Fluid Bed Steam Cracking Direct Heating
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Solution Overview
Problem
Conventional steam cracking processes face challenges with coke formation, inefficient heating control, and the need for specialized catalysts, especially when processing feeds with resid boiling range components, leading to shortened process cycles and large refinery footprints.
Innovation Solution
The use of direct heating with a cracking zone cooler than the heating zone, employing silica particles for heat transfer, and operating at an oxygen stoichiometric ratio of 1.2 or less to form synthesis gas, which reduces coke buildup and allows for improved control over cracking temperatures and residence time, while also facilitating integration with other refinery processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If indirect heating is used in conventional steam crackers, then heating control is achieved through furnace design, but coke accumulates rapidly on reactor tube walls requiring multiple furnaces and shortened process cycles
Solution Approach 1:
The invention extracts the heating function from the reaction environment by introducing external hot particles into the cracking zone. This separates the heating source from the reactor tubes, preventing coke accumulation on tube walls while maintaining effective heating control through particle circulation and temperature regulation.
Solution Approach 2:
Hot particles serve as an intermediary heat transfer medium between the heating zone and the cracking zone. These particles carry thermal energy from the heating zone to the cracking zone, enabling indirect heating within the direct heating system and preventing direct contact between fuel combustion products and the cracking environment.
2Use of energy by moving object
If direct heating is used with fuel combustion in the same reactor, then heating efficiency improves, but flue gases dilute the desired light olefins products
Solution Approach 1:
The reactor is segmented into distinct heating zone and cracking zone. The heating zone contains fuel combustion for heat generation, while the cracking zone maintains a separate environment for steam cracking. Hot particles circulate between zones to transfer heat without mixing combustion flue gases with the cracking products, preserving light olefins concentration.
Solution Approach 2:
Hot particles act as an intermediary that transfers thermal energy from the heating zone to the cracking zone without requiring direct mixing of combustion gases and cracking feed. This maintains heating efficiency while preventing dilution of light olefins with flue gases.
3Productivity
If high temperature direct heating is used for steam cracking, then cracking efficiency improves, but controlling residence time becomes difficult leading to overcracking
Solution Approach 1:
The system uses dynamic particle circulation to control residence time. Particles are continuously circulated between the heating zone and cracking zone at controlled rates, allowing the feed to be exposed to high temperatures for precisely controlled durations. This dynamic control prevents overcracking while maintaining high cracking efficiency.
Solution Approach 2:
The particle circulation system provides feedback control for residence time. By monitoring particle temperature and circulation rate, the system adjusts the time feed material spends in the cracking zone, ensuring optimal cracking conditions without excessive residence time that would lead to overcracking.
4Productivity
If multiple furnaces operate in parallel for continuous production, then production continuity is maintained, but refinery footprint increases substantially
Solution Approach 1:
The system maintains continuous production through continuous circulation of hot particles between heating and cracking zones within a single reactor. This eliminates the need for multiple furnaces operating in parallel, as the particle circulation provides continuous heat supply without requiring shutdowns for decoking, thereby reducing refinery footprint while maintaining productivity.
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 enables longer cycle lengths, reduced coke accumulation, minimized catalyst concerns, and increased control over cracking conditions, allowing for efficient processing of heavy feeds and reducing the refinery footprint by utilizing coke as fuel and generating beneficial synthesis gas.
Implementation Method 1
transporting heat transfer particles from a heating zone to a cracking zone
Implementation Method 2
A fluidized bed of heat transfer particles can be sufficiently well-mixed to allow the bed to have a substantially uniform temperature throughout the fluidized bed
Implementation Method 3
at least a portion of the coke that forms on the heat transfer particles can be combusted in the heating zone
Data Source
AI summary
Systems and methods are provided for performing steam cracking on a feed while using direct heating of the reaction environment. The heating of the reaction environment can be achieved in part by transporting heat transfer particles from a heating zone to cracking zone. This can be performed in a fluidized bed reactor, a moving bed reactor, a riser reactor, or another type of reactor that can allow for catalyst movement and regeneration during operation.