Lube Plant Feedstocks Are Taken from the Bottom of the Crude Barrel.

KEY POINTS IN TYPICAL CONVENTIONAL SOLVENT LUBE PLANTS... 

Results of the plant test are reviewed with a focus on lube plant manufacturing performance and Base stock product quality to determine if the new erude can be approved for Base stock manufacture. 

Lube plant manufacturing performance - actual rate, yield and operability. The actual operating conditions are compared to the predicted processing conditions to assess if the new crude processed as expected. 

The extraction process is a physical separation that is used in all conventional lube plants. The solvent is added to the distillate and then separated to produce a raffinate (the desired product) and an extract that contains a higher percentage of aromatics and impurities. Typical solvents used are N-methyl-2-pyrrolidone, furfural, and phenol. Properties of the solvents are shown in Figure 11. 

Distillate is brought in contact with the solvent, and aromatics and polars are preferentially dissolved in the solvent phase. Saturates do not dissolve and remain in the hydrocarbon or dispersed phase. The hydrocarbon phase is lower in density than the solvent phase and rises as bubbles through the continuous phase. After separation the raffinate and extract solution are sent to their respective solvent recovery sections. Integration of a hydrofiner on the raffinate product is in some lube plants for heat integration because this eliminates the need for an additional hydrofiner furnace. 

There are several types of continuous treater tower designs used in conventional lube plants. These include trayed towers, packed towers and rotating disc contactors (see Figure 13). The treater tower internals are designed to promote contact and separation of the oil and the solvent phases. 

A composite of several possible schemes for basestock and specialties manufacture (that no single lube plant employs in total) is illustrated in Figure 3. 

Middle distillates (jet and diesel) from high-conversion hydrocrackers meet or exceed finished product specifications. The heavy naphtha, however, usually goes to a catalytic reformer for octane improvement. The fractionator bottoms from partial conversion units can be sent to an FCC unit, an olefins plant, or a lube plant. 

The raffinate from the solvent extraction unit in a traditional lube plant contains a considerable amount of wax. To recover the wax, the raffinate is mixed with a solvent, usually propane, and cooled in a series of heat exchangers. Further cooling is provided by the evaporation of propane in the chiller and filter feed tanks. The wax forms crystals, which are continuously removed, filtered, and washed with cold solvent. The solvent is recovered by flashing and steam stripping. The wax is purified by heating with hot solvent, after which it is re-chilled, re-filtered and given a final wash. 

Many mild hydrocrackers contain at least one bed of cracking catalyst, which allows them to achieve higher conversion - between 20 and 40 wt%. The unconverted bottoms can go to an FCC unit, a lube plant, or fuel-oil blender. Due to its high value in other applications, the bottoms are blended into fuel oil only when there is no other feasible option. 

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