Catalytic cracking unit

Abstract

The invention discloses a catalytic cracking unit. The catalytic cracking unit mainly comprises a heavy oil descendent tube reactor, a light hydrocarbon descendent tube reactor, a precipitator, a riser regenerator, a turbulent bed regenerator and the like, wherein the turbulent bed regenerator is communicated with the precipitator respectively through the heavy oil descendent tube reactor and light hydrocarbon descendent tube reactor; the precipitator is communicated with the riser regenerator; and the riser regenerator is communicated with the turbulent bed regenerator. The unit can improve the catalytic cracking product distribution, enhance the light oil yield and lower the yield of the cracked gas and coke; the unit can be used for producing low-olefin-content catalytic gasoline and high-cetane-number catalytic diesel; and the unit enhances the charring efficiency and decelerates the hydrothermal inactivation of the catalyst.

Description

technical field [0001] The invention relates to the field of catalytic cracking of hydrocarbon oil in the absence of hydrogen, in particular to a catalytic cracking device. Background technique [0002] At present, although the devices used in the catalytic cracking process in the petrochemical industry are various, the process form of the reaction regeneration system is basically the same. Most of them use a single riser reactor (or a combination of a single riser and a fast stage reactor) and a turbulent bed regenerator (or a two-stage regenerator combining a turbulent bed and a fast bed). Catalyst and raw oil are contacted and mixed at the bottom of the riser and then reacted upward along the riser. The reactant flow enters the settler from the outlet at the top of the riser to separate the reaction oil gas from the catalyst; Enter the regenerator to regenerate coke; the regenerated catalyst returns to the bottom of the riser for recycling. In the above-mentioned conven...

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Problems solved by technology

In the above-mentioned conventional catalytic cracking unit, there are the following disadvantages: first, because the length of the riser reactor determines that the reaction time of the raw material is longer (generally about 4s), the longer reaction time is increasing the raw material per pass. At the same time, the conversion rate also intensifies the secondary reaction of the raw material cracking products, so that the yield of cracked gas (the sum of dry gas and liquefied gas yields) is higher, and the yield of gasoline and diesel fractions is lower. At the same time, the catalytic diesel cetane The value is low, not suitable as a vehicle fuel

Second, due to the upward movement of the catalyst against the gravitational field in the riser reactor, the coking catalyst slips and back-mixes. On the upper part of the feed nozzle of the riser reactor, the coking catalyst that slips, the atomized raw material and the primary cracking product Re-contacting reactions, thereby deteriorating product distribution and reducing product selectivity of catalysts for feedstock cracking

Third, due to the relatively low coking intensity of the turbulent bed regenerator, the catalyst storage in the regenerator is relatively high and the catalyst stays in the regenerator for a long time, resulting in serious hydrothermal deactivation of the catalyst

Fourth, catalytic gasoline cannot be modified separately, and its quality is low

However, this technology still has the following shortcomings: First, the inertial separator used at the end of the downcomer reactor is not completely separated from the oil agent, and some oil and gas have a long reaction time

Second, it is not possible to individually upgrade gasoline with a single reactor

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