Deoiling process

FIGURE 6.11 DILCHILL dewaxing/warm-up deoiling process. 

The deoiling process is used to produce a hard wax containing a very low oil content. Waxes produced in deoiling have melting point and needle penetration specifications. Waxes intended for food grade use must also meet UV absorption specifications and require wax hydrotreating. 

Solvent dewaxing removes wax (normal paraffins) from deasphalted lube base stocks. The main process steps include mixing the feedstock with the solvent, chilling the mixture to crystallize wax, and recovering the solvent. Commonly used solvents include toluene and methyl ethyl ketone (MEK). Methyl isobutyl ketone (MIBK) is used in a wax deoiling process to prepare food-grade wax. 

Further improvements of this basic deoiling process could be reached by additional options. 

Purification Processes. Separation of neutral and polar Hpids, so-called deoiling, is the most important fractionation process in lecithin technology (Fig. 3). Lecithin is fluidized by adding 15—30% acetone under intensive agitation with acetone (fluidized lecithin acetone, 1 5) at 5°C. The mixture goes to a separator where it is agitated for 30 minutes. The agitator is then stopped and the lecithin separates. The oil micella is removed and the acetone evaporated. After condensation the acetone is returned into the process. 

Due to possible environmental problems with acetone, new technologies are being developed for the production of deoiled lecithins involving treatment of Hpid mixtures with supercritical gases or supercritical gas mixtures (10—12). In this process highly viscous cmde lecithin is fed into a separation column at several levels. The supercritical extraction solvent flows through the column upward at a pressure of 8 MPa (80 bar) and temperature between 40 and 55°C. The soy oil dissolves together with a small amount of lecithin. 

To produce highly purified phosphatidylcholine there are two industrial processes batch and continuous. In the batch process for producing phosphatidylcholine fractions with 70—96% PC (Pig. 4) (14,15) deoiled lecithin is blended at 30°C with 30 wt % ethanol, 90 vol %, eventually in the presence of a solubiHzer (for example, mono-, di-, or triglycerides). The ethanol-insoluble fraction is separated and dried. The ethanol-soluble fraction is mixed with aluminum oxide 1 1 and stirred for approximately one hour. After separation, the phosphatidylcholine fraction is concentrated, dried, and packed. 

Pig. 4. Batch process for producing phosphatidylcholine fractions. 1, Ethanol storage tank 2, deoiled lecithin 3, solubiHzer 4, blender 5, film-type evaporator 6, ethanol-insoluble fraction 7, ethanol-soluble fraction 8, aluminum oxide 9, mixer 10, decanter 11, dryer 12, aluminum oxide removal 13, phosphatidylcholine solution 14, circulating evaporator 15, cooler 16, dryer and 17, phosphatidylcholine. 

It is reported (40) that the liquid-liquid process for separation of wax and oil is particularly suited for deoiling of waxes and that in some instances it is replacing the sweating process in Europe for the production of commercial waxes. 

The wax cake obtained from paraffin-distillate solvent dewaxing sweats more readily than that obtained from pressing, because the former has less oil. The amorphous wax recovered from the more viscous oils will not sweat, and therefore solvent processes for deoiling ljiave to be installed. These usually involve a repulping or resolution of the wax in... 

In most properly operated process plants, most of the boiler feedwater should be recovered condensate, that is, when steam condenses to water, the condensate produced should be recovered and returned to the boiler house. Often, the recovered condensate will first pass through a deoiling clay bed, to remove any hydrocarbon contaminants. To calculate the percent of condensate recovered, we need to know two numbers ... 

Separation of neutral and polar lipids, so-called deoiling, is the most important fractionation process in lecithin technology. A classic solvent for the deoiling is acetone. 

Due tit the possible environmenial problems with acetone, new technologies are being developed for the production of deoiled lecithins like an ethanol-based extraction and fractionation or a process involving treatment of lipid mixtures with supercritical gases or supercritical gas mixtures. 

Paraffin wax from a solvent dewaxing operation is commonly known as slack wax, and the processes employed for the production of waxes are aimed at deoiling the slack wax (petroleum wax concentrate). 

Lecithin may also be deoiled and sold as a granulated product high in phospha-tyol choline. This process typically involves an acetone extraction, leaving a granulated product for packaging. 

An unfortunate consideration associated with bleaching is the generation and subsequent disposal of the spent cake. Not only does the residual oil in the cake represent a loss to the processor, but spent cake is prone to spontaneous combustion under certain conditions when exposed to air. For that reason, spent cake may be classified as a hazardous material, making its environmentally responsible disposal difficult. The traditional landfill option may be restricted, not only because of this classification but also because of the limited space available at many locations. Spent cake can be added to meal in some cases, but this practice is frowned upon, especially when processing multiple types of oil. While deoiling the cake does help reduce the risk of combustion (and work is underway to reuse some of this material), most emphasis will be focused on alternate uses for the spent clay. Some... 

We summarize the data from one example of an early coffee decaffeination patent to highlight the specifics of the process (Roselius, Vitzthum and Hubert, 1974). Four hundred grams of rough-ground deoiled roast coffee is wetted with 200 ml of water and is treated with supercritical CO2 with an... 

Figure 10.6 Schematic diagram of the process for deoiling potato chips with supercritical carbon dioxide.

The new process involves the production of de-oiled lecithin by subjecting crude lecithin to supercritical CO2 extraction. The soy bean oil dissolves in CO2 and lecithin does not. One of the examples relates that 1,000 g of cmde lecithin is extracted with CO2 at 60 °C and 400 aun for 4 hours. The CO2 extracts 380 g of a yellow, clear oil, 30 g of water, and the residual material, 580 g of a solid, light yellow substance, which is the deoiled lecithin, is removed from the extraction vessel at the end of the cycle. 

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