FCC Light Olefin Recovery via Catalyst Regeneration and Fractionation
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Solution Overview
Problem
Current hydrocarbon processing methods, such as fluidized catalytic cracking (FCC), face inefficiencies in producing and separating light olefins like ethylene and propylene, as they result in coke deposition on catalysts, which interferes with catalytic activity and requires energy-intensive regeneration, and existing separation methods may co-absorb olefins, reducing recovery efficiency.
Innovation Solution
A process involving a catalyst composition with a large pore molecular sieve and a zeolite with no greater than medium pore size, used in a fluidized reactor to crack heavy hydrocarbons, followed by a detailed separation system including deethanization, demethanization, and splitting to isolate and enrich ethylene and propylene streams, minimizing coke formation and optimizing light olefin recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fluidized catalytic cracking is used to produce light olefins, then the yield of light olefins is improved, but coke deposition on catalyst occurs which interferes with catalytic activity
Solution Approach 1:
The patent implements a catalyst regeneration system where spent catalyst is periodically removed from the reactor, burned to remove deposited coke in a regenerator, and then returned to the reactor. This cyclic discarding and recovering process maintains catalyst activity while enabling continuous production of light olefins.
Solution Approach 2:
The patent employs a two-stage cracking process with different operating parameters: the first stage uses higher temperature (700-900°C) and shorter residence time to maximize light olefin yield, while the second stage uses lower temperature (400-600°C) and longer residence time to convert heavier fractions. This parameter optimization improves light olefin selectivity while managing catalyst deactivation rates.
2Manufacturing precision
If traditional separation methods are used to separate light olefins, then hydrocarbon fractions can be separated, but olefins may be co-absorbed which reduces recovery efficiency
Solution Approach 1:
The patent employs a series of fractionation columns (deethanizer, depropanizer, debutanizer) each designed with specific local characteristics - different tray configurations, operating pressures, and temperature profiles - to selectively separate specific hydrocarbon components. This localized optimization at each separation stage maximizes olefin recovery while minimizing co-absorption.
Solution Approach 2:
The separation process is divided into multiple sequential stages: initial condensation, deethanization, depropanization, and debutanization. Each stage handles a specific fraction of the cracked gas, progressively separating lighter from heavier components. This segmentation prevents overwhelming a single separator and reduces olefin loss through targeted separation at each stage.
3Reliability
If catalyst regeneration by oxidation is performed to remove coke, then catalyst activity is restored, but large amount of heat is released which escapes with flue gas
Solution Approach 1:
The patent converts the harmful effect of heat loss into a beneficial feature by using the exothermic heat from coke combustion during regeneration to preheat the incoming feedstock and to generate steam for process requirements. The regenerator is designed as a heat exchanger system where the hot regenerated catalyst transfers heat to the feed, converting what would be waste heat into useful process energy.
Solution Approach 2:
The patent combines the regeneration function with heat recovery function in a single integrated system. The regenerator simultaneously performs coke removal and heat generation, which is then coupled with feed preheating and steam generation systems. This merging of functions eliminates the need for separate heat recovery equipment and maximizes energy utilization.
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 enhances the yield and separation efficiency of light olefins, maintaining catalyst activity and reducing energy consumption by effectively cracking heavy hydrocarbons and utilizing fractionation to produce desired hydrocarbon streams with high ethylene and propylene content.
Implementation Method 1
contacting a heavy hydrocarbon feedstock with a hydrocarbon cracking catalyst to produce a hydrocarbon effluent comprising a range of hydrocarbon products including light olefins
Implementation Method 2
a fluidized reactor zone wherein the heavy hydrocarbon feedstock contacts a hydrocarbon cracking catalyst
Implementation Method 3
The hydrocarbon effluent is separated in a separation section to form at least one separator liquid stream and a separator vapor stream
Implementation Method 4
At least a portion of the separator vapor stream is deethanized to at least form a first deethanizer process stream comprising C2− hydrocarbons including a quantity of ethylene
Implementation Method 5
The second demethanizer product stream is subsequently split in a C2 hydrocarbon splitter to form a first C2 hydrocarbon splitter process stream comprising ethylene
Data Source
AI summary
Processing schemes and arrangements are provided for the processing a heavy hydrocarbon feedstock via hydrocarbon cracking processing with selected hydrocarbon fractions being obtained via fractionation-based product recovery.