Equilibrium Catalyst Separation by Size and Density
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Solution Overview
Problem
The Fluid Catalytic Cracking (FCC) process faces challenges in efficiently recycling equilibrium catalysts (ECAT) due to high metal content, leading to catalyst deactivation and economic losses, as existing methods are costly and inefficient, particularly for catalysts with high nickel and vanadium levels.
Innovation Solution
The process employs air classifying and sieving to separate ECAT into narrow size fractions, followed by density separation using cyclonic or other density separation methodologies, enabling the recovery of valuable fractions with improved catalytic properties, such as a ZSM-5 enriched fraction for propylene production and a gasoline-selective fraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If equilibrium catalysts with high metal content are recycled, then catalyst inventory is maintained, but catalyst deactivation and economic losses increase
Solution Approach 1:
The patent applies segmentation by dividing the equilibrium catalyst into different size fractions using cyclonic separation. This separates the catalyst into recoverable fractions (larger particles) and lost fractions (fine particles below 20 microns), allowing selective recycling of valuable catalyst material while removing deactivated portions.
Solution Approach 2:
The patent extracts fine particles (<20 microns) from the equilibrium catalyst using cyclonic separation systems. This removes the most deactivated and metal-loaded catalyst portions, preventing them from further deactivating the overall catalyst inventory while maintaining the quantity of active catalyst.
2Reliability
If fine particles below 20 microns are removed from equilibrium catalyst, then catalyst deactivation is reduced, but catalyst losses increase
Solution Approach 1:
The patent converts the harmful effect of fine particle removal (catalyst loss) into a benefit by implementing a fines recovery system. The cyclonic separation captures fine particles that would otherwise be lost, and these recovered fines are recycled back to the FCC unit, transforming a waste stream into a valuable catalyst resource.
Solution Approach 2:
The patent implements a discarding and recovering system where fine particles are temporarily separated and held in a fines inventory system, then recovered and recycled back to the FCC unit. This allows selective removal of highly deactivated fines while preserving and reusing less deactivated fine particles.
3Reliability
If catalyst addition rate is increased to maintain activity, then catalyst activity is maintained, but operating costs increase
Solution Approach 1:
The patent implements a feedback system where catalyst fractions are continuously monitored for metal content and deactivation level. Based on this feedback, the system adjusts the rate of fresh catalyst addition and fine particle recycling to maintain optimal catalyst activity, minimizing unnecessary catalyst purchases and reducing operating costs.
Solution Approach 2:
The patent changes the physical parameters of the catalyst system by separating and recycling specific size fractions. This alters the catalyst inventory composition to contain a higher proportion of active, less metal-loaded particles, thereby maintaining catalyst activity at lower addition rates and reducing operating costs.
4Reliability
If cyclonic separation is used to remove fine particles, then catalyst deactivation is reduced, but separation efficiency decreases below 20 microns
Solution Approach 1:
The patent applies preliminary action by using a classifier screen before the cyclonic separation system. This pre-separation step removes the finest particles (<20 microns) that are difficult to separate efficiently in the cyclone, allowing the cyclonic system to focus on separating larger particles where it operates more efficiently.
Solution Approach 2:
The patent introduces a classifier screen as an intermediary device between the equilibrium catalyst feed and the cyclonic separation system. This intermediary performs the difficult fine particle separation task, while the cyclone handles the coarser separation, optimizing the overall separation efficiency of the system.
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 method effectively recycles ECAT by separating high-value fractions from those with limited application, enhancing catalytic performance and reducing waste, thereby improving the economic viability of FCC units by utilizing previously discarded catalysts.
Implementation Method 1
The physical properties of the catalysts used in FCC units... Two important parameters are the percent by weight of the total below 20 microns and the percent by weight of the total below 40 microns... Cyclonic systems or cyclones and air separators are well known devices used to separate materials of different physical properties. In particular, cyclones can separate mixtures of solids with different particle size, density, relative mass or any combination thereof.
Implementation Method 2
Cyclonic systems or cyclones and air separators are well known devices used to separate materials of different physical properties. In particular, cyclones can separate mixtures of solids with different particle size, density, relative mass or any combination thereof.
Implementation Method 3
The physical properties of the catalysts used in FCC units, 'FCC Catalysts' are designed such that even though the catalyst is a solid, it behaves like a liquid when enough fluidizing media (i.e. vapors, air) are present.
Data Source
Figure 1
AI summary
Useful portions of equilibrium catalyst from a Fluid Catalytic Cracking unit are obtained by fractionating to obtain a narrow size fraction, followed by separation of the narrow size fraction using density as a fractionating criterion. Size fractionating may be performed in vibrating sieves, and the density fractionating may be performed in an air cyclone. Both beneficial and detrimental fractions can be identified; in one embodiment, large particles are removed from ECAT to improve the coking factor.