Viscosity breaking

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. 

Viscosity breaking aims to thermally crack long-chain feed molecules to shorter ones, thus reducing the viscosity and the pour point of the product. 

Analysis of feed and products from viscosity breaking ... 

After the completion of the fracturing treatment, the fluid viscosity should decrease to allow the placement of the proppant and a rapid fluid return through the fracture. It is important to control the time at which the viscosity break occurs. In addition, the degraded polymer should produce little residue to restrict the flow of fluids through the fracture. 

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. 

In viscosity breaking only a mild decomposition take place, the oil is decomposed just enough to lower the viscosity and pour point, so it can be pumped more easily. Little or no gasoline is produced. 

The temperature must be based on experience with the particular fluid. For crude petroleum and residues, temperatures of around 725 to 750° F are commonly given as maximums. Such temperature limits do not apply when the purpose of the heater is to produce a molecular rearrangement, as in thermal cracking, reforming or viscosity breaking. 

Interactions with other additives Some nudeators or darifiers may interact with other additives in the compound. Sodium benzoate, for example, is reactive with caldum stearate which is used as a lubricant and add scavenger—though not with hydrotaldte-based add scavengers. Or haze may be inaeased by the peroxides used in controlled-rheology PP for viscosity-breaking and improved melt flow. Different darifiers reportedly can limit this haze inaease such as RiKA s nonsorbitol PCI product [10-4, 10-19]. 

Molding Viscosity Break, Elong, Modulus, Izod Temp,°C (I.V ) 10 psi % 10 psl Impact... 

Generally one observes that up to a mole fraction of 40% of the acid the structural relaxation time T4 increases by a factor 10 (from 7 ms to 70 ms). From this result the growth of the micellar aggregates can be concluded. The short time constant T3 does not notably change and amounts to about 0.1 ms. At a molar ratio of more than 50% of the acid the viscosity breaks down due to a decreasing length of the micelles. In this case it is not possible anymore to measure the samples with the HF rheometer. 

Surfactant-gelled acid systems (also known as viscoelastic acid systems) represent a more recent development. Such systems have found success in carbonate matrix acidizing applications in particular. Certain special surfactant formulations can be added to acid that is above a certain concentration (e.g., >15% HCl) at which the surfactant does not impart appreciable viscosity. However, as the acid is injected and reacts in the formation, the surfactant generates viscosity (as a function of dissolved chloride ion and pH), thereby retarding reaction and providing, potentially, in situ diversion. As acid spends further, viscosity breaks back to reduced level (in the ideal case). 

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