Viscosity breaking process

Visbreaking. Viscosity breaking (reduction) is a mild cracking operation used to reduce the viscosity of residual fuel oils and residua (8). The process, evolved from the older and now obsolete thermal cracking processes, is classed as mild because the thermal reactions are not allowed to proceed to completion. 

Rao et al. (1981) studied the influence of temperature and total solids content (c) on the apparent viscosity at 100 s (i a,ioo) of tomato concentrates prepared from the varieties grown at the New York State Agricultural Experiment Station Nova, New Yorker, 475, 934 hot break process, and 934 cold break process. The results of... 

Figure 5-14 Log-log Plot of the Apparent Viscosity at 100 versus Total Solids of Tomato Concentrates from Hot-break Nova Tomato Concentrates, and 934 Hot-break and Cold-break Process The Slopes of the Lines Were 2.7,2.4, and 2.5, Respectively.

In the early days of the industry, gasoline was of little value. Cracking was used to produce more kerosene than could be obtained by steam or simple distillation. At first, cracking was done by the decomposition of vapors, later liquid-phase cracking processes would include viscosity breaking and reforming. 

The viscosities above c increase abruptly according to the power law of equation (10.11) with an exponent of X > 3.5, while the exponent of the power law for the shear modulus Go is always about 2.3. For the explanation of this behaviour it was assumed that the structural relaxation times are affected both by reptation of the rods and by bond-breaking processes. Cates distinguished three different kinetic mechanisms (9). The first mechanism assumes the breaking of a rod with the formation of two new end-caps and the recombination of two rods by collision at the ends and fusion into a new rod. In the second mechanism, the end-cap of one rod collides with a second rod and via a three-armed transition state a new rod and a new end-cap is formed. In the third mechanism, two rods collide and form two new rods through a four-armed transition state. Of course, an applied stress can relax by all three mechanisms. These mechanisms lead to somewhat different power laws for the kinetic time constant r according to the following ... 

Liquid Injection. Liquid injection units are the most common type of incinerator today for the destmction of Hquid hazardous wastes such as solvents. Atomizers break the Hquid into fine droplets (100—150 microns) which allows the residence time to be extremely short (0.5—2.5 s). The viscosity of the waste is very important the waste must be both pumpable and capable of being atomized into fine droplets. Both gases and Hquids can be incinerated in Hquid injection units. Gases include organic streams from process vents and those from other thermal processes in the latter case, the Hquid injection incinerator operates as an afterburner. Aqueous wastes containing less than 75% water can be incinerated in Hquid injection units. 

The emulsification process in principle consists of the break-up of large droplets into smaller ones due to shear forces (10). The simplest form of shear is experienced in lamellar flow, and the droplet break-up may be visualized according to Figure 4. The phenomenon is governed by two forces, ie, the Laplace pressure, which preserves the droplet, and the stress from the velocity gradient, which causes the deformation. The ratio between the two is called the Weber number. We, where Tj is the viscosity of the continuous phase, G the velocity gradient, r the droplet radius, and y the interfacial tension. 

In the wet process, the clay is masticated in a pug mill to break up lumps and then dispersed with a dispersing aid and water to make a 40 percent solids slip of low viscosity. A hi -speed agitator such as a Cowles dissolver is used for this purpose. Sands are settled out, and then the clay is classified into two size fractious in either a Hydrosettler or a continuous Sharpies or Bird centrifuge. The fine fraction, with sizes of less than 1 [Lm, is used as a pigment and for paper coating, while the coarser fraction is used as a paper filler. 

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