Flash Drum Nucleating Liquid for Coke Precursor Removal
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Solution Overview
Problem
Conventional steam cracking processes face challenges in efficiently processing hydrocarbon feedstocks containing non-volatile components, such as crude oil and atmospheric residue, which lead to coke deposition and fouling issues due to the inability to effectively separate and vaporize these components.
Innovation Solution
A process involving preheating the hydrocarbon feedstock with steam and optionally water, followed by flashing to separate a vapor phase and a liquid phase, where the vapor phase is treated with a hydrocarbon-containing nucleating liquid to coalesce coke precursors, and then heated for cracking in a pyrolysis furnace, thereby reducing fouling and increasing the efficiency of olefin production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional steam cracking is used to process heavy feedstocks containing non-volatile components, then light olefins can be produced, but coke deposition occurs in the convection section reducing furnace efficiency and increasing maintenance needs
Solution Approach 1:
The invention applies preliminary action by introducing a nucleating liquid into the flash drum before the vapor phase enters the pyrolysis furnace. This nucleating liquid pre-coalesces coke precursors in the vapor phase, preventing their deposition in the convection section downstream. The coalescence action occurs in advance within the flash drum, eliminating the harmful coke formation problem before it affects the furnace system.
2Productivity
If more non-volatile components are vaporized to increase olefin yield, then productivity improves, but coke formation and fouling increase
Solution Approach 1:
The nucleating liquid acts as an intermediary substance that facilitates the coalescence of coke precursors. By introducing this mediator into the vapor phase within the flash drum, the system enables effective separation and removal of coke-forming components. This intermediary action allows higher vaporization rates for increased olefin yield while the nucleating liquid continuously coalesces the harmful precursors, preventing fouling downstream.
3Object-generated harmful factors
If flash separation is used to remove non-volatile components, then coke deposition is reduced, but vaporization of lighter fractions is limited
Solution Approach 1:
The invention applies parameter changes by modifying the operating conditions within the flash drum, specifically maintaining a residence time of at least 5 seconds and introducing a nucleating liquid. These parameter changes enable the system to achieve both effective coalescence of coke precursors (reducing deposition) and sufficient vaporization of lighter fractions (maintaining productivity). The altered parameters allow simultaneous achievement of both goals that were previously contradictory.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces coke formation and fouling by partially condensing the vapor phase, allowing for the removal of coke precursors and enhancing the vaporization of lighter fractions, thus improving the processing of heavy hydrocarbon feedstocks and increasing the yield of valuable steam cracker feed.
Implementation Method 1
mixing the heated hydrocarbon feedstock with steam and optionally water to form a mixture stream; introducing the mixture stream to a flash/separation apparatus to form a vapor phase and a liquid phase
Implementation Method 2
treating the overhead by contacting with a hydrocarbon-containing nucleating liquid under conditions sufficient to at least partially coalesce the uncoalesced condensate to provide coke precursor liquid
Implementation Method 3
cracking the heated vapor phase in a pyrolysis furnace to produce an effluent comprising olefins
Implementation Method 4
heated and vaporized by indirect contact with hot flue gas from the radiant section and by direct contact with steam
Data Source
AI summary
Hydrocarbon feedstock containing resid is cracked by a process comprising: (a) heating the hydrocarbon feedstock; (b) mixing the heated hydrocarbon feedstock with steam and optionally water to form a mixture stream; (c) introducing the mixture stream to a flash/separation apparatus to form i) a vapor phase at its dew point which partially cracks and loses/or heat causing a temperature decrease and partial condensation of the vapor phase in the absence of added heat to provide coke precursors existing as uncoalesced condensate, and ii) a liquid phase; (d) removing the vapor phase as overhead and the liquid phase as bottoms from the flash/separation apparatus; (e) treating the overhead by contacting with a hydrocarbon-containing nucleating liquid substantially free of resid and comprising components boiling at a temperature of at least about 260° C. (500° F.) under conditions sufficient to at least partially coalesce the coke precursors to provide coke precursor liquid, in the form of hydrocarbon droplets or a continuous hydrocarbon liquid phase; (f) collecting and removing the droplets; (g) directing the treated overhead from which the droplets are removed, to a heater to provide a heated vapor phase; (h) cracking the heated vapor phase in a radiant section of a pyrolysis furnace to produce an effluent comprising olefins, the pyrolysis furnace comprising a radiant section and a convection section; and (i) quenching the effluent and recovering cracked product therefrom. An apparatus for carrying out the process is also provided.