Single Riser Cracking Reactor for Light Olefin Production
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Solution Overview
Problem
Current processes for producing light olefins, such as ethylene and propylene, face challenges including low yields, high capital expenditures due to dual riser configurations, catalyst deactivation, and inefficient heat management, which affect the production efficiency and economics of the catalytic cracking process.
Innovation Solution
A thermo-neutral catalytic conversion process in a single riser with multiple zones, utilizing a combination of endothermic and exothermic cracking reactions, and burning coke deposits to maintain heat balance, employing ZSM-5 or alkaline metal modified ZSM-5 catalysts with USY or Beta zeolites, allows for sequential cracking of diverse hydrocarbon feeds to optimize light olefin production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a dual riser configuration is used to increase light olefin yield, then productivity improves, but device complexity and capital expenditure increase
Solution Approach 1:
The single riser reactor is segmented into multiple zones (first zone, second zone, third zone) with different temperatures and functions. The first zone operates at higher temperature for initial cracking, the second zone at intermediate temperature for further conversion, and the third zone at lower temperature for selective propylene production. This segmentation allows complex chemical transformations to occur in sequence within a single reactor, achieving dual-riser-level productivity without the complexity of multiple reactors.
2Productivity
If high reaction severity is applied to maximize propylene yield, then productivity improves, but catalyst deactivation increases
Solution Approach 1:
The catalytic cracking process is divided into sequential zones with decreasing temperature and severity. The first zone uses high severity conditions for maximum conversion, the second zone uses moderate conditions, and the third zone uses lower severity conditions optimized for propylene selectivity. This segmentation allows the catalyst to operate at high activity in the first zone without immediate deactivation, as subsequent zones provide gentler conditions that extend catalyst life while maintaining high overall propylene yield.
Solution Approach 2:
The feedstock undergoes preliminary cracking in the first zone at high temperature to break down heavy molecules into lighter fragments. This preliminary action prepares the hydrocarbon molecules for further selective conversion in subsequent zones, allowing the catalyst to achieve high propylene yields without requiring all reactions to occur under maximally severe conditions that would cause rapid deactivation.
3Productivity
If endothermic cracking reactions are intensified to increase light olefin production, then productivity improves, but energy consumption increases
Solution Approach 1:
The process merges endothermic cracking reactions with exothermic combustion reactions in an integrated single-riser system. The combustion of coke deposits on the catalyst occurs concurrently with the cracking reactions, and the heat generated from this exothermic combustion is used to supply the heat required for the endothermic cracking processes. This merging of opposing thermal processes creates a self-sustaining thermal system that intensifies light olefin production without proportionally increasing external energy consumption.
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 light olefin yields, reduces capital expenditures by eliminating the need for dual riser systems, and minimizes catalyst deactivation, achieving higher production efficiency and economic viability.
Implementation Method 1
the continuous burning of fuel in regenerator accelerates hydrothermal deactivation of catalyst
Implementation Method 2
endothermic cracking reaction of C4 to residue
Implementation Method 3
exothermic cracking of methanol
Implementation Method 4
burning the coke deposited on catalyst is utilized further
Data Source
AI summary
A process for catalytic conversion of low value hydrocarbon streams to light olefins in comparatively higher yields is disclosed. Propylene is obtained in amounts higher than 20 wt. % and ethylene higher than 6 wt. %. The process is carried out in a preheated cracking reactor having a single riser and circulating an FCC catalyst. The riser is divided into three temperature zones in which different hydrocarbon feeds are introduced. An oxygenate feed is introduced in the operative top zone in the riser. Heat for the endothermic cracking is obtained by the exothermic reaction of converting the oxygenate feed into gas and/or from a regenerator in which the spent FCC catalyst is burnt.