What is visbreaker unit?
A visbreaker is a processing unit in an oil refinery whose purpose is to reduce the quantity of residual oil produced in the distillation of crude oil and to increase the yield of more valuable middle distillates (heating oil and diesel) by the refinery.
What is visbreaking in refinery?
Visbreaking is a mild form of thermal cracking, with primarily aim to lower the viscosity of vacuum residues. Two visbreaking processes are available: the coil or furnace type and the soaker type. In each process, viscosity control is necessary to adjust heating parameters and optimize distillation.
What is the difference between coil and soaker visbreaking?
The coil visbreaker is operated at high temperatures (885–930°F, 473–500°C) and low residence times (one to three minutes), while in a soaker unit, by adding an adiabatic drum after the coil furnace, the product is held for a longer time so that the coil is kept at a relatively lower temperature (800–830°F, 427–443°C).
What do you mean by visbreaking?
Visbreaking is thermal cracking, when the vacuum residue is less viscous and it can then be used to produce valuable products. Visbreaking is thermal cracking, when the vacuum residue is less viscous and it can then be used to produce valuable products.
Why is it called delayed coking?
Refineries commonly employ one of three types of coking processes: Delayed coking—a thermal cracking process that converts residuum into gasified product streams and concentrated carbon coke. It is called “delayed coking” because cracking takes place in a coke drum rather than in a furnace or reactor.
What is delayed coking process?
Delayed coking is a thermal cracking process used in petroleum refineries to upgrade and convert petroleum residuum (bottoms from vacuum distillation of crude oil) into liquid and gas product streams leaving behind a solid concentrated carbon material—petroleum coke.
What is the feedstock for visbreaking?
tar sand bitumen
In the process, the feedstock (usually residuum or tar sand bitumen) is passed through a furnace where it is heated to a temperature of 480 °C (895 F) under an outlet pressure of about 100 psi (Figure 1).
What is hydrotreated oil?
Hydrotreating or hydrodesulfurization refers to a set of operations that remove sulfur and other impurities (Figure 1). During hydrotreating, crude oil cuts are selectively reacted with hydrogen in the presence of a catalyst at relatively high temperatures and moderate pressures.
What is coking and decoking?
petroleum refining In petroleum refining: Visbreaking, thermal cracking, and coking. Decoking is a routine daily occurrence accomplished by a high-pressure water jet. First the top and bottom heads of the coke drum are removed. Next a hole is drilled in the coke from the top to the bottom of the vessel.
What is the difference between Flexicoking and fluid coking?
Fluid coking can process heavier VDR and gives a higher distillate yield (and lower coke yield) than delayed coking. Depending on the demand, the flexi-coking process can produce both fluid coke and fuel gas, or gasify all the coke to produce only fuel gas.
What is HVO made from?
HVO is produced by hydrogenation and hydrocracking of vegetable oils and animal fats using hydrogen and catalysts at high temperatures and pressures. In this hydrotreating process, oxygen is removed from the feedstocks consisting of triglycerides and/or fatty acids.
What is the severity of visbreaker operation?
The severity of visbreaker operation is normally limited by the need to produce a visbreaker tar that can be blended to make a stable fuel oil. Stability in this case is taken to mean the tendency of a fuel oil to produce sediments when stored.
What is the yield of hydrocarbon products from a visbreaker furnace?
The yields of the various hydrocarbon products will depend on the “severity” of the cracking operation as determined by the temperature the oil is heated to in the visbreaker furnace. At the low end of the scale, a furnace heating to 425 °C would crack only mildly, while operations at 500 °C would be considered as very severe.
What is the percentage of tar in a visbreaker?
Arabian light crude residue when visbroken at 450 °C would yield around 76% (by weight) of tar, 15% middle distillates, 6% gasolines and 3% gas and LPG. The severity of visbreaker operation is normally limited by the need to produce a visbreaker tar that can be blended to make a stable fuel oil.
What is the chemistry of visbreaking?
Overall chemistry of visbreaking – breaking up long chains of hydrocarbons. As in all chemical reactions, conversion in visbreaking depends primarily on temperature and time. As a measure of “thermal severity” under reactions conditions, one can use a thermal severity index (TSI) as a function of temperature and time that is shown in Figure 6.4.