Bitumen Residues

Crude oil or petroleum product is a substance on which modern life depends. One-third of the world s power and most organic chemicals come from it. It is used as fuel in automobiles, aircraft and ships, and provides heat and light to homes, schools and businesses. It can be distilled to form lubricants to keep machinery running smoothly and it can give bitumen residues that are used as tar to surface roads and runways for aircraft. The derivatives from crude oils can also be used to make plastics, fibres, drugs, detergents, paints, polishes, ointments, solvents, insecticides and weed killers. 

The bituminization process is performed basically by adding a concentrated waste slurry or even a predried waste mixture to the molten bitumen. Residual water is evaporated and the solids are evenly distributed in the bitumen. After solidification a homogeneous product is obtained. Figure 11.23 shows a flow sheet of a screw extruder plant for bituminization Figure 11.24 is a photograph of the screw extruder evaporator,... 

Bitumens are residues of the vacuum distillation of suitable crude oils (distillation bitumen). Residues of less suitable crudes must be partially oxidized by blowing to achieve the desired technical properties (semi-blown bitumen). Blown bitumens for special purposes can also be produced from vacuum residues. The process is executed by blowing a stream of finely distributed air through the molten bitumen (sometimes reduced in viscosity by addition of flux oil) at temperatures of 250-290 "C. 

Apart from the tests performed on bitumen emulsions, tests are also performed on the residual bitumen contained in the emulsion. The tests on the bitumen residue (see Tables 3.14 and 3.15) have been described in the previous paragraphs of this chapter. 

It is noted that the percentage of bitumen residue in the emulsion, if desired, may be determined from the deduction [100 - water percentage (w)]. 

Determination of bitumen residue by evaporation of bitumen emulsion... 

After cooling the beaker, the sample and the rod are weighed. The percentage of bitumen residue is specified as a percentage to the initial emulsion weight. Report the average of three determinations to the nearest 0.1% as the percentage of bitumen residue by evaporation. 

This test method for residue by evaporation tends to give a bitumen residue lower in penetration and ductility than the distillation test method. If the residue from evaporation fails to meet the requirements for properties specified for residue from distillation, tests shall be re-run using the distillation test method. 

After thoroughly mixing 100 g of bitumen emulsion with the appropriate solution, the product passes through a 1.4 mm wire cloth as well as the rinse water for cleaning the beaker and the rod. Washing is continued until the rinse water drains clear. Then, the wire cloth enclosing the bitumen residue is placed in an oven at 163°C to dry completely (for 1 h or longer). 

The classification test determines the relative compatibility between an aggregate filler of specific gradation and an emulsified bitumen residue. 

The use of tack coat is not usually required unless the old surface is smooth or the construction is conducted on an uphill/downhill section. However, when used, a light tack coat is applied using a diluted bitumen emulsion at a rate of 60 to 100 g/m of bitumen residue. 

In all the above treatments, thorough cleaning of the surface and application of the proper amount of tack coat before laying the new asphalt layer are essential cationic emulsion is recommended to obtain 0.15 to 0.35 g/m of bitumen residue on the surface (quantity depends on the surface s bitumen absorption). 

The distillation of crudes chosen for their yield in heavy fractions is the most common means. Bitumen is extracted from the residue from a vacuum distillation column (a few dozen mm of mercury), the latter being fed by atmospheric distillation residue. Unlike the practice of a decade ago, it is now possible to obtain all categories of bitumen, including the hard grades. 

Solvent deasphalting. This is an extraction of the heaviest fractions of a vacuum residue or heavy distillate. The extract is used to produce the bitumen. The separation is based on the precipitation of asphaltenes and the dissolution of the oil in an alkane solvent. The solvents employed are butane or propane or a butane-propane mixture. By selecting the proper feedstock and by controlling the deasphalting parameters, notably temperature and pressure, it is possible to obtain different grades of bitumen by this process. 

Large amounts of tar or pitch by-products are produced by industrial processes. The distillation of cmde petroleum (qv) yields a pitch-like residue termed bitumen or asphalt (qv). In the United States, these terms are interchangeable, but in Europe the term asphalt is generally restricted to naturally occurring rock or lake asphalt, whereas the residual product of cmde-od distillation is termed bitumen. Although these are important industrial materials produced in millions of metric tons annually, they are not included herein (see Asphalt Petroleum, products). 

It is incorrect to refer to bitumen as tar or pitch. Although the word tar is somewhat descriptive of the black bituminous material, it is best to avoid its use in referring to natural materials. More correctly, the name tar is usually appHed to the heavy product remaining after the destmctive distillation of coal (qv) or other organic matter. Pitch is the distillation residue of the various types of tar (see Tar and pitch). 

Asphalt (qv) is prepared from petroleum and often resembles bitumen. When asphalt is produced simply by distillation of an asphaltic cmde, the product can be referred to as residual asphalt or straight-mn petroleum asphalt. If the asphalt is prepared by solvent extraction of residua or by light hydrocarbon (propane) precipitation, or if blown or otherwise treated, the term should be modified accordingly to qualify the product, eg, propane asphalt. 

Another interesting, but rather complex system, which couples flow injection analysis, EC and GC has been recently reported (47). This system allows the determination of the total amount of potentially carcinogenic polycyclic aromatic compounds (PACs) in bitumen and bitumen fumes. This system could also be used for the analysis of specific PACs in other residual products. 

Table II. Mass % of Total Bitumen Remaining After Heating and Elemental Composition of the Residue Produced...

Table III. Mass % of Total Bitumen and of C, H, and S Remaining as Residue After Heating...

Initial rates of oxidation were determined as described in Reference 1. Mass of residual coke was determined by ashing, and carbon and hydrogen content of the residual coke was determined by microanalysis. Because the relative error in the total heat produced by oxidation of the bitumen exceeded 50%, the heats were considered unreliable and are not reported here. 

Table VI. Residual Coke and Conversion of Available Carbon During Wet Oxidation of Athabasca Bitumen at 225°C a ...

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