Integrated Hydrocarbon Cracking for Light Olefin Yield
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Solution Overview
Problem
Conventional hydrocarbon cracking processes, such as fluidized catalytic cracking, fail to effectively increase the yield of light olefins like ethylene and propylene, which are crucial for petrochemical production, due to coke deposition on catalysts reducing their activity and heat management inefficiencies.
Innovation Solution
An integrated process involving a primary fluidized bed reactor for cracking heavy hydrocarbon feedstocks to produce C4-C7 olefins, followed by further cracking of these olefins to enhance the production of C2 and C3 olefins, utilizing a gas concentration system for separation and recycling of products to optimize light olefin recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional fluidized catalytic cracking is used to process heavy hydrocarbons, then the process is simple and well-established, but the yield of light olefins (ethylene and propylene) is insufficient
Solution Approach 1:
The cracking process is divided into two distinct stages: first, heavy hydrocarbons are cracked in a fluidized bed reactor to produce C4-C7 olefins; second, these C4-C7 olefins are cracked again in a fixed bed reactor to produce light olefins (C2-C3). This segmentation allows each reactor to be optimized for its specific function, thereby increasing overall light olefin yield while managing complexity through functional specialization
Solution Approach 2:
The invention merges two cracking processes (fluidized bed cracking and fixed bed cracking) into an integrated system where the effluent from the first reactor becomes the feed for the second reactor. This combination allows the system to leverage the advantages of both reactor types - the fluidized bed's ability to handle heavy feeds and the fixed bed's effectiveness for light olefin production - achieving higher light olefin yields than either process alone
2Productivity
If catalyst is used to crack heavy hydrocarbons, then cracking activity is enhanced, but coke deposition on the catalyst reduces its activity over time
Solution Approach 1:
The catalytic cracking function is segmented across two different reactor systems. The fluidized bed reactor uses a catalyst designed for heavy hydrocarbon cracking, while the fixed bed reactor uses a catalyst optimized for light olefin cracking. This segmentation prevents coke accumulation from heavy feeds from deactivating the catalyst in the second stage, maintaining reliable cracking activity throughout the process
Solution Approach 2:
The harmful effect of coke deposition is extracted and isolated to the first reactor stage. By using a fluidized bed reactor with appropriate catalyst and operating conditions, coke formation is concentrated in the first stage where it can be managed through catalyst regeneration, protecting the second stage catalyst from deactivation and maintaining overall process reliability
3Reliability
If catalyst is regenerated by oxidizing coke, then catalyst activity is restored, but a large amount of heat is released that must be managed
Solution Approach 1:
The heat management function is merged with the process design by utilizing the endothermic cracking reactions in both reactors to absorb the exothermic heat from catalyst regeneration. The fluidized bed and fixed bed reactors serve dual purposes: performing cracking reactions while also acting as heat sinks for the regeneration process, thereby restoring catalyst activity while managing temperature through integrated heat exchange
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 significantly increases the yield of light olefins, improves processing efficiency, and reduces material and energy requirements, making the process more economically viable compared to conventional methods.
Implementation Method 1
contacting a heavy hydrocarbon feedstock with a fluidized catalytic cracking catalyst to crack the heavy hydrocarbon feedstock
Implementation Method 2
The fluidized catalyst, as well as providing a catalytic function, acts as a vehicle for the transfer of heat from zone to zone
Implementation Method 3
transferred to a regenerator for purposes of removing the coke by oxidation with an oxygen-containing gas
Implementation Method 4
Cracked vapors from the FCC unit enter a separation zone, typically in the form of a main column, that provides a gas stream, a gasoline cut, light cycle oil (LCO) and clarified oil (CO)
Data Source
AI summary
Processing scheme and arrangement for increasing the relative yield of light olefins involves integration of the cracking a heavy hydrocarbon feedstock to produce an effluent comprising a range of hydrocarbon products including C4-C7 olefins and the subsequent cracking at least a portion of the C4-C7 olefins to produce additional light olefins.