Split-Feed Injection for FCC Riser LPG Yield
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Solution Overview
Problem
Current fluid catalytic cracking (FCC) processes face challenges in maximizing yields of light fractions like LPG when processing mixed hydrocarbon feeds from different sources, as they often result in increased coke production and altered catalyst circulation rates, leading to reduced conversion and selectivity to valuable products.
Innovation Solution
The process involves split-feed injection of hydrocarbon streams with different crackability and contaminant content, where one stream is injected downstream in the riser, optimized for higher coke selectivity and contaminant content, using high-efficiency injection devices to maintain constant outlet temperature and catalyst circulation rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If mixed feedstocks from different sources are processed in conventional FCC, then hydrocarbon conversion occurs, but coke production increases and catalyst circulation rate must be altered, reducing conversion and selectivity to valuable products
Solution Approach 1:
The feedstock stream is segmented into two separate injection points within the riser: a first injection point introducing a first feedstock and a second injection point introducing a second feedstock. This spatial segmentation allows different feedstocks with varying properties to be processed under optimized conditions, increasing LPG yield while controlling coke production by preventing excessive mixing that would lead to higher coke formation.
Solution Approach 2:
Different regions of the riser are given different qualities by injecting feedstocks at different locations. The first feedstock is injected at a first location and the second feedstock at a second location, creating localized reaction zones with different characteristics. This allows each feedstock to undergo cracking under conditions optimized for its specific properties, maximizing valuable product formation while minimizing harmful coke production.
2Productivity
If feedstocks with different crackability are injected together at the base of the riser, then processing occurs, but catalyst deactivation increases and conversion to valuable products decreases
Solution Approach 1:
The injection system is segmented into multiple injection points along the riser length. By separating the injection of different feedstocks into distinct locations, the system prevents premature mixing that would cause catalyst deactivation. Each feedstock contacts the catalyst in a controlled manner, maintaining catalyst activity and improving conversion to valuable products.
Solution Approach 2:
The feedstocks are preliminarily separated and injected at different locations before fully mixing. This preliminary spatial separation allows each feedstock to be processed under optimized conditions, preventing the catalyst from being overwhelmed by the combined properties of multiple feedstocks, thereby maintaining high conversion efficiency.
3Productivity
If catalyst circulation rate is increased to improve conversion, then valuable product yield increases, but equipment capacity is overloaded and operation stability decreases
Solution Approach 1:
Instead of uniformly increasing catalyst circulation throughout the entire riser, the system creates localized high-conversion zones by injecting feedstocks at specific points. This localized approach achieves high valuable product yield without requiring a proportional increase in overall catalyst circulation rate, thereby maintaining operation stability and preventing equipment overload.
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 increases LPG production by creating localized severe reaction conditions for the better-quality feed, minimizing catalyst deactivation and coke production, while maintaining stable operation and equipment capacity, resulting in higher yields of valuable products without overloading regeneration systems.
Implementation Method 1
fluid catalytic cracking (FCC) of mixed feedstocks of hydrocarbons from different sources
Implementation Method 2
convert them to lighter, more valuable hydrocarbon streams
Implementation Method 3
coke deposited on the surface and in the catalyst pores is burned
Implementation Method 4
catalyst is also the heat transport medium from the regenerator to the reaction zone
Implementation Method 5
The fluidization of the catalyst particles by gaseous streams allows the catalyst transport between the reaction zone and the regeneration zone
Data Source
AI summary
A process for the fluid catalytic cracking of mixed hydrocarbon feeds from different sources is described, such as feeds A and B of different crackability, the process being especially directed to obtaining light fractions such as LPG and comprising injecting feed A in the base of the riser reactive section and feed B, of lower crackability, at a height between 10% and 80% of the riser, with feed B comprising between 5% and 50% of the total processed feed. The process requires that the feeds present differences in the contaminant content, improved dispersion of feeds A and B and feed B injection temperature same or higher than that of feed A.